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IGBT功率模块寿命预测的研究与设计王瑞【摘要】电子信息技术的发展极大的改进了人们的生产生活方式，具有饱和压降小，载流密度大等许多优点的功率器件IGBT，在超高电压电力传输、新能源的开发利用等方面获得广泛应用。
然而其工作在电压高、电流强、状态切换频繁等复杂环境中。
这就导致其容易损耗，使模块寿命大大降低。
目前，国内外在IGBT功率模块寿命研究领域已经取得了一定的成绩。
本文在介绍了IGBT结构的基础上通过建模对其寿命预测进行了研究并具体阐述了功率循环中叠加效应、任务曲线、雨流计数法。
%The development of electronic information technology greatly improved people’s production and life style, with a low saturation voltage drop, power device IGBT current density and many other advantag-es, is widely used in the new energy of ultra high voltage power transmission, development and utilization. However, the work in the high voltage, strong current, switching frequent complex environment. This makes it vulnerable to loss, the module greatly reduces life expectancy. At present, research in the field of external IGBT power module life in China has made certain achievements. In this paper, based on the IGBT structure by modeling the life prediction were studied and elaborates the superposition effect, task curve, power cycle rain flow counting method.【期刊名称】《电子测试》【年(卷),期】2013(000)021【总页数】3页(P5-7)【关键词】IGBT;寿命预测;损耗;建模【作者】王瑞【作者单位】宝鸡文理学院物理系 721016【正文语种】中文0 前言绝缘栅双极型晶体管IGBT是1980年代中期发展起来的一种新型的复合元件，它综合了金氧半场效晶体管与双极性晶体管的优点，故具有高输入阻抗，容易驱动，切换速度快，低导通电压降，及耐高压与大电流等特性。
IGBT功率循环IGBT功率循环实验室IGBT功率循环⽬的IGBT功率循环/哪⾥能做IGBT功率循环
⽬前⼤部分的新能源汽车⼚家都认为他们的产品在未来将会⼤⾯积使⽤第三代半导体技术，⼴电计量检测股份有限公司致⼒于为⼴⼤IGBT⼚家打通可靠性⼤门；
为什么要做IGBT功率循环试验
IGBT是电动汽车中的核⼼部件,IGBT寿命直接关系到电动汽车的寿命,因此检验IGBT的长期寿命成为了电动汽车的重要环节。
,IGBT的寿命要求往往在10年或20万公⾥以上,所以通过功率循环对IGBT进⾏功率加速⽼化实验,通过进⾏等效的功率循环实验条件加速⽼化实验,进⽽估计实际应⽤中IGBT的使⽤寿命。
IGBT功率循环⽬的
两种失效⽅式:
功率循环实验主要是针对IGBT的封装可靠性⾏进⾏实验,通过控制实验条件再现IGBT封装的主要两种失效⽅式
键合线失效和焊料层⽼化
键合线失效和焊料层⽼化。
实验的关键是控制结温的波动范围以及最⾼温度,得到不同条件下的实验寿命,从⽽得到IGBT的寿命。
⼴电计量IGBT试验能⼒
模块检测：静态参数、动态参数、连接层检测（SAM）、IPIM、OMA；
模块特性测试：寄⽣杂散电感、热阻值、短路耐量、绝缘测试、机械参数检测；
环境测试：热冲击、机械振动、机械冲击；
寿命测试：功率循环（PCsec）、功率循怀（PCmin）、⾼温存储、低温存储、⾼温反偏、⾼温棚偏置、⾼温⾼湿反偏；
技术探讨：冯⼯183********（WX同步）。
IGBT的工作原理和工作特性IGBT的开关作用是通过加正向栅极电压形成沟道，给PNP晶体管提供基极电流，使IGBT导通。
反之，加反向门极电压消除沟道，流过反向基极电流，使IGBT关断。
IGBT的驱动方法和MOSFET基本相同，只需控制输入极N一沟道MOSFET，所以具有高输入阻抗特性。
当MOSFET的沟道形成后，从P+基极注入到N一层的空穴（少子），对N一层进行电导调制，减小N一层的电阻，使IGBT在高电压时，也具有低的通态电压。
IGBT的工作特性包括静态和动态两类：1．静态特性IGBT的静态特性主要有伏安特性、转移特性和开关特性。
IGBT的伏安特性是指以栅源电压Ugs为参变量时，漏极电流与栅极电压之间的关系曲线。
输出漏极电流比受栅源电压Ugs的控制，Ugs越高，Id越大。
它与GTR的输出特性相似．也可分为饱和区1、放大区2和击穿特性3部分。
在截止状态下的IGBT，正向电压由J2结承担，反向电压由J1结承担。
如果无N+缓冲区，则正反向阻断电压可以做到同样水平，加入N+缓冲区后，反向关断电压只能达到几十伏水平，因此限制了IGBT的某些应用范围。
IGBT的转移特性是指输出漏极电流Id与栅源电压Ugs之间的关系曲线。
它与MOSFET的转移特性相同，当栅源电压小于开启电压Ugs(th)时，IGBT处于关断状态。
在IGBT导通后的大部分漏极电流范围内，Id与Ugs呈线性关系。
最高栅源电压受最大漏极电流限制，其最佳值一般取为15V左右。
IGBT的开关特性是指漏极电流与漏源电压之间的关系。
IGBT 处于导通态时，由于它的PNP晶体管为宽基区晶体管，所以其B值极低。
尽管等效电路为达林顿结构，但流过MOSFET的电流成为IGBT总电流的主要部分。
此时，通态电压Uds(on)可用下式表示:Uds(on)＝Uj1＋Udr＋IdRoh （2－14）式中Uj1——JI结的正向电压，其值为0.7～IV；Udr——扩展电阻Rdr上的压降；Roh——沟道电阻。
1 引言2060 年中国将实现“碳中和”的目标，高效利用绿色能源是实现这一目标的重要途径。
功率模块是实现绿色能源转换的重要部件，绝缘栅门极晶体管( Insulated Gate Bipolar Translator，IGBT) 作为使用频率最高的电源转换芯片，是出现故障频率最高的器件，其失效机理及检测方式被大量研究。
可靠的封装为芯片工作提供稳定的电气连接、良好的绝缘性能和充分的抗干扰能力，是IGBT 功率模块可靠性的重要组成部分。
现在被主流使用的封装形式有焊接型和压接型封装。
两种封装结构在功率密度、串并联能力、制造费用、封装可靠性和散热能力等方面有所不同，其性能对比如图 1 所示。
由于压接型封装具有双面冷却和失效自短路效应，其在散热、可靠性及串联能力上优于焊接型封装，因此被广泛用于高功率密度场合，如高压电网和高功率机械设备，但封装复杂笨重。
焊接型封装结构因其制造工艺简单、成本低和并联能力强被广泛使用在中低功率密度场合，如消费电子、汽车电子。
两种封装结构导致了不同的失效机理，但其本质多是IGBT 芯片工作产生的热量未即时耗散，引起温度梯度，最终导致的封装材料疲劳致使失效。
因此，本文首先对两种IGBT 功率模块封装结构及失效机理进行阐述，然后对IGBT 功率模块封装失效监测方法进行了分析，最后提出IGBT 功率模块封装可靠性及失效监测存在的问题和发展方向。
2 IGBT 功率模块封装结构及失效机理2. 1 焊接型IGBT 功率模块封装结构及失效机理2. 1. 1 焊接型IGBT 功率模块封装结构自1975 年，焊接型IGBT 功率模块封装被提出，便被广泛使用，其典型封装结构如图 2 所示。
其中，直接覆铜陶瓷板( Direct Bonded Copper，DBC)由上铜层、陶瓷板和下铜层组成，其一方面实现对IGBT 芯片和续流二极管的固定和电气连接，另一方面形成了模块散热的主要通道。
欲加入IGBT交流群，加VX：tuoke08。
图1 某IGBT的失效率数据分析
IGBT与封装相关的失效
模块具有多层结构，不同部件具有不同的热膨胀系数，不同板层受热膨胀的大小有偏差，长期在热循环冲击作用下引起其焊接材料和键合线的疲劳老化，最终造成器件失效。
与封装相关失效主要包括键合线疲劳脱落、键合线疲劳受损、焊层疲劳受损引起芯片温度增加和或承受机械应力而失效。
与环境
封装失效有：由于设计或安装不良
（3）机械应力
机械应力引起的IGBT封装失效主要有
率端子对外连接承受过大机械应力，或者安装时操作不规范，导致端子和焊层之间出现裂纹，载流量下降；②散热器过于粗糙，导致IGBT底板变形受损，热阻增大导致芯片结温增加过热损坏，或直接导致芯片机械受损。
（4）环境应力
IGBT功率循环试验，χ表示失效的周期数，
数，表征分布的范围，β是形状参数，表征曲线的基本形状。
由失效机制决定，不同的失效机制β不同。
β越大，试验数据越集中，表明失效更能被某一种失效机制描述。
Weibull
函数是拓展的指数分布函数，β=1是指数分布函数，
（3）参数最低值参数最高值系数
2,03E+14k。
Smart Grid 智能电网, 2019, 9(5), 218-226Published Online October 2019 in Hans. /journal/sghttps:///10.12677/sg.2019.95024Review on the Reliability Research of HighPower IGBT DevicesBin Ren, Erping Deng, Yongzhang HuangState Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources,North China Electric Power University, BeijingReceived: Sep. 29th, 2019; accepted: Oct. 9th, 2019; published: Oct. 16th, 2019AbstractWith the development of high-voltage transmission and electric locomotive, the high voltage and high power IGBT device, as the most important power electronic device in those application fields, have been widely concerned by domestic and foreign research institutions on their reliability. To provide more reliability information to reliability designers and end users, this paper reviews the development and research status of high voltage and high power IGBT devices reliability. Accord-ing to the different research purposes of high voltage and high power IGBT devices, the reliability research is divided into three aspects: fault diagnosis, life prediction and condition monitoring.Then the research methods of fault diagnosis and condition monitoring are analyzed and the life prediction model is classified and summarized and its advantages and disadvantages are com-pared and analyzed. Finally, based on the current reliability research methods and contents of the high voltage and high power IGBT device, the challenge and developing trend of reliability re-search in the future are put forward.KeywordsHigh Voltage and High Power IGBT Device, Reliability, Fault Diagnosis, Lifetime Prediction,Condition Monitoring, Developing Trend高压大功率IGBT器件可靠性研究综述任斌，邓二平，黄永章华北电力大学新能源电力系统国家重点实验室，北京收稿日期：2019年9月29日；录用日期：2019年10月9日；发布日期：2019年10月16日任斌 等摘要随着高压直流输电和电力机车等领域的不断发展，高压大功率IGBT 器件作为其中重要的电力电子器件，其可靠性问题得到了国内外研究机构的广泛关注。
三相逆变系统中IGBT模块功率循环实验设计李晓光【摘要】由于风力发电系统的电流器中IGBT模块寿命主要受风速随机性和内部温度变化的影响,采用电压型三相SPWM逆变电路的结构对IGBT模块功率循环实验进行设计,搭建功率循环系统实验平台,通过分析其输出结果,验证了实验平台可以很好的模拟IGBT实际工作环境,对研究IGBT功率循环的失效分析有着重要意义.【期刊名称】《河北电力技术》【年(卷),期】2016(035)002【总页数】3页(P32-34)【关键词】三相逆变系统;功率循环;实验平台【作者】李晓光【作者单位】国网河北省电力公司沧州供电分公司,河北沧州 061113【正文语种】中文【中图分类】TM322.8随着风力发电的成熟以及市场的不断扩大，风力发电正逐步实现产业化和规模化。
而风力发电系统中换流器的IGBT模块是系统运行中可靠性最薄弱的环节，IGBT 不断的工作在开通关断状态下，会导致温度高低不停的变化，从而产生温差，温差越大功率循环次数越低。
因此搭建功率循环实验平台模拟以上情况的出现，对研究功率循环和温度变化带来的损伤对IGBT寿命的影响有着十分重要的意义［1］。
目前的研究多是针对功率循环与IGBT寿命的关系。
文献［2］采用功率循环测试对IGBT进行加速寿命实验来研究循环次数与电压、温度间的关系。
文献［3］运用功率循环技术对功率模块的疲劳寿命进行了预测。
文献［4］提出一种机侧变流器IGBT模块的功率循环能力评估方法，研究了风速对功率循环能力的影响。
文献［5］利用电子设备评估模型，对IGBT模块的功率循环能力进行了评估。
以上文献均未对功率循环系统搭建进行说明。
采用电压型三相SPWM逆变电路结构对模型进行设计，根据此模型搭建三相逆变系统实验平台，通过仿真实验，对其工作原理、控制电路及谐波等进行分析，为研究IGBT模块的电气性能及逆变系统的运行可靠性奠定了良好的基础。
逆变具有实现直流电转换成交流电的功能。
前沿技术IGBT 模块结构及老化简介・汽车功率电子导读：对于工程设计人员来讲，IGBT 芯片的性能，可以从规格书中很直观地得到。
但是，系统设计时，这些性能能够发挥出来多少，就要看“封装“了，毕竟夏天穿着棉袄工作任谁也扛不住，因此，对于怕热的IGBT 芯片来讲，就是要穿得“凉快”。
电动汽车逆变器的应用上，国际大厂还是倾向于自主封装的IGBT,追求散热效率的同时，以最优化空间布局，匹配系统需求。
4. IGBT 制造流程4.4晶圆生产包含硅提炼及提纯、单晶硅生长、晶圆成型三个步骤，目前国际主流是8英寸晶圆，部分晶圆厂12英寸产线逐步投产，晶圆尺寸越大，良品率越高，最终生产的单个器件成本越低，市场竞争力越大。
4.2芯片设计IGBT 制造的前期关键流程，目前主流的商业化产 品基于Trench-FS 设计，不同厂家设计的IGBT 芯片特点不同，表现在性能上有一定差异。
4.3芯片制造芯片制造高度依赖产线设备和工艺，全球能制造出第四代 沟槽栅非:穿通型(TRENCHNP)第一代平面栅穿 通型(PT)栅穿通型(NP)(PLANAR PT)目前英飞凌等主流汽车IGBT 芯片1第7代第六代■精细沟槽第五代-沟槽栅场栅场截止沟槽栅软截止型型穿通型(TRENCH(TRENCH(TRENCHFS)FS)SP)t丁导通压降逐渐降低/拖尾电流逐渐减小 /损耗逐渐降低英飞凌IGBT 芯片发展历程40 THE WORLD OFINVERTERSTHE WORLD OF INVERTERS《变频器世界》April,2021顶尖光刻机的厂商不足五家；要把先进的芯片设计在工艺上实现有非常大的难度，尤其是薄片工艺和背面工艺,目前这方面国内还有一些差距。
4.4器件封装器件生产的后道工序，需要完整的封装产线，核心设备依赖进口。
性能，目前常用的导热陶瓷材料参数:强度/MPa600-800350400断袈韧性(MPam)&0~&0 2.7 3.0热导率W/(mK)80-10015020~2. IGBT 芯片以英飞凌IGBT 芯片发展历程为例(如图)： 不同厂商技术路线略有不同。
IGBT模块的寿命和可靠性研究系统寿命与可靠性关系：可靠性：产品在一定条件下无故障完成规定功能的能力或可能性IGBT模块的失效模式：功率周次 Power cycling：功率周次用于评估绑定线和Die焊层的机械寿命Power cycling can estimate the bonding wire and die solder’s lifetime π测试方法: 加载自加热，周期≤ 3秒，测试ΔTvjπ Test method: Self heating by load, T_cycle ≤ 3 seconds, measure ΔTvj π失效判据：饱和压降 Vcesat 增大+5%π Failure criteria: Vcesat increase more than 5%温度周次 Thermal cycling温度周次用于评估DCB下焊接层的寿命Thermal cycling can estimate DCB solder’s lifetimeπ测试方法: 通电加热，周期5分钟，测量ΔTcπ Test method: Self heating by l oad, 5 min/, measure ΔTc π失效判据：热阻Rthjc 增大+20%π Failure criteria: R_thjc increase 20%失效机理是两种材料不同的膨胀系数(Different material’s CTE)[ppm/K]不同应用下IGBT模块的寿命Lifetime of IGBT module in different applicationThere are many applications and similar types of power modules.Main objective is: how to select an active device in order to reach desired system lifetime?Is it possible to have power module suiting to all applications?由周期内系统工况变化获得温度变化Get the temperature profile by power profile in a cycle温度变化导致的失效模式Failure modes with ΔTThere are two key factors in the selection of the appropriate power module:1)thermal: Tvj op < Tvj max2)reliability: wear out mechanisms which determine module lifetime as result of modulereliability curves and thermal stressesNote: RBSOA and other electrical phenomena are not covered in the presentation. Factors and impacts:1)TjFWD max ≤ Tvj opTjIGBT max ≤ Tvi opNowadays Tvj op = 150°C2)DTjFWD & DTjIGBT refer to Power Cycling reliability curvesΔTC refers to Thermal Cycling reliability curvesReliability curves are always given by power module manufacturer绑定线老化——功率周次曲线Bond wire degradation – PC curve功率周次曲线修正因数PC curve correction factor基板焊层老化——热循环曲线Solder on baseplate degradation – TC curve功率温度循环（PC）次数评估计算No. of cycle estimation calculation with Power cycling curve实例：稳态周期系统的寿命估算Simple mission cycle -- example of lifetime estimationFor relative simple mission cycles the module lifetime based on the three presented reliabilitycurves and power losses converted into a junction and case temperature swing can be easilyestimated. PrimePACK™ module in use: FF900R12IP4D实例：稳态周期系统的寿命估算Simple mission cycle -- example of lifetime estimationQuestion from last page: how to estimate the power module lifetime under the mission cycle,has to be repeated again. Let’s calculate the module wear out as a function of mission cycle and time.Final lifetime module estimation:wear out / year = 0,3% + 5.8% + 4,38ppm + 8,76ppm ≌ 6.1%As reliability curves are given for 100% lifetime the module can work in the example applicationfor :100% / 6.1% ≌ 16.4yearsNote: These calculations are made for IGBT only. FWD has to be calculated separately.动态负载周期的寿命估算方法Dynamic load cycle – lifetime estimateMatlab calculates losses for given number of the load cycles and applies them to the thermal networks specific for selected module in Simulink. As a result the junction temperature profile for IGBT, Diode and the profile of the solder temperature is obtained.In that case, the simulation will be stopped. Over the graph the information says, which element has higher temperature than allowed. If its below..雨流计数法---随机负载谱转化为变幅或恒幅的负载谱•把负载变化周次种类减少•根据有限的试验数据推算整个寿命周期的变化规律，获得典型谱From the temperature profile analysis the life time (and wear of the life time in %) for each element and solder will be calculated. The graphs will show the life time wear for each deltaT. The sum of the percents is calculated and also shown on the graph.IGBT4模块的性能提升High performance of IGBT4 moduleIGBT4模块的150度最高允许工作结温，源于内部焊线工艺的改进，使其可靠性指标-功率周次（PC）数大幅增加！铜绑定线 Copper Bonding Wire-- EconoDUAL™3 600A真正实现 EconoDUAL™3 最大输出电流能力--- @ TC=100°C, Tvj=175°C降低引线电阻 R CC‘EE‘保证功率周次，满足风力发电，电动汽车需求提供焊接/PressFIT 两种兼容版本提供650V,1200V,1700V IGBT4 全系列，便于现有设计的功率升级PressFIT 端子压接技术Press + FIT = PressFITPressFIT Technology无铅以达到RoHS环保要求简易无焊接安装节约生产组装的成本和时间高可靠性减少工人焊接端子中失误导致的过温和静电损坏可靠性已在多个高端客户的产品中得到验证超声波焊接的功率端子 Ultrasonic welded terminals功率端子采用超声波焊接Internal terminal connections ultrasonic welded- 可增加模块端子的鲁棒性 Increased mechanical robustness- 可增加模块端子电流通过能力 Higher terminal currents possible- 无焊料可增加热传导能力 maximum temperature even reduced已应用在以下的模块封装中：PrimePACK, IHM-B Traction series, EconoPACK™4 模块基板和衬底材料的选择以提高温度周次。
Cycling Capability of IGBT ModulesThomas Schütze, Hermann Bergeupec GmbH & Co. KGMax-Planck-Straße 559581 Warstein, GermanyIntroductionSince their market introduction in the beginning of 1995, eupec IGBT high power modules (IHM) got a quick access to several applications in the lower and medium voltage range because of their obvious advantages with regard to controllability, isolation and mounting.When introducing high voltage 3.3 kV IGBTs (IHV) intended for the upper power range and traction applications additional demands are made to the electrical and mechanical characteristics of the modules. These growing requirements are met by continuous progresses of the module design in the areas of substrate, bond wire and base plate technology as well as partial discharge immunity.BondingA high power IGBT module comprises approx. 450 wires together with 900 wedge bonds. For many years the reliability of this contact technology has been a concern especially for traction applications. Considerable work, e.g. in the LESIT-program, has been concentrated on accelerated power cycling tests, analysis of failure mechanisms and improvements in bonding technology. Disconnection of bond wires due to heel cracks, bond lift-offs, reconstruction of Al-metallization on the chips and corrosion of wires were step-by-step identified as reliability limiting weak points. Development activities on the composition of wires, the shape of bonding tools and bonding parameters, the metallization of chips and leads and the introduction of protective coatings have led to considerable improvements in the reliability of the bond contact. Test results of short time power cycling on IGBT modules with up to 24 paralleled IGBT chips are shown in Fig. 1, comparing the number of cycles versus the junction temperature swing.The …IHM (standard)“ modules are designed for the Array needs of standard industrial applications while thecurve labeled …IHV (traction)“ represents theresults for modules applying all the abovementioned improvements, therefore fulfilling eventhe severest requirements of traction applications.These modules are available in the tractionrelevant IGBT voltage classes with a blockingcapability of 1700, 2500 or 3300 V.Tests with temperature swings of 40°C, 50°C and60°C have been performed to get reliable data forpractical operating conditions. Runs at delta T j =70°C and 80°C have been made to gaininformation about accelerating factors. The failure criteria was an increase of forward voltage by more than 5%.The test at ∆T j = 40°C with 20 modules under test took one year while the run at ∆T j = 60 °C could be finished within 4 weeks. It is worthwhile to mention that these two tests were carried out with the same production lot of IGBT modules on the same test equipment controlled by the same team. Diode parts and IGBT parts of high power modules were tested separately.Concluding from the technological analysis of failed modules out of the test programs it can be stated: there are no more bond wire lift-offs and no corrosion of the wire to be found. The failure mechanism has been changed throughout. Even after 9 million cycles all bond wire connections to the IGBT chips are still good. An additional overload test of the IGBTs with 8 kA subsequent to power cycling was passed without failure.Base plateThe use of copper as base plate material is common for its well known advantages with regard to high thermal conductivity, easy mechanical handling and galvanic plating as well as adequate pricing. Disadvantages are non reversible changes of mechanical properties above 300°C and the mismatch of the coefficient of thermal expansion (CTE) between copper and the ceramic substrate.The soldering between substrate and base plate is therefore a failure source. Because of their different CTEs thermal stress occurs and generates mechanical strain on the solder. Repetitive, heavy load cycling will create solder cracks and therefore an increase of the thermal impedance between chip and base plate.Efforts have been made to mitigate the bimetallic effect of the soldered system metal / ceramic by an adequate shaping. A machined convex bow as shown on the right side of Fig. 2. clearly improves the heat transmission between base plate and heat sink.of the module isthJCthe renunciation of additional intermediate layerswhen using CTE-matched materials, the increaseis even less. Furthermore the diminishedbimetallic effect results in a well-balanced contactsurface between Al/SiC baseplate and heat sink.The most outstanding advantage can be seen inthe gain of reliability. At highly accelerated cyclingtests with ∆T c = 80 K the solder layer between copper base plate and ceramic showed a delamination at the edges of the substrate after 4000 cycles. With the new Al/SiC base plate and under the same test conditions we have reached 20.000 cycles so far without any signs of delamination. Tests will be continued to define the exact factor of the reliability improvement.Fig. 4 shows this gain of reliability when comparing the high voltage IGBT traction module …KF1“ (Cu base plate) with the new generation …KF2“ (Al/SiC base plate).Partial DischargeTo estimate the lifetime of the insulation without the need of high voltages as in the dielectric test, the …partial discharge test“ has been introduced.Partial discharge (PD) is a partial breakdown of the insulation material. An example for a PD source is a small void in ceramics. If the voltage exceeds the breakdown voltage of the gas included, a sudden flash-over discharges the void. The recharge can be measured. PD occurs when increasing the voltage beyond the inception voltage and it disappears when decreasing the voltage below the extinction voltage.Following the development steps between 1995 and 1997 the partial discharge level of the 3.3 kV IGBT modules has been considerably reduced as shown in Fig. 5.In 1995 we started using DCB on 0.63 mm thick Array Al2O3 ceramics. We had the low inception andextinction voltages typical for this material andpartial discharge values in the range of 200 to 300pC. We limited the voltage during these first testruns on complete modules to 5 kV rms , 1 min. Bychanging the ceramics from Al2O3 to AlN inFebruary 1996 the inception voltage was increasedand the devices could meet the specification target10 pC as per IEC 1287. Further improvements ofsubstrates and silicone gel resulted in an evenlower partial discharge. The 10 pC at 6 kV targetwas reached in September 1996.In addition to the requirements of the IEC 1287-standard we have considered the behavior of themodules under long term high voltage stress. Werecorded PD during a one hour test at a voltageU p = 6 kV see Fig. 6. PD decreased and wassignificantly lower than the required 10 pC.ConclusionAs explained above, a lot of measures were taken to insure the reliability of the modules and to meet the customer’s requirements. Due to the low number of devices under test during the production ramp up, it was very difficult to predict a lifetime for the modules operated under field conditions only from the results of accelerated reliability tests. First estimates, based on an operation under the following conditions: load current 50% I nom , blocking voltage 50% V ces , ambient temperature 40°C and period of operation > 1000 h resulted in aIn the meantime eupec has delivered more than 250.000 IHM and IHV IGBT modules to customers. High attention has been paid to the rejects from the customer and especially from the field. In tight cooperation with key customers detailed investigations of all failures have been performed. With these new informations, based on more than 1.400 Mio. estimated hours of module operation, we can now expect a future failure rate for our high power modules of 50 FIT or less.。
