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LMZ14202H failures, different substrates

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 We have had a few failures of part number LMZ14202HTZNOPB after a couple hours of service.  All of the failures are shorts that cause a fuse to blow on the board.  All failures come from a date code of 1344.  I ready that a process change occurred in this product on 1335.  Can anyone explain what that process change was?  

These failures are spread over several manufacturing lots.  They are not heat related as the boards are processed with leaded solder, highest temp the device ever sees is 212 degrees.

We x-rayed a failed device with a date code of 1344 and a newer, unused part with a date code of 1527 and there are some interesting differences in the substrate.  The substrate in the 1344 device has a bunch of holes in it while the newer device doesn't.  Are those holes right, or are they indicative of a bad part?  When did the process change from a substrate with holes to one without?  Two pictures attached showing the different parts.  We have x-rayed 2 of the failed parts so far and both have the holes in the substrate.

  • Let me pass this along to the PE.

  • In reply to Frank De Stasi:

    Jeff, please send your email address to the following email and we will contact you off the forum:  simpleswitcherapps@ti.com

    Thanks

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