Effect of Mechanical Characteristics of Gold Wire on Microstructure and Properties of Ball Bonding

Abstract:

Microstructure of gold wires with different mechanical characteristics was characterized by electron backscattering diffractometer. The loop profile, the heat affected zone and bonding point morphology were observed by scanning electron microscopy and optical microscopy, and the pulling force and ball shear force were measured by push-pull tester. Finally, the influence of mechanical characteristics of gold wires on the ball bonding quality was analyzed. The results show that there is obvious difference in microstructure along the radial direction. The core of the gold wire in semi-hard state 1 and 2 retains fibrous structure, and the edge grains are fine equiaxed grains. The length of the heat affected zone (HAZ) formed after forming the ball is short, the structure of the ball neck has obvious step, and the loop height after bonding is small compared with the soft state. The soft gold wire shows coarser equiaxed crystal, lower pulling force, and is prone to ball slip. The gold wire in semi-hard 2 state has strong bonding force to the pad, high pulling force and excellent overall bonding quality, which is the most suitable for the ball bonding process.

Key words:gold wire;ball bonding process;mechanical characteristics;heat affected zone length;bonding quality