Electromigration Study in Flip-chip with 15μm Thick Sn2.3Ag Solder Joints at High Temperatures

• Main Authors: Tang, Pao-Ming, 唐葆明
• Other Authors: Chen, Chih
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/mgqc9r

碩士 === 國立交通大學 === 工學院半導體材料與製程設備學程 === 104 === Because the miniaturization of integrated circuits (ICs), flip-chip become main packaging technology for wafer-end jointing. In recent years, the miniaturization trend still continues for portable and functional product. Traditional flip-chip packaging technology cannot meet the requirement of high density packaging. Three-dimensional ICs packaging technology has been developed. Micro bumps with 20μm diameter has been adopted for the interconnects between chips. The height of the microbumps is less than 20μm. Thus, microbumps are easy to transform into intermetallic compounds (IMCs) during the electro-migration tests. The IMCs would affect the failure mode of flip-chip solder joints. As a result, it is of interests how the IMCs would affect the EM behavior of microbumps. In this study, the SnAg solder joints with Cu UBM (under-bump-metallization) was used. The solder joints were with 50 μm thick Cu column UBMs. The bump height of the SnAg solder joints is 15 μm. Test current density was 1.32x104 A / cm2, and the actual temperature was measured to be 198°C. For electrical observation, Kevin structure was used to measure the resistance change during electromigration tests. Cross-section microstructure observations were performed at different stages of the bump resistance increases. Porous Cu3Sn structure was found after the bump resistance increased to 29%, and it would affect the reliability of solder joints. The porous Cu3Sn would be formed on thinner Sn2.3Ag solder joints at high temperature and current stressing. High current density stressing would accelerate the formation of the porous Cu3Sn.