Ulrich,
The "zipper effect" is exactly what you describe, with solder joints on one
side failing one after another (not exactly in an ordered pattern), and one
side of the TSOP separating from the board (the other side may also have
failures).  On occasion, when thermal cycling is pursued,  TSOPs may fall off
the boards!
Thanks for the update on your test.
With best regards,
Jean-Paul
________________________________________________________________
Jean-Paul Clech
EPSI Inc., P. O. Box 1522, Montclair, NJ 07042 - USA
tel: +1 (201)746-3796  fax: + 1 (201)655-0815
Home page: <A HREF="http://members.aol.com/Epsiinc1/index.html">http://members
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(click or copy)
__________________________________________________________________

In a message dated 97-01-08 19:31:18 EST, you write:

<< Subj:	Re: ASSY: TSOP with Alloy 42 lead frame field failures
 Date:	97-01-08 19:31:18 EST
 From:	[log in to unmask] (Ulrich Korndoerfer)
 Reply-to:	[log in to unmask]
 To:	[log in to unmask]
 CC:	[log in to unmask]
 
 Jean-Paul,
 
 thank you for your response.
 
 Answering to your question, I'm sorry, bud we did stop temp-cycling
 short afterwards due to other reasons than tsop-failures. We plan to
 start again next week with new samples and reach at least 100 cycles or
 more.
 
 By the way, what do you mean with "zipper effect"?
 
 We also saw concentration of lift-offs on one side of the tsop's. If im
 remembering right, there was nearly no tsop which showed lift offs on
 both sides. To my understanding the reason is that initially one pin
 lifts off (which side is determined by chance) and then others on the
 same side are following because the load per pin now is bigger on this
 side than on the other. Is this what you mean with "zipper effect"?
 
 Sincerely,
 
 Ulrich
 
  >>

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