Packaging and labeling

Packaging is the science, art and technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of designing, evaluating, and producing packages. Packaging can be described as a coordinated system of preparing goods for transport, warehousing, logistics, sale, and end use. Packaging contains, protects, preserves, transports, informs, and sells. In many countries it is fully integrated into government, business, institutional, industrial, and personal use.
Package labeling (American English) or labelling (British English) is any written, electronic, or graphic communication on the package or on a separate but associated label.
History of packaging.
Ancient era.
The first packages used the natural materials available at the time: baskets of reeds, wineskins (bota bags), wooden boxes, pottery vases, ceramic amphorae, wooden barrels, woven bags, etc. Processed materials were used to form packages as they were developed: first glass and bronze vessels. The study of old packages is an essential aspect of archaeology.
The first usage of paper for packaging was sheets of treated mulberry bark used by the Chinese to wrap foods as early as the first or second century BC.
The usage of paper-like material in Europe was when the Romans used low grade and recycled papyrus for the packaging of incense.
The earliest recorded use of paper for packaging dates back to 1035, when a Persian traveller visiting markets in Cairo, Arab Egypt, noted that vegetables, spices and hardware were wrapped in paper for the customers after they were sold.
Modern era.
Tinplate.
The use of tinplate for packaging dates back to the 18th century. The manufacturing of tinplate was the monopoly of Bohemia for a long time; in 1667 Andrew Yarranton, an English engineer, and Ambrose Crowley brought the method to England where it was improved by ironmasters including Philip Foley. By 1697, John Hanbury had a rolling mill at Pontypool for making "Pontypoole Plates". The method pioneered there of rolling iron plates by means of cylinders enabled more uniform black plates to be produced than was possible with the former practice of hammering.
Tinplate boxes first began to be sold from ports in the Bristol Channel in 1725. The tinplate was shipped from Newport, Monmouthshire. By 1805, 80,000 boxes were made and 50,000 exported. Tobacconists in London began packaging snuff in metal-plated canisters from the 1760s onwards.
Canning.
With the discovery of the importance of airtight containers for food preservation by French inventor Nicholas Appert, the tin canning process was patented by British merchant Peter Durand in 1810. After receiving the patent, Durand did not himself follow up with canning food. He sold his patent in 1812 to two other Englishmen, Bryan Donkin and John Hall, who refined the process and product and set up the world's first commercial canning factory on Southwark Park Road, London. By 1813, they were producing the first canned goods for the Royal Navy.
The progressive improvement in canning stimulated the 1855 invention of the can opener. Robert Yeates, a cutlery and surgical instrument maker of Trafalgar Place West, Hackney Road, Middlesex, UK, devised a claw-ended can opener with a hand-operated tool that haggled its way around the top of metal cans. In 1858, another lever-type opener of a more complex shape was patented in the United States by Ezra Warner of Waterbury, Connecticut.
Paper-based packaging.
Set-up boxes were first used in the 16th century and modern folding cartons date back to 1839. The first corrugated box was produced commercially in 1817 in England. Corrugated (also called pleated) paper received a British patent in 1856 and was used as a liner for tall hats. Scottish-born Robert Gair invented the pre-cut paperboard box in 1890—flat pieces manufactured in bulk that folded into boxes. Gair's invention came about as a result of an accident: as a Brooklyn printer and paper-bag maker during the 1870s, he was once printing an order of seed bags, and the metal ruler, commonly used to crease bags, shifted in position and cut them. Gair discovered that by cutting and creasing in one operation he could make prefabricated paperboard boxes.
Commercial paper bags were first manufactured in Bristol, England, in 1844, and the American Francis Wolle patented a machine for automated bag-making in 1852.
20th century.
Packaging advancements in the early 20th century included Bakelite closures on bottles, transparent cellophane overwraps and panels on cartons. These innovations increased processing efficiency and improved food safety. As additional materials such as aluminum and several types of plastic were developed, they were incorporated into packages to improve performance and functionality.
In 1952, Michigan State University became the first university in the world to offer a degree in Packaging Engineering.
In-plant recycling has long been typical for producing packaging materials. Post-consumer recycling of aluminum and paper-based products has been economical for many years: since the 1980s, post-consumer recycling has increased due to curbside recycling, consumer awareness, and regulatory pressure.
Many prominent innovations in the packaging industry were developed first for military use. Some military supplies are packaged in the same commercial packaging used for general industry. Other military packaging must transport materiel, supplies, foods, etc. under severe distribution and storage conditions. Packaging problems encountered in World War II led to Military Standard or "mil spec" regulations being applied to packaging, which was then designated "military specification packaging". As a prominent concept in the military, mil spec packaging officially came into being around 1941, due to operations in Iceland experiencing critical losses, ultimately attributed to bad packaging. In most cases, mil spec packaging solutions (such as barrier materials, field rations, antistatic bags, and various shipping crates) are similar to commercial grade packaging materials, but subject to more stringent performance and quality requirements.
, the packaging sector accounted for about two percent of the gross national product in developed countries. About half of this market was related to food packaging.
In 2019 the global food packaging market size was estimated at USD 303.26 billion, exhibiting a CAGR of 5.2% over the forecast period. Growing demand for packaged food by consumers owing to quickening pace of life and changing eating habits is expected to have a major impact on the market.
The purposes of packaging and package labels.
Packaging and package labeling have several objectives
Packaging types.
Packaging may be of several different types. For example, a "transport package" or "distribution package" can be the shipping container used to ship, store, and handle the product or inner packages. Some identify a "consumer package" as one which is directed toward a consumer or household.
Packaging may be described in relation to the type of product being packaged: medical device packaging, bulk chemical packaging, over-the-counter drug packaging, retail food packaging, military materiel packaging, pharmaceutical packaging, etc.
It is sometimes convenient to categorize packages by layer or function: "primary", "secondary", etc.
These broad categories can be somewhat arbitrary. For example, depending on the use, a shrink wrap can be primary packaging when applied directly to the product, secondary packaging when used to combine smaller packages, or tertiary packaging when used to facilitate some types of distribution, such as to affix a number of cartons on a pallet.
Packaging can also have categories based on the package form. For example, "thermoform packaging" and "flexible packaging" describe broad usage areas.
Labels and symbols used on packages.
Many types of symbols for package labeling are nationally and internationally standardized. For consumer packaging, symbols exist for product certifications (such as the FCC and TÜV marks), trademarks, proof of purchase, etc. Some requirements and symbols exist to communicate aspects of consumer rights and safety, for example the CE marking or the estimated sign that notes conformance to EU weights and measures accuracy regulations. Examples of environmental and recycling symbols include the recycling symbol, the recycling code (which could be a resin identification code), and the "Green Dot". Food packaging may show food contact material symbols. In the European Union, products of animal origin which are intended to be consumed by humans have to carry standard, oval-shaped EC identification and health marks for food safety and quality insurance reasons.
Bar codes, Universal Product Codes, and RFID labels are common to allow automated information management in logistics and retailing. Country-of-origin labeling is often used. Some products might use QR codes or similar matrix barcodes. Packaging may have visible registration marks and other printing calibration and troubleshooting cues.
The labelling of medical devices includes many symbols, many of them covered by international standards, foremost ISO 15223-1.
Consumer package contents.
Several aspects of consumer package labeling are subject to regulation. One of the most important is to accurately state the quantity (weight, volume, count) of the package contents. Consumers expect that the label accurately reflects the actual contents. Manufacturers and packagers must have effective quality assurance procedures and accurate equipment; even so, there is inherent variability in all processes.
Regulations attempt to handle both sides of this. In the USA, the Fair Packaging and Labeling Act provides requirements for many types of products. Also, NIST has Handbook 133, Checking the Net Contents of Packaged Goods. This is a procedural guide for compliance testing of net contents and is referenced by several other regulatory agencies.
Other regions and countries have their own regulatory requirements. For example, the UK has its Weights and Measures (Packaged Goods) Regulations as well as several other regulations. In the EEA, products with hazardous formulas need to have a UFI.
Shipping container labeling.
Technologies related to shipping containers are identification codes, bar codes, and electronic data interchange (EDI). These three core technologies serve to enable the business functions in the process of shipping containers throughout the distribution channel. Each has an essential function: identification codes either relate product information or serve as keys to other data, bar codes allow for the automated input of identification codes and other data, and EDI moves data between trading partners within the distribution channel.
Elements of these core technologies include UPC and EAN item identification codes, the SCC-14 (UPC shipping container code), the SSCC-18 (Serial Shipping Container Codes), Interleaved 2-of-5 and UCC/EAN-128 (newly designated GS1-128) bar code symbologies, and ANSI ASC X12 and UN/EDIFACT EDI standards.
Small parcel carriers often have their own formats. For example, United Parcel Service has a MaxiCode 2-D code for parcel tracking.
RFID labels for shipping containers are also increasingly used. A Wal-Mart division, Sam's Club, has also moved in this direction and is putting pressure on its suppliers to comply.
Shipments of hazardous materials or dangerous goods have special information and symbols (labels, placards, etc.) as required by UN, country, and specific carrier requirements. On transport packages, standardized symbols are also used to communicate handling needs. Some are defined in the ASTM D5445 "Standard Practice for Pictorial Markings for Handling of Goods" and ISO 780 "Pictorial marking for handling of goods".
Package development considerations.
Package design and development are often thought of as an integral part of the new product development process. Alternatively, the development of a package (or component) can be a separate process but must be linked closely with the product to be packaged.
Package design starts with the identification of all the requirements: structural design, marketing, shelf life, quality assurance, logistics, legal, regulatory, graphic design, end-use, environmental, etc. The design criteria, performance (specified by package testing), completion time targets, resources, and cost constraints need to be established and agreed upon. Package design processes often employ rapid prototyping, computer-aided design, computer-aided manufacturing and document automation.
An example of how package design is affected by other factors is its relationship to logistics. When the distribution system includes individual shipments by a small parcel carrier, the sorting, handling, and mixed stacking make severe demands on the strength and protective ability of the transport package. If the logistics system consists of uniform palletized unit loads, the structural design of the package can be designed to meet those specific needs, such as vertical stacking for a longer time frame. A package designed for one mode of shipment may not be suited to another.
With some types of products, the design process involves detailed regulatory requirements for the packaging. For example, any package components that may contact foods are designated food contact materials.
Toxicologists and food scientists need to verify that such packaging materials are allowed by applicable regulations. Packaging engineers need to verify that the completed package will keep the product safe for its intended shelf life with normal usage. Packaging processes, labeling, distribution, and sale need to be validated to assure that they comply with regulations that have the well being of the consumer in mind.
Sometimes the objectives of package development seem contradictory. For example, regulations for an over-the-counter drug might require the package to be tamper-evident and child resistant: These intentionally make the package difficult to open. The intended consumer, however, might be disabled or elderly and unable to readily open the package. Meeting all goals is a challenge.
Package design may take place within a company or with various degrees of external packaging engineering: independent contractors, consultants, vendor evaluations, independent laboratories, contract packagers, total outsourcing, etc. Some sort of formal project planning and project management methodology is required for all but the simplest package design and development programs. An effective quality management system and Verification and Validation protocols are mandatory for some types of packaging and recommended for all.
Environmental considerations.
Package development involves considerations of sustainability, environmental responsibility, and applicable environmental and recycling regulations. It may involve a life cycle assessment
which considers the material and energy inputs and outputs to the package, the packaged product (contents), the packaging process, the logistics system, waste management, etc. It is necessary to know the relevant regulatory requirements for point of manufacture, sale, and use.
The traditional "three R's" of reduce, reuse, and recycle are part of a waste hierarchy which may be considered in product and package development.
Development of sustainable packaging is an area of considerable interest to standards organizations, governments, consumers, packagers, and retailers.
Sustainability is the fastest-growing driver for packaging development, particularly for packaging manufacturers that work with the world's leading brands, as their CSR (Corporate Social Responsibility) targets often exceed those of the EU Directive.
Packaging machinery.
Choosing packaging machinery includes an assessment of technical capabilities, labor requirements, worker safety, maintainability, serviceability, reliability, ability to integrate into the packaging line, capital cost, floorspace, flexibility (change-over, materials, multiple products, etc.), energy requirements, quality of outgoing packages, qualifications (for food, pharmaceuticals, etc.), throughput, efficiency, productivity, ergonomics, return on investment, etc.
Packaging machinery can be:
Efforts at packaging line automation increasingly use programmable logic controllers and robotics.
Packaging machines may be of the following general types:


Bottling line

Bottling lines are production lines that fill a product, generally a beverage, into bottles on a large scale. Many prepared foods are also bottled, such as sauces, syrups, marinades, oils and vinegars.
Beer bottling process.
Packaging of bottled beer typically involves drawing the product from a holding tank and filling it into bottles in a filling machine ("filler"), which are then capped, labeled and packed into cases or cartons. Many smaller breweries send their bulk beer to large facilities for contract bottling—though some will bottle by hand. Virtually all beer bottles are glass.
The first step in bottling beer is "depalletising", where the empty bottles are removed from the original pallet packaging delivered from the manufacturer, so that individual bottles may be handled. The bottles may then be rinsed with filtered water or air, and may have carbon dioxide injected into them in attempt to reduce the level of oxygen within the bottle. The bottle then enters a "filler" which fills the bottle with beer and may also inject a small amount of inert gas (usually carbon dioxide or nitrogen) on top of the beer to disperse the oxygen, as oxygen can ruin the quality of the product via oxidation. Finally, the bottles go through a "capper", which applies a bottle cap, sealing the bottle. A few beers are bottled with a cork and cage.
Next the bottle enters a labelling machine ("labeller") where a label is applied. To ensure traceability of the product, a "lot number", generally the date and time of bottling, may also be printed on the bottle. The product is then packed into boxes and warehoused, ready for sale.
Depending on the magnitude of the bottling endeavor, there are many different types of bottling machinery available. Liquid level machines fill bottles so they appear to be filled to the same line on every bottle, while volumetric filling machines fill each bottle with exactly the same amount of liquid. Overflow pressure fillers are the most popular machines with beverage makers, while gravity filling machines are most cost effective. In terms of automation, inline filling machines are most popular, but rotary machines are much faster albeit much more expensive.
Wine bottling process.
The process for bottling wine is largely similar to that for bottling beer, except wine bottles differ in volumes and shapes. Traditionally, a cork is used to provide closure to wine bottles. After filling, a bottle travels to a corking machine ("corker") where a cork is compressed and pushed into the neck of the bottle. Whilst this is happening, the corker vacuums the air out of the bottle to form a negative pressure "headspace". This removes any oxygen from the headspace, which is useful as latent oxygen can ruin the quality of the product via oxidation. A negative pressure headspace will also counteract pressure caused by the thermal expansion of the wine, preventing the cork from being forced from the bottle. Champagnes and sparkling wines may further be sealed with a muselet, which ensures the cork will not explode off in transit. Alternative wine closures such as screw caps are available.
Some bottling lines incorporate a "fill height detector" which reject under or over-filled bottles, and also a metal detector.
After filling and corking, a plastic or tin capsule is applied to the neck of the bottle in a "capsular". Next the bottle enters a "labeller" where a wine label is applied. The product is then packed into boxes and warehoused, ready for sale.


IR welding

IR welding is a welding technique that uses a non-contact heating method to melt and fuse thermoplastic parts together using the energy from infrared radiation. The process was first developed in the late 1900s, but due to the high capital cost of IR equipment the process was not commonly applied in industry until prices dropped in the 1990s. IR welding typically uses a range of wavelengths from 800 to 11,000 nm on the electromagnetic spectrum to heat, melt, and fuse the interface between two plastic parts through the absorption and conversion of the IR energy into heat. Laser welding is a similar joining process that applies IR radiation at a single wavelength.
There are many different welding techniques that use IR heating, with the three major modes being surface heating, through transmission IR welding (TTIr), and IR staking. A variety of heating configurations have been applied to these techniques such as scanning, continuous illumination, and mask welding. Advantages such as faster and controllable non-contact heating applicable for a wide range of simple or complex part geometries sets IR welding apart from other forms of plastic welding. CO detectors, IV bags, and brake transmission lines are just a few of the many products that utilize IR welds.
History.
IR welding is categorized as a form thermal plastic welding alongside hot gas welding, hot tool welding, and extrusion welding. Although infrared radiation was first discovered in the 1800s, IR was not applied as a source of heat until the beginning of WWII when it was found to be more effective than the fuel convection ovens of that time. IR radiation was first tested for the welding of thermoplastic polymers in the late 1900s, but the process was relatively new and not fully understood. IR welding systems offered faster heating times than the other forms of thermal welding, but the high capital costs limited its development. With a decrease in the price of equipment in the 1990s, IR welding has become more popular in the industry.
Physics of IR welding.
IR welding typically uses wavelengths from 800 to 11,000 nm on the electromagnetic spectrum. Plastics interact with IR radiation through reflection, transmission, and absorption. Incident IR radiation can either be reflected off the surface of the plastic, transmitted through the plastic, or absorbed into the plastic as other forms of energy including thermal energy. The ratio of these three interactions depends on the wavelength of the IR radiation and the receiving plastic's properties. Amorphous plastics are generally optically clear and can transmit almost all incident IR radiation. For this reason they are commonly used in TTIr. Semi-crystalline plastics can diffuse incident IR radiation between the amorphous and crystalline boundaries, reducing the transmittance and increasing the absorbance of the material. The higher absorptivity results in more heat generation for a given IR source. Additives such as clarifying agents can be used increase a plastic's transmittance while dies and pigments can be used increase the absorbance of a material. Increasing amounts of these additives can decrease the strength of both the material and the welded joint.
The closer the IR radiation source, the higher incidence efficiency on the material. IR radiation is most effective when directing radiation normal to the part. Radiation energy always affects the surface of a part while the depth of penetration that the energy can reach is dependent on the plastic's crystallinity.
Equipment.
IR Sources.
Potential IR welding sources include quartz lamps and ceramic heaters which can generate a wide range of IR wavelengths. Laser welding employs IR sources that operate at a single wavelength such as CO2 lasers, s, laser diodes. The equipment selected for each welding process stems from the type of radiation produced. Quartz lamps produce wavelengths of around 1,000 to 5,000 nm and ceramic heaters produce wavelengths of around 5,000 to 10,000 nm.
Attachments.
P-wave technology utilizes an IR lamp and a pre-placed focusing device such as an IR transducer or film that can filter and focus IR radiation at a desired wavelength and increased intensity within a selected area to improve weld penetration with minimal surface damage. This method allows improved IR welding of polymers with higher melting temperatures such as most fluoropolymers and polyketones.
IR welding techniques.
The three major welding techniques used in the industry today include surface heating, through transmission IR welding, and IR staking. All IR welding techniques contain the following six basic steps in some form:
Surface Heating.
Surface heating includes heating and melting of the interface between plastic parts with IR radiation and forcing the parts together into a molten joint that solidifies as one part. This process can be split into 3 phases as shown in the figure to the right: A) Loading of parts, insertion of the IR source, and IR application. B) Change-over with the removal of IR source and clamping of the parts to join them. C) Unloading of the parts after the weld was made.
Through Transmission IR Welding (TTIr).
TTIr welding is the joining of an IR transparent part to a second part such that the IR radiation travels through the transparent part and heat the surface of the second part as shown in the figure to the right. IR wavelengths are generally within 800 to 1050 nm. To make a transparent part absorbent to IR radiation, the addition of dies or colorants such as carbon black can be used. Highly absorbent thermoplastic films can be placed at the joint to receive the IR radiation and melt the interface during welding. Using these methods, TTIr welds can be completed between parts of both the same or different materials.
IR Staking.
IR staking includes the localized welding of a thermoplastic stud or stake from one part into the cavity of a non-weldable part to form a mechanical fastener. As shown in the figure to the right, the polymer part and non-weldable part are first placed together (A), then the projecting polymer is melted and formed around the non-weldable part to fasten the two together (B). The stud can be heated through directed TTIr when pre-placed within the cavity of an IR transparent part, then melted to deform it into a button shape required to fill the cavity before solidifying. Surface IR radiation can also be used to soften a plastic stud which is then pressed into a button-shaped die to form a head before cooling and solidifying.
Heating Configurations.
IR systems generally rely on one of three surface heating methods: scanning, continuous illumination, and mask welding.
Scanning.
Scanning involves the movement of an IR beam across the surface of a part using either an automated motion system or galvanic mirrors. Equipment is limited by the speed of movements across the part's surface to maintain uniform temperatures on the surface. In TTIr welding, scanning allows the un-melted portion of the part to act as a mechanical stop in order to maintain the joint gap between the two parts.
Continuous illumination.
Continuous illumination uses more than one IR radiation source to heat the entire joint interface at the same time. Part tolerances or fit is not as crucial with this method as the entire surface will be melted before welding. This method is useful when welding parts with complex geometries, employing the multiple IR sources to evenly heat all forms of joint interfaces.
Mask welding.
Similar to continuous illumination, mask welding utilizes multiple IR sources to completely illuminate a joint interface while placing an IR radiation mask over the parts to control which regions will form a melt layer.
Materials.
Below is a list of materials well known for their IR weldability:
Applications.
New joining technologies using IR welding are critical for fabricating complex parts and assemblies at high speeds and low costs. Although IR plastic welding has many advantages over other types of plastic welding, limitations such as equipment costs and susceptible materials properties reduce the amount of industrial applications of the method. A few examples of current industrial applications are shown below:


Interconnect (integrated circuits)

In integrated circuits (ICs), interconnects are structures that connect two or more circuit elements (such as transistors) together electrically. The design and layout of interconnects on an IC is vital to its proper function, performance, power efficiency, reliability, and fabrication yield. The material interconnects are made from depends on many factors. Chemical and mechanical compatibility with the semiconductor substrate and the dielectric between the levels of interconnect is necessary, otherwise barrier layers are needed. Suitability for fabrication is also required; some chemistries and processes prevent the integration of materials and unit processes into a larger technology (recipe) for IC fabrication. In fabrication, interconnects are formed during the back-end-of-line after the fabrication of the transistors on the substrate.
Interconnects are classified as "local" or "global" interconnects depending on the signal propagation distance it is able to support. The width and thickness of the interconnect, as well as the material from which it is made, are some of the significant factors that determine the distance a signal may propagate. Local interconnects connect circuit elements that are very close together, such as transistors separated by ten or so other contiguously laid out transistors. Global interconnects can transmit further, such as over large-area sub-circuits. Consequently, local interconnects may be formed from materials with relatively high electrical resistivity such as polycrystalline silicon (sometimes silicided to extend its range) or tungsten. To extend the distance an interconnect may reach, various circuits such as buffers or restorers may be inserted at various points along a long interconnect.
Interconnect properties.
The geometric properties of an interconnect are width, thickness, spacing (the distance between an interconnect and another on the same level), pitch (the sum of the width and spacing), and aspect ratio, or AR, (the thickness divided by width). The width, spacing, AR, and ultimately, pitch, are constrained in their minimum and maximum values by design rules that ensure the interconnect (and thus the IC) can be fabricated by the selected technology with a reasonable yield. Width is constrained to ensure minimum width interconnects do not suffer breaks, and maximum width interconnects can be planarized by chemical mechanical polishing (CMP). Spacing is constrained to ensure adjacent interconnects can be fabricated without any conductive material bridging. Thickness is determined solely by the technology, and the aspect ratio, by the chosen width and set thickness. In technologies that support multiple levels of interconnects, each group of contiguous levels, or each level, has its own set of design rules.
Before the introduction of CMP for planarizing IC layers, interconnects had design rules that specified larger minimum widths and spaces than the lower level to ensure that the underlying layer's rough topology did not cause breaks in the interconnect formed on top. The introduction of CMP has made finer geometries possible.
The AR is an important factor. In technologies that form interconnect structures with conventional processes, the AR is limited to ensure that the etch creating the interconnect, and the dielectric deposition that fills the voids in between interconnects with dielectric, can be done successfully. In those that form interconnect structures with damascene processes, the AR must permit successful etch of the trenches, deposition of the barrier metal (if needed) and interconnect material.
Interconnect layout are further restrained by design rules that apply to collections of interconnects. For a given area, technologies that rely on CMP have "density rules" to ensure the whole IC has an acceptable variation in interconnect density. This is because the rate at which CMP removes material depends on the material's properties, and great variations in interconnect density can result in large areas of dielectric which can dish, resulting in poor planarity. To maintain acceptable density, "dummy interconnects" (or "dummy wires") are inserted into regions with spare interconnect density.
Historically, interconnects were routed in straight lines, and could change direction by using sections aligned 45° away from the direction of travel. As IC structure geometries became smaller, to obtain acceptable yields, restrictions were imposed on interconnect direction. Initially, only global interconnects were subject to restrictions; were made to run in straight lines aligned eastwest or northsouth. To allow easy routing, alternate levels of interconnect ran in the same alignment, so that changes in direction were achieved by connecting to a lower or upper level of interconnect though a via. Local interconnects, especially the lowest level (usually polysilicon) could assume a more arbitrary combination of routing options to attain the a higher packing density.
Materials.
In silicon ICs, the most commonly used semiconductor in ICs, the first interconnects were made of aluminum. Aluminum was an ideal material for interconnects due to its ease of deposition and good adherence to silicon and silicon dioxide. Al interconnects are deposited by physical vapor deposition or chemical vapor deposition methods. They were originally patterned by wet etching, and later by various dry etching techniques.
Initially, pure aluminum was used but by the 1970s, substrate compatibility, junction spiking and reliability concerns (mostly concerning electromigration) forced the use of aluminum-based alloys containing silicon, copper, or both. By the late 1990s, the high resistivity of aluminum, coupled with the narrow widths of the interconnect structures forced by continuous feature size downscaling, resulted in prohibitively high resistance in interconnect structures. This forced aluminum's replacement by copper interconnects.
In gallium arsenide (GaAs) ICs, which have been mainly used in application domains (e.g. monolithic microwave ICs) different to those of silicon, the predominant material used for interconnects is gold.
Performance enhancements.
To reduce the delay penalty caused by parasitic capacitance, the dielectric material used to insulate adjacent interconnects, and interconnects on different levels (the inter-level dielectric [ILD]), should have a dielectric constant that is as close to 1 as possible. A class of such materials, Low-κ dielectrics, were introduced during the late 1990s and early 2000s for this purpose. As of January 2019, the most advanced materials reduce the dielectric constant to very low levels through highly porous structures, or through the creation of substantial air or vacuum pockets (air gap dielectric). These materials often have low mechanical strength and are restricted to the lowest level or levels of interconnect as a result. The high density of interconnects at the lower levels, along with the minimal spacing, helps support the upper layers. Intel introduced air-gap dielectric in its 14nm technology in 2014.
Multi-level interconnects.
IC with complex circuits require multiple levels of interconnect to form circuits that have minimal area. As of 2018, the most complex ICs may have over 15 layers of interconnect. Each level of interconnect is separated from each other by a layer of dielectric. To make vertical connections between interconnects on different levels, vias are used. The top-most layers of a chip have the thickest and widest and most widely separated metal layers, which make the wires on those layers have the least resistance and smallest RC time constant, so they are used for power and clock distribution networks. The bottom-most metal layers of the chip, closest to the transistors, have thin, narrow, tightly-packed wires, used only for local interconnect. Adding layers can potentially improve performance, but adding layers also reduces yield and increases manufacturing costs. ICs with a single metal layer typically use the polysilicon layer to "jump across" when one signal needs to cross another signal.
The process used to form DRAM capacitors creates a rough and hilly surface, which makes it difficult to add metal interconnect layers and still maintain good yield.
In 1998, state-of-the-art DRAM processes had four metal layers, while state-of-the-art logic processes had seven metal layers.
In 2002, five or six layers of metal interconnect was common.
In 2009, 1Gbit DRAM typically had three layers of metal interconnect; tungsten for the first layer and aluminum for the upper layers.


Coining (metalworking)

Coining is a form of precision stamping in which a workpiece is subjected to a sufficiently high stress to induce plastic flow on the surface of the material. A beneficial feature is that in some metals, the plastic flow reduces surface grain size, and work hardens the surface, while the material deeper in the part retains its toughness and ductility. The term comes from the initial use of the process: manufacturing of coins.
Coining is used to manufacture parts for all industries and is commonly used when high relief or very fine features are required. For example, it is used to produce coins, badges, buttons, precision-energy springs and precision parts with small or polished surface features.
Coining is a cold working process similar in other respects to forging, which takes place at elevated temperature; it uses a great deal of force to elastically deform a workpiece, so that it conforms to a die. Coining can be done using a gear driven press, a mechanical press, or more commonly, a hydraulically actuated press. Coining typically requires higher tonnage presses than stamping, because the workpiece is elastically deformed and not actually cut, as in some other forms of stamping. The coining process is preferred when there is a high tonnage.
Coining in electronic industry.
In soldering of electronic components, bumps are formed on bonding pads to enhance adhesion, which are further flattened by the coining process. Unlike typical coining applications, in this case the goal of coining is to create a flat, rather than patterned, surface.


Pritchel

A pritchel is a type of punch used in forging, particularly in making nail holes in horseshoes. The horseshoe is heated and a hole is punched through 90 percent of the steel with a forepunch or drift punch. The pointed end of the tool should be kept sharp and so that the burr is cut out smoothly. The punched hole is lined up over the pritchel hole and the pritchel is driven into the hole, knocking out the remaining metal at the bottom of the punched hole.
The temperature of the pritchel should be always below the "red-hot" stage as the tool itself will bend and lose the temper. When over-heated it is advised to cool it in water intermediately.
Back pritcheling.
The pritchel should normally be driven from the bottom of the shoe, similarly as the nail is driven. "Back pritcheling" is the process of driving it from the opposite side —the hoof side— leaving burrs and resulting in the weakening and cutting the nails.
Pritchel hole.
A pritchel hole is a round hole in an anvil. Its primary purpose is to provide clearance for punching tools, but it can also be used to hold tools that have round shanks. Pritchel tools are tools such as punches whose functions do not require them to be held at a particular orientation. A square hole in an anvil is called a Hardy hole, not to be confused with
tapered square holes seen in tinsmith's equipment.


Shot peening

Shot peening is a cold working process used to produce a compressive residual stress layer and modify the mechanical properties of metals and composites. It entails striking a surface with shot (round metallic, glass, or ceramic particles) with force sufficient to create plastic deformation.
In machining, shot peening is used to strengthen and relieve stress in components like steel automobile crankshafts and connecting rods. In architecture it provides a muted finish to metal.
Shot peening is similar mechanically to sandblasting, though its purpose is not to remove material, but rather it employs the mechanism of plasticity to achieve its goal, with each particle functioning as a ball-peen hammer.
Details.
Peening a surface spreads it plastically, causing changes in the mechanical properties of the surface. Its main application is to avoid the propagation of microcracks in a surface. By putting a material under compressive stress, shot peening prevents such cracks from propagating.
Shot peening is often called for in aircraft repairs to relieve tensile stresses built up in the grinding process and replace them with beneficial compressive stresses. Depending on the part geometry, part material, shot material, shot quality, shot intensity, and shot coverage, shot peening can increase fatigue life up to 1000%.
Plastic deformation induces a residual compressive stress in a peened surface, along with tensile stress in the interior. Surface compressive stresses confer resistance to metal fatigue and to some forms of stress corrosion. The tensile stresses deep in the part are not as troublesome as tensile stresses on the surface because cracks are less likely to start in the interior.
"Intensity" is a key parameter of the shot peening process. After some development of the process, an analog was needed to measure the effects of shot peening. John Almen noticed that shot peening made the side of the sheet metal that was exposed begin to bend and stretch. He created the Almen strip to measure the compressive stresses in the strip created by the shot peening operation. One can obtain what is referred to as the "intensity of the blast stream" by measuring the deformation on the Almen strip that is in the shot peening operation. As the strip reaches a 10% deformation, the Almen strip is then hit with the same intensity for twice the amount of time. If the strip deforms another 10%, then one obtains the intensity of the blast stream.
Another operation to gauge the intensity of a shot peening process is the use of an Almen round, developed by R. Bosshard.
"Coverage", the percentage of the surface indented once or more, is subject to variation due to the angle of the shot blast stream relative to the workpiece surface. The stream is cone-shaped, thus, shot arrives at varying angles. Processing the surface with a series of overlapping passes improves coverage, although variation in "stripes" will still be present. Alignment of the axis of the shot stream with the axis of the Almen strip is important. A continuous compressively stressed surface of the workpiece has been shown to be produced at less than 50% coverage but falls as 100% is approached. Optimizing coverage level for the process being performed is important for producing the desired surface effect.
SAE International's includes several standards for shot peening in aerospace and other industries.
Process and equipment.
Popular methods for propelling shot media include air blast systems and centrifugal blast wheels. In the air blast systems, media are introduced by various methods into the path of high pressure air and accelerated through a nozzle directed at the part to be peened. The centrifugal blast wheel consists of a high speed paddle wheel. Shot media are introduced in the center of the spinning wheel and propelled by the centrifugal force by the spinning paddles towards the part by adjusting the media entrance location, effectively timing the release of the media. Other methods include ultrasonic peening, wet peening, and laser peening (which does not use media).
Media choices include spherical cast steel shot, ceramic bead, glass bead or conditioned (rounded) cut wire. Cut wire shot is preferred because it maintains its roundness as it is degraded, unlike cast shot which tends to break up into sharp pieces that can damage the workpiece. Cut wire shot can last five times longer than cast shot. Because peening demands well-graded shot of consistent hardness, diameter, and shape, a mechanism for removing shot fragments throughout the process is desirable. Equipment is available that includes separators to clean and recondition shot and feeders to add new shot automatically to replace the damaged material.
Wheel blast systems include satellite rotation models, rotary throughfeed components, and various manipulator designs. There are overhead monorail systems as well as reverse-belted models. Workpiece holding equipment includes rotating index tables, loading and unloading robots, and jigs that hold multiple workpieces. For larger workpieces, manipulators to reposition them to expose features to the shot blast stream are available.
Cut wire shot.
"Cut wire shot" is a metal shot used for shot peening, where small particles are fired at a workpiece by a compressed air jet. It is a low-cost manufacturing process, as the basic feedstock is inexpensive. As-cut particles are an effective abrasive due to the sharp edges created in the cutting process; however, as-cut shot is not a desirable shot peening medium, as its sharp edges are not suitable to the process.
Cut shot is manufactured from high quality wire in which each particle is cut to a length about equal to its diameter. If required, the particles are conditioned (rounded) to remove the sharp corners produced during the cutting process. Depending on application, various hardness ranges are available, with the higher the hardness of the media the lower its durability.
Other cut-wire shot applications include tumbling and vibratory finishing.
Coverage.
Factors affecting coverage density include: number of impacts (shot flow), exposure time, shot properties (size, chemistry), and work piece properties. Coverage is monitored by visual examination to determine the percent coverage (0-100%). Coverage beyond 100% cannot be determined. The number of individual impacts is linearly proportional to shot flow, exposure area, and exposure time. Coverage is not linearly proportional because of the random nature of the process (chaos theory). When 100% coverage is achieved, locations on the surface have been impacted multiple times. At 150% coverage, 5 or more impacts occur at 52% of locations. At 200% coverage, 5 or more impacts occur at 84% of locations.
Coverage is affected by shot geometry and the shot and workpiece chemistry. The size of the shot controls how many impacts there are per pound, where smaller shot produces more impacts per pound therefore requiring less exposure time. Soft shot impacting hard material will take more exposure time to reach acceptable coverage compared to hard shot impacting a soft material (since the harder shot can penetrate deeper, thus creating a larger impression).
Coverage and intensity (measured by Almen strips) can have a profound effect on fatigue life. This can affect a variety of materials typically shot peened. Incomplete or excessive coverage and intensity can result in reduced fatigue life. Over-peening will cause excessive cold working on the surface of the workpiece, which can also cause fatigue cracks. Diligence is required when developing parameters for coverage and intensity, especially when using materials having different properties (i.e. softer metal to harder metal). Testing fatigue life over a range of parameters would result in a "sweet-spot" where there is near exponential growth to a peak fatigue life (x = peening intensity or media stream energy, y = time-to-crack or fatigue strength) and rapidly decay fatigue life as more intensity or coverage is added. The "sweet-spot" will directly correlate with the kinetic energy transferred and the material properties of the shot media and workpiece.
Applications.
Shot peening is used on gear parts, cams and camshafts, clutch springs, coil springs, connecting rods, crankshafts, gearwheels, leaf and suspension springs, rock drills, and turbine blades. It is also used in foundries for sand removal, decoring, descaling, and surface finishing of castings such as engine blocks and cylinder heads. Its descaling action can be used in the manufacturing of steel products such as strip, plates, sheets, wire, and bar stock.
Shot peening is a crucial process in spring making. Types of springs include leaf springs, extension springs, and compression springs. The most widely used application are for engine valve springs (compression springs) due to high cyclic fatigue. In an OEM valve spring application, the mechanical design combined with some shot peening ensures longevity. Automotive makers are shifting to more high performance higher stressed valve spring designs as engines evolve. In aftermarket high performance valve spring applications, the need for controlled and multi-step shot peening is a requirement to withstand extreme surface stresses that sometimes exceeds material specifications. The fatigue life of an extreme performance spring (NHRA, IHRA) can be as short as two passes on a 1/4 mile drag racing track before relaxation or failure occurs.
Shot peening may be used for cosmetic effect. The surface roughness resulting from the overlapping dimples causes light to scatter upon reflection. Because peening typically produces larger surface features than sand-blasting, the resulting effect is more pronounced.
Shot peening and abrasive blasting can apply materials on metal surfaces. When the shot or grit particles are blasted through a powder or liquid containing the desired surface coating, the impact plates or coats the workpiece surface. The process has been used to embed ceramic coatings, though the coverage is random rather than coherent. 3M developed a process where a metal surface was blasted with particles with a core of alumina and an outer layer of silica. The result was fusion of the silica to the surface. The process known as peen plating was developed by NASA. Fine powders of metals or non-metals are plated onto metal surfaces using glass bead shot as the blast medium. The process has evolved to applying solid lubricants such as molybdenum disulphide to surfaces. Biocompatible ceramics have been applied this way to biomedical implants. Peen plating subjects the coating material to high heat in the collisions with the shot and the coating must also be available in powder form, limiting the range of materials that can be used. To overcome the problem of heat, a process called temperature moderated-collision mediated coating (TM-CMC) has allowed the use of polymers and antibiotic materials as peened coatings. The coating is presented as an aerosol directed to the surface at the same time as a stream of shot particles. The TM-CMC process is still in the R&D phase of development.
Compressive residual stress.
A sub-surface compressive residual stress profile is measured using techniques such as x-ray diffraction and hardness profile testings. The X-axis is depth in mm or inches and the Y-axis is residual stress in ksi or MPa. The maximum residual stress profile can be affected by the factors of shot peening, including: part geometry, part material, shot material, shot quality, shot intensity, and shot coverage. For example, shot peening a hardened steel part with a process and then using the same process for another unhardened part could result in over-peening; causing a sharp decrease in surface residual stresses, but not affecting sub-surface stresses. This is critical because maximum stresses are typically at the surface of the material. Mitigation of these lower surface stresses can be accomplished by a multi-stage post process with varied shot diameters and other surface treatments that remove the low residual stress layer.
The compressive residual stress in a metal alloy is produced by the transfer of kinetic energy (K.E.) from a moving mass (shot particle or ball peen) into the surface of a material with the capacity to plastically deform. The residual stress profile is also dependent on coverage density. The mechanics of the collisions involve properties of the shot hardness, shape, and structure; as well as the properties of the workpiece. Factors for process development and the control for K.E. transfer for shot peening are: shot velocity (wheel speed or air pressure/nozzle design), shot mass, shot chemistry, impact angle and work piece properties. Example: if you needed very high residual stresses you would likely want to use large diameter cut-wire shot, a high-intensity process, direct blast onto the workpiece, and a very hard workpiece material.


Strebor

Strebor Diecasting (the name comes from Roberts spelled backwards) was a die-casting company in Radcliffe, Lancashire which was founded in 1926 as the Roberts Company. In 1933 the name was changed to the Strebor Diecasting company. During WW2 it made war material, after the war it made metal toys, and eventually achieved widespread notice as makers of cylinder locks and locking devices for the motor trade during the 1960s and 1970s under the STREBOR and STRONIS trade names. Their locks were to be found on British cars such as the Mini. The company was finally dissolved in 2003/2004 following a period of rundown and some industrial relations problems.


Dip soldering

Dip soldering is a small-scale soldering process by which electronic components are soldered to a printed circuit board (PCB) to form an electronic assembly. The solder wets to the exposed metallic areas of the board (those not protected with solder mask), creating a reliable mechanical and electrical connection.
Dip soldering is used for both through-hole printed circuit assemblies, and surface mount. It is one of the cheapest methods to solder and is extensively used in the small scale industries of developing countries .
Dip soldering is the manual equivalent of automated wave soldering. The apparatus required is just a small tank containing molten solder. A PCB with mounted components is dipped manually into the tank so that the molten solder sticks to the exposed metallic areas of the board.
Dip solder process.
Dip soldering is accomplished by submerging parts to be joined into a molten solder bath. Thus, all components surfaces are coated with filler metal. Solders have low surface tension and high wetting capability. There are many types of solders, each used for different applications:
Because of the toxicity of lead, lead-free solders are being developed and more widely used. The molten bath can be any suitable filler metal, but the selection is usually confined to the lower melting point elements. The most common dip soldering operations use zinc-aluminum and tin-lead solders.
Process schematic.
The workpieces to be joined are treated with cleaning flux. Then the workpiece is mounted in the workholding device and immersed in the molten solder for 2 to 12 seconds. The workpiece is often agitated to aid the flow of the solder. The workpiece holder must allow an inclination of so that the solder may run off to ensure a smooth finish.
Workpiece geometry.
This process is generally limited to all-metal work pieces, although other materials, such as circuit boards can also tolerate momentary contact with the hot molten solder without damage.
Setup and equipment.
There is not much equipment or setup for this process. All that is needed is the solder pot with its temperature control panel, the bath of molten solder, and the work holding device. Usually the work holding device is custom made for each respective workpiece for either manual or automated dipping.
Solderability.
Some materials are easier to solder than others. Copper, silver, and gold are easy to solder. Iron and nickel are a little more difficult. Titanium, magnesium, cast irons, steels, ceramics, and graphites are hard to solder. However, if they are first plated they are more easily soldered. An example of this is tin-plating, in which a steel is sheet coated with tin so that it can be soldered more easily.
Applications.
Dip soldering is used extensively in the electronics industry. However, they have a limited service use at elevated temperatures because of the low melting point of the filler metals. Soldered materials do not have much strength and are therefore not used for load-bearing.


Carton flow

Carton flow is a form of shelving that uses a gravity feed rear-load design. Each unit consists of one or more inclined runways. Merchandise is loaded in the rear of each runway. As an item is removed from the front, the item directly behind it slides forward in place of the previous.
The main advantage of carton flow rack over static rack or shelving systems is that merchandise remains better organized and easier to find or pick. With carton flow rack, the product is automatically rotated on a first-in, first-out basis. Merchandise is stocked in the rear of the carton flow rack and moves toward the picking station in front on an inclined shelf equipped with specially designed roller track. When a carton is removed from the picking station, the next one in line rolls to the front. Carton flow always keeps items within reach. Inventory is easier to monitor and control since products are fully visible at all times. A limitation worth mentioning is that carton flows are not well suited for larger volume or full case applications.
Restocking and picking typically offer the greatest opportunity for improving efficiency within order-picking operations. With carton flow rack systems, labor savings of up to 75% can be realized almost immediately. Because items are picked from the front and stocked from the rear, both functions can be performed without interference and with minimized travel.
In a static storage system such as standard shelving, stockers and pickers often do a lot of unnecessary travel.
History.
Lansing Peter Shield, President of Grand Union Co., applied for patents for the original gravity-feed rear-load design using Unistrut and Nylon strips in 1945 (later approved in 1948). The unit consisted of several inclined runways. The device was driven by gravity. A stockman would place merchandise in the rear of each runway and, as a shopper selected an item, the item behind it would slide forward in place of the previous one.
Grand Union formed a company called Food-O-Mat to sell the carton flow system, and made Gardner Hinckley the president. Gauer Metal Products, Inc manufactured the carton flow units for Grand Union/Food-O-Mat. When Lansing Shield died of a heart attack, Thomas Butler was appointed the new president. Butler had no interest in continuing to use carton flow units in Grand Union supermarkets, so Food-O-Mat went off on its own to sell the product with Gauer Metal Products as its manufacturer.
Carton flow today.
The carton flow design has gone through countless changes over the years, and has now evolved to full shelving units. These units consist of polyethylene or aluminum roller runways and can be stand-alone racks or can be installed into pallet racks. Conveyor systems are sometimes used as an alternative option to carton flow shelving.


Duplex worm

A duplex worm or dual lead worm is a worm gear set where the two flanks are manufactured with slightly different modules and/or diameter quotients. As a result of this, different lead angles on both tooth profiles are obtained, so that the tooth thickness is continuously increasing all over the worm length, while the gap between two threads is decreasing. This allows control of backlash.
At the worm wheel, the different modules result in different addendum modification coefficients and rolling circle diameters at both flanks. Because of this the profiles are different at the front and at the rear flank. The thickness of each tooth and the tooth gaps remain constant at the circumference of the wheel.
Backlash adjustment is done by shifting the worm axially, so that the section of the worm with the needed tooth thickness will be in contact with the wheel, giving the desired backlash (fig. 1).
This way, backlash can be easily adjusted to any desired value when mounting the gear, and even worn gears can be readjusted at any time delicately and continuously, without modifying the tooth contact or creating meshing interference.
Other possibilities of backlash adjustment.
Besides the above explained duplex method, there are various possibilities to adjust the backlash of worm gears:
However all these methods demonstrate substantial disadvantages:
Duplex gearings do not create these kind of problems.
They permit an always geometrically accurate teeth contact and beyond that, very delicate backlash adjustment. Neither the evolved contact area, the load-carrying capacity nor the actual efficiency are affected. In addition as duplex teeth are executed as involute gear they are insensitive in regards to modifications of the center distance, e.g. caused by worm shaft deflections.
Setting of backlash.
Installing and resetting of a duplex worm wheelset is typically done as follows:
Applications.
Duplex gears are mainly utilized where any backlash is unwanted or can be harmful, to maintain repeated high precision positioning in both directions, to prevent impulse loaded damage, and when the contact flanks are alternating. Common applications include: rotary and tilting tables, milling machines, and presses.


2022–23 Albanian Cup

2022–23 Albanian Cup  was the seventy-first season of Albania's annual cup competition, the Albanian Cup. Egnatia won the cup, their first title in the competition.
Format.
Ties are played in a two-legged format similar to those of European competitions. If the aggregate score is tied after both games, the match is decided by extra time and a penalty shoot-out, if necessary.
Preliminary round.
In order to reduce the number of participating teams for the first round to 32, a preliminary tournament is played. In contrast to the main tournament, the preliminary tournament is held as a single-leg knock-out competition. The matches were played on 15 September 2022.
Veleçiku advanced to the first round.
Devolli advanced to the first round.
First round.
All 26 eligible teams of the 2022–23 Kategoria Superiore and 2022–23 Kategoria e Parë will enter in this round along with 8 teams from Kategoria e Dytë. The matches were played on 25, 26, 28 September 2022 as well as 11 and 12 October 2022.
Tirana advanced to the second round.
Partizani advanced to the second round.
Vllaznia advanced to the second round.
Kastrioti advanced to the second round.
Dinamo Tirana advanced to the second round.
Bylis advanced to the second round.
Korabi advanced to the second round.
Lushnja advanced to the second round.
Laçi advanced to the second round.
Kukësi advanced to the second round.
Teuta advanced to the second round.
Egnatia advanced to the second round.
Skënderbeu advanced to the second round.
Erzeni advanced to the second round.
Apolonia advanced to the second round.
Tomori advanced to the second round.
Second round.
All the 16 qualified teams from the first round progressed to the second round. The first legs were played on 17 and 18 January 2023 while the second legs took place on 2 and 3 February 2023.
Tirana advanced to the quarter finals.
Partizani advanced to the quarter finals.
Vllaznia advanced to the quarter finals.
Kastrioti advanced to the quarter finals.
Laçi advanced to the quarter finals.
Kukësi advanced to the quarter finals.
Teuta advanced to the quarter finals.
Egnatia advanced to the quarter finals.
Quarter-finals.
All eight qualified teams from the second round progressed to the quarter-finals. The first legs were played on 28 February and 1 March 2023 while the second legs took place on 14 and 15 March 2023.
Tirana advanced to the semi finals.
Vllaznia advanced to the semi finals.
Egnatia advanced to the semi finals.
Teuta advanced to the semi finals.
Semi-finals.
The first legs were played on 26 April while the second legs took place on 10 May 2023.
Egnatia advanced to the final.
Tirana advanced to the final.


Vacuum arc remelting

Vacuum arc remelting (VAR) is a secondary melting process for production of metal ingots with elevated chemical and mechanical homogeneity for highly demanding applications. The VAR process has revolutionized the specialty traditional metallurgical techniques industry, and has made possible tightly-controlled materials used in biomedical, aviation and aerospace.
Overview.
VAR is used most frequently in high value applications. It is an additional processing step to improve the quality of metal. Because it is time consuming and expensive, a majority of commercial alloys do not employ the process. Nickel, titanium, and specialty steels are materials most often processed with this method. The conventional path for production of titanium alloys includes single, double or even triple VAR processing. Use of this technique over traditional methods presents several advantages:
Process description.
The alloy to undergo VAR is formed into a cylinder typically by vacuum induction melting (VIM) or ladle refining (airmelt). This cylinder, referred to as an electrode is then put into a large cylindrical enclosed crucible and brought to a metallurgical vacuum . At the bottom of the crucible is a small amount of the alloy to be remelted, which the top electrode is brought close to prior to starting the melt. Several kiloamperes of DC current are used to start an arc between the two pieces, thus a continuous melt is derived. The crucible (typically made of copper) is surrounded by a water jacket to cool the melt and control the solidification rate. To prevent arcing between the electrode and the crucible walls, the diameter of the crucible is larger than the electrode. As a result, the electrode must be lowered as the melt consumes it. Control of the current, cooling water, and electrode gap is essential to effective control of the process and production of defect-free material.
Ideally, the melt rate stays constant throughout the process cycle, but monitoring and control of the vacuum arc remelting process is not simple. This is because there is a complex heat transfer occurring involving conduction, radiation, convection within the liquid metal, and advection caused by the Lorentz force. Ensuring the consistency of the melt process in terms of pool geometry, and melt rate is crucial in ensuring the best possible properties of the alloy.
Materials and applications.
The VAR process is used on many different materials. Certain applications almost always use a material that has been VAR treated. A list of materials that may be VAR treated include:
Note that pure titanium and most titanium alloys are double or triple VAR processed. Nickel-based super alloys for aerospace applications are usually VAR processed. Zirconium and niobium alloys used in the nuclear industry are routinely VAR processed. Pure platinum, tantalum, and rhodium may be VAR processed.


Optical interconnect

In integrated circuits, optical interconnects refers to any system of transmitting signals from one part of an integrated circuit to another using light. Optical interconnects have been the topic of study due to the high latency and power consumption incurred by conventional metal interconnects in transmitting electrical signals over long distances, such as in interconnects classed as "global interconnects". The International Technology Roadmap for Semiconductors (ITRS) has highlighted interconnect scaling as a problem for the semiconductor industry.
In electrical interconnects, nonlinear signals (e.g. digital signals) are transmitted by copper wires conventionally, and these electrical wires all have resistance and capacitance which severely limits the rise time of signals when the dimension of the wires are scaled down. Optical solution are used to transmit signals through long distances to substitute interconnection between dies within the integrated circuit (IC) package.
In order to control the optical signals inside the small IC package properly, microelectromechanical system (MEMS) technology can be used to integrate the optical components (i.e. optical waveguides, optical fibers, lens, mirrors, optical actuators, optical sensors etc.) and the electronic parts together effectively.
Problems of the current interconnect in the package.
Conventional physical metal wires possess both resistance and capacitance, limiting the rise time of signals. Bits of information will overlap with each other when the frequency of signal is increased to a certain level.
Benefits of using optical interconnection.
Optical interconnections can provide benefits over conventional metal wires which include:
Challenges for optical interconnect.
However, there are still many technical challenges in implementing dense optical interconnects to silicon CMOS chips. These challenges are listed as below:


Multi-leaded power package

 The multi-leaded power package is a style of electronic component package, commonly used for high power integrated circuits, especially for monolithic audio amplifiers. It was derived from single in-line package. The difference is the lead arrangement; multi-leaded power packages usually have the lead bent to zig-zag pattern. Multi-leaded power packages commonly have more than three leads; nine-, thirteen- and fifteen-lead units are common, units with five or seven leads with TO-220 style are also manufactured. A notable characteristic is a metal tab with a hole, used in mounting the case to a heatsink. The physical view of multi-leaded power packages are simply stretched TO-220 packages. Components made in multi-leaded power packages can handle more power than those constructed in TO-220 cases, or even TO3 cases with thermal resistance no less than 1.5 C/W.
One well-known STMicroelectronics brand of this type of package is Multiwatt.
Typical applications.
Multi-leaded power packages are heatsinkable, and thus can be used in projects where a large amount of power is being drawn. The top of the package has a metal tab with a hole used in mounting the component to a heatsink. Thermal compound is also used to provide greater heat transfer.
The metal tab is often connected electrically to the internal circuitry, ground and supply connection are common. This does not normally pose a problem when using isolated heatsinks, but an electrically-insulating pad or sheet may be required to electrically isolate the component from the heatsink if the heatsink is grounded or otherwise non-isolated. The material used to electrically isolate the multi-leaded power package, like mica, needs to have a high thermal conductivity.
In applications where vertical clearance is at a premium (such as ISA cards in computers), it is often feasible to bend the leads at a right angle and mount the component flat to the printed wiring board using a screw and nut. This often provides enough surface area to heatsink the component when power dissipation is moderately high.


Metal fabrication

Metal fabrication is the creation of metal structures by cutting, bending and assembling processes. It is a value-added process involving the creation of machines, parts, and structures from various raw materials.
Typically, a fabrication shop bids on a job, usually based on engineering drawings, and if awarded the contract, builds the product. Large fab shops employ a multitude of value-added processes, including welding, cutting, forming and machining.
As with other manufacturing processes, both human labor and automation are commonly used. A fabricated product may be called a "fabrication", and shops specializing in this type of work are called "fab shops". The end products of other common types of metalworking, such as machining, metal stamping, forging, and casting, may be similar in shape and function, but those processes are not classified as fabrication.
Processes.
Fabrication comprises or overlaps with various metalworking specialties:
Raw materials.
Standard metal fabrication materials are:
Cutting and burning.
A variety of tools are used to cut raw material. The most common cutting method is shearing.
Special band saws for cutting metal have hardened blades and feed mechanisms for even cutting. Abrasive cut-off saws, also known as chop saws, are similar to miter saws but have a steel-cutting abrasive disks. Cutting torches can cut large sections of steel with little effort.
Burn tables are CNC (computer-operated) cutting torches, usually powered by natural gas. Plasma and laser cutting tables, and water jet cutters, are also common. Plate steel is loaded on the table and the parts are cut out as programmed. The support table consists of a grid of bars that can be replaced when worn. Higher-end burn tables may include CNC punch capability using a carousel of punches and taps. In fabrication of structural steel by plasma and laser cutting, robots move the cutting head in three dimensions around the cut material.
Forming.
Forming converts flat sheet metal into 3-D parts by applying force without adding or removing material. The force must be great enough to change the metal's initial shape. Forming can be controlled with tools such as punches and dies. Machinery can regulate force magnitude and direction. Machine-based forming can combine forming and welding to produce lengths of fabricated sheeting (e.g. linear grating for water drainage). Most metallic materials, being at least somewhat ductile and capable of considerable permanent deformation without cracking or breaking, lend themselves particularly well to these techniques.
Proper design and use of tools with machinery creates a repeatable form that can be used to create products for many industries, including jewelry, aerospace, automotive, construction, civil and architectural.
Machining.
Machining is a specialized trade of removing material from a block of metal to make it a desired shape. Fab shops generally have some machining capability, using metal lathes, mills, drills, and other portable machining tools. Most solid components, such as gears, bolts, screws and nuts, are machined.
Welding.
Welding is the main focus of steel fabrication. Formed and machined parts are assembled and tack-welded in place, then rechecked for accuracy. If multiple weldments have been ordered, a fixture may be used to locate parts for welding. A welder then finishes the work according to engineering drawings (for detailed welding) or by their own experience and judgement (if no details are provided).
Special measures may be needed to prevent or correct warping of weldments due to heat. These may include redesigning the piece to require less welding, employing staggered welding, using a stout fixture, covering the weldment in sand as it cools, and post-weld straightening.
Straightening of warped steel weldments is done with an oxyacetylene torch. In this highly specialized work, heat is selectively applied to the steel in a slow, linear sweep, causing the steel to contract in the direction of the sweep as it cools. A highly skilled welder can remove significant warpage this way.
Steel weldments are occasionally annealed in a low-temperature oven to relieve residual stresses. Such weldments, particularly those for engine blocks, may be line-bored after heat treatment.
After the weldment has cooled, seams are usually ground clean, and the assembly can be sandblasted, primed and painted. Any additional manufacturing is then performed, and the finished product is inspected and shipped.
Specialties.
Many fabrication shops offer specialty processes, including :


Thermoforming

Thermoforming is a manufacturing process where a plastic sheet is heated to a pliable forming temperature, formed to a specific shape in a mold, and trimmed to create a usable product. The sheet, or "film" when referring to thinner gauges and certain material types, is heated in an oven to a high-enough temperature that permits it to be stretched into or onto a mold and cooled to a finished shape. Its simplified version is vacuum forming.
In its simplest form, a small tabletop or lab size machine can be used to heat small cut sections of plastic sheet and stretch it over a mold using vacuum. This method is often used for sample and prototype parts. In complex and high-volume applications, very large production machines are utilized to heat and form the plastic sheet and trim the formed parts from the sheet in a continuous high-speed process and can produce many thousands of finished parts per hour depending on the machine and mold size and the size of the parts being formed.
Thermoforming differs from injection molding, blow molding, rotational molding and other forms of processing plastics. Thin-gauge thermoforming is primarily the manufacture of disposable cups, containers, lids, trays, blisters, clamshells, and other products for the food, medical, and general retail industries. Thick-gauge thermoforming includes parts as diverse as vehicle door and dash panels, refrigerator liners, utility vehicle beds and plastic pallets.
Most thermoforming companies recycle their scrap and waste plastic, either by compressing in a baling machine or by feeding into a granulator (grinder) and producing ground flake, for sale to reprocessing companies or re-use in their own facility. Frequently, scrap and waste plastic from the thermoforming process is converted back into extruded sheet for forming again.
Procedure.
In the most common method of high-volume, continuous thermoforming of thin-gauge products, plastic sheet is fed from a roll or from an extruder into a set of indexing chains that incorporate pins, or spikes, that pierce the sheet and transport it through an oven for heating to forming temperature. The heated sheet then indexes into a form station where a mating mold and pressure-box close on the sheet, with vacuum then applied to remove trapped air and to pull the material into or onto the mold along with pressurized air to form the plastic to the detailed shape of the mold. (Plug-assists are typically used in addition to vacuum in the case of taller, deeper-draw formed parts in order to provide the needed material distribution and thicknesses in the finished parts.) After a short form cycle, a burst of reverse air pressure is actuated from the vacuum side of the mold as the form tooling opens, commonly referred to as air-eject, to break the vacuum and assist the formed parts off of, or out of, the mold. A stripper plate may also be utilized on the mold as it opens for ejection of more detailed parts or those with negative-draft, undercut areas. The sheet containing the formed parts then indexes into a trim station on the same machine, where a die cuts the parts from the remaining sheet web or indexes into a separate trim press where the formed parts are trimmed. The sheet web remaining after the formed parts are trimmed is typically wound onto a take-up reel or fed into an inline granulator for recycling.
Developments.
Microprocessor and computer controls on more modern machinery allow for greatly increased process control and repeatability of same-job setups from one production run with the ability to save oven heater and process timing settings between jobs. The ability to place formed sheets into an inline trim station for more precise trim registration has been improved due to the common use of electric servo motors for chain indexing versus air cylinders, gear racks, and clutches on older machines. Electric servo motors are also used on some modern and more sophisticated forming machines for actuation of the machine platens where form and trim tooling are mounted, rather than air cylinders which have traditionally been the industry standard, giving more precise control over closing and opening speeds and timing of the tooling. Quartz and radiant-panel oven heaters generally provide more precise and thorough sheet heating over older cal-rod type heaters, and better allow for zoning of ovens into areas of adjustable heat.
A new technology, ToolVu, has been developed to provide real-time feedback on thermoformer machines. This stand-alone system connects directly to the thermoformer and utilizes multiple sensors to record production-run data in real time including air pressure, temperature, tool strain gauge and other specifications. The system sends out multiple warnings and alerts whenever pre-set production parameters are compromised during a run. This reduces machine down time, lowers startup time and decreases startup scrap.
An integral part of the thermoforming process is the tooling, which is specific to each part that is to be produced. Thin-gauge thermoforming as described above is almost always performed on in-line machines and typically requires molds, plug assists, pressure boxes and all mounting plates as well as the trim tooling and stacker parts that pertain to the job. Thick or heavy-gauge thermoforming also requires tooling specific to each part, but because the part size can be very large, the molds can be cast aluminum or some other composite material as well as machined aluminum as in thin gauge. Typically, thick-gauge parts must be trimmed on CNC routers or hand trimmed using saws or hand routers. Even the most sophisticated thermoforming machine is limited to the quality of the tooling. Some large thermoforming manufacturers choose to have design and tool making facilities in house while others will rely on outside tool-making shops to build the tooling.
Thin-gauge and heavy-gauge (thick) thermoforming.
There are two general thermoforming process categories. Sheet thickness less than 1.5 mm (0.060 inches) is usually delivered to the thermoforming machine from rolls or from a sheet extruder. Thin-gauge roll-fed or inline extruded thermoforming applications are dominated by rigid or semi-rigid disposable packaging. Sheet thicknesses greater than 3 mm (0.120 inches) are usually delivered to the forming machine by hand or an auto-feed method already cut to final dimensions. Heavy, or thick-gauge, cut sheet thermoforming applications are primarily used as permanent structural components. There is a small but growing medium-gauge market that forms sheet 1.5 mm to 3 mm in thickness.
Heavy-gauge forming utilizes the same basic process as continuous thin-gauge sheet forming, typically draping the heated plastic sheet over a mold. Many heavy-gauge forming applications use vacuum only in the form process, although some use two halves of mating form tooling and include air pressure to help form. Aircraft windscreens and machine gun turret windows spurred the advance of heavy-gauge forming technology during World War II. Heavy-gauge parts are used as cosmetic surfaces on permanent structures such as kiosks, automobiles, trucks, medical equipment, material handling equipment, refrigerators, spas, and shower enclosures, and electrical and electronic equipment. Unlike most thin-gauge thermoformed parts, heavy-gauge parts are often hand-worked after forming for trimming to final shape or for additional drilling, cutting, or finishing, depending on the product. Heavy-gauge products typically are of a "permanent" end use nature, while thin-gauge parts are more often designed to be disposable or recyclable and are primarily used to package or contain a food item or product. Heavy-gauge thermoforming is typically used for production quantities of 250 to 3000 annually, with lower tooling costs and faster product development than competing plastic technologies like injection molding.
Olimunllum CF/PEEK is obtained by thick gauge thermoforming of thin layers of previously impregnated fibers to form fully consolidated sheets. The main difference from custom-made composite plates lies in the standardized orientation of the reinforcing fibers, the standardized weight content of the polymer and standardized sheet thicknesses. This allows easy design and post-processing using identical or similar tools as commonly used when working with metallic light-weight materials like aluminium, titanium and steel.
Industry.
The more than US$10 billion North American market has traditionally been thin gauge and heavy gauge. In 2003 there were about 150 thin-gauge thermoformers in North America. Sixty percent formed proprietary products. Thirty percent were custom formers and 10 percent were OEMs with in-house forming capability. There were nearly a dozen thin-gauge formers having annual sales of at least $100 million. The largest had annual sales in excess of $1,000 million. There were about 250 heavy-gauge formers in North America. Nearly all were custom formers. Only two or three heavy-gauge formers had annual sales of more than $100 million. The largest had annual sales of about $140 million. Beaverton, Michigan, is known as the Plastic Thermoforming capital of the world fueled by the proximity of Dow Chemical Company of Midland, Michigan.


Vacuum forming

Vacuum forming is a simplified version of thermoforming, where a sheet of plastic (in various forms HIPS (High impact polystyrene) for low impact products, or for Bathroom shower trays ABS, and exterior vehicle parts HDPE, plus various other types of vacuum formable materials) is heated to a forming temperature, stretched onto a single-surface mould, and forced against the mould by a vacuum. This process can be used to form plastic into permanent objects such as turnpike signs and protective covers. Normally draft angles are present in the design of the mould (a recommended minimum of 3°) to ease removal of the formed plastic part from the mould.
Relatively deep parts can be formed if the formable sheet is mechanically or pneumatically stretched prior to bringing it into contact with the mold surface and applying the vacuum.
Suitable materials for use in vacuum forming are conventionally thermoplastics. The most common and easiest to use thermoplastic is "high impact polystyrene sheeting" (HIPS). This is molded around a wood, structural foam or cast or machined aluminium mold, and can form to almost any shape. This high impact material is hygienic and capable of retaining heat and its shape when warm water is applied and is commonly used to package taste and odor sensitive products. Vacuum forming is also appropriate for transparent materials such as acrylic, which are widely used in applications for aerospace such as passenger cabin window canopies for military fixed wing aircraft and compartments for rotary wing aircraft. Vacuum forming is often used in low-level technology classes for an easy way to mold.
Modern vacuum-forming equipment is based on a series of US patents awarded in 1950, 1964, and 1974.
Typical applications.
Original equipment manufacturers (OEMs) utilize heavy gauge vacuum formed components for production quantities in the range of 250–3000 units per year. Vacuum-formed components can be used in place of complex fabricated sheet metal, fiberglass, or plastic injection molding. Typical industry examples besides product packaging include: fascias for outdoor kiosks and automated teller machines, enclosures for medical imaging and diagnostic equipment, engine covers in a truck cab or for construction equipment, and railcar interior trim and seat components. Vacuum formers are also often used by hobbyists, for applications such as masks and remote control cars.
Common problems.
There are some problems encountered in the vacuum forming process. Absorbed moisture can expand, forming bubbles within the plastic's inner layers. This significantly weakens the plastic. However, this can be solved by drying the plastic for an extended period at high but sub-melting temperature. Webs can form around the mold, which is due to overheating the plastic and so must be carefully monitored. Webbing can also occur when a mold is too large or parts of the mold are too close together. Finally, objects that are formed often stick to the mold, which is remedied by using a draft angle of three degrees or more in the mold.
Types of molds.
There are numerous patterns one can make with vacuum forming. The most inventive way to use vacuum forming is to take any small item, replicate it many times and then vacuum form the new pattern to create a more cohesive form. The vacuum forming helps tie the individual pieces together and make one mold out of many pieces that can easily be replicated. From there plaster, concrete, etc. can be cast into the plastic form.
Wood patterns are a common material to vacuum form as it is relatively inexpensive and allows the customer to make changes to the design easily. The number of samples that one is able to get from any pattern depends on the size of the part and the thickness of the material. Once the specifications of the part have been met, the pattern is then used to create a ceramic composite mold, or cast aluminum mold for regular production. Potentially, there are ways to create holes in plaster with a vacuum form if the replicated forms made from the vacuum form are deep enough and gaps are left between them for the plastic to form into. Then, once the plastic is used to cast a plaster mold, the deep plastic areas will leave holes if the mold is not completely filled.
Cast aluminium molds are cast at a foundry and typically have temperature control lines running through them. This helps to set the heat of the plastic being formed as well as speed up the fabrication process. Aluminium molds can be male or female in nature, and can also be used in pressure forming applications. The main drawback with this type of mold is the cost.
Machined aluminium molds are like cast aluminium, but are cut out of a solid block of aluminium using a CNC machine and a CAD program. Typically, machined aluminium is used for shallow draw parts out of thin gauge material. Applications may include packaging and trays. Cost is a significant factor with this type of tooling.
Composite molds are a lower cost alternative to cast or machined aluminium molds. Composite molds are typically made from filled resins that start as a liquid and harden with time. Depending on the application, composite molds can last a very long time and produce high quality parts.
Finishing methods.
Once a vacuum forming has been created out of a sheet of plastic, a finishing operation will be needed in most cases to turn it into a usable product. Common vacuum forming finishing methods include:


Knurling

Knurling is a manufacturing process, typically conducted on a lathe, whereby a pattern of straight, angled or crossed lines is rolled into the material.
Etymology.
The terms "knurl" and "knurled" are from an earlier "knur" ‘knot in wood’ and the diminutive "-le", from Middle English "knaur" or "knarre" ‘knot in wood; twisted rock; crag’. This descends from Old English "cnearra" but the vowel in Middle English may have been influenced by Old Norse "knǫrr" ‘merchant ship’ which was known as "cnearr" in Old English. The modern "gnarl" is a back-formation of "gnarled" which itself is first attested in Shakespeare’s works and is apparently a variant of "knurled".
Uses.
The operation is performed for producing indentations on a part of a workpiece. Knurling allows hands or fingers to get a better grip on the knurled object than would be provided by the originally smooth metal surface. Occasionally, the knurled pattern is a series of straight ridges or a helix of "straight" ridges rather than the more-usual criss-cross pattern.
Knurling may also be used as a repair method: because a rolled-in knurled surface has raised areas surrounding the depressed areas, these raised areas can make up for wear on the part. In the days when labor was cheap and parts expensive, this repair method was feasible on pistons of internal combustion engines, where the skirt of a worn piston was expanded to the nominal size using a knurling process. As auto parts have become less expensive, knurling has become less prevalent than it once was, and is specifically discouraged by performance engine builders.
Knurling can also be used when a component will be assembled into a low precision component, for example a metal pin into a plastic molding. The outer surface of the metal pin is knurled so that the raised detail "bites" into the plastic irrespective of whether the size of the hole in the plastic closely matches the diameter of the pin.
Tool handles, mechanical pencils, the grips of pistols, barbell bars, the clamping surface of a motorcycle handlebar and the control knobs on electronic equipment are frequently knurled. Knurling is also used on the grips of darts and the footpegs of BMX bicycles. Knurling is also found in many surgical instruments, where it is used for instrument identification, and its ease of being brushed clean.
Process.
More common than knurl cutting, "knurl rolling" is usually accomplished using one or more very hard rollers that contain the reverse of the pattern to be imposed. It is possible for a "straight" knurl (not criss-crossed) to be pressed with a single roller, however the material needs to be supported adequately to avoid deformation. A criss-cross pattern can be accomplished using any of:
Use stock with a circumference that's a multiple of the circular pitch, or stock with a diameter of the circular pitch over π. Blank diameter is critical to quality knurling. The wrong blank diameter can cause the knurl(s) to double track, giving a pattern finer than the knurl was designed to produce, one that is generally unsatisfactory. Picking the correct stock diameter is very similar to having two gears of the same diametrical pitch that fit together. Every time you add a tooth, the diameter increases by a discrete amount. There are no in-between diameters that work correctly. The same is true of knurls and the blank to be knurled, though fortunately knurls do tolerate a certain amount of error before problems occur. The integer number of knurls for any given diameter typically varies by three repetitions from the bottom to the top of the pattern. By comparison, for cut knurls, the spacing of the cuts is not preset and can be adjusted to allow an integral number of patterns around the workpiece no matter what the diameter of the workpiece.
Hand knurling tools are available. These resemble pipecutters but contain knurling wheels rather than cutting wheels. Usually, three wheels are carried by the tool: two left-handed wheels and one right-handed wheel or vice versa.
Cut knurling often employs automatic feed. The tooling for cut knurling resembles that for rolled knurling, with the exception that the knurls have sharp edges and are presented to the work at an angle allowing the sharp edges to cut the work. Angled, diamond and straight knurling are all supported by cut knurling. It is impossible to cut knurling "Like extremely coarse pitch threads" both because lathe gear trains will not support such longitudinal speeds and because reasonable cutting speeds would be impossible to achieve.