Abstract:
An electronic card that includes an integrated circuit which is coupled to a substrate. The substrate is located between two thermally conductive covers. The assembly may further include a fastener that attaches the covers. Alternatively, the covers may be crimped or welded together. As another alternative embodiment the covers may be bonded to integrated circuit located on opposite sides of the substrate.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This U.S. patent application filed by inventor Steven Lofland claims the benefit and is a continuation-in-part of U.S. patent application Ser. No. 08/992,617, filed by inventors Lofland et al on Dec. 17, 1997, now issued as U.S. Pat. No. 5,966,287. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electronic card. 
     2. Background Information 
     Integrated circuits are typically assembled into packages that are mounted to a printed circuit board. By way of example memory devices are commonly assembled into packages that are soldered to a single printed circuit board. One edge of the printed circuit board may have a plurality of contact pads that can be plugged into a connector that is mounted to a motherboard of a computer. The packages and circuit board provide a memory card that can be easily installed and detached from the computer. 
     The integrated circuits generate heat which must be removed from the packages to insure that the junction temperatures of the circuits do not exceed specified values. Memory cards are typically plugged into computer system which contain a fan that generates a flow of air. The air flows across the memory cards and removes heat from the packages by forced convection. 
     Inducing a flow of air across the packages may be insufficient to remove heat from integrated circuits that generate a relatively large amount of power. Heat slugs, heat spreaders, heat sinks and heat pipes have all been incorporated into various electronic assemblies to increase the heat transfer rate from the package to the air. These thermal components add cost to the overall assembly. It is desirable to minimize the cost of mass producing a memory card. It would therefore be desirable to provide a thermal element(s) that can be assembled into an electronic card in a cost effective manner. 
     SUMMARY OF THE INVENTION 
     One embodiment of the present invention is an electronic card that includes an integrated circuit which is coupled to a substrate. The substrate is located between two thermally conductive covers. The assembly may further include a fastener that attaches the covers. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of an embodiment of an electronic card of the present invention; 
     FIG. 2 is an enlarged sectional view showing a rivet that attaches a first cover to a second cover of the card; 
     FIG. 3 is an enlarged sectional view showing an alternate embodiment of a card with a staked rivet that attaches a first cover to a second cover; 
     FIG. 4 is an enlarged sectional view showing an alternate embodiment of a card with an extruded rivet that attaches a first cover to a second cover; 
     FIG. 5 is an enlarged sectional view showing an alternate embodiment of a card with a snap fastener that attaches a first cover to a second cover; 
     FIG. 6 is an enlarged sectional view showing an alternate embodiment of a card which has a first cover that is crimped onto a second cover; 
     FIG. 7 is an enlarged sectional view showing an alternate embodiment of a card that has a first cover welded to a second cover; 
     FIG. 8 is an enlarged sectional view showing an alternate embodiment of a card with a pair of covers bonded to integrated circuit packages that are mounted to a substrate. 
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings more particularly by reference numbers, FIG. 1 shows an embodiment of an electronic card  10  of the present invention. The card  10  may include a substrate  12  which has a first side  14  and a second side  16 . One or more integrated circuit packages  18  may be mounted to each side  14  and  16  of the substrate  12 . Each package  18  may contain one or more integrated circuits  20 . By way of example the integrated circuits  20  may be dynamic random access memory (DRAM) devices. 
     The card substrate  12  may be a printed circuit board which has surface pads, routing traces, power/ground planes, etc. (not shown) that interconnect the integrated circuits  20  to each other and to a plurality of contact pads  22  which extend along one edge of the substrate  12 . The contact pads  22  may be plugged into a connector (not shown) that is mounted to a motherboard (not shown) of a computer (not shown). 
     The integrated circuits  20  generate heat which must be removed from the packages  18 . To facilitate the removal of heat the card  10  may include a first thermally conductive cover  24  located on the first side  14  of the substrate  12  and a second thermally conductive cover  26  that is located on the second side  16  of the substrate  12 . The covers  24  and  26  are thermally coupled to the packages  18  so that heat flows from the integrated circuits  20  and into the covers  24  and  26 . The first  24  and second  26  covers may be thermally coupled to the integrated circuit packages  18  by placing the covers  24  and  26  into direct contact with the outer top surfaces of the packages  18 . The first  24  and second  26  covers are preferably constructed from a thermally conductive material such as aluminum or copper so that the heat flows throughout the covers  24  and  26 . The covers  24  and  26  provide a large surface area for the heat to transfer into the ambient either by forced or natural convection. The covers  24  and  26  may also be referred to as thermal spreader plates. Each of the covers  24  and  26  have a heat spread area  27  and a heat sink area  29 . The heat spread area  27  matches the area of the card substrate  12 . The heat sink area  29  enlarges the surface area of heat spread area  27 . 
     As shown in FIG. 2 the card  10  may include a rivet fastener  36  which extends through the openings  30 ,  32  and  34  to attach the first cover  24  to the second cover  26 . The rivet  36  shown in FIG. 2 may be swaged onto the first cover  24 . The rivet  36  may be solid or have an inner channel  38 . FIG. 3 shows a solid rivet  36 ′ that is heat staked into the openings  30 ,  32  and  34 . 
     FIG. 4 shows an embodiment wherein the rivet  36 ″ is extruded from the second cover  26  and attached to the first cover  24 . Extruding the rivet  36 ″ from the cover  26  reduces the number of parts required for inventory and assembly of mass produced cards  10 . Although a rivet  36 ″ extruded from the second cover  26  is shown and described, it is to be understood that the rivet  36 ″ could alternatively be extruded from the first cover  24 . 
     FIG. 5 shows an alternate embodiment wherein a plastic snap-in fastener  38  is inserted through the openings  30 ,  32  and  34  to attach the first cover  24  to the second cover  26 . 
     FIG. 6 shows another embodiment wherein a first cover  24 ′ has a lip  40  that is crimped onto the second cover  26 ′. 
     FIG. 7 shows an embodiment of a card with covers  24 ″ and  26 ″ which have dimpled portions  42  and  44 , respectively, that are welded together. FIG. 8 shows yet another embodiment of a card wherein the first cover  24  is bonded to one or more first integrated circuit packages  18  located on the first side  14  of the substrate  12  and the second cover  26  is bonded to one or more integrated circuit packages  18  located on the second side  16  of the substrate  12 . The covers  24  and  26  may be bonded to the integrated circuit packages  18  by a thermally conductive epoxy  46 . 
     The covers  24  and  26  and various fastening means provide thermal elements which can be readily assembled in a mass production process at a relatively inexpensive cost. 
     While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that this invention not be limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those ordinarily skilled in the art. Although integrated circuit packages are shown and described, it is to be understood that the integrated circuits may be directly coupled to the substrate  12  and/or the cover(s)  24  and/or  26 .