Extended surface area heat sink

A heat sink for cooling a high power consumption device, such as a central processing unit (device), has extended heat transfer areas. In an embodiment, the extended heat transfer areas may include fins protruding from portions of a heat sink base. The extended heat transfer area of the heat sink may overhang an area of a circuit board adjacent to the high power consumption device. Low power consumption components, such as memory chips, can be mounted on the circuit board in close proximity to the high power consumption device and beneath the heat sink. The low power consumption component may have separate heat sinks that attach to the low power consumption components and extend beyond the base of the high power consumption device heat sink.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 This invention generally relates to heat sinks for computer systems, and
 more particularly to a heat sink for a high energy consumption device,
 such as a central processing unit, which may be placed in close proximity
 to low power consumption components, such as memory chips.
 2. Description of the Related Art
 Computer systems such as workstations, personal computers, and portable
 computers may include components housed within an enclosure. Some
 components, such as central processing unit (devices) and memory chips,
 typically mount on circuit boards within the enclosure. Other components,
 such as circuit boards and disk drives, typically mount to a chassis of
 the computer system.
 Only a limited amount of space exists within a computer enclosure. Computer
 systems may be designed to make the best use of the available space.
 Computer components need to be in close proximity to each other so that
 the best performance from the computer components may be obtained.
 However, having computer components in close proximity to each other may
 be problematic due to geometry and heat generation factors within the
 computer enclosure.
 A computer component may function properly only when an operating
 temperature of the component is at or below a maximum operating
 temperature. In some instances, a package surface area of a component is
 too small to permit sufficient heat transfer from the package to keep the
 component at or below maximum operating temperatures using natural
 convection. Such a component requires additional cooling. If the
 temperature of a computer component exceeds the maximum operating
 temperature of the component, or if the temperature within the computer
 enclosure exceeds a maximum operating temperature, a reduction of computer
 performance may occur. Eventually, the components of the computer system
 may be permanently damaged or destroyed if the computer components or the
 computer system are operated at too hot a temperature.
 Some computer components may be high power consumption devices. High power
 consumption devices typically generate large amounts of heat during use.
 Generally, high power consumption devices require cooling to function
 properly. The cooling of a high power consumption device may be
 accomplished by attaching a heat sink to the high power consumption
 device. The high power consumption device transfers heat to the heat sink,
 and the heat sink transfers the heat to the surroundings. One type of heat
 sink provides a thermal connection between a heat transfer surface of the
 high power consumption device and a convection cooled surface area of the
 heat sink. A cooling fan, or cooling fans, within the computer enclosure
 may provide forced convection to transfer heat from the heat sink to the
 surroundings if natural convection within the computer enclosure does not
 provide enough heat transfer to the surroundings. It is desirable to
 provide a heat sink for a high power consumption device that has a large
 heat transfer surface area. The heat sink should allow the device to
 operate at as low a temperature as possible.
 One type of heat sink for a high power consumption device includes a base
 having a plurality of fins extending from an upper surface of the base.
 The base has a lower surface that generally corresponds to the principal
 heat transfer surface of the high power consumption device. The upper
 surface of the base typically has the same shape as the lower surface of
 the base. The fins provide extended heat transfer surface area for the
 heat sink.
 Another type of heat sink for a high power consumption device is shown in
 U.S. Pat. No. 5,412,535, issued to Chao et al, and is incorporated by
 reference as if fully set forth herein. The heat sink comprises a base
 with a vertically mounted heat pipe connected to the base. The lower
 surface of the base thermally contacts the heat transfer surface of the
 high power consumption device. Horizontal fins extend from the heat pipe
 to increase the heat transfer surface area of the heat sink.
 Some computer components, such as a collection of static random access
 memory (SRAM) units, may be low power consumption components. Low power
 consumption components may require heat sinks to keep the components
 functioning properly. A heat sink for a low power consumption component
 may be required if the component generates excessive heat during use, or
 if the component is placed near a high power consumption device.
 Individual heat sinks may be provided for individual low power consumption
 components, or one heat sink may be used to cool several low power
 consumption components.
 SUMMARY OF THE INVENTION
 A finned heat sink for a high power consumption device includes extended
 heat transfer surface area that overhangs portions of a circuit board
 adjacent to the high power consumption device. Low power consumption
 components may be mounted in close proximity to the high power consumption
 device. A portion of the heat sink may extend over the low power
 consumption components. Sufficient room may exist between overhanging
 portions of the heat sink and the low power consumption components to
 allow an optional heat sink or a plurality of optional heat sinks to be
 attached to the low power consumption components.
 The heat sink for the high power consumption device may require the
 addition of a high thermal conductivity material to a portion of the heat
 sink that contacts a heat transfer surface of the high power consumption
 device. The high thermal conductivity material may help to spread heat
 transferred from the high power consumption device throughout the heat
 sink. The high thermal conductivity material may absorb high heat flux
 generated by the high power consumption device. The high thermal
 conductivity material may spread the heat flux throughout the finned heat
 sink to promote efficient heat transfer from fins of the heat sink to the
 surroundings. The high thermal conductivity material may be a metal, such
 as copper or a copper alloy, and/or the high thermal conductivity material
 may include a heat pipe or heat pipes. A heat pipe may be a vapor chamber
 plate type of heat pipe. A heat pipe may be mounted or interleaved in a
 surface of the extended area heat sink. A heat pipe or a surface of the
 extended area heat sink immediately adjacent to the heat pipe may be
 placed in thermal contact with the high power consumption device.
 An extended area heat sink for a high power consumption device may allow
 the components of a computer system to be placed close together within a
 computer enclosure. Placing the components of a computer system close
 together may allow the computer enclosure to be small. Close placement of
 the computer components and devices may allow for improved performance of
 a computer system. Because the heat sink for the high power consumption
 device has extra heat transfer surface area, cooling fans within the
 computer system may be operated at lower speeds while still providing
 sufficient system cooling. Operating system fans at low speeds may reduce
 acoustic noise generated by the computer system. Operating the system fans
 at low speeds may also extend the life of the fans.
 An advantage of an extended area heat sink is that the heat sink may allow
 the development of faster and more efficient electronic devices.
 Components of a system may be located adjacent to a high power consumption
 device that generates a large amount of heat. The heat generated by the
 high power consumption device may be dissipated by the extended area heat
 sink. The close proximity of components to the high power device may allow
 for more efficient, faster, and smaller electronic systems.
 Another advantage of an extended area heat sink is that the heat sink may
 allow for a reduction in noise generated by a system. The extended area
 heat sink may allow system fans to run at low speeds so that the overall
 noise generated by a system is reduced. Running a fan at a low fan speed
 may help to extend the life of the fan. A low fan speed may also help to
 ensure that the system meets environmental regulatory requirements. An
 extended area heat sink may also be sturdy, durable, light weight, simple,
 efficient, reliable and inexpensive; yet the heat sink may also be easy to
 manufacture, install, maintain and use.

While the invention is susceptible to various modifications and alternative
 forms, specific embodiments thereof are shown by way of example in the
 drawings and will herein be described in detail. It should be understood,
 however, that the drawings and detailed description thereto are not
 intended to limit the invention to the particular form disclosed, but to
 the contrary, the intention is to cover all modifications, equivalents and
 alternatives falling within the spirit and scope of the present invention
 as defined by the appended claims.
 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 With reference to the drawings, and particularly to FIGS. 1 and 2, a heat
 sink system is designated generally as 20. The heat sink system 20 may
 include device heat sink 22 and component heat sinks 24. FIGS. 3 and 4
 show circuit board 26 without the heat sink 22 and without the component
 heat sinks 24 to show the components located beneath the heat sinks. The
 heat sink 22 may be used to cool a high power consumption device 28, such
 as central processing unit (device). The device 28 may be a part of a
 computer system. Upper surface 30 of the device 28 is a heat transfer
 surface for the device. Component heat sinks 24 may cool components 32
 that are located in close proximity to the device 28. Some components 34
 located in close proximity to the device 28 may not require a heat sink
 24. The upper surfaces 36 of the components 32 may be heat transfer
 surfaces. Various methods and systems exist for attaching computer
 components and devices to a circuit board. Such systems and methods are
 well known in the art and are not described herein.
 As shown in FIGS. 1, 2, and 3, device module 38 may include a circuit board
 26, device 28, heat sink 22, components 32 in close proximity to the
 device, component heat sinks 24, and other computer components 40. FIG. 5
 shows a bottom view of a device module 38. Bolster plate 42 may support
 heat sink 22. The bolster plate 42 may have threaded posts 44 that extend
 through circuit board 26, and through holes 46 in the heat sink 22 (holes
 46 shown in FIGS. 7 and 8). Fasteners 48 (shown in FIG. 1) may connect to
 the posts 44 to secure the heat sink 22 to the circuit board 26. Securing
 the heat sink 22 to the circuit board 26 thermally connects surface 50 of
 the heat sink to the heat transfer surface 30 of the device 28. The heat
 sink surface 50 has a perimeter. The perimeter of the surface 50 may
 generally correspond to the perimeter of the heat transfer surface 30 of
 the device 28.
 Heat sink 22 may be supported by the device 28, the bolster plate 42, and
 the posts 44. Component heat sinks 24 may be supported by the components
 32, and by posts 52 extending from the circuit board 26, as shown in FIG.
 2.
 A portion of heat sink 22 may extend over component heat sinks 24 and
 components 34. The heat sink 22 may be inhibited from contacting the
 component heat sinks 24 and components 34. Air gaps 54 may exist between
 the heat sink 22 and the component heat sinks 24 and components 34. An air
 gap 54 may help to thermally isolate the component heat sinks 24 and
 components 34 from the heat sink 22.
 FIG. 6 shows a perspective view of an embodiment of a heat sink 22. The
 heat sink 22 may have fins 56 and base 58. The fins 56 may extend from
 upper surface 60 of the base 58. The fins 56 may provide extra heat
 transfer surface area for dissipation of heat. The base 58 may have
 thermal contact surface 50 located on lower surface of the base. The
 thermal contact surface 50 may thermally connect the heat sink 22 to a
 heat transfer surface 30 of the device 28. The base 58 may also have
 extensions 62. Extensions 62 extend beyond the perimeter of the heat sink
 contact surface 50. When the heat sink 22 is mounted to a circuit board
 26, the extensions 62 may overhang sections of the circuit board adjacent
 to the device 28. Portions of the extensions 62 may extend over and above
 portions of the components 32, as shown in FIG. 2. The extensions 62 may
 extend beyond the perimeter of the heat sink contact surface 50 greater
 than approximately 1/4 of an inch from an edge of the contact surface. The
 extensions 62 may extend beyond each edge of the contact surface 50.
 Alternatively, the extensions 62 may extend beyond only selected edges of
 the contact surface 50.
 The base 58 and fins 56 of the heat sink 22 may be made of a lightweight,
 high thermal conductivity metal. The lightweight metal may minimize the
 mass of the heat sink 22. The high thermal conductivity of the metal may
 promote heat transfer. A preferable metal is aluminum or an aluminum
 alloy. Because the heat sink 22 has extensions 62 which extend beyond the
 heat sink contact surface 50, a portion of the contact surface may be made
 of a metal with a higher thermal conductivity than the lightweight, high
 thermal conductivity metal used to form the base 58. The higher thermal
 conductivity metal may help spread heat transferred from the device 28
 throughout the heat sink 22. FIG. 7 shows a bottom view of the heat sink
 22 wherein the contact surface 50 is a copper plate. The extensions 62 may
 be located on each side of the contact surface 50, or only on selected
 sides of the contact surface. FIG. 8 shows a bottom view of an alternate
 embodiment of a heat sink 220. The contact surface 50 of the heat sink 220
 includes high thermal conductivity heat pipes 64. A heat pipe 64 may be a
 vapor chamber plate heat pipe, or another type of heat pipe. Heat pipes 64
 may help to spread heat transferred from the device 28 throughout the heat
 sink 22.
 The heat sink 22 shown in FIG. 8 has only two extensions 62 adjacent to the
 contact surface 50. A heat sink 22 may have from one to four extensions
 62. The extensions 62 may be irregularly shaped to avoid obstacles
 positioned on a circuit board 26. For example, an extension 62 may have a
 half circle cut-out located adjacent to an edge of the extension. The
 cutout may allow the heat sink 22 to be positioned near a post or device
 that extends from the circuit board 26.
 FIG. 9 shows a perspective view of a component heat sink 24. The heat sink
 24 may include a base 66. As shown in FIG. 2, a portion of the base 66 may
 extend beyond edge 68 of the heat sink extensions 62 when the device
 module 38 is assembled. Thermal contact surface 70 of the base 66 may
 contact the component heat transfer surface 36. A portion of the base 66
 that extends beyond the heat sink extensions 62 may have protruding fins
 72. The fins 72 may provide extended surface area for the heat sink 24.
 The heat sink base 66 may be made of a high thermal conductivity material
 such as copper, copper alloys, aluminum, or aluminum alloys. A heat sink
 24 may be formed for each individual component 32, or one heat sink may
 serve as a heat sink for several components. Heat sinks 24 may have shapes
 designed to avoid contact with nearby computer components 40.
 A device module 38 may optionally include mounting fasteners 74, upper
 plate 76, and contacts 78. The contacts 78 may allow the device module 38
 to be electrically coupled to another circuit board 80. Multiple device
 modules 38 may be located in close vertical or horizontal proximity to
 each other. FIG. 10 shows an embodiment of three device modules 38 coupled
 to a circuit board 80. Fans 82 may provide forced convection cooling of
 the device modules 38. Fan shrouds 84 may be attached to the fans 82 to
 direct air flow produced by the fans.
 A high energy consumption device 28, such as a CPU, may be mounted to a
 circuit board 26 or to other support structure. Component devices 32 may
 be mounted to the circuit board 26 in close proximity to the device 28. To
 form a heat sink system 20, component heat sinks 24 may be attached to
 selected components 32 adjacent to the device 28. A thermally conductive
 paste or glue may be placed between a heat transfer surface 70 of the
 component heat sink 24 and the component heat transfer surfaces 36. In
 alternate embodiments, component heat sinks 24 may be attached directly to
 the components 32, to posts 52 extending from the circuit board 26, or the
 component heat sinks may be attached by any other method that establishes
 good thermal contact between the component heat sinks and the selected
 components. Some components 34 that are in close proximity to the device
 28 may not require component heat sinks 24.
 After the component heat sinks 24 are placed in thermal contact with
 components 32 that require additional cooling, a heat sink 22 may be
 placed on the device 28. Air gaps 54 may exist between the heat sink 22
 and the component heat sinks 24 and/or the components 34. Heat transfer
 surface 30 of the device 28 may be placed in direct thermal contact with
 the heat transfer surface 50 of the heat sink 22. In an embodiment, a high
 thermal conductivity paste or thermal glue may be placed between heat
 transfer surface 30 of the device 28 and the heat transfer surface 50 of
 the heat sink 22. The device 28 may be coupled to the circuit board by a
 bolster plate 42, bolster plate posts 44, and fasteners 48. Alternatively,
 another system for fastening a heat sink 22 to a device 28 may be used.
 After installing the device 28, remaining components and devices of a
 system may be coupled together to form a system. The remaining components
 and devices may include a fan or fans for forced convection cooling of the
 system. The system may be connected to a power supply.
 When power is supplied to the system, the high energy consumption device 28
 may dissipate heat. Some of the heat dissipated by the device 28 may be
 transferred to the heat sink 22. The heat sink 22 may transfer heat to the
 surroundings by natural convection, or by forced convection if the system
 includes a cooling fan or cooling fans. The air gaps 54 between the heat
 sink 22 and the component heat sinks 24 and/or components 34 may inhibit
 the component heat sinks and/or the components from being heated by the
 device 28 and the heat sink 22. Heat dissipated by the selected components
 32 may be transferred to the component heat sinks 24. The component heat
 sinks 24 may dissipate heat to the surroundings by convection, or by
 forced convection if the system includes cooling fans.
 Further modifications and alternative embodiments of various aspects of the
 invention will be apparent to those skilled in the art in view of this
 description. Accordingly, this description is to be construed as
 illustrative only and is for the purpose of teaching those skilled in the
 art the general manner of carrying out the invention. It is to be
 understood that the forms of the invention shown and described herein are
 to be taken as the presently preferred embodiments. Elements and materials
 may be substituted for those illustrated and described herein, parts and
 processes may be reversed, and certain features of the invention may be
 utilized independently, all as would be apparent to one skilled in the art
 after having the benefit of this description of the invention. Changes may
 be made in the elements described herein without departing from the spirit
 and scope of the invention as described in the following claims.