Homebrew PCBs

David Griffith wrote:
> On Sat, 5 Nov 2005, superone0319 wrote:
> 
> 
>>Thanks Adam,
>>
>>  I'm in the US.  I found the smallest $85 at Think & Tinker, Ltd.
>>It's still too much for a beginner since I will never use up all of
>>it. I did most my boards on presensitized copper clads.  It turned
>>out prety good but I still want some experiments with dry film.
>>
>>  I just wonder if someone have bought the stuff from Think & Tinker,
>>Ltd. and sell it on Ebay or something like that for a small quantity.
> 
> 
> I might be interested in doing something like that.  Adam, what did you
> use to apply the photoresist film?
> 
> 

After many hours experimenting and frustration, I eventually found that 
the "wet lamination" method was the only way I could apply the film with 
the least likelihood of creating wingless, trapped air bubbles, and a 
poor bonds. For small PCBs <= 150x150mm (6"x6"), you can pour very hot 
water on to PCB laying horizontally in a kitchen sink so that the copper 
surface is hot and wetted with film of water. Then take the dryfilm 
photoresist which you have removed the protective backing, and very 
gently lower it down over the PCB starting at one end and working it 
across. The film will not immediately bond to the copper, and you have a 
few seconds to flatten down the film and draw out excess water by 
sweeping a soft flat object over the film while applying a little 
pressure. The larger the PCB the more difficult this method is to 
perform. Wrinkles are your worst nightmare.

I actually made a wet laminator machine that applies the film and PCB 
between two rubber rollers (from an old ink press machine), while 
simultaneous a small pond pump circulates heated water and squirting it 
directly at the copper/film interface between the rollers of which I 
manually feed via by a turning handle.

I obviously don't expect anyone to build something like the above 
machine, but I found it being necessary to laminate A4 sized PCBs and do 
so reliably.

Adam