This work reports two different characteristic patterns detected in IGBT chips failed in real operation (railway application) by failure analysis procedures. The analysed chips have been recovered from the rheostatic chopper leg and from the three legs which supplies the traction motor. It is observed that depending on the location and characteristics of the detected default (burn-out spot), this failure can be attributed to a latch-up process or a secondary breakdown mechanism. These results are corroborated with tests at limit, obtaining the same result. Consequently, each failure can be linked to overcurrent (latch-up) or overtemperature (secondary breakdown) events, which makes possible to distinguish between problems coming from driving strategies or thermal issues (uneven temperature distribution inside the module or packaging wear-out).

This work has been partially supported by the European project PORTES (Power Reliability for Traction Electronics, MTKI-CT-2004- 517224) and the Consejo Superior de Investigaciones Científicas (CSIC) (under contract ‘‘Junta para la Ampliación de Estudios”, JAE-Doc).

5 páginas, 8 figuras.

Peer reviewed