Electromechanical responses of Cu strips

报告题目：Electromechanical responses of Cu strips
报告人：Prof. Fuqian Yang
　　　  Department of Chemical and Materials Engineering
　　　  University of Kentucky
时间：2013年6月21日（星期五）上午10：00 
地点：力一楼二楼227会议室 

报告摘要： 
The continuous demand for high speed and great performance of electronic devices and systems has led to the miniaturization of electronics and a significant increase in electric current density. This trend has led to the replacement of Al by Cu as electronic interconnects in high-performance electronics and high-power IC chips due to the low resistivity and low RC delay of Cu. It is known that electronic interconnects of small scales can carry electric current of high densities of 1 MA/cm2 or higher, and high current density can seriously affect device’s reliability and potentially cause electromechanical failure of electronic interconnects. 

In this talk, I will present our recent study on the electromechanical responses of Cu strips. The electromechanical response of Cu strips was studied for the current densities ranging from 12.34 to 29.60 kA/cm2. The experimental results showed that the passage of the electric current of high current densities caused the growth of a hot spot starting at the center of the Cu strips and eventually led to the electric fusing of the strips. There were three regions related to the growth of the hot spot; they are a) a melted region, b) a heat–affected zone, and c) an oxidation region. Grain growth and grain rotation occurred in both the melted region and heat–affected zone.

The passing of the electric current of high current densities caused the buckling of the Cu strips. The maximum deflection of the Cu strips linearly increased with increasing the electric current density, and there was a quasi-steady state in which the buckling profile of the Cu strips approximately remained unchanged. The total strain is a quadratic function of the electric current density. An integral equation describing the dependence of the current-induced stress in the Cu strip on electric current density was developed. From the measurement of the change of the electric potential difference across two electrodes, it was found that there was a steady state in which the electric resistance of the Cu strips linearly increased with time, which was likely due to the increase of the local temperature and surface oxidation. The experimental results show that the time-to-failure (electric fusing) was a power function of the electric current density, which can be divided into two regions. For the region of relatively low current densities, the current exponent ranged from 17.9 to 44.6; for the region of high current densities, the current exponent ranged 
from 2.5 to 5.2.
报告人简介： 
Dr. Fuqian Yang received his B.S. in Engineering Physics from Tsinghua University, and Ph.D. in Materials Science and Engineering from the University of Rochester. He is a full professor in the Department of Chemical and Materials Engineering at the University of Kentucky. He is a member of editorial board for Materials Science and Engineering A, Smart Grid and Renewable Energy and Open Mechanics Journal. He has published more than 190 papers in peer-reviewed journals. Dr. Yang’s research focuses on micromechanics of advanced materials, including creep behavior of materials, adhesive deformation of materials, surface instability, electromechanical interaction of materials, stress-diffusion interaction, and fluid flow.

http://www.engr.uky.edu/~fyang0/
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