Granted Patent B2

US 9,142,738 · App. 14/536,148 · Granted Sep 22, 2015

Abstract

Claims (80)

1. A method of fabricating a light-emitting device comprising a bare light-emitting die having (i) a top face and a bottom face opposite the top face, at least one of the top or bottom faces being configured for emission of light therefrom, and (ii) a sidewall spanning the top and bottom faces, the method comprising:

applying over at least the top face of the light-emitting die (i) a binder and (ii) a plurality of wavelength-conversion particles for absorbing at least a portion of light emitted from the light-emitting die and emitting converted light having a different wavelength, converted light and unconverted light emitted by the light-emitting die combining to form substantially white light, the plurality of wavelength-conversion particles comprising a first plurality of wavelength-conversion particles of a first type and a second plurality of wavelength-conversion particles of a second type different from the first type;

applying a settling force to the wavelength-conversion particles, whereby each of the first and second plurality of wavelength-conversion particles form a predetermined concentration gradient of wavelength-conversion particles in at least a portion of the binder; and

at least partially curing the binder to fix the predetermined concentration gradient of wavelength-conversion particles in the at least a portion of the binder to result in a divergence of color temperature of the substantially white light emitted from the light-emitting device varying, over an angular range of 0° to 70° , no more than 0.01 in terms of a Δu′v′ deviation from a spatially weighted averaged chromaticity, where u′ and v′ are chromaticity coordinates on a chromaticity diagram.

2. The method of claim 1 , wherein a total concentration of the wavelength-conversion particles varies in a direction substantially perpendicular to at least one of the top or bottom faces without varying radially toward or away from the light-emitting die.

3. The method of claim 1 , whereby the wavelength-conversion particles form a spatial distribution in which, throughout the at least a portion of the binder, a concentration of the first plurality of wavelength-conversion particles relative to a total concentration of wavelength-conversion particles is within 20% of a concentration of the second plurality of wavelength-conversion particles relative to the total concentration of wavelength-conversion particles.

4. The method of claim 1 , wherein the divergence of color temperature of the substantially white light emitted from the light-emitting device varies, over an angular range of 10° to 75°, no more than 0.005 in terms of Δu′v′ deviation from a spatially weighted averaged chromaticity.

5. The method of claim 1 , wherein at least a portion of the binder extends laterally beyond the sidewall of the light-emitting die.

6. The method of claim 1 , further comprising coating the first plurality of the wavelength-conversion particles with a coating material.

7. The method of claim 6 , wherein the coating material has a density greater than a density of the first type of wavelength-conversion particle.

8. The method of claim 7 , wherein (i) the first type of wavelength-conversion particle has a first density, and (ii) the second type of wavelength-conversion particle has a second density greater than the first density.

9. The method of claim 6 , wherein the coating material has a density less than a density of the first type of wavelength-conversion particle.

10. The method of claim 9 , wherein (i) the first type of wavelength-conversion particle has a first density, and (ii) the second type of wavelength-conversion particle has a second density less than the first density.

11. The method of claim 6 , wherein an index of refraction of the coating material is substantially equal to an index of refraction of the binder.

12. The method of claim 6 , wherein an index of refraction of the coating material is between (i) an index of refraction of wavelength-conversion particles of at least one of the first or second types, and (ii) an index of refraction of the binder.

13. The method of claim 6 , wherein the coating material and the binder comprise the same material.

14. The method of claim 6 , wherein the coating material and the binder comprise different materials.

15. The method of claim 1 , wherein a total concentration of the wavelength-conversion particles does not vary radially toward or away from the light-emitting die within a plane parallel to at least one of the top or bottom faces of the light-emitting die.

16. The method of claim 1 , wherein (i) the first type of wavelength-conversion particle emits light of a first color when excited by light emitted by the light-emitting die, and (ii) the second type of wavelength-conversion particle emits light of a second color when excited by light emitted by the light-emitting die, the second color being different from the first color.

17. The method of claim 16 , wherein (i) the first color is at least one of yellow or green, and (ii) the second color is red.

18. The method of claim 1 , wherein a total concentration of the wavelength-conversion particles increases in a direction extending from the top face of the light-emitting die to the bottom face of the light-emitting die.

19. The method of claim 1 , wherein a total concentration of the wavelength-conversion particles decreases in a direction extending from the top face of the light-emitting die to the bottom face of the light-emitting die.

20. The method of claim 1 , wherein a portion of the binder extends proximate the sidewall of the light-emitting die below a plane defined by the top face of the light-emitting die.

21. The method of claim 1 , wherein the light-emitting die comprises a light-emitting diode die.

22. The method of claim 1 , further comprising mixing the plurality of wavelength-conversion particles into the binder before the binder is applied over the light-emitting die.

23. The method of claim 1 , wherein at least a portion of the binder is applied over the light-emitting die before the plurality of wavelength-conversion particles is applied over the light-emitting die.

24. The method of claim 1 , wherein at least a portion of the plurality of wavelength-conversion particles is applied over the light-emitting die before the binder is applied over the light-emitting die.

25. The method of claim 1 , wherein the settling force comprises a neutral gravitational force.

26. The method of claim 1 , wherein the settling force comprises a non-neutral-gravity settling force.

27. The method of claim 26 , wherein applying the non-neutral-gravity settling force comprises tilting the die, whereby gravitational force acts along a direction not perpendicular to the top or bottom faces of the light-emitting die.

28. The method of claim 26 , wherein applying the non-neutral-gravity settling force comprises rotating the light-emitting die.

29. The method of claim 26 , wherein applying the non-neutral-gravity settling force comprises applying an electric field across the binder.

30. The method of claim 26 , wherein applying the non-neutral-gravity settling force comprises applying acoustic energy to the binder.

31. The method of claim 30 , wherein the acoustic energy is applied to the binder as a standing wave, wavelength-conversion particles being repelled from peaks in the standing wave and attracted to troughs in the standing wave.

32. The method of claim 1 , wherein the binder is at least partially cured while the settling force is applied.

33. The method of claim 1 , further comprising electrically connecting the light-emitting die to a substrate.

34. The method of claim 33 , wherein the light-emitting die is electrically connected to the substrate before the binder is applied over at least the top face of the light-emitting die.

35. The method of claim 33 , wherein the light-emitting die is electrically connected to the substrate after the binder is applied over at least the top face of the light-emitting die.

36. The method of claim 33 , wherein the light-emitting die is electrically connected to the substrate by at least one of (i) a wire bond, (ii) a solder joint, (iii) an anisotropic conductive adhesive, or (iv) a conductive adhesive.

37. The method of claim 33 , wherein the substrate comprises a flexible material.

38. The method of claim 33 , wherein the substrate comprises at least one of polyethylene naphthalate, polyethylene terephthalate, polycarbonate, polyethersulfone, polyester, polyimide, polyethylene, or paper.

39. The method of claim 33 , wherein electrically connecting the light-emitting die to the substrate comprises electrically connecting each of at least two contact pads on the light-emitting die to a different conductive trace on the substrate, the conductive traces comprising at least one of copper, aluminum, silver, gold, silver ink, or carbon.

40. The method of claim 1 , wherein (i) the first type of wavelength-conversion particle has a first density, and (ii) the second type of wavelength-conversion particle has a second density different from the first density.

41. The method of claim 1 , wherein (i) the first type of wavelength-conversion particle has a first shape, and (ii) the second type of wavelength-conversion particle has a second shape different from the first shape.

42. The method of claim 1 , wherein (i) the first type of wavelength-conversion particle has a first radius, and (ii) the second type of wavelength-conversion particle has a second radius different from the first radius.

43. The method of claim 42 , wherein a ratio of the first radius and the second radius is defined by

R

1

R

2

=

ρ

p

⁢

⁢

2

-

ρ

f

ρ

p

⁢

⁢

1

-

ρ

f

wherein R 1 is the first radius, R 2 is the second radius, ρ p1 is a density of the first type of wavelength-conversion particle, ρ p2 is a density of the second type of wavelength-conversion particle, and ρ f is a pre-cured density of the binder.

44. The method of claim 1 , further comprising disposing the light-emitting die on a substrate before the binder is applied over the light-emitting die.

45. The method of claim 44 , further comprising removing the substrate from the light-emitting die after at least partially curing the binder.

46. The method of claim 1 , wherein a total concentration of the wavelength-conversion particles varies substantially linearly.

47. The method of claim 1 , wherein at least one of a concentration of the first plurality of the wavelength-conversion particles or a concentration of the second plurality of the wavelength-conversion particles varies substantially linearly.

48. The method of claim 1 , wherein a total concentration of the wavelength-conversion particles varies substantially step-wise linearly.

49. The method of claim 1 , wherein at least one of a concentration of the first plurality of the wavelength-conversion particles or a concentration of the second plurality of the wavelength-conversion particles varies substantially step-wise linearly.

50. The method of claim 1 , wherein a portion of the binder is substantially free of wavelength-conversion particles after the settling force is applied.

51. The method of claim 50 , wherein the portion of the binder containing wavelength-conversion particles is between the light-emitting die and the portion of the binder that is substantially free of wavelength-conversion particles.

52. The method of claim 1 , wherein at least partially curing the binder comprises (i) partially curing the binder while a non-neutral-gravity settling force is applied, and, (ii) after the partial cure, performing additional curing of the binder while or after applying a second non-neutral-gravity settling force different from the non-neutral-gravity settling force.

53. The method of claim 52 , wherein applying the second non-neutral-gravity settling force comprises at least one of (i) tilting the light-emitting die whereby gravitational force acts along a direction not perpendicular to the top or bottom faces of the light-emitting die, (ii) rotating the light-emitting die around a fixed axis, (iii) applying an electric field across the binder, or (iv) applying acoustic energy to the binder.

54. The method of claim 1 , wherein applying the binder over the top face of the light-emitting die comprises (i) disposing the binder in a mold, and (ii) disposing the light-emitting die in the mold to at least partially surround the light-emitting die with the binder.

55. The method of claim 54 , wherein the binder is at least partially cured while the light-emitting die is disposed in the mold.

Assignments (6)