Connect with us

Luxeon Star ?

Discussion in 'Electronic Design' started by Jorge Omar, Jan 9, 2004.

Scroll to continue with content
  1. Jorge Omar

    Jorge Omar Guest

    Hello,

    Could someone inform if the die is insulated from the mounting plate in the
    Star or is it necessary to use insulation between LED and heathsink?

    Thanks,

    Jorge
     
  2. Jorge Omar wrote...
    I know the smaller individual high-output Luxeon LEDs are isolated
    from the metal heat-sink plate.

    Thanks,
    - Win

    whill_at_picovolt-dot-com
     
  3. I have some bare emitters, and they are NOT isolated.
    The base on my red an yellows are directly in contact with the anode.
    And on my green and blue, the bases have a parasitic pn-unction to the
    cathode.
    I don't have any Stars to test on at the moment.

    Regards,
    Mikael
     
  4. R.Lewis

    R.Lewis Guest

    The Emitters are *NOT* isolated from their bases - see the datasheet!
     
  5. Jorge Omar

    Jorge Omar Guest

    Thanks!
    I've looked at the datasheet, but did not look close enough to the right
    side banner...

    Jorge
     
  6. Jorge Omar

    Jorge Omar Guest

    Thanks everyone for your time.

    Jorge
     
  7. S.M.Taylor

    S.M.Taylor Guest

    A pain isn't it ? I suppose it gets the junction/base thermal
    resistance down though.

    Steve
     
  8. Ian Stirling

    Ian Stirling Guest

    I have dissasembled an emitter, to mount it on a sapphire baseplate.

    From memory.

    There is a 3mm dia *8mm copper bar, with a 7mm dia*4mm height copper cylinder
    on the end.

    Onto the narrow end is soldered a hexagonal base, on which is mounted the
    emitter chip. From the emitter come a couple of gold bondwires which
    connect to two segments of copper that are wrapped round the copper bar
    just after it narrows. These are connected to the terminals.

    On top of the bar is a hemispherical shell of acrylic (?) filled with
    clear silicone.
    If you want to, you can pull the acrylic lens off, and get access to the
    chip.

    I'm unsure how the phosphor is attatched.
     
  9. Jorge Omar

    Jorge Omar Guest

    Yes, I will be mounting 3 different colors in the same heathsink.
    Oh, well...

    When I get the parts, I will see if the same side (anode or cathode) is
    in contact with the base.
    If so, maybe I will redesign the driver.

    Jorge
     
  10. Posting before first coffee of day , doh!

    From experience do not rely on the emitter slug to be any particular
    connection....
    What should have said is that the emitters are not consistently and reliably
    connected to their slug.
    My thanks to R Lewis for correcting this before any LSs were smoked.

    The emitter slug is silver plated and solderable, perhaps not reccomended
    but possible.

    Interesting thought about detaching the chip and remounting it on a sapphire
    substrate, just wait for commercial diamond production to ramp up, then can
    really get into overdriving.

    Adam
     
  11. Posting before first coffee of day , doh!

    From experience do not rely on the emitter slug to be any particular
    connection....
    What should have said is that the emitters are not consistently and reliably
    connected to their slug.
    My thanks to R Lewis for correcting this before any LSs were smoked.

    The emitter slug is silver plated and solderable, perhaps not reccomended
    but possible.

    Interesting thought about detaching the chip and remounting it on a sapphire
    substrate, just wait for commercial diamond production to ramp up, then can
    really get into overdriving.

    Adam
     
  12. Ian Stirling

    Ian Stirling Guest

    Yep.
    The sapphire substrate isn't very good, it's about a tenth of the
    thermal conductivity of copper. (this is countered by the fact that it's
    a better shape than the long bar of the emitter)
    However, copper isn't transparent, and I'm using a reflector to bounce
    light back past the LED.
    For a rather silly upgrade to a minimag solitare.

    I'd really like to use diamond, but it's only really a bit better at
    these sorts of power densities.
    Sapphire does 40W/m/K, diamond 2000W/m/K.
    The chip is around 2mm square.
    80mw/2mm/K.
    So the cube behind the chip adds around 12C, and the four in contact
    with it around 3C, and the the rest maybe another couple.
    So, call it 17C rise for a watt, for a 4mm thick infinite disk.
    Diamond would be interesting to try to overdrive it, but in this case,
    sapphire is just fine.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-