Illumination devices comprising white light emitting diodes and diode arrays and method and apparatus for making them

• US 7,157,745 B2
• Filed: 04/09/2004
• Issued: 01/02/2007
• Est. Priority Date: 04/09/2004
• Status: Active Grant

• Current Assignee: Lighting Science Group Corporation (Pegasus Capital Advisors, L.P.)
• Original Assignee: Lamina Lighting, Inc.
• Inventors: Blonder, Greg E., Amaya, Edmar M.
• Primary Examiner(s): CRANE, SARA W
• Application Number:
  US10/822,236
• Publication Number:
  US 20050224830A1
• Time in Patent Office: 998 Days
• Field of Search: 257/88, 257/98, 257/100, 438/26, 438/27, 438/29, 427/474, 427/475
• US Class Current: 257/98
• CPC Class Codes: H01L 2224/45124 Aluminium (Al) as principal constituent
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 2224/8592 Applying permanent coating, e.g. protective coating
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 33/507 the elements being in intimate contact with parts other than the semiconductor body or integrated with parts other than the semiconductor body

Abstract

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.

Claims

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.

26. The illumination device of claim 1, wherein the adhesive material comprises silicone.

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.

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.

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.