THERMOSONIC FLIP-CHIP BONDING USING LONGITUDINAL ULTRASONIC VIBRATION

Flip-chip assembly is an important technology for first level electron ic packaging, Among different assembly approaches, thermosonic bonding is becoming an attractive choice because it is cost-effective, To inc rease the bonding capability for high input/output (I/O) assembly, a n ovel longitudinal bonding system was developed in this study, This bon ding system has two advantages over the transverse bonding system: it overcomes the planarity problem and simplifies bonding tool configurat ion, During the development, an end-effector was designed with rigorou s considerations of ultrasonic wave propagation, bonding force and co- planarity between the chip holder and hot stage, The bonding system wa s then characterized to make sure that it is suitable for hip-chip ass embly, This bonding technology was proven successful by mechanical bon ding tests as well as a functional complementary metal-oxide-semicondu ctor/static random access memory (CMOS/SRAM) module demonstration, Dur ing the bonding profess, the chip is under longitudinal ultrasonic ''h ammering.'' However, there is no apparent damage because the impact st ress is low due to the low ultrasonic vibration amplitude.