Printed_circuit_board

context: When the board has no embedded components it is more correctly called a printed wiring board (PWB) or etched wiring board. However, the term printed wiring board has fallen into disuse. A PCB populated with electronic components is called a printed circuit assembly (PCA), printed circuit board assembly or PCB assembly (PCBA). The IPC preferred term for assembled boards is circuit card assembly (CCA), and for assembled backplanes it is backplane assemblies. The term PCB is used informally both for bare and assembled boards.
qas: answers: text: PWB
question: What's the abbreviation for a printed wiring board?

answers: text: IPC
question: What organization likes the term "circuit card assembly" for boards that have already been assembled?

answers: text: printed circuit assembly
question: What would we call a printed circuit board with embedded electronics, abbreviated PCA?

answers: text: printed wiring board
question: What's the more appropriate, but mostly unused, name for a printed circuit board when it doesn't have embedded components?

answers: text: CCA
question: What abbreviation would the IPC use for an assembled circuit board?

context: Initially PCBs were designed manually by creating a photomask on a clear mylar sheet, usually at two or four times the true size. Starting from the schematic diagram the component pin pads were laid out on the mylar and then traces were routed to connect the pads. Rub-on dry transfers of common component footprints increased efficiency. Traces were made with self-adhesive tape. Pre-printed non-reproducing grids on the mylar assisted in layout. To fabricate the board, the finished photomask was photolithographically reproduced onto a photoresist coating on the blank copper-clad boards.
qas: answers: text: traces
question: In the old PCB design method, what was used to connect component pin pads?

answers: text: photomask
question: What did PCB designers used to employ on a mylar sheet?

answers: text: self-adhesive tape
question: What were traces originally made out of?

answers: text: common component footprints
question: Designers would rub on a dry transfer of what to make the process of laying out components simpler?

answers: text: copper
question: What kind of metal coated the blank boards used to make PCBs?

context: Panelization is a procedure whereby a number of PCBs are grouped for manufacturing onto a larger board - the panel. Usually a panel consists of a single design but sometimes multiple designs are mixed on a single panel. There are two types of panels: assembly panels - often called arrays - and bare board manufacturing panels. The assemblers often mount components on panels rather than single PCBs because this is efficient. The bare board manufactures always uses panels, not only for efficiency, but because of the requirements the plating process. Thus a manufacturing panel can consist of a grouping of individual PCBs or of arrays, depending on what must be delivered.
qas: answers: text: Panelization
question: What process groups PCBs before transfer to a panel?

answers: text: a single design
question: Is it more common for panels to have a single design or many designs?

answers: text: assembly panels
question: What type of panels can also be referred to as an "array?'

answers: text: the plating process
question: What step of the bare board manufacture would be impossible if panels weren't always used?

answers: text: bare board manufacturing panels
question: Besides assembly panels, what's the other type of panel?

context: The panel is eventually broken apart into individual PCBs; this is called depaneling. Separating the individual PCBs is frequently aided by drilling or routing perforations along the boundaries of the individual circuits, much like a sheet of postage stamps. Another method, which takes less space, is to cut V-shaped grooves across the full dimension of the panel. The individual PCBs can then be broken apart along this line of weakness. Today depaneling is often done by lasers which cut the board with no contact. Laser panelization reduces stress on the fragile circuits.
qas: answers: text: depaneling
question: What is the process called whereby the individual PCBs are separated?

answers: text: individual circuits
question: What boundaries would you follow to separate PCBs on a panel?

answers: text: lasers
question: What technology has made depaneling possible without needing to physically interact with the board?

answers: text: space
question: What does the V-shaped groove method save?

answers: text: circuits
question: What delicate component is less likely to be damaged if laser depanelization is used?

context: Subtractive methods remove copper from an entirely copper-coated board to leave only the desired copper pattern. In additive methods the pattern is electroplated onto a bare substrate using a complex process. The advantage of the additive method is that less material is needed and less waste is produced. In the full additive process the bare laminate is covered with a photosensitive film which is imaged (exposed to light through a mask and then developed which removes the unexposed film). The exposed areas are sensitized in a chemical bath, usually containing palladium and similar to that used for through hole plating which makes the exposed area capable of bonding metal ions. The laminate is then plated with copper in the sensitized areas. When the mask is stripped, the PCB is finished.
qas: answers: text: additive
question: Do additive or subtractive methods use less raw materials?

answers: text: mask
question: What object is used to expose selected parts of the photosensitive film to light?

answers: text: palladium
question: What chemical element is often present in the bath used to sensitive exposed film after it's been imaged?

answers: text: copper
question: In subtractive methods, what metal covers the board and is then partially removed?

answers: text: sensitized areas
question: In the additive method, which parts of the laminate are plated with copper?

context: Semi-additive is the most common process: The unpatterned board has a thin layer of copper already on it. A reverse mask is then applied. (Unlike a subtractive process mask, this mask exposes those parts of the substrate that will eventually become the traces.) Additional copper is then plated onto the board in the unmasked areas; copper may be plated to any desired weight. Tin-lead or other surface platings are then applied. The mask is stripped away and a brief etching step removes the now-exposed bare original copper laminate from the board, isolating the individual traces. Some single-sided boards which have plated-through holes are made in this way. General Electric made consumer radio sets in the late 1960s using additive boards.
qas: answers: text: traces
question: In the semi-additive process, what do the areas exposed by the mask become at the end?

answers: text: copper
question: What metal is used to plate the unmasked parts of the board in the semi-additive method?

answers: text: etching
question: After the mask comes off of the board, what step takes off the original plating?

answers: text: General Electric
question: What company used to make radios with additive boards in the mid-20th century?

answers: text: any
question: What weight of plating is possible with copper?

context: The simplest method, used for small-scale production and often by hobbyists, is immersion etching, in which the board is submerged in etching solution such as ferric chloride. Compared with methods used for mass production, the etching time is long. Heat and agitation can be applied to the bath to speed the etching rate. In bubble etching, air is passed through the etchant bath to agitate the solution and speed up etching. Splash etching uses a motor-driven paddle to splash boards with etchant; the process has become commercially obsolete since it is not as fast as spray etching. In spray etching, the etchant solution is distributed over the boards by nozzles, and recirculated by pumps. Adjustment of the nozzle pattern, flow rate, temperature, and etchant composition gives predictable control of etching rates and high production rates.
qas: answers: text: hobbyists
question: What non-professionals might use immersion etching, since it's the easiest way to make a PCB?

answers: text: Heat
question: If you wanted to speed up the etching process, you could agitate the bath up or add what to it?

answers: text: long
question: Is the immersion etching process long or short compared to other production methods?

answers: text: bubble etching
question: What funny name is used for the etching process where air is blown through the etching solution to get it moving around?

answers: text: spray etching
question: What's the fastest and most easily controlled process for etching?

context: Multi-layer printed circuit boards have trace layers inside the board. This is achieved by laminating a stack of materials in a press by applying pressure and heat for a period of time. This results in an inseparable one piece product. For example, a four-layer PCB can be fabricated by starting from a two-sided copper-clad laminate, etch the circuitry on both sides, then laminate to the top and bottom pre-preg and copper foil. It is then drilled, plated, and etched again to get traces on top and bottom layers.
qas: answers: text: four
question: If you started with a two-sided laminate etched on either side, laminated to the top and bottom, and processed it again to get traces on the outside layers, how many layers would your final PCB have?

answers: text: trace layers
question: What makes up the inside of a multi-layer PCB?

answers: text: heat
question: Pressure is one thing you need to apply to make a multi-layer PCB; what's the other thing?

answers: text: press
question: What tool is used to push the trace layers in a multi-layer PCB together?

context: Holes through a PCB are typically drilled with small-diameter drill bits made of solid coated tungsten carbide. Coated tungsten carbide is recommended since many board materials are very abrasive and drilling must be high RPM and high feed to be cost effective. Drill bits must also remain sharp so as not to mar or tear the traces. Drilling with high-speed-steel is simply not feasible since the drill bits will dull quickly and thus tear the copper and ruin the boards. The drilling is performed by automated drilling machines with placement controlled by a drill tape or drill file. These computer-generated files are also called numerically controlled drill (NCD) files or "Excellon files". The drill file describes the location and size of each drilled hole.
qas: answers: text: high-speed-steel
question: What kind of material sometimes used for drilling will lose sharpness quickly if used for PCBs?

answers: text: abrasive
question: What property do PCBs have that makes them tough to drill through?

answers: text: coated tungsten carbide
question: What kind of drill bit do you need to drill holes in a PCB?

answers: text: Excellon files
question: What's another name for NCD files that has an "x" in it?

answers: text: numerically controlled drill
question: What does the "NCD" in "NCD files" mean?

context: The hole walls for boards with two or more layers can be made conductive and then electroplated with copper to form plated-through holes.  These holes electrically connect the conducting layers of the PCB. For multi-layer boards, those with three layers or more, drilling typically produces a smear of the high temperature decomposition products of bonding agent in the laminate system. Before the holes can be plated through, this smear must be removed by a chemical de-smear process, or by plasma-etch. The de-smear process ensures that a good connection is made to the copper layers when the hole is plated through. On high reliability boards a process called etch-back is performed chemically with a potassium permanganate based etchant or plasma. The etch-back removes resin and the glass fibers so that the copper layers extend into the hole and as the hole is plated become integral with the deposited copper.
qas: answers: text: conductive
question: What do the hole walls in two-layer PCBs have to be before they can be electroplated?

answers: text: three
question: What's the minimum number of layers a PCB can have to be considered "multi-layer"?

answers: text: de-smear
question: What process does a multi-layer PCB usually undergo before plating to make sure the layers have good connectivity with each other?

answers: text: high reliability
question: What type of boards undergo the etch-back process?

answers: text: resin
question: Etch-back removes glass fibers and what other material?

context: Matte solder is usually fused to provide a better bonding surface or stripped to bare copper. Treatments, such as benzimidazolethiol, prevent surface oxidation of bare copper. The places to which components will be mounted are typically plated, because untreated bare copper oxidizes quickly, and therefore is not readily solderable. Traditionally, any exposed copper was coated with solder by hot air solder levelling (HASL). The HASL finish prevents oxidation from the underlying copper, thereby guaranteeing a solderable surface. This solder was a tin-lead alloy, however new solder compounds are now used to achieve compliance with the RoHS directive in the EU and US, which restricts the use of lead. One of these lead-free compounds is SN100CL, made up of 99.3% tin, 0.7% copper, 0.05% nickel, and a nominal of 60ppm germanium.
qas: answers: text: oxidizes
question: What happens to untreated copper that makes it difficult to solder?

answers: text: benzimidazolethiol
question: What chemical treatment will prevent bare copper from oxidizing?

answers: text: hot air solder levelling
question: What's the process by which bare copper gets covered in solder?

answers: text: solderable surface
question: What does hot air solder leveling ensure the coated copper will have?

answers: text: tin-lead
question: What alloy can no longer be used in HASL because of restrictions on the use of one of its metal components?

context: Other platings used are OSP (organic surface protectant), immersion silver (IAg), immersion tin, electroless nickel with immersion gold coating (ENIG), electroless nickel electroless palladium immersion gold (ENEPIG) and direct gold plating (over nickel). Edge connectors, placed along one edge of some boards, are often nickel plated then gold plated. Another coating consideration is rapid diffusion of coating metal into Tin solder. Tin forms intermetallics such as Cu5Sn6 and Ag3Cu that dissolve into the Tin liquidus or solidus(@50C), stripping surface coating or leaving voids.
qas: answers: text: organic surface protectant
question: What does OSP stand for?

answers: text: nickel
question: What metal is often under the gold plating on edge connectors?

answers: text: IAg
question: What's the abbreviation for immersion silver plating?

answers: text: Cu5Sn6
question: Ag3Cu is one intermetallic that tin forms; what's the other one?

answers: text: voids
question: What might the rapid diffusion of coating metal into tin solder leave in the surface coating?

context: Electrochemical migration (ECM) is the growth of conductive metal filaments on or in a printed circuit board (PCB) under the influence of a DC voltage bias. Silver, zinc, and aluminum are known to grow whiskers under the influence of an electric field. Silver also grows conducting surface paths in the presence of halide and other ions, making it a poor choice for electronics use. Tin will grow "whiskers" due to tension in the plated surface. Tin-Lead or solder plating also grows whiskers, only reduced by the percentage Tin replaced. Reflow to melt solder or tin plate to relieve surface stress lowers whisker incidence. Another coating issue is tin pest, the transformation of tin to a powdery allotrope at low temperature.
qas: answers: text: Electrochemical migration
question: What's the process whereby metal filaments are grown on or in a PCB via DC voltage?

answers: text: zinc
question: Along with silver and aluminum, what metal grows metal filaments when exposed to an electric field?

answers: text: conducting surface paths
question: In addition to "whiskers," what does silver sprout around ions like halide?

answers: text: tin pest
question: What do scientist call the function whereby tin changes when it's very cold?

answers: text: tension
question: What's present in plated surfaces that causes tin to grow metal filaments?

context: Areas that should not be soldered may be covered with solder resist (solder mask). One of the most common solder resists used today is called "LPI" (liquid photoimageable solder mask).  A photo-sensitive coating is applied to the surface of the PWB, then exposed to light through the solder mask image film, and finally developed where the unexposed areas are washed away. Dry film solder mask is similar to the dry film used to image the PWB for plating or etching. After being laminated to the PWB surface it is imaged and develop as LPI. Once common but no longer commonly used because of its low accuracy and resolution is to screen print epoxy ink. Solder resist also provides protection from the environment.
qas: answers: text: solder resist
question: If part of a PCB isn't solderable, what can be used instead?

answers: text: solder mask
question: What's another term used for "solder resist"?

answers: text: liquid photoimageable solder mask
question: What solder resist with a four-word name is a popular choice in the industry?

answers: text: photo-sensitive
question: What kind of coating gets applied to the PWB before light exposure?

answers: text: screen print epoxy ink
question: What solder resist is so inaccurate that few choose it anymore?

context: Unpopulated boards are usually bare-board tested for "shorts" and "opens". A short is a connection between two points that should not be connected. An open is a missing connection between points that should be connected. For high-volume production a fixture or a rigid needle adapter is used to make contact with copper lands on the board. Building the adapter is a significant fixed cost and is only economical for high-volume or high-value production. For small or medium volume production flying probe testers are used where test probes are moved over the board by an XY drive to make contact with the copper lands. The CAM system instructs the electrical tester to apply a voltage to each contact point as required and to check that this voltage appears on the appropriate contact points and only on these.
qas: answers: text: "shorts"
question: What are bare-board tests looking for besides "opens"?

answers: text: copper
question: What conductive metal are the lands on a circuit board made out of?

answers: text: An open
question: What's an absent connection that needs to be linked up on an unpopulated board called?

answers: text: voltage
question: What does a flying probe tester deliver to the contact points during testing?

answers: text: CAM system
question: What system tells the flying probe where to go and what to do?

context: Often, through-hole and surface-mount construction must be combined in a single assembly because some required components are available only in surface-mount packages, while others are available only in through-hole packages. Another reason to use both methods is that through-hole mounting can provide needed strength for components likely to endure physical stress, while components that are expected to go untouched will take up less space using surface-mount techniques. For further comparison, see the SMT page.
qas: answers: text: through-hole
question: Surface-mount is one type of construction used in PCB assembly; what's the other one?

answers: text: through-hole
question: Which type of construction makes components that use more space?

answers: text: surface-mount
question: Which of the two kinds of construction is weaker under strain?

answers: text: surface-mount
question: If you're building a circuit board that has a lot of components that won't be used, which construction would be better?

context: In boundary scan testing, test circuits integrated into various ICs on the board form temporary connections between the PCB traces to test that the ICs are mounted correctly. Boundary scan testing requires that all the ICs to be tested use a standard test configuration procedure, the most common one being the Joint Test Action Group (JTAG) standard. The JTAG test architecture provides a means to test interconnects between integrated circuits on a board without using physical test probes. JTAG tool vendors provide various types of stimulus and sophisticated algorithms, not only to detect the failing nets, but also to isolate the faults to specific nets, devices, and pins.
qas: answers: text: Joint Test Action Group
question: What's the most frequently used test configuration procedure for ICs?

answers: text: temporary
question: Do test circuits create permanent or temporary connections between traces?

answers: text: ICs
question: What component of the printed circuit board is appraised with boundary scan testing?

answers: text: JTAG tool vendors
question: To whom would you go to acquire the algorithms you'd use for the Joint Test Action Group procedures?

answers: text: physical test probes
question: What would you avoid by using the Joint Test Action Group standard?

context: PCBs intended for extreme environments often have a conformal coating, which is applied by dipping or spraying after the components have been soldered. The coat prevents corrosion and leakage currents or shorting due to condensation. The earliest conformal coats were wax; modern conformal coats are usually dips of dilute solutions of silicone rubber, polyurethane, acrylic, or epoxy. Another technique for applying a conformal coating is for plastic to be sputtered onto the PCB in a vacuum chamber. The chief disadvantage of conformal coatings is that servicing of the board is rendered extremely difficult.
qas: answers: text: conformal coating
question: If a PCB is intended for use in an setting with extreme conditions, what would probably be applied?

answers: text: corrosion
question: The conformal coating can prevent leaking, shorts, and what other type of moisture damage?

answers: text: dipping
question: A conformal coating can be applied by spraying the PCB or by doing what else to it?

answers: text: wax
question: What material was first used for conformal coating?

answers: text: servicing
question: What action is made much more difficult for boards that have a conformal coating?

context: Many assembled PCBs are static sensitive, and therefore must be placed in antistatic bags during transport. When handling these boards, the user must be grounded (earthed). Improper handling techniques might transmit an accumulated static charge through the board, damaging or destroying components. Even bare boards are sometimes static sensitive. Traces have become so fine that it's quite possible to blow an etch off the board (or change its characteristics) with a static charge. This is especially true on non-traditional PCBs such as MCMs and microwave PCBs.
qas: answers: text: antistatic bags
question: What special protection are most PCBs shipped in?

answers: text: static charge
question: What force can easily change or even completely destroy an etch on a PCB?

answers: text: earthed
question: What's another term for "grounded" in the context of PCBs?

answers: text: MCMs
question: Non-traditional PCBs include microwave PCBs and what other type of board?

answers: text: non-traditional
question: What class of PCBs are even more susceptible to static than standard ones?

context: The first PCBs used through-hole technology, mounting electronic components by leads inserted through holes on one side of the board and soldered onto copper traces on the other side. Boards may be single-sided, with an unplated component side, or more compact double-sided boards, with components soldered on both sides. Horizontal installation of through-hole parts with two axial leads (such as resistors, capacitors, and diodes) is done by bending the leads 90 degrees in the same direction, inserting the part in the board (often bending leads located on the back of the board in opposite directions to improve the part's mechanical strength), soldering the leads, and trimming off the ends. Leads may be soldered either manually or by a wave soldering machine.
qas: answers: text: wave soldering machine
question: If a lead wasn't soldered manually, what device was used?

answers: text: through-hole
question: Which type of PCB construction technique was used first?

answers: text: copper traces
question: In through-hole construction, what are the leads on the front attached to on the back?

answers: text: 90 degrees
question: For boards with two sides, to what angle are leads bent to in order to install them horizontally?

answers: text: mechanical strength
question: What is improved by bending leads in opposite directions on the back of double-sided PCBs?

context: Through-hole manufacture adds to board cost by requiring many holes to be drilled accurately, and limits the available routing area for signal traces on layers immediately below the top layer on multi-layer boards since the holes must pass through all layers to the opposite side. Once surface-mounting came into use, small-sized SMD components were used where possible, with through-hole mounting only of components unsuitably large for surface-mounting due to power requirements or mechanical limitations, or subject to mechanical stress which might damage the PCB.
qas: answers: text: Through-hole
question: Which type of construction is more expensive?

answers: text: multi-layer
question: What type of boards end up with limited routing space in through-hole manufacture?

answers: text: mechanical stress
question: What force might damage a PCB if large components are surface mounted?

answers: text: small-sized SMD components
question: What components can be surface mounted to save space?

answers: text: power requirements
question: A component might not be able to be made any smaller because of its mechanical limitations or what other need?

context: Surface-mount technology emerged in the 1960s, gained momentum in the early 1980s and became widely used by the mid-1990s. Components were mechanically redesigned to have small metal tabs or end caps that could be soldered directly onto the PCB surface, instead of wire leads to pass through holes. Components became much smaller and component placement on both sides of the board became more common than with through-hole mounting, allowing much smaller PCB assemblies with much higher circuit densities. Surface mounting lends itself well to a high degree of automation, reducing labor costs and greatly increasing production rates. Components can be supplied mounted on carrier tapes. Surface mount components can be about one-quarter to one-tenth of the size and weight of through-hole components, and passive components much cheaper; prices of semiconductor surface mount devices (SMDs) are determined more by the chip itself than the package, with little price advantage over larger packages. Some wire-ended components, such as 1N4148 small-signal switch diodes, are actually significantly cheaper than SMD equivalents.
qas: answers: text: mid-1990s
question: When did surface-mount become a commonly used manufacturing process?

answers: text: wire leads
question: What did the new components with end tabs replace?

answers: text: automation
question: What improvement is possible with surface-mounting that enables higher production and lower labor costs?

answers: text: surface mount devices
question: What are SMDs?

answers: text: chip
question: Is it the chip or the package that influences the price of an SMD more?

context: Each trace consists of a flat, narrow part of the copper foil that remains after etching. The resistance, determined by width and thickness, of the traces must be sufficiently low for the current the conductor will carry. Power and ground traces may need to be wider than signal traces. In a multi-layer board one entire layer may be mostly solid copper to act as a ground plane for shielding and power return. For microwave circuits, transmission lines can be laid out in the form of stripline and microstrip with carefully controlled dimensions to assure a consistent impedance. In radio-frequency and fast switching circuits the inductance and capacitance of the printed circuit board conductors become significant circuit elements, usually undesired; but they can be used as a deliberate part of the circuit design, obviating the need for additional discrete components.
qas: answers: text: etching
question: What process is a trace left over from?

answers: text: width
question: Along with thickness, what determines the resistance of a trace?

answers: text: signal
question: What type of trace is often narrower than a ground trace?

answers: text: copper
question: In a multi-layer board, what metal would a ground plane be mostly made out of?

answers: text: microwave circuits
question: What type of circuits use a stripline and microstrip format?

context: The cloth or fiber material used, resin material, and the cloth to resin ratio determine the laminate's type designation (FR-4, CEM-1, G-10, etc.) and therefore the characteristics of the laminate produced. Important characteristics are the level to which the laminate is fire retardant, the dielectric constant (er), the loss factor (tδ), the tensile strength, the shear strength, the glass transition temperature (Tg), and the Z-axis expansion coefficient (how much the thickness changes with temperature).
qas: answers: text: type designation
question: What element of a laminate is designated by the cloth to resin ratio, among other things?

answers: text: Z-axis expansion coefficient
question: What's the name for the measurement of a laminate's change in thickness as its temperature changes?

answers: text: Tg
question: What's the abbreviation for the glass transition temperature of a laminate?

context: There are quite a few different dielectrics that can be chosen to provide different insulating values depending on the requirements of the circuit. Some of these dielectrics are polytetrafluoroethylene (Teflon), FR-4, FR-1, CEM-1 or CEM-3. Well known pre-preg materials used in the PCB industry are FR-2 (phenolic cotton paper), FR-3 (cotton paper and epoxy), FR-4 (woven glass and epoxy), FR-5 (woven glass and epoxy), FR-6 (matte glass and polyester), G-10 (woven glass and epoxy), CEM-1 (cotton paper and epoxy), CEM-2 (cotton paper and epoxy), CEM-3 (non-woven glass and epoxy), CEM-4 (woven glass and epoxy), CEM-5 (woven glass and polyester). Thermal expansion is an important consideration especially with ball grid array (BGA) and naked die technologies, and glass fiber offers the best dimensional stability.
qas: answers: text: Teflon
question: What's the common name of polytetrafluoroethylene?

answers: text: phenolic cotton paper
question: What pre-preg material is designated by "FR-2"?

answers: text: ball grid array
question: To what type of packaging is thermal expansion particularly critical?

answers: text: glass fiber
question: What material delivers optimum dimensional stability?

answers: text: FR-6
question: What dielectric is matte glass and polyester?

context: The reinforcement type defines two major classes of materials - woven and non-woven. Woven reinforcements are cheaper, but the high dielectric constant of glass may not be favorable for many higher-frequency applications. The spatially nonhomogeneous structure also introduces local variations in electrical parameters, due to different resin/glass ratio at different areas of the weave pattern. Nonwoven reinforcements, or materials with low or no reinforcement, are more expensive but more suitable for some RF/analog applications.
qas: answers: text: woven
question: Along with the non-woven class, what makes up the reinforcement type materials?

answers: text: non-woven
question: Which is the more expensive reinforcement type?

answers: text: spatially nonhomogeneous
question: What type of structure do woven reinforcements have that cause them to have variation in their electrical parameters?

answers: text: resin/glass
question: Which ratio varies because of the structure of woven reinforcements?

answers: text: RF/analog
question: For what kind of applications are non-woven reinforcement materials better than woven ones?

context: At the glass transition temperature the resin in the composite softens and significantly increases thermal expansion; exceeding Tg then exerts mechanical overload on the board components - e.g. the joints and the vias. Below Tg the thermal expansion of the resin roughly matches copper and glass, above it gets significantly higher. As the reinforcement and copper confine the board along the plane, virtually all volume expansion projects to the thickness and stresses the plated-through holes. Repeated soldering or other exposition to higher temperatures can cause failure of the plating, especially with thicker boards; thick boards therefore require high Tg matrix.
qas: answers: text: glass transition temperature
question: What's the temperature at which resin softens and expands called?

answers: text: joints
question: Along with vias, what makes up the components of a board?

answers: text: mechanical overload
question: What will happen to the components when the temperature of resin goes above that of glass transition?

answers: text: high Tg matrix
question: What do thick boards require to resist plating failure?

answers: text: glass
question: When resin stays below Tg, its thermal expansion is similar to that of copper and what other material?

context: Moisture absorption occurs when the material is exposed to high humidity or water. Both the resin and the reinforcement may absorb water; water may be also soaked by capillary forces through voids in the materials and along the reinforcement. Epoxies of the FR-4 materials aren't too susceptible, with absorption of only 0.15%. Teflon has very low absorption of 0.01%. Polyimides and cyanate esters, on the other side, suffer from high water absorption. Absorbed water can lead to significant degradation of key parameters; it impairs tracking resistance, breakdown voltage, and dielectric parameters. Relative dielectric constant of water is about 73, compared to about 4 for common circuitboard materials. Absorbed moisture can also vaporize on heating and cause cracking and delamination, the same effect responsible for "popcorning" damage on wet packaging of electronic parts. Careful baking of the substrates may be required.
qas: answers: text: Moisture absorption
question: What will happen to the materials when a board gets wet or is in a humid area?

answers: text: cracking
question: If materials absorb moisture and then are heated enough to vaporize the water, the board might show delamination or what other type of damage?

answers: text: 0.15%
question: What percentage absorption do F-4 epoxies have?

answers: text: 4
question: What's the approximate relative dielectric constant of most materials in circuit boards?

answers: text: Teflon
question: What material has an absorption rate of only 0.01%?

context: The printed circuit board industry defines heavy copper as layers exceeding three ounces of copper, or approximately 0.0042 inches (4.2 mils, 105 μm) thick. PCB designers and fabricators often use heavy copper when design and manufacturing circuit boards in order to increase current-carrying capacity as well as resistance to thermal strains. Heavy copper plated vias transfer heat to external heat sinks. IPC 2152 is a standard for determining current-carrying capacity of printed circuit board traces.
qas: answers: text: three ounces
question: What's the minimum amount of copper a layer in a PCB can have to be considered "heavy copper"?

answers: text: 0.0042 inches
question: About how thick would a PCB layer be if it contained three oz. of copper?

answers: text: current
question: What will a circuit board with heavy copper carry very well?

answers: text: thermal strains
question: What would a PCB designer use heavy copper to make their circuit board resist?

answers: text: external heat sinks
question: Where does the heat go when it leaves heavy copper-plated vias?

context: Since it was quite easy to stack interconnections (wires) inside the embedding matrix, the approach allowed designers to forget completely about the routing of wires (usually a time-consuming operation of PCB design): Anywhere the designer needs a connection, the machine will draw a wire in straight line from one location/pin to another. This led to very short design times (no complex algorithms to use even for high density designs) as well as reduced crosstalk (which is worse when wires run parallel to each other—which almost never happens in Multiwire), though the cost is too high to compete with cheaper PCB technologies when large quantities are needed.
qas: answers: text: routing of wires
question: What arduous aspect of the process can designers skip in Multiwire?

answers: text: a connection
question: What does the machine create by drawing a straight line between two points on the board?

answers: text: crosstalk
question: Along with quick design times, what problem does Multiwire cut down on?

answers: text: cost
question: What makes Multiwire impractical to use when large quantities of a board are needed?

answers: text: wires
question: In simple language, what are the interconnections in an embedding matrix?

context: Cordwood construction can save significant space and was often used with wire-ended components in applications where space was at a premium (such as missile guidance and telemetry systems) and in high-speed computers, where short traces were important. In cordwood construction, axial-leaded components were mounted between two parallel planes. The components were either soldered together with jumper wire, or they were connected to other components by thin nickel ribbon welded at right angles onto the component leads. To avoid shorting together different interconnection layers, thin insulating cards were placed between them. Perforations or holes in the cards allowed component leads to project through to the next interconnection layer. One disadvantage of this system was that special nickel-leaded components had to be used to allow the interconnecting welds to be made. Differential thermal expansion of the component could put pressure on the leads of the components and the PCB traces and cause physical damage (as was seen in several modules on the Apollo program). Additionally, components located in the interior are difficult to replace. Some versions of cordwood construction used soldered single-sided PCBs as the interconnection method (as pictured), allowing the use of normal-leaded components.
qas: answers: text: Cordwood
question: What type of construction is best for applications that need to portion space carefully?

answers: text: axial-leaded components
question: What gets mounted in the middle of two parallel planes in a cordwood construction?

answers: text: nickel-leaded
question: What type of component has to be used in cordwood construction to its detriment?

answers: text: shorting
question: What do insulating cards prevent between interconnection layers?

answers: text: Differential thermal expansion
question: What force caused the physical damage to components that affected the Apollo program?

context: Development of the methods used in modern printed circuit boards started early in the 20th century. In 1903, a German inventor, Albert Hanson, described flat foil conductors laminated to an insulating board, in multiple layers. Thomas Edison experimented with chemical methods of plating conductors onto linen paper in 1904. Arthur Berry in 1913 patented a print-and-etch method in Britain, and in the United States Max Schoop obtained a patent to flame-spray metal onto a board through a patterned mask. Charles Ducas in 1927 patented a method of electroplating circuit patterns.
qas: answers: text: Albert Hanson
question: Who was the German inventor who wrote in 1903 about conductors being laminated in layers to a board?

answers: text: linen paper
question: What material did Thomas Edison experiment with by trying to chemically attach conductors to it?

answers: text: 1913
question: What year did Arthur Berry patent his print-and-etch method?

answers: text: a patterned mask
question: In Max Schoop's method, what was used to create the flame-sprayed pattern on the board?

answers: text: Charles Ducas
question: Who obtained a patent in 1927 for his method of electroplating circuit patterns?

context: The Austrian engineer Paul Eisler invented the printed circuit as part of a radio set while working in England around 1936. Around 1943 the USA began to use the technology on a large scale to make proximity fuses for use in World War II. After the war, in 1948, the USA released the invention for commercial use. Printed circuits did not become commonplace in consumer electronics until the mid-1950s, after the Auto-Sembly process was developed by the United States Army. At around the same time in Britain work along similar lines was carried out by Geoffrey Dummer, then at the RRDE.
qas: answers: text: a radio set
question: What was Paul Eisler making when he came up with the printed circuit?

answers: text: World War II
question: What event prompted the United States to adopt the printed circuit to make proximity fuses?

answers: text: 1948
question: When was the printed circuit released for commercial use in the U.S.?

answers: text: Geoffrey Dummer
question: Who was working on the same type of large-scale application of printed circuits as the U.S. in Britain in the mid-1950s?

answers: text: Auto-Sembly
question: What process was created by the U.S. Army that led to innovation in consumer electronics?

context: During World War II, the development of the anti-aircraft proximity fuse required an electronic circuit that could withstand being fired from a gun, and could be produced in quantity. The Centralab Division of Globe Union submitted a proposal which met the requirements: a ceramic plate would be screenprinted with metallic paint for conductors and carbon material for resistors, with ceramic disc capacitors and subminiature vacuum tubes soldered in place. The technique proved viable, and the resulting patent on the process, which was classified by the U.S. Army, was assigned to Globe Union. It was not until 1984 that the Institute of Electrical and Electronics Engineers (IEEE) awarded Mr. Harry W. Rubinstein, the former head of Globe Union's Centralab Division, its coveted Cledo Brunetti Award for early key contributions to the development of printed components and conductors on a common insulating substrate. As well, Mr. Rubinstein was honored in 1984 by his alma mater, the University of Wisconsin-Madison, for his innovations in the technology of printed electronic circuits and the fabrication of capacitors.
qas: answers: text: Globe Union
question: What company developed the first electronic circuit that could be mass produced and was durable enough to be fired from a gun?

answers: text: Harry W. Rubinstein
question: Who was in charge of the Centralab Division of Globe Union when the PCB used in anti-aircraft fuses was invented?

answers: text: University of Wisconsin-Madison
question: Where did Harry Rubinstein attend college?

answers: text: ceramic
question: What was the plate used for anti-aircraft proximity fuses in World War II made out of?

answers: text: Cledo Brunetti Award
question: What award did Rubinstein win in 1984 for his contributions?

context: Originally, every electronic component had wire leads, and the PCB had holes drilled for each wire of each component. The components' leads were then passed through the holes and soldered to the PCB trace. This method of assembly is called through-hole construction. In 1949, Moe Abramson and Stanislaus F. Danko of the United States Army Signal Corps developed the Auto-Sembly process in which component leads were inserted into a copper foil interconnection pattern and dip soldered. The patent they obtained in 1956 was assigned to the U.S. Army. With the development of board lamination and etching techniques, this concept evolved into the standard printed circuit board fabrication process in use today. Soldering could be done automatically by passing the board over a ripple, or wave, of molten solder in a wave-soldering machine. However, the wires and holes are wasteful since drilling holes is expensive and the protruding wires are merely cut off.
qas: answers: text: through-hole
question: What type of construction was originally used for all electronic components?

answers: text: 1949
question: In what year was the Auto-Sembly process created?

answers: text: 1956
question: What year was the patent for the Auto-Sembly process granted?

answers: text: U.S. Army
question: Although two men developed the Auto-Sembly process, to whom was the patent officially granted?

answers: text: drilling holes
question: Which part of the Auto-Sembly manufacturing process is the most costly?