Study On IGBT Accelerated Life Test Based On Step-down Temperature Stress

With the rapid growth of new energy power generation,new energy power generation technology puts forward higher requirements on the reliability of converters.The power semiconductor device in the converter——Insulate Gate Bipolar Transistor?IGBT?has a multi-layer package structure,and the thermal expansion coefficients of the materials in each layer are not matched,which is affected by the use of new energy power generation.The effect of power fluctuations,the module is prone to failure under the action of thermo-mechanical stress.According to research,power semiconductor devices have become one of the most inefficient components in converters.Therefore,studying the reliability of IGBT devices is very important to improve the reliability of the converter,which is of great significance for ensuring the long-term stable operation of new energy power generation equipment.The designing life of IGBT devices is generally more than twenty years.In order to quickly obtain the life data of devices,accelerated life test methods are often used.The accelerated life test is able to obtain the required test data in a short period of time and is an effective method for studying long-life products.This paper focuses on the topic of accelerated life test of IGBT modules,and studies the test plan scheme,the designing of the test platform,the theoretical analysis of the test method and the data processing of the accelerated life test.?1?For the accelerated life test method,the IGBT step-down stress test scheme was innovatively proposed.The proposed step-down stress test scheme effectively solves the problem that the conventional constant stress test method has long time and low test efficiency under the small stress,and the test data of the module under small stress is effectively obtained.The theory of statistical analysis of step-down stress test is summarized.The model hypothesis analysis of the step-down stress test model is carried out.According to the three model assumptions,the analysis method of the step-down stress model is summarized.The parameter estimation method of the model and the hypothesis testing method of whether the failure mechanism changes under different stress conditions are summarized.?2?A power cycling test setup was built.The main design requirements for completing the test were analyzed,and the overall framework of the design of the platform was studied through demand analysis.According to the platform scalability,the main circuit topology is analyzed,and the design of the series topology plus bypass switch is proposed.The junction temperature of the IGBT module was measured by the Temperature Sensitive Electrical Parameter?TSEP?.According to the characteristics of the junction temperature rise of the IGBT module during the heating process,the variable sampling period method was used to measure the junction temperature of the device.For the measurement and test needs,an IGBT drive circuit board with small interference,adjustable gate drive voltage and safe and practical design is designed.For the heat dissipation of the module,the control of the water flow through the radiator realizes the effect of rapid temperature rise and rapid cooling of the junction temperature,which greatly improves the test efficiency.Through the reasonable waterway design,the independence of the module water cooling is realized,and the water flow is avoided,which ensures the consistency of the heat dissipation performance.According to the control flow,the main control design idea based on FPGA is proposed and the software design is completed.A set of host computer interface program has been written to provide good human-computer interaction.The module thermal resistance measurement scheme is verified and the thermal resistance of the module is measured.Through the efficiency comparison analysis,the improvement of the device reduces the temperature rise ans fall time and improves the power cycling test efficiency.?3?Proper IGBT device sample selection based on the power rating and test capacity of the test platform.The IGBT step-down stress test procedure of the system is proposed to ensure that all aspects of the test are carried out reasonably and effectively,and that the test data is scientific,complete and effective.The step-down stress test of the IGBT module was completed on the test platform,and the failure characteristic parameters of the module were measured and the failure life of the module was recorded.After the test,optical inspection of the bonding wire confirmed that the bond wire was broken or broken is one of the causes of module failure,and V_cesat as a failure feature of the IGBT module is reasonable,and the health of the bonding wire can be monitored online.Statistical analysis of the failure data shows that the Weibull failure distribution parameters and acceleration factor parameters of the IGBT module can be analogized to the lifetime of the module under small stress conditions.The IGBT step-down stress test is carried out to verify the feasibility of the test method,and provides a new method and idea for the research of IGBT accelerated life test.