Measurement of electromigration parameters of lead-free SnAg3.5 solder using U-groove lines

Abstract

Measurement of electromigration parameters in the lead-free solder SnAg3.5 was carried out by utilizing U-groove solder lines and atomic force microscopy in the temperature range of 100–150 °C. The drift velocity was measured, and the threshold current densities of the SnAg3.5 solder were estimated to be 4.4 × 104 A/cm2 at 100 °C, 3.3 × 104 A/cm2 at 125 °C, and 5.7 × 103 A/cm2 at 150 °C. These values represent the maximum current densities that the SnAg3.5 solder can carry without electromigration damage at the three stressing temperatures. The critical products for the SnAg3.5 solder were estimated to be 462 A/cm at 100 °C, 346 A/cm at 125 °C, and 60 A/cm at 150 °C. In addition, the electromigration activation energy was determined to be 0.55 eV in the temperature range of 100–150 °C. These values are very fundamental for current carrying capability and mean-time-to-failure measurement for solder bumps. This technique enables the direct measurement of electromigration parameters of solder materials.