Solid State Bidirectional Light Sheet for General Illumination

• US 20110058372A1
• Filed: 11/01/2010
• Published: 03/10/2011
• Est. Priority Date: 08/27/2010
• Status: Active Grant

• Current Assignee: Quarkstar LLC
• Original Assignee: Quarkstar LLC
• Inventors: Ogonowsky, Brian D., Lerman, Louis, Steele, Robert, York, Allan Brent, Henry, Michael David
• Granted Patent: US 8,210,716 B2
• Time in Patent Office: Days
• US Class Current: 362/235
• 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 first plurality of non-packaged light emitting dies having electrodes;

at least a first substrate and a second 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 an opposing second light emitting surface emitting light from the lighting device in a second direction different from the first direction; and

conductors formed on the at least first substrate and second substrate electrically connected to the electrodes of the light emitting dies without wires for connecting the light emitting dies to a source of power.

2. The device of claim 1 wherein,

the first substrate has first connection locations electrically connected to first conductors formed on the first substrate, 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, wherein

some of the dies have their first die electrode aligned with and electrically connected to an associated one of the first connection locations on the first substrate without wire bonds, wherein

the second substrate has second connection locations electrically connected to second conductors formed on the second substrate, wherein

other ones of the dies 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 wherein

the first substrate and the second substrate have light output surfaces for emitting light in different directions from at least the primary light output surfaces of the dies.

3. The device of claim 2 further comprising an intermediate layer between the first substrate and the second substrate.

4. The device of claim 2 wherein the first substrate and the second substrate directly contact each other with no intermediate layer between them.

5. The device of claim 2 wherein at least some of the dies are connected in series by the first conductors and the second conductors.

6. The device of claim 5 wherein the at least some of the dies are connected in series by the first conductors and the second conductors interconnecting the first die electrodes to the second die electrodes.

7. The device of claim 1 further comprising:

an intermediate layer over the first substrate, the intermediate layer having holes corresponding to locations of the dies on the first substrate such that the dies are surrounded by walls of an associated hole,

wherein the plurality of dies are sandwiched between the first substrate and the second substrate, with the intermediate layer there between, wherein portions of the first conductors and portions of the second conductors connect at least some of the dies in series without using wire bonds.

8. The device of claim 1 further comprising at least third substrate sandwiched between the first substrate and the second substrate, the third substrate having a reflective layer for reflecting light out through the first substrate and the second substrate.

9. The device of claim 8 wherein the third substrate has third conductors formed on its surface for interconnecting at least some of the dies in series.

10. The device of claim 1 further comprising a reflective layer between the first substrate and the second substrate, wherein some of the dies are located between the reflective layer and a light output surface of the first substrate, and other ones of the dies are located between the reflective layer and a light output surface of the second substrate.

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

12. The device of claim 11 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.

13. The device of claim 1 wherein the device is a flexible light sheet having transparent opposing light emitting surfaces.

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

15. The device of claim 1 further comprising a wavelength conversion material provided on or in the device for converting light emitted from the dies to white light.

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

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

4 foot ceiling fixture.

18. The device of claim 1 wherein the first substrate and the second substrate each have dimensions of approximately 2×

4 feet.