Folks,

Thanks for the initial input and interest.

1) The first two photos exhibit what was initially thought to be, as many of
you have or will suggest. ESD/EOS damage. The supplier, unnamed concurs.

2) The plot thickens as the other images show several possibilities:

    Acuoustic studies show signifigant voiding in the die attach eutectic
    material.

    The heat sink, for this device, also has significant voiding it its
    initial design as a prototype - not yet a die casting.

    The device has some coplanarity issues associated with its mounting and
    thermal dissipation capabilities. As my company has elected not to go
    with thermal grease, this could contribute to the problem.

    The initial junction temperature was 180C and, with sinking, went to 150
    C.

    Could the part, a high power/speed amplifier with clearly shown 4
    transistors be too sensitive to the commercial assembly operations now
    being used as we successfully assembled and tested about 60 parts in
    house before going outside and finding the parts.

    We have known cleanliness issues but to what extent, I don't know yet as
    the supplier is being audited for all factors including ESD/EOS and
    cleanliness issues, among others. A bit late in the ball game to be
    qualifying suppliers - in my mind.

    An interesting point is the failure seems to be propagating from the
    drain side toward the input gate. Interesting to anyone?

    Could a combination of all the above, or just one, or a bad design, or a
    component issue, be causes. Of course, but where to go as we had four
    labs, and the big customer, working on the problem before my arrival. We
    have run every test imaginable including loose particle. Still, we need
    to find root cause.

I have to run back to work now and I will be online all day there.

Any help MUCH appreciated.

Earl Moon

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