DIY UV Exposure Unit

Discussion in 'The Projects Forum' started by Mad Professor, May 22, 2010.

  1. Mad Professor

    Thread Starter Active Member

    Apr 15, 2009
    Good day all.

    I am looking for advice with regards to making an DIY UV Exposure Unit for use with Double-sided boards.

    I have looked at premade units by RS, Maplin, and MegaUK.

    Single side units start around £100, but Double Side units are silly in price.

    So I am looking at making my own double sided uv exposure unit

    At my local car boot sale I picked up four Germicidal 8 Watt UV Lamps for £10.00

    I understand this type of lamp is classed as a (T5) style.

    How meny lamps will I need each side, and how far away do they need to be.

    By once again looking at the premade units, it looks like 2 or 3 8 watt lamps per side will do.

    But does it matter how far or close the lamps will be from the PCB board.

    How where is the best / cheapest place to get the lamp holders with built in transformer.

    Thanks for your time.

    Best Regards.
  2. bertus


    Apr 5, 2008
  3. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    Germicidal lamps make lousy UV sources for photoresists. Almost all of the light is at 254 nm which will not penetrate any glass hold down or most film masks. That wavelength needs quartz or similar materials.

    Check the specification for what you are using. I suspect it recommends UV at about 366 to 390 nm or so, which requires a tube with the proper phosphor.

    As for total wattage, I used to use just one, 15W, type BL tube. As I went to wider boards, I made a unit with three, 15W tubes. I used three mainly because I had the fixture already. I think two per side would work just fine. However, I just flip my exposure frame when I do double-sided boards.

    Last edited: May 22, 2010
  4. retched

    AAC Fanatic!

    Dec 5, 2009
    This may help get the price down:

    300nm - 460nm 15w 18inch - £5.25

    As foe making your own unit, its not rocket science. Just make the box light tight.

    I used .5in plywood, painted white on the inside and caulked the joints with UV opaque caulk (outdoor type)

    I used a drawer with a recessed front. nice and easy. Use glass as the bottom layer of the drawer and a removable piece of glass to hold the film tight when exposing. A old photography exposure timer I had, and whalla.

    I have transfer to silk screening since then, and bought a uv exposure box / light box combo. Real nice for blackout pen work on the transparency.
    Last edited: May 22, 2010