Imported: 13 Feb '17 | Published: 18 Jan '11
USPTO - Utility Patents
An electronic device comprises a printed circuit board, an electronic component mounted on the printed circuit board, a heat dissipation device dissipating heat generated by the electronic component and a plurality of wires on the printed circuit board. The heat dissipation device comprises a heat sink and a pair of fasteners securing the heat sink to the printed circuit board. Each fastener comprises a frame body having a gap defined at a top portion thereof. The wires in a form of a wire harness extend through the gap of the frame body and into the frame body.
1. Technical Field
The disclosure relates to a heat dissipation device and, more particularly, to a heat dissipation device having a fastener for securing a heat sink to an electronic component mounted a printed circuit board.
2. Description of Related Art
With the increasing development of computer technology, electronic components mounted on a printed circuit board such as central processing units (CPUs) of computers are being made to operate at higher operational speeds and to have greater functional capabilities. When an electronic component operates at a high speed, it frequently generates large amounts of heat. The heat must be quickly removed from the electronic component to prevent it from becoming unstable or being damaged. Typically, a heat sink is attached to an outer surface of the electronic component to absorb heat from the electronic component. The heat absorbed by the heat sink is then dissipated to ambient air.
In order to keep the heat sink in intimate contact with the electronic component, a fastener is used to secure the heat sink to the electronic component. A conventional fastener comprises a pin and a spring disposed around the pin. The pin has a head at an end thereof and a clamping portion at an opposite end thereof. The clamping portion has an anchor-shaped cross-section, and comprises a pair of hooks extending upwardly and outwardly from a bottom thereof towards two opposite sides thereof. A tab extends upwardly from an inner side of each hook. The pin of the fastener passes through the heat sink and the printed circuit board. The spring is compressed between the head of the pin and the heat sink to provide a spring force which makes the hooks of the clamping portion clamping a bottom face of the printed circuit board, thereby attaching the heat sink to the electronic component.
Before the fastener is preassembled to the heat sink, the spring and the pin are separated from each other and not tied together. Operators must coil the spring around the pin of the fastener beforehand. Thus, it is time-consuming to preassemble the fastener on the heat sink.
What is needed, therefore, is a heat dissipation device having a fastener which can overcome problems mentioned above.
Referring to FIGS. 1-2, a heat dissipation device in accordance with an embodiment of the disclosure is disposed in a computer enclosure. The heat dissipation device comprises a heat sink 10 and a pair of fasteners 20 for attaching the heat sink 10 to an electronic component 32 mounted on a printed circuit board 30 in the computer enclosure. The heat sink 10 dissipates heat generated by the electronic component 32 to ambient air. A plurality of wires in the computer enclosure are bundled together to form a wire harness 40. The wire harness 40 extends through a top portion of one of the fasteners 20 and the heat sink 10, and is bundled in the fastener 20.
The heat sink 10 is formed with metal materials having good thermal conductivity, such as copper or aluminum. The heat sink 10 comprises a flat base 12 and a fin unit 14 extending upwardly and perpendicularly from a center of the base 12. The fin unit 14 comprises a plurality of spaced parallel fins 141. Two extending holes 120 are defined at two diagonal corners of the base 12, respectively. The fin unit 14 defines two grooves 140 at two opposite lateral sides thereof. The grooves 140 are respectively corresponding to the extending holes 120 and extend through the fin unit 14. In this embodiment, two adjacent fins 141 at each of the two opposite lateral sides of the fin unit 14 have a same height lower than that of other fins 141 therearound to form the grooves 140 for receiving the wire harness 40 therein.
Referring to FIG. 3 also, each fastener 20 is integrally made of plastic materials. It is obvious that the fastener 20 can also be made of metal materials. The fastener 20 comprises a frame body 22 and a clamping portion 24 extending downwards from a center of a bottom end of the frame body 22.
The frame body 22 comprises a U-shaped frame 220 and two symmetrical guiding portions 222 extending inwardly from two opposite top ends of the frame 220. The frame 220 and the guiding portions 222 cooperatively define a space 226 for receiving the wire harness 40. Each guiding portion 222 has an acute angle with a corresponding top end of the frame 220 in this embodiment. Alternatively, the angle between the guiding portion 222 and the corresponding top end of the frame 220 can be a right angle. The guiding portions 222 have a gap 228 therebetween so that the wire harness 40 can extend downwards through the gap 228 into the space 226. A width of the gap 228 is smaller than a diameter of the wire harness 40 for preventing the wire harness 40 from escaping from the frame body 22 via the gap 228 after the wire harness 40 is pressed into the space 226. A substantially round cutout 224 is defined at a joint between each guiding portion 222 and the corresponding top end of the frame 220 so that the guiding portion 222 can be elastically bent inwardly and downwardly. The cutout 224 communicates with the space 226 of the frame body 22. When a pressure is exerted on each guiding portion 222 downwardly, the guiding portion 222 is rotated relative to the corresponding top end of the frame 220, and the gap 228 between the guiding portions 222 becomes larger in such a manner that the wire harness 40 having the diameter larger than that of the original gap 228 can extend through the enlarged gap 228.
The clamping portion 24 comprises a strip-shaped pin 240 extending from the center of the bottom end of the frame body 22, a pair of wings 242 extending outwardly and downwardly from a top end of the pin 240 to two opposite lateral sides of the pin 240, and a clasp 244 extending from a bottom end of the pin 240. The wings 242 are symmetric to the pin 240, and define cooperatively an arch arching upwardly from two opposite ends to a center thereof. In other words, the arch cooperatively formed by the wings 242 has a concave facing downwardly and a convex facing upwardly. The wings 242 are spaced from the bottom end of the frame body 22. The clasp 244 has an anchor-shaped cross-section and has a maximum outer diameter thereof greater than that of each of the extending holes 120 of the heat sink 10 so that the clasp 244 can clasp a bottom surface of the heat sink 10. The clasp 244 comprises a pair of hooks 2440 extending upwardly and outwardly from a bottom thereof towards two opposite sides thereof. A tab 2442 extends upwardly from an inner side (i.e., top side) of each hook 2440. An outer diameter of the tab 2442 is slightly greater than that of each of the extending holes 120 so that the tab 2442 can abut against an inner surface of the extending hole 120. A slot (not labeled) is formed between each hook 2440 and the bottom end of the pin 240 so that the hooks 2440 can be deformed elastically when they are compressed towards each other.
The printed circuit board 30 defines two through holes 34 which are disposed adjacent to two diagonally opposite corners of the electronic component 32. The through holes 34 are aligned with the extending holes 120 of the heat sink 10, respectively. The maximum outer diameter of the clasp 244 of each fastener 20 is also greater than that of each of the through holes 34 so that the clasp 244 can clasp a bottom of the printed circuit board 30 after the fastener 20 is fixed on the printed circuit board 30.
Also referring to FIG. 4, in order to preassemble the fasteners 20 on the heat sink 10, the clasps 244 of the fasteners 20 are aligned with the extending holes 120 of the heat sink 10, respectively, and then the frame bodies 22 are pushed downwardly so that the clasps 244 are inserted into and pass through the extending holes 120. In process of preassembling, the hooks 2440 of each clasp 244 are compressed toward each other and then return to its original position. Due to the maximum outer diameter of each clasp 244 being greater than that of each of the extending holes 120, the fasteners 20 are preassembled on the heat sink 10. At the same time, the wings 242 of the fasteners 20 are in a free state.
In order to attach the heat sink 10 with the fasteners 20 to the electronic component 32, the clasps 244 are aligned with the through holes 34 of the printed circuit board 30, and the frame bodies 22 are further pushed downwardly to cause the clasps 244 to insert into and pass through the through holes 34. When the clasps 244 have passed through the through holes 34, the clasps 244 return to their original position. The wings 242 of each fastener 20 are compressed towards the base 12 to provide an upward force which makes each clasp 244 tightly clasp the bottom of the printed circuit board 30. The tabs 2442 of each clasp 244 abut against an inner surface of a corresponding through hole 34, and the hooks 2440 of each clasp 244 have an outer portion thereof abut against a bottom surface of the printed circuit board 30.
An operator pushes downwardly the fasteners 20 and makes the clasps 244 of the fasteners 20 pass through the heat sink 10 and the printed circuit board 30 in sequence. Due to the upward forces produced by the wings 242 of the fasteners 20, the clasps 244 clasp tightly the bottom of the printed circuit board 30, whereby the heat sink 10 is mounted on the printed circuit board 30 and attached to the electronic component 32 tightly. Thus, there is no need to coil a spring around the pin 240 of each fastener 20 beforehand. As a result, it is time-saving and convenient to preassemble the fasteners 20 on the heat sink 10. Additionally, the fasteners 20 each have a frame body 22 which can receive the wire harness 40 therein, which avoids the wire harness 40 from rambling disorderly in the computer enclosure.
It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.