Systems and methods for application of optical materials to optical elements

• US 8,940,561 B2
• Filed: 03/03/2010
• Issued: 01/27/2015
• Est. Priority Date: 01/15/2008
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Donofrio, Matthew, Cannon, Nathaniel O.
• Primary Examiner(s): TRAN, MINH LOAN
• Application Number:
  US12/717,048
• Publication Number:
  US 20100155763A1
• Time in Patent Office: 1,791 Days
• Field of Search: 438/48, 438/65, 438/69, 438/26, 438/27, 438/29, 257/98, 257/100, 257/E33.061, 257/E33.067
• US Class Current: 438/26
• CPC Class Codes: B05B 7/066 with an inner liquid outlet surrounded by at least one annular gas outlet
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/8592 Applying permanent coating, e.g. protective coating
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 33/50 Wavelength conversion elements

Abstract

Methods are disclosed including heating an optical element. An optical material is applied to the heated optical element to provide a conformal layer that is cured via the thermal energy in the heated optical element.

Claims

1. A method, comprising:

heating an optical element that includes at least one non-planar surface; and

after heating the optical element, applying an optical material to at least one non-planar surface on the heated optical element,

wherein heating the optical element comprises heating a plurality of LED chips arranged on a common surface.

2. The method of claim 1, further comprising curing the optical material upon application to the optical element.

3. The method of claim 2, wherein the optical material comprises a luminescent material.

4. The method of claim 3, wherein the optical material further comprises a binder and wherein curing the optical material further comprises curing the binder.

5. The method of claim 3 wherein the optical material further comprises a binder and a solvent and wherein curing the optical material comprises curing the binder and evaporating the solvent.

6. The method of claim 1, wherein the optical element comprises a LED structure.

7. The method of claim 1, wherein applying the optical material comprises:

atomizing a luminescent solution comprising an optical material suspended in a solution using a flow of pressurized gas; and

spraying the atomized luminescent solution onto the heated optical element using the flow of pressurized gas.

8. The method of claim 7, wherein spraying the luminescent solution comprises spraying the luminescent solution with an air pressurized spray system.

9. The method of claim 7, wherein the luminescent solution comprises wavelength conversion particles suspended in a solution including a volatile solvent and a binder material, the method further comprising evaporating the volatile solvent via thermal energy in the heated LED structure from the luminescent solution to provide a conformal layer including wavelength conversion particles on the LED structure.

10. The method of claim 7, wherein the luminescent solution comprises wavelength conversion particles suspended in a solution including a nonvolatile solvent and a binder material, the method further comprising curing the nonvolatile solvent and/or binder via thermal energy in the heated LED structure to provide a conformal layer including the wavelength conversion particles on the LED structure.

11. The method of claim 1, wherein the optical element comprises an LED chip having a top surface and a wirebond pad on the top surface, the method further comprising bonding a wire to the wirebond pad before heating the LED chip and before applying the optical material on the heated optical element.

12. The method of claim 1, wherein the optical element comprises a LED structure, further comprising:

energizing the LED structure to cause the LED structure to emit light;

testing the optical characteristics of the LED structure using the emitted light; and

in response to the optical characteristics of the LED structure not being within a predetermined binning threshold, applying additional optical material comprising wavelength conversion particles suspended in a solution including a volatile solvent and a binder material onto the heated LED structure.

13. The method of claim 1, wherein the optical element comprises an LED chip having a top surface and a wirebond pad on the top surface, the method further comprising mounting the LED within an optical cavity of an LED package before heating the LED chip and applying the optical material comprising wavelength conversion particles suspended in a solution including a solvent and a binder material onto the heated LED chip.

14. The method of claim 13, further comprising:

curing the binder material via thermal energy from the heated LED chip; and

dispensing an encapsulant material into the optical cavity over the LED chip, thereby covering the LED chip including the wavelength conversion materials and the cured binder material with the encapsulant material.

15. The method of claim 1, wherein heating the optical element comprises heating the optical element to a temperature in a range of about 90 degrees Celsius to about 155 degrees Celsius.

16. The method of claim 1, wherein heating the optical element comprises applying heat to the optical element before applying the optical material on the heated optical element.

17. The method of claim 1, wherein heating the optical element comprises applying heat to the optical element while applying the optical material on the heated optical element.

18. The method of claim 1, wherein applying the optical material onto the heated optical element comprises spraying a first layer of an atomized luminescent solution onto a heated LED structure and then spraying a second layer of an atomized luminescent solution onto the first layer of the atomized luminescent solution.

19. The method of claim 18, wherein the first layer of the atomized luminescent solution is cured before spraying the second layer of the atomized luminescent solution.

20. The method of claim 18,

wherein the atomized luminescent solution comprises a first luminescent solution that is sprayed in the first layer and a second luminescent solution that is sprayed in the second layer, and

wherein the first luminescent solution is different from the second luminescent solution.

21. The method of claim 1, wherein applying the optical material comprises:

atomizing a luminescent solution comprising an optical material suspended in a solution using a flow of pressurized gas; and

spraying the atomized luminescent solution onto the heated optical element using the flow of pressurized gas, and

wherein spraying the atomized luminescent solution onto the heated optical element comprises spraying the atomized luminescent solution onto the heated optical element using a plurality of spray heads positioned to spray towards the heated optical element at a plurality of angles relative to a surface of the heated optical element.

22. The method of claim 1, further comprising agitating the optical materials before and/or during applying an optical material.

23. The method according to Claim 1, wherein applying the optical material comprises applying the optical material on the heated plurality of LED chips that are arranged on the common surface.

24. The method according to claim 23, further comprising positioning a lens that includes a cavity that is in a receiving relationship to the plurality of LED chips.

25. The method according to claim 24, further comprising dispensing an encapsulate material within the cavity of the lens.

26. The method according to claim 25, wherein the encapsulant secures the lens to the common surface.

27. The method according to Claim 1, wherein the plurality of LED chips include a first portion of the LED chips that are configured to emit might having a first dominant wavelength and a second portion of the LED chips that are configured to emit light having a second dominant wavelength that is different from the first dominant wavelength.

28. The method according to claim 1, wherein the optical element includes an LED flip-chip having a wire bond free electrical termination.

29. The method according to claim 1, wherein applying the optical material comprises applying first phosphor particles that are configured to emit light having a first dominant wavelength.

30. The method according to claim 29, wherein applying the optical material further comprises applying second phosphor particles that are configured to emit light having a second dominant wavelength that is different from the first dominant wavelength.

31. The method according to claim 30, wherein applying the optical material further comprises applying the first phosphor particles and the second phosphor particles in a same layer.

32. The method of claim 1, wherein the optical element includes at least one beveled surface and the optical material is applied to the at least one beveled surface.

33. A method, comprising:

heating an optical element that includes at least one non-planar surface; and

after heating the optical element, applying an optical material to at least one non-planar surface on the heated optical,

wherein the optical element comprises an LED wafer, the method further comprising singulating the LED wafer into a plurality of LED chips after applying the optical material on the heated LED wafer.

34. A method, comprising:

heating an optical element that includes at least one non-planar surface; and

after heating the optical element, applying an optical material to at least one non-planar surface on the heated optical element, wherein the optical element comprises an LED wafer, the method further comprising

forming a plurality of sacrificial patterns on a surface of the LED wafer, wherein applying the optical material onto the heated LED structure comprises spraying an atomized luminescent solution onto the sacrificial patterns and onto exposed surfaces of the LED wafer between the sacrificial patterns.

35. The method of claim 34, further comprising:

before forming the plurality of sacrificial patterns, forming a plurality of electrical contacts on the surface of the LED wafer,

wherein forming the plurality of sacrificial patterns comprises forming at least a portion of the plurality of sacrificial patterns on the plurality of electrical contacts.

36. The method of claim 34, further comprising removing the sacrificial patterns and the portion of the applied optical material on the sacrificial patterns to expose the plurality of electrical contacts.

37. A method of forming a device for interacting with emitted light, the method comprising:

heating an optical element;

applying a first conformal layer of optical material to the heated optical element;

testing a light emission characteristic of the optical element; and

in response to the light emission characteristic of the optical element not being acceptable, applying a second conformal layer of optical material on the optical element.

38. The method of claim 37, wherein applying the first conformal layer comprises:

atomizing a luminescent solution comprising an optical material suspended in a solution using a flow of pressurized gas;

spraying the atomized luminescent solution onto the heated optical element using the flow of pressurized gas to provide a first conformal layer of optical material that is cured via thermal energy of the heated optical element.

39. The method of claim 38, wherein the optical element comprises an LED structure, further comprising:

before testing the light emission characteristic, allowing the heated LED structure to cool; and

in response to the light emission characteristic of the LED structure not being acceptable, heating the LED structure before applying the second conformal layer.

40. The method of claim 38, wherein the first conformal layer of optical material comprises a first phosphor particle that is configured to emit light having a first wavelength in response to light emitted by the LED structure, and wherein the second conformal layer of optical material comprises a second phosphor particle that is configured to emit light having a second wavelength that is different from the first wavelength, in response to light emitted by the LED structure.

41. A method, comprising:

curing an optical material on a light transmissive optical element during application of the optical material to the light transmissive optical element,

wherein curing the optical material comprises heating the light transmissive optical element before application of the optical material to the light transmissive optical element.

42. The method of claim 41, wherein the light transmissive optical element is spaced apart from a light emitting element.

43. The method of claim 42, wherein the light transmissive optical element includes a substantially transparent carrier on which the optical material is applied.

44. The method according to claim 41, wherein the light transmissive optical element includes a reflective element that is configured to receive light from the light emitting element.