In electronics industry, the coming electronic devices will be expected to be high integration and convergence electronics. And also, it will be expected that the coming electronics will be flexible, bendable and wearable electronics. Therefore, the demands and interests of bonding technology between flexible substrate and chip for mobile electronics, e-paper etc. have been increased because of weight and flexibility of flexible substrate. Considering fine pitch for high density and thermal damage of flexible substrate during bonding process, the micro solder bump technology for high density and low temperature bonding process for reducing thermal damage will be required. In this study, we researched on bonding technology of chip and flexible substrate by using 25um Cu pillar bumps and Sn-Bi solder bumps were formed by electroplating. From the our study, we suggest technology on Cu pillar bump formation, Sn-Bi solder bump formation, and bonding process of chip and flexible substrate for the coming electronics.