The effect of intermetallic compound evolution on the fracture behavior of Au stud bumps joined with Sn-3.5Ag solder

• Published in: Electronic materials letters 2013, 9(1), , pp.31-39
• Main Authors: Lee, Young-Kyu, Ko, Yong-Ho, Kim, Jun-Ki, Lee, Chang-Woo, Yoo, Sehoon
• Format: Article
• Language: English
• Subjects: Bonding; Bonding strength; Characterization and Evaluation of Materials; Chemistry and Materials Science; Chips; Condensed Matter Physics; Fracture mechanics; Gold; Materials Science; Nanotechnology; Nanotechnology and Microengineering; Optical and Electronic Materials; Solders; Studs; Tin; Tin base alloys; 전자/정보통신공학
• ISSN: 1738-8090; 2093-6788
• DOI: 10.1007/s13391-012-2128-5

The microstructure and joint properties of Au stud bumps joined with Sn-3.5Ag solder were investigated as functions of flip chip bonding temperature and aging time. Au stud bumps were bonded on solder-onpad (SOP) at bonding temperature of 260°C and 300°C for 10 s, respectively. Aging treatment was carried out at 150°C for 100 h, 300 h, and 500 h, respectively. After flip chip bonding, intermetallic compounds (IMCs) of AuSn, AuSn 2 , and AuSn 4 were formed at the interface between the Au stud bump and Sn-3.5Ag solder. At a bonding temperature of 300°C, AuSn 2 IMC clusters, which were surrounded by AuSn 4 IMCs, were observed in the Sn-3.5Ag solder bump. After flip chip bonding, bonding strength was approximately 220.5mN/bump. As aging time increased, the bonding strength decreased. After 100 h of aging treatment, the bonding strength of the joint bonded at 300°C was lower than that bonded at 260°C due to the fast growth rate of the AuSn 2 IMCs. The main failure modes were interface fractures between the AuSn 2 IMCs and AuSn 4 IMCs, fractures through the AuSn 2 IMCs and pad lift. Initial joint microstructures after flip chip bonding strongly affected the bonding strengths of aged samples.