Yes, there are results from studies that show the impact of 'soldermask
encroachment' onto soldering pads; the most important one being the
intentional soldermask defined (SMD) solder pads for BGAs. The results of
accelerated thermal cycling tests show that SMD-pads can reduce the fatigue
life of these solder joints by between 30% to a factor of 3--it depends on
the geometry of the soldermask edge (sharp vs. rounded) and on the severity
of the accelerated test.

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]

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