Junction temperature

About: Junction temperature is a research topic. Over the lifetime, 5058 publications have been published within this topic receiving 58643 citations.

Physics of thermoelectric cooling

Abstract: A new approach is suggested to explain the Peltier effect. It assumes that the Peltier effect is not an isothermal effect. The approach is based on the occurrences of induced thermal fluxes in a structure which consists of two conducting media, through which a dc electric current flows. These induced thermal diffusion fluxes arise to compensate for the change in the thermal flux caused by the electric current (the drift thermal flux) flowing through the junction, in accordance with the general Le Chprinciple. The occurrence of these thermal diffusion fluxes leads to temperature heterogeneity in the structure and, as a result, to a cooling or heating of the junction. Within the framework of this concept, the thermoelectric cooling is analysed. It is shown that in the general case the Peltier effect always occurs together with another thermoelectric effect. This thermoelectric effect is predicted for the first time, and we have called it the barrierless thermoelectric effect. Both these effects essentially depend on the junction surface thermal resistance. The Peltier effect disappears in the limiting case of a very large surface thermal resistance, while the barrierless effect disappears in the limiting case of a very small surface thermal resistance. The dependence of thermoelectric cooling on the geometrical dimensions of the structure is noted, and the corresponding interpretation of this fact is discussed. It is shown that the thermoelectric cooling (heating) is a thermodynamically reversible process in the linear approximation of the electric current applied.

Performance and Reliability Characteristics of 1200 V, 100 A, 200°C Half-Bridge SiC MOSFET-JBS Diode Power Modules

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.

Radiation detector with remote temperature reference

Abstract: A radiation detector employs a thermopile having a potentiometer for calibrating the thermopile output to best suit a particular output meter and sensing application. A thermocouple may be connected in series with the thermopile. The output of the thermopile is calibrated to best match a linear function which intersects the thermopile output function at a temperature in the center of a temperature range of interest. A total output signal of the detector is the sum of the thermopile signal and the thermocouple signal, and is indicative of the temperature of a target emitting radiation sensed by the thermopile. The series connection of the thermopile and the thermocouple allow the thermopile hot junction temperature to be referenced to the cold junction temperature of the thermocouple. Thus, the reference temperature may be remote from the thermopile sensor. A filtering lens may be used to prevent short wavelength radiation from reaching the thermopile sensor, improving the linearity of the thermopile response. To improve the response to low emissivity targets, long wavelength radiation may be filtered out at a loss of linearity. Two detectors may be connected differentially to provide a differential output indicative of the temperature difference between two targets. Additionally, a temperature dependent variable resistor may be coupled to the thermopile, providing a variable resistance that combines with the thermopile output response to produce a linearized thermopile output response. Then, the total output signal of the detector for a particular target temperature is independent of fluctuations in local temperature.

Experimental and Numerical Investigation of a Microjet-Based Cooling System for High Power LEDs

Abstract: The optical extraction efficiency and reliability of light emitting diodes (LEDs) relies heavily on successful thermal management due to their inherit dependence on the low junction temperature of LED chips. In this paper, a microjet-based cooling system is proposed for the thermal management of high power LEDs. Experimental and numerical investigations on such an active cooling system were conducted. Thermocouples were packaged with LED chips to conduct an online measurement of the temperature and evaluate the cooling performance of the proposed system. The experimental results demonstrate that the microjet-based cooling system has good cooling performance. For a 2 × 2 LED chip array, when the input power is 5.6 W and the environmental temperature is 28°C, the temperature of the 2 × 2 LED chip array reaches 72°C within 2 minutes and continues to increase sharply if no active cooling technique is applied. By using the proposed cooling system to cool the LEDs, however, the maximum LED temperature measured ...

Comparison of junction temperature evaluations in a power IGBT module using an IR camera and three thermo-sensitive electrical parameters

Abstract: The measurement of the junction temperature with thermo-sensitive electrical parameters (TSEPs) is largely used by electrical engineers or researchers but the obtained temperature value is generally not verified by any referential information of the actual chip temperature distribution. In this paper, we propose to use infrared (IR) measurements in order to evaluate the relevance of three commonly used TSEP with IGBT chips: the saturation voltage under a low current, the gate-emitter voltage and the saturation current. The IR measurements are presented in details with an estimation of the emissivity of the black paint deposited on the power module. The temperatures obtained with IR measurement and with the different TSEPs are then compared in two cases: the use of only one chip and the use of two paralleled chips.