Abstract:
A system is disclosed for thermal conduction interfacing. The system for thermal conduction interfacing is provided with a first layer formed substantially of a pliable thermally conductive material. The system includes a second layer formed substantially of a pliable thermally conductive material and coupled at the edges to the first layer forming a pliable packet, wherein the first layer and the second layer conform to a set of thermal interface surfaces. Additionally, the system includes a plurality of thermally conductive particles disposed within the packet, wherein thermal energy is transferred from the first layer to the second layer through the thermally conductive particles. Beneficially, such a system would provide effective thermal coupling between a heat generating device and a heat dissipating device. Additionally, the system would be modular, reusable, and easy to install or replace without a significant mess.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional application and claims priority to U.S. patent application Ser. No. 11/343,673 entitled “Apparatus, System, and Method for Thermal Conduction Interfacing” and filed on Jan. 31, 2006 for Timothy S. Farrow, et al., which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to dissipation of thermal energy generated by an electronic component and more particularly relates to thermal conduction interfacing. 
       BACKGROUND 
       [0003]    One of the primary problems encountered in electronics design is excess thermal energy generated by inefficiencies in the electronic components. For example, as current flows through electric circuitry, some of the electric energy is converted to thermal energy through inefficiencies in the circuit components. Unless the excess thermal energy is dissipated, the electronic components may become increasingly inefficient. The increased inefficiency generates additional thermal energy, and the cycle continues until the component fails. 
         [0004]    For example, in an electrical transistor, heat is generated as current flows from one gate of the transistor to another. The heat is generated by inefficiencies in the transistor. Such inefficiencies may include impurities in the silicon, imperfect electron doping, and certain inefficiencies are unavoidably inherent in the device structure and material. As heat is generated, the transistor becomes more and more inefficient, and may eventually fail due to a thermally induced current run-away. 
         [0005]    Heat issues are particularly critical in microelectronic circuit packages, such as computer processor chip packages. These microelectronic circuit packages may contain thousands of transistors and other electronic components within a confined space. Additionally, these circuits are typically enclosed in a single chip package for protection and modularity. Consequently, these processor chip packages may reach temperatures of well over 100 degrees Fahrenheit within minutes of operation. Obviously, without a highly efficient method of dissipating the heat generated in such circuits, these microelectronic chip packages would fail to operate properly. 
         [0006]    Electronics designers have implemented several different methods of heat dissipation in electronic components. These methods include the use of fans and enclosure venting, heatsink devices, liquid cooling, and the like. However, improvements in electronic technology make possible higher processing speeds and more components within a smaller space. These improvements, while beneficial, complicate the task of heat dissipation. Many of the smaller components are more sensitive to heat. Since more components can be placed in a smaller space, the heat generated is greater. Therefore, the need for improved heat dissipation is ever increasing. 
         [0007]    Certain of the methods described above, such as heatsinks, can dissipate heat effectively, but only when installed properly and used in combination with efficient thermal coupling products. For example, a heatsink coupled directly to a processor package will not adequately dissipate heat unless thermal grease is spread between the heatsink and the processor package. Thermal grease fills the gaps between the thermal interface surfaces on the heatsink and the processor package formed by irregularities in those surfaces. Even slight irregularities in these surfaces may result in air gaps which may significantly reduce thermal coupling between the processor package and the heatsink. 
         [0008]    The major drawback with thermal grease is that it is very messy. The grease is difficult to contain once placed in the thermal interface. The grease may run when the temperature is elevated because the viscosity of grease decreases with increased temperature. Additionally, thermal grease does not have an indefinite shelf life. Thermal grease may crust over, or become runny or separated, or become soiled by dust. Any changes in the physical properties of the thermal grease may decrease its effectiveness. 
         [0009]    If the thermal grease spoils it must be replaced to insure the protection and proper operation of the processor. Typically, only trained technicians are able to properly change thermal grease. In general, thermal grease is not an optimal solution, because it is messy and costly to regularly replace. 
         [0010]    From the foregoing discussion, it should be apparent that a need exists for an apparatus, system, and method that facilitate a more efficient thermal conduction interface between an electronic component and a heat dissipating device such as a heatsink. Beneficially, such an apparatus, system, and method would provide effective thermal coupling between a heat generating device and a heat dissipating device. Additionally, the apparatus, system, and method would be modular, reusable, and easy to install or replace without a significant mess. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available thermal interface products. Accordingly, the present invention has been developed to provide an apparatus, system, and method for thermal conduction interfacing that overcome many or all of the above-discussed shortcomings in the art. 
         [0012]    The apparatus for thermal conduction interfacing is provided with a first layer formed substantially of a pliable thermally conductive material. The apparatus includes a second layer formed substantially of a pliable thermally conductive material and coupled at the edges to the first layer forming a pliable packet, wherein the first layer and the second layer conform to a set of thermal interface surfaces. Additionally, the apparatus includes a plurality of thermally conductive particles disposed within the packet, wherein thermal energy is transferred from the first layer to the second layer through the thermally conductive particles. 
         [0013]    In one embodiment, the apparatus further comprises a mechanism for application of force on the first and second layers, the thermally conductive particles, and the thermal interface surfaces. In a certain embodiment, the mechanism further comprises rounded packet edges to provide a spring member for application of force. The first and the second layers are further configured to conform to an uneven interface surface and substantially fill air gaps between the thermal interface surfaces when force is applied. 
         [0014]    In a further embodiment, the thermally conductive particles may be structurally compliant forming a semisolid thermally conductive structure within the packet when force is applied. Additionally, the thermally conductive particles may be structurally resilient making the apparatus reusable. The apparatus may be further configured to conduct thermal energy between the thermal interface surfaces of an electronic component package and a heatsink. 
         [0015]    A system of the present invention is also presented for thermal conduction interfacing. In one embodiment, the system includes a heat generating device, a heat dissipating device, and a thermal conduction interface packet. In a further embodiment, the thermal conduction interface packet may include a first layer formed substantially of a pliable thermally conductive material, a second layer formed substantially of a pliable thermally conductive material and coupled at the edges to the first layer forming a pliable packet, and a plurality of thermally conductive particles disposed within the packet. Additionally, the first layer may conform to the surface of the heat generating device and the second layer may conform to the surface of the heat dissipating device. The system may be further configured to transfer thermal energy form the first layer to the second layer through the thermally conductive particles. In a particular embodiment, the heat generating device may be an electronic component package and the heat dissipating device may be a heatsink. 
         [0016]    A method of the present invention is also presented for thermal conduction interfacing. The method in the disclosed embodiments substantially includes the steps necessary to carry out the functions presented above with respect to the operation of the described apparatus and system. In one embodiment, the method includes providing a first layer formed substantially of a pliable thermally conductive material, coupling a second layer, formed substantially of a pliable thermally conductive material, to the edges of the first layer forming a pliable packet, wherein the first layer and the second layer conform to a set of thermal interface surfaces, and inserting a plurality of thermally conductive particles into the packet, wherein thermal energy is transferred from the first layer to the second layer through the thermally conductive particles. 
         [0017]    The method also may include applying a perpendicular force to the thermal interface surfaces and the packet, wherein the first and second layer are further configured to conform to an uneven interface surface and substantially fill air gaps between the thermal interface surfaces when force is applied. In one embodiment, the method includes transferring thermal energy through a semisolid thermally conductive structure formed within the packet when force is applied. The method may further include reusing the packet to facilitate efficient thermal conduction between a plurality of sets of thermal interface surfaces. 
         [0018]    Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present invention should be or are in any single embodiment of the invention. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, discussion of the features and advantages, and similar language, throughout this specification may, but do not necessarily, refer to the same embodiment. 
         [0019]    Furthermore, the described features, advantages, and characteristics of the invention may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize that the invention may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the invention. 
         [0020]    These features and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    In order that the advantages of the invention will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which: 
           [0022]      FIG. 1A  is a cross-section view of an apparatus for thermal conduction interfacing token through  1 - 1  of  FIG. 1B ; 
           [0023]      FIG. 1B  is a cross-section view of an apparatus for thermal conduction interfacing token through  1 - 1  of  FIG. 1B ; 
           [0024]      FIG. 2  is a side view of a system for thermal conduction interfacing; 
           [0025]      FIG. 3A  is a partially enlarged cross-section view of an uncompressed thermal conduction interface packet; 
           [0026]      FIG. 3B  is a partially enlarged cross-section view of a compressed thermal conduction interface packet; 
           [0027]      FIG. 4A  is an exaggerated view of thermal interface surfaces of a heat generating device and a heat dissipating device; 
           [0028]      FIG. 4B  is an exaggerated view of a thermal conduction interface packet implemented at the interface of the heat generating device and the heat dissipating device; 
           [0029]      FIG. 5  is a schematic flow chart diagram illustrating one embodiment of a method for thermal conduction interfacing; and 
           [0030]      FIG. 6  is a detailed schematic flow chart diagram illustrating one embodiment of a method for implementing a thermal conduction interface packet. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment. 
         [0032]    Furthermore, the described features, structures, or characteristics of the invention may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention. 
         [0033]      FIG. 1A  depicts a cross-section view token through line  1 - 1  of an apparatus  100  for thermal conduction interfacing. In one embodiment, the apparatus includes a first layer  102  and a second layer  104  coupled at the edges  106  and filled with a plurality of thermally conductive particles  108 . The first layer  102  and the second layer  104  may be coupled at the edges to form a packet. Alternatively, a packet may be formed of a single layer  102  or bag and coupled to itself on one edge  106 . 
         [0034]    In one embodiment, the first layer  102  and the second layer  104  are formed of a pliable thermally conductive material. In one embodiment the material is copper foil. Alternatively, the material may include thin layers of aluminum, gold, or other thermally conductive metals, and alloys thereof. In these various embodiments, the first layer  102  and the second layer  104  may be flexible, pliable, and resilient. In such embodiments, these layers  102 ,  104  may conform to a set of thermal interface surfaces when force is applied. The pliability and flexibility of the layers  102 ,  104  allow the apparatus  100  to substantially fill air gaps created by irregularities in the thermal interface surfaces. This characteristic of the apparatus  100  are described in greater detail with respect to  FIG. 4B . 
         [0035]    In one embodiment, the first layer  102  and the second layer  104  are coupled at the edges  106  to form a packet. In one embodiment, the layers  102 ,  104  may be coupled with an adhesive. Alternatively, the layers  102 ,  104  may be coupled using heat bonding, ultrasonic welding, current welding, heat welding, or the like. In an alternative embodiment, the first layer  102  and the second layer  104  may be replaced by a bag or sack structure for holding the thermally conductive particles  108 . 
         [0036]    In one embodiment, the thermally conductive particles  108  are formed of thermally conductive metal or metal alloy. For example, the thermally conductive particles  108  may be copper microspherules. Alternatively, the thermally conductive particles  108  may include gold microspherules. In another alternative embodiment, the thermally conductive particles  108  may be formed of diamond. The thermally conductive particles are in one embodiment sized between one thousandth of an inch and five thousands of an inch in diameter of course any suitable size may be used. In another embodiment, the particles are sized in a range of between about 0.0001 inches and about 0.01 inches in diameter. 
         [0037]    In another alternative embodiment, the thermally conductive particles  108  may include a thermally conductive fluid compound such as thermal grease or a water/helium combination. 
         [0038]      FIG. 1B  depicts a cross-sectional view of a thermal conduction interface packet  110  token through line  1 - 1  of  FIG. 1B . In one embodiment, the apparatus  100  comprises a thermal conduction interface packet  110 . The thermal conduction interface packet  110  may include a first layer  112  and a second layer  114  coupled at the edges to form a thermal conduction interface packet  110 . In a further embodiment, the thermal conduction interface packet includes a plurality of thermally conductive particles  118  disposed within the packet  110 . In certain embodiments, the thermal conduction interface packet  110  is rectangular. Alternatively, the thermal conduction interface packet  110  may be square, circular, oval, or other shape specifically suited for the thermal interface surfaces with which the packet  110  is intended to be used. 
         [0039]      FIG. 2  illustrates one embodiment of a system  200  for thermal conduction interfacing. In one embodiment, the system  200  includes a structural support base  202 , such as a circuit card. Additionally, the system  200  may include a heat generating device  204 , and a heat dissipating device  208 . The heat generating device  204  may include a thermal interface surface  206 , and the heat dissipating device  208  may include a thermal interface surface  210 . Additionally, the system may include a thermal conduction interface packet  110  as illustrated in  FIGS. 1A and 1B . In one further embodiment, the system  200  may include a mechanism  212 ,  214  for applying force on the system components. 
         [0040]    In one embodiment, the heat generating device  204  is an electronic component package. For example, the heat generating device  204  may include a computer processor package. In alternative embodiments, the heat generating device may include high performance microelectronic circuit packages such as Digital Signal Processing (DSP) chip packages or MODEM chip packages. In a further embodiment, the heat generating device  204  may include a large scale electronic component such as a solid state RF amplifier or an electronic circuit enclosure or housing. 
         [0041]    In one particular embodiment, the heat dissipating device  208  is a heatsink. The heatsink may include a thermal interface surface  210  and a plurality of heat dissipating fins for spreading thermal energy from the thermal interface surface  210  to the ambient air. In alternative embodiments, the heat dissipating device  208  may include a heat dissipating device which incorporates heat pipe or other liquid cooling system. 
         [0042]    In one embodiment, the system  200  further comprises a mechanism  212 , 214  for applying force perpendicular to the thermal interface surface  206  of the heat generating device  204 , the thermal interface surface  210  of the heat dissipating device  208 , and the thermal conduction interface packet  110 . In a certain embodiment, the mechanism includes a threaded screw  212  for coupling the heat dissipating device  208  to the structural support base  202  over the area of the heat generating device  204 . The threaded screws  212  may screw into threaded posts attached at predetermined positions on the structural support base  202 . Additionally, the mechanism may include rounded edges on the thermal conduction interface packet  110  which may act as a spring member to facilitate application of force using the screws  212  and the posts  214 . In another alternative embodiment, the screws  212  and the posts  214  may be replaced by a mounted clamp, or the like. 
         [0043]    In one embodiment, the thermal conduction interface packet  110  may conduct thermal energy from the thermal interface surface  206  of the heat generating device  204  to the thermal interface surface  210  of the heat dissipating device  208  through a semisolid structure of thermally conductive particles  108 ,  118  formed when force is applied to the components of the system  200 . The characteristics of the thermally conductive particles  108 ,  118  under force are described in further detail with relation to  FIG. 3B . 
         [0044]      FIG. 3A  is a partially enlarged cross-sectional view of an uncompressed thermal conduction interface packet  302 . In the depicted embodiment, the thermal conduction interface packet includes a first layer  112  and a second layer  114  coupled to form a packet  110  as depicted in  FIG. 1 . The thermal conduction interface packet  302  includes a plurality uncompressed thermally conductive particles  304 . In the embodiment depicted in the exploded view, each particle  306  may be a microspherule of a substantially spherical shape. The particles  306  be randomly distributed without any particular structure and may be loosely packed within the packet  302 . 
         [0045]      FIG. 3B  is a partially enlarged cross-sectional view of a compressed thermal conduction interface packet  312 . In one embodiment, a force  318  is applied to the thermal conduction interface packet  312  compressing the thermally conductive particles  314 . In certain embodiments, the edges  320  of the thermal conduction interface packet are rounded. The rounded edges allow the thermal conduction interface packet  312  to expand and retract slightly. In such an embodiment, the thermal conduction interface packet  312  acts as a spring member to facilitate application of the force  318 . Some mechanism for facilitating application of the force  318  is required to compress the thermally conductive particles. The application of pressure on rigid bodies will not result in force  318  on the bodies unless there is some mechanism, such as a spring member, to facilitate application of the force  318 . In an alternative embodiment, some other mechanism for facilitating application of the force  318 , such as coil springs, or the like may be provided. In another embodiment, the edges  320  may be thicker than other portions of the first layer  102 , and the second layer  104  to create the spring member for application of the force  318 . 
         [0046]    The exploded view of the thermally conductive particles  316  illustrate compressed particles under the force  318 . In one embodiment, the particles  316  are structurally compliant. For example, the particles  316  may distort to conform to the surfaces of the other particles  316  when tightly packed. In a further embodiment, the particles  316  may pack tightly in a lattice type semisolid structure. In such an embodiment, the semisolid structure has increased thermal conductivity, because the surfaces are each conforming, one to another, and the air gaps between particles  316  are reduced. In a further embodiment, the thermally conductive particles  316  are structurally resilient, substantially returning to their original shape and distribution, as depicted by the particles  306  in  FIG. 3A , when the force  318  is removed. Consequently, the thermal conduction interface packet  312  may be reusable. 
         [0047]      FIG. 4A  is an exaggerated illustration of thermal interface surfaces of a heat generating device  402  and a heat dissipating device  404 . Although the irregularities would typically not be as clearly visible as depicted in this drawing, some irregularities may exist in the thermal conduction surfaces of the heat generating device  402  and the heat dissipating device  404 . Irregularities may include surface bumps or voids, slight variants in the surface levels, and the like. Consequently, some portions of the conduction interface surfaces may come into contact before others. The resulting air gaps  406  may reduce thermal conduction efficiency. 
         [0048]      FIG. 4B  is an exaggerated view of a thermal conduction interface packet  416  implemented at the interface between a heat generating device  412  and a heat dissipating device  414 . In such an embodiment, the pliable surfaces of the thermal conduction interface packet  416  conform to the surfaces of the heat generating device  412  and the heat dissipating device  414  respectively. In one embodiment, thermal conduction interface packet is capable of flexibly conforming to the irregularities in the surfaces of the heat generating device  412  and the heat dissipating device  414  and substantially filling air gaps between the surfaces when force is applied. Consequently, the thermal conduction interface packet  416  may improve thermal conduction between the thermal interface surfaces of the heat generating device  412  and the heat dissipating device  414 . 
         [0049]    The schematic flow chart diagrams that follow are generally set forth as logical flow chart diagrams. As such, the depicted order and labeled steps are indicative of one embodiment of the presented method. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the illustrated method. Additionally, the format and symbols employed are provided to explain the logical steps of the method and are understood not to limit the scope of the method. Although various arrow types and line types may be employed in the flow chart diagrams, they are understood not to limit the scope of the corresponding method. Indeed, some arrows or other connectors may be used to indicate only the logical flow of the method. For instance, an arrow may indicate a waiting or monitoring period of unspecified duration between enumerated steps of the depicted method. Additionally, the order in which a particular method occurs may or may not strictly adhere to the order of the corresponding steps shown. 
         [0050]      FIG. 5  illustrates one embodiment of a method  500  for thermal conduction interfacing. In one embodiment, the method starts  502  with providing  504  a first layer  102 . In one particular embodiment, the first pliable layer  102  is formed substantially of a pliable thermally conductive material. In one embodiment, a second layer  104  is coupled  506  to the first layer  102 . In a further embodiment, the second layer  104  is also formed substantially of a pliable thermally conductive material. Additionally, the second layer  104  may be coupled to the first layer  102  at the edges forming a pliable packet  110 . The first layer  102  and the second layer  104  may be configured to conform to a set of thermal interface surfaces  206 ,  210 . In a further embodiment, the method  500  includes inserting  508  a plurality of thermally conductive particles  108  into the packet  110 . In an additional embodiment, thermal energy is transferred from the first layer  102  to the second layer  104  through the thermally conductive particles  108 , and the method  500  ends  510 . 
         [0051]    For example, the method  500  may include providing  504  a first layer  102  formed substantially of a pliable copper foil. Then a second layer  104 , formed substantially of a pliable copper foil, is coupled  506  at the edges to the first layer  102  forming a flexible packet  110 . Then, a plurality of copper microspherules are inserted  508  within the packet  110  forming a pliable thermal conduction interface packet  110  configured to conform to the edges of a set of thermal interface surfaces  206 ,  210 , and transfer heat from the first layer  102  to the second layer  104  through the thermally conductive particles  108 . 
         [0052]      FIG. 6  illustrates one embodiment of a method  600  for thermal conduction interfacing. In one embodiment, the method  600  starts  602  with forming  500  a thermal conduction interface packet  110 . The method  600  may additionally include providing  604  rounded packet edges  320  for facilitating application of force  318 . In a further embodiment, the method  600  includes placing  606  the thermal conduction interface packet  110  between the thermal interface surfaces  206 ,  210  of a heat generating device  204  and a heat dissipating device  208 . In a particular embodiment, the heat generating device  204  is an electronic component package and the head dissipating device  208  is a heatsink. 
         [0053]    The method  600  may additionally include applying  608  force  318  to the thermal interface surfaces  206 ,  210  and the thermal conduction interface packet  110 . Then thermal energy may be transferred  610  through a semisolid particle structure created by compressed thermally conductive particles  316  within the thermal conduction interface packet  110 . If it is determined  612  that the heat generating device  204  or the heat dissipating device  208  is obsolete or not needed, the thermal conduction interface packet  110  may be removed and reused  614  between a new heat generating device  204  and a new heat dissipating device  208  and the method ends  616 . If it is determined  612  that the electronic components are not obsolete, the thermal interface packet  110  may remain in use throughout the lifetime of the heat generating device  204  and the heat dissipating device  208 , and the method ends  616 . 
         [0054]    For example, the method  600  may include providing  500  a thermal conduction interface packet  110  in accordance with the example described with relation to  FIG. 5  above. Additionally, the method  600  may include providing  604  rounded edges on the thermal conduction interface packet  110  making the packet  110  act as a spring member for facilitating the application of force  318  on the system  200 . The copper thermal conduction interface packet  110  may be placed  606  between a computer system processor  204  and a heatsink device  208 . 
         [0055]    The method  600  may additionally include applying  608  a force  318  to the system  200  by applying pressure with the threaded screws  212  and the threaded posts on the components including the thermal conduction interface packet  110  with rounded edges  320  configured to act as a spring member for the system  200 . When the processor chip is powered, it may transfer  610  heat from the thermal interface surface  206  through the thermal conduction interface packet  110  to the thermal interface surface  210  of a heatsink  208 . If it is determined  612  that the processor  204  is obsolete or not needed, the thermal conduction interface packet  110  may be removed from the system  200  and reused  614  in a new system  200 . 
         [0056]    The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.