A novel thermal conductivity meter for thermal interface materials in optoelectronic device

Nowadays, the light emitting diode (LED) is one of the most valuable light resources. However, it is well known that the optical output power is degraded with the heat integration. Hence, thermal management and evaluation system is required. Thermal conductivity is regarded as one of the most important properties that directly influence the thermal performance for thermal interface materials (TIMs). Different methods have been used to measure the thermal conductivity of TIM. Some testers with satisfied accuracy have also been discussed in papers. However, they are generally of high cost and complex structure design. In this paper, a novel thermal conductivity tester for optoelectronic materials with low cost was designed and built based on one-dimension heat transfer theory and the processing technology. Details of the measurement methodology and the apparatus development were introduced. The tester was designed based on ASTM D5470 which is specified to the thermal conductivity measurement of TIM. According to modular design principle, the apparatus can be divided into five parts, including frame, loading, heating and cooling units and in-situ thickness measurement. In determination of the external loads on the test samples, a force transducer was located in the loading module, which would improve the accuracy and repeatability during the tests. A circulating water cooling system and a flexible heating source were utilized to provide temperature gradient. Moreover, an in situ thickness meter was used for the specimen thickness measurement and monitoring, consequently, the error in thickness estimation could be minimized. On the other hand, by using finite element method, the structures of heating and cooling modules were optimized to achieve uniform temperature distribution and the simulated results matched well with the experiment. Thermistors were used for experimental comparison and characterization. A data acquisition system was developed via Labview software for data fitting and result analysis.