LED接端温度量测系统之开发

T-Junction Measurement Development on LED Lighting Device

摘要: 目前高功率LED的发光效率约是15%~20%，约80%~85%转变成热能，愈高功率的LED产生热能也愈多。因此，在封装设计上，解决散热问题才是根本之道。依据JESD51-1要求，必须维持环境温度，本实验设计一个T.E.C.控制器用来控制与维持致冷芯片保持恒温状态的T. E. Cooler测试平台，让LED发光产生的热量能透过T. E. Cooler测试平台移出，将LED Sample固定并施压，并使用本实验室团队自行开发之热接口材料进行试验。Ta为进行TJ量测时T. E. Cooler测试平台所维持的温度；温度敏感参数(TSP)乃是对LED施加量测电流IM时之顺向电压值变化；K系数是对LED施加量测电流IM时所对应之顺向电压与温度之关系，即为呈线性关系区域内的V–T曲线斜率倒数；透过上述关系，可求取接点温度之温差值∆T，再配合初始温度Ta即可换算出接点温度TJ。

Abstract: Only 15% - 20% of high power LED’s power changes into light, and the rest becomes waste heat. In order to improve the result of development in high power LED, a measurement system is needed to prove it. Based on the requirement of JESD51-1, a constant environmental temperature is necessary. In this project, we designed a T. E. Cooler Test Board with Thermoelectric Cooling Module, which can be controlled in constant temperature by the T.E.C. Controller, letting the generated heat pass through the LED chip (die) to the T. E. Cooler Test Board without any difficulties. We also put a pressure on the LED by using thermal interface material between LED and T. E. Cooler Test Board when we measure the LED sample. TJ0 is the initial temperature before heater power is applied; TSP (Tempe- rature-Sensitive Parameter) is the voltage drop across a forward biased diode, which is the difference between VF0 and VFSS. VF0 is the initial voltage with measurement current, and VFSS is the voltage in measurement current after high power is removed; K factor is a constant parameter in the same LED. We can use the relationship between TSP and K factor to find out the changes in temperature ∆T. Having these three different parameters helps us to calculate the junction temperature.