LIGHT EMITTING MODULE WITH OPTICALLY-TRANSPARENT THERMALLY-CONDUCTIVE ELEMENT

• US 20110001157A1
• Filed: 01/28/2009
• Published: 01/06/2011
• Est. Priority Date: 01/28/2008
• Status: Active Grant

• Current Assignee: Lumileds Holding B.V. (Apollo Global Management, Inc.)
• Original Assignee: PhotonStar LED Limited (Cizzle Biotechnology Holdings Plc)
• Inventors: McKenzie, James Stuart, Zoorob, Majd
• Granted Patent: US 8,324,647 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• 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 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• 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
• CPC Class Codes: H01L 33/58 Optical field-shaping elements
• CPC Class Codes: H01L 33/641 characterized by the materials
• CPC Class Codes: H01L 33/644 in intimate contact or integrated with parts of the device other than the semiconductor body

Abstract

A light emitting module with improved optical functionality and reduced thermal resistance is described, which comprises a light emitting device (LED), a wavelength converting (WC) element and an inorganic optically-transmissive thermally-conductive (OTTC) element. The WC element is capable of absorbing light generated from the LED at a specific wavelength and re-emitting light having a different wavelength. The re-emitted light and any unabsorbed light exits through at least one surface of the module. The OTTC is in physical contact with the WC element and at least partially located in the optical path of the light. The OTTC comprises one or more layers of inorganic material having a thermal conductivity greater than that of the WC element. As such, a compact unitary integrated module is provided with excellent thermal characteristics, which may be further enhanced when the OTTC provides a thermal barrier for vertical heat propagation through the module but not lateral propagation.

Claims

1. A light emitting module comprising:

a light emitting device having a light generating region for generating light when activated;

a submount comprising a thermally conductive material, the light emitting device being attached to the submount;

a wavelength converting element comprising a layer of material capable of absorbing light having a first wavelength generated by the light emitting device and re-emitting light having a second wavelength, the second wavelength being different to the first wavelength; and

a conductive element which is arranged to be at least partially in physical contact with the wavelength converting element and at least partially located in a light path of the generated light, the conductive element comprising at least one layer of inorganic material which is thermally conductive, having a thermal conductivity greater than that of the wavelength converting element, and which is optically transparent at the first and second wavelengths,

wherein the wavelength converting element and the conductive element have been formed over the light emitting device so as to create a unitary integrated structure.

2. A light emitting module according to claim 1, wherein the conductive element is adapted to be thermally conducting in a plane parallel to the layer of inorganic material and to provide a thermal barrier in a direction perpendicular to the plane

3. A light emitting module according to claim 1, wherein the conductive element comprises at least two stacked layers of different inorganic materials which are optically transparent at the first and second wavelengths.

4. A light emitting module according to claim 3, wherein at least one of the at least two stacked layers of inorganic material has a lower thermal conductivity than one or more of the other layers, thereby forming the thermal barrier in a direction perpendicular to the plane.

5. A light emitting module according to claim 4, wherein the conductive element comprises three stacked layers of inorganic material which are optically transparent at the first and second wavelengths, wherein the middle layer of the three layers has a lower thermal conductivity than the other two layers.

6. A light emitting module according to claim 3, wherein the at least two stacked layers of inorganic material are adapted to provide an optical bandpass filter whereby at least 50% of re-emitted light incident on the conductive element is reflected and at least 50% of generated light incident on the conductive element is transmitted.

7. A light emitting module according to claim 3, wherein the at least two stacked layers of inorganic material are adapted to provide an optical anti-reflection coating for generated light incident on the conductive element.

8. A light emitting module according to claim 3, wherein the at least two stacked layers of inorganic material are adapted to provide an optical colour correction filter for light incident on the conductive element.

9. A light emitting module according to claim 1, wherein at least part of the conductive element is disposed between the light emitting device and the wavelength converting element.

10. A light emitting module according to claim 1, wherein the conductive element comprises a material or combination of materials selected from a group which includes Aluminium Nitride, amorphous Aluminium Nitride, crystalline Aluminium Nitride, Aluminium Oxide, amorphous Aluminium Oxide, Silicon Nitride, Diamond Like Carbon, Fluorinated Diamond Like Carbon, CVD Diamond, Tantalum Pentoxide and Hafnium Oxide.

11. A light emitting module according to claim 1, wherein the conductive element is in-filled with dispersed thermally conductive features.

12. A light emitting module according to claim 1, wherein the conductive element is partially in contact with the submount.

13. A light emitting module according to claim 1, wherein the light emitting module further comprises a first encapsulant disposed at least partially on an upper surface of the light emitting device.

14. A light emitting module according to claim 13, wherein the first encapsulation is in-filled with dispersed thermally conductive features.

15. A light emitting module according to claim 11, wherein the thermally conductive features comprise one or more of dielectric or metal colloids, dielectric or metal nanoshells, nano-columns, nano-rice or arbitrary shaped nanoclusters.

16. A light emitting module according to claim 1, further comprising a second encapsulant disposed at least partially on the wavelength converting element and the inorganic optically transparent thermally conductive element.

17. A light emitting module according to claim 16, wherein a profile of an upper surface of the second encapsulant is selected form the group which includes concave, hemispherical, semi-ellipsoidal, convex, multifaceted polyhedron, pyramidal, conical, frusto-conical, and modulated.

18. A light emitting module according to claim 16, wherein an upper surface of the second encapsulant is patterned.

19. A light emitting module according to claim 18, wherein the upper surface of the second encapsulant is patterned so as to act as one of a grating, a Fresnel lens, and a Diffractive Optical Element (DOE).

20. A light emitting module according to claim 1, further comprising a reflector cup.

21. A light emitting module according to claim 20, wherein the reflector cup comprises a thermally conductive material and the conductive element is partially in contact with the reflector cup.

22. A light emitting module according to claim 1, wherein the wavelength converting element comprises a sheet of wavelength converting material affixed to the light emitting module.

23. A method of manufacturing the light emitting module of claim 1, wherein the at least one layer of inorganic material of the conductive element is deposited using a low temperature deposition techniques selected from a group which includes evaporation, sputtering, plasma assisted deposition, plasma enhanced deposition, Ion Beam assisted deposition, electron beam assisted deposition, Remote Plasma assisted deposition, electron beam evaporation, open and closed field magnetron sputtering.