Method of fabricating a light-emitting device (LED) utilizing powder/pelletized homogeneously mixed molding compound

• US 8,269,409 B2
• Filed: 03/14/2005
• Issued: 09/18/2012
• Est. Priority Date: 07/19/2002
• Status: Active Grant

• Current Assignee: Microsemi Corporation (Microchip Technology Incorporated)
• Original Assignee: Microsemi Corporation (Microchip Technology Incorporated)
• Inventors: Kelly, Stephen G.
• Primary Examiner(s): MAI, ANH D
• Application Number:
  US11/079,323
• Publication Number:
  US 20050158908A1
• Time in Patent Office: 2,745 Days
• Field of Search: 252/301.17, 252/301.33, 313/501, 313/502, 438/29, 438/127, 523/334, 524/346
• US Class Current: 313/501
• CPC Class Codes: C09K 11/7774 Aluminates
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating
• 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: H05B 33/10 Apparatus or processes specially adapted to the manufacture of electroluminescent light sources
• CPC Class Codes: H05B 33/14 characterised by the chemical or physical composition or the arrangement of the electroluminescent material , or by the simultaneous addition of the electroluminescent material in or onto the light source
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

The present invention comprises a process of mixing a luminous substance in powder form to a transferable grade molding compound in a pelletized or powder form, such as a clear epoxy, to derive a homogeneous mixture that can be pressed and sintered into solid pellets. The solid pellets are further processed so as to permit their deposition on and around a light emitting semiconductor driver so as to obtain a white light emitting semiconductor device. This white light emitting device can be used in a variety of lighting applications.

Claims

1. A method of fabricating a light emitting chip comprising:

pressing and sintering a homogeneous mixture of epoxy and a luminous substance into solid pellets; and

processing the solid pellets for application on a semiconductor surface.

2. The method of claim 1, further comprising depositing the homogeneous mixture of epoxy and the luminous substance around an LED chip located on a copper lead frame.

3. The method of claim 2, further comprising the LED chip having a semiconductor junction operable to emit light when biased;

and

the homogenous mixture of epoxy and the luminous substance adapted to filter and combine predetermined wavelengths of light from the semiconductor junction.

4. The method of claim 3, further comprising the luminous substance being in powder form of less than or equal to 5 microns in size prior to sintering and pelletization.

5. The method of claim 3, further comprising incorporating a thixotorpic agent to thicken the epoxy.

6. The method of claim 3, wherein the luminous substance further comprises a Cerium doped garnet.

7. The method of claim 3, wherein the luminous substance further comprises YAG:

Ce.

8. The method of claim 3, wherein the luminous substance includes a predetermined amount of mineral diffuser so as to optimize a luminous pattern.

9. The method of claim 7, wherein the mineral diffuser comprises CaF2.

10. The method of claim 3, further comprising predetermining a chromaticity of emitted light based on the luminous substance'"'"'s percentage by weight of the homogeneous mixture and micron size, before pelletizing.

11. The method of claim 1 wherein the solid pellets are cooled after sintering in a manner reducing UV bleed through at an elevated drive current than without said cooling.

12. A method of fabricating a light emitting device, comprising:

admixing a luminous substance with a transferable grade molding compound to derive a homogeneous mixture;

pressing and sintering the homogeneous mixture into solid pellets; and

depositing the processed solid pellets on a semiconductor surface.

13. A method of fabricating a light emitting device, comprising:

admixing a luminous substance with a transferable grade molding compound to derive a homogeneous mixture;

pressing and sintering the homogeneous mixture into solid pellets;

storing the solid pellets in a freezer;

removing the solid pellets from the freezer;

raising a temperature of the solid pellets to room temperature;

processing the solid pellets for application on a semiconductor surface; and

depositing the processed solid pellets on a semiconductor surface.

14. The method of fabricating a light emitting device of claim 13 wherein the molding compound is in a pelletized form prior to pressing and sintering the homogeneous mixture into solid pellets.

15. The method of fabricating a light emitting device of claim 14 wherein the pelletized molding compound further comprises a clear epoxy.

16. The method of fabricating a light emitting device of claim 13 wherein the molding compound is in a powdered form prior to pressing and sintering the homogeneous mixture into solid pellets.

17. The method of fabricating a light emitting device of claim 16 wherein the powdered molding compound further comprises a clear epoxy.

18. The method of fabricating a light emitting device of claim 13 wherein the luminous substance is in powdered form prior to pressing and sintering the homogeneous mixture into solid pellets.

19. The method of claim 13 wherein raising a temperature of the solid pellets to room temperature comprises storing the solid pellets in a gas until they reach about room temperature.

20. The method of claim 19 wherein the gas is Nitrogen.