Definitions of Basic PCB Terms

August 11, 2025

1.Basic Terms

PCB (Printed Circuit Board) – The board used for electrical connections between electronic components.
Bare Board – A PCB without any components mounted.
Substrate – The base insulating material of a PCB (e.g., FR-4).
Copper Clad Laminate (CCL) – A substrate coated with copper foil.
Trace – The conductive copper lines on a PCB.
Pad – The metal area where components are soldered.
Via – A hole that connects traces on different layers (through-hole, blind via, buried via).
Plated Through Hole (PTH) – A via with conductive plating (copper) for electrical connection.

2. Material-Related Terms

FR-4 – The most common glass-reinforced epoxy laminate (UL94-V0 flame retardant).
High-Tg Material – High glass transition temperature material (e.g., Tg ≥170°C) for better heat resistance.
Flex PCB – Flexible circuit board, typically using polyimide (PI) substrates.
Rigid-Flex PCB – A hybrid design combining rigid and flexible sections.
Prepreg – Pre-impregnated bonding material used in lamination.
Solder Mask – A protective coating to prevent solder bridging (commonly green or black).
Silkscreen – Printed markings for component labels, polarity, etc.

3. Process Terms

Etching – Chemical removal of excess copper to form circuit traces.
Lamination – Bonding multiple layers under heat and pressure.
Drilling – Creating holes (mechanical or laser drilling).
Electroless Copper Deposition – Chemical copper plating for via conductivity.
Electroplating – Electrolytic deposition of copper, gold, or tin.
Hot Air Solder Leveling (HASL) – Traditional solder surface finish.
ENIG (Electroless Nickel Immersion Gold) – A high-reliability surface finish.
OSP (Organic Solderability Preservative) – Temporary anti-oxidation coating.
Impedance Control – Designing traces to match signal transmission requirements.

4.Design Terms

Gerber File – Standard PCB fabrication file describing layers (copper, solder mask, etc.).
Drill File – Specifies hole locations and sizes.
Footprint – The physical layout of a component’s pads and outline.
Bill of Materials (BOM) – List of all components used.
Design Rule Check (DRC) – Validates PCB design against manufacturing constraints.
High-Speed PCB – Focuses on signal integrity (e.g., differential pairs, length matching).
EMC/EMI (Electromagnetic Compatibility/Interference) – Critical for reducing noise.

5.Advanced Technologies

HDI (High-Density Interconnect) – Uses microvias (<150μm) and fine traces.
Buried/Blind Via – Buried (internal layers only) / Blind (surface to inner layer).
Via-in-Pad – Via placed within a component pad (requires filling).
Microvia – Small laser-drilled via (≤100μm diameter).
Stackup – Layer arrangement in a multilayer PCB (e.g., 4-layer: signal-GND-power-signal).

6.Testing & Reliability

AOI (Automated Optical Inspection) – Detects visual defects.
ICT (In-Circuit Test) – Electrical performance verification.
Flying Probe Test – Contactless electrical testing.
Thermal Cycling Test – Evaluates thermal endurance.
IPC Standards – Industry standards (e.g., IPC-6012, IPC-A-600).