Transient Thermal Impedance Curve Research Articles

Comparative Study of the Parameter Acquisition Methods for the Cauer Thermal Network Model of an IGBT Module

Under the operating conditions of high power and high switching frequency, an insulated gate bipolar transistor (IGBT) chip can produce relatively large power loss, causing the junction temperature to rise rapidly; consequently, the reliability of the IGBT module can be seriously affected. Therefore, it is necessary to accurately predict the junction temperature of the IGBT chip. The resistance capacitance (RC) thermal network model is a commonly used method for IGBT junction temperature prediction. In this paper, the model parameters are obtained by two methods to establish the Cauer thermal network models of the IGBT module. The first method is to experimentally obtain the transient thermal impedance curve of the IGBT module and the structure function and then extract the individual thermal parameters of the Cauer thermal network model; the second method is to obtain the thermal parameters of the thermal network model directly by using theoretical formulas that consider the influence of the heat spreading angle. The predicted junction temperatures of the Cauer thermal network models established by the two methods are compared with the junction temperatures obtained from infrared (IR) measurements during the power cycling test, the junction temperatures measured by the temperature-sensitive electrical parameter (TSEP) method, and the junction temperatures calculated by finite element (FE) analysis. Additionally, the Cauer thermal network models established by the two methods are compared and verified. The results indicate that the Cauer thermal network model established based on theoretical formulas can accurately predict the maximum junction temperature of the IGBT chip, and the calculated temperature for each layer, from the IGBT chip layer to the ceramic layer, also accords well with the FE results. The Cauer thermal network model established based on the experimental test and the structure function can accurately predict the average junction temperature of the IGBT chip.

Online correction method of IGBT lifetime evaluation based on bonding wire failure monitoring

Insulated gate bipolar transistor (IGBT) modules are widely used as power switching devices. In actual working conditions, the failure of bonding wires is one of the most important failure modes. At present, the influence of bonding wire failure is not considered in the reliability evaluation of the device, resulting in a large error in the life prediction result. Therefore, this paper proposes a life evaluation method for IGBT modules that takes into account the failure of the bonding wire. The transient thermal impedance of 1200 V/50 A IGBT module under the failure conditions of different numbers of bonding wires is calculated by constructing a finite element simulation model of device electro-thermal coupling. Both simulation and experimental results show that with the increase of the number of bonding wire failures, the transient thermal impedance curve of the device rises and the steady-state thermal impedance increases. The Foster thermal network models of the devices are updated, and the number of power cycles of the device with bonding wire failure under DC and sinusoidal pulse width modulation (SPWM) conditions is calculated. When the number of bonding wire failures and fatigue accumulation have a linear relationship, the life will be reduced by 48.29% compared to the healthy state.

Self-attention-based adaptive remaining useful life prediction for IGBT with Monte Carlo dropout

Insulated gate bipolar transistor (IGBT) is one of the most crucial and fragile components in an electronic system. The remaining useful life (RUL) prediction of IGBTs can precisely forecast the unexpected failure and mitigate the potential risk to guarantee system reliability. In this paper, the IGBTs’ run-to-failure (RtF) aging tests are performed to simulate the degradation process, and a self-attention-based prognostic framework named SA-MCD is proposed for RUL prediction. 21 hand-crafted candidate features are extracted from the transient thermal impedance curve, and half of the sensitive ones are selected to construct the health indicator (HI) based on the self-attention mechanism. Monte Carlo (MC) dropout is combined to provide the confidence intervals by increasing the uncertainty. For standalone online data, the proposed method is proved valid in making high-precision RUL predictions at an early stage. When offline data is available, the adaptation performance is also excellent by updating the model with a small part of initial online data. Through the comparisons with some popular methods, we confirm our proposed method’s superiority.

Study on the Method to Measure Thermal Contact Resistance Within Press Pack IGBTs

The accurate measurement of the thermal contact resistance between multilayers within press pack insulated gate bipolar transistors (PP IGBTs) is significant for optimizing their thermal resistance to improve reliability, as thermal contact resistance accounts for about 50% of their total thermal resistance under the rated clamping force. The components within PP IGBTs are very small, and an external clamping force is needed to ensure they work normally. Thus, the methods of thermal contact resistance measurement of steady-state and transient methods are no longer suitable. In this paper, the method of thermal structure function is proposed to measure the thermal contact resistance between multilayers within PP IGBTs. The accurate measurement of the transient thermal impedance curve of PP IGBTs is the key to this method, and it can then be transformed to a cumulative and differential structure function to determine the thermal contact resistance accurately. A single fast recovery diode chip submodule is fabricated to predict the thermal contact resistance behavior within PP IGBTs in this experiment, and the experimental results agree well with theoretical values. Furthermore, the influence of both the high temperature and the clamping force on the thermal contact resistance can also be obtained from this method accurately.

Study on the Method to Measure the Junction-to-Case Thermal Resistance of Press-Pack IGBTs

Accurate measurement of the junction-to-case thermal resistance of press-pack insulated gate bipolar transistors (PP IGBTs) is a great challenge due to their special packaging style and working conditions. The traditional thermocouple and transient dual interface methods have been successfully applied to measure the junction-to-case thermal resistance of wire-bonded IGBT modules. In this paper, a single fast-recovery diode (FRD) chip submodule is fabricated to determine the best method to measure the junction-to-case thermal resistance of PP IGBTs. Therefore, both the traditional thermocouple method and the transient dual interface method were used to measure the junction-to-case thermal resistance of the collector-side cooling with the emitter-side adiabatic. The transient dual interface method, which does not require locating a thermocouple to measure the case temperature, is ideal for the PP IGBTs measurement based on the experimental results and theoretical verification. Most importantly, both bulk thermal resistance of specific layers and thermal contact resistance between multilayers in PP IGBTs can be obtained by transforming the transient thermal-impedance curve.

The effect of electro-thermal parameters on IGBT junction temperature with the aging of module

This paper presents the effect of the change of electro-thermal parameters on IGBT junction temperature with module aging. Five IGBT modules are subjected to advance power thermal cycling, and IGBT I–V characterization, switching loss, and transient thermal impedance curve are measured every 1000 power thermal cycles. Then, electro-thermal models of IGBT module under power thermal cycles were built by change electro-thermal parameters, and the influence of various parameters of the electro-thermal model on the junction temperature was researched respectively. Experimental results demonstrate that IGBT collector-emitter voltage, switching loss and thermal resistance increase more quickly with the aging process of module. Simulation results indicate that the variations of electro-thermal parameters have crucial influences on the IGBT junction temperature. After 6000 power thermal cycles, the IGBT steady state junction temperature mean and variation are increased 1.97K and 0.1656K over its initial value, respectively. The relative temperature rise is 38.10% and relative temperature variation is 15.08% after 6000 power thermal cycles. The rise in switching loss increases both the steady state junction temperature mean and variation. The change of thermal impedance has great influence on the steady state junction temperature mean, but has little effect on steady state junction temperature variation.

The influence of the phosphor layer as heat source and up-stream thermal masses on the thermal characterization by transient thermal analysis of modern wafer level high power LEDs

In the last years Waver Level LED Packages (WLP-LEDs) were developed. They are thin film flip chips where the sapphire substrate remains attached on top of the epitaxial light emitting layer (EPI) which can be assembled directly on a printed circuit board. The thermal resistance and the thermal path of WLP-LED packages are measured by transient thermal analysis and transient finite element simulation. This study investigates the impact of the upstream thermal masses, i.e. the sapphire (SP), phosphor layer (PL) and the side coating (SC) on the transient thermal impedance curve and the cumulative structure function. It is shown that the standard approach to extract thermal properties by features (steps) within the structure function is misleading for thermal networks with upstream thermal load and distributed heat source (EPI and PL) because they influence the shape of the structure function. By transient thermal measurements and finite element (FE) simulation the transient thermal measurements are analysed to extract information about the thermal parameters and the thermal path. Starting from the analysis of the blue flip chip LED (FC-LED, no PL and no SC) the FE-model is set up. Stepwise the FE model is extended and the influence of the PL and the SC on the transient thermal measurement is investigated. A FE model is validated and calibrated which allows simulating the transient thermal curves of these modern LEDs. Using the model the impact of structural changes in the LED package on the transient thermal curves can be identified for reliability analysis.

Test of IGBT Transient Thermal Impedance and Modeling Research on Thermal Model

As the operation performances and reliability of semiconductor devices are tightly related to its operating temperature, the research on the heat transfer characteristic and thermal modeling do a significant meaning to extend services lifetime and improve application reliability of the IGBT modules. The physical structure and the conception, RC component network of thermal resistance, test principle and platform of the transient thermal impedance of IGBT module and three modeling methods are briefly introduced. The parameters of Cauer RC thermal network of a certain type IGBT is derived based on transmission line method. The junction-case thermal resistance can be deduced by Finite Element Method in the numerical simulator ANSYS and the transient thermal impedance curve. Thermal compact model can also be deduced from the numerical simulation and experimental results. An excellent agreement is obtained between experimental results derived by the transient thermal impedance curve and numerical simulation results based on FEM. The thermal compact model and experimental results could be helpful for modeling of thermal model and heat sink design for such electronic devices.

An Experimentally Validated Transient Thermal Impedance Model for High Power Diodes and Thyristors

In this paper a thermal model that allows to obtain the transient thermal impedance curve of high power diodes and thyristors is presented. The results obtained from the model are compared with the experimental measurements performed on the most diffused families of device packages. In the last section of the paper a method for predicting the transient junction temperature by using PSPICE is outlined. The method is based on the fitting of the transient thermal impedance curve with a finite series of exponential terms.

Instantaneous junction temperature evaluation of high-power diodes (thyristors) during current transients

In this paper, an approach to the instantaneous junction temperature evaluation of high-power diodes (thyristors) is presented. The model allows obtaining the instantaneous junction temperature waveform starting from the expressions of the device transient thermal impedance and forward voltage drop. The linearity properties of resistors and capacitors (RCs) networks are used to obtain the thermal system transfer function from the transient thermal impedance curve. Thus, an expression that relates the forward voltage drop to the forward current and the junction temperature is used to feedback the influence of the temperature variation on the device forward characteristic. The model is also validated by comparing the results obtained from simulation against the one obtained from surge tests performed on one sample device.

Estimation of transient thermal impedance for constant current of a power thyristor using temperature field calculation

Transient thermal impedance for constant current is calculated by dividing the overtemperature of a given spot within a silicon pellet by power losses. The calculation of the temperature field in the silicon pellet is based on the assumption that losses are produced in the silicon pellet only. Calculated results for one power thyristor are compared to its catalog values. The best agreement was obtained in the case of uniform loss distribution throughout the silicon pellet volume, with the temperature at the r/2 spot in the central silicon pellet plane being taken as virtual junction temperature. Understandably, the best agreement obtained was for a temperature at the r/2 spot in silicon pellet's central plane, since the catalog curve is based on the measurement of forward voltage drop which is dependent on total temperature field in a silicon pellet. The difference between calculated transient thermal impedance curve for constant current and its catalog curve in the entire time area is, in this case, for cooling from the anode side, from the cathode side, and from both sides, 11.4, 10.3, and 3.6%, respectively.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Thermal parameter estimation using recursive identification

A novel method that converts a semiconductor transient thermal impedance curve (TTIC) into an equivalent thermal RC network model is presented. Thermal resistance (R) and thermal capacitance (C) parameters of the model are identified using manufacturer's data and offline recursive least square techniques. Relevant estimation theory concepts and the formulation of an appropriate model for the identification process are given. Model synthesis is illustrated using an isolated base power transistor module. The application of time decoupled theory for high order thermal models is outlined. Simulation of junction temperature responses using model and manufacturer TTICs are compared. Estimated parameter validity is further confirmed by parameter calculation obtained from module physical dimensions. >