计及疲劳累积效应的IGBT模块焊料层失效机理及疲劳损伤研究

发布时间：2019-05-23 14:34

【摘要】：作为电动汽车驱动、新能源发电、智能电网、轨道交通等领域中电能转换的关键单元,IGBT功率模块逐步成为全球发展“绿色经济”的重要支点,其安全可靠性为解决能源短缺和降低碳排放量提供重要保证。焊料层是构成IGBT模块内部电气连接、机械支撑以及散热通道的重要部分,其可靠连接保证了功率模块功能的正常实现。面对各种复杂、严苛的工作环境,焊料层的热疲劳损伤是模块失效的主要模式之一,因此,充分了解焊料层疲劳失效机理、探究焊料层损伤在IGBT模块中产生的影响,对提高IGBT模块的可靠性有重要意义。尽管目前已经有很多学者对封装模块焊料层的疲劳失效机理进行了研究,但主要侧重于从表面检测或外部电参量来分析焊料层的失效状态,缺乏从物理机制方面来深入探究焊料层失效机理。此外,大多数研究忽略了焊料层累积损伤对IGBT模块疲劳失效的影响,造成目前IGBT模块的在线监测、寿命评估方法存在一定的误差。基于此,本文以SKM50GB12T4型号的IGBT模块为研究对象,通过有限元仿真技术,结合理论分析以及老化实验,开展了对IGBT模块焊料层的失效机理分析和疲劳损伤研究。文章考虑了焊料层的损伤累积效应,研究成果为更准确地进行IGBT模块可靠性评估和状态监测提供理论基础和技术支持。本文研究的主要内容包括:(1)针对目前单一的电-热或热-力仿真模型无法同时考虑电、热和机械特性对IGBT模块疲劳失效的影响,文章建立了考虑焊料层粘塑性效应的电-热-力多物理场耦合模型,对IGBT模块的失效机理进行分析。首先,利用MATLAB/Simulink仿真平台,建立IGBT模块的等效Foster热网络模型,计算芯片在额定电流下产生的功率损耗。其次,基于有限元仿真软件ANSYS 14.5,建立了IGBT模块的等比例有限元模型,综合Foster热网络模型结果对IGBT模块进行电-热-应力耦合分析。最后,针对焊料层的粘塑性力学行为,对其随时间发生的疲劳失效机制进行详细研究。(2)焊料层疲劳寿命模型以应力应变相关参数作为输入值,每次寿命评估前都需要进行耗时的有限元分析,针对这一问题,文章以温度参量代替应力应变参数,提出一种焊料层疲劳失效评估模型。首先,基于现有疲劳寿命模型选取了能表征焊料层疲劳失效的力学指示参数,分析功率循环中结温波动、最小结温、功率循环周期对焊料层疲劳指示参数的影响程度及影响规律。之后,基于得到的影响规律和仿真数据,通过最小二乘法建立了温度变量与焊料层疲劳指示参数之间的曲面函数。(3)裂纹的萌生和扩展是焊料层最主要的失效模式之一,但目前对IGBT模块及焊料层的寿命预测和失效评估研究往往忽略了裂纹损伤的作用,针对这一问题,文章分析了裂纹损伤模块的失效机制,并提出计及疲劳累积效应的焊料层失效评估模型。首先,基于裂纹扩展的物理机制,在ANSYS中建立IGBT模块的裂纹损伤有限元模型,分析功率循环下损伤模型内部的热-应力场特点,详细探究了裂纹长度对IGBT模块热阻的影响规律。其次,通过对比相同结温波动载荷在损伤模型和完整模型中产生的老化效果,提出了包含损伤因子的焊料层疲劳失效评估模型。最后,通过加速老化实验对仿真结果进行了定性的验证。
[Abstract]:As the key unit of electric energy conversion in the fields of electric vehicle driving, new energy power generation, intelligent power grid, rail transit and the like, the IGBT power module is gradually becoming an important fulcrum of the global development "green economy", and the safety and reliability of the IGBT power module are an important guarantee for solving the energy shortage and reducing the carbon emission amount. The solder layer is an important part of the internal electrical connection, mechanical support and heat dissipation channel of the IGBT module, and the reliable connection of the solder layer ensures the normal realization of the function of the power module. In the face of complex and demanding working environment, the thermal fatigue damage of the solder layer is one of the main modes of the module failure. Therefore, the mechanism of the fatigue failure of the solder layer is fully understood, the influence of the damage of the solder layer on the IGBT module is investigated, and the reliability of the IGBT module is of great significance. Although many scholars have studied the mechanism of the fatigue failure of the solder layer of the package module, the failure state of the solder layer is analyzed mainly from the surface detection or the external electric parameters, and the failure mechanism of the solder layer is deeply explored from the physical mechanism. In addition, most of the studies have neglected the effect of the accumulated damage of the solder layer on the fatigue failure of the IGBT module, resulting in an on-line monitoring of the IGBT module and a certain error in the service life evaluation method. Based on this, the study of the failure mechanism and fatigue damage of the solder layer of the IGBT module is carried out by using the IGBT module of the SKM50GB12T4 model as the research object. The failure mechanism of the solder layer of the IGBT module and the fatigue damage study are carried out by the finite element simulation technology, the combination of the theoretical analysis and the aging experiment. In this paper, the damage accumulation effect of the solder layer is considered, and the research results provide the theoretical basis and technical support for the reliability evaluation and state monitoring of the IGBT module more accurately. The main contents of this paper are as follows: (1) For the current single electric-thermal or thermal-force simulation model, the effect of electric, thermal and mechanical properties on the fatigue failure of the IGBT module can not be considered at the same time, and the electric-thermal-force multi-physical field coupling model considering the viscoplastic effect of the solder layer is established. The failure mechanism of IGBT module is analyzed. First, using the MATLAB/ Simulink simulation platform, the equivalent Foster thermal network model of the IGBT module is established, and the power loss generated by the chip at the rated current is calculated. Secondly, based on the finite element simulation software ANSYS, the equal-scale finite element model of the IGBT module is established, and the electric-thermal-stress coupling analysis of the IGBT module is carried out by the comprehensive Foster thermal network model. Finally, a detailed study of the fatigue failure mechanism of the solder layer over time is carried out for the viscoplastic mechanical behavior of the solder layer. (2) The fatigue life model of the solder layer takes the stress-strain-related parameter as the input value, and the time-consuming finite element analysis is required before each life evaluation. In view of this problem, the fatigue failure evaluation model of the solder layer is put forward by using the temperature parameter instead of the stress-strain parameter. First, based on the existing fatigue life model, a mechanical indication parameter which can be used to characterize the fatigue failure of the solder layer is selected, and the influence degree and the influence rule of the junction temperature fluctuation, the minimum junction temperature and the power cycle period of the power cycle on the fatigue indication parameters of the solder layer are analyzed. Then, based on the obtained influence law and the simulation data, the surface function between the temperature variable and the fatigue indication parameter of the solder layer is established by the least square method. (3) The initiation and expansion of the crack is one of the most important failure modes of the solder layer, but the current prediction and failure evaluation of the IGBT module and the solder layer often ignore the effect of the crack damage. In the light of this problem, the failure mechanism of the crack damage module is analyzed. And a solder layer failure evaluation model taking into account the fatigue accumulation effect is provided. First, based on the physical mechanism of crack propagation, the finite element model of the crack damage of the IGBT module is established in the ANSYS, the thermal-stress field in the damage model under the power cycle is analyzed, and the influence of the crack length on the thermal resistance of the IGBT module is discussed in detail. Secondly, by comparing the aging effect of the same junction temperature fluctuation load in the damage model and the complete model, the fatigue failure evaluation model of the solder layer containing the damage factor is put forward. Finally, the simulation results are verified by the accelerated aging experiment.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN322.8

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