TECHNICAL FIELD 
     This invention relates to computer systems, and more particularly to devices for transferring heat away from internal computer system components. 
     BACKGROUND 
     Heat dissipation is a major issue in the design and operation of semiconductor devices (“chips”). Too much heat can destroy the structure of a chip and affect its operation. The tight packing of chips in today&#39;s computer systems makes them even more vulnerable to damage from heat. 
     One approach to avoiding overheating is with the use of an active cooling device, such as a fan. Conventionally, a fan is a component of the computer system, contained in the computer chassis. 
     Another approach to avoiding overheating is the use of a passive cooling device, such as a heatsink. A heatsink provides a surface area from which heat can radiate. Many heatsinks have fins or some other geometry that increases their surface area. They are made from a material having good thermal conduction, such as aluminum. Some computers are designed so that the computer chassis provides a heatsink. An advantage of passive cooling devices is that no power-consuming mechanism is required; the heatsink operates by natural convection whereby warm air rises away from the heatsink and cool air flows toward the heatsink to replace the warm air. 
     Both fans and heat sinks present design challenges because they must be placed where they will be effective, yet not add bulk to the computer system. Also, electrical design considerations result in competition between electrical components and thermal components for the same “real estate”. 
     Heat pipes have been used to alleviate design problems to some extent. Heat pipes are used in conjunction with heatsinks, and conduct heat away from a heat-generating component to the heat sink. A popular design of today&#39;s computers is the use of the computer chassis as a heatsink with heat pipes conducting heat from the internal components to the chassis. However, the addition of heat pipes has often resulted in increased manufacturing complexity and reduced serviceability after manufacture, because of the connections required for the heat pipes. 
     SUMMARY 
     One aspect of the invention is a thermal connection system for cooling integrated circuit components. The thermal connection system has a number of component heat conductors. One end of the component heat conductor is connectable to an integrated circuit component, such that the heat conductor extends from the integrated circuit component generally parallel to other component heat conductors. Each component heat conductor has an associated arterial heat conductor, which is connectable to a heat sink at one end such that it extends from the heat sink. A thermal connector orthogonally connects the free end of each component heat conductor to the free end of each arterial heat conductor. The thermal connector is removably attached to the component heat conductor, and it may also be removably attached to the arterial heat conductor. In this manner, each thermal connector provides a complete heat transfer path from a heat-generating component to the heat sink. 
     As a result of the above-described thermal connection system, components are thermally connected to one or more arterial heat conductors, rather than directly to the heat sink. The thermal connectors permit components to be easily added and removed. The connector provides a self-aligned connection, which reduces manufacturing effort. 
     The design provides for a central cooling location for all components, and relaxes constraints related to the need for cooling devices immediately proximate to the components to be cooled. This permits even the most critical components, such as processor and memory units, to be reduced in size, more tightly packed, and more easily serviced. 
     The above-described thermal connection system is consistent with a removable modular design for processing and memory components of a computer system. Each module contains one or more integrated circuit components. The thermal connectors permit the modules to have “plug in” thermal connections. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front perspective view of a digital processing unit having a thermal connection system in accordance with the invention. 
     FIG. 2 is a rear perspective view of the digital processing unit of FIG.  1 . 
     FIG. 3 is a rear perspective view of a single module unattached to the thermal connector. 
     FIG. 4 is a detailed perspective view of one of the connectors of FIG.  2 . 
     FIG. 5 illustrates the internal structure of the connector of FIG.  4 . 
     FIGS. 6-8 illustrate alternative embodiments of the connector of FIGS. 4 and 5. 
     FIG. 9 illustrates an example of components of a module and its component heat conductors. 
    
    
     DETAILED DESCRIPTION 
     FIGS. 1 and 2 are front and rear perspective views, respectively, of a digital processing unit  10 , comprised of a number of modules  11  and a heat sink  12 . In the example of this description, processing assembly  10  has four modules, but the number of modules is not significant to the invention. 
     Modules  11  are designed for use in a computer system, and may contain any type of integrated circuitry associated with digital processing, controlling, or micro-electromechanics. For example, processing unit  10  may function as the system unit of a computer, akin to a “system board” or an “expansion board”. The term “digital processing” is used herein in a broad sense to include any function associated with a computing system—processing unit  10  need not necessarily contain any module  11  having a processor. Although not illustrated, each module  11  typically has appropriate electrical connections to a bus or other data communications link. 
     Each module  11  has at least one heat conductor  13  that extends to the rear of the module  11  and connects to heat sink  12 , via a special thermal connection system. In the example of this description, each module  11  has two heat conductors  13 , the second being hidden from view in FIG. 1 but shown extending from the rear of each module  11  in FIG.  2 . Component heat conductors  13  are substantially parallel to each other. 
     Each module  11  is comprised of a housing  14 , which contains an integrated circuit card  15 . One or more integrated circuit devices (ICs) are mounted on card  15 . An example of a card  15  and its ICs is described below in connection with FIG.  6 . In the example of this description, each module  11  appears the same. However, modules  11  may differ with respect to their internal circuitry or even their shape and size. In a broad sense, a module  11  may simply comprise a single IC. 
     Heat sink  12  may be any type of heat sink, such as those used in computing equipment. Examples of suitable heat sinks may be found in today&#39;s desktop and portable computer systems. In the example of this description, heat sink  12  has fins for enhancing its ability to dissipate heat. Heat sink  12  could alternatively be in the form of metal plates attached to a computer chassis, or could have any one of a number of other configurations. A fan (not shown) may be used in conjunction with heatsink  12  to increase convection. 
     Referring especially to FIG. 2, an array of arterial heat conductors  21  lies along the back of unit  10 . Each arterial heat conductor  21  is connected to a module heat conductor  13  at a heat input end, and to the heat sink  12  at a heat output end. In the example of FIG. 2, the arterial heat conductors  21  are substantially parallel to each other, so as to be in a common plane along the backplane of modules  11 . However, other configurations are possible. 
     Heat conductors  13  and heat conductors  21  may be conventional heat pipes or any other type of heat conductor. They are characterized by being constructed of one or more materials that provides them with efficient heat conductivity. An example of a suitable heat conductor is a heat pipe having a porous wick or inner core to carry heated liquid or vapor inside the heat conductor. However, heat conductors  13  and  21  could be solid or could have some other structure. 
     In the example of this description, component heat conductors  13  and arterial heat conductors  21  are both round and have substantially the same diameter. However, differently shaped heat conductors may be used, and heat conductors  21  need not have the same shape or diameter as heat conductors  13 . However, typically, component heat conductors  13  will have the same size and shape at their heat output ends, so as to facilitate the connection scheme described herein. 
     A special thermal connector  22  joins each component heat conductor  13  to each arterial heat conductor  21 . The connection is orthogonal, that is, it provides a right angle turn for the heat path from a module  11  to the heat sink  12 . 
     Each thermal connector  22  is made from a material that conducts heat, so that heat from a component heat conductor  13  may be transferred to an arterial heat conductor  21  via the connector  22 . Examples of suitable materials are copper and aluminum or their alloys. Connector  22  could be a conductive plastic, which as explained below, would give it elastic properties. A special design for a “die cast” connector  22  is described below in connection with FIG.  5 . Regardless of the particular design of connector  22 , it provides a thermal connection so that a path of heat conduction from the module  11  to the heat sink  12  is complete. 
     Although each module  11  may have different circuitry and may have differently shaped housings  14 , modules are configured so that they may be connected in the same manner to arterial heat conductors  21 , using connectors  22 . Thus, each module has at least one component heat conductor  13  extending from its housing  14  in a manner that permits the module  11  to join to an arterial heat conductor  21 . 
     FIG. 3 is a rear perspective view of a single module  11 , unattached to an arterial heat conductor  21 . In the example of FIG. 3, as in FIGS. 1 and 2, module  11  has two component heat conductors  13  connected to its ICs or directly to its board. The use of two component heat conductors  13  from each module is for purposes of example; a single heat conductor or three or more heat conductors could be used. As explained below, the number of heat conductors per module  11  may be related to the number of ICs from which heat is to be transported. 
     FIGS. 4 and 5 illustrate one embodiment of a connector  22 . FIG. 4 is a perspective view, and FIG. 6 illustrates the internal structure. 
     Each connector  22  is generally solid piece of material having orthogonal internal channels for insertion of a heat conductor  13  and heat conductor  21 . In the example of FIG. 4, the top portion of connector  22  receives an arterial heat conductor  21 ; the bottom portion receives a module heat conductor  13 . Thus, connector  22  has a height slightly greater than the sum of the diameter of a component heat conductor  13  and the diameter of an arterial heat conductor  22 . Its width is sufficient to accommodate the diameter of a heat conductor  13  and a heat conductor  21 . 
     The embodiment of FIGS. 5 and 6 is especially suitable when connectors  22  are to be translatable along, and rotatable around, component heat conductor  13  and arterial heat conductor  21 . A first channel  51  receives a heat conductor  21 ; a second channel  52  receives a heat conductor  13 . The heat conductors may be inserted from either direction. The two channels  51  and  52  are orthogonal to each other for an orthogonal connection of the respective heat conductors. The ends of the conductors may be chamfered to facilitate insertion, as is the end of conductor  13  in FIG.  5 . 
     The external profile of connector  22  can be squared, as is the top portion of connector  22 , or rounded, as is the bottom portion of connector  22 . The external shape of connector  22  is not particularly important. Connector  22  could be entirely rectangular, as is the top portion. Or, connector  22  could be rounded around the respective channels, as is the bottom portion. Furthermore, although the component heat pipe  13  is illustrated as being used with the rounded (bottom) portion, and the arterial heat pipe  21  is illustrated as being used with a rectangular (top) portion, this arrangement could easily be reversed. 
     To better secure heat conductor  13  within connector  22 , at least one seating tab  53   a  is attached to the inner surface of channel  52 . In the example of this description, seating tab  53   a  is spring loaded, such that a spring  53   b  in channel  53   c , applies a constant force that pushes tab  53   a  against heat conductor  13  after heat conductor  13  is inserted into channel  52 . Multiple tabs  53   a  may be used, or tab  53   a  could be in the shape of a collar that partially or completely encircles heat conductor  13 . In other embodiments, other means for removably securing heat conductors  13  within connectors  22  could be used. For example, the force applied to each heat conductor  13  could simply be the result of a tight fit and friction. A thermal grease may be used to coat the mating surfaces. 
     An optional feature of connector  22  is an inner core  55  especially designed for heat transport. Core  55  could be hollow or could contain a porous material similar to that used for heat conductors  13  and  21 . A die cast manufacturing process could be used to manufacture a connector  22  having a core  55 . 
     The attachment of each connector  22  to a module heat conductor  13  is designed to be removable. As illustrated, the ends of heat conductors  13  are chamfered to facilitate insertion into connector  22 . An advantage of the channel type attachment of FIGS. 4 and 5 is that the heat conductor  13  may be inserted from either side of connector  22 , may be translated within the channel. The channel type attachment further permits connector  22  to rotate around arterial heat conductor  21  and would even permit a “Christmas tree” type arrangement of modules  11 . 
     An advantage of a translatable and/or rotatable connection is that some play is provide to accommodate modules  11  of different sizes and shapes. However, where modules  11  are all the same size, the spacing of connectors  22  on arterial heat conductors  21  may be predetermined, and each connector  22  may have a fixed attachment to arterial heat conductor  21 . 
     The removable attachment of connectors  22  to heat conductors  13  is especially useful during assembly of processing unit  10 . Each module&#39;s heat conductor(s)  13  may be simply inserted into a connector  22 . At this point, connectors  22  and arterial heat conductor  21  may be already assembled as a unit, or the insertion of arterial heat conductor  21  into connectors  22  may occur later. 
     Connectors  22  permit each heat conductor  13  to have a removable connection to arterial heat conductor  21 . However, once a heat conductor  13  is inserted into connector  22 , it is sufficiently secure to as to remain inserted until force is applied to remove it. Similar means could be used to attach connectors  22  to arterial heat conductors  21 , when connectors  22  are to be removable, translatable, and/or rotatable. 
     The attachment of connectors  22  to heat conductors  21  may be removable or may be fixed. An advantage of a removable attachment, or at least one that is translatable along arterial heat conductor  21 , is that modules  11  of varying shapes and sizes may be connected. 
     FIGS. 6-8 illustrate alternative embodiments of connector  22 , having various means for attachment of the heat conductors. Like connector  22 , each embodiment is designed so that a component heat conductor  13  and an arterial heat conductor  21  may be easily attached. The attachments may optionally be removable, translatable along one or both conductors, or rotatable around one or both heat conductors, or any combination of these alternatives. 
     In FIGS. 6-8, various means for attachment of component heat conductor  13  are illustrated as alternatives to the channels of FIGS. 4 and 5. The means for attachment for arterial heat conductor  21  is a channel. However, the illustrated attachment mechanism could be also, or alternatively, used for the component heat conductor  21 . 
     Regardless of the specific attachment means implemented for connector  22 , a common characteristic of all embodiments of connector  22  is that the attachment means provides a self aligning connection between a heat connector  13  and a heat connector  21 . In other words, the mechanical structure guides the connection, and reduces the effort required during manufacture. 
     FIG. 6 is a perspective view of a connector  62  having an indentation  63  for receiving a component heat conductor  13 . As illustrated, the leading tip  64  of the component heat conductor  13  is chamfered to provide a mating connection within the indentation. To increase the contacting surface area, the tip  64  may be enlarged relative to the diameter of the component heat conductor  13 . This increased surface area provides enhanced heat conduction. Spring loaded tabs, similar to those of FIG. 5, may be used to secure the connection. 
     FIG. 7 is a perspective view of a connector  72  having a mating surface  73  for receiving a component heat conductor  13 . The leading tip  74  of the component heat conductor  13  is fluted, so as to increase the contacting surface area. The connection may be soldered, bonded, or otherwise attached. 
     FIG. 8 is perspective view of a connector  82  that is a modification of connector  22 . Connector  82  only partially surrounds component heat conductor  13 , such that channel  52  is partially open to form a collar. A clip  83  is used to encircle the open portion of the channel  52 . This embodiment is most suitable when connector  82  is made from a deformable material, such as a plastic. The fit of connector  82  around heat conductor  13  may be initially loose, with clip  83  used to tighten the attachment. The loose fit facilitates manufacture, with the clip  83  ensuring that a good thermal connection is accomplished. Clip  83  may also be of an elastic material, to provide a self clamping effect, or may include some sort of mechanical clamp (not shown) may be used. 
     FIG. 9 illustrates an example of a card  15  within module  11 , and shows various ICs mounted on the card. The card  15  of this example has two processors  91 , a memory bank  92 , and a control logic chip  93 . However, as indicated above, card  15  could have any type or types of ICs, in addition to or instead of processing and memory components. A heat conductor  13  is connected to each processor  91 , but additional heat conductors could be connected to memory bank  92 , control logic chip  93 , or to the substrate  94  upon which the ICs are mounted. 
     OTHER EMBODIMENTS 
     Although the present invention has been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereto without departing from the spirit and scope of the invention as defined by the appended claims.
A method and system of thermally connecting internal components of a computer system to a heat sink. The components are arranged as modular units, each having at least one component heat conductor extending from it. For each component heat conductor, an arterial heat conductor extends from the heat sink. Each module heat conductor is attached orthogonally to its associated arterial heat conductor, using a special thermal connector.