Thermal property is one of the most important properties of light-emitting diode (LED).Thermal property of LED packaging material determines the heat dissipations of the phosphor and the chip surface,accordingly having an influence on the light-emitting efficiency and the life-span of the device.In this paper,photoacoustic piezoelectric (PAPE) technique has been employed to investigate the thermal properties of polyvinyl alcohol (PVA) and silicon dioxide,which are the new and the traditional packaging materials in white LED,respectively.Firstly,the theory of PAPE technique has been developed for two-layer model in order to investigate soft materials;secondly,the experimental system has been set up and adjusted by measuring the reference sample;thirdly,the thermal diffusivities of PVA and silicon dioxide are measured and analysed.The experimental results show that PVA has a higher thermal diffusivity than silicon dioxide and is a better packaging material in the sense of thermal diffusivity for white LED.
