LED lamp assembly with means to conduct heat away from the LEDS

• US 6,045,240 A
• Filed: 10/20/1997
• Issued: 04/04/2000
• Est. Priority Date: 06/27/1996
• Status: Expired due to Term

• Current Assignee: Relume Technologies, Inc. (Revolution Lighting Technologies, Inc.)
• Original Assignee: Relume Corporation
• Inventors: Hochstein, Peter A.
• Primary Examiner(s): O'Shea, Sandra
• Assistant Examiner(s): Negron, Ismael
• Application Number:
  US08/953,942
• Time in Patent Office: 897 Days
• Field of Search: 362/800, 362/249, 362/294, 362/373, 257/81, 257/82, 257/88-93, 257/99
• US Class Current: 362/294
• CPC Class Codes: B60Q 1/2696 Mounting of devices using LEDs
• CPC Class Codes: B61L 2207/02 using light-emitting diodes [LEDs]
• CPC Class Codes: B61L 5/1854 Mounting and focussing of the light source in a lamp, fixing means
• CPC Class Codes: F21S 43/14 Light emitting diodes [LED]
• CPC Class Codes: F21S 45/37 specially adapted for signal lamps
• CPC Class Codes: F21S 45/47 Passive cooling, e.g. using fins, thermal conductive elements or openings
• CPC Class Codes: F21V 29/74 with fins or blades
• CPC Class Codes: F21V 29/83 the elements having apertures, ducts or channels, e.g. heat radiation holes
• CPC Class Codes: F21V 29/89 Metals
• CPC Class Codes: F21W 2111/02 for roads, paths or the like
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: G08G 1/095 Traffic lights
• CPC Class Codes: H01L 33/64 Heat extraction or cooling elements
• CPC Class Codes: H05K 1/0206 by printed thermal vias
• CPC Class Codes: H05K 2201/0209 Inorganic, non-metallic particles
• CPC Class Codes: H05K 2201/09781 Dummy conductors, i.e. not used for normal transport of current; Dummy electrodes of components
• CPC Class Codes: H05K 2201/10106 Light emitting diode [LED]
• CPC Class Codes: H05K 3/0061 onto a metallic substrate, e.g. a heat sink heat sinks for electric apparatus H05K7/20
• CPC Class Codes: H05K 3/42 Plated through-holes or plated via connections
• CPC Class Codes: Y10S 362/80 Light emitting diode

Abstract

An electrically driven L.E.D. lamp assembly (14) comprising an electrically insulating circuit board (26) having opposed first and second surfaces with light emitting diodes (28) having positive and negative leads (30, 32) mounted on the first surface. A plurality of holes extend through the board (26) and a plurality of pads (50) of thermally conductive plating are disposed on the second side with each pad (50) associated with the leads to conduct heat from each of the leads to one of the pads (50) while maintaining electrical isolation between the pads. A heat sink includes a base (36) overlying the second surface and an adhesive layer (58) of thermally conductive adhesive is disposed between the conductive plating and the heat sink (36) to secure the conductive plating and the circuit board (26) to the heat sink (36). The assembly is characterized by an electrically non-conductive spacer (56, 156) for preventing contact between the conductive plating (50) and the heat sink to prevent electrical shorting between the conductive plating (50) and the heat sink (36) while maximizing heat transfer. The spacer may comprise a pre-cured coating of the same material as the adhesive (58) or discrete elements (156).

Claims

1. An electrically driven L.E.D. lamp assembly comprising;

an electrically insulating circuit board having opposed first and second surfaces,

light emitting diodes mounted on said first surface,

each of said light emitting diodes having positive and negative leads,

a thermally conductive plating on said second surface,

said conductive plating being thermally connected to said leads to conduct heat from said leads to said conductive plating,

a heat sink overlying said conductive plating,

an adhesive layer of thermally conductive adhesive disposed between said conductive plating and said heat sink to secure said conductive plating and said board to said heat sink,

said assembly characterized by an electrically non-conductive spacer for preventing contact between said conductive plating and said heat sink to prevent electrical shorting between said conductive plating and said heat sink while maximizing heat transfer from said conductive plating to said heat sink.

2. An assembly as set forth in claim 1 wherein said conductive plating is divided into a plurality of pads, said pads being separated form one another a discrete distance which only of a magnitude sufficient to prevent electrical conductivity from pad to pad,

each of said pads being thermally connected to one of said leads to conduct heat from each of said leads to one of said pads while maintaining electrical isolation between said pads.

3. An assembly as set forth in claim 1 wherein said conductive plating is divided into conductors for electrically connecting one of said leads of adjacent light emitting diodes, said conductive plating covering over fifty percent of the area between the leads of adjacent diodes for maximizing the heat transfer to said heat sink.

4. An assembly as set forth in claim 3 including solder connecting said leads to said conductive plating on said second surface.

5. An assembly as set forth in claim 1 wherein said adhesive layer is also electrically insulating.

6. An assembly as set forth in claim 5 wherein said spacer is also thermally conductive.

7. An assembly as set forth in claim 6 wherein said spacer comprises a thin layer.

8. An assembly as set forth in claim 7 wherein said thin layer comprises the same material as said adhesive layer but cured differently from said adhesive layer.

9. An assembly as set forth in claim 6 wherein said spacer comprises elements defining spaces therebetween and said adhesive layer fills said spaces and interconnects said conductive plating and said heat sink.

10. An assembly as set forth in claim 9 wherein said circuit board includes holes therein and said elements are supported in said holes and extend from said second surface of said circuit board.

11. A method of fabricating a L.E.D. lamp assembly comprising the steps of:

providing an electrically insulating circuit board having opposed first and second surfaces with light emitting diodes mounted on the first surface and a thermally conductive plating on the second surface and thermally connected to the leads of the light emitting diodes to conduct heat from each of the light emitting diodes to the thermally conductive plating,

providing a heat sink for overlying the thermally conductive plating,

applying an adhesive layer of thermally conductive adhesive between the thermally conductive plating and the heat sink to secure the thermally conductive plating and the board to the heat sink,

said method characterized by disposing an electrically non-conductive spacer between the heat sink and the thermally conductive plating for preventing contact between the thermally conductive plating and the heat sink to prevent electrical shorting between the thermally conductive plating and the heat sink while maximizing heat transfer from the thermally conductive plating to the heat sink.

12. A method as set forth in claim 11 further defined as applying a thin layer over the heat sink to define the spacer.

13. A method as set forth in claim 12 further defined as applying the thin layer in soft state and curing the thin layer into a hard state.

14. A method as set forth in claim 12 further defined as applying the thin layer of the same material as the adhesive layer in a soft state and curing the thin layer into a hard state, and applying the adhesive layer after the thin layer is cured whereby the hard thin layer prevents contact between the conductive plating and the heat sink.

15. A method as set forth in claim 11 further defined as disposing elements defining spaces therebetween to define the spacer, and applying the adhesive layer to fill the spaces to interconnect the conductive plating and the heat sink.

16. A method as set forth in claim 15 further defined employing a circuit board including holes therein and disposing the elements in the holes to extend from the holes and the second surface of the circuit board.

17. A method as set forth in claim 11 including the step of urging said circuit board toward the heat sink while curing the adhesive layer as the spacer prevents contact between the conductive plating and the heat sink.

18. A method as set forth in claim 17 further defined as applying an adhesive layer which is also electrically insulating.

19. A method as set forth in claim 18 further defined as disposing a spacer which is also thermally conductive.