Peel Strength of Soldered Joint in Stainless Steel with Surface Treatment

Abstract

The purpose of this study is to improve solderability of stainless steel with various kinds of electro plating such as Sn, Cu, Ni, Ag, and Au of thickness from 0.5μ to 10μ.
At first we have tried to investigate the solderability of plated or not plated stainless steel sheet with special designed speading machine. Next we have carried out peel test of soldered joint which seems to be most suitable method to examine the mechanical property of soldered joint. Results of our investigation are summerised as follows:
1) Among various electroplating of stainless steel, Sn plating shows best spreading.
2) It was found in the peel test that the kind of plating and the soldering temperature affects the peel strength. It decreases in the following turn in terms of plating metals Cu, Ni, Ag, So, and Au from 48 kg/cm in case of Cu to 12 kg/cm in case of Au.
3) In So plating, bright plating contributes to the peel strength by 20% lower than dull plating.
4) In Ag pating the peel strength decreases with the soldering temperature. In Au plating it is affected by the degree of diffusion between Au and Sn-Pb solder. The more the diffusion proceeds the greater the strength is.
5) The platingthickness does not affect much the peel strength in such kind of metal as Cu and Ni with little solubility. On the other hand in such metals as Ag and Au with rapid diffusion in solder, it has an remarkable influence.
6) Concluding from fracture study by micro-scopic and E.P.M.A. examination, it could be made clear that the peel strength lowers when the plated layer disappears during soldering process.