Hi Paul, Steve, and all others,
Paul is right; when you have less then good quality drilling or poor/thin
plating, PTV barrel failure can occur at less severe use conditions. For good
quality PTVs higher loads are necessary to fatigue a PTV barrel in a time
frame that matters. Any stress concentration, as results from a partial
solder fill will add to the load near the fill/no-fill interface or a
localized thin plating due to glass fiber rip-out during drilling, will
shorten the time to failure for a given loading condition.
From a purely a solder joint reliability issue a 75% (or even 50% fill) makes
liitle practical difference. That is what has driven the recent attempts to
change 610; but one has to look at the whole picture.
For PTV barrel reliability 75% fill is a little bit better than 50% fill
because 50% fill would typically end near the barrel center where the highest
loads occur in an unfilled PTV, but given a partial fill the location of
maximum load will move towards the unfilled section.
Lands at layers 1, 2, N-1 and N typically see higher loading because they
experience more land rotation during soldering operations. In my experience I
have not seen the significant quality differences that Paul mentions at these
locations.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask], Website: www.engelmaier.com

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