Abstract:
A system for supporting integrated circuit packages to prevent mechanical failure of the packages at their connection to a printed circuit board or card involves bracing the packages to the board or card, the packages may also be braced against one another. The structure is particularly well adapted to supporting vertical surface mount packages at a point spaced from the point where they connect to a printed circuit board or card.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 09/152,659, filed Sep. 14, 1998, which is a continuation of U.S. application Ser. No. 09/152,376, filed Sep. 14, 1998 now U.S. Pat. No. 6,031,733 which is a continuation of U.S. application Ser. No. 08/978,397, filed Nov. 25, 1997, now U.S. Pat. No. 5,944,199. 
    
    
     BACKGROUND 
     This invention relates generally to packages with a tall aspect ratio, such as vertical surface mount packages (“VSMP”), for integrated circuits and particularly, to techniques for supporting those structures. 
     In a variety of computer applications it is desired to reduce bus lengths to enable higher operating frequencies. For example, a number of memory and other devices may be connected to a bus in a computer system. The more space the devices take, generally the longer the bus length. The longer bus length normally adds resistance and capacitance which may be adverse to achieving higher bus operating frequencies. By mounting the devices on edge, the devices may be packed more closely, reducing bus lengths and making possible higher bus operating frequencies. 
     Because VSMP technology involves positioning the packages in an on-edge vertical alignment, the devices have considerable moment arms about their points of connection to the printed circuit board (“PCB”) or card. The VSMP is generally supported on a pair of L-shaped leads and may have no other connection to the PCB or card. 
     Although the VSMP package improves signal integrity at high frequencies by minimizing the bus length, the VSMP packages may be prone to a variety of stress and vibration induced failures because of their on-edge orientation. Thus, it would be desirable to have a way to provide tall aspect ratio packages which are more resistant to mechanical failures. 
     SUMMARY 
     In accordance with one aspect of the present invention, a support for an integrated circuit package extending upwardly from a surface includes a first portion arranged to engage the package at a point spaced above the location where the package is connected to the surface. A second portion, connected to the first portion, is adapted to prevent movement of the package relative to the surface. 
     In accordance with another aspect of the present invention, an integrated circuit device, electrically connectable to a surface, includes an electrical connection from the surface to the device. A first portion is arranged to engage the device at a point spaced above the connection. A second portion is connected to the first portion and is adapted to prevent movement of the device relative to the surf ace. 
     In accordance with still another aspect of the present invention, an electronic device includes a plurality of integrated circuit packages. A surface is electrically connected to each of the plurality of packages. A support is arranged to engage each of the packages at a point spaced above the surface to prevent movement of the packages relative to the surface. 
     In accordance with yet another aspect of the present invention, a method for preventing relative movement between a surface and an integrated circuit package connected to the surface includes the step of engaging the package at a point spaced away from the location where the package is connected to the surface. The package is braced to the surface to prevent movement of the package relative to the surface at the point of engagement of the package. 
     In accordance with yet another aspect of the present invention, a device for preventing relative movement between a plurality of vertical surface mount packages and a surface includes a first portion arranged to engage a pair of packages at a point spaced away from the location of the connection between the packages and the surface. A second portion is connected to the first portion and to the surface. 
     In accordance with but another aspect of the present invention, a method for stabilizing vertical surface mount packages mounted on a surface includes the step of inserting a member between two adjacent packages. The packages are braced against movement relative to the surface. 
     In accordance with another aspect of the present invention, a computer system includes a printed circuit board and an integrated circuit connected to and extending away from the board. A device is arranged to engage the integrated circuit at a point spaced from the connection to the board to prevent relative movement between the board and the integrated circuit. 
     In accordance with but another aspect of the present invention, a method for preventing relative movement between a surface and an integrated circuit package connected to the surface includes the step of engaging the package at a point spaced away from the location where the package is connected to the surface. The integrated package is braced to the surface to prevent movement of the package relative to the surface at the point of engagement of the package. 
     In accordance with another aspect of the present invention, a method for stabilizing a vertical surface mount package secured to a surface includes the step of sliding an engaging framework over the package. The framework is secured to a structure other than the package. 
     In accordance with still another aspect of the present invention, a method for stabilizing integrated circuit packages secured to a surface involves arranging a support about the package. The support is expanded into engagement with the package. 
     In accordance with another aspect of the present invention, a support for an integrated package is connectable to a surface. A member is adapted to be positioned about said package. The member is expandable in response to heat into engagement with the package. A connection is made between the member and the surface. 
     The details of one or more embodiments of the inventions are set forth in the accompanying drawing 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 THE DRAWINGS 
         FIG. 1  is a cross-sectional view taken generally along the line  1 - 1  in  FIG. 2 ; 
         FIG. 2  is a top plan view of the embodiment shown in  FIG. 1 ; 
         FIG. 3  is a vertical cross-sectional view through a second embodiment of the present invention; 
         FIG. 4  is a top plan view of the embodiment shown in  FIG. 3 ; 
         FIG. 5  is a vertical cross-sectional view through another embodiment of the present invention; 
         FIG. 6  is a top plan view of the embodiment shown in  FIG. 5 ; 
         FIG. 7  is a top plan view of another embodiment of the present invention; 
         FIG. 8  is a vertical cross-sectional view through another embodiment of the present invention; and 
         FIG. 9  is a schematic depiction of a computer system in accordance with one aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawing wherein like reference characters are utilized for like parts throughout the several views, a PCB or card  10  includes an upper surface  11  which secures a plurality of the VSMPs  12  or other packages on the surface  11  by way of a support  14 . Each package  12  extends vertically from a pair of opposed, L-shaped contacts  16 . While the present invention is described with respect to an illustrated embodiment involving VSMPs, the present invention may be applied for any package having a substantial height or a tall aspect ratio. 
     The support  14  includes a pair of parallel rails  18 , shown in  FIG. 2 , which engage the opposed side edges  20  of each package  12 . Each rail  18  includes a post  22 , shown in  FIG. 1 , which may pluggingly engage the PCB or card  10 . For example, each of the packages  12  may include a notched portion  24  which is engaged by a bump or tab  26  connected to each of the rails  18 . 
     In this way, each of the packages  12  is supported from below on the contacts  16  and also at a point spaced above the point of connection to the PCB or card  10  by the rails  18  which in turn are connected to the posts  22 . This stabilizes the vertically mounted packages  12  against vibration and excessive bending forces around their point of connection to the PCB or card  10 . 
     Referring to  FIGS. 3 and 4 , a support  14   a  includes a pair of spaced lugs  28  (shown in  FIG. 4 ) and a transverse cross piece  30  which engages the top edges of the packages  12 . The support lugs  28  provide a wide base for connection to the cross piece  30  to stabilize the connection between the cross piece  30  and the tops of the packages  12 . The lugs  28  may plug into the board  10 . 
     The undersurface  31  of the cross piece  30  has a combed configuration with a plurality of teeth  32  which 5 extend downwardly and engage each package  12  snugly on two sides. The entire support  14   a  may be molded of plastic material. Alternatively, the teeth  32  could be formed of foam material attached to a plastic molded cross piece  30 . 
     Again, the connection between the package  12  and teeth  32  results in diminished relative vibration forces on the packages  12  and stabilization against bending forces acting about the contacts  16 . Thus, if the packages  12  are securely retained at a point spaced from their points of connection  16  to the PCB or card  10 , mechanical failures should be reduced. 
     Turning now to  FIGS. 5 and 6 , a support  14   b  may be entirely or partly formed of a plastic foam material. Advantageously, the foam is an antistatic foam such as a high density polystyrene foam. As shown in  FIG. 6 , the foam may be in the form of a block having a plurality of slits  34  formed therein. Each slit  34  preferably has a cross-sectional size corresponding to that of the packages  12 . As a result, when the support  14   b  is slid over and down on the packages  12 , they telescope through the foam support  14   b . Thus, the packages  12  are snugly engaged by the resiliency of the foam against their sides  36 . The height of the foam support  14   b  is subject to considerable variation but, as illustrated, the foam may extend a substantial portion of the height of the packages  12 . In this way, the packages  12  are stabilized at a point spaced from their point of connection  16  to the PCB card  10 . 
     Advantageously the lower surface  38  of the foam is covered with an adhesive material to adhesively secure the foam support  14   b  to the upper surface  11  of the board or card  10 . In addition, if desired, transversely extending slots  40  may be formed in the support  14   b  which allow air circulation from the exterior to the underside section of each package  12  and particularly to the opening  42  under each package. 
     In addition, the support  14   c  may be made in whole or in part of a heat expandable material. Suitable expandable plastics include thermoplastic elastomers including ethylene-propylene copolymers, polyethylene, ethylene copolymers, ionomers, polyvinyl chloride polymers, and styrene butadiene block polymers. These polymers may be combined with a blowing or foaming agent so that when the support  14   c  is subjected to a predetermined temperature it expands volumetrically. In this way, the support  14   c  can be positioned about a package  12 , as shown in  FIG. 7 , with the slots  34  having a larger cross-sectional area than the packages  12 . The support  14  volumetrically expands to resiliently engage package  12 , as illustrated in  FIG. 6 . 
     It is also advantageous if the foam or other conformal material is heat conductive to spread the heat and reduce package temperature. The foam or other conformal material could be antistatic foam or a material with heat conductiving fibers or particles such as metal fibers dispersed through the material. 
     The support  14  may also be spaced from the board  10 , as shown in  FIG. 8 . While a foam or conformal support  14   b  is shown in  FIG. 8 , other rigid supports, such as the support  14   a  without the vertical portions, shown in  FIG. 3 , may be used. By blocking the devices  12  against one another in this fashion, the stresses on the devices  12  may be reduced. 
     Referring to  FIG. 9 , an exemplary computer system  50  in accordance with the present invention is illustrated. As illustrated, the system  50  includes a microprocessor  52  and a system bus  54 . The system bus  54  connects to a memory controller  56  which in turn connects to a plurality of memory devices  58  which may be implemented as packages  12 . The microprocessor  52  also connects to a bridge  60  which in turn connects to at least one additional bus, such as a peripheral component interconnect or PC 1  bus  62 . A plurality of input-output devices  64 , such as a keyboard, monitor, hard disk drive, modem or the like may be connected to the bus  62 . 
     While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations and it is intended that all variations and modifications as fall within the true spirit and scope of the present invention should be covered by the appended claims.