LED surface-mount device and LED display incorporating such device

• US 20090072251A1
• Filed: 12/14/2007
• Published: 03/19/2009
• Est. Priority Date: 09/14/2007
• Status: Abandoned Application

• Current Assignee: Cree Huizhou Solid State Lighting Company Limited (Smart Global Holdings Incorporated)
• Original Assignee: COTCO Luminant Device Ltd. (Wolfspeed, Inc.)
• Inventors: Wang, Xuan, Chan, Alex Chi Keung
• Application Number:
  US12/002,410
• Publication Number:
  US 20090072251A1
• Time in Patent Office: Days
• US Class Current: 257/89
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/4809 Loop shape
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• 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 2924/09701 Low temperature co-fired ceramic [LTCC]
• 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 one embodiment, a surface-mount device comprises a casing having opposed, first and second main surfaces, side surfaces, and end surfaces. A lead frame partially encased by the casing comprises (1) an electrically conductive LED chip carrier part having a surface carrying a linear array of three LEDs adapted to be energized to produce in combination a substantially full range of colors, each LED having a first electrical terminal and a second electrical terminal, the first terminal of each of the three LEDs being electrically and thermally coupled to the chip carrying surface of the chip carrier part; and (2) three electrically conductive connection parts separate from the chip carrier part, each of the three connection parts having a connection pad, the second terminal of each of the three LEDs being electrically coupled to the connection pad of a corresponding one of the three connection parts with a single wire bond. The linear array of LEDs extends in a first direction, and each of the chip carrier part and three connection parts has a lead. The leads are disposed in parallel relationship with each other and extend through the end surfaces of the casing in a second direction, the second direction being orthogonal to the first direction. An array of the surface-mount devices may be used in an LED display such as an indoor LED screen.

Claims

1. A lead frame for a surface-mount device, the lead frame comprising:

an electrically conductive LED chip carrier part having a surface carrying a linear array of three LEDs adapted to be energized to produce in combination a substantially full range of colors, each LED having a first electrical terminal and a second electrical terminal, the first terminal of each of the three LEDs being electrically and thermally coupled to said chip carrying surface of said chip carrier part;

three electrically conductive connection parts separate from said chip carrier part, each of said three connection parts having a connection pad; and

the second terminal of each of said three LEDs being electrically coupled to the connection pad of a corresponding one of said three connection parts.

2. The lead frame of claim 1 wherein:

the first and second electrical terminals of each of said LEDs comprise a cathode and an anode, respectively.

3. The lead frame of claim 1 wherein:

the linear array of LEDs extends in a first direction; and

each of said chip carrier part and three connection parts has a lead, said leads being disposed in parallel relationship with each other and extending in a second direction, and wherein said second direction is orthogonal to said first direction.

4. The lead frame of claim 1 wherein:

the chip carrier part and the three connection parts are made of sheet metal.

5. The lead frame of claim 1 wherein:

said chip carrier part has a lead electrically coupled to said chip carrying surface, said lead having a thickness; and

the chip carrying surface of the chip carrier part comprising a surface of a thermally conductive body extending in a direction normal to said chip carrying surface, said thermally conductive body having a thickness greater than the thickness of said chip carrier part lead.

6. The lead frame of claim 1 wherein:

the three LEDs comprise a red, a green, and a blue LED.

7. The lead frame of claim 1 wherein:

the second electrical terminal of each of said LEDs is electrically coupled to the connection pad of the associated connection part by means of a single wire bond.

8. A surface-mount device, comprising:

a casing comprising opposed, first and second main surfaces, opposed side surfaces, and opposed end surfaces, the casing defining a cavity extending into the interior of the casing from the first main surface; and

a lead frame partially encased by the casing, the lead frame comprising;

an electrically conductive LED chip carrier part having a surface carrying a linear array of three LEDs adapted to be energized to produce in combination a substantially full range of colors, each LED having a first electrical terminal and a second electrical terminal, the first terminal of each of the three LEDs being electrically and thermally coupled to said chip carrying surface of said chip carrier part;

three electrically conductive connection parts separate from said chip carrier part, each of said three connection parts having a connection pad; and

the second terminal of each of said three LEDs being electrically coupled to the connection pad of a corresponding one of said three connection parts.

9. The device of claim 8 wherein:

the first and second electrical terminals of each of said LEDs comprise a cathode and an anode, respectively.

10. The device of claim 8 wherein:

the linear array of LEDs extends in a first direction; and

each of said chip carrier and three connection parts has a lead, said leads being disposed in parallel relationship with each other and extending through the end surfaces of the casing in a second direction, and wherein said second direction is orthogonal to said first direction.

11. The device of claim 8 wherein:

the chip carrier part and the three connection parts are made of sheet metal.

12. The device of claim 8 wherein:

the chip carrying surface of the chip carrier part comprises a surface of a thermally conductive body extending in a direction normal to said chip carrying surface to a bottom surface of the body exposed through an aperture formed in the second main surface of the casing.

13. The device of claim 8 wherein:

the three LEDs comprise a red, a green, and a blue LED.

14. The device of claim 8 wherein:

the second electrical terminal of each of said LEDs is electrically coupled to the connection pad of the associated connection part by means of a single wire bond.

15. The device of claim 8 wherein:

the casing has a black color.

17. The display of claim 8 wherein:

each SMD includes a casing having a black color.

16. An LED display comprising:

a substrate carrying an array of surface-mount devices arranged in vertical columns and horizontal rows, each of said SMDs containing a vertically oriented, linear arrangement of three LEDs adapted to be energized to produce in combination a substantially fill range of colors and to define one pixel of the display; and

signal processing and LED drive circuitry electrically connected to selectively energize said array of SMDs for producing visual images on said display.