Engineered-phosphor LED packages and related methods

• US 8,933,478 B2
• Filed: 01/28/2014
• Issued: 01/13/2015
• Est. Priority Date: 02/19/2013
• Status: Active Grant

• Current Assignee: Epistar Corporation
• Original Assignee: Cooledge Lighting Inc.
• Inventors: Tischler, Michael A., Ashdown, Ian, Pinnington, Tom, Ip, Henry
• Primary Examiner(s): Fan, Michele
• Application Number:
  US14/166,329
• Publication Number:
  US 20140231850A1
• Time in Patent Office: 350 Days
• Field of Search: 257/98, 257/100, 257/E33.059, 257/E33.06, 257/E33.061
• US Class Current: 257/98
• CPC Class Codes: H01L 2224/13 of an individual bump connector
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 24/97 the devices being connected to a common substrate, e.g. interposer, said common substrate being separable into individual assemblies after connecting
• 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 2924/00014 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 2924/01322 Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/07802 not being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/07811 Extrinsic, i.e. with electrical conductive fillers
• CPC Class Codes: H01L 2924/12035 Zener diode
• CPC Class Codes: H01L 2924/12041 LED
• CPC Class Codes: H01L 2924/12042 LASER
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 2933/0025 relating to coatings
• CPC Class Codes: H01L 2933/0033 relating to semiconductor body packages
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 2933/005 relating to encapsulations
• CPC Class Codes: H01L 2933/0066 relating to arrangements for conducting electric current to or from the semiconductor body
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/486 adapted for surface mounting
• CPC Class Codes: H01L 33/501 characterised by the materials, e.g. binder
• CPC Class Codes: H01L 33/502 : Wavelength conversion materials
• CPC Class Codes: H01L 33/504 : Elements with two or more wavelength conversion materials
• CPC Class Codes: H01L 33/505 : characterised by the shape, e.g. plate or foil
• CPC Class Codes: H01L 33/508 : having a non-uniform spatial arrangement or non-uniform concentration, e.g. patterned wavelength conversion layer, wavelength conversion layer with a concentration gradient of the wavelength conversion material
• CPC Class Codes: H01L 33/54 : having a particular shape
• CPC Class Codes: H01L 33/62 : Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

Abstract

In accordance with certain embodiments, regions of spatially varying wavelength-conversion particle concentration are formed over light-emitting dies.

Claims

1. 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 face being configured for emission of light therefrom, and (ii) a sidewall spanning the top and bottom faces;

a binder having top and bottom surfaces, at least one of which is substantially parallel to the top face of the die, wherein at least a portion of the binder is disposed over the top face of the light-emitting die; and

disposed within the binder, 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, wherein (i) converted light and unconverted light emitted by the light-emitting die combine to form substantially white light, (ii) a divergence of color temperature of the substantially white light emitted from the light-emitting device varies, over an angular range of 0°

to 70°

, no more than 0.01 in terms of a Δ

u′

v′

deviation from a spatially weighted averaged chromaticity, and (iii) u′ and

v′

are chromaticity coordinates on a chromaticity diagram,

wherein (i) the plurality of wavelength-conversion particles comprises 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, (ii) throughout 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, (iii) the 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, (iv) the first type of wavelength-conversion particle has a first density, and (v) the second type of wavelength-conversion particle has a second density different from the first density.

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

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

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

5. The device of claim 1, wherein, throughout the binder, the concentration of the first plurality of wavelength-conversion particles relative to the total concentration of wavelength-conversion particles is within 10% of the concentration of the second plurality of wavelength-conversion particles relative to the total concentration of wavelength-conversion particles.

6. The device of claim 1, wherein each of the first plurality of the wavelength-conversion particles is coated with a coating material.

7. The device of claim 6, wherein the coating material has a density greater than the first density.

8. The device of claim 7, wherein the second density is greater than the first density.

9. The device of claim 6, wherein the coating material has a density less than the first density.

10. The device of claim 9, wherein the second density is less than the first density.

11. The device 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 device 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 device of claim 6, wherein the coating material and the binder comprise the same material.

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

15. The device of claim 1, wherein the 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.

16. The device of claim 1, wherein the 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.

17. The device 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.

18. The device of claim 1, wherein a portion of the binder is substantially free of wavelength-conversion particles.

19. The device of claim 1, wherein the light-emitting die comprises a GaN-based semiconductor material.

20. The device of claim 1, wherein the wavelength-conversion particles comprise phosphor particles.

21. The device 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 0°

to 80°

, no more than 0.01 in terms of Δ

u′

v′

deviation from a spatially weighted averaged chromaticity.

22. The device 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 Δ

u′

v′

deviation from a spatially weighted averaged chromaticity.

23. The device of claim 1, further comprising:

a substrate (i) having at least two conductive traces thereon and (ii) disposed proximate the bottom face of the light-emitting die; and

a contact pad disposed on the light-emitting die and electrically connected to one of the at least two conductive traces on the substrate,

wherein the contact pad is electrically connected to the conductive trace by at least one of (i) a wire bond, (ii) a solder joint, (iii) an anisotropic conductive adhesive, or (iv) a conductive adhesive.

24. The device of claim 23, wherein the substrate comprises a leadframe.

25. The device of claim 23, wherein the substrate comprises a rigid material selected from the group consisting of Si, SiC, AlN, AlON, sapphire, silicon oxide, SiAlON, SiCAlON, and alloys thereof.

26. The device of claim 23, further comprising a package in which at least a portion of the light-emitting die and at least a portion of the substrate are disposed.

27. The device of claim 26, wherein the package comprises at least one of a plastic material or a ceramic material.

28. The device of claim 1, wherein (i) the first type of wavelength-conversion particles emit light of a first color when excited by light from the light-emitting die, and (ii) the second type of wavelength-conversion particles emit light of a second color when excited by light from the light-emitting die, the second color being different from the first color.

29. The device of claim 28, wherein light emitted from the first type of wavelength-conversion particles, the light emitted from the second type of wavelength-conversion particles, and light emitted from the light-emitting die combine to form substantially white light.