Junction Temperature Measurement Research Articles

Considerations on SiC MOSFET TSEP-based junction temperature measurement routines in practical use

Considerations on SiC MOSFET TSEP-based junction temperature measurement routines in practical use

LED Junction Temperature Measurement: From Steady State to Transient State.

In this review, we meticulously analyze and consolidate various techniques used for measuring the junction temperature of light-emitting diodes (LEDs) by examining recent advancements in the field as reported in the literature. We initiate our exploration by delineating the evolution of LED technology and underscore the criticality of junction temperature detection. Subsequently, we delve into two key facets of LED junction temperature assessment: steady-state and transient measurements. Beginning with an examination of innovations in steady-state junction temperature detection, we cover a spectrum of approaches ranging from traditional one-dimensional methods to more advanced three-dimensional techniques. These include micro-thermocouple, liquid crystal thermography (LCT), temperature sensitive optical parameters (TSOPs), and infrared (IR) thermography methods. We provide a comprehensive summary of the contributions made by researchers in this domain, while also elucidating the merits and demerits of each method. Transitioning to transient detection, we offer a detailed overview of various techniques such as the improved T3ster method, an enhanced one-dimensional continuous rectangular wave method (CRWM), and thermal reflection imaging. Additionally, we introduce novel methods leveraging high-speed camera technology and reflected light intensity (h-SCRLI), as well as micro high-speed transient imaging based on reflected light (μ_HSTI). Finally, we provide a critical appraisal of the advantages and limitations inherent in several transient detection methods and offer prognostications on future developments in this burgeoning field.

Reliability evaluation of IGBT power module on electric vehicle using big data

There are challenges to the reliability evaluation for insulated gate bipolar transistors (IGBT) on electric vehicles, such as junction temperature measurement, computational and storage resources. In this paper, a junction temperature estimation approach based on neural network without additional cost is proposed and the lifetime calculation for IGBT using electric vehicle big data is performed. The direct current (DC) voltage, operation current, switching frequency, negative thermal coefficient thermistor (NTC) temperature and IGBT lifetime are inputs. And the junction temperature (T j) is output. With the rain flow counting method, the classified irregular temperatures are brought into the life model for the failure cycles. The fatigue accumulation method is then used to calculate the IGBT lifetime. To solve the limited computational and storage resources of electric vehicle controllers, the operation of IGBT lifetime calculation is running on a big data platform. The lifetime is then transmitted wirelessly to electric vehicles as input for neural network. Thus the junction temperature of IGBT under long-term operating conditions can be accurately estimated. A test platform of the motor controller combined with the vehicle big data server is built for the IGBT accelerated aging test. Subsequently, the IGBT lifetime predictions are derived from the junction temperature estimation by the neural network method and the thermal network method. The experiment shows that the lifetime prediction based on a neural network with big data demonstrates a higher accuracy than that of the thermal network, which improves the reliability evaluation of system.

Steady-State Temperature-Sensitive Electrical Parameters’ Characteristics of GaN HEMT Power Devices

Gallium nitride high-electron-mobility transistor (GaN HEMT) power devices are favored in various scenarios due to their high-power density and efficiency. However, with the significant increase in the heat flux density, the junction temperature of GaN HEMT has become a crucial factor in device reliability. Since the junction temperature monitoring technology for GaN HEMT based on temperature-sensitive electrical parameters (TSEPs) is still in the exploratory stage, the TSEPs’ characteristics of GaN HEMT have not been definitively established. In this paper, for the common steady-state TSEPs of GaN HEMT, the variation rules of the saturation voltage with low current injection, threshold voltage, and body-like diode voltage drop with temperature are investigated. The influences on the three TSEPs’ characteristics are considered, and their stability is discussed. Through experimental comparison, it is found that the saturation voltage with low current injection retains favorable temperature-sensitive characteristics, which has potential application value in junction temperature measurement. However, the threshold voltage as a TSEP for certain GaN HEMT is not ideal in terms of linearity and stability.

IGBT Junction Temperature Extraction via Voltage Integral over Voltage Rise Period

In this paper, a temperature sensitive electrical parameter (TSEP) method for insulated gate bipolar transistor (IGBT) modules junction temperature estimation based on voltage integral over-voltage rise period (VIVRP) is proposed. Firstly, combined with the principles of thermodynamic physics, the movement characteristics of internal carriers and holes are discussed, and the waveform of voltage and current during the turn-off process is studied. The feasibility of using voltage integral overvoltage period instead of voltage rise loss in junction temperature measurement is discussed and proved. At the beginning of the turn-off process, the holes in the IGBT almost remain in spatial and temporal distribution (the collector current IC remains constant), which leads the VIVRP to a cheaper TSEP method for junction temperature detection, without the high-frequency current detection equipment. Finally, the junction temperature model based on VIVRP and the extraction circuit of VIVRP are proposed. In addition, it is compared with the junction temperature detection method based on the voltage rise time and voltage rise loss. The results show that the junction temperature detection method based on VIVRP proposed in this paper is detection with high precision and low cost.

Precise and Fast Real-Time Measurement of Junction Temperature in SiC Power MOSFETs

Precise and Fast Real-Time Measurement of Junction Temperature in SiC Power MOSFETs

Calibration methods and power cycling of double-side cooled SiC MOSFET power modules

Reliability analysis depends heavily on accurate measurements of junction temperatures for power semiconductors. It forms the foundation for precise reliability tests such as power cycling tests. One of the most established methods for junction temperature measurement in MOSFETs is the VSD(T) method. With the introduction of new module configurations such as the DSC (double-side cooled) module with cooling on both sides, conventional calibration methods for single side cooling require a critical review regarding their applicability. This article will highlight various calibration options and analyse them in regard to sensitivity and reproducibility for DSC modules. Subsequently, the most promising methods are evaluated experimentally. It was found that by heating the modules on both sides, a better temperature uniformity can be achieved than from single side heating alone. This allows to apply the VSD(T) method on DSC modules also during power cycling. A power cycling test with in situ mechanical force measurement was conducted to verify the results.

Junction Temperature Optical Sensing Techniques for Power Switching Semiconductors: A Review.

Recent advancements in power electronic switches provide effective control and operational stability of power grid systems. Junction temperature is a crucial parameter of power-switching semiconductor devices, which needs monitoring to facilitate reliable operation and thermal control of power electronics circuits and ensure reliable performance. Over the years, various junction temperature measurement techniques have been developed, engaging both non-optical and optical-based methods, highlighting their advancements and challenges. This review focuses on several optical sensing-based junction temperature measuring techniques used for power-switching devices such as metal-oxide-semiconductor field-effect transistors (MOSFETs) and insulated-gate bipolar transistors (IGBTs). A comprehensive summary of recent developments in infrared camera (IRC), thermal sensitive optical parameter (TSOP), and fiber Bragg grating (FBG) temperature sensing techniques is provided, shedding light on their merits and challenges while providing a few possible future solutions. In addition, calibration methods and remedies for obtaining accurate measurements are discussed, thus providing better insight and directions for future research.

Junction Temperature Measurement Based on the Internal Gate Resistance for a Wide Range of Power Semiconductors

This paper presents research results on the junction temperature measurement via the internal gate resistance in converter operation for IGBTs and its applicability to other types of active power semiconductors. A junction temperature monitor has been developed to determine the value of the temperature-dependent internal gate resistance by using a sinusoidal voltage superimposed on the gate voltage at the resonance frequency. The device enables a simple and robust junction temperature measurement in inverter operation, which is in excellent agreement with an infrared reference measurement. The method's applicability to semiconductors other than Si-IGBTs, such as SiC-MOSFETs, JFETs, and GaN devices, is verified by gate impedance measurements using a network analyzer. The gate impedance's quality factor is decisive. Other temperature-sensitive electrical parameters (TSEPs) related to the switching behavior depend on the internal gate resistance. Therefore, the findings presented are relevant for many junction temperature measurement methods.

2-D Photo-Thermal Distribution and Structures of Flip-Chip Mini Light-Emitting Diodes by Microscopic Hyperspectral Imaging

Given the growing interest in micro-scale thermal management of mini- and micro-light-emitting diodes (LEDs), it’s crucial to develop an effective two-dimensional (2D) junction temperature measurement method. In this paper, the microscopic hyperspectral imaging (μ-HSI) technique has been proposed to probe the 2D photo-thermal distribution of the flip-chip mini-LEDs. Running on a two-axis rotating platform, μ-HSI is able to directly focus on the epitaxial layer surface (episurface) and lateral side of the LED chips to acquire their 2D spectral distributions. Subsequently, the full width at half maximum matrix was extracted to deduce the 2D junction temperature distributions. As a result, the location and temperature distribution of the active layer, i.e., PN junction, can be determined accurately. The mean temperature of the episurface approximately matches that of the active layer. The Raman shift method was applied to verify the accuracy of the μ-HSI technique. In addition, the extra fine structures as well as temperature distributions of the interface between the episurface and sapphire or electrodes are distinguished and analyzed by this technique. This work offers an effective tool for the quality improvement and thermal management of mini-LEDs.

Indirect Thermographic Temperature Measurement of a Power-Rectifying Diode Die Based on a Heat Sink Thermogram

This article concerns the indirect thermographic measurement of the junction temperature of a D00-250-10 semiconductor diode. Herein, we show how the temperature of the semiconductor junction was estimated on the basis of the heat sink temperature. We discuss the methodology of selecting the points for thermographic measurement of the heat sink temperature and the diode case. The method of thermographic measurement of the heat sink temperature and the used measurement system are described. The simulation method used to obtain the temperature of the semiconductor diode junction on the basis of the thermographic measurement of the heat sink temperature, as well as the method of determining the emissivity and convection coefficients, is presented. In order to facilitate the understanding of the discussed issues, the construction of the diode and heat sink used, the heat flow equation and the finite element method are described. As a result of the work carried out, the point where the diode casing temperature is closest to the junction temperature was indicated, as well as which fragments of the heat sink should be observed in order to correctly estimate the temperature of the semiconductor junction. The indirect measurement of the semiconductor junction temperature was carried out for different values of the power dissipated in the junction.

Online Measurement of Power MOSFET Junction Temperature With Storage Charge During Current Fall Process

Online Measurement of Power MOSFET Junction Temperature With Storage Charge During Current Fall Process

Online Junction Temperature Measurement of Double-sided Cooling IGBT Power Module through On-state Voltage with High Current

The aim of this study is to achieve online monitoring of the junction temperature of double-sided-cooling insulated gate bipolar transistor (IGBT) power modules by using the on-state voltage under a high current to maximize the utilization of IGBT power chips. Online junction temperature measurement plays an important role in improving the reliability of the inverter with IGBT, increasing the power density of the motor controller of electric vehicles, and reducing the cost of electric vehicles.

Conventional and topologically optimized polymer manifolds for direct cooling of power electronics

Single-phase liquid-cooled heat sinks are a preferred mode of thermal management for many power dense electronic applications. This paper studies the design, optimization, and thermal-hydraulic performance of polymer manifolds directing coolant to the base plate of multi-chip power modules. Direct cooling eliminates the need for thermal interface materials which form a major bottleneck to junction-to-coolant thermal resistance reduction in state-of-the-art metallic cold plates. We use 2D topology optimization (TO) to develop designs using side view (SVTO) and top view (TVTO) sections of the flow domain in contact with the power module base plate. We also use 3D TO design (CTO) which combines SCTO and TVTO. The TO designs are compared against conventional mini-channel designs including rectangular, zig-zag and serpentine channels. Cooling performance of the different designs is computed using computational fluid dynamic (CFD) simulations. Experimental quantification is achieved through measurements of the silicon carbide device junction temperature and inter-device temperature difference along with the pressure drop influencing the pumping power requirement. The CFD simulations were used to identify optimized manifold designs which were fabricated using selective laser sintering of PA12 and validated experimentally using surrogate heaters. Zig-zag designs showed the best performance among the conventional designs (0.93 (cm2·K)/W), at the cost of high pressure drop (> 2.4 kPa). Serpentine channel designs were effective in limiting inter-device temperature difference (< 0.26⁰C) through multiple changes of flow direction. The TO designs improved the performance (1.1 (cm2·K)/W) when compared against conventional channels showing lower maximum temperatures with lower pressure drops (0.8 kPa). Fluid manifolds are shown to greatly influence the coolant flow field, leading to flow maldistribution with low velocity pockets, emphasizing the need for optimizing the complete manifold design.

FBG Head Size Influence on Localized On-Chip Thermal Measurement in IGBT Power Modules

This article studies the influence of fiber Bragg grating (FBG) head length on insulated gate bipolar transistor (IGBT) direct on-chip thermal sensing performance of FBG sensors. To this end, the surface of a commercial IGBT chip is thermally simulated and experimentally characterized. Uniform FBG sensors with three head sizes are then tested in two promising thermal sensing locations. The study has found that the large thermal gradients in this application create an additional constraint when using longer head lengths. A distortion in the reflected spectrum of the 5-mm FBG sensor is used to illustrate the underlying physical effect, which causes this limitation for IGBT junction temperature measurement. This additionally affects the length of head sizes providing accurate temperature readings of the IGBT surface hotspots, and significantly, this limit is location-dependent in a given IGBT geometry.

Electrothermal Coupling Model With Distributed Heat Sources for Junction Temperature Calculation During Surges

High junction temperature is usually the main factor leading to device failures in high-power working conditions, such as surges or avalanches. It is of great significance to obtain the junction temperature quickly and accurately. Direct measurement of junction temperature is inconvenient, and usually indirect electrical measurement combined with model calculation is used. An electrothermal coupling junction temperature calculation model with distributed heat sources is proposed in this article. This model can accurately and quickly predict the device behavior during the surge process, as well as the voltage drop and temperature changes of each part of the device, without actually performing surge tests. This article describes the theoretical basis and calculation principles of the model. By taking a commercial SiC merged PiN Schottky diode as an example, this article also explains the details of the establishment of the electrical and thermal characteristic models of the device, as well as the calculation steps of the junction temperature by the thermal coupling model. The calculated device voltage drop curve of the device is in good agreement with the measured ones, and the calculated junction temperature curve is more consistent with the device failure mechanism than the one by the traditional RC thermal circuit model.

A Critical Review on the Junction Temperature Measurement of Light Emitting Diodes.

In the new age of illumination, light emitting diodes (LEDs) have been proven to be the most efficient alternative to conventional light sources. Yet, in comparison to other lighting systems, LEDs operate at low temperatures while junction temperature (Tj) is is among the main factors dictating their lifespan, reliability, and performance. This indicates that accurate measurement of LED temperature is of great importance to better understand the thermal effects over a system and improve performance. Over the years, various Tj measurement techniques have been developed, and existing methods have been improved in many ways with technological and scientific advancements. Correspondingly, in order to address the governing phenomena, benefits, drawbacks, possibilities, and applications, a wide range of measurement techniques and systems are covered. This paper comprises a large number of published studies on junction temperature measurement approaches for LEDs, and a summary of the experimental parameters employed in the literature are given as a reference. In addition, some of the corrections noted in non-ideal thermal calibration processes are discussed and presented. Finally, a comparison between methods will provide the readers a better insight into the topic and direction for future research.

Monolithic Integration of 1.2kV Optically-Controlled SiC npn Transistor and Antiparallel Diode

In this letter, a 1.2kV optically-controlled SiC transistor (OCT) is proposed and fabricated. A pin diode is monolithically integrated with the SiC OCT for reverse conducting and online junction temperature measurement capability. Field limiting rings are designed as terminal structure for forward blocking capability. The test results indicated that, besides full optical control and high blocking voltage performances, the fabricated transistor chip was also capable of reverse conducting and online junction temperature measurement. The forward breakdown voltage of the transistor was about 1400V and the leakage current at 1200V was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${2.5}\,\,\times \,\,{10}\,\,^{-{8}}\text{A}$ </tex-math></inline-formula> . The reverse turn-on voltage was about 2.6V, while the temperature sensitivity of the integrated diode was 2.99mV/K at 5mA. Under 365nm ultraviolet (UV) light with 300mW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> incident intensity, the forward current of the OCT chip was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$203.2\mu \text{A}$ </tex-math></inline-formula> at 0.3V, which is about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${1.2}\,\,\times \,\,{10}\,\,^{{5}}$ </tex-math></inline-formula> times the corresponding dark current. The transient characteristic was tested at a 600V bias voltage in a resistive load circuit and the results indicate that the OCT can be switched using a 365nm UV light emitting diode.

Machine Learning to Predict Junction Temperature Based on Optical Characteristics in Solid-State Lighting Devices: A Test on WLEDs.

While junction temperature control is an indispensable part of having reliable solid-state lighting, there is no direct method to measure its quantity. Among various methods, temperature-sensitive optical parameter-based junction temperature measurement techniques have been used in practice. Researchers calibrate different spectral power distribution behaviors to a specific temperature and then use that to predict the junction temperature. White light in white LEDs is composed of blue chip emission and down-converted emission from photoluminescent particles, each with its own behavior at different temperatures. These two emissions can be combined in an unlimited number of ways to produce diverse white colors at different brightness levels. The shape of the spectral power distribution can, in essence, be compressed into a correlated color temperature (CCT). The intensity level of the spectral power distribution can be inferred from the luminous flux as it is the special weighted integration of the spectral power distribution. This paper demonstrates that knowing the color characteristics and power level provide enough information for possible regressor trainings to predict any white LED junction temperature. A database from manufacturer datasheets is utilized to develop four machine learning-based models, viz., k-Nearest Neighbor (KNN), Radius Near Neighbors (RNN), Random Forest (RF), and Extreme Gradient Booster (XGB). The models were used to predict the junction temperatures from a set of dynamic opto-thermal measurements. This study shows that machine learning algorithms can be employed as reliable novel prediction tools for junction temperature estimation, particularly where measuring equipment limitations exist, as in wafer-level probing or phosphor-coated chips.

Junction temperature measurement in optically-activated power MOSFET

The temperature-dependent optical properties of silicon carbide (SiC), such as refractive index and reflectivity, have been used for a direct monitoring of the junction temperature of a power MOSFET. In particular, the optical response of a 4H–SiC MOSFET-integrated Fabry–Perot (FP) cavity to temperature changes has been investigated through parametric optical simulations at the wavelength of λ = 450 nm. The reflected optical power exhibited oscillatory patterns caused by the multiple beam interference for which the MOSFET epilayer, between the gate-oxide and the doped 4H–SiC substrate, acts as a FP etalon. These results were used to calculate the refractive index change and, therefore, the optical phase shift of Δϕ = π/2 corresponding to a temperature variation that can be considered as a warning for the device ‘health’. In practical applications, the periodic monitoring of the optic spectrum at the interferometric structure output gives an essential information about the device operating temperature condition that, for high power operations, may lead to device damages or system failure. Moreover, the optical monitoring of the junction temperature has been combined with the optical activation of the same device in order to design an all-optically controlled power MOSFET. Electro-optical simulation results show that the application of an UV optical beam (λ = 285 nm) leads to the creation of the electrical channel between drain (D) and source (S). The corresponding current density–voltage (J D–V DS) characteristics have been calculated under different values of the optical power density up to 10 kW cm−2.