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DIY PhotoResist?

Discussion in 'Electronic Design' started by Jon Slaughter, Nov 9, 2007.

  1. Anyone here have any experience with adding photoresist yourself? I have a
    few copper clad boards with no resist on them and I'd like to maybe add some
    myself.

    Even going farther I was wondering how difficult it would even be to make
    the copper clad board itself? Copper is pretty cheap... just a few pennies
    and I'm not sure about the prepreg but I'm sure for prototyping one could
    probably using just about anything? (hell maybe even cardboard?) I imagine
    it might be difficult to get decent results but maybe its not all that
    difficult? (either by copper sheets or melt some copper and roll them
    yourself? (I don't actually mean roll them)) I know everyone is going to say
    its better to buy, but I at 20 bucks a pop for double sides it seems to
    expensive for prototyping or making small quantities of circuits that don't
    need the high quality insulative material(Which I imagine can probably still
    be done DIT even cheaper than buying(although I'm not taking into account
    labor)).

    (Main point here is not that I will probably actually end up doing it myself
    but just curious if anyone has tried)

    Thanks,
    Jon
     
  2. Tim Williams

    Tim Williams Guest

    I would guess PCB is made by gluing foil with the PCB board stuff when it's
    molded. You could try electroforming on top of blank board, but don't
    expect nice results, and certainly don't expect a good bond. If you have a
    vacuum chamber you could deposit copper vapor before electroplating, but
    somehow I doubt that's any cheaper.

    I don't know what photoresist consists of, but I'm sure it's a bitch to
    cook up at home.

    Tim
     
  3. D from BC

    D from BC Guest

    Huhhhh... I've posted this so times....
    'Try out dry film photoresist..'.. :p
    mmmm...maybe I should start selling the stuff on here.. :)

    You could try out toxic potassium dichromate + a protein. (So I've
    heard.)
    But I don't think it's popular.


    D from BC
     
  4. Tom Bruhns

    Tom Bruhns Guest

    http://www.thinktink.com/ -- but if you offered dry film for sale in
    modest quantities, you very well could find some takers. Supposedly
    Injectorall will coat boards for you, too.

    I used to coat my own boards with Shipley AZ-111, but that was when I
    needed enough for other things to buy it by the quart, and a couple
    quarts wasn't all that expensive. I believe it's now close to $1000 a
    quart and is sold in 6 quart lots, minimum--though I may be mistaken.
    But given the time it takes to lay out a board and the cost of the
    parts to put on it, even paying one of the fast-turn proto shops to
    make a board for you isn't all that bad. And if you do etch your own,
    paying something like 30 cents per square inch for top-quality pre-
    coated double sided board material seems cheap.
     
  5. D from BC

    D from BC Guest

    $1000.00/qrt !!!
    Damn might be more expensive than ink jet ink.

    For small boards, I use precoated Injectorall boards from Digikey.
    For larger boards, I wet laminate the dry film onto cheapo surplus
    boards.

    Using keyword 'photoresist' on ebay returns no relevant results.
    Time to set up shop :)
    Or figure out why no one else has... :p


    D from BC
     
  6. Guest

    norland 60 or norlan 61 UV optical cured cement is 16$ a bottle for a
    ounce or two. start there.
    They probably have something hackable on their web site.

    Steve
     
  7. These guys have KPR-3 for only $478 US a quart.

    http://www.dalpro.net/Page.html


    Best regards,
    Spehro Pefhany
     
  8. John Larkin

    John Larkin Guest

    The classic glop was KPR, Kodak PhotoResist. I still have some around.
    You'd spin or spray it on some copperclad, bake dry, and expose
    through a negative. There was a developer which was mostly xylene. It
    polymerized where UV hit it, making those regions insoluble to the
    developer.

    I think KPR and/or its developer were mildly toxic, so I don't know if
    they're still on the market. I've seen references to KPR3, maybe the
    newer generation. Google <kpr photoresist>

    It was easy to do clean 8 mil lines/spades with KPR and decent
    emulsion-down film.

    John
     
  9. Tom Bruhns

    Tom Bruhns Guest

    KPR?? Yeccchhhhh!

    Sorry, but I'd a lot rather pay the price for some good resist. That
    could be a personal bias, but I gave up on KPR within, um,
    microseconds of trying the Azoplate resist. It ended up being a good
    choice also from the standpoint of what I was doing; the processing
    took fewer steps with the AZ111 than it would have with KPR. But the
    world of photoresists has moved on, rather a long ways I suppose,
    since the days of KPR and AZ111. These days, perhaps Rohm and Haas
    Photoposit SN66??

    Cheers,
    Tom
     
  10. Robert Baer

    Robert Baer Guest

    Photoresist is cheap as hell to make: egg white for the base and
    potassium dichromate for photosensitivity.
    After exposure, use the universal solvent (water) as the developer.
     
  11. Robert Baer

    Robert Baer Guest

    Correct, not "popular" but useable.
     
  12. So what's the difference between the various KPRs?


    Best regards,
    Spehro Pefhany
     
  13. Sarason

    Sarason Guest

    I studied the chemistry of photoresists with a view to making a homebrew
    or a cheap'n safe version for the homebrew market. The evolution of
    photoresists is way to complex to cover in a single post. But their is a
    book called oddly enough "Photoresists" by Williams which IIRC was
    published about 1970. Photoresists have moved on a lot from there, as
    the IC industry has required better and better lithography for IC
    manufacture. Now the gotcha's wet resist needs to be of a consistent
    thickness to get consistent exposure times. This is a real PITA for home
    use. One solution to this is a record player used as the spin on table.
    The best solution are dry negative resists which are used by the PCB
    manufacturers. Applying them with a machine made for the process, or
    wetting the circuit board and then floating a precut out sheet of resist
    you can do at home. Then the film is rolled onto the board, so that no
    bubbles get to form. Exposure with an inkjet negative and etching will
    get you a very nicely made board. If you want very high resolution lines
    a homebuilt spray etcher is the way to go. There is a Yahoo group
    devoted to Homebrew.

    http://groups.yahoo.com/group/Homebrew_PCBs

    There are allsorts of tips and techniques in that group

    Best of luck

    Andrew
     
  14. Barry Lennox

    Barry Lennox Guest

    Yes, KPR, I used it for many years with good results (Xylene was the
    'cheap' developer instead of the real ($$$) stuff. It was very
    important to get a thin coat, I used to swab it on, as thin as
    possible, then spin it on a much-modified turntable

    Actually, I still have much of the quart bottle I paid (IIRC) $16 for
    in about 1973. I last used some a year ago, and it still works
    perfectly!

    I'll bet it's not as cheap as surplus PCB stock, I have acquired good
    stocks that way. Also check out a local PCB house, if nearby, they
    will generally give you offcuts free, I still operate from a donated
    boxful from about 10 years ago.
     
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