Reliability of Substrate Solder Joints from Power Cycling Tests

The lifetime of the solder joint between base plate and ceramic substrate is usually tested by passively heating and cooling the IGBT module (thermal cycling). This provokes failures (delamination) in that solder layer. But, the IGBT and diode dies are actively heated in the application. Other failure modes (e.g. bond wire lift off) are addressed and limit the lifetime. This kind of stress is usually tested via power cycling. In the present paper the power cycling test results are evaluated with respect to failures in the substrate solder. Those tests with their high number of cycles are utilized as an effective thermal cycling test for the substrate solder. Key factor is the prediction of the solder temperature during power cycling. A comparison of the solder joint lifetime from passive thermal and active power cycling at low temperature swings was carried out.