Homebrew Circuit Boards: Methods? Supplies?

Jeff Walther trag at io.com
Mon Sep 12 14:15:08 CDT 2005


>Date: Wed, 07 Sep 2005 12:58:30 -0400
>From: Roger Merchberger <zmerch at 30below.com>
>Subject: Re: Homebrew Circuit Boards:  Methods?  Supplies?

>>In fact, I have not been able to find precoated board (photoresist coated)
>>in the .050" thickness.  So I will either need to use a liquid photoresist
>>or try a toner transfer system.
>
>I dunno about 0.050", but would the 1/32" thickness be close enough?
>(That's 0.03125" thickness, if you can believe the Winders calcaputer
>applet ;-)

I am building SIMMs of various sorts, so the .047" - .053" 
requirement is firm.  They must fit properly in the sockets.

>>Do the developer and/or stripper usually turn out to be some commonly
>>(cheaply) available chemical?  I would prefer to avoid paying $6+ for a
>>small bottle if I can avoid it.
>
>One kg of ammonium persulfate will make 4 liters of etchant,

Developer and stripper are not etchant.  After applying and exposing 
photoresist, one uses developer to remove the unexposed (or exposed 
for positive) photoresist without affecting the exposed (or 
unexposed) photoresist.  After etching the excess copper away with an 
etchant, the polymerized photoresist is still present on the 
protected copper traces and must be removed using a stripper.

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.

Thank you for the helpful information and for sharing your 
experiences.   The supply source and books look interesting.

Jeff Walther



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