The ultrasonic solder bump flip chip bonding was investigated as a method of fluxless bonding. The 100 \\micron-diameter Sn–3.5 mass%Ag solder bumps were formed at 12 positions on a test Si-die by laser ball bonding process. The test flip chip dies were bonded to a TSM-coated glass substrate on a hotplate at different bonding loads and ultrasonic power condition. The die shear strength was evaluated and fracture surfaces were examined with SEM. The Sn–Ag solder flip chip bonding was possible at lower temperature than the melting point of Sn–3.5Ag solder. The die shear strength increased with increasing bonding temperature, bonding load, and ultrasonic power. However, at excessive bonding load condition over 0.8 N/bump, the die shear strength decreased. The bump height decreased with increasing bonding load.