Solid State Light Sheet for General Illumination

• US 20110195532A1
• Filed: 08/27/2010
• Published: 08/11/2011
• 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 8,338,199 B2
• Time in Patent Office: Days
• US Class Current: 438/27
• 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 2933/0033 relating to semiconductor body packages
• CPC Class Codes: H01L 2933/0066 relating to arrangements for conducting electric current to or from the semiconductor body
• CPC Class Codes: H01L 2933/0075 relating to heat extraction or cooling elements
• CPC Class Codes: H01L 33/48 characterised by the semiconductor body packages
• 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: H01S 5/4025 Array arrangements, e.g. constituted by discrete laser diodes or laser bar H01S5/42 takes precedence

Abstract

A solid state light sheet and method of fabricating the sheet are disclosed. In one embodiment, bare blue-light 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. In one embodiment, an intermediate sheet having holes is then affixed to the bottom substrate, with the LEDs passing through the holes. A transparent top substrate having conductors is then laminated over the intermediate sheet. In another embodiment, no intermediate sheet is used. Various ways to connect the LEDs in series are described along with many embodiments. The light sheet provides a practical substitute for a standard 2×4 foot fluorescent ceiling fixture. A phosphor is used to generate white light.

Claims

1. A method for fabricating a lighting device comprising:

providing a flexible first substrate;

providing a plurality of non-packaged light emitting dies, each die having at least two die electrodes;

affixing each die to an associated attachment location on the first substrate;

after the affixing, applying an intermediate sheet over the first substrate, the intermediate sheet having holes corresponding to locations of the dies on the first substrate, a thickness of the intermediate sheet being approximately a thickness of each die;

encapsulating each die by filling each hole with an encapsulant; and

applying a transparent second substrate over the intermediate sheet, wherein at least one of the first substrate, the intermediate sheet, and the second substrate has first electrodes connected to associated die electrodes and has conductors extending from the first electrodes for electrically interconnecting the dies.

2. The method of claim 1 wherein the first substrate has at least some of the first electrodes, wherein the dies have at least a bottom electrode affixed to the first electrodes on the first substrate.

3. The method of claim 1 wherein the second substrate has at least some of the first electrodes, wherein the dies have at least a top electrode affixed to the first electrodes on the second substrate.

4. The method of claim 1 wherein the dies are vertical dies having top and bottom electrodes, wherein the first substrate has at least some of the first electrodes, wherein the dies have at least a bottom electrode affixed to the first electrodes on the first substrate, wherein the second substrate has at least some of the first electrodes, and wherein the dies have at least a top electrode affixed to the first electrodes on the second substrate.

5. The method of claim 1 wherein at least some of the first electrodes are located in the holes in the intermediate sheet, wherein the dies are positioned within the holes so as to have the die electrodes electrically contacting the first electrodes in the holes.

6. The method of claim 1 wherein the conductors are connected in at least series within outer boundaries of the first substrate.

7. The method of claim 1 wherein the dies are vertical dies with top and bottom die electrodes.

8. The method of claim 1 wherein each die has cathode and anode die electrodes formed on a single surface of the die.

9. The method of claim 1 wherein the dies are light emitting diodes (LEDs).

10. The method of claim 1 wherein at least some of the dies are connected in series by connectors extending through the intermediate sheet.

11. The method of claim 1 wherein the first substrate has metal vias extending completely through its surface, the dies being thermally coupled to the metal vias for sinking heat from the dies.

12. The method of claim 1 wherein the conductors are formed on a bottom surface of the first substrate.

13. The method of claim 1 wherein the conductors are formed on a top surface of the first substrate.

14. The method of claim 1,

wherein the dies are vertical dies having top and bottom electrodes, wherein the first substrate has at least some of the first electrodes, wherein the dies have at least a bottom electrode affixed to the first electrodes on the first substrate,

wherein the second substrate has at least some of the first electrodes, wherein the dies have at least a top electrode affixed to the first electrodes on the second substrate;

the method further comprising;

affixing metal vias to at least some of the first electrodes on the first substrate,

the intermediate sheet having some holes corresponding to locations of the metal vias,

wherein the metal vias connect first electrodes on the first substrate to first electrodes on the second substrate to connect dies in series.

15. The method of claim 1 wherein the first substrate contains a reflector layer.

16. The method of claim 1 wherein the intermediate sheet contains at least one reflector.

17. The method of claim 1 wherein each die has a reflector formed over a top surface of the die so that the dies only emit light through side walls of the dies.

18. The method of claim 1 wherein the encapsulant in the holes contains a wavelength conversion material for generating white light.

19. The method of claim 1 wherein the lighting device is a flexible sheet forming a 2×

4 foot ceiling luminaire.

20. The method of claim 1 further comprising forming the lighting device in strips, each strip providing light similar to that produced by a T8 fluorescent lamp in a ceiling luminaire.