LED with high thermal conductivity particles in phosphor conversion layer

In one embodiment, a solid cylindrical tablet is pre-formed for a reflective cup containing an LED die, such as a blue LED die. The tablet comprises uniformly-mixed phosphor particles and transparent/translucent particles of a high TC material, such as quartz, in a hardened silicone binder, where the index of refraction of the high TC material is matched to that of the silicone to minimize internal reflection. Tablets can be made virtually identical in composition and size. The bulk of the tablet will be the high TC material. After the tablet is placed in the cup, the LED module is heated, preferably in a vacuum, to melt the silicone so that the mixture flows around the LED die and fills the voids to encapsulate the LED die. The silicone is then cooled to harden.