Glueless light emitting device with phosphor converter
A multi-stage lamination process is used to laminate a wavelength conversion film to a transparent substrate, and subsequently to a light emitting element. The wavelength conversion film may be an uncured phosphor-embedded silicone polymer, and the lamination process includes heating the polymer so that it adheres to the transparent substrate, but is not fully cured. The phosphor-laminated transparent substrate is sliced/diced and the wavelength conversion film of each diced substrate is placed upon each light emitting element. The semi-cured wavelength conversion film is then laminated to the light emitting element via heating, consequently curing the phosphor film. Throughout the process, no glue is used, and the optical losses associated with glue material are not introduced.
1. A method of producing a light emitting device, comprising:
providing a plurality of light emitting elements on a support substrate;
forming a wafer by laminating a wavelength conversion film to a transparent substrate that is glass or sapphire at a first temperature that semi-cures the wavelength conversion film and adheres the wavelength conversion film to the transparent substrate;
slicing the wafer into a plurality of platelets each comprising a portion of the wavelength conversion film which has been semi-cured;
placing each of the plurality of platelets on a respective light-emitting element of the plurality of light emitting elements, so that the portion of the wavelength conversion film of each of the plurality of platelets is in direct contact with the respective light-emitting element; and
laminating each of the plurality of platelets to the respective light-emitting element at a second temperature that adheres the portion of the wavelength conversion film directly to the respective light-emitting element and fully cures the wavelength conversion film to form the light emitting device including a light emitting surface of the transparent substrate.
2. The method of claim 1 , further comprising:
applying a reflective mold material to completely cover each of the plurality of light emitting elements with laminated wavelength conversion layers on the support substrate; and
finishing the reflective mold material to expose a surface of the transparent substrate.
3. The method of claim 1 , wherein the first temperature is 70° C. to 100° C. for a polymer having a curing temperature of 140° C. to 160° C.
4. The method of claim 3 , wherein the second temperature is 120° C. to 150° C.
5. The method of claim 3 , further comprising forming the wavelength conversion film prior to laminating the wavelength conversion film to the transparent substrate.
6. The method of claim 1 , further comprising
binning each of a plurality of light emitting elements into bins having different wavelength ranges of light emitted by each of the plurality of light emitting elements;
testing the wavelength conversion characteristic of the wavelength conversion film; and
matching the wavelength conversion film to one of the bins of the plurality of light emitting elements based on a desired composite color output of at least some of the plurality of light emitting elements and the wavelength conversion film.
7. The method of claim 2 , further comprising
after finishing the reflective mold material, dicing the reflective mold material and the support substrate to form individual light emitting devices each comprising the respective one light emitting element.
8. The method of claim 2 , wherein the finishing comprises microbead blasting.
9. The method of claim 2 , wherein the finishing roughens the surface of the transparent substrate, reducing total internal reflections (TIR) at the surface.
10. The method of claim 1 , wherein the wavelength conversion film includes one or more phosphors embedded in a polymer material.
11. The method of claim 10 , wherein the polymer material is a silicone polymer.
12. The method of claim 1 , wherein the transparent substrate includes a non-planar surface opposite a surface that is in direct contact with the wavelength conversion film.
13. The method of claim 1 , further comprising disposing a reflective material to surround each of the plurality of platelets and the respective light emitting element.
14. The method of claim 13 , wherein the reflective material is a mixture of silicone and TiO 2 , with a concentration of at least 20% TiO 2 .
15. The method of claim 1 , wherein the transparent substrate is between 50 and 200 microns thick, and the wavelength conversion film is between 50 and 150 microns thick.