the cavity walls coated with the reflective coating in certain embodiments the reflective coating is further coated with a layer of phosphor preferably the layer of phosphor is thick enough such that almost all the light is back scattered and little of it reaches the mirror surface this results in only a small amount of light emitted from the led reaching the mirror surface fig5 is a simplified diagram illustrates a processing of coating phosphor material fig6 is a simplified diagram illustrating an led device coupled to conductive material through vias coating the phosphor on the side walls has advantages including i the output of the aperture is not blocked by phosphor enabling higher package efficiencies ii the phosphor can be coated on surfaces that can have a heat sink to cool the phosphor and iii phosphor backscattering is used advantageously to increase reflection from the package surfaces the led device is mounted on a thermally conductive but electrically insulating substrate the substrate has electrically conductive patterns formed on the top and bottom surfaces these top and bottom surfaces are connected by electrical vias in one embodiment the substrate is made of a ceramic material such as alumina or alumina nitride for example the vias are fabricated by laser drilling and plating in another embodiment the substrate is made of silicon the surface of the silicon is made electrically insulating by a formation of a thermal oxide of sio2 on top of which the electrically conductive patterns are formed through the silicon material via are used to connect the top and bottom conductive patterns in another embodiment the vias are formed by etching holes alone the.