Damage mechanics of microelectronics solder joints under high current densities

The electromigration damage in flip chip solder joints of eutectic SnPb was studied under current stressing at room temperature with a current density of 1.3 × 10^4 A/cm^2. The height of the solder joints was 100 (mu)m. The mass accumulation near anode side and void nucleation near cathode were observed during current stressing. The nano-indentation test was performed on solder joints for electromigration test. Surface marker movement was used to measure the atomic flux driven by electromigration and to calculate the product of effective charge number and diffusivity, D×Z*, of the solder at room temperature. The effective charge number can be extracted with the solder diffusivity at room temperature known. Pb phase coarsening was observed during current stressing.