How to etch a PCB at home: from a sketch or Gerber to a finished board

What you need

• Copper-clad board (FR4 or FR1), single or double sided, and fine steel wool.
• A laser printer (inkjet ink does not resist etchant) and glossy paper: magazine pages, photo paper for laser, or toner transfer paper.
• An iron or a laminator, isopropyl alcohol, acetone, and a permanent marker for touch-ups.
• Etchant: ferric chloride, or sodium persulfate, or hydrochloric acid with hydrogen peroxide.
• A plastic tray, gloves, eye protection, and a drill with 0.8 mm and 1.0 mm bits.

Step 1: get the artwork at 1:1

Artwork comes from one of three places: a design in KiCad or EasyEDA exported as Gerber, a picture of a logo or a circuit, or a sketch you drew. Whichever it is, the thing to get right is the size. A board 3% too big does not take its chips: a 14-pin DIP spans 15.24 mm between its outer pins, and 3% is half a millimetre, enough to miss the pads.

• From Gerber files: PCB etch mask, mirrored and at 1:1
• From a hand-drawn sketch: sketch to PCB
• From a phone photo or scan: photo to PCB
• From a logo or image: image to PCB

For a sketch, draw at 1:1 on plain white paper with a black marker at least 1 mm wide, mark the corners of the board, and measure the width before converting. A picture has no real size; you give it one.

Step 2: mirror the right layer

Toner transfer puts the print face down on the copper, so the print is reversed on the board. The top copper layer must therefore be printed mirrored. The bottom layer must not be: a Gerber already shows the bottom as seen from the top, which is mirrored compared with looking at the bottom, and the transfer reverses it back.

Step 3: print it so the toner is solid

• Print at 100%, "Actual size". Never "Fit to page". Measure the scale bar on the print before you go further.
• Put two or more copies on the sheet. Transfer paper and toner are cheap; a second attempt without reprinting saves the evening.
• Use the darkest setting with toner saving off. Grey toner is porous toner, and etchant gets through it.
• Glossy paper releases the toner; plain copy paper holds on to it.
• Handle the print by the edges. A fingerprint on the toner side stops it sticking.

Step 4: clean the copper

Scrub the board with fine steel wool until it is uniformly bright, then wipe with isopropyl alcohol and do not touch it again. Oxide and skin oil are the commonest reason toner lifts in patches.

Step 5: transfer

Lay the print toner side down, cover with a sheet of plain paper, and press with an iron on its hottest dry setting for 3 to 5 minutes with firm, even pressure, edges included. A laminator run 6 to 10 times is more even than an iron. The paper should turn evenly yellow. Too cool (under about 150 degrees C at the board) and the toner does not bond; tracks then come away with the paper.

Soak the board in warm water for 10 minutes and roll the paper off with a thumb, without scrubbing. Hold it to the light: every gap in a track is a break after etching. Fill gaps with a permanent marker.

Safety before you etch

Etchants are corrosive chemicals. The safety data sheet (SDS) that comes with the one you buy is the authority: read it before you open the bottle, and where it says something different from this guide, follow it.

• Wear nitrile gloves and splash goggles, and clothes you do not mind staining. Ferric chloride and sodium persulfate irritate skin and eyes; hydrochloric acid burns them.
• Work where the air moves: outdoors or with an extractor. Hydrochloric acid with hydrogen peroxide gives off corrosive fumes and belongs outdoors.
• Never mix different etchants, and never add bleach to any of them. When a recipe needs acid mixed in, pour the acid slowly into the other liquid, never the other way round.
• Use plastic or glass trays and tools only. Ferric chloride eats metal, including a steel sink.
• Warm an etchant by standing its tray in hot water, never on a hob or a hot plate.
• Keep children and pets away while you work, and store etchant labelled, sealed and out of their reach.
• If it touches skin or eyes, rinse with plenty of running water for at least 15 minutes and follow the first-aid section of the SDS; get medical help if irritation continues.

Step 6: etch

Rock the tray or bubble air through it: fresh etchant at the copper speeds the job and keeps it even. Check every few minutes and stop as soon as the bare areas are clear. Every extra minute undercuts the edges of the tracks, and a 0.3 mm track can lose half its width.

Step 7: clean up, drill and protect

Remove the toner with acetone. Drill at the centring dots (0.8 mm for most component leads, 1.0 mm for pin headers and larger leads) with the board on scrap wood. Tin the copper with a soldering iron or a tinning solution, or spray it with solder-through lacquer, so it does not oxidise before you solder.

1. Used etchant is full of dissolved copper, which is toxic to fish and water life: never pour it down a drain or onto the ground, even after neutralising it. Take it, sealed and labelled, to a household hazardous-waste collection point; your local council or waste authority can tell you where.
2. Store etchant in a plastic bottle with a vented cap, labelled, away from metal.

Design rules for boards you etch yourself

The image to PCB pages measure the narrowest line in your artwork and say which of these it passes.

When to stop etching and order instead

Home etching wins for a single-sided board this week. Once you need two sides with plated holes, fine-pitch surface-mount chips, or more than a couple of copies, a board house is cheaper than your time: the same Gerbers this guide prints from are what they make the board from. Check them first in the Gerber viewer.

• Gerber viewer: check the files before you order