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Printed Circuit Board Technical Terms: Comprehensive Guide Part I


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Key PCB Terms and Definitions

Understanding printed circuit boards (PCBs) is crucial for anyone involved in electronics and manufacturing. This guide delves into the key technical terms that form the foundation of PCB design and production.

Acid Trap

A feature of copper tracking which captures excess etching chemistry during processing, resulting in under or over etching.

Analogue Circuit

A type of circuit where the variation of the voltage is the signal quantity. These circuits have short signal paths with large areas of screening.

Annular Ring

The width of the copper pad area that remains after a hole is drilled through a pad.

Annular Ring


The shape and size of the tool which draws or flashes pads or tracks respectively. Historically, tracks and pads were created by shining a light through selected apertures in a wheel, indexed over photographic film.

Aperture List

A list of the shapes and sizes of the apertures used to create pads and tracks.


The photographic tool used to manufacture a printed circuit board, usually film work, but could also refer to the Gerber files.

ATE (Automatic Test Equipment)

Machines used to automatically test the functionality of a PCB.


The process by which a CAD layout package automatically places copper tracking and components according to the connectivity defined by the net-list.

Bare Board

Refers to a PCB before any components have been placed on it.

Bare Board

Base Material

The material forming the structural and insulating layer between the copper layers of a PCB.

Bed of Nails Electrical Tester

A machine that uses an adaptor jig to connect every test point of a PCB under test to a computer, which scans the test points and compares the connectivity to a net-list file or a "golden" board.

Bill of Materials (BOM)

A document detailing the quantity required, manufacturer's part numbers, device descriptions, value, type or size, and reference designators.

Blind Via

A copper plated hole which passes from the surface of a PCB and terminates at a copper feature on an inner layer, not passing all the way through the PCB.


A PCB fault where part of a drilled hole cuts through its associated copper pad.


A PCB fault where excess solder or copper causes a short between adjacent copper features.

Buried Via

A copper plated hole interconnecting two internal layers of a multi-layer PCB, not visible externally.


Epoxy paper laminate with glass fabric coating.


Epoxy felt laminate with glass fabric coating.


Usually applied to an edge connector area of a PCB to relieve sharp edges where the PCB is inserted into an edge connector.


The copper connections allowing electrical currents to pass between components, creating a functioning electrical or electronic device.

Circuit Boards

Another term for printed circuit boards.

Circuit Layer

One of the layers of a PCB containing conductors, including tracking, ground, and voltage planes.

Component Hole

The holes through which leaded components are fitted.

Conductor Spacing

The gap between adjacent copper tracks.

Controlled Impedance

Defined in ohms, it is a characteristic of a copper track governed by the dielectric constant of the base laminate, track width, dielectric thickness, copper track thickness, and configuration of adjacent copper features.

Copper Foils

Commonly used in multilayer PCB construction, available in various thicknesses.


A material applied to the outside layers of a flexible circuit to insulate the copper conductor, normally produced with a drilling process.

Design Rules Check

A computer program identifies features on the circuit that breach design rules, including track gaps, annular ring sizes, acid trap detection, etc.


The process of removing resin smeared over exposed copper when drilling multilayer PCBs to ensure a sound electrical connection by plated copper.

DFM (Document Exchange Format)

Files format by which many mechanical drawing programs share data, commonly used to transfer PCB designs to manufacturers.


A file format for sharing mechanical drawing data, often used to convert PCB designs for manufacturing.

Digital Circuits

Characterized by signals that are either on or off, typically 0 or 5 volts, increasingly replacing analogue circuits.

Dielectric Constant (Dk)

The property of a dielectric determining the electrostatic energy per unit volume for unit potential grade. It affects the transmission speed of an electromagnetic wave in a dielectric medium.

Dielectric Loss (tan d)

The energy absorbed by the dielectric media, affecting signal attenuation at high frequencies.

Double-sided Board

A PCB with copper tracking on both sides but no inner layers.

Drill Table

A list of drill sizes used in making the PCB.

DPF (Disc Plotter Format)

A proprietary file format for plotting PCB files, generally considered superior to Gerber.

E-test Fixture and (E/T) Cost

Charges related to electrical testing of PCBs, either via flying probe tests for prototypes or fixture tests for mass production.

Edge Connector

Gold plated tags at the edge of the PCB that mate with an appropriate connector.

Electroless Copper

Copper deposited on the inside of drilled holes through catalytic deposition, followed by electrolytic plating.

Electroless Nickel - Immersion Gold

A finish providing a flat, oxidation-free surface for mounting surface mount components.

Etch Factor

The ratio of etch depth to the resist undercut amount during etching.


The process of removing copper from copper-clad laminate to create insulation between copper tracking.

Fiducial Marker

A copper pad used as a common datum for registering other PCB layers or machines to the component placement points on the PCB.


Vector plotters would "flash" an image of the pads required on a PCB. Tracking would be "drawn".

Flexible Circuits

Single-sided or double-sided flexible circuits, consisting of copper layers on a flexible dielectric film.

Flexible Printed Circuit

A PCB manufactured on non-rigid material, commonly polyimide sheet.

Flying Probe Electrical Tester

A machine that tests PCBs by moving test probes to the nets under test, capable of testing over 2000 points per minute.


Phenolic paper laminate.


Epoxy paper laminate.


Standard glass epoxy substrate with a glass transition temperature of 135°C, offering superior mechanical strength and impact resistance. FR stands for flame resistant.

Glass Transition Temperature (Tg)

The temperature at which a resin system transforms from a rigid state to a softened state.

Gerber Data

Data encapsulating a PCB design in a vector format, widely used for transferring data from CAD packages to PCB manufacturers.

Ground Plane

A large area of solid or hatched copper on a PCB used as an electrical ground or shield.

HASL (Hot Air Solder Leveled)

A process immersing a PCB in molten solder, then rapidly withdrawing it to remove surplus solder, ensuring excellent solderability and shelf life.

HPGL (Hewlett Packard Graphics Language)

A vector-driven language used for driving pen plotters, similar to Gerber.

For more information, please contact Syspcb.

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