Package Structure Design And Interconnect Technology Analysis Of Double-sided Cooling IGBT Module

The interconnection material is a key part of the power module,it is prone to be aging and failure at high temperature.The development of power modules to high temperature and high power density have been limited duetothe poor performance of traditional solder alloys.Nanosilver paste as a new kind of lead-free interfacial bonding material,with its excellent mechanical,electrical and thermal properties,has been widely concerned.In view of the problem that the high power density module is unable to dissipate heat efficiently,which leads to the poor reliability.This dissertation proposes a double-sided cooling packaging technology with low thermal resistance and high reliability to encapsulate the IGBT module.The electrical,thermal performance and reliability were studied.First of all,the 650 V/240 A double-sided cooling IGBT module was designed from the aspects of circuit topology,packaging structure,thermal management technology,parasitic parameters,reliability design,material selection and packaging technology.The simulation results show that the adoption of nanosilver paste and double-sided cooling packaging structure can effectively improve the heat dissipation capacity,reducing the temperature gradient of the IGBT module.And the thermal coupling effect of the IGBT module is also increased,making the temperature distribution more uniform.Case with Sn5Pb92.5Ag2.5 as the intermediate connecting layer has the maximum equivalent plastic strain,and its maximum cumulative equivalent plastic strain is 92.0% higher than the case with Sn5Pb92.5Ag2.5 as the connecting layer between the Mo plate and DBC substrate.The equivalent plastic strain of the case with three sintered nanosilver layer is the minimum,which is 70% lower than that of in case with Sn5Pb92.5Ag2.5 as the connecting layer between the Mo plate and DBC substrate.Then the electric andthermal performance of the double-sided cooling IGBT module were analyzed.The results showed that the static I-V curve of the up and down bridge arms of the double-sided cooling IGBT module has good consistency and the on-state voltage drop is consistent with the reference value,which means the packaging structure will not cause the degradation of the chip's electrical performance.The switching loss of the double-sided cooling IGBT module was reduced by 21% compared with that of the commercial wire bonding module due to the eliminating of bonding wires in the double-sided packaging structure,which greatly reduces the parasitic parameters of the module.Thermal resistance research showed that the thermal resistance of the IGBT module under double-sided cooling condition is 0.273?/W,which is 18.8% lower than that of IGBT module under single-sided cooling condition.And when the junction temperature rise and power loss remain unchanged,the changeof the coolant temperature has no effect on the thermal resistance of the double-sided IGBT module.The chip junction temperature difference of the double-sided cooling IGBT module at different positions was effectively improved by using double-sided cooling condition.Finally,the aging behaviors of the double-sided cooling IGBT module with different packaging strategies under temperature shocking(55?-150?)were studied.The reliability evaluation showed that the double-sided cooling IGBT module packaged by case with Sn5Pb92.5Ag2.5 as the connecting layer between the Mo plate and DBC substrate has experienced 800 cycles of temperature shocking test,while the double-sided cooling IGBT module was packaged by case with Sn5Pb92.5Ag2.5 as the intermediate connecting layer has failed after less than 50 cycles of temperature shocking test.This shows that the reliability of the proposed double-sided cooling IGBT module using sintered nanosilver preliminarily meets the requirements.By optimizing the material and structure,the reliability of planar packaging IGBT module can be greatly improved.