Lifetime Prediction for Lift-off of Bond Wires in IGBTs Using Paris Law With Analytical Calculation of Crack Length
Xin Yang, Junjie Ye, Xinlong Wu, Ke Heng, Yunze He, Guoyou Liu
Abstract
Lift-off of aluminum bond wires is one of the main failure mechanisms of insulated gate bipolar transistor (IGBT) modules. Its root cause is the crack propagation, which causes reduction in the contact area of bond wires at the bond-metallization interface. Thus, lifetime prediction based on the classic Paris law is very appealing due to its capability to account for such a failure mechanism. However, Paris law is currently restricted due to its dependency on inaccurate but expensive means to observe the crack rate. In this article, an analytical calculation method for the crack length of bond wires is proposed by the degradation curves of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V<sub>CE,on</sub></i> measured during normal power cycling tests. The dye-and-pry method has been used to measure crack lengths to further validate the proposed analytical calculation method. The proposed analytical calculation method can avoid time-consuming measurement of crack length, and can economically calibrate the key constants <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> of Paris law, which has been employed to predict the lifetime of bond wires of IGBT modules by finite element method. Finally, the calibrated values of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> make Paris law have better applicability to predict the lifetime of bond wires comparing <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> values reported in existing papers.