Electromigration induced interfacial microstructure evolution of solder joints in electronic packaging

Electromigration (EM) of eutectic SnBi and SnCu solder joints with NiPdAu surface finish are studied at temperatures above their melting points. The interfacial microstructure evolutions are discussed in detail. EM induced quick cathode side metallization dissolution happens in both solder alloys. The dissolved metallization diffuses through liquid solder under EM and form thick IMCs on anode side. It is also observed that local self-heating can impact the cathode side interfacial microstructures. With oven temperature above melting points and uniform temperature distributions on the testing coupons, Ni-P and Cu metallization are fully dissolved in both SnBi and SnCu, replaced by a mixture of solder and IMCs. However, high self-heating can induce local deformation and induce NiSnP/Cu separation before EM can dissolve Cu in SnCu solder joints.