A new COP bonding using non-conductive adhesives for LCDs driver IC packaging

In this study, attempts were made to develop a reliable and low cost chip on plastic (COP) bonding process by using electroplated Sn bump and non-conductive adhesives. Results showed that the bumped chip was successfully bonded with PES, and the initial average contact resistance was less than 30 mΩ, which is much lower than that of ACF bonding. Thermal cycling (TC) test was performed to study the reliability of the COP assembly. The joints passed over 1000 thermal cycles without failure. The contact resistance decreased and leveled off during the TC test. 30 μm fine pitch joints were fabricated and electrically tested. Microstructure observation disclosed that interfacial intermetallic compound formed at the Sn/pad interface, indicating a chemical bonding was achieved. EDS analysis showed that its average composition was very close to (Cu, Au)6Sn5. During thermal cycling, the interfacial IMC layers were observed to gain dramatic growth.