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Diode Lead Length

Discussion in 'Electronic Basics' started by Anand P. Paralkar, Feb 6, 2013.

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  1. Hi,

    I would like to use the 1N5283 diode in a certain application. Like
    some other applications in power electronics, this diode datasheet too
    mentions a certain Lead Length to be maintained.

    (See http://www.datasheetcatalog.org/datasheet/motorola/1N5298.pdf)

    Could someone please explain this? Why does this distance have to be
    maintained? (Its got to do with the thermal characteristics alright -
    but how?)

    I also see thermal resistance versus lead length curve and a note which
    says "(MOST HEAT CONDUCTION IS THROUGH THE CATHODE LEAD)". How's this?

    I tried searching and found some other datasheets mentioning 3/8" lead
    length, but no explanation.

    Your inputs please?

    Regards,
    Anand
     
  2. I've never used one of those. But the app note sorta spells it out.
    The current is temperature dependent,
    The temperature depends on power dissipation and thermal conductivity,
    For best control keep power low (low forward voltage)
    and thermal conductivity low... short leads.

    Jim nailed the cathode part.

    George H.
     
  3. Phil Allison

    Phil Allison Guest

    "Anand P. Paralkar"
    ** No such requirement is in the data.
    ** There is no distance to be maintained.

    FFS learn to read - it only says " keep leads short ".





    ..... Phil
     
  4. they assume the full lead acts as a heatsink, and if you chop it off, you
    lose heatsinking, and power rating.

    Of course they don't really account for a PCB with a trace also acting as
    a heatsink, and that's upto you to determine if it's less or more
    effective than a lead sticking out into the air.

    I've seen things such as solder turrets used as heatsinks for power
    diodes.
     
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