Hi 'NickN,'
Nobody can guarantee you 100% filled vias for all vias on a board. The
concern is primarily for the partially solder-filled PTVs to get fractured
barrels due to the stress concentration at the filled/unfilled interface.
This is only a problem with small hole diameters and high aspect ratio PTVs.
The stress concentration at the filled/unfilled interface of a partially
filled PTV increases the stress on the PTV barrel at this location. Of
course, partially solder-filled PTVs become a problem only for severe use
conditions and very long design lives.

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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