Abstract:
An electronic product having a double-PCB sandwich structure includes a PCB assembly, and a casing having an open side. The electronic product is configured such that a protuberance is respectively formed on the inner sides of two side walls of the casing in the longitudinal direction, the PCB assembly comprises an electronic component, a base PCB and a main PCB, the length of the base PCB and the length of the main PCB in the longitudinal direction of the casing are substantially equal to each other and slightly smaller than the length of the casing so that the PCB assembly can be installed into the casing by mating with the protuberances.

Description:
FIELD OF INVENTION 
       [0001]    The invention relates to an electronic product having a double-PCB sandwich structure and a method of assembling the same. More specifically, the invention relates to an electronic product consisting of a casing having protuberances and a PCB assembly having a double-PCB sandwich structure, and a method of assembling a PCB assembly having a double-PCB sandwich structure into a casing having protuberances. 
       BACKGROUND ART 
       [0002]    Generally, in an electronic product, an electronic component such as a transformer is fixed to a plastic base, then the transformer is soldered to a PCB through pins of the transformer. Thus a PCB assembly consisting of a transformer, a plastic base and a PCB is formed, wherein the transformer is installed on the plastic base and soldered to the PCB through pins of the transformer and the plastic base is supported on the PCB. Then, the thus formed PCB assembly is fixed into the casing by means of screws or slots on the plastic base and so on. 
         [0003]    However, the distance between the plastic base and the PCB must be defined properly so as to ensure proper solder penetration and to prevent noises, and to achieve the required creepage distances in some applications. 
         [0004]      FIG. 1  shows the way of constructing a PCB assembly and a method of assembling the PCB assembly into a casing in the prior art. As shown in  FIG. 1 , a transformer  21  is installed on and supported by a plastic base. Pins  211  extending from the transformer  21  run through a PCB, the transformer  21  is soldered on the PCB through pins  211  to form a PCB assembly consisting of the transformer  21 , the plastic base and the PCB. Then, the PCB assembly is installed on the casing by mechanical means. As shown in  FIG. 1 , the thickness of the plastic base is generally relatively large so as to support the transformer  21 . In order to ensure a proper distance between the plastic base and the PCB, a recess is required to be formed in the lower surface of the plastic base, the thickness of the recess is the distance between the plastic base and the main PCB. However, in consideration of the thickness of the base and the manufacturing of the recess in the lower surface of the base, the material of the base needs to be plastic. However, the manufacturing of plastic base needs specialized mould, which can not be modified in size and is expensive. 
       SUMMARY OF THE INVENTION 
       [0005]    Therefore, in view of the above problems, the invention devises an electronic product having a novel double-PCB sandwich structure which adopts a base PCB instead of the plastic base in the prior art, thereby simplifying the structure and facilitating the manufacture so that the cost is reduced. Also, by utilizing the protuberances in the casing of the prior art, a PCB assembly consisting of the double-PCB sandwich structure and an electronic component can be easily installed into the casing without using any other mechanical means such as screws. 
         [0006]    According to a first aspect of the invention, the invention provides an electronic product having a double-PCB sandwich structure, comprising a PCB assembly and a casing having an open side, wherein a protuberance is respectively formed on the inner sides of two side walls of the casing in the longitudinal direction, the PCB assembly consists of an electronic component, a base PCB and a main PCB, the length of the base PCB and the length of the main PCB in the longitudinal direction of the casing are substantially equal to each other and slightly smaller than the length of the casing so that the PCB assembly can be installed into the casing by mating with the protuberances. 
         [0007]    According to a second aspect of the invention, the invention provides an electronic product having a double-PCB sandwich structure, wherein a first protuberance is respectively formed on the inner sides of the two side walls of the casing in the longitudinal direction, and the distance between an upper surface of the main PCB and an lower surface of the base PCB is substantially equal to the thickness of the first protuberance so that after the PCB assembly is inserted into the casing along the first protuberances, the first protuberances snap between the base PCB and the main PCB so as to install the PCB assembly into the casing 
         [0008]    According to a third aspect of the invention, the invention provides an electronic product having a double-PCB sandwich structure, wherein a second protuberance is respectively formed under the first protuberances in parallel with the first protuberances, and the thickness of the main PCB is substantially equal to the distance between a lower surface of the first protuberances and an upper surface of the second protuberances so that after the PCB assembly is inserted into the casing, the main PCB can be supported on the upper surface of the second protuberances and snap between the first protuberances and second protuberances so as to install the PCB assembly into the casing. Preferably, the lower surface of the first protuberances and the upper surface of the second protuberances are chamfered to facilitate the insertion of the PCB assembly. 
         [0009]    According to a fourth aspect of the invention, the invention provides a method of assembling an electronic product, the method comprising installing an electronic component on the base PCB and soldering the electronic component onto the main PCB through pins of the electronic component so as to form a PCB assembly; inserting the PCB assembly into the casing along the protuberances so that the PCB assembly can be installed into the casing by mating with the protuberances; and injection potting the casing from the open side of the casing. 
         [0010]    According to a fifth aspect of the invention, the invention provides a method of assembling an electronic product, the method comprising installing an electronic component on the base PCB and soldering the electronic component onto the main PCB through pins of the electronic component so as to form a PCB assembly, wherein the distance between an upper surface of the main PCB and a lower surface of the base PCB is substantially equal to the thickness of the first protuberance; inserting the PCB assembly into the casing along the first protuberances so that the first protuberances snap between the base PCB and the main PCB to install the PCB assembly into the casing; and injection potting the casing from the open side of the casing. 
         [0011]    According to a sixth aspect of the invention, the invention provides a method of assembling an electronic product, the method comprising installing an electronic component on the base PCB and soldering the electronic component onto the main PCB through pins of the electronic component so as to form a PCB assembly, wherein the distance between an upper surface of the main PCB and a lower surface of the base PCB is substantially equal to the thickness of the first protuberances and the thickness of the main PCB is substantially equal to the distance between a lower surface of the first protuberances and an upper surface of the second protuberances; inserting the main PCB into the casing along the first protuberances and the second protuberances so that the main PCB is supported on an upper surface of the second protuberances and snaps between the first protuberances and the second protuberances so as to install the PCB assembly into the casing; and injection potting the casing from the open side of the casing. Preferably, the lower surface of the first protuberances and the upper surface of the second protuberances are chamfered to facilitate the insertion of the PCB assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The invention will be more fully understood from the detailed description of the preferred and non-limiting embodiments of the invention when taken in conjunction with the drawing, in which: 
           [0013]      FIG. 1  shows a PCB assembly having an electronic component (shown as a transformer  21  in the description) in the prior art, wherein a plastic base, a PCB, a transformer  21  and pins thereof are shown; 
           [0014]      FIG. 2  is a perspective view of a casing having a protuberance and used in the embodiments of the invention; 
           [0015]      FIG. 3  is a front view of the casing; 
           [0016]      FIG. 4  is a top view of the casing; 
           [0017]      FIG. 5  is a cross-sectional view of the casing taken along the line A-A in  FIG. 4 ; 
           [0018]      FIG. 6   a  is an enlarged view of part B in  FIG. 5 , showing the details of the protuberance; 
           [0019]      FIG. 6   b  is an enlarged view of part D in  FIG. 3 , showing the details of the protuberance; 
           [0020]      FIG. 7  is a schematic view showing the PCB assembly and the casing are assembled together according to a first embodiment of the invention; and 
           [0021]      FIG. 8  is a schematic view showing the PCB assembly and the casing are assembled together according to a second embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0022]    Firstly, a casing used in the invention will be described with reference to  FIGS. 2-6 . As shown in  FIG. 2 , the casing used in the invention is generally designated at  1 . In the following description, the left and right direction of the plane of  FIG. 7  is defined as the longitudinal direction of the casing  1 , i.e., the lengthwise direction. The up and down direction of the plane of  FIG. 7  is defined as the up and down direction of the casing  1 , i.e., the height direction. 
         [0023]    As shown in  FIG. 2 , casing  1  is generally formed into a hollow rectangular parallelepiped configuration to form an internal space therein and has an open side for facilitating the insertion of a PCB assembly into the casing and receipt of the PCB assembly inside the internal space, as will be described later. Two through holes are shown on the top wall  11  of the casing for wiring of electronic components of the PCB assembly. The casing  1  is generally formed integrally from plastic material. 
         [0024]    As can be seen from  FIG. 2 , a first protuberance  121  and  131  is respectively formed on the inner side of the two side walls  12 ,  13  of the casing  1  in the longitudinal direction. Optionally, a second protuberance  122  and  132  is respectively formed under the first protuberance  121  and  122  in parallel with the first protuberance  121  and  131 . The protuberances  121 ,  122  are formed symmetrically with the protuberances  131 ,  132  inside the internal space, namely, the first protuberance  121  is located at the same height as the first protuberance  131 , the second protuberance  122  is located at the same height as the second protuberance  132 . The protuberances may be formed integrally with the casing  1 . Now turn to  FIGS. 6   a  and  6   b , which respectively show part B in  FIG. 5  and part D in  FIG. 3  in enlarged view. As can be seen in  FIG. 6   a , the lower surface of the first protuberance  121 ,  131  and the upper surface of the second protuberance  122 ,  132  are chamfered so as to facilitate the insertion and withdrawal of the PCB assembly. 
         [0025]    Now, the PCB assembly  2  and casing  1  according to a first embodiment of the invention will be described with reference to  FIG. 7 , which is a schematic view showing the PCB  2  assembly and the casing  1  assembled together according to a first embodiment of the invention. For the sake of simplicity, the transformer  21  is not shown in  FIG. 7 . In the casing used in the embodiment, a first protuberance is respectively formed on the inner side of the side walls on both ends of the casing in the longitudinal direction, i.e., a first protuberance  121  and  131 . In the case of this embodiment, the distance between the upper surface of the main PCB  23  and the lower surface of the base PCB  22  is set substantially equal to the thickness of the first protuberance, so that upon sliding of the PCB assembly  2  into the casing  1  along the first protuberances (the upper surface of the main PCB  23  contacts the lower surface of the protuberance, and the lower surface of the base PCB  22  contacts the upper surface of the first protuberance), the PCB assembly  2  snaps onto the first protuberances so as to be fixed, thus limiting the movement of PCB assembly  2  in the up and down direction of the casing. 
         [0026]    The method of assembling the PCB assembly  2  into the casing  1  according to the first embodiment of the invention will be described hereinafter. The casing  1  has a first protuberance  121  and  131  on the inner side of the side walls on both ends of the casing  1  in the longitudinal direction. The method comprises: installing the transformer  21  onto the base PCB  22 , and soldering the transformer  21  onto the main PCB  23  through the pins of the transformer  21  to form a PCB assembly  2 , wherein the distance between the upper surface of the main PCB  23  and the lower surface of the base PCB  22  is substantially equal to the thickness of the first protuberances; inserting the PCB assembly  2  into the casing  1  along the first protuberances, so that the first protuberances snap between the base PCB  22  and the main PCB  23  to install the PCB assembly  2  inside the casing  1 ; and injection potting the casing from the open side of the casing. 
         [0027]    Now, the PCB assembly  2  and casing  1  according to a second embodiment of the invention will be described with reference to  FIG. 8 , which is a schematic view showing the PCB assembly  2  and the casing  1  assembled together according to a second embodiment of the invention. In this embodiment, a second protuberance  122 ,  132  is respectively provided under the first protuberance  121 ,  131  in parallel with the first protuberance  121 ,  131 , and the thickness of the main PCB  23  is substantially equal to the distance between the lower surface of the first protuberance and the upper surface of the second protuberance, so that upon insertion of the PCB assembly  2  into the casing  1 , the main PCB  23  can be supported on the upper surface of the second protuberance and snaps between the first protuberances and the second protuberances to install the PCB assembly  2  inside the casing  1 . 
         [0028]    The method of assembling the PCB assembly  2  into the casing  1  according to the second embodiment of the invention will be described hereinafter. A second protuberance  122 ,  132  is respectively provided under the first protuberance  121 ,  131  in parallel with the first protuberance  121 ,  131 . The method comprises: installing the transformer  21  onto the base PCB  22 , and soldering the transformer  21  onto the main PCB  23  through the pins of the transformer  21  to form a PCB assembly  2 , wherein the distance between the upper surface of the main PCB  23  and the lower surface of the base PCB  22  is substantially equal to the thickness of the first protuberance, and the thickness of the main PCB is substantially equal to the distance between the lower surface of the first protuberance and the upper surface of the second protuberance; inserting the main PCB  23  into the casing  1  along the first protuberances and the second protuberances, so that the main PCB  23  can be supported on the upper surface of the second protuberances and snaps between the first protuberances and the second protuberances to install the PCB assembly  2  inside the casing  1 ; and injection potting the casing from the open side of the casing. 
         [0029]    While the preferred embodiments of the casing are described herein, it is understood by those skilled in the art that various variations and modifications can be made to the casing without departing the spirit and scope of the invention. For example, the size, shape, structure and number can be appropriately modified, as long as the protuberances can properly mate with the PCB assembly. In addition, while a transformer is used in the description as an example of the electronic components to describe the invention, not limited to this, any other electronic component may be used to form a PCB assembly having a double-PCB assembly structure without departing the scope of the invention. The scope of protection is defined by the appended claims.