etching printed circuit boards

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tvman
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etching printed circuit boards

Post by tvman » Thu Aug 15, 2002 11:02 am

i must be getting old and forgetfull. i need info on how to make a PC board from a blank that i can then etch w/my radio shack pc kit.
a web page with tutorial would be fine

russlk
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Re: etching printed circuit boards

Post by russlk » Thu Aug 15, 2002 11:24 am

Digi-Key sells two types of PC board materials, a transfer where you copy your design onto a plastic sheet and iron it onto the copper clad board. I have not had success in ironing it on, but it works if I sandwich the plastic sheet between two pieces of glass and clamp it with a metal clamp, put it in the oven at 375 deg F. for 10 minutes. Let it cool completly, then open it up and peel the plastic off. I usually have to do minor touchup, but most of the pattern sticks.<p>The other method uses sensitized copper clad board that works with a positive pattern. You can take your layout to the copy shop, have it copied onto clear plastic and expose the sensitized PC board with ultraviolet light. A flourescent grow lite works. Instructions come with the materials. Don't forget that you want to turn the transparancy so the copy side is down, and consider whether it is top side or bottom side layout.

billdar
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Re: etching printed circuit boards

Post by billdar » Thu Aug 15, 2002 1:10 pm

For small designs I just used a film marker ( use on photo negatives ) to trace the pattern and then use the etching solution. But they were indeed small and fairly low speed (40khz).

wd5gnr
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Re: etching printed circuit boards

Post by wd5gnr » Thu Aug 15, 2002 3:18 pm

You mention the Radio Shack kit. Here's a few tips:<p>1) Clean the board really well before you start. After you clean it, rinse in alchohol and then don't touch the copper surface.<p>2) Draw your pattern using the resist pen. You can use any permanent marker, in general. You can also buy "rub on" patterns. If you draw your layout on paper, you can use carbon paper to transfer it and then go over it with the marker. Another trick: mark your holes first and center punch them. Then use a sharp marker to draw the pad by circling the center punch. Use a broader marker for traces.<p>3) Etch. Watch out for the FeCl3 as it stains everything. I got maybe 5ml on my patio 5 years ago and it is just starting to be hard to find. Your hands and clothes are definitely suspect. Heating the etch is very helpful although not totally necessary. Some use Ammonium Persulphate, but I haven't tried it. <p>If you have a laser printer or access to a dry toner copier, you might try the "toner transfer" method. Read about it at http://www.wd5gnr.com/pcb.htm<p>BTW, the 1/16" bit RS gives you is way too big for most things. If you can get a smaller bit made for PCB (they have numeric sizes; try a local electronics store or a machine shop supply) great. Carbide is best, but a regular drill is not really fast enough for a carbide bit. A Dremel tool works OK especially with the drill press attachment (those tiny bits break with the least amount of lateral pressure). If all else fails, anybody who sells Dremel should have their kit of drill bits. The smallest one in that kit is the biggest you should use (1/32").<p>Some links:
http://www.aphs.nsw.edu.au/student_work ... cb/pcb.htm<p>http://www.angelfire.com/tx4/ionwind/makePCB.html

L. Daniel Rosa
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Re: etching printed circuit boards

Post by L. Daniel Rosa » Thu Aug 15, 2002 4:25 pm

Try http://www.fullnet.com/u/tomg/gooteepc.htm . For my non-critical stuff with wide traces, I use paper. For dense or complicated items, I'll use Press'n'Peel blue. I get fair results either way, some minor touch-up may be needed before etching. You'll probably want to find another source for your blanks, I've had some bad experiences with RS's copper clad board. Their press-on stuff is okay, IMO, but now that I have a laser printer I don't use decals anymore.

Faulkner
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Re: etching printed circuit boards

Post by Faulkner » Fri Aug 16, 2002 12:12 pm

My little experience with radioshack etching is: works ok, press-on pads sometimes don't stick well (good cleaning is a must); the Sharpie permanent marker I signed my name with worked better than the pads, and electrical tape works well, too.<p>By the way, I think I used a #40 drill bit. It seemed a little large.

Faulkner
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Re: etching printed circuit boards

Post by Faulkner » Fri Aug 16, 2002 12:18 pm

Sorry. I meant a #60

russlk
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Re: etching printed circuit boards

Post by russlk » Fri Aug 16, 2002 12:38 pm

I use #68 drill for most holes & #71 for ICs.

tvman
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Re: etching printed circuit boards

Post by tvman » Fri Aug 16, 2002 6:19 pm

i want to thank every who posted a response to my query on making a pc board.
it comes back to me after reading all the advice.
i guess i was hoping not to sit for hours tracing the pattern by hand on the blank.
i wish when nuts and volts has a project, the list of parts would have a source of a board already etched and drilled for us patience challenged individuals..

Dean Huster
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Re: etching printed circuit boards

Post by Dean Huster » Fri Aug 16, 2002 7:19 pm

Once you really get into making the PC boards using a product such as PNP Blue and start doing enough of them that you want to put a little more money into the process to make it better and faster, you'll find that your one best investment will be for a dry mount press or a T-shirt iron. With the dry mount press, you get a large flate area, set the temperature as hot as it will go and then experiment until you get the platen to close with the right amount of pressure and get the timing right for the "exposure" to the pressure and heat. Your results will end up being so consistent that you'll rarely have to do any touchup work if you've properly cleaned the boards to start. I"ve never, ever had good results using a clothing iron to do the job because I can't get the same results consistently over even the same board, let alone repeat boards. And large boards are impossible that way.<p>My favorite etchant is ammonium persulfate, but never make the mistake of storing it in a damp environment or on a concrete floor!<p>Dean
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

R.I.P.

tvman
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Re: etching printed circuit boards

Post by tvman » Mon Aug 26, 2002 8:11 am

thanks dean.
my pc board needs are small.
so i am better off using the trace,resist ink method as described in earlier posts.
also my wife thinks i have too many goodies as it is. however using my junk to repair something of hers doesn't count.
barry the ex tvman

L. Daniel Rosa
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Re: etching printed circuit boards

Post by L. Daniel Rosa » Mon Aug 26, 2002 6:46 pm

How small? I could justify putting something small in my next batch, if it's not too esoteric. It won't look as good as PCBExpress, but it'll be a lot cheaper.

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Edd
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Re: etching printed circuit boards

Post by Edd » Tue Aug 27, 2002 12:01 am

Barry...Mr (ex) TV man:
I will throw in one more technique, of my own, that I used back in the 60's when I made circuitry using "pull" xstrs from IBM com-
puter boards. Nothing like we have available today for fab was available in those days !
I tend to still use it today,for low tech fabrication of a simple, single unit,if no hair thin traces are required nor dense- multi pin IC sockets....eg >~16 are involved.
After you get your component template/ layout planned for the foil side of the board, drill all of the holes that will be required.
Take a sheet of ~#600 grit wet/n/dry paper and use just enuff pressure to knock down any drill burrs / ridges / ferrules, to get a flat surface again. Clean its copper surface with a
Scotchbrite pad with a touch of copper cleaning powder. When you get a clean-rosy copper, rinse off, using a toothbrush's bristles to help in the cleaning out of the caked powder in the holes. Make a final water cleansing rinse and let the board dry. Lastly, do a Degreasing/
cleaning of the copper surface with an aggressive
...non waterbearing...solvent/degreaser like acetone/methyl ethyl ketone/xylene toluene or lacquer thinner. Cleanse and make NO finger contamination after that.
Cut a piece of CONTACT paper (plastic)...matte Clear or White works best...just larger than your PCB blank and cover the copper side. Do a pressure rolling to assure optimum adhesion.
Take a sewing needle that is large enough to not pass thru the drilled holes in the PCB, when inserted from the foil side....pierce thru to mark all holes.
Place your template /or/ draw your foil paths on the CONTACT paper...a soft lead pencil will let u correct errors. Once all foil paths are completed, the points where lands/pads for component leads are required, can be drawn as appropriately larger squares. On transistors, triangular pads seem to work best. I've always
had zero/error aligning the artwork to the holes, compared to having a walking drill bit later on. The next step is to take a clear plastic ruler and an EXACTO with a new #11 blade and just cut thru the CONTACTS marked foil paths, not over-extending your cut, and then taking the tip of the knife to lift the CONTACT out of the path just made, exposing the clean
copper. When the final copper circuitry path has been completed, and all checked out, the resist stage is ready to be done.This requires the board to be placed at work level ~1 ft in front of you and a hand held lightbulb/floodlight be held behind the bd ~1-2 ft. It will be manipulated as you spray.The resist will be FLAT BLACK KRYLON spray paint. Start at the top of the board and at a CONSTANT 9-12 in distance from the board make linear sweeps across the board from top to bottom ,til coated.
The purpose of the frontal lighting is to produce a reflection of your coating going onto the surface. This will give you a PRECISE evaluation of the amount of coating going on, and its UNIFORMITY. Test this technique on a piece of cardboard/wood, etc if you're uncertain of, or want to hone your skill level. This should reveal just how sloppy/non-uniform your previous spray paint jobs probably were.
Anytime I spray paint project cases,furniture,
cars....this is the ONLY way to do it.(Unless you have access to one of Detroit's programmed spray robots!)
Your PCB resist coating should have been just enough to have adequately coated the copper,but not enough to have filled up the CONTACT
"troughs". When just dry, carefull peel off the
surplus Contact covering, revealing the clean bare copper that is to be etched away.Any add on resist repairs can be made with a bit of paint shot into the cans plastic cap and applied with a toothpick tip. It does have a quick drying time though!
Etch away the copper in an agitated ,warm Ferric Cloride solution. When thru etching, cleanse the resist from the board with any of the afore-
mentioned solvents.
This technique was the result of not being satisfied with any the resist Pens (SHARPIES) or the other family of them, that required
multiple overstrokes of the fine lines that they produced. The success of this resist medium is the decreased "filming / coagulation" characteristics of the formulation of the matte/ flat surface mixes. Try using a gloss version, and if you pull off the CONTACT masking too soon, the paint will have crept under
the masking medium. Let it dry too long and the paint will have filmed and will either tear or pull away from the foil.Touchy-touchy-touchy!
If a layout for an IC socket holes was required I still prefer the dry transfer lettering patterns, put on just after the degreasing
stage and then they were just barely exposed by a window cut into the clear CONTACT at masking stage, so that interconnecting foil paths could be made to them.<p>73's de Edd<p>[email protected] (Interstellar~~~~Warp~~~~Speed)<p>[email protected] (Firewalled-Spam*Cookies*Crumbs)<p> :D<p>[ August 27, 2002: Message edited by: Edd Whatley ]</p>

tvman
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Re: etching printed circuit boards

Post by tvman » Tue Aug 27, 2002 2:47 pm

mr.EDD :&gt ;)
i would think the resulting board would look factory made.

but i am going to try the trace,resist pen way first.
if it doesn't turn out well, then i'll go the way you just described.<p> anyone curious as to what the the project is and what the circuit trace looks like, go check the feb issue of N&V page 55.
perhaps after viewing,other good ideas may get posted here.

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