Extensive fatigue investigation of solder joints in IGBT high powermodules

摘要

IGBT (Insulated Gate Bipolar Transistor) power modules are moreand more used in traction applications, where they replace thyristorsand GTO (Gate Turn Off thyristors). Unlike the press-pack packaging ofthe latter, these modules contain numerous IGBT chips in parallel, andthus numerous solder joints which play a key role in the reliability ofthis stack packaging. Accelerated aging tests have been carried out withmore than one hundred representative samples divided in seven batches.They differed in the type of solder (two compositions including alead-free one), cooling rate after the reflow, and metallization of theceramic substrate. Most cycled samples have been extensively analyzed tomake a ranking of the different technological choices. Moreover, theinfluence of the main technological and manufacturing process parametershas been evaluated. Results have shown that the solder composition andthe cooling rate after the renew have a strong influence on the thermalfatigue resistance of the tests specimens