Liquid encapsulation for monochromatic LED emitter packages: Enhancement of thermal-optical performance and reliability

A special liquid encapsulant and the liquid encapsulation process are developed for enhancing passive cooling for the packaging of monochromatic LED emitters. It was observed that the liquid encapsulation process is superior than the conventional solid silicone encapsulation process in terms of the junction temperature for all the packaged emitters of various wavelengths using the liquid encapsulant. An enhanced reliability in terms of lifetime is thus expected for the emitters encapsulated with the liquid encapsulant. Moreover, an enhanced light output is also demonstrated for the emitters packaged with the liquid encapsulant, which can be attributed to be a result of the improved heat dissipation by convection and conduction in the upward direction through the liquid as well as in the downward direction through the contact area between the liquid and the reflective cup.