Study of EM and TM of Sn0.3Ag0.7Cu solder joints under high current stress and thermal gradient

Abstract

Electromigration (EM) of solder joints in microelectronic devices have become a critical reliability issue due to the continuous miniaturization and requirements for enhanced performance of the devices. At present, besides EM, thermomigration(TM) has been regarded as another reliability concern as it has been found to accompany EM in flip chip solder joints. Both EM and TM effect are the main factors leading to the failure of the solder joints. In this study, TM and EM were studied in Cu/Sn0.3Ag0.7Cu/Cu solder joints by applying a 1×10(4) A/cm(2) DC current and a thermal gradient of 1×10(3)°C/cm to the joints respectively. The microstructure and composition of the solder joints were observed by means of Scanning Electron Microscope. This research include two possible aspects. Firstly, the solder joint was subjected to current stress and thermal gradient. Secondly, analyzing the microstructure and composition of the joints. According to the microstructure and composition, the behavior of the joints under current stress and thermal gradient were found. The results indicated that, with a thermal gradient of 1×10(3)°C/cm, the Cu atoms were found to migrate towards the lower temperature side while the Sn atoms were found to migrate towards the higher temperature side firstly, with the time prolonging, the Sn atoms were found to migrate towards the slower temperature side. And with a 1×10(4) A/cm(2) DC current stressing, The IMC in cathode decrease much, and some voids and cracks occur. In anode, the IMC increase a lot. And there are some bump. The couple of thermal and electrical field of solder joint will be studied in the future.