Method of applying light-converting material and device thereof

• US 20050248271A1
• Filed: 05/07/2004
• Published: 11/10/2005
• Est. Priority Date: 05/07/2004
• Status: Active Grant

• Current Assignee: Document Security Systems, Inc.
• Original Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Tan, Kheng Leng, Ng, Kee Yean, Ou, Wen Ya
• Granted Patent: US 7,315,119 B2
• Time in Patent Office: Days
• US Class Current: 313/512
• CPC Class Codes: C09K 11/02 Use of particular materials as binders, particle coatings or suspension media therefor
• CPC Class Codes: C09K 11/08 containing inorganic luminescent materials
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 33/505 characterised by the shape, e.g. plate or foil

Abstract

A light emitting device having a die that includes a light source that generates light of a first wavelength and a layer of phosphor particles covering the die is disclosed. The phosphor particles convert a portion of the light of the first wavelength to light of a second wavelength. The light source can be fabricated by attaching the light source to a substrate, and converting the light source by applying a light converting layer that includes a volatile carrier material and particles of a phosphor that convert light of the first wavelength to light of the second wavelength over the light source. The volatile carrier material is then caused to evaporate leaving a layer of the phosphor particles over the light source. A binder material can be incorporated in the volatile carrier for binding the phosphor particles to one another after the volatile carrier material is evaporated.

Claims

1. A light emitting device comprising:

a light source that generates light of a first wavelength; and

a layer of phosphor particles covering said light source, said phosphor particles converting at least a portion of said light of said first wavelength to light of a second wavelength, said layer having a thickness of less than 100 μ

m over said light source.

2. The light emitting device of claim 1 wherein said light source comprises an LED.

3. The light emitting device of claim 1 further comprising a layer of clear material covering said layer of phosphor particles.

4. The light emitting device of claim 3 wherein said clear material further comprises a diffusing material for scattering light generated by said light source and said phosphor particles.

5. The light emitting device of claim 4 further comprising a layer of transparent bulk encapsulating material over said layer of clear material.

6. The light emitting device of claim 1 further comprising a reflecting cup, said die being located in said cup such that a portion of said light generated by said light source is reflected from said cup, said layer of phosphor particles covering a portion of said cup.

7. A method for fabricating a light emitting device comprising:

attaching a light source that generates light of a first wavelength to a substrate;

applying a light converting layer comprising a volatile carrier material and particles of a phosphor that convert light of said first wavelength to light of a second wavelength over said die;

causing said volatile carrier material to evaporate thereby leaving a layer of said phosphor particles over said die.

8. The method of claim 7 wherein said light converting layer comprises a binder material for binding said phosphor particles to one another when said volatile carrier material is evaporated.

9. The method of claim 8 wherein said carrier material evaporates at a temperature less than 200°

C.

10. The method of claim 8 wherein said binder material also causes said phosphor particles to bind to said die and a portion of said substrate.

11. The method of claim 7 wherein said layer of said phosphor particles is less than 100 μ

m thick over said light source.

12. The method of claim 7 wherein said carrier material comprises epoxy resins, silicone, polyurethanes, polyvinyl acetates, cyanoacrylate, phatalate, glass, aluminum nitride or silicone dioxide.

13. The method of claim 10 wherein said binder material comprises a polymer comprising acrylic resin, di-butyl phathalate, diacetone alcohol, or tetra ethyl orthosilicate.

14. A light emitting device comprising:

a light source that generates light of a first wavelength; and

a layer of phosphor particles covering said light source, said phosphor particles converting at least a portion of said light of said first wavelength to light of a second wavelength, said layer comprising a residue of a slurry of said phosphor particles in a volatile solvent, said residue comprising the portion of said slurry that remains when a portion of said volatile solvent is removed.

15. The light emitting device of claim 14 wherein said light source comprises an LED.

16. The light emitting device of claim 14 further comprising a layer of clear material covering said layer of phosphor particles.

17. The light emitting device of claim 16 wherein said clear material further comprises a diffusing material for scattering light generated by said light source and said phosphor particles.

18. The light emitting device of claim 17 further comprising a layer of transparent bulk encapsulating material over said layer of clear material.

19. The light emitting device of claim 14 further comprising a reflecting cup, said die being located in said cup such that a portion of said light generated by said light source is reflected from said cup, said layer of phosphor particles covering a portion of said cup.

20. The light emitting device of claim 14 further comprising a layer of clear material between said light source and said layer of phosphor particles.