Light emitting diodes packaged for high temperature operation

• US 20040222433A1
• Filed: 08/11/2003
• Published: 11/11/2004
• Est. Priority Date: 05/05/2003
• Status: Active Grant

• Current Assignee: Lighting Science Group Corporation (Pegasus Capital Advisors, L.P.)
• Original Assignee: Lamina Ceramics, Inc.
• Inventors: Mazzochette, Joseph, Blonder, Greg
• Granted Patent: US 7,095,053 B2
• Time in Patent Office: Days
• US Class Current: 257/99
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45139 Silver (Ag) as principal constituent
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• 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 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01012 Magnesium [Mg]
• CPC Class Codes: H01L 2924/0102 Calcium [Ca]
• CPC Class Codes: H01L 2924/01025 Manganese [Mn]
• CPC Class Codes: H01L 2924/01046 Palladium [Pd]
• CPC Class Codes: H01L 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/09701 Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H01L 2924/12041 LED
• CPC Class Codes: H01L 2924/19041 being a capacitor
• CPC Class Codes: H01L 2924/207 Diameter ranges
• CPC Class Codes: H01L 33/486 adapted for surface mounting
• CPC Class Codes: H01L 33/642 characterized by the shape
• CPC Class Codes: H01L 33/647 the elements conducting electric current to or from the semiconductor body

Abstract

In accordance with the invention, an LED packaged for high temperature operation comprises a metal base including an underlying thermal connection pad and a pair of electrical connection pads, an overlying ceramic layer, and a LED die mounted overlying the metal base. The LED is thermally coupled through the metal base to the thermal connection pad, and the electrodes are electrically connected to the underlying electrical connection pads. A low thermal resistance insulating layer can electrically insulate other areas of die from the base while permitting heat passage. Heat flow can be enhanced by thermal vias to the thermal connector pad. Ceramic layers formed overlying the base can add circuitry and assist in distributing emitted light. The novel package can operate at temperatures as high as 250° C.

Claims

1. A packaged LED for high temperature operation comprising:

a metal base, the metal base including an underlying thermal connection pad and a pair of underlying electrical connection pads;

a layer of ceramic overlying the metal base; and

an LED having a pair of electrodes overlying the metal base, the LED thermally coupled through the metal base to the thermal connection pad and the electrodes electrically connected to respective underlying electrical connector pads.

2. The packaged LED of claim 1 wherein the layer of ceramic includes a cavity and the LED is mounted in the cavity.

3. The packaged LED of claim 2 wherein the cavity has tapered sides to reflect light from the LED.

4. The packaged LED of claim 1 wherein the metal base includes a concave region to reflect light and the LED is mounted overlying the concave region.

5. The packaged LED of claim 1 wherein the underlying electrical connection pads and the underlying thermal connection pad are coplanar to permit surface mounting on corresponding pads of a PC board.

6. The packaged LED of claim 1 wherein the LED is mounted on the ceramic layer overlying the thermal connection pad and the LED is thermally coupled by the thermal vias to the metal base overlying the thermal connector pad.

7. The packaged LED of claim 1 wherein at least one electrode of the LED is connected to an underlying electrical connection pad by an electrical path including a bonding wire from the electrode to a bonding pad on the ceramic layer.

8. The packaged LED of claim 1 wherein at least one electrode of the LED is connected to an underlying electrical connection pad by an electrical path including an insulated conducting via through the metal base.

9. The packaged LED of claim 1 wherein at least one electrode of the LED is connected to an underlying electrical connection pad by an electrical path including the metal base.

10. An array of LEDs comprising a plurality of LEDs according to claim 1 overlying a common metal base.

11. A low temperature co-fired on metal (LTCC-M) light emitting diode (LED) assembly for high temperature operation comprising:

a metal base, the metal base including a thermal connection surface;

at least one LED die, the LED die having a pair of electrodes overlying and electrically insulated from the metal base, the die thermally coupled through the metal base to the thermal connection surface;

a layer of ceramic overlying the metal base, the layer of ceramic having at least one opening to house the LED die; and

a plurality of conductive traces insulated from the metal base, the LED electrodes electrically connected to the conductive traces.

12. The LED assembly of claim 11 further comprising a plurality of edge connector fingers, wherein the fingers are connected to the LED electrodes.

13. The LED assembly of claim 11 further comprising a plurality of edge connector fingers, wherein the fingers are connected to decoder/driver electronics that control the LED electrodes.

14. The LED assembly of claim 13 wherein the decoder/driver electronics that control the LED electrodes is embedded in the LTCC-M package.

15. The LED assembly of claim 11 further comprising an additional metal block on which the LED assembly is mounted to further improve heat dissipation.

16. The LED assembly of claim 11 wherein the LED die is a flip-chip.

17. The LED assembly of claim 16 wherein the flip-chip is bonded to the traces by conductive balls comprising solder or gold.

18. The LED assembly of claim 11 further comprising isolated terminals formed on the metal base, the isolated terminals electrically connected to the LED electrodes.

19. The LED assembly of claim 11 further comprising isolated terminals formed on the metal base, the isolated terminals electrically connected to decoder/driver electronics, the electronics mounted within the LTCC-M assembly.

20. The LED assembly of claims 18 and 19 further comprising vias in the insulating layer, the vias electrically connecting traces to the isolated terminals.