Making PCBs at home: toner transfer and photoresist, step by step

Cheap board houses have made home-made PCBs less common, but a home process still wins when you need a simple single-sided board today: a test adapter, a breakout for a repair, a quick prototype. There are two reliable methods — toner transfer (cheapest, good down to about 0.4 mm tracks) and photoresist (more setup, finer detail and more repeatable).

Design for home etching

• Tracks at least 0.4 mm (16 mil) wide, 0.6–1 mm for power; clearance at least 0.3–0.4 mm.
• Bigger pads than a factory needs — 1.8–2 mm for through-hole parts — so drilling doesn't eat the copper ring.
• No plated vias at home: for double-sided boards use wire links or component leads soldered on both sides.
• A ground pour saves etchant and time; give it generous clearance (0.5 mm or more).

From KiCad, plot the copper layer as PDF or SVG in solid black, with the Edge.Cuts layer included so you can see the outline. For both methods below the toner (or ink) side goes against the copper, so print the top layer mirrored and the bottom layer not mirrored (KiCad plots the bottom layer as seen from the top). Print at 100 % scale and check a known dimension with calipers.

Method 1: toner transfer

1. Print with a laser printer at maximum darkness onto glossy paper — photo paper for laser printers, thin magazine paper or dedicated transfer paper.
2. Clean the copper with a fine abrasive pad and isopropyl alcohol until water sheets off without beading. Don't touch it with your fingers afterwards.
3. Transfer the toner with an iron on its hottest dry setting, pressing firmly for 3–5 minutes, or pass the board through a laminator 5–10 times.
4. Soak in warm water until the paper softens, then rub it away gently with your thumb.
5. Inspect under good light and repair small gaps with a permanent marker. Missing areas are usually a sign of dirty copper or too little heat.

Method 2: photoresist

Use either presensitized boards (usually positive resist) or dry-film resist that you laminate onto bare copper (negative resist).

1. Artwork: print on transparency film. Positive resist needs positive artwork (copper = black); dry film needs a negative (copper = clear). Stack two aligned prints if one isn't opaque enough.
2. Expose under UV — a UV LED box or a UV nail lamp works — with the artwork pressed flat under glass. Find the time with a test strip rather than guessing.
3. Develop: positive boards in a weak sodium hydroxide solution (follow the board maker's concentration), dry film in about 1 % sodium carbonate. Stop as soon as the pattern is clean.
4. Rinse and check under magnification before etching.

Etching

• Ferric chloride: the classic. Warm it to about 40–50 °C and keep it moving; a small board takes 10–20 minutes. It stains everything, so work in a plastic tray.
• Sodium or ammonium persulfate: clear solution, so you can watch progress; also works best warm.
• Remove toner with acetone, or strip the resist (re-expose and develop again for positive boards; a stronger alkaline stripper for dry film).

Drilling and finishing

• Typical drill sizes: 0.8 mm for resistors and DIP ICs, 1.0 mm for pin headers, 1.2–1.5 mm for terminal blocks and power connectors.
• Carbide PCB drills cut cleanly but snap if they wobble — use a drill stand or a rotary tool in a press.
• Protect the copper with chemical tin plating, a coat of solder flux lacquer, or a clear PCB lacquer you can solder through.
• Double-sided boards: drill two or three registration holes first, transfer and etch one side, then align the second print to those holes.