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Grown-junction Transistor
The grown-junction transistor was the first type of bipolar ''junction'' transistor made. It was invented by William Shockley at Bell Labs on June 23, 1948 (patent filed June 26, 1948), six months after the first bipolar point-contact transistor. The first germanium prototypes were made in 1949. Bell Labs announced Shockley’s grown-junction transistor on July 4, 1951. An NPN grown-junction transistor is made of a single crystal of semiconductor material which has two PN junctions grown into it. During the growth process, a seed crystal is slowly pulled from a bath of molten semiconductor, which then grows into a rod-shaped crystal ( boule). The molten semiconductor is doped N-type at the start. At a predetermined moment in the growth process a small pellet of a P-type dopant is added, almost immediately followed by a somewhat larger pellet of an N-type dopant. These dopants dissolve in the molten semiconductor changing the type of semiconductor subsequently grown. The resul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boule (crystal)
A boule is a single crystal, single-crystal ingot produced by synthetic means. A boule of silicon is the starting material for most of the integrated circuits used today. In the semiconductor industry synthetic boules can be made by a number of methods, such as the Bridgman technique and the Czochralski process, which result in a cylindrical rod of material. In the Czochralski process a seed crystal is required to create a larger crystal, or ingot. This seed crystal is dipped into the pure molten silicon and slowly extracted. The molten silicon grows on the seed crystal in a crystalline fashion. As the seed is extracted the silicon solidifies and eventually a large, cylindrical boule is produced. A semiconductor crystal boule is normally cut into circular wafer (electronics), wafers using an inside hole diamond saw or diamond wire saw, and each wafer is lapped and polished to provide substrates suitable for the fabrication of semiconductor devices on its surface. The process ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrode Transistor
A tetrode transistor is any transistor having four active terminals. Early tetrode transistors There were two types of tetrode transistor developed in the early 1950s as an improvement over the point-contact transistor and the later grown-junction transistor and alloy-junction transistor. Both offered much higher speed than earlier transistors. *Point-contact transistor having two emitters. It became obsolete in the middle 1950s. *Modified grown-junction transistor or alloy-junction transistor having two connections at opposite ends of the base. It achieved its high speed by reducing the input to output capacitance. It became obsolete in the early 1960s with the development of the diffusion transistor. Modern tetrode transistors *Dual-emitter transistor, used in two-input transistor–transistor logic gates *Dual-collector transistor, used in two-output integrated injection logic gates * Diffused planar silicon bipolar junction transistor, - ''Tetrode transistor memory logic cell' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hermetic Seal
A hermetic seal is any type of sealing that makes a given object airtight (preventing the passage of air, oxygen, or other gases). The term originally applied to airtight glass containers but, as technology advanced, it applied to a larger category of materials, including metals, rubber, and plastics. Hermetic seals are essential to the correct and safe functionality of many electronic and healthcare products. Used technically, it is stated in conjunction with a specific test method and conditions of use. Colloquially, the exact requirements of such a seal varies with the application. Etymology The word ''hermetic'' comes from the Greek god Hermes. A hermetic seal comes from alchemy in the tradition of Hermeticism. The legendary Hermes Trismegistus supposedly invented the process of making a glass tube airtight using a secret seal. Uses Some kinds of packaging must maintain a seal against the flow of gases, for example, packaging for some foods, pharmaceuticals, chemicals, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gold
Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal, a group 11 element, and one of the noble metals. It is one of the least reactivity (chemistry), reactive chemical elements, being the second-lowest in the reactivity series. It is solid under standard temperature and pressure, standard conditions. Gold often occurs in free elemental (native state (metallurgy), native state), as gold nugget, nuggets or grains, in rock (geology), rocks, vein (geology), veins, and alluvial deposits. It occurs in a solid solution series with the native element silver (as in electrum), naturally alloyed with other metals like copper and palladium, and mineral inclusions such as within pyrite. Less commonly, it occurs in minerals as gold compounds, often with tellurium (gold tellurides). Gold is resistant to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Welding
Welding is a fabrication (metal), fabrication process that joins materials, usually metals or thermoplastics, primarily by using high temperature to melting, melt the parts together and allow them to cool, causing Fusion welding, fusion. Common alternative methods include solvent welding (of thermoplastics) using chemicals to melt materials being bonded without heat, and #Solid-state welding, solid-state welding processes which bond without melting, such as pressure, cold welding, and diffusion bonding. Metal welding is distinct from lower temperature bonding techniques such as brazing and soldering, which do not melt the base metal (parent metal) and instead require flowing a filler metal to solidify their bonds. In addition to melting the base metal in welding, a filler material is typically added to the joint to form a pool of molten material (the weld pool) that cools to form a joint that can be stronger than the base material. Welding also requires a form of shield to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Solder
Solder (; North American English, NA: ) is a fusible alloy, fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces after cooling. Metals or alloys suitable for use as solder should have a lower melting point than the pieces to be joined. The solder should also be resistant to oxidative and corrosive effects that would degrade the joint over time. Solder used in making electrical connections also needs to have favorable electrical characteristics. Soft solder typically has a melting point range of , and is commonly used in electronics, plumbing, and sheet metal work. Alloys that melt between are the most commonly used. Soldering performed using alloys with a melting point above is called "hard soldering", "silver soldering", or brazing. In specific proportions, some alloys are eutectic — that is, the alloy's melting point is the lowest possible for a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dopant
A dopant (also called a doping agent) is a small amount of a substance added to a material to alter its physical properties, such as electrical or optics, optical properties. The amount of dopant is typically very low compared to the material being doped. When doped into crystalline substances, the dopant's atoms get incorporated into the crystal lattice of the substance. The crystalline materials are frequently either crystals of a semiconductor such as silicon and germanium for use in solid-state electronics, or transparency and translucency, transparent crystals for use in the production of various laser types; however, in some cases of the latter, noncrystalline substances such as glass can also be doped with impurities. In solid-state electronics using the proper types and amounts of dopants in semiconductors is what produces the p-type semiconductors and n-type semiconductors that are essential for making transistors and diodes. Transparent crystals Lasing media The p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Doping (semiconductor)
In semiconductor production, doping is the intentional introduction of impurities into an intrinsic (undoped) semiconductor for the purpose of modulating its electrical, optical and structural properties. The doped material is referred to as an extrinsic semiconductor. Small numbers of dopant atoms can change the ability of a semiconductor to conduct electricity. When on the order of one dopant atom is added per 100 million intrinsic atoms, the doping is said to be ''low'' or ''light''. When many more dopant atoms are added, on the order of one per ten thousand atoms, the doping is referred to as ''high'' or ''heavy''. This is often shown as ''n+'' for n-type doping or ''p+'' for p-type doping. (''See the article on semiconductors for a more detailed description of the doping mechanism.'') A semiconductor doped to such high levels that it acts more like a conductor than a semiconductor is referred to as a degenerate semiconductor. A semiconductor can be considered i-typ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seed Crystal
A seed crystal is a small piece of single crystal or polycrystal material from which a large crystal of typically the same material is grown in a laboratory. Used to replicate material, the use of seed crystal to promote growth avoids the otherwise slow randomness of natural crystal growth, and allows manufacture on a scale suitable for industry. Crystal enlargement The large crystal can be grown by dipping the seed into a supersaturated solution, into molten material that is then cooled, or by growth on the seed face by passing vapor of the material to be grown over it. Theory The theory behind this effect is thought to derive from the physical intermolecular interaction that occurs between compounds in a supersaturated solution (or possibly vapor). In solution, liberated (soluble) molecules (solute) are free to move about in random flow. This random flow permits for the possibility of two or more molecular compounds to interact. This interaction can potentiate intermolecular ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bipolar Junction Transistor
A bipolar junction transistor (BJT) is a type of transistor that uses both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor (FET), uses only one kind of charge carrier. A bipolar transistor allows a small current injected at one of its terminals to control a much larger current between the remaining two terminals, making the device capable of amplification or switching. BJTs use two p–n junctions between two semiconductor types, n-type and p-type, which are regions in a single crystal of material. The junctions can be made in several different ways, such as changing the doping of the semiconductor material as it is grown, by depositing metal pellets to form alloy junctions, or by such methods as diffusion of n-type and p-type doping substances into the crystal. The superior predictability and performance of junction transistors quickly displaced the original point-contact transistor. Diffused trans ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
