Warpage modeling for semiconductor power module manufacturing flow improvement

The hybrid and battery electric vehicle market is heavily increasing the demand for semiconductor power modules. The manufacturing of such products is more complex than discrete devices. Some parameters, such as module deformation (warpage), play a major role. Power modules have to comply with customer Geometric Dimensioning & Tolerancing (GD&T) targets in order to avoid coolant leakage during operation and to guarantee mechanical compatibility with the driving board. Compliance with an appropriate flatness tolerance reduces rejects during manufacturing processes such as ultrasonic welding, and the consequent impact on reliability. Due to these requirements, there is a need to implement dedicated countermeasures during manufacturing flows and to develop the proper methodologies to monitor flatness tolerances. Appropriate component selection at the design stage also limits flatness through the prediction of deformations during assembly flows using finite element model. This activity outlines the manufacturing flow for a direct cooled semiconductor power module and presents a method for product optimization in terms of flatness tolerance using a dedicated finite element model that calculates the warpage deformation induced by baseplate soldering and different ceramic substrate layouts. Furthermore, we describe experimental methodologies for measuring power module flatness and straightness across the manufacturing phases. Dedicated experiments were conducted for methodological and design validation.