Crystallographic characterization and growth behavior of (Cu,Ni,Pd)6Sn5 intermetallic compound in Ni(P)/Pd/Au/SnAgCu/Cu assembled solder joint

The interfacial reaction and crystallographic orientation of Ni(P)/Au/SnAgCu/Cu and Ni(P)/Pd/Au/SnAgCu/Cu assembled solder joints were investigated. With the aid of crystallographic analysis, the Pd influence on the grain structure and preferred growth orientation of intermetallic compound (IMC) on both Cu and Ni(P) substrates were revealed. On the Ni(P) substrate, the enhanced nucleation of (Cu,Ni,Pd)6Sn5 resulted in the random grain texture and needle-like morphology in the Pd-doping assembled joints. This random texture of (Cu,Ni,Pd)6Sn5 could hinder the crack propagation directly through (0 0 0 1) plane of adjacent grains. As for the Cu substrate, the granular (Cu,Ni,Pd)6Sn5 formed near the substrate and subsequently grew into a layer-like morphology after thermal aging. The granular grains of (Cu,Ni,Pd)6Sn5 exhibited the concentrated texture after aging, whereas (Cu,Ni)6Sn5 stilled revealed the random texture. Most important, the absence of high angle grain boundary among (Cu,Ni,Pd)6Sn5 grains on the Cu substrate could further guarantee the lifetime of solder joint during the reliability test. Finally, the detailed correlation between microstructure variation and grain orientation will be investigated and discussed as well as the possible mechanism.