PCBs

Hi,
Probably a bit off-topic, but I was wondering if anyone here had ever had a
go at making their own PCBs using photo paper? If so could they recommend
one?
Cheers,
Michael
Reply to
Michael
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"> Hi,
If you go to YAHOO Groups, you will find a fairly active homemade PCB group.
The title is "Homebrew_PCBs"
Check it out for a while and you may get some useful information.
Good luck.
Ian.
Reply to
Ian French
I did it years ago but you still have all that faffing around with chemicals. It's much easier to just use someone like PCBPool or get a PCB mill like a T-Tech or a LPKF. One day I'll convince them to let me have a LPKF laser mill!
Chris
Reply to
Chris Eilbeck
I tried a few, but for some reason never got the ease of removal that some people seem to. I gave up and went for Press-n-Peel instead and haven't regretted it. I only use as much as is required, taped to a piece of A4 to go through the printer to keep the costs down. It's not cheap, but I get a board ready to etch in 15 minutes rather than the best part of an hour it used to take me, most of which was spent scrubbing tenacious bits of paper off (and often breaking a few tracks in the process).
Tim
Reply to
Tim Auton
Thanks Ian, I'll be sure to sign up.
Michael
Reply to
Michael
Chris, have you compared PCBPool's prices with other companies? Are they fairly competitive?
Cheers,
Michael
Reply to
Michael
Thanks Tim,
Michael
Reply to
Michael
I've never used "photo" paper, so I can't comment except to say that I've heard that the usual transfer papers work better with a laser printer than an inkjet.
However, if you ar doing single- or double- sided boards without plated through holes, you can use photosensitive board. You will need to faff about with exposures, tanks and chemicals a bit, but it isn't hard. Initial costs may be a bit more that you might expect, but afterwards boards are cheap enough to make.
I use inkjet overhead projector film for the positives, and print on an ... inkjet, surprise surprise :)
If you want plated through holes or multilayer though, go to a shop and get it done.
Reply to
Peter Fairbrother
Thanks Peter,
Do you heat the etchant when you do it? I've found a instruction guide on the Rapid site and it says to heat the etchant up to 45oC. Do you just use it at room temperature?
Michael
Reply to
Michael
I've not used them myself but I know someone who does and finds them to be reasonable on price, quality and delivery.
I tend to use Exception
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myself but I don't know if they'll deal with an individual on a credit card basis like Pcbpool will. Exception do a fantastic job.
Chris
Reply to
Chris Eilbeck
There's a good article on PCB making here :
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I haven't followed his methods, but I do know the author and have confidence that he knows what he's talking about. If you look around the rest of the site you'll probably agree !
-adrian
Reply to
Adrian Godwin
Yes, I do heat it - and perhaps more important is agitation in the tank. I use a fishtank heater and an air bubbler. Both of these make the etch quicker, which gives crisper track edges. Note, some fishtank airstones will dissolve, test first - I use plastic tubing with holes in it, but I know a chap who uses fishtank stones.
Alternatively you can buy ready-made tanks, and sets of tanks for developer, wash, etchant, wash, perhaps cleaner/tinner as well, with all the gubbins - but they ain't cheap.
However I have done etching at room temperature (with ferric chloride - don't try this with the etchant described below) in a flat photograher's developer type tray, and it works okay for 0.1" track spacing, just not quite so well; however if I am doing thin tracks for surface mount chips they usually don't come out right without heat and agitation.
Some other tricks and tips - make sure that the positive is in close contact with the board when exposing, and the ink side of the positive is down (ie the positive is printed in mirror image).
You'll have to learn about exposures and timing etc by experiment, as materials vary, but they usually give some guidance when you buy them.
I use mixed ferric chloride and hydrochloric acid* for etchant as it's cheaper than pure ferric and may work a little better. By weight: 3 parts water, 1 part ferric chloride, 1 part hydrochloric acid. You can add another part of hydrochloric acid when the etchant gets partly used up and etching times start to increase. Nasty stuff though.
Take care when adding the ferric as the water will get hot. Let it get cold. In theory you should then add the HCl slowly with stirring, allowing the mixture to cool between portions, but in practice it doesn't matter much how you do it. However I am a chemist and have training and practice in handling such stuff - if you are not confident then pure ferric chloride will work just as well.
*
available at decorator's merchants and better hardware stores under the name "spirits of salt(s)" - it isn't made that way any more, what you now get under that name is technical HCl which is purer than HCl made by the old spirits of salts method
I usually use positive board as it's easier for me to get, but negative board is slightly better and if you are doing something really tricky it might be worth using negative board.
If you use carbide drill bits you will need a good quality drill stand, drilling by hand will break the bits in no time. You can do a small board with HSS bits by hand though.
Reply to
Peter Fairbrother
The one thing that you MUST avoid, if the HCl is concentrated, is adding the water to the HCl; always add the HCL to the water.
You really don't want to be in the vicinity of anyone adding water to conc HCl!
Regards, Tony
Reply to
Tony Jeffree
This is much more a problem with conc H2SO4 - when you add the acid to the water (you NEVER add water to the acid)* it crackles - that's bubbles of water boiling then collapsing, as the mixing happens under the surface and the bubbles are surrounded by cold water. That doesn't happen with conc HCl.
I can't say it's safe to add water to conc HCl, and please don't do it, but conc HCl is at most 35% HCl and the mixing does not give off as much heat anyway, so it's not nearly as dangerous as adding water to conc H2SO4. Also, H2SO4 is _much_ more poisonous than HCl, and is a carcinogen by inhalation to boot.
It is however fairly safe to add conc HCl to water, if done with care and the realisation that it may spit out hot acid, though that is unlikely unless the water is already hot.
However, unless you have been shown how to do it, no-one should add sulphuric acid to water, never mind the other way round! Diluting conc sulphuric acid, or worse oleum (H2SO4.SO3), is really a job for a trained person, in full safety gear, with a second trained person available and aware of what you are doing in case of emergency.
*
Of course, being an idiot, I have done that, once - still got the holes. I was lucky none got in my eyes.
I also have holes from adding conc sulphuric acid to conc hydrochloric acid - the sulphuric takes the water from the hydrochloric and forms HCl gas, as well as simply boiling if you add too much sulphuric at once.
Reply to
Peter Fairbrother

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