Electromigration in Pb-free SnAg3.8Cu0.7 solder stripes

Abstract

Electromigration behavior in the eutectic SnAg3.8Cu0.7 solder stripes was investigated in the vicinity of the device operation temperature of 100°C by using the edge displacement technique. Measurements were made for relevant parameters for electromigration of the solder, such as drift velocity, threshold current density, activation energy, as well as the product of diffusivity and effective charge number (DZ*). The threshold current densities were estimated to be 4.3×104A∕cm2 at 80°C, 3.2×104A∕cm2 at 100°C, and 1.4×104A∕cm2 at 120°C. These values represent the maximum current densities that the SnAg3.8Cu0.7 solder can carry without electromigration damage at the three stressing temperatures. The electromigration activation energy was determined to be 0.45eV in the temperature range of 80–120°C. The measured products of diffusivity and the effective charge number, DZ*, were −1.8×10−10cm2∕s at 80°C, −5.0×10−10cm2∕s at 100°C, and −7.2×10−10cm2∕s at 120°C.