非线性场控电导复合材料参数对IGBT模块内DBC三结合点电场影响规律仿真研究

Simulation Study on the Influence Rule of Parameter of No-linear Field Grading Composite on Electric Field at Triple-junction Point of DBC in IGBT Modules

高压大功率(insulation gate bipolar transistor,IGBT)模块内覆铜陶瓷基板的覆铜层、陶瓷基板与有机硅凝胶形成的三结合点处电场集中,增加了器件局部放电及绝缘失效的风险。随着IGBT模块电压等级的提高,DBC基板的绝缘水平成为制约器件研制及可靠运行的关键因素。文中拟采用非线性场控电导(nonlinear field grading,NFG)复合材料作为涂层,涂覆于DBC基板三结合点处的局部高场区,以改善电场分布,提高DBC三结合点处的放电起始电压。为此,文中首先通过实验获得了纯硅凝胶灌封的DBC试样三结合点的局放起始电压,然后以局放起始电压作为控制值,借助于有限元仿真获得了对应的电场分布及局放起始场强,依次分析了NFG涂层材料的电气参数对DBC基板三结合点处电场的影响规律,最后给出了NFG参数的选型建议。文中的研究成果对用于改善DBC基板局部电场的非线性材料设计提供了理论指导。

The electric field concentration at the triple junction point formed by the copper clad layer,ceramic substrate and organic gel of copper clad ceramic substrate in the model of IGBT(insulation gate bipolar transistor)increases the risk of partial discharge and insulation failure of elements. With the increase of voltage class of IGBT module,the insulation level of Direct-Bond Copper(DBC)substrate becomes the key factor restricting the development and reliable operation of elements. In this paper,nonlinear field grading(NFG)composite is intended to be used as the coating to apply at the partial high electric field region at the triple junction point of DBC substrate so to improve the electric field distribution and enhance the discharge inception voltage of the triple junction point of DBC. For this purpose,the partial discharge inception voltage of the triple junction point of DBC sample encapsulated by pure silicone gel is obtained. Then,the partial discharge inception voltage is taken as the control value,the corresponding electric field distribution and initial the electric field strength of partial discharge is obtained with the help of the finite element method(FEM)simulation. The influence rule of electrical parameters of NFG coating material on the electric field at the triple junction point of DBC substrate is analyzed in sequence. Finally,the suggestion on the selection of parameters of NFG is given. The study result in this paper has provided theoretical guidance for improving the design of non-linear material of partial electric field of DBC substrate.