Manufacturing Methods for Solid State Light Sheet or Strip with LEDs Connected in Series for General Illumination

• US 20110193114A1
• Filed: 03/09/2011
• 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 8,198,109 B2
• Time in Patent Office: Days
• US Class Current: 257/91
• CPC Class Codes: F21K 9/20 Light sources comprising attachment means
• CPC Class Codes: F21K 9/64 using wavelength conversion means distinct or spaced from the light-generating element, e.g. a remote phosphor layer
• CPC Class Codes: F21S 8/06 by suspension
• 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 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 33/08 with a plurality of light emitting regions, e.g. laterally discontinuous light emitting layer or photoluminescent region integrated within the semiconductor body H01L27/15 takes precedence
• CPC Class Codes: H01L 33/507 the elements being in intimate contact with parts other than the semiconductor body or integrated with parts other than the semiconductor body
• CPC Class Codes: H01L 33/60 Reflective 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: 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 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 is then formed over the bottom substrate. Various ways to connect the LEDs in series are described along with many embodiments. In one method, the top substrate contains a conductor pattern that connects to LED electrodes and conductors on the bottom substrate. In another embodiment, a conductor layer is formed on the outer surface of the top substrate and makes contact with the LED electrodes and conductors on the bottom substrate via openings formed in the top substrate.

Claims

1. A lighting device comprising:

a first layer having a first conductor pattern formed thereon;

a plurality of non-packaged light emitting diode (LED) dies, each die having at least a first die electrode and a second die electrode, the LED dies being supported on the first layer, the first die electrode of each LED die being electrically connected to the first conductor pattern on the first layer without wire bonds;

a second layer overlying the LED dies, the second layer having first openings over at least the second die electrode of the LED dies; and

a conductor layer overlying the second layer and in electrical contact with the second die electrode through the first openings, the conductor layer connecting a plurality of the LED dies in series.

2. The device of claim 1 wherein the second layer also has second openings over portions of the first conductor pattern, and wherein the conductor layer makes electrical contact with the first conductor pattern through the second openings to connect the plurality of LED dies in series.

3. The device of claim 2 further comprising conductive interconnectors extending between the first conductor pattern and the second layer, wherein the conductor layer makes electrical contact with the first conductor pattern through the second openings by electrically contacting the interconnectors.

4. The device of claim 1 wherein the first openings are filled with a metal stud prior to the conductor layer being formed.

5. The device of claim 1 wherein the first openings are holes extending through the second layer.

6. The device of claim 1 wherein the second layer conforms to an outer surface of the LED dies and encapsulates the LED dies.

7. The device of claim 1 wherein the second layer contains a wavelength conversion material to convert light from the LED dies into white light.

8. The device of claim 1 wherein the first layer and the second layer are strips that sandwich a column of series-connected LED dies in-between.

9. A method of forming a light emitting structure comprising:

providing a first layer having a first conductor pattern formed thereon;

providing a plurality of non-packaged light emitting diode (LED) dies, each die having at least a first die electrode and a second die electrode;

bonding the first die electrode of each LED die to the first conductor pattern on the first layer without wire bonds;

applying a light-transmissive second layer over the LED dies, the second layer being formed of a dielectric material;

forming first openings in the second layer over at least the second die electrode of the LED dies; and

forming a conductor layer overlying the second layer and in electrical contact with the second die electrode through the first openings, the conductor layer connecting a plurality of the LED dies in series.

10. The method of claim 9 further comprising:

forming second openings in the second layer over portions of the first conductor pattern; and

forming the conductor layer to be in electrical contact with the first conductor pattern through the second openings to connect the plurality of LED dies in series.

11. The method of claim 9 wherein forming the first openings comprises forming holes extending through the second layer.

12. The method of claim 9 further comprising:

attaching metal studs to the second die electrodes prior to applying the second layer over the LED dies; and

forming the conductor layer overlying the second layer and in electrical contact with the second die electrode through the metal studs.

13. The method of claim 9 wherein applying the second layer over the LED dies comprises applying a liquid or softened second layer material over the LED dies to encapsulate the LED dies.

14. The method of claim 9 wherein forming first openings in the second layer comprises laser drilling holes in the second layer.

15. The method of claim 9 wherein forming first openings in the second layer comprises:

forming posts over the second die electrodes;

applying the second layer over the LED dies and around the posts; and

removing the posts to create holes in the second layer.

16. The method of claim 9 wherein forming the conductor layer overlying the second layer comprises forming a seed layer and plating the seed layer.

17. The method of claim 9 wherein forming the conductor layer overlying the second layer comprises printing the conductor layer.

18. The method of claim 9 wherein forming the conductor layer overlying the second layer comprises:

forming a dielectric layer having trenches and holes;

depositing the conductor layer over the dielectric layer; and

etching away a top portion of the conductor layer while leaving the conductor layer in the trenches and holes to interconnect the plurality of LED dies in series.

19. The method of claim 9 further comprising providing a wavelength conversion layer overlying the LED dies to cause the light emitting structure to emit white light.

20. The method of claim 9 wherein the light emitting structure comprises a column of series-connected LED dies.