LED WITH SILICONE LAYER AND LAMINATED REMOTE PHOSPHOR LAYER
A method for fabricating a light emitting device is described where an array of flip-chip light emitting diode (LED) dies are mounted on a submount wafer. Over each of the LED dies is simultaneously molded a hemispherical first silicone layer. A preformed flexible phosphor layer, comprising phosphor powder infused in silicone, is laminated over the first silicone layer to conform to the outer surface of the hemispherical first silicone layer. A silicone lens is then molded over the phosphor layer. By preforming the phosphor layer, the phosphor layer may be made to very tight tolerances and tested. By separating the phosphor layer from the LED die by a molded hemispherical silicone layer, color vs. viewing angle is constant, and the phosphor is not degraded by heat. The flexible phosphor layer may comprise a plurality of different phosphor layers and may comprise a reflector or other layers.
1 . A method for fabricating a light emitting device comprising:
providing a plurality of light emitting diode (LED) dies on a submount wafer;
molding a first silicone layer over each LED die on the wafer;
forming a flexible phosphor layer separately from the wafer;
laminating the phosphor layer over the wafer such that the phosphor layer directly contacts and conforms to an outer surface of the first silicone layer, the phosphor layer wavelength-converting light emitted from the LED dies; and
molding a second silicone layer over the phosphor layer.
2 . The method of claim 1 wherein the second silicone layer comprises a lens.
3 . The method of claim 1 wherein the first silicone layer is substantially hemispherical.
4 . The method of claim 1 wherein the phosphor layer comprises phosphor powder infused in silicone.
5 . The method of claim 1 wherein the first silicone layer has a first index of refraction and the second silicone layer has a second index of refraction higher than the first index of refraction.
6 . The method of claim 1 wherein the phosphor layer has an area approximately the same as or larger than an area of the wafer.
7 . The method of claim 1 wherein the phosphor layer has a substantially uniform thickness.
8 . The method of claim 1 wherein the phosphor layer comprises multiple layers, wherein at least two of the layers contain different phosphors.
9 . The method of claim 1 wherein the phosphor layer comprises multiple layers, wherein at least one of the layers comprises a reflector.
10 . The method of claim 1 wherein the phosphor layer is molded to have optical features.
11 . The method of claim 1 wherein providing a plurality of LED dies on the submount wafer comprises bonding electrodes on the submount wafer to corresponding electrodes of the plurality of LED dies.
12 . The method of claim 1 further comprising singulating the submount wafer to separate LED dies mounted on their respective submount portions, after the step of molding the second silicone layer.
13 . A light emitting device comprising:
a light emitting diode (LED) die mounted on a submount;
a first silicone layer coating the LED die, wherein the first silicone layer has a substantially hemispherical shape over the LED die;
a phosphor layer laminated over the first silicone layer to conform to an outer surface of the first silicone layer, the phosphor layer extending beyond the LED die over the submount, the phosphor layer comprising phosphor powder infused in silicone; and
a second silicone layer molded over the phosphor layer.
14 . The device of claim 13 wherein the phosphor layer comprises a plurality of layers of different phosphors infused in silicone.
15 . The device of claim 13 wherein the phosphor layer has a substantially uniform thickness.