PCB Basics

Circuit board vocabulary
Blind via Connects outer layer with inner layer; exposed only on one side of the board.
Buried via Connects internal layers without being exposed on either surface.
Chip on board Integrated circuits glued and wire-bonded to boards (foregoing packaging) culminating in a chip with fine wires bonded to both it and landing pads.
LPI Liquid photoimageable solder mask. For purpose of controlling deposition, a mask is applied through the use of photographic imaging techniques.
Plane Copper layer connected to the ground that covers most of the board layer it inhabits.
Substrate Surface adhesive substance spread for bonding or coating, this material (most commonly FR-4) is a non-conductive carrier of copper traces.
Surface finish Selected by customer; assembly component process determines plating for top and bottom layers; factors considered: application and shelf life.
Trace Copper strip used for carrying signal between two points on a circuit board.
Via Plated-through hole between one or more layers transferring heat from top layer to inner and/or bottom layers connected to internal ground plane.
Heavy copper At least three ounces of total copper used in the inner and outer layers.
Etch-down Start with one ounce base copper than desired finished copper weight and plate up to the target copper weight.
Plate-up Start with Cu weight significantly less than target and repeat image through plating processes until achieving target Cu weight.
Conductor A single conductive path in a conductive pattern.
Silkscreen Non-conductive layer.
Dielectric Non-conductive insulating layer between conducting Cu layers to keep them isolated from one another.
Component Part(s) used to perform a design function.
Annular The area of the pad surrounding the via.
Fiducial Provides common measurable point for component mounting in regards to a land pattern.
Tented via Via covered with soldermask that bridges over the opening.
Copper plating Electro-chemical process where layer of copper is deposited on metallic surface by electric current.
Ionic contamination Ionic residue that interfere with reliability and functionality.
Laminates Contains inner prepreg like a copper-clad laminate.
Prepreg Base material reinforced with resin or polyimide that is partially cured.
Multilayer pressing use of high temperature and high pressure to make the semi-cured sheet heat melt, and make it flow, and then transformed into a cured sheet.
Controlled impedance Regulation of resistance exerted by signal traces.
HDI High density interconnects PCBs have tracks and/or vias with a width or diameter of under 152 micrometers.
FR-2 Phenolic paper or phenolic cotton paper, paper impregnated with a phenol formaldehyde resin.
FR-4 Woven fiberglass cloth impregnated with an epoxy resin. Low water absorption (up to about 0.15%), good insulation properties, good arc resistance.
Aluminum board Metal core board or insulated metal substrate (IMS), clad with thermally conductive thin dielectric - used for parts requiring significant cooling.
Flexible substrates Standalone copper-clad foil; can also be laminated to a thin stiffener.
Polyimide Polyimide is a flexible material and is used for flex and rigid/flex boards, while FR4 is for rigid PCBs.
Electrical resistance Measure of opposition circuit gives to flow of electric current.
Ground plane Electrically conductive surface, usually connected to electrical ground; acts as the return path for most components and current in the circuit.
Transmission line Connects moving signals from their transmitters to their receivers on PCB.
Relative permittivity Dielectric constant (Dk) measures capacitance between pair of conductors in a laminate and that pair of conductors in a vacuum.
Dissipation factor Loss tangent (Df) measures signal attenuation as signal propagates down transmission line.
Ball grid array Surface mount chip package that uses a grid of solder balls as its connectors.
Tg Glass transition temperature of polymer is temp at which material changes from a relatively stiff, "glassy" state to a more pliable or softened state.
Propagation delay One-way time required by a signal to travel on a particular PCB trace.
Capacitor Device used to store an electric charge, consisting of one or more pairs of conductors separated by an insulator.
Via fill Via hole completely filled; hole closed with conductive or non-conductive epoxy material or copper plating.
Solder mask Thin coating of polymer required to protect board from any uncertain short circuits and maintaining the integrity of the copper traces.
Pre-baking Pre-treatment to dry boards and moisture-sensitive components before assembly to remove moisture from inside or on surface.
Peel strength Bond strength between the copper conductor and the dielectric material.
HATS Highly accelerated thermal shock; air-to-air thermal cycling procedure that quickly heats and cools test vehicles at min/max temperatures.
IST Interconnect stress testing; electrical charge to heat the coupon and stress the vias.
Fine lines / spaces Boards with 2-5 mil line and spacing.
Heatsink PCBs that ensure cooling by absorbing and dissipating heat from electronic components.
Resin Starvation Voids; area with insufficient resin needed to completely wet out reinforcement.
Td Decomposition Temperature is the temperature at which a PCB material chemically decomposes.

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Domestic PCB Fabricator

Bare printed circuit board manufacturer (NAICS: 334412)
Romulus, MI (since 1985)
(734) 941-8100

BREAKING: DPA for PCBs: Defense Production Act prioritizes domestic circuit boards.

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