A-stage The condition of low molecular weight of a resin polymer during which the resin is readily soluble and fusible.

absorbtivity The percentage of infrared absorbed by a substrate as compared with the total incident infrared.

acceptance tests A set of tests performed to determine the acceptability of a board or assembly.

access holes A series of holes in successive layers, each set having a common center or axis. These holes in a PCB provide access to the surface of the land in one of the layers of the board.

accuracy (1) The difference between measured results and target values. (2) The difference between the measured result and the target value.

activated Condition in which a mixture has a higher chemical activity than normally found.

activated flux Rosin- or resin-based flux, with one or more activators added.

activating A treatment that renders nonconductive material receptive to electroless deposition.

activator Additive in a flux that aids the flux’s cleaning ability.

active component Electronic components such as transistors and diodes that can operate on an applied signal, changing its basic character.

active temperature The ratio of the actual temperature to the melting temperature of solder.

adaptor A device that locates and supports products to be tested.

additive process A process for obtaining conductive patterns by the selective deposition of conductive material on unclad base metal.

adhesion The force of attraction between unlike molecules.

adhesive A material used for bonding, sealing, and joining laminates, films, foils, coils, and conductors.

aerosol Liquid particles small enough to be airborne.

air leveling A process used in solder dipping of bare copper circuitry in which high-velocity air is used to blow solder clear from plated-through holes and minimize solder thickness. Also known as hot air leveling (HAL) and hot air solder leveling (HASL).

alloy A combination of two or more elements whereby at least one is a metal.

ambient The surrounding environment that contacts the system, assembly, or component of interest.

ambient temperature Dry bulb temperature of the surrounding atmosphere.

amorphous Condition where atoms and molecules of a material are not arranged in a definite pattern or form (non-crystalline). Amorphous materials typically lack certain well-defined physical properties such as a distinct melting point or boiling point. These materials usually have poor thermal and electrical conductivity properties. Examples include glass, carbon, and rosin.

analog circuits Circuits that provide a continuous relationship between input and output.

analog functional testing A functional testing of a PCB at board level. Various analog test signals are applied to the board through a switch or multiplexor. Most effectively used on analog and hybrid boards.

analog in-circuit testing A system of testing that measures component values on a loaded PCB before power is applied. Best used for analog or hybrid boards.

analog test A functional test of a PCB at board level in which signals are applied through a switch to pinpoint outputs.

angle of attack The angle between the squeegee face and the plane of the stencil.

anion A negatively charged atom or radical.

anisotropic adhesive A material filled with a low concentration of large conductive particles designed to conduct electricity in the Z-axis but not the X- or Y-axis. Also called a Z-axis adhesive.

annotation Text or legend pertinent to a board design. Text appears off the board area and consists of lettering and symbols, while legend appears on the board.

annular ring The portion of conductive material completely surrounding a hole.

anode Positive pole of a plating cell from which negatively charged ions leave the plating solution by conversion back to their parent atoms or atom groups.

ANSI American National Standards Institute

anti-static material An electrostatic discharge (ESD) protective material having a surface resistivity greater than 10⁹ but not greater than 10¹⁴ ohms per square centimeter.

aqueous cleaning A water-based cleaning methodology that may include the addition of the following chemicals: neutralizers, saponifiers, surfactants, dispersants, and anti-foaming agents.

array A group of elements arranged in rows and columns.

artwork The image of the PCB conductive pattern that then generates the artwork master. It is generally scaled at either 3:1 or 4:1, but can be made at any scale. Accuracy in scaling is imperative because PCBs will be less accurate than artwork by virtue of the scale factor.

artwork generation The process of transferring the idea for a circuit pattern into a precise, reproducible artwork master for mass production manufacturing. Generation can be executed by the traditional manual drafting and photographic technique or via electronic means.

artwork master The photographic film or plate that embodies the image of the PCB pattern, usually on a 1:1 scale. Commonly a sensitized gelatin plate, but for high precision work, a chromium plate can be used.

artwork registration system Equipment of various sizes and complexities used to achieve artwork registration. Accuracy, repeatability of precision tolerances, loading and unloading simplicity, and speeds are significant aspects.

aspect ratio A ratio of the PCB thickness to the diameter of the smallest hole.

assembly Refers to inserting, placing, and joining the components or subassemblies to a bare board surface.

assembly drawings Documents that depict the physical relationship of two or more parts, their combination and accompanying assemblies.

ASTM American Society for Testing and Materials

atom Smallest particle of an element that can enter into a chemical combination.

auto-ignition point Temperature where vapor from a material in air will burst spontaneously into flame.

automated optical inspection (AOI) Test fixture method in which printed circuit boards are checked at bare-board, pre- or post-soldered stages of assembly by optical means.

automatic component insertion Insertion of components into a through-hole printed circuit board by automatic means.

automatic debridging A process in which a hot air knife removes excess solder and exposes poor solderability conditions. Used largely in stress testing and wave soldering.

automatic test equipment (ATE) Equipment designed to automatically analyze functional or static parameters in order to evaluate performance degradation. It may also be designed to perform fault isolation.

automatic test generation (ATG) Computer generation of a test program based solely on the circuit topology, requiring little or no manual programming effort.

available hours The actual number of hours available in a shift after taking into consideration breaks, meetings, etc.

axial leads Leads coming out of the ends of discrete component or device along the central axis.

azeotrope A mixture of two or more polar and non-polar solvents that behaves like a single solvent to remove polar and non-polar contaminants. The boiling point is lower than its individual components and reaches one boiling point temperature as if it were a single component solvent.