Papers by Author: Lei Han

Abstract: An assembly bed on thermosonic flip chip bonding was set up, two different structures of tool tips were designed, and a series of experiments on flip chip and bonding machine variables were carried out. Lift-off characteristics of thermosonic flip chip were investigated by using Scanning Electron Microscope (JSM-6360LV), and vibration features of tool tips driven by high frequency were tested by using PSV-400-M2 Laser Doppler Vibrometer. Results show that, for chip-press model, slippage and rotation phenomena between tool tip and chip have been solved by using tool with greater area tip pattern during flip-chip bonding process, and welding failures appeared in chip-collet model have been controlled. Greater area pattern on tool tip is better than small area pattern. The power of ‘n’ bumps on flip chip bonding is far smaller than that of n×(the power of single wire bonding). The power is directly proportion to vibration displacement driven by the power, high-power decrease positioning precision of flip chip bonding or result in slippage and rotation phenomena. The proper machine variables ranges for thermosonic flip chip had been obtained.

Abstract: Vertical section features in bonding point were produced by ion-sputter thinning, and were tested by using TEM-F30. Lift-off characteristics at the interface of Ultrasonic bond are observed by using SEM (JSM-6360LV). Results show that thickness of Au/Al atomic diffusion interface was about 500 Nanometer under ultrasonic and thermal energy. Ultrasonic vibration activates dislocations at metal crystal lattice. Fracture morphology of lift-off interface was dimples. Tensile fracture appeared by pull-test not in bonded interface but in basis material, and bonded strength at interface was enhanced by diffused atom from the other side.