Light emitting diode package assembly that emulates the light pattern produced by an incandescent filament bulb
View Patent ↗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.
1. A light emitting diode package assembly for emulating the pattern of light produced by an incandescent filament bulb comprising:
a first subassembly and a second subassembly, each subassembly comprising a substrate having a front surface and a back surface, the substrates being disposed in back-to-back adjacency with a thermally conductive adhesive disposed between the back surfaces to form a heat sinking base having the respective front surfaces opposing each other, each of the front surfaces having an overlying dielectric layer disposed thereon, and each of the overlying dielectric layers having a reflective surface layer formed thereon;
a plurality of LEDs disposed directly on each of the reflective surface layers;
wherein edges of each reflective surface layer extend beyond edges of the LEDs disposed thereon; and
a transverse reflecting element disposed on each overlying dielectric layer and configured to reflect a portion of the light emitted by each of the plurality of LEDs, wherein each transverse reflecting element is a cone, a truncated cone, or a barrel formed of two truncated cones.
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 thermally conductive ceramic substrate.
4. A light emitting diode package assembly according to claim 1 wherein the heat sinking base comprises a metallic layer that has a coefficient of thermal expansion matched to the coefficient of thermal expansion of the plurality of LEDs, the metallic layer further comprising two metallic substrates.
5. A light emitting diode package assembly according to claim 4 wherein the metallic substrates include claddings comprising copper/molybdenum/copper.
6. A light emitting diode package assembly according to claim 1 wherein the heat sinking base comprises a sintered powder metallic mixture.
7. A light emitting diode package assembly according to claim 6 wherein the sintered powder metallic mixture comprises tungsten copper.
8. A light emitting diode package assembly according to claim 1 wherein the overlaying dielectric layer comprises a high glass transition polymer.
9. A light emitting diode package assembly according to claim 8 wherein the high glass transition polymer comprises polyimide.
10. A light emitting diode package assembly according to claim 1 wherein each of the overlying dielectric layers is co-fired to the respective front surfaces of the heat sinking base.
11. A light emitting diode package assembly according to claim 1 wherein each reflective surface layer comprises a specularly reflective surface layer.
12. A light emitting diode package assembly according to claim 1 wherein the plurality of LEDs are arranged for low mutual obstruction.
13. A light emitting diode package assembly according to claim 8 wherein the plurality of LEDs on each front surface are arranged in a closed curve.
14. A light emitting diode package assembly according to claim 1 wherein each reflective surface layer is planar.
15. A light emitting diode package assembly according to claim 8 wherein the plurality of LEDs on at least one front surface of the heat sinking base are arranged in a single linear array.
16. A light emitting diode package assembly according to claim 1 further comprising at least one transverse reflecting element to reflect light emitted by at least one of the plurality of LEDs that would otherwise impinge upon one or more neighboring LEDs.
17. A light emitting diode package assembly according to claim 16 wherein the plurality of LEDs are arranged in a closed curve and the transverse reflecting element is disposed in the interior of the closed curve.
18. A light emitting diode (LED) package assembly comprising:
a first subassembly and a second subassembly, each subassembly comprising a substrate having a front surface and a back surface, the substrates being disposed in back-to-back adjacency and adhered to each other with a thermally conductive adhesive disposed between the back surfaces to form a heat sinking base having the respective front surfaces opposing each other, wherein each of the opposing front surfaces has disposed thereon an overlying dielectric layer comprising a non-crystallizing glass or a glass ceramic having a thermal coefficient of expansion matched to the thermal coefficient of expansion of the heat sinking base, and each overlying dielectric layer having a reflective surface layer formed thereon;
a plurality of LEDs disposed directly on each of the reflective surface layers wherein edges of each reflective surface layer extend beyond edges of the LEDs disposed thereon;
a transverse reflecting element disposed on each overlying dielectric layer and configured to reflect a portion of the light emitted by each of the plurality of LEDs, wherein each transverse reflecting element is a cone, a truncated cone, or a barrel formed of two truncated cones.
19. A light emitting diode package assembly according to claim 18 wherein the plurality of LEDs are arranged in a closed curve.
20. A light emitting diode package assembly according to claim 19 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 reflective surface layer.
21. A light emitting diode package assembly according to claim 19 wherein each reflective surface layer comprises a specular material.
22. A light emitting diode package assembly according to claim 21 wherein the specular material comprises a metal film.
23. A light emitting diode package assembly according to claim 21 wherein the specular material comprises a thin metal film.
24. A light emitting diode package assembly for emulating the pattern of light produced by an incandescent filament bulb, comprising:
a first subassembly and a second subassembly, each subassembly comprising a substrate having a front surface and a back surface, each front surface having an overlying dielectric layer disposed thereon, each overlying dielectric layer having a reflective surface layer formed thereon, and each reflective surface layer having more than one LED disposed directly thereon;
wherein the first subassembly and the second subassembly are disposed in back-to-back adjacency with a thermally conductive adhesive disposed between the back surfaces to form a heat sinking base having the respective front surfaces facing away from each other; and
a transverse reflecting element disposed on each overlying dielectric layer and configured to reflect a portion of the light emitted by each of the plurality of LEDs, wherein each transverse reflecting element is a cone, a truncated cone, or a barrel formed of two truncated cones.
25. The light emitting diode package assembly according to claim 24 , wherein each substrate comprises a metallic layer having a coefficient of thermal expansion matched to a coefficient of thermal expansion of the respective LED.