Study On The Relationship Between Bonding Wire Failure And The Gate Stray Impedance Of IGBT Module

IGBT as the core of power converter devices,in the field of new energy power generation has a wide range of applications,at the same time,IGBT module also appeared in a variety of reliability issues,such as module internal bonding wire failure.How to judge the running status of IGBT module by the end measurable signal is an urgent problem to be solved.In this paper,the IGBT power module is discussed,and the relationship between the bonding wire failure and the spurious parameters of the IGBT module is discussed by studying the variation of the gate voltage.The main work of this paper is as follows:?1?The failure mechanism and failure type of IGBT module are summarized in this paper.One of the most common failure modes of IGBT module is bonding wire shedding.According to the encapsulation structure,internal structure and the spurious parameters related to the chip and connecting wires inside the IGBT module,the influence of the bonding wire shedding fault on the internal circuit and the output characteristics of the IGBT module is analyzed.The variation trend of stray parameters and gate turn-on voltage during bonding wire shedding is analyzed.?2?According to the failure mode of bonding wire shedding in IGBT module,the stress theory is analyzed.The finite element model of the IGBT module is established,and the thermal stress simulation is carried out.The relationship between the shedding degree of the bonding wire and the temperature distribution and thermal stress distribution in the module is obtained.The influence with the increasing of the number of shedding wires on the life of IGBT module is discussed,and the necessity of condition monitoring of IGBT module is discussed.?3?The failure of the bonding wire will affect the end measurable signal of the module,and the idea of using the characteristic of the end to characterize the failure of the module is presented.The failure state of the IGBT module can be judged by the change of the end characteristic parameter.By comparing the characteristics of each measurable signals,the gate voltage is selected as a characterization of the bonding wire shedding failure characteristics of the parameters.The measuring circuit designed and built to measure the gate turn-on voltage of normal module and abnormal module which bonding wire has shed,and the variation of gate voltage during the shedding process of bonding wire is obtained.?4?There are limitations in the initial recognition of the fault,and there is a big error in judging the bonding wire state of the IGBT module from the waveform of the gate voltage.Therefore,the voltage signal of the gate turning-on is processed to extract the difference from the characteristics of normal signal.The energy of each frequency band is extracted by wavelet packet decomposition of V_GE,and the energy of a node shows certain regularity in the process of bonding wire falling off.On this basis,the energy entropy of the spectrum is obtained,and the wavelet entropy of the wavelet of the gate turning-on voltage is taken as the quantity of the failure feature.Finally,the process of determining the relationship between the bonding wire failure and the gate stray impedance is summarized.