Heat sink assembly

[0002] 1. Field of the Invention

[0003] The present invention relates to heat sink assemblies, and particularly to heat sink assemblies incorporating spring-loaded standoffs.

[0004] 2. Related Art

[0005] Computer electronic devices such as central processing units (CPUs) frequently generate large amounts of heat, which can destabilize operation and cause damage. A heat sink placed in thermal contact with an electronic device transfers heat from the electronic device through conduction.

[0006] U.S. Pat. No. 5,757,621 discloses a conventional heat sink assembly for attachment to a motherboard. The heat sink assembly comprises a heat sink, a plurality of top screws, a plurality of bottom screws, a plurality of standoffs, a plurality of springs and a plurality of pads. Each standoff comprises a shoulder, and a neck extending upwardly from the shoulder.

[0007] In assembly, the necks of the standoffs are extended through a base of the heat sink, and the shoulders abut the motherboard. The bottom screws are threaded through the shoulders into the necks. The springs are then slid over the necks to abut the base. The pads are placed on the springs. The top screws are threaded into the necks and compress the springs to press the heat sink onto an integrated circuit on the motherboard.

[0008] Nevertheless, the screws cannot be guided into the standoffs before the screws are threadedly engaged with threads in the standoffs. This results in undue inconvenience when threading the screws into the standoffs. Furthermore, there is an excessive number of components in the assembly, thereby inflating costs and rendering the assembly process unduly complicated.

[0009] Accordingly, an object of the present invention is to provide a heat sink assembly incorporating standoffs which can easily and conveniently guide bolts in the standoffs.

[0010] To achieve the above-mentioned object, a heat sink assembly in accordance with the present invention comprises a heat sink, a plurality of standoffs, and a plurality of springs. The heat sink comprises a base defining a plurality of through apertures. Each standoff comprises a body extending through a corresponding through aperture, and a head formed on a top end of the body. The springs are placed over the corresponding bodies and located between the heads and the base. The body comprises a hollow part for fixedly receiving a bolt. The hollow part comprises an expandable portion at a bottom end thereof, a smooth guiding portion above and adjacent the expandable portion, and a threaded portion above and adjacent the guiding portion. The guiding portion guides the bolt in the standoff to facilitate the bolt engaging in the threaded portion. The expandable portions are expanded to thereby combine the heat sink, standoffs and springs as a single unit.

[0011] Other objects, advantages and novel features of the present invention will be drawn from the following detailed description of a preferred embodiment of the present invention with attached drawings, in which:

[0012] FIG. 1 is an exploded perspective view of a heat sink assembly in accordance with the present invention, together with a motherboard, a CPU and a back plate;

[0013] FIG. 2 is a perspective cutaway view of one standoff of the heat sink assembly of FIG. 1;

[0014] FIG. 3 is a pre-assembled view of a heat sink, springs and standoffs of the heat sink assembly of FIG. 1;

[0015] FIG. 4 is a fully assembled view of FIG. 1, partly cut away for better illustration; and

[0016] FIG. 5 is an enlarged view of a circled portion V of FIG. 4.

[0017] FIG. 1 of the attached drawings shows a heat sink assembly in accordance with the present invention, together with a motherboard 50, a central processing unit (CPU) 60 attached on the motherboard 50, and a back plate 70.

[0018] The motherboard 50 defines four first through apertures 52 that surround the CPU 60. The back plate 70 is made of metal, and comprises a rectangular central portion 72 and two pairs of fingers 74. The fingers 74 extend radially outwardly from corresponding corners of the central portion 72. A rectangular opening 76 is defined in the central portion 72, for improving elastic deformability of the back plate 70 and reducing a weight of the back plate 70. A thin pad 78 is secured on the back plate 70. The pad 78 is made of insulative elastic material so that when the back plate 70 is secured to the motherboard 50, the back plate 70 is electrically isolated from the motherboard 50 by the pad 78. Furthermore, the pad 78 functions as a cushion between the back plate 72 and the motherboard 50 to protect the motherboard 50 from being damaged by the back plate 70.

[0019] The heat sink assembly comprises a heat sink 10, four standoffs 20, four springs 40, and four bolts 45. The heat sink 10 comprises a rectangular base 12, and a plurality of fins 14 extending upwardly from the base 12. Four second through apertures 16 are respectively defined at four corners of the base 12, corresponding to the first through apertures 52 of the motherboard 50. Each bolt 45 comprises an upper threaded part 45a.

[0020] Referring to FIG. 2, each standoff 20 comprises a body 22 and a head 24 formed on a top end of the body 22. The body 22 comprises a hollow part 26 spanning middle and bottom portions thereof. The hollow part 26 comprises an expandable portion 28 at a bottom end thereof, a smooth guiding portion 31 above and adjacent the expandable portion 28, and a threaded portion 33 above and adjacent the guiding portion 31. The expandable portion 28 longitudinally defines a plurality of evenly-spaced slits 281 in a wall of the hollow part 26. The threaded portion 33 has an internal thread formed therein.

[0021] Referring also to FIGS. 3-5, in assembly, the springs 40 are placed over the bodies 22 of the standoffs 40. The bodies 22 of the standoffs 20 are extended downwardly through the second through apertures 16 of the heat sink 10. The springs 40 are thus located between the heads 24 of the standoffs 20 and the base 12 of the heat sink 10. The expandable portions 28 of the standoffs 20 are exposed below an underside of the base 12. The expandable portions 28 are expanded outwardly by inserting a tool (not shown) successively into each expandable portion 28. This expanding operation is well known by those skilled in the art. The standoffs 20 are thereby securely attached to the heat sink 10, and the base 12 is sandwiched between the expandable portions 28 and the springs 40. The heat sink 10, standoffs 20 and springs 40 are thus pre-assembled as a single unit. The bolts 45 are fixedly engaged in end portions of the fingers 74 of the back plate 70. The threaded parts 45aof the bolts 45 are completely exposed above the pad 78. The combined back plate 70 and bolts 45 is attached below the motherboard 50. The bolts 45 are extended through the first through apertures 52 of the motherboard 50. The combined heat sink 10, standoffs 20 and springs 40 is then attached to the motherboard 50. The threaded parts 45aof the bolts 45 are extended through the expandable portions 28 into the guiding portions 31 of the standoffs 20. The bolts 45 are thus guided by the guiding portions 31 to enter the threaded portions 33 of the standoffs 20. The standoffs 20 are then threaded downwardly to cause the threaded portions 33 to engage with the threaded parts 45aof the bolts 45. The springs 40 are compressed to thereby firmly press the heat sink 10 onto the CPU 60.

[0022] In the present invention, the expandable portions 28 and the guiding portions 31 of the standoffs 20 facilitate easy and accurate engagement of the bolts 45 with the threaded portions 33 of the standoffs 20. This accordingly facilitates engagement of the bolts 45 in the standoffs 20. In addition, the pad 78 electrically isolates the back plate 70 from the motherboard 50, and prevents the back plate 70 from damaging the motherboard 50.

[0023] It is understood that the invention may be embodied in other forms without departing from the spirit thereof. Thus, the present example and embodiment is to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.