Micro-channel-cooled high heat load light emitting device

• US 8,723,146 B2
• Filed: 01/04/2013
• Issued: 05/13/2014
• Est. Priority Date: 01/27/2010
• Status: Expired due to Fees

• Current Assignee: Heraeus Noblelight America LLC (Heraeus Holding GMBH)
• Original Assignee: Heraeus Noblelight Fusion UV Inc. (Heraeus Holding GMBH)
• Inventors: Dahm, Jonathan S., Jongewaard, Mark, Campbell, Geoff
• Primary Examiner(s): Berman, Jack
• Assistant Examiner(s): Smith, David E
• Application Number:
  US13/734,253
• Publication Number:
  US 20130187063A1
• Time in Patent Office: 494 Days
• Field of Search: 250/493.1, 250/494.1, 250/496.1, 250/503.1, 250/504.R, 362/218, 362/227, 362/230, 362/235
• US Class Current: 250/494.1
• CPC Class Codes: B05D 3/067 Curing or cross-linking the coating
• CPC Class Codes: F21K 9/20 Light sources comprising attachment means
• CPC Class Codes: F21V 29/56 using liquid coolants F21V29/51 takes precedence
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48465 the other connecting portion not on the bonding area being a wedge bond, i.e. ball-to-wedge, regular stitch
• 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

Abstract

Micro-channel-cooled UV curing systems and components thereof are provided. According to one embodiment, a lamp head module includes an optical macro-reflector, an array of LEDs and a micro-channel cooler assembly. The array is positioned within the reflector and has a high fill factor and a high aspect ratio. The array provides a high irradiance output beam pattern having a peak irradiance of greater than 25 W/cm² at a work piece surface at least 1 mm away from an outer surface of a window of the reflector. The micro-channel cooler assembly maintains a substantially isothermal state among p-n junctions of the LEDs at less than or equal to 80° Celsius. The micro-channel cooler assembly also provides a common anode substrate for the array. A thermally efficient electrical connection is formed between the array and the common anode substrate by mounting the array to the micro-channel cooler assembly.

Claims

1. A lamp head module comprising:

an optical macro-reflector including a window having an outer surface;

an array of light emitting diodes (LEDs) positioned within the optical reflector, the array having a high fill factor and a high aspect ratio operable to provide a high irradiance output beam pattern having a peak irradiance of greater than 25 W/cm² at a work piece surface at least 1 mm away from the outer surface of the window of the optical reflector, wherein the peak irradiance does not require operation of the array at a pulsed emission duty cycle; and

a micro-channel cooler operable to maintain a substantially isothermal state among p-n junctions of the light emitting devices at a temperature of less than or equal to 80°

Celsius, the micro-channel cooler assembly also providing a substrate for the array, wherein a thermally efficient connection is formed between the array and the substrate by mounting the array to the micro-channel cooler wherein deep and long coolant flow channels in fluid communication with the micro-channel cooler serve to balance flow of coolant through the microchannel cooler.

2. The lamp head module of claim 1, wherein the array is directly mounted to the micro-channel cooler.

3. The lamp head module of claim 1, wherein the micro-channel cooler maintains a substantially isothermal state among the p-n junctions at a temperature of substantially less than or equal to 45°

Celsius.

4. The lamp head module of claim 1, wherein the LEDs are electrically paralleled.

5. The lamp head module of claim 4, wherein at least one of the LEDs is an ultraviolet emitting LED.

6. The lamp head module of claim 5, wherein an aspect ratio of a width to a length of the array is substantially between approximately 1:

2 to 1;

100.

7. The lamp head module of claim 6, wherein the aspect ratio is approximately 1:

68.

8. The lamp head module of claim 5, wherein the peak irradiance is greater than or equal to 100 W/cm² and the work piece surface is at least 2 mm away from the outer surface of the window of the optical reflector.

9. The lamp head module of claim 1, wherein a plurality of the LEDs are connected in series.

10. The lamp head module of claim 1, wherein microchannels of the micro-channel cooler that are closest to a bottom surface of the array are in thermal parallel across a shortest dimension of the array.

11. The lamp head module of claim 10, wherein coolant flow through the microchannels is substantially balanced.

12. The lamp head module of claim 1, further comprising a flex-circuit, bonded to the micro-channel cooler, the flex-circuit operable to individually address the LEDs or groups of the LEDs.

13. The lamp head module of claim 1, wherein the micro-channel cooler is clamped between one or more cathode connectors and one or more anode bus bodies to facilitate factory replaceability.

14. The lamp head module of claim 1, further comprising:

a flex-circuit, including a patterned cathode layer, to independently address a plurality of groups of one or more LEDs of the array;

a thermally conductive lamp body having opposing thin outer walls and having formed therein deep and long coolant flow channels in fluid communication with the micro-channel cooler; and

wherein the deep and long coolant flow channels serve to balance flow of coolant through the micro-channel cooler.

15. The lamp head module of claim 1, further comprising:

integrated LED drivers;

a thermally conductive body; and

wherein the integrated LED drivers comprise a plurality of metal core printed circuit boards (MCPCBs) mounted to opposing sides of the thermally conductive body and wherein the plurality of MCPCBs are conduction cooled through the thermally conductive body.

16. The lamp head module of claim 1, wherein the optical macro-reflector is field replaceable.

17. The lamp head module of claim 1, wherein the optical macro-reflector comprises a right-hand half and a left-hand half each of which represent a portion of an ellipse, each ellipse having two focuses, wherein the two focuses of the right-hand half have corresponding focal points that are offset to the left of a centerline of an intended output beam and the two focuses of the left-hand half have corresponding focal points that are offset to the right of the centerline.

18. The lamp head module of claim 1, wherein a plurality of the light emitting diodes are connected in a series/parallel arrangement.

19. The lamp head module of claim 1, wherein the optical macro-reflector comprises two non-rotationally symmetric, non-transparent halves.

20. A lamp head module comprising:

a high aspect ratio monolithically bonded foil micro-channel cooler substrate layer having a greater length than width wherein deep and long coolant flow channels in fluid communication with the micro-channel cooler serve to balance flow of coolant through the microchannel cooler;

a high aspect ratio light emitting diode array layer having a greater length than width mounted to the micro-channel cooler substrate layer, the light emitting diode array layer having a high fill-factor and comprising a p-n junction layer, wherein the high aspect ratio monolithically bonded foil micro-channel cooler substrate layer has formed therein a plurality of microchannels and those of the plurality of microchannels that are closest to a bottom surface of the high aspect ratio light emitting diode array layer are in thermal parallel across the width of the high aspect ratio light emitting diode array layer;

a flex-circuit layer, including a patterned cathode circuit material layer and a thin dielectric layer, mounted to the micro-channel cooler substrate layer, the cathode circuit material layer separated from the micro-channel cooler substrate layer by the thin dielectric layer, wherein the cathode circuit material layer and the thin dielectric layer combine in thickness to be less than 3×

a thickness of the light emitting diode array layer; and

an optical reflector layer to direct photons emitted by said light emitting diode array layer, the optical reflector layer being at least 25×

a thickness of the light emitting diode array layer, wherein the thicknesses are measured in a direction substantially perpendicular to the p-n junction layer.

21. The lamp head module of claim 20, wherein the light emitting diode array layer emits incoherent light.

22. The lamp head module of claim 20, wherein the light emitting diode array layer is connected to the cathode circuit material layer via at least one wire, the at least one wire terminating in a connection to the cathode circuit material layer at a point lying between the cathode circuit material layer and a bottom surface of the optical reflector layer.

23. The lamp head module of claim 22, further comprising a spacer layer between the optical reflector layer and the cathode circuit material layer, the spacer layer having a thickness of at least a diameter of the at least one wire.

24. The lamp head module of claim 20, wherein the optical reflector layer comprises a macro-reflector having an entrance aperture and an exit aperture, the entrance aperture being at least as wide as a sum of a width of the light emitting diode array layer plus 2×

the diameter of the at least one wire but no more than 3×

the sum.

25. The lamp head module of claim 20, wherein the optical reflector layer has a center section that is wider than either the entrance aperture or the exit aperture.

26. The lamp head module of claim 20, wherein the optical reflector layer comprises a macro-reflector having an entrance aperture and an exit aperture, the entrance aperture being at least as wide as a sum of a width of the light emitting device array layer plus 2×

the diameter of the at least one wire but no more than 5×

the sum.

27. The lamp head module of claim 20, wherein the macro-reflector comprises a right-hand half and a left-hand half each of which represent a portion of an ellipse, each ellipse having two focuses, wherein the two focuses of the right-hand half have corresponding focal points that are offset to the left of a centerline of an intended output beam and the two focuses of the left-hand half have corresponding focal points that are offset to the right of the centerline.

28. The lamp head module of claim 20, wherein:

the optical reflector layer is separated from the micro-channel cooler substrate layer by the flex-circuit layer; and

the flex-circuit layer is less than approximately 3×

the thickness of the light emitting diode array layer.

29. The lamp head module of claim 20, further comprising a wire layer and wherein the optical reflector layer is positioned with respect to the light emitting diode array layer such that a bottom surface of the optical reflector layer is between approximately a thickness of the wire layer and 1.5×

the thickness of the wire layer above a top surface of the light emitting diode array layer.

30. The lamp head module of claim 20, wherein the light emitting diode array layer is connected to the cathode circuit material layer via at least one electrical conductor, the at least one electrical conductor terminating in a connection to the cathode circuit material layer at a point lying between the cathode circuit material layer and a bottom surface of the optical reflector layer.

31. The lamp head module of claim 30, further comprising a spacer layer between the optical reflector layer and the cathode circuit material layer, the spacer layer having a thickness of at least a thickness of the at least one electrical conductor.

32. The lamp head module of claim 20, wherein the optical reflector layer comprises a macro-reflector having an entrance aperture and an exit aperture, the entrance aperture being at least as wide as a sum of a width of the light emitting device array layer plus 2×

the thickness of the at least one electrical conductor but no more than 3×

the sum.

33. The lamp head module of claim 20, wherein the optical reflector layer comprises a macro-reflector having an entrance aperture and an exit aperture, the entrance aperture being at least as wide as a sum of a width of the light emitting diode array layer plus 2×

the thickness of the at least one electrical conductor but no more than 5×

the sum.

34. The lamp head module of claim 20, wherein the macro-reflector comprises a right-hand half and a left-hand half each of which represent a portion of an ellipse, each ellipse having two focuses, wherein the two focuses of the right-hand half have corresponding focal points that are offset to the left of a centerline of an intended output beam and the two focuses of the left-hand half have corresponding focal points that are offset to the right of the centerline.

35. The lamp head module of claim 20, further comprising an electrical conductor layer and wherein the optical reflector layer is positioned with respect to the light emitting diode array layer such that a bottom surface of the optical reflector layer is between approximately a thickness of the electrical conductor layer and 1.5×

the thickness of the electrical conductor layer above a top surface of the light emitting diode array layer.

36. A lamp head module comprising:

a package including;

a high aspect ratio array of light emitting diode (LEDs), the high aspect ratio array having a greater length than width;

a flex circuit having a segmented cathode layer to which bond pads of the high aspect ratio array are electrically coupled; and

a high aspect ratio monolithically bonded foil micro-channel cooler having a length that is greater than a width and providing a substrate surface to which the high aspect ratio array is mounted; and

a lamp body having formed therein an input coolant fluid channel and an output coolant fluid channel, wherein coolant fluid flows from the input coolant fluid channel through the micro-channel cooler and to the output coolant fluid channel to remove waste heat from the high aspect ratio array, wherein a length and a width of the input coolant fluid channel and the output coolant fluid channel is substantially similar to the length and the width of the high aspect ratio monolithically bonded foil micro-channel cooler, respectively, and a depth of the input coolant fluid channel and the output coolant fluid channel is at least one third the length of the high aspect ratio monolithically bonded foil micro-channel cooler and wherein the input and output coolant flow channels balance the flow of coolant through the microchannel cooler.

37. An ultraviolet (UV) light emitting diode (LED) curing system comprising:

a plurality of end-to-end serially connected UV LED lamp head modules each including;

an optical macro-reflector including a window having an outer surface;

a LED array positioned within the optical reflector, the array having a high fill factor and a high aspect ratio operable to provide a substantially uniform high irradiance output beam pattern having a peak irradiance of greater than 25 W/cm² at a work piece surface at least 1 mm away from the outer surface of the window of the optical reflector, wherein the peak irradiance does not require operation of the LED array at a pulsed emission duty cycle; and

a micro-channel cooler assembly operable to maintain a substantially isothermal state among p-n junctions of LED in the LED array at a temperature of less than or equal to 80°

Celsius, the microchannel cooler assembly also providing a substrate for the LED array, wherein a thermally efficient electrical connection is formed between the LED array and the substrate by mounting the LED array to the micro-channel cooler assembly wherein deep and long coolant flow channels in fluid communication with the micro-channel cooler serve to balance flow of coolant through the microchannel cooler.

38. A lamp head module comprising:

an array of light emitting diodes (LEDs) having a high fill factor and a high aspect ratio operable to provide a substantially uniform high irradiance output beam along a long-axis of the array, wherein the LEDs include one or more ultraviolet emitting LEDs;

a high-aspect ratio micro-channel cooler assembly, including a micro-channel cooler portion and outer capping layer portions, operable to maintain a substantially isothermal state among p-n junctions of the LEDS, the high-aspect ratio micro-channel cooler assembly also providing a substrate for the array, wherein a thermally efficient electrical connection is formed between the array and the substrate by mounting the array to the high-aspect ratio micro-channel cooler assembly;

wherein a thickness of a heat spreader layer of the micro-channel cooler portion is less than approximately 200 microns;

wherein a width of the micro-channel cooler portion is approximately 1.1 to 1.7 times a width of the array in a shortest dimension of the array and wherein deep and long coolant flow channels in fluid communication with the micro-channel cooler serve to balance flow of coolant through the microchannel cooler.

39. The lamp head module of claim 38, wherein the array is directly mounted to a top surface of the micro-channel cooler portion.

40. The lamp head module of claim 39, wherein a vapor phase oven is used to reflow solder thereby mounting the array to the top surface of the micro-channel cooler portion.

41. The lamp head module of claim 40, wherein the solder is lead-free.

42. The lamp head module of claim 41, wherein a tacky flux is used to tack the LEDs in place prior to placing the high-aspect ratio micro-channel cooler assembly in the vapor phase oven.

43. The lamp head module of claim 38, wherein the thickness of the heat spreader layer is less than or equal to approximately 125 microns.

44. The lamp head module of claim 38, wherein the width of the micro-channel cooler portion is approximately 1.2 times the width of the array.

45. The lamp head module of claim 38, wherein:

the array includes at least one LED in the shortest dimension of the array;

the micro-channel cooler portion includes a plurality of internal channels running in the shortest dimension of the array and substantially directly under a bottom surface of the array; and

each of the LEDs are cooled in thermal parallel.

46. A lamp head module comprising:

a package including;

a high aspect ratio array of light emitting diodes, wherein the high aspect ratio array has a greater length than width;

a flex circuit having a segmented cathode layer to which bond pads of the high aspect ratio array are electrically coupled; and

a high aspect ratio monolithically bonded foil micro-channel cooler having a length that is greater than a width and providing a substrate surface to which the high aspect ratio array is mounted;

a lamp body having formed therein an input coolant fluid channel and an output coolant fluid channel, wherein coolant fluid flows from the input coolant fluid channel through the micro-channel cooler and to the output coolant fluid channel to remove waste heat from the high aspect ratio array, wherein a length and a width of the input coolant fluid channel and the output coolant fluid channel is substantially similar to the length and the width of the high aspect ratio monolithically bonded foil micro-channel cooler, respectively, and a depth of the input coolant fluid channel and the output coolant fluid channel is at least one third the length of the high aspect ratio monolithically bonded foil micro-channel cooler and wherein the input and output coolant flow channels balance the flow of coolant through the microchannel cooler; and

wherein the package is affixed to the lamp body.

47. The lamp head module of claim 46, wherein the high aspect ratio array is directly mounted to the substrate surface.