Thermal Aging and Ball Shear Characterization of SAC-X Solders for Wafer Level Packaging

Abstract

Current industry trends in the microelectronics packaging is going towards increasing in I/O density and small size packaging. Common use of solder material in packaging are the lead free solders. The popular lead free alloys include the SnAgCu (SAC) family such as SAC 305 and SC405. SAC solder alloys are favor due to high stains rate transient load and reliable operation at high temperature. Hence, it is suitable for application such as military application, avionics, and automotive [1], [2]. SAC alloy is frequently used in Wafer Level Chip Scale Package designs but achieving board level reliability especially when footprint go beyond a certain size causes challenge for SAC solder ball [3]. To overcome this issues, new type of solder alloy, SACQ and QSAC, has been established in current market to improve board level reliability performance. In this paper, studies of the 2nd level solder joint of the SAC305, SAC-Q and QSAC solder ball in terms of ball shear strength measurement at time zero and its failure mode will be shared. The SAC305, SACQ and QSAC solder alloys are also subjected to High Temperature storage (HTS) at 150°C for up to 1000hrs. The different IMC layers and the IMC growth will be investigated in this work. In this paper, studies of the 2nd level solder joint of the SAC305, SAC-Q and QSAC solder ball in terms of ball shear strength measurement at time zero and its failure mode will be shared. The SAC305, SACQ and QSAC solder alloys are also subjected to High Temperature storage (HTS) at 150°C for up to 1000hrs. The different IMC layers and the IMC growth will be investigated in this work.