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Is it safe to use a hot-glue gun to keep LED's in place?

Discussion in 'Electronic Basics' started by [email protected], May 28, 2005.

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  1. Guest

    I'm building some LED headlights for my radio-controlled car, and I
    plan to use one of those project boards or whatever they're are called
    to wire my LEDs and their resistors. But my RC car is gas powered, and
    the engine puts out a lot of vibration. I'm concerned that my big white
    LED's will be tugging a little on their solder joints without some sort
    of brace, and I would like to just use some hot-glue form a glue gun.

    But I'm new to electronics, and I do not know if the glue would be too
    hot? and I doubt it, but does the glue conduct electricity?

    --Farrell F.
  2. Ban

    Ban Guest

    I have seen ugly hot-glue work on cheap boards to hold cables and big
    components in place and even to insulate mains carrying traces on PCBs, so
    there doesn't seem to be much conductivity. It is another question if the
    epoxy surface of the LEDs will stick to it, but worth a try.
  3. Rich Grise

    Rich Grise Guest

    I'd build in some kind of strain relief for the LED leads, and smother
    the assembly in RTV silicone rubber, that you can get at any hardware
    store, "Home Club"-type store, or auto-parts store.

    I wouldn't trust hot glue unless it's the type that dries resilient.
    (Is there even any such of a thing?) Rigid stuff will crack, although
    epoxy might have the kind of toughness that you need.

    Good Luck!
  4. I'd say it's safe, if your question is about whether the glue
    will hurt the components.

    But my experience with hot glue is that it tends to be less permanent,
    ie it gets too warm or too old and things fall apart. At least,
    with plastics.

    Epoxy, or as someone said RTV silicone whatever, tends to be
    more permanent. The latter, which can be a real drag to remove
    if you need to, has the advantage that there's a level of flexibility
    to cushion those vibrations.

  5. wrote in
    When making connections to really small parts of circuit boards (ie
    soldering a 30awg wire to a via on a motherboard) - I often will put a blob
    of hot glue on it as a form of very basic strain relief. I've done various
    tests with hot glue and at least whatever I'm using (from craft store) does
    not conduct at all.

  6. Guest

    Thanks all! I guess I will go with the RTV silicone stuff. My only
    other question is if the silicone will effect the light output... my
    LED's project their light in about a 60degree angle, and I wonder if
    the silicone stuff will refocus the light?

    What would be the best way to apply the stuff... just at the base of
    the LEDs, or totally cover the LEDs in a think layer of the RTV silicon

    Lastly, since this will be on my RC car, dirt and other stuff will soon
    cover parts of my stuff. I use the general parts-cleaners that
    mechanics etc. use... spray can. Will that eat away at the RTV silicone
    stuff, or cause harm to the resistors and LED's? Would just using soapy
    warm water be better...and just let it dry thoroughly overnight?

    Thanks again,
    --Farrell F.
  7. Rich Grise

    Rich Grise Guest

    Not if you don't slop it all over the top of the LED. :)
    Put it between the LED and the board, with just enough excess to bring
    its level up to the rim around the LED base, maybe a teeny tiny bit more:

    top of LED
    / \
    / \
    | |
    | |
    | |
    --------------_| |_---- <- surface of goo
    |___________| <- "rim" of LED

    etc. - be sure it gets forcefully squirted underneath the LED (unless
    it's mounted flush, of course) so that you don't leave an air pocket.
    There's almost nothing that will attack RTV silicone. Acetone might
    attack the plastic LED surface, although they should be epoxy, which
    is also pretty impervious. Resistors are also inert, although there's
    a possibility it could wash the paint stripes off, which won't harm
    the actual resistor.

    But be sure and use a cleaner spray that leaves no residue. Do NOT use
    WD-40 for cleaning - that just gums stuff up. </voice of experience>

    Hope This Helps!

  8. Be careful with RTV. There are two types and one corrodes wire. It
    is marked, Not for electronic use.

  9. I see a lot of LEDs mounted in consumer electronics with a little dab
    of hot melt glue.
  10. jibberjabber

    jibberjabber Guest

    There is hot-melt and there is hot-melt. We use a polyamide stick (Tec-bond
    7718, black) and it's much better than the craft variety we used to use.
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