Research On Vacuum Welding Technology Of Plastic Encapsulation IPM

Plastic encapsulation IPM is an advanced and highly integrated new type of power module,which can realize self-protection of main switching devices in complex circuit environments such as overvoltage,overcurrent,overheat,short circuit and undervoltage.The key technology of IPM packaging process is welding technology.The welding effect is mainly guaranteed by the control of void rate,which will directly affect the mechanical properties,connection strength and thermal conductivity of the welding layer.Therefore,low void rate is an important guarantee for IPM performance and application reliability of IPM,Vacuum reflow welding process has higher void rate after welding because its reflow temperature range setting deviates from the ideal curve.In order to meet the production recquirements of IPM,an in-depth study on IPM vacuum welding process is conducted in this paper,and the specific work is as follows:Firstly,the thermal characteristics of IPM are simulated by using Ansys software.The structure model is established,and the temperature distribution is simulated.The simlation results when there is no void in the welding and the void rate of 1%to 5%are compared and analyzed.The simulation curve of temperature with the change of void rate is given.Secorndly,the characteristics,fabrication process and influencing factors of the Plastic encapsulation IPM are analyzed.The influences of welding voids and blowholes on welding quality,stability and service life of modules are discussed.Finally,Plastic encapsulation IPM vacuum reflow test is carried out.According to solder past reflux curve,the preheating chamber and the temperature value of the heating chauber are adjusted,and the orthogonal experiment method is used to carry out the process test for four groups of modules(four in each group).By comparing and analyzing the experirmental results,the more suitable technological conditions were found and the reflux curve was optimizecd.