Influence of Coating Metals on Stress Conditions in Silicon during Copper Thermosonic Wire Bonding
Copper wire has attracted increasing attention in the thermosonic wire bonding of integrated circuits, thanks to its lower cost and higher strength than the traditional gold wire. One of the key problems that limit the large scale application of copper wire is the under pad damage, which closely related to the stress conditions during wire bonding process. In this study, an incrementally coupled “thermal-mechanical-ultrasonic model was employed to model the copper thermosonic wire bonding processes using three types of pad coatings, i.e., Al, Ag, and Ni. Results show that Ni coating leads to highest tensile stress in silicon substrate, followed by Al and Ag coatings. Compressive stresses are the highest with Ag coating, lower with Al coating, and the lowest with Ni coating. As for shear stress, Al coating produces the highest value and the Ni coating produces the lowest. Considering the shear stresses are more determinative to under pad damage, the Ni coating should be more favorable in copper wire bonding. It has little effects between coating materials and stress concentration positions in the silicon substrate.
Wire bonding Coating Stress conditions Copper Under pad crack
CHANG Baohua BAI Xiaoyi JIANG Wei DU Dong ZHOU Yunhong
Department of Mechanical Engineering, Tsinghua University, Key Laboratory for Advanced Materials Pro Department of Mechatronical Engineering, University of Waterloo, Waterloo, N2L 3G1, Canada
国际会议
济南
英文
1-11
2012-08-24（万方平台首次上网日期，不代表论文的发表时间）