Light emitting diode package assembly that emulates the light pattern produced by an incandescent filament bulb

• US 20050189557A1
• Filed: 02/26/2004
• Published: 09/01/2005
• Est. Priority Date: 02/26/2004
• Status: Active Grant

• Current Assignee: Lighting Science Group Corporation (Pegasus Capital Advisors, L.P.)
• Original Assignee: Lighting Science Group Corporation (Pegasus Capital Advisors, L.P.)
• Inventors: Li, Lin, Blonder, Greg E., Mazzochette, Joseph, Amaya, Edmar
• Granted Patent: US 7,964,883 B2
• Time in Patent Office: Days
• US Class Current: 257/100
• CPC Class Codes: F21K 9/68 Details of reflectors forming part of the light source
• CPC Class Codes: F21V 29/70 characterised by passive heat-dissipating elements, e.g. heat-sinks
• CPC Class Codes: F21V 29/89 Metals
• CPC Class Codes: F21Y 2107/90 on two opposite sides of supports or substrates
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48465 the other connecting portion not on the bonding area being a wedge bond, i.e. ball-to-wedge, regular stitch
• 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 2924/19107 off-chip wires
• CPC Class Codes: H05K 1/053 the metal substrate being covered by an inorganic insulating layer

Abstract

In accordance with the invention, a light emitting diode package assembly is provided to emulate the pattern of light produced by an incandescent filament bulb. The package assembly is composed of a substrate for LEDs comprising a heat-sinking base having a pair of opposing major surfaces. Each major surface has an overlying of thermally conducting ceramic and an outer surface layer of light reflective material. Disposed on each surface layer is a plurality of LEDs. Advantageously, the LEDs are arranged on the surface in a configuration of low mutual obstruction. Advantageously, reflecting elements transverse to each surface layer are positioned and shaped to reflect a substantial portion of the light emitted from the LEDs that would otherwise enter neighboring LEDs. In a preferred embodiment, the LEDs are arranged in the general form of a closed curve, and a transverse reflector is disposed in the interior of the curve. Alternatively, the LEDs can be arranged in a linear array. The assembly can be efficiently fabricated by back-to-back assembly of two similar subassemblies.

Claims

1. A light emitting diode package assembly for emulating the pattern of light produced by an incandescent filament bulb comprising:

a substrate for LEDs comprising a beat sinking thermally conductive base having at least one pair of opposing major surfaces, each of the major surfaces having an overlying dielectric layer and an outer surface layer of light reflective material; and

disposed on each of the surface layers a plurality of LEDs.

2. A light emitting diode package assembly according to claim 1 wherein the heat sinking base comprises a metallic layer.

3. A light emitting diode package assembly according to claim 1 wherein the heat sinking base comprises a highly conductive ceramic substrate such as alumina, beryllia, siliconcarbide or aluminum nitride.

4. A light emitting diode package assembly according to claim 1 wherein the heat sinking base comprises of a metallic layer that is coefficient of thermal expansion matched to the LED such as copper molybdenum copper clad.

5. A light emitting diode package assembly according to claim 1 wherein the heat sinking base comprises a sintered powder metallic mixture such as tungsten copper.

6. A light emitting diode package assembly according to claim 1 wherein the overlaying dielectric layer comprises of a high glass transition polymer such as polyimide.

7. A light emitting diode package assembly according to claim 1 wherein the overlaying dielectric layer comprises of a non-crystallizing glass or a glass ceramic.

8. A light emitting diode package assembly according to claim 1 wherein the non-conductive ceramic layer is co-fired to the metal base.

9. A light emitting diode package assembly according to claim 1 wherein the heat sinking base comprises a pair of metallic layers adhered together.

10. A light emitting diode package assembly according to claim 1 wherein the outer surface layer comprises a specularly reflective surface layer.

11. A light emitting diode package assembly according to claim 1 wherein the plurality of LEDs on each surface is arranged for low mutual absorbance.

12. A light emitting diode package assembly according to claim 6 wherein plurality of LEDs on at least one surface is arranged in the general form of a closed curve.

13. A light emitting diode package assembly according to claim 1 wherein the surface layer is planar.

14. A light emitting diode package assembly according to claim 6 wherein a plurality of LEDs on at least one surface is arranged in a single linear array.

15. A light emitting diode package assembly according to claim 1 further comprising at least one transverse reflecting element to reflect light from and LED) that would otherwise impinge upon a neighboring LED.

16. A light emitting diode package assembly according to claim 1 wherein the plurality of LEDs are arranged in a closed curve and the reflecting element is disposed in the interior of the closed curve.

18. A light emitting diode package assembly according to claim 12 wherein the plurality of LEDs are arranged in linear array.

19. A light emitting diode package assembly according to claim 12 wherein the plurality of LEDs are arranged in a closed curve.

20. A light emitting diode package assembly according to claim 14 further comprising a reflecting element in the interior of the closed curve, the reflecting element shaped to reflect light emitted from the LEDs at an angle away from the surface.

21. A light emitting diode package assembly according to claim 14 wherein the specular material comprises of a metal thin film.

22. A light emitting diode package assembly according to claim 14 wherein the specular material comprises of a metal thick film.

17. A light emitting diode package assembly for emulating the pattern of light produced by an incandescent filament bulb comprising:

a substrate for LEDs comprising a metal base, an overlying ceramic co-fired to the metal base and a surface layer of reflective metal overlying the ceramic;

a plurality of LEDs disposed on the surface thermally coupled to the metal base through the secularly reflecting metal film and the insulated glass layer, the LEDs arranged on the surface in a configuration to minimize for each LED absorbance of light from other LEDs In the plurality.