PCB fabrication (homebrew): Difference between revisions

There are two popular methods of masking the copper laminate from the etchant, the toner transfer method is cheap and simpler but takes a lot of patience and fiddling about. The more expensive photo resist method can be much more accurate and one printout can be used multiple times but also requires an [[UV exposure box]] and developing the board.<ref>[http://www.diystompboxes.com/smfforum/index.php?topic=102924.msg914631#msg914631 Re: DIY etching PCB's - Toner Method or Photo Resist Method?] by R O Tiree, 27 May 2013</ref>

===Toner transfer===

Using a laser printer or copier, this does not work with an inkjet printer, to print an image of the PCB tracks on glossy paper. Laying this printed side onto the de-oxidised and de-greased copper laminate and using an iron at a high temperature, on the rear of the paper to transfer the toner from the paper onto the copper. After soaking in water to remove the paper, the toner now transferred to the copper laminate acts as an etch resist.<ref>[http://fullnet.com/~tomg/gooteepc.htm ''Easy Printed Circuit Board Fabrication, Using Laser Printer Toner Transfer''] by Thomas P. Gootee, 2007</ref> This can also be used to print component side parts and legends. ''Press'n'Peel'' is similar to this method. If you don't tin the board, coat the copper laminate with rework flux to prevent it oxidising.<ref name="mh">''[http://www.electricstuff.co.uk/pcbs.html How to make really really good homemade PCBs]'' by Mike Harrison</ref>

===Photo resist===

Print the PCB layout onto clear or translucent film - this is the ''mask''. Plastic transparency might deform from the heat of the printing. Place the printed side against photo-resist coated PCB and expose to ultra-violet light. Pre-sensitised copper clad boards are easier than spray photo-resist where it's difficult to attain consistent thickness needed to estimate a correct exposure time. For double sided boards, first tape the two masks printed sides together then tape the board in place between them and expose both sides to the UV.<ref name="mega">Mega [http://www.megauk.com/video.php PCB Instructional Video]</ref> Use the recommended developer not sodium hydroxide, this removes the coating where it has been exposed to UV. Follow the manufacturers directions for correct concentration and temperature. Leaving the photo-resist on the board prevents the copper oxidising and it acts as half reasonable a solder flux,<ref name="mega"/> unless the board is going to be tinned.