- Absorbtivity : The property of a material to absorb radiation. E.g. the amount of IR radiation absorbed as a percentage of total exposure - Accelerated ageing : exposure of e.g. PCBs to high humidity and raised temperature environment to simulate certain ageing conditions - Acceptance Test : Special tests defined and chosen to determine whether a PCB or assembly meets certain requirements - Acceptable Quality Level : The maximum number of defects per 100 opportunities, which are accepted as satisfactory average process performance. - Acid Flux : A flux based on acid components, mostly utilizing water as a solvent - Acrylic : type of glue used in SMT technology - Acrylic Resin : A resin that is cured thermally and usually is transparent - Activation : Chemical treatment of a metal surface in order to improve the wetting behavior of this surface.Also used to describe the amount of activator [salts, acids] in a flux. - Activated Rosin Flux : A flux based on rosin dissolved in alcohol to whichsome organic acid has been added - Activator : That part of the flux that enables it to remove oxides from metal surfaces - Adaptor : A device that is designed to hold and locate assemblies, which are tested - Adhesive : A polymer that is used to join two surfaces, a glue. - Air knife : well-defined blast of air. is being used by some after the last wave to remove bridges - Alcohol : volatile organic compound. used to help remove ionizable residues or as a solvent in fluxes - Analog Functional Test : A series of tests utilizing analog signals that checks boards for certain current output signals. - Analog In-Circuit Test : Test procedure to measure component performance prior to power-up - Annular Ring : The ring of copper around a drilled or punched hole on a PCB - Anions : negative ions - Angle of Attack : The angle formed between the front of the squeegee and the surface of the stencil. - Aperture : That opening in a stencil that corresponds to some pattern to be printed - Aqueous Cleaning : Any cleaning method using water as its main solvent - Array : An arrangement of items in rows and colums. A matrix. [e.g. arrays of solder balls on the bottom of a BGA] - Artwork Generation : The act of creating the graphic aspects of a circuit pattern for production purposes. Traditionally, this was done by manual drafting. Today most shops use software based programs. - Assembly : The production process of mounting parts and components onto a PCB. The soldering or joining process is sometimes considered part of assembly. - Aspect Ratio : That ratio, which reflect the board thickness divided by the diameter of the smallest via or through-hole - ASQC : American Society for Quality Control - ATE : Automatic Test Equipment - Automatic Component Placement : In Artwork Generation: The program that determines the actual positioning of components on the PCB. In Production: The use of automatic equipment to place components - Automatic Test Equipment (ATE) : Test equipment that performs automatic testing of assemblies - Automatic Test Generation : A test program generated by software with or without human programming assistance - Azeotrop : A mixture of chemicals that exhibit the same proportion in the liquid and vapor - µBGA : Name for certain BGAs that belong to the family of CSP [Chip Scale Packages ]. µBGAs have been developed by Tessera and are, as SLIC at most 20% larger than the packaged chip.
- Backdriving : An in-circuit test used with digital circuits - Bare Board : A fully manufactured PCB, however, not containing any electronic parts such as active or passive components, jumpers, connectors etc. - Bed-of-Nails : A special in-line testing method that utilizes needle-based fixtures to contact predetermined areas on the assembly - Bed-of-Needles : A test for assemblies or PCBs whereby spring loaded needles are directed from a tooling plate onto special contact areas on the PCB. The test is carried out by specialized computerized equipment. It can check for continuity [PCB] or certain component values and performances. - BGA : A component of square form that shows all the solderable connection on the bottom side. The metallizations are in spherical form. - Blade Attack Angle : The angle between squeegee and stencil during solder paste printing - Blind via : Conductive connection between inner layers of a multilayer board. They are plated holes, which are drilled and then plated. ‚Blind‘ because the hole does not pass through the entire PCB but is open to only one side - Blowhole : A crater-like hole in a solder joint, which was produced by outgassing of volatile material from the PCB. - Bond Liftoff : The separation of a bonded lead from its pad - Boundary Scan : A testing procedure that uses internal circuitry of the IC to carry out testing on the wafer level - Bow : One directional deviation from the straight of a PCB - Bridge : A solder defect characterized by connecting to otherwise electrically non-connected conductors (leads, pads, lines) - Buried via : Conductive connection between inner layers of a multilayer PCB, that is produced by drilling and then plating. ‘Buried’ because the hole is closed to both outer surfaces of the PCB and thus connects only inner layers. - Burn-In : A concept and certain test methods which try, by means of stressing and temperature exposure, to cause early failure. Thus all those components or assemblies, which would have failed early anyway (infant mortality), are supposed to be eliminated and only long lasting ones are to remain. Depending on the procedure there may be side effects such as oxidation and/or increase in intermetallic. - Burn-In Test : Testing procedure that utilizes exaggerated usage conditions to find infant mortality or 'weak links' in the design. Also used as aging method.
- CAD : Computer Aided Design. Software for engineers, which assist during design, and actually often performs calculations. - CAD/CAM : A term referring to the use of software programs to design and layout circuitry as well as to transfer such generated data directly to manufacturing equipment. - Capillary Action : The filling of small gaps or capillaries produced by the forces of wetting and surface tension. The physical phenomenon of liquids to rise into narrow gaps (capillaries) under certain circumstances - Catalyst : A chemical that affects the a chemical process without participating in it. E.g. a chemical that accelerates a chemical process. - Center-to-Center Spacing : Referring to the way the pitch of leads on components is measured: center lead to adjacent center lead. - Central Component Orientation : A special approach when designing that defines the area for major parts and then associates supporting components in their vicinity. - Chemical solvents : are those substances - liquids, gases, or solids - that can dissolve another substance - Chip Carrier : A special IC packaging form in which the leads (or contacts) protrude on all four sides of the package - Chip Component : The class of passive components packaged in leadless ceramic, glass or plastic form (resistors, capacitors and inductors) - Chip Tester : Involved software based testing equipment for the evaluation of ICs and other active devices - Chip Wave : For a doble-wave, the first wave. It is used when wave soldering SM assemblies and is to overcome the rejection behavior against solder by the component bodies. The chip wave exhibits short contact length and it is mostly rather turbulent. - Chip-on-board (COB) : A joining technique. Bare silicone chips (ICs) are directly mounted without any component body onto the PCB. The connections are either made by wire bonding or solder bumps and reflow. - Circuit Verifier : A response based testing procedure that activates the assembly or device to diagnose defects and performance - Clamshell Fixture : A fixture that allows testing of both sides of a PCB, mostly hinged. - Cluster Testing : Tests performed on a group of (assemblies) components,rather than on individual ones - Co-Polymer : The result of the reactive process of two dissimilar polymers. - Cold Solde : Joint A defect of soldering caused by adhesion of solder without proper chemical reaction between the base metal and the tin of the solder. Usually caused by inadequate thermal conditions. - Cold Solder Joint : A defect of soldering caused by adhesion of solder without proper chemical reaction between the base metal and the tin of the solder. Usually caused by inadequate thermal conditions. - Component : An electrical building block of an electronic circuit. They function as resistors, capacitors or inductors. There are others, which are processors and memory modules. Components come in a variety of body shapes and forms. - Condensation : a method of reflow soldering using highly specialized liquids. These liquids are boiled and the latent heat of evaporation is used to heat those items which have been lowered into the vapor. - Conductive Adhesive : An adhesive that is mixed with certain metal flakes (copper, silver, gold) to make it electrically conductive. There are also intrinsically conductive polymers, however, at this point in time, they do not play any significant role in electronic joining. - Conductive Epoxy : Material to which has been added metallic flakes (mostly silver) to improve its electrical conductivity. - Conformal Coating : A (thin) non-conductive coating of an assembly, which is used to limit environmental impact (humidity, dust). It is also used to enhance mechanical properties. Conformal coatings are usually applied by a dipping process, however, they can also be sprayed or brushed. - Contact Angle : The angle formed between the surface of a solder fillet and the wetted surface - used as a measure of the quality of wetting - Continuity In Testing : A current based test that checks for opens between connected land areas - Convection : a method of reflow soldering. Convection is a heating method which employs either gases, liquids or vapors [see: condensation] - Conveyor : The system of transport used to carry the PCB or assembly throughout the production process. Several forms of conveyors are in use [e.g. pallet, finger, chain, belt] - Copper-Mirror Test : A test designed to identify corrosive behavior of fluxes. It consists essentially of the examination of a copper film that has been vapor-deposited onto a glass plate. - Corrosiveness : Action of aggressive acids etc. on metals etc. - Cosmetic Defect : A visual defect that otherwise does not inhibit thereliability or function of the product - Cross Section : A destructive test. A part of an assembly is cut and polished to be inspected under a microscope. - Cure : The polymerization of a material that usually changes it from a soft to a harder form by lengthening and intertwining the molecular chains. Curing needs the application of energy in form of heat (convection, radiation) - Cut & Clinch : A process during insertion of leaded components, where a mechanism cuts and clinches the lead, which is protruding below the board, in order to shorten it and to bend it against the underside of the board. - Cycle Rate : In Assembly: The time a piece of placing equipment needs to pick-up and position a component and then return for the next component. In Testing: The number of heat excursion per time unit. In reference to pick-and-place equipment, the time for the placement unit to move from pickup of the component to placement and back
- De-Wetting : The effect of de-wetting is indicated whenever solder has spread onto a surface and then retracted leaving puddles and webbing. The original color of the base metal (e.g. copper) has changed to a silvery shine. The physical/chemical mechanism of de-wetting is not yet fully understood. De-wetting from the copper-rich intermetallic has been shown and it has been shown in the presence of silicate contaminants. - Dendrite : Spikes or filaments growing from metals under certain conditions - Deposit Height : The thickness of printed paste on the PCB - Dewetting : A condition where the solder has withdrawn from a previously wetted surface - Discrete Component : Single components such as resistors, capacitors, diodes etc. - Dispenser : an equipment for soldering machines to deposit glue (or solder paste) prior to mounting components onto the boards for wave (or reflow) soldering - Dispersant : An additive for liquids that reduces their surface tension to facilitate cleaning action - Documentation : Paperwork and/or electronic data that is associated with all aspects of assembly. - Double-wave system : a two-wave system used to solder many SMT or mixed-technology assemblies - Doublesided Assembly : An assembly for which both sides of a PCB have been used for component mounting. - Drag soldering : an early soldering method where a PCB is being dragged over the static surface of a pool of liquid solder - Dragout : The amount of liquid which is removed from the equipment due to adhesion to the assembly when the latter is moved out of the machine - Dross : A mixture of solder oxides (usually tin oxides) and solder. May contain flux and other impurities. - Dry-Strength : The adhesive strength of a glue right after curing - Dual Fixture : Test equipment that allows setting up one assembly on a first bed of nails fixture while a second one is tested in a second fixture. - Dummy : The precise simulation of normal component package, however lacking its functional inner part. Dummies are used to control costs for initial process evaluation purposes - Dummy Component : A component which is dimensionally identical with a real component, however, lacks its functionality [i.e. does not contain a chip]. Used for testing of processes.
- Emulsion : A chemical that is used when producing screens for screen-printing [paste; adhesive]. It serves to cover all those areas of the weave, which are not to print. Frequently: Polyvinylazetate. - Epoxy : one of the main types of glue used in SM technology - Epoxy Resin : A synthetic resin derived from epoxy formulations - Eutectic : refers to metal alloys and in a binary system: it is that composition where two descending liquidus curves meet. The alloy behaves like a single metal and melts at one temperature rather than over an entire range. - Eutectic Alloy : Those alloys that are determined by two liquidus lines meeting. Liquidus and solidus temperatures are the same.
- Fault List : A listing of all defects found during board testing - Fiducial : A specially designed marking on the PCB used to identify location and orientation by vision systems. Global fiducials describe the overall location parameters; local fiducials are used for fine-pitch application to describe special features more precisely and at closer range These are part of the artwork and are incorporated onto the etched pattern on the PCB - Fillet : The entirety of solder making up the solder joint - Finger conveyors : a conveyor type in wave soldering machines that holds the assembly in titanium fingers. It allows to change the width of the conveyor and thus is appropriate for the soldering of large batches of the same product - First-Pass-Yield : That percentage of all finished assemblies, which has passed all tests without ever having to undergo repair or touch-up. - Flat Pack (FP) : A low profile IC package, which typically has gull wing type of leads on two or four sides. - Flood Bar : In paste printers, a mechanism that returns the paste to its original position after the printing stroke of the squeegee. Returning the paste prepares the printer for the next printing stroke. - Flow Soldering : A soldering technique which uses a system that flows solder against the bottom of a PWB, making connections between solderable surfaces that are close enough for the solder surface tension. This is sometimes also called wave soldering. - Flurinert : Trade name of a liquid widely used in condensation reflow equipment. - Flux : A material (solid, liquid or gas) promoting wetting during soldering - Flux Activity : The level of aggressiveness of a flux, i.e. its ability to remove oxides. - Foam fluxing : an arrangement in which clean, compressed air is forced through a porous "stone" (today, generally plastic material) into the flux. The flux, which has to be of the foaming type, rises in the chimney of the fluxer and forms a foam head. The board is passed through or over this foam head thus fluxing the bottom of the assembly. If the board or the pallet is hot, the foam head may collapse. A very fast conveyor may also cause the foam to break, leaving unfluxed areas on the bottom of the board (also depends on flux). As the flux is constantly aerated, it may be contaminated, ages by oxidation, and loses solvent. Controlling its density is absolutely necessary, however difficult for Low Solids Fluxes. - Footprint : The layout of pads or lands designed to match the leads of a specific SMC - Functional Testing : Testing the functionality of an electronic module from its external connector.
- Galden : Trade name of a liquid that is extensively used in condensation reflow equipment. - Glob Top : The result of a protective coating process usually employed in such applications as CoB to increase the reliability of the package. After a resin has been spread over the entire package, it is cured to give it the required strength - Glue : See: adhesive - Golden Boy : An assembly that has successfully passed all relevant tests and now is used as a comparison model - Green Strength : The 'tackiness' of the uncured resin or the ability to keep a component in place by adhesive force prior to curing The ability of pastes, glues and adhesives to hold parts in position prior to curing - Grid : In CAD application the use of a rectangular line system to facilitate location of points on a PCB - Gull Wing : Leads which exit the package body and bend down then outward similar to a seagull in flight. They are typically used on a SO package.
- Halide Content : The proportion of free halides (chlorine, bromine, fluorine etc.) in the solids of a flux - Halides : The class of chemicals consisting of: fluorine, chlorine, bromine,iodine or astative - Hardener : A chemical that is added to promote or accomplish the curing or polymerization of an adhesive - Heat-and-Pull : As applied to soldering irons, a method that combines the means of heating and the means of removing a component during 'rework' - High Speed Digital Test : A test for assemblies containing micro-processor that employs data compression methods to check performance - Hole Breakout : A hole on the PCB is not entirely encircled by land area - Hybrid : an electronic substrate material: alumina - Hygroscopic : The tendency of attracting and/or absorbing humidity
- IC : Integrated Circuit - Image Fiducial : Global fiducials used on ganged PCB board panels - In-circuit Testing : A test method that uses probes to make connections to the internal nodes of a circuit for signal injection or signal monitoring. - Inert : A situation in which (nearly) no chemical reaction takes place. When soldering ‚inert‘ refers to an atmospheric cover under which no oxidation occurs. The cover gas is usually nitrogen. - Ionic Contamination : Contaminants on the PCB, the components or the finished product which, once water is added (humidity), become corrosive and conductive. There are many sources of ionic contamination (e.g. PCB production, HAL, handling etc.) and they may not necessarily derive from flux residues. - IR reflow : in a IR reflow, heaters arranged above and below a conveyor that carries the product radiate IR energy onto it. Once the assembly’s temperature has reached the melting point of solder, reflow begins. The paste, consisting of solder powder and flux, accomplishes wetting and forms the joint. A number of panels, rods, bars, and/or lamps permit a gradual increase in temperature during the travel of the board. Once molten, the solder solidifies on leaving the machine.
- J-lead : Leads which are rolled under the body of a package in the shape of "J". The are typically used on plastic chip carriers.
- Kari Butanol Value : A system to measure solvent strength widely used in the paint industry and also applied to solvents used to clean electronic material - Known Good Board : An assembly that is known to function well and that is used as a model or for comparison purposes.
- Laminar Wave : A smooth flowing solder wave with no turbulence. Minimizes the formation of solder bridges and icicles. - Land : Those copper areas on the a PCB to which components or other circuitry will be soldered - laser : A non-contact reflow process based on radiation technology. The laser (an acronym for light amplification by stimulated emission of radiation) supplies radiation energy that is coherent, oscillates in phase, and consists of only one wavelength. - LCCC (CLCC) : Leadless Ceramic Chip Carrier (Ceramic Leadless Chip Carrier). A hermetically sealed ceramic package that has pads (castellation) around its sides for solder connection in a surface mounting application. - Lead : That part of the lead-frame which protrudes beyond the body of the component and which is used to make the connection with the metallized lands on the PCB usually by means of a soldered connection. - Lead Configuration : The form into which the extended ends of the lead frame (i.e. the protruding leads) of a component package have been shaped: J-leads, gull-wing and I-leads - Leadless Ceramic Chip Carrier : A ceramic package (housing) for an IC that uses solderable connectors rather than - Line Certification : Based on some standard or specification, the process of assessing whether a production line meets certain of the requirements for efficient performance. - Liquidus : The temperature at which an alloy becomes fully liquid and fluid - Liquidus Temperature : The temperature at which the (solder) alloy reaches its full liquid state - Low-solid flux : flux with low-solid content, which may provide benefits when no-clean processes are considered. Nowadays fluxes in the 2% region are considered LSF.
- MCMs : multichip modules - MELF : Metal Electrode Face. A component derived from the old form of cylindrical resistors using metal cap endings rather than leads and intended for the use as a surface mounted device - Mixed Technology : Refers to an assembly that employs SM and traditional (through-hole) components. - MLB : Multi-Layer Board. A PWB that has more than two conductor layers. - Modifier : A chemical that is added to another to change its normal properties (e.g. surface tension, wetting) - Multilayer : A PCB which is designed like a ‚sandwich‘; i.e. it consists of several layers of dielectric material and conductors. Through-holes or vias establish the electrical path between the different layers.
- Neutralizer : An alkaline chemical that is used to counteract acidic action - nitrogen : Gas. Colorless, no taste, no smell. Basic chemical with the chemical name: ‚N‘. Atomic weight: 14,008; Order number: 7; Boiling Point: -195,8 ºC. Air contains 78,08 % by volume of nitrogen. This element does not react easily and under normal conditions does not form compounds with other elements. In particular, no oxidation takes place in pure nitrogen. - No-Clean Soldering : A soldering process using fluxes or pastes that do not require the cleaning of the final product - Node : A tests point on the assembly that is contacted to check for performance of circuitry connected to it - Noncoductive Epoxy : A resin that is used to conduct heat rather than electricity - Nonpolar Compound : Chemicals that do not become conductive in solution - Nonwetting : The condition which results when solder was not accepted or did not move onto a surface
- Open : On board level: A non-continuity situation where continuity is required. May be caused by copper defects or solder defects (e.g. lacking coplanarity of leads) When soldering: An air gap exists where electrical continuity is expected. Solder has not bridged between two metal points or parts have separated - Organic solvents : solvents that contain carbon atoms in their molecular structure. - Organic-Activated : An old classification of fluxes using organic acids for activation - usually with water soluble residues - Outgassing : Emission of gas and/or vapors from a PCB or component during heating or when exposed to low pressure - Oxide : a compound of oxygen and one other element - Ozone : the earth’s natural shield against dangerous levels of UV radiation from the sun.
- Pad : The metal on the surface of a substrate or PWB through which the hole is drilled for a via connection, or the conductor point designed to be a test probe landing area. - Peel-Away Speed : The speed of lifting the stencil from the PCB after printing - Percent Area Coverage : The percentage of footprint area that has been covered by the printing process - Pick & Place : The method of certain placement equipment of picking components (mechanically or by vacuum) from tapes or magazines (etc.) and placing them in the correct position of the PCB. - Pitch : The distance between a feature and the adjacent feature on the same component. - Placement Machine : (Automatic) equipment used to mount components onto a PCB - Plastic flat-pack : A FP with the body made with plastic - PLCC (PCC) : Plastic Leaded Chip Carrier (Plastic Chip Carrier). A plastic IC package for surface mounting applications that has leads, generally "J" leads, on all four sides. - Poise : Unit of viscosity. It is one for a liquid that requires the force of one dyne to be moved from a one square centimeter surface area with velocity of one centimeter per second. - Polymers : A class of chemical whose main feature are the long chains of molecules. Epoxies and other resins are polymers - Preheat : it evaporates the solvent component of the flux (95 to 99% of its action takes place right in the wave). Its main function is to raise the board’s temperature. - Preproduction Test Board : An assembly that is to determine whether a sub-contractor is able to build the product in large runs. - Primer : A first coating that is applied to improve the holding strength of an adhesive - Print Head : That part of a printer that contains all the elements for holding the squeegee - Printed Circuit Board [PCB] : General designation of the support structure of an electronic assembly. Also referred to as a PWB [Printed Wire Board]. It consists essentially of a dielectric material (the substrate) onto which metallic conductors have been applied (etched copper foil and additional plating) to reflect the electronic circuit. - Pyrometer : IR detector to measure the temperature of the board
- Quad flat pack : A component package for ICs that utilizes leads (gall-wing) on all four sides
- Radial Component : Those components that have the leads attached radially, i.e. at the ends - RCC : A chip carrier [Rectangular Chip Carrier] with unequal length and width dimensions. - reflow soldering : A process in which solder, either in paste or solid form, is placed between the component lead and land, before soldering heat is applied. When sufficient heat to melt the solder is applied, the solder forms the connection. - Repair : The correction of a visual or functional defect. The process of changing a non-functional unit into a working unit - Resin : A synthetic polymer of high-molecular-weight - Resolution : In vision systems, the number of pixels of a camera or screen image. The higher the number of pixels, the better the resolution - however, for processing the number of pixels may put a strain on the computer's ability - Rework : Efforts to remedy process defects - Rheologie : A term of general reference for all those characteristics which relate to flow, viscosity and surface tension. The collective denotation for properties relating to the flowing behavior of liquids - Rosin : a major ingredient in flux. It is composed of several related acids and may be harvested from pine trees or chemically produced - Rosin Flux : A flux consisting of powdered colophony dissolved in some alcohol - Rotational Error : Angular deviation of a component from the required position when placing it.
- Sagging : After printing of solder paste, the slow loss of definition of the print as the board rests under the influence of gravity. - Saponifier : A chemical that changes organic material (e.g. oil, fat, colophony not soluble in water) into a chemical soap (soluble in water) - SCC : A chip carrier [Square Chip Carrier] with a square body. - SCC : Solder Column Connector. Form of the BGA-family, where short solder columns are used instead of the spherical balls. - Screen : In screen-printing the weave (metal or plastic) onto which a pattern is created by means of an epoxy coating (emulsion) which determines the print. The screen is stretched into a frame prior to printing. - Screen mesh : The woven fibers or metal wires used to support the emulsion and allow the solder paste to flow through for printing. The diameter and spacing (number per inch) of the fibers determine the "size" of the mesh. - Screen-Printing : A printing process that presses paste through a screen onto the PCB. - Screenability : The qualitative characteristic of the solder paste with respect to how easy it spreads and prints without any detrimental behavior. - Semiaqueous Cleaning : A cleaning method employing a first chemical process that changes soils on the assembly into water soluble residues and then washing those off by a water rinse process - Shadowing : A general condition in IR and some Convection Reflow equipment where parts do not receive the intended amount of energy for heating. This can occur due to direct blocking of radiation or due to laminar convective flow - SMA : Surface Mounted Assembly. Any electronic assembly or module that is manufactured with surface mounted components and using surface mount technology. - SMC (SMD) : Surface Mounted Components (Surface Mounted Devices). Any electrical or mechanical component that can be attached to the surface of a substrate with solder. - SMT : Surface Mount Technology. The technology used to manufacture electronic assemblies using components that are soldered directly to the substrate or PWB. - Snap-Back : The action of a screen or stencil to return into its original position after having been deflected by a squeegee during non-contact printing - Snap-Off : The action of return during non-contact printing of the screen just after the squeegee passes. - Snap-Off Distance : The distance setting between a screen or stencil during non-contact printing. - SO : Small Outline. A package resembling a flat pack with leads on only two sides. - Soft soldering : is characterized by a more-or-less arbitrary limit for the value of the melting point of the third metal or alloy: in particular 450°C (approx. 840°F) - Soft Water : Water that is naturally 'soft' or that has gone through a water-softening process. Such a process replaces 'hard' ions by 'soft' ions - SOIC : Small Outline Integrated Circuit. A plastic IC package for surface mounting applications that has leads on two opposite sides. - SOJ : A plastic IC package with "J" leads on two sides. It resembles a plastic DIP, except for lead spacing and forming. - SOL (SOW) : Small Outline - Large (Small Outline - Wide). SO generally refers to a package that is approximately 150 mils wide, while SOL/SOW refers to packages that are approximately 300 mils wide. - Solder : Relatively low melting metals or alloys [< 450 ºC] which are used to join relatively high melting metals. - Solder Alloy : this is given according to the standard QQ-S-571 - Solder Ball : Individual spheres of solder found on the assembly after soldering. Their mechanism of creation is different in flow (wave) soldering and reflow soldering. - Solder dip : taking the PCB to the solder by a dipping movement of the conveyor - Solder Fillet : The entirety of solidified solder between pad and lead - Solder Joint : A conductive joint which was created by soldering between the conductors of the PCB and the leads (or metallizations) of the component. - Solder Paste : A mixture of small solder particles in a flux and viscosity moderating solvent. - Solder paste, also called solder cream : consists mainly of solder particles and flux and is a rather complicated concoction of these elements and is distinguished according to: Metal content - Solder Slump : The flow of solder paste after the printing process that occurs under the force of gravity - Solderability : Evaluations of the capability of any surface, either component or PWB land, to wet with molten solder. - soldering : is that process in which two metals, each having a relatively high melting point, are joined together by means of a third metal or alloy having a relatively low melting point - Solids Content : The amount (by weight) of non-volatile chemicals in a flux - Solidus : highest temperature at which a metal is completely solid. - Solvent Extraction Method : A cleanliness test method that uses a mixture of alcohol and water to remove polar contaminants from the soldered assembly. By measuring the change in conductivity of the fluid a deduction is madeabout the soil removed from the product - SOT : Small Outline Transistor. A plastic leaded package for diodes and transistors used in surface mounting applications. - Spray fluxing : a flux application which employs a method of producing tiny solder droplets and directing them onto the bottom of the PCB. it is the only system that can control the amount of flux deposited and newer spray fluxers always provide fresh flux. - Spring-Loaded Probes : Spring-loaded needles of a bed-of-needle fixture that contact the assembly at pre-determined points for test purposes. - Squeegee : A blade used to press paste or adhesive through a screen or stencil during printing - Squeegee Downstop : The distance, which the squeegee has to traverse in z-direction to reach the stencil or screen - Squeegee Pressure : The pressure exerted by the squeegee on the stencil during printing - Squeegee Speed : The velocity with which the squeegee travels over the stencil or screen during printing - Squeegee Stroke : The distance that the squeegee travels over the stencil during printing - Stencil : A foil (mostly metal) into which apertures are made to reflect the pattern to be printed and which is used for printing purposes - Step-and-Repeat : The repetition of the same pattern on the PCB - Step-Down Stencil : A stencil that has areas, which have been thinned out to allow for thinner solder paste deposition when compared to the thicker areas - Substrate : The base material which is used to support the printed interconnections and the components of the electronic assembly. - Surface Insulation Resistivity [SIR] Test : A test which measures the level of resistivity of a dielectric (e.g. FR-4) between conductive parts [comb pattern]. - Surface Mount Device : A component intended for use on the surface of a PCB - Surface mounted : a method to supply an assembly with components where the components are mounted to the board without the use of through-holes. leadless components ("leadless" is a misnomer; plenty of leadless components have leads)
- Tape & Reel : A presentation method in placement equipment where the component is offered in cavities of a tape. The tape employs cavities to house the component. In order to ensure safety of operation, the cavities are covered by a continuous tape and the whole is rolled up in a spool similar to an old fashioned film reel - Temperature Profile : The record of time vs temperature as measured by thermocouples placed on an assembly during a pass through a soldering machine - Test Coupon : A part of an assembly used for certain testing (e.g. SIR tests) - Test Frame : A holding fixture that properly presents a given assembly to a testing procedure. - Test Pattern : A special area of the board designed for special testing reasons (e.g. SIR tests utilize comb patterns). Such patterns are an integral part of the assembly - or may be break-away features. - Thermal Bridge : a small amount of molten solder to couple in the energy from the tip of a soldering iron into the base metal of the joint to be created during hand soldering - Thermal Expansion : The absolute geometric increase or decrease due to a change in temperature. It is equal to the TCE multiplied times the change in temperature. - Thermal Resistance : The ability to resist the flow of heat from a hot region to a cooler region. For ICs, it indicates the increase in silicon temperature depending upon the power dissipated in the silicon. It is measured in ºC per watt. - Thermocouple : A device used to measure temperatures consisting of two wires of different metals that due to their potential differences produce small currents on contact during temperature changes - Thixotropy : Usually applied to the change in viscosity (hysteresis) of a liquid under shear stress and relaxation - Through via : A via or connection between the two outside layers of a PWB. - Through-Hole : In double-sided PCBs or multilayers holes which connect conductors of layers. The holes are drilled and then plated. - Tinning : In soldering: the process of coating a surface with solder - To set : To change a liquid resin into its polymerized state - Tombstoning : A soldering defect that exhibits wetting of only one end of a component. Usually the component is lifted by the wetting force in combination with the solder's surface tension - Tube Feeder : A presentation method in placement equipment where the component is offered in tubes. The components usually slide out of the tube into an area for easy pick-up by the placement head. Mechanical means for advancing the components are sometime employed (vibration, pusher, spring) - Type I SMA : A surface mount assembly that only uses surface mounted components. Joining is mostly achieved by reflow solder process only. However, single-sided assemblies are also flow soldered and occasionally double-sided ones as well. It can have components on one or on both sides. - Type II SMA : A surface mount assembly that uses traditional (through-hole) components on one side and SM components on the other. For joining one usually uses a wave solder process to attach through-hole components inserted from the top of the board and surface mounted components attached to the bottom of the board with adhesives. - Type III SMA : SM assemblies that have traditional (through-hole) components and SM components together on at least one side of the assembly. Several soldering processes are generally required to achieve proper joining.
- Universal-Grid Access Fixture : A device for testing bare board inner layers or backplanes - Unpopulated Board : A bare board (PCB) that exhibits all pads, layers and metallizations in a fucntional way, but has not been equipped with components.
- Vacuum Fixture : A holding device for assemblies or PCBs that employs vacuum. - Vacuum Pick-up : A method of picking up components that uses vacuum tips to pick-up, hold and move the components - Vapor Phase : a heat transfer method based on the condensation principle - Vapor-Phase Soldering : A reflow method using a liquid with high boiling point. The vapor is the actual heat transfer medium. - Via : An electrical connection between two or more conductor layers of a multilayer substrate or printed wiring board. - Viscosity : The resistance of a liquid to be moved. It depends on the velocicty of flow. - Vision : The use of cameras, imaging systems and image analyses in placement equipment, printers etc. to enhance accuracy. - Void : A bubble or cavity within a solder joint
- Water Separator : A device used to remove water from an (organic) solvent system - Wave fluxing : a fluxing method employing a wave (flow) of flux. It is not so popular today because it applies too much flux and loses even more solvent than foam fluxing. It plays a role whenever hot boards (e.g., solder-cut-solder) have to be fluxed. - wave soldering : See: flow soldering - Wetting : The formation of a relatively uniform, smooth, unbroken, and adherent film of solder to a base metal. - Wetting Angle : The angle which after wetting is formed between the surface of the solder meniscus and the base metal (PCB or Component). The wetting angle may best be measured using a cross sectioning technique. Good wetting would exhibit a wetting angle from 0 to 30 °. Satisfactory wetting is still present with wetting angles between 30 and 60 °. Whether a wetting angle between 60 and 90 ° is still acceptable, must be decided by the user case by case. At 90 ° the solder comes to a stand-still. Wetting angles of more than 90 ° usually indicate a de-wetting condition. - Work Life : One of the 'windows' of paste referring to the time a paste may be left on the stencil prior to ist deterioration - Worknest : The plate that holds the PCB during printing


- Z-Stroke : Movement of the placement-head of an automatic placement machine in the third direction of an x-y-z coordinate system