Papers by Author: Ji An Duan

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: To find out the effect mechanism of technological parameters on the performance of fiber coupler, the relationship between the technological parameters and the optical performance is investigated by using a six-axes optical fiber coupler machine as experimental setup. It is discovered that the technological parameters such as drawing speed and fused temperature have a great effect on optical performance of fibre coupler. The fused region and taper region of fiber coupler are tested with scanning electron microscope (SEM). It is discovered that there are crystalline grains in the fused region. And the crystalline grains decrease while drawing speed increase. In the taper region, there are micro cracks. And the cracks are more obvious while drawing speed increases. When the fused temperature is above some point (here is 1350
), the micro cracks in the taper region disappear and the optical performance of fiber coupler is the highest at this time.

Abstract: Fused-taper fiber coupler is usually fabricated by using a microburner. The coupler’s excess loss and performance repeatability are unstable. To simulate the fabrication process and to find solution to the performance questions, A viscoelastic rheological model of fused biconical taper process is presented by using generalized Maxwell model to simulate the viscoelastic characteristic of fused fiberglass, and the rheological numerical analysis under the non-isothermal condition is carried out with ANSYS software. The effect of technical parameters such as drawing speed and fused temperature on the fabrication process is studied. Drawing speed is in direct proportion to the maximum stress, and fused temperature affect extremely the fabrication process. The fluctuation of fused temperature by 5
can lead to the change of maximum stress by 30%. It is found by experiments that the flame temperature fluctuates in the range of 5-30
, while the drawing speed is rather stable. It can be reached a conclusion that it is the fluctuation of fused temperature that induces the poor performance repeatability and unstable excess loss.

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.