Power Module With Low Common-Mode Noise and High Reliability

Abstract

Silicon carbide devices provide higher switching speed and switching frequency than their silicon counterpart. However, these characteristics generate significant electromagnetic interference such as conducted common-mode (CM) noise. This paper proposes a novel power module to reduce CM noise without compromising size, thermal performance, and reliability of the power module. A specific part of the bottom copper layer of a directed-bonded copper is etched to reduce CM capacitance. Epoxy is used to increase mechanical reliability by supporting ceramic and top copper layers. This supporting epoxy also prevents an encapsulant from leaking into the etched area. Design methodologies for the proposed power module are provided in detail. Conventional and proposed power modules were prototyped and CM noise was experimentally measured with 400-V input, 200-V output, and 50-kHz switching frequency. The CM noise of the proposed power module was reduced by 5 dB $\mu $ V. Thermal cycling tests were conducted to confirm the degradation of the proposed power module. Cross-sections of the power modules and measured electrical characteristics verify the reliability of the proposed power module.

Keywords

• Power module design
• common-mode noise
• parasitic capacitance
• thermal resistance
• thermal cycling test