《Novel Silicone Materials for LED Packaging》.pdf

Novel Silicone Materials for LED Packaging Ann W. Norris*#, Maneesh Bahadur*, Makoto Yoshitake** * Dow Corning Corporation, P.O. Box 994 Midland, MI 48686 ** Dow Corning Toray, Chiba, Japan ABSTRACT Silicone based materials have attracted considerable attention from Light Emitting Diode (LED) manufacturers for use as encapsulants and lenses for many next generation LED device designs. Silicones can function in several roles that include protective lenses, stress relieving encapsulants, mechanical protection and light path materials. The key attributes of silicones that make them attractive materials for high brightness (HB) LEDs include their high transparency in the UV-visible region, controlled refractive index (RI), stable thermo-mechanical properties, and tuneable hardness from soft gels to hard resins. The high current and high operating temperatures of HB-LEDs present a significant materials challenge for traditional organic materials such as epoxies, acrylics and cyclo olefin copolymers (COC) that lack the thermal and molecular stability needed to provide optical clarity and mechanical performance required for next generation devices. In addition, the retention of optical clarity over the lifetime of the device, which involves long term exposure to high flux in the UV-visible wavelength region, is a critical requirement. Silicones have been demonstrated to provide the required stability. This paper will describe recent silicone materials development efforts directed towards providing LED manufacturers with silicone materials solutions for LED device fabrication. Injection molding of novel silicone resin based materials will be discussed as a surmountable challenge for high throughp