Volume Shrinkage Induced by Interfacial Reaction In Micro Joints

• Main Authors: Cheng-Chieh Li, 李澄傑
• Other Authors: C. Robert Kao
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/82765863623943124198

博士 === 國立臺灣大學 === 材料科學與工程學研究所 === 102 === Imminent ending of Moore’s law is the most critical issue threatening the continuing development of semiconductor industry. The strategy of consensus in order to go beyond Moore’s law is through the Three-Dimensional Integrated Circuit (3D IC) architecture. Among many 3D IC integration schemes under development today, solder micro-bumping is a very promising one. Due to the extremely small size of solder joints in 3D IC packages, interfacial reaction features are quite different to that in the conventional solder joints. The space confinement behavior must be considered in the soldering reactions. In this proposal, data analysis and experimental implementation of the volume shrinkage induced by interfacial reaction in micro joints is investigated. Theoretically, there is a 5% shrinkage in volume to produce Cu6Sn5 from the reaction between Cu and Sn. The shrinkages for Cu3Sn and Ni3Sn4 are 7.5% and 11.3%, respectively. Consequently, micro joints would be in highly stressed states and prone to failure. Experimentally, stylus surface profilometer and SEM are carried out to measure the actual volume shrinkages and observe microstructure for Ni/Sn/Ni, Ni/Sn-Ag/Ni, and Cu/Sn/Cu sandwich structures during an isothermal aging at 180℃. The results show that the internal stress and the forming of voids in micro joints during solid state aging might induce potential reliability issues. It is the first time that the reaction induced volume shrinkage is experimentally measured in common solder system. Theoretical analysis and experimental evidence are presented in this proposal to illustrate these issues, and implications based on the findings will be also discussed.