Detecting Soldering Quality in Power Modules with Zth in the Loading Phase

Abstract:
A thermal impedance (Zth) measurement method in the loading phase is used to detect the soldering quality in power modules. This method decreases the detecting time owing to the immediate start of Zth recording during the power semiconductor heating phase. In this article, we present the IGBT DeltaZth measurement results for different soldering qualities between the direct bonded copper (DBC) substrate and baseplate under the heating phase of high-power and low-power conduction mode. Furthermore, it has been determined that the value of the IGBT DeltaZth is proportional to the soldering quality. The behavior of DeltaZth in high-power conduction mode tends to show clearer distinction on the various soldering quality than the DeltaZth in low-power conduction mode. These results have proven the feasibility of the detection method of the DeltaZth in the heating phase.