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Surface-mount technology (SMT) is a method for producing electronic circuits in which the components are mounted or placed directly onto the surface of printed circuit boards (PCBs). An electronic device so made is called a surface-mount device (SMD). In industry, it has largely replaced the through-hole technology construction method of fitting components with wire leads into holes in the circuit board. Both technologies can be used on the same board, with the through-hole technology used for components not suitable for surface mounting such as large transformers and heat-sinked power semiconductors.
Electronics comprises the physics, engineering, technology and applications that deal with the emission, flow and control of electrons in vacuum and matter. The identification of the electron in 1897, along with the invention of the vacuum tube, which could amplify and rectify small electrical signals, inaugurated the field of electronics and the electron age.
A printed circuit board (PCB) mechanically supports and electrically connects electronic components or electrical components using conductive tracks, pads and other features etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate. Components are generally soldered onto the PCB to both electrically connect and mechanically fasten them to it.
Through-hole technology, refers to the mounting scheme used for electronic components that involves the use of leads on the components that are inserted into holes drilled in printed circuit boards (PCB) and soldered to pads on the opposite side either by manual assembly or by the use of automated insertion mount machines.
By employing SMT, the production process speeds up, but the risk of defects also increases due to component miniaturization and to the denser packing of boards. In those conditions, detection of failures has become critical for any SMT manufacturing process.
An SMT component is usually smaller than its through-hole counterpart because it has either smaller leads or no leads at all. It may have short pins or leads of various styles, flat contacts, a matrix of solder balls (BGAs), or terminations on the body of the component.
In electronics, a lead is an electrical connection consisting of a length of wire or a metal pad (SMD) that is designed to connect two locations electrically. Leads are used for many purposes, including: transfer of power; testing of an electrical circuit to see if it is working, using a test light or a multimeter; transmiting information, as when the leads from an electrocardiograph, or ECG are attached to a person's body to transmit information about their heart rhythm; and sometimes to act as a heatsink. The tiny leads coming off through-hole components are also often called pins.
In integrated circuit packaging, a solder ball, also a solder bump is a ball of solder that provides the contact between the chip package and the printed circuit board, as well as between stacked packages in multichip modules. The solder balls can be placed manually or by automated equipment, and are held in place with a tacky flux.
A ball grid array (BGA) is a type of surface-mount packaging used for integrated circuits. BGA packages are used to permanently mount devices such as microprocessors. A BGA can provide more interconnection pins than can be put on a dual in-line or flat package. The whole bottom surface of the device can be used, instead of just the perimeter. The traces connecting the package's leads to the wires or balls which connect the die to package are also on average shorter than with a perimeter-only type, leading to better performance at high speeds.
Surface mounting was originally called "planar mounting".
Surface-mount technology was developed in the 1960s and became widely used in the mid 1980s. By the late 1990s, the great majority of high-tech electronic printed circuit assemblies were dominated by surface mount devices. Much of the pioneering work in this technology was done by IBM. The design approach first demonstrated by IBM in 1960 in a small-scale computer was later applied in the Launch Vehicle Digital Computer used in the Instrument Unit that guided all Saturn IB and Saturn V vehicles.Components were mechanically redesigned to have small metal tabs or end caps that could be directly soldered to the surface of the PCB. Components became much smaller and component placement on both sides of a board became far more common with surface mounting than through-hole mounting, allowing much higher circuit densities and smaller circuit boards and, in turn, machines or subassemblies containing the boards.
International Business Machines Corporation (IBM) is an American multinational information technology company headquartered in Armonk, New York, with operations in over 170 countries. The company began in 1911, founded in Endicott, New York, as the Computing-Tabulating-Recording Company (CTR) and was renamed "International Business Machines" in 1924.
The Saturn Launch Vehicle Digital Computer (LVDC) was a computer that provided the autopilot for the Saturn V rocket from launch to Earth orbit insertion. Designed and manufactured by IBM's Electronics Systems Center in Owego, N.Y., it was one of the major components of the Instrument Unit, fitted to the S-IVB stage of the Saturn V and Saturn IB rockets. The LVDC also supported pre- and post-launch checkout of the Saturn hardware. It was used in conjunction with the Launch Vehicle Data Adaptor (LVDA) which performed signal conditioning to the sensor inputs to the computer from the launch vehicle.
The Saturn IB was an American launch vehicle commissioned by the National Aeronautics and Space Administration (NASA) for the Apollo program. It replaced the S-IV second stage of the Saturn I with the much more powerful S-IVB, able to launch a partially fueled Apollo command and service module (CSM) or a fully fueled lunar module (LM) into low Earth orbit for early flight tests before the larger Saturn V needed for lunar flight was ready.
Often only the solder joints hold the parts to the board; in rare cases parts on the bottom or "second" side of the board may be secured with a dot of adhesive to keep components from dropping off inside reflow ovens if the part has a large size or weight.[ citation needed ] Adhesive is sometimes used to hold SMT components on the bottom side of a board if a wave soldering process is used to solder both SMT and through-hole components simultaneously. Alternatively, SMT and through-hole components can be soldered on the same side of a board without adhesive if the SMT parts are first reflow-soldered, then a selective solder mask is used to prevent the solder holding those parts in place from reflowing and the parts floating away during wave soldering. Surface mounting lends itself well to a high degree of automation, reducing labor cost and greatly increasing production rates.
A reflow oven is a machine used primarily for reflow soldering of surface mount electronic components to printed circuit boards (PCB).
Wave soldering is a bulk soldering process used in the manufacture of printed circuit boards. The circuit board is passed over a pan of molten solder in which a pump produces an upwelling of solder that looks like a standing wave. As the circuit board makes contact with this wave, the components become soldered to the board. Wave soldering is used for both through-hole printed circuit assemblies, and surface mount. In the latter case, the components are glued onto the surface of a printed circuit board (PCB) by placement equipment, before being run through the molten solder wave. Wave soldering is mainly used in soldering of through hole components.
Conversely, SMT does not lend itself well to manual or low-automation fabrication, which is more economical and faster for one-off prototyping and small-scale production, and this is one reason why many through-hole components are still manufactured. Some SMDs can be soldered with a temperature-controlled manual soldering iron, but unfortunately, those that are very small or have too fine a lead pitch are impossible to manually solder without expensive hot-air solder reflow equipment[ dubious ]. SMDs can be one-quarter to one-tenth the size and weight, and one-half to one-quarter the cost of equivalent through-hole parts, but on the other hand, the costs of a certain SMT part and of an equivalent through-hole part may be quite similar, though rarely is the SMT part more expensive.
Different terms describe the components, technique, and machines used in manufacturing. These terms are listed in the following table:
|SMp term||Expanded form|
|SMD||Surface-mount devices (active, passive and electromechanical components)|
|SMT||Surface-mount technology (assembling and mounting technology)|
|SMA||Surface-mount assembly (module assembled with SMT)|
|SMC||Surface-mount components (components for SMT)|
|SMP||Surface-mount packages (SMD case forms)|
|SME||Surface-mount equipment (SMT assembling machines)|
Where components are to be placed, the printed circuit board normally has flat, usually tin-lead, silver, or gold plated copper pads without holes, called solder pads. Solder paste, a sticky mixture of flux and tiny solder particles, is first applied to all the solder pads with a stainless steel or nickel stencil using a screen printing process. It can also be applied by a jet-printing mechanism, similar to an inkjet printer. After pasting, the boards then proceed to the pick-and-place machines, where they are placed on a conveyor belt. The components to be placed on the boards are usually delivered to the production line in either paper/plastic tapes wound on reels or plastic tubes. Some large integrated circuits are delivered in static-free trays. Numerical control pick-and-place machines remove the parts from the tapes, tubes or trays and place them on the PCB.
The boards are then conveyed into the reflow soldering oven. They first enter a pre-heat zone, where the temperature of the board and all the components is gradually, uniformly raised. The boards then enter a zone where the temperature is high enough to melt the solder particles in the solder paste, bonding the component leads to the pads on the circuit board. The surface tension of the molten solder helps keep the components in place, and if the solder pad geometries are correctly designed, surface tension automatically aligns the components on their pads.
There are a number of techniques for reflowing solder. One is to use infrared lamps; this is called infrared reflow. Another is to use a hot gas convection. Another technology which is becoming popular again is special fluorocarbon liquids with high boiling points which use a method called vapor phase reflow. Due to environmental concerns, this method was falling out of favor until lead-free legislation was introduced which requires tighter controls on soldering. At the end of 2008, convection soldering was the most popular reflow technology using either standard air or nitrogen gas. Each method has its advantages and disadvantages. With infrared reflow, the board designer must lay the board out so that short components don't fall into the shadows of tall components. Component location is less restricted if the designer knows that vapor phase reflow or convection soldering will be used in production. Following reflow soldering, certain irregular or heat-sensitive components may be installed and soldered by hand, or in large-scale automation, by focused infrared beam (FIB) or localized convection equipment.
If the circuit board is double-sided then this printing, placement, reflow process may be repeated using either solder paste or glue to hold the components in place. If a wave soldering process is used, then the parts must be glued to the board prior to processing to prevent them from floating off when the solder paste holding them in place is melted.
After soldering, the boards may be washed to remove flux residues and any stray solder balls that could short out closely spaced component leads. Rosin flux is removed with fluorocarbon solvents, high flash point hydrocarbon solvents, or low flash solvents e.g. limonene (derived from orange peels) which require extra rinsing or drying cycles. Water-soluble fluxes are removed with deionized water and detergent, followed by an air blast to quickly remove residual water. However, most electronic assemblies are made using a "No-Clean" process where the flux residues are designed to be left on the circuit board, since they are considered harmless. This saves the cost of cleaning, speeds up the manufacturing process, and reduces waste. However, it is generally suggested to wash the assembly, even when a "No-Clean" process is used, when the application uses very high frequency clock signals (in excess of 1 GHz). Another reason to remove no-clean residues is to improve adhesion of conformal coatings and underfill materials. Regardless of cleaning or not those PCBs, current industry trend suggests to carefully review a PCB assembly process where "No-Clean" is applied, since flux residues trapped under components and RF shields may affect surface insulation resistance (SIR), especially on high component density boards.
Certain manufacturing standards, such as those written by the IPC - Association Connecting Electronics Industries require cleaning regardless of the solder flux type used to ensure a thoroughly clean board. Proper cleaning removes all traces of solder flux, as well as dirt and other contaminants that may be invisible to the naked eye. No-Clean or other soldering processes may leave "white residues" that, according to IPC, are acceptable "provided that these residues have been qualified and documented as benign".However, while shops conforming to IPC standard are expected to adhere to the Association's rules on board condition, not all manufacturing facilities apply IPC standard, nor are they required to do so. Additionally, in some applications, such as low-end electronics, such stringent manufacturing methods are excessive both in expense and time required.
Finally, the boards are visually inspected for missing or misaligned components and solder bridging. If needed, they are sent to a rework station where a human operator repairs any errors. They are then usually sent to the testing stations (in-circuit testing and/or functional testing) to verify that they operate correctly. Automated Optical Inspection (AOI) systems are commonly used in PCB manufacturing. This technology has proven highly efficient for process improvements and quality achievements.
The main advantages of SMT over the older through-hole technique are:
Defective surface-mount components can be repaired by using soldering irons (for some connections), or using a non-contact rework system. In most cases a rework system is the better choice because SMD work with a soldering iron requires considerable skill and is not always feasible.
Reworking usually corrects some type of error, either human- or machine-generated, and includes the following steps:
Sometimes hundreds or thousands of the same part need to be repaired. Such errors, if due to assembly, are often caught during the process. However, a whole new level of rework arises when component failure is discovered too late, and perhaps unnoticed until the end user of the device being manufactured experiences it. Rework can also be used if products of sufficient value to justify it require revision or re-engineering, perhaps to change a single firmware-based component. Reworking in large volume requires an operation designed for that purpose.
There are essentially two non-contact soldering/desoldering methods: infrared soldering and soldering with hot gas.
With infrared soldering, the energy for heating up the solder joint is transmitted by long- or short-wave infrared electromagnetic radiation.
During hot gas soldering, the energy for heating up the solder joint is transmitted by a hot gas. This can be air or inert gas (nitrogen).
Surface-mount components are usually smaller than their counterparts with leads, and are designed to be handled by machines rather than by humans. The electronics industry has standardized package shapes and sizes (the leading standardisation body is JEDEC). These include:
The codes given in the chart below usually tell the length and width of the components in tenths of millimeters or hundredths of inches. For example, a metric 2520 component is 2.5 mm by 2.0 mm which corresponds roughly to 0.10 inches by 0.08 inches (hence, imperial size is 1008). Exceptions occur for imperial in the two smallest rectangular passive sizes. The metric codes still represent the dimensions in mm, even though the imperial size codes are no longer aligned. Problematically, some manufacturers are developing metric 0201 components with dimensions of 0.25 mm × 0.125 mm (0.0098 in × 0.0049 in), but the imperial 01005 name is already being used for the 0.4 mm × 0.2 mm (0.0157 in × 0.0079 in) package. These increasingly small sizes, especially 0201 and 01005, can sometimes be a challenge from a manufacturability or reliability perspective.
Mostly resistors and capacitors.
|Package||Approximate dimensions, length × width||Typical resistor |
power rating (W)
|0201||008004||0.25 mm × 0.125 mm||0.010 in × 0.005 in|
|03015||009005||0.3 mm × 0.15 mm||0.012 in × 0.006 in||0.02|
|0402||01005||0.4 mm × 0.2 mm||0.016 in × 0.008 in||0.031|
|0603||0201||0.6 mm × 0.3 mm||0.02 in × 0.01 in||0.05|
|1005||0402||1.0 mm × 0.5 mm||0.04 in × 0.02 in||0.062 –0.1|
|1608||0603||1.6 mm × 0.8 mm||0.06 in × 0.03 in||0.1|
|2012||0805||2.0 mm × 1.25 mm||0.08 in × 0.05 in||0.125|
|2520||1008||2.5 mm × 2.0 mm||0.10 in × 0.08 in|
|3216||1206||3.2 mm × 1.6 mm||0.125 in × 0.06 in||0.25|
|3225||1210||3.2 mm × 2.5 mm||0.125 in × 0.10 in||0.5|
|4516||1806||4.5 mm × 1.6 mm||0.18 in × 0.06 in|
|4532||1812||4.5 mm × 3.2 mm||0.18 in × 0.125 in||0.75|
|4564||1825||4.5 mm × 6.4 mm||0.18 in × 0.25 in||0.75|
|5025||2010||5.0 mm × 2.5 mm||0.20 in × 0.10 in||0.75|
|6332||2512||6.3 mm × 3.2 mm||0.25 in × 0.125 in||1|
|7451||2920||7.4 mm × 5.1 mm||0.29 in × 0.20 in|
|Package||Length, typ. × width, typ. × height, max.|
|EIA 2012-12 (KEMET R, AVX R)||2.0 mm × 1.3 mm × 1.2 mm|
|EIA 3216-10 (KEMET I, AVX K)||3.2 mm × 1.6 mm × 1.0 mm|
|EIA 3216-12 (KEMET S, AVX S)||3.2 mm × 1.6 mm × 1.2 mm|
|EIA 3216-18 (KEMET A, AVX A)||3.2 mm × 1.6 mm × 1.8 mm|
|EIA 3528-12 (KEMET T, AVX T)||3.5 mm × 2.8 mm × 1.2 mm|
|EIA 3528-21 (KEMET B, AVX B)||3.5 mm × 2.8 mm × 2.1 mm|
|EIA 6032-15 (KEMET U, AVX W)||6.0 mm × 3.2 mm × 1.5 mm|
|EIA 6032-28 (KEMET C, AVX C)||6.0 mm × 3.2 mm × 2.8 mm|
|EIA 7260-38 (KEMET E, AVX V)||7.2 mm × 6.0 mm × 3.8 mm|
|EIA 7343-20 (KEMET V, AVX Y)||7.3 mm × 4.3 mm × 2.0 mm|
|EIA 7343-31 (KEMET D, AVX D)||7.3 mm × 4.3 mm × 3.1 mm|
|EIA 7343-43 (KEMET X, AVX E)||7.3 mm × 4.3 mm × 4.3 mm|
|Panasonic / CDE A, Chemi-Con B||3.3 mm × 3.3 mm|
|Panasonic B, Chemi-Con D||4.3 mm × 4.3 mm|
|Panasonic C, Chemi-Con E||5.3 mm × 5.3 mm|
|Panasonic D, Chemi-Con F||6.6 mm × 6.6 mm|
|Panasonic E/F, Chemi-Con H||8.3 mm × 8.3 mm|
|Panasonic G, Chemi-Con J||10.3 mm × 10.3 mm|
|Chemi-Con K||13.0 mm × 13.0 mm|
|Panasonic H||13.5 mm × 13.5 mm|
|Panasonic J, Chemi-Con L||17.0 mm × 17.0 mm|
|Panasonic K, Chemi-Con M||19.0 mm × 19.0 mm|
|SOD-923||0.8 × 0.6 × 0.4 mm|
|SOD-723||1.4 × 0.6 × 0.59 mm|
|SOD-523 (SC-79)||1.25 × 0.85 × 0.65 mm|
|SOD-323 (SC-90)||1.7 × 1.25 × 0.95 mm|
|SOD-128||5 × 2.7 × 1.1 mm|
|SOD-123||3.68 × 1.17 × 1.60 mm|
|SOD-80C||3.50 × ⌀ 1.50 mm|
Mostly resistors and diodes; barrel shaped components, dimensions do not match those of rectangular references for identical codes.
|Package||Dimensions, length × diameter||Typical resistor rating|
|Power (W)||Voltage (V)|
|MicroMelf (MMU), 0102||2.2 mm × 1.1 mm||0.2–0.3||150|
|MiniMelf (MMA), 0204||3.6 mm × 1.4 mm||0.25–0.4||200|
|Melf (MMB), 0207||5.8 mm × 2.2 mm||0.4–1.0||300|
Commonly used for rectifier, Schottky, and other diodes
|Package||Dimensions (incl. leads)|
|DO-214AA (SMB)||5.30 × 3.60 × 2.25 mm|
|DO-214AB (SMC)||7.95 × 5.90 × 2.25 mm|
|DO-214AC (SMA)||5.20 × 2.60 × 2.15 mm|
Although surface-mount, these devices require specific process for assembly.
There are often subtle variations in package details from manufacturer to manufacturer, and even though standard designations are used, designers need to confirm dimensions when laying out printed circuit boards.
For 5% precision SMD resistors usually are marked with their resistance values using three digits: two significant digits and a multiplier digit. These are quite often white lettering on a black background, but other colored backgrounds and lettering can be used.
The black or colored coating is usually only on one face of the device, the sides and other face simply being the uncoated, usually white ceramic substrate. The coated surface, with the resistive element beneath is normally positioned face up when the device is soldered to the board, although they can be seen in rare cases mounted with the uncoated underside face up, whereby the resistance value code is not visible.
For 1% precision SMD resistors, the code is used, as three digits would otherwise not convey enough information. This code consists of two digits and a letter: the digits denote the value's position in the E96 sequence, while the letter indicates the multiplier.
Typical examples of resistance codes
There is an online tool to translate codes to resistance values. Resistors are made in several types; a common types uses a ceramic substrate. Resistance values are available in several tolerances defined in EIA Decade Values Table :
Non-electrolytic capacitors are usually unmarked and the only reliable method of determining their value is removal from the circuit and subsequent measurement with a capacitance meter or impedance bridge. The materials used to fabricate the capacitors, such as nickel tantalate, possess different colours and these can give an approximate idea of the capacitance of the component. [ citation needed ]
Generally physical size is proportional to capacitance and (squared) voltage for the same dielectric. For example, a 100 nF 50 V capacitor may come in the same package as a 10 nF 150 V device.
SMD (non-electrolytic) capacitors, which are usually monolithic ceramic capacitors, exhibit the same body color on all four faces not covered by the end caps.
SMD electrolytic capacitors, usually tantalum capacitors, and film capacitors are marked like resistors, with two significant figures and a multiplier in units of picofarads or pF, (10−12 farad.)
The electrolytic capacitors are usually encapsulated in black or beige epoxy resin with flat metal connecting strips bent underneath. Some film or tantalum electrolytic types are unmarked and possess red, orange or blue body colors with complete end caps, not metal strips.
Smaller inductance with moderately high current ratings are usually of the ferrite bead type. They are simply a metal conductor looped through a ferrite bead and almost the same as their through-hole versions but possess SMD end caps rather than leads. They appear dark grey and are magnetic, unlike capacitors with a similar dark grey appearance. These ferrite bead type are limited to small values in the nH (nano Henry) range and are often used as power supply rail decouplers or in high frequency parts of a circuit. Larger inductors and transformers may of course be through-hole mounted on the same board.
SMT inductors with larger inductance values often have turns of wire or flat strap around the body or embedded in clear epoxy, allowing the wire or strap to be seen. Sometimes a ferrite core is present also. These higher inductance types are often limited to small current ratings, although some of the flat strap types can handle a few amps.
As with capacitors, component values and identifiers for smaller inductors are not usually marked on the component itself; if not documented or printed on the PCB, measurement, usually removed from the circuit, is the only way of determining them. Larger inductors, especially wire-wound types in larger footprints, usually have the value printed on the top. For example, "330", which equates to a value of 33uH (micro Henry).
Discrete semiconductors, such as diodes and transistors are often marked with a two- or three-symbol code. The same code marked on different packages or on devices from different manufacturers can translate to different devices.
Many of these codes, used because the devices are too small to be marked with more traditional numbers used on larger packages, correlate to more familiar traditional part numbers when a correlation list is consulted.
GM4PMK in the United Kingdom has prepared a correlation list, and a similar .pdf list is also available, although these lists are not complete.
Generally, integrated circuit packages are large enough to be imprinted with the complete part number which includes the manufacturer's specific prefix, or a significant segment of the part number and the manufacturer's name or logo.
Examples of manufacturers' specific prefixes:
In microelectronics, a dual in-line package, or dual in-line pin package (DIPP) is an electronic component package with a rectangular housing and two parallel rows of electrical connecting pins. The package may be through-hole mounted to a printed circuit board (PCB) or inserted in a socket. The dual-inline format was invented by Don Forbes, Rex Rice and Bryant Rogers at Fairchild R&D in 1964, when the restricted number of leads available on circular transistor-style packages became a limitation in the use of integrated circuits. Increasingly complex circuits required more signal and power supply leads ; eventually microprocessors and similar complex devices required more leads than could be put on a DIP package, leading to development of higher-density packages. Furthermore, square and rectangular packages made it easier to route printed-circuit traces beneath the packages.
The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element. Derivatives provide two (556) or four (558) timing circuits in one package.
A QFP or Quad Flat Package is a surface-mounted integrated circuit package with "gull wing" leads extending from each of the four sides. Socketing such packages is rare and through-hole mounting is not possible. Versions ranging from 32 to 304 pins with a pitch ranging from 0.4 to 1.0 mm are common. Other special variants include low-profile QFP (LQFP) and thin QFP (TQFP).
Reflow soldering is a process in which a solder paste is used to temporarily attach one or thousands of tiny electrical components to their contact pads, after which the entire assembly is subjected to controlled heat. The solder paste reflows in a molten state, creating permanent solder joints. Heating may be accomplished by passing the assembly through a reflow oven or under an infrared lamp or by soldering individual joints [unconventionally] with a desoldering hot air pencil.
Moisture sensitivity level relates to the packaging and handling precautions for some semiconductors. The MSL is an electronic standard for the time period in which a moisture sensitive device can be exposed to ambient room conditions.
Laser trimming is the manufacturing process of using a laser to adjust the operating parameters of an electronic circuit.
The TO-220 is a style of electronic package used for high-powered, through-hole components. The "TO" designation stands for "transistor outline". TO-220 packages have three leads. Similar packages with two, four, five or seven leads are also manufactured. A notable characteristic is a metal tab with a hole, used in mounting the case to a heatsink, allowing the component to dissipate more heat than one constructed in a TO-92 case. Common TO-220-packaged components include discrete semiconductors such as transistors and silicon-controlled rectifiers, as well as integrated circuits.
Selective soldering is the process of selectively soldering components to printed circuit boards and molded modules that could be damaged by the heat of a reflow oven or wave soldering in a traditional surface-mount technology (SMT) or Through-hole technology assembly processes.This usually follows an SMT oven reflow process; parts to be selectively soldered are usually surrounded by parts that have been previously soldered in a surface-mount reflow process, and the selective-solder process must be sufficiently precise to avoid damaging them.
Flat no-leads packages such as quad-flat no-leads (QFN) and dual-flat no-leads (DFN) physically and electrically connect integrated circuits to printed circuit boards. Flat no-leads, also known as micro leadframe (MLF) and SON, is a surface-mount technology, one of several package technologies that connect ICs to the surfaces of PCBs without through-holes. Flat no-lead is a near chip scale plastic encapsulated package made with a planar copper lead frame substrate. Perimeter lands on the package bottom provide electrical connections to the PCB. Flat no-lead packages include an exposed thermal pad to improve heat transfer out of the IC. Heat transfer can be further facilitated by metal vias in the thermal pad. The QFN package is similar to the quad-flat package (QFP), and a ball grid array (BGA).
Automated optical inspection (AOI) is an automated visual inspection of printed circuit board (PCB) manufacture where a camera autonomously scans the device under test for both catastrophic failure and quality defects. It is commonly used in the manufacturing process because it is a non-contact test method. It is implemented at many stages through the manufacturing process including bare board inspection, solder paste inspection (SPI), pre-reflow and post-reflow as well as other stages.
The 2N7000 and BS170 are two different N-channel, enhancement-mode MOSFETs used for low-power switching applications, with different lead arrangements and current ratings. They are sometimes listed together on the same datasheet with other variants 2N7002, VQ1000J, and VQ1000P.
Metal electrode leadless face (MELF) is a type of leadless cylindrical electronic surface mount device that is metallized at its ends. MELF devices are usually diodes and resistors.
A semiconductor package is a metal, plastic, glass, or ceramic casing containing one or more discrete semiconductor devices or integrated circuits. Individual components are fabricated on semiconductor wafers before being diced into die, tested, and packaged. The package provides a means for connecting the package to the external environment, such as printed circuit board, via leads such as lands, balls, or pins; and protection against threats such as mechanical impact, chemical contamination, and light exposure. Additionally, it helps dissipate heat produced by the device, with or without the aid of a heat spreader. There are thousands of package types in use. Some are defined by international, national, or industry standards, while others are particular to an individual manufacturer.
In electronics, a chip carrier is one of several kinds of surface-mount technology packages for integrated circuits. Connections are made on all four edges of a square package; Compared to the internal cavity for mounting the integrated circuit, the package overall size is large.
A small outline transistor (SOT) is a family of small footprint, discrete surface mount transistor commonly used in consumer electronics. The most common SOT are SOT23 variations, also manufacturers offer the nearly identical thin small outline transistor (TSOT) package, where lower height is important.
Film capacitors, plastic film capacitors, film dielectric capacitors, or polymer film capacitors, generically called “film caps” as well as power film capacitors, are electrical capacitors with an insulating plastic film as the dielectric, sometimes combined with paper as carrier of the electrodes.
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