vovut@prism.cs.orst.edu (03/08/91)
Does anybody etch their own PCBs? If so, would you mind describing how you do it and what kind of set up you need? Thanks in advance.. vovut@prism.cs.orst.edu
whit@milton.u.washington.edu (John Whitmore) (03/12/91)
In article <1991Mar08.084952.7323@lynx.CS.ORST.EDU> vovut@prism.CS.ORST.EDU () writes: > >Does anybody etch their own PCBs? If so, would you mind describing how you >do it and what kind of set up you need? I assume you want something quick-and-dirty. We have made PCB's by various methods, and I will describe the do-it-yourself approach (rather than the way you'd do it if you had all the equipment in the world). First, prepare a negative of the printed circuit; two negatives, with alignment bullseyes, if double-sided. We use Kodalith transparency film (UV-exposure, alcohol (xylol) developed), available at many art/graphic supply houses. Touchup the negative as necessary (keep the original artwork pristine). This requires a UV lamp (sun lamp is OK) with timer; typical exposure 1 minute for a contact print. Then clean and coat a copper-clad board; we use steel wool and soapy water, rinsing and blow-drying with compressed air. Coat with photoresist (KPR type is available in aerosol cans); we used to have an old 45 rpm turntable that we'd start up with the PC board atop it, spraying while it spun. The excess photoresist went to the edges (and dripped off). It is best to make a VERY thin coat of photoresist. Bake for 15 minutes or air-dry for 3 hours (longer is better). Then place the negative on the coated board and expose (same UV lamp as before) for about a minute. Develop the photoresist (with KPR developer); we dip a cotton ball in the developer and wipe, but you can also soak it. Optionally, here, you can dye the photoresist (after developing, it's VERY hard to see) with any of several kinds of dye. Rinse off the developer and blow dry with compressed air. Then etch the board in a heated (120 F) agitated (we blew air into the bottom of the vat to stir it) vessel of ferric chloride solution. FeCl will cheerfully etch through copper, stainless steel, you name it (and stains your hands and clothes a terrible yellow-brown color); the only materials that should contact it are glass, plastic, and titanium. I believe the solution was bought already mixed, though I think you can buy the chloride dry and dissolve it in diluted hydrochloric acid. When the etching is complete, rinse the board and blow it dry; scrub off the photoresist and (optionally) tin or silver plate the board. Tin-plating can be done by dipping in an electroless plating solution, silver plating by rubbing with 'Cool-Amp' powder with a damp cloth (again, electroless plating). Some people polish the copper surface with Brasso... After inspection, drill the holes with a carbide drill (typically #61 size). Proper drill spindle speed is in the 10k-40kRPM range. A Dremel tool is the way to do this in small lots (and you can use tool steel drill bits, but they'll wear down FAST going through fiberglass). If you're really serious about making PC boards, you should at least browse through _Printed Circuits Handbook_, edited by C. F. Coombs, Jr. John Whitmore
meharp01@ulkyvx.bitnet (03/12/91)
In article <18205@milton.u.washington.edu>, whit@milton.u.washington.edu (John Whitmore) writes: > In article <1991Mar08.084952.7323@lynx.CS.ORST.EDU> vovut@prism.CS.ORST.EDU () writes: >> >>Does anybody etch their own PCBs? If so, would you mind describing how you >>do it and what kind of set up you need? > >[Excellent description of making a PC board deleted for brevity] > > If you're really serious about making PC boards, you should > at least browse through _Printed Circuits Handbook_, edited by > C. F. Coombs, Jr. > > John Whitmore Can you post a complete citation for that book? I am trying to gather info on getting into the PC board business. --------------------------------------------------------------------- Michael Harpe, N4PLE | BITNET: MEHARP01@ULKYVX North Computer Center | VOICE: 502-588-6882 University of Louisville | FAX: 502-588-5055 Louisville, KY 40292 | AURAL: "Mike!" ---------------------------------------------------------------------
simoni@strat.Stanford.EDU (Richard Simoni) (03/13/91)
In article <1991Mar12.092641.939@ulkyvx.bitnet>, meharp01@ulkyvx.bitnet writes: > In article <18205@milton.u.washington.edu>, whit@milton.u.washington.edu (John Whitmore) writes: > > > > If you're really serious about making PC boards, you should > > at least browse through _Printed Circuits Handbook_, edited by > > C. F. Coombs, Jr. > > > > John Whitmore > > Can you post a complete citation for that book? AUTHOR: Coombs TITLE: Printed Circuits Handbook 3 Ed IMPRINT: Mcgraw Hill Book Company, 1987. (Hardback. ISBN:0-07-012609-7) PRICE: $59.50 (as of 12/18/87) Rich Simoni
rpw3@rigden.wpd.sgi.com (Rob Warnock) (03/14/91)
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
donrm@hpnmdla.hp.com (Don Montgomery) (03/16/91)
Here's my $0.02 worth after many years of making pc boards in the kitchen: excerpts from the responses- > Then clean and coat a copper-clad board; we use steel wool >and soapy water, rinsing and blow-drying with compressed air. ^^^^^ Be careful here. Some soaps leave stearates on the board and the resist will slough off, particularly the real Kodak KPR. If in doubt, use a degreaser, but make sure it's not contaminated. > Bake for 15 minutes or air-dry for 3 hours (longer is better). I bake my boards in the oven at the lowest setting. Place a muffin fan (150 F or so won't hurt it) to displace any temperature gradients that occur. Let the board air-dry enough to evaporate the volatiles before placing in the oven or you may be picking the door off the floor or out of the wall. Close the door to keep the ambient (and oven) light out. One interesting note: Positive photoresist (like Shipley) that devel- ops with potassium hydroxide solution requires humidity during the dry- ing process. I fretted over this for hours with one failure after another when using a new electric oven. Previously, I had used a gas oven that raised the humidity by virtue of combustion products. One of the ChemE's here at work told me what I was doing wrong... >solution. FeCl will cheerfully etch through copper, stainless >steel, you name it (and stains your hands and clothes a terrible You ought to see what this stuff does to aluminum! Post your results to rec.pyrotechnics. I have also used ammonium persulfate (with a mercury chloride catalyst) as an etch. It's only advantage is you can tell how "used" the solution is as it turns blue from the dissolved copper sulfate. The stuff is very poisonous (due to the catalyst) and should probably be avoided. >plate the board. Tin-plating can be done by dipping in an electroless >plating solution, silver plating by rubbing with 'Cool-Amp' powder with The electroless tin-plating works great, but requires a VERY clean board. Touch it with your fingers and it won't plate in that area! Also, be careful of silver plating pc boards that are going to be used in a high humidity. They tend to grow dendrites that short out everything in sight. > After inspection, drill the holes with a carbide drill >(typically #61 size). Proper drill spindle speed is in the 10k-40kRPM >range. A Dremel tool is the way to do this in small lots (and you Dremel makes a dandy little drill press fixture that works just great for this. You can drill a lot of holes in a hurry. >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! This method works great! You can use any brand of copper cleaner that contains phosphoric acid. >DON'T use steel wool, as it will scratch (gouge, really) the surface, which >creates channels for the etchant to run under the resist. Boy, this is the absolute truth. If you're running 0.031 inch or smaller lines, you WILL have trouble!! Don Montgomery donrm@hpnmdla.HP.COM The usual disclaimers apply.