Frequency dependence of fatigue life of aluminium wires for power modules

In order to improve the accuracy of fatigue life predictions for power modules under future operating conditions, fully-reversed cyclic bending test method was developed for aluminum wires with a diameter of 0.4 mm. The tests were conducted at a temperature of 175 degrees with frequencies of f = 10, 4, 1, 0.4 and 0.1 Hz, and the fatigue life increases with increasing f. When f was converted to the operating time of the power module, ton, it was observed that the slope α of ton and fatigue life on a double-logarithmic scale decreases with increasing ton, approaching 0. For power modules operating at 175 degrees, α is a function of ton, and incorporating this relationship enables accurate fatigue life prediction.