Patent Publication Number: US-2010128443-A1

Title: Heat dissipating module

Description:
FIELD OF THE INVENTION 
     The present invention relates to a heat dissipating module, and more particularly to a heat dissipating module having a mechanism for facilitating fixing a heat sink on a circuit board. 
     BACKGROUND OF THE INVENTION 
     With the rapid progress of semiconductor industries, the integrated circuits (ICs) used in electronic apparatuses are developed toward minimization, high operating speed and increasing integration level. Due to the reduced size and the increased performance, power semiconductor devices such as power transistors have achieved a great deal of advance. The power transistors are used in many electronic apparatuses such as control equipment, measuring equipment, electrical apparatuses and computer peripheral devices because they are very suitable to process high-power signals. During operation of the electronic apparatus, the power transistors may generate energy in the form of heat, which is readily accumulated and difficult to dissipate away. If no proper heat-dissipating mechanism is provided to transfer enough heat to the ambient air, the elevated operating temperature may result in damage of the electronic components, a breakdown of the whole electronic apparatus or reduced operation efficiency. Therefore, it is important to dissipate the heat generated from the power transistors in order to stabilize the operation and extend the operational life of the electronic apparatus. 
     For dissipating the heat generated from the electronic components, a variety of heat sinks are attached onto a surface of the circuit board of the electronic device. By means of the heat sink, the heat generated from the electronic components on the circuit board is transferred to the ambient air. Since the heat sink is developed toward increased heat transfer area and reduced thermal resistance, it is important to provide a process of assembling the heat sink in a simplified manner. 
     Generally, the power transistors are fastened onto a surface of a heat sink in order to increase heat-dissipating efficiency.  FIG. 1A  is a schematic layout configuration of a circuit board. As shown in  FIG. 1A , the circuit board  10  includes an upper surface  101  and a lower surface  102 , which are opposed to each other. Several electronic components  11  are mounted on the upper surface  101  of the circuit board  10 . The electronic components  11  include for example at least a transistor, at least a resistor, at least a capacitor, at least a diode, at least a magnetic element and the like. The power converting circuit cooperatively defined by these electronic components  11  and the trace pattern of the circuit board  10  is responsible for power conversion. In addition, at least one heat sink  12  is fixed on the upper surface  101  of the circuit board  10  for dissipating heat generated from the electronic components  11 . For example, as shown in  FIG. 1A , the heat sink  12  is substantially a flat metallic plate. The heat sink  12  has a first surface  121 , a second surface  122  and several perforations  123 . 
       FIG. 1B  is a schematic perspective view illustrating the backside of the heat sink shown in  FIG. 1A . Please refer to  FIGS. 1A and 1B . A power transistor  111  is fastened onto the second surface  122  of the heat sink  12 . Furthermore, several fixing elements  13  are disposed on the second surface  122  of the heat sink  12 . Each fixing element  13  comprises a first part  131  and a second part  132 . The first part  131  is substantially perpendicular to the second part  132 . Several openings  133  are formed in the first part  131  and aligned with corresponding perforations  123  of the heat sink  12 . By penetrating a screw  14  through the openings  133  and corresponding perforations  123 , the fixing elements  13  are fastened on the heat sink  12 . After the fixing elements  13  are fastened on the heat sink  12 , the heat sink  12  is turned over. Then, the tips of the second parts  132  of the fixing elements  13  are penetrated through corresponding insertion holes (not shown) of the circuit board  10 . The tips of the fixing elements  13  are then twisted by an angle (as shown in  FIG. 1C ), so that the tips of the fixing elements  13  are sustained against the sidewalls of the insertion holes. The backside of the resulting structure is shown in  FIG. 1C . Meanwhile, the heat sink  12  is fixed on the circuit board  10  through the fixing elements  13 . As shown in  FIGS. 1B and 1C , after the pins  111   a  of the power transistor  111  are penetrated through the corresponding insertion holes (not shown) of the circuit board  10 , solder paste  15  is applied to the insertion holes in order to bond the power transistor  111  on the circuit board  10 . 
     The process of fixing the heat sink on the circuit board includes the steps of: fixing the fixing elements  13  in corresponding perforations  123  of the heat sink  12 , penetrating the tips of the fixing elements  13  through corresponding insertion holes of the circuit board  10 , and twisting the tips of the fixing elements  13  by an angle. This process is labor-intensive, time-consuming and troublesome. Moreover, since the fixing elements  13  are fixed in corresponding perforations  123  of the heat sink  12 , the flexibility of arranging the fixing elements  13  is restricted because the fixing elements  13  are only located on specified positions. 
     There is a need of providing an improved a heat dissipating module to obviate the drawbacks encountered from the prior art. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a heat dissipating module having a mechanism for facilitating fixing a heat sink on a circuit board. 
     Another object of the present invention provides a heat dissipating module that is assembled in a simplified, labor-saving and time-saving manner. 
     A further object of the present invention provides a heat dissipating module comprising a heat sink and at least a fixing element, in which the location of the fixing element is varied as required. 
     In accordance with an aspect of the present invention, there is provided a heat dissipating module mounted on a circuit board. The circuit board includes at least an insertion hole. The heat dissipating module includes a heat sink and at least a fixing element. The heat sink has at least a guiding track, wherein at least an electronic component is attached on the heat sink or the circuit board. The fixing element includes a first fixing part and a second fixing part. The first fixing part is embedded in the guiding track. The second fixing part is partially penetrated through the insertion hole and sustained against a lower surface of the circuit board, thereby facilitating fixing the heat sink on the circuit board. 
     In accordance with another aspect of the present invention, there is provided an electronic device. The electronic device includes a housing, a circuit board, a heat sink, at least an electronic device and at least a fixing element. The housing has a receptacle therein. The circuit board is disposed within the housing and includes at least an insertion hole. The heat sink has at least a guiding track. The electronic device is attached on the heat sink or the circuit board. The fixing element includes a first fixing part and a second fixing part. The first fixing part is embedded in the guiding track. The second fixing part is partially penetrated through the insertion hole and sustained against a lower surface of the circuit board, thereby facilitating fixing the heat sink on the circuit board. 
     The above contents of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic layout configuration of a circuit board; 
         FIG. 1B  is a schematic perspective view illustrating the backside of the heat sink shown in  FIG. 1A ; 
         FIG. 1C  is a schematic perspective view illustrating the backside of the circuit board shown in  FIG. 1A ; 
         FIG. 2  is a schematic cross-sectional view illustrating an electronic device according to the present invention; and 
         FIG. 3A  is a schematic exploded view illustrating a heat dissipating module according to a preferred embodiment of the present invention; and 
         FIG. 3B  is a schematic assembled view of the heat dissipating module shown in  FIG. 3A . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed. 
       FIG. 2  is a schematic cross-sectional view illustrating an electronic device according to the present invention. The electronic device  2  comprises a housing  20 , a circuit board  21 , one or more electronic components  22  and a heat dissipating module  25 . The electronic components  22  and the heat dissipating module  25  are mounted on the circuit board  21 . A receptacle  201  is defined within the housing  20  for accommodating the circuit board  21  as well as the electronic component  22  and the heat dissipating module  25 . The heat dissipating module  25  comprises a heat sink  23  and a fixing mechanism. The fixing mechanism comprises several fixing elements  24 . The fixing element  24  is used for facilitating fixing the heat sink  23  on the circuit board  21 . The heat sink  23  is used for dissipating heat generated from the electronic components  22  that are attached on the circuit board  21  or the heat sink  23 . For example, a power transistor  221  is attached on the heat sink  23 . 
     An example of the electronic device  2  includes but is not limited to a power supply apparatus. The circuit board  21  is for example a printed circuit board. As shown in  FIG. 2 , the circuit board  21  includes an upper surface  211 , a lower surface  212  and several insertion holes. The upper surface  211  and the lower surface  212  are opposed to each other. Several electronic components  22  are mounted on the upper surface  211  of the circuit board  21 . The electronic components  22  include for example at least a transistor, at least a resistor, at least a capacitor, at least a diode, at least a magnetic element and the like. The power converting circuit cooperatively defined by these electronic components  22  and the trace pattern of the circuit board  21  is responsible for power conversion. In addition, the heat sink  23  is fixed on the upper surface  211  of the circuit board  21  for dissipating heat generated from the electronic components  22 . In this embodiment, the heat sink  23  is an aluminum extrusion element. It is preferred that the heat sink  23  is integrally formed. 
     Please refer to  FIG. 2  again. The heat sink  23  has a first surface  230  and a second surface  235 . The first surface  230  and the second surface  235  are opposed to each other. The heat sink  23  principally comprises a first part  231 , a second part  232  and a third part  233 , which are disposed on the first surface  230  of the heat sink  23 . The first part  231  of the heat sink  23  is substantially parallel with the circuit board  21 . The second part  232  of the heat sink  23  is arranged on the first part  231  and vertically extended from the upper surface  211  of the circuit board  21 . In particular, the second parts  232  are fins for increasing the overall heat transfer area of the heat sink  23 . The number of the second parts  232  may be varied according to the practical requirements. The third part  233  is arranged on the second part  232 . The third part  233  is substantially perpendicular to the second part  232  but parallel to the first part  231 . In accordance with a key feature of the present invention, the first part  231 , the second part  232  and the third part  233  collectively define a guiding track  234 . 
       FIG. 3A  is a schematic exploded view illustrating a heat dissipating module according to a preferred embodiment of the present invention. As shown in  FIGS. 2 and 3A , the fixing mechanism comprises several fixing elements  24 . Each fixing element  24  has a first fixing part  241  and a second fixing part  242 . The first fixing part  241  is embedded in the guiding track  234 , and the second fixing part  242  is partially penetrated through the insertion hole  213  and sustained against a lower surface  212  of the circuit board  21 . In addition, an insertion part  243  is formed at the terminal of the second fixing part  242 . The diameter of the insertion part  243  is smaller than that of a corresponding insertion hole  213  of the circuit board  21 , so that the insertion part  243  can be penetrated through the insertion hole  213 . It is preferred that the first fixing part  241 , the second fixing part  242  and the insertion part  243  are made of metallic material and integrally formed. 
     In addition, a first engaging part  241   a  and a second engaging part  243   a  are formed on the first fixing part  241  and the insertion part  243 , respectively. In some embodiments, the first engaging part  241   a  and the second engaging part  243   a  are hooks that are adjacent corresponding slots and have respective slant surfaces, and thus the first engaging part  241   a  and the second engaging part  243   a  are resilient. In a case that the first engaging part  241   a  is inserted into the guiding track  234  of the heat sink  23 , the first engaging part  241   a  is firstly compressed by the third part  233  of the heat sink  23 , and the compressed first engaging part  241   a  is restored due to the elastic force thereof. Consequently, the first engaging part  241   a  is sustained against the third part  233  of the heat sink  23  and the fixing element  24  is fixed onto the heat sink  23 . 
       FIG. 3B  is a schematic assembled view of the heat dissipating module shown in  FIG. 3A . As shown in  FIG. 3B , the heat sink  23  has a plurality of guiding tracks  234  of the same dimension. The fixing elements  24  may be embedded into respective guiding tracks  234  at any desired positions according to the practical requirements. In other words, the flexibility of using the fixing elements  24  is enhanced. Moreover, since the fixing elements  24  are identical and the heat sink  23  is easily produced, the heat dissipating module  25  of the present invention is more advantageous over the conventional heat dissipating module. 
     Please refer to  FIGS. 2 and 3B  again. The power transistor  221  is fastened on the second surface  235  of the heat sink  23  such that the heat sink may facilitate dissipating the heat generated from the power transistor  221 . After the pins  221   a  of the power transistor  221  are penetrated through the corresponding insertion holes  213  of the circuit board  21 , solder paste  26  is applied to the insertion holes  213  in order to bond the power transistor  221  on the lower surface  212  of the circuit board  21 . 
     Please refer to  FIGS. 2 and 3B  again. For fixing the heat dissipating module  25  on the circuit board  21 , the heat dissipating module  25  is firstly placed on the upper surface  211  of the circuit board  211  and then the insertion parts  243  are aligned with corresponding insertion holes  213  of the circuit board  21 . Next, the insertion parts  243  are inserted into corresponding insertion holes  213  of the circuit board  21 . During the insertion parts  243  are inserted into corresponding insertion holes  213 , the second engaging parts  243   a  are compressed by the sidewalls of the insertion holes  213 . After the second engaging parts  243   a  are completely penetrated through the insertion holes  213 , the second engaging parts  243   a  are restored due to the elastic forces thereof, so that the second engaging parts  243   a  are sustained against the lower surface  212  of the circuit board  21 . Consequently, the heat sink  23  is securely fixed onto the circuit board  21 . Since the procedure of turning over the circuit board and twisting the tips of the fixing elements are omitted, the process of mounting the heat dissipating module on the circuit board according to the present invention is largely simplified and more user-friendly. 
     From the above description, the heat dissipating module of the present invention includes a heat sink and a mechanism for facilitating fixing the heat sink on a circuit board. For enhancing the heat dissipating efficiency, the number of fins on the heat sink may be increased. Since the fixing elements may be embedded into respective guiding tracks at any desired positions, the flexibility of using the fixing elements is enhanced. Moreover, since the procedure of turning over the circuit board and twisting the tips of the fixing elements are omitted, the process of mounting the heat dissipating module on the circuit board according to the present invention is largely simplified and more user-friendly 
     While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.