Abstract:
According to an aspect of the present invention, there is provided a printed wiring board including: a substrate including an edge and a fixing hole located adjacent to the edge, the fixing hole configured to receive a bolt; and a land formed in a vicinity of the fixing hole and extending in at least a first direction and a second direction, the first direction being a direction from the fixing hole toward a center of the substrate, the second direction being direction along the edge.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/470,370 filed May 21, 2009, which is based upon and claims the benefit of priority from Japanese Patent Application No. 2008-232390, filed on Sep. 10, 2008, the entire contents of both which are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     An aspect of the present invention relates to a printed wiring board having lands and an electronic apparatus equipped with it. 
     2. Description of the Related Art 
     For example, a printed wiring board is disclosed in which lands for grounding are disposed around fixing holes for bolting of the printed wiring board. This printed wiring board is equipped with a substrate, the fixing holes which penetrate through the substrate, the lands which are donut-shaped and are formed around the respective fixing holes on the surface of the substrate, and cream solder members which are printed on the surfaces of the lands. 
     In printed wiring boards of this type, usually, the surfaces of the lands are subjected to solder plating to prevent corrosion of the lands and attain reliable grounding. A printed wiring board having a cost advantage over ones in which the lands are subjected to solder plating is provided by supplying solder also to the land surfaces when cream solder is supplied to mounting patterns of other components (see JP-A-2000-244080, for instance). 
     In recent years, with the increase in miniaturization and functionality of digital equipment, the high-density mounting on a printed wiring board and the securing of a wide mounting area have come to be required increasingly. However, the above donut-shaped lands raise a problem that the mounting area on the printed wiring board is reduced by areas corresponding to the spaces for formation of the lands. For another thing, to secure a wide mounting area on a printed wiring board, it is effective to locate the fixing holes as close to the outer periphery of the board as possible. However, in the printed wiring boards, the fixing holes cannot be located sufficiently close to the outer periphery because margins for formation of the donut-shaped lands need to be secured around the respective fixing holes. 
     Each of these margins needs to be set taking into consideration not only the space for formation of the land but also a variation that may occur when a land pattern is formed by etching. This is because if a land is formed in contact with the periphery the land is exposed in an end face of the printed wiring board, as a result of which the printed wiring board may be short-circuited with another component. This also requires sufficient margins around the respective fixing holes. 
     On the other hand, one method for reducing the above margins is to narrow the widths of the donut-shaped lands. However, if the land widths are narrowed, a land pattern may be disconnected due to a variation in forming the pattern. Furthermore, since the lands are reduced in strength, the land patterns are prone to peel off when bolting is performed through the fixing holes. 
     For the above reasons, the printed wiring boards cannot sufficiently satisfy the recent requirements of high-density mounting and securing of a wider mounting area. 
     SUMMARY 
     According to an aspect of the invention, there is provided a printed wiring board including: a substrate including an edge and a fixing hole located adjacent to the edge, the fixing hole configured to receive a bolt; and a land formed in a vicinity of the fixing hole and extending in at least a first direction and a second direction, the first direction being a direction from the fixing hole toward a center of the substrate, the second direction being direction along the edge. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       A general architecture that implements the various feature of the present invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the present invention and not to limit the scope of the present invention. 
         FIG. 1  is an exemplary perspective view of a portable computer according to a first embodiment; 
         FIG. 2  is an exemplary sectional view, taken in a horizontal plane, of a main body unit of the portable computer shown in  FIG. 1 ; 
         FIG. 3  is an exemplary plan view of a printed wiring board which is housed in a casing of the main body unit shown in  FIG. 2 ; 
         FIG. 4  is an exemplary sectional view, taken in a vertical plane, of the printed wiring board shown in  FIG. 3 ; 
         FIG. 5  is an exemplary plan view of a printed wiring board of a portable computer according to a modification of the first embodiment; 
         FIG. 6  is an exemplary plan view of a printed wiring board of a portable computer according to a second embodiment; 
         FIG. 7  is an exemplary sectional view, taken in a vertical plane, of the printed wiring board shown in  FIG. 6 ; 
         FIG. 8  is an exemplary plan view of a printed wiring board of a portable computer according to a third embodiment; 
         FIG. 9  is an exemplary plan view of a printed wiring board of a portable computer according to a fourth embodiment; 
         FIG. 10  is an exemplary perspective view of a printed wiring board which is housed in a casing of a hard disk drive according to a fifth embodiment; and 
         FIG. 11  is an exemplary sectional view, taken in a vertical plane, of the printed wiring board shown in  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
     An electronic apparatus according to a first embodiment will be described below with reference to  FIGS. 1 to 4 . As shown in  FIG. 1 , a portable computer as an example electronic apparatus is a so-called notebook personal computer. A description will be made with a notation that the forward direction and the backward direction are denoted by arrows F and R, respectively. 
     As shown in  FIG. 1 , the portable computer  11  is equipped with a main body unit  12 , a display unit  13 , and hinge mechanisms  14  which connect the main body unit  12  and the display unit  13 . Supporting the display unit  13 , the hinge mechanisms  14  make it possible to rotate the display unit  13  with respect to the main body unit  12 . The display unit  13  has a display  15  and a cover  16  surrounding the display  15 . The display  15  is a liquid crystal display, for example. 
     The main body unit  12  has a casing  21  made of a synthetic resin, a keyboard  22 , a touch pad  23  which is a pointing device, and buttons  24 . As shown in  FIGS. 2 and 4 , the main body unit  12  also has, inside the casing  21 , a printed circuit board  25  and bolts  26  for fixing of the printed circuit board  25  to the casing  21 . The printed circuit board  25  has a printed wiring board  31  and plural circuit components  32  which are mounted on the printed wiring board  31 . The plural circuit components  32  include a CPU and a north bridge. The bolts  26  are not illustrated in  FIG. 2 . The inside surfaces of the casing  21  are uniformly covered with a conductive ground layer  46 . The ground layer  46  prevents outward leakage of electromagnetic waves from the portable computer  11 . 
     For example, the printed wiring board  31  is a copper-clad lamination plate in which plural copper wiring layers are laminated. The printed wiring board  31  has a substrate  33  and a land  34  which is formed on the substrate  33 . The substrate  33  is formed by alternately laminating insulating layers (base members) made of a glass-cloth-incorporated resin and wiring layers sandwiched between the insulating layers. The substrate  33  has a first edge  35 A and a second edge  35 B which define part of the periphery of the substrate  33 , a fixing hole  36  which is located adjacent to the first edge  35 A and the second edge  35 B, and a conductive plating member  37  which covers the inside surface of the fixing hole  36 . The fixing hole  36  is located as close to the first edge  35 A and the second edge  35 B as possible. 
     As shown in  FIGS. 3 and 4 , the plating member  37  is made of a metal material, assumes a cylindrical shape, and is electrically connected to a ground member  41  which is disposed inside the substrate  33 . The plating member  37  is continuous with and is electrically connected to the land  34 . The ground member  41  is grounded to the ground layer  46  via the plating member  37  and the bolt  26 . 
     The substrate  33  has, in addition to the fixing hole  36 , through-holes  42  for bolting of the printed wiring board  31  to the casing  21 . A second land  43  having a conventional shape (i.e., a donut shape) is formed around the opening of each through-hole  42 . When the printed circuit wiring  31  is fixed to the casing  21 , the bolts  26  are inserted through the fixing hole  36  and the through-holes  42 . 
     The substrate  33  has, on its top surface, a pair of first regions  44  which extend along the respective edges  35  so as to assume band shapes. The land  34  is formed around (in a vicinity of) the fixing hole  36 . The land  34  extends from the fixing hole  36  in a range that is defined between a direction D 1  from the fixing hole  36  toward a central portion  45  of the substrate  33  and directions D 2  along the respective edges  35 . That is, the land  34  is sector-shaped and is formed so as to extend toward the central portion  45  of the substrate  33 . An angle of the sector shape of the land  34  is about 90 degrees. The land  34  is positioned outside the first regions  44 . For example, the land  34  is formed into the sector shape by etching the surface copper foil layer of the substrate  33 . 
     Although in the embodiment the plural through-holes  42  and the one fixing hole  36  are provided, the invention is not limited to such a case; plural fixing holes  36  may be provided so as to replace part of the through-holes  42 . In the embodiment, the fixing hole  36  is located adjacent to the two edges  35 A and  35 B, that is, the corner edge, of the printed wiring board  31  and the sector-shape angle of the land  34  is equal to about 90 degrees. However, the invention is not limited to such a case. As shown in  FIG. 5 , the fixing hole  36  may be located adjacent to one edge  35  of the printed wiring board  31 , in which case the sector-shape angle of the land  34  is equal to about 180 degrees (described later in detail). 
     In the first embodiment, the printed wiring board  31  is equipped with the substrate  33  having the edges  35  which define part of the periphery of the printed wiring board  31  and the fixing hole  36  which is located adjacent to the edges  35  and through which the bolt  26  is inserted and the land  34  which is formed around the fixing hole  36  and extends outward from the fixing hole  36  in the range that is defined between the direction D 1  going from the fixing hole  36  toward the central portion  45  of the substrate  33  and the directions D 2  that are along the edges  35 . 
     With this structure, the land  34  is formed along the direction D 1  which goes toward the central portion  45  of the substrate  33  and the land  34  is not formed between the fixing hole  36  and the edges  35 . As a result, no space for formation of the land  34  is required between the fixing hole  36  and the edges  35  and hence the fixing hole  36  can be located as close to the edges  35  as possible. Therefore, a wide mounting area can be secured on the printed wiring board  31 , which makes it possible to cope with the miniaturization of the printed wiring board  31  flexibly. Furthermore, since the land  34  need not be formed narrowly, a land pattern can be made sufficiently strong. This prevents a phenomenon that the land  34  is so weak that its pattern peels off when the bolt  26  is inserted through the fixing hole  36  for the purpose of fixing. Another problem can be prevented that a pattern of the land  34  is disconnected halfway when it is formed by etching. 
     The land  34  is formed outside the band-shaped first regions  44  which extend along the edges  35 . This structure prevents a problem that the land  34  is deviated to be exposed in an end face of the printed wiring board  31 . This makes it possible to locate the fixing hole  36  even closer to the edges  35 . Therefore, an even wider mounting area can be secured on the printed wiring board  31 . 
     The land  34  has the sector shape whose virtual apex is located in the fixing hole  36 , and extends toward the central portion  45 . With this structure, the land  34  is given sufficient strength though it is simple in shape. In particular, since the land  34  has the sector shape, the head of the bolt  26  can easily be brought into contact with the land  34 , whereby the printed wiring board  31  can be grounded to the ground layer  46  of the casing  21  reliably. 
     In the embodiment, the printed wiring board  31  is provided with the conductive plating member  37  which covers the inside surface of the fixing hole  36  and is continuous with the land  34 . With this structure, the contact area between the bolt  26  and the land  34 /plating member  37  is increased, whereby the printed wiring board  31  can be grounded to the ground layer  46  of the casing  21  more reliably. 
     A modification of the portable computer  11  according to the first embodiment will be described below with reference to  FIG. 5  (differences will be described mainly). In  FIG. 5 , members having the same members in the first embodiment are given the same reference symbols as the latter. 
     As shown in  FIG. 5 , a printed wiring board  31  has a substrate  33  and a land  34  which is formed on the substrate  33 . The substrate  33  has an edge  35  which defines part of the periphery of the substrate  33 , a fixing hole  36  which is located adjacent to the edge  35 , and a conductive plating member  37  which covers the inside surface of the fixing hole  36 . The fixing hole  36  is located as close to the edge  35  as possible. 
     The substrate  33  has, on its top surface, a pair of first regions  44  which extend along the edge  35  so as to assume band shapes. The land  34  is formed around (in the vicinity of) the fixing hole  36 . The land  34  extends outward from the fixing hole  36  in a range that is defined between a direction D 1  going from the fixing hole  36  toward a central portion  45  of the substrate  33  and directions D 2  that are along the edge  35 . That is, the land  34  is sector-shaped and is formed so as to extend toward the central portion  45  of the substrate  33 . The angle of the sector shape of the land  34  is about 180 degrees. The land  34  is disposed outside the first regions  44 . 
     According to the modification of the first embodiment, a wide mounting area can be secured on the printed wiring board  31  even in the case where the fixing hole  36  is located in the vicinity of one edge  35 . Furthermore, since the land  34  does not overlap with the band-shaped first regions  44  which extend along the edge  35 , a phenomenon that the land  34  is deviated to be exposed in an end face of the printed wiring board  31  can be prevented. 
     Next, a portable computer according to a second embodiment will be described with reference to  FIGS. 6 and 7 . The portable computer  11  as an example electronic apparatus according to the second embodiment is the same as that according to the first embodiment except that a printed wiring board  51  is not provided with the plating member  37  and through-hole plating members  52  which connect a land  34  to the ground member  41  are provided separately from a fixing hole  36 . Therefore, members that are different than in the first embodiment will mainly be described below, and members having the same members in the first embodiment will be given the same reference symbols as the latter and will not be described. 
     The printed wiring board  51  of the portable computer according to the second embodiment has a substrate  33 , the land  34  which is formed on the substrate  33 , and the through-hole plating members  52  which connect the land  34  to the ground member  41 . The through-hole plating members  52  are separate from the fixing hole  36 . The substrate  33  has, on its top surface, a pair of first regions  44  which extend along edges  35  so as to assume band shapes. The land  34  is formed around (in the vicinity of) the fixing hole  36 . The land  34  extends outward from the fixing hole  36  in a range that is defined between a direction D 1  going from the fixing hole  36  toward a central portion  45  of the substrate  33  and directions D 2  that are along the edges  35 . That is, the land  34  is sector-shaped and is formed so as to extend toward the central portion  45  of the substrate  33 . The angle of the sector shape of the land  34  is about 90 degrees. The land  34  does not overlap with the first regions  44 . 
     According to the second embodiment, a wide mounting area can be secured on the printed wiring board  51  as in the first embodiment even in the case where the plating member  37  is not provided. Furthermore, a manufacturing process can be made simpler than in the printed wiring board  31  according to the first embodiment by a degree corresponding to the elimination of the plating member  37 . 
     Next, a portable computer according to a third embodiment will be described with reference to  FIG. 8 . The portable computer  11  as an example electronic apparatus according to the third embodiment is the same as that according to the first embodiment except for the shape of a land  72  of a printed wiring board  71 . Therefore, members that are different than in the first embodiment will mainly be described below, and members having the same members in the first embodiment will be given the same reference symbols as the latter and will not be described. 
     The printed wiring board  71  of the portable computer  11  according to the third embodiment has a substrate  33  and the land  72  which is formed on the substrate  33 . The substrate  33  has, on its top surface, a pair of first regions  44  which extend along edges  35  so as to assume band shapes. The land  72  is formed around (in the vicinity of) the opening of a fixing hole  36 . The land  72  extends outward from the fixing hole  36  in a range that is defined between a direction D 1  going from the fixing hole  36  toward a central portion  45  of the substrate  33  and directions D 2  that are along the edges  35 . The land  72  is disposed outside the first regions  44  or a second region  73  that is located between the fixing hole  36  and the central portion  45 . More specifically, the land  72  extends outward from the fixing hole  36  in two directions that are along the edges  35  so as to generally assume an L shape as a whole. The land  72  is continuous with a plating member  37 . 
     In the third embodiment, the land  72  is disposed outside the second region  73  which is located between the fixing hole  36  and the central portion  45 . With this structure, the second region  73  can be used as a mounting area; for example, interconnections and circuit components can be disposed in the second region  73 . Therefore, a wider mounting area can be secured on the printed wiring board  71  than even on the printed wiring board  31  of the first embodiment. Furthermore, since a pattern of the land  72  is formed by, for example, etching a copper foil, the manufacturing process is not made more complex than in the first embodiment. 
     Next, a portable computer according to a fourth embodiment will be described with reference to  FIG. 9 . The portable computer  11  as an example electronic apparatus according to the fourth embodiment is the same as that according to the second embodiment except for the shape of lands  82  of a printed wiring board  81 . Therefore, members that are different than in the second embodiment will mainly be described below, and members having the same members in the second embodiment will be given the same reference symbols as the latter and will not be described. 
     The printed wiring board  81  of the portable computer  11  according to the fourth embodiment has a substrate  33 , the lands  82  which are formed on the substrate  33 , and through-hole plating members  52  which connect the respective lands  82  to a ground member  41 . The substrate  33  has, on its top surface, a pair of first regions  44  which extend along edges  35  so as to assume band shapes. The lands  82  are formed around (in the vicinity of) the opening of a fixing hole  36 . The lands  82  extend outward from the fixing hole  36  in a range that is defined between a direction D 1  going from the fixing hole  36  toward a central portion  45  of the substrate  33  and directions D 2  that are along the edges  35 . The lands  82  are disposed outside the associated first regions  44 . 
     The land  82  is located outside a second region  73  that is located between the fixing hole  36  and the central portion  45 . More specifically, the lands  72  extend outward from the fixing hole  36  in two respective directions that are along the edges  35 . In this embodiment, the lands  82  are disposed separately at the two positions around the fixing hole  36 . 
     In the fourth embodiment, the lands  82  do not overlap with the second region  73  which is located between the fixing hole  36  and the central portion  45 . With this structure, as in the third embodiment, a wider mounting area can be secured on the printed wiring board  81  than even on the printed wiring board  51  of the second embodiment. Furthermore, the manufacturing process is not made more complex than in the second embodiment even if the lands  82  have the above-described shapes. 
     Next, an electronic apparatus according to a fifth embodiment will be described with reference to  FIGS. 10 and 11 . The fifth embodiment is directed to a case that the invention is applied to a hard disk drive  91  which is an example electronic apparatus. Although individual components of the hard disk drive are different in structure than in the first to fourth embodiments, the structure of a printed wiring board  51  is approximately the same as in the second embodiment. Therefore, members that are different than in the second embodiment will mainly be described below, and members having the same members in the second embodiment will be given the same reference symbols as the latter and will not be described. 
     The hard disk drive  91  is equipped with a casing  21 , a printed circuit board  25  which is housed in the casing  21 , a housing  92  which houses plural disks, a spindle motor  93  for rotationally driving the plural disks, and other components. The hard disk drive  91  also has bolts  26  (not shown in  FIG. 10 ) for fixing of the printed circuit board  25  to the casing  21 . The printed circuit board  25  has the printed wiring board  51  and plural circuit components (not shown in  FIGS. 10 and 11 ) which are disposed on the printed wiring board  51 . 
     The printed wiring board  51  is different from that of the second embodiment in that the former has an opening  94  where the spindle motor  93  is disposed, they are the same in structure in the other points. A substrate  33  of the printed wiring board  51  has one fixing hole  36  around which a sector-shaped land  34  is formed and two through-holes  42  around which donut-shaped second lands  43  are formed, respectively. The land  34  is the same as that of the second embodiment. 
     According to the fifth embodiment, even in the hard disk drive  91  which is an example electronic apparatus, the fixing hole  36  can be located as close to the edges  35  as possible and hence a wide mounting area can be secured on the printed wiring board  51 . This makes it possible to cope with the miniaturization of the printed wiring board  51  flexibly and to thereby miniaturize the hard disk drive  91  as a whole. 
     Although the printed wiring board  51  of the fifth embodiment is similar to that of the second embodiment, this aspect of the invention is not limited to such a case. That is, a printed wiring board similar to the printed wiring board of the first, third, or fourth embodiment may be used. 
     The electronic apparatus according to the invention is not limited to portable computers and hard disk drives, and the invention can also be applied to other kinds of electronic apparatus such as a cell phone. Other various modifications can be made of the above-described electronic apparatus without departing from the spirit and scope of the invention.