Hi Bill,
I agree that the solder viscosity at Liquidus is too high for good flow 
anywhere, let alone capillaries. That is one of the reasons—the thermal 
energy needed to affect wetting, that is the dissolution of the surface metal 
into the tin, is the other—why good reflow requires peak temperatures of 
Liquidus+20C.
On voiding, I have yet to see any evidence of any problems for solder joints 
with the typical void contents observed. So my take is, do not worry too much 
about it; other things are much more important for reliability.

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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