Mechanical Properties ofCu6Sn5, Cu3Sn, andNi3Sn4 Intermetallic CompoundsMeasured by Nanoindentation

We report inthis paper Young's moduli andhardness of Cu6Sn5, Cu3Sn, andNi3Sn4 intermetallic compounds (IMCs) measured bynanoindentation. Thesamples wereprepared by annealing Sn-CuandSn-Nidiffusion couples. Indentations performed along thedirections lateral andperpendicular to theIMClayers showstatistically indistinguishable Young's moduli andhardness foreachofthethree IMCs,implying thatthesepolycrystalline IMC aggregates arerather isotropic. Nanomechanical responses oftheIMCswere showntodepend greatly onthestrain rateduring loading whileindependent ofthestrain rateduring unloading. Multiple pop-in events wereobserved forCu6Sn5 during loading atastrain ratelower thanabout 0.1s-1 to0.5s-1. Topographies oftheresidual impressions werequantitatively measured andthepile-up features wereapparent forthethree IMCs.