Patent Publication Number: US-8125783-B2

Title: Printed circuit board and electronic apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 12/042,182, filed Mar. 4, 2008, now U.S. Pat. No. 7,639,503, which is based upon and claims the benefit of priority from Japanese Patent Application No. 2007-088831, filed Mar. 29, 2007, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     One embodiment of the invention relates to a printed circuit board with a reinforcing plate for preventing warps, and an electronic apparatus incorporating the printed circuit board. 
     2. Description of the Related Art 
     Jpn. Pat. Appln. KOKAI Publication No. 2006-202525, for example, discloses a connection structure in which a connector is attached to a circuit board for vehicle control. This connection structure comprises a printed circuit board and first and second connectors attached to the printed circuit board and having different sizes. The printed circuit board has three screw holes. Two of the three screw holes are used as a pair of first screw holes for screwing the first connector, and two of the three screw holes are used as a pair of second screw holes for screwing the second connector. Namely, one of the three screw holes is used in common to connect the first and second connectors. 
     In the meantime, reinforcing plates may be employed for a printed circuit board to prevent it from warping. In this case, to screw reinforcing plates of different sizes to the printed circuit board, the above-mentioned structure may be used. Namely, a plurality of screw holes for screwing reinforcing plates of different sizes are formed in the printed circuit board, and parts of the screw holes are used in common. However, even if some screws are used in common, two reinforcing plates of different sizes must be prepared, which inevitably increases the number of components and increases the manufacturing cost. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       A general architecture that implements the various feature of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention. 
         FIG. 1  is an exemplary perspective view illustrating a portable computer according to a first embodiment; 
         FIG. 2  is an exemplary upper view illustrating part of a printed circuit board received in the housing of the portable computer shown in  FIG. 1 ; 
         FIG. 3  is an exemplary sectional view taken along line F 3 -F 3  in  FIG. 2 ; 
         FIG. 4  is an exemplary upper view illustrating part of a printed circuit board incorporated in a portable computer according to a second embodiment; 
         FIG. 5  is an exemplary sectional view taken along line F 5 -F 5  in  FIG. 4 ; 
         FIG. 6  is an exemplary upper view illustrating part of a printed circuit board incorporated in a portable computer according to a third embodiment; 
         FIG. 7  is an exemplary sectional view taken along line F 7 -F 7  in  FIG. 6 ; 
         FIG. 8  is an exemplary upper view illustrating part of a printed circuit board incorporated in a portable computer according to a fourth embodiment; 
         FIG. 9  is an exemplary sectional view taken along line F 9 -F 9  in  FIG. 8 ; 
         FIG. 10  is an exemplary upper view illustrating the interior of the housing of a portable computer according to a fifth embodiment; 
         FIG. 11  is an exemplary upper view illustrating a modification of the portable computer according to the fifth embodiment; 
         FIG. 12  is an exemplary upper view illustrating the interior of the housing of a portable computer according to a sixth embodiment; 
         FIG. 13  is an exemplary upper view illustrating a modification of the portable computer according to the sixth embodiment; and 
         FIG. 14  is an exemplary upper view illustrating the interior of the housing of a portable computer according to a seventh embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Various embodiments according to the invention will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment of the invention, a printed circuit board comprises a printed wiring board, circuit component, reinforcing plate and first and second fixing portion. The printed wiring board includes first and second areas. The first fixing portion is provided on a border line that defines the first and second areas. The first fixing portion can fix the reinforcing plate to both the first and second areas. The second fixing portion comprises a pair of elements arranged symmetrical with respect to the border line. 
     Referring first to  FIGS. 1 to 3 , a description will be given of an electronic apparatus according to a first embodiment. As shown in  FIG. 1 , a portable computer  11  as an example of the electronic apparatus comprises a main unit  12 , display unit  13 , and hinge sections  14  provided therebetween. The hinge sections  14  support the display unit  13  so that the display unit  13  can angularly move or rotate with respect to the main unit  12 . The display unit  13  includes a display  15  and latch  16 . 
     The main unit  12  includes a housing  21 , keyboard  22 , touch pad  23  (pointing device), and button  24 . As shown in  FIG. 2 , the main unit  12  includes a printed circuit board  26  with circuit components  25  mounted thereon, which is housed in the housing  21 . 
     As shown in  FIGS. 2 and 3 , the printed circuit board  26  comprises a printed wiring board  27  having a first area  27 A and second area  27 B adjacent thereto, circuit components  25  mounted on the first surface  27 C of the printed wiring board  27 , a cooling mechanism  28  for cooling the circuit components  25 , a reinforcing plate  29  attached to the second surface  27 D of the printed wiring board  27  in the area corresponding to one of the circuit components  25 , and first and second fixing portion  31  and  32  provided at the printed wiring board  27  to fix the reinforcing plate  29  to the wiring board  27 . The cooling mechanism  28  is formed of, for example, a heat-dissipating metal plate and is pressed against the circuit components  25 . However, the cooing mechanism  28  is not limited to this member, but may be formed of, for example, a heat sink of a pin support shape. The printed circuit board  26  has a plate spring  33  that presses the cooling mechanism  28  against the circuit components  25 . The plate spring  33  and reinforcing plate  29  are fixed to the printed wiring board  26  by screws  34 . 
     The printed wiring board  27  is formed of copper wiring layers stacked on each other. The printed wiring board  27  has the first area  27 A located on the left side in  FIG. 2 , the second area  27 B located adjacent thereto on the right side, and a border line  27 E defining the first and second areas  27 A and  27 B. 
     The circuit components  25  are, for example, a north bridge  25 A and graphics chip  25 B. The north bridge  25 A is fixed to the first area  27 A of the printed wiring board  27 , and the graphics chip  25 B is fixed to the second area  27 B of the printed wiring board  27 . 
     The reinforcing plate  29  is fixed to the second area  27 B, corresponding to the graphics chip  25 B. The reinforcing plate  29  is a so-called electrolytic zinc-coated steel sheet, and prevents the printed circuit board  26  from warping when the cooling mechanism  28  is pressed against one of the circuit components by the plate spring  33 , thereby preventing the Ball Grid Array (BGA) of the circuit components  25  from peeling off. The reinforcing plate  29  has a rectangular main body  29 A, a pair of arm portions  29 B obliquely extending from the main body  29 A, and a projection  29 C projecting from one side of the main body  29 A. The pair of arm portions  29 B and projection  29 C have screw holes  35 . The reinforcing plate  29  is screwed to the printed wiring board  26  by screws  34  inserted through the screw holes  35 . 
     The first fixing portion  31  comprises a pair of elements provided at the printed wiring board  27  on the border line  27 E thereof. Specifically, the first fixing portion  31  comprises a pair of screw holes in the printed wiring board  27  on the border line  27 E. Similarly, the second fixing portion  32  comprises a pair of elements provided at the printed wiring board  27  symmetrical with respect to the border line  27 E. Specifically, the second fixing portion  32  comprises a pair of symmetrical screw holes formed in the printed wiring board  27 . The reinforcing plate  29  is secured to the printed wiring board  27  by the first and second fixing portion  31  and  32 . In this structure, the heat generated by the graphics chip  25 B is dissipated by the dissipation metal plate of the cooling mechanism  28 . 
     Referring then to  FIGS. 4 and 5 , an electric device according to a second embodiment will be described. A portable computer  41  as an example of the electronic apparatus according to the second embodiment differs from the first embodiment in the arrangement of the circuit component  25  and reinforcing plate  29 , and is similar thereto in the other portions. Therefore, in this embodiment, elements similar to those of the first embodiment are denoted by corresponding reference numbers, and a description will be mainly given of different portions. 
     A printed circuit board  42  according to the second embodiment comprises a printed wiring board  27  having a first area  27 A and second area  27 B adjacent thereto, a circuit component  25  mounted on the first surface  27 C of the printed wiring board  27 , a cooling mechanism  28  for cooling the circuit component  25 , a reinforcing plate  29  attached to the second surface  27 D of the printed wiring board  27  in the area corresponding to the circuit component  25 , and first and second fixing portion  31  and  32  provided at the printed wiring board  27  to fix the reinforcing plate  29  to the wiring board  27 . The cooling mechanism  28  is formed of, for example, a heat-dissipating metal plate. The printed circuit board  42  has a plate spring  33  that presses the cooling mechanism  28  against the circuit component  25 . The plate spring  33  and reinforcing plate  29  are fixed to the printed wiring board  27  by screws  34 . 
     The printed wiring board  27  has a first area  27 A, second area  27 B adjacent thereto, and a border line  27 E defining the first and second areas  27 A and  27 B. The circuit component  25  is, for example, a north bridge  25 A that contains a graphics chip. The north bridge  25 A is fixed to the first area  27 A of the printed wiring board  27 . 
     The reinforcing plate  29  has the same shape as that employed in the first embodiment, and is fixed to the first area  27 A, corresponding to the north bridge  25 A. The reinforcing plate  29  is screwed to the printed wiring board  27  by screws  34  inserted through screw holes  35  formed in a pair of arm portions  29 B and a projection  29 C. The first and second fixing portion  31  and  32  of the printed wiring board  27  have the same structures as the corresponding portion of the first embodiment. The reinforcing plate  29  is secured to the printed wiring board  27  by the first and second fixing portion  31  and  32 . In this structure, the heat generated by the north bridge  25 A is dissipated by the dissipation metal plate of the cooling mechanism  28 . 
     In the first and second embodiments, the first fixing portion  31  is located on the border line  27 E that defines the first and second areas  27 A and  27 B, and can fix the reinforcing plate  29  regardless of whether the reinforcing plate  29  is attached to the first area  27 A or second area  27 B. The second fixing portion  32  comprises a pair of elements arranged symmetrical with respect to the border line  27 E. The thus-fixed reinforcing plate  29  can prevent the printed wiring board  27  from being warped when the cooling mechanism  28  is pressed against it. Further, since the distance between one screw hole of the first fixing portion  31  and one screw hole of the second fixing portion  32  is set equal to that between the other screw hole of the first fixing portion  31  and the other screw hole of the second fixing portion  32 , reinforcing plates  29  of the same size and shape can be attached to both the first and second areas  27 A and  27 B. As a result, the types of reinforcing plates  29  can be reduced to thereby reduce the manufacturing cost. 
     Further, the first fixing portion  31  formed of a pair of screw holes can be used in common when the reinforcing plate  29  is attached to the first area  27 A and when it is attached to the second area  27 B. In general, on printed circuit boards, a large number of circuit components are mounted at high density, and a large number of interconnects are provided at high density. Under these circumstances, the second embodiment, in which the number of required screw holes can be reduced to enhance the mounting density of the printed circuit board  42  and shorten the lengths of the interconnects, is very advantageous. 
     Referring then to  FIGS. 6 and 7 , an electronic apparatus according to a third embodiment will be described. A portable computer  51  as an example of the electronic apparatus according to the third embodiment differs from the first embodiment in a printed circuit board  52 , and is similar thereto in the other portions. Therefore, in this embodiment, elements similar to those of the first embodiment are denoted by corresponding reference numbers, and a description will be mainly given of different portions. 
     The printed circuit board  52  according to the third embodiment comprises a printed wiring board  27  having a first area  27 A and second area  27 B adjacent thereto, circuit components  25  mounted on the first surface  27 C of the printed wiring board  27 , a cooling mechanism  28  for cooling the circuit components  25 , a reinforcing plate  53  attached to the second surface  27 D of the printed wiring board  27  in the area corresponding to one of the circuit components  25 , and first fixing portion  31  and second fixing portion  54  provided at the printed wiring board  27  to fix the reinforcing plate  53  to the wiring board  27 . The cooling mechanism  28  is formed of, for example, a heat-dissipating metal plate. The printed circuit board  52  has a plate spring  33  that presses the cooling mechanism  28  against the one circuit component  25 . The plate spring  33  and reinforcing plate  53  are fixed to the printed wiring board  27  by screws  34 . 
     The printed wiring board  27  has the first area  27 A located on the left side in  FIG. 6 , and the second area  27 B located adjacent thereto on the right side, and a border line  27 E defining the first and second areas  27 A and  27 B. 
     The circuit components  25  are, for example, a north bridge  25 A and graphics chip  25 B. The north bridge  25 A is fixed to the first area  27 A of the printed wiring board  27 , and the graphics chip  25 B is fixed to the second area  27 B of the printed wiring board  27 . 
     The reinforcing plate  53  is attached to the second area  27 B corresponding to the graphics chip  25 B. The reinforcing plate  53  comprises a rectangular main body  53 A, a pair of arm portions  53 B obliquely extending from the main body  53 A, and a hook portion  53 C projecting from one side of the main body  53 A. The hook portion  53 C is bent at right angles. The pair of arm portions  53 B and hook portion  53 C have screw holes  35 . The reinforcing plate  53  is screwed to the printed wiring board  27  by screws  34  inserted through the screw holes  35 . 
     The first fixing portion  31  comprises a pair of elements provided at the printed wiring board  27  on the border line  27 E thereof. Specifically, the first fixing portion  31  comprises a pair of screw holes in the printed wiring board  27  on the border line  27 E. The printed wiring board  27  also has a center point  27 F between the pair of elements, i.e., between the pair of screw holes. The second fixing portion  54  comprises a pair of elements arranged point symmetrical with respect to the center point  27 F. Specifically, the second fixing portion  54  comprises a pair of screw holes formed in the printed wiring board  27  point symmetrical with respect to the center point  27 F. In this structure, the heat generated by the graphics chip  25 B is dissipated by the dissipation metal plate of the cooling mechanism  28 . 
     As indicated by the two-dot chain lines in  FIGS. 6 and 7 , the reinforcing plate  53 , cooling mechanism  28  and plate spring  33  may be provided on the first area  27 A. In this case, the reinforcing plate indicated by the solid line is rotated through 180°. 
     In the third embodiment, the first fixing portion  31  includes a pair of elements provided on the border line  27 E that defines the first and second areas  27 A and  27 B, and can attach the reinforcing plate  53  to any one of the first and second areas  27 A and  27 B. Further, the printed wiring board  27  has the center point  27 F located between the pair of fixing portion  31 . The second fixing portion  54  includes a pair of elements arranged point symmetrical with respect to the center point  27 F. In this structure, the distance between the center point  27 F and one screw hole of the second fixing portion  54  is set equal to the distance between the center point  27 F and the other screw hole of the second fixing portion  54 . Therefore, reinforcing plates  53  of the same size and shape can be attached to both the first and second areas  27 A and  27 B. 
     Further, the first fixing portion  31  formed of a pair of screw holes can be used in common between the time when the reinforcing plate  53  is attached to the first area  27 A and the time when it is attached to the second area  27 B. This can increase the mounting density of the printed circuit board  52 , and the required length of each interconnect on the printed circuit board  52  can be shortened. 
     Referring then to  FIGS. 8 and 9 , an electronic apparatus according to a fourth embodiment will be described. A portable computer  61  as an example of the electronic apparatus according to the fourth embodiment differs from the first embodiment in a printed circuit board  62 , and is similar thereto in the other portions. Therefore, in this embodiment, elements similar to those of the first embodiment are denoted by corresponding reference numbers, and a description will be mainly given of different portions. 
     The printed circuit board  62  according to the fourth embodiment comprises a printed wiring board  27  having a first area  27 A and second area  27 B adjacent thereto, circuit components  25  mounted on the first surface  27 C of the printed wiring board  27 , a cooling mechanism  28  for cooling the circuit components  25 , a reinforcing plate  65  attached to the second surface  27 D of the printed wiring board  27  in the area corresponding to the circuit components  25 , and first fixing portion  31  and second fixing portion  54  provided at the printed wiring board  27  to fix the reinforcing plate  65  to the wiring board  27 . The printed circuit board  62  has a plate spring  66  that presses the cooling mechanism  28  against the circuit components  25 . The plate spring  66  is obtained by coupling two plate springs similar to the plate spring  33  employed in the first embodiment. The plate spring  66  and reinforcing plate  65  are fixed to the printed wiring board  62  by screws  34 . 
     The printed wiring board  27  has the first area  27 A located on the left side in  FIG. 8 , and the second area  27 B located adjacent thereto on the right side, and a border line  27 E defining the first and second areas  27 A and  27 B. The circuit components  25  are, for example, a north bridge  25 A and graphics chip  25 B. The north bridge  25 A is fixed to the first area  27 A of the printed wiring board  27 , and the graphics chip  25 B is fixed to the second area  27 B of the printed wiring board  27 . The cooling mechanism  28  is formed of a first heat-dissipating metal plate  63  attached to the north bridge  25 A, and a second heat-dissipating metal plate  64  attached to the graphics chip  25 B. 
     The reinforcing plate  65  is obtained by coupling two reinforcing plates similar to the reinforcing plate  53  of the third embodiment. The reinforcing plate  65  is a so-called electrolytic zinc-coated steel sheet. The reinforcing plate  65  comprises first and second rectangular portions  65 A and  65 B, a pair of arm portions  65 C coupling the first and second portions  65 A and  65 B, and hook portions  65 D projecting from the first and second portions  65 A and  65 B. The first portion  65 A is positioned in the first area  27 A corresponding to the north bridge  25 A. The second portion  65 B is positioned in the second area  27 B corresponding to the graphics chip  25 B. The pair of arm portions  65 C and hook portions  65 D have screw holes  35 . The reinforcing plate  65  is screwed to the printed wiring board  27  by screws  34  inserted through the screw holes  35 . 
     The first fixing portion  31  comprises a pair of elements provided at the printed wiring board  27  on the border line  27 E thereof. Specifically, the first fixing portion  31  comprises a pair of screw holes in the printed wiring board  27  on the border line  27 E. The printed wiring board  27  also has a center point  27 F between the pair of elements, i.e., the pair of screw holes. The second fixing portion  32  comprises a pair of elements arranged point symmetrical with respect to the center point  27 F. Specifically, the second fixing portion  32  comprises a pair of screw holes formed in the printed wiring board  27  point symmetrical with respect to the center point  27 F. In this structure, the heat generated by the north bridge  25 A is dissipated by the first dissipation metal plate  63  of the cooling mechanism  28 , and the heat generated by the graphics chip  25 B is dissipated by the second dissipation metal plate  64  of the cooling mechanism  28 . 
     In the fourth embodiment, when both the north bridge  25 A and graphics chip  25 B should be cooled, both the first and second areas  27 A and  27 B can be reinforced by the reinforcing plate  65 . 
     Referring to  FIG. 10 , an electronic apparatus according to a fifth embodiment will be described. A portable computer  71  as an example of the electronic apparatus according to the fifth embodiment differs from the fourth embodiment in that the former incorporates a fan unit  72  and heat pipe  73 , and is similar to the latter in the other portions. Therefore, in this embodiment, elements similar to those of the first embodiment are denoted by corresponding reference numbers, and a description will be mainly given of different portions. 
     The portable computer  71  incorporates, in a housing  21 , a printed circuit board  26  with circuit components  25  mounted thereon. 
     The printed circuit board  26  comprises a printed wiring board  27  having a first area  27 A and second area  27 B adjacent thereto, circuit components  25  mounted on the first surface  27 C of the printed wiring board  27 , a cooling mechanism  28  for cooling the circuit components  25 , a reinforcing plate  29  attached to the second surface  27 D of the printed wiring board  27  in the area corresponding to one of the circuit components  25 , and first and second fixing portion  31  and  32  provided at the printed wiring board  27  to fix the reinforcing plate  29  to the wiring board  27 . The printed circuit board  26  further comprises a plate spring that presses the cooling mechanism  28  against the circuit components  25 . The reinforcing plate  29  is screwed to the printed wiring board  27  by screws (not shown). Although  FIG. 10  shows no plate spring and no screws, this embodiment employs the same plate spring structure as the first embodiment. 
     The printed wiring board  27  has the first area  27 A located on the left side in  FIG. 10 , the second area  27 B located adjacent thereto on the right side, and a border line  27 E defining the first and second areas  27 A and  27 B. The circuit components  25  are, for example, a north bridge  25 A and graphics chip  25 B. The north bridge  25 A is fixed to the first area  27 A of the printed wiring board  27 , and the graphics chip  25 B is fixed to the second area  27 B of the printed wiring board  27 . 
     The cooling mechanism  28  has a second heat-dissipating metal plate  64  attached to the graphics chip  25 B. 
     The reinforcing plate  29  has the same shape as that employed in the first embodiment, and is fixed to the second area  27 B. The first fixing portion  31  comprises a pair of elements provided at the printed wiring board  27  on the border line  27 E thereof. Specifically, the first fixing portion  31  comprises a pair of screw holes in the printed wiring board  27  on the border line  27 E. Similarly, the second fixing portion  32  comprises a pair of elements provided at the printed wiring board  27  symmetrical with respect to the border line  27 E. Specifically, the second fixing portion  32  comprises a pair of symmetrical screw holes in the printed wiring board  27 . 
     The main unit  12  of the fifth embodiment further comprises a fan unit  72  for accelerating the cooling operation of the cooling mechanism  28 , a heat pipe  73  for transmitting the heat of the cooling mechanism  28  to the fan unit  72 , and a heat sink  74  for accelerating the cooling operation of the heat pipe  73 . The heat sink  74  comprises a plurality of fins. One end of the heat pipe  73  is connected to the heat sink  74 , and the other end is connected to the cooling mechanism  28  secured to the graphics chip  25 B. 
     The heat pipe  73  is a cylindrical copper pipe and contains a liquid. The heat pipe  73  transmits the heat of the graphics chip  25 B to the heat sink  74  located near the fan unit  72 . The heat pipe  73  is located so that it does not overlap the first or second fixing portion  31  or  32  in position. The heat generated by the graphics chip  25 B is transmitted to the heat sink  74  via the second heat-dissipating metal plate  64  of the cooling mechanism  28  and heat pipe  73 . The heat of the heat sink  74  is exhausted to the outside of the housing  21  through the opening thereof by the air blown through the fan unit  72 . 
     In the portable computer  71  of the fifth embodiment, the first and second fixing portion  31  and  32  do not overlap the heat pipe  73 . With this structure, interference between the first and second fixing portion  31  and  32  and the heat pipe  73  can be avoided. Therefore, when, for example, the reinforcing plate  29  is detached from the printed circuit board  26 , the heat pipe  73  does not hinder the detachment. 
       FIG. 11  shows a modification of the fifth embodiment. In this modification, a circuit component  25  that comprises a north bridge  25 A containing a graphics chip is provided. The reinforcing plate  29  employed therein has the same shape as that of the first embodiment, and is attached to the first area  27 A. The other end of the heat pipe  73  is connected to the cooling mechanism  28  secured to the north bridge  25 A. The heat generated by the north bridge  25 A is transmitted to the heat sink  74  via the first heat-dissipating metal plate  63  of the cooling mechanism  28 , and the heat pipe  73 . In the fifth embodiment and its modification, the reinforcing plate  29  can be attached to any one of the first and second areas  27 A and  27 B. Further, since the first and second fixing portion  31  and  32  do not overlap the heat pipe  73  in position, the heat pipe  73  does not hinder the detachment when, for example, the reinforcing plate  29  is detached from the printed circuit board  26 . 
     Referring then to  FIG. 12 , an electronic apparatus according to a sixth embodiment will be described. A portable computer  81  as an example of the electronic apparatus according to the sixth embodiment differs from the fifth embodiment in that the former incorporates a fan unit  72  and heat pipe  73 , and is similar to the latter in the other portions. Therefore, in this embodiment, elements similar to those of the first embodiment are denoted by corresponding reference numbers, and a description will be mainly given of different portions. 
     The portable computer  81  of the sixth embodiment incorporates, in a housing  21 , a printed circuit board  82  with circuit components  25  mounted thereon. 
     The printed circuit board  82  comprises a printed wiring board  27  having a first area  27 A and second area  27 B adjacent thereto, circuit components  25  mounted on the first surface  27 C of the printed wiring board  27 , a cooling mechanism  28  for cooling the circuit component  25 , a reinforcing plate  53  attached to the second surface  27 D of the printed wiring board  27  in the area corresponding to one of the circuit components  25 , and first and second fixing portion  31  and  83  provided at the printed wiring board  27  to fix the reinforcing plate  53  to the wiring board  27 . The printed circuit board  82  further comprises a plate spring that presses the cooling mechanism  28  against the one circuit component  25 . The reinforcing plate  53  is screwed to the printed wiring board  27  by screws. Although  FIG. 12  shows no plate spring and no screws, this embodiment employs the same plate spring and screw structures as the first embodiment. 
     The printed wiring board  27  has the first area  27 A located on the left side in  FIG. 12 , the second area  27 B located adjacent thereto on the right side, and a border line  27 E defining the first and second areas  27 A and  27 B. The circuit components  25  are, for example, a north bridge  25 A and graphics chip  25 B. The north bridge  25 A is fixed to the first area  27 A of the printed wiring board  27 , and the graphics chip  25 B is fixed to the second area  27 B of the printed wiring board  27 . The cooling mechanism  28  has a second heat-dissipating metal plate  64  attached to the graphics chip  25 B. 
     The reinforcing plate  53  has the same shape as that employed in the third embodiment. The first fixing portion  31  comprises a pair of elements provided at the printed wiring board  27  on the border line  27 E thereof. Specifically, the first fixing portion  31  comprises a pair of screw holes in the printed wiring board  27  on the border line  27 E. The printed wiring board  27  also has a center point  27 F between the pair of elements, i.e., the pair of screw holes. The second fixing portion  83  comprises a pair of elements arranged point symmetrical with respect to the center point  27 F. Specifically, the second fixing portion  83  comprises a pair of screw holes formed in the printed wiring board  27  point symmetrical with respect to the center point  27 F. 
     The main unit  12  of the sixth embodiment further comprises a fan unit  72  for accelerating the cooling operation of the cooling mechanism  28 , a heat pipe  73  for transmitting the heat of the cooling mechanism  28  to the fan unit  72 , and a heat sink  74  for accelerating the cooling operation of the heat pipe  73 . The heat sink  74  comprises a plurality of fins. One end of the heat pipe  73  is connected to the heat sink  74 , and the other end is connected to the cooling mechanism  28  secured to the graphics chip  25 B. 
     The heat pipe  73  transmits the heat of the graphics chip  25 B to the heat sink  74  located near the fan unit  72 . The heat pipe  73  is located so that it does not overlap the first or second fixing portion  31  or  83  in position. The heat generated by the graphics chip  25 B is transmitted to the heat sink  74  via the second heat-dissipating metal plate  64  of the cooling mechanism  28  and heat pipe  73 . The heat of the heat sink  74  is exhausted to the outside of the housing  21  through the opening thereof by the air blown through the fan unit  72 . 
     In the sixth embodiment, the distance between the center point  27 F and one screw hole of the second fixing portion  83  is set equal to the distance between the center point  27 F and the other screw hole of the second fixing portion  83 . Therefore, reinforcing plates  53  of the same size and shape can be attached to both the first and second areas  27 A and  27 B. Further, the first fixing portion  31  formed of a pair of screw holes can be used in common when the reinforcing plate  29  is attached to the first area  27 A and when it is attached to the second area  27 B. 
     Furthermore, the first and second fixing portion  31  and  83  do not overlap the heat pipe  73  in position. With this structure, interference between the first and second fixing portion  31  and  83  and the heat pipe  73  can be avoided. Therefore, when, for example, the reinforcing plate  53  is detached from the printed circuit board  82 , the heat pipe  73  does not hinder the detachment. 
       FIG. 13  shows a modification of the sixth embodiment. In this modification, a circuit component  25  that comprises a north bridge  25 A containing a graphics chip is provided. The reinforcing plate  53  employed therein has the same shape as that of the third embodiment, and is attached to the first area  27 A. The other end of the heat pipe  73  is connected to the cooling mechanism  28  secured to the north bridge  25 A. 
     In the sixth embodiment and its modification, the reinforcing plate  29  can be attached to any one of the first and second areas  27 A and  27 B. Further, since the first and second fixing portion  31  and  83  do not overlap the heat pipe  73  in position, the heat pipe  73  does not hinder the detachment when, for example, the reinforcing plate  53  is detached from the printed circuit board  82 . 
     Referring last to  FIG. 14 , an electronic apparatus according to a seventh embodiment will be described. This embodiment employs the same reinforcing plate  65  as the fourth embodiment of  FIG. 8 . One end of the heat pipe  73  is connected to the heat sink  74 , and the other end is connected to the part of the cooling mechanism  28  secured to the graphics chip  25 B. The middle portion of the heat pipe  73  is connected to the part of the cooling mechanism  28  secured to the north bridge  25 A. In the seventh embodiment, the heat generated by the north bride  25 A and graphics chip  25 B is transmitted to the heat sink  74  via the heat-dissipating plates  63  and  64  of the cooling mechanism  28  and the heat pipe  73 . 
     In the seventh embodiment, when both the north bride  25 A and graphics chip  25 B are cooled by the heat pipe  73 , the heat pipe  73  does not interfere with the first and second fixing portion  31  and  83 . 
     The printed circuit boards and electronic apparatuses according to the above-described embodiments are not limited to portable computers, but also applicable to other type of electronic apparatuses such as cellular phones. Further, the printed circuit boards and electronic apparatuses can be modified in various ways without departing from the scope of the invention. Further, in each of the embodiments, although the first fixing portion  31  comprises a pair of screw holes in the printed wiring board  27  on the border line  27 E, it is not limited to them, but may be a single screw hole arranged on the border line  27 E. 
     While certain embodiments of the inventions 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 methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems 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.