Apparatus and methods for attaching thermal spreader plate to an electronic card

[0002] 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.

[0003] 1. Field of the Invention

[0004] The present invention relates to an electronic card.

[0005] 2. Background Information

[0006] 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.

[0007] 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.

[0008] 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.

[0009] 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.

[0010] FIG. 1 is an exploded view of an embodiment of an electronic card of the present invention;

[0011] FIG. 2 is an enlarged sectional view showing a rivet that attaches a first cover to a second cover of the card;

[0012] 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;

[0013] 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;

[0014] 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;

[0015] 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;

[0016] FIG. 7 is an enlarged sectional view showing an alternate embodiment of a card that has a first cover welded to a second cover;

[0017] 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.

[0018] 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.

[0019] 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).

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] FIG. 6 shows another embodiment wherein a first cover 24′ has a lip 40 that is crimped onto the second cover 26′.

[0025] 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.

[0026] 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.

[0027] 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.