Homebrew PCBs

jcarlosmor wrote:
>  
> 
> If you refer to the green soldermask in the video, that is real 
> soldermask for industrial PCB making. However, the last shot on the 
> finished PCB shows very poor finish, because is almost for sure that the 
> datasheet for that soldermask states that it must be baked in an 
> air-forced oven before imaging with UV. Also, it must be applied by 
> screen printing, not manually with a card. If the user follows all the 
> steps according to the manufacturer you end with a professional board, 
> since the soldermask in the video is "the real thing" used in industry.

I've recently been playing with Liquid Photoimageable Solder Mask 
(LPISM). Your right, it needs a proper bake before exposure or it gets 
damaged in the developer.

* LPISM part A and B are mixed on a metal spatula (typ. 1 gram)
* screen printed (polyester mesh 125 thread/inch)
* baked 80C 20min,
* UV exposed (2 minutes from 4 x 8W UV BL tubes)
* developed (10g/l Na2CO3 @ 35C, manual paint brush agitation)
* baked 150C 20min.

notes:
* All equipment is readily cleaned in the developer tray.
* It goes a long way, 1 gram of LPISM does your typical 10 x 10cm PCB.
* A PCB holding jig is required for double sided printing.
* working in a artificial lighting area seems safe.

The link below is of a board I did recently. I know its quite ugly, but 
I'm only just learning about this solder mask stuff.
http://members.optusnet.com.au/eseychell/revH_photo.jpg

I'd like to know what experience people have with dry film soldermasks. 
Might be lot more practical for hobbyist.