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semi OT- removing plastic lens from LED

Discussion in 'Electronic Design' started by George Herold, Sep 26, 2013.

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  1. Hi guys, Is there a fairly easy way to remove the plastic lens on the 'standard' 5mm through hole LED? I've used a file to get ~90% down to the element, but I'm afradi if I go further I'll wreck it.
    I tried some acetone but it did nothing. A chemical would be nice, but hopefully *not* methylene chloride.
     
  2. Syd Rumpo

    Syd Rumpo Guest

    This may be folklore.

    I often work with high-temperature stuff, and the wisdom is that you
    can't use conventional LEDs at 180C because the lenses melt. I've never
    needed to and haven't tried, but just maybe they'll soften sufficiently
    to aid removal.

    Some of the small SM ones seem to have Silicone lenses which it might be
    possible to remove carefully under a microscope. Silicone oil will
    soften Silicone rubber a little.

    Cheers
     
  3. Try hot (~85'C) red fuming nitric acid. You said a chemical would be
    nice, but that is not a nice chemical.
     
  4. Joerg

    Joerg Guest


    Johne Wayne would have put the LED on a fence post, step back 30ft, draw
    and pull the trigger.

    When looking at the 5mm through-hole LEDs I have here they are all fully
    encapsulated, "immersed in plastic". And as John said, with the
    placement precision all over the map. Not sure what you are trying to
    design but you may be better off buying bare die. I don't know them,
    just as an example:

    http://www.tech-led.com/LED_die_bare_chips.shtml
     
  5. Well, I'm using this red led as a light sensor. I was taking some data on response vs light intensity. (using a yellow led as a light source) And then I tried a green led (as a source) And though there were more photons I got a lot smaller signal. WTF I thought to myself, well maybe the red palstice lens is absorbing all the green light. So I filed it down and increased the signal by a factor of 5 or so... Now if I could just get more of itoff...
    When hitting this with a file I'm afraid I'll 'take out' the little bondingwire and that will be the end of it.

    George H.
     
  6. Hmm OK maybe I can 'dig' around a bit with a soldering iron tip.
    Thanks,

    george H.
     
  7. "Arghhhh... Run Away!!" I've never heard of red fuming nitric acid but it sound like methyelene chloride would be safer.

    George H.
     
  8. "I'd never shoot an LED in the back."

    I guess I'm just going to have to settle for a bit of filing... I tried digging a bit out with the soldering iron and broke one.

    George H.
     
  9. Ecnerwal

    Ecnerwal Guest

    Run, don't walk, to your nearest library that keeps old books, and get a
    copy of "Some Birds Don't Fly" for a fuller appreciation of RFNA (and
    quite a few chuckles.)
     
  10. Last time I went to Home Depot I didn't see any consumer grade
    methylene chloride.. has it been outlawed or something?
     
  11. Joerg

    Joerg Guest

  12. Joerg

    Joerg Guest

    Even whole tail light assemblies. But then you also need a lowering kit
    and a major tchk tchk *BOOM* stereo.
     
  13. Den fredag den 27. september 2013 00.54.12 UTC+2 skrev Phil Hobbs:
    many types of acrylic craze and break in to little pieces
    if it cleaned with any kind of alcohol

    -Lasse
     
  14. hamilton

    hamilton Guest

    Light Sensor ??

    What does hacking an LED do that a regular "light sensor" won't do ??

    h
     
  15. Well this is a bit embarrasing since it's written by my boss.
    http://teachspin.com/newsletters/TeachSpin_MAY13FINALFOR WEB.pdf

    But basically it detects single photons. Which is way cool for ~$0.10.

    This is all old news, but there's been a redesign to the elecronics box.. adding a voltage source (lm317) some series resistors and an LED light source. Yellow led's are great and greens stink.. visible light led's seem OK..so the spectral response is mostly unknown.* (I need a monochrometer... Well maybe just a wideband light source.)

    George H.
    *like being mostly harmless.
     
  16. Got it, I mostly found chemistry to be confusing.

    George H.
     
  17. Guest

    180C? RoHS reflow solder processes go up to 260C. Yeah, a lot of
    LEDs melt there, but...
     
  18. Guest

    RFNA is rocket fuel (specifically an oxidizer). It's truly nasty
    stuff.
     
  19. I've seen stress corrosion cracking in acrylic when PCBs were cleaned
    with certain solvents. Nothing like the visible crazing but where
    there were stress risers (eg. threads) cracks would gradually
    propagate. This was in some very nice clear acrylic moldings we had
    made for instrument faces. The problem was solved by baking off the
    boards to remove small amounts of residual volatiles before assembly.



    Best regards,
    Spehro Pefhany
     
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