Abstract:
A heat sink assembly, having a number of mounting holes therethrough, is installed on a heat generating surface of an electronic component for removing heat therefrom. A heat dissipating member having a base portion having a bottom surface and an upper surface with heat dissipating elements connected thereto is provided. The bottom surface is adapted to be matable in flush thermal communication with a heat generating surface of an electronic component. A cam assembly includes a support body as well as a connection body that is pivotally connected thereto about a pivot axis. At least one leg is connected to the support body with a retention member on its free end. The leg is routed through a selected one of the base apertures and one of the mounting holes corresponding thereto. The connection body is rotated about the pivot axis to provide a camming action against the top surface of the base portion of the heat dissipating member to maintain the heat dissipating member in flush thermal communication with the heat generating surface of the electronic component. The retention member on the leg prevents the leg from being removed from the apertures in which is resides thus maintaining the connection body in communication with the top of the base of the heat dissipating member.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to electronic solid state and integrated circuit devices. More specifically, the present invention relates to apparatuses for dissipating heat generated by such devices. 
     In the electronics and computer industries, it has been well known to employ various types of electronic device packages and integrated circuit chips, such as the PENTIUM central processing unit chip (CPU) manufactured by Intel Corporation and RAM (random access memory) chips. These integrated circuit chips have a pin grid array (PGA) package and are typically installed into a socket which is soldered to a computer circuit board. These integrated circuit devices, particularly the CPU microprocessor chips, generate a great deal of heat during operation which must be removed to prevent adverse effects on operation of the system into which the device is installed. For example, a PENTIUM microprocessor, containing millions of transistors, is highly susceptible to overheating which could destroy the microprocessor device itself or other components proximal to the microprocessor. 
     In addition to the PENTIUM microprocessor discussed above, there are many other types of semiconductor device packages which are commonly used in computer equipment, for example. Recently, various types of surface mount packages, such as BGA (ball grid array) and LGA (land grid array) type semiconductor packages have become increasingly popular as the semiconductor package of choice for computers. 
     In addition, microprocessors are commonly being installed onto a circuit board which is, in turn, installed into a motherboard or other similar primary circuit board. For example, microprocessors, such as the Pentium II and the Celeron from Intel, are “processor cards” which are installed into a motherboard of a computer in similar fashion to the way a modem is installed into a motherboard. On a given processor card is typically the processor semiconductor device package itself along with any other chips or semiconductor devices that are necessary for the operation of the card, such cache chips, or the like. The processor package may be installed into the processor card via a pin grid, ball grid, land grid array and with a socket such as a ZIF or ball grid socket. 
     In similar fashion to the earlier semiconductor devices discussed above, the processor cards like the Pentium II and Celeron also suffer from excessive generation of heat. In particular, the processor semiconductor device package on the card generates the heat which is of most concern. A given surface of the component will, as a result, be very hot. If such heat is not properly dissipated, the processor semiconductor device package and the entire processor card or component will eventually fail. Understanding the need for heat dissipation and the connection of heat sinks, the manufacturers of processor cards typically include holes completely or partially through the processor card to facilitate the installation of heat sink assemblies thereto. Commonly, an array of at least four holes are present to receive heat sink devices. 
     In view of the foregoing, efforts have been made to supply a heat dissipating member, such as a heat sink, into thermal communication with the processor card and more specifically, the processor semiconductor device package. These efforts commonly employ the available holes present in the processor card to serve as anchors for the receipt of a heat sink assembly. For example, prior art attempts include an extruded heat sink assembly with a base and an array of fin members emanating upwardly therefrom. The base includes a number of through holes which correspond with the arrangement of the holes provided by the manufacturer of the processor card. The heat sink assembly is secured to the processor card by screws which are hand-tightened to the desired tension and communication between the base of the heat sink and the processor card. These heat sinks attach directly to the heat generating package or the housing containing the package, such as in a Pentium II environment. 
     In addition, heat sink assemblies have also been available which provide a heat sink base and associated fins along with a spring clip which engages the holes in the processor card and spans across the heat sink base to secure it in place. While relative easy to install, this attempt in the prior art is not capable of fast tension adjustment of communication between the heat sink base and surface to be cooled and requires tools for installation. 
     In addition to the processor cards of the prior art, processor semiconductor device packages may also be installed directly into a main circuit board, such a motherboard, in similar fashion to the older Pentium or 486 processor packages. Some manufacturers are also providing through holes in the motherboard itself to permit the attachment of heat sink assemblies as an alternative to attaching the heat sink assembly to the semiconductor package itself or the socket into which it is installed. In similar fashion to the processor cards discusses above, these processor package arrangement suffer from similar problems associated with the attachment of heat sink assemblies to avoid overheating problems. 
     In view of the foregoing, there is a demand for a heat sink assembly that attach to a heat generating semiconductor device package without attaching to the semiconductor package itself. In addition, there is a demand for a heat sink assembly that can quickly and easily attach to holes provided proximal to the device to be cooled without the need for tools for installation. 
     SUMMARY OF THE INVENTION 
     The present invention preserves the advantages of prior art heat sink assemblies for integrated circuit devices, such as microprocessors. In addition, it provides new advantages not found in currently available assemblies and overcomes many disadvantages of such currently available assemblies. 
     The invention is generally directed to the novel and unique heat sink assembly with particular application in cooling microprocessor integrated circuit devices, such as Pentium II and Celeron semiconductor device packages. The heat sink assembly of the present invention enables the simple, easy and inexpensive assembly, use and maintenance of a heat sink assembly while realizing superior heat dissipation. 
     A heat sink assembly, having a number of mounting holes therethrough, is installed on a heat generating surface of an electronic component for removing heat therefrom. A heat dissipating member having a base portion having a bottom surface and an upper surface with heat dissipating elements connected thereto is provided. The bottom surface is adapted to be matable in flush thermal communication with a heat generating surface of an electronic component. A cam assembly includes a support body as well as a connection body that is pivotally connected thereto about a pivot axis. At least one leg is connected to the support body with a retention member on its free end. The leg is routed through a selected one of the base apertures and one of the mounting holes corresponding thereto. The connection body is rotated about the pivot axis to provide a camming action against the top surface of the base portion of the heat dissipating member to maintain the heat dissipating member in flush thermal communication with the heat generating surface of the electronic component. The retention member on the leg prevents the leg from being removed from the apertures in which is resides thus maintaining the connection body in communication with the top of the base of the heat dissipating member. 
     In operation, the legs of the cam lock assembly are installed through selected base apertures and corresponding mounting holes in the electronic component. The free ends of the legs carry retention members which pass through the holes and apertures to provide stop members on the opposing side of the circuit board or electronic component. The armature emanating from the connection body is manipulated to rotate the connection body about the pivot axis thereby causing the portion of the connection body with the greater transverse distance from the pivot axis to engage the top of the base portion of the heat dissipating member to urge the base portion into flush thermal communication with the heat generating surface of the electronic component where the stops are snugly positioned against the back of the circuit board or electronic component to prevent removal of the legs. As a result of the flush thermal communication of the bottom of the heat sink assembly and the heat generating surface, efficient thermal transfer to the heat dissipating member can be realized. 
     It is therefore an object of the present invention to provide a heat sink assembly which can accommodate a wide array of semiconductor device packages. 
     It is an object of the present invention to provide a heat sink assembly that can accommodate a semiconductor device mounted on a processor card. 
     It is a further object of the present invention to provide a heat sink assembly that can accommodate a semiconductor device without attaching to the device itself or the socket into which it is installed. 
     Another object of the present invention is to provide a heat sink assembly that can quickly and easily attach to a circuit board carrying a semiconductor device package. 
     It is a further object of the present invention to provide a heat sink assembly that can be locked without the use of tools to provide a flush thermal communication between the heat sink member and the device or surface to be cooled. 
     It is yet a further object of the present invention to provide a heat sink that can attach to and cool a heat generating surface. 
     It is also an object of the present invention to provide a heat sink that can be both easily installed on a heat generating surface and tension adjusted without the use of tools. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features which are characteristic of the present invention are set forth in the appended claims. However, the inventions preferred embodiments, together with further objects and attendant advantages, will be best understood by reference to the following detailed description taken in connection with the accompanying drawings in which: 
     FIG. 1 is a perspective view of the heat sink assembly of the present invention with cam locks installed; 
     FIG. 2 is an exploded perspective view of the heat sink assembly of the present invention shown in FIG. 1; 
     FIG. 3A is a perspective view of a cam lock of the present invention in an unlocked position; 
     FIG. 3B is a bottom view of the cam lock of FIG. 3A; 
     FIG. 4 is a side view of the cam lock of the present invention in FIG. 3 in a locked position; 
     FIG. 5 is a side view of the cam lock of the present invention in FIG. 3 in an unlocked position; 
     FIG. 6 is an exploded perspective view of the heat sink assembly of the present invention illustrating attachment to a semiconductor device package on a circuit board; 
     FIG. 7 is a partially exploded view of the heat sink assembly of the present invention illustrating interconnection of the cam locks to a circuit board carrying a semiconductor device to be cooled; 
     FIG. 8 is a cross-sectional view through the line  8 — 8  of FIG. 7; 
     FIG. 9 is perspective view of the heat sink assembly of the present invention installed on a circuit board and in an unlocked condition; 
     FIG. 10 is a cross-sectional view through the line  10 — 10  of FIG. 9 with cam lock in an open position; 
     FIG. 11 is a cross-section view through the line  10 — 10  of FIG. 9 with cam lock in a locked position; 
     FIG. 12 is a perspective view of the heat sink assembly of the present invention illustrating the ability to be installed on a circuit board carrying a BGA socket semiconductor device package arrangement; and 
     FIG. 13 is a perspective view of the heat sink assembly of the present invention illustrating the ability to be installed on the housing an edge connector type semiconductor package. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     It should be noted that the present invention provides a heat sink assembly  10  for attachment to any semiconductor device package attached to a circuit board with an array of holes completely therethrough or partially therethrough. The present invention is shown in FIGS. 1-11 as attaching to a surface mount semiconductor device package  42  is for illustration purposes only. It should be understood that various other types of semiconductor packages may be installed on a circuit board and accommodated by the present invention. FIG. 12, as discussed in detail below, illustrates the attachment of the present invention to a BGA semiconductor device package  56  within a BGA socket  52  to illustrate the flexibility of applications of the present invention. FIG. 13 shows a further application to attach to a heat generating surface. 
     Further, for ease of illustration, the following description addresses the attachment of the heat sink assembly of the present invention to a semiconductor package installed on a circuit board. This is intended to the include an a semiconductor arrangement where the circuit board is a “semiconductor card,” such as a Pentium II or Celeron product, or where the circuit board is the motherboard or main circuit board itself. It further includes an arrangement, as in a Pentium II processor, where the circuit board is encased in a housing which includes holes therein. In this arrangement, an outer surface of the housing will generate heat, as shown in FIG.  13 . The present invention is, therefore, suitable for dissipating heat generated by a given surface of an electronic component. As will be readily apparent, the heat sink assembly of the present invention can accommodate a wide range of semiconductor arrangements where holes are provided proximal to the package or surface to be cooled. 
     Referring to FIGS. 1 and 2, the preferred embodiment of the heat sink assembly  10  of present invention is generally shown to include a heat dissipating member  14  with a base portion  18  and a number of fins  16  extending upwardly therefrom. Cam lock assemblies  12  are provided each with a pair of legs  30  which extend downwardly therefrom. The length of legs  30  may be selected to accommodate the particular size of the member to be cooled. Each assembly  12  includes an armature  28  for securing the cam lock in a locked position. Further, as will be discussed in detail below, bottom surface  20  of heat dissipating member  14  communicates with a heat generating surface and cam lock assemblies ensure that such communication is securely maintained. 
     Turning now to FIGS. 3-5 details of the cam lock assembly  12  is shown. In general, it should be understood that for illustration purposes only, 2 cam lock assemblies  12  shown to accommodate the particular heat dissipating member  14  shown in FIGS. 1 and 2. In certain applications only one cam lock assembly  12  may be required and, further, more or less than  2  legs may be employed by cam lock assembly  12  to address the given application. For ease of illustration, discussion of the cam lock assemblies  12  will be discussed in connection with a single cam lock assembly as the operation of all cam lock assemblies with a give heat sink assembly  10  are identical. 
     FIG. 3A illustrates a perspective view of the cam lock  12  in accordance with the present invention while FIG. 4 illustrates the cam lock  12  in a locked position and FIG. 5 illustrates the cam lock  12  in an opened position. The cam lock  12  includes a support body  22  with, preferably a pair of upstanding walls  23 . A pivot pin  24  is transversely positioned through body  22 . A pair of legs  30  are provided each with an upper circumferential flange  70  and a lower circumferential flange  72 . To facilitate compression of legs  30 , slot  74  is provided longitudinally up from the free ends of legs  30  a selected distance at least up past upper flange  70 . The legs  30  may be made of compressible plastic so that slot  74  need not be used. The legs preferably emanate downwardly from support body  22 . As shown in FIG. 3B, a bottom view of the cam lock  12  shown in FIG. 3A, cam plate  26  is pivotally connected to support body  22  via pin  24 . Cam plate  26  is permitted to rotate within cavity  27  with support body  22 . 
     Turning now to FIGS. 4 and 5, pivotal rotation of cam plate  26  is shown in further detail. With the assistance of armature  28 , cam plate  26  may be easily rotated about pin  24 . FIG. 4 illustrated the rotation of cam plate  26  into a locked position. In particular, cam plate  26  includes a configuration where at different portions of the cam plate  26 , the length from pin  24  to an outer edge is different. In particular, edge  78  and edges  76  are provided. Movement of armature  28  to the side position shown in FIG. 4 causes edge  76  to emanate down below the lower edge of support body  22 . In contrast, movement of armature  28  to an upward position, as shown in FIG. 5, causes rotation of cam plate  26  and edge  78  to be the downwardmost edge. Since the distance from pin  24  to edge  78  is less than the distance from pin  24  to edge  76 , positioning armature in the position shown in FIG. 5 causes cam plate  26  to not protrude as far down as if the armature is positioned to the side as in FIG.  4 . As will be discussed in detail below the rotational movement of cam plate  26 , facilitated by armature  28 , will effectively lock the heat sink assembly in place onto a heat generating surface. It should also be understood that two different distances from pin  24  are shown to designate a locked and open condition. Additional distances and more than two edges may be employed to accommodate different height processors, or the like. For example, edges  76  are shown to have the same distance from pin  24 . Alternatively, one of the edges could be different than the other edge  76  and further different than edge  78  to accommodate processors of different thicknesses by the same cam lock assembly. 
     Referring now to FIGS. 6-11, details of the assembly and installation of the heat sink assembly  10  of the present invention is shown. FIG. 6 illustrates an exploded perspective view of the heat sink assembly  10  in a position to be installed on circuit board  34 . In this arrangement, two cam lock assemblies  12  are provided each with a pair of legs  30  for routing through holes  19 , as in FIG. 8, and through holes  36  through circuit board  34 . Channels  80  are provided within pin grid array  16  to facilitate installation of cam lock assemblies  12 . 
     Referring to FIGS. 6-8, both of the cam lock assemblies  12  are installed into corresponding holes  19  through base  18  of heat dissipating member  14 . FIG. 8 shows a cross-sectional view through the line  8 — 8  of FIG. 7 to further illustrate the routing of legs  30  through holes  19  in base  18 . Legs  30  are routed into corresponding holes  19  in base  18  so that both sets of flanges  70  and  72  clear past the bottom surface  20  of base  18 . The compressibility of flanges  70  and  72  permits legs  30  to be routed into holes  19  in one-way fashion in that once the flanges  70  and  72  clear the bottom of base  18 , they will expand preventing easy removal. 
     Once both of the cam locks  12  are installed into heat dissipating member  14 , the assembled structure can now be installed on the desired heat generating device. Referring to FIG. 7 the assembled structure is generally aligned with corresponding holes  36  on circuit board  34 . First, the pair of legs  30  on one of the cam lock assemblies  12  is routed through corresponding holes  36  so that lower flanges  72  clear past holes  36 . This routing is accomplished by simply pressing on the heat dissipating member  14  itself without the use of tools. The bottom surface  20  of base  18  engages with top flanges  70  of the pair of legs  30  to urge this pair of legs  30  through corresponding holes  36 . Once the legs  30  associated with one cam lock  12  are installed, the opposing pair of legs associated with the other cam lock  12  may now be installed. The entire heat dissipating member  14  is tilted to take up the slack between top flanges  70  of the first pair of legs and support body  22  to permit the second pair of legs to be routed into their corresponding holes  36  with the assistance of the bottom surface  20  of base  18  urging against top flanges  70 . This two step installation of the two pairs of legs  30  must be done so that the heat sink assembly  10  may be installed properly onto a semiconductor device  42  that must have a height, including circuit board, that is greater than the distance from flanges  70  to  72  so that, as will be seen below, the bottom surface  20  of base  18  contacts semiconductor device  42  not top flanges  70 . 
     Now that the heat sink assembly  10  has now been initially attached to the device to be cooled, as shown in FIG. 9, it can now be locked into place as shown in FIGS. 10 and 11; namely, the slack between the bottom surface  20  of base  18  and the top surface  43  of semiconductor device  42  can now be eliminated. In FIG. 10, a cross-sectional view through the line  10 — 10  of FIG. 9, this slack can be seen. This slack is necessary for preparation for the installation of the heat sink assembly  10 . In FIG. 10, armature  28  is positioned upwardly so that edge  78  contacts top surface  21  of base  18 . In FIG. 11, armature  28  is rotated counter-clockwise about pin  24  to cause base  18  to lift off of edge  78 . As a result, edge  76  now is urged into communication with top surface  21  of base  18  thus urging bottom surface  20  of base  18  into flush communication with the top surface  43  of semiconductor device  42  to be cooled. Engagement of bottom flanges  72  with holes  36  prevent removal of legs  30  from holes  36 . It should be noted that while the heat sink assembly  10  is locked in place, upper flanges  70  are not used. Flanges  70  are only used during the initial installation of legs  30  through holes  36 . 
     It should be understood that heat sink assembly  10  is employed to dissipate heat from heat generating semiconductor device package  42  which includes a top surface  43  and is electrically interconnected to circuit board  34  via electrical interconnections  44 . Circuit board  34 , as commonly found in the industry, includes a number of holes  36  positioned about the semiconductor package  42  to be cooled. the assembly  10  is illustrated to provide four downwardly depending legs  30  to communicated with corresponding four holes  36  through circuit board  34 . It should be understood that the provision of four legs  30  and four corresponding receiving holes  36  is by way of example only and that fewer or greater than four legs  30  and corresponding receiving holes  36  may be provided in accordance with the application at hand. Further, individual cam locks  12  may be provided for each hole  36  where each cam lock  12  has a single leg  30 . In the alternative, a single cam lock assembly  12  may be provided with four legs connected to a single support body  22 . Also, armature  28  may be offset relative to what is shown in FIG. 11 so that locking occurs when armature  28  is vertical as opposed to the side. Such alternate positioning of armature  28  may be selected in accordance with the application at hand and the configuration and height of heat dissipating member  14 . 
     FIG. 12 illustrates an alternative application of the heat sink assembly  10  to a BGA package and socket arrangement. In particular, circuit board  34  carries BGA socket  52  with contact array  54  thereon. Positioned about socket  52  is an array of holes  36 . BGA package  56 , with ball array  58 , communicates with socket  52  and ball array  58  electrically communicates with contact array  54 . As described above, assembly  10  is installed into circuit board  34  with flanges  72  engaging below holes  36 . Heat sink  14  is secured so that bottom surface  20  of base  18  contacts top surface  60  of BGA package  56 . Locking of cam lock  12  not only provides a quality thermal connection between heat dissipating member  14  and BGA package  56  but also maintains BGA package in electrical connection between ball array  58  and contact array  54  of its socket  52 . 
     As can be understood from the application in FIG. 12, the present invention has a wide range of applications and can be easily adapted for such applications. Further applications include any circuit board configuration where a heat generating device is provided on a circuit board or similar substrate and where a receiving structure, such as an array of holes, are provided. The present invention may be easily adapted to an application where the circuit board containing the heat generating device is encased in a housing, such as a Pentium II configuration. In this arrangement, as shown in FIG. 13, receiving structures, such as holes or slots  36 , are provided in the housing  62  with electrical interconnect  64 , which are capable of receiving the legs  30  so that heat dissipating member  14  can be placed in flush thermal communication with a heat generating region  66  of the surface of housing  62  which is proximal to the heat generating device contained therein. 
     It is preferred that the cam lock assemblies  12  be manufactured of plastic material, such as a high temperature resistant and high creep resistant plastic for better withstanding the high temperatures associated with microprocessors. Cam lock assemblies may be made of a combination of metal an plastic where some parts are manufactured of metal and other parts are manufactured of plastic. For example, the plastic material may be LNP VERTON UF-700-10-HS (P.P.A. 50% long fiber) for use in high temperate heat sink applications. In addition, heat dissipating member  14  is preferably metal, such as aluminum, for optimum thermal transfer and dissipation of heat from semiconductor device packages  42 . Alternatively, heat dissipating member  14  may be manufactured of a conductive plastic material if so desired and depending on the application. Fins  16  are provided in a pin grid array but various other heat sink fin configurations, such as a radial fin array, may be employed. 
     It would be appreciated by those skilled in the art that various changes and modifications can be made to the illustrated embodiments without departing from the spirit of the present invention. All such modifications and changes are intended to be covered by the appended claims.