Retention mechanism for an electrical assembly

[0002] This non-provisional United States (U.S.) Patent Application claims the benefit of and is continuation application of U.S. patent application Ser. No. 09/137,520 filed on Aug. 20, 1998 by inventors Llapitan et al., titled “A RETENTION MECHANISM FOR AN ELECTRONIC ASSEMBLY”, which is assigned to Intel Corp.

[0003] 1. Field of the Invention

[0004] The present invention relates to a retention mechanism for securing an electronic assembly to a motherboard that has studs provided.

[0005] 2. Background Information

[0006] FIG. 1 shows a product marketed by Intel Corporation, the assignee of this application, which is referred to as a single edge contact cartridge (SECC). The Intel SECC includes a microprocessor which is assembled into a package 1 that is mounted to a substrate 2. The SECC may also have other integrated circuit packages 3 which contain static random access memory (SRAM) integrated circuits.

[0007] One edge of the substrate 2 has a plurality of conductive pads 4 which can be inserted into an electrical connector 5. The electrical connector 5 can be mounted to a printed circuit board 6 such as the motherboard of a computer. The pads 4 and connector 5 electrically couple the substrate 2 to the circuit board 6.

[0008] The substrate 2 and integrated circuit packages 1 and 3 are enclosed by a cover 7 and a thermal plate 8. The cover 7, plate 8 and substrate 2 provide an electronic cartridge which can be plugged into a computer motherboard 6.

[0009] The electrical system shown in FIG. 1 can sustain to external shock and vibration loads. Such loads may produce intermittent separation between the pads 4 and the connector 5. Intermittent separation between the pads 4 and connector 5 may create electrical “opens.” The system is provided with a retention mechanism 9 to secure the substrate 2 to the connector 5 and prevent contact separation under shock and vibration loads.

[0010] The retention mechanism 9 includes a pair of posts 10 that are mounted to the circuit board 6. Each post 10 includes an aperture 11 which receives a latch 12 that extends from the cover 7 of the cartridge. When inserted into the aperture 11 each latch 12 prevents the substrate 2 from being pulled out of the connector 5. The substrate 2 can be unplugged from the connector 5 by pressing a pair of latch levers 13 and pulling the cartridge away from the board 6. Pressing the levers 13 moves the latches 12 out of the apertures 11 of the posts 10.

[0011] The integrated circuits generate heat which must be removed from the circuits. The thermal plate 8 is thermally coupled to the integrated circuit package 1 of the SECC to provide a thermal path for the heat generated by the microprocessor. A heat sink 14 may be mounted to the thermal plate 8 to further facilitate the removal of the heat.

[0012] The heat sink 14 is typically constructed from a thermally conductive material such as aluminum or copper. Metal heat sinks 14 have a weight which increases the magnitude of loads on the cartridge, particularly when the system is subjected to shock or vibration.

[0013] The Intel SECC includes a heat sink support assembly 15 that is mounted to the printed circuit board 6 and supports the heat sink 14. The support assembly 15 includes a support bar 16 that is inserted into holes of the circuit board 6. The assembly 15 also includes a tie bar 17 that is inserted into a groove 18 of the heat sink 14 and snapped onto posts 19 of the support bar 16.

[0014] It is desirable to reduce the number of parts in an electrical assembly to reduce the complexity and cost of mass producing the product. It would therefore be desirable to provide a single retention mechanism which secures the substrate to the connector and supports a heat sink of the electronic assembly. Additionally, it would be desirable to eliminate the through holes required to install the support bar of the SECC. The through holes occupy valuable routing space on the printed circuit board.

[0015] One embodiment of the present invention is a retention mechanism for an electronic assembly which has a substrate and a heat sink. The assembly includes a heat sink slot that receives the heat sink, and a substrate slot that receives the substrate.

[0016] FIG. 1 is a perspective view of an electrical assembly of the prior art;

[0017] FIG. 2 is a perspective view of an embodiment of an electrical assembly of the present invention;

[0018] FIG. 3 is a rear view showing a clip that attaches a heat sink to a substrate;

[0019] FIG. 4 is an end view showing a substrate being inserted into a retention mechanism;

[0020] FIG. 5 is a side sectional view of a substrate and a heat sink inserted into a retention mechanism;

[0021] FIG. 6 is a perspective view of an alternate embodiment of the retention mechanism.

[0022] One embodiment of the present invention is a retention mechanism for an electronic assembly which has a substrate and a heat sink. The retention mechanism includes a first slot that receives the heat sink and a second slot that receives the substrate. The heat sink guides the substrate into the connector. There may be two retention mechanisms that are attached to a printed circuit board adjacent to an electrical connector.

[0023] There may be two heat sink slots symmetrically located about the substrate slot so that the mechanism can be mounted to a left side or a right side of the connector. The symmetric slots eliminate the need for a left side mechanism and a right side mechanism. Providing a single mechanism reduces the complexity and cost of mass producing an electrical assembly which contains the substrate, heat sink and mechanism. Supporting both the substrate and the heat sink with a single mechanism also eliminates the need to provide a separate support assembly for the heat sink.

[0024] The retainer mechanism may also have a nut retainer that captures a nut that is used to attach the mechanism to the printed circuit board with studs. The nut retainer allows the nut to be transported with the retainer mechanism during an assembly process.

[0025] Referring to the drawings more particularly by reference numbers, FIG. 2 shows an embodiment of an electrical assembly 30 of the present invention. The assembly 30 includes an electronic assembly 32 that can be plugged into an electrical connector 34. The connector 34 may be mounted to a printed circuit board 36. The printed circuit board 36 may be a motherboard of a computer.

[0026] The electronic assembly 32 may include an integrated circuit package 38 that is mounted to a substrate 40. The integrated circuit package 38 may contain an integrated circuit (not shown) such as a microprocessor. The substrate 40 may be a printed circuit board. One edge of the substrate 40 may have a plurality of contacts 42 that can be inserted into the electrical connector 34. The substrate 40 may have routing traces, power/ground planes, vias, surface pads, etc. which electrically connect the integrated circuit package 38 to the contacts 42.

[0027] The electronic assembly 32 may further have a heat sink 44 that is mounted to the substrate 40. The heat sink 44 may be pressed against the integrated circuit package 38 to provide a thermal path for the heat generated by the integrated circuit. The assembly 32 may include a clip 46 which attaches the heat sink 44 to the substrate 40.

[0028] The clip 46 may have a plurality of L-shaped ears 48 that are inserted through clearance holes 50 in the substrate 40 and corresponding attachment holes 51 in the heat sink 44. The clip 46 may have four ears 48 which extend from a center plate portion 52. The L-shaped ears 48 are bent during insertion through the holes 50 and 52. There may be provided a tool (not shown) which bends the ears 48 during the insertion step. The clip 46 may be constructed from a steel material which does not yield during the assembly process. The center plate portion 52 may have a pair of handles 53 that allow an operator to more easily grasp the clip 46 during installation.

[0029] As shown in FIG. 3, the L-shaped ears 48 snap back after clearing the attachment holes 51 of the heat sink 44. When assembled, the clip 46 may exert a spring force that pushes the heat sink 44 into the integrated circuit package 38.

[0030] Referring to FIG. 2, the assembly 30 may include a pair of retention mechanisms 54 that are mounted to the printed circuit board 36. The retention mechanisms 54 retain and support the electronic assembly 32. Each retention mechanism 54 may have a back wall 56 that extends from the printed circuit board 36. The mechanism 54 may include a plurality of first walls 58 which extend from the backwall 56 and are separated from each other by a pair of heat sink slots 60. The walls 58 are adjoined by a base portion 62. A pedestal 64 portion of the heat sink 44 may be inserted into either heat sink slot 60. Insertion of the heat sink 44 into the heat sink slot 60 guides the substrate 40 into the connector 34.

[0031] As shown in FIG. 4, walls 58 may be separated from each other by a substrate slot 66. The substrate slot 66 may receive the substrate 40.

[0032] Referring to FIG. 2, each retention mechanism 54 may have a pair of studs 72 that are pressed into a pair of corresponding holes 74 in the printed circuit board 36 through clearance holes 75 in the mechanism 54. Pins 76 may be pressed into the retention studs 72 to expand the studs 72 and secure the retention mechanism 54 to the circuit board 36. The retention mechanism 54 may have a pair of latch apertures 78.

[0033] As shown in FIG. 5, one of the latch apertures 78 may receive a tab 80 of the heat sink 44. When inserted into the aperture 78, the tab 80 prevents the electronic assembly 32 from being pulled out of the connector 34. The retention mechanism 54 may have an inward angle of approximately 3.2° to apply a compressive force on the heat sink 44. The compressive force prevents the substrate 40 from moving relative to the connector 34. The compressive force has been found to be adequate to allow the retention mechanism to withstand 50 G's in all axes. To remove the assembly 32 an operator can depress a latch arm 82 to move the backwall 56 so that the tab 80 is separated from the retention mechanism 54. For an assembly 30 with two retention mechanisms 54 the operator can decouple tabs 80 that are located on both sides of the heat sink 44 from the latch apertures 78. Once the tabs 80 are decoupled from the retention mechanisms 54 the operator can pull the substrate 40 out of the connector 34.

[0034] The widths of each slot 60 are preferaby such that the walls 58 apply a spring force onto the sides of the heat sink 44. The slots 60 may be symmetrically located on the retention mechanism so that a mechanism can be installed on either the right side or left side of the connector 34. This design eliminates the need for a right hand part and a separate left hand part. Separate right hand and left hand parts would increase the complexity of the assembly process and the inventory required for the assembly 30. The walls and studs of the retention mechanisms may all be integrated into a single injection molded part. Additionally, the insertion of the heat sink 44 into the retention mechanism creates a “clicking” sound which provides an indication to the person installing the electronic assembly that the substrate 40 is connected to the circuit board.

[0035] FIG. 6 shows another embodiment of a retention mechanism 54′ which has a pair of nut retainers 84 which extend from the backwall 56 adjacent to the clearance holes 75. The nut retainers 84 may each have a channel 86 that receives a nut 88. The nuts 88 can be screwed onto threaded studs 90 that extend up from the printed circuit board 36. The nuts 88 and studs 90 secure the retention mechanism 54′ to the circuit board 36.

[0036] Each nut retainer 84 may have a pair of arms 92 which extend about the channel 86 in a circular pattern. The arms 92 are flexible enough so that the nuts 88 can be snapped into the channels 86. The distance between the ends of the arms 92 is less than the diameter of the nuts 88 so that the nuts 88 are captured by the nut retainers 84. The nuts 88 may each have a flange 94 that extends into a groove 96 of a nut retainer 84. The flange 94 may have a thickness that is less than a height of the groove 96 to provide space for the nut to move up when initially placed on the stud 90. This allows the nut 88 to be tightened onto the stud 90 without cross threading.

[0037] The nut retainers 84 allow a manufacturer of the retainer mechanism 54′ to ship the mechanism 54′ with the nuts 88. An assembler can install the retainer mechanism 54′ by placing the mechanism 54 onto the printed circuit board 36 so that the studs 90 extend through the holes 75. The nuts 88 can be rotated onto the studs 90 to attach the retainer mechanism 54′ to the circuit board 36.

[0038] 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.