Analysis of soldering processes using in-situ X-Ray observations

Current developments in power electronics are driving the need for higher operating temperatures. At temperatures above 200 °C conventional solders can no longer be used. Therefore new technologies for Die-Attachment are necessary. One solution is to use diffusion soldering. Khaja et al. [1] presented an approach for diffusion soldering by printing a conventional solder paste with a 20 μm thin stencil. Since in power electronics a good thermal coupling between chip and environment is needed, the void content is typically required to be less than 10 %. Khaja et al. showed that the application of a vacuum vapour phase soldering process can ensure a very low void content of the resulting solder joints. In this work we present our method and results of a detailed analysis of videos gained by In-Situ X-Ray observations of soldering processes on large-area solder joints. With this method we can quantify the influence of pressure changes on the soldering process. By analyzing the gray-values of our videos we can also make the 3D-dynamics of soldering visible. Based on this data we make recommendations for an optimal soldering profile with pressure changes for conventional and diffusion soldering. Furthermore this data gives new insights in the origin and development of voids in solder joints.