Engineered-phosphor LED packages and related methods

• US 8,722,439 B1
• Filed: 12/03/2013
• Issued: 05/13/2014
• Est. Priority Date: 02/19/2013
• Status: Active Grant

• Current Assignee: Epistar Corporation
• Original Assignee: Cooledge Lighting Inc.
• Inventors: Tischler, Michael A., Ashdown, Ian
• Primary Examiner(s): Fan, Michele
• Application Number:
  US14/095,419
• Time in Patent Office: 161 Days
• Field of Search: 438/29, 438/37, 438/22, 438/26, 257/E33.059, 257/E33.061
• US Class Current: 438/29
• 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 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/50 Wavelength conversion elements
• CPC Class Codes: H01L 33/502 Wavelength conversion materials
• 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 33/56 Materials, e.g. epoxy or silicone resin

Abstract

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

Claims

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 face being configured for emission of light therefrom, and (ii) a sidewall spanning the top and bottom faces, the method comprising:

applying a polymeric binder over at least the top face of the light-emitting die, the polymeric binder (i) having top and bottom surfaces, at least one of which is substantially parallel to the top face of the light-emitting die, (ii) comprising a portion extending laterally beyond the sidewall of the light-emitting die, (iii) comprising a portion extending proximate the sidewall of the light-emitting die below a plane defined by the top face of the light-emitting die, and (iii) having, disposed therewithin, 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;

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

at least partially curing the polymeric binder to fix the predetermined concentration gradient of wavelength-conversion particles in the at least a portion of the polymeric binder,

wherein 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 u′ and

v′

are chromaticity coordinates on a chromaticity diagram.

2. The method of claim 1, wherein applying the polymeric binder over the top face of the light-emitting die comprises (i) disposing the polymeric 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 polymeric binder.

3. The method of claim 2, wherein the polymeric binder is at least partially cured while the light-emitting die is disposed in the mold.

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

5. The method of claim 1, wherein the light-emitting die comprises a light-emitting diode die, the light-emitting die comprising a GaN-based semiconductor material.

6. The method of claim 1, wherein the wavelength-conversion particles comprise phosphor particles.

7. 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 0°

to 80°

, no more than 0.01 in terms of the Δ

u′

v′

deviation from a spatially weighted averaged chromaticity.

8. 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 the Δ

u′

v′

deviation from a spatially weighted averaged chromaticity.

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

10. The method of claim 9, wherein the light-emitting die is electrically connected to the substrate before the polymeric binder is applied over at least the top face of the light-emitting die.

11. The method of claim 9, wherein the light-emitting die is electrically connected to the substrate after the polymeric binder is applied over at least the top face of the light-emitting die.

12. The method of claim 9, 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.

13. The method of claim 9, wherein the substrate comprises a leadframe.

14. The method of claim 9, 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.

15. The method of claim 9, further comprising disposing at least a portion of the light-emitting die and at least a portion of the substrate within a package.

16. The method of claim 15, wherein the package comprises at least one of a plastic material or a ceramic material.

17. The method of claim 9, wherein the substrate comprises a flexible material.

18. The method of claim 9, wherein the substrate comprises at least one of polyethylene naphthalate, polyethylene terephthalate, polycarbonate, polyethersulfone, polyester, polyimide, polyethylene, or paper.

19. The method of claim 9, wherein electrically connecting the light-emitting die to the substrate comprises electrically connecting contact pads on the light-emitting die to at least two conductive traces on the substrate, the conductive traces comprising at least one of copper, aluminum, silver, gold, silver ink, or carbon.

20. The method of claim 1, wherein the polymeric binder and the light-emitting die collectively define a substantially rectangular solid shape or a substantially cubic solid shape.

21. The method of claim 1, wherein the predetermined concentration gradient of wavelength-conversion particles varies substantially linearly.

22. The method of claim 1, wherein the predetermined concentration gradient of wavelength-conversion particles varies in a direction substantially perpendicular to the top and bottom faces of the light-emitting die without varying 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.

23. The method of claim 1, wherein the predetermined concentration gradient of 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.

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

25. The method of claim 1, wherein applying the 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 polymeric binder, or (iv) applying acoustic energy to the polymeric binder.

26. The method of claim 1, wherein applying the settling force comprises rotating the light-emitting die around a fixed axis.

27. The method of claim 1, wherein applying the settling force comprises applying acoustic energy to the polymeric binder as a standing wave, wavelength-conversion particles being repelled from peaks in the standing wave and attracted to troughs in the standing wave.

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