Illumination devices comprising white light emitting diodes and diode arrays and method and apparatus for making them
View Patent ↗In accordance with the invention, an illumination device comprises a substrate having a surface and a cavity in the surface. At least one light emitting diode (“LED”) is mounted within the cavity, and a monolayer comprising phosphor particles overlies the LED. The phosphor monolayer is adhered to the LED by a monolayer of transparent adhesive material. An optional optical thick layer of transparent material overlies the phosphor monolayer to encapsulate the LED and optionally to form a lens. Methods and apparatus for efficiently making the devices are disclosed.
1. An illumination device comprising:
a substrate having a surface and a cavity in the surface;
at least one light emitting diode (LED) mounted within the cavity;
a phosphor monolayer comprising phosphor particles overlying the LED, the phosphor particles for converting the emitted light into white light, the phosphor monolayer adhered to the LED by a monolayer of adhesive material.
2. The illumination device of claim 1 further comprising a thick layer of transparent material encapsulating the LED.
3. The illumination device of claim 1 wherein the substrate comprises a heat sink and the LED is thermally coupled to the heat sink.
4. The illumination device of claim 1 wherein the LED is a blue or ultraviolet LED.
5. The illumination device of claim 1 wherein the phosphor monolayer is a monolayer of phosphor particles.
6. The illumination device of claim 1 wherein the phosphor comprises a YAG:Ce phosphor.
7. A method for making an illumination device comprising one or more white light LEDs comprising the steps of:
providing a workpiece comprising a substrate having a surface including one or more cavities that contain one or more LEDs connected to electrical leads;
forming a coating of tacky adhesive material overlying at least one of the LEDs;
exposing the coating of tacky material to particles comprising phosphor material to form a self-limiting coating of particles overlying the at least one LED; and
curing the tacky adhesive material.
8. The method of claim 7 further comprising the steps of applying an optical material in the cavity to encapsulate the coated LED.
9. The method of claim 7 wherein the substrate comprises a heat sink and the LED is thermally coupled to the heat sink.
10. The method of claim 7 wherein at least one of the LEDs is a blue or ultraviolet LED.
11. The method of claim 7 wherein the coating of tacky adhesive material comprises a monolayer of tacky adhesive material.
12. The method of claim 7 wherein the coating of particles comprises a monolayer of particles.
13. The method of claim 7 wherein the tacky adhesive material is cured by heating.
14. The method of claim 8 wherein the optical material applied to encapsulate the LED is applied by syringe injection or by injection molding.
15. The method of claim 7 further comprising the step of dicing the workpiece into a plurality of white light LED devices.
16. The method of claim 7 further comprising the step of masking portions of the workpiece prior to coating with tacky adhesive.
17. Apparatus for coating phosphor particles on adhesive-coated LED workpieces comprising:
an enclosed particle coating chamber for receiving the workpieces,
a reservoir of phosphor particles to be coated, coupled to the chamber;
a source of pressurized gas coupled to the chamber through a Venturi Nozzle; and
a recycling chamber for receiving and recycling unused particles coupled to the chamber.
18. An illumination device comprising:
a substrate having a cavity;
at least one light emitting diode (LED) mounted within the cavity;
a self-limiting layer comprising phosphor particles adhered to the LED by a layer of adhesive material.
19. The illumination device according to claim 18 further comprising an encapsulant overlying the layer comprising phosphor particles.
20. The illumination device according to claim 18 , wherein the substrate comprises a heat sink and the at least one LED is thermally coupled to the heat sink.
21. The illumination device according to claim 18 , wherein the at least one LED comprises a blue LED.
22. The illumination device according to claim 18 , wherein the at least one LED comprises an ultraviolet LED.
23. The illumination device according to claim 18 , wherein the phosphor particles comprise YAG:Ce.
24. The illumination device according to claim 18 , wherein the adhesive material is silicone.
25. The illumination device according to claim 18 , wherein the adhesive material has an index of refraction between about 1.7 and about 3.0.
26. The illumination device of claim 1 , wherein the adhesive material comprises silicone.
27. The method of claim 7 , wherein the tacky adhesive material comprises partially cured silicone.
28. The method of claim 7 , wherein the tacky adhesive material has an index of refraction between about 1.7 and about 3.0.