Various solderability tests have been developed over the years to quan
tify the wetting behavior of solder on metallic surfaces. None offer a
n exact measure of capillary flow normally associated with conventiona
l plated-through-hole and surface mount soldering. With shrinking pack
age designs, increasing reliability requirements, and the emergence of
new soldering technologies, there is a growing need to better underst
and and predict the flow of solder on printed wiring board (PWB) surfa
ces. Sandia National Laboratories has developed a capillary flow solde
rability test, through a joint effort with the National Center for Man
ufacturing Sciences, that considers this fundamental wetting issue for
surface mount technology. The test geometry consists of a metal strip
(width, delta) connected to a circular metal pad (radius, r(c)). Sold
er flow from the pad onto the strip depends on the geometric relations
hip between delta and r(c). Test methodology, experimental results, an
d validation of a flow model are presented in this paper.