Study On Accelerated Aging And Characteristic Parameters Of IGBT Module

Power converters have been widely used in renewable energy,automobile industry,aerospace and other fields.The reliability of converter has been also paid more and more attention in these fields.IGBT module is the core device of power converter and one of the most vulnerable devices to aging and damage.The unforeseeable failure caused by the aging of the device will bring high maintenance costs and may even lead to disastrous accidents.In order to prolong the service life and improve its reliability of power module,the research on the reliability of the power device in the power electronic system become the research hot spot.The aging mechanism of IGBT modules,the relationship between the main factors influencing the aging and the aging process need to be studied.In particular,the research and extraction method of characteristic parameters of aging process are the key and difficult points in the reliability study of power module.The accelerated aging and aging characteristic parameters of IGBT module are studied.?1?Firstly,the IGBT module aging process is slow,and it is difficult to extract the characteristic parameter data of the aging process online in engineering applications.Based on accelerated aging theory and model,a DC power cycle accelerated aging experimental platform was designed and constructed.According to the aging failure phenomenon of bonding wire lift-off,Two accelerated aging control strategies,constant?T_j and constant?T_c are proposed,and the range of temperature fluctuations is determined.Accelerated aging experiments at different thermal stress levels were completed.The circuit topology with single current source and multiple devices under test and automatic measurement method are realized.According to the power cycle times of each batch of IGBT modules and the set of accelerated aging test conditions,it provides experimental data and experimental basis for the subsequent selection and analysis of aging characteristic parameters and the aging condition monitoring method.?2?In view of the existing literature on the characteristic parameters of characterizing aging process,there is a problem of insufficient theoretical analysis and immature measurement methods.According to the variation law of output characteristic curves and transmission characteristic curves in the aging process,combined with the established equivalent mathematical model of V_CE?on?and module transconductance,the relationship between module saturation voltage drop and drive voltage,junction temperature,collector current and bonding wire aging is analyzed,and the relationship between transconductance and drive voltage,junction temperature,collector current and bonding wire aging is analyzed.A method for measuring the saturation voltage drop of emitter is presented.Aiming at the problems of large measurement error,slow speed,poor continuity and low efficiency in the traditional method of measuring transconductance,a continuous variable voltage drive measuring circuit is proposed,the rapid measurement of the transmission characteristic curve of IGBT module is realized,which lays a foundation for IGBT module aging condition monitoring.?3?At present,most of the characteristic parameters that characterize the aging state have little change in the aging process and are greatly affected by the junction temperature.It is difficult to accurately detect and obtain in practical application.a method for monitoring aging failure in IGBT module based on V_CE?on?under certain condition is presented.The V_CE?on?is measured under certain collector current I_C condition,which is the crossover point of output characteristic curves under different temperatures,The influence of temperature on the aging characteristic parameters can be eliminated,and the aging condition of IGBT module bonding wire can be monitored under different working conditions.The experimental results indicate that the V_CE?on?of IGBT module is not affected by junction temperature under certain collector current condition,but only related to the aging situation of modules.The method has been successfully applied to the parameter test of aging platform.?4?In view of the problems reported in the literature,the characteristic parameters of the aging state have little change,low sensitivity and measurement difficulty.A new characteristic parameter-module transconductance and extraction method are proposed.The failure mechanism of bonding wires and the relationship between bonding wires lift-off and the modules transconductance are analyzed in detail.The quantitative relationship between the number of bond wires lift-off and module transconductance is determined by experimental measurement.Because the temperature has a good linear relationship with module transconductance,the temperature normalization is carried out for module transconductance at any temperature for avoiding the influence of temperature on the aging state of the monitoring bonding line.A quasi-online method monitoring healthy state of bond wires in IGBTs based on module transconductance is realized.Compared with the existing methods for monitoring the aging state of bonding wires,it is proved that the method presented has good sensitivity in this paper.