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Building a UV PCB exposure box?

Discussion in 'Electronic Basics' started by Aly, Apr 6, 2007.

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  1. Aly

    Aly Guest

    Hello,

    Ideas please?

    A small professional UV box with two 8W tubes will cost about £100, and is,
    professionally made and neat and tidy. I'm wondering if for sake of ease it
    would be easier to just go out and buy one?

    I've seen the UV "fly killer," tubes on eBay for say £10, which are
    mentioned in a few of the tutorials online. Ballasts I have at home
    somewhere. Would need a neat little case, cut glass, switches, bits bobs,
    and time.

    This is all purely for making the odd PCB so nothing commercial. There's
    also those little UV nail boxes for curing the plastic, they're only about
    £20 although I wonder about even coverage with those, and if indeed it is
    the right type of UV?

    Circular tubes? U-shaped tubes? Straight tubes? Little 9W dual parallel
    tubes?

    I'm just wondering in the end if it would be easier to just buy one,
    although that's not really in keeping with the spirit of diy.

    Many thanks for any input, I'm just looking for ideas and opinons really.
    I'd also be half tempted to put in regular tubes too so that it can be used
    as a light box.

    Friendly regards,

    Alison

    ps. There's this one at Rapid for £110 in a little kit;

    <http://www.rapidonline.com/searchresults.aspx?style=0&kw=34-0690>
     

  2. The DIY spirit found a real cheap method some years ago. Use an obsolete
    face tanner and an old scanner. An example can be found on
    http://gathering.tweakers.net/forum/list_messages/730455///
    Although the text is Dutch, the pictures tell the story. I build one this
    way. Bought scanner and tanner for less then $15,-- on a flee market. The
    only extras were some pieces of scrapwood, some wire, two screws and piece
    of hot melt glue. Works like a charm. Two minutes exposure is enough to get
    perfect PCBs.

    You only must make sure that your positives are pitchblack. My printer,
    although perfect in normal printing, does not make the artwork black enough.
    I have to stack two sheets to block the UV.

    petrus bitbyter
     
  3. larwe

    larwe Guest

    You need _quartz_ glass to pass all UV. Apart from this issue, all the
    mechanical needs are satisfied by taking an old scanner and removing
    the innards; put the UV tubes and reflector inside where the scan
    mechanism used to go, and put your PCB on the glass, then close the
    lid.
    Not advisable. If you're building a UV box, you should interlock it so
    that the tubes cannot come on while the lid is open. There are fun
    ways of going blind, and dumb ways... stick to the fun ways.
     
  4. _Quartz_ glass? I was told so very often. But the glas of scanner is
    apparently good enough.

    Face tanners have no lid. So the need for an interlock will not be that
    strong. Nevertheless you should not look into the light. If you want to tan
    your face with it, you need to keep your eyes closed. The light can do
    serious damage to your eyes.

    petrus bitbyter
     
  5. Coyoteboy

    Coyoteboy Guest

    Are scanner glasses usually quartz glass? I have an old scanner here now....
     
  6. Aly

    Aly Guest

    Thank you to those who are replying. I'm following with interest.

    At the moment I'm swaying towards the £100 for sake of ease. Oh, printer,
    photo inkjet, transparances, Brother DCP-340CW apparently 1200x6000dpi...
    we'll see about that.

    :) Aly

    Aly :)
     
  7. Leon

    Leon Guest

    I built one using two UV tubes in standard 12" fluorescent fittings,
    with a box made from MDF and a sheet of glass. It cost me about 20
    GBP.

    Leon
     
  8. Leon

    Leon Guest


    You don't need quartz, ordinary window glass is transparent to the
    long-wave UV used for PCB exposure. The light isn't particularly
    hazardous.

    Leon
     
  9. Leon

    Leon Guest

    I use an HP 5940 printer with JetStar premium film, results are
    excellent.

    Leon
     
  10. Bob Masta

    Bob Masta Guest

    I don't use the photo method much anymore, but
    for many years I did it wifh a UV tanning floodlamp
    in one of those clamp-on utility lights with a spun aluminum
    reflector. I'd lay the PCB on a piece of plywood on the
    floor, with the artwork taped over it and a sheet of
    ordinary window glass on top to make sure everything
    was flat. The tanning light was clamped to the back
    of a chair so it was 2-3 feet from the work, and
    pointing straight down at the center of the board.

    True, that plain glass probably blocked some UV,
    but so what? The tanning flood puts out a ton of it,
    and you don't really want a super-short exposure here.
    Several minutes is fine, since it gives you some
    room to adjust exposure times.

    Best regards,


    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    www.daqarta.com
    Scope, Spectrum, Spectrogram, Signal Generator
    Science with your sound card!
     
  11. Pete

    Pete Guest

  12. larwe

    larwe Guest

    It depends on the UV wavelength required for this application, I
    assumed it was rather short-wave. Below 170nm or so quartz glass is
    really necessary. Germicidal lamps have a quartz envelope.
     
  13. Aly

    Aly Guest

    What nM are we talking about for photoresist exposure?

    I'm looking at UV LEDs on eBay at the moment. 150mcd, about 400nM.

    Search for inside the brackets. ( UV "LEDs" ) to weed out the other stuff.
     
  14. Coyoteboy

    Coyoteboy Guest

    Not sure they have the intensity needed for etching, youd probably need
    hundreds of them lol. That said they're fairly cheap.
     
  15. Leon

    Leon Guest

    UV LEDs can work, Elektor mag. had a design a few months ago.

    Leon
     
  16. Aly

    Aly Guest

  17. Hershel

    Hershel Guest

    I would think that used ones would be plentiful. I probably haven't
    erased a UV chip in 10 years, and would sell you mine if I could find it.

    Hershel
     
  18. For the occasional home made PCB, I find that the sun works much
    better than any UV tube. Depending on the time of day, I normally
    expose pre-coated PCB material for 20 to 80 seconds. This works
    quite well and it is fairly easy to produce boards with 12thou tracks
    with 12thou clearance. With a bit more care, one can do 10 thou.
    I have used a UV box bought from RS Components in the past, but
    I found the sun to give better results.

    Regards
    Anton Erasmus
     
  19. John  Larkin

    John Larkin Guest

    A light box is about the worst possible way to expose pcb's. To get
    good resolution, you need sharp shadows hence collimated light. The
    typical light box is a maze of position-dependent blurs. The light
    source should be far away from the film and the board, not close.

    Get a bright light with decent UV concentration. A 175 watt
    warehouse-type mercury vapor lamp is ideal, and perfectly safe. Mount
    it about 3 feet above a table and add a bit of foil on top if it
    deosn't already have a reflector. Place the pcb, film, and a top piece
    of glass or plexiglass, on the table. Try 10 minutes to start. This
    will cast much sharper shadows than any light box can.

    A tanning lamp isn't bad, and they're cheap.

    The sun is pretty far away, too.

    John
     
  20. Aly

    Aly Guest

    Hi John,

    Noted. Tell you what I do have.. A full size sunbed in the bathroom, hold
    on.. Eight 100W 6' tubes.

    I've just been playing with the idea of fitting one of those small 25W 9"
    U-shaped tubes in a 12"x10"x5" flight case, or an 22W 8" circular tube.

    But with what you've said here it's made me wonder..

    Thanks again (and to everyone)

    Aly :)
     
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