Abstract:
According to one embodiment, a circuit board attachment structure comprise a housing to which a circuit board is attached, a mount provided on the housing and provided outside a portion of the housing where the circuit board is attached, holding piece detachably attached to the mount and pressing the circuit board against the housing with a predetermined force, and fixing unit for detachably fixing the holding piece to the mount.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2015-201205, filed Oct. 9, 2015, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    Embodiments described herein relate generally to a circuit board attachment structure for attaching a circuit board to a housing. 
       BACKGROUND 
       [0003]    For example, in a tablet computer or the like, if a circuit board is attached to a housing with double-sided adhesive tape, there is a possibility of degrading the maintainability at the time of repairing the circuit board because the circuit board cannot be detached from the housing easily. Therefore, a circuit board is generally attached to the housing of an electronic device with screws. 
         [0004]    However, in the case of attaching a circuit board with a male screw, it is necessary to provide a female screw corresponding to the male screw in the housing. When the female screw is provided in the housing, the attachment position of the circuit board rises by the height of the female screw, which is not desirable for a thin electronic device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    A general architecture that implements the various features of the embodiments will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate the embodiments and not to limit the scope of the invention. 
           [0006]      FIG. 1  is a perspective view of a tablet computer as an example of an electronic device. 
           [0007]      FIG. 2  is an exploded view of the tablet computer. 
           [0008]      FIG. 3  is a top plan view of a housing of the tablet computer. 
           [0009]      FIG. 4  is an exploded view of the housing of the tablet computer. 
           [0010]      FIG. 5  is a partial top plan view of the housing. 
           [0011]      FIG. 6  is a top plan view of a holding piece. 
           [0012]      FIG. 7  is a side view of the holding piece. 
           [0013]      FIG. 8  is a front view of the holding piece. 
           [0014]      FIG. 9  is a rear view of the holding piece. 
           [0015]      FIG. 10  is an exploded view of a part of a circuit board attachment structure. 
           [0016]      FIG. 11  is a plan view of a part of the circuit board attachment structure. 
           [0017]      FIG. 12  is a plan view of a part of the circuit board attachment structure. 
           [0018]      FIG. 13  is a sectional view of a part of the circuit board attachment structure. 
           [0019]      FIG. 14  is an exploded view of a part of the circuit board attachment structure. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Various embodiments will be described hereinafter with reference to the accompanying drawings. 
         [0021]    In general, according to one embodiment, a circuit board attachment structure of an embodiment will be described with reference to the accompanying drawings.  FIG. 1  is a perspective view of a tablet computer  12  as an example of an electronic device adopting the circuit board attachment structure. The tablet computer  12  comprises an image display panel  14  on the front and a housing  16  on the rear of the image display panel  14  as shown in  FIG. 1 . 
         [0022]      FIG. 2  is an exploded view of the tablet computer  12 , showing the image display panel  14  and the housing  16  separately. The image display panel  14  is, for example, a liquid crystal display panel which displays an image by driving crystal liquid and transmitting light through the crystal liquid. The housing  16  is attached to the rear of the image display panel  14 . Note that the image display panel  14  is not necessarily limited to a liquid crystal display panel. 
         [0023]    The housing  16  comprises a flat base plate  18  and an edge  20  continuously formed along the four sides of the base plate  18 . In the housing  16 , the side on which the edge  20  rises from the base plate  18  is assumed to be the upper side or the front, while the other side is assumed to be the lower side or the rear. 
         [0024]      FIG. 3  is a top plan view of the housing  16 .  FIG. 4  is an exploded view of the housing  16 , showing attached components such as the circuit board and the like separately.  FIG. 5  is a partial top plan view of a part of the housing  16  from which the circuit board  22  is detached. 
         [0025]    The base plate  18  is made of carbon fiber impregnated with resin and then solidified, that is, a carbon-fiber-reinforced resin material. Note that the base plate  18  is not necessarily limited to a carbon-fiber-reinforced resin material but may be another material. 
         [0026]    The base plate  18  is rectangular, having predetermined dimensions. The base plate  18  is strong enough to add predetermined stiffness to the housing  16  when the housing  16  is assembled, but still the base plate  18  is desirably light. Around the periphery of the base plate  18 , the edge  20  is provided as shown in  FIGS. 2 and 3 . 
         [0027]    The edge  20  is made of a synthetic resin material and is formed integrally with the base plate  18 , for example, by an injection molding method. The edge  20  rises from the base plate  18  as shown in  FIG. 4 . The upper part of the edge  20  comprises a step  27 , and the image display panel  14  is attached to the step  27 . Further, the edge  20  comprises various electrical connectors, various card slots and the like. 
         [0028]    The edge  20  comprises a pair of short sides  20   a  along the lateral base plate  18  and a pair of long sides  20   b  along the longitudinal base plate  18 . The short sides  20   a  face each other, and the long sides  20   b  face each other. 
         [0029]    Still further, a position determination projection  29  is provided on the surface of the base plate  18 . The projection  29  is formed in a predetermined position of the base plate  18  in the same process in which the edge  20  is formed on the base plate  18 . 
         [0030]    A conductive film  32  is formed on substantially the entire surface of the base plate  18 . The conductive film  32  is formed of, for example, vapor-deposited metal. Note that the conductive film  32  may be formed on the base plate  18  in such a manner that a sheet is attached to the base plate  18 . The circuit board  22  is attached to the upper surface of the base plate  18 . 
         [0031]    To the housing  16 , as separately shown in  FIG. 4 , the circuit board  22 , a heat-dissipating sheet  28 , an insulating sheet  30 , a first attachment plate  36 , a second attachment plate  38 , and a card socket plate  40  are attached. 
         [0032]    To the circuit board  22 , more specifically, to the surface on which a predetermined pattern of traces is formed, an electronic component  100  is attached as shown in  FIG. 13 . The circuit board  22  is a basically inflexible and rigid board and comprises traces on its surface. 
         [0033]    The circuit board  22  further comprises, as shown in  FIG. 12 , a position determination engagement recess  46  at one edge. The engagement recess  46  is formed in accordance with an engagement projection  42 , which will be described later. As shown in  FIGS. 2  and  14 , a ground pad (electrode)  26  is provided on the back surface of the circuit board  22 . 
         [0034]    The ground pad  26  is formed in such a manner as to be aligned with a holding piece  72 , which will be described later, and is connected to a ground line provided on the circuit board  22 . The ground pad  26  and the like are provided by a printing method or the like and are basically formed evenly on the back surface of the circuit board  22 . Further, a test pad may also be provided on the back surface of the circuit board  22 . 
         [0035]    The first attachment plate  36  is in the shape of a long, thin rectangle and comprises the engagement projection  42  and a striking portion  44 . The first attachment plate  36  is fitted into the edge  20  of the housing  16  and is screwed into the edge  20 . 
         [0036]      FIG. 12  shows the engagement projection  42 . The engagement projection  42  is provided near one end of the first attachment plate  36 . The engagement projection  42  is formed in accordance with the engagement recess  46  provided in the circuit board  22  and engages with the engagement recess  46  of the circuit board  22 . 
         [0037]      FIG. 11  shows the striking portion  44 . The striking portion  44  in a planar view is substantially trapezoid, projecting inside the housing  16 . When the first attachment plate  36  is fixed to the housing  16 , the upper side of the trapezoid is placed in a predetermined position of the back plate  18 , and thus the striking portion  44  forms a reference surface for the circuit board  22  to be fixed to the housing  16 . 
         [0038]    The second attachment plate  38  comprises a first piece  56  and a second piece  58  connected to each other at substantially a right angle and forming an L-shape. The second attachment plate  38  comprises three position alignment holes  47  as shown in  FIG. 4 . 
         [0039]    The position alignment holes  47  correspond to the position determination projections  29  provided in the base plate  18 . When the position alignment holes  47  are slid onto the projections  29  of the base plate  18 , the second attachment plate  38  is arranged in a predetermined position of the base plate  18 . 
         [0040]    In the second attachment plate  38 , the first piece  56  of the second attachment plate  38  is perpendicular to the first attachment plate  36 , and the second piece  58  of the second attachment plate  38  is parallel to the first attachment plate  36 . The second attachment plate  38  is attached to the base plate  18  with an adhesive agent. 
         [0041]    Further, the second attachment plate  38  comprises a first mount  48 , a second mount  50  and a third mount  52 . The first piece  56  of the second attachment plate  38  is provided with the first mount  48 , and the second piece  58  of the second attachment plate  38  is provided with the second mount  50  and the third mount  52 . 
         [0042]    The card socket plate  40  is attached to the base plate  18  in such a manner that the one end of the card socket plate  40  is inserted into the long side edge  20   b  of the housing  16 . In the card socket plate  40 , a card socket is provided, and a card slot into which a SIM card, a card-type storage medium or the like is inserted is formed. The card socket plate  40  comprises a fourth mount  60 . 
         [0043]    The second attachment plate  38  and the card socket plate  40 , when attached to predetermined positions of the base plate  18 , form a substantially rectangular circuit board attachment region  62  on the base plate  18  together with the first attachment plate  36 . 
         [0044]    Next, each of the first mount  48  to the fourth mount  60  of the second attachment plate  38  and the card socket plate  40  will be described. The first mount  48  is provided at the end of the first piece  56  of the second attachment plate  38  adjacent to the first attachment plate  36 . 
         [0045]    Note that, since the first mount  48  to the fourth mount  60  have structures substantially the same as each other, the second mount  50  of  FIG. 10  will be mainly described below but the first mount  48 , the third mount  52  and the fourth mount  60  will be described only with respect to points different from the second mount  50  of  FIG. 10  and detailed description thereof will be omitted. 
         [0046]    The second mount  50  comprises a female screw  66  and a position determination member  68 . The female screw  66  is higher than the level of the upper surface of the circuit board  22  attached to the base plate  18  when the second attachment plate  38  is attached to the base plate  18 . 
         [0047]    The female screw  66  is formed in such a manner that a screw sleeve  69  is buried in the second mount  50  as shown in  FIG. 13 . The female screw  66  has a depth sufficient for a male screw  70  to be engaged with the second mount  50 . Note that the female screw  66  may also be tapped directly in the second mount  50 . 
         [0048]    The position determination member  68  is provided on the second mount  50  at a predetermined distance from the female screw  66 . The position determination member  68  is substantially cylindrical and has a diameter corresponding to the position determination hole  73  formed in the holding piece  72 , which will be described later. The female screw  66  and the position determination member  68  are arranged in such a manner that a contacting portion  74  of the holding piece  72  is located above the circuit board  22  when the holding piece  72  is attached to the second mount  50  with the female screw  66  and the position determination member  68 . 
         [0049]    Further, a vertical wall  76  is provided around the second mount  50 . In the vertical wall  76 , the upper edge is higher than the uppermost portion of the male screw  70  when the holding piece  72  is attached to the second mount  50 . Although having differences in arrangement of the vertical wall  76  and the like, the first mount  48 , the third mount  52  and the fourth mount  60  have structures basically the same as that of the above-described second mount  50 . 
         [0050]    In the circuit board attachment region  62 , as shown in  FIGS. 4 and 5 , the heat-dissipating sheet  28  is attached to the upper surface of the conductive film  32 . The heat-dissipating sheet  28  is formed of a material having excellent thermal conductivity and conducts heat from the circuit board  22  provided above the heat-dissipating sheet  28  to the base plate  18 . Further, the insulating sheet  30  is provided on the surface of the heat-dissipating sheet  28 . The insulating sheet  30  is formed of an electrically insulating material. 
         [0051]    The heat-dissipating sheet  28  and the insulating sheet  30  are shaped substantially the same as each other while having areas slightly greater than that of the circuit board  22 . Further, the heat-dissipating sheet  28  and the insulating sheet  30  respectively comprise notches  80  as shown in  FIG. 4  and the like. Each notch  80  is provided in proximity to each of the first mount  48  to the fourth mount  60  in alignment with the attachment position of the holding piece  72  and is formed in a predetermined size. 
         [0052]    The heat-dissipating sheet  28  and the insulating sheet  30  are attached to the base plate  18  in such a manner as to fully cover the lower surface of the circuit board  22  to be attached to the base plate  18  except for the portions corresponding to the notches  80 . 
         [0053]    To the portions corresponding to the notches  80 , gaskets  84  are attached. Each gasket  84  is of a conductive material having appropriate elasticity, and in a free state, the gasket  84  has a thickness slightly greater than the total thickness of the heat-dissipating sheet  28  and the insulating sheet  30 , as shown in  FIG. 14 . The gasket  84  is attached to the conductive film  32  with a conductive adhesive agent or the like in such a manner as to be fitted into the notch  80  without contacting the heat-dissipating sheet  28  or the insulating sheet  30 . 
         [0054]    Next, the holding piece  72  will be described. The holding piece  72  is shown in  FIGS. 6 to 9 .  FIG. 6  is a top plan view of the holding piece  72 .  FIG. 7  is a side view of the holding piece  72 . The holding piece  72  is formed of a metal material having appropriate elasticity. Note that the holding piece  72  may be formed of any material other than a metal material as long as the material has appropriate elasticity. 
         [0055]    The holding piece  72  comprises, as shown in  FIGS. 6 and 7 , a base  78  and the contacting portion  74  continuously formed from the end of the base  78 . The base  78  comprises a screw hole  75  and the position determination hole  73 . 
         [0056]    The screw hole  75  has an internal diameter slightly greater than the diameter of the male screw  70  to be engaged with the female screw  66  of each mount and is thus slightly loose for the male screw  70 . The position determination hole  73  has an internal diameter substantially the same as the diameter of the position determination member  68  of each mount and is engaged tightly with the position determination member  68 . 
         [0057]    The contacting portion  74  has an entirely-curved shape. The contacting portion  74  has a notch  82  in the center. The contacting portion  74  is formed in such a manner as to be divided into two by the notch  82  and then the two divisions connected to each other at an end  77  as shown in  FIGS. 8 and 9 . 
         [0058]    Further, the connecting portion  74  is formed in such a manner that the end  77  of the contacting portion  74  in a free state will be arranged in a position lower than the level of the upper surface of the circuit board  22  attached to the housing  16  when the holding piece  72  is attached to the first mount  48 . With this structure, when screwed into the first mount  48  or the like, the contacting portion  74  is pushed and deformed upward by the circuit board  22 , and thus the holding piece  72  applies predetermined pressure to the circuit board  22 . 
         [0059]    Further, when each holding piece  72  is fixed to each mount with the male screw  70 , as shown in  FIG. 13 , the whole holding piece  72  including the male screw  70  will be lower than the upper edge of the vertical wall  76  formed around each mount. The above-described structure of the holding piece  72  is commonly adopted to the first mount  48  to the fourth mount  60 . 
         [0060]    Still further, an elastic member  86  is attached to each of the second mount  50  and the third mount  52  as shown in  FIGS. 4, 10 and 13 . The elastic member  86  is provided between the vertical wall  76  and the circuit board  22 , and pushes back the circuit board  22  toward the first attachment plate  36  by an elastic force. 
         [0061]    Next, a procedure for attaching the circuit board  22  to the housing  16  will be described. First, the housing  16  is formed. In the housing  16 , a synthetic resin is injected into the base plate  18  formed of a carbon-fiber-reinforced resin plate and the edge  20  is thereby formed around the base plate  18 , and then the projections  29  are formed in predetermined portions. The conductive film  32  is then formed on substantially the entire surface of the base plate  18 . 
         [0062]    After the conductive film  32  is formed, the first attachment plate  36  is inserted between the base plate  18  and the upper part of the edge  20  and screwed into the edge  20 . The second attachment plate  38  is positioned on the base plate  18  in accordance with the projections  29  and is attached to the base plate  18  with double-sided adhesive tape. The card socket plate  40  is positioned in accordance with a groove formed in the edge  20  and is attached to the base plate  18  with double-sided adhesive tape. 
         [0063]    On the base plate  18 , the substantially rectangular circuit board attachment region  62  is formed by the first attachment plate  36 , the second attachment plate  38  and the card socket plate  40 . To the circuit board attachment region  62 , the heat-dissipating sheet  28  and the insulating sheet  30  are attached with an adhesive agent or the like. 
         [0064]    The heat-dissipating sheet  28  and the insulating sheet  30  cover substantially the entire circuit board attachment region  62 . In contrast, the conductive film  32  is exposed from the notches  80  of the heat-dissipating sheet  28  and the insulating sheet  30 , that is, conductive portions are formed in proximity to the first mount  48  to the fourth mount  60 . 
         [0065]    To the conductive portions formed by the notches  80 , the gaskets  84  are attached. The gaskets  84  are attached to the conductive film  32  with conductive double-sided adhesive tape or the like. Further, the elastic members  86  are respectively attached in proximity to the second mount  50  and the third mount  52  as shown in  FIG. 13 . 
         [0066]    The circuit board  22  is provided in the circuit board attachment region  62  as shown in  FIG. 4 . The circuit board  22  is attached in such a manner that the engagement recess  46  engages with the engagement projection  42  and the edge of the circuit board  22  on the side opposite to that provided with the engagement recess  46  is brought into contact with the elastic member  86  attached to the second attachment plate  38 . The circuit board  22  is pushed back toward the first attachment plate  36  by the elastic force of the elastic member  86 . Then, in the circuit board  22 , the edge of the circuit board  22  is brought into contact with the striking portion  44  while the engagement recess  46  engages with the engagement projection  42 . 
         [0067]    Subsequently, the holding pieces  72  are respectively attached to the first mount  48  to the fourth mount  60 . Each of the holding pieces  72  is attached in such a manner that the contacting portion  74  is brought into contact with the circuit board  22 , the position determination hole  73  of the base  78  is slid onto the position determination member  68 , the male screw  70  is inserted into the screw hole  75 , and the male screw  70  is screwed into the female screw  66 . 
         [0068]    When the holding pieces  72  are fixed to the respective mounts with the male screws  70 , the contacting portions  74  of the holding pieces  72  appropriately deform and press the circuit board  22  against the base plate  18  with a predetermined force. This state is shown in  FIG. 13 . 
         [0069]    In this way, the lower surface of the circuit board  22  is pressed against the base plate  18  via the heat-dissipating sheet  28  and the insulating sheet  30 . The circuit board  22  is fixed to a predetermined position of the housing  16  by being engaged with the engagement projection  42 , brought into contact with the striking portion  44  and held by the holding pieces  72 . 
         [0070]    Further, as shown in  FIG. 14 , the gasket  84  is pressed against the conductive film  32  of the base plate  18  by the pressure from the holding piece  72 . In this way, the ground pad  26  of the circuit board  22  is electrically connected to the conductive film  32  of the housing  16  via the gasket  84 . Consequently, the ground line of the circuit board  22  can function as a ground electrode having a capacitance substantially the same as that of the conductive film  32  extending on the entire base plate  18  of the housing  16 . Therefore, it is possible to form a stable ground having little voltage change on the circuit board  22 . 
         [0071]    Still further, since the vertical wall  76  of each mount is higher than the top of the male screw  70 , the image display panel  14  attached to the housing  16  will not directly contact the male screw  70  even if the image display panel  14  bends in the thickness direction of the tablet computer  12 . 
         [0072]    Still further, since the holding piece  72  is formed in such a manner as to be divided into two and then the two divisions connected to each other at the end  77 , the holding piece  72  has a wide contacting area with the circuit board  22  and pushes back the circuit board  22  by an appropriate elastic force but will not concentrate the contact pressure or impose an inappropriate force on the circuit board  22 . 
         [0073]    In the case of replacing or repairing the circuit board  22  of the tablet computer  12 , the image display panel  14  is removed from the housing  16 , the male screws  70  attached to the respective mounts are detached, and the holding pieces  72  are removed from the housing  16 . 
         [0074]    In this way, the circuit board  22  is released from a fixed state and can be easily detached from the housing  16 . Further, the repaired or replacement circuit board  22  can be attached to the tablet computer  12  easily and reliably in the same manner. Note that the holding piece  72  may be attached to the mount not with the male screw  70  but with a detachable socket or the like. Further, the holding piece  72  is not necessarily formed in the above-described shape but may be formed in another shape. 
         [0075]    Still further, the electronic device is not necessarily limited to a tablet computer. It is possible to apply the present embodiment, for example, to other electronic devices such as a clamshell computer by adopting the circuit board attachment structure to the housing of a keyboard and the like. 
         [0076]    While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.