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Electro Leakage ?

Discussion in 'Electronic Design' started by Phil Allison, Mar 7, 2008.

  1. Phil Allison

    Phil Allison Guest

    ** Hi to all,

    I have Google searched without luck for the formula ( or even a good rule
    of thumb ) for how DC leakage current varies with temperature for common
    electrolytic capacitors - ie the usual 85C and 105C types.

    My own testing suggests it is strongly positive and increases by a factor of
    2 or more with a temp rise of 20C.

    Anyone help ?



    ........ Phil
     
  2. whit3rd

    whit3rd Guest

    There's strong history dependence; after storage, the oxide can
    perforate,
    and a quarter hour at max temperature and voltage makes it heal.
    The 'healing' process generates lots of nonrepeatable leakage current.

    So consistent measurement requires a temperature/bias prestress
    cycle (I've used a curve tracer and hot air blower). After that,
    the measured leakage might be meaningful . Manufacturer's data
    on leakage is ... sketchy at best. There aren't even any limits
    except
    at 25 C, in the datasheets I see.
     
  3. Phil Allison

    Phil Allison Guest

    "whit3rd"
    "Phil Allison"

    " Manufacturer's data on leakage is ... sketchy at best.
    There aren't even any limits except at 25 C, in the datasheets I see. "


    ** The DC leakage figures I see published are ambiguous or just plain
    wrong - particularly in relation to the temperature.

    If you apply the formula quoted ( ie 3.sq.rt CV uA) and that is for 25 C -
    then allow the leakage to rise by a factor of 5 or possibly 10 at max temp
    of 85 C or 105C - a high voltage cap will be dissipating several watts &
    EXPLODE.

    ( note " C " in the above formula is in uF )



    ........ Phil
     
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