We are convinced that immersion silver is the best RoHS compliant finish for the majority of our customers and their applications. Our testing has shown that silver gives the best solder joint of any of the other finishes tested.
Silver immersion plating has been on the market for 10 years and end users have befitted from this finish long before RoHS requirements came into play. Silver, when stored properly, has a shelf life of 12 months (easily as long as OSP), and can withstand multiple heat cycles during assembly. Silver immersion does not require any special fluxes or solders and fits in perfectly with the “quick turn” mode of operation.
The contact resistance is very low (see chart) and the co-planarity of the finish provides a completely flat surface for solder paste application on fine pitch devices. The silver immersion finish is easily electrical tested without damage or “puncture” of the surface of the silver plating.
We have found that the Immersion Silver plating process is not limited to just a “post mask” finish, but can be applied to boards prior to mask and can also be processed through nickel/gold tab operations without any adhesion complications. When we process an Immersion Silver plating order, we not only give our customers the best finish (in our opinion) but, for complete RoHS compliance and assembly needs, we put this finish on high Tg, high Td and low CTE material; all at no extra cost.
For more information on the immersion silver plating process used by Sunstone please go to: Microvoids.org