Effect of load sequence interaction on bond-wire lifetime due to power cycling

Experimental investigations on the effects of load sequence on degradations of bond-wire contacts of Insulated Gate Bipolar Transistors power modules are reported in this paper. Both the junction temperature swing ( Δ T_j ) and the heating duration ( t_ON ) are investigated. First, power cycling tests with single conditions (in Δ T_j and t_ON ), are performed in order to serve as test references. Then, combined power cycling tests with two-level stress conditions have been done sequentially. These tests are carried-out in the two sequences: low stress/high stress (LH) and high stress/low stress (HL) for both Δ T_j and t_ON . The tests conducted show that a sequencing in Δ T_j regardless of the direction “high-low” or “low–high” leads to an acceleration of degradations and so, to shorter lifetimes. This is more pronounced when the difference between the stress levels is large. With regard to the heating duration ( t_ON ), the effect seems insignificant. However, it is necessary to confirm the effect of this last parameter by additional tests.