Junction temperature

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

Determination of junction temperature in AlGaAs/GaAs heterojunction bipolar transistors by electrical measurement

Abstract: A method of measuring the junction temperature and associated thermal resistance of heterojunction bipolar transistors by using the temperature dependence of the DC gain is described. >

Design optimization of an integrated liquid-cooled IGBT power module using CFD technique

Abstract: This paper presents a novel approach to optimize pin array design of an integrated, liquid-cooled, insulated gate bipolar transistor (IGBT) power module. With the aid of a computational fluid dynamics (CFD) code, the fluid field and heat transfer inside the module were analyzed, and several design options on pin arrays were examined. For IGBT die circuitry, the uniformity of temperature distribution among dies is as critical as the magnitude of the die temperature. A noticeable variation in temperature among dies can accelerate the thermal runaway and reduce the reliability of the devices. With geometrically-optimized-pin designs located both upstream and downstream of the channel, a total power dissipation of 1200 W was achieved. The maximum junction temperature was maintained at 100/spl deg/C and the maximum variation among dies was controlled within 1/spl deg/C. The results from this study indicated that the device junction temperatures were not only reduced in magnitude but were equalized as well. In addition, the maximum power dissipation of the module was enhanced. Comparison with other direct- (pool boiling) and indirect- (cold plate) liquid cooling techniques was also discussed.

Thermal Analysis of High Power LED Array Packaging with Microchannel Cooler

Abstract: The efficiency and reliability of solid-state lighting devices strongly depend on successful thermal management. High-brightness light emitting diodes (LEDs), as a strong candidate for the next generation general illumination applications, were developed by improving luminous efficiency and integrating multi-chips within limited areas. One of key problems is cooling in developing high power LED for illumination. This paper explores the thermal analysis of high power LED array packaging with a microchannel cooler, which is a relatively new cooling technology. The packaging structure of a high power LED array integrated with a microchannel cooler is discussed. Detailed thermal performance is analyzed using the FEA (finite element analysis) technology. The effects are discussed on the cooling of a multi-chip LED module with different internal fin geometries of module, flow velocity and its total power. Simulation results, in the form of average die temperature, show that the microchannel cooler reduces the average die temperature, and improves the heat dissipation capability of LED array. However, the results also demonstrates that, without proper design the junction temperature of the module is non-uniform across the LED array, and the downstream or central chips were hotter than the upstream or edge chips. This may accelerate thermal runaway problems and reduce the reliability of the LED arrays device. The cooling scheme is optimized by using staggered fins in our microchannel cooler to increase the heat transfer coefficient of the multi-chip LED packaging module. The result shows that the packaging structure of the microchannel cooler with staggered fins achieves good thermal performance for high power LED arrays

A Temperature Compensation Circuit for Thermal Flow Sensors Operated in Constant-Temperature-Difference Mode

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.

Measurement of junction temperature in GaN-based laser diodes using voltage-temperature characteristics

Abstract: We present a method to determine junction temperature in GaN-based laser diodes (LDs) for simple, fast, and reliable characterization of thermal properties. The large change of forward operation voltage with temperature in GaN laser diodes is advantageously used to measure junction temperature. Using this method, we compare junction temperature of LD structures with different substrates and chip mounting methods. It is found that the junction temperature can be reduced considerably by employing GaN substrates or epi-down bonding. For epi-down bonded LDs, as much as two-fold reduction in junction temperature is achieved compared to epi-up bonded ones and junction temperature rise in this case is only about 13 degrees for more than 100 mW-output power.