Parts of a PCB – Traces, Pads, Vias and the Layers

All 11 parts on the diagram

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From above 6

Trace Traces do the job of wires. They are also called tracks.
Surface-mount component Here, a chip with a row of legs down each side.
Through-hole component Here it is a resistor. Its leads are soldered on the other side.
Pad The solder mask is left off it so that solder can stick.
Silkscreen (legend) It was once printed through a silk screen. That gave it the name.
Via It is smaller than a hole made for a lead. Nothing is put through it.

Cut through 5

Solder mask It also protects the copper from corrosion. It is sometimes called solder resist.
Copper layer This board has two, one on each face. Many boards have more inside.
Substrate It is usually fiberglass and gives the board its thickness.
Plated through hole It can take a component lead, or act as a via.
Annular ring Seen from above it is a ring. In this cut it shows as the copper on each side of the hole.

How this list was compiled: Every name checked on 2026-09-30, a name kept only where two independent sources use it: SparkFun Electronics, PCB Basics, https://learn.sparkfun.com/tutorials/pcb-basics/all (substrate, copper, soldermask, silkscreen, and its terminology list: annular ring, pad, plated through hole, surface mount, trace, via); Wikipedia, text only, Printed circuit board, https://en.wikipedia.org/wiki/Printed_circuit_board (substrate, copper layers, traces or tracks, pads, vias, solder resist or solder mask, the printed legend, through-hole and surface-mount components) and Via (electronics), https://en.wikipedia.org/wiki/Via_(electronics) (via, plated through hole); and a board fabricator's published specifications, OSH Park, https://docs.oshpark.com/services/two-layer/ and https://docs.oshpark.com/submitting-orders/drill-specs/ (substrate, soldermask, silkscreen, annular ring, plated holes, vias). Hints and detail lines are in our own words. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; no maker's board, nothing traced. Licence: own work

How it works

A printed circuit board, or PCB, is a stack of thin layers with parts soldered on. The top view shows what is on the surface, and the cut shows what the board itself is made of.

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On the surface

Traces are copper paths that do the job of wires. A pad is bare metal where a part is soldered. A surface-mount component sits flat on its pads; a through-hole component has leads that pass through the board. A via carries a signal to the other side, and the silkscreen is the printed legend.

Inside the board

The substrate is the stiff insulating middle, usually fiberglass. Copper foil is laminated to it and etched into traces. Solder mask covers the copper, leaving pads bare. A plated through hole joins the two copper layers, and the copper around it is its annular ring.

Via or plated through hole? Both are plated. A via only links layers, and a lead goes through the other.

Questions and answers

What are the main parts of a PCB board?

The substrate, the copper layers etched into traces and pads, the solder mask over the copper and the silkscreen printed on top make up the board itself. Vias and plated through holes link one copper layer to another.

What are the lines on a circuit board called?

Traces, or tracks. Each one is a continuous path of copper that carries a signal or power between two points, doing the job of a wire fixed in place.

Why are circuit boards green?

The color is the solder mask, the coat over the copper. Green is the most common, but a mask can be almost any color.

What is a via on a PCB?

A small hole, made conductive by plating, that connects a trace on one copper layer to a trace on another.