Homebrew PCBs

Don wrote:
>  
> 
> I am trying to use MG chemicals dry film as a photo resist for etching 
> metal parts but so far I have had difficulty with the emulsion not 
> adhering well to the metal and leaving lots of holes in the mask. I am 
> doing precision fine-line work (50 micron lines). I can not use a 
> laminator to cure the film so I have been using a clothes iron with poor 
> results. any recommendations for curing the film? Also, is it possible 
> to remove the upper (outer) protective plastic layer before exposing?
> 
> Thanks very much.

For 50um lines you want to be exposing with a very parallel light 
source, and possible machine spray developing. 50um is about the 
thickness of dry film resists.

If the metal parts are flat then you can try wet lamination using hot 
water. I have found repeatedly that laminating cold (<35C) and heating 
after does not produce adequate adhesion for *reliable* fine line work.

Dry film photoresist are are designed for copper substrates, so it is 
possible that some metals are not as good. A small amount of etching 
improves adhesion. What is the metal ?

The protective mylar cover acts as an oxygen barrier and 
photopolymerisation will be inhibited without this cover.