Junction temperature

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

Improvement of Interface Thermal Resistance for Surface-Mounted Ultraviolet Light-Emitting Diodes Using a Graphene Oxide Silicone Composite.

Abstract: In this study, based on silicone composites with graphene oxide (GO) as a filler, a novel packaging strategy was proposed to reduce the interface thermal resistance of surface-mounted ultraviolet light-emitting diodes (UV-LEDs) and provide a potentially effective way for enhancing the long-term stability of devices. The 4 wt % GO-based composite showed an excellent performance in the thermal conductivity, and the interface thermal resistance was reduced by 34% after embedding the 4 wt % GO-based composite into the air gaps of bonding interfaces in the UV-LEDs, leading to a reduction of junction temperature by 1.2 °C under the working current of 1000 mA. Meanwhile, a decrease of thermal stress in bonding interfaces was obtained based on the finite element analysis. What is more, it was found that the lifetime of UV-LEDs with the proposed structure could be obviously improved. It is believed to provide a simple and effective approach for improving the performance of surface-mounted UV-LEDs.

Temperature transients in IMPATT diodes

Abstract: A model for computing the thermal transient response of a diamond-heat-sinked IMPATT diode has been formulated as a means for accurately predicting the degree of heating or cooling of the junction when the diode is pulsed into or out of avalanche. The model consists of an electrical network analog for the heat conduction process, and the transient analysis of this network has been performed using the IBM Advanced Statistical Analysis Program (ASTAP). Also incorporated into the model are the results of previous numerical determinations of steady-state temperature distributions in IMPATT diamond heat sinks. The thermal responses for diode turnon and turnoff and for power surges have been found for several different designs of IMPATT diodes, both Si and GaAs. Turnon transients calculated with this model have been compared with transients calculated by a published method [11] involving a transcendental equation. The two models were roughly in agreement. However, because the previously published method neglects the heat flow path through the chip, it yielded lower values than the network analog model described here for the junction temperature in the first few microseconds after turnon of the diode. The results of these calculations showed that the transient response varied depending on the size of the chip and that significant temperature changes occurred in time intervals ranging from less than 0.1 µs to several microseconds for practical diodes. The results also showed that a description of the transient response in terms of a simple time constant is not meaningful, because the early response does not approximate an exponential curve. To provide a means for making quite accurate desk calculations of diode thermal transients, two approximations have been derived which can be used without computer programs.

Junction temperature considerations in evaluating electronic parts for use outside manufacturers-specified temperature ranges

Abstract: When assessing the suitability of active electronic parts for use over a temperature range outside the manufacturer specified range, some manufacturers use a limiting value of junction temperature to define the maximum allowable thermal stress applied to the die. This process of thermal uprating based on junction temperature includes the following steps: (1) the maximum junction temperature limit is defined (obtained directly from the part data sheet, is calculated from other parameters listed on the part data sheet, or is decided by the equipment manufacturers design practices); (2) a margin is subtracted from the maximum junction temperature limit thus defining the maximum design value; (3) the maximum operating part junction temperature is computed for the given application; (4) the maximum operating part junction temperature is compared with the maximum design value. This approach to junction temperature based thermal uprating is appealing, because it offers the opportunity to avoid expensive and time-consuming part level electrical tests; however, the process may be more complicated than it appears. This paper discusses some of the limitations in the data available on data sheets and some of the uncertainties in the calculations and shows that calculated results do not always agree with experimental results. There is a possibility of error in each of the above steps; the major error may lie in the fact that the device manufacturer has also calculated the junction temperature from an assumed application configuration that may give a gross error in localized dissipation in the actual application. Results of a case study of the Fairchild Octal Tri-state buffer MM74HC244N are reported. Recommendations are then made for applying the junction temperature based thermal uprating process in the future.

Transient electro-thermal analysis for a MOSFET based traction inverter

Abstract: In this paper, an approach to evaluate the instantaneous junction temperature of MOSFET modules used in a high-power three-phase inverter is introduced. A Cauer resistor-capacitor model for the whole system is presented which is based on the MOSFET foster network model. In addition, a thermal impedance matrix of an air-forced cooling heat sink is developed by transient thermal analysis using computational fluid dynamics (CFD). Temperature dependence of power losses has been analyzed and a dynamic electro-thermal simulation considering the thermal coupling effect between different phases under real motor operating conditions is performed. Then, the wide time scale separation of the thermal time constants and transient temperature fluctuation caused by the small heat capacity of the chips are discussed. The thermal performance of the inverter under stall torque condition is also analyzed. The proposed approach is an effective tool for the reliability analysis and thermal management system design in traction inverters.