Abstract:
A heat pipe system including a heat transfer block and a heat pipe coupled to the heat transfer block by a clip. By utilizing a clip to couple the heat pipe to the heat transfer block, a higher degree of thermal coupling may be achieved, thereby allowing more heat to be transferred from the heat transfer block to the heat pipe. The heat pipe system has particular application in transferring heat away from heat-producing electronic components, such as computer chips.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a method and apparatus for a heat pipe system for removing heat from electronic equipment, and in particular, a heat pipe system for removing heat from a laptop computer.  
         DESCRIPTION OF THE RELATED ART  
         [0002]    A basic heat pipe comprises a closed or sealed envelope or a chamber containing an isotropic liquid-transporting wick and a working fluid capable of having both a liquid phase and a vapor phase within a desired range of operating temperatures. When one portion of the chamber is exposed to relatively high temperature it functions as an evaporator section. The working fluid is vaporized in the evaporator section causing a slight pressure increase forcing the vapor to a relatively lower temperature section of the chamber defined as a condenser section. The vapor is condensed in the condenser section and returned through the liquid-transporting wick to the evaporator section by capillary pumping action.  
           [0003]    Because it operates on the principle of phase changes rather than on the principles of conduction or convection, a heat pipe is theoretically capable of transferring heat at a much higher rate than conventional heat transfer systems. Consequently, heat pipes have been utilized to cool various types of high heat-producing apparatus, such as electronic equipment (See, e.g., U.S. Pat. Nos. 5,884,693, 5,890,371, and 6,076,595).  
           [0004]    Heat pipe assemblies are often used to remove heat from the Central Processing Unit (CPU) and other high power chips in computers. Maintenance of a good contact between the CPU (or other chip) and the heat pipe assembly is essential for insuring good overall heat transfer.  
           [0005]    Some conventional heat pipe assemblies create a contact between the CPU (or other chip) and a portion of the heat pipe through a heat transfer plate. Such heat transfer plates are disposed either above or below the CPU or chip, and are typically centered on the CPU or chip by guide members on the heat transfer plate which interface with guide members on the CPU or chip.  
           [0006]    Most conventional heat transfer plates comprises metal blocks with at least one tunnel or recess therein for receiving a flattened end of the associated heat pipe. FIG. 1 shows such a conventional heat pipe system  200 . The heat pipe system  200  includes a heat transfer block  210 , a heat pipe  220 , and a heat dissipation structure  230 . In a typical environment, such heat pipe system  200  would be disposed in proximity to a heat-producing apparatus (e.g. CPU, chip, etc.), such that the heat transfer block  210  would be in direct contact with the heat-producing apparatus. The heat transfer block  210  includes a tunnel  211  therein for receiving a flattened portion  221  of the heat pipe  220 . The heat pipe  220  also includes a crimped end or ‘pinchoff’ portion  222  disposed at one end of the flattened portion  221 . An end of the heat pipe  220  opposite the flattened portion  221  is coupled to the heat dissipation structure  230  (e.g., fin block). During manufacture of the heat pipe system shown in FIG. 1, the flattened portion  221  of the heat pipe  220  is inserted into the tunnel  211  in the heat transfer block  210 , and is secured therein.  
           [0007]    Since this tunnel  211  in the heat transfer block  210  must be made large enough to receive the flattened end  221  of the heat pipe  220 , and the pinchoff portion  222  of the heat pipe, the tunnel must be made at least as wide as the pinchoff. Since the pinchoff  222  is almost always wider than the flattened portion  221  of the heat pipe  220 , the flattened portion of the heat pipe does not fit snugly in the tunnel  211 , and thus, a poor heat contact is created between the flattened portion of the heat pipe and the heat transfer block  210 . Due to the poor heat contact between the flattened portion of the heat pipe  220  and the heat transfer block  210 , maximum heat cannot be transferred from the CPU or chip to the heat pipe through the heat transfer plate.  
           [0008]    Therefore, there is currently a need for a heat pipe system for effectively transferring maximum heat from a CPU (or other chip) to a heat pipe assembly in a computer.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention is a heat pipe system including a heat transfer block and a heat pipe coupled to the heat transfer block by a clip.  
           [0010]    The above and other advantages and features of the present invention will be better understood from the following detailed description of the exemplary embodiments of the invention which is provided in connection with the accompanying drawings.  
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a perspective view showing a conventional heat pipe system.  
         [0012]    [0012]FIG. 2 is a perspective view showing a heat pipe system according to a first exemplary embodiment of the present invention.  
         [0013]    [0013]FIG. 3 is a perspective view showing a magnified version of the heat pipe system shown in FIG. 2.  
         [0014]    [0014]FIG. 4 is a perspective view showing an exploded and magnified version of the heat pipe system shown in FIG. 2.  
         [0015]    [0015]FIG. 5 is a perspective view showing a heat pipe system according to a second exemplary embodiment of the present invention.  
         [0016]    [0016]FIG. 6 is a perspective view showing an exploded version of the heat pipe system shown in FIG. 5.  
         [0017]    [0017]FIG. 7 is a perspective view showing a heat pipe system according to a third exemplary embodiment of the present invention.  
         [0018]    [0018]FIG. 8 is a perspective view showing an enlarged of the heat pipe system shown in FIG. 7. 
     
    
     DETAILED DESCRIPTION  
       [0019]    The present invention comprises an improved apparatus and method for transferring heat from a heat-producing electronic equipment (e.g., CPU or other computer chip) to a heat pipe through the use of a heat transfer plate. By attaching the heat pipe to the heat transfer plate through a clip placed in the center of the heat transfer plate, maximum heat transfer from the heat transfer plate to the heat pipe can be achieved.  
         [0020]    Referring to FIG. 2, there is shown a heat pipe system  100  according to a first exemplary embodiment of the present invention. The heat pipe system  100  comprises a heat transfer block  110 , a heat pipe  120 , and a heat dissipation structure  130 .  
         [0021]    The heat transfer block  110  includes a channel  111  therein for receiving a flattened portion  121  of the heat pipe  120 . The heat pipe  120  also includes a pinchoff portion  122  disposed at one end of the flattened portion  121 . An end of the heat pipe  120  opposite the flattened portion  121  is coupled to the heat dissipation structure  130  (e.g., fin block). One end of the channel  111  of the heat transfer block  110  has a flared portion  112  for receiving the pinchoff portion  122  of the heat pipe  120 . A clip member  140  overlies and secures the flattened portion  121  of the heat pipe  120  in the channel  111 . It will be noted that the clip member  140  includes a main surface  141 , and two side surfaces  142 ,  143  disposed orthogonal to the main surface. The main surface  141  primarily overlies the flattened portion  121  of the heat pipe  120 , and the two side surfaces  142 ,  143  primarily reside in clip channels  113 , when the clip  140  is coupled to the heat transfer block  110 .  
         [0022]    [0022]FIG. 3 shows an enlarged view of the heat pipe  120  and heat transfer block  110  of the heat pipe system  100  according to the first exemplary embodiment of the present invention. It will be noted that the flattened portion  121  of the heat pipe is secured in the channel  111  of the heat transfer block  110  by the clip member  140 .  
         [0023]    [0023]FIG. 3 explicitly shows that the two side surfaces  142 ,  143  of the clip are received in clip channels  113  formed in the heat transfer block  110 . It will be noted that although the clip channels  113  are formed as channels of a specific length which is less then the length of the transfer block  110 , the clip channels may also be formed as full-length channels, such as channel  111 . As will be understood by those skilled in the art, forming the clip channels  113  as full-length channels may reduce the expense of producing the heat transfer block  110  by allowing the transfer block to be formed completely by extrusion processes. The flattened portion  121  of the heat pipe  120  and the clip  140  may be secured in the channel  111  and the clip channels  113  respectively by fasteners (e.g., screws, bolts, stakes, rivets, etc.), solder, epoxy or other known materials.  
         [0024]    Alternatively, the flattened portion  121  of the heat pipe  120  and the clip  140  may be secured in the channel  111  and the clip channels  113  by the surface friction of the flattened portion and the clip  140  against the walls of the channel  111  and the clip channels  113 . In order to accomplish a tight friction contact between the channel  111  and the flattened portion  121  of the heat pipe  120 , the channel is made only slightly wider than the flattened portion, so that the flattened portion fits snugly in the channels. To effect a tight friction contact between the clip  140  and the clip channels  113 , the side surfaces  142 ,  143  of the clip are splayed out (i.e., away from the main surface) slightly, so that the side surfaces of the clip are urged against the clip channel walls when the clip is disposed in the heat transfer block  110 .  
         [0025]    The heat transfer block  110  also includes guide members  114  with openings  115  formed therein for securing the heat transfer block to a CPU or chip. Typically, a CPU or chip will include complementary guide members, such as posts, which may be received in the openings  115  in order to secure the heat transfer block  110  to the CPU or chip.  
         [0026]    The above-described heat pipe system  100  may be formed by various methods. For example, the heat transfer block  110  may be formed as a single substantially uniform part which is later milled to create the heat pipe channel  111  and clip channels  113 . Once the milled part has been manufactured, the heat pipe  120  and clip  140  may be bonded to the heat transfer block  110  by the methods discussed above (e.g., solder, epoxy, friction, fasteners), or by other means known to those skilled in the art. Alternatively, the heat transfer block  110  may be formed with the heat pipe channel  111  and the clip channels  113  already formed therein, by a process such as extrusion.  
         [0027]    Since, in the present invention, the flattened portion  121  of the heat pipe  120  fits tightly within the channel  111  in the heat transfer block  110 , and is further secured using clip  140 , maximum heat transfer from the heat transfer block to the heat pipe can be achieved. As explained above, in conventional heat pipe systems such maximum heat transfer could not be realized due to the fact that the flattened portion of the heat pipe did not fit snugly within the channel (See FIG. 1). Thus, the present invention it is submitted that the present invention represents a significant advance in heat transfer technology.  
         [0028]    [0028]FIG. 4 shows an enlarged and exploded view of the heat pipe  120  and heat transfer block  110  of the heat pipe system  100  according to the first exemplary embodiment of the present invention. FIG. 4 clearly shows that the channel  111  includes a flared portion  112  which is wider than the rest of the channel. As stated above, this flared portion  112  operates to receive the pinchoff portion  122  of the heat pipe  120 . FIG. 4 also clearly shows the clip channels  113 . Although the clip channels  113  are oval-shaped in FIG. 4, it will be understood that these channels may take various geometrical shapes (e.g., rectangles, etc.).  
         [0029]    One of the main reasons for utilizing the channel structure  111  described above is to provide a means of applying downward pressure on the heat transfer block  110 . The downward pressure must be applied at the physical center of the CPU or chip to which the transfer block  110  is coupled to assure that the transfer block is seated squarely on the CPU or chip without creating a gap therebetween. Often times when the transfer block  110  is not seated squarely on the CPU or chip a wedge-shaped gap is formed between the transfer block and the CPU or chip. Such a gap could result in poor thermal contact between the CPU or chip and the transfer block  110 , and could, in the case of a CPU having an exposed silicon die, cause cracking or splaying from the edges of the die, and subsequently reduce heat transfer area or cause electrical malfunction. The downward pressure cannot be applied through the wall of the heat pipe because the wall is often made of a thin metal (e.g., Copper) sheet which does not have sufficient tensile strength to transfer the force without deformation of the metal. Such deformation may result in diminution of the contact pressure, and reduction in heat pipe performance due to the local reduction in vapor flow area. The channel structure  111  is designed to circumvent the deformation problem, while allowing pressure to be applied at the center of the CPU or chip to which the transfer block  110  is coupled.  
         [0030]    Additionally, in the first exemplary embodiment described above, the heat pipe  120  is disposed at the physical center of the CPU or chip, the region of maximum heat production. Location of the heat pipe  120  in this region produces a heat pipe system  100  with a low thermal resistance.  
         [0031]    Referring to FIG. 5, there is shown a heat pipe system  300  according to a second exemplary embodiment of the present invention. Similar to the heat pipe system  100 , the heat pipe system  300  includes a heat transfer block  310 , a heat pipe  320 , and a heat dissipation structure (not shown). However, the heat pipe system  300  includes only a single clip channel  313  for receiving a clip  340 .  
         [0032]    [0032]FIG. 5 shows that the heat transfer block  310  includes a channel  311  therein for receiving a flattened portion  321  of the heat pipe  320 . The heat pipe  320  also includes a pinchoff portion  322  disposed at one end of the flattened portion  321 . An end of the heat pipe  320  opposite the flattened portion  321  is coupled to the heat dissipation structure not shown). One end of the channel  311  of the heat transfer block  310  has a flared portion  312  for receiving the pinchoff portion  322  of the heat pipe  320 . A clip member  340  overlies and secures the flattened portion  321  of the heat pipe  320  in the channel  311 . It will be noted that the clip member  340  includes a main surface  341 , and two side surfaces  342 ,  343  disposed orthogonal to the main surface. The main surface  341  primarily overlies the flattened portion  321  of the heat pipe  320 , and the two side surfaces  342 ,  343  primarily reside in single clip channel  313 , when the clip  340  is coupled to the heat transfer block  310 .  
         [0033]    It will be noted that the two side surfaces  342 ,  343  of the clip are received in a single clip channel  313  formed in the heat transfer block  310 . The flattened portion  321  of the heat pipe  320  and the clip  340  may be secured in the channel  311  and the single clip channel  313  respectively by fasteners (e.g., screws, bolts, etc.), solder, epoxy or other known materials.  
         [0034]    Alternatively, the flattened portion  321  of the heat pipe  320  and the clip  340  may be secured in the channel  311  and the single clip channel  313  by the surface friction of the flattened portion and the clip  340  against the walls of the channel  311  and the single clip channel  313 . As stated above with respect to the first exemplary embodiment, in order to accomplish a tight friction contact between the channel  311  and the flattened portion  321  of the heat pipe  320 , the channel is made only slightly wider than the flattened portion, so that the flattened portion fits snugly in the channels. To effect a tight friction contact between the clip  340  and the single clip channel  313 , the side surfaces  342 ,  343  of the clip are splayed out (i.e., away from the main surface) slightly, so that the side surfaces of the clip are urged against the clip channel walls when the clip is disposed in the heat transfer block  310 .  
         [0035]    The heat transfer block  310  also includes guide members  314  with openings  315  formed therein for securing the heat transfer block to a CPU or chip. Typically, a CPU or chip will include complementary guide members, such as posts, which may be received in the openings  315  in order to secure the heat transfer block  310  to the CPU or chip.  
         [0036]    As described above with reference to the heat pipe system  100  of the first exemplary embodiment, the heat pipe system  300  may be formed by various means such as milling and extrusion.  
         [0037]    Referring to FIGS. 7 and 8, there is shown a heat pipe system  400  according to a second exemplary embodiment of the present invention. Similar to the heat pipe system  100 , the heat pipe system  400  includes a heat transfer block  410 , a heat pipe  420 , and a heat dissipation structure  430 . However, the heat pipe system  400  includes a flattened clip member  440  which extends across the heat transfer block  410  with tabs  441 ,  442  formed therein for being received in respective channels  451 ,  452  of the heat transfer block (See FIG. 8).  
         [0038]    [0038]FIG. 7 shows that the heat transfer block includes a channel  411  therein for receiving a flattened portion  421  of the heat pipe  420 . A clip member  440  overlies and secures the flattened portion  421  of the heat pipe  420  in the channel  411 . It will be noted that the clip member  440  includes a top surface  445 , and a bottom surface  446  with tabs  441 ,  442  extending orthogonally therefrom (See FIG. 8).  
         [0039]    The flattened portion  421  of the heat pipe  420  and the clip  440  may be secured in the channel  411  and the clip channels  451 ,  452  respectively by fasteners (e.g., screws, bolts, etc.), solder, epoxy or other known materials.  
         [0040]    Alternatively, the flattened portion  421  of the heat pipe  420  and the clip  440  may be secured in the channel  411  and the clip channels  451 ,  452  by the surface friction of the flattened portion and the clip  440  against the walls of the channel  411  and the clip channels  451 ,  452 . As stated above with respect to the first exemplary embodiment, in order to accomplish a tight friction contact between the channel  411  and the flattened portion  421  of the heat pipe  420 , the channel is made only slightly wider than the flattened portion, so that the flattened portion fits snugly in the channels. Similarly, to effect a tight friction contact between the clip  440  and the clip channels  451 ,  452 , the channels are made only slightly wider than the respective tabs  441 ,  442 .  
         [0041]    The heat transfer block  410  also includes guide members  414  with openings  415  formed therein for securing the heat transfer block to a CPU or chip. Typically, a CPU or chip will include complementary guide members, such as posts, which may be received in the openings  415  in order to secure the heat transfer block  410  to the CPU or chip.  
         [0042]    As described above with reference to the heat pipe system  100  of the first exemplary embodiment, the heat pipe system  400  may be formed by various means such as milling and extrusion.  
         [0043]    Although the invention has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly, to include other variants and embodiments of the invention which may be made by those skilled in the art without departing from the scope and range of equivalents of the invention.