Abstract:
A technique is provided for improvement in convenience and in cost reduction of a fixing part of a printed board unit. A printed board unit includes a plurality printed board including a first printed board and a second printed board; and at least one fixing part, interposed between the first printed board and the second printed board, fixing the first printed board and the second printed board such that the first printed board and the second printed board overlap and keep a predetermined space between the first printed board and the second printed board, and the fixing part variably determines the predetermined space.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Application No. 2008-001267, filed on Jan. 8, 2008 in Japan, the entire contents of which are hereby incorporated by reference. 
       FIELD 
       [0002]    The embodiments discussed herein are directed to a fixing part to fix two printed boards of a printed board unit, keeping a predetermined space between the boards. 
       BACKGROUND 
       [0003]    In accordance with improvement in functions and throughput of recent electronic devices, there have been provided a composite substrate (hereinafter called a printed board unit) in which a number of printed boards have different functions and are one another coupled by flexible wiring boards with the intention of avoiding the generation of interference (noise) caused by signal patterns having different functions. 
         [0004]    Since demands for electronic devices highly integrated and compact in size increase the number of elements to be mounted to a specific board region, a single printed board is incapable of accommodating all the elements. As one of the solutions, there are provided many printed board units each in which a number of printed board are formed into a stack and are one another coupled via cables and connectors. 
         [0005]    Some techniques have conventionally arranged a number of printed boards to keep predetermined space via fixing parts (spacers) in such a printed board unit. 
         [0006]    For example, as shown in  FIGS. 24A and 24B , conventional printed board unit  100  includes printed boards  101  and  102  fixed to each other such that printed board  103  overlaps printed board  101  via spacer  102 .  FIG. 24A  is the top view of printed board unit  100 , and  FIG. 24B  is the front view of printed board unit  100 . 
         [0007]    Spacer  102  is coupled to printed boards  101  and  103  by screws or sets of a bolt and a nut. 
         [0008]    Signal patterns formed on printed boards  101  and  103  are connected to each other by flexible wiring board (FPC: Flexible Printed Circuit board)  104  to let printed boards  101  and  103  cooperate. For example, printed board  101  and printed board  103  function as a common circuit and a high-speed signal unit, respectively. (For example, Japanese Patent Application Laid-Open No. 2003-110210, Japanese Patent Application Laid-Open No. 2003-283072, and Japanese Patent Application Laid-Open No. HEI 8-330699) 
         [0009]    Conventionally, spacer  102  has been designed for each printed board unit  100 . In other words, the height and other outlines of spacer  102  is determined according to elements to be mounted on printed board  101  and printed board  103  and a location of installation of printed board unit  100  when printed board unit  100  is designed. 
         [0010]    For this reason, if a variation or addition of elements to be mounted on printed board  101  or  103  requires modification of spacer  102 , the height of spacer  102  is re-determined and another spacer is newly produced, giving inconvenience and increasing the production cost for another spacer. 
         [0011]    In production of a number of different kinds of printed board units  100 , spacers  102  have to be designed one for each kind of printed board unit  100 , requiring both workload and cost. 
       SUMMARY 
       [0012]    There is provided a printed board unit comprising: a plurality printed board including a first printed board and a second printed board; and at least one fixing part, interposed between the first printed board and the second printed board, fixing the first printed board and the second printed board such that the first printed board and the second printed board overlap and keep a predetermined space between the first printed board and the second printed board, wherein the fixing part variably determines the predetermined space. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The nature of this invention, as well as other objects and advantages thereof, will be explained in the following with reference to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures and wherein: 
           [0014]      FIGS. 1A-1C  are diagrams schematically illustrating a printed board unit according to a first embodiment;  FIG. 1A  is the top view,  FIG. 1B  is a side view seen from the right; and  FIG. 1C  is the front view; 
           [0015]      FIGS. 2A and 2B  are diagrams schematically illustrates the divided structure of a fixing part of the printed board unit of the first embodiment;  FIG. 2A  is a front view of the fixing part being combined; and  FIG. 2B  is a front view of the fixing part being divided; 
           [0016]      FIGS. 3A and 3B  are diagrams showing increase or decrease in the length of the fixing unit of the printed board unit of the first embodiment;  FIG. 3A  is a front view of the printed board unit with the fixing part formed of a first fixing piece, a second fixing piece, and first intermediate fixing piece; and  FIG. 3B  is a front view of the printed board with the fixing part additionally including a second intermediate fixing piece to that shown in  FIG. 3A ; 
           [0017]      FIGS. 4A and 4B  are diagrams showing an exemplary fixing part of the printed board unit of the first embodiment;  FIG. 4A  shows a state before pieces are combined; and  FIG. 4B  shows a state after all the pieces shown in  FIG. 4A  are combined; 
           [0018]      FIGS. 5A and 5B  are diagrams showing the first intermediate fixing piece of the fixing part of the printed board unit of the first embodiment;  FIG. 5A  is the top view; and  FIG. 5B  is the A-A′ sectional view of  FIG. 5A ; 
           [0019]      FIGS. 6A and 6B  are diagrams showing a connection structure between the printed board and the fixing part of the printed board unit of the first embodiment;  FIG. 6A  is the top view of the printed board; and  FIG. 6B  is a perspective view of the printed board with lands into which tips of the fixing part are being inserted; 
           [0020]      FIG. 7  is a B-B′ sectional view of  FIG. 6A  showing the state of a tip of the fixing part being inserted into a land of the printed board and soldered to the land on a printed board of the printed board unit according to the first and the second embodiments; 
           [0021]      FIG. 8  is a diagram schematically showing a configuration of a rigid wiring board of a conventional printed board unit; 
           [0022]      FIGS. 9A-9C  are diagrams schematically illustrating a printed board unit according to a second embodiment;  FIG. 9A  is the top view,  FIG. 9B  is a side view seen from the right; and  FIG. 9C  is the front view; 
           [0023]      FIG. 10  is a perspective view showing an exemplary fixing part of the printed board unit according to the second embodiment; 
           [0024]      FIGS. 11A and 11B  are diagrams an exemplary configuration of the fixing part of the printed board unit of the second embodiment;  FIG. 11A  shows a state before pieces are combined; and  FIG. 11B  shows a state after all the pieces shown in  FIG. 11A  are combined; 
           [0025]      FIGS. 12A-12D  are diagrams showing the structure of a first fixing piece and a second fixing piece of the fixing part of the printed board unit of the second embodiment;  FIG. 12A  is the front view of the first fixing piece and the second fixing piece;  FIG. 12B  is the top view thereof;  FIG. 12C  is the bottom view thereof; and  FIG. 12D  is the side view seen from the right; 
           [0026]      FIGS. 13A-13E  are diagrams showing the configuration of the second intermediate fixing piece of the fixing part of the printed board of the second embodiment;  FIG. 13A  is the front view of the second intermediate fixing piece;  FIG. 13B  is the top view thereof;  FIG. 13C  is the bottom view thereof,  FIG. 13D  is the side view seen from the right; and  FIG. 13E  is the C-C′ sectional view of  FIG. 13B ; 
           [0027]      FIG. 14  is a perspective view showing a second intermediate fixing piece of the fixing part of the printed board unit of the second embodiment; 
           [0028]      FIGS. 15A-15G  are diagrams showing transition of from the combining state of the second fixing piece and the second intermediate fixing piece to the drawing state of the pieces;  FIG. 15A  shows a state before the combining;  FIG. 15B  shows a state of the start of the combining;  FIG. 15C  shows a state of being in the middle of the combining;  FIG. 15D  shows a state of the completion of the combining;  FIG. 15E  shows a state of being in the middle of the drawing;  FIG. 15F  shows a state of being at the end of the drawing and  FIG. 15G  shows S a state of being the completion of the drawing; 
           [0029]      FIGS. 16A-16E  are diagrams showing the configuration of the first intermediate fixing piece of the fixing part of the printed board unit of the second embodiment;  FIG. 16A  is the front view of the first intermediate fixing piece;  FIG. 16B  is the top view;  FIG. 16C  is the bottom view;  FIG. 16D  is the side view seen from the right; and  FIG. 16E  is the D-D′ sectional view of  FIG. 16B ; 
           [0030]      FIG. 17  is a perspective view illustrating the first intermediate fixing piece of the fixing part of the printed board unit of the second embodiment; 
           [0031]      FIGS. 18A and 18B  are diagrams showing an exemplary fixing part of the printed board unit of a modification of the present invention;  FIG. 18A  shows a state before pieces are combined; and  FIG. 18B  shows a state after all the pieces shown in  FIG. 18A  are combined; 
           [0032]      FIGS. 19A and 19B  are diagrams showing an exemplary fixing part of the printed board unit of another modification;  FIG. 19A  shows a state before pieces are combined; and  FIG. 19B  shows a state after all the pieces shown in  FIG. 19A  are combined; 
           [0033]      FIG. 20  is a perspective view illustrating a fixing part of a printed board unit according to a modification; 
           [0034]      FIG. 21  is a diagram showing the configuration of the fixing part of the printed board unit of  FIG. 20 ; 
           [0035]      FIG. 22  is a diagram showing the configuration of a printed board of the printed board unit of  FIG. 20 ; 
           [0036]      FIGS. 23A and 23B  are diagram showing the configuration of the fixing part shown in  FIG. 20 ;  FIG. 23A  shows a state before adjustment of the predetermined space between printed boards; and  FIG. 23B  shows a state in which the predetermined space has been adjusted to be narrow; and 
           [0037]      FIGS. 24A and 24B  are diagram showing the configuration a conventional printed board unit;  FIG. 24A  is the top view of the printed board unit, and  FIG. 24B  is the front view thereof. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0038]    Various preferred embodiments of the present invention will now be described with reference to the accompanying drawings. 
       (1) First Embodiment 
       [0039]    First, the configuration of printed board unit  1 - 1  of the first embodiment will now be described with reference to  FIGS. 1A-1C .  FIGS. 1A ,  1 B, and  1 C are the top view, the side view seen from the right and the front view of printed board unit  1 - 1 . 
         [0040]    As shown in  FIGS. 1A-1C , printed board unit  1 - 1  comprises printed boards (rigid wiring boards)  2  and  3 , flexible wiring board (e.g., FPC)  4 , and two fixing parts  10 . 
         [0041]    Printed boards  2  and  3  mount electronic parts and elements thereon, but the parts and elements do not appear in  FIGS. 1A-1C  and  FIGS. 2A ,  2 B,  3 A,  3 B,  6 A and  6   b  to be detailed below for the purpose of simplification. 
         [0042]    Wiring board  4  connects wiring patterns on printed board  2  and  3  to each other and has flexibility. 
         [0043]    The connection established by wiring board  4  makes printed boards  2  and  3  to co-operate. For example, printed board  2  and printed board  3  function as a common circuit and a high-speed signal unit, respectively. 
         [0044]    Fixing part  10  is interposed between printed board  2  and printed board  3  and fixes printed board  2  and printed board  3  such that printed boards  2  and  3  overlap, keeping a predetermined space. 
         [0045]    Fixing part  10  is coupled to printed boards  2  and  3  by solder, which is represented by reference number  10   a  in  FIGS. 1A-1C . 
         [0046]    Fixing part  10  has a divided structure and specifically includes first fixing piece  11  fixed to printed board  3 , second fixing piece  12  fixed to printed board  2 , and first intermediate fixing piece  13  interposed between first fixing piece  11  and second fixing piece  12 . 
         [0047]    In other words, fixing part  10  is formed of a number of fixing pieces  11 - 13  connected in the direction in which the predetermined space between printed boards  2  and  3  varies. An increase or a decrease in the number of second intermediate fixing pieces  14  (see  FIGS. 3 and 4  to be described below) to be detailed below can vary the length of the predetermined space between printed boards  2  and  3 . 
         [0048]    Specifically as shown in  FIG. 2A , first fixing piece  11  and second fixing piece  12  are individually coupled to first intermediate fixing piece  13  via spring washers  10   b.  Here, spring washer  10   b  is a piece of a washer having elasticity (repulsion). The presence of spring washers  10   b  makes it possible to prevent vibration or other causes from loosing the fitting state between first fixing piece  11  and first intermediate fixing piece  13  and between second fixing piece  12  and first intermediate fixing piece  13 . 
         [0049]    Further, first fixing piece  11  includes conductive tips (leads)  11   a,  which electrically couple first fixing piece  11  to printed board  3 . Similarly, second fixing piece  12  includes conductive tips  12   a,  which electrically couple second fixing piece  12  to printed board  2 . The electrically connection between first fixing piece  11  and printed board  3  and that between second fixing piece  12  and printed board  2  are detailed below with reference of  FIGS. 6A ,  6 B and  7 . 
         [0050]    First fixing piece  11 , second fixing piece  12 , first intermediate fixing piece  13 , and second intermediate fixing piece  14  each individually takes the form of a hexagonal prism. In particular, first intermediate fixing piece  13  and second intermediate fixing piece  14  are configured to be easily rotatable with hands and spanners. Such a configuration allows a fabricator to easily attach and remove first intermediate fixing piece  13  and second intermediate fixing piece  14 . 
         [0051]    Fixing part  10  is configured to be divided into pieces as shown  FIG. 2B  from a state shown in  FIG. 2A . 
         [0052]    First fixing piece  11  comprises male screw  11   b  projecting toward printed board  2 , which screw screws into a female screw (i.e., female screw  13   a  shown in  FIG. 5B  detailed below) of first intermediate fixing piece  13  to couple first fixing piece  11  to first intermediate fixing piece  13 . The structure detachably couples first fixing piece  11  and first intermediate fixing piece  13 . 
         [0053]    Similarly, second fixing piece  12  comprises male screw  12   b  projecting toward printed board  3 , which screw screws into a female screw (female screw  13   b  of FIG.  5 B to be described below) of first intermediate fixing piece  13  to couple second fixing piece  12  to first intermediate fixing piece  13 . The structure detachably couples second fixing piece  12  and first intermediate fixing piece  13 . 
         [0054]    Fixing part  10  is configured to vary from a state shown in  FIG. 3A  to a state shown in  FIG. 3B  in which fixing part  10  additionally includes single second intermediate fixing piece  14 . 
         [0055]    The example shown in  FIG. 3B  additionally have second intermediate fixing piece  14  interposed between first fixing piece  11  and first intermediate fixing piece  13 . The addition changes the predetermined space W 1  between printed boards  2  and  3  shown in  FIG. 3A  to space W 2  larger than space W 1 . Here, since wiring board  4  is flexible, the bending of wiring board  4  varies with an increase or a decrease (widening or narrowing) in the length of fixing part  10 . Accordingly, wiring board  4  does not inhibit the adjustment of the predetermined space between printed boards  2  and  3  conducted by increasing and decreasing the length of fixing part  10 . 
         [0056]    Here, description will be made in relation to the detailed structure of first intermediate fixing piece  13  and second intermediate fixing piece  14  of fixing part  10  with reference to  FIGS. 4A ,  4 B,  5 A and  5 B. The example shown in  FIGS. 4A and 4B  has second intermediate fixing pieces  14  interposed between first fixing piece  11  and first intermediate fixing piece  13  and between second fixing piece  12  and first intermediate fixing piece  13 . 
         [0057]    As shown in  FIG. 4A , second intermediate fixing piece  14  comprises female screw  14   a  into which male screw  11   b  of first fixing piece  11  or male screw  12   b  of second fixing piece  12  is screwed. Further, second intermediate fixing piece  14  comprises male screw  14   b  projecting toward printed board  2  or printed board  3  on the opposite side to that with female screw  14   a.  In  FIG. 4A , female screw  14   a  of second intermediate fixing piece  14  does not appear which screw is to be coupled to second fixing piece  12 . However, the same second intermediate fixing piece  14  coupled to second fixing piece  12  comprises female screw  14   a  on the opposite side to that with female screw  14   b  similarly to another second intermediate fixing piece  14  to be coupled to first fixing piece  11 . 
         [0058]    First intermediate fixing piece  13  comprises female screw  13   a  into which male screw  11   b  of first fixing piece  11  or female screw  14   b  of second intermediate fixing piece  14  is screwed. 
         [0059]    Namely, in the example shown in  FIGS. 4A and 4B , into female screw  13   a  of first intermediate fixing piece  13 , female screw  14   b  of second intermediate fixing piece  14  is screwed, but removal of second intermediate piece  14  causes male screw  11   a  of first fixing piece  11  to screw into female screw  13   a.    
         [0060]    Here,  FIG. 5A  is the top view of first intermediate fixing piece  13  and  FIG. 5B  is the A-A′ sectional view of  FIG. 5A . 
         [0061]    As shown in  FIG. 5B , first intermediate fixing piece  13  includes female screw  13   b,  into which male screw  12   b  of second fixing piece  12  or female screw  14   b  of second intermediate fixing piece  14  is screwed, on the opposite side to the side with female screw  13   a.    
         [0062]    Counterclockwise turning first intermediate fixing piece  13  when pieces are combined one another to form fixing part  10  shown in  FIG. 4B  unscrews male screw  14   b  of second intermediate fixing piece  14  between first intermediate fixing piece  13  and first fixing piece  11  from first intermediate fixing piece  13   a  and concurrently unscrews male screw  14   b  of second intermediate fixing piece  14  between first intermediate fixing piece  13  and second fixing piece  12  from female screw  13   b.    
         [0063]    Conversely, in order to screw second intermediate fixing pieces  14  between first intermediate fixing piece  13  and first fixing piece  11  and between first intermediate fixing piece  13  and second fixing piece  12  into first intermediate fixing piece  13 , clockwise turning first intermediate fixing piece  13  while predetermined force is applied to contact each of male screws  14   b  of both of second intermediate fixing pieces  14  with corresponding one of female screws  13   a  and  13   b,  so that two male screws  14   b  simultaneously screw into corresponding female screws  13   a  and  13   b  to couple two second intermediate fixing pieces  14  to first intermediate fixing piece  13 . 
         [0064]    Further, in the example shown in  FIGS. 4A and 4B , into female screw  13   b  of first intermediate fixing piece  13 , male screw  13   a  of second intermediate fixing piece  14  is screwed. When second intermediate fixing piece  14  is removed, male screw  12   a  of second fixing piece  12  screws into female screw  13   a.    
         [0065]    Properly coupling all the pieces shown in  FIG. 4A  forms fixing part  10  shown in  FIG. 4B . Removal of second intermediate fixing piece  14  decrease the height of fixing part  10 , so that the space between printed boards  2  and  3  can be adjusted to be narrower. 
         [0066]    On the other hand, fixing part  10  being in the state shown in  FIG. 4B  has a structure in which one of more second intermediate fixing pieces  14  can be inserted between first fixing piece  11  and second intermediate fixing piece  14 , between second intermediate fixing piece  14  and first intermediate fixing piece  13 , and/or between second intermediate fixing piece  14  and second fixing piece  12 . In other words, female screw  14   a  of second intermediate fixing piece  14  is accommodatable female screw  14   b  of another second intermediate fixing piece  14 , so that the female screw  14   b  can screw into female screw  14   a.    
         [0067]    Addition of one of more second intermediate fixing pieces  14  to fixing part  10  increases the height of fixing part  10 , so that the space between printed boards  2  and  3  is adjusted to be wider. 
         [0068]    Fixing part  10  is made of conductive material and is connected to the power supplying wire of printed board  2  to supply electricity to printed board  3 . 
         [0069]    For example, spring washer  10   b,  first fixing piece  11 , second fixing piece  12 , first intermediate fixing piece  13  and second intermediate fixing piece  14  are formed of conductive material, which is preferably covered with insulation material (e.g., insulation resin). That avoids generation of noise caused from electricity supply through fixing part  10 , so that there is no adverse effect on electronic parts (not shown) and signal patterns (not shown) of printed boards  2  and  3 . In addition, the insulation cover can prevent a person touching fixing part  10  from receiving an electric shock. 
         [0070]    Here, description will now be made in relation to a specific connection structure between fixing part  10  and each of printed boards  2  and  3  with reference to  FIGS. 6A ,  6 B and  7 . 
         [0071]    As shown in  FIG. 6A , printed board  3  includes through-hole lands (hereinafter simply called lands)  5  which have been plated for insertion and into which tips  11   a  of first fixing piece  11  are inserted. Here, since first fixing piece  11  includes four tips  11   a,  printed board  3  has four lands  5  corresponding one to each tip  11   a.    
         [0072]    As shown in  FIG. 6B , each of lands  5  in which tip  11   a  is being inserted is soldered such that tip  11   a  is covered, and first fixing piece  11  of fixing part  10  is thereby coupled to printed board  3 . 
         [0073]      FIG. 6B  shows only insertion of first fixing piece  11 , but tips  12   a  of second fixing piece  12  are inserted to lands  5  of printed board  2  similarly to tips  11   a.  Keeping the above insertion state, lands  5  on printed board  2  are soldered such that tips  12   a  are covered, and second fixing piece  12  of fixing part  10  is thereby is coupled to printed board  2 . 
         [0074]      FIG. 7  is a B-B′ sectional view of  FIG. 6A  in which tip  11   a  of first fixing piece  11  is inserted into land  5  and is soldered to a printed board. Here, although solder  10   a  shown in above  FIGS. 1A-1C  collectively solders the four tips  11   a  to cover all the tips, solder  10   a  shown in  FIG. 7  solders an individual tip  11   a.  The present invention does not limit the soldering manner. 
         [0075]    As shown in  FIG. 7 , printed board  3  has an inner layer with power supplying patterns  3   a  and  3   b,  and lands  5  are formed of conductive material and contacting electricity supply patterns  3   a  and  3   b.    
         [0076]    Soldering land  5  and tip  11   a  of first fixing piece first fixing piece  11  being inserted into the land  5  electrically couples the tip  11   a  and the land  5 . 
         [0077]    Accordingly, tips  11   a  of first fixing piece  11  are electrically coupled to power supplying patterns  3   a  and  3   b  via land  5 . 
         [0078]    In the same manner, tips  12   a  of second fixing piece  12  are electrically coupled to power supplying pattern (an electricity source wire) or the like on printed board  2  via lands  5 . It is preferable that printed board  2  has an inner layer with an electricity supply pattern. 
         [0079]    Electrically coupling first fixing piece  11  to printed board  3  makes it possible to supply power to printed board  3  from printed board  2  through fixing part  10 . 
         [0080]    For example, when fixing part  10  shown in  FIG. 4B  is coupled to printed boards  2  and  3 , electricity from printed board  2  is flown through, in sequence from the bottom of  FIG. 4B , second fixing piece  12 , second intermediate fixing piece  14 , first intermediate fixing piece  13 , second intermediate fixing piece  14 , and first fixing piece  11  and is finally supplied to printed board  3  by tips  11   a.  Alternatively, electricity may also be flown through spring washers  10   b.    
         [0081]    Tips  12   a  of second fixing piece  12  are preferably coupled to lands  5  of printed board  2  in the same manner as the connection between tips  11   a  of first fixing piece  11  and lands  5  of printed board  3  because soldering first fixing piece  11  and second fixing piece  12  respectively to printed board  3  and printed board  2  improves the conductivity as compared with connection by means of screws. 
         [0082]    To ensure power supplying to printed board  103  from printed board  101 , there has conventionally been formed electricity supply pattern  105  on flexible wiring board  104 , as shown in  FIG. 8 . 
         [0083]    However, power supplying pattern  105  has adverse effects such as noise on signal pattern  106  of wiring board  104 . To avoid this, wiring board  104  has required a space more than a predetermined length between electricity supply pattern  105  and signal pattern  106 , resulting in widening wiring board  104  and hindering the high integration. 
         [0084]    Another solution may form wiring board  104  into a multilayer and may position signal pattern  106  and power supplying pattern  105  in different layers. However, this case also results in an increase in the thickness of wiring board  104 , hindering the high integration and rising the cost. 
         [0085]    Printed board unit  1 - 1  of the present invention supplies power from printed board  2  to printed board  3  through fixing part  10  without wiring board  4 . Electronic devices incorporating printed board unit  1 - 1  of the present invention can therefore be highly integrated without cost rise. 
         [0086]    As described above, printed board unit  1 - 1  of the first embodiment of the present invention has fixing part  10  which fixes printed boards  2  and  3  such that the printed boards  2  and  3  overlap and keep a predetermined space and which can vary the predetermined space. With this configuration, since the space between printed boards  2  and  3  can vary without requiring another fixing part, fixing part  10  serving as a spacer has an improved convenience and lowers the cost as compared with the preparation of another fixing part. 
         [0087]    Further, in fabrication of a different printed board unit from printed board unit  1 - 1 , there is no requirement to design and produce another fixing part for the new printed board unit, improving the convenience and decreasing the fabrication cost. In addition, even if the space between printed boards  2  and  3  needs to vary according to electronic devices to be mounted on printed board unit  1 - 1 , a conventional printed board unit cannot endure the variation, but printed board unit  1 - 1  of the first embodiment can cope with the variation. 
         [0088]    Fixing part  10  consists of a number pieces coupled in a direction in which the predetermined space between printed boards  2  and  3  is lengthened and shortened, and increase or decrease in the number of pieces can be vary the predetermined space. In other words, fixing part  10  has a divided structure and can increase or decrease the number of pieces constituting fixing part  10 . Accordingly, the predetermined space between printed boards  2  and  3  can be freely modified any number of times after the formation of printed board unit  1 - 1 , improving the convenience. 
         [0089]    Specifically, since fixing part  10  includes first fixing piece  11 , second fixing piece  12 , first intermediate fixing piece  13 , and optionally one or more second intermediate fixing pieces  14 , the above advantages can be surely attained, and even after the fabrication of printed board unit  1 - 1 , the space between printed boards  2  and  3  can be easily modified. 
         [0090]    The divided structure of fixing part  10  makes it possible to adjust the space by adding or removing one or more second intermediate fixing pieces  14 , keeping first fixing piece  11  and second fixing piece  12  to be fixed to printed boards  2  and  3 , respectively. Therefore, first fixing piece  11  and second fixing piece  12  can be soldered to printed boards  2  and  3 , respectively. As compared with a fixing part coupled to printed boards by screwing as performed in conventional techniques, the conductivity can be enhanced between first fixing piece  11  and printed board  2  and between second fixing piece  12  and printed board  3 . 
         [0091]    Further, first fixing piece  11  has male screw  11   b  projecting toward printed board  2 ; second fixing piece  12  has male screw  12   b  projecting toward printed board  3 ; second intermediate fixing piece  14  has female screw  14   a  into which male screw  11   b  of first fixing piece  11  or male screw  12   b  of second fixing piece  12  is screwed and male screw  14   b  projecting toward printed board  2  or printed board  3  on the opposite side to that with female screw  14   a;  and first intermediate fixing piece  13  has female screw  13   a  into which male screw  11   b  of first fixing piece  11  and male screw  14   b  of second intermediate fixing piece  14  is screwed and female screw  13   b  into which male screw  12   b  of second fixing piece  12  or female screw  14   b  of second intermediate fixing piece  14  is screwed. With this configuration, simple rotation of first intermediate fixing piece  13  and/or second intermediate fixing piece  14  in a specific direction divides and assembles fixing part  10 , so that increase and decrease in the length of fixing part  10 , i.e., the space between printed boards  2  and  3 , can be adjusted with ease, further improving the convenience. 
         [0092]    Further, fixing part  10  is made of a conductive material and supplies electricity from printed board  2  to printed board  3 , so that printed board unit  1 - 1  can be fabricated to be compact in size with a low cost. 
         [0093]    Since the outer circumference of the conductive material forming fixing part  10  is covered with an insulation material, an adverse effect such as noise does not affect wiring patterns on printed boards  2  and  3  even when fixing part  10  supplies electricity from printed board  2  to printed board  3 . 
         [0094]    Fixing part  10  has conductive tips  11   a  and  12   a,  and printed boards  2  and  3  have lands  5  into which corresponding tips are inserted. Soldering tips  11   a  and  12   a  being inserted into lands  5  of printed boards  2  and  3  to lands  5  fixes fixing part  10  to printed boards  2  and  3 , resulting in improved conductivity between fixing part  10  and printed boards  2  and  3 . 
         [0095]    Since power supplying patterns  3   a  and  3   b  of printed board  3  are connected to lands  5  and tips  11   a  and  12   a  are electrically connected to power supplying patterns  3   a  and  3   b  via lands  5 , it is possible to greatly reduce an adverse effect such as noise affecting signal patterns on the surface of printed boards  2  and  3 . Power supply from printed board  2  to printed board  3  via fixing part  10  may cause an adverse effect such as noise affecting on elements mounted to printed boards  2  and  3  and wiring patterns on the printed board. However, forming power supplying patterns  3   a  and  3   b  on inner layers of printed boards  2  and  3  for power source supply and electrically connecting the power supplying patterns  3   a  and  3   b  to fixing part  10  inhibits adverse effects on wiring patterns and others. 
       (2) Second Embodiment 
       [0096]    Next, description is made for printed board unit  1 - 2  of a second embodiment of the present invention. 
         [0097]    As shown in  FIGS. 9A-9C , printed board unit  1 - 2  is different only in the structure of fixing part  20  from printed board unit  1 - 1  of the foregoing first embodiment, and the remaining configuration of printed board unit  1 - 2  is identical to printed board unit  1 - 1 .  FIGS. 9A ,  9 B, and  9 C are the top view, the side view seen from the right and the front view of printed board unit  1 - 2 . In  FIGS. 9A-9C , like reference numbers designate similar parts or elements to the first embodiment of different illustrated example, so any repetitious description is omitted here. Accordingly, fixing part  20  is hereinafter detailed. 
         [0098]    As understood from  FIGS. 9A-9C  and  FIG. 10 , fixing part  20  takes a form of a rectangular parallelpiped, and comprises first fixing piece  21  fixed to printed board  3 , second fixing piece  22  fixed to printed board  3  and first intermediate fixing piece  23  interposed between first fixing piece  21  and second fixing piece  22  similarly to fixing part  10  of the first embodiment. 
         [0099]    Further, fixing part  20  optionally includes one or more second intermediate fixing piece  24  detachably positioned at least one of between first fixing piece  21  and first intermediate fixing piece  23  and between second fixing piece  22  and first intermediate fixing piece  23 , as shown in  FIGS. 11A and 11B . 
         [0100]    As shown in  FIG. 10 , first fixing piece  21  and second fixing piece  22  includes conductive tips  21   a  and tips  22   a,  respectively. Similarly to first fixing piece  11  and second fixing piece  12  of the first embodiment, power supplying patterns  3   a  and  3   b  on printed board  3  are electrically connected to first fixing piece  21  and at the same time power supplying patterns  3   a  and  3   b  on printed board  2  are electrically connected to second fixing piece  22  by soldering tips  21   a  and tips  22   a  being inserted into lands  5  and lands  5  on the printed boards  2  and  3  as shown in  FIGS. 6A and 7  to printed boards  2  and  3 , respectively. 
         [0101]    As shown in  FIG. 11A , first fixing piece  21  includes protrusion  21   b  with a V-shape section projecting toward printed board  2 . 
         [0102]    Similarly, second fixing piece  22  has protrusion  22   b  with a V-shape section projecting toward printed board  3 . 
         [0103]    First fixing piece  21  and second fixing piece  22  (hereinafter also called fixing pieces  21  and  22 ) have a structure shown in  FIG. 12A through 12D . Specifically, first fixing piece  21  and second fixing piece  22  are identical in shape but different in the orientation.  FIG. 12A  is a front view of fixing parts  21  and  22 ;  FIG. 12B  is the top view;  FIG. 12C  is the bottom view; and  FIG. 12D  is the side view seen from the right. 
         [0104]    Protrusions  21   b  and  22   b  of fixing parts  21  and  22  are configured to be deformed by elasticity such that interior angle α of the V shape comes to be smaller. In other words, Protrusions  21   b  and  22   b  are configured to have elasticity that affects in the directions X 1  and X 2  perpendicular or substantially perpendicular to the direction toward corresponding recesses  23   a,    23   b,  and  24   a  that protrusions  21   b  and  22   b  are to be fit. The elasticity latches protrusions  21   b  and  22   b  onto the insides of corresponding recesses  23   a,    23   b,  and  24   a.    
         [0105]    Protrusions  21   b  and  22   b  of fixing parts  21  and  22  have respectively latches  21   c  and  22   b  that are to be latched inside corresponding recesses  23   a,    23   b,  and  24   a.  In the illustrated example, latches  21   c  and  22   c  are portions of fixing parts  21  and  22  extending from protrusions  21   b  and  21   c  along directions X 1  and X 2 , respectively. 
         [0106]    As shown in  FIG. 11A , second intermediate fixing piece  24  includes recess  24   a  into which protrusion  21   b  of first fixing piece  21  or protrusion  22   b  of second fixing piece  22  is detachably fitted, and protrusion  24   b  with a V-shape section projecting toward printed board  2  or  3  on the opposite face of that with recess  24   a.    
         [0107]    Specifically, second intermediate fixing piece  24  is configured as shown in  FIGS. 13A-13E  and  FIG. 14 .  FIG. 13A  is the front view of second intermediate fixing piece  24 ;  FIG. 13B  is the top view;  FIG. 13C  is the bottom view;  FIG. 13D  is the side view seen from the right;  FIG. 13E  is a C-C′ sectional view of  FIG. 13B ; and  FIG. 14  is a perspective view of second intermediate fixing piece  24 . 
         [0108]    Protrusion  24   b  of second intermediate fixing piece  24  is identical to protrusions  21   b  and  22   b  of fixing parts  21  and  22 , respectively. 
         [0109]    Recess  24   a  of second intermediate fixing piece  24  accommodates any one of protrusions  21   b,    22   b,  and  24   b,  and has latch receptors  24 d to latch protrusions  21   b,    22   b,  or  24   b  onto the inside of recess  24   a.  Each latch receptor  24   d  takes a C-shape to accommodate the shapes of latches  21   c,    22   c,  and  24   c.    
         [0110]    Recess  24   a  of second intermediate fixing piece  24  includes projections  24   e  that exerts elasticity of protrusions  21   b,    22   b,  and  24   b.  In other words, protrusions  24   e  make the center portion of recess  24   a  constrict, so that protrusions  21   b,    22   b,  and  24   b  are elastically deformed to exert elasticity at the constriction. 
         [0111]    Protrusions  24   e  also function to guide protrusions  21   b,    22   b,  or  24   b  inserting into and drawing from recess  24   a.    
         [0112]    Here, description is made in relation to a state transition of protrusion  22   b  of second fixing piece  22  from fitting into recess  24   a  of second intermediate fixing piece  24  to drawing from recess  24   a  with reference to  FIGS. 15A-15G . A state transition of protrusion  21   b  of first fixing piece  21  when being fitted into and drawn from recess  24   a  of second intermediate fixing piece  24 , a state transition to protrusion  24   b  of second intermediate fixing piece  24  when being fitted into and drawn from recess  24   a  of another second intermediate fixing piece  24 , and a state transition of protrusion  24   b  of second intermediate fixing piece  24 , protrusion  21   b  of first fixing piece  21 , or protrusion  22   b  of second fixing piece  22  when being fitted into and drawn from recess  23   a  or recess  23   b  of first intermediate fixing piece  23  also proceed as shown in  FIGS. 15A-15G . 
         [0113]    Recess  24   a  of second intermediate fixing piece  24  being in a state shown in  FIG. 15A  moves in the direction that arrow Y 1  indicates to fit protrusion  22   b  of second fixing piece  22  into recess  24   a.    
         [0114]    Then, further application of a predetermined force or more in direction Y 1  to second intermediate fixing piece  24  with recess  24   a  being in contact with protrusion  22   b  at the entrance of the recess  24   a  as shown in  FIG. 15B  elastically deforms protrusion  22   b  such that the interior angle α becomes smaller while being guided along the inner circumference of recess  24   a,  i.e., projections  24   e  as shown in  FIG. 15C . 
         [0115]    Further movement of second intermediate fixing piece  24  in the Y 1  direction fits latches  22   c  of protrusion  22   b  into latch receptors  24   d  of second intermediate fixing piece  24   a  to be latched as shown in  FIG. 15D . As a consequence, protrusion  22   b  is fitted into recess  24  to couple second intermediate fixing piece  24  to second fixing piece  22 . 
         [0116]    At that time, protrusion  22   b  is preferably in contact with projections  24   e  of recess  24   a  as shown in portions Z 1  and Z 2  of  FIG. 15D . In detail, it is preferable that protrusion  22   b  is elastically deformed in recess  24   a  to exert elasticity in X 1  and X 2  directions. Thereby, connection between second fixing piece  22  and second intermediate fixing piece  24  is stabilized. 
         [0117]    Then, application of a predetermined force or more in the direction indicated by arrow Y 2  to second intermediate fixing piece  24  being in a fitting state shown in  FIG. 15D  draws latches  22   c  of second fixing piece  22   b  from latch receptors  24   d  of recess  24   a,  deforms protrusion  22   b  being guided along projections  24   e,  as shown in  FIGS. 15E and 15F , and finally draws protrusion  22   b  from recess  24   a  as shown in  FIG. 15G . 
         [0118]    First intermediate fixing piece  23  includes recess  23   a  into which protrusion  24   b  of first fixing piece  21  or protrusion  24   b  of second intermediate fixing piece  24  positioned between first intermediate fixing piece  23  and first fixing piece  21  is detachably fitted and recess  23   b  into which protrusion  22   b  of second fixing piece  22  or protrusion  24   b  of second intermediate fixing piece  24  positioned between first intermediate fixing piece  23  and second fixing piece  22  is detachably fitted, as shown in  FIG. 11A . 
         [0119]    More specifically, first intermediate fixing piece  23  has a structure detailed in  FIGS. 16A-16E  and  FIG. 17 .  FIG. 16A  is the front view of first intermediate fixing piece  23 ;  FIG. 16B  is the top view;  FIG. 16C  is the bottom view;  FIG. 16D  is the side view seen from right;  FIG. 16E  is the D-D′ sectional view of  FIG. 16B ; and  FIG. 17  is a perspective view of first intermediate fixing piece  23 . 
         [0120]    Recesses  23   a  and  23   b  of first intermediate fixing piece  23  are both identical to recess  24   a  of second intermediate fixing piece  24  to have latch receptors  23   c  and projections  23   d.    
         [0121]    In the example shown in  FIG. 11A , protrusion  21   b  of first fixing piece  21  is fitted into recess  24   a  of second intermediate fixing piece  24 ; protrusion  22   b  of second fixing piece  22  is fitted into recess  24   a  of (another) second intermediate fixing piece  24 ; and protrusions  24   b  of the two second intermediate fixing pieces  24  are fitted into recesses  23   a  and  23   b  of first intermediate fixing piece  23 . Thereby, fixing part  20  shown in  FIG. 11B  is formed. 
         [0122]    As described above, second intermediate fixing piece  24  is detachably inserted, and one or more second intermediate fixing pieces  24  can therefore be added to between first fixing piece  21  and second intermediate fixing piece  24 , between second intermediate fixing piece  24  and first intermediate fixing piece  23 , or between second intermediate fixing piece  24  and second fixing piece  22 . 
         [0123]    With this configuration, fixing part  20  can vary the length thereof in the direction in which the predetermined space between printed boards  2  and  3  increases or decreases. In other words, fixing part  20  can adjust the space between printed boards  2  and  3 . 
         [0124]    Further, fixing part  20  is made of conductive material and is connected to the power supplying wire of printed board  2  to supply power to printed board  3 . 
         [0125]    In other words, first fixing piece  21 , second fixing piece  22 , first intermediate fixing piece  23 , and second intermediate fixing piece  24  are formed of conductive material. In this case, the outer circumference surface of fixing part  20  is preferably covered with insulation material. 
         [0126]    For example, if fixing part  20  shown in  FIG. 11B  is coupled to printed boards  2  and  3 , the electricity from printed board  2  is supplied trough, in sequence from the bottom of  FIG. 11B , second fixing piece  22 , second intermediate fixing piece  24 , first intermediate fixing piece  23 , second intermediate fixing piece  24 , first fixing piece  21 , and tips  21   a  to printed board  3 . 
         [0127]    Printed board unit  1 - 2  of the second embodiment can obtain the same advantages as the first embodiment because of the structure described above. 
         [0128]    Protrusions  21   b,    22   b,  and  24   b  are latched inside corresponding recesses  24   a,    23   a  and  23   b  to surely join pieces  21 - 24  one another, concurrently improving the conductivity through the pieces  21 - 24 . 
         [0129]    Further, protrusions  21   b,    22   b,  and  24   b  include latches  21   c,    22   c,  and  24   c  and recesses  24   a,    23   a,  and  23   b  include latch receptors  24   d  and  23   c  to latch corresponding latches  21   c,    22   c,  and  24   c.  This structure surely fit pieces  21 - 24  one another. 
         [0130]    (3) Others: 
         [0131]    The present invention should by no means be limited to the foregoing embodiments and various changes and modifications can be suggested without departing from the sprit of the present invention. 
         [0132]    For example, the shape of fixing parts  10  and  20  of the above first and second embodiments, that is, first fixing pieces  11  and  21 , second fixing pieces  12  and  22 , first intermediate fixing pieces  13  and  23 , and second intermediate fixing pieces  14  and  24  are not limited to those described above and can be variously modified without departing from the concept of the present invention. 
         [0133]    In particular, the shapes of protrusions  21   b,    22   b,  and  24   b  possessed by pieces  21 ,  22 , and  24  of fixing part  20  and the corresponding recesses  23   a,    23   b,  and  24   a  are not limited to the above example. Alternatively, it is sufficient that protrusions  21   b,    22   b,  and  24   b  are elastically deformed to exert elasticity as being fitted into recesses  23   a,    23   b,  and  24   a;  that protrusions  21   b,    22   b,  and  24   b  have latches to be latched inside recess  23   a,    23   b  and  24   a;  and that recesses  23   a,    22   b,  and  24   b  possess latch receptors to receive these latches. 
         [0134]    Alternatively, fixing part  20  may have a structure shown in  FIGS. 18A and 18B . Specifically, first fixing piece  21 ′ may include recess  21   b ′ as a substitute for protrusion  21   b,  and second intermediate fixing piece  24  may be fitted into recess  21   b ′ of first fixing piece  21 ′. 
         [0135]    In other words, second intermediate fixing piece  24  functions as an intermediate fixing piece that is to be interposed between first fixing piece  21 ′ and second fixing piece  22 , and fixing part  20  can increase or decrease the number of second intermediate fixing pieces  24 . 
         [0136]    This alternative structure can obtain same advantages as the second embodiment. 
         [0137]    Further alternatively, fixing part  20  may have a structure shown in  FIGS. 19A and 19B . Specifically, second fixing piece  22 ′ may include recess  22   b ′ as a substitute for protrusion  22   b,  and second intermediate fixing piece  24  may be fitted to recess  22   b ′ of second fixing piece  22 ′. 
         [0138]    In other words, second intermediate fixing piece  24  functions as an intermediate fixing piece that is to be interposed between first fixing piece  21  and second fixing piece  22 ′, and fixing part  20  can increase and decrease the number of second intermediate fixing pieces  24 . 
         [0139]    That also secures the same advantages as the second embodiment. 
         [0140]    Still further alternatively, spring plate  31  may function as fixing part  30  having one end fixed to printed board  2  and the other end fixed to printed board  3 , as shown in  FIG. 20 . 
         [0141]    In this alternation, fixing part  30  has a configuration exemplified by that shown in  FIG. 21 . Fixing part  30  comprises elastic spring plate  31 , a set of bolt  32 , nut  33 , and spring washer  34  for attachment of to printed board  3  and a set of bolt  35 , nut  36  and spring washer  37  for attachment of to printed board  2 . Here, portions  31   a  and  31   b  to be fixed respectively to printed boards  2  and  3  are preferably formed non-elastic material. 
         [0142]    Also in this case, printed boards  2  and  3  include screw holes  6  through which bolts  32  and  35  penetrate, lands  7  with copper foil, and wiring patterns  8  coupled to land  7 , as shown in  FIG. 22 . 
         [0143]    As shown in  FIG. 23A , spring plate  31  is fixed at end portion  31   a  (to printed board  3 ) with bolt  32 , nut  33 , and spring washer  34  and fixed at the other end portion  31   b  (to printed board  2 ) with bolt  35 , nut  36  and spring washer  37 . 
         [0144]    Further, plastically deformation of spring plate  31  being in the state shown in  FIG. 23A  varies the space W 3  between printed boards  2  and  3  from space W 3  to the space W 4  narrower than space W 3  as shown in  FIG. 23B . 
         [0145]    This configuration can attain the same advantages as the foregoing embodiments. 
         [0146]    In addition, fixing part  30  is preferably formed of conductive material and preferably supplies electricity from printed board  2  to printed board  3  in the same manner as the foregoing embodiments. 
         [0147]    In the foregoing embodiments, fixing parts  10  and  20  are fixed to printed boards  2  and  3  by soldering, but the present invention does not limit the fixing method to soldering. Alternatively, fixing parts  10  and  20  may be fixed to printed boards  2  and  3  with screws. 
         [0148]    From the invention thus described, it will be obvious that the same may be varied in many ways. Such variations are not regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.