PCB design glossary
PCB
AKA: printed circuit board
Printed Circuit Board — the physical board that holds components and routes signals between them.
A PCB is the physical implementation of a circuit. It consists of one or more conductive copper layers separated by insulating FR4, with components mounted on the outer layers and signals routed as traces and vias.
Common stack-ups are 2-layer (cheapest, for simple boards) and 4-layer (necessary for high-speed signals or denser designs). Higher layer counts (6, 8, 12+) are common in production hardware.
What a PCB is made of
- Substrate: usually FR-4 glass-reinforced epoxy. Standard board thickness is 1.6 mm.
- Copper layers: 2 on simple boards, 4 or more on denser or faster ones.
- Soldermask over the copper, and silkscreen on top for labels.
- A surface finish on exposed pads: HASL (solder-coated), lead-free HASL, ENIG (gold over nickel) or OSP.
How a PCB is designed
The usual flow is schematic, then footprints, then layout (placement and routing), then checks (ERC and DRC), then fabrication files: Gerbers, drill, and for assembly a BOM and CPL. Each step feeds the next, so a mistake early on carries through.
Choosing the number of layers
Two layers are cheapest and enough for most simple and low-speed boards. Four layers add inner ground and power planes, which makes routing easier and greatly improves noise and signal integrity; they are the norm for USB, fast microcontrollers and anything with RF. Six or more layers are for dense, high-speed designs.
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