Junction temperature

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

Observation of chip solder degradation by electrical measurements during power cycling

Abstract: IGBT power modules used in traction applications undergo large load variations. Thermo-mechanically induced stress then leads to material fatigue which limits the module's lifetime. In this paper a method is presented for non-destructively quantifying the chip solder degradation during a power cycling experiment. The method is based on measuring the cooling rate after turn-off. A 20% increase in the chip solder thermal resistance has been measured after 1'800'000 cycles from 73°C to 127°C junction temperature. The solder degradation is also analysed using X-ray inspection and scanning acoustic microscopy. Based on these images and the simulated stress profile in the solder, two failure mechanisms have been identified.

Alternate PCM with air cavities in LED heat sink for transient thermal management

Abstract: Purpose The purpose of this paper is to optimize the configuration of a heat sink with phase change material for improving the cooling performance of light emitting diodes (LED). Design/methodology/approach A numerical three-dimensional time-dependent model is developed with COMSOL Multiphysics to simulate the phase change material melting process during both the charging and discharging period. Findings The model is validated with previously published works. It found a good agreement. The difference between filled cavities with phase change materials (PCM) and alternate cavities air-PCM is discussed. The last-mentioned showed a good ability for reducing the junction temperature during the melting time. Three cases of this configuration having the same total volume of PCM but a different number of cavities are compared. The case of ten fins with five PCM cavities is preferred because it permit a reduction of 21 per cent of the junction temperature with an enhancement ratio of 2:4. The performance of this case under different power input is verified. Originality/value The use of alternate air-PCM cavities of the heat sink. The use of PCM in LED to delay the peak temperature in the case of thermal shock (for example, damage of fan) An amount of energy is stored in the LED and it is evacuated to the ambient of the accommodation by the cycle of charging and discharging established (1,765 Joule stored and released each 13 min with 1 LED chip of 5 W).

Thermal performance of heatsink and thermoelectric cooler packaging designs in LED

Abstract: Active heat dissipation method plays a vital role in thermal management of high power light emitting diode (LED) packaging. As a new cooling device, thermoelectric cooler (TEC) is applied in electronic packaging, for which the extensively applied devices are the heatsink and the fan by now. In order to evaluate the cooling performance of the heatsink and TEC, three different cooling models for light emitting diode (LED) packaging, which include the heatsink model, the heatsink and fan model and the TEC, heatsink and fan model, are established and their thermal performance of packaging are investigated in present study. Junction temperatures of the chip are measured by experimental measurement method, the thermal resistances of TEC, thermal interface material (TIM) and heatsink are analyzed by thermal resistance network method in the situation of different chip power, different TEC input current and different wind speed caused by the fan. The optimal input currents of TEC in different conditions are analyzed. Based on the cooling performance of the different models, the critical chip power is 35 W between the TEC method and the heatsink method at the same time the junction temperature is 40 °C. For optimizing the TEC, it's necessary to reduce the thermal resistance of TEC as same as improve its cooling capacity because the thermal resistance of TEC plays a major role in the total resistance of LED package.

Numerical study on thermal management of LED packaging by using thermoelectric cooling

Abstract: The heat generated from LED (Light-emitting Diode) keeps rising with the rapid development of LED luminous flux and brightness in recent years. So it's urgent to find effective heat dissipation ways for thermal management of LED packaging. The finite element model of LED packaging heat dissipation, based on the thermal resistance model of flip-chip LED packaging and the principle of thermoelectric refrigeration, was founded by ANSYS in this paper. Performance parameters such as LED junction temperature (T 0 ), substrate temperature (T sub ), hot end and cold end temperature of Thermoelectric Cooler (TEC) (T h , T c ), heat sink temperature (T sink ) and coefficient of performance (COP) were investigated systematically in the situation of different chip power and different TEC input current. The optimized parameters of packaging heat dissipation in different conditions were analyzed through comparing simulation results of the thermoelectric cooling method and the natural convection cooling method with and without heat sink.

Thermocouple temperature measurement circuit having cold junction compensation

Abstract: A thermocouple temperature measuring circuit has input terminals connectable to the thermocouple to form the cold junctions of the thermocouple. An input amplifier amplifies the thermocouple signal. A cold junction temperature compensation circuit includes means for sensing the temperature of the cold junctions and for providing an output signal which exhibits a predetermined coefficient between cold junction temperature and output signal magnitude. The output signals of the amplifier and compensation circuit are summed at a summing junction and provided to an output amplifier for supply to a temperature indicating meter. A bias means is also coupled to the summing junction for providing a bias suitable for adjusting the magnitude of the output signal in accordance with the low temperature to be indicated on the meter. The gain of the output amplifier may be adjusted so that the variation in output signal responsive to hot junction temperatures is sufficient to drive the meter through the temperature range displayed on the meter.