Electromigration behaviors in Sb particle-reinforced composite eutectic SnAgCu solder joints
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Due to the limited capacity of solder joints in microprocessors for the higher current density (usually 103–104 A/cm2), electromigration (EM), known as the mass movement resulting from imposition of high current density, has gained extensive attention during the last decades, specifically, the EM-induced damages in the eutectic 95.5Sn–3.8Ag–0.9Cu (e-SAC) that were heavily used in the electronic packaging industry. In order to conquer the instable physical properties of e-SAC in the severe service environment, composite approach was developed. One of the promising ways was intentionally incorporated metal-particles reinforcements. In this study, the e-SAC with 1 wt% Sb particles additive was investigated under the current density of 104 A/cm2 and 120 °C the ambient temperature. Unlike the non-composite solders that had obvious formation of hillock and valley at the anode side and cathode side, respectively. The crack initiated at the edge of the cathode interface and propagated to the center in the Sb particle-reinforced composite solder. The Sn–Sb phase, formed near the cathode interface after the first-reflow, blocked the movement of metal atoms/ions, but then induced the current crowding. In addition, synergistic influence of the compressive and tensile stress caused the fracturing of the Sn–Sb phase in the solder matrix due to its brittleness and immobility.
KeywordsSolder Joint IMCs Layer Composite Solder Cathode Side Solder Matrix
The authors acknowledge the financial support of this work from the Beijing Natural Science Foundation Program and Scientific Research Key Program of Beijing Municipal Commission of Education (KZ200910005004), the Academic Innovation Group Supporting Program of Beijing Municipality, and the China Scholarship Council (2008654006). The authors also acknowledge the revision of manuscript from writing centre at Michigan State University.