A rough guide to the DIY methods of PCB manufacture
There are a number of ways of making printed circuit boards once you’ve designed them on the computer. The popular ones are:
- UV lithography
- Toner transfer
- Direct inkjet printing
- Isolation milling
The basic process is:
- Print a mirror-image PCB design onto OHP Transparencies (inkjet or laser will do fine)
- Place printout on top of a blank PCB which has been treated with photo sensitive etch resist (aka photoresist) with ink or toner side touching the PCB.
- Shine UV light through the transparency onto the photoresist. The toner or ink blocks the UV light. The photoresist is either fixed or broken down by the UV light (depending on whether you use positive or negative acting resist).
- Develop the PCB (i.e. wash away the unwanted photoresist)
- Etch the PCB
- Clean off the remaining photoresist
- Protect the bare copper – coat with tin (roller tin or chemical tin) or simply paint it wth flux.
- Print a mirror-image PCB design on to glossy paper (either dedicated transfer paper or glossy magazine paper) using a Laser printer.
- Place the design onto a clean blank PCB and use heat to re-melt the toner and cause it to stick to the PCB (i.e. with a household iron, pouch laminator or the fuser unit from an old printer)
- Wash off the paper leaving the toner stuck to the PCB – the toner makes good etch-resist.
- Etch the PCB
- Clean off the toner with acetone (nail varnish remover) or wire wool
- Protect the exposed copper – coat with tin or paint with flux
This is a new and experimental method of making a PCB. Someone (by the name of Volkan) has discovered that by heating some kinds of inkjet ink, it can be made into an etch resist. The process is:
- Print your PCB design direct onto a clean blank PCB using a modified inkjet printer
- Heat your board to turn the ink into etch resist
- Etch the board
- Clean off the hardened ink (acetone or wire wool)
- Protect the exposed copper (tin or flux).
This is a method requiring a CNC router. You design your board as normal and output a file containing the gap between your traces (rather than the traces themselves). You convert this file to g-code (motion commands for the CNC machine) and the CNC machine cuts the gaps between traces out of the copper clad board. If you already have a CNC router, its a great way to make boards in very few steps without messing with chemicals.