Solid state bidirectional light sheet for general illumination

• US 8,210,716 B2
• Filed: 11/01/2010
• Issued: 07/03/2012
• Est. Priority Date: 08/27/2010
• Status: Active Grant

• Current Assignee: Quarkstar LLC
• Original Assignee: Quarkstar LLC
• Inventors: Lerman, Louis, York, Allan Brent, Henry, Michael David, Steele, Robert, Ogonowsky, Brian D.
• Primary Examiner(s): Shallenberger, Julie
• Application Number:
  US12/917,319
• Publication Number:
  US 20110058372A1
• Time in Patent Office: 610 Days
• Field of Search: 362/612, 362/613, 362/616, 362/545, 362/249.02, 362/249.06, 362/249.14, 257/88
• US Class Current: 362/249.02
• CPC Class Codes: F21K 9/00 Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
• CPC Class Codes: F21K 9/27 Retrofit light sources for lighting devices with two fittings for each light source, e.g. for substitution of fluorescent tubes
• CPC Class Codes: F21K 9/60 Optical arrangements integrated in the light source, e.g. for improving the colour rendering index or the light extraction
• CPC Class Codes: F21K 9/90 Methods of manufacture
• CPC Class Codes: F21S 8/06 by suspension
• CPC Class Codes: F21V 19/005 by permanent fixing means, e.g. gluing, riveting or embedding in a potting compound
• CPC Class Codes: F21V 23/00 Arrangement of electric circuit elements in or on lighting devices characterised by cooling arrangements F21V29/508
• 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 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• 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 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 33/50 Wavelength conversion elements
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls
• CPC Class Codes: H05K 1/0204 using means for thermal conduction connection in the thickness direction of the substrate H05K1/0207 takes precedence
• CPC Class Codes: H05K 1/0206 by printed thermal vias
• CPC Class Codes: H05K 1/183 Components mounted in and supported by recessed areas of the printed circuit board
• CPC Class Codes: H05K 2201/10106 Light emitting diode [LED]
• CPC Class Codes: H05K 2201/2054 Light-reflecting surface, e.g. conductors, substrates, coatings, dielectrics

Abstract

A solid state light sheet and method of fabricating the sheet are disclosed. In one embodiment, bare LED chips have top and bottom electrodes, where the bottom electrode is a large reflective electrode. The bottom electrodes of an array of LEDs (e.g., 500 LEDs) are bonded to an array of electrodes formed on a flexible bottom substrate. Conductive traces are formed on the bottom substrate connected to the electrodes. A transparent top substrate having conductors is then laminated over the bottom substrate. Various ways to connect the LEDs in series are described along with many embodiments. The light sheets may be formed to emit light from opposite surfaces of the light sheet, enabling it to be used in a hanging fixture to illuminate the ceiling as well as the floor. The light sheet provides a practical substitute for a standard 2×4 foot fluorescent ceiling fixture.

Claims

1. A bidirectional lighting device comprising:

a plurality of non-packaged light emitting dies having electrodes;

a first transparent substrate and a second transparent substrate sandwiching the light emitting dies and forming a light emitting structure having a first light emitting surface emitting light from the lighting device in a first direction and a second light emitting surface emitting light from the lighting device in a second direction opposing from the first direction;

first conductors formed on the first transparent substrate and second conductors formed on the second transparent substrate, the first and second connectors being electrically connected to the electrodes of the light emitting dies without wires for connecting the light emitting dies to a source of power; and

an intermediate sheet between the first and second transparent substrates, the intermediate sheet having holes corresponding to locations of the dies on the transparent substrates such that each of the plurality of dies is surrounded by walls of an associated hole,

wherein;

each die has at least a first die electrode and a second die electrode, the first die electrode being formed on a primary light output surface of the die, and each die has sidewalls perpendicular to the primary light output surface,

the first transparent substrate has first connection locations electrically connected to the first conductors, such that a first set of the plurality of dies have their first die electrode aligned with and electrically connected to an associated one of the first connection locations on the first transparent substrate without wire bonds,

the second substrate has second connection locations electrically connected to the second conductors, such that a second set of the plurality of dies different from the first set have their first die electrode aligned with and electrically connected to an associated one of the second connection locations on the second substrate without wire bonds, and

the intermediate sheet has a plurality of prisms on a bottom or top surface of the intermediate sheet to reflect light emitted through side walls of the plurality of dies, the light reflected by the prisms being directed in the first and second directions and output from the bidirectional lighting device through the first and second light emitting surfaces.

2. The device of claim 1, wherein the first set of dies and the second set of dies are connected in series by the first conductors and the second conductors.

3. The device of claim 1 wherein the device is formed as a light sheet.

4. The device of claim 3 wherein the device is suspended from a ceiling so that the first light emitting surface faces the ceiling and the second light emitting surface faces away from the ceiling.

5. The device of claim 1, wherein the device is a flexible light sheet.

6. The device of claim 1, wherein the dies are vertical light emitting diodes (LEDs).

7. The device of claim 1, further comprising a wavelength conversion material that fills the holes of the intermediate sheet to encapsulate the corresponding dies and to convert light emitted through side surfaces of the dies to white light.

8. The device of claim 1, wherein at least some of the dies are connected in series by conductors internal to the device within outer boundaries of the first transparent substrate and the second transparent substrate.

9. The device of claim 1 wherein the device is part of a 2×

4 foot ceiling fixture.

10. The device of claim 1, wherein the first transparent substrate, the second substrate and the intermediate sheet each have dimensions of approximately 2×

4 feet.

11. The device of claim 7, further comprising a plurality of tiles formed on the first and second transparent substrates at locations corresponding to the plurality of dies, the tiles comprising a wavelength conversion material to convert light emitted through the primary light output surface of the dies.

12. The device of claim 7, further comprising

a plurality of tiles formed on the first transparent substrate at locations corresponding to the dies of the first set, the tiles comprising a wavelength conversion material,

wherein the device emits white light in the first direction through the plurality of tiles, and monochromatic light in the second direction through the second light emitting surface.

13. The device of claim 12, where the monochromatic light is blue light emitted by the dies.

14. The device of claim 12, where the monochromatic light is UV light emitted by the dies.

15. The device of claim 1, where a light level emitted by the device from the first light emitting surface is modulated differently from another light level emitted by the device from the second light emitting surface.

16. A bidirectional lighting device comprising:

a reflective substrate having a first surface and a second surface opposing the first surface;

a plurality of non-packaged light emitting dies having electrodes;

a first transparent substrate sandwiching a first subset of the plurality of dies between the first surface of the reflective substrate and the first transparent substrate, an outer surface of the first transparent substrate forming a first light emitting surface of the bidirectional lighting device through which light is emitted from the bidirectional lighting device in a first direction;

a second transparent substrate sandwiching a second subset of the plurality of dies between the second surface of the reflective substrate and the second transparent substrate, an outer surface of the second transparent substrate forming a second light emitting surface of the bidirectional lighting device through which light is emitted from the bidirectional lighting device in a second direction opposing the first direction;

first and second conductors formed on the respective first and second surfaces of the reflective substrate connected to the electrodes of the respective first and second sets of light emitting dies without wires for connecting the plurality of light emitting dies to a source of power;

a first intermediate sheet between the first and reflective substrates, the first intermediate sheet having holes corresponding to locations of the dies of the first set on the first surface of the reflective substrate, such that each of the first set of dies is surrounded by walls of an associated hole of the first intermediate sheet; and

a second intermediate sheet between the second and reflective substrates, the second intermediate sheet having holes corresponding to locations of the dies of the second set on the second surface of the reflective substrate, such that each of the second set of dies is surrounded by walls of an associated hole of the second intermediate sheet,

wherein

each die of the first set has a primary light output surface facing the first light emitting surface of the bidirectional lighting device, and each die of the second set has the primary light output surface facing the second light emitting surface of the bidirectional lighting device, wherein each die of the first and second sets have side walls perpendicular to the primary light output surface,

the electrodes of the first set of dies are electrically connected to the first conductors on the first surface of the reflective substrate without wire bonds, and the electrodes of the second set of dies are electrically connected to the second conductors on the second surface of the reflective substrate without wire bonds,

the first intermediate sheet has a first plurality of prisms on a surface of the first intermediate sheet adjacent to the reflective substrate to reflect light emitted through side walls of the first set of dies, the light reflected by the first plurality of prisms being directed in the first direction and output from the bidirectional lighting device through the first light emitting surface, and

the second intermediate sheet has a second plurality of prisms on a surface of the second intermediate sheet adjacent to the reflective substrate to reflect light emitted through side walls of the second set of dies, the light reflected by the second plurality of prisms being directed in the second direction and output from the bidirectional lighting device through the second light emitting surface.

17. The device of claim 16, wherein at least some of the dies of the first set of dies are connected in series by the first conductors, and at least some of the dies of the second set of dies are connected in series by the second conductors.

18. The device of claim 16, further comprising a wavelength conversion material that fills the holes of the first and second intermediate sheets to encapsulate the corresponding dies and to convert light emitted through side surfaces of the dies to white light.

19. The device of claim 18, further comprising multiple tiles formed on the first and second transparent substrates at locations corresponding to the locations of the first and second sets of dies, the tiles comprising a wavelength conversion material to convert light emitted through the primary light output surface of the dies.

20. The device of claim 18, further comprising

multiple tiles formed on the first transparent substrate at locations corresponding to the dies of the first set, the tiles comprising a wavelength conversion material,

wherein the bidirectional lighting device emits white light in the first direction through the multiple tiles, and monochromatic light in the second direction through the second light emitting surface.