外部汇流母排对压接型IGBT器件内部多芯片并联均流特性的影响

Influence of the External Busbar on Current Sharing Performance Inside a Multi-chip Press-pack IGBT Device

压接型IGBT器件内部芯片之间的动态均流特性直接影响着IGBT器件的坚固性与可靠性。考虑到并联均流实验的困难,现有的压接型IGBT芯片级并联均流研究通常都是通过提取器件内部封装结构的寄生参数,并结合IGBT芯片的等效电路模型,在电路仿真环境中开展的,不考虑器件外部电磁条件对器件内部电流分布的影响。然而,该文通过9枚压接型IGBT芯片的并联均流实验发现,各个通流支路之间存在显著的动态电流不均衡,而且电流的分布特性不仅与内部并联芯片的相对位置有关,还与连接器件的外部汇流母排存在明显的关联。为了揭示器件内部电流分布特性与外部汇流母排之间的耦合关系,该文对被测器件与外部汇流母排进行三维有限元建模,从频域和时域2个方面,计算IGBT器件内部的电磁场分布特性。频域计算表明,由于外部汇流母排与内部并联芯片存在磁场耦合(即电感耦合),当频率超过一定数值后,外部汇流母排会对各个通流支路的电流产生显著影响。时域计算进一步再现了并联均流实验中外部汇流母排对各个通流支路上动态电流分布的影响规律。结果表明,在压接型IGBT器件的设计和应用中,不仅需要关注器件内部芯片间的相对位置对动态均流特性的影响,同时也要关注外部汇流母排引入的电磁不对称性。最后提出一种对称化的母排设计方案,并通过三维有限元计算,证实对称化母排设计可明显改善器件内部的动态均流特性。

The dynamic current sharing performance inside a multi-chip Press-pack IGBT device affects its ruggedness and reliability.Since the difficulty of the experiment,the existing current sharing research of Press-pack IGBT chips was merely carried out in the circuit simulation environment by extracting the electromagnetic parasitic parameters of the device and by combining the circuit model of the IGBT chips.The effect of external electromagnetic conditions on the current distribution inside the device was usually ignored.However,through the current sharing experiment of 9 Press-pack IGBT chips,it is found that there is a significant dynamic current imbalance among these current flow branches.The current distribution is not only related to the relative position of internal chips but also affected by the external busbars that connect the devices.Hence,the three-dimensional finite element modeling of the IGBT device together with the external busbar was carried out to reveal the relationship between the current sharing characteristics and the external busbar.After that,the electromagnetic field distribution characteristics inside the IGBT device were calculated from the frequency and the time domain.The frequency-domain results show that since the external busbar has magnetic field coupling(i.e.,inductive coupling)with the internal parallel chips,the external busbar will have a significant influence on the current of each flow branch when the frequency exceeds a specific value.The time-domain calculation further reproduces the impact of the external busbar on the dynamic current distribution of each flow branch in the current sharing experiment.The results show that in the design and application of the Press-pack IGBT device,it is necessary to pay attention not only to the influence of the relative position between the parallel chips on the dynamic current distribution characteristics but also the impact of the asymmetric external busbar.Finally,the symmetry busbar design scheme was proposed,and the current sharing performance of the device under this busbar were improved by three-dimensional frequency domain finite element simulation.