Prediction Model Of The Substrate’s Warpage During The Packaging Process For IGBT Module

IGBT is the most widely used power semiconductor in the field of high voltage,high current and high frequency power electronic devices,which is usually packaged in the form of success rate module by reflow soldering process.Reflow packaging process will cause the warpage of the IGBT module’s package substrate,which will also reduce the contact area between the back of the module’ s substrate and the radiator,affecting the heat dissipation performance of IGBT module adversely.However,there are many factors affecting the surface shape of the package substrate’s back after reflow,and the cost of determining the surface shape by the traditional test method is high.It is of great practical significance to predict the package substrate’s warpage caused by reflow efficiently and accurately.The development of FEA technology enables module developers to study the warpage of IGBT module’s substrate in the packaging process through simulation modeling.In this paper,ANSYS was used to establish the simulation model for IGBT module’s reflow packaging process to predict the warpage of the module’s substrate during the packaging process.In order to improve the accuracy of the physical model,the mechanical and thermodynamic properties of AlSiC materials for package substrates were tested,and a universal testing method for the mechanical and thermodynamic properties of AlSiC materials was established.The creep and phase change characteristics of solder in reflow process were described in FEA model based on Anand constitutive model,element life and death,and the definition of enthalpy.In order to verify the warpage prediction model,experiments were carried out in this paper.In the packaging process test,the temperature change of IGBT module surface during reflow process was detected by using furnace temperature tracker,and the back surface shape of package substrate after reflow was measured by using CMM.The experimental results showed that the model could predict the shape characteristics of the back of the welded packaging substrate,but due to the inhomogeneity of temperature distribution in the reflux furnace,the shape characteristics predicted by the model have some deviation from the actual situation.At the same time,the prediction error of the camber of the back surface of the welded substrate was 10.35%,which mainly comes from the simplification of the model and some experimental errors.The prediction model for IGBT module’s substrate proposed in this paper can provide reference for the design of IGBT module.The prediction model and related test methods in the modeling process have universal applicability,and can be used to predict the warpage of IGBT power module,during reflow,with similar structure.Based on the prediction model,in the IGBT module’s package development stage,the surface shape of the package substrate’s back after reflow can be determined according to the prediction results of this model,and the contact area between the substrate and the radiator after reflow can be judged,thus effectively reducing the test cost and greatly shortening the research and development cycle.