MICRO-CHANNEL-COOLED HIGH HEAT LOAD LIGHT EMITTING DEVICE

• US 20110204261A1
• Filed: 01/26/2011
• Published: 08/25/2011
• Est. Priority Date: 01/27/2010
• Status: Active Grant

• Current Assignee: Heraeus Noblelight America LLC (Heraeus Holding GMBH)
• Original Assignee: Fusion UV Systems, Inc. (Heraeus Holding GMBH)
• Inventors: Campbell, Geoff, Jongewaard, Mark, Dahm, Jonathan S.
• Granted Patent: US 8,378,322 B2
• Time in Patent Office: Days
• US Class Current: 250/492.1
• 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; and

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

Celsius, the micro-channel cooler assembly also providing a common anode substrate for the array, wherein 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.

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

3. The lamp head module of claim 1, wherein the micro-channel cooler assembly 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 no significant number of the LEDs are connected in series.

10. The lamp head module of claim 1, wherein coolant flow through the micro-channel cooler across and underneath the array is configured to be in a direction substantially parallel to a shortest dimension of the array.

11. The lamp head module of claim 10, wherein the coolant flow through micro-channels of the micro-channel cooler 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;

integrated LED drivers mounted to the outer walls of the lamp body;

wherein the deep and long coolant flow channels serve to balance flow of coolant through the micro-channel cooler and create a sufficient surface area to reduce heat transfer coefficient to maintain operational temperature requirements of the integrated LED drivers; and

wherein the thin outer walls of the lamp body allow for the lamp head module to be narrow which (i) reduces length requirement of the patterned cathode layer and (ii) reduces thermal resistance between coolant in the coolant flow channels and the integrated LED drivers.

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. A lamp head module comprising:

a high aspect ratio monolithically bonded foil micro-channel cooler substrate layer having a greater length than width;

a high aspect ratio light emitting device array layer having a greater length than width mounted to the micro-channel cooler substrate layer, wherein the micro-channel cooler substrate layer serves a common anode function for the light emitting device array layer, the light emitting device array layer having a high fill-factor and comprising a p-n junction 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 device array layer; and

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

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

19. The lamp head module of claim 18, wherein the light emitting device array layer emits incoherent light.

20. The lamp head module of claim 18, wherein the light emitting device 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.

21. The lamp head module of claim 20, 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.

22. The lamp head module of claim 18, 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 3×

the sum.

23. The lamp head module of claim 18, wherein the optical reflector layer has a center section that is wider than either the entrance aperture or the exit aperture.

24. The lamp head module of claim 18, 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.

25. The lamp head module of claim 18, 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.

26. The lamp head module of claim 18, 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 device array layer.

27. The lamp head module of claim 18, further comprising a wire layer and wherein the optical reflector layer is positioned with respect to the light emitting device 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 device array layer.

28. A lamp head module comprising:

a package including;

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

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

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

at least two anode bodies affixed to opposing sides of the lamp body, running substantially parallel to one another and orthogonal to the common anode substrate surface; and

a plurality of cathode bodies each having a first surface substantially parallel to the common anode substrate surface and a second surface substantially parallel to the at least two anode bodies, wherein the package is clamped to the lamp body and the at least two anode bodies by the plurality of cathode bodies.

29. 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;

an 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 an 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; and

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

Celsius, the micro-channel cooler assembly also providing a common anode substrate for the LED array, wherein a thermally efficient electrical connection is formed between the LED array and the common anode substrate by directly mounting the LED array to the micro-channel cooler assembly.

30. 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 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 LEDs in the array, the micro-channel cooler assembly also providing a common anode substrate for the array, wherein 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;

wherein 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.

31. The lamp head module of claim 30, wherein the array is directly mounted to a top surface of the micro-channel cooler portion.

32. The lamp head module of claim 31, wherein a vapor phase oven is used to reflow solder thereby mounting the array to the top surface of the micro-channel cooler portion.

33. The lamp head module of claim 32, wherein the solder is lead-free.

34. The lamp head module of claim 33, wherein a tacky flux is used to tack the LEDs in the array in place prior to placing the micro-channel cooler assembly in the vapor phase oven.

35. The lamp head module of claim 30, wherein the heat spreader layer is less than or equal to approximately 125 microns.

36. The lamp head module of claim 30, wherein the width of the micro-channel cooler portion is approximately 1.2 times the width of the array.

37. The lamp head module of claim 30, wherein:

the array includes at least two LEDs 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 individual LED of the array are cooled in thermal parallel.

38. A lamp head module comprising:

a package including;

a high aspect ratio array of light emitting devices having a greater length than width;

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

a high aspect ratio monolithically bonded foil micro-channel cooler having a greater length than width providing a common anode 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;

an anode body affixed to the lamp body, the anode body being substantially parallel to the input coolant fluid channel and the output coolant fluid channel and orthogonal to the common anode substrate surface;

a cathode body having a surface substantially parallel to the common anode substrate surface; and

wherein the package is clamped to the lamp body and the anode body.

39. The lamp head module of claim 38, wherein the high aspect ratio array is directly mounted to the common anode substrate surface.