Evaluation of Cutting Forces for Intermetallic Compounds Formed on Solder Joint Interface by Instrumented Ultramicrotome

Observing interface states is especially important in evaluating solder joint reliability. Cross-section samples of intermetallic compounds generated by copper metallization with lead-free solders (Sn8Zn3Bi, and Sn9Zn, Sn3Ag0.5Cu), with Sn37Pb as a reference, were prepared using an ultramicrotome. We used an instrumented ultramicrotome to study the cutting force profiles of the intermetallic compounds. When we measured them with a needle-like diamond knife (60 μm in width), we found peaks in the profiles consisting of two elements that corresponded to those of the intermetallic compounds. These profiles also correlated well with the hardness of the constituent phases at the solder joint interface.