Showing papers on "Junction temperature published in 2010"
23 Dec 2010
TL;DR: In this article, an alternative 3-level topology referred to as T-type is presented, which is very high efficient for medium switching frequencies (4-20 kHz) for low voltage converter.
Abstract: In the low voltage converter range, 3-phase 3-level VSC topologies are not wide spread in industry because of the increased part count and higher costs, although they are more efficient for higher switching frequencies. In this paper an alternative 3-level topology referred to as T-type is presented, which is very high efficient for medium switching frequencies (4–20 kHz). Additionally, it is shown that the total silicon chip area of a 3-level topology can be lower than in a 2-level topology since the losses are distributed over more components leading to only a small increase in the junction temperature. This allows for the design of a chip area and cost optimized 3-level bridge leg module for the mass market.
170 citations
TL;DR: In this paper, an analysis of thermoelectric cooler (TEC) performance is conducted for high power electronic packages such as processors, and two sets of analytical solutions for TECs in system constraints are derived for the junction temperature T j at a fixed cooling power Q c, and for Q c at fixed T j, respectively.
146 citations
TL;DR: In this article, a new thermal model based on the Fourier series solution of heat conduction equation has been introduced in detail, which can provide high simulation speed with high accuracy, which has proved to be more favorable in dynamic thermal characterization on power semiconductor switches.
Abstract: In this paper, a new thermal model based on the Fourier series solution of heat conduction equation has been introduced in detail. 1-D and 2-D Fourier series thermal models have been programmed in MATLAB/Simulink. Compared with the traditional finite-difference thermal model and equivalent RC thermal network, the new thermal model can provide high simulation speed with high accuracy, which has been proved to be more favorable in dynamic thermal characterization on power semiconductor switches. The complete electrothermal simulation models of insulated gate bipolar transistor (IGBT) and power diodes under inductive load switching condition have been successfully implemented in MATLAB/Simulink. The experimental results on IGBT and power diodes with clamped inductive load switching tests have verified the new electrothermal simulation model. The advantage of Fourier series thermal model over widely used equivalent RC thermal network in dynamic thermal characterization has also been validated by the measured junction temperature.
135 citations
TL;DR: An aging test of high-power 1 W white light emitting diodes underwent an aging test, to identify both their degradation mechanisms and the limitations of the LED chip and package materials, providing a complete understanding of the degradation mechanisms.
110 citations
TL;DR: In this article, a high-temperature wirebond package for multichip phase-leg power module using SiC devices was designed, developed, fabricated, and tested.
Abstract: In order to take full advantage of SiC, a high-temperature wirebond package for multichip phase-leg power module using SiC devices was designed, developed, fabricated, and tested. The details of the material comparison and selection are described, thus culminating a feasible solution for high-temperature operation. A thermal cycling test with large temperature excursion (from -55°C to 250°C) was carried out to evaluate the thermomechanical reliability of the package. During the test, the substrate failed before other parts in 20 cycles. A sealing edge approach was proposed to improve the thermal reliability of the substrate. With the strengthening of the sealing material, the substrate, die-attachment, and wirebond assemblies exhibited satisfactoriness in the thermomechanical reliability tests. In order to evaluate the high-temperature operation ability of designed package, one prototype module was designed and fabricated. The high-temperature continuous power test shows that the package presented in this paper can perform well at 250°C junction temperature.
101 citations
TL;DR: In this paper, a phase-leg power module is packaged by a novel planar packaging technique for high-temperature (250°C) operation, where the nanosilver paste is chosen as the die-attach material as well as playing the key functions of electrically connecting the devices' pads.
Abstract: This paper presents the design, development, and testing of a phase-leg power module packaged by a novel planar packaging technique for high-temperature (250°C) operation. The nanosilver paste is chosen as the die-attach material as well as playing the key functions of electrically connecting the devices' pads. The electrical characteristics of the SiC-based power semiconductors, SiC JFETs, and SiC Schottky diodes have been measured and compared before and after packaging. No significant changes (<;5%) are found in the characteristics of all the devices. Prototype module is fabricated and operated up to 400 V, 1.4 kW at junction temperature of 250°C in the continuous power test. Thermomechanical robustness has also been investigated by passive thermal cycling of the module from -55°C to 250°C. Electrical and mechanical performances of the packaged module are characterized and considered to be reliable for at least 200 cycles.
90 citations
TL;DR: In this article, the authors developed a detailed model of GaSb and GaInAsSb PV diodes, which describes the electrical behavior of the diode as a function of the operating point defined by a photocurrent and a junction temperature.
83 citations
TL;DR: In this article, the spectral radiant flux of commercial single color LED packages have been measured in a custom made integrating sphere at several junction temperatures by active cooling and heating with a Peltier element.
Abstract: Spectral radiant flux is the primary optical characteristic of a light source, determining the luminous flux and color. Much research is dedicated to the modeling of light-emitting diode (LED) spectra and their temperature dependence, allowing for the simulation of optical properties in various applications. Most of the spectral radiant flux models that have been published so far are purely mathematical. For this paper, spectral radiant fluxes of commercial single color LED packages have been measured in a custom made integrating sphere at several junction temperatures by active cooling and heating with a Peltier element. A spectrum model at 300 K is constructed where the Boltzmann free carrier distribution and carrier temperature are included. Subsequently, the model is extended with the carrier temperature variation, the band gap energy shift, and the nonradiative recombination rate decrease with junction temperature. As a result, the skewness variation, peak frequency shift, and peak value change in th...
78 citations
TL;DR: A new temperature compensation technique for thermal flow sensors that are operated in a constant-temperature-difference (CTD) mode by means of a simple analog circuit that includes a potentiometer capable of changing the resistance of the temperature sensor and its temperature coefficient of resistance (TCR) for an easy adjustment for temperature compensation.
Abstract: This paper presents a new temperature compensation technique for thermal flow sensors that are operated in a constant-temperature-difference (CTD) mode by means of a simple analog circuit. The resistive heater of a thermal flow sensor is maintained at a constant temperature some tens of Kelvins above fluid temperature with the help of a Wheatstone bridge circuit. In case of a change in media temperature, an adjustment of the heater temperature is necessary; otherwise, the temperature difference falls/rises with respect to the temperature change, and the sensor output signal deviates from its calibration. Temperature compensation can be performed by the use of an additional resistive temperature sensor. The circuit design presented here includes a potentiometer that is capable of changing the resistance of the temperature sensor and its temperature coefficient of resistance (TCR) for an easy adjustment for temperature compensation. This gives the freedom to use any material such as platinum, aluminum, or, in our case, an alloy of tungsten and titanium (WTi) for the temperature sensor, regardless of its resistance value and TCR with respect to the heater of a thermal flow sensor.
64 citations
TL;DR: In this article, a fast response thermocouple was developed for measuring surface temperatures of aluminum components in ICE combustion chambers, which can measure average surface temperatures within 0.19°C and the magnitude of temperature swings within 6% of true values.
63 citations
TL;DR: In this paper, a dynamic electrothermal model that can be simulated with the power electronic circuit simulator is proposed to estimate the transient junction temperature of the semiconductor devices, which is used to facilitate the power sharing between parallel-connected converters.
Abstract: This paper proposes a dynamic electrothermal model that can be simulated with the power electronic circuit simulator. It includes a temperature-dependent loss calculation of power semiconductor devices. The proposed model is used to estimate the transient junction temperature of the semiconductor devices. In so doing, the resulting junction temperature is used to facilitate the power sharing between parallel-connected converters. The use of power-cycling method based on junction temperature helps in increasing the over all system efficiency and reliability of the system. This part of the paper focuses on the method of thermal modeling and discusses how the model can be used for different converters, modulation techniques, and devices.
TL;DR: In this article, a double-coupled-quantum-dot molecule is sandwiched between two metallic electrodes, and the value of ZT can exceed 1 at room temperature by controlling the chemical potential or magnetic flux.
Abstract: We propose a high-efficiency molecular junction consisting of a double-coupled-quantum-dot molecule sandwiched between two metallic electrodes. ZT can be enhanced in the Fano-line-shape regime, and it is sensitive to the magnetic flux threading through the double-coupled-quantum-dot molecular junction. This is mainly due to the local density of states in the Fano-line-shape regime may become narrower, and an abrupt changing in the conductance (transmission) spectrum is developed. We find the value of ZT can exceed 1 at room temperature by controlling the chemical potential or magnetic flux. So our results indicate such a molecular junction may be used to the solid-state thermoelectric energy-conversion device at room temperature.
01 Jan 2010
TL;DR: In this paper, a custom multi-chip power module packaging was designed to exploit the electrical and thermal performance potential of silicon carbide MOSFETs and JBS diodes.
Abstract: A custom multi-chip power module packaging was designed to exploit the electrical and thermal performance potential of silicon carbide MOSFETs and JBS diodes. The dual thermo-mechanical package design was based on an aggressive 200°C ambient environmental requirement and 1200 V blocking and 100 A conduction ratings. A novel baseplate-free module design minimizes thermal impedance and the associated device junction temperature rise. In addition, the design incorporates a free-floating substrate configuration to minimize thermal expansion coefficient induced stresses between the substrate and case. Details of the module design and materials selection process will be discussed in addition to highlighting deficiencies in current packaging materials technologies when attempting to achieve high thermal cycle life reliability over an extended temperature range.
TL;DR: In this paper, the authors present the development and experimental performance of a 10kW high-power-density three-phase ac-dc-ac converter, which consists of a Vienna-type rectifier front end and a two-level voltage source inverter.
Abstract: This article presents the development and experimental performance of a 10-kW high-power-density three-phase ac-dc-ac converter. The converter consists of a Vienna-type rectifier front end and a two-level voltage source inverter (VSΓ)To reduce the switching loss and achieve a high operating junction temperature, the SiC JFET and SiC Schottky diode are used. Design considerations for the phase-leg units, gate drivers, integrated input filter-combining electromagnetic interference (EMI) and boost inductor stages-and the system protection are described in full detail. Experiments are carried out under different operating conditions, and the results obtained verify the performance and feasibility of the proposed converter system.
01 Jan 2010
TL;DR: In this article, a GaN-based vertical light-emitting diodes (VLEDs) on metal alloy over conventional LEDs is presented. And the GaN VLED on metal Alloy exhibits very good currentvoltage behavior with low operated voltage and low serial dynamic resistance.
Abstract: In this paper, we show the many advantages of the GaN-based vertical light-emitting diodes (VLEDs) on metal alloy over conventional LEDs in terms of: better current spreading, vertical current path for low operation voltage, better light extraction, flexible chip size scaling, higher driving current density, faster heat dissipation, and good reliability. The GaN VLED on metal alloy exhibits very good current-voltage behavior with low operated voltage and low serial dynamic resistance. The low operation junction temperature of GaN VLED on metal alloy demonstrates excellent heat dissipation capabilities. Chip size scaling without efficiency loss shows a unique property of GaN VLED on metal alloy. The GaN VLED on metal alloy also enables top surface engineering for efficient light extraction to further light output. A high-power white LED having efficiency of 120 lumen/W was achieved through a combination of reflector, surface engineering, and optimiza- tion of the n-GaN layer thickness. Coupled with good reliability and mass production ability, the GaN VLED on metal alloy is very suitable for general lighting application.
TL;DR: In this article, the thermal properties of unpackaged LED chips are described by a single time constant, that is, the thermal time constant associated with the substrate, and a multistage RthCth thermal model for packaged LEDs is developed.
Abstract: The thermal properties, including thermal time constants, of GaInN light-emitting diodes LEDs and laser diodes LDs are analyzed. The thermal properties of unpackaged LED chips are described by a single time constant, that is, the thermal time constant associated with the substrate. For unpackaged LD chips, we introduce a heat-spreading volume. The thermal properties of unpackaged LD chips are described by a single time constant, that is, the thermal time constant associated with the heat spreading volume. Furthermore, we develop a multistage RthCth thermal model for packaged LEDs. The model shows that the transient response of the junction temperature of LEDs can be described by a multiexponential function. Each time constant of this function is approximately the product of a thermal resistance, Rth, and a thermal capacitance, Cth. The transient response of the junction temperature is measured for a high-power flip-chip LED, emitting at 395 nm, by the forward-voltage method. A two stage RthCth model is used to analyze the thermal properties of the packaged LED. Two time constants, 2.72 ms and 18.8 ms are extracted from the junction temperature decay measurement and attributed to the thermal time constant of the LED GaInN/sapphire chip and LED Si submount, respectively. © 2010 American Institute of Physics.
03 May 2010
TL;DR: The GaN VLED on metal alloy exhibits very good current-voltage behavior with low operated voltage and low serial dynamic resistance, coupled with good reliability and mass production ability, and is very suitable for general lighting application.
Abstract: In this paper, we show the many advantages of the GaN-based vertical light-emitting diodes (VLEDs) on metal alloy over conventional LEDs in terms of: better current spreading, vertical current path for low operation voltage, better light extraction, flexible chip size scaling, higher driving current density, faster heat dissipation, and good reliability. The GaN VLED on metal alloy exhibits very good current-voltage behavior with low operated voltage and low serial dynamic resistance. The low operation junction temperature of GaN VLED on metal alloy demonstrates excellent heat dissipation capabilities. Chip size scaling without efficiency loss shows a unique property of GaN VLED on metal alloy. The GaN VLED on metal alloy also enables top surface engineering for efficient light extraction to further light output. A high-power white LED having efficiency of 120 lumen/W was achieved through a combination of reflector, surface engineering, and optimization of the n-GaN layer thickness. Coupled with good reliability and mass production ability, the GaN VLED on metal alloy is very suitable for general lighting application.
TL;DR: This paper presents a LED junction temperature measurement technique for a pulsewidth modulation diode forward current controlled RGB LED lighting system that has been automated and can effectively stabilize the color without the need for using expensive feedback systems that involve light sensors.
Abstract: The efficiency of light-emitting-diode (LED) lights approaches that of fluorescent lamps. LED light sources find more applications than conventional light bulbs due to their compactness, lower heat dissipation, and real-time color-changing capability. Stabilizing the colors of red-green-blue (RGB) LED lights is a challenging task, which includes color light intensity control using switching-mode power converters, color point maintenance against LED junction temperature change, and limiting LED device temperature to prolong the LED lifetime. In this paper, we present a LED junction temperature measurement technique for a pulsewidth modulation diode forward current controlled RGB LED lighting system. The technique has been automated and can effectively stabilize the color without the need for using expensive feedback systems that involve light sensors. Performance in terms of chromaticity and luminance stability for a temperature-compensated RGB LED system will be presented.
21 Jun 2010
TL;DR: In this paper, a measurement system for thermal impedance is developed to evaluate three die-attach materials, and three samples using three die attach materials were thermally cycled from -400C to 1250C, and the experimental results show that after 500 cycles, the thermal impedance of SAC305 samples and SN100C samples is increased by 12.8% and 15% respectively, which is much higher than the sample using nano-silver paste for die attach.
Abstract: Since a die-attach layer has significant impact on the thermal performance of a power module [1], its quality can be characterized using thermal performance. In this paper, a measurement system for thermal impedance is developed to evaluate three die-attach materials. Thanks to its high temperature sensitivity (10mV/0C), the gate-emitter voltage of an IGBT is used as the temperature-sensitive parameter. The power dissipation in the IGBT is maintained constant regardless of the junction temperature by a feedback loop. Experimental results show that the sample using sintered nano-silver for die-attach has 12.1% lower thermal impedance than the samples using SAC305 and SN100C solders. To check the degradation of the die-attachment, three samples using three die-attach materials were thermally cycled from -400C to 1250C. The experimental results show that after 500 cycles, the thermal impedance of SAC305 samples and SN100C samples is increased by 12.8% and 15% respectively, which is much higher than the sample using nano-silver paste for die-attach (increased by 4.1%).
02 Jun 2010
TL;DR: In this paper, the authors numerically and experimentally characterize the performance of a three-tier chip stack with a footprint of 1cm2 and show that the implementation of 100µm pitch area array interconnect compatible heat transfer structures results in a maximal junction temperature increase of 54.7K at 1bar pressure drop with water as coolant for 250W/cm2 hot-spot and 50W/ cm2 background heat flux.
Abstract: Interlayer cooling is the only heat removal concept which scales with the number of active tiers in a vertically integrated chip stack. In this work, we numerically and experimentally characterize the performance of a three tier chip stack with a footprint of 1cm2. The implementation of 100µm pitch area array interconnect compatible heat transfer structures results in a maximal junction temperature increase of 54.7K at 1bar pressure drop with water as coolant for 250W/cm2 hot-spot and 50W/cm2 background heat flux. The total power removed was 390W which corresponds to a 3.9kW/cm3 volumetric heat flow.
13 Dec 2010
TL;DR: In this paper, a three-phase voltage source inverter is used to increase the life-time of power semiconductor devices based on an online estimation of the junction temperatures, and the switching frequency is modified through the control to decrease thermal cycles.
Abstract: This paper presents a novel control strategy, on the example of a three-phase voltage source inverter, to increase the life-time of power semiconductor devices. Based on an online estimation of the junction temperatures the switching frequency is modified through the control to decrease thermal cycles. In addition the neutral point potential can be shifted using a flat-top method, resulting in an additional reduction of thermal cycles. So using the presented control system in-stead of an ordinary pulse width modulation the lifetime of power semiconductor devices is increased significantly.
TL;DR: In this article, the authors describe fabrication and characterization of a solar simulator which utilizes light emitting diode (LED) as a lighting source, and the detailed thermal performance of the LED lighting was projected using a computational fluid dynamics (CFD) method for the various design parameters such as layout of LED package and number of fins of the heat sink.
TL;DR: A detailed finite element model of LED lighting module, MR-16, with a corresponding input power and suitable boundary conditions is established by using the ANSYS finite element analysis program.
Abstract: Light emitting diode (LED) with a long lifetime, low power consumption, and low pollution has been successfully applied in many products. However, due to its low electro-optical conversion efficiency, high percentage of input power transformed to redundant heat, thus increasing the LED temperature. This phenomenon decreases the luminous flux, changing light color, and useful life span of LED. Therefore, thermal management becomes an important issue in high power LED. In this paper, the variation of luminous flux and light color for different LED lighting modules under long time operation has been measured and discussed. In addition, a detailed finite element model of LED lighting module, MR-16, with a corresponding input power and suitable boundary conditions is established by using the ANSYS finite element analysis program. Furthermore, to validate the simulation results, the current-voltage-temperature method for characterization of a diode is utilized to measure the junction temperature of LED chip indirectly and compare with simulation results. After the simulation is validated, various thermal performance assessments under the different design parameters of the LED package and lighting module are also investigated in this paper. The methodology and analysis results of this paper can provide a guideline for the LED lighting module such as MR-16 design in the future.
TL;DR: An analytical model has been developed and validated by experimental measurements in order to evaluate self-heating effects and to understand high temperature effects and should also allow to highlight the role of some physical parameters in the voltage-temperature dependence and to clarify such thermal calibration.
TL;DR: In this paper, a self-consistent model was developed to describe the internal heating of high power light emitting diodes (LEDs) and use this model to simulate the operation of GaAs-AlGaAs double heterostructure LEDs.
Abstract: We develop a self-consistent model to describe the internal heating of high power light emitting diodes (LEDs) and use this model to simulate the operation of GaAs–AlGaAs double heterostructure LEDs. We account for the heating by nonradiative recombination processes in the simulations and solve self-consistently the steady state junction temperature. Based on the simulation results, we discuss the plausibility of unity conversion efficiency in LEDs and also the mechanisms underlying the efficiency droop. We show that the rise in the junction temperature limits the light output available from LEDs and further degrades the efficiency of operation at high operating currents. In addition to high power applications we study the optimal operating point and discuss the methods to increase the efficiency of LEDs toward the thermodynamical limits.
01 Nov 2010
TL;DR: In this article, an active gate control method was proposed to achieve current balancing of the IGBTs in parallel with thermal imbalance, which can be applied to an actual 160kW/380V power electronics converter prototype for improving the utilization of the switching devices and enhancing system reliability.
Abstract: For large current, switching devices such as MOSFET and IGBT, often have to be connected in parallel. Due to this reason, derating and preselection of the switching devices become necessary to develop high-power converters. The current imbalance can be produced by stray inductances, device characteristic difference or asymmetric circuit. Moreover, thermal imbalance is anther important reason for current balancing. The static and transient characteristics of an IGBT vary sensitively with its junction temperature. This paper focuses on the current sharing of IGBTs in parallel with thermal imbalance. In this paper, an active gate control method which can achieve current balancing of the IGBTs in parallel with thermal imbalance, is explained and verified by experiments. This method can be applied to an actual 160kW/380V power electronics converter prototype for improving the utilization of the switching devices and enhancing system reliability.
TL;DR: In this paper, a hierarchical model is proposed to assess the lifetime of an actively cooled LED-based luminaire that can provide light output equivalent to a 100 W incandescent lamp.
Abstract: The lifetime of an actively-cooled light emitting diode (LED)-based luminaire is dependent not only on the junction temperature of LEDs, but also on the reliability of active cooling devices. We propose a novel hierarchical model to assess the lifetime of an actively cooled LED-based luminaire that can provide light output equivalent to a 100 W incandescent lamp. After design considerations for LED-based luminaires with active cooling are discussed, the proposed model is described using component-level sub-physics-of-failure models. The model is implemented to predict the lifetime of a LED-based recessed downlight with synthetic jet cooling. The effects of the time-dependent performance degradation mechanisms of the active cooling device on the lifetime of the luminaire are also discussed.
21 Jun 2010
TL;DR: In this article, a setup for performing power cycling tests of IGBT modules for the purpose of reliability analysis is presented, where experimental data for the parameterization and verification of a newly developed physical model of solder deformation leading to the failure of power electronic devices is provided.
Abstract: In this paper a setup for performing power cycling tests of IGBT modules for the purpose of reliability analysis is presented. The main purpose of the setup is to provide experimental data for the parameterization and verification of a newly developed physical model of solder deformation leading to the failure of power electronic devices. The design procedure, including considerations of reliability, measurement, and cooling, for a 5 kW flexible power cycling system is presented. Experimental results of a sub-1 kW prototype setup are shown, demonstrating the ability of the system to force the junction temperature of the device under test to follow an arbitrary temperature profile.
23 Sep 2010
TL;DR: In this article, an analytical solution is established to calculate equivalent thermal resistances of the through silicon via (TSV) structure in both z direction and x y directions and is verified by the finite element simulation.
Abstract: Analytical solution is established to calculate equivalent thermal resistances of the through silicon via (TSV) structure in both z direction and x y directions and is verified by the finite element simulation. The effects of the structural parameters such as the thickness of die, the diameter of copper via and the pitch of the copper via on the equivalent thermal conductivity of composite TSV structure have been investigated. It is found that the thermal conductivity in z direction increases with the diameter of copper via and decrease with pitch of TSV and keep constant with the thickness. While the thermal conductivity of in x y directions increases with the pitch of TSV and decreases with the thickness of the TSV and copper diameter. The SiO 2 layer with thermal conductivity of only about 1.57 W/mK plays an important role in determining the equivalent thermal conductivity of TSV composite structure. A thermal resistance network model for the stacked-die package is built up to estimate the junction temperature. FEM simulation is conducted to investigate the thermal performance of the stacked-die package simplified with equivalent thermal conductivity. With equivalent thermal properties and thermal resistance network model the thermal performance of the stacked-die package can be estimated quickly and to obtain the optimization package structure of the high thermal dissipation.
TL;DR: In this article, an approach for directly determining the dependence of junction temperature on injected currents in InGaN and AlGaInP LEDs is proposed. But the junction temperature of a light-emitting diode (LED) directly affects its performances.
Abstract: The junction temperature of a light-emitting diode (LED) directly and greatly affects its performances. Therefore, the reliable measurement and accurate estimation of the junction temperature of an LED is extremely important. This paper proposes an approach for directly determining the dependence of junction temperature on injected currents in InGaN and AlGaInP LEDs. Various important physical parameters that affect the junction temperature of an LED are also considered.