The polarity effect of electromigration on intermetallic compound (IMC) formation in solder V-groove samples
Hua Gan and King-Ning Tu
Dept. of Materials Science and Engineering, UCLA, Los Angeles, CA90095-1595
The polarity effect of electromigration on intermetallic compound (IMC) formation at cathode and anode in the solder joints has been investigated. We used solder V-groove samples with width about 100 mm to study the polarity effect of electromigration on IMC formation in the solder joints. Lead free solder was reflowed into the V-grooved silicon wafer and two copper wires were used as electrodes. We focused on morphology and thickness changes of IMC in lead free solder 95.5Sn3.8Ag0.7Cu/Cu system under different current density and constant temperature settings. The current densities used were 103 to 104 A/cm2 and the temperature settings were in the range of 120oC to 180oC. The growth of IMC has been enhanced by electric current at anode and inhibited at cathode comparing with the samples without applying current. We found that electromigration has different effect on morphology and thickness changes at cathode and anode sides, and this effect will be discussed.