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From: hoffman@pitt.UUCP (Bob Hoffman)
Newsgroups: sci.electronics,rec.audio,rec.ham-radio
Subject: Re: PC board photo etching kits
Message-ID: <5775@pitt.UUCP>
Date: Wed, 8-Jul-87 13:40:45 EDT
Article-I.D.: pitt.5775
Posted: Wed Jul  8 13:40:45 1987
Date-Received: Sat, 11-Jul-87 05:43:53 EDT
References: <2392@uwmcsd1.UUCP> <885@kodak.UUCP>
Reply-To: hoffman@pitt.UUCP (Bob Hoffman)
Organization: Univ. of Pittsburgh Computer Science
Lines: 31
Xref: mnetor sci.electronics:911 rec.audio:2404 rec.ham-radio:1880

In article <885@kodak.UUCP> ornitz@kodak.UUCP (barry ornitz) writes:
>In article <2392@uwmcsd1.UUCP> neighbor@csd4.milw.wisc.edu.UUCP (Jeffrey Alan Ding) writes:
>>
>>Hello.  Does anybody out there etch PC boards?  I have a kit from
>>GC electronics that uses chemicals to transfer a pattern onto the PC board.
  ...
>>I'm wondering if anybody out there has used this stuff.  I'm having a bit
>>of trouble photo sensitizing my own PC boards.  I've tried the process
>>with PRE-sensitized boards and it works great.  But the boards that I
>>sensitize do not work at all.  If any of you have any experience doing
>>this I would appreciate any info on how to make it work.  Oh one more thing,
>>I'm using POSITIVE method.  There are both positive and negative methods.
  ...
>I have rarely had any luck using the spray-
>on resists sold by GC, etc.  This products rarely sells quickly and is useless
>if overheated in the can.

I have used the GC negative-acting photoresist with excellent results, but I
had a fresh can.  I guess I was lucky!  What Barry says is true about its
aging properties.  I have learned that if the spray comes out a dark purple
color, then it's OK.  If it comes out yellowish, it's shot.  Another important
thing is extreme cleanliness of the board being sensitized -- this means taking
scouring powder to clean any oxidation and oil off the board.  Use 600-grit
wet emery paper or steel wool if necessary.  I don't like steel wool for the
bits of steel it leaves behind.  That board should positively GLEAM when you're
done.  Then, handle it only by the edges -- the oil on your fingers is enough
to screw up the photoresist.

-- 
Bob Hoffman, N3CVL       {allegra, bellcore, cadre, idis, psuvax1}!pitt!hoffman
Pitt Computer Science    hoffman%pitt@relay.cs.net