Abstract:
To manage heat in a computer environment or the like, a base plate and/or a input/output (I/O) plate includes an integrated heat pipe. For example, the base plate, located between a bottom surface of a laptop computer chassis and a printed circuit board (PCB) or motherboard would include a heat-pipe network that draws heat away from the heat generating components of the PCB (e.g., a processor) and distributes the heat over the base plate. The I/O plate may also serve the same purpose, located at an end of the PCB. The base plate heat pipe and I/O plate heat pipe are thermally coupled together or are of a unitary design so as to distribute the heat generated in the laptop computer over a larger area achieving a relatively low-temperature isothermal design.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention pertains to an apparatus for managing heat in a computer environment or the like. More particularly, the present invention pertains to a method and apparatus for managing heat generated by electronic circuitry using a base plate and/or input/output plate with an integrated heat pipe. 
     2. Background Information 
     Electronic circuits, particularly integrated circuit (IC) chips, tend to generate an appreciable amount of heat during operation. If the heat is not sufficiently removed from the ambient area surrounding the IC chip, the electronic circuit therein may not operate properly. For example, specifications for a Pentium® processor (Intel Corporation, Santa Clara, Calif.) operating at 66 Megahertz (MHZ) provide a maximum temperature of 70° C. for the ambient air surrounding the processor. Thus, if the temperature of the ambient air surrounding the processor exceeds this maximum temperature, there exists a possibility that the processor will not operate correctly. 
     Referring to FIG. 1, a view of a laptop computer  10  is shown. Laptop computer  10  includes a screen  11  and a main chassis  12 . As is known in the art, the main chassis includes a keyboard component  13  having a support plate onto which is mounted a printed circuit board (PCB) and a plurality of keys. Under keyboard component  13  is another PCB  15  (sometimes referred to as a motherboard) which may include components such as one or more processors (e.g., a Pentium® processor), memory modules, and a variety of other electronic components. PCB  15  may be mounted to a base plate  17  extending over an area of a base  18  of laptop computer  10 . Laptop computer  10  also includes an Input/Output (I/O) plate  19  which is at a back end  20  of the computer  10  in this example. The I/O plate  19  includes a number of openings that house connections that may be coupled to any of a variety of peripheral devices (e.g., an external floppy drive, a docking station, etc.). 
     Certain components on PCB  15  (e.g., the processor) generate more heat than others. Some known methods for dissipating heat from the Pentium® processor set forth above are described in Application Note APA480 “Pentium® Processor Thermal Design Guidelines Rev. 2.0,” Nov. 1995 (see, e.g., Pentium® and Pentium® Pro Processors and Related Products, 1996, pp. 2-1337 to 2-1363 obtainable from McGraw-Hill Book Company). These methods include the placement of a heat sink on top of the processor and increasing air flow over the processor so that the ambient air (heated by the processor) may be removed. In a personal computer environment, the processor is typically coupled electrically to other devices on a PCB. These other devices also generate heat and employ the above identified heat removing methods to operate correctly. 
     Another device for removing heat from a component, such as a processor, is a heat pipe. A heat pipe typically has a round cross-section including two paths extending the length of the pipe. The heat pipe (e.g., an end of the heat pipe) is placed proximately to a component, such as a processor. Working fluid in the heat pipe (e.g., water) is heated at the component and vaporized. The vapor travels away from the component in a hollow, first path of the heat pipe (this first path typically has a relatively large cross-sectional area). Eventually, the vapor is cooled at another location in the heat pipe. For example, the vapor may be cooled over a heat sink device mentioned above. The vapor condenses to form working fluid and the working fluid travels back to the processor through a second path, sometimes referred to as a wick structure, via capillary action. Thus, the heat pipe continuously circulates working fluid and vapor to remove heat from the processor. Further details on the operation of heat pipes can be found in  Handbook of Applied Thermal Design  (1989, ed., Eric C. Guyer, pp. 7-50 to 7-58). 
     The use of devices for managing heat becomes very important in mobile computer systems, such as laptop computer  10  shown in FIG.  1 . Because of their small size, especially in height, there is generally insufficient space for air flow past components in a laptop computer. Base plate  17  is made of a metal such as steel or aluminum which tends to conduct the heat generated by components on PCB  15  to all areas of base plate  17 . Also, base plate  17  and I/O plate  19  may be combined into a single L-shaped plate  25  shown in FIG.  2 . Doing so expands the area for spreading the heat generated by PCB components. Due to the relatively poor thermal conductivity of these metals, thermal gradients do occur in the base plate, which in turn causes some sections of base plate  17  and/or I/O plate  19  to be warmer than others thus limiting the thermal capabilities. 
     Heat pipes, as described above, may be used to improve heat management in laptop computers having a base plate  17  and I/O plate  19 . The heat pipe is typically used to couple the heat of the processor to the base plate  17 . Doing so has at least two significant drawbacks. First, incorporating heat pipes into the computer structure increases manufacturing costs and complexity in that it is desirable for the heat-pipe to be precisely placed and attached to the PCB adding a number of manufacturing steps to laptop computer fabrication. Also, the heat pipe is attached to the PCB in different locations creating a situation where some areas on the PCB are hotter than others. These differences in temperature may be perceived by a user, and the efficiency of the heat removal system is reduced. Accordingly, there is a need for an apparatus for improving heat management for electronic circuits, especially for laptop and notebook computers. 
     SUMMARY OF THE INVENTION 
     One embodiment of an apparatus of the present invention provides a base plate in a computer system having an integrated heat pipe. Alternatively, in another embodiment, an apparatus of the present invention provides an I/O plate in a computer system having an integrated heat pipe. With a base plate or I/O plate constructed according to embodiments of the present invention, the thermal management of a computer system or the like is improved, allowing for a better distribution of heat over the areas of the base plate or I/O plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a view of a laptop computer as is known in the art. 
     FIG. 2 is a side view of a combined base plate and I/O plate as is known in the art 
     FIG. 3 is a view of a base plate constructed according to an embodiment of the present invention. 
     FIG. 4 is a view of an I/O plate constructed according to an embodiment of the present invention. 
     FIG. 5 is a view of a base plate and an I/O plate constructed according to an embodiment of the present invention. 
     FIG. 6 is a side view of the base plate of FIG. 6 adjacent to a PCB. 
     FIG. 7 is a view of base plate constructed according to an another embodiment of the present invention. 
     FIG. 8 is a cross-sectional view of the base plate of FIG.  7 . 
    
    
     DETAILED DESCRIPTION 
     As described in further detail, herein, a base plate and an I/O plate with an integrated heat pipe are described for cooling components in a laptop computer environment. One skilled in the art will appreciate that the base plate heat pipe and I/O base plate heat pipe may be used in a variety of other environments involving electronic circuits such as in personal computers, testing equipment, etc. 
     Referring to FIG. 3, a base plate  31  constructed according to an embodiment of the present invention is shown. The base plate  31  includes one or more integrated heat pipes  33 . In this embodiment, a plurality of heat pipes  33  are provided, arranged in a parallel configuration, although the invention is not limited in scope in this respect. Heat pipes  33  are separated by sidewalls  35  and each heat pipe  33  is sealed so as to contain a vaporizable liquid which serves as the working fluid for the heat pipe. In operation in this embodiment, a heat pipe draws vaporized fluid away from a heat source (the evaporator region of the heat pipe) to a condenser region of the heat pipe. Each heat pipe  33  includes a wick structure (not shown), which by means of capillary flow, transports the condensed liquid from the condenser region back into the evaporator region of the heat pipe. The wick structure may include a wire mesh or grooves along the heat pipe walls, or any other porous member. Each heat pipe  33  can be made from a thermally conductive and rigid material such as aluminum or copper, although the invention is not limited in scope in this respect. Base plate  31  may be placed adjacent to a PCB (as described below with reference to FIG. 6) and may include a hole  37  for insertion of one or more IC chips into the PCB. 
     Referring to FIG. 4, an I/O plate  41  constructed according to an embodiment of the present invention is shown. As with base plate  31  of FIG. 3, the I/O plate is formed with an integrated heat pipe. I/O plate  41  includes a number of openings  43  for the appropriate connector structure (not specifically shown in FIG. 4) that connects components in the laptop computer  10  (see FIG. 1) with any of a variety of peripheral devices. In this embodiment, a single heat pipe structure  45  is provided that extends around the periphery of I/O plate  41  and extends between connectors  43 . One skilled in the art will appreciate that heat pipe structure  45  may be modified so as to be customized to meet laptop computer design features. 
     In FIGS. 3 and 4, base plate heat pipe  31  and I/O plate heat pipe  41  are shown as separate components. These components may be thermally coupled together (e.g., using a standard heat pipe as is known in the art). Referring to FIG. 5, a combined base plate-I/O plate heat pipe according to an embodiment of the present invention is shown. Combined base plate-I/O plate heat pipe  51  comprises a unitary structure and extends adjacent to and under the PCB. This unitary structure  51  may include a hole  53  for the insertion of ICs into the PCB (the PCB is discussed below with reference to FIG.  6 ). Combined base plate-I/O plate heat pipe  51  comprises an integrated heat pipe structure  55 . In this embodiment, structure  55  includes more than one heat pipe (e.g., element  55   a ) that extends in parallel along the base plate portion of combined structure  51  and extends up a face of the I/O plate portion of the combined structure  51 . Structure  55  may also include element  55   b  in the I/O plate portion of the combined structure  51  (as described above with respect to FIG.  4 ). All of the heat pipes of structure  55  may be coupled together so that heat from one portion of the structure may be effectively distributed throughout the base plate and I/O plates of structure  55 , although the invention is not limited in scope in this respect. 
     Referring to FIG. 6, a side view of the combined base plate-I/O plate heat pipe  51  of FIG.  5  is shown. The combined plate heat pipe is shown coupled adjacent to and beneath a PCB  62 , which encompasses an electronic circuit including IC chips  63 ,  64 . In this embodiment, IC chip  63  is a processor, although the invention is not limited in scope in this respect. Referring back to FIGS. 3 and 5, the hole  37 ,  53  in the base plate portion of the heat pipe plate may be placed in the location of a processor to allow easy insertion thereof on PCB  62 . Heat pipe plate  51  may be coupled to the PCB  62  or to the chassis of a laptop computer  100  by any of a variety of fastening techniques such as screws. The design of heat pipe plate  51  may be modified by providing a projection portion  65  which extends toward a heat producing component, such as processor  63 . Such a projection portion  65  reduces the possibility of a warm spot appearing in the chassis  100  in the area near processor  63 . The projection portion  65  may be thermally coupled to processor  63  via a standard heat pipe as is known in the art or through conductive grease or the like (not shown). 
     Using a base plate or I/O plate with an integrated heat pipe results in improved thermal conductivity for these components. For example, a steel or aluminum base plate that is not made with an integrated heat pipe has a thermal conductivity of 16-50 and 80-200 W/m-K, respectively. A base plate constructed according to an embodiment of the present invention has a thermal conductivity over 10,000 W/m-K. This improved thermal conductivity allows a base plate and/or I/O plate of an embodiment of the present invention to effectively distribute heat generated in a laptop computer or the like. In an embodiment of the present invention, heat tends to be evenly distributed (e.g., isothermal), thus reducing areas of the base plate and/or I/O plate that are excessively warm. 
     In addition to thermal efficiency, the base and I/O plates of an embodiment of the present invention have a low weight, are mechanically rigid, and are cost efficient. As described above, the base plate or I/O plate may be integrated with a plurality of parallel, round heat pipes as shown in FIG.  3 . An alternative structure for the base and I/O plates is shown in FIGS. 4,  5 , and  7 . Referring to FIG. 7, a base plate  71  is shown including two thin metal plates  72  and  73  that are joined by a roll pressing process. The base plate  71  may be made by first stamping, milling or otherwise forming one or more heat pipe channels  74  within one, or both, of metal plates  72  and  73 . Channels  74  may include a wicking structure such as grooves within the channel that are formed during the stamping or milling process. Alternatively, a metal mesh or other porous member may be attached to the walls of channels  74 . Once plates  72  and  73  have been joined and sealed, channels  74  are evacuated and then charged with a working fluid. In the embodiment shown in FIG. 7, channels  74  radiate from area  76 . Placing area  76  close to an IC chip (e.g., a processor) may result in an improved distribution of heat generated by the IC chip. 
     Referring to FIG. 8, a cross-sectional view of the base plate  71  of FIG. 7 along line A—A is shown. In this example, each channel  74  includes grooves  75  that extend along a channel&#39;s length although the invention is not limited in scope in this respect. As described above, the grooves  75  may serve as a wicking structure in the channel  74 . 
     Although several embodiments are specifically illustrated and described herein, it will be appreciated that modifications and variations of the present invention are covered by the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention. For example, the base plate and/or I/O plates described herein with integrated heat pipes may be substantially planar or may have other shapes as needed to improve heat management in conjunction with electronic circuitry or the like.