Explanation of PCBA terms

2022-05-07 416

Accuracy: the difference between the measurement result and the target value.

Additive Process: a method of manufacturing PCB conductive wiring by selectively depositing conductive materials (copper, tin, etc.) on the board layer.

Adhesion: similar to the attraction between molecules.

Aerosol (Aerosol): Liquid or gas particles small enough to be airborne.

Angle of attack: the angle between the screen printing scraper and the screen printing plane.

Anisotropic adhesive (anisotropic adhesive): An electrically conductive substance whose particles only pass current in the Z-axis direction.

Annular ring: the conductive material around the borehole.

Application specific integrated circuit (ASIC): a circuit customized by customers for special purposes.

Array: A group of elements, such as tin ball dots, arranged in rows and columns.

Artwork (wiring diagram): the conductive wiring diagram of PCB, which is used to produce the original photo. It can be made in any scale, but it is generally 3:1 or 4:1.

Automated test equipment (ATE automatic test equipment): in order to evaluate the performance level, the equipment designed for automatic analysis of functional or static parameters is also used for fault isolation.

Automatic optical inspection (AOI): on an automatic system, a camera is used to inspect models or objects.

Ball array (BGA ball grid array): a packaging form of integrated circuits, in which the input and output points are tin balls arranged in a grid pattern on the bottom surface of components.

Blind via: the conductive connection between the outer layer and the inner layer of PCB, which does not continue to the other side of the board.

Bond lift-off: a fault that separates the solder pins from the pad surface (circuit board substrate).

Bonding agent: an adhesive that bonds a single layer to form a multilayer board.

Bridge (tin bridge): Solder that connects two conductors that should not be electrically connected, causing a short circuit.

Buried via: conductive connection between two or more inner layers of PCB (i.e. invisible from the outer layer).

CAD/CAM system (Computer Aided Design and Manufacturing System): Computer Aided Design (CAD) is the use of special software tools to design the printed circuit structure; Computer-aided manufacturing transforms this design into an actual product. These systems include large-scale memory for data processing and storage, input for design and creation, and output devices for converting stored information into graphics and reports.

Capillary action: It is a natural phenomenon that molten solder flows against gravity on the surfaces of closely spaced solids.

Chip on board (COB board): a hybrid technology, which uses the chip components glued face up, and is traditionally specially connected to the substrate layer of the circuit board through flying wires.

Circuit tester: a method of testing PCB in mass production. Comprises a needle bed, component pin footprints, guide probes, internal traces, loading boards, empty boards and component tests.

Cladding (covering layer): A thin layer of metal foil is bonded on the board layer to form PCB conductive wiring.

Coefficient of the thermal expansion: when the surface temperature of the material increases, the measured expansion rate of the material per degree of temperature (ppm).

Cold cleaning (cold cleaning): an organic dissolution process, in which liquid contacts to finish the residue removal after welding.

Cold solder joint: a kind of solder joint reflecting insufficient wetting, which is characterized by gray and porous appearance due to insufficient heating or improper cleaning.

Component density: the number of components on the PCB divided by the area of the board.

Conductive epoxy (conductive epoxy resin): a polymeric material that is made to pass through an electric current by adding metal particles, usually silver.

Conductive ink (conductive ink): Adhesive used on thick film materials to form PCB conductive layout.

Conformal coating: A thin protective coating applied to PCB conforming to the assembly shape.

Copper foil (copper foil): a kind of negative electrolytic material, a thin, continuous metal foil deposited on the base layer of circuit board, which serves as the conductor of PCB. It is easy to adhere to the insulating layer, accept the printed protective layer, and form a circuit pattern after corrosion.

Copper mirror test: a kind of flux corrosion test, which uses a vacuum deposited film on the glass plate.

Cure (Bake Cure): Changes in the physical properties of materials, through chemical reactions, or pressure/non-pressure reactions to heat.

Cycle rate: a component placement term used to measure the machine speed from taking, positioning and returning on the board, also called test speed.

Data recorder: a device that measures and collects the temperature from the thermocouple attached to the PCB at specific time intervals.

Defect: A component or circuit unit deviates from the normally accepted characteristics.

Delamination: the separation of layers and the separation between layers and conductive coating.

De-soldering: Disassemble the welded components to repair or replace them. The methods include: sucking tin with a tin sucking tape, vacuum (solder suction pipe) and hot drawing.

Dewetting: The process of covering the melted solder first and then taking it back, leaving an irregular residue.

DFM (Design for Manufacturing): A method of producing products in an efficient way, taking time, cost and available resources into account.

Dispersant: A chemical that is added to water to increase its ability to remove particles.

Documentation: information about assembly, explaining basic design concepts, types and quantities of components and materials, special manufacturing instructions and versions. Three types are used: prototype and small quantity operation, standard production line and/or production quantity, and those contracts that specify actual drawings.

Downtime: the time when the equipment does not produce products due to maintenance or failure.

Durometer: Measure the hardness of rubber or plastic of scraper blade.

Environmental test: one or a series of tests to determine the total external influence on the structural, mechanical and functional integrity of a given component package or assembly.

Eutectic solders: Two or more metal alloys with melting points. When heated, eutectic alloys directly change from solid to liquid without going through plastic stage.

Fabrication (): the empty board manufacturing process after design and before assembly. The separate processes include lamination, metal addition/subtraction, drilling, electroplating, wiring and cleaning.

Fiducial (Reference Point): A special mark integrated with the circuit wiring diagram, which is used for machine vision to find out the direction and position of the wiring diagram.

Fillet (fillet): the connection formed by solder between the pad and the component pins. That is, solder joints.

Fine-pitch technology (FPT close pitch technology): The pin center spacing distance of surface mount package is 0.025″(0.635mm) or less.

Fixture: a device that connects PCB to the center of processing machine.

Flip chip (flip chip): A leadless structure, which generally contains circuit units. Designed to be electrically and mechanically connected to the circuit through an appropriate number of solder balls (covered with conductive adhesive) on its surface.

Full liquidus temperature: the solder reaches the temperature level of liquid state, which is suitable for good wetting.

Functional test: simulate its expected operating environment, and test the electrical equipment of the whole assembly.

Golden boy: a component or circuit assembly, which has been tested and known to meet the technical specifications, is used to test other units by comparison.

Halides: Compounds containing fluorine, chlorine, bromine, iodine or astatine. It is the catalyst part of flux, which must be removed because of its corrosiveness.

Hard water: The water contains calcium carbonate and other ions, which may gather on the inner surface of clean equipment and cause blockage.

Harder (Hardener): a chemical added to a resin to make it cure in advance, that is, a hardener.

In-circuit test: a component-by-component test to check the placement and orientation of components.

Just-in-time (JIT just on time): By supplying materials and components to the production line directly before putting into production, the inventory can be reduced to a minimum.

Lead configuration: a conductor extending from the component, which serves as a mechanical and electrical connection point.

Line certification: confirm that the production line sequence is controlled and reliable PCB can be produced according to the requirements.

Machine vision: one or more cameras, which are used to help find the component center or improve the component mounting accuracy of the system.

Mean time between failure (MTBF mean time between failure): the average statistical time interval of expected possible running unit failures, usually calculated every hour, and the results should indicate the actual, predicted or calculated results.

Non-wetting: a condition in which solder does not adhere to the metal surface. Due to the pollution of the surface to be welded, the non-wetting feature is the visible exposure of the base metal.

Omegameter (Omega meter): an instrument used to measure the residual ions on the surface of PCB. After dipping the assembly into the mixture of alcohol and water with known high resistivity, the resistivity drop caused by the residual ions is measured and recorded.

Open (open circuit): two electrically connected points (pins and pads) become separated. The reason is either insufficient solder or poor coplanarity of the connecting point pins.

Organic activated (OA): a kind of flux system with organic acid as active agent, which is water-soluble.

Packaging density: the number of components (active/passive components, connectors, etc.) placed on the PCB; Expressed as low, medium or high.

Photoploter (photo plotter): basic wiring diagram processing equipment, which is used to produce original PCB wiring diagram (usually actual size) on photographic negative.

Pick-and-place (pick-and-place equipment): a programmable machine with a mechanical arm that picks up components from an automatic feeder, moves them to a fixed point on the PCB, and puts them in the right direction and position.

Placement equipment: a machine that combines high-speed and accurate positioning to place components on PCB. It can be divided into three types: mass transfer of SMD, X/Y positioning and online transfer system, which can be combined to adapt components to circuit board design.

Low soldering: the process of putting surface mount components into solder paste to achieve connection through various stages, including preheating, stabilizing/drying, reflowing peak and cooling.

Repair: the action of restoring the function of defective assembly.

Repeatability: the process ability to return to the characteristic goal. An index to evaluate the processing equipment and its continuity.

Rework (Rework): a repeated process of bringing the incorrect assembly back to meet the specifications or contract requirements.

Rheology (Rheology): Describe the flow of liquid, or its viscosity and surface tension characteristics, such as solder paste.

Saponifier: an aqueous solution of organic or inorganic main ingredients and additives, which is used to promote the removal of rosin and water-soluble flux by, for example, dispersible detergent.

Schematic: A diagram that uses symbols to represent circuit layout, including electrical connections, components and functions.

Semi-aqueous cleaning: a technology involving solvent cleaning, hot water washing and drying cycle.

Shadowing: In infrared reflow soldering, the component body blocks the energy from some areas, resulting in the phenomenon that the temperature is not enough to completely melt the solder paste.

Silver chromate test: A qualitative inspection of the existence of halogenated ions in RMA flux. (RMA reliability, maintainability and availability)

Slump (slump): the diffusion of solder paste, adhesive and other materials before the template is cured after screen printing.

Solder bump (solder ball): The spherical solder material is bonded to the contact area of passive or active components, and plays the role of connecting with circuit pads.

Solderability: The ability of a conductor (pin, pad or trace) to melt wet (become solderable) in order to form a strong connection.

Soldermask (Solder Mask): the processing technology of printed circuit board, in which all surfaces except the connection points to be soldered are covered with plastic coating.

Solids: the weight percentage of rosin in flux formula, (solid content)

Solidus (Solidus): The temperature at which the solder alloy of some components begins to melt (liquefy).

Statistical process control (SPC): use statistical techniques to analyze the process output, and use the results to guide actions, adjust and/or maintain the quality control status.