Heat sink assembly

[0002] 1. Field of the Invention

[0003] The present invention relates to cooling of electronic devices, and particularly to heat sink assemblies with fixing devices for readily and firmly attaching a heat sink to an electronic device.

[0004] 2. Related Art

[0005] Developments in today's highly information-intensive society have led to remarkable improvements in performances of electronic devices. During operation of many contemporary electronic devices, large amounts of heat are produced. Such heat must be efficiently removed from the electronic device, to prevent the system from becoming unstable or being damaged. Typically, a heat sink is attached to an outer surface of the device to facilitate removal of heat therefrom.

[0006] A conventional heat sink assembly often uses a clip to attach a heat sink to an electronic device. The clip is placed into a channel of the heat sink and presses a top surface of a base of the heat sink. However, the channel is a space which would otherwise be occupied by a number of heat-dissipating fins. This results in lower heat dissipation efficiency of the heat sink.

[0007] Another heat sink assembly uses a clip placed under the heat sink to attach the heat sink to the electronic device. An example of such assembly is disclosed in Taiwan Patent Application No. 83204483. The clip defines a circular opening with a screw thread thereat, to engage with a complementarily threaded disc-shaped base of a heat sink. Space available for heat-dissipating fins is not compromised. However, the manufacturing process requires machining of a thread at both the opening of the clip and at the base of the heat sink. This is unduly cumbersome and time-consuming. Furthermore, it is difficult to precisely adjust the amount of pressing force exerted by the heat sink on the electronic device. If the base is rotated downwardly too much, it can easily damage the electronic device. If the base is not rotated downwardly far enough, it will not firmly contact a top face of the electronic device. This reduces the efficiency of heat dissipation. Additionally, when the assembly is subjected to vibration, the engagement between the clip and the heat sink is prone to become loose over time. The base gradually loses firm contact with the top face of the electronic device.

[0008] Therefore, an improved means of securing a heat sink to an electronic device which overcomes the above problems is desired.

[0009] Accordingly, an object of the present invention is to provide a heat sink assembly having a fixing device which firmly and reliably attaches a heat sink to a CPU.

[0010] Another object of the present invention is to provide a heat sink assembly which readily attaches a heat sink to a CPU and which allows ready detachment of the heat sink from the CPU.

[0011] To achieve the above-mentioned objects, a heat sink assembly comprises a heat sink, a fixing device, and a fan. The heat sink has a base, an engaging body, and an annular groove defined in a periphery of a topmost portion of the engaging body. A plurality of external teeth extends outwardly from a periphery of the engaging body. A plurality of radial fins extends upwardly from the base. A protrusion extends outwardly from a bottom portion of one fin, and an engaging space is defined adjacent the protrusion. The fins cooperatively define a central space for accommodating the fan therein. The fixing device has a frame defining an engaging opening. A plurality of internal teeth extends inwardly from the frame at the opening. The internal teeth are engaged in the groove against the external teeth of the heat sink. The fixing device also has a stop tab accommodated in the engaging space, and a latch extending coplanarly and horizontally from the stop tab. The stop tab abuts the protrusion, and the latch presses against the protrusion.

[0012] 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 together with the attached drawings, in which:

[0013] FIG. 1 is an exploded view of a heat sink assembly in accordance with the present invention, together with a fan;

[0014] FIG. 2 is a partly assembled view of a heat sink and a fixing device of the heat sink assembly of FIG. 1, but not showing the fan;

[0015] FIG. 3 is an assembled view of FIG. 1, but viewed from another aspect; and

[0016] FIG. 4 is a perspective view of an assembled heat sink assembly of FIG. 1 attached to a socket on which a CPU is mounted, thereby pressing the heat sink against the CPU.

[0017] Referring to FIG. 1, a heat sink assembly in accordance with the present invention comprises a heat sink 10, a fixing device 40, and a fan 30. Referring to FIG. 4, the heat sink assembly is attached to a CPU 70 mounted on a socket 80. A pair of spaced catches 86 is formed on each of opposite sides of the socket 80.

[0018] The heat sink 10 has a disc-shaped base 16, and a generally disc-shaped engaging body 12. An annular groove 14 is defined in a periphery of a topmost portion of the engaging body 12. A plurality of external teeth 122 extends radially outwardly from a periphery of the engaging body 12. The external teeth 122 are spaced evenly apart, and each contiguous pair of external teeth 122 are separated by an external gap 123. A plurality of radial fins 18 extends upwardly from an upper face of the base 16. The radial fins 18 comprise a first bulky fin (not labeled), a second bulky fin (not labeled), and a plurality of L-shaped thin fins (not labeled). The first and second bulky fins are separated from each other by a plurality of thin fins. Each first and second bulky fin resembles a combination of a plurality of thin fins, but with outmost vertical portions thereof integrally joined together to form an outer wall (not labeled). A protrusion 20 extends horizontally outwardly from a bottom portion of each thin fin, except the thin fins which are disposed between the bulky fins. A protrusion 20 also extends horizontally outwardly from a bottom portion of the first bulky fin, at a position farthest from the second bulky fin (see FIG. 3). A protrusion (not labeled) also extends horizontally outwardly from a bottom portion of the second bulky fin, at a position farthest from the first bulky fin. An engaging space 22 (best seen in FIG. 3) is thereby defined between the protrusion 20 of the first bulky fin and the protrusion (not labeled) of the second bulky fin. The radial fins 18 cooperatively define a central receiving space 24 at top portions of the radial fins 18, for accommodating the fan 30 therein.

[0019] The fixing device 40 has a horizontal frame 42, which defines an engaging opening 44 in a center thereof. A plurality of internal teeth 442 extends radially inwardly from the frame 12 at a periphery of the engaging opening 44, corresponding to the external gaps 123 of the engaging body 12. Each contiguous pair of internal teeth 442 is separated by an internal gap 443. A first spring portion 46 and a second spring portion 48 extend upwardly and outwardly from opposite sides of the frame 42 respectively. A pair of spaced resilient first fixing arms 50 depends from a topmost end of the first spring portion 46. A stop tab 52 extends upwardly from a center of the first spring portion 46, generally between upper portions of the first fixing arms 50. A latch 54 (see FIG. 3) extends coplanarly and horizontally from a top end of the stop tab 52. A pair of spaced resilient second fixing arms 56 extends upwardly and then downwardly from the second spring portion 48. A connecting beam 58 connects lower portions of the second fixing arms 56. A handling tab 60 extends horizontally from an upper edge of the connecting beam 58 toward the frame 42, and then doubles back over itself to extend horizontally outwardly and protrude beyond the upper edge of the connecting beam 58. An aperture 68 is defined in the vicinity of a distal end of each first fixing arm 50 and each second fixing arm 56. A reinforcing rib 64 is formed on a bottom surface of the frame 42 near edges thereof adjacent the engaging opening 44, and is also integrally formed on bottom surfaces of the first and second spring portions 46, 48.

[0020] Referring particularly to FIGS. 2-4, in assembly, the engaging body 12 of the heat sink 10 is centered above the fixing device 40, such that the external teeth 122 of the engaging body 12 oppose the internal gaps 443 of the fixing device 40. The external teeth 122 are passed through the internal gaps 443, and the frame 42 of the fixing device 40 is accommodated around a perimeter of the groove 14 of the engaging body 12 (see FIG. 2). The stop tab 52 of the fixing device 40 is accommodated in the engaging space 22 of the heat sink 10. Then, the fixing device 40 is rotated (see FIG. 2) until the stop tab 52 thereof abuts against the protrusion 20 of the first bulky fin of the heat sink 10. In this position, the latch 54 of the fixing device 40 abuts a top portion of the protrusion 20 of the first bulky fin (see FIG. 3). The external teeth 122 of the engaging body 12 abut the corresponding internal teeth 442 of the fixing device 40. The fixing device 40 is thereby prevented from separating from the heat sink 10.

[0021] The combined heat sink 10 and fixing device 40 is then placed onto the CPU 70. A bottom surface of the engaging body 12 abuts against a top surface of the CPU 70. The apertures 68 of the first fixing arms 50 loosely receive the corresponding catches 86 of the socket 80. Then, the handling tab 60 of the fixing device 40 is depressed to drive the apertures 68 of the second fixing arms 56 to engagingly receive the corresponding catches 86 of the socket 80. The latch 54 of the fixing device 40 thereby presses against the top portion of the protrusion 20 of the first bulky fin of the heat sink 10. The fan is then mounted inside the central receiving space 24 of the heat sink 10 by conventional means.

[0022] It is understood that the invention may be embodied in other forms without departing from the spirit thereof. Thus, the present example and embodiment 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.