Hot Spots Caused by Voids and Cracks in the Chip Mountdown Medium in Power Semiconductor Packaging

The temperature increase under power dissipation in large semiconductor Chips mounted down with solder containing voids or cracks is explained in terms of two void types. They are distinguished on the basis of transient and steady-state thermal resistance measurements, and differ from each other in that for one the increased thermal resistance is mitigated by a reduced current density, but not for the other. They have been verified experimentally, and explain a large range of thermal and electrical characteristics, Such as occur in fatigue cycling.