Abstract:
A structure and method for increasing a locking friction force on a circuit board allow a connecting face to be disposed on at least one of upper and lower faces of a substrate at a clamped position, the connecting face having a multiple relative indented portions and raised portions interlacing structure so as to allow the connecting face to have a larger friction coefficient. Whereby, when the connecting face is clamped, a larger friction force is exerted thereon and a displacement relative to a clamper is rather not yielded.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a structure for locking a circuit board on a housing of an electronic device, and more particularly to a structure and method for increasing a locking friction force on a circuit board. 
         [0003]    2. Description of Related Art 
         [0004]    There are many patents concerning mounting a circuit board on a housing of an electronic device, such as U.S. Pat. No. 6,934,162 entitled as “Circuit board mounting method”, U.S. Pat. No. 6,781,055 entitled as “Circuit board mounting device” and U.S. Pat. No. 6,771,512 entitled as “Mounting system for circuit board”. 
         [0005]    Furthermore, for example, Taiwan Patent No. 562,390 discloses a circuit board with an element fixing device in which holes are opened. A fixing element has a substrate and a connecting portion extended outward from one side of the substrate; screw holes communicated between the substrate and the connecting portions are disposed therein. A welding pad engaged at the outside of the connecting element is welded to the substrate. The connecting portions are accepted in the holes of the circuit board. A bolt is used to screw in the screw hole communicating the substrate with the connecting portion to allow the circuit board to be fixed on the fixing element. 
         [0006]    Please refer to  FIG. 1 . A bolt  11  is passed through holes  121  and  131  of a first housing  12  and a circuit board  13  in a sequence and then screwed into screw hole  142  of the projecting portion  141  of a second housing  14  in a general electronic device  10  to cause the circuit board  13  to be sandwiched between the first housing  12  and the projecting portion  141  of the second housing  14 . 
         [0007]    Because a gap still exists between the through hole  131  of the circuit board  13  and the bolt  11 , when the electronic device  10  is dropped to touch a floor  20 , the circuit board  13  and an electronic component  15  such as a switch still move downward owing to acceleration of gravity, and the first housing  12 , the second housing  14  and another electronic component  16  such as a key combined with the first housing  12  and the second housing  14  are moved upward because they are exerted with a reaction force while touching the floor  20 , two electronic components  15  and  16  will touch each other to cause soldering tin welded on the electronic component  15  and the circuit board  13  to be fallen off or the electronic components  15  and  16  to be deformed to loose functions. 
         [0008]    Please refer to  FIG. 2 . A tin ring  132  is disposed around the through hole  131  used for allowing a bolt to be passed through in a general circuit board  13  sometimes owing to the requirement of electric current conduction; but the whole tin ring  132  is usually flat, it is rather not able to increase a friction force when the circuit board  13  is locked. 
       SUMMARY OF THE INVENTION 
       [0009]    For improving a conventional structure for locking a circuit board on an electronic device, the present invention is proposed. 
         [0010]    The main object of the present invention is to provide a structure and method for increasing a locking friction force on a circuit board, allowing the circuit board to be combined stably with a housing of an electronic device. 
         [0011]    Another object of the present invention is to provide a structure and method for increasing a locking friction force on a circuit board, allowing a displacement rather not to be generated between the circuit and a housing when an electronic device is dropped down onto a floor to cause components assembled on the circuit board rather not to touch the housing or other electronic components mounted on the housing to cause damage or loose functions. 
         [0012]    The present invention provides a structure for increasing a locking friction force on a circuit board, allowing a larger friction coefficient to be existed at a position where a substrate is clamped; comprising: the substrate, a connecting face being disposed on at least one of upper and lower faces thereof at the clamped position, the connecting face having a multiple relative indented portions and raised portions interlacing structure so as to allow the connecting face to have a larger friction coefficient, when the connecting face is clamped, a larger friction force being exerted thereon and a displacement relative to a clamper being rather not yielded. 
         [0013]    The present invention provides a method for increasing a locking friction force on a circuit board, allowing a larger friction coefficient to be existed at a position where a substrate is clamped; comprising: allowing a connecting face with a multiple relative raised portions and indented portions interlacing structure to be formed on at least one of upper and lower faces of the substrate at the clamped position so as to allow the connecting face to have a larger friction coefficient, when the connecting face is clamped, a larger friction force being exerted thereon and a displacement relative to a clamper being rather not yielded. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The present invention can be more fully understood by reference to the following description and accompanying drawings, in which: 
           [0015]      FIG. 1  is a schematic view of a mounting structure of a conventional circuit board when a housing touches a floor; 
           [0016]      FIG. 2  is a schematic view, showing a tin ring disposed around a through hole of a conventional circuit board; 
           [0017]      FIG. 3  is a schematic view, showing a substrate mounting structure of a first preferred embodiment according to the present invention; 
           [0018]      FIG. 4  is a schematic view, showing a substrate mounting structure of a second preferred embodiment according to the present invention; and 
           [0019]      FIGS. 5A ,  5 B,  5 C and  5 D are schematic views, showing connecting faces of substrates of various preferred embodiments according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    Please refer to  FIG. 3 . A structure and method for increasing a locking friction force on a circuit board of a first preferred embodiment according to the present invention are to form a upper connecting face  32  and lower connecting face  33  with an interlacing structure of a plurality of relative indented portions and raised portions at a position that a substrate  30  is sandwiched to fix by a first clamping part  41  and a second clamping part  42  or a position that the substrate  30  is sandwiched to fix by a nut  431  of a bolt  43  and the second clamping part  42 , for example, at the surroundings of each through hole  31  allowing the bolt  43  to be passed through. The structure in which the relative indented and raised portions are interlaced allows the upper and the lower connecting faces  32  and  33  to have a larger friction coefficient. When the bolt  43  is passed through a through hole  411  of the first clamping part  41  and/or the through hole  31  of the substrate  30  and screwed into a screw hole  421  of the second clamping part  42  to cause the upper and lower faces  32  and  33  of the substrate  30  to be sandwiched by the first clamping part  41  and the second clamping part  42  or the upper and lower faces  32  and  33  of the substrate  30  to be sandwiched by the nut  431  of the bolt  43  and the second clamping part  42 , a larger static friction force will be generated to cause a relative displacement between the substrate  30  and the first and the second clamping parts  41  and  42  rather not to be generated, and enable a component combined on the substrate  30  rather not to touch other components combined on a housing when the housing is dropped down onto a floor to cause soldering tin to be fallen off to loose functions or the components to be deformed to damage or fallen off to loose functions. 
         [0021]    Please refer to  FIG. 4 . A structure and method for increasing a locking friction force on a circuit board of a second preferred embodiment according to the present invention further allow a first clamping part  61  and second clamping part  62  corresponding to a upper connecting face  51  and lower connecting face  52  of a substrate  50  respectively have knurling portions  611  and  621 . When the bolt  63  is passed the through hole of the first clamping part  61  and/or the through hole of the substrate  50  to screw into the screw hole  622  of the second clamping part  62  to cause a larger static friction force to be yielded when the substrate  50  to be sandwiched by the first clamping part  61  and the second clamping part  62  or the substrate  50  is sandwiched by the nut  631  and the second clamping part  62 ; this allows relative displacements even more not to be generated between the substrate  50  and the first clamping portion  51  and the second clamping portion  62 . 
         [0022]    Please refer to  FIGS. 5A ,  5 B,  5 C and  5 D. Structures of interlacing indented and raised portions on a connecting face of a substrate have various different types. For example, a plurality of tiny first portions  711 , a plurality of rectangular first portions  721 , a plurality of circular first portions  731  and a plurality of divergently arranged rectangular first portions  741  are respectively distributed on the surrounding areas of through holes  71 ,  72 ,  73  and  74 , and rest areas thereof respectively are second portions  712 ,  722 ,  732  and  742 . 
         [0023]    The first portions  711 ,  721 ,  731  and  741  on the connecting faces of the substrates can respectively be raised portions, for example, those using metallic material such as tin or tin alloy capable of being stuck with a copper foil of a circuit board to form on a substrate, and more particularly to those integrated with the substrate at a soldering tin spreading step in the process of circuit board manufacturing; this needs no extra work and can further save the production cost. The metallic material can be other metals such as gold, silver and copper besides tin or tin alloy such as tin silver, tin zinc, tin silver bismuth, tin copper bismuth and tin zinc bismuth. And, the second portions  712 ,  722 ,  732  and  742  can be formed to be indented portions relative to the raised portions, for example, the face of the substrate lower than the raised portions. Otherwise, the first portions  711 ,  721 ,  731  and  741  can respectively indented potions, which are indentations formed by punching or drilling holes on the substrate. And the second portions  712 ,  722 ,  732  and  742  are raised portions formed on the face of the substrate relative to the indentions. The manufacturing methods mentioned above all allow the connecting face of each substrate to have indented portions and raised portions interlacing structure to increase the static friction coefficient on the connecting face of the substrate. Furthermore, the through holes  71 ,  72 ,  73  and  74  can be formed before, after or at the same time as the time that the connecting face is formed on each substrate. 
         [0024]    There is no need for the present invention to use other fixing structure, only forming a connecting face with indented portions and raised portions interlacing structure on a substrate, it then allows the connecting face to have a larger friction coefficient and the substrate rather not to yield a displacement relatively to a clamping part when it is clamped to cause components combined on the substrate rather not to touch other components combined on a housing to cause soldering tin of the component to be fallen off to loose function or cause the component to be deformed, damaged or fallen off when the housing is dropped down onto the floor. Besides, the present invention allows the substrate to form the connecting face with a indented portions and raised portions interlacing structure thereon, the structure thereof is simple and the manufacturing thereof is easy, it can be formed at the same time when the soldering tin is spread on a circuit, and needs no extra work so that the production cost can be saved. 
         [0025]    Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.