Alt-BEAM Archive
Message #06753
To: beam@sgiblab.sgi.com, beam@sgiblab.sgi.com
From: Robert Stein rastein@dakotacom.net
Date: Fri, 15 Oct 1999 07:03:02 -0700
Subject: [alt-beam] Re: PCB etching
At 08:17 AM 10/15/99 -0500, John Leo Zimmer wrote:
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>No one has mentioned using a laser printer or copier to make a
>circuit board.
>
>I do not have a laser printer available here at home so I print my
>circuit with my inkjet printer. (Must be mirror image of the desired
>final result. Your software has to provide that.) Then carry it to
>the office and "Xerox" it. (Printing double size at home and reducing
>it increases the resolution and allows for some touchup or freehand
>additions to the origional.) The toner is plastic fused to the paper
>with heat. It can be fused to your clean copper with the right amount
>of heat and pressure ... too much of either makes a blob, not enough
>and it won't stick. Use Mom's iron :-)
>
>Then you throw the thing into water to soak off the paper. And you
>have your circuit printed to the copper. Touch up with Sharpie Ultra
>Fine point, or other resist. Etch as described elsewhere in this
>thread.
>
>DigiKey, etc. will sell special paper for this purpose, but it is not
>necessary. I've experimented papers. Try fingerpaint paper. You want
>something that disolves easily (coated) and does not fuse excessively
>with the toner. In my hands the whole process is very much an art,
>rather than science. And trial and error pays off. The results are
>much nicer than hand drawn. And once you have a circuit you like and
>you've developed the right touch, turning out multiple copies is like
>making cookies. Developing the resist is a lot like working in a
>darkroom and watching your photo rise out of the blank paper. Great
>fun.
>
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There is another process, but it takes another chemical, but you will get a
higher quality printed board.
You will need to get a kit that contains some photoresist solution
or pretreated copper clad, developer and etchant. Make the masks as
mentioned as above, but on transparencies (make sure it is a negative of
the trace file you created.) The photoresist or pretreated copper clad IS
light sensitive. Use an ordinary yellow bug light to work in. Sandwich
the mask on top of the board. Expose it to the sun for approx 30
sec. Develop it for about 1 - 2 min. Rinse, bake at 60 -80 C for approx
10 min. Then etch as normal. You can also get tinning solution. It stinks,
but does a great job of tinning all of the traces and pads.
I know some of you might be wondering Why go through all of this
trouble.....If you want a smaller circuit make it double sided. make too
masks, with a crosshair off to the side and use a double sided copper
clad. Line up the crosshairs of the mask, with the copperclad
between. Then expose both sides of the copper clad. etc. etc
It sounds like more work, but the results far outweigh and more
inconvienence, but I don't think that it is any harder. I have made a few
boards already from Ian. They turned out great.
later,
Robert Stein
Applications Scientist
Spectral Instruments, Inc.
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