Homebrew Circuit Boards: Methods? Supplies?

[Holger Veit]

Tony Duell wrote:

>
>Most photoresists can be 'soldered through' so it's not necessary to 
>strip them. On the other hand, boards look a lot better if you do strip...
>  
>
Besides better look, you'd better strip it in case you want to solder SMDs.

>The method I've always used is to etch the board as usual, wash it, then 
>give it another (longer-than-normal) UV exposure with no artwork -- thus 
>'fogging' the remaining resist. Then pop it back in the developer and it 
>will all strip off nicely. Remember on most photoresist boards, the bits 
>that are exposed to UV are the bits you want to etch away (the artwork is 
>black for the traces, etc), so the resist that's been exposed is the 
>stuff that comes off.
>  
>
I am wondering what you have against a stripper like acetone. I have 
even used nail varnish remover in the
past which contains acetone, but unfortunately also some soap (which is 
not bad) but also some hand-friendly oils
and perfumes, which then require another cleaning with water.

>>So, when using a photoresist system, one needs developer, etchant and 
>>stripper.  However, I suspect that the stripper, at least, may be 
>>some commonly available chemical such as acetone.  And I believe that 
>>Tony mentioned that developer is usually just a strong alkalai.
>>    
>>
>
>It's actally not _that_ strong. Strong enough to feel 'soapy' (it 
>hydrolyses the fats in your fingers), but not strong enough to cause an 
>alkali burn in my experience.
>
>  
>
Infact, sodium hydroxide is not strong in the concentrations used for 
developping. The recipe I remember is
7 grams  NaOH in 1 litre of water. One can use normal rubber gloves (as 
used for cleaning puroses) if one is
afraid to touch the developer. I tried higher concentrations than 7g of 
NaOH but this will likely attack also
the unexposed traces - you'll unfortunately encounter this during 
etching :-(

Regards
Holger