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Glossary of terms for printed circuit board production

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Active component: Semiconductor devices that change their charactertics when placed in a powered circuit on a PCB.

Annular Ring: The width of a conductor pad on a PCB that surrounds a drilled hole.

Artwork: Normally held at the bare PCB supplier and is used in PCB production. Normally the PCB data is printed onto clear film and is produced from the gerber data.

Aspect Ratio: This is the ratio between the printed circuit board thickness and the smallest drilled hole size of the PCB.

Automated test equipment (ATE):  Equipment that tests the PCB normally in its assembled state for functionality.

Ball Grid Array (BGA): A surface mount package in which solder balls on the underside of the device are soldered to the printed circuit board pads.

Bare PCB: An unassembled printed circuit board.

BBT: Bare Board Test. A test carried out on the PCB for continuity before any parts are assembled to the PCB.

Bill of materials (BOM):
A listing showing all the components with manufacturer’s part numbers and normally PCB references in order for the printed circuit board to be assembled.

Chip on Board (COB): A wafer of silicon is assembled directly to the printed circuit board by the use of solder or conductive adhesive.

Component side: The side of a PCB on which the components are fitted

Coating: A thin layer of resin is applied to the PCB to protect the PCB from its environment.

Coefficient of thermal expansion (CTE): The ratio of dimensional change of the PCB to the original dimension when the temperature changes. Sometimes expressed as stretch or shrink of the bare PCB.

Copper Foil (Base Copper Weight): Normally the copper weight is expressed in oz per square foot typically 0.5, 1 or 2 oz depending on the current carrying nature of the PCB.

DFSM: Dry Film Solder Mask. Used when making the bare PCB.

DIP: Dual in line package were two rows of pins on the opposite side of a device make the connection with the printed circuit board.

Double sided assembly:
PCB assembly with components on both side of the bare PCB.

DRC: Design Rule Check. Carried out to make sure the data given to manufacture a PCB follows good practise before the artworks are made to produce the printed circuit board.

Dry-Film resist: Photosensitive film is used on the copper foil of the PCB. This film is resistant to the chemicals used in PCB manufacture.

Edge Connector:
A connector on the edge of a printed circuit board quite often plated with gold to connect the PCB with another PCB or electronic device.

Edge Clearance: The smallest distance a component or track is from the edge of a PCB.

Electroless Deposition: The coating of normally Gold or Silver on to the track of a PCB by the reduction of metal ions in a chemical solution without using electrodes.

Electroplating: The opposite to the above electrodes are used to deposit the plating from a electrolytic solution onto a PCB track using a DC current.

Fine Pitch:
Mostly used when describing surface mount components that had a lead pitch of 25 mils or less.

Flux: A material that remove oxides and enables wetting of the a metal with solder.

FR4: The most common base material a PCB is made from. Made from woven glass fibre impregnated with epoxy resin.

Gerber File: Data used to enable photo plotting of the artwork to produce a PCB.

Ground Plane: A layer normally within a multilayer PCB that provides a common ground reference with the circuit.

Hermetic: Airtight sealing

In circuit test: Electrical test of  part of a circuit on a PCB,

Hole Density: The amount of holes on area of PCB.

Legend: The print on a PCB showing the location of components and orientation. Can also be used to display a logo or part number of the printed circuit board.

Minimum conductor width: The minimum tack width specified on a PCB that is producible.

Multilayer PCB: A PCB made up by laminating thin PCBS each with a different part of a circuit on each and interconnecting them with via holes. 4-16 layers are common.

NC Drill:  Numeric Control machine used to drill the holes in a PCB.

Netlist: Lists  the parts and their connections to each on a printed circuit board.

Pad: The area of exposed track by which a component can be soldered to the PCB.

PCB: Printed circuit board. Also known as Printed wiring board (PWB)

Pick and Place: A manufacturing process when assembling surface mount components to a PCB. The component is selected and placed onto a specific location on to the printed circuit board by means of a dedicated machine.

Pitch: The centre to centre spacing of a track or pad on a PCB.

PTH (Plated through Hole): A hole through a PCB in which an electrical connection is made to the other side of the hole thus connecting the two sides of the PCB together.

Plating Resist: Other wise known as solder resist which is the normally green material used to stop the PCB being covered with solder. This also provides electrical insulation to the tracks.

Reflow Soldering:
The heating of solder paste through an oven to solder a component to the PCB.

Screen-printing:
A metal screen is produced from the gerber data in order to print onto the pads on the PCB solder paste before the pick and place process.

Small Outline Integrated Circuit (SOIC):
An integrated circuit with two rows of parallel pins in a surface mount format.

SMD: Surface mount Device

SMT: Surface mount technology

Solder Bridge: Solder that connects two parts of a circuit on a PCB that should not be electrically connected.

UL: Underwriters Laboratories an American approval carried by many bare PCB manufacturers.

Via: A plated hole used for the interconnection normally of the two sides of a PCB or can be buried within side a multilayer pcb to connect inner layers electrically.

Wave Soldering:
A machine is used to coat the solder side of a PCB with molten solder speeding up the assembly process.