UV LEDs as replacement for UV tubes or CFLs

Discussion in 'General Electronics Chat' started by electrophile, Dec 5, 2016.

  1. electrophile

    Thread Starter Member

    Aug 30, 2013
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    I'm building a UV exposure unit for curing photoresist films and till now I've been using UV tubes. However, I'm wondering if UV leds also work for this purpose? Do UV leds actually emit UV light or are they just blue leds?
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    They emit UV but not great for exposure unless you get a bunch. Even then, expect some light / dI'm areas because the lens dictates the flux of UV in any given spot - unlike bulbs that emit in all directions. Even Tubes are difficult if boards are wider than 4".

    Anyhow, LED options would be expensive. Time consuming and inferior.

    The only benefit would be the directional light and possibly less undercutting but you need some pretty fine traces for that to be a concern. A plastic anti glare grid used in drop ceilings could solve that problem for a few bucks.
     
  3. electrophile

    Thread Starter Member

    Aug 30, 2013
    126
    1
    Ah I see. I'm planning to make a 60-led grid. Getting more LEDs packed in to make it very dense and then I'll add reflector surfaces all around the casing. I read that their effectiveness vastly diminishes as the distance from the exposure surface increases.
     
  4. bertus

    Administrator

    Apr 5, 2008
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  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Yes, all lights do. You need about 4x the exposure time each time you double the distance from the light.

    UV doesn't reflect well. You need good mirrors, not just foil.
     
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