Enhancing the Reliability of Power Packages Combining SiC and Diffusion Solder Die Attach Technologies

To fulfil the increasing power demand and enable high operation temperatures, employment of wide-bandgap semiconductors, such as SiC, is rapidly expanding. Diffusion solder die attach technology, specifically AuSnCu alloys, have demonstrated excellent thermal properties and, in combination with SiC technology, offer best in class performance in terms of power and high temperature operation capability. However, for very high temperature cycling amplitudes beyond today's standard application conditions, diffusion solder fatigue and cracks is observed in package prototypes. Finite Element (FE) analysis is used to assess stress and strains in the diffusion solder layer during temperature cycling and to identify potentials for improvement. Detailed investigation is dedicated for the improvement of the material model used for the diffusion solder layer. The plastic and creep properties of the layer are calibrated by means of temperature dependent warpage measurements.