US 20070091618 A1
The present invention provides a high power LED electro-optic assembly (40) including conductive heat sink (18) and an LED (14) mounted at one end of the heat sink. The LED (14) is in electrical engagement with the heat sink (18). The assembly (40) also includes a reflector (2) mounted at the other end of the heat sink. An insulating bond material (19) is provided between the reflector and the sink. The assembly (40) further includes a conductive bonding pin (15) extending through the reflector (12) and is in conductive engagement therewith and an electrical engagement (16) which electrically engages the pin (15) to the LED (14). Finally, an electric sleeve assembly (30) where the sleeve (32) is coated with an electrical insulating coating (34) is applied to the LED electro-optic assembly.
20. A method of forming a LED electro-optic assembly comprising the steps of;
conductively attaching at least one LED to a conductive heat sink.
surrounding said LED with a conductive reflector, said reflector including a bonding pin extending through; and
electrically engaging said bonding pin to said LED.
21. The method of
interposing an insulator between said reflector and said heat sink.
22. The method of
disposing an insulative bonding agent between said reflector and said heat sink.
23. The method of
interposing a conductive bonding wire between said pin and said LED.
24. The method of
25. A LED electro-optic retaining assembly comprising:
a generally cylindrical sleeve having an upper portion and a lower portion, said sleeve coated with an electrical insulator;
at least one passage located at an upper portion for insertion of a bonding agent, wherein said upper portion is modified to retain said electro-optic.
26. The assembly of
27. The assembly of
28. The assembly of
29. The assembly of
30. The assembly of
31. The assembly of
The present invention relates to light emitting diode (“LED”) technology, particularly to improvements in LED assemblies to provide a desired optical output for various lighting applications.
LED assemblies are well-known and commercially available. Such assemblies are employed in a wide variety of applications, typically for the production of ultraviolet radiation, used, for example, in effecting the curing of photo initiated adhesives and coative compositions.
Several factors play into the fabrication of LED assemblies. One is the control of high current supplied to the LEDs to provide a stable and reliable UV source. Another is the position of the lens to hold the output optic in place. Also, a means to provide a path for electrical conduction is required to supply control for the LED. As the current increases to the LED, the need for a high current, high reliability electrical contact becomes necessary. Additionally, a reflector forming the rays coming from the LED is often required. Furthermore, a cooling system is required to carry the heat away from the assembly. Presently, available, LED assemblies may not adequately offer all of these requirements.
Currently, manufacturers are providing a wide range of LED packages in a variety of forms. These packages range from conventional LED lamps to LEDs that use emitter chips of various sizes. While, many of the known LED assemblies produce a high light output, they produce a very disperse wide angle beam that is difficult to capture for efficient collimation and beam imaging in practical application, such as in a flashlight. As a result, a great deal of the output energy is lost as leakage out from the side of the LED package.
Additionally, light emitted from the LED assembly is ordinarily not evenly distributed. The shape of the light-emitting chip is projected on the target as a high intensity area. Reflections from the electrodes and walls from unpredictable patterns of light are superimposed on the main beam of light. As a result, undesirable hot spots and shadows appear on the object being illuminated. Accordingly, for any lighting application requiring a substantially even or uniform distribution of light over a predetermined area, a transmitting or partial diffuser must be used to scatter the light emitted from each individual LED assembly so that the hot spots and shadows do not appear on the object being illuminated. But, while a diffuser will eliminate hot spots and shadows, it is important that the “directivity” or geometry of the light beam emitted from an individual LED assembly not be degraded or diminished.
In order to overcome these above-noted disadvantages of known light sources, there is a need to provide an LED curing lamp assembly that has a flexible design, is easy to manufacture and reduces assembly cost.
In one embodiment of the present invention there is disclosed a LED electro-optic electrical sleeve assembly having a generally cylindrical sleeve coated with an electrical insulator. The assembly is divided into an upper portion and a lower portion, the upper and lower portion separated by an insulating material. At least one LED and a conductive reflector is mounted at the upper portion, where the reflector surrounds the LED. A conductive heat sink is mounted at the lower portion, and is in electrical engagement with the LED. Additionally a conductive bonding pin extends through the conductive reflector and is in conductive engagement therewith. An electrical engagement electrically engages the bonding pin to the LED, where the heat sink and the reflector form an electrically conductive location for supplying power to said LED.
When current flows through a chip in an individual LED assembly, both light and heat are generated. Increasing the current through the chip raises the light output but increased current flow also raises the temperature of the chip in the individual LED assembly. This temperature increase lowers the efficiency of the chip. Overheating is the main cause of the failure of individual LED assemblies. To assure safe operation, either the current, and as a result the light output, must be kept at a low level or some other means of transferring heat away from the chip in the individual LED assembly must be provided. Therefore, lower electrode 10 b may be defined by with an electrically conducting thermal heat sink 18 which also serves to carry heat away from the LED chip 14. The upper electrode 10 a and the lower electrode 10 b are held together by an electrically insulating material 19 such as a non-conductive adhesive. The LED 14 is disposed in the assembly 10 in such a manner that the bottom surface is bonded or soldered to the thermal heat sink 18 via the bond material 19. In order to allow the electrical connection through the LED 14, voltage is applied to both upper and lower electrodes 10 a and 10 b respectively. This causes the heat sink 18 to carry off heat and the curved surface of the reflector 12 forms the light from the LED 14 into a desired pattern. Even though only single LED 14 is shown in
By providing one of the electrical contacts 10 a in conjunction with the reflector and the other electrical contact 10 b in conjunction with thermal heat sink, the LED ray forming contact assembly 10 is easy to manufacture, reduces the assembly cost and simplifies the final assembly. Furthermore, the LED ray forming contact assembly 10 also allows the scaling up to multiple LEDs in an assembly without adding significant complexity.
To further exemplify the operation of the entire optical assembly
The converging action of the lens 22 depends on both the radius of lens 22 and the positioning of the lens 22 with respect to the individual LED assembly 20. Both the radius and position of the lens 22 may be established during the design process to optimize illumination of the object. The ability to precisely locate and fixture the optic lens 22 is a critical concept in this application. The lens 22 needs to be positioned at right distance from the LED 14 in order to achieve the desired light output.
The number of LED assemblies employed determines the size of a LED array and the desired output intensity. An end user can easily increase or decrease the output intensity by adding/removing LED assemblies to/from the LED array. Also, a user can change the operating wavelength of the assembly by replacing one or more LED assemblies of a first operating wavelength with one or more replacement assemblies having a second wavelength. In addition, a user can replace damaged or expired LED assemblies without replacing the entire LED array.
Regarding the optical properties of the optical assembly 10 and 20, each, LED 14, emits diffuse light at a predetermined optical power and a predetermined optical wavelength. Exemplary LEDs 14 according to the present invention emit preferably greater than 500 mw of optical power at desirably 405 nm. The reflective cavity collimates a majority of the diffuse light emitted by the LED 14 when the LED 14 is placed at the desired location within the reflective cavity. The parabolic reflector 12 represents an exemplary reflective cavity that collimates the majority of the light when the LED 14 is placed at or near the focal point of elliptic reflector 12, as shown in
In order to make small optical assemblies, preferably such as LED optical assemblies, it is necessary to have a means to hold the output optic in place and also provide a path for electrical conduction. One such means is an electrical sleeve assembly 30 shown in
The LED 14 is combined with the ray forming contact assembly 10, LED variable optical assembly 20 and the LED lens retaining electrical sleeve assembly 30 to form a complete LED electro-optic assembly 40 as shown in
Finally, the LED lens retaining electrical sleeve assembly 30 is installed while applying the structural adhesive 34 on the thermal heat sink 18. The reflector 12 is preferably bonded to the thermal heat sink 18 with the structural adhesive 34. So, the structural adhesive 34 functions to hold the assembly securely together, providing some thermal conduction and additional electrical insulation from the thermal heat sink 18. Additionally, a conductive adhesive 36 is preferably applied to the slots 36 to bond the outside sleeve 32 to the reflector 12. Alternatively, as discussed above, a wire, preferably aluminum (not shown) may be used to wire bond between the reflector 12 inside the assembly and the outside sleeve 32 preferably made of aluminum. Preferably, multiple wire bonds are used to bond the reflector 12 and a recess (not shown) below the surface of the outside sleeve 32. Also, the recess is desirably coated for protection. The conductive material is heat cured and the complete LED electro-optic assembly 40 is formed. Again, the assembly 40 shows only a single LED 14, multiple LED devices may preferably be bonded to the assembly.
Individual alignment of the LED 14 or multiple LEDs is required because no two individual LED assemblies are exactly the same. Differences arise from the positioning of the chip 14 inside the reflector 12, the positioning of the reflector cup 12, the positioning of the electrodes 10 a and 10 b, and the positioning of the optic lens 22. All of these factors affect the geometry and direction of the beam of light. Due to the manufacturing process of individual LED assemblies, the components in individual LED assemblies exhibit a very wide range of positional relationships. Therefore, for any application that requires illumination of a specific area, each individual LED assembly must be manually aligned and then permanently held in place by some means of mechanical support.
While a single LED is used herein to illustrate the invention, it will be understood by those skilled in the art that the invention described herein applies to a plurality of LEDs or LED array. A plurality of LEDs may be arranged in any manner as desired for illumination.
Even though, in the present invention the LED 14 is shown to be a rectangular frame, those of ordinary skill in the art will understand that according to the disclosed invention, LED illuminators may be formed in any shape suitable to provide light for a wide array of applications, including but not limited to photocuring, video, shop windows, photography or specialty product displays. Because of the durability and rugged construction of the disclosed LED illuminator, it may be used in outdoor settings, marine applications, or hostile environments.