Abstract:
A method and apparatus for assembling a high speed, high density VLSI module in a computer system that enables attachment, support, electromagnetic interference containment, and thermal management of the VLSI module. The present invention packages a high speed, high density VLSI module within a limited space and in a single assembly that attaches, aligns, and manages electromagnetic interference and heat dissipation of the VLSI module. The present invention aligns a land grid array of a circuit board and an interposer socket assembly, and the interposer socket assembly and a land grid array of the VLSI module; in the single VLSI module assembly. An even, controlled load is placed on the interposer socket interface thereby reducing the risk of damage to the interposer socket from overloaded connections between the land grid array of the VLSI module, the interposer socket assembly, and the land grid array of the circuit board. The present invention is easy-to-use in upgrading and handling of the VLSI module.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a method and apparatus for integrated circuit assembly. More particularly, the present invention relates to a method and apparatus for assembling a high speed, high density VLSI module that enables attachment, support, electromagnetic interference containment, and thermal management of the VLSI module. 
     1. Description of Related Art 
     The following applications are related to the present application, U.S. patent application entitled “METHOD AND APPARATUS FOR A MODULAR INTEGRATED APPARATUS FOR HEAT DISSIPATION, PROCESSOR INTEGRATION, ELECTRICAL INTERFACE, AND ELECTROMAGNETIC INTERFERENCE MANAGEMENT,” Ser. No. 09/195256, naming inventor S. Daniel Cromwell, et al., assigned to the assignee of the present invention; and U.S. Patent Application entitled “METHOD AND APPARATUS FOR PRECISE ALIGNMENT OF A CERAMIC MODULE TO A TEST APPARATUS,” Ser. No. 08/898327, naming inventors Rajendra D. Pendse, et al., assigned to the assignee of the present invention. 
     2. Background of the Invention 
     The use of increasingly high speed very large scale integrated circuit (VLSI) modules in computer systems has given rise to new assembly challenges related to their attachment, support, electromagnetic interference containment, and thermal management. For example high speed VLSI modules have input/output counts of 2000. 
     Often, due to the large thermally induced stresses that impact the long term reliability of solder joints, these high speed, high density VLSI module assemblies cannot employ standard solder techniques for connecting the VLSI modules to a circuit board. Therefore, there has been the emergence of interposer socket assembly techniques including a land grid array configuration of a VLSI module. 
     Another problem with high density, high speed VLSI modules is the difficulty of aligning the circuit board and an interposer socket assembly, and aligning the interposer socket assembly and the VLSI module. That is, as the pitch of a land grid array is reduced, the alignment becomes more difficult. It will be appreciated that the “pitch” of a land grid array refers to the distance from pad to pad, and that a “pad” refers to the individual contacts or connections in an interposer configuration. 
     Further, assembly space for high speed VLSI modules is limited. Also, high speed VLSI modules emit electromagnetic interference and heat that requires management. Therefore an efficient, high speed VLSI assembly should also include a tight Faraday Cage and a high performance heat dissipation device in the same package. 
     Further, improvements in high speed VLSI assemblies have been hindered by the difficulty of upgrading and handling of the VLSI module outside of a manufacturing or assembly environment. 
     Also, the difficulty of scaling high speed VLSI assemblies to large or small configurations has hindered improvements in high speed, high density VLSI module assembly. 
     SUMMARY OF THE INVENTION 
     The present invention is a method and apparatus for assembling a high speed, high density VLSI module in a computer system that enables attachment, support, electromagnetic interference containment, and thermal management of the VLSI module. 
     Accordingly it is an object of the invention to package a high speed, high density VLSI module within a limited space and in a single assembly that attaches, aligns, and manages electromagnetic interference and heat dissipation of the VLSI module, thereby efficiently using minimal space for the VLSI module assembly. 
     The VLSI module may include any general purpose application specific integrated circuit (ASIC) such as an area grid array or a socket-based VLSI module. However, as the I/O count has increased the ASIC package size has become too large for solder-attachment techniques and presents special problems that are solved by the present invention. Therefore, it is another object of the invention to align a land grid array of a circuit board and an interposer socket assembly, and to align the interposer socket assembly and a land grid array of the VLSI module in the single VLSI module assembly. 
     It is also an object of the invention to enable an alignment mechanism for the interposer socket assembly that is easy to manufacture and that supports tight tolerances that are required between the interposer socket assembly and the VLSI module. Therefore, the present embodiment employs the use of a solder ball and socket configuration between the VLSI module and the interposer socket assembly to manage the tight tolerance and close alignment requirements of the VLSI module. 
     It is also an object of the invention to enable ease-of-use in upgrading and handling of the VLSI module. For example in the present embodiment, due to the management of the alignment and orientation of the elements of the VLSI module assembly it is difficult to assemble the elements incorrectly. 
     It is another object of the invention to ensure that an even, controlled load is placed on the interposer socket interface thereby reducing the risk of damage to the interposer socket from overloaded connections between the land grid array of the VLSI module, the interposer socket assembly, and the land grid array of the circuit board. For instance the present embodiment may include the use of an overhead clamp and a single heat sink screw for a single load point that ensures an even load on the VLSI module. That is, by pressure from the overhead load clamp, the single heat sink screw applies load to a heat sink that is connected to the VLSI module. Therefore even loading may be accomplished by reusing the heat sink as a load spreader. It will be appreciated that the term “connect” refers to an element being held in proximity to another element while not bolting the elements together. 
     It is yet another object of the present invention to enable scaling of the VLSI module assembly to large or small configurations. For instance, the present invention novelly employs the overhead clamp that may be configured for large or small VLSI assemblies while maintaining an even load on the VLSI module. 
     It is another object of the invention to include a heat dissipation device in the VLSI module assembly. Therefore, the present embodiment includes a heat sink having heat fins and a heat sink base. The heat sink base is in optimal thermal proximity to the VLSI module to absorb heat, and to transfer the heat to the heat fins for efficient heat dissipation. 
     It is another object of the invention to integrate a Faraday Cage in the VLSI module assembly. Therefore, the present embodiment includes a Faraday Cage having the circuit board, an electromagnetic interference frame including a compliant electrically conductive electromagnetic interference gasket, and the heat sink base. 
     Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a top, perspective view that illustrates the VLSI module assembly; 
     FIG. 1B is a bottom, perspective view that illustrates the VLSI module assembly; 
     FIG. 2 A is a perspective view that illustrates the assembly of the heat sink and the VLSI module; 
     FIG. 2B illustrates the overhead clamp assembly along with the heat sink screw; 
     FIG. 2C is a side view that illustrates the overhead clamp and the heat sink screw; 
     FIG. 2D is a perspective view that illustrates an alternative embodiment of the overhead clamp; 
     FIG. 2E illustrates the heat fins, the heat sink well, and the heat sink base; 
     FIG. 2F illustrates the VLSI module assembly; 
     FIG. 3A is a bottom view that illustrates the electromagnetic interference frame and the interposer socket assembly; 
     FIG. 3B illustrates the interposer socket assembly; 
     FIG. 4A is a top view that illustrates the electromagnetic interference frame; 
     FIG. 4B is a bottom view that illustrates the electromagnetic interference frame; and 
     FIG. 5 is a side view that illustrates the alignment ball that fits into the interposer socket assembly. 
    
    
     DETAILED DESCRIPTION 
     In the following detailed description and in the several figures of the drawings, like elements are identified with like reference numerals. 
     Broadly stated, FIG. 1A illustrates a top, exploded, perspective view of the VLSI module assembly  100  that enables attachment, support, electromagnetic interference containment, and thermal management of the VLSI module  102 . 
     The embodiment includes a circuit board  108  that is electrically connected to the VLSI module  102 . A bolster plate  104  is also included that supports a circuit board  108  thereby supporting the load that is placed on an interposer socket assembly  106 . The interposer socket assembly  106  requires careful load management and alignment of the connections between the interposer socket assembly  106  and a land grid array  101  (as shown in FIG. 1B) of the VLSI module  102 , and between the interposer socket assembly  106  and the land grid array  101  of the circuit board  108 . 
     The circuit board  108  may be sandwiched between the bolster plate  104  and an electromagnetic interference frame  110 . The bolster plate  104  may be attached to the circuit board  108  by bolster screws  114  that fit into the electromagnetic interference frame  110 , that pass through the circuit board  108 , and that terminate in bolster sockets  112  in the bolster plate  104 . In the present embodiment, the electromagnetic interference frame  110  circumscribes the VLSI module  102  and attenuates electromagnetic interference generated by the VLSI module  102 . That is, in the present embodiment the electromagnetic interference frame  110  surrounds the VLSI module  102  and includes electrically conductive material thereby attenuating electromagnetic interference from the VLSI module  102 . 
     Further in the present embodiment a Faraday Cage  117  is created by the electromagnetic interference frame  110 , the circuit board  108 , a heat sink base  121 , and an electromagnetic interference gasket  116  sandwiched between the circuit board  108  and the electromagnetic interference frame  110  (as shown in FIG. 1B) and between the electromagnetic interference frame  110  and the heat sink base  121 . Therefore, the electromagnetic interference gasket  116  seals the Faraday Cage  117  at the junctions of the electromagnetic interference frame  110  thereby attenuating electromagnetic interference from the VLSI module  102 . Further, the electromagnetic interference gasket  116  may be molded into electromagnetic interference grooves  402  (as shown in FIGS. 4A and 4B) to minimize gaps in the seal it creates. Further, the electromagnetic interference frame  110  aligns and orients the VLSI module  102  so that it is properly assembled and may be used as an alignment frame. 
     It will be appreciated that the VLSI module  102  may be a multi-chip module or a single VLSI module  102 . For instance the VLSI module  102  may be a flip-chip assembly. Typically a land grid array may implement a compression assembly technique in which the interposer socket assembly  106  is sandwiched between the land grid array  101  of the VLSI module  102  and the land grid array  101  of the circuit board  108 . As will be appreciated by those skilled in the art, interposer technologies provide a reliable, low inductance, low resistance electrical connection between the land grid array  101  of the circuit board  108  and of the VLSI module  102 . The interposer socket assembly  106  requires an even load distribution to ensure even loading and pressure on the contacts of the land grid array  101  of the circuit board  108  and of the VLSI module  102 . It will be appreciated that even load distribution will minimize damage to the contacts on the interposer socket assembly  106  by overloading and possible short circuiting of the electrical connections between the VLSI module  102 , the interposer socket assembly  106 , and the circuit board  108 . Reference herein to a circuit board  108  may include a printed circuit board such as a mother board. 
     The bolster plate  104  may be made of metal and may be laminated with an insulating material (not shown) such as mylar to protect from electrical shorts on contact with the circuit board  108 . The pad  105  of the interposer socket assembly  106  connects to the land grid array  101  of the VLSI module  102  and to the land grid array  101  of the circuit board  108 . 
     The present invention manages the load imposed by the connection of the heat sink  120  to the VLSI module  102 . That is, the heat sink base  121  operates as a load spreader. A single heat sink screw  124 , that is centrally located relative to the heat sink base  121 , transfers load to a heat sink well  123  (as shown in FIG. 2E) in the heat sink base  121 . By tightening the heat sink screw  124 , the load from the overhead clamp 122  is transferred to the heat sink base  121  which spreads the load in a controlled and even fashion to the VLSI module  102 , and the pads  105  on the interposer socket assembly  106 . 
     In the present embodiment the heat sink  120  includes the heat sink base  121  that is thermally connected to the VLSI module  102 , and heat fins  127  that divert heat from the VLSI module  102  by moving heat to a space where there is sufficient air flow to cool the system. Further, an optional thermal pad  118  may be sandwiched between the heat sink  120  and the VLSI module  102  to enhance the thermal interface and thereby improve heat dissipation. Therefore, the heat sink  120  is reused as a load plate and an element of the Faraday Cage  117  in addition to managing heat dissipation. 
     In the present embodiment, the overhead clamp  122  is a heat-treated steel spring that straddles the heat sink  120  and latches on two sides of the electromagnetic interference frame  110  to enable quick and easy assembly or replacement of the VLSI module  102 . Further, tightening the heat sink screw  124  straightens the overhead clamp  122  and ensures a tight fit of the overhead clamp  122  to the electromagnetic interference frame  110 . By tightening the centrally located heat sink screw  124  and evenly spreading the load through the heat sink base  121 , the load is transferred to the VLSI module  102 . Therefore, the VLSI module  102  is compressed on the interposer socket assembly  106  and completes the electrical connection between the land grid array  101  of the VLSI module  102  and the interposer socket assembly  106 , and between the interposer socket assembly  106  and the land grid array  101  of the circuit board  108 . By adjusting the overhead clamp  122  and heat sink screw  124  length, the load can be managed as required. Therefore, the overhead clamp  122  significantly improves a typical four corner attach point process by maintaining even loading while the heat sink screw  124  is tightened. Compared to previous techniques that include tedious multiple-pass cross pattern tightening to evenly load and unload the VLSI module  102  the present embodiment enables more efficient loading of the VLSI module  102 . 
     FIG. 1B illustrates a bottom, exploded, perspective view of the VLSI module assembly  100  that includes the circuit board  108  that is attached to the bolster plate  104 . The bolster sockets  112  on the bolster plate  104  are the terminus for the bolster screws  114  that fit into the electromagnetic interference frame  110 . 
     Both the top (as shown in FIG. 1A) and bottom of the electromagnetic interference frame  110  are interfaced with the electromagnetic interference gasket  116  to form a seal for the Faraday Cage  117 . The electromagnetic interference gasket  116  may be made of metal impregnated, silicon-based polymer, that enables an efficient electrical conduction, such as a product marketed under the trademark CHO-SEAL™ which is injection molded over the electromagnetic interference frame  110  in grooves or seats for such purpose. 
     The VLSI module  102  is aligned and oriented for proper positioning with respect to the interposer socket assembly  106 . The VLSI module  102  includes the land grid array  101 . Further the heat sink  120  and the heat sink base  121  are also aligned and oriented for proper positioning with respect to the VLSI module  102 . In the present embodiment, the heat sink base  121  is a pedestal that optimally connects to the VLSI module  102  to enable thermal coupling of the heat sink  120  to the VLSI module  102  with a sufficiently low resistance thermal path. In the present embodiment, the heat sink base  121  includes a chamfered heat sink corner  125  that interfaces to a frame chamfered corner  111  (as shown in FIG. 2A) on the electromagnetic interference frame  110  that ensures proper assembly and orientation between the heat sink  120  and the electromagnetic interference frame  110 . The optional thermal pad  118  may be sandwiched between the heat sink  120  and the VLSI module  102 . 
     Finally in the present embodiment, the overhead clamp  122  fits over the heat sink  120  and attaches on two sides of the perimeter of the electromagnetic interference frame  110 . The heat sink screw  124  is inserted into the overhead clamp  122  and sits in the heat sink well  123  (as shown in FIG.  2 E). 
     FIG. 2A illustrates the assembly of the heat sink  120  and the VLSI module  102  with respect to the electromagnetic interference frame  110  that has been attached to the circuit board  108 . The optional thermal pad  118  may be sandwiched between the heat sink  120  and the VLSI module  102 . That is, the thermal pad  118  is held in place by squeezing it between the heat sink  120  and the VLSI module  102 . Use of the thermal pad  118  is especially advantageous to enhance the thermal communication between the VLSI module  102  and the heat sink  120 . 
     The heat sink  120 , the bolster plate  104  (as shown in FIG.  1 A), and the electromagnetic interference frame  110 , which all may be made of metal and may be manufactured by any appropriate technique, such as the technique marketed under the trademark THIXOMOLDING®. Such a molding technique produces a part with little or no post-machining required thereby reducing manufacturing cost. For example, the following features of the heat sink  120  may be molded without post-machining: the heat sink base  121  (as shown in FIG.  1 A), the heat fins  127 , the heat sink well  123  (as shown in FIG.  2 E), and the extreme flatness required on the bottom of the heat sink base  121 . Additionally, the detail and function of the electromagnetic interference frame  110  is molded in without machining. It will be appreciated that producing a very flat surface on the bottom of the heat sink base  121  may eliminate the requirement for the thermal pad  118 . That is, since the flat molded surface enables a sufficient thermal interface between the VLSI module  102  and the heat sink base  121  use of the thermal pad  118  is optional. Further, the even load on the heat sink base  121  that is transferred to the interposer socket assembly  106  is enhanced by a flat surface connection between the heat sink base  121  and the VLSI module  102 . Since the substrate of the VLSI module  102  may be made of ceramic material and is therefore subject to cracking due to strain induced in a non-uniform load distribution, an even, flat surface connection is also advantageous to minimize damage due to cracked ceramic material. Those skilled in the art will appreciate the use of a substrate. 
     The VLSI module  102  includes a VLSI module chamfered corner  103  that fits into the frame chamfered corner  111  and matches the shape of the heat sink base  121  thereby orienting the assembly of the VLSI module  102  in the electromagnetic interference frame  110 . Also the position of the electromagnetic interference frame  110  pre-positions the VLSI module  102  above the interposer socket assembly  106  (as shown in FIG. 1A) so that the VLSI module  102  will easily find its final position with respect to the interposer socket assembly  106  and the circuit board  108 . In the present embodiment alignment balls  502  (as shown in FIG. 5) attached to the VLSI module  102  interface into sockets in the interposer socket assembly  110  (as are discussed with respect to FIG. 3A) to facilitate positioning of the VLSI module  102  with regard to the interposer socket assembly  106 . 
     As shown in FIG. 2B, the overhead clamp  122  is bowed prior to being tightened by the heat sink screw  124 , thus functioning as a spring. The overhead clamp  122  is a spring and when the clamp edges  202  are depressed the bottom edges of the overhead clamp  122  are spread, thus enabling insertion and removal of the overhead clamp  122  of the attachment to the electromagnetic interference frame  110 . In the present embodiment the clamp edges  202  are separated from the center of the overhead clamp  122  and are straight as depicted in FIG.  2 B. It will be appreciated that the clamp edges  202  may function as handles to enable ease-of-use for manipulating the overhead clamp  122  during installation and removal. 
     As shown in FIG. 2C, when the heat sink screw  124  is tightened the overhead clamp  122  is unbent thereby loading the heat sink  120  through pressure from the heat sink screw  124 . Therefore the VLSI module  102  will bear the load from the heat sink base  121  and little load is borne on the electromagnetic interference frame  110 . It will be appreciated that in the present embodiment, the heat sink base  121  is formed in the shape of a pedestal that creates a gap between the heat sink  120  and the electromagnetic interference frame  110 . Therefore, the load created by the tightened heat sink screw  124  and the heat sink  120  does not rest on the electromagnetic interference frame  110 . The heat sink screw  124  may include a washer  206  to ensure that a fully formed thread (not shown) on the heat sink screw  124  bears the load as it interfaces with the threads (not shown) on the overhead clamp  122 . Also, the washer  206  enables adjustment of the load on the overhead clamp  122  by changing the height of the heat sink screw  124 . It will be appreciated that when the heat sink screw  124  is fully set, variability in the load is separated from the assembly process and is a function of the tolerance of the components. 
     The position of the overhead clamp  122  with respect to the heat fins  127  may be oriented to ensure maximum air flow through the heat sink  120 , especially when the computer system includes a fan (not shown) that directs the flow of air. 
     FIG. 2D is a perspective view that illustrates an alternative embodiment of the overhead clamp  129  that may enable the use of a VLSI module  102  that is soldered to the circuit board  108  (as are shown in FIG.  1 A). In the present embodiment the alternate clamp  129  fits over the heat fins  127  and includes slots (not shown) into which the heat fins  127  are inserted. The alternate clamp  129 , the electromagnetic interference frame  110 , and the heat sink  120  are preassembled before attachment to the printed circuit board  108  (as are shown in FIG.  1 A). The electromagnetic interference frame  110  is oriented and aligned by its interface with the VLSI module  102 . When the electromagnetic interference frame  110  is attached to the printed circuit board  108  the alternate clamp  129  delivers load to the heat sink base  121  to ensure an optimal thermal interface. The alternate clamp  129  may be snapped off and on the electromagnetic interference frame  110 . The electromagnetic interference frame  110  may include receiving features for both the alternate clamp  129  and the overhead clamp  122  (as shown in FIG.  2 C). The solder-based VLSI module  102  may be attached to the circuit board  108  without orientation management, enabling this cost efficient solution. This alternate embodiment does not require field upgrade of the VLSI module  102 . It will be appreciated that the bolster plate  104  (as shown in FIG. 1) may be optional if a solder-based VLSI module  102  is used since less force is applied to attach the VLSI module  102  to the circuit board  108  by the alternate clamp  129 . 
     The present embodiment, therefore, allows computer system development with socketed VLSI modules  102  during the early stages of development and efficiently supports conversion to solder-attached VLSI modules  102  in the later stages of development and in manufacturing by reusing the same electromagnetic interference frame  110  and heat sink  120 . Therefore, the present embodiment enables flexible assembly of VLSI modules  102  that may be permanently assembled or may support insertion and removal in the field. The alternate clamp  129  may be the only part that changes. 
     As shown in FIG. 2E, in the present embodiment a heat fin  127  is separated and the heat sink well  123  is centrally located in the heat sink base  121 . In the present embodiment the heat sink well  123  is a depression in the heat sink base  121  that is the terminus point for the heat sink screw  124  (as shown in FIG.  1 A). Recall that the heat sink screw  124  is inserted into the overhead clamp  122  (as shown in FIG. 1A) and sits in the heat sink well  123 . By advantageously integrating the heat sink well  123  into the heat sink base  121  it will be appreciated that the load from the heat sink screw  124  is transferred to the heat sink base  121  thereby reusing the heat sink base  121  as a load spreader. 
     More particularly in the present embodiment, the heat sink well  123  is a small counter bore in the center of the heat sink base  121  that provides a seat for the heat sink screw  124 . The heat sink well  123  keeps the heat sink screw  124  centered and positioned. The heat sink screw  124  includes a spherical end (not shown) to minimize moment loads to the heat sink  120  (as shown in FIG. 1A) and to minimize metal debris from use. It will be appreciated that metal debris may impair the functioning of the VLSI module  102  by creating extraneous electrical contacts between the VLSI module  102  and the interposer socket assembly  106  (as are shown in FIG.  1 A). 
     FIG. 2F illustrates the VLSI module assembly  100  after assembly, and includes the circuit board  108 , the electromagnetic interference frame  110  that is attached to the circuit board  108  by the bolster screws  114 . In the present embodiment, the overhead clamp  122  is snapped into two sides of the electromagnetic interference frame  110  by clamp notches  204  in the bottom edges of the overhead clamp  122 . The heat sink  120  includes the heat fins  127  and the heat sink base  121 . The overhead clamp  122  is connected to the heat sink  120  by the heat sink screw  124 . 
     It will be appreciated that the position and orientation of the heat sink  120  is tightly constrained to ensure even load transfer from the heat sink  120  to the VLSI module  102 . Therefore, both rotational and translational movement is constrained in the X, Y, and Z directions. The heat sink is rotationally constrained in the Z direction by the electromagnetic interference frame  110 , and in the X and Y directions by the circuit board  108 . The heat sink  120  is translationally constrained by the electromagnetic interference frame  110  in the X and Y directions, by the circuit board  108  in the minus Z direction, and by the heat sink screw  124  in the positive Z direction. It will be appreciated that translational movement refers to the movement within a plane and rotational movement refers to rotation about an X, Y, or Z axis. 
     FIG. 3A illustrates a bottom view of the electromagnetic interference frame  110  and the interposer socket assembly  106 . The distance between the electromagnetic interference frame  110  and the interposer socket assembly  106  is tightly constrained. By this tight fit, the landing zone of the alignment socket  302  relative to the alignment balls  502  (as shown in FIG. 5) that are attached to the VLSI module  102  (as shown in FIG.  1 A), is constrained thereby ensuring a proper placement of the interposer socket assembly  110  with respect to the land grid array  101  of the VLSI module  102 . The alignment socket  302  is diagonally opposite an oblong alignment socket  308 . This ensures an accurate fit of the VLSI module  102  in the interposer socket assembly  106 . Further, the tight positioning of the interposer socket assembly  106  ensures proper orientation and positioning of the electromagnetic interference frame  110 , which ensures proper orientation and prealignment of the VLSI module  102 . 
     Movement of the VLSI module  102  is constrained by the alignment socket  302  and the oblong alignment socket  308  which bound the translational movement in the X and Y direction. Rotational movement of the VLSI module  102  about the Z axis is constrained by the oblong alignment socket  308  on the interposer socket assembly  106 . Further, translational movement of the VLSI module  102  in the Z direction is constrained by gravity and the overhead clamp  122  (as shown in FIG.  1 A). Additionally the circuit board  108  (as shown in FIG. 1A) constrains rotational movement of the VLSI module  102  about the X and Y direction. 
     The shape of the electromagnetic interference frame  110  includes space for alignment pins  304  that are asymmetrically located, with respect to each other, on the interposer socket assembly  106 . By advantageously asymmetrically positioning the alignment pins  304 , and by including an interposer chamfered corner  107  on the interposer socket assembly  106  and the frame chamfered corner  111  on the electromagnetic interference frame  110 , the interposer socket assembly  106  may be fully assembled only in its proper orientation to the printed circuit board  108 . The shape of the interposer socket assembly  110 , as depicted in FIG. 3A allows room for alignment pins  304  without sacrificing any connections on the VLSI module  102 . 
     FIG. 3B illustrates the interposer socket assembly  106  that is oriented and aligned with respect to the land grid array  101  of the VLSI module  102  (as are shown in FIG. 1B) and the land grid an-ay  101  of the circuit board  108  (as are shown in FIG.  1 A). In the present embodiment there are two alignment pins  304  that are part of the interposer socket assembly  106  and whose size and location are precise to ensure that they fit into circuit board sockets (not shown), thereby ensuring the proper position of the interposer socket assembly  106  with respect to the circuit board  108 . This precise positioning of the alignment pins  304  ensures proper electrical contacts are made between the interposer socket assembly  106  and the circuit board  108 . 
     The space required by the interposer socket assembly  106  may be the same as that of the VLSI module  102  except for the area used by the two alignment pins  304 . This nearly zero additional space feature enables a minimum space requirement for the interposer socket assembly  106  and allows for close positioning of the VLSI module  102  to other components of the computer system. 
     In the present embodiment the interposer socket assembly  110  includes a deflection limiter  306  that is shelf shaped and that circumscribes the interposer socket assembly  110 . The deflection limiter  306  ensures that the pads  105  of the interposer socket assembly  110  will not be damaged by over deflection from the load. By bearing any additional load, the deflection limiter  306  controls the maximum deflection of the pads  105  of the interposer socket assembly  110  on both sides. 
     To enable replacement in the field of the VLSI module  102  the interposer socket assembly  110  is reusable. That is, the VLSI module  102  may be changed without requiring replacement of the original interposer socket assembly  110 . 
     FIG. 4A illustrates the top side of the electromagnetic interference frame  110 . More particularly, electromagnetic interference from the VLSI module  102  is also attenuated by the electromagnetic interference gasket  116  that may be made of a compliant metalized polymer and that may be molded into the electromagnetic interference groove  402  in the top of the electromagnetic interference frame  110 . The electromagnetic interference gasket  116  contacts the perimeter of the heat sink base  121  thereby creating a seal for the Faraday Cage  117  (as are shown in FIG.  1 A). 
     FIG. 4B is a bottom view that illustrates the electromagnetic interference frame  110 . More particularly, the electromagnetic interference gasket  116  is molded into the electromagnetic interference groove  402  on the bottom of the electromagnetic interference frame  110  that interfaces to the circuit board  108  thereby creating a seal for the Faraday Cage  117  (as shown in FIG.  1 A). The electromagnetic interference gasket  116  may be reusable in the event that the VLSI module assembly  100  is disassembled and later reassembled. 
     Also, the electromagnetic interference frame  110  is undercut as shown in element  404  thereby allowing close placement of bypass capacitors and resistors on the circuit board  108  (as shown in FIG. 1A) and minimizing space on the circuit board  108 . 
     FIG. 5 is a side view that illustrates the alignment ball  502  that is attached to the VLSI module  102 , and that fits into the alignment socket  302  and the oblong alignment socket  308  of the interposer socket assembly  106 . In the present embodiment, the alignment balls  502  are solder balls that are attached to small pads in three of the four extreme corner positions of the VLSI module  102 . The alignment balls  502  have a precise alignment with respect to the land grid array  101  of the VLSI module  102  and the pads  105  (as shown in FIG. 1A) of the interposer socket assembly  106 . Therefore the alignment balls  502  enable proper placement of the VLSI module  102  when it is assembled onto the interposer socket assembly  106 . 
     The positioning of the electromagnetic interference frame  110  constrains and confines the VLSI module  102  so that in it worst positional alignment the center of the alignment balls  502  are well inside the landing zone of the alignment socket  302  and the oblong alignment socket  308 . Due to the spherical shape of the alignment balls  502 , when the VLSI module  102  is placed in the electromagnetic interference frame  110  it falls into proper position because of its own weight. 
     The use of the alignment balls  502  that interface to the alignment socket  302  and the oblong alignment socket  308 , combined with the alignment of the electromagnetic interference frame  110  to the interposer socket assembly  106  by the alignment pins  304  (as shown in FIG. 3A) enables the electromagnetic interference frame  110  to be used to prealign the VLSI module  102  as it is assembled in the VLSI module assembly  100  (as shown in FIG.  1 A). 
     Alterative Embodiments 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the invention. Thus, the foregoing descriptions of specific embodiments of the VLSI module assembly are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, obviously many modifications and variations are possible in view of the above teachings. Those skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the invention. The invention is limited only by the claims.