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Abstract
Silicone/phosphor composite, which serves as mechanical protection and light conversion material, is an integral part of the white light-emitting diode (LED) package. This study investigates the effect of humidity and phosphor on moisture absorption, hygroscopic swelling, and mechanical behavior, as well as thermal properties of silicone/phosphor composite compared to pure silicone. SEM/EDAX and FTIR were performed to identify phosphor and silicone compositions. A moisture sorption test revealed that the addition of phosphor significantly lowers the capacity of moisture absorption but accelerates the diffusivity of moisture absorption. A hygroscopic swelling test showed that phosphor has little effect on swelling compared to the pure silicone sample. Both moisture absorption/desorption and hygroscopic swelling/de-swelling are reversible. A strain ramp test revealed that phosphor enhances the stiffness of the composite. Moisture absorption, however, has negligible impact on mechanical stiffness for both pure and composite samples. Finally, a thermal expansion test showed that the coefficient of thermal expansion does not change with the addition of phosphor into pure silicone.
