PTHs that are 75% solder filled are not as strong against pin/lead pull-out
than are those that are 100% filled. But pulling out of component leads is
not a real reliability threat. In terms of functional reliability not much
difference should be expected between 75% and 100% filled PTHs.
Rework is another matter entirely. Every additional excursion to soldering
temperatures is a threat to reliability, both short-term and long-term.
Complete fractures can occur producing opens (in most cases intermittent at
elevated temperatures) and failures right at manufacture; partial fractures
will propagate during operational use thermal cycles to completion in the
longer term. Particularly rework with its manual soldering operations are bad
news, since manual soldering is in most cases the most severe thermal
excursion in the whole manufacturing process (see Engelmaier, W., "Quality
and Reliability Optimization Through Design for Reliability and Design for
Manufacturability," Proc. Int. Electronics Packaging Conf. (IEPS), Austin,
Texas, September 1996, pp. 81-93).

Werner Engelmaier
Engelmaier Associates, Inc.
Electronic Packaging, Interconnection and Reliability Consulting
23 Gunther Street
Mendham, NJ  07945  USA
Phone & Fax: 201-543-2747
E-mail: [log in to unmask]


***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.        *
***************************************************************************