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June 1998

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From:
TOSTEVIN_BC <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 25 Jun 1998 15:31:01 -0400
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     We've been doing some investigative work into tantalum capacitor
     failures.  Some portion of the failures has been traceable to defects
     within a vendor's lotcode.  Other failures are undoubtedly caused by
     well-meaning, but incorrect hand placement of missing components.
     However, there is a third group of failed parts, where the capacitor
     was installed backwards, but for which no rework or operator
     intervention is indicated in the card's production history.  This
     leads to several questions.

     1.   Is anyone aware of studies or data, which attempted to determine
     a DPM for reversed tantalum capacitors, as received on the tape & reel
     from the component manufacturer?  The vendors would have you believe
     that the DPM is zero, but we all know, nothing is perfect.

     2.   What are some of the inspection / test methods,  and equipment
     that you're using (or not using as the case may be), to ensure that
     these parts are installed correctly on the final assemblies?

     3)   What about through-hole caps, where the polarity markings are
     less visible on the side of the part than on the top of smt caps?

     Bruce Tostevin
     Benchmark Electronics
     Hudson, NH

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