How to make a PCB: from circuit idea to a board in your hand

Before drawing anything, write one paragraph: what the board does, what powers it (USB, a battery, a 12 V adapter) and how much current it draws, the main parts by part number, the connectors, and the size it must fit. Every number you leave out gets decided for you later, by you or by a tool, often badly. This paragraph is also exactly what an AI PCB tool needs as a prompt.

The schematic is the circuit as a diagram: every part as a symbol, every connection as a wire or a shared net name. Draw it in a circuit diagram maker or an EDA tool, or describe it and let the AI draw a first version. If the symbols are new to you, the schematic symbols chart covers the common ones.

A schematic can be tidy and still wrong. Before any layout, check the parts that decide whether the board works:

• Power from the connector to every chip, and every supply against every part’s absolute maximum rating.
• Reset, boot and enable pins, each with the pull-up or pull-down and capacitor the datasheet asks for.
• Special-function pins (I²C, SPI, UART, USB, ADC, crystal, programming header) on pins that have that hardware.
• Decoupling capacitors at the values the datasheet gives, one per supply pin.

This is where most mistakes hide. In our six-board test, four boards passed every automated check with a schematic mistake still in them: a reset button on a spare GPIO, an LED that could never light. More in how to review a PCB with AI.

A footprint is the pattern of copper pads the part is soldered to, plus its outline and courtyard (the keep-clear area around it). It must match the exact package you will buy: a resistor in 0603 and one in 0805 are the same symbol on two different footprints. Most parts have one in the KiCad libraries. For the rest, build one from the datasheet’s land pattern with a footprint generator.

Draw the board outline, choose the layer count (two is enough for most boards) and enter the design rules your manufacturer can build: minimum trace width and spacing, minimum drill and via size, copper-to-edge distance. Then size the traces that carry real current; the trace width calculator gives the width for a current and a temperature rise.

Placement decides most of how a board performs. Put connectors on the edges, facing out. Put decoupling capacitors next to the pins they serve, and keep a radio module’s antenna at the board edge with no copper under it. Then place the rest to keep the important connections short. The ESP32 board below passed every rule check in its first layout and still had its antenna over a ground pour. A review caught it, and one move fixed it.

Routing turns each connection into copper. Route power first and wide, then the sensitive signals (crystal, USB pair, analog inputs) short and direct, then everything else. Fill the spare area with a ground pour. An autorouter does the bulk well once placement is good. Check what it did with critical signals, though.

The design-rule check (DRC) compares the copper against your manufacturer’s limits: clearances, widths, drills, unrouted connections, overlapping parts. Fix every error. Then review what DRC cannot see: the circuit, the connector orientation, the antenna keep-out. Review my design runs the rule and electrical checks together and explains each finding.

Export the Gerber files (one per layer) and the drill files, usually as one zip. If you want the boards assembled, also export the BOM and the pick-and-place file. Before uploading, open the zip in a Gerber viewer and look at each layer. It is the file the fab will build from, and the place where a missing outline or holes off the pads show up. The full list is in how to check Gerber files before you order.

Upload the zip to a PCB manufacturer and pick the options. The standard ones suit most boards: FR-4, 1.6 mm thick, 1 oz copper, HASL or ENIG finish, green solder mask. Budget prototype services usually make a minimum of five boards. For assembly, the same services can solder the parts from your BOM and pick-and-place file, or you solder them yourself, smallest parts first.

The first power-up

1. Inspect the board under good light for solder bridges, especially on fine-pitch chips.
2. With a multimeter, check that no supply rail is shorted to ground.
3. Power it from a bench supply with a low current limit, not straight from a battery or adapter.
4. Measure each rail before you plug in modules or programme the microcontroller.

Simple boards can be made at home. Transfer the copper layout onto copper-clad board, with laser-printer toner ironed on or a photoresist film, etch away the bare copper in ferric chloride or a similar etchant, and drill the holes. It works for single-sided and simple double-sided boards with wide traces. You get no solder mask, no silkscreen and no plated holes, and the etchant stains, corrodes and must be disposed of properly. Ordered prototypes are now cheap and fast enough that most people etch only when they need a board the same day.