Abstract: Electromigration (EM) behavior of Cu/Sn3:5Ag/Cu solder reaction couple was investigated with a high current density of 5 × 10³ A/cm² at room temperature. One dimensional structure, copper wire/solder ball/copper wire SRC was designed and fabricated to dissipate the Joule heating induced by the current flow. In addition, thermomigration effect was excluded due to the symmetrical structure of the SRC. The experimental results indicated that micro-cracks initially appeared near the cathode interface between solder matrix and copper substrate after 474 h current stressing. With current stressing time increased, the cracks propagated and extended along the cathode interface. It should be noted that the continuous Cu6Sn5 intermetallic compounds (IMCs) layer both at the anode and at the cathode remained their sizes. Interestingly, tiny cracks appeared at the root of some long column-type Cu6Sn5 at the cathode interface due to the thermal stress.

Key words: electromigration,  cracks,  intermetallic compounds,  thermal stress