Phenomenological understanding of Sn migration in ceramic-chip capacitors

Electrochemical migration (ECM) is a well documented phenomenon in literature involving the transport of metal ions under the influence of voltage and in the presence of an electrolyte. This paper describes the classic Sn migration phenomenon that occurs with SAC305 solder used to attach capacitors on Intel's microelectronic packages, under accelerated humidity voltage tests. Additional lab-scale surface insulation resistance (SIR) tests, which replicated the accelerated test failures, were performed to understand the impact of moisture level, the critical voltage required and effect of ionic environment on the Sn migration phenomenon. As capacitor sizes continue to get smaller, leading to a greater risk of solder metal migration with electrode lines getting closer to each other, results from this study can be expected to improve the design of packages in future technologies.