[sdiy] Photo sensitve PCB base material

[Mark Rivera]

> Can anybody recommend any good sources for photo sensitive base 
> material? Single Sides and Double Sided 1.0mm or 0.8mm  PCB 35µm Photos 
> resistive. Maybe 10 packs or so.

I get my photoresist pcbs and developer concentrate from mpja.com. They 
turn out pretty good with two layers of the positive pcb pattern on 
inkjet transparencies for the mask (aligned and glued with superglue 
dabs on the corners of the sheets). I place the mask over the pcb in the 
dark using a red LED for a work light, and sandwich between two panes of 
glass.

I haven't got the timing etc down just yet, sometimes I have to scrap a 
couple before I get it right, but it's something like 100W lightbulb at 
about 10 inches for about 12 minutes. No guarantees on that, though - I 
really need to make a proper setup that is more repeatable!

I microwave the developer solution for a little bit to heat it up before 
use.

I think these are 12mil traces - pretty good results...
http://lumin.us/msr/forums/photoresist.jpg

Mark