Heat sink clip assembly

[0001] 1. Field of the Invention

[0002] The present invention relates to means for securing heat sinks in apparatus such as computers, and particularly to a clip assembly for attaching a heat sink to a computer electronic package.

[0003] 2. Related Art

[0004] Developments in integrated circuits have resulted in greater circuit density and complexity, thus increasing heat generated by operation of such integrated circuits within an electronic package. Heat sinks are often attached on the electronic packages to efficiently remove the heat.

[0005] Nowadays, a resilient clip is popularly used to attach a heat sink on an electronic package such as a central processing unit (CPU). The clip engages with a socket of the CPU. However, the CPU bears an entire weight of the heat sink. If a large, heavy heat sink is employed, it is difficult for the assembly to pass a standard vibration test. Furthermore, when a large heat sink is attached to the CPU, it is difficult to ensure that the retaining forces applied by the clip are uniform. If the retaining forces are not uniform, the heat sink is unlikely to have uniform thermal contact with the corresponding surface of the CPU. In such case, the efficiency of heat dissipation is reduced.

[0006] Another means for attaching a heat sink on a CPU comprises four through holes defined in four corners of the heat sink, and four threaded holes defined in a motherboard. Screws are extended through the through holes of the heat sink and engaged in the threaded holes of the motherboard, thereby attaching the heat sink to the CPU. However, the heat sink is rigidly connected to the CPU. It is difficult to ensure that the heat sink applies uniform pressure on the CPU, thus tending to reduce the efficiency of heat dissipation. Furthermore, the rigid connection is prone to deform the motherboard.

[0007] Therefore, an improved means for securing a heat sink which overcomes the above-mentioned problems is desired.

[0008] Accordingly, an object of the present invention is to provide a heat sink clip assembly for readily attaching a heat sink to an electronic package such as a CPU.

[0009] To achieve the above-mentioned object, a heat sink clip assembly in accordance with a preferred embodiment of the present invention attaches a heat sink to a CPU that is mounted on a motherboard. The motherboard and the heat sink each respectively define through apertures and through holes therein. The heat sink clip assembly includes four sleeves, four posts, four fasteners, and four spring members. Each sleeve comprises a top section and a bottom section. The top sections of the sleeves engage in the through holes respectively to attach the sleeves to the heat sink. The posts extend through the through apertures and received in the bottom sections of the sleeves. Each fastener includes a top head and a bottom end, the bottom ends extend into the sleeves and coupled to the top portions of the posts. The spring members are compressed between the top heads of the fasteners and the heat sink urging the heat sink toward the motherboard.

[0010] Other objects, advantages and novel features of the present invention will be drawn from the following detailed description of the preferred embodiment of the present invention with the attached drawings, in which:

[0015] Referring to FIG. 1, a heat sink clip assembly in accordance with the present invention is used to attach a heat sink 10 to a CPU 60 that is mounted on a motherboard 50.

[0016] The motherboard 50 defines therein four through apertures 52 surrounding the CPU 60. The heat sink 10 comprises a base 12, and a plurality of parallel fins 14 extending upwardly from the base 12. Four through holes 16 are defined in four corners of the base 12, corresponding to the through apertures 52 of the motherboard 50.

[0017] The heat sink clip assembly comprises a back plate 30, four fasteners 41, and four sleeves 46. The back plate 30 comprises a main body 32, and four posts 36 extending upwardly from corners of the main body 32. Each post 36 comprises an annular groove 34 defined in a middle portion thereof, and an engaging end 38 at a top portion thereof. An internal threaded hole (not labeled) is defined in the engaging end 38. Four plastic rings 40 are for respective engagement in the annular grooves 34 of the posts 36, preventing the back plate 30 from being pulled away the motherboard 50. Each plastic ring 40 is tapered, and has a break (not labeled) to provide resilient deformation. The back plate 30 also comprises an electrically insulative shock absorber 39 on a face thereof that contacts the motherboard 50, preventing the motherboard 50 from being damaged by the shock of the back plate 30.

[0018] Each fastener 41 comprises a generally cylindrical shank portion 42 having a top head 45 and a bottom threaded end 43, and a spring member such as a coil spring 44 disposed around the shank portion 42. The threaded end 43 of the fastener 41 is for engagement in the internal threaded hole of a corresponding post 36. A diameter of the head 45 is greater than a diameter of the coil spring 44, and a diameter of the coil spring 44 is greater than a diameter of a corresponding through hole 16 of the heat sink 10, so that the coil spring 44 is compressible between the head 45 of the fastener 41 and the base 12 of the heat sink 10. A diameter of the shank portion 42 is less than a diameter of the threaded end 43, so that the shank portion 42 can readily pass through the through hole 16 of the heat sink 10.

[0019] Referring also to FIG. 2, each sleeve 46 is generally cylindrical, and comprises a hollow top section 460 and a hollow bottom section 463. A break 462 radially and axially extending through the wall portion of the top and bottom sections 460, 463. This break 462 provides the sleeve 46 with an amount of resiliency. An external diameter of the bottom section 463 is greater than an external diameter of the top section 460. An external diameter of the top section 460 is greater than a diameter of the through hole 16. The top section 460 serves as a connecting portion to be engaged in the through hole 16 for joint of the sleeve 46 and the heat sink 10. The top section 460 defines an internal threaded hole therein, corresponding to the threaded end 43 of the fastener 41.

[0020] Referring also to FIGS. 3 and 4, in pre-assembly, the sleeves 46 are depressed to enable the top sections 460 of the sleeves 46 to interferentially engage in the through holes 16 of the heat sink 10 receptively, so that the sleeves 46 are secured to the heat sink 10. Alternatively, the sleeves 46 can be secured to the heat sink 10 by other means, such as by soldering. The threaded ends 43 pass through the coil springs 44, and engage in the internal threaded holes of the top sections 460. Therefore, the fasteners 41 and the sleeves 46 are pre-assembled to the heat sink 10.

[0021] The plastic rings 40 are received in the annular grooves 34 of the posts 36 of the back plate 30. The motherboard 50 is placed on the back plate 30, and the posts 36 are pressed through the through apertures 52 of the motherboard 50. The plastic rings 40 are thereby elastically compressed so that they pass through the through apertures 52. The back plate 30 is thus pre-assembled to the motherboard 50. The plastic rings 40 deformably and firmly retain the back plate 30 on the motherboard 50. Alternatively, the plastic rings 40 can be received in the annular grooves 34 of the posts 36 after the annular grooves 34 are exposed above the top surface of the motherboard 50.

[0022] The combination of the heat sink 10, the fasteners 41 and the sleeves 46 is then placed on the CPU 60 that is on the motherboard 50. The engaging ends 38 of the posts 36 are received in the bottom sections 463 of the sleeves 46 with the internal threaded holes of the posts 36 precisely aligning with the internal threaded holes of the top sections 460 of the sleeves 46, respectively. The fasteners 41 are depressed and rotated, so that the threaded ends 43 of the fasteners 41 respectively engage in the internal threaded holes of the posts 36. The coil springs 44 are compressed between the base 12 of the heat sink 10 and the heads 45 of the fasteners 41, and therefore exert resilient forces on the heat sink 10 toward the motherboard 50. The heat sink 10 is thus secured on the motherboard 50.

[0023] In the present invention, the engagement of each fastener 41 with its corresponding post 36 can be adjusted, so that the coil springs 44 cooperatively apply even clamping forces to the heat sink 10. In addition, before fastening the fasteners 41, bottom sections 463 of the sleeves 46 receive the engaging ends 38 of the posts 36 therein to guide and pre-position the heat sink 10 in place, with the internal threaded holes of the posts 36 precisely aligning with the internal threaded holes of the top sections 460. This makes the fastening operation of the fasteners 41 into the internal threaded holes of the posts 36 relatively easier.

[0024] It is understood that the invention may be embodied in other forms without departing from the spirit thereof. Thus, the present examples and embodiments are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.