Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!decwrl!sgi!rpw3@rigden.wpd.sgi.com From: rpw3@rigden.wpd.sgi.com (Rob Warnock) Newsgroups: sci.electronics Subject: Re: Etching PCBs ?? Message-ID: <91121@sgi.sgi.com> Date: 14 Mar 91 12:01:38 GMT References: <1991Mar08.084952.7323@lynx.CS.ORST.EDU> <18205@milton.u.washington.edu> Sender: guest@sgi.sgi.com Reply-To: rpw3@sgi.com (Rob Warnock) Organization: Silicon Graphics, Inc., Mountain View, CA Lines: 48 In article <18205@milton.u.washington.edu> whit@milton.u.washington.edu (John Whitmore) writes: +--------------- | Then clean and coat a copper-clad board; we use steel wool | and soapy water, rinsing and blow-drying with compressed air. +--------------- The absolutely *best* method I have ever found is to use "Twinkle" brand copper cleaner (intended for use on the bottom of Revereware pots and such) and warm water and a sponge, according to directions. The "Twinkle" will chemically clean off the oxides, and leave you with copper so pure it's almost pink in color! DON'T use steel wool, as it will scratch (gouge, really) the surface, which creates channels for the etchant to run under the resist. The "Twinkle" leaves the surface coated with a little lemon oil, which is good and bad. The good is that you don't have to use the boards immediately, they'll keep without re-oxidizing for some time. The bad is that the micro- scopic coating of lemon oil is a very good resist in itself, and the boards won't etch properly. [Yes, I had this problem! That's why I'm telling you about it...] The solution is quite simple: Any detergent will strip the lemon oil right off, so a little warm soapy water and that sponge again and you're ready to go. [Of course, the copper's no longer oxidation-resistant at this point, so move directly after drying to coating with the photo-resist...] You can of course combine this with the original "Twinkle" cleaning in a two-step process. [Just don't mix the detergent with the Twinkle; neither will work as well.] Note: If you use *HOT* water with the detergent, the board will dry faster. Also, a *slightly* warm board will help the photo-resist spread more evenly. Despite the hazard I mentioned [which is no hazard now that you know about it], using "Twinkle" is the most reliable, easiest copper-cleaning method I know. Many a board was coated/exposed/developed/etched/stuffed/soldered/used after an initial "Twinkle" cleaning [circa 1970-74, Emory University Chemistry Dept]. -Rob p.s. You know, I hope they still make that stuff... ----- Rob Warnock, MS-1L/515 rpw3@sgi.com rpw3@pei.com Silicon Graphics, Inc. (415)335-1673 Protocol Engines, Inc. 2011 N. Shoreline Blvd. Mountain View, CA 94039-7311