Influence of the Combined Effects of Solder Voids and Wire Lift-Off on the Power-Cycling Lifetime of Power Semiconductor Packages

• In this paper, we evaluate the effect of solder voids at asymmetric positions on the power cycle life under asymmetric chip heating assuming wire lift-off. • Samples were prepared in which heated and unheated regions were controlled through chip wiring and void positions were artificially changed. As a result of the power cycle test, solder cracks were generated around the chip in the heated region, but voids had little effect on the chip life in the unheated region. • The relationship between power cycle life and maximum creep strain obeys the Coffin–Manson law even under the combined condition of asymmetric temperature distribution and void formation. For the high-reliability design of power modules used in power electronics applications, the power-cycling lifetime under combined conditions of asymmetric chip heating caused by wire lift-off and solder voids was evaluated. In addition, the effect of the positional relationship between the voids and the heated region on the power-cycling lifetime was investigated. To simulate wire lift-off, the heated and non-heated regions were controlled through chip wiring, and the void positions were artificially varied. When the position of the void coincides with that of the wire lift-off, the void has no effect on the power cycling lifetime. However, when the void is located at a position where wire lift-off does not occur and is near the chip edge, the power cycling lifetime is reduced to 0.80 times that of the reference case. Simulation results show that this is because the temperature variation increases by a factor of 1.04, the stress at the chip edge increases by a factor of 1.19, and solder crack propagation is accelerated. Even under asymmetric heat generation, the maximum creep strain varies depending on the void position, as in the case of uniform heat generation over the entire chip, thereby affecting the power-cycling lifetime. The relationship between the power-cycling lifetime and the maximum creep strain follows the Coffin–Manson law. From these results, predicting the maximum creep strain is effective even under combined conditions of non-uniform temperature distribution and void formation.