Hi Paul,
The concern is primarily for the partially solder-filled PTVs to get fractured
barrels due to the stress concentration at the filled/unfilled interface.
Testing of earlier PWBs, not having the small hole diameters and high aspect
ratios of todays PTVs by contributors like Roger Wild, IBM, and Joe Keller,
Motorola, showed the unfilled PTVs more reliable, the partially filled PTVs
less so, and the fully filled PTVs with the lowest reliability in highly
accelerated thermal cyclic testing.
Your concern is with the reliability of partially filled PTVs during wave
soldering.
Because the PTVs heat up significantly, with at least a part of the solder
plug in a PTY melting, I do not think that your concern represents any real
danger to the integrity of your MLBs.

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]

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