Engineered-phosphor LED packages and related methods
View Patent ↗In accordance with certain embodiments, a phosphor element at least partially surrounding a light-emitting die is shaped to influence color-temperature divergence.
1. A light-emitting device comprising:
a light-emitting die having (i) a top face and a bottom face opposite the top face, at least one of the top or bottom face being configured for emission of light therefrom, and (ii) a sidewall spanning the top and bottom faces; and
at least partially surrounding the light-emitting die, a phosphor element comprising (i) a binder and (ii) disposed within the binder, one or more wavelength-conversion materials for absorbing at least a portion of light emitted from the light-emitting die and emitting converted light having a different wavelength, converted light combining with unconverted light emitted from the light-emitting die to form substantially white light, and a divergence of color temperature of the substantially white light emitted from the device varies, over an angular range of 0° to 85°, no more than 0.01 in terms of Δu′v′ deviation from a spatially weighted averaged chromaticity,
wherein the phosphor element has an outer contour having (i) a curved region that defines only a portion of a hemisphere having a hemisphere radius, (ii) a planar region (a) disposed over the light-emitting die, (b) having a non-zero z-offset within the hemisphere, and (c) substantially parallel to the top face of the light-emitting die, a ratio of the z-offset of the planar region within the hemisphere to the hemisphere radius having a value ranging from 0.02 to 0.15, and (iii) a base opposite the planar region having a non-zero centroid z-offset within the hemisphere, a ratio of the centroid z-offset to the hemisphere radius having a value ranging from 0.3 to 0.8.
2. The light-emitting device of claim 1 , wherein the bottom face of the light-emitting die is substantially coplanar with the base of the phosphor element opposite the planar region.
3. The light-emitting device of claim 1 , wherein the ratio of the z-offset of the planar region within the hemisphere to the hemisphere radius is a value ranging from 0.04 to 0.12.
4. The light-emitting device of claim 1 , wherein the outer contour of the phosphor element has a region defined by a cylindrical cutoff within the hemisphere.
5. The light-emitting device of claim 4 , wherein a ratio of a length of the cylindrical cutoff to the hemisphere radius is a value ranging from 0.75 to 0.95.
6. The light-emitting device of claim 5 , wherein the length of the cylindrical cutoff is a value ranging from 50 μm to 500 μm.
7. The light-emitting device of claim 4 , wherein a length of the cylindrical cutoff is a value ranging from about 0.2 mm to about 20 mm.
8. The light-emitting device of claim 1 , wherein the hemisphere radius is a value ranging from about 0.5 mm to about 5 mm.
9. The light-emitting device of claim 1 , wherein (i) light emitted from the light-emitting die has a Lambertian distribution and (ii) the converted light has an isotropic distribution.
10. The light-emitting device of claim 1 , wherein the divergence of color temperature of the substantially white light emitted from the device varies, over an angular range of 0° to 85°, no more than 0.005 in terms of Δu′v′ deviation from a spatially weighted averaged chromaticity.
11. The light-emitting device of claim 1 , wherein the one or more wavelength conversion materials comprise one or more phosphor particles.
12. The light-emitting device of claim 1 , further comprising, disposed beneath at least one of (i) at least a portion of the light-emitting die or (ii) the phosphor element, a mounting surface reflective to at least one of converted light or unconverted light emitted by the light-emitting die.
13. The light-emitting device of claim 12 , wherein the mounting surface has a reflectivity to visible light of approximately 95% to approximately 98%.
14. The light-emitting device of claim 1 , wherein at least a portion of the outer contour of the phosphor element has a surface texture for reducing total internal reflection.
15. The light-emitting device of claim 1 , wherein the light-emitting die is a bare light-emitting diode die.
16. The light-emitting device of claim 1 , wherein the light-emitting die comprises a GaN-based semiconductor material.
17. The light-emitting device of claim 1 , wherein the light-emitting die emits blue or ultraviolet light.
18. The light-emitting device of claim 1 , wherein the hemisphere radius is a value ranging from about 0.2 mm to about 20 mm.
19. The light-emitting device of claim 1 , wherein the ratio of the centroid z-offset to the hemisphere radius has a value ranging from 0.5 to 0.77.
20. The light-emitting device of claim 1 , wherein the ratio of the centroid z-offset to the hemisphere radius has a value ranging from 0.3 to 0.5.
21. The light-emitting device of claim 1 , wherein the planar region has a radius having a value ranging from 50 μm to 1000 μm.
22. The light-emitting device of claim 1 , wherein the ratio of the z-offset of the planar region within the hemisphere to the hemisphere radius is approximately defined by −1.9×F+0.67, where F is a ratio of the z-offset value of the planar region within the hemisphere to the hemisphere radius.
23. The light-emitting device of claim 1 , wherein the z-offset of the planar region within the hemisphere is approximately defined by 1.41×R−0.8, where R is the hemisphere radius.
24. The light-emitting device of claim 1 , wherein (i) the phosphor element has a base radius having a value ranging from 0.6 mm and 1.0 mm, (ii) the planar region has a radius having a value ranging from about 0.15 mm to about 0.45 mm, and (iii) a height from a base of the phosphor element to the planar region is a value ranging from about 0.15 mm to about 0.5 mm.
25. The light-emitting device of claim 1 , further comprising at least one additional light-emitting die at least partially surrounded by the phosphor element.
26. The light-emitting device of claim 1 , further comprising:
a second light-emitting die having (i) a top face and a bottom face opposite the top face, at least one of the top or bottom face being configured for emission of light therefrom, and (ii) a sidewall spanning the top and bottom faces; and
at least partially surrounding the second light-emitting die, a second phosphor element comprising (i) a binder and (ii) disposed within the binder, one or more wavelength-conversion materials for absorbing at least a portion of light emitted from the second light-emitting die and emitting converted light having a different wavelength, converted light combining with unconverted light emitted from the second light-emitting die to form substantially white light,
wherein the second phosphor element has an outer contour having (i) a curved region that defines only a portion of a hemisphere having a hemisphere radius, (ii) a planar region (a) disposed over the light-emitting die, (b) having a non-zero z-offset within the hemisphere, and (c) substantially parallel to the top face of the light-emitting die, a ratio of the z-offset of the planar region within the hemisphere to the hemisphere radius having a value ranging from 0.02 to 0.15, and (iii) a base opposite the planar region having a non-zero centroid z-offset within the hemisphere, a ratio of the centroid z-offset to the hemisphere radius having a value ranging from 0.3 to 0.8.
27. The light-emitting device of claim 26 , wherein the phosphor element and the second phosphor element are separated by a web therebetween, the web comprising the binder.
28. The light emitting-device of claim 1 , further comprising a substrate having a plurality of conductive elements disposed thereon, wherein (i) the light-emitting die has at least two contacts on the bottom face, and (ii) each contact on the bottom face is electrically coupled to a different conductive element on the substrate.
29. The light-emitting device of claim 28 , wherein each contact on the bottom face of the light-emitting die is electrically coupled to a different conductive element via at least one of a conductive adhesive, an anisotropic conductive adhesive, a wire bond, or solder.
30. A light-emitting device comprising:
a light-emitting die having (i) a top face and a bottom face opposite the top face, at least one of the top or bottom face being configured for emission of light therefrom, and (ii) a sidewall spanning the top and bottom faces; and
at least partially surrounding the light-emitting die, a phosphor element comprising (i) a binder and (ii) disposed within the binder, one or more wavelength-conversion materials 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,
wherein the phosphor element comprises (i) a first region having a sidewall substantially parallel to the sidewall of the light-emitting die and (ii) disposed over the first region, a second region having a top surface defining a portion of an oblate ellipsoid described by the equation
z
(
r
)
=
r
2
R
(
1
+
1
-
(
1
+
K
)
(
r
2
/
R
2
)
)
,
where z is a height of the second region above a top surface of the light-emitting die, r is a radius of the oblate ellipsoid, R is approximately 2.38, and K is approximately 6.0.