Abstract:
The invention provides a heat sink assembly having a positionable heat sink permitting the heat sink to be mounted to a substrate in more than one configuration. Various features are described for permitting multiple degrees of freedom in the arrangement of the heat sink assembly. Such features permit the heat sink assembly to be adapted to different environments. The heat sink assembly also has features such as a vane for directing air flow relative to the heat sink. Features for varying and maintaining pressure between the heat sink and a component to be cooled are also included.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority under 35 U.S.C. § 119(e) to provisional patent application No. 60/426,910 filed Nov. 15, 2002; the disclosure of which is incorporated herein by reference. 
     
    
     
       FIELD OF INVENTION  
         [0002]    The invention relates generally to the field of electronic component cooling. In particular, the invention relates to a heat sink for cooling one or more electronic components.  
         BACKGROUND OF INVENTION  
         [0003]    The cooling of electronics components in convection cooling applications is typically achieved using a fluid velocity source to direct a fluid about a heat sink associated with one or more electronic components. The fluid draws heat away from the heat sink, which in turn draws heat from any associated electronic component. The fluid may be a gas, such as air, which is directed by the velocity source, which may be a fan. The fan generally directs the air to flow along a predetermined path about the heat sink. The heat sink must therefore be positioned to co-operate with a particular air flow path in order to cool electronic components associated with the heat sink.  
           [0004]    A typical installation may include a substrate upon which one or more electronic components are mounted. The substrate may then be mounted within an enclosure having air inlets and outlets to permit the removal warm air from within the enclosure. Air flow through the enclosure is encouraged by a fan. A heat sink is mounted to the substrate or the electronic components, and is used to encourage the transfer of heat generated by the electronic components to the air to be carried to the exterior of the enclosure. Pressure is preferably maintained at the interface between the heat sink and the electronic component to encourage thermal transfer therebetween. However, it can be difficult to ensure that such pressure is evenly maintained at the interface.  
           [0005]    To promote this heat transfer, the heat sink has one or more fins to increase the surface area thereof. The fins are generally aligned so that the air flow is directed therethrough. The air flow pathway is often determined by the location of the inlets and outlets of the enclosure, and the location of the fan.  
           [0006]    Once mounted, the orientation of the heat sink may generally not be modified without removing and re-mounting the heat sink. If securing screws for a heat sink are arranged at the vertexes of a square, then the heat sink may be removed, rotated 90 degrees, and reattached. However, the possible orientations of the heat sink is limited to four (i.e., four turns of 90 degrees each). Many arrangements of the prior art are limited in that they permit the mounting of the heat sink in one position only.  
           [0007]    When mass produced, heat sinks are often pre-mounted to a substrate before installation within an enclosure. If the heat sink is not located within the air flow path generated by the fan, thermal-transfer from the heat sink may be sub-optimal. This arrangement may be remedied by removing and re-mounting the heat sink to align the fins of the heat sink with the flow of air generated by the fan. This remedy can increase the time and expense required to install the heat sink, and may not even be possible if suitable alternative mounting locations are not available on the substrate or electronic components. To accommodate different configurations of electronic components and fans, differently configured heat sinks are manufactured. This can increase manufacturing and inventory costs because specialized heat sinks need to be manufactured for different applications. If installations of electronic components require a non-standard orientation of the heat sink then addition effort and expense may need to be expended to fashion a solution.  
           [0008]    The foregoing creates challenges for heat dissipation in the design and manufacture of assemblies of electronic components. Accordingly, there is a need for an alternative heat sink as compared to the existing art.  
         SUMMARY OF INVENTION  
         [0009]    Electronics components heat sink in convection cooling applications rely on a fluid velocity source directing the fluid to the heat sink in a particular direction. Heat sinks and their mounting features are then designed to work with that one air direction path.  
           [0010]    This invention provides a mounting feature that can be adapted to different heat sinks. It provides complete freedom of orientation of the heat sink, independent of the mounting location to the board.  
           [0011]    Typically heat sinks are mounted in the orientation of the flow given by fluid movers located within the electronics enclosure. The orientation is derived by system requirements, which define the inlet and outlet air direction. This particular heat sink attachment method provides flexibility in the orientation of the heat sink within the enclosure.  
           [0012]    The invention may define the spring clip as well as its attachment method to the heat sink. The spring clip is the part of the heat sink assembly that provides the required pressure to the chip ensuring a good thermal conduction path.  
           [0013]    In particular, in one aspect, the invention provides a heat sink assembly comprising a heat sink and a bracket for mounting the heat sink to a component located on a circuit board. The bracket cooperates with the heat sink allowing the heat sink to be set in an installation orientation from a set of orientations relative to the bracket prior to mounting the heat sink against the component.  
           [0014]    The heat sink may further comprise a pedestal and the bracket may further define an opening, such that the pedestal cooperates with the opening allowing the heat sink to be set in the installation orientation.  
           [0015]    The bracket may be mountable about the component to the circuit board.  
           [0016]    The heat sink assembly may further comprise a retaining ring cooperable with the pedestal and the bracket, such that when the pedestal is positioned through the bracket, the ring located on the pedestal in the portion extending through the bracket to retain the heat sink within the bracket.  
           [0017]    The heat sink assembly may further comprise a housing enclosing the heat sink therein, the housing having at least one open end. Further, the housing may be rotatable about the heat sink.  
           [0018]    In the heat sink assembly, the bracket may further comprise a bevel directing airflow towards the heat sink.  
           [0019]    In the heat sink assembly, the bracket may comprise stamped metal. Also, the bracket may be mounted about the component to the circuit board by a fastener securing a leaf on the bracket to the circuit board. Further, the leaf may be initially biased away from the circuit board prior to being secured to the circuit board by the fastener.  
           [0020]    In the heat sink assembly, a feature on the bracket may cooperate with a feature on the pedestal to provide the installation orientation for the heat sink. The feature on the bracket may be a key and the feature on the pedestal may be a rebate. Alternatively, the feature on the pedestal may be a key and the feature on the bracket may be a rebate.  
           [0021]    In the heat sink assembly, a feature on the bracket may cooperate with a feature on the pedestal to inhibit rotation of the heat sink about the bracket in one direction. The feature on the pedestal may be a key and the feature on the bracket may be a raised flange.  
           [0022]    In heat sink assembly, the bracket may comprise formed wire.  
           [0023]    In a second aspect, a heat sink assembly is provided comprising a heat sink, a bracket and a vane connected to the bracket. The bracket is for mounting the heat sink to a component associated with a circuit board. The vane directs air flow from the bracket to the heat sink. The bracket permits the heat sink to be set in a position relative to the bracket prior to final mounting of the heat sink to the circuit board.  
           [0024]    Other combinations, subset and variations of the above described aspects are also provided by other aspects of the invention. Other aspects the invention are described below. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0025]    For the purposes of description, but not of limitation, the foregoing and other aspects of the invention are explained in greater detail with reference to the accompanying drawings, in which:  
         [0026]    [0026]FIG. 1 is an exploded perspective view of a heat sink assembly for mounting to a substrate in accordance with an embodiment of the invention;  
         [0027]    [0027]FIG. 2A is an exploded view of a heat sink assembly according to an embodiment of the invention;  
         [0028]    [0028]FIG. 2B is an assembled perspective view of the heat sink assembly of FIG. 2A;  
         [0029]    [0029]FIG. 2C is an assembled side view of the heat sink assembly of FIG. 2A  
         [0030]    [0030]FIG. 3A is an exploded view of an embodiment of the heat sink assembly having a ratchet mechanism;  
         [0031]    [0031]FIG. 3B is a side exploded view of the heat sink assembly of FIG. 3A;  
         [0032]    [0032]FIG. 3C is an assembled side view of the heat sink assembly of FIG. 3A;  
         [0033]    [0033]FIG. 3D is an assembled perspective view of the heat sink assembly of FIG. 3A;  
         [0034]    [0034]FIG. 4A is an exploded perspective view of a heat sink assembly according to an embodiment of the invention;  
         [0035]    [0035]FIG. 4B is an exploded side view of the heat sink assembly of FIG. 4A;  
         [0036]    [0036]FIG. 4C is an assembled side view of the heat sink assembly of FIG. 4A;  
         [0037]    [0037]FIG. 5A is an exploded perspective view of a heat sink assembly according to an embodiment of the invention;  
         [0038]    [0038]FIG. 5B is an exploded side view of the heat sink assembly of FIG. 5A;  
         [0039]    [0039]FIG. 5C is an assembled side view of the heat sink assembly of FIG. 5A;  
         [0040]    [0040]FIG. 6A is an exploded perspective view of a heat sink assembly according to an embodiment of the invention;  
         [0041]    [0041]FIG. 6B is an exploded side view of the heat sink assembly of FIG. 6A;  
         [0042]    [0042]FIG. 6C is an assembled side view of the heat sink assembly of FIG. 6A;  
         [0043]    [0043]FIG. 7A is an exploded perspective view of a heat sink assembly according to an embodiment of the invention;  
         [0044]    [0044]FIG. 7B is an assembled perspective view of the heat sink assembly of FIG. 7A;  
         [0045]    [0045]FIG. 7C is an assembled side view of the heat sink assembly of FIG. 7A;  
         [0046]    [0046]FIG. 8A is an exploded perspective view of a heat sink assembly according to an embodiment of the invention;  
         [0047]    [0047]FIG. 8B is an exploded side view of the heat sink assembly of FIG. 8A;  
         [0048]    [0048]FIG. 8C is an assembled side view of the heat sink assembly of FIG. 8A;  
         [0049]    [0049]FIG. 8D is a cross-section view of the heat sink assembly of FIG. 8C;  
         [0050]    [0050]FIG. 9A is an exploded side view of a heat sink assembly according to an embodiment of the invention;  
         [0051]    [0051]FIG. 9B is an exploded perspective view of the heat sink assembly of FIG. 9A;  
         [0052]    [0052]FIG. 9C is an assembled side view of the heat sink assembly of FIG. 9A;  
         [0053]    [0053]FIG. 10A is an exploded perspective view of a heat sink assembly according to an embodiment of the invention;  
         [0054]    [0054]FIG. 10B is an assembled perspective view of the heat sink assembly of FIG. 10A;  
         [0055]    [0055]FIG. 10C is an assembled side view of the heat sink assembly of FIG. 10A;  
         [0056]    [0056]FIG. 11 is a perspective view of examples of various embodiments of the heat sink assembly  
         [0057]    [0057]FIG. 12A is an exploded perspective view of a heat sink assembly according to an embodiment of the invention;  
         [0058]    [0058]FIG. 12B is an assembled perspective view of the heat sink assembly of FIG. 12A;  
         [0059]    [0059]FIG. 13A is an exploded perspective view of a heat sink assembly according to an embodiment of the invention;  
         [0060]    [0060]FIG. 13B is an assembled perspective view of the heat sink assembly of FIG. 13A;  
         [0061]    [0061]FIG. 13C is an exploded side view of a heat sink assembly according to an embodiment of the invention; and  
         [0062]    [0062]FIG. 13D is an assembled side view of the heat sink assembly of FIG. 13C. 
     
    
     DETAILED DESCRIPTION OF EMBODIMENTS  
       [0063]    The description which follows, and the embodiments described therein, are provided by way of illustration of an example, or examples, of particular embodiments of the principles of the present invention. These examples are provided for the purposes of explanation, and not limitation, of those principles and of the invention. In the description which follows, like parts are marked throughout the specification and the drawings with the same respective reference numerals.  
         [0064]    Referring to FIG. 1, a heat sink assembly  20  is shown according to an embodiment of the invention is shown. Heat sink assembly  20  may be mounted to a substrate  22 , such as a motherboard, so that it cools an electronic component such as an integrated circuit chip  24 . Heat sink assembly  20  includes a heat sink, which may have any of a number of configurations that are well known in the art. In this particular embodiment, heat sink  26  is generally rectangular and has spaced, generally parallel, fins  28 . Heat sink  26  is connected to a heat sink mounting plate  30 . Mounting plate  30  is secured to substrate  22  (or a component thereof) using fasteners  32 . Fasteners  32  are inserted through one or more holes  34 , defined in mounting plate  30 . Fasteners  32  are retained in bores  36  located in substrate  22 . Fasteners  32  may be screws, and bores  36  may be threaded bores. Heat sink  26  may be located within an enclosure  38 . Fins  28  are oriented to allow a fluid, such as air, to travel along fins  28  in the enclosure  38  in direction A, thereby allowing for improved air contact with fins  28 . Air is circulated about heat sink  26  by a fluid circulating means, such as a fan  37 . Fan  37  can be operated to impel or propel air as design requirements dictate. Air is introduced to enclosure  36  at an air inlet in a direction such as direction A, and air exits enclosure  36  at an outlet in a direction such as direction B. The combined heat sink assembly  20  and substrate  22  may alternatively be located together within an enclosure having at least one inlet through which air is permitted to circulate. Cooling may also be achieved without the use of an enclosure or similar structure if there is sufficient air flow about heat sink  26  to cool it. Circulation of the air may be encouraged by an apparatus or structure such as a fan, or in some other manner.  
         [0065]    Referring to FIGS. 2A to  2 C, an embodiment of the heat sink assembly is shown as  40 . Heat sink assembly  40  includes a heat sink  42  having a plurality of fins  44 . Fins  44  are shown as being aligned in side-by-side relationship and are generally spaced parallel to one another. Fins  44  may be arranged in other orientations known in the art, such as those described for the other embodiments (see, for example FIG. 3A or FIG. 9B). On a side of heat sink  42  generally opposite to fins  44 , a projection in the nature of a base, slug, or pedestal  46  is connected to heat sink  42 . Pedestal  46  may be any regular shape but is preferably generally cylindrical, as shown in FIG. 2A.  
         [0066]    Pedestal  46  is inserted through an opening  48  in mounting plate  50  of heat sink assembly  40 . Opening  48  is preferably the same size and shape as a lateral cross-section of pedestal  46  to allow relatively easy rotation of heat sink  42  within opening  48 . Pedestal  46  is retained within opening  48  by a retaining assembly  52 . Retaining assembly  52  includes a retainer in the nature of a clip or spring clip  54  and a corresponding feature such as groove  56 . Clip  54  is retained by groove  56 , which is located about the circumference of pedestal  46 .  
         [0067]    Clip  54  is preferably penannular, having free ends  57  and  59  spaced by a gap  61 . Gap  61  is smaller than the diameter of pedestal  46  so that clip  54  may be retained thereon. To attach clip  54  within groove  56 , free ends  57  and  59  are moved apart to create a gap sufficient to permit passage of pedestal  46  therethrough. Once pedestal  46  is placed within clip  54 , clip  54  is aligned with groove  56 , and free ends  57  and  59  are moved, or permitted to resiliently return, to their initial position. Groove  56  may be a partial or circumferential groove, as long as it extends sufficiently to effectively retain clip  54 . While the present embodiment is illustrated using a clip and groove arrangement to retain pedestal  46 , any other retaining mechanism known in the art may be used to retain pedestal  46 . In the present configuration, heat sink  42  is rotatably moveable about the axis of pedestal  46  and is retained to mounting plate  50  by retaining assembly  52 .  
         [0068]    If pedestal  46  is generally cylindrical, it may be freely rotated within opening  48 . However, if pedestal  46  has a cross-section that is some other regular polygonal shape, such as a regular pentagon, square or other shape, and opening  48  is configured accordingly, pedestal  46  may only be positioned by removing it from opening  48 , then rotating it, and reinserting it into opening  48 . This manipulation permits the orientation of heat sink  42  to be changed relative to mounting plate  50 , as is possible when pedestal  46  has a generally round cross-section.  
         [0069]    Prior to an attachment to substrate  22 , mounting plate  50  is positioned relative to substrate  22  so that holes  58  are aligned with corresponding bores  36 . This permits heat sink assembly  40  to be mounted to substrate  22  using fasteners  32 . Since mounting plate  50  is rotatable relative to heat sink  42 , bores  36  may be located anywhere that is convenient, without affecting the orientation of heat sink  42 . Bores  36  do not need to be located at the vertexes of a virtual square (not shown) which is aligned and centred about chip  24 . Bores  36  may have some other relationship to the location of chip  24  so long as holes  58  in mounting plate  50  are configured to align therewith, and sufficient force can be exerted on a free end of pedestal  46  (as described in greater detail below).  
         [0070]    Once holes  58  and bores  36  are aligned, fasteners  32  may be partially threaded therethrough, but not tightened. At this stage of assembly, heat sink  42  may be rotated relative to mounting plate  50 . This rotation permits fins  44  to be aligned with an airflow A to assist cooling of heat sink  42 , and, ultimately, cooling of chip  24 . Heat sink assembly  40  thus permits heat sink  42  to be readily oriented to co-operate with airflow A. Accordingly, the configuration of substrate  22  and any electronic components such as chip  24  is not constrained by the location of the source of air flow A (such as a fan), nor by the direction of air flow A, because heat sink  42  may be conveniently aligned therewith during mounting of heat sink assembly  40  to substrate  22  (or a component thereof).  
         [0071]    Once heat sink  42  is oriented, fasteners  32  may be tightened in bores  36 . This tightening brings a thermal transfer interface  60  of pedestal  46  into contact with a surface of chip  24 . Thermal transfer interface  60  may be located at the distal end of pedestal  46 . This physical connection between pedestal  46  and chip  24  permits heat generated by chip  24  to be conducted by pedestal  46  into heat sink  42  and dissipated into air flow A by fins  44 .  
         [0072]    The force exerted by thermal transfer interface.  60  on chip  24  may be increased by locating the openings  65  of bores  36  in a plane that is closer to substrate  22  than the plane of the surface of chip  24  that contacts thermal transfer interface  60 . In this configuration, thermal transfer interface  60  is brought into contact with the surface of chip  24 , and fasteners  32  are inserted through holes  58  and into bores  36 . Before fasteners  32  are tightened, there is a gap between mounting plate  50  and the openings  65  of bores  36 . As fasteners  32  are tightened within bores  36 , portions of mounting plate  50  adjacent holes  58  are deflected toward the bores  36 . This deflection causes plate  50  to act as a spring to bias pedestal  46  against chip.  24 , increasing the pressure applied thereto. An increase in pressure at the interface between pedestal  46  and chip  24  provides improved contact between heat conducting surfaces of chip  24  to pedestal  46 . The degree to which pedestal  46  is biased towards chip  24  may vary depending on the requirements and characteristics of chip  24  and heat sink  42 . Maintaining pressure at the interface between pedestal  46  and chip  24  also keeps heat sink  42  in thermal contact with chip  24  during moving and vibration thereof. This arrangement also maintains generally even pressure at the interface between pedestal  46  and chip  24 .  
         [0073]    Plate  50  is preferably made from a metal, but it may be made from any of a number of appropriate materials. For example, it may be made from steel, beryllium, copper, aluminium (e.g., 2024 or 7075) or some other metal or composite having a high modulus elasticity and high yield strength.  
         [0074]    As discussed above, heat sink assembly  40  is adaptable to many different configurations of substrate assembly  22 , and different air flow pathways, by rotating heat sink  42  relative to mounting plate  50  to obtain an advantageous orientation of mounting plate  50  and heat sink  42 .  
         [0075]    Referring to FIGS. 3A to  3 D, an embodiment of the heat sink assembly is shown generally as  62 . Heat sink assembly  62  is similar to heat sink assembly  40  and functions in a similar manner, except as indicated below. Heat sink assembly  62  includes a heat sink  64  having fins  66 . Fins  66  are arranged in a generally circular oblong arrangement having spaces therebetween. Fins  66  are generally parallel to one another, but are oriented in a direction generally perpendicular to the orientation of fins  44 . This configuration permits cooling of heat sink  64  when the air flow is from a direction generally perpendicular to that of the example described for heat sink assembly  40 . It should be noted that the particular configuration of the fins of any heat sink described herein for any of the various embodiments, is not essential. The fins need only be configured as appropriate for a particular installation having a given air flow.  
         [0076]    Heat sink  64  includes a pedestal  68  for insertion through an opening  70  of mounting plate  72 . A retaining assembly  74  maintains pedestal  68  within opening  70 . Retaining assembly  74  includes a retainer which may be in the nature of a clip  76 . Clip  76  is in turn retained by a corresponding groove  78  about pedestal  68 , which groove may be a circumferential groove. Holes  80  located in plate  72  receive fasteners  32  that are inserted into bores  36  to retain heat sink assembly  62  to substrate  22 . Thermal transfer interface  82  is brought into abutting relationship with chip  24 , and a force is applied by thermal transfer interface  82  upon chip  24  by the tightening of fasteners  32 .  
         [0077]    Heat sink assembly  62  additionally includes a ratchet  84 . Ratchet  84  includes one or more unidirectional keys, or stops  86 , that co-operate with one or more raised flange, or tooth  88 . Unidirectional stops  86  may be attached to or formed in mounting plate  72 . Teeth  88  are flanges which are attached at one end to pedestal  60  and are raised at a free end from pedestal  60 . Teeth  88  are located about pedestal  60  (alternatively teeth  88  could be located about opening  70 ). Teeth  88  co-operate with unidirectional stops  86  to permit rotation of heat sink  64  about the axis of pedestal  68  in one direction. Prior to the tightening of fasteners  32 , heat sink  64  may be past a predetermined number of the unidirectional stops  86 . Stops  86  thus provide an indication of rotation of heat sink  64  through a given arc. A greater or lesser number of stops may be spaced evenly about opening  70  to indicate degrees of rotation of heat sink  64 . This arrangement may help to more precisely align heat sink  64  with a given air flow. For example, written instructions to a technician for mounting heat sink assembly  62  to substrate  22  may indicate that heat sink  64  should be rotated past three unidirectional stops  86  prior to tightening of fasteners  32 .  
         [0078]    In operation, as heat sink  64  is rotated within opening  70 , teeth  88  come into contact with sloped sides  90  of unidirectional stops  86 . Unidirectional stops  86  are preferably made of a resilient material that permits stops  86  to deflect toward plate  72  as teeth  88  are forced along slope side  90 . As teeth  88  clear slope side  90 , resilient unidirectional stops  86  return to their original positions. In this position, stops  88  abut a side of teeth  88  to inhibit rotation of heat sink  64  in an opposite direction.  
         [0079]    It will be appreciated that the number of teeth  88  does not need to correspond with the number of unidirectional stops  86 , as illustrated in FIG. 3C, for example. A greater number of teeth  88  than stops  86  provides an indication of rotation through smaller increments than there are stops  86 . The relative spacing of teeth  88  and stops  86  need not be uniform. Different spacings can provide various indications of the degree of rotation of heat sink  64 .  
         [0080]    Since heat sink  64  is non-circular, rotation thereof changes the effect an airflow A has on the heat transfer characteristics of heat sink  64 . For example, in FIG. 3C, rotation of heat sink  64  through an arc of 90 degrees takes heat sink  64  substantially out of the path of air flow A. Accordingly, the effect of air flow A on heat sink  64  may be varied by rotating heat sink  64  through different arcs.  
         [0081]    Referring to FIGS. 4A to  4 C, a further embodiment of a heat sink assembly is shown generally as  92 . Heat sink assembly  92  operates in generally the same manner as described for heat sink assembly  62  and heat sink assembly  40 , except as described below. Heat sink assembly  92  includes a heat sink  94  having fins  96  and a pedestal  98 . Pedestal  98  is inserted through opening  100  which is located in mounting plate  102 . Pedestal  98  is retained within opening  100  by a retaining assembly  104 , which includes a retainer in the nature of a clip  106 . Clip  106  is located within a groove  108  of pedestal  98 .  
         [0082]    Heat sink assembly  92  differs from the other embodiments described herein, in that it has one or more protrusions  110  in the nature of nibs or keys located at an edge of opening  100 . Keys  110  may be evenly spaced from each other. Pedestal  98  has one or more rebates  112  running transverse to groove  108  and generally parallel to a central axis of pedestal  98 . Rebates  112  are sized and located to correspond with the size and location of keys  110 . When pedestal  98  is inserted into opening  100 , keys  110  are aligned with rebates  112  to permit passage of pedestal  98 . In this position, rotation of heat sink  94  is inhibited by keys  110 . However, heat sink  94  may be oriented relative to mounting plate  102  prior to insertion of pedestal  98  into opening  100 . This permits heat sink  94  to be oriented relative to airflow A as described for earlier embodiments. Unlike the previously described embodiments, once pedestal  98  is inserted into opening  100 , further rotation of heat sink  94  is inhibited. This arrangement permits greater securement of heat sink  94 . Once inserted through opening  100 , pedestal  98  is secured with clip  106 . Heat sink assembly  92  otherwise operates in a similar manner as described for the previous embodiments.  
         [0083]    In another embodiment, keys (as described earlier) may be located on a mounting plate and rebates (as described earlier) may be located on a pedestal of a heat sink. The pedestal of the heat sink and the mounting plate cooperate in a similar manner to provide a set of orientations as described above. Also, rather than having keys  110 , pedestal  98  could instead be configured to have a cross-section of any regular shape other than a circle, such as an equilateral triangle (not shown). Opening  100  would be configured to have substantially the same shape so that it could receive the pedestal. Since a non-circular cross-section is used, rotation of the pedestal within opening  100  would be inhibited. In a similar manner as the embodiment described above, the pedestal (and heat sink) could be rotated to a desired orientation before inserting the pedestal to the opening. Once inserted, rotation of the pedestal would be impeded.  
         [0084]    Referring to FIGS. 5A to  5 C, an embodiment of a heat sink assembly is shown generally as  114 . Heat sink assembly  114  is similar to the other embodiments described in that it includes a heat sink  116  having fins  118  and a pedestal  120 . Pedestal  120  may be inserted through opening  122 , which is located in mounting plate  124 . Opening  122  has protrusions in the nature of keys  126 , which are received by transverse rebates  128  located along pedestal  120 .  
         [0085]    Heat sink assembly  114  differs from the other embodiments described in that it does not include a retaining assembly as described, for example, for heat sink assembly  92 . Instead, pedestal  120  is inserted into opening  122  by aligning keys  126  with transverse rebates  128 . When keys  126  are aligned with a retainer in the nature of a groove  130 , heat sink  116  is rotated about the axis of pedestal  120 . Groove  130  is preferably circumferential and is configured to receive keys  126 . Once keys  126  enter groove  130 , movement of heat sink  116  in a direction perpendicular to the plain of mounting plate  124  is inhibited. Once keys  126  are located in rebates  128 , mounting plate  124  may be fastened to substrate  22  in the manner described above. As fasteners  32  are tightened, mounting plate  124 , and in particular keys  126 , bear against a surface of groove  130  to inhibit further rotational movement of heat sink  116 .  
         [0086]    Heat sink  116  may be rotated to a preferred orientation prior to the fastening of mounting plate  124  to substrate  22 . However, if heat sink  116  is rotated through an arc that corresponds to the distance between keys  126 , then keys  126  will realign with transverse rebates  128 , and heat sink  116  will no longer be retained to mounting plate  124 . Accordingly, the spacing of keys  126  and rebates  128 , and the number of keys  126  and rebates  128 , may be varied to permit rotation of heat sink  116  through different arcs of rotation.  
         [0087]    Referring to FIGS. 6A to  6 C, an embodiment of the heat sink assembly is shown generally as  132 . Heat sink assembly  132  is most similar to heat sink assembly  114 , described above. In particular, heat sink assembly  132  includes a heat sink  134 , having fins  136  and a pedestal  138  mounted thereto. Pedestal  138  may be inserted through an opening  140  in a mounting plate  142 . Movement of pedestal  138  relative to mounting plate  142  is inhibited in a direction transverse to the plain of mounting plate  142  by rotating pedestal  138  about its axis to cause keys  144  to enter groove  146 .  
         [0088]    Heat sink assembly  132  differs from heat sink assembly  114  in that one or more steps  148  are located along groove  146 . Steps  148  are circumferentially located about pedestal  138  and are spaced to correspond to the spacing of keys  144 . Steps  148  are preferably located in a side of groove of  146  that is adjacent to a free end  150  of pedestal  138 .  
         [0089]    To mount heat sink assembly  132 , heat sink  134  is rotated to an orientation that aligns keys  144  with transverse rebates  152 . As pedestal  138  is inserted into opening  140 , keys  144  move along transverse rebates  152  until they encounter groove  146 . At this point heat sink  116  is rotated towards a desired orientation (alternatively, or in conjunction, mounting plate  142  is rotated to a desired orientation), and keys  144  enter groove  146 . Further insertion or removal of pedestal  138  into opening  140  is thereby inhibited. As heat sink  134  is rotated, keys  144  become positioned adjacent steps  148 .  
         [0090]    Next, fasteners  32  are inserted and tightened in holes  154 . As fasteners  32  are tightened, plate  142  is drawn towards substrate  22 . At the same time, thermal transfer interface  156  bears against a surface of chip  24  so that its displacement towards substrate  22 , if any, is less than that of plate  142 . This causes keys  144  to enter steps  148  as mounting plate  142  is deflected towards substrate  22 . Once fasteners  32  are tightened, further rotational movement of pedestal  138  (and therefore heat sink  134 ) is inhibited by keys  144 , which are retained within step  148 .  
         [0091]    Referring to FIGS. 7A to  7 C, an embodiment of the heat sink assembly is shown generally as  158 . Heat sink assembly  158  includes heat sink  160  having fins  162 , and a pedestal  164  depending therefrom. Mounting plate  165  differs in configuration from the mounting plates described above. In particular, opening  166  of mounting plate  165  does not permit passage of pedestal  164  in the manner described above. Instead, mounting plate  165  has a passage  168  defined therein located between an edge of mounting plate  165  and opening  166 . Passage  168  permits pedestal  164  to be laterally introduced into opening  166 , as described below. To inhibit lateral removal of pedestal  164  from opening  166 , the width W of passage  168  is less than a diameter of pedestal  164 . The size and shape of opening  166  is configured to be generally the same as the void defined by groove  170 .  
         [0092]    To introduce pedestal  164  into opening  166 , free ends  172  and  174  of mounting plate  165  are deflected in opposite directions out of the plane of mounting plate  165 . This has the effect of increasing the size of passage  168  to permit pedestal  164  to pass therethrough. Opening  166  is then aligned with groove  170  so that the portions of mounting plate  165  defining opening  166  enter into, and are retained by, groove  170 . At the same time, free ends  172  and  174  are returned (or are permitted to resiliently return, if materials allow) to their initial location in the same plane as mounting plate  165 . Mounting plate  165  is preferably made of a resilient and flexible material so that free ends  172  and  174  return to their initial positions when a force is no longer applied to them.  
         [0093]    One or more cutaways  176  may be made in mounting plate  165  to increase the flexibility thereof, and to permit increased airflow about heat sink  160  and chip  24 . Mounting plate  165  is secured to substrate  22  in a manner similar to that described above. This causes mounting plate  165  to act as a spring and bear against pedestal  164  about groove  170  so that thermal transfer interface  178  bears against a surface of chip  24 , and further rotation of heat sink  160  is inhibited.  
         [0094]    Referring to FIGS. 8A to  8 D, an embodiment of a heat sink assembly is shown generally as  180 . Heat sink assembly  180  is similar to heat sink assembly  40 , but shares many of the characteristics and functionality described for the other embodiments as well. Heat sink assembly  180  includes a heat sink  182  having fins  184  on one side thereof, and a pedestal  186  projecting from another side thereof. Pedestal  186  may be inserted into an opening  188  of a mounting plate  190 . Removal of pedestal  186  from opening  188  is inhibited by a retaining assembly  192 , which may include a retainer in the nature of a clip  194 . Clip  194  co-operates with a corresponding groove  196  located about pedestal  186 . As for the other embodiments, fasteners  32  may be inserted through holes  198  to secure heat sink assembly  180  to a substrate  22 .  
         [0095]    In the present embodiment, mounting plate  190  differs from those previously described. Mounting plate  190  has a bevel or vane portion  200 , which may be added to or integral with mounting plate  190 . Vane  200  is preferably integral with mounting plate  190 . Vane portion  200  is bevelled having a generally frustoconical shape, and defines an opening  188  at an end  189  thereof. Sides  202  of vane  200  are generally arcuate and taper from opening  188  to gradually merge with mounting plate  190 .  
         [0096]    In operation, air flow is directed to heat sink assembly  180  in direction A (see FIGS. 8C and 8D). Air is drawn through fins  184  and encounters vane  200 . Arcuate sides  202  of vane  200  direct air which has been heated by its passage through fins  184 , away from heat sink assembly  180  in air flow direction C. This configuration reduces the pressure drop required to pass the air through heat sink assembly  180  in order to encourage re-direction of air flow across mounting plate  190  and laterally away from heat sink  182 .  
         [0097]    The shape of vane  200  is not limited to the shape illustrated in FIGS. 8A to  8 D. Any other shape may be used to encourage the flow of air in a desired direction in order to improve cooling of heat sink  182  and any associated electronic components. For example, vane portion  200  could have spiral grooves, it could be cup shaped, it could have generally straight sides, or it could have concave sides. Vane  200  may also have some irregular shape which may be used to direct airflow to a particular portion or portions of an enclosure that houses substrate  22  and heat sink assembly  180 .  
         [0098]    As shown in the cross section of FIG. 8D, vane portion  200  is formed by a thicker section in mounting plate  190  about opening  188 . Vane  200  may be formed in some other manner, such as stamping or pressing it from plate  190 , injection moulding or casting plate  190 , or in some other manner.  
         [0099]    Referring to FIGS. 9A to  9 C, an embodiment of a heat sink assembly is shown generally as  204 . Heat sink assembly  204  is generally similar to heat sink assembly  40 , but shares many of the features and advantages of the other embodiments described. In particular, heat sink assembly  204  includes a heat sink  206  having fins  208  and a pedestal  210 . Heat sink assembly  204  differs from the other embodiments in that the mounting assembly is in the nature of a wire frame  214 .  
         [0100]    Wire frame  214  may be formed from a single piece of wire, or some other appropriate material. Alternatively, it may be formed in sections which are inserted, welded or otherwise connected to one another.  
         [0101]    Wire frame  214  defines an opening  216  which is similar in function to opening  48  of heat sink assembly  40 . Wire frame  214  has two or more arms  218 , having arcuate free ends  220  defining holes  222 . Holes  222  function in a similar manner to holes  58 , and receive fasteners  32  for securing heat sink assembly  204  to substrate  22 . When fasteners  32  are secured to substrate  22 , arms  218  are caused to flex and bear down on an installed clip  224  of retaining assembly  215 , which is retained within a groove  226 . This causes thermal transfer interface  228  to exert pressure against chip  24  in a manner similar to that described above for the other embodiments.  
         [0102]    The particular size and shape used for arms  218 , free ends  220 , and the other parts of wire frame mounting assembly  214  may be varied depending on the location of any mounting bores  36 . The components of wire frame  214  preferably all lie in the same plane, but arms  218  do not necessarily need to be of the same length, nor do they need to be evenly spaced from one another. The relative configuration of arms  218  and free ends  220  need only be sufficient to apply appropriate force to retaining clip  224  in order to cause thermal transfer interface  228  to bear upon chip  24  with sufficient force to permit transfer of heat away from chip  24 .  
         [0103]    Wire frame assembly  214  permits increased air flow as compared to, for example, mounting plates  50 .  
         [0104]    Referring to FIGS. 10A to  10 C, an embodiment of a heat sink assembly is shown generally as  229 . Heat sink assembly  229  is similar to heat sink assembly  204 . As will be noted from the various Figures, different heat sinks are shown in conjunction with the different embodiments. Operation of the various embodiments is generally not reliant on the type or configuration of heat sink used. However, some heat sink assemblies may more effectively use heat sinks having one configuration rather than another. For example, heat sink assembly  204  may be best used for installations requiring, or having, an air flow running generally parallel to a central axis of pedestal  210 . Alternatively, the heat sink shown as part of heat sink assembly  40  may be more appropriately used for installations having a flow of air that is generally transverse to the axis of pedestal  60 . Nevertheless, the various heat sinks shown in the various embodiments, and any other known heat sinks, may be applied to different embodiments as required.  
         [0105]    Heat sink assembly  229  has a heat sink  230  which includes fins  232  and a pedestal  234 . Pedestal  234  may be inserted through an opening  236  defined by a mounting assembly in the nature of a wire frame  238 . Wire frame  238  is similar to wire frame  214 . Wire frame  238  additionally includes a member in the nature of a plate, which is preferably an annular plate  240 . Annular plate  240  has an opening  242  that generally corresponds to the size and shape of an opening  236  so that it permits passage of pedestal  234  therethrough. While annular plate  240  may be attached to either side of wire frame  238 , it is preferably attached to a side of wire frame  238  opposite to heat sink  230 . Wire frame  238  has arms  244 , which have free ends  246  that define holes  248 .  
         [0106]    To assemble heat sink assembly  229 , pedestal  234  is inserted through opening  236  and opening  242  of annular plate  240 . Pedestal  234  is then retained by a retainer  250 , which includes a clip  252  that engages a groove  254  of pedestal  234 . Fasteners  32  are inserted through holes  248  and are tightened to secure heat sink assembly  229  to substrate  22 . As fasteners are tightened, they bear on free ends  246  drawing them towards substrate  22 . This causes thermal transfer interface  256  to bear against chip  24 . As free ends  246  are forced towards substrate  22 , annular plate  240 , which is connected or otherwise mounted to wire frame  238 , resists deflection of arms  244 . This resistance serves to increase the force that may ultimately be applied by thermal transfer interface to chip  24 . Annular plate  240  thereby increases the effective resilience of arms  244 . Annular plate  240  may also serve to reinforce the structure of wire frame  238 .  
         [0107]    Referring to FIGS. 12A and 12B, an embodiment of a heat sink assembly is shown generally as  274 . Heat sink assembly  274  is similar to heat sink assembly  204 , but shares many of the features and advantages of the other embodiments described. In particular, heat sink assembly  274  includes a heat sink  275  having fins  276  and a pedestal  278 . Heat sink assembly  274  differs from the other embodiments in that the retainer is integral with or fixed to pedestal  278 . The retainer is identified by the reference numeral  290 . As with heat sink assembly  274 , a wire frame mounting assembly  282  is used to mount heat sink  275  to substrate  22 .  
         [0108]    Wire frame  282  may be formed from a single piece of wire, or some other appropriate material. Alternatively, it may be formed in sections which are inserted, welded or otherwise connected to one another.  
         [0109]    Wire frame  282  defines an opening  280 . Wire frame  282  has two or more arms  284 , having arcuate free ends  286  defining holes  288 . Holes  288  function in a similar manner to holes  58 , and receive fasteners  32  for securing heat sink assembly  274  to substrate  22 . When fasteners  32  are secured to substrate  22 , arms  284  are caused to flex and bear down on retainer  290 . This causes thermal transfer interface  292  to exert pressure against chip  24  in a manner similar to that described above for the other embodiments.  
         [0110]    Wire frame  282  is mounted to pedestal  278  by applying a force to one or more of portions  294  which define opening  280 . Force is applied to cause one or more of portions  294  to deform to permit passage of pedestal  278 , together with retainer  290 , through opening  280 . Wire frame portions  294  are made of a flexible, and preferably resilient, material to permit such deformation, and to permit such portions  294  to return to their initial shape once retainer  290  is inserted through opening  280 . Retainer  290  and wire frame  282  thus inhibit removal of pedestal  278 .  
         [0111]    Referring to FIGS. 13A to  13 D, a further embodiment of a heat sink assembly is shown generally as  296 . Heat sink assembly  296  operates in generally the same manner as described for heat sink assembly  40 , and the other embodiments, except as described below. Heat sink assembly  296  includes a heat sink  298  having fins  300  and a pedestal  302 . Pedestal  302  is positionable within an opening  304 , which is defined by mounting plate  306 . Pedestal  302  may be retained to mounting plate  306  by a retainer  308 . In a similar manner as heat sink assembly  274 , retainer  308  is integral with or fixed to pedestal  302 .  
         [0112]    Heat sink assembly  296  differs from the other embodiments described herein in that mounting plate  306  is separable into at least two sub-plates  306   a  and  306   b . Each sub-plate  306   a  and  306   b  define at least a portion of opening  304 . Each sub-plate is removably connectable to the other via connection features  310  and  312 . Sub-plates  306   a  and  306   b  may be similar, as shown in FIGS. 13A to  13 D, or they may be significantly different from one another. Having a similar configuration can reduce manufacturing costs.  
         [0113]    In the present embodiment, connection feature  310  is similar to  312 . Accordingly, only feature  310  is described herein. Feature  310  includes mating parts  310   a  and  310   b , which maintain the resiliency of mounting plate  306  to a degree similar to the mounting plates of the other embodiments, including mounting plate  50 . In the present embodiment, part  310   a  has a finger  314  which forms part of plate  306   a ; and part  310   b  includes a corresponding receptacle  316 , which is formed in plate  306   b , that mates with finger  314 . Finger  314  may be stepped so that sub-parts  306   a  and  306   b  may be better integrated.  
         [0114]    To mount plate  306  to pedestal  302 , sub-plates  306   a  and  306   b  are positioned to either side of pedestal  302 . Each sub-plate  306   a  is tilted to form an angle with the axis of pedestal  302 . Each sub-plate  306  preferably forms a 45 degree angle with respect to the axis of pedestal  302  and also form a 90 degree angle relative to each other. Sub-plates  306   a  and  306   b  are then brought together and corresponding parts of connection features  310  and  312  are aligned and engaged. Sub-plates  306   a  and  306   b  are then moved into a common plane to fully engage such connection features and to engage pedestal  302  between retainer  308  and heat sink  298 . Heat sink assembly may then be attached to substrate  22  in a manner similar to that described for the other embodiments.  
         [0115]    It should be emphasised that the particular connection features employed may be different so long as mounting plate  306  may be at least partially separated (e.g., sub-parts  306   a  and  306   b  may be hinged) and then reconnected in order to engage pedestal  302 , between retainer  308  and heat sink  298 .  
         [0116]    Referring to FIG. 11, a number of embodiments are illustrated. Each embodiment would be attached alone to substrate  22 . They would not be attached all at the same time as suggested by the exploded view of FIG. 11. The four sample embodiments  258 ,  260 ,  262  and  264  are all shown in one figure for convenience.  
         [0117]    Heat sink assembly  20  is the same as the assembly illustrated in FIG. 1. Mounting bracket  30  of heat sink assembly  20  is different than that described for the other embodiments. Mounting bracket  30  is somewhat similar to mounting bracket  50  shown in FIG. 2A, but it differs at least in that it has one or more cutaways  266  therein. Mounting plate  30  may also have bends or deflection points  268  at a point along an arm  270  thereof, adjacent to end  272 . Bend  268  causes end  272  to lie outside of the plane of mounting plate  30 , which also causes hole  34 , which is located through end  272 , to be outside of the plane of mounting plate  30  as well.  
         [0118]    During installation, mounting plate  30  is preferably oriented so that ends  272  are oriented so that they deflect away from bores  36  as fasteners  32  are inserted through holes  34  and tightened into bores  36 . Each fastener  32  bears down on deflected ends  272  drawing them closer to the opening of bore  36 . This arrangement encourages the connection to act as a fixed joint that can carry a bending moment. As described for mounting plate  165 , cutaways  266  serve to permit greater air flow about mounting plate  30  and increase the resiliency of arms  270 .  
         [0119]    Referring to embodiment  258 , enclosure  38  may be rotated in concert with heat sink  42  to a convenient orientation. At the same time, mounting bracket  30  may retain its original orientation. Alternatively, when embodiment  258  is installed on a different substrate  22 A, having a similar, but not identical, circuit and component arrangement thereon, enclosure  38  and heat sink  42  may be kept in a particular fixed orientation, and mounting plate  30  may be rotated to a position that is more convenient for mounting to substrate  22 A.  
         [0120]    Referring to embodiment  260 , enclosure  38  may be rotated without the need to rotate heat sink  206  or mounting plate  30  to accommodate for different circuit and component arrangements on different substrates. Alternatively, mounting plate  30  may be rotated to a more convenient orientation while maintaining the orientation of enclosure  38 . Since heat sink  206  is circular, rotation thereof will not affect thermal transfer.  
         [0121]    Referring to embodiment  262 , enclosure  38  and heat sink  64  may be oriented in a manner similar to that described for embodiment  258 . Similarly, embodiment  264  may be manipulated in the manner similar to that described for embodiment  258 .  
         [0122]    In another embodiment, a heat sink, an enclosure for the heat sink and a mounting plate are provided. The mounting plate is formed and is fixed to a circuit board in a manner as described above. The enclosure is mounted about the mounting plate and may be oriented in a plurality of positions as described above. However, in the embodiment, the heat sink remains in a fixed position relative to the mounting plate as the enclosure is positioned in different orientations about the heat sink.  
         [0123]    While the various embodiments have been described in relation to different embodiments of heat sinks, mounting plates, attachment assemblies, and other components, these components are generally interchangeable, depending on the needs of a particular installation. The particular combination of components in each embodiment are not limited to the combinations illustrated in the examples above.  
         [0124]    Accordingly, those skilled in the art will appreciate that numerous modifications, adaptations and variations may be made to the embodiments without departing from the scope of the invention.