Effect of Ultrasound on the Reliability of Ni/Sn/Ni Micro Copper Pillar Solder Joints

Abstract

As the interconnection density of chips continues to increase, the reliability of solder joints under complex working conditions has become increasingly prominent. Therefore, altering the interfacial microstructure of solder joints to enhance their reliability has become a crucial direction in the study of chip service reliability. The research investigates the regulation of ultrasonic treatment on the electromigration (EM) resistance, thermal aging resistance, and the performance under thermoelectric coupling of microcopper pillar solder joints. It analyzes the corresponding failure modes, the growth behavior of intermetallic compounds (IMCs), and the influence of $\beta $ -Sn grain orientation on EM resistance. The results indicate that ultrasonic regulation has limited improvement on the thermal aging resistance and EM resistance under thermoelectric coupling of Ni/Sn/Ni structured microcopper pillar solder joints. However, by increasing the initial IMC thickness and altering the $\beta $ -Sn grain structure in the solder, the EM resistance of the solder joints is significantly enhanced. Under thermoelectric coupling, for microcopper pillar solder joints with a lower proportion of Sn-based solder, Cu3Sn exhibits cathodic polarity growth. When the angle between the c-axis of the $\beta $ -Sn grains and the current direction is large, EM is effectively suppressed; conversely, when the angle is small, EM is promoted. These findings provide theoretical insights for improving the reliability of micro copper pillar solder joints in practical applications.