Abstract:
A thermally controllable substrate is disclosed. The substrate supports a heat generating source. One of more microchannels are embedded within the substrate and preferably circulate a cooling fluid to dissipate heat being generated by the source. The flow of the cooling fluid serves to remove heat entering the substrate proximate the source providing for the use of enhanced electrical devices which generate more heat in their normal operation.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to a substrate for supporting a heat generating source. More particularly, the present invention relates to a substrate for supporting a heat generating source capable of dissipating heat away from the source.  
       BACKGROUND OF THE INVENTION  
       [0002]     Computer components can generate substantial heat which needs to be dissipated. For example, light-emitting diodes (LED), frequently used as light sources, generate a fair amount of heat. It is preferable to dissipate such heat to improve the operability and longevity of the heat source. Currently, the preferred way to achieve this is through the use of a substrate which incorporates a heat sink. Usually the heat sink is a mechanical radiator having a plurality of fins. The heat generated by the LED dissipates through the substrate and into the fins. In this matter, the heat is dissipated.  
         [0003]     A disadvantage of such a design is that the heat removal rate is relatively low. Additionally, the overall profile of the LED, substrate, and heat sink is relatively thick which limits its usefulness in certain applications where the dimension of the LED assembly is critical. Furthermore, the use of a plurality of such LED assemblies having a passive heat sink can increase the overall weight of the unit.  
         [0004]     As electrical components, such as an LED, improve in overall design and assume more significant operational requirements, the amount of heat generated by such units increases. This is also the case for other types of heat-generating computer components such as microprocessors. Therefore, the need exists for an improved substrate which can dissipate heat faster allowing such electrical devices to operate at faster rates and generate more heat.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     The present invention is a thermally controllable substrate for a heat-generating source, such as an LED, which includes an electrically conductive base having a longitudinal axis. At least one channel is formed within the base that is capable of conducting a cooling fluid.  
         [0006]     In the manufacture of such a substrate, an electrically conductive layer is provided having a first and second side. A strip is created along the first side of the layer. A second electrically conductive layer is attached to the first side of the first layer defining at least one enclosed channel capable of conducting a cooling fluid.  
         [0007]     The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which:  
         [0009]      FIG. 1  is a cross-sectional view of a portion of a substrate, according to embodiments of the present invention;  
         [0010]      FIG. 2  is a cross-sectional view of an alternate arrangement of a portion of a substrate, according to embodiments of the present invention;  
         [0011]      FIG. 3  is an unassembled top view of a substrate, according to embodiments of the present invention;  
         [0012]      FIG. 4  is an assembled top view of a substrate, according to embodiments of the present invention;  
         [0013]      FIG. 5  is an elevation view of yet another alternate arrangement of a substrate, according to embodiments of the present invention;  
         [0014]      FIG. 6  is a perspective view of the alternate arrangement shown in  FIG. 5 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]     Referring to  FIG. 1 , substrate  10  supports a heat generating source or electrical device, such as an LED chip  12 . Substrate  10  may support any type of heat generating device, such as a microprocessor, which generates heat during operation and, for optimal operational capability and reliability, requires the dissipation of that heat. Referring still to  FIG. 1 , LED chip  12  is electrically connected by a bond wire  14  to an electrical circuit. In this manner, light, and in turn heat, emanates from LED chip  12 . LED chip  12  may be encapsulated by a compliant and transparent material  16  for reliability and protectability. Substrate  10  is shown as comprising cathode pad  101 , anode pad  102 , layer  18  and layer  19 . Layers  18  and  19  are electrically conductive in whole or in part. Layer  18  is attached to pads  101  and  102 . Spaced intermediately between  18  and  19  are conductive spacers  11  which are attached, or at a minimum electrically connected, to the inside surfaces of layers  18  and  19 . In this manner, one or more open channels  13  are formed. Occasionally, channels  13  may be referred to as microchannels.  
         [0016]     In this manner, heat generated by LED chip  12  or other heat generating electrical device emanates through layer  18  and into microchannels  13 . A cooling fluid, such as a liquid, is circulated through channels  13  permitting transfer of the heat away from that portion of layer  19  and spacers  11  proximate LED chip  12 . Thus, substrate  10  acts as a heat dissipater transferring heat away from LED chip  12  through the circulation of the cooling fluid within microchannels  13 .  
         [0017]     Referring to  FIG. 2 , one or more microchannels  23  may be created by etching each microchannel on the inside surface of layer  18 . In this manner, separate spacers  11  are not required. Once layers  18  and  19  are attached, a cooling fluid is permitted to circulate within microchannels  23 . Etched microchannels  23  may be formed on layer  19  rather than layer  18 , or a combination of both.  
         [0018]     Referring to  FIGS. 3 and 4 , substrate  10  is shown during the assembly phase. Preferably, substrate  10  is manufactured of a flexible and pliable material, which is easily bendable into a final shape. As show in  FIG. 3 , substrate  10  may include one or more heat generating devices or sources such as LED chips  12 . Microchannels  13  pass through substrate  10 , preferably substantially parallel with the longitudinal axis of substrate  10 . During the manufacturing phase, substrate  10  may be bent and joined at its ends  31  as shown in  FIG. 4 . During the joining phase, the open ends of each microchannel are aligned to ensure fluid conductivity once ends  31  are joined. Thus, the cooling fluid may circulate through microchannels  13  in a loop fashion dissipating heat.  
         [0019]     Referring still to  FIG. 4 , an embodiment of the present invention may include a microelectrical mechanical system (MEMS) pump or similar device  41 , which is housed near or adjacent to one or more of microchannels  13 . A commercially available MEM pump  41  may be used to circulate the cooling fluid within each microchannel  13 . The circulating fluid within microchannel  13  withdraws the heat from that portion of substrate  10  proximate LED chip  12 . The heat within the fluid is then transferred to cooler portions of the substrate which serve to remove the heat and allow the fluid circulating within microchannels  13  to cool. Thus, the fluid circulating within microchannels  13  act as a fluid dissipating the heat and permitting the use of enhanced electrical devices such as faster microprocessors and brighter LEDs that improve the operability of the overall electrical system.  
         [0020]     Referring now to  FIG. 5 , yet another alternate embodiment of the present invention is shown. Rather than using a relatively flexible and pliable substrate  10  as shown in  FIGS. 3 and 4 , substrate  10  of  FIG. 5  comprises a relatively inflexible material such as aluminum or other metallic or metallic alloy materials. A heat-generating device, such as LED chips  12 , is shown attached to layer  51 . One or more microchannels  54  are machined or etched between layers  51 ,  52  and  53  so that when layers  51 ,  52  and  53  are joined a fully enclosed microchannel  54  is created. A cooling fluid is permitted to circulate within microchannel  54  thereby dissipating the heat being generated by LED chips  12 . A MEM pump  55  may be located proximate microchannel  54 . As discussed above, MEM pump  55  would be used to circulate the cooling fluid within microchannel  54  dissipating the heat being generated by each heat generating device.  
         [0021]     Referring now to  FIG. 6 , either the flexible substrate embodiment shown in  FIGS. 3 and 4  or the more inflexible substrate embodiment shown in  FIG. 5  may include auxiliary cooling systems. In  FIG. 6 , such an auxiliary cooling system is shown as auxiliary fins  56  preferably mounted perpendicular to the planer surface of layer  53 . Fins  56  are also shown in  FIG. 5 . In this manner, fins  56  serve to accelerate the dissipation of heat through the substrate  10  as the cooling fluid circulating within microchannel  54  dissipates heat away from the heat generating devices. In substitution of, or in addition to, fins  56 , the surface of layers  51 ,  52  and  53  may include a rough textured surface to further enhance the heat dissipating characteristics of substrate  10 .  
         [0022]     In any of the embodiments shown in  FIGS. 1-7 , microchannels  13 / 23 / 54  may be oriented to take advantage of gravitational forces. That is, the microchannels may be oriented to permit the hotter fluid circulating in each microchannel to rise distal the heat generating device thereby encouraging the cooler fluid circulating within the microchannel to sink and advance toward the heat generating device. This effect may be coupled with the circulatory flow provided by MEM pump  41 / 53  accelerates the dissipation of heat.  
         [0023]     It will be apparent to those skilled-in-the-art that the number of microchannels  13 / 23 / 54  can be modified to accommodate the particular heat generating properties of each electrical device. It may be beneficial, for example, to have a single large microchannel rather than several smaller microchannels with a larger MEMS pump operating through one channel to improve heat dissipation. Each microchannel  13 / 23 / 54  is filled with the cooling fluid through a pilot hole (not shown) which is sealed following filling.  
         [0024]     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.