Abstract:
An electronic apparatus includes a substrate that includes a component, a first cover member that includes a first position control section for controlling a position of the substrate, and a second cover member that forms an internal space in cooperation with the first cover member and includes a second position control section for controlling the position of the substrate relatively more precisely than the first position control section, wherein when the substrate is supported by either one of the first cover member and the second cover member, the substrate is not fixed to the one of the cover members, and when the first cover member and the second cover member are fastened together, the substrate is fixed in the internal space.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2009-234433 filed on Oct. 8, 2009, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    Various embodiments discussed herein relate to an electronic apparatus including a substrate on which components are mounted. 
       BACKGROUND 
       [0003]    An electronic apparatus having a structure in which a housing having an inner space is formed by two cover members and a substrate on which components are mounted is contained in the inner space is widely known. The two covers are, for example, a bottom cover having a dish-shape that opens upward and a top cover that is placed on the bottom cover and forms the inner space with the bottom cover. In an assembling operation of an electronic apparatus having such a structure, a process in which a substrate is fixed inside the bottom cover by screws or the like, the top cover is placed on the bottom cover, and then the top cover and the bottom cover are fixed with screws is widely employed. As a screw fixing structure of the top cover and the bottom cover, from the viewpoint of design, in many cases, a structure is employed in which the bottom cover and the top cover are fixed with screws from the bottom cover so that the screw heads do not appear on the top cover. A component replacement procedure when a component fails in an electronic apparatus having the above structure is as follows. First, an operator puts the electronic apparatus upside down so that the bottom cover is placed over the top cover, and removes the screws fixing the bottom cover and the top cover. Next, the operator puts the electronic apparatus upside down again so that the bottom cover is placed under the top cover, removes the top cover, and removes the screws fixing the substrate to the electronic apparatus if necessary. When the component to be replaced is mounted on a surface of the substrate facing the bottom cover, the operator further takes out the substrate from the bottom cover, puts the substrate upside down, and removes the component to be replaced from the substrate. 
         [0004]    When replacing a component of an electronic apparatus having such a structure, the component replacement operation by an operator is cumbersome. In many cases, the substrate is not present separately in the housing, but connected to various other components via connectors or the like. This makes the component replacement operation more cumbersome. 
         [0005]    Japanese Unexamined Patent Application Publication No. 2002-246767 discloses a structure in which a circuit board contained in a case which is divided into an upper case and a lower case is tightened together with the upper case and the lower case and position control of the circuit board is performed by only one of the cases. 
         [0006]    Japanese Unexamined Patent Application Publication No. 2008-4659 discloses a specific structure which does not cause a position gap or a drop out even when an open/close button is placed upside down during an assembly operation. 
       SUMMARY 
       [0007]    An electronic apparatus includes a substrate that includes a component; a first cover member that includes a first position control section for controlling a position of the substrate; and a second cover member that forms an internal space in cooperation with the first cover member and includes a second position control section for controlling the position of the substrate relatively more precisely than the first position control section, wherein when the substrate is supported by either one of the first cover member and the second cover member, the substrate is not fixed to the one of the cover members, and when the first cover member and the second cover member are fastened together, the substrate is fixed in the internal space. 
         [0008]    The object and advantages of the various embodiments will be realized and attained by means of the elements and combinations particularly pointed out in the claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the various embodiments, as claimed. 
         [0009]    Additional aspects and/or advantages will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the various embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is an external perspective view of a notebook PC which is an embodiment of an electronic apparatus. 
           [0011]      FIG. 2  is a perspective view of showing a bottom surface of the notebook PC shown in  FIG. 1  in a closed state seen from a back side of  FIG. 1 . 
           [0012]      FIG. 3  is a rear perspective view showing a bottom cover member from which a top cover member is removed. 
           [0013]      FIG. 4  is a perspective view showing various components inside the bottom cover member from which the top cover member is removed in the same manner as in  FIG. 3 . 
           [0014]      FIG. 5  is a perspective view showing a surface (a surface facing the top cover member) of the bottom cover member from which a circuit board is removed from a state shown in  FIGS. 3 and 4 . 
           [0015]      FIG. 6  is a perspective view showing a surface (a surface facing the top cover member) of the circuit board removed from the bottom cover member. 
           [0016]      FIG. 7  is a perspective view showing a state in which the bottom cover member is removed and the circuit board is mounted on the top cover member. 
           [0017]      FIG. 8  is a perspective view of a surface of the circuit board facing the bottom cover member. 
           [0018]      FIG. 9  is a view showing an inner surface of the top cover member. 
           [0019]      FIG. 10  is a view showing an assembling procedure of a main body unit of the notebook PC. 
           [0020]      FIG. 11  is a view showing the assembling procedure of the main body unit of the notebook PC. 
           [0021]      FIG. 12  is a view showing a work procedure for replacing a fan. 
           [0022]      FIG. 13  is a plan view of a state in which the circuit board is mounted on the bottom cover member. 
           [0023]      FIG. 14  is a perspective view showing a cross-section taken along arrows X 1 -X 1  in  FIG. 13 . 
           [0024]      FIG. 15  is a cross-sectional view taken along arrows X 1 -X 1  in  FIG. 13 . 
           [0025]      FIG. 16  is an enlarged cross-sectional view of a portion of a circle R 1  shown in  FIG. 15 . 
           [0026]      FIG. 17  is an enlarged cross-sectional view of a portion of a circle R 2  shown in  FIG. 14 . 
           [0027]      FIG. 18  is an enlarged perspective view of a portion corresponding to the circle R 1  or the circle R 2  of the circuit board. 
           [0028]      FIG. 19  is an enlarged perspective view of a portion corresponding to the circle R 1  or the circle R 2  of the bottom cover member. 
           [0029]      FIG. 20  is an enlarged perspective view of a portion corresponding to the circle R 1  or the circle R 2  in a state in which the circuit board is mounted on the bottom cover member. 
           [0030]      FIG. 21  is an enlarged cross-sectional view of a portion of a circle R 3  shown in  FIG. 15 . 
           [0031]      FIG. 22  is an enlarged cross-sectional perspective view of a portion of a circle R 4  shown in  FIG. 14 . 
           [0032]      FIG. 23  is a perspective view of a portion corresponding to the circle R 3  or the circle R 4  of the bottom cover member. 
           [0033]      FIG. 24  is a perspective view of a portion corresponding to the circle R 3  or the circle R 4  in a state in which the circuit board is mounted on the bottom cover member. 
           [0034]      FIG. 25  is a cross-sectional perspective view showing a cross-section taken along arrows X 2 -X 2  in  FIG. 13 . 
           [0035]      FIG. 26  is a cross-sectional view taken along arrows X 2 -X 2  in  FIG. 13 . 
           [0036]      FIG. 27  is an enlarged cross-sectional view of a portion of a circle R 5  shown in  FIG. 26 . 
           [0037]      FIG. 28  is an enlarged cross-sectional perspective view of a portion of a circle R 6  shown in  FIG. 25 . 
           [0038]      FIG. 29  is a view of a portion of the circle R 5  or the circle R 6  of the surface of the circuit board facing the bottom cover member. 
           [0039]      FIG. 30  is an enlarged perspective view of a portion of the circle R 5  or the circle R 6  of the bottom cover member. 
           [0040]      FIG. 31  is a plan view of a state in which the circuit board is mounted on the top cover member. 
           [0041]      FIG. 32  is a cross-sectional view taken along arrows X 3 -X 3  in  FIG. 31 . 
           [0042]      FIG. 33  is an enlarged cross-sectional view of a portion of a circle R 7  shown in  FIG. 32 . 
           [0043]      FIG. 34  is an enlarged perspective view of a portion of the circle R 7 . 
           [0044]      FIG. 35  is an enlarged cross-sectional view of a portion of a circle R 8  shown in  FIG. 32 . 
           [0045]      FIG. 36  is an enlarged perspective view of a portion of the circle R 8 . 
           [0046]      FIG. 37  is an enlarged perspective view of a portion of a circle R 9  shown in  FIG. 31 . 
           [0047]      FIG. 38  is an enlarged perspective view of a portion of a circle R 10  shown in  FIG. 31 . 
           [0048]      FIG. 39  is an enlarged perspective view of a portion of a circle R 11  shown in  FIG. 31 . 
           [0049]      FIG. 40  is an enlarged perspective view of a portion of the circle R 11  shown in  FIG. 31  as seen from a direction different from that of  FIG. 39 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0050]    Hereinafter, embodiments of the present invention will be described. 
         [0051]      FIG. 1  is an external perspective view of a notebook type personal computer (hereinafter referred to “notebook PC) which is an embodiment of an electronic apparatus of the present invention. 
         [0052]    A notebook PC  10  includes a main body unit  20  and a display unit  30 . The main body unit  20  includes a housing  100  defining an outer shape thereof. The housing  100  includes two housing members, which are a top cover member  101  and a lower cover member  102  (also referred to as a bottom cover member). The main body unit  20  has an internal space enclosed by the top cover member  101  and the lower cover member  102 . Various electronic components, such as a CPU (Central Processing Unit) and a circuit board on which a fan to cool the CPU and the like are mounted, are accommodated in the internal space. The main body unit  20  has a calculation function realized by the CPU and the like. The main body unit  20  includes a power button  21 , a keyboard  22 , and a pointing device  23 , and the like on the surface thereof. The pointing device includes a touchpad  231  and left/right click buttons  232 . The main body unit  20  also includes a lock hole  25  in the top surface thereof. A hook  31  provided on the display unit  30  enters the lock hole  25  and is locked in the lock hole  25 , so that the display unit  10  is held in a closed state. The main body unit  20  includes various connectors  26  on both sides thereof. 
         [0053]    The display unit  30  of the notebook PC  10  includes the above-mentioned hook  31 , a display screen  32 , and the like. The display unit  30  is supported by hinges  40  so that the display unit  30  can be opened and closed freely between an opened state in which the display screen  32  is opened as shown in  FIG. 1  and a closed state in which the display unit  30  is closed on the main body unit  20  with the display screen  32  facing down. 
         [0054]      FIG. 2  is a perspective view showing the bottom surface of the notebook PC shown in  FIG. 1  in the closed state seen from a back side (hinges  40  side) of  FIG. 1 . 
         [0055]    The main body unit  20  includes an exhaust outlet  111  and three connector inlets  112  in the rear side surface. The exhaust outlet  111  is an outlet for blowing out air from a fan inside the main body unit  20  to the outside of the housing. 
         [0056]      FIG. 3  is a rear perspective view showing the bottom cover member from which the top cover member is removed.  FIG. 4  is a perspective view showing various components inside the bottom cover member from which the top cover member is removed in the same manner as in  FIG. 3 . 
         [0057]    A circuit board  50  on which various electronic components are mounted is disposed at a portion near the exhaust outlet  111  inside the bottom cover member  102 . The circuit board  50  includes an opening  51 . As shown in  FIG. 4 , blades of a fan  60  mounted on a back surface of the surface shown in  FIG. 4 , in other words, mounted on a surface of the circuit board  50  facing the bottom cover member  102  are viewed from the opening  51 . A shield plate  113  is fixed inside the bottom cover member  102 . 
         [0058]      FIG. 5  is a perspective view showing the surface (the surface facing the top cover member) of the bottom cover member from which the circuit board  50  is removed from a state shown in  FIGS. 3 and 4 .  FIG. 6  is a perspective view showing the surface (the surface facing the top cover member) of the circuit board removed from the bottom cover member. 
         [0059]    The bottom cover member  102  includes a plurality of bosses  114  inside the bottom cover member  102 . The bosses  114  and portions formed higher than the other portions inside the bottom cover member  102  have a through-hole for a screw clamp. Fixing portions  113   a  of the shield plate  113  are mounted on the portions where the through-hole for screw fixing is formed. The fixing portions  113   a  include a hole. The circuit board  50  and mounting brackets fixed to the circuit board  50  also include a screw fixing hole  52  passing through from the top surface to the bottom surface at a position corresponding to each boss  114  or the like. In a screw fixing operation, screws are inserted from the bottom surface of the bottom cover member  102 , and the screws pass through the holes of the circuit board  50 , and then the screws are fastened into screw holes (described below) formed in the top cover member  101 . In this way, when the top cover member  101  is fixed to the bottom cover member  102  by the screws, the circuit board is also fixed by the screw. The circuit board  50  does not have portions individually fixed to the bottom cover member  102  or the top cover member  101  by screws, and only has a structure to be tightened together with the bottom cover member  102  and the top cover member  101  when the bottom cover member  102  and the top cover member  101  are fixed together by screws. Before the screw fixing operation, the position of the circuit board  50  needs to be precisely controlled. The position control structure will be described below. 
         [0060]      FIG. 7  is a perspective view showing a state in which the bottom cover member is removed and the circuit board is mounted on the top cover member.  FIG. 8  is a perspective view of a surface of the circuit board facing the bottom cover member. 
         [0061]    As shown in  FIG. 7 , the circuit board  50  and the pointing device  23  are arranged on the top cover member  101 .  FIG. 7  shows the back surface (the surface facing the bottom cover member) of the circuit board  50 .  FIG. 7  shows the back surface of the pointing device  23  whose outer surface is shown in  FIG. 1 . 
         [0062]    The fan  60 , a heatsink  61  disposed on the side of the exhaust outlet  111  (refer to  FIGS. 2 and 3 ) of the fan  60 , a plurality of connectors  62  and  63 , and other components are mounted on the surface of the circuit board  50  facing the bottom cover member. The CPU (not shown in the figures) is mounted on the circuit board  50  at a position immediately below the heatsink  61 . When the CPU is running, the CPU generates a considerable amount of heat. Therefore, a cooling structure is employed in which the heat generated from the CPU is absorbed by the heatsink, the heatsink is cooled by air blown from the fan  60 , and the air is exhausted from the exhaust outlet to the outside of the housing. In the same manner as in  FIG. 6 , the screw fixing holes  52  used to tighten the circuit board  50  together with the bottom cover member  102  and the top cover member  101  appear in the circuit board  50  shown in  FIGS. 7 and 8 . 
         [0063]      FIG. 9  is a view showing an inner surface of the top cover member. 
         [0064]    Inside the top cover member  101 , screw holes  521  are formed at each position corresponding to the screw fixing holes of the bottom cover member  102  and the screw fixing holes  52  of the circuit board  50 . Screws inserted from the bottom surface of the bottom cover member  102  pass through the circuit board  50 , and are fastened into the screw holes  521  formed in the inner surface of the top cover member  101 . As described above, the circuit board  50  is tightened together with the top cover member  101  and the bottom cover member  102 . However, the circuit board  50  is not individually fixed to the bottom cover member  102  or individually fixed to the top cover member  101  by screws. Therefore, the circuit board  50  can be taken out from either a state in which the top cover member is removed as shown in  FIG. 4  or a state in which the bottom cover member is removed as shown in  FIG. 7 . 
         [0065]      FIGS. 10 and 11  are views showing an assembling procedure of the main body unit of the notebook PC. 
         [0066]    When assembling the main body unit, first, as shown in  FIG. 10 , the circuit board  50  is placed inside the bottom cover member  102 . Next, as shown in  FIG. 11 , the top cover member  101  is placed on the bottom cover member  102  on which the circuit board  50  is placed. Then, as described above, screws are inserted from the bottom surface of the bottom cover member  102  and the screws are fastened. 
         [0067]      FIG. 12  is a view showing a work procedure for replacing the fan. 
         [0068]    The fan  60  has a mechanical movable portion, so that the life of the fan  60  is shorter than that of other components, and thus the fan  60  may often be replaced. 
         [0069]    In the notebook PC, the fan  60  is mounted on the surface of the circuit board  50  facing the bottom cover member. 
         [0070]    When replacing the fan, first, the bottom cover member  102  is set to face upward, and the screws fixing the bottom cover member  102  are removed. Thereafter, as shown in  FIG. 12 , the bottom cover member  102  is removed, and in this state, the fan  60  is removed and replaced by a new fan  60 . If necessary, in this state, the circuit board  50  can be removed. 
         [0071]    In the above description with reference to  FIGS. 10 and 11 , the assembling procedure for assembling the components sequentially from the bottom cover member  102  is described. However, as shown in  FIG. 12 , it is also possible to assemble the main body unit by a procedure in which, first, the top cover member  101  is put down, next, the circuit board  50  is placed on the top cover member  101 , and further the bottom cover member  102  is placed on the circuit board  50  and fixed with screws. 
         [0072]    Next, the position control structure of the circuit board will be described. 
         [0073]    In the main body unit  20  of the notebook PC  10 , the position control structure of the circuit board  50  is included in both the bottom cover member  102  and the top cover member  101 . However, when a structure for precisely controlling the position of the circuit board  50  is included in both the bottom cover member  102  and the top cover member  101 , the, position control structures of both members may interfere with each other due to manufacturing dimensional variation or the like of the bottom cover member  102  and the top cover member  101 . Because of this, the position control of the circuit board may be impossible. Therefore, in this embodiment, the bottom cover member  102  has a position control structure for precisely controlling the position of the circuit board  50 , and the top cover member  101  has a position control structure for controlling the position of the circuit board  50  less precisely than the bottom cover member  102 . 
         [0074]    As described above with reference to  FIG. 12 , the circuit board  50  is placed on the top cover member  101 , and then the bottom cover member  102  may be placed over the circuit board  50 . Therefore, the bottom cover member  102  includes a guiding structure for guiding the circuit board  50  that is roughly positioned on the top cover member  101  into a precisely controlled position. When, instead of the top cover member  101 , the bottom cover member  102  has a structure for precisely controlling the position, the advantages described below appear. The connectors  62 ,  63 , and the like are mounted on the circuit board  50 . The bottom cover member  102  has openings to which connectors connected to the connectors  62 ,  63 , and the like of the circuit board  50  are inserted. Even when the top cover member  101  is removed from a state in which the bottom cover member  102  is placed under the top cover member  101  (a normal setting state of the notebook PC) and a connecter needs to be inserted from outside while the circuit board  50  is placed on the bottom cover member  102 , the connector from the outside can be correctly inserted into a connector on the circuit board  50  through an opening of the bottom cover member  102  because the bottom cover member  102  has a structure for precisely controlling the position. 
         [0075]    Hereinafter, first, the position control structure of the bottom cover member  102  will be described. Thereafter, the position control structure of the top cover member  101  will be described. 
         [0076]      FIG. 13  is a plan view of a state in which the circuit board is mounted on the bottom cover member.  FIG. 14  is a perspective view showing a cross-section taken along arrows X 1 -X 1  in  FIG. 13 .  FIG. 15  is a cross-sectional view taken along arrows X 1 -X 1  in  FIG. 13 . 
         [0077]      FIG. 16  is an enlarged cross-sectional view of a portion of a circle R 1  shown in  FIG. 15 .  FIG. 17  is an enlarged cross-sectional view of a portion of a circle R 2  shown in  FIG. 14 . The circle R 1  and the circle R 2  show the same portion. 
         [0078]      FIG. 18  is an enlarged perspective view of a portion corresponding to the circle R 1  or the circle R 2  of the circuit board.  FIG. 19  is an enlarged perspective view of a portion corresponding to the circle R 1  or the circle R 2  of the bottom cover member.  FIG. 20  is an enlarged perspective view of a portion corresponding to the circle R 1  or the circle R 2  in a state in which the circuit board is mounted on the bottom cover member. 
         [0079]    The circuit board has the connector  62  shown in  FIG. 18  (also refer to  FIG. 7 ) at a position viewed from the openings  112  shown in  FIG. 19  (also refer to  FIG. 2 ). 
         [0080]    When a bracket that supports the connector  62  comes into contact with a wall of the bottom cover member  102  at which the openings  112  are formed, first, the position of the bracket is controlled. 
         [0081]      FIG. 21  is an enlarged cross-sectional view of a portion of a circle R 3  shown in  FIG. 15 .  FIG. 22  is an enlarged cross-sectional perspective view of a portion of a circle R 4  shown in  FIG. 14 . The circle R 3  and the circle R 4  show the same portion. 
         [0082]      FIG. 23  is a perspective view of a portion corresponding to the circle R 3  or the circle R 4  of the bottom cover member.  FIG. 24  is a perspective view of a portion corresponding to the circle R 3  or the circle R 4  in a state in which the circuit board is mounted on the bottom cover member. 
         [0083]    As shown in  FIG. 24 , the bottom cover member  102  has a rib  64  formed upright on the inner surface thereof. The rib  64  includes a guide slope  641  which forms a part of a guide section defined in the present invention, and following the guide slope  641 , the rib  64  includes a position control standing wall  642  which controls the position of the circuit board  50 . The rib  64  further includes a support platform  643  that supports the circuit board  50 . 
         [0084]    When the circuit board is placed on the bottom cover member  102 , the circuit board  50  is guided by the guide slope  641  to be mounted on the support platform  643 , and a side edge of the circuit board  50  comes into contact with the position control standing wall  642 . At this time, the bracket that supports the connector  62  described above with reference to  FIGS. 16 to 20  comes into contact with the wall in which the openings  112  are formed. Based on this, the position of the circuit board  50  is controlled in the horizontal direction in  FIG. 13  with respect to the bottom cover member  102  (the depth direction in  FIG. 1 ). 
         [0085]      FIG. 25  is a cross-sectional perspective view showing a cross-section taken along arrows X 2 -X 2  in  FIG. 13 .  FIG. 26  is a cross-sectional view taken along arrows X 2 -X 2  in  FIG. 13 .  FIG. 27  is an enlarged cross-sectional view of a portion of a circle R 5  shown in  FIG. 26 .  FIG. 28  is an enlarged cross-sectional perspective view of a portion of a circle R 6  shown in  FIG. 25 .  FIG. 29  is a view of a portion of the circle R 5  or the circle R 6  of the surface of the circuit board facing the bottom cover member.  FIG. 30  is an enlarged perspective view of a portion of the circle R 5  or the circle R 6  of the bottom cover member. 
         [0086]    As shown in  FIG. 29  (also refer to  FIG. 8 ), the circuit board  50  has the connector  63  on the surface thereof facing the bottom cover member. As shown in  FIG. 30 , the bottom cover member  102  has a rib  65  formed upright on the inner surface thereof. The rib  65  includes a guide slope  651  which forms a guide section defined in the present invention, and following the guide slope  651 , the rib  65  includes a position control standing wall  652  which controls the position of the connector  63 . The rib  65  further includes a support platform  653  that supports the connector  63 . 
         [0087]    When the circuit board  50  is placed on the bottom cover member  102 , the connector  63  mounted on the circuit board  50  is guided by the guide slope  651  to be mounted on the support platform  653 . At this time, the connector  63  is sandwiched between the position control standing wall  652  and an inner surface  101   a  of the side wall of the bottom cover member  102 . Based on this, the position of the connector  63 , in other words, the position of the circuit board  50  on which the connector  63  is mounted is controlled in the left-right direction. 
         [0088]    Next, the position control structure of the circuit board  50  by the top cover member  101  will be described. 
         [0089]      FIG. 31  is a plan view of a state in which the circuit board is mounted on the top cover member.  FIG. 32  is a cross-sectional view taken along arrows X 3 -X 3  in  FIG. 31 .  FIG. 33  is an enlarged cross-sectional view of a portion of a circle R 7  shown in  FIG. 32 .  FIG. 34  is an enlarged perspective view of a portion of the circle R 7 . 
         [0090]    The top cover member  101  includes a rib  71  formed upright on the inner surface thereof. The rib  71  performs a part of the position control of the circuit board  50 . A reinforcement bracket  59  that reinforces the connector mounted on the circuit board  50  faces the rib  71 . There is a space of a gap d between the rib  71  and the reinforcement bracket  59 . 
         [0091]      FIG. 35  is an enlarged cross-sectional view of a portion of a circle R 8  shown in  FIG. 32 .  FIG. 36  is an enlarged perspective view of a portion of the circle R 8 . 
         [0092]    As shown in  FIGS. 35 and 36 , a rib  72  is formed on the inner wall surface of the top cover member  101 . A dimensional allowance d is provided between the rib  72  and a side edge of the circuit board  50 . 
         [0093]      FIG. 37  is an enlarged perspective view of a portion of a circle R 9  shown in  FIG. 31 . 
         [0094]    As shown in  FIG. 37 , the top cover member  101  also has a rib  73  in this portion. A gap is formed between the rib  73  and the circuit board  50 . 
         [0095]      FIG. 38  is an enlarged perspective view of a portion of a circle R 10  shown in  FIG. 31 . 
         [0096]    As shown in  FIG. 38 , the top cover member  101  has a rib  74  also in this portion. A gap is formed between the rib  74  and the circuit board  50 . 
         [0097]      FIG. 39  is an enlarged perspective view of a portion of a circle R 11  shown in  FIG. 31 .  FIG. 40  is an enlarged perspective view of a portion of the circle R 11  shown in  FIG. 31  as seen from a direction different from that of  FIG. 39 . 
         [0098]    As shown in  FIGS. 39 and 40 , the top cover member  101  has a rib  75  also in this portion. As shown in  FIG. 39 , a gap d is formed between a support bracket  69  that supports a connector mounted on the circuit board  50  and the rib  75  in the left-right direction. As shown in  FIG. 40 , a gap d is formed between the rib  75  and the circuit board  50  in the depth direction in the state of  FIG. 1 . 
         [0099]    In this way, the position of the circuit board  50  placed on the top cover member  101  is roughly controlled by the ribs  71  to  75  of the top cover member  101  and the like in both the depth direction and the left-right direction. In this state, when the bottom cover member  102  is placed on the top cover member  101 , the circuit board  50  is guided by the guide slope  641  ( FIG. 23 ) and the guide slope  651  ( FIG. 30 ) described above to a position precisely controlled by the bottom cover member  102 . 
         [0100]    In this way, in this embodiment, the position of the circuit board  50  is precisely controlled by only the bottom cover member  102  between the top cover member  101  and the bottom cover member  102 , so that even when a dimensional error occurs during manufacturing, it is possible to avoid interference between the position control structures of the bottom cover member  102  and the top cover member  101  for the circuit board  50 . 
         [0101]    In addition, even when the circuit board  50  is placed on the top cover member  101  and the position of the circuit board  50  is roughly controlled, the position of the circuit board  50  is precisely controlled in the main body unit  20  when the bottom cover member  102  is placed on the top cover member  101 . Based on this, a smooth screw fixing operation is realized. 
         [0102]    Although a notebook PC is described as the embodiment, the present invention need not be a notebook PC, and the present invention can be applied to general electronic apparatuses. Although an example is described in which a fan is used as a component to be replaced, the component to be replaced is not limited to a fan, but the component to be replaced may be any component mounted on the circuit board. 
         [0103]    All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiment(s) of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.