A direct bonding copper degradation monitoring method for insulated gate bipolar transistor modules: Boundary‐dependent thermal network combined with feedback control

Abstract

The direct bonding copper (DBC) substrates of insulated gate bipolar transistor (IGBT) modules degrade inevitably under cycling thermo‐mechanical stress, causing potential threat to the reliability of IGBT modules. However, little attention has been paid to monitoring their degradation. This paper proposes a DBC degradation monitoring method for IGBT modules, which combines boundary‐dependent thermal network and feedback control. A thermal network is employed to describe the internal material degradation of IGBT modules and can be extracted from a finite‐element method model. The boundary conditions including power losses and DBC degradation are considered, enabling the thermal network suitable for various working conditions and different DBC degradation conditions of IGBT modules. The DBC degradation is characterised by its equivalent thermal conductivities measured in the thermal cycling ageing experiments. On the basis of the boundary‐dependent thermal network, feedback control is applied to monitor DBC degradation by regulating boundary‐dependent thermal impedances. Finally, the proposed model is verified from the effectiveness and accuracy of DBC degradation monitoring and junction temperature calculation. This method casts new light on thermal network modelling and could provide a feasible method for the monitoring of DBC degradation.

A first-principles study of the formation and regulation of the electric double layers at Cu (0 0 1)/mineral oil interfaces

“…It is believed that the accumulation of this interfacial charge and the formation of an EDL at the interface can severely affect the local electric field, causing additional heat to be generated, etc, which is responsible for power transformer insulation failures [29]. Despite a vast literature concerned with the experimental characterization of its electrical properties related to charge accumulation and transport at this particular interface [19,[30][31][32], very little is known about the details of the electrical behavior of this insulating material, and others like it, at the molecular level. Therefore, exploring the effect of EDLs on the electrical properties of the Cu/MO interface is a key to understanding interfacial charge transport at the microscopic level, which has never been studied before, but is believed to be an important theoretical basis for improving the insulating properties of oilimpregnated power transformers.…”