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"Heat Sink Putty" ?

Discussion in 'Electronic Repair' started by (PeteCresswell), Mar 2, 2008.

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  1. Any such thing?

    I'll have a little bridge rectifier and voltage regulator serving
    a bicycle hub alternator (6v 4w) and want to use the bike frame
    as the heat sink.

    My thought was that, if there's such a thing as heat-conductive
    putty, I'd just embed the two components in some of it and stick
    it to a frame tube.
  2. I've never heard of putty. Silicone grease is common, of course.
  3. Eeyore

    Eeyore Guest

    Aluminium powder mixed with epoxy might work.

  4. **Do you need heat sinking? 4 Watts is not much power. You could use a 6 Amp
    bridge, which can dissipate quite a bit of power, before requiring any heat
    sink. If you do need it, then use silicon glue (the stuff used for
    guttering, kitchens, bathrooms, etc). It remains flexible and will transfer
    reasonable heat to the frame. I seriously doubt that you need it though.

    Trevor Wilson
  5. Smitty Two

    Smitty Two Guest

    Don't they make thermally conductive epoxy? OP might not want anything
    electrically conductive.
  6. GregS

    GregS Guest

    Thermal epoxy is better than regular epoxy but the conductivity
    is very poor compared to copper, and copper is poor compared to diamond.
    Might try the suggestion of adding metal filings to regular epoxy putty.
    Thermal epoxy is not really putty.

  7. GregS

    GregS Guest

    The thermal epoxy I am currently using on a project is a lot thicker than
    regular epoxy. Its Omega Bond 101.

  8. PeterD

    PeterD Guest

    Then use zinc oxide with epoxy, that should not be conductive... But
    regardless, nothing will work very well, IMHO...
  9. GregS

    GregS Guest

    Seems like there are atachments to the frame for accesories, and if they
    are aluminum, it will make a great way to do it. Curved surface aluminum

  10. Jim Yanik

    Jim Yanik Guest

    (GregS) wrote in
    whatcha need is diamond-filled epoxy..... :cool:

    you can buy very finely powdered copper at craft stores.
    by the time you get enough copper or other filler mixed in the epoxy,it IS
    the consistency of putty..... ;-)

    better to machine an aluminum mount to mate closely with the bike tubing
    and coat it with thermal paste,mount the circuit to the Al. plate. with
    thermal paste.

    Or use a switcher-type regulator for lower heat dissipation.
  11. Jim Yanik

    Jim Yanik Guest

  12. whit3rd

    whit3rd Guest

    If there's a brazed boss in some convenient spot, you can screw a
    block of aluminum to that (or even a 1" square plate). The rectifier
    won't need conduction cooling at these power levels, so it's just
    the (three terminal TO-220?) regulator or pass transistor that gets

    Generator mount bracket or headlamp bracket are good candidates.
    If they get warm, it sinks to the frame quick enough.
  13. Guest

  14. Eeyore

    Eeyore Guest

    Bridge tectifiers usually have isolated cases anyway.

    Trevor's idea is good though. Use a larger bridge than actually needed
    (they're not expensive) and it'll happilly dissipate the heat without
    additional cooling.

  15. Eeyore

    Eeyore Guest

    That's a particularly good idea.

  16. Per Trevor Wilson:
    I just checked the specs on the one I ordered. 25 amps/50v.

    Sounds like my dinky little hub alternator will barely warm it
    up. So much for the heat sink requirement....
  17. Guest

    Heat sink putty is old hat.It's been around for many years.
  18. Jimmie D

    Jimmie D Guest

    There is an epoxy but it doesnt work like you want.It must be applied thinly
    and used to conduct heat to a heatsink.
    Just get a really big rectifier. I have a 5 amp power supply that uses a 20
    amp bridge and its bolted to a piece of wood.

  19. Per Jimmie D:
    That's what I (inadvertently) did. 25 amp/50 volt to handle
    about 1 amp/20 volts max.
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