LED surface-mount device and LED display incorporating such device
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.
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.
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.
17 . The display of claim 8 wherein:
each SMD includes a casing having a black color.