PCB Etch Mask: Print Gerber for Toner Transfer at 1:1

Toner transfer and photoresist: an etch mask that comes out the right size and the right way round

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A PCB toner transfer print has to be three things: the right size, the right way round, and solid black. This page makes the PCB etching mask from your copper layer at exactly 1:1, mirrored for the top layer (it goes face down onto the copper, so it must be printed reversed) and not mirrored for the bottom (a Gerber shows the bottom as seen from the top, already reversed).

Choose the paper (A4, US Letter, A5, Legal, A3, or a page cut to the board), portrait, landscape or automatic, and how many copies: two or more on one sheet gives you a spare if a transfer fails, and "as many as fit" fills the page for a batch. The page tells you what it laid out.

Drill holes are left as small white dots in the pads. After etching, the copper ring around each dot centres the drill bit, so holes land in the middle of the pads instead of wandering.

For a transparency (photoresist, UV exposure) print the same PDF on film; the mask is black where copper stays, which is what positive-acting presensitised board wants.

My traces came out broken

Usually too little heat or pressure in the transfer, or toner-saving mode. Print at the darkest setting, no economy mode, on glossy magazine or transfer paper; iron or laminate until the paper is evenly yellowed; soak it off without rubbing. Tracks under 0.3 mm break easily with toner transfer: keep home-etched tracks at 0.4 mm or more.

The board came out the wrong size

The printer scaled the page. Print at 100% ("Actual size") and measure the 50 mm scale bar before transferring.

Everything is backwards

The top layer must be mirrored for toner transfer and the bottom layer must not; this page does both by default. Text on the copper reads backwards on the paper and correctly on the board.

Ferric chloride or sodium persulfate?

Ferric chloride is cheap and forgiving, warm (35 to 40 degrees C) and agitated it etches a board in 10 to 20 minutes, but it stains everything. Sodium persulfate is clear, so you can watch the copper go, and needs about 50 degrees C. Check every few minutes: over-etching undercuts thin tracks.

How to etch a PCB at home with toner transfer

1. Download the etch mask and print it at 100% on a laser printer, darkest setting, on glossy paper.
2. Measure the 50 mm scale bar. Scrub the copper with steel wool and degrease it with alcohol.
3. Lay the print toner side down on the copper and iron or laminate it for 3 to 5 minutes until evenly yellowed.
4. Soak in warm water and roll the paper off. Touch up any gap with a permanent marker.
5. Etch in warm ferric chloride or sodium persulfate, rocking the tray, until the bare copper is gone.
6. Remove the toner with acetone, drill at the white dots, and tin the copper.

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