Layers, traces & vias
A PCB is a sandwich of copper sheets separated by insulating fiberglass and laminated into one board. Each copper sheet is a layer where conductors can be drawn. Simple boards use two, top and bottom. Denser designs stack four, six, or more, interleaving signal layers with power and ground. The layer arrangement, called the stackup, gets chosen at the start of layout and shapes everything after it.
Traces are the wires: copper paths etched into a layer, connecting pad to pad. Width matters because a trace has resistance, and current through it makes heat. Power traces get drawn wide while signal traces stay thin. As a rough anchor, a 0.25 mm trace in standard copper carries about an amp comfortably. Width calculators handle the rest.
Vias are small plated holes that carry a connection from one layer to another, letting a trace dive under congestion and come back up elsewhere. They’re nearly free and you’ll use them constantly, but each one adds a little resistance and inductance. High-current paths deserve several vias in parallel, and (a preview of the advanced unit) fast signals prefer as few layer changes as possible.
Key points
- A PCB is stacked copper layers separated by insulator. The stackup is chosen early.
- Traces are etched copper wires. Wider traces carry more current with less heat.
- Signal traces can be thin. Power traces get sized for their current, and calculators make that easy.
- Vias connect layers through plated holes. Use several in parallel for high-current paths.
Practice
0 of 3 answered · Not startedWrong answers just let you try again, and hints are there if you want them. Answering every question first time, without hints, is what earns mastery.
- 1
What is the main electrical cost of using a via on a fast signal?
- 2
Which two factors most directly determine how much current a trace can carry?
- 3
Which factors change how much current a trace can safely carry?
Select every answer that applies.
