Patent Publication Number: US-2012043058-A1

Title: Heat dissipation device

Description:
BACKGROUND 
     1. Technical Field 
     The disclosure relates to heat dissipation devices, and particularly to a heat dissipation device for dissipating heat generated from an electronic component. 
     2. Description of Related Art 
     Nowadays, with the development of electronics technology, an electronic device such as a computer or a server is much thinner and smaller than before. Yet the device is able to hold many more electronic components than before. The electronic components generate a large amount of heat during operation. Usually a heat sink assembly is installed on a printed circuit board for cooling a major heat-generating electronic component mounted on the printed circuit board. 
     Referring to  FIG. 3 , a conventional heat sink assembly is shown. The heat sink assembly includes a heat pipe  30  thermally contacting the electronic component, a fin assembly  40  thermally connecting the heat pipe  30 , and a centrifugal fan  50  located at a side of the fin assembly  40 . The fin assembly  40  includes a plurality of fins stacked together. The centrifugal fan  50  has an air inlet and an air outlet. The centrifugal fan  50  draws cool air through the air inlet. The cool air under the action of an impeller in the centrifugal fan  50  is blown through and out of the air outlet towards the fins, and turns into hot air at the fins. The hot air then flows out of the fin assembly  40 . However, the heat pipe  30  is attached to the fin assembly  40  by inserting and soldering an end of the heat pipe  30  inside the fin assembly  40 . Therefore when the air flows through the fins of the fin assembly  40 , the heat pipe  30  in the fin assembly  40  blocks some of the air from flowing out of the fin assembly  40 . 
       FIG. 4  shows another conventional heat sink assembly, which is similar to the above-described heat sink assembly. In this other heat sink assembly, the heat pipe  30  is attached to the fin assembly  40  by soldering an end of the heat pipe  30  on a top face of the fin assembly  40 . However, this solution increases the thickness of the entire heat sink assembly and correspondingly the thickness of the electronic device. 
     What is needed, therefore, is a heat dissipation device which can overcome the limitations described. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the views. 
         FIG. 1  is an isometric, assembled view of a heat dissipation device in accordance with an embodiment of the disclosure. 
         FIG. 2  is an exploded view of the heat dissipation device of  FIG. 1 . 
         FIGS. 3-4  are isometric views of two heat sinks in accordance with related art. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a heat dissipation device in accordance with an embodiment of the present disclosure is shown. The heat dissipation device is adapted for cooling an electronic device (not shown) mounted on a printed circuit board (not shown), and includes a heat sink  10  and a centrifugal fan  20 . 
     Also referring to  FIG. 2 , the centrifugal fan  20  includes a fan frame  22 , and an impeller  24  mounted in the fan frame  22 . The fan frame  22  includes a base  26 , and a cover plate  28  covering the base  26 . A first air inlet  280  is defined in a central portion of the cover plate  28 . A plurality of through holes  282  is defined in a periphery of the cover plate  28 . The base  26  includes a base plate  260 , and a side wall  262  extending vertically upwardly from an outer edge of the base plate  260 . The base plate  260  includes a fixing seat  2602  near a center thereof. Three second air inlets  2600  are defined in the base plate  260  around the fixing seat  2602 , corresponding to the first air inlet  280  of the cover plate  28 . The impeller  24  is fixed on the fixing seat  2602  of the base plate  260 . An air outlet  202  is defined in the side wall  262  of the base  26 , and includes a first portion  2021  and a second portion  2022 . An angle between the first portion  2021  and the second portion  2022  is an obtuse angle. The air outlet  202  is perpendicular to the first air inlet  280  and the second air inlet  2600 . A plurality of protruding posts  2620  protrude from a top face of the side wall  262 , corresponding to the through holes  282  of the cover plate  28 . The protruding posts  2620  extend through the through holes  282  of the cover plate  28  to fasten the cover plate  28  on the side wall  262 . Thereby, the cover plate  28  and the base  26  cooperatively form a space (not labeled) where the impeller  24  is received. 
     The heat sink  10  includes a heat spreader  12 , a heat pipe  14 , and a fin assembly  16 . The heat pipe  14  is flat, and includes an evaporating section  142  attached to the heat spreader  12  and a condensing section  144  attached to the fin assembly  16 . The evaporating section  142  has a flat top face and a flat bottom face. The top and bottom faces of the evaporating section  142  are parallel to each other. The bottom face of the evaporating section  142  thermally contacts a top face of the heat spreader  12 . The condensing section  144  has an inner side face and an outer side face. The inner side face and the outer side face of the condensing section  144  are parallel to each other. The inner and outer side faces of the condensing section  144  are perpendicular to the top and bottom faces of the evaporating section  14 . 
     The heat spreader  12  is made of metal such as aluminum, copper or an alloy thereof. A bottom of the heat spreader  12  thermally contacts the electronic device to absorb heat from the electronic device. Two fastening elements  122  are disposed at two lateral sides of the top face of the heat spreader  12 , for fastening the heat spreader  12  on the printed circuit board on which the electronic device is mounted. 
     The fin assembly  16  includes a plurality of spaced, parallel fins  162 . Two opposite flanges  164  are bent and formed at two opposite lateral sides (i.e., inner and outer sides) of each fin  162 . The fins  162  are stacked together one above another along a direction parallel to a central axis of the centrifugal fan  20 . A plurality of horizontal airflow channels (not labeled) are formed between adjacent fins  162  of the fin assembly  16 . The flanges  164  of adjacent fins  162  abut against each other and form first and second side faces  165 ,  166  at the outer and inner sides of the fin assembly  16 . The first and second side faces  165 ,  166  are respectively parallel to the central axis of the centrifugal fan  20 . A portion at an end of each fin  162  which is located adjacent to the impeller  24  is cut away to thereby form an arc-shaped cutout  168 , making a length of the second side face  166  smaller than that of the first side face  165 . 
     In assembly, the fin assembly  16  is disposed at the air outlet  202 . The first side face  165  of the fin assembly  16  is in alignment with the second portion  2022  of the air outlet  202 , the second side face  166  of the fin assembly  16  is disposed in the first portion  2021  of the air outlet  202  and abuts against the side wall  262  of the base  26 , and the cutout  168  of the fin assembly  16  is disposed near the impeller  24  of the centrifugal fan  20 . The inner side face of the condensing section  144  of the heat pipe  14  is attached to and thermally contacts the first side face  165  of the fin assembly  16  via a heat conductive material  13 . In the illustrated embodiment, the heat conductive material  13  is a thermal tape. 
     During operation of the heat dissipation device, the heat spreader  12  absorbs heat generated from the electronic device, and the heat pipe  14  transfers heat in the heat spreader  12  to the fin assembly  16 . The centrifugal fan  20  draws air through the first air inlet  280  and the second air inlets  2600  into the space formed by the cover plate  28  and the base  26 . The air under the action of the impeller  24  is blown from the first portion  2021  of the air outlet  202  and out of the fin assembly  16 . Since the condensing section  144  of the heat pipe  14  is attached on the first side face  165  of the fin assembly  16 , the heat pipe  14  does not block the air flowing through the fin assembly  16 , and yet the thickness of the entire heat dissipation device is kept to a minimum. 
     It is believed that the embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the disclosure.