LED with molded reflective sidewall coating
View Patent ↗A submount wafer, having mounted on it an array of LEDs with a phosphor layer, is positioned with respect to a mold having an array of indentions. A mixture of silicone and 10%-50%, by weight, TiO 2 , is dispensed between the wafer and the indentions, creating a molded substantially reflective material. The molded mixture forms a reflective wall covering the sidewalls of the LED. The reflective material is then cured, and the submount wafer is separated from the mold such that the reflective material covering the sidewalls contains light emitted from the LED. The submount wafer is then diced. A piece (e.g., a reflector, support bracket, etc.) may then be affixed to the submount so the LED protrudes through a center hole in the piece. The inner edge of the piece is easily formed so that it is located at any height above or below the top surface of the LED.
1. A light emitting device comprising:
a light emitting diode (LED) having sidewalls and a top surface;
a submount on which the LED is mounted, the submount having side edges and a bottom surface, the bottom surface having metal pads for bonding to a circuit board;
a substantially reflective material provided directly over the sidewalls, the reflective material comprising a substantially transparent material containing inert non-phosphor particles causing reflection, the particles being at least 10% by weight of the reflective material, the particles having a substantially white color under white ambient light,
the reflective material not substantially covering the top surface of the LED, such that the reflective material covering the sidewalls at least partially contains light emitted from the LED; and
a reflector, formed separately from the LED, submount, and reflective material, the reflector having an opening in which the LED is inserted, the reflector having inner edges forming a perimeter around the LED that are positioned above a top surface of the submount but below the top surface of the LED,
wherein the reflector has outer edges that extend beyond the side edges of the submount and has an indent in which the submount is seated, wherein a bottom surface of the reflector does not extend below the bottom surface of the submount, and wherein the reflector has reflective walls that extend above the reflective material.
2. The device of claim 1 wherein the particles comprise one of TiO x , ZrO x , or Al 2 O 3 .
3. The device of claim 1 wherein the particles comprise about 20%-50%, by weight, of the reflective material.
4. The device of claim 1 wherein an average diameter of the particles is less than one micron.
5. The device of claim 1 wherein the substantially transparent material comprises silicone.
6. The device claim 1 wherein the LED comprises a phosphor layer, the reflective material covering sidewalls of the phosphor layer.
7. The device of claim 6 wherein the phosphor layer is a plate affixed to a top surface of a semiconductor portion of the LED.
8. The device of claim 1 wherein the inner edges of the reflector are spaced from outer edges of the reflective material.
9. The device of claim 1 wherein the reflective material extends at least as high as the top surface of the LED.
10. A method of manufacturing a light emitting device comprising:
providing a light emitting diode (LED) mounted on a submount, the LED having sidewalls and a top surface;
positioning the submount with respect to a mold having an indention;
providing a substantially reflective material between the submount and the mold, the reflective material comprising a substantially transparent material containing inert non-phosphor particles causing reflection, the particles being at least 10% by weight of the reflective material,
the particles having a substantially white color under white ambient light, the indention having dimensions larger than an outer dimension of the LED such that the reflective material forms a reflective wall covering the sidewalls of the LED, and such that no significant thickness of reflective material exists between the top surface and the indention;
curing the reflective material;
separating the submount from the mold such that the reflective material covering the sidewalls contains light emitted from the LED, the submount having side edges and a bottom surface, the bottom surface having metal pads for bonding to a circuit board; and
affixing a reflective piece to the submount, the reflective piece having an opening in which the LED is inserted, inner edges of the reflective piece surrounding the reflective material, wherein the reflector has outer edges that extend beyond the side edges of the submount and has an indent in which the submount is seated, wherein a bottom surface of the reflector does not extend below the bottom surface of the submount, and wherein the reflector has reflective walls that extend above the reflective material.
11. The method of claim 10 wherein the particles comprise comprise one of TiO x , ZrO x , or Al 2 O 3 .
12. The method of claim 10 wherein the LED comprises a phosphor layer, the reflective material covering sidewalls of the phosphor layer.
13. The method of claim 10 wherein positioning the submount with respect to the mold comprises positioning a submount wafer, having mounted thereon a plurality of LEDs, with respect to the mold having a plurality of identical indentions corresponding to each LED position on the submount wafer.