Abstract:
A stacked electronic device module is constructed incorporating heat pipes within the module, enabling efficient cooling of the electronic devices within the module. The heat pipes may extend outside of the stacked electronic device modules for more efficient operation. Heat pipes may be placed selectively between some layers of the module or placed between each layer of the module.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to the field of stacked electronic device modules, and more specifically to the field of thermal cooling of stacked electronic device modules.  
         BACKGROUND OF THE INVENTION  
         [0002]    Modern electronics have benefited from the ability to fabricate devices on a smaller and smaller scale. This shrinking is occurring not only with integrated circuits themselves, but also with systems incorporating multiple integrated circuits. One example of this decrease in size is the current capability of closely stacking modules containing one or more integrated circuit. Unfortunately, this stacking, while dramatically increasing the density of the resulting module, dramatically reduces or eliminates entirely the dissipation of heat from the incorporated integrated circuits to the surrounding atmosphere.  
           [0003]    This heat may build up within the stacked electronic device module to the point that circuits within the module fail to operate correctly due to their internal temperature rising above their design limits. Also, it is well known that most integrated circuit devices switch slower at high temperature than they do at lower temperatures, resulting in a decrease in performance of the device.  
           [0004]    As the power density of electronic device modules increases, heat transfer from the heat generating devices to the surrounding environment becomes more and more critical to the proper operation of the devices. Many current electronic devices incorporate heat sink fins to dissipate heat to the surrounding air moving over the fins. However, as alluded to above, stacked electronic device modules often are not configured to allow airflow over all of the integrated circuits, or other electronic devices, within the module.  
         SUMMARY OF THE INVENTION  
         [0005]    A stacked electronic device module is constructed incorporating heat pipes within the module, enabling efficient cooling of the electronic devices within the module. The heat pipes may extend outside of the stacked electronic device modules for more efficient operation. Heat pipes may be placed selectively between some layers of the module or placed between each layer of the module.  
           [0006]    Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is an illustration of three example electronic device modules.  
         [0008]    [0008]FIG. 2 shows an example stack up of seven example electronic device modules.  
         [0009]    [0009]FIG. 3 is a cross-section diagram of an example embodiment of stacked electronic device modules.  
         [0010]    [0010]FIG. 4 is a cross-section diagram of a portion of the example embodiment of a stacked electronic device module from FIG. 3.  
         [0011]    [0011]FIG. 5 is a cross-section diagram of an example embodiment of stacked electronic device modules including heat pipes according to an example embodiment of the present invention.  
         [0012]    [0012]FIG. 6 is a cross-section diagram of a portion of the example embodiment of stacked electronic device modules including heat pipes according to an example embodiment of the present invention from FIG. 5.  
         [0013]    [0013]FIG. 7 is a cross-section diagram of an example embodiment of stacked electronic device modules including heat pipes according to an example embodiment of the present invention including heat pipes that extend beyond the body of the stacked electronic device modules.  
         [0014]    [0014]FIG. 8 is a cross-section diagram of an example embodiment of stacked electronic device modules including heat pipes according to an example embodiment of the present invention including heat pipes that extend beyond the body of the stacked electronic device modules and are thermally coupled to an external heat sink.  
         [0015]    [0015]FIG. 9 is a flowchart of an example method for the fabrication of stacked electronic device modules including heat pipes according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0016]    [0016]FIG. 1 is an illustration of three example electronic device modules. The first electronic device module  100 , second electronic device module  102 , and third electronic device module  104 , shown in FIG. 1 are all identical in this example of a plurality of electronic device modules. Each of the electronic device modules includes an electronic device  108 , such as an integrated circuit, attached to the substrate  106  of the module. Also shown are signal conductors  110  connecting the electronic device  108  to signal contacts  112 . Further, wide power conductors  114  connect the electronic device  108  to power contacts  116 . These signal contacts  112  and power contacts  116  may be electrically connected to signal and power conductors within the substrate  106  of the module or may connect to signal and power conductors on other modules after the three modules  100 ,  102 , and  104  are incorporated into a single stacked electronic device module similar to that shown in FIG. 2. This stacking of individual modules is facilitated by the use of alignment holes  118  in this example, however, many other methods of alignment of the individual modules may be used, such as external assembly jigs, pins and sockets, or clips.  
         [0017]    [0017]FIG. 2 shows an example stack up of seven example electronic device modules. In this example stack up  200 , seven electronic device modules  202  are aligned through the use of pins  204  through individual alignment holes of the individual modules similar to those shown in FIG. 1.  
         [0018]    [0018]FIG. 3 is a cross-section diagram of an example embodiment of stacked electronic device modules. Four electronic device modules  304  are shown stacked with four heat spreaders  306  in this example embodiment of stacked electronic device modules. Similar to the example in FIG. 2, pins  300  are used to align the modules  304 , and spacers  302  are used to keep the modules coplanar. The area enclosed by the dashed line of reference number  308  is enlarged and shown in FIG. 4.  
         [0019]    [0019]FIG. 4 is a cross-section diagram of a portion of the example embodiment of a stacked electronic device module from FIG. 3. This cross-section view, shows the stack up of two electronic device modules. Each module includes a substrate  404 , and an electronic device  400  electrically connected to signal conductors  406  through pads  402 . The modules are stacked with heat spreaders  408  connected to the electronic devices  400  with a thermally conductive paste  410  or other similarly thermally conductive material.  
         [0020]    [0020]FIG. 5 is a cross-section diagram of an example embodiment of stacked electronic device modules including heat pipes according to an example embodiment of the present invention. Four electronic device modules  504  are shown stacked with four heat pipes  506  in this example embodiment of stacked electronic device modules. Pins  500  are used to align the modules  504 , and spacers  502  are used to keep the modules coplanar. The area enclosed by the dashed line of reference number  508  is enlarged and shown in FIG. 6.  
         [0021]    [0021]FIG. 6 is a cross-section diagram of a portion of the example embodiment of stacked electronic device modules including heat pipes according to an example embodiment of the present invention from FIG. 5. This cross-section view, shows the stack up of two electronic device modules. Each module includes a substrate  404 , and an electronic device  400  electrically connected to signal conductors  406  through pads  402 . The modules are stacked with heat pipes  600  connected to the electronic devices  400  with a thermally conductive paste  410  or other similarly thermally conductive material. The heat pipe  600  comprises a vapor  604  surrounded by a wick  602  within the vessel of the heat pipe  600 . Where the heat pipe  600  is thermally connected to the electronic device  400  through thermal paste  410 , the liquid within the wick  602  evaporates to form a vapor  604 . This heated vapor travels within the heat pipe  600  to the cooler area outside of the stacked electronic device module, where the vapor  604  condenses on the wick  602  into a liquid that then flows back through the wick  602  to the warmer area of the heat pipe  600 , where the process continues.  
         [0022]    [0022]FIG. 7 is a cross-section diagram of an example embodiment of stacked electronic device modules including heat pipes  700  according to an example embodiment of the present invention including heat pipes  700  that extend beyond the body of the stacked electronic device modules. In some embodiments of the present invention it may be useful to extend the heat pipes  700  beyond the body of the stacked electronic device modules allowing air to flow over the surfaces of the heat pipes  700  external to the body of the stacked electronic device modules resulting in greater efficiency of cooling the module.  
         [0023]    [0023]FIG. 8 is a cross-section diagram of an example embodiment of stacked electronic device modules including heat pipes according to an example embodiment of the present invention including heat pipes that extend beyond the body of the stacked electronic device modules and are thermally coupled to an external heat sink. In other embodiments of the present invention further efficiency may be obtained by thermally coupling an external heat sink  800  to the heat pipes  700 . In this example embodiment, an external heat sink  800  is thermally and mechanically coupled to heat pipes  700  similar to those shown in FIG. 7 that extend beyond the body of the stacked electronic device module. However, other embodiments of the present invention may attach an external heat sink  800  to the ends of heat pipes  700  that do not extend beyond the body of the module.  
         [0024]    [0024]FIG. 9 is a flowchart of an example method for the fabrication of stacked electronic device modules including heat pipes according to the present invention. In order to construct a stacked electronic device module including heat pipes according to the present invention, at least two electronic modules must be provided in a step  900 . In an optional step  902 , thermally conductive material such as a thermal paste is placed over at least some of the electronic devices included on the electronic modules. In a step  904 , at least one heat pipe is placed between the electronic modules. In a step  906 , the heat pipes and electronic modules are affixed together to form a stacked electronic device module. This step may be accomplished by mechanical means such as nuts and bolts, pins, glue, or encapsulation. Many such methods for affixing the heat pipes and electronic modules together may be used within the scope of the present invention. In an optional step  908 , an external heat sink may be thermally coupled to at least one of the heat pipes to improve cooling efficiency.  
         [0025]    In some example embodiments of the present inventions, stacked modules (such as the memory stacks and memory modules produced by DPAC Technologies, 1721 Lincoln Way, Garden Grove, Calif., 92841, www.dpactech.com, or the memory modules and processor cores produced by 3D Plus USA, Inc., 1947 Ave. K, Suite D, Plano, Tex. 75074) may be built with heat pipes interspersed between the individual layers of the stack or module. For modules including electrical connections on the outside of the module, some implementations of the present invention may eliminate some or all of the electrical connections on one or more sides of the module to allow the heat pipes access to the external atmosphere for increased cooling performance.  
         [0026]    The foregoing description of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and other modifications and variations may be possible in light of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the appended claims be construed to include other alternative embodiments of the invention except insofar as limited by the prior art.