Sunday, April 11, 2010

Photo Circuit Boards

Custom Photo Circuit Boards

I have been investigating how to make precise homemade circuit boards. I have tried toner transfer and have been disappointed more time than not.

Back in the day when I had a full blown dark room setup – making boards was easier, partially because you could actually see the parts, and you could run down to any number of local distributors and get chemicals and boards. Plus a 1/16” drill did the job for most off the drilling.

25 years later I am in the mood to try my hand at it again. When there is no PCB for sale, there is usually an eagle cad brd and sch available.

So I installed Eagle Cad from here. Impressive package, a steep learning curve to make you own boards, but since I had the artwork already I just opened the files and looked at them. Printing them yields a positive – perfect for toner transfer but I am a little more adventurous.

To convert the positive to negative – I installed ghostscript and gsview. Eagle cad can output Postscript files so these applications interpret them into a printable version.

How I did that

Open the brd file in Eagle – then from the File Menu select Cam Processor. The layers ( in this case there was only one side so I selected bottom, pads and vias. Some people recommended that the fill pads be checked – but I find that it makes drilling easier if the holes are there to help position the drill.

On eBay there was a place that sold 6”x8” sheets of resist that could be applied with a laminator or with a hot iron – the critical piece of information that I gleaned from their page was you could use velum or tracing paper to creative the negatives.

A United states source on ebay (jaded_caveman) Dry Film Photoresist Sheets+Developer

Here is a link to a great video – using positive pre-sensitized boards. Circuit Skills: Circuit Board Etching

A lot of good information here : PCB Processing Manual