Abstract:
A power module fabrication method and structure thereof is disclosed. The method includes steps of: providing a metal plate and defining a pattern on the metal plate; cutting the metal plate according to the pattern to form a plurality of pins and the heat-conducting plate, wherein the pin is coupled to each other or to the metal plate via a connection part and the heat-conducting plate is coupled to the connection part via a fixing part; bending a first end of the pin to form an extension part and bending the fixing part to dispose the heat-conducting plate and the metal plate at different levels; providing a circuit board with a plurality of via holes and inserting the extension part into the via hole correspondingly and fixing the pin on the circuit board; forming a housing to encapsulate the circuit board therein, wherein the heat-conducting plate is inlaid on the housing and a second end of the pin is extended out of the housing; and cutting the connection part and the fixing part to separate the pin from each other and from the metal plate and isolate the pin and the heat-conducting plate.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a power module fabrication method and the structure thereof, and more particularly to a fabrication method of a miniaturized power module and the structure thereof. 
   BACKGROUND OF THE INVENTION 
   Generally speaking, the electronic equipment relies on the power module like adaptor or built-in power for converting the input voltage into the working voltage, therefore the working voltage can drive the electronic equipment. Take the conventional adaptor for example; the structure comprises the upper and lower housings to encapsulate the circuit board therein. The input voltage is converted into the working voltage by the electronic components such as capacitor, resistor, transformer, and diode on the circuit board of the power module for keeping the operation of the electronic equipment. 
   The voltage converting efficiency of the power module is getting higher with the increasing working efficiency of the electronic equipment; therefore a lot of heat is produced by those high power electronic components on the circuit board. For dissipating the heat produced by those high power electronic components, a certain space is designed in the housing or a heat sink is attached on those high power electronic components to dissipate heat by conduction, so as to avoid over-temperature shutdown of the electronic components. 
   With the requirement of the miniaturization, portability, high efficiency and stability of the electronic equipments, it is necessary to fabricate a miniaturized power module with high stability and low cost. However, to reduce the volume of the power module is not a simple task if a certain space has to be reserved in the housing or a heat sink is to be attached on the electronic component on the circuit board for dissipating heat. 
   Although the miniaturized power module to be plugged into the system circuit board of the electronic equipment directly for generating the working voltage has already been developed in the market, the heat is dissipated only by conducting to the system circuit board through the pins of the miniaturized power module plugged into the system circuit board or by convection or radiation through the housing. Moreover, more heat is produced by the high power electronic components in the miniaturized power module, so the heat cannot be dissipated efficiently from the housing and the accumulated heat may cause the shutdown of the electronic equipment. 
   Therefore, it is required to develop a power module fabrication method and the structure thereof to improve the heat dissipation of the miniaturized power module, simplify the fabrication method and lower the cost. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a fabrication method of a power module and the structure thereof, wherein the heat-conducting plate is inlaid on the housing directly while forming the housing, so as to simplify the fabrication method, secure the heat-conducting plate firmly and raise the heat dissipating efficiency of the power module. Moreover, the pins and the heat-conducting plate are made from the same metal plate for saving material and lowering the fabrication cost. 
   According to an aspect of the present invention, a fabrication method of a power module is provided. The fabrication method comprises steps of: providing a metal plate and defining a pattern on the metal plate; cutting the metal plate according to the pattern to form a plurality of pins and a heat-conducting plate, wherein the pin is coupled to each other or to the metal plate via a connection part and the heat-conducting plate is coupled to the connection part via a fixing part; bending a first end of the pin to form an extension part and bending the fixing part to dispose the heat-conducting plate and the metal plate at different levels; providing a circuit board with a plurality of via holes and inserting the extension part into the via hole correspondingly and fixing the pin on the circuit board; forming a housing to encapsulate the circuit board therein, wherein the heat-conducting plate is inlaid on the housing and a second end of the pin is extended out of the housing; and cutting the connection part and the fixing part to separate the pin from each other and from the metal plate and isolate the pin and the heat-conducting plate. 
   In an embodiment, the extension part of the pin is fixed in the via hole of the circuit board by soldering. 
   In an embodiment, the housing is formed by molding. 
   In an embodiment, the power module is a surface mounted device (SMD) power module and the second end of the pin is extended outwardly from two opposite sides of the housing, wherein the second end of the pin is further bent for connecting to a system circuit board. 
   In an embodiment, the power module is a single in-line package (SIP) power module and the second end of the pin is extended outwardly from one side of the housing for plugging into a system circuit board. 
   In an embodiment, the housing further comprises a protrusion having a length shorter than that of the pin outside the housing so as to form a heat-dissipating space among the protrusion, the housing and the system circuit board when the pin is plugged into the system circuit board. 
   In an embodiment, the heat-conducting plate is connected to a connecting area of a system circuit board by soldering for assisting heat dissipation. 
   In an embodiment, the heat-conducting plate is connected to a system heat-dissipater by soldering for assisting heat dissipation. 
   In an embodiment, the metal plate is a copper plate. 
   According to another aspect of the present invention, a structure of a power module is disclosed. The structure of a power module comprising: a circuit board with a plurality of via holes; a housing for encapsulating the circuit board therein; a plurality of pins, each having an extension part at a first end thereof, wherein the extension part is inserted into the via hole correspondingly to fix the pin on the circuit board, and a second end of the pin is extended out of the housing; and a heat-conducting plate inlaid on the housing for assisting heat dissipation of the power module. 
   In an embodiment, the pin and the heat-conducting plate are made from the same metal plate, wherein the metal plate is a copper plate. 
   In an embodiment, the heat-conducting plate is isolated from the circuit board. 
   The above objects and advantages 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. 1  is a flow chart for fabricating the power module according to the present invention; 
       FIGS. 2(   a )-( d ) are schematic diagrams showing the fabrication processes of the power module according to a first preferred embodiment of the present invention; 
       FIGS. 3(   a )-( d ) are schematic diagrams showing the fabrication processes of the power module according to a second preferred embodiment of the present invention; 
       FIG. 4  is a schematic diagram showing the cross section along A′-A′ line of the SMD power module shown in  FIG. 2(   d ) while connecting to the system circuit board; 
       FIG. 5  is a schematic diagram showing the SIP power module of  FIG. 3(   d ) plugged into the system circuit board; and 
       FIG. 6  is a schematic diagram showing the side view of the SIP power module of  FIG. 5  connected to a system heat-dissipater. 
   

   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. 
   The power module in the first preferred embodiment of the present invention is a surface mounted device (SMD) power module  2  as shown in  FIG. 2(   d ) by using the fabrication method as shown in  FIG. 1  with the metal plate  20  and the circuit board  26  as shown in  FIGS. 2(   a )-( c ). 
   Please refer to  FIGS. 1 and 2(   a )-( c ), a metal plate  20  is provided and a pattern is defined on the metal plate  20  (step S 10 ). The metal plate  20  can be any high thermal conductivity material, such as copper, but not limited thereto. Then the metal plate  20  is cut according to the pattern to form a plane structure with a plurality of pins  21 , a heat-conducting plate  22 , a plurality of connection parts  23 , and a plurality of fixing parts  24  on the metal plate  20  (step S 11 ) as shown in  FIG. 2(   a ). The connection parts  23  are located between two pins  21  and between the pin  21  and the metal plate  20 , therefore the pins  21  are connected to each other and retained on the metal plate  20  even after the cutting step S 11 . The fixing part  24  is located between the heat-conducting plate  22  and the connection part  23 , so as to maintain the heat-conducting plate  22  on the metal plate  20 . 
   Next, the first end of each pin  21  is bent downwardly in an angle, such as 90°, to form the extension part  211 , meanwhile, the fixing part  24  is bent upwardly to lift the heat-conducting plate  22  up for a height h (step S 12 ). Therefore the heat-conducting plate  22  and the extension part  211  are disposed at different sides of the metal plate  20  respectively. Since the heat-conducting plate  22  and the metal plate  20  are disposed at different levels, a space  25  is formed therebetween, as shown in  FIG. 2(   b ). 
   Please refer to  FIGS. 1 and 2(   c ), a circuit board  26 , such as a printed circuit board, with a plurality of via holes  261  is provided. The extension part  211  of each pin  21  is inserted into the via hole  261  of the circuit board  26  correspondingly and penetrated therethrough, and then the extension part  211  of the pin  21  is fixed in each via hole  261  of the circuit board  26  (step S 13 ). The fixing method can be soldering, but other fixing method applicable to the present invention can also be considered. Hence the pin  21  can be secured on the circuit board  26  firmly through the extension part  211  fixed in the via hole  261 . 
   Then, a housing  27  is formed for encapsulating the circuit board  26  therein. The heat-conducting plate  22  is inlaid on the housing  27 , as well as partial of the fixing part  24 . The second end of each pin  21  is extended out of the housing  27  from two opposite sides thereof and parallel to the heat-conducting plate  22 , and the connection part  23  is exposed out of the housing  27 . In some embodiments, the housing  27  can be formed by molding, but not limited thereto. Afterward, the connection parts  23  between two pins  21  and between the pin  21  and the metal plate  20  are cut for separating the plural pins  21  from each other and from the metal plate  20  and also isolating each pin  21 . Meantime, the fixing part  24  connecting to the heat-conducting plate  22  is cut for isolating the heat-conducting plate  22  from the plural pins  21  (step S 14 ). 
   Finally, the pins  21  extended outwardly from the housing  27  are bent toward the normal direction of the heat-conducting plate  22 , so as to form the SMD power module  2  as shown in  FIG. 2(   d ). 
   While in the second preferred embodiment of the present invention, the power module is a single in-line package (SIP) power module  3  as shown in  FIG. 3(   d ) by using the fabrication method as shown in  FIG. 1  with the metal plate  30  and the circuit board  36  as shown in  FIG. 3(   a )-( c ). 
   Please refer to  FIGS. 1 and 3(   a )-( c ), a metal plate  30  is provided and a pattern is defined on the metal plate  30  (step S 10 ). The metal plate  30  can be any high thermal conductivity material, such as copper, but not limited thereto. Then the metal plate  30  is cut according to the pattern to form a plane structure with a plurality of pins  31 , a heat-conducting plate  32 , a plurality of connection parts  33 , and a plurality of fixing parts  34  on the metal plate  30  (step S 11 ) as shown in  FIG. 3(   a ). The connection parts  33  are located between two pins  31  and between the pin  31  and the metal plate  30 , therefore the pins  31  are connected to each other and retained on the metal plate  30  even after the cutting step S 11 . The fixing part  34  is located between the heat-conducting plate  32  and the connection part  33 , so as to maintain the heat-conducting plate  32  on the metal plate  30 . 
   Next, the first end of each pin  31  is bent downwardly in an angle, such as 90°, to form the extension part  311 , meanwhile, the fixing part  34  is bent upwardly to lift the heat-conducting plate  32  up for a height h (step S 12 ). Therefore the heat-conducting plate  32  and the extension part  311  are disposed at different sides of the metal plate  30  respectively. Since the heat-conducting plate  32  and the metal plate  30  are disposed at different levels, a space  35  is formed therebetween, as shown in  FIG. 3(   b ). 
   Please refer to  FIGS. 1 and 3(   c ), a circuit board  36 , such as printed circuit board, with a plurality of via holes  361  is provided. The extension part  311  of each pin  31  is inserted into the via hole  361  of the circuit board  36  correspondingly and penetrated therethrough, and then the extension part  311  of the pin  31  is fixed in each via hole  361  of the circuit board  36  (step S 13 ). The fixing method can be soldering, but other fixing method applicable to the present invention can also be considered. Hence the pin  31  can be secured on the circuit board  36  firmly through the extension part  311  fixed in the via hole  361 . 
   Then, a housing  37  is formed for encapsulating the circuit board  36  therein. The heat-conducting plate  32  is inlaid on the housing  37 , as well as partial of the fixing part  34 . The second end of each pin  31  is extended out of the housing  37  from two opposite sides thereof and parallel to the heat-conducting plate  32 , and the connection part  33  is exposed out of the housing  37 . In some embodiments, the housing  37  can be formed by molding, but not limited thereto. Afterward, the connection parts  33  between two pins.  31  and between the pin  31  and the metal plate  30  are cut for separating the plural pins  31  from each other and from the metal plate  30  and also isolating each pin  31 . Meantime, the fixing part  34  connecting to the heat-conducting plate  32  is cut for isolating the heat-conducting plate  32  from the plural pins  31  (step S  14 ). Furthermore, the pins  31  extended outwardly from one of the two opposite sides of the housing  37  are cut for making the housing with pins on one side only, so as to form the SIP power module  3  as shown in  FIG. 3(   d ). 
   Please refer to  FIG. 4 , which is a schematic diagram showing the cross section along A′-A′ line of the SMD power module shown in  FIG. 2(   d ) while connecting to the system circuit board. As shown in  FIG. 4 , the SMD power module  2  includes the housing  27 , the circuit board  26 , the plural pins  21  and the heat-conducting plate  22 . The pins  21  are disposed at two opposite sides of the housing  27  with the first ends fixed on the circuit board  26  and the second ends extended outwardly and connected to the system circuit board  28  of an electronic equipment (not shown), thereby the circuit board  26  of the SMD power module  2  is electrically connected to the system circuit board  28  of the electronic equipment. The heat-conducting plate  22 , which is inlaid on the housing  27  and separated from the circuit board  26 , is connected to the connecting area  282  of the system circuit board  28  via solder  281 , for example, but not limited thereto. Hence the heat generated by the SMD power module  2  can be dissipated not only by radiation or convection through five walls of the SMD power module  2  but also by conduction from the plural pins  21  of the SMD power module to the system circuit board  28 . In addition, the heat generated by the SMD power module  2  of the present invention can also be dissipated from the wall adjacent to the system circuit board  28  quickly and efficiently by conducting the heat from the heat-conducting plate  22  thereon to the connecting area  282  of the system circuit board  28  for assisting heat dissipation. 
   Please refer to  FIG. 5 , which is a schematic diagram showing the SIP power module of  FIG. 3(   d ) plugged into the system circuit board. As shown in  FIG. 5 , the SIP power module  3  includes the housing  37  with the protrusions  371 , and plural pins  31  on only one side of the housing  37 . Similarly, the heat-conducting plate  32  is inlaid on the housing  37  and separated from the circuit board (not shown). Moreover, please refer to  FIG. 5  and cooperate with  FIG. 3(   d ), because the lengths of the protrusions  371  are substantially shorter than those of the pins  31  extended outside the housing  37 , the protrusions  371  are against the system circuit board  38  while the pins  31  are plugged into the system circuit board  38 , so as to form a heat-dissipating space  381  among the protrusions  371 , the housing  37 , and the system circuit board  38 . Hence the SIP power module  3  is electrically connected to the system circuit board  38 , and the heat generated by the SIP power module  3  can be dissipated from six walls and the heat-dissipation space  381  thereof by radiation or convection, meantime, the heat can also be dissipated efficiently through the heat-conducting plate  32  for assisting heat dissipation of the SIP power module  3 . 
   Please refer to  FIG. 6 , which is a schematic diagram showing the side view of the SIP power module of  FIG. 5  connected to a system heat-dissipater. As shown in  FIG. 6 , the heat-conducting plate  32  of the SIP power module  3  is connected to the system heat-dissipater  39  via solder  40 , but not limited thereto, and both the SIP power module  3  and the system heat-dissipater  39  are disposed on the system circuit board  38 , so as to assist heat dissipation. 
   To sum up, the fabrication method is simplified and the material is saved by using the same metal plate to form the heat-conducting plate and the pins of the power module. Besides, the mismatch of the pins and the via holes of the circuit board caused by the shift of the pins can be avoided because the pins are still retained on the metal plate during the fixing step (step S 13 ), so as to facilitate the fabrication process. In addition, the heat-conducting plate is connected to the metal plate indirectly by the fixing part connecting to the connection part, therefore it is to be understood that the heat-conducting plate can be directly inlaid on the housing while forming the housing and firmly fixed thereon. Furthermore, the heat generated by the miniaturized power module of the present invention can be dissipated not only by radiation and convection through the housing and by conduction through the pins as those conventional miniaturized power modules, but also by conduction from the heat-conducting plate to the connecting area of the system circuit board or the system heat-dissipater. Therefore the heat dissipating efficiency can be raised up comparing to that of the conventional power module. 
   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.