采用改进的激光多普勒振动测量系统,获得小直径激光斑,解决了大量数据采集和分析、同步触发等技术问题,实时精密测量热超声倒装键合过程中工具和芯片的运动。通过分析运动曲线,发现“速度分离”是表征键合过程状态改变的重要临界现象;发现在“速度分离”前工具/芯片粘着在一起运动,之后它们间是“粘滑”交替的过程:在“速度分离”后的运动过程中,工具能量一部分通过芯片传递到键合界面,形成键合强度;另一部分消耗在芯片/工具间的摩擦上,磨损芯片和工具,损害键合界面结构和强度。根据研究结果提出了新的超声加载过程思路,以期减小磨损,提高键合强度。
A laser Doppler vibration (LDV) measurement system was setup to monitor the real time vibration of bonding tool and flip chip in thermosonic flip chip bonding. By analyzing the vibration of chip and comparing with the vibration of tool tip, the "stall" phenomena of chip is elucidate, which is significant critical phenomena indicating bonding states changing during bonding process. Stall means that the initial bonding strength is formed at the bonding interface. The chip was vibrated with tool tip before "stall". After "stall", relative movement produced between them, a part of tool energy is propagated to the bonding interface via chip and formed bonding strength, and a part of energy is consumed at the tool/chip interface friction, which caused damage to bonding strength and bonding interface structure, caused damage on the surface of chip and tool. Finally, a novel bonding parameter apply method is developed to reduce the friction and to enhance the bonding strength.