Temperature-dependence of dielectric properties for copper clad laminate used in integrated power module

Abstract

As the rapid growth of integration level in the power electronic devices, the high dissipation power and low withstand voltage greatly affect the reliability of Integrated Power Module (IPM). Therefore, it is essential to study the performance of the devices or their substrates at the elevated temperatures. In the present work, we studied the temperature-dependence of dielectric properties for the copper clad laminate (CCL) substrate used in IPM at different frequencies. Two samples with different insulating coating layers (epoxy resin + alumina powder) thickness (d=70, 125μm) have been employed. Both of our two samples show that similar temperature-dependence tendency: At the elevated temperature with the frequency of 30Hz, 1) the dielectric loss angle tangent of CCL increased by about two orders of magnitude at 110°C compared with room temperature. 2) the dielectric permittivity increased over 30% at the elevated temperature ranging from 40°C to 80°C. The variation of the dielectric properties for the insulating coating also appeared obviously at other frequency band as temperature increased. Moreover, an additional relaxation polarization was generated by the elevated temperature in the high frequency band. Therefore, we can conclude that temperature for CCL is the most critical factor, which significantly affects its dielectric properties, in particular the dielectric loss. And thermal effect might greatly influence the breakdown of insulating layers, which leads to the insulation failure of CCL. The relaxation and polarization phenomena of CCL was discussed when the temperature changed. In addition, the breakdown voltage of 125μm thick insulating layer was 4.04kV and increased by 31.6% in comparison with that of CCL with 75μm one.