---
title: PCB — printed circuit board
lang: en
type: notion
tags:
  - eee
  - notion
prerequis:
  - analyse-de-schema-electronique-en
aa:
  - RA-PROJET-C03-3/EEE/5
phases:
  - preuve-de-concept
  - dossier-technique
draft: false
source_fr: embarque/pcb/pcb.md
source_sha256: bc5d2b6984af1dafd6cffc0ace21cf2d28f275d5cca88a95ce80525be628d2c0
---

**A printed circuit board** (PCB) is what replaces point-to-point wiring: an insulating board carrying **copper tracks** that connect components soldered permanently in place. Designing a PCB means turning a working [[analyse-de-schema-electronique-en|schematic]] into a **manufacturable physical board** — reliable, compact and reproducible. This page is the **way in** to board design: it sets out the **flow** common to every tool (from schematic to manufacturing files) and points you to the design tool. **Manufacturing** itself (etching, drilling, plating) belongs to the workshop and to the course devoted to it. The wiki points at it without going into it.

## What is it for?

A *breadboard* or a piece of perfboard is enough for prototyping, but they show their limits soon enough: intermittent contacts, bulk, a build nobody can reproduce, interference on fast signals. Moving to a PCB brings:

- **reliability** — soldered connections rather than wires that pull out;
- **compactness** — a dense build that fits in an enclosure;
- **reproducibility** — the same board, identical, as many times as you want;
- **signal quality** — controlled tracks, a ground plane, essential above a few kHz;
- **production** — the only realistic route to building several units.

A PCB is designed **once the prototype has been proved** on a breadboard and in [[simulation-electronique-en|simulation]]: the board freezes a solution that already works, it is not there for experimenting.

## From schematic to board: the flow

Whatever the tool, design follows the same sequence.

1. **Capture the schematic** — place the components and their logical connections (*schematic capture*), as a clean [[analyse-de-schema-electronique-en|schematic]], then run the **electrical rules check** (*ERC*), which catches forgotten pins and inconsistencies before you go any further.
2. **Assign the footprints** — every component on the schematic has a physical **footprint** (the shape of the pads and the real pitch of the package). A wrong footprint means a component that will not fit.
3. **Place the components** on the surface of the board — group them by function, think about ergonomics (connectors at the board edge, heat dissipation).
4. **Route the tracks** — draw the copper that carries out the schematic's connections, by hand or with the help of an autorouter.
5. **Run the design rules check** (*DRC*) — track width, minimum clearance, pads: an automatic check catches mistakes before manufacturing.
6. **Generate the manufacturing files** — the **Gerbers** (copper layers, silkscreen, solder mask) and the **drill** file, which describe the board to the manufacturer.
7. **Manufacture** — etching and drilling in the workshop, or an order placed with a manufacturer. *This stage is outside the scope of the wiki (see the manufacturing course and workshop).*

![The board design flow: schematic, footprints, placement, routing, DRC, Gerbers, then manufacturing (workshop, outside the wiki), separated by the boundary of the Gerber files.|640](/ressources/img/pcb/flux.svg)

## Single, double or multilayer

The number of **copper layers** depends on the density and on the signals.

- **Single-sided (1 layer)** — the easiest to manufacture, enough for a build that is not dense; routing sometimes acrobatic (wire links).
- **Double-sided (2 layers)** — the standard for a student project: two routing planes, room for a ground plane, a good compromise.
- **Multilayer (4 layers and more)** — for high density and fast signals (internal ground and supply layers); rarely needed at the scale of a school project.

## Choosing a tool

An EDA package (*Electronic Design Automation*) covers the whole flow, from schematic capture to Gerber export.

| Tool | What sets it apart | When to use it |
| --- | --- | --- |
| [[kicad-en\|KiCad]] | free, open source, complete, cross-platform, the standard | serious board design, for the project and beyond |
| [[easyeda-en\|EasyEDA]] | the footprint comes with the component, offline mode | the school's tool, right through to etching in the lab |

For a project going out to an external manufacturer, [[kicad-en|KiCad]] is the default choice: free, unlimited, and widely documented. For a board etched at school, [[easyeda-en|EasyEDA]] is what is used, and its page goes as far as the file handed to the workshop.

> [!note]
> **Designing is not manufacturing.** The wiki covers **design**, from the schematic through to the files handed to whoever does the etching. The physical **manufacture** of the board (etching the copper, drilling, plating the holes, silkscreen) belongs to the workshop and to the manufacturing course. The boundary is the **manufacturing file**: what the designer produces, what the manufacturer consumes. Its format depends on who is doing the manufacturing. With an external manufacturer, it is the **Gerbers**. At school, the workshop works from an **EasyEDA `.json`** together with the schematic (see [[easyeda-en|EasyEDA]]).

## Pitfalls

**Routing before the schematic is frozen.** Any change to the schematic after routing means redoing the tracks. You only route a schematic that has passed the ERC.

**A wrong footprint.** Assigning the wrong footprint (wrong package, wrong pitch) gives you a board the real component will not solder onto. Check every footprint against the component's [[lire-une-datasheet-en|datasheet]].

**Forgetting the ground plane.** A ground routed as a thin track, awkwardly shared, generates noise and floating references. A ground plane (a dedicated copper area) steadies the signals.

**Undersizing a power track.** A track too thin for the current it carries heats up, and can melt. Supply and power tracks are wider (see the track-width charts).

**Ordering without reviewing the output.** A Gerber viewer shows the board as it will be etched. One last look saves you from committing a whole batch of wrong boards. At school, the same check is done by printing the board at 1:1 scale and laying the components on it.

## Where it fits in the project

- **[[preuve-de-concept-en|Proof of concept]] phase** — the build is **proved first** on a breadboard and in [[simulation-electronique-en|simulation]], and the PCB comes *afterwards*, to freeze the solution chosen.
- **[[dossier-technique-en|Technical design file]] phase** — board design (RA-PROJET-C03-3/EEE/5) belongs here: this is where you **design and build** the board that brings together [[microcontroleur-en|microcontroller]], sensors and actuators (see [[chaine-energie-en|energy and information chains]]).
- **Manufacturing interface** — the manufacturing file is the deliverable handed to the workshop or to the manufacturer, the boundary with the manufacturing course. Gerbers with an external manufacturer, `.json` and schematic at the school workshop.

## See also

- [[kicad-en|KiCad]] — the open-source tool for designing a board (tool tutorial)
- [[easyeda-en|EasyEDA]] — the school's tool, from schematic through to the board etched in the lab (tool tutorial)
- [[analyse-de-schema-electronique-en|Analysing a circuit schematic]] — the schematic you capture before routing (prerequisite)
- [[simulation-electronique-en|Circuit simulation]] — proving the build before drawing the board
- [[lire-une-datasheet-en|Reading a datasheet]] — where footprints and component constraints come from
- [[microcontroleur-en|Microcontroller]] — often the heart of the board being designed
- [[chaine-energie-en|Energy and information chains]] — what the board carries out physically
- [[dossier-technique-en|Technical design file]] — where the board design is recorded