Abstract:
An intercoupling component (e.g., socket or adapter) is provided for increasing the dissipation of heat generated within an integrated circuit (IC) array positioned within the intercoupling component, while maintaining a relatively low profile. The intercoupling component includes a heat sink positioned within the package support member configured to contact both a lower surface of the integrated circuit package disposed within the package support member and a substrate such as a printed circuit board. The package support member includes contact terminals disposed within associated openings of the package for electrically connecting the contacting areas of the integrated circuit package to the corresponding connection regions of the substrate. The openings extend from an upper surface to an opposite lower surface of the support member and are located in a pattern corresponding to a pattern of the connection contacts. The heat sink may be configured to be removable and replaceable.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to removing heat from integrated circuit (IC) array packages. 
     As the densities of integrated circuits (e.g., microprocessors, gate arrays, ASICs) continue to increase, the size of the packages used to house the circuits continue to shrink. These smaller, higher performing integrated circuits generate tremendous amounts of heat which is required to be dissipated. Thus, externally mounted heat sinks with profiles having large surface areas are typically mounted on the IC packages. In some cases, the size of the heat sink mounted to the IC package can dwarf the size of the package itself. 
     IC packages are either connected directly to circuit boards, or through adapters or sockets. Adapters and sockets are described in Advanced Interconnections Catalog No. 14-A (available from 5 Energy Way, West Warwick, R.I. 02893). In general, they consist of a glass epoxy frame having pins which are used to electrically connect a PC board with an IC or other electrical component. 
     Adapters are used to permanently convert one type of package to another. For example, a ball grid array (BGA) package having rounded solder ball contacts may be soldered to an adapter array having terminals pins, thereby converting the BGA package to a pin grid array (PGA) package. 
     Sockets, on the other hand, are used to allow particular IC packages to be interchanged without permanent connection to a circuit board. More recently, sockets for use with PGA, BGA and LGA packages have been developed to allow these packages to be non-permanently connected (e.g., for testing) to a substrate, such as a printed circuit board. 
     SUMMARY OF THE INVENTION 
     This invention features an intercoupling component (e.g., socket or adapter) for increasing the dissipation of heat generated within an integrated circuit (IC) array package positioned within the intercoupling component by providing a thermal path for heat dissipation from an IC through a heat sink to a substrate. The increased level of heat dissipation is provided while maintaining a reliable, non-permanent and low-loss electrical interconnection between electrical contacting areas of the IC array package and connection regions of a substrate (e.g., printed circuit board). 
     The term “integrated circuit array package” is intended to mean those packages, including PGA (pin grid array), PQFP (plastic quad flat pack), BGA (ball grid array) and LGA (land grid array) packages. The term “substrate” is intended to mean any base member having electrical contact areas including printed circuit boards, IC chip substrates or the packages supporting such chip substrates. The term “thermal path” is intended to mean a physical path by which heat is conducted. 
     In one aspect of the invention, the intercoupling component includes a heat sink, removable and replaceable within a package support member, having a surface in contact with both the substrate and the IC array package which is also disposed within the package support member. The package support member includes contact terminals disposed within associated openings of the package for electrically connecting the contacting areas of the IC array package to the corresponding connection regions of the substrate. The openings extend from an upper surface to an opposite lower surface of the support member and are located in a pattern corresponding to a pattern of the connection contacts. 
     In one embodiment of the invention, upper and lower surfaces of the heat sink and IC array package contact each other, respectively. 
     In another aspect of the invention, the intercoupling component includes a heat sink positioned within a package support. The heat sink has a surface for contacting a surface of the integrated circuit package and a surface for contacting a first surface of the substrate. The package support includes two support members spaced apart to allow air communication between the heat sink, the support members, and contact terminals disposed within associated openings of the package. The contact terminals electrically connect the contacting areas of the IC array package to the corresponding connection regions of the substrate. The openings extend from an upper surface to an opposite lower surface of each support member and are located in a pattern corresponding to a pattern of the connection contacts. 
     In yet another aspect, the intercoupling component includes a heat sink, removable and replaceable within the package support member, configured to provide a thermal path between the integrated circuit package and the substrate. The package support member includes contact terminals disposed within associated openings of the package for electrically connecting the contacting areas of the IC array package to the corresponding connection regions of the substrate. The openings extend from an upper surface to an opposite lower surface of the support member and are located in a pattern corresponding to a pattern of the connection contacts. 
     An intercoupling component having these arrangements are dual-purposed in that the component serves to reliably interconnect (either temporarily or permanently) the IC package to a printed circuit board while supporting a removable and replaceable heat sink within the component. The ability to remove and replace the heat sink facilitates interchanging heat sinks whose size and shape may differ on the basis of the operating characteristics (e.g., power level) of the integrated circuit placed within the package support member of the intercoupling component. Additionally, the heat sink provides a thermal path by which heat is dissipated from the IC package to the substrate. In certain embodiments in which the IC is mounted on or near the bottom of the array package, the presence of a thermal path from the underside of the package array to the substrate decreases the magnitude of heat dissipation necessary on the top surface of the package. In these embodiments, the size of top mounted heat sinks can be reduced such that the overall profile of the heat sink is reduced. 
     In still another aspect, the invention features a method of dissipating heat between an integrated circuit and a printed circuit board. The method includes providing an intercoupling component including a heat sink, placing an integrated circuit within the intercoupling component, and contacting a first surface of the heat sink with the underside of an integrated circuit. Additionally, the method also can include contacting a second surface of the heat sink to a printed circuit board. 
     Embodiments of all aspects of the invention may include one or more of the following features. The package support member includes a central region within which the heat sink is positioned with the openings disposed along an outer periphery of the central region. 
     The intercoupling component further includes a retaining member positioned to apply a downward force on the integrated circuit package. The retaining member includes a second, upper heat sink having a surface contacting an upper surface of the IC package. This arrangement, provides upper and lower heat sinks which “sandwich” the IC package so that a greater amount of heat can be dissipated from the IC package. A rigid member having peripheral sidewalls is positioned between the retaining member and integrated circuit package. The peripheral sidewalls contact peripheral regions of the integrated circuit package. With this arrangement, stress applied to the body portion of the IC package is relieved by conveying the downward force applied by the retaining member to the peripheral sidewalls contacting the peripheral regions of the IC package. 
     The intercoupling component may include an electrically insulative locator sheet (e.g., polyimide) including an aperture extending therethrough from an upper surface to an opposite lower surface of the locator sheet. The aperture is positioned and sized to engage an upper peripheral portion of the heat sink. The electrically insulative locator sheet includes openings extending therethrough and located in a pattern corresponding to a pattern of the contact terminals. The openings are sized to allow the contact terminals to pass through the upper and lower surfaces of associated openings, whereby the contact terminals are aligned with associated connection regions of the substrate. 
     The contact terminals each include a socket body having an upper end with an opening and a lower end configured to contact the corresponding connection region of the printed circuit board. Each contact terminals further include a pin having an upper end adapted to contact the electrical contacting area of the IC package and a lower end configured to be inserted within the opening of the socket body. The pins are disposed within holes of an electrically insulative support member, thereby providing an adapter assembly received by a socket assembly which supports the socket bodies. A contact spring may be disposed within a first end of the opening of the socket body to receive and apply a frictional force sufficient to retain the lower end of the pin within the opening of the socket body. A resilient member can also be disposed within a second, opposite end of the opening, to apply, to the lower end of the pin and in response to a downward force applied to the pin, an upward force sufficient to overcome the frictional force of the contact spring. 
     The intercoupling component can further include a second heat sink in thermal contact with the heat sink. The heat sink can include a central bore for receiving a distal end of the second heat sink through a hole in the substrate, e.g., a printed circuit board. 
     Other features of the invention will be apparent from the following description of the preferred embodiments and from the claims. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is an exploded, somewhat diagrammatic, isometric view of an intercoupling component assembly, an integrated circuit package, heat sink, and hold-down assembly positioned over a printed circuit board. 
     FIG. 2 is a cross-sectional side view of a portion of the intercoupling component assembly of FIG.  1 . 
     FIG. 3 is a bottom view of the insulative member of FIG.  1 . 
     FIG. 4 is a cross-sectional side view of an enlarged portion of the intercoupling component assembly of FIG.  2 . 
     FIG. 5 is an enlarged version of a portion of a male terminal pin used within the intercoupling component assembly of FIG.  1 . 
     FIG. 6 is a top view of the polymeric sheet layer of FIG.  2 . 
     FIG. 7 is an enlarged version of a portion of the lower heat sink of the intercoupling component assembly of FIG.  1 . 
     FIGS. 8A-8C are cross-sectional side views illustrating the operation of the intercoupling component assembly. 
     FIG. 9 is an alternative embodiment of an intercoupling component assembly. 
     FIG. 10 is another alternative embodiment of an intercoupling component assembly. 
     FIG. 11 is another alternative embodiment of an intercoupling component assembly. 
     FIG. 12 is yet another alternative embodiment of an intercoupling component assembly. 
    
    
     DESCRIPTION 
     Referring to FIGS. 1 and 2, a socket converter assembly  10  for intercoupling an IC package  12  to a printed circuit board  14  is shown. In this embodiment, IC package  12  is in the form of a BGA package having a number of rounded solder balls  22  (FIG. 4) attached to contacts on the undersurface of the package. Socket converter assembly  10 , which serves as an intercoupling component, includes an electrically insulative member  16  for supporting converter socket terminals  18 , each of which is press-fit within a corresponding one of an array of holes  20  (FIG. 3) in the insulative member. The array of holes  20  are provided in a pattern corresponding to a footprint of the solder balls  22  of package  12  as well as a footprint of surface mount pads  24  of printed circuit board  14 . Insulative member  16  with converter socket terminals  18  is press-fit into a guide box  26  having alignment members  28  along which the peripheral edges of IC package  12  are guided so that solder balls  22  are aligned over converter socket terminals  18 . In particular embodiments, insulative member  16  and guide box  26  may be formed as a one-piece, integral unit. 
     Socket converter assembly  10  also includes a lower heat sink  30  positioned within a bore hole  42  of insulative member  16 . Heat sink  30  lies between an upper surface  15  of printed circuit board  14  and an undersurface  34  (FIG. 8C) of IC package  12 . Spaced fins  36  extend radially from a central body  38  (FIG. 2) of the lower heat sink. Lower heat sink  30  provides a thermal path from undersurface  34  of IC package  12  to an upper surface  45  of heat sink  30  for dissipating heat generated within IC package  12 . Likewise, lower heat sink  30  provides a thermal path from a lower surface  40  of heat sink  30  to upper surface  15  of printed circuit board  14 . Thus, heat sink  30  provides a thermal path, i.e., from the IC package through the heat sink to the printed circuit board, for dissipating heat generated within IC package  12 . The printed circuit board is made from an insulated metal printed circuit board (IMPCB) laminate available from Thermagon, Inc., located in Cleveland, Ohio. IMPCB laminates include a dielectric layer, e.g., T-preg, sandwiched between a top copper foil for circuitry connections and a metal base plate. The dielectric layer has three major functions: (1) conducts heat, (2) electrically insulates, and (3) serves as an adhesive. Some IMPCB laminates include a dielectric sandwiched between two outer layers of copper foil such that both sides of the printed circuit board can be used for circuitry connections. Alternatively, the printed circuit board is a standard PCB such as FR-4 copper. 
     Socket converter assembly  10  also includes a hold-down cover  50  for securing the IC package  12  into the socket converter assembly. Cover  50  includes a pair of opposite walls  52  having tab members  54  which engage recessed portions  56  along the underside of insulative member  16 . As will be described in greater detail below, in some embodiments, a stiffening member  63  formed of a rigid material (e.g., aluminum) may be positioned between cover  50  and IC package  12 . Hold-down cover  50  includes a threaded thru-hole  58  which threadingly receives an upper heat sink  60  to dissipate heat passing through stiffening member  63  from an upper surface  62  of IC package  12 . A slot  66  formed in the heat sink facilitates threading the heat sink within the cover, for example, with a screwdriver or coin. Other latching mechanisms (e.g., clips or catches) may also be used to secure IC packages within the socket converter assembly. It is also appreciated that other heat sink arrangements, including those with increased surface area (e.g. heat sinks with fans), may be substituted for the finned version shown in FIGS. 1 and 2. In certain lower power applications, upper heat sink  60  may not be required with only cover  50  providing the downward compressing force to IC package  12 . Of course, the size of upper heat sink  60 , i.e., height and diameter, can be adjusted to provide sufficient heat dissipation for different power levels. Stiffening member  63  (FIG. 8C) resembles a box having a cavity  65  defined by peripheral walls  67  for receiving body portion  13  of IC package  12 . As described in greater detail below and in conjunction with FIGS. 8A-8C, stiffening member  63  relieves stress applied to body portion  13  by conveying the downward force applied by heat sink  60  to peripheral walls which, in turn, transfers the force to peripheral regions  15 ′ and  62  of IC package  12  (FIGS.  1  and  8 C). 
     Referring to FIG. 4, each converter socket terminal  18  includes a female socket  70  positioned within one of the array of holes  20  of insulative member  16 . Female socket  70  includes a solder ball  72  pre-attached (e.g., by soldering) to its bottom end  74  to provide an identical mating condition to surface mount pads  24  as would have been the case had IC package  12  been connected directly to the printed circuit board  14 . Solder balls  72  are eventually soldered to corresponding surface mount pads  24  of circuit board  14 . Positioned within the interior of female socket  70  is a contact spring  76  press-fit within the interior and upper end of the female socket. 
     Each contact spring  76  includes spring leaves  78  attached at circumferentially spaced points of an upper end of a barrel  79 . Contact spring  76  is sized to receive a male terminal  80  which passes through barrel  79  to frictionally engage spring leaves  78 . Contact springs of this type are commercially available from Advanced Interconnections, West Warwick R.I. or other stamping outfits providing such contact springs (e.g., in an open-tooling arrangement). Spring leaves  78  provide a “wiping”, reliable electrical contact to the male terminal pins by applying a frictional force in a direction substantially transverse to the longitudinal axis of the male terminals sufficient to ensure good electrical contact. A more detailed description of converter socket terminal  18  and its parts is found in co-pending application Ser. No. 09/094,957 which is assigned to the assignee of the present invention and incorporated herein by reference. 
     Each male terminal  80  has a head  82  adapted to receive a corresponding ball  22  of the IC package  12  and a pin  84 , thereby forming an electrical connection between ball  22  of package  12  and solder ball  72  of converter socket terminal  18 . Head  82  has a concave upper surface  87  (FIG. 5) for accommodating the rounded shape of solder ball  22 . 
     Referring to FIG. 5, in an alternative embodiment, concave upper surface  87  includes a relatively sharp projection  85  disposed concentrically on the upper surface of the head. Projection  85  is used to pierce the outer surface of the IC package&#39;s solder balls  22  which, due to exposure to the atmosphere, may have a layer of oxidation. Projection  85  is positioned at the lowest point within upper surface  87  with the tip of the projection substantially below the plane defined by the outer peripheral edge of head  82 . Thus, projection  85  is protected during tumbling operations, commonly performed on machined parts to remove sharp and irregular edges. Other approaches for improving the electrical connection between solder balls  22  and socket terminal  18  may be used including the use of particle interconnection (PI) contacts. As described in U.S. Pat. No. 5,083,697 (incorporated by reference), particle interconnection contacts include relatively hard metallized particles deposited in a soft metal layer such that they protrude from the surface of the contact. When a second contacting surface (e.g., ball) is compressively brought into contact with the PI contact, the hard particles penetrate any oxides and contamination present on the contacting surface. PI contacts minimize the resistance between the contacts, particularly after repeated insertions. Alternatively, a dendritic growth process may be used to improve the conductivity between contacts. Head  82  of each male terminal  80  also includes a V-groove  92  used to capture a relatively thin polymeric sheet  94  made, for example from Kapton 7 (a product of E. I. DuPont de Nemours and Co., Wilmington, Del.). 
     Referring to FIG. 6, sheet  94  has a thickness of about 5 mils and includes openings  96  sized slightly smaller than the diameter of the heads  82 . This arrangement maintains male terminals  80  together in proper spaced relationship so that the pins can be easily aligned over and inserted into female sockets  70 . Sheet  94  also prevents tilting of the pins which can cause electrical shorting. As shown in FIG. 8A, sheet  94  also includes an opening  98  to allow heat sink  30  to be retained in bore hole  42  of insulative member  16  (FIG.  2 ). 
     Referring to FIG. 7, an upper end  95  of heat sink  30  includes a beveled upper peripheral edge  100  which is received by opening  98 . Opening  98  in sheet  94  is sized to be slightly smaller than upper end  95  of heat sink  30  and has sufficient flexibility for allowing it to be fitted around the upper end of the heat sink. 
     Each of pins  84  are received within corresponding contact springs  76  with spring leaves  78  configured to provide a lateral force, generally transverse to the longitudinal axis of pins  84 , thereby frictionally engaging outer surfaces of the pins. 
     Referring to the embodiment shown in FIG. 4, the lower end of pin  84  includes a flattened head  99  having a diameter slightly larger than the diameter of pin  84  so that after head  99  passes through spring leaves  78  of contact spring  76 , male terminal  80  is captured within female socket  70 . 
     Metallic coiled springs  102  are loosely positioned within the interiors of each of female sockets  70  and provide an upward force to the lower ends of pins  84 . As mentioned earlier, spring leaves  78  of contact springs  76  provide a sufficient amount of lateral frictional force generally transverse to the longitudinal axis of the pins, to ensure a reliable electrical contact to pins  84  of male terminals  80 . However, when hold-down cover  50  is removed from insulative member  16 , guide box  26  and IC package  12 , metallic coiled springs  102  expand causing each of male terminals  80  to release and extend to their most upper vertical position within female sockets  70 . Thus, it is important that coiled springs  102  provide an upward force to male terminal pins  80  that overcomes the frictional force, transverse to the upward force, applied by spring leaves  78 . The upward force of coiled springs  102  also minimizes the risk of pins  84  “sticking” within corresponding female sockets  70 . 
     FIGS. 8A-8C illustrate the operation of socket converter assembly  10 . Referring to FIG. 8A, heat sink  30  is positioned within sheet  94  and bore hole  42  of insulative member  16 , with lower surface  40  supported on upper surface  15  of printed circuit board  14 . The height and pitch of upper peripheral edge  100  is selected to initially capture heat sink  30  within sheet  94  prior to IC package  12  being seated in its final position within socket converter assembly  10 . 
     Referring to FIG. 8B, IC package  12  is positioned within guide box  26  using alignment members  28  of guide box  26 , and over insulative member  16  with solder balls  22  of IC package  12  resting on concave upper surface  87  of male terminals  80 . In this position, male terminals  80  vertically extend from contact springs  76  to their greatest degree. Additionally, sheet  94  and insulative member  16  are spaced apart by L (FIG. 8B) to provide an air gap to allow heat to dissipate from heat sink  30  and socket terminals  18 . Typically, L can be between 0.01 and 0.1 inches. 
     Referring to FIG. 8C, cover  50  is slid over insulative member  16 , guide box  26 , stiffening member  63 , and IC package  12 . Upper heat sink  60  is then rotated within cover  50  using slot  66  until the upper heat sink contacts stiffening member  63 . Further rotation of heat sink  60  applies a downward force to stiffening member  63  which, in turn, transfers the force to peripheral region  65  of IC package  12 , thereby causing male terminal pins  84  to extend within female sockets  70  and against the bias of spring coils  102 . Thus, electrical interconnections are completed from each of solder balls  22  of IC package  12  to corresponding pads  24  of board  14 , after solder balls  72  have been soldered to pads  24 . When IC package  12  is lowered by the compressing force applied by upper heat sink  60 , sheet  94  is also lowered and moves away from the upper end of upper peripheral edge  100 . At the same time, the downward force applied by upper heat sink  60  causes IC package  12  to be compressed against upper surface  45  of lower heat sink  30 . Likewise, the same downward force causes lower surface  40  of heat sink  30  to be compressed against upper surface  15  of printed circuit board  14 . 
     Raising upper heat sink  60  from cover  50  removes the downward force applied to IC package  12  with spring coils  102  returning male terminal pins  84  to their fully extended vertical position of FIG.  8 B. With upper heat sink  60  in its raised position, cover  50  can be removed to allow, for example, substituting a different IC package within the BGA converter socket assembly. The likelihood that one or more of male terminal pins  84  become stuck within female socket  70  is minimized because the pins are “ganged” together by polymeric sheet  94  which assists in ensuring that all of the pins return to their vertically extended position and at a consistent height. 
     It is also important to note that each time an IC package is secured within socket converter assembly  10 , pins  84  of male terminals  80  are “wiped” against spring leaves  78  of contact spring  76  to remove oxidation and ensure a reliable electrical connection there between. 
     Other embodiments are within the following claims. For example, the invention is applicable to other socket and adapter assemblies. 
     Referring to FIG. 9, an intercoupling assembly  120  includes many of the same features as socket converter assembly  10  of FIGS. 1-7 and  8 A- 8 C. For example, intercoupling assembly  120  includes an upper heat sink  121  and a socket assembly  122  having a bore hole  124  for a lower section  126  of a lower heat sink  128 . Socket assembly  122  also includes an array of socket terminals  130  similar to socket terminals  18  of FIG. 2, except that coiled springs are not positioned within the socket terminals. Intercoupling assembly  120  also includes an adapter assembly  132  for supporting an array of male terminal pins  134  which are received within corresponding socket terminals  130  of socket assembly  122 . Socket terminals  130  extend through holes  125  of socket assembly  122  to an underside  131  of adapter assembly  132 . A sheet  194  positioned on the top surface of socket assembly  122  includes an inner edge  195  extending in between the fins of lower heat sink  128  just above lower section  126 . As a result, inner edge  195  maintains heat sink  128  in bore hole  124  when upper heat sink  121  and the IC package are removed. Of course, heat sink  128  can be removed by physically disengaging the inner edge from the heat sink fins. Additionally, adapter assembly  132  and socket assembly  122  are spaced apart by L to provide an air gap for heat dissipation from heat sink  128  and socket terminals  130 . Typically, L can be between 0.01 and 0.1 inches. 
     In this particular embodiment, lower heat sink  128  is of increased height to permit greater airflow which, in turn, provides greater dissipation of heat. Thus, with an increase in height, however, the height of intercoupling assembly  120  is also increased. In order to accommodate the relatively tall lower heat sink, the height of sidewalls  136  of a cover  138 , is increased in proportion to the height of heat sink  128 . In certain embodiments, the height of the sidewalls and the height of socket terminals  130  can both be increased to accommodate a tall lower heat sink. The increased length of socket terminals  130  has the additional benefit of providing greater heat dissipation through the socket terminals themselves as well as through solder balls  140  preattached to the terminals. Alternatively, as shown in FIG. 10, the length of socket terminals  230  is decreased and male terminal pins  234  are elongated. Furthermore, the outer diameter M of male pins  234  is less than the outer diameter F of socket terminals  230 . Thus, increased length of male pins  234  and decreased length of socket terminals  230  has the additional benefit of providing greater heat dissipation by creating more air space between adapter  232  and socket assembly  222 . 
     Referring back to FIG. 9, intercoupling assembly  120  may also include thermoconductive material  150 , e.g., thermoconductive tape or grease, located on upper surface  127  and lower surface  129  of heat sink  128 , respectively, to allow for better thermal contact between heat sink  128  and both the undersurface of the IC and the upper surface of the printed circuit board. 
     Referring now to FIG. 11, a BGA package  140  may include additional solder balls  142 , independent of solder balls  143 , electrically isolated from the internal circuitry (not shown) within the BGA package. Rather, additional solder balls  142  serve as miniature heat sinks for dissipating heat generated within BGA package  140 . In these applications, a lower heat sink  144  may have a recess  146  formed in its upper surface so that contact between the lower heat sink  144  and those portions of the undersurface of BGA package  140  is maintained when an upper heat sink  148  is lowered to sandwich IC package  12 . In the sandwiched position, solder balls  142  are positioned within recess  146  and provide a thermal path to lower heat sink  144 . 
     It is also important to appreciate that use of a lower heat sink is beneficial for IC packages enclosing integrated circuits mounted in both the “chip-up” and “chip-down” arrangements, particularly, when both a lower and an upper heat sink is used to sandwich the IC package therebetween. 
     In certain applications, space may be available at the underside of a printed circuit board. In these applications, an additional heat sink can be included to provide further heat dissipation. Referring to FIG. 12, for example, a printed circuit board  514  includes a through hole  510  for receiving a radially extending edge  502  of a lower heat sink  500 . Lower heat sink  500 , in turn, includes a central bore  505 , accessible through hole  510 , for threadedly engaging a backside heat sink  550 . When fully assembled, an annular shoulder  504  of lower heat sink  500  contacts a top surface  516  of printed circuit board  514  and a surface  555  of backside heat sink  550  contacts a bottom surface  515  of printed circuit board  514 . Backside heat sink  550  helps to dissipate heat from both printed circuit board  514  and from the bottom surface of the IC package, i.e., through lower heat sink  500 . 
     In alternative embodiments, the lower heat sink can be any shape such as square or oval. Accordingly, the insulative members and Kapton sheets include bore holes of various shapes to receive the lower heat sink. Additionally, the walls of hold down cover can include fins or through holes thereby creating an air path to further assist in dissipating heat from the socket terminals and lower heat sink. 
     Still further embodiments are supported by the following claims.