Study on mechanical behavior and interfacial strength of YAG phosphor-filled silicone

Among several materials used in LED packaging, phosphor-filled silicone plays an important role on optical performance and long-time reliability of the module. Many researchers have studied optical properties of phosphor, but few have considered mechanical behavior of phosphor-filled silicone. In this paper, mechanical properties of YAG phosphor-filled silicone are obtained. Tensile tests, which are conducted by universal testing machine, are adopted to investigate mechanical behaviors of materials. The results of tests indicate that elevated temperature has negative effects on the mechanical properties of both pure silicone and phosphor-filled silicone. At the temperature of 125°C, the ultimate tensile strength of the material is only about half that of the material at 25°C. Further studies demonstrate that phosphor addition can strengthen phosphor-filled silicone material. Elastic modulus, ultimate tensile strength and elongation of the material increase with the increased phosphor mass fraction. Nevertheless, interfacial tests of phosphor-filled silicone on the GaN substrate show that higher phosphor addition will result in lower interfacial strength of the material. The interfacial strength of silicone on GaN substrate reduces sharply as phosphor added into silicone.