Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!rochester!pt!cadre!pitt!hoffman 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