Homebrew PCBs

fredbutz wrote:
>  
> 
> I'm using the Solder Mask UV Film from Think and Tinker -- with 
> outstanding results. I've never had a problem. No smell, nothing.
> I simply laminate it, expose it for 50 seconds using a image made on a 
> laser printer with clear acetate. Develop it in Washing Soda. Expose it 
> again for 15 mins, then bake it for an hour in a toaster over.
> 

What is your light source ? Using LPI solder mask, I found a 2 minute 
exposure requirement from 4 x 8W BL tubes box. My UV LED box (15x15mm 
pitch grid, 395nm LED) will actually cure the solder mask after ~7 
minutes, but it leaves a mat finish after developing. The datasheet 
states that inadequate exposure intensity, will cause dullness after 
developing. Do you have this problem ?  I can easily mechanically buff 
the solder mask to return it's luster.

The 150C 60 minute post baking completes the cure. Only methylene 
chloride based paint strippers will remove solder mask, but will also 
attack the epoxy base.