Patent Publication Number: US-2018035536-A1

Title: Wiring board and electronic apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2016-146518, filed on Jul. 26, 2016, the entire contents of which are incorporated herein by reference. 
     FIELD 
     The embodiments discussed herein relate to a wiring board and an electronic apparatus. 
     BACKGROUND 
     Flexible wiring boards, which are also referred to as flexible circuit boards or the like, have conventionally been known. Among these known substrates, there is a flexible wiring board including a base made of an elastic material such as an elastomer. On this base, corrugated wirings that are extendable, contractible, or deformable in one direction (for example, in a longitudinal direction of the base) are formed by using metal foils. 
     For example, see Japanese Laid-open Patent Publication No. 2013-187308 
     When the flexible wiring board is deformed and is then extended as a result, a crack or a fracture could be caused in a wiring on the base. Such a crack in a wiring could change the resistance of the wiring and characteristics of the wiring board. If such a wiring board, whose characteristics could change when the wiring board is extended, is used for an electronic apparatus, the electronic apparatus could fail to operate stably. 
     SUMMARY 
     According to one aspect, there is provided a wiring board including: a base that has extensibility; a first wiring portion that is formed on the base and extends in a first direction crossing a longitudinal direction of the base; and a first conductor portion that is formed on the first wiring portion and extends in the first direction. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIGS. 1A and 1B  illustrate a wiring board according to a first example; 
         FIG. 2  illustrates an extended wiring board according to the first example; 
         FIGS. 3A and 3B  illustrate a wiring board according to a second example; 
         FIGS. 4A and 4B  illustrate a wiring board according to a third example; 
         FIGS. 5A and 5B  illustrate a wiring board according to a first embodiment; 
         FIGS. 6A and 6B  illustrate extensibility of the wiring board according to the third example; 
         FIGS. 7A and 7B  illustrate extensibility of the wiring board according to the first embodiment; 
         FIGS. 8A and 8B  illustrate resistance of the wiring board according to the third example before a crack is caused; 
         FIGS. 9A and 9B  illustrate resistance of the wiring board according to the third example after a crack is caused; 
         FIGS. 10A and 10B  illustrate resistance of the wiring board according to the first embodiment before a crack is caused; 
         FIGS. 11A and 11B  illustrate resistance of the wiring board according to the first embodiment after a crack is caused; 
         FIGS. 12A to 12C  illustrate the extension direction of a wiring of a wiring board according to a fourth example; 
         FIGS. 13A to 13C  illustrate the extension direction of a wiring of a wiring board according to a first variation of the first embodiment; 
         FIGS. 14A and 14B  illustrate a main extension axis of the wiring boards according to the first embodiment and the first variation thereof, respectively; 
         FIG. 15  illustrates a bent wiring board according to the first embodiment or the first variation thereof; 
         FIGS. 16A and 16B  illustrate structure examples of wiring boards according to second and third variations of the first embodiment; 
         FIGS. 17A to 17D  illustrate structure examples of a wiring of the wiring board according to the first embodiment; 
         FIGS. 18A to 18C  illustrate structure examples of a wiring of the wiring board according to the first embodiment; 
         FIGS. 19A and 19B  illustrate structure examples of a wiring of the wiring board according to the first embodiment; 
         FIGS. 20A and 20B  illustrate structure examples of wirings of wiring boards according fourth and fifth variations of the first embodiment; 
         FIGS. 21A to 21C  illustrate a structure example of a beacon according to a fifth example; 
         FIG. 22  illustrates a structure example of a beacon according to a second embodiment; 
         FIG. 23  illustrates a beacon according to a first variation of the second embodiment; 
         FIG. 24  illustrates a beacon according to a second variation of the second embodiment; 
         FIG. 25  illustrates a beacon according to a third variation of the second embodiment; 
         FIGS. 26A and 26B  illustrate examples of a conductor portion according to the second embodiment; 
         FIG. 27  illustrates an example of a wiring board according to the second embodiment; 
         FIGS. 28A and 28B  illustrate other examples of the conductor portion according to the second embodiment; 
         FIGS. 29A and 29B  illustrate other examples of the wiring board according to the second embodiment; and 
         FIG. 30  illustrates an example of an electronic apparatus according to a third embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First, a wiring board having extensibility will be described. 
       FIG. 1A  to  FIG. 2  illustrate a wiring board according to a first example. More specifically,  FIG. 1A  is a schematic plan view of a main portion of a wiring board according to a first example.  FIG. 1B  is a schematic sectional view taken along line M 1 -M 1  in  FIG. 1A .  FIG. 2  is a schematic plan view of a main portion of an extended wiring board according to the first example. 
     This wiring board  1 A illustrated in  FIGS. 1A and 1B  includes a base  10  having flexibility and extensibility and a wiring portion  20   a  formed on the base  10 . 
     The base  10  is made of an elastic material (an elastomer) such as silicone rubber. For example, as illustrated in  FIG. 1A , the base  10  is made of a material whose planar shape is rectangular or substantially rectangular. In addition, the wiring portion  20   a  is made of metal foil such as copper (Cu) foil having lower extensibility than that of the base  10 . In  FIGS. 1A and 1B , a single wiring portion  20   a , which is formed on the base and extends in a direction Q in parallel with a longitudinal direction X of the base  10 , is illustrated as an example. The “extensibility” of an object represents how much the object is elastically extendable in a certain direction when pulled in that certain direction. 
     Because of the flexibility and extensibility of the base  10 , the wiring board  1 A is installable on a curved surface, for example. In addition, the wiring board  1 A is deformable or extendable by external force. In such cases, the wiring board  1 A is extended temporarily or continuously.  FIG. 2  is a schematic plan view of the wiring board  1 A extended along its main extension axis S in parallel with the longitudinal direction X of the base  10 . The wiring board  1 A is mainly extended along the main extension axis S, depending on the installation site or usage environment thereof. 
     When the wiring board  1 A is extended along the main extension axis S, the force extending the wiring board  1 A is also applied to the wiring portion  20   a  on the base  10 . The wiring portion  20   a  made of metal foil has higher elasticity and lower extensibility than those of the base  10  made of an elastomer. Thus, the wiring portion  20   a  could hinder the extension of the base  10  in the longitudinal direction X in parallel with the main extension axis S. In addition, because of the relatively low extensibility of the wiring portion  20   a , as illustrated in  FIG. 2 , a crack  50  such as a fracture that runs in a lateral direction Y of the base  10  could be caused in the wiring portion  20   a  when the wiring board  1 A is extended in the longitudinal direction X of the base  10 . 
     For example, the base  10  of the wiring board  1 A is made of an elastomer having an elasticity of 20 MPa to 40 MPa and an extensibility of 200%. In contrast, the wiring portion  20   a  on the base  10  is made of Cu foil having an elasticity of 110 GPa to 128 GPa and an extensibility of 0.2%. When the wiring board  1 A including the base  10  and wiring portion  20   a  made of the above materials is used, the wiring portion  20   a  could hinder the extension of the base  10  or the crack  50  could be caused in the wiring portion  20   a.    
     This hindrance of the extension of the base  10  could limit the deformation amount, the installation site, or the usage environment of the wiring board  1 A. In addition, the crack  50  in the wiring portion  20   a  could increase the resistance of the wiring board  1 A or could break a current path on the base  10 . 
       FIGS. 3A and 3B  illustrate a wiring board according to a second example. More specifically,  FIG. 3A  is a schematic plan view of a main portion of a wiring board according to a second example, and  FIG. 3B  is a schematic sectional view taken along line M 2 -M 2  in  FIG. 3A . 
     This wiring board  1 B according to the second example illustrated in  FIGS. 3A and 3B  also includes a base  10  having extensibility and a wiring portion  20  extending in a direction Q (a longitudinal direction X of the base  10 ) on the base  10 . However, the wiring board  1 B differs from the wiring board  1 A according to the first example in that the wiring portion  20  is made of material having higher extensibility. 
     The wiring portion  20  is made of conductive paste. For example, the conductive paste is made by including conductive fillers such as silver (Ag) fillers in an insulating binder such as silicone rubber or epoxy resin. The wiring portion  20  is formed by printing the conductive paste on the base  10 . As an example,  FIG. 3A  illustrates a partial enlargement of the wiring portion  20  including a binder  22  and fillers  23 . 
     The wiring portion  20  made of the above conductive paste has extensibility. In the case of the wiring board  1 B, since the wiring portion  20  on the base  10  made of an elastomer has extensibility, the extension of the base  10  in the longitudinal direction X thereof in parallel with the main extension axis S is less hindered, compared with the wiring board  1 A including the wiring portion  20   a  made of metal foil on the base  10 . In addition, since the wiring portion  20  has extensibility, even when the base  10  is extended in its longitudinal direction X in parallel with the main extension axis S, the chance of occurrence of a crack is lower. 
     However, the conductive paste serving as the wiring portion  20  is formed by including conductive fillers in an insulating binder, the wiring portion  20  has higher resistivity than that of the wiring portion  20   a  made of metal foil. When the wiring portion  20  made of conductive paste is formed to have a relatively thin film thickness that does not hinder the extension of the base  10 , the wiring portion  20  has higher resistance than that of the wiring portion  20   a  made of metal foil. As a result, when a current flows from an upstream circuit (not illustrated) on one end of the wiring portion  20  to a downstream circuit (not illustrated) on the other end of the wiring portion  20  in the direction Q, a relatively large voltage drop could be caused. Namely, the downstream circuit could suffer from a lack of power and could not operate stably. 
       FIGS. 4A and 4B  illustrate a wiring board according to a third example. More specifically,  FIG. 4A  is a schematic plan view of a main portion of a wiring board according to a third example, and  FIG. 4B  is a schematic sectional view taken along line M 3 -M 3  in  FIG. 4A . 
     This wiring board  1 C according to the third example illustrated in  FIGS. 4A and 4B  also includes a base  10  having extensibility and a wiring portion  20  extending in a direction Q (a longitudinal direction X of the base  10 ) on the base  10 . However, the wiring board  1 C differs from the wiring board  1 B according to the second example in that the wiring board  1 C includes a conductor portion  30  on the wiring portion  20 . 
     The wiring portion  20  of the wiring board  1 C is made of conductive paste as described above. The conductor portion  30  is made of material having lower resistivity than that of the conductive paste used for the wiring portion  20 . For example, the conductor portion  30  is made of metal foil such as Cu foil. 
     By forming the conductor portion  30  on the wiring portion  20 , the conductor portion  30  having resistivity lower than that of the wiring portion  20  made of conductive paste, the resistance of a wiring  40 , which is formed by the wiring portion  20  and the conductor portion  30 , is reduced. The conductor portion  30  serves as an auxiliary pattern that helps the flow of electric charges that need to be transmitted through the wiring portion  20 , which is a wiring pattern whose resistance is relatively high. By forming the conductor portion  30  on the wiring portion  20 , the resistance of the wiring  40  is consequently reduced. Thus, the voltage drop that occurs when a current flows an upstream circuit (not illustrated) on one end of the wiring  40  to a downstream circuit (not illustrated) on the other end of the wiring  40  in the direction Q is reduced. In addition, a lack of the power of the downstream circuit caused by the voltage drop is reduced. 
     However, in the case of the wiring board  1 C, when metal foil is used as the conductor portion  30  on the wiring portion  20 , the conductor portion  30  could have the same problem with the above first example. Namely, when the wiring board  1 C is extended in the longitudinal direction X of the base  10  in parallel with the main extension axis S, the conductor portion  30  having lower extensibility than that of the base  10  and of the wiring portion  20  could hinder the extension. Thus, for example, the deformation amount or the installation site of the wiring board  1 C could be limited. In addition, a crack that runs in a lateral direction Y perpendicular to the extension of the base  10  in the longitudinal direction X in parallel with the main extension axis S could be caused in the conductor portion  30 . As a result, the resistance of the wiring  40  could be increased. 
     In the case of the wiring  40  of the wiring board  1 C, even when a crack is caused in the conductor portion  30 , the wiring portion  20  thereunder serves as a current path. However, the wiring  40  exhibits different resistance, depending on whether a crack is caused in the conductor portion  30 . Thus, since the level of the voltage drop accordingly varies, the power supplied to a downstream circuit through the wiring  40  could vary. When the wiring board  1 C exhibits different characteristics depending on whether a crack is caused in the conductor portion  30 , a downstream circuit could not stably operate. 
     In view of the above points, techniques according to the following embodiments will be described. The following techniques reduce the resistance of a wiring board, improve the extensibility of a wiring board along a main extension axis, and reduce the change of characteristics caused by extension of a wiring board along a main extension axis. 
     First, a first embodiment will be described. 
       FIGS. 5A and 5B  illustrate a wiring board according to a first embodiment. More specifically,  FIG. 5A  is a schematic plan view of a main portion of a wiring board according to a first embodiment, and  FIG. 5B  is a schematic sectional view taken along line M 4 -M 4  in  FIG. 5A . 
     This wiring board  1  illustrated in  FIGS. 5A and 5B  includes a base  10  having flexibility and extensibility, a wiring portion  20  (a wiring pattern) formed on the base  10 , and a conductor portion  30  (an auxiliary conductor pattern) formed on the wiring portion  20 . The “extensibility” of an object represents how much the object is elastically extendable in a certain direction when pulled in that certain direction. 
     The base  10  is made of an elastomer such as silicone rubber or urethane rubber. Alternatively, other than such an elastomer, the base  10  may be made of a fluorine, styrene, olefinic, ester, amide, vinyl chloride, or butadiene elastomer. For example, as illustrated in  FIG. 5A , a material whose planar shape is rectangular or substantially rectangular is used as the base  10 . A longitudinal direction X of the base  10  is in parallel with a main extension axis S of the wiring board  1 . The wiring board  1  is mainly extended along the main extension axis S, depending on the installation site or usage environment thereof. 
     The wiring portion  20  is made of conductive paste made by including conductive fillers in an insulating binder. As the insulating binder, an elastomer such as silicone rubber or resin material such as epoxy resin is used, for example. As the conductive fillers, for example, any one of various metal particles such as Ag particles or Cu particles, materials obtained by coating organic particles with any one of various metal materials such as Ag or Cu, or carbon materials such as carbon nanotubes (CNTs) are used. The wiring portion  20  is formed by printing such conductive paste on the base  10 . The wiring portion  20  has extensibility. The wiring portion  20  is extended in a direction P perpendicular to the longitudinal direction X of the base  10 , which is in parallel with the main extension axis S of the wiring board  1 . As illustrated in  FIG. 5A , for example, the wiring portion  20  is extended in a lateral direction Y perpendicular to the longitudinal direction X. 
     The conductor portion  30  is made of material having lower resistivity than that of the wiring portion  20 . For example, the conductor portion  30  is made of any one of various kinds of metal foil (including alloy foil) such as Cu foil, aluminum (Al) foil, nickel (Ni) foil, gold (Au) foil, Ag foil, tin (Sn) foil, or solder foil. The conductor portion  30  has lower extensibility than that of the wiring portion  20 . In the same way as the wiring portion  20 , the conductor portion  30  extends in the direction P on the wiring portion  20  that extends in the direction P in parallel with the lateral direction Y of the base  10 . 
     The wiring portion  20  and the conductor portion  30  thereon form a wiring  40 , which serves as at least a part of a current path of the wiring board  1 .  FIGS. 5A and 5B  illustrate, as an example, a single wiring  40  (the wiring portion  20  and the conductor portion  30 ) extending in the direction P. 
     The wiring board  1  differs from the wiring board  1 C including the wiring  40  extending in the direction Q in parallel with the main extension axis S as illustrated in  FIGS. 4A and 4B  in that the wiring  40  formed by the wiring portion  20  and the conductor portion  30  extends in the direction P perpendicular to the main extension axis S. 
     On the wiring board  1 , the relatively highly resistive wiring portion  20  is formed first. Next, the conductor portion  30  having lower resistivity than that of the wiring portion  20  is formed on the wiring portion  20 . In this way, the wiring  40  having low resistivity is formed. In addition, on the wiring board  1 , the wiring  40  extends in the direction P perpendicular to the main extension axis S. Thus, compared with the case in which the wiring  40  extends in the direction in parallel with the main extension axis S, the extensibility of the base  10  is improved. In addition, since the wiring  40  on the wiring board  1  extends in the direction P perpendicular to the main extension axis S, the chance of occurrence of a crack when the wiring board  1  is extended along the main extension axis S is reduced, and the resistance increase by the extension is also reduced. Namely, change of the characteristics of the wiring board  1  is reduced. These points will be described with reference to  FIGS. 6A to 11B . 
       FIGS. 6A to 7B  illustrate extensibility of wiring boards. 
       FIGS. 6A and 6B  illustrate, for comparison, extensibility of the wiring board  1 C according to the third example.  FIGS. 7A and 7B  illustrate extensibility of the wiring board  1  according to the first embodiment. More specifically,  FIG. 6A  is a schematic plan view of a main portion of the wiring board  1 C, and  FIG. 6B  is an enlarged view of a dotted line region (a wiring region)  60  in  FIG. 6A . In addition,  FIG. 7A  is a schematic plan view of a main portion of the wiring board  1 , and  FIG. 7B  is an enlarged view of a dotted line region (a wiring region)  70  in  FIG. 7A . 
     Regarding the wiring board  1 C illustrated in  FIGS. 6A and 6B , an extension ΔL of the wiring region  60  by force F along the main extension axis S is expressed by the following expression (1), wherein L represents an initial length, Ee and Ae represent Young&#39;s modulus and a cross-sectional area of the base  10 , and Ec and Ac represent Young&#39;s modulus and a cross-sectional area of the conductor portion  30 . The cross-sectional areas Ae and Ac are the cross-sectional areas of the base  10  and the conductor portion  30 , respectively, in the lateral direction Y. 
       Δ L=FL /( EeAe+EcAc )  (1)
 
     Regarding the wiring board  1  illustrated in  FIGS. 7A and 7B , an extension ΔL of the wiring region  70  by force F along the main extension axis S is expressed by the following expressions (2) and (3), wherein L represents an initial length, Ee and Ae represent Young&#39;s modulus and a cross-sectional area of the base  10 , and Wc, Ec, and Ac represent a width, Young&#39;s modulus, and a cross-sectional area of the conductor portion  30 . The cross-sectional areas Ae and Ac are the cross-sectional areas of the base  10  and the conductor portion  30 , respectively, in the lateral direction Y. 
       Δ L=FWc /( EeAe+EcAc )+ F ( L−Wc )/ EeAt   (2)
 
         At=Ac+Ae   (3)
 
     The following description assumes that the base in each of the wiring regions  60  and  70  has Young&#39;s modulus Ee of 40 MPa, a thickness Te of 2 mm, and a width We of 20 mm. The following description also assumes that the conductor portion  30  in each of the wiring regions  60  and  70  has Young&#39;s modulus Ec of 120 GPa, a thickness Tc of 0.05 mm, and a width We of 4 mm. In this case, the wiring region  70  of the wiring board  1  represents extensibility 12.8 times larger than that of the wiring region  60  of the wiring board  1 C. 
     Extending the conductor portion  30  (the wiring  40 ) in the direction P perpendicular to the main extension axis S as illustrated on the wiring board  1  achieves higher extensibility than that achieved by extending the conductor portion  30  (the wiring  40 ) in the direction Q in parallel with the main extension axis S as illustrated on the wiring board  1 C. 
     In addition, with the wiring board  1 C including the conductor portion  30  extending in the direction Q in parallel with the main extension axis S, a crack is caused in the conductor portion  30  when a force of 5.2 kgf is applied. In contrast, with the wiring board  1  including the conductor portion  30  extending in the direction P perpendicular to the main extension axis S, a crack is not caused in the conductor portion  30  until a force of 24.8 kgf is applied. The conductor portion  30  of the wiring board  1  achieves resistance (load bearing) against tensile stress 4.7 times larger than that of the conductor portion  30  of the wiring board  1 C. 
     The wiring board  1  including the conductor portion  30  (the wiring  40 ) extending in the direction P perpendicular to the main extension axis S is more advantageous in both extensibility and load bearing. 
       FIG. 8A  to  FIG. 11B  illustrate resistances of wiring boards. 
       FIGS. 8A to 9B  illustrate, for comparison, resistances of the wiring  40  of the wiring board  1 C according to the third example before and after a crack is caused.  FIGS. 10A to 11B  illustrate resistances of the wiring  40  of the wiring board  1  according to the first embodiment before and after a crack is caused. 
     For comparison, first, the resistance of the wiring  40  extending in the direction Q in parallel with the main extension axis S before a crack is caused will be described with reference to  FIGS. 8A and 8B . 
       FIG. 8A  schematically illustrates the wiring  40  in the wiring region  60  ( FIGS. 6A and 6B ) of the wiring board  1 C before a crack is caused.  FIG. 8B  illustrates an equivalent circuit of the wiring  40  in  FIG. 8A . 
     An equivalent circuit of the wiring  40  as illustrated in  FIG. 8A  including the wiring portion  20  and the conductor portion  30  without a crack (the direction of a current I is indicated by a dotted arrow) is represented by a parallel circuit as illustrated in  FIG. 8B . The parallel circuit is formed by a resistance Ra of the wiring portion  20  and a resistance Rc of the conductor portion  30 . 
     The following description assumes that the wiring  40  (the wiring portion  20  and the conductor portion  30 ) has a length L, the wiring portion  20  has a thickness Ta, a width Wa, and a resistivity Ka, and the conductor portion  30  has a thickness Tc, a width Wc, and a resistivity Kc. Under these conditions, the resistance Ra of the wiring portion  20  and the resistance Rc of the conductor portion  30  are represented by the following expressions (4) and (5), respectively. 
         Ra=KaL /( TaWa )  (4)
 
         Rc=KcL /( TcWc )  (5)
 
     From the expressions (4) and (5), the resistance R(1/R=1/Ra+1/Rc) of the wiring  40  is expressed by the following expression (6). 
         R=KaKcL /( TaWaKc+TcWcKa )  (6)
 
     Next, the resistance of the wiring  40  extending in the direction Q in parallel with the main extension axis S after a crack is caused will be described with reference to  FIGS. 9A and 9B . 
       FIG. 9A  schematically illustrates the wiring  40  in the wiring region  60  ( FIGS. 6A and 6B ) of the wiring board  1 C after a crack is caused.  FIG. 9B  illustrates an equivalent circuit of the wiring  40  in  FIG. 9A . 
     When the wiring board  1 C is extended along the main extension axis S, as illustrated in  FIG. 9A , a crack running in the direction P perpendicular to the direction Q could be caused in the conductor portion  30  on the wiring portion  20 . The equivalent circuit of the wiring  40  (the direction of the current I is indicated by a dotted arrow) having the crack  51  is illustrated in  FIG. 9B . The equivalent circuit includes a parallel circuit of a resistance Ra1 of the wiring portion  20  and a resistance Rc1 of the conductor portion  30  on one side of the crack  51 . The equivalent circuit also includes a parallel circuit of a resistance Ra2 of the wiring portion  20  and a resistance Rc2 of the conductor portion  30  on the other side of the crack  51 . These parallel circuits are connected to each other via a resistance Rcr of the wiring portion  20  corresponding to the crack  51 . 
     The following description assumes that the wiring (the wiring portion  20  and the conductor portion  30 ) has a length L and that the wiring portion  20  has a thickness Ta, a width Wa, and a resistivity Ka. The following description also assumes that the conductor portion  30  has a thickness Tc, a width Wc, and a resistivity Kc and that the crack  51  has a width Lcr. Under these conditions, the resistance R (R=(1/Ra1+1/Rc1)−1+(1/Ra2+1/Rc2)−1+Rcr) of the wiring  40  including the conductor portion  30  having the crack  51  is represented by the following expression (7). 
         R=KaKcL /( TaWaKc+TcWcKa )+ KaLcr/TaWa   (7)
 
     From these expressions (7) and (6), it is seen that the resistance (expression (7)) of the wiring  40  including the conductor portion  30  having the crack  51  is higher than that of the wiring  40  (expression (6)) without the crack  51  by KaLcr/TaWa. Among the paths of the current I flowing from one end to the other end of the wiring  40 , the path of the current flowing through the conductor portion  30  is divided by the crack  51  into the upstream and downstream sides. Thus, the resistance R of the wiring  40  is increased by the resistance Rcr of the wiring portion  20  at the point of the division. 
     Thus, since the crack  51  in the conductor portion increases the resistance of the wiring  40 , the characteristics of the wiring board  1 C vary. With the wiring board  1 C including the conductor portion  30  having the crack  51 , the wiring  40  undergoes a larger voltage drop, compared with the wiring board  1 C including the conductor portion  30  without the crack  51 . As a result, since a downstream circuit connected to the wiring  40  receives an insufficient amount of power, the downstream circuit could not stably operate or fail to operate at all. 
     Next, the resistance of the wiring  40  extending in the direction P perpendicular to the main extension axis S before a crack is caused will be described with reference to  FIGS. 10A and 10B . 
       FIG. 10A  schematically illustrates the wiring  40  in the wiring region  70  ( FIGS. 7A and 7B ) of the wiring board  1  before a crack is caused.  FIG. 10B  illustrates an equivalent circuit of the wiring  40  in  FIG. 10A . 
     An equivalent circuit of the wiring  40  as illustrated in  FIG. 10A  including the wiring portion  20  and the conductor portion  30  without a crack (the direction of a current I is indicated by a dotted arrow) is represented by a parallel circuit as illustrated in  FIG. 10B . The parallel circuit is formed by a resistance Ra of the wiring portion  20  and a resistance Rc of the conductor portion  30 . A resistance R (1/R=1/Ra+1/Rc) of the wiring  40  is expressed by the following expression (8), which is the same as the above expression (6). 
         R=KaKcL /( TaWaKc+TcWcKa )  (8)
 
     Next, the resistance of the wiring  40  extending in the direction P perpendicular to the main extension axis S after a crack is caused will be described with reference to  FIGS. 11A and 11B . 
       FIG. 11A  schematically illustrates the wiring  40  in the wiring region  70  ( FIGS. 7A and 7B ) of the wiring board  1  after a crack is caused.  FIG. 11B  illustrates an equivalent circuit of the wiring  40  in  FIG. 11A . 
     When the wiring board  1  is extended along the main extension axis S, a crack  52  running in the direction P perpendicular to the main extension axis S could be caused in the conductor portion  30  on the wiring portion  20 , as illustrated in  FIG. 11A . The equivalent circuit of the wiring  40  (the direction of the current I is indicated by a dotted arrow) having the crack  52  is represented by a parallel circuit as illustrated in  FIG. 11B . The parallel circuit is formed by a resistance Ra of the wiring portion  20 , a resistance Rc1 of the conductor portion  30  on one side of the crack  52 , and a resistance Rc2 of the conductor portion  30  on the other side of the crack  52 . 
     The following description assumes that the wiring (the wiring portion  20  and the conductor portion  30 ) has a length L and that the wiring portion  20  has a thickness Ta, a width Wa, and a resistivity Ka. The following description also assumes that the conductor portion  30  has a thickness Tc, a width Wc, and a resistivity Kc and that the conductor portion  30  on one side of the crack  52  has a width W. Under these conditions, the resistor Ra of the wiring portion  20 , the resistor Rc1 of the conductor portion  30  on one side, and the resistor Rc2 of the conductor portion  30  on the other side are expressed by the following expressions (9) to (11), respectively. 
         Ra=KaL /( TaWa )  (9)
 
         Rc 1= KcL /( TcW )  (10)
 
         Rc 2= KcL/{Tc ( Wc−W )}  (11)
 
     From these expressions (9) to (11), when the crack  52  is caused in the conductor portion  30  on the wiring portion  20  of the wiring  40  extending in the direction P perpendicular to the main extension axis S, the resistance R (1/R=1/Ra+1/Rc1+1/Rc2) of the wiring  40  is expressed by the following expression (12). 
         R=KaKcL /( TaWaKc+TcWcKa )  (12)
 
     This expression (12) is the same as the above expression (8). Namely, even when the crack  52  running in the direction P is caused in the conductor portion  30  on the wiring portion  20  of the wiring board  1 , regardless of the value of the width W (or a width We−W) of the conductor portion  30  divided by the crack  52 , the resistance R of the wiring  40  represents the same value as that before the crack  52  is caused. Among the paths of the current I flowing through from one end to the other end of the wiring  40 , the path of the current flowing through the conductor portion  30  is not divided by the crack  52  into the upstream and downstream sides. Thus, whether the crack is caused or not, the resistance R of the wiring  40  does not change. Therefore, the increase of the resistance is prevented. 
     In this way, even when the wiring  40  extending in the direction P perpendicular to the main extension axis S is extended along the main extension axis S and the crack running in the direction P is thereby caused, the resistance of the wiring  40  is not increased, and the characteristics of the wiring board  1  are not changed. As a result, whether the crack  52  is caused or not, the voltage drop of the wiring  40  is prevented, and change of the amount of power supplied to the downstream circuit connected to the wiring  40  is prevented. Therefore, the downstream circuit is able to operate stably. 
     The wiring board  1  including the conductor portion  30  (the wiring  40 ) extending in the direction P perpendicular to the main extension axis S is more advantageous in that the characteristics (resistance) of the wiring board  1  are not changed even when a crack is caused. 
     The above description has been made on the basis of an example in which the wiring  40  (the wiring portion  20  and the conductor portion  30 ) extends in the direction P perpendicular to the main extension axis S of the wiring board  1 . However, the wiring  40  may be formed to extend in a direction other than the direction P perpendicular to the main extension axis S. This will be described with reference to  FIGS. 12A to 13C . 
       FIGS. 12A to 13C  illustrate the extension directions of wirings of wiring boards. 
     More specifically,  FIG. 12A  is a schematic plan view of a main portion of a wiring board according to a fourth example.  FIG. 12B  is a schematic plan view of a wiring of the wiring board in  FIG. 12A , the wiring including a wiring portion and a conductor portion, which is formed on the wiring portion and in which a crack has been caused.  FIG. 12C  is a schematic plan view of the conductor portion of the wiring board in  FIG. 12A . In addition,  FIG. 13A  is a schematic plan view of a main portion of a wiring board according to a first variation of the first embodiment.  FIG. 13B  is a schematic plan view of a wiring of the wiring board in  FIG. 13A , the wiring including a wiring portion and a conductor portion, which is formed on the wiring portion and in which a crack has been caused.  FIG. 13C  is a schematic plan view of the conductor portion of the wiring board in  FIG. 13A . 
     For example, the following description assumes that the wiring board  1 D as illustrated in  FIG. 12A  includes a base  10  and a wiring  40  thereon. The wiring  40  includes a wiring portion  20  extending in a direction P diagonally crossing a main extension axis S (a longitudinal direction X of the base  10 ) and a conductor portion  30  on the wiring portion  20 . 
     As in the case of the wiring board  1 D, when the direction P in which the wiring  40  extends has a certain angle or more with respect to a direction (a lateral direction Y of the base  10 ) perpendicular to the main extension axis S, if the wiring board  1 D is extended along the main extension axis S, a crack  53  as illustrated in  FIG. 12B  running in the direction perpendicular to the main extension axis S is caused. As a result, the resistance of the wiring  40  increases. This is because the path of the current flowing through the conductor portion  30  from one end of the wiring  40  to the other end thereof is divided by the crack  53  into the upstream and downstream sides. Namely, the same situation as described with reference to  FIGS. 9A and 9B  arises. 
     In contrast, as illustrated in  FIG. 13A , the direction P in which the wiring  40  of the wiring board  1   a  extends has the certain angle or less with respect to the direction (the lateral direction Y of the base  10 ) perpendicular to the main extension axis S. In this case, unlike the wiring board  1 D, the increase of the resistance of the wiring  40  is prevented. This is because, even when the wiring board  1   a  is extended and a crack  54  as illustrated in  FIG. 13B  running in the direction perpendicular to the main extension axis S is caused in the conductor portion  30 , the path of the current flowing through the conductor portion  30  from one end of the wiring  40  to the other end thereof is not divided by the crack  54  into the upstream and downstream sides. Namely, the same situation as described with reference to  FIGS. 11A and 11B  is maintained. 
     The following knowledge is obtained from these viewpoints. 
     Namely, as illustrated in  FIG. 12C , when an angle α between a direction Sv (the lateral direction Y of the base  10 ) perpendicular to the main extension axis S (the longitudinal direction X of the base  10 ) and the direction P of the conductor portion  30  is larger than an angle β between the direction P of the conductor portion  30  and a diagonal line  31 , the resistance of the wiring  40  is increased by the crack  53 . 
     In contrast, as illustrated in  FIG. 13C , when the angle α between the direction Sv (the lateral direction Y of the base  10 ) perpendicular to the main extension axis S (the longitudinal direction X of the base  10 ) and the direction P of the conductor portion  30  is smaller than the angle β between the direction P of the conductor portion  30  and the diagonal line  31 , the resistance of the wiring  40  by the crack  54  is not increased. 
     When the longitudinal direction X of the base  10  is in parallel with the main extension axis S, the wiring may be formed to extend in the direction P while satisfying the above relationship α&lt;β. In this way, even when the base  10  is extended along the main extension axis S, the increase of the resistance of the wiring  40  is effectively prevented. 
     The wiring boards  1  and  1   a  have been described as examples, assuming that the longitudinal direction X of the base  10  is in parallel with the main extension axis S. However, the main extension axis S may diagonally cross the longitudinal direction X of the base  10 . This will be described with reference to  FIGS. 14A and 14B . 
       FIGS. 14A and 14B  illustrate a main extension axis of wiring boards. More specifically,  FIGS. 14A and 14B  are schematic plan views of main portions of the wiring boards according to the first embodiment and the first variation thereof, respectively. 
     As illustrated in  FIG. 14A , the wiring board  1  includes the wiring  40  (the wiring portion  20  and the conductor portion  30 ) extending in the direction P perpendicular to the longitudinal direction X of the base  10 . The main extension axis S of the wiring board  1  may diagonally cross the longitudinal direction X of the base  10 . For example, in this case, the angle (α) of the direction P of the conductor portion  30  with respect to the direction (Sv) perpendicular to the main extension axis S needs to be smaller than the angle (β) between the direction P of the conductor portion  30  and the diagonal line, from the viewpoints described with reference to  FIGS. 13A to 13C . In this way, even when a crack running in the direction perpendicular to the main extension axis S is caused in the conductor portion  30  on the wiring portion  20 , the resistance of the wiring  40  is not increased by the crack. 
     As illustrated in  FIG. 14B , the wiring board  1   a  includes the wiring  40  (the wiring portion  20  and the conductor portion  30 ) extending in the direction P diagonally crossing the longitudinal direction X of the base  10 . In this case, too, the main extension axis S of the wiring board  1   a  may diagonally cross the longitudinal direction X of the base  10 . In this case, from the viewpoints described with reference to  FIGS. 10A to 11B , the main extension axis S is in the direction Q perpendicular to the direction P of the wiring  40 . In this way, even when a crack running in the direction P perpendicular to the main extension axis S is caused in the conductor portion  30  on the wiring portion  20 , the resistance of the wiring  40  is not increased by the crack. 
     In addition, the wiring boards  1  and  1   a  could be extended in the direction P in which the wiring  40  extends. This will be described with reference to  FIG. 15 . 
       FIG. 15  illustrates an example of a bent wiring board. More specifically,  FIG. 15  is a schematic sectional view of a main portion of a bent wiring board according to the first embodiment or the first variation thereof. 
     In the case of the wiring board  1  or  1   a , for example, as illustrated in  FIG. 15 , the wiring  40  (the wiring portion  20  and the conductor portion  30 ) extending in the direction P could be bent and extended in the direction P. In this case, the wiring  40  undergoes tensile stress by the extension. Thus, a crack running in the direction Q could be caused in the conductor portion  30  of the wiring  40 . If such a crack is caused, the path of the current flowing through the conductor portion  30  could be divided, and as a result, the resistance of the wiring  40  could be increased. To avoid this, the following conditions may be set on the bent wiring board  1  or  1   a.    
     Namely, assuming that the thickness of the base  10  of the wiring board  1  or  1   a  bent as illustrated in  FIG. 15  is T, the radius of curvature when the wiring board  1  or  1   a  is bent is r, and the central angle is θ, distortion U of the wiring  40  on the base  10  is expressed by the following expression (13). 
         U ={2π( r+T )θ−2π r θ}/2π rθ=T/r   (13)
 
     Assuming that fracture strain of the conductor portion  30  is V, when U≦V, fracture of the conductor portion  30  is avoided. From this relationship U≦V and the above expression (13), fracture of the conductor portion  30  is avoided when a condition expressed by the following expression (14) is met. 
         T/r≦V     T≦rV     r≦T/V   (14)
 
     When the wiring board  1  or  1   a  is bent in the direction P, it is preferable that the wiring board  1  or  1   a  be bent to satisfy the condition expressed by the above expression (14) or that the installation location of the wiring board  1  or  1   a  be determined to satisfy the condition expressed by the above expression (14). In other words, it is preferable that the wiring board  1  or  1   a  be designed to satisfy the condition expressed by the above expression (14) when the wiring board  1  or  1   a  is bent or installed. 
     While the above wiring board  1  or  1   a  includes the wiring  40  extending in the direction P crossing the main extension axis S, the wiring board  1  or  1   a  may include another wiring extending in a direction different from the direction P. Structure examples of wiring boards each including a wiring extending in a different direction will be described with reference to  FIGS. 16A and 16B . 
       FIGS. 16A and 16B  illustrate structure examples of wiring boards according to the first embodiment. More specifically,  FIGS. 16A and 16B  are schematic plan views of main portions of wiring boards according to second and third variations of the first embodiment, respectively. 
     The wiring board  1   b  illustrated in  FIG. 16A  includes a wiring  100  extending in the direction Q in parallel with the main extension axis S, in addition to the wiring  40  extending in the direction P perpendicular to the main extension axis S on the base  10 . The wiring  100  extending in the direction Q is made of conductive paste, which is made by including conductive fillers such as Ag fillers in an insulating binder such as silicone rubber, as with the wiring portion  20  of the wiring  40  extending in the direction P. 
     Regarding the wiring board  1   b , the wiring  40  extending in the direction P includes the wiring portion  20  and the conductor portion  30  made of metal foil or the like on the wiring portion  20 . Thus, the wiring  40  has low resistivity. Namely, even when the wiring board  1   b  is extended along the main extension axis S and a crack running in the direction P is caused, the increase of the resistance of the wiring  40  is prevented. Consequently, the wiring  40  representing stable characteristics against the extension along the main extension axis S is obtained. 
     In addition, regarding the wiring board  1   b , the wiring  100  extending in the direction Q is made of conductive paste, and no conductor portion made of metal foil or the like is formed on the wiring  100 . Thus, even when the wiring board  1   b  is extended along the main extension axis S, a crack is not caused easily. Accordingly, the increase of the resistance of the wiring  100  is prevented. Consequently, the wiring  100  representing stable characteristics against the extension along the main extension axis S is obtained. 
     The wiring board  1   b  including the wirings  40  and  100  represents stable characteristics against the extension along the main extension axis S. When the wiring board  1   b  is used for an electronic apparatus, the electronic apparatus stably operates even when the wiring board  1   b  is extended along the main extension axis S. 
     In  FIG. 16A , the wirings  100  and  40  formed on the base  10  are separated from each other. However, these wirings  100  and  40  formed on the base  10  may be connected to each other. 
     The wiring board  1   c  illustrated in  FIG. 16B  differs from the wiring board  1   b  illustrated in  FIG. 16A  in that the wiring board  1   c  includes a wiring  140  on the base  10 . The wiring  140  includes a wiring portion  120  extending in the direction Q in parallel with the main extension axis S and a conductor portion  130  on the wiring portion  120 . The wiring portion  120  is made of conductive paste, which is made by including conductive fillers such as Ag fillers in an insulating binder such as silicone rubber, as with the wiring portion  20  extending in the direction P. The conductor portion  130  is made of metal foil or the like having lower resistivity than that of the wiring portion  120 . 
     As described above, even when the wiring board  1   c  is extended along the main extension axis S, the wiring  40  extending in the direction P represents stable characteristics. 
     In addition, since the wiring  140  extending in the direction Q includes the wiring portion  120  and the conductor portion  130  formed thereon, the wiring  140  has low resistivity. However, when the wiring board  1   c  is extended along the main extension axis S, a crack running in the direction P could be caused in the conductor portion  130  of the wiring  140 . If a crack is caused in the conductor portion  130 , the resistance of the wiring  140  could be increased. However, unless such a crack is caused in the conductor portion  130 , the resistance of the wiring  140  is maintained low. 
     By using the wirings  40  and  140 , the wiring board  1   c  having low resistivity is obtained. By using the wiring board  1   c  for an electronic apparatus, a high-performance electronic apparatus is achieved. 
     In  FIG. 16B , the wirings  140  and  40  formed on the base  10  are separated from each other. However, these wirings  140  and  40  formed on the base  10  may be connected to each other. 
     In addition, while  FIGS. 16A and 16B  each illustrate an example in which the direction P in which the wiring  40  extends is perpendicular to the main extension axis S, the direction P may have a certain angle with respect to the direction perpendicular to the main extension axis S, as in the example illustrated in  FIGS. 13A to 13C . In addition, the direction Q in which the wirings  100  and  140  extend may also have a certain angle with respect to the main extension axis S or the direction perpendicular thereto. The main extension axis S need not match the longitudinal direction X of the base  10 . 
     The wiring board  1  and the like may have wiring structures as illustrated in  FIGS. 17A to 17D . 
       FIGS. 17A to 17D  illustrate structures of the wiring of the wiring board according to the first embodiment. More specifically,  FIG. 17A  is a schematic plan view of a main portion of the wiring board according to the first embodiment. Each of  FIG. 17B to 17D  is a schematic sectional view of the main portion of the wiring on the wiring board, taken along line M 5 -M 5  in  FIG. 17A . 
     As illustrated in  FIG. 17A , the wiring board  1  includes the wiring  40  extending in the direction P on the base  10  (in the lateral direction Y perpendicular to the longitudinal direction X in  FIG. 17A ). The wiring  40  including the wiring portion  20  and the conductor portion formed thereon may have any one of the structures illustrated in  FIGS. 17B to 17D . 
     For example, as illustrated in  FIG. 17B , the wiring  40  may be formed by forming the conductor portion on an upper surface  21  of the wiring portion  20 . Alternatively, for example, as illustrated in  FIG. 17C , the wiring  40  may be formed by embedding a part of the conductor portion  30  into the upper surface  21  of the wiring portion  20 . Alternatively, for example, as illustrated in  FIG. 17D , the wiring  40  may be formed by embedding the entire conductor portion  30  into the wiring portion  20 . The low-resistivity wiring  40  is formed by adopting any one of the structures illustrated in  FIGS. 17B to 17D . Since the structures illustrated in  FIGS. 17C and 17D  improve the contact area and the bonding strength between the conductor portion  30  and the wiring portion  20 , peeling of the conductor portion  30  from the wiring portion  20  is effectively prevented. 
     For example, the wiring  40  as illustrated in  FIG. 17B  may be formed by printing conductive paste serving as the wiring portion  20  on the base  10 , allowing the conductive paste to cure, and laminating metal foil serving as the conductor portion  30  on the conductive paste. For example, the wirings  40  as illustrated in  FIGS. 17C and 17D  may be formed by printing conductive paste serving as the wiring portion  20  on the base  10  and laminating metal foil serving as the conductor portion  30  on the conductive paste before the conductive paste cures (or when the conductive paste partially cures). 
     In addition, the wiring board  1  and the like may adopt wiring structures as illustrated in  FIGS. 18A to 18C . 
       FIGS. 18A to 18C  illustrate structures of the wiring of the wiring board according to the first embodiment. More specifically,  FIG. 18A  is a schematic plan view of a main portion of the wiring board according to the first embodiment. Each of  FIGS. 18B and 18C  is a schematic sectional view of the main portion of the wiring on the wiring board according to the first embodiment, taken along line M 6 -M 6  in  FIG. 18A . 
     The wiring board  1  illustrated in  FIG. 18A  includes the wiring  40  extending in the direction P on the base  10  (in the lateral direction Y perpendicular to the longitudinal direction X in  FIG. 18A ). On the wiring portion  20  on the wiring  40 , a member  33  such as a metal column or a metal thin line is formed as the conductor portion  30 . The member  33  may be made of any one of various kinds of metal material such as Cu or Al. 
     The conductor portion  30  is formed on the wiring portion  20  made of conductive paste. As long as the conductor portion  30  is made of material having lower resistivity than that of the wiring portion  20 , the member  33  such as a metal column or a metal thin line may be formed as the conductor portion  30 . By forming the member on the wiring portion  20 , the increase of the resistance of the wiring  40  is prevented. In addition, even when the wiring board  1  is extended along the main extension axis S (in the longitudinal direction X of the base  10  in  FIG. 18A ), damage such as a crack running in the direction P perpendicular to the main extension axis S is not caused easily in the member  33 . Thus, the resistance of the wiring  40  including the member  33  formed on the wiring portion  20  is maintained low. 
     For example, as illustrated in  FIG. 18B , the member  33  such as a metal column or a metal thin line is formed on an upper surface  21  of the wiring portion  20 . Alternatively, for example, as illustrated in  FIG. 18C , a part of the member  33  may be embedded into the upper surface  21  of the wiring portion  20 . The member  33  may be entirely embedded into the wiring portion  20 . The low-resistivity wiring  40  is formed by adopting any one of the structures illustrated in  FIGS. 18B and 18C . Since the structure illustrated in  FIG. 18C  improves the contact area and the bonding strength between the member  33  serving as the conductor portion  30  and the wiring portion  20 , peeling of the member  33  from the wiring portion  20  is effectively prevented. In addition, the resistance of the wiring  40  is maintained low. 
     For example, the wiring  40  as illustrated in  FIG. 18B  may be formed by printing conductive paste serving as the wiring portion  20  on the base  10 , allowing the conductive paste to cure, and laminating the member  33  such as a metal column or a metal thin line serving as the conductor portion  30  on the conductive paste. For example, the wiring  40  as illustrated in  FIG. 18C  may be formed by printing conductive paste serving as the wiring portion  20  on the base  10  and laminating the member  33  such as a metal column or a metal thin line serving as the conductor portion  30  on the conductive paste before the conductive paste cures or when the conductive paste partially cures. 
     In addition, the wiring board  1  and the like may adopt wiring structures as illustrated in  FIGS. 19A and 19B . 
       FIGS. 19A and 19B  illustrate structures of the wiring of the wiring board according to the first embodiment. Each of  FIGS. 19A and 19B  is a schematic plan view of a main portion of the wiring board according to the first embodiment. 
     The wiring board  1  illustrated in  FIG. 19A  includes the wiring  40  extending in the direction P on the base  10  (in the lateral direction Y perpendicular to the longitudinal direction X in  FIG. 19A ). On the wiring portion  20  on the wiring  40 , at least one CNT  34  (a plurality of CNTs  34 , for example) is formed as the conductor portion  30 . The CNT  34  has high electron mobility, and by forming the CNT  34  on the wiring portion  20 , the resistance of the wiring  40  is maintained low. In addition, even when the wiring board  1  is extended along the main extension axis S (in the longitudinal direction X of the base  10  in  FIG. 19A ), the CNT  34  is not easily damaged. Thus, the resistance of the wiring  40  including the CNT  34  on the wiring portion  20  is maintained low. 
     The wiring board  1  illustrated in  FIG. 19B  includes the wiring  40  extending in the direction P on the base  10  (in the lateral direction Y perpendicular to the longitudinal direction X in  FIG. 19B ). In addition, on the wiring portion  20  on the wiring  40 , at least one layer of graphene  35  is formed as the conductor portion  30 . Any one of various shapes such as a graphene sheet, graphene and nanoribbons may be used for the graphene  35 . The graphene  35  has high electron mobility, and by forming the graphene  35  on the wiring portion  20 , the resistance of the wiring  40  is maintained low. In addition, even when the wiring board  1  is extended along the main extension axis S (in the longitudinal direction X of the base  10  in  FIG. 19B ), the graphene  35  is not easily damaged. Thus, the resistance of the wiring  40  including the graphene  35  on the wiring portion  20  is maintained low. 
     While the CNT  34  and the graphene  35  have been used as examples, another carbon material having high electron mobility may alternatively be used as the conductor portion  30  formed on the wiring portion  20 . A composite material made of carbon and metal materials, such as a carbon material including a metal material, may be used as the conductor portion  30 . 
     For example, each of the wirings  40  as illustrated in  FIGS. 19A and 19B  may be formed by printing conductive paste serving as the wiring portion  20  on the base  10  and laminating the CNT  34  or the graphene  35  serving as the conductor portion  30  on the conductive paste before or after the conductive paste cures. 
     The wiring structures as illustrated in  FIGS. 17A to 19B  may also be applied to the wiring boards  1   a  to  1   c . Namely, these wiring structures may be applied not only to the wirings  40  extending in the direction P but also to the wiring  140  extending in the direction Q perpendicular to the direction P as illustrated in  FIG. 16B . 
     The wiring board  1  and the like may adopt wiring structures as illustrated in  FIGS. 20A and 20B . 
       FIGS. 20A and 20B  illustrate structures of wirings of wiring boards according to fourth and fifth variations of the first embodiment.  FIGS. 20A and 20B  are schematic sectional views of main portions of wiring boards according to fourth and fifth variations of the first embodiment, respectively. 
     The wiring board  1   d  illustrated in  FIG. 20A  includes a wiring  40  on a base  10 . The wiring  40  includes a conductor portion  30  made of metal foil, graphene, etc. and a wiring portion  20  made of conductive paste. The wiring portion  20  covers the conductor portion  30 . 
     In addition, the wiring board  1   e  illustrated in  FIG. 20B  includes a wiring  40  on a base  10 . The wiring  40  includes a conductor portion  30  formed as a metal column, a metal thin line, CNT, etc. and a wiring portion  20  made of conductive paste. The wiring portion  20  covers the conductor portion  30 . 
     As illustrated in  FIGS. 20A and 20B , the wiring may be formed by the conductor portion  30  and the wiring portion  20  covering the conductor portion  30 . By covering the conductor portion  30  with the wiring portion  20 , the conductor portion  30  is not easily peeled from the base  10 . In addition, even when the base  10  is extended, a crack is not easily caused in the conductor portion  30 . Thus, the resistance of the wiring  40  is maintained low. 
     For example, each of the wirings  40  as illustrated in  FIGS. 20A and 20B  may be formed by forming metal foil, a metal column, a metal thin line, a CNT, graphene, or the like serving as the conductor portion  30  on the base  10 , printing conductive paste serving as the wiring portion  20  in such a manner that the conductive paste covers the conductor portion  30 , and allowing the conductor portion  30  and the wiring portion  20  to cure. 
     Next, a second embodiment will be described. 
     Because of its extensibility, a wiring board is installed on a curved surface or is suitably adopted by an electronic apparatus that is bent or extended by external force. Examples of such an electronic apparatus include beacons, which are wireless communication devices that transmit predetermined information (electronic signals), and wearable terminals worn by users when used. 
     For example, as a service provided by a beacon, there is a service in which a beacon installed on a certain location transmits predetermined information to a terminal such as a smartphone or a tablet, to provide the terminal with location information (location information or location-related information). Such information transmitted by beacons is used at facilities such as underground shopping malls where a global positioning system (GPS) is not available, so that users are provided with current locations or are guided to their destinations. In this case, it is preferable that beacons be installable on various places regardless of flat surfaces and curved surfaces. For example, it is preferable that beacons be installable on outer surfaces of devices (lighting equipment, etc.) in facilities or inside these devices. 
     In addition, as a service provided by a beacon, there is a service in which location information of a terminal is acquired by using information transmitted from a beacon included in the terminal. For example, when a user of a terminal including a beacon is lost or wanders around, searching for the user is performed by using information about the user transmitted by the beacon. In this case, it is preferable that the terminal be a wearable terminal in the shape of a wristwatch, a wristband, a ring, or the like that is worn on the user&#39;s body, that does not hinder the user&#39;s movement, and that is not lost easily. 
     A wiring board having extensibility is suitable for a beacon or a wearable terminal installable on various places as described above. In the second embodiment, a beacon will be described as an example of an electronic apparatus in which a wiring board having extensibility is adopted. 
     First, for comparison, a beacon according to a fifth example will be described. 
       FIGS. 21A to 21C  illustrate a structure example of a beacon according to a fifth example. More specifically,  FIG. 21A  is a schematic plan view of a main portion of a beacon according to a fifth example.  FIG. 21B  is a schematic sectional view taken along line M 7 -M 7  in  FIG. 21A .  FIG. 21C  is a schematic sectional view taken along line M 8 -M 8  in  FIG. 21A . In  FIG. 21A , for convenience, a part of an exterior material is not illustrated. 
     The beacon  200 A illustrated in  FIGS. 21A to 21C  includes: a wiring board  300 A having extensibility; a power supply portion  400 , at least one electricity storage element  500 , and a load portion  600 , which are mounted on the wiring board  300 A; and an exterior material  700  covering these components. 
     For the wiring board  300 A of the beacon  200 A, the technique corresponding to the wiring board  1 C as described with reference to  FIGS. 4A and 4B  has been adopted. The wiring board  300 A includes a base  310  having extensibility (corresponding to the base  10  of the wiring board  1 C), a pair of wiring portions  320  (each corresponding to the wiring portion  20  of the wiring board  1 C) formed side by side on the base  310 , and conductor portions  330  (each corresponding to the conductor portion  30  of the wiring board  1 C) formed on the respective wiring portions  320 . 
     An elastomer such as silicone rubber whose planar shape is substantially rectangular is used as the base  310 . The base  310  has its longitudinal direction X in parallel with a main extension axis S of the wiring board  300 A. Each of the wiring portions  320  is formed by printing conductive paste on the base  310 . The conductive paste is obtained by including conductive fillers such as Ag particles in an insulating binder such as silicone rubber. On the wiring board  300 A, each of the wiring portions  320  extends in a direction Q in parallel with the main extension axis S. On each of the wiring portions  320 , a conductor portion  330  made of metal material or carbon material having lower resistivity than that of the wiring portions  320  is formed. A wiring portion  320  and a conductor portion  330  thereon form a wiring  340  (corresponding to the wiring  40  of the wiring board  1 C) that serves as a part of the current paths of the wiring board  300 A. 
     The power supply portion  400 , the electricity storage element  500 , and the load portion  600  are mounted on the wiring board  300 A of the beacon  200 A. 
     Any one of various kinds of power supply such as primary cells, secondary cells, or solar cells is used for the power supply portion  400 . Among these power supplies, it is preferable that solar cells be used for the power supply portion  400 , since solar cells are flexibly deformable in accordance with the installation site of the beacon  200 A and no or little maintenance work such as replacement is needed. The power supply portion  400  is electrically connected to the pair of wirings  340  of the wiring board  300 A. 
     Between the pair of wirings  340  connected to the power supply portion  400 , at least one electricity storage element  500  is implemented. In  FIG. 21A , as an example, four electricity storage elements  500  connected in parallel are illustrated between the pair of wirings  340 . Capacitors such as chip capacitors are used as the electricity storage elements  500 . The electricity storage elements  500  are implemented on the wiring portions  320  of the pair of wirings  340 , as illustrated in  FIG. 21C . The electricity storage elements  500  may be implemented on the conductor portions  330  of the pair of wirings  340 . 
     The pair of wirings  340  connected to the electricity storage elements  500  is electrically connected to the load portion  600 . The load portion  600  includes a control unit  610  and a wireless communication module  620 . The control unit  610  includes various kinds of electronic component, such as semiconductor elements such as transistors, resistors, and capacitors, which are connected by wirings. The control unit  610  controls various kinds of operation, such as supplying a power supply to the wireless communication module  620  and transmitting information from the wireless communication module  620 . 
     The exterior material  700  (a part of which is not illustrated in  FIG. 21A ) is formed on the wiring board  300 A on which the power supply portion  400 , the electricity storage elements  500 , and the load portion  600  are mounted. The exterior material  700  covers the wirings  340 , the power supply portion  400 , the electricity storage elements  500 , and the load portion  600 . An elastomer such as silicone rubber is used as the exterior material  700 , as with the base  310 . 
     In the beacon  200 A, electric charges discharged from the power supply portion  400  are transmitted to the electricity storage elements  500  via the wirings  340 . The electric charges are temporarily accumulated in the electricity storage elements  500 . After a certain quantity of electric charges is accumulated, the electric charges are transmitted from the electricity storage elements  500  to the load portion  600  via the wirings  340 . For example, the control unit  610  monitors the quantity of electric charges accumulated in the electricity storage elements  500 . After the certain quantity of electric charges is accumulated, the control unit  610  supplies the electric charges from the electricity storage elements  500  to the wireless communication module  620 . When receiving the electric charges, the wireless communication module  620  transmits predetermined information to the outside. 
     For example, the beacon  200 A having the above structure is bent and attached to a curved surface of a device in a facility, bent and mounted inside a wearable terminal, or bent in accordance with deformation of a wearable terminal. Since the base  310 , the wiring portions  320 , and the exterior material  700  are each made of an elastomer such as silicone rubber, the beacon  200 A may be bent as described above. In addition, for example, since components having flexibility such as solar cells are used for the power supply portion  400  and small electronic components are used for the electricity storage elements  500  and the load portion  600 , the beacon  200 A may be bent more easily. 
     For example, the beacon  200 A is attached to a device in a facility or mounted on a wearable terminal (including a deformable wearable terminal) in such a manner that the direction in which the beacon  200 A is bent and extended is in parallel with the main extension axis S, which is in parallel with the longitudinal direction X of the base  310 . 
     The wirings  340 , each including a wiring portion  320  and a conductor portion  330  formed thereon, are formed on the wiring board  300 A of the beacon  200 A. The wirings  340  of the beacon  200 A extend in the direction Q in parallel with the main extension axis S (the longitudinal direction X of the base  310 ). An individual wiring  340  is formed by forming a wiring portion  320  made of conductive paste and forming a conductor portion  330 , which is made of metal material or carbon material having lower resistivity than that of the wiring portion  320 , on the wiring portion  320 . In this way, the wirings  340  have lower resistance than that of the wirings  340  formed only by the wiring portions  320 . As a result, the reduction of the voltage drop when a current flows through the wirings  340  is achieved (see the above description made with reference to  FIGS. 3A to 4B , as needed). 
     However, the conductor portions  330 , which are included in the wirings  340  of the beacon  200 A and that extend in the direction Q in parallel with the main extension axis S, could hinder extension of the beacon  200 A along the main extension axis S ( FIGS. 4A and 4B  and  FIGS. 6A and 6B ). Hindrance of the extension of the beacon  200 A by the conductor portions  330  could limit the installation site of the beacon  200 A or the kind of wearable terminal on which the beacon  200 A is mounted. 
     In addition, when the conductor portions  330  extending in the direction Q in parallel with the main extension axis S is extended along the main extension axis S, a crack running in a direction perpendicular to the main extension axis S could be caused in any one of the conductor portions  330  (see the above description made with reference to  FIGS. 4A and 4B  and  FIGS. 8A to 9B , as needed). The crack in a conductor portion  330  could increase the resistance of the corresponding wiring  340 . When the crack increases the resistance of the wiring  340 , if the voltage drop when a current flows through the wiring  340  increases, the load portion  600  suffers from a lack of power. As a result, the wireless communication module  620  could not stably operate or fail to operate at all. Thus, when the beacon  200 A is extended, the characteristics of the wiring board  300 A could change, and as a result, the characteristics of the beacon  200 A could change. 
     Next, a beacon according to a second embodiment will be described. 
       FIG. 22  illustrates a structure example of a beacon according to a second embodiment. More specifically,  FIG. 22  is a schematic plan view of a main portion of a beacon according to a second embodiment. In  FIG. 22 , for convenience, a part of an exterior material is not illustrated. 
     A beacon  200  illustrated in  FIG. 22  includes: a wiring board  300  having extensibility; a power supply portion  400 , at least one electricity storage element  500 , and a load portion  600 , which are mounted on the wiring board  300 ; and an exterior material  700  covering these components. 
     For the wiring board  300  of the beacon  200 , the technique corresponding to the wiring board  1  as described with reference to  FIGS. 5A and 5B  is adopted. The wiring board  300  includes a base  310  having extensibility (corresponding to the base  10  of the wiring board  1 ), a pair of wiring portions  320  (each corresponding to the wiring portion  20  of the wiring board  1 ) formed side by side on the base  310 , and conductor portions  330  (each corresponding to the conductor portion  30  of the wiring board  1 ) formed on the respective wiring portions  320 . The base  310  of the wiring board  300  of the beacon  200  has a longitudinal direction X in parallel with a main extension axis S, and the wiring portions  320  and the conductor portions  330  are formed on the base  310  to extend in a direction P perpendicular to the main extension axis S. A wiring portion  320  and a conductor portions  330  thereon form a wiring  340  (corresponding to the wiring  40  of the wiring board  1 ) that serves as a part of the current paths of the wiring board  300 . 
     The wiring board  300  further includes a pair of wiring portions (wirings)  350  that electrically connects the power supply portion  400  such as solar cells and the load portion  600  including a control unit  610  and a wireless communication module  620 . The wirings  350  are formed on the base  310  to extend in a direction Q in parallel with the main extension axis S. One of the wirings  350  extending in the direction Q is connected to one of the wirings  340  extending in the direction P, and the other wiring  350  extending in the direction Q is connected to the other wiring  340  extending in the direction P. 
     At least one electricity storage element  500  such as a chip capacitor is mounted between the wirings  340  extending in the direction P of the wiring board  300 . In  FIG. 22 , as an example, four electricity storage elements  500  connected in parallel are illustrated between the pair of wirings  340 . 
     The beacon  200  differs from the beacon  200 A including the wiring board  300 A as illustrated in  FIGS. 21A to 21C  in that the beacon  200  includes the wiring board  300  as described above. The beacon  200  may include the same power supply portion  400 , electricity storage elements  500 , load portion  600  (the control unit  610  and the wireless communication module  620 ), and exterior material  700  as those of the above beacon  200 A. 
     In the beacon  200 , electric charges discharged from the power supply portion  400  are transmitted to the electricity storage elements  500  via the wirings  340  and  350 . The electric charges are temporarily accumulated in the electricity storage elements  500 . After a certain quantity of electric charges is accumulated, the electric charges are transmitted from the electricity storage elements  500  to the load portion  600  via the wirings  340  and  350 . For example, the control unit  610  monitors the quantity of electric charges accumulated in the electricity storage elements  500 . After the certain quantity of electric charges is accumulated, the control unit  610  supplies the electric charges from the electricity storage elements  500  to the wireless communication module  620 . When receiving the electric charges, the wireless communication module  620  transmits predetermined information to the outside. 
     For example, the beacon  200  having the above structure is bent and attached to a curved surface of a device in a facility, bent and mounted inside a wearable terminal, or bent in accordance with deformation of a wearable terminal. For example, the beacon  200  is attached to a device in a facility or mounted on a wearable terminal (including a deformable wearable terminal) in such a manner that the direction in which the beacon  200  is bent and extended is in parallel with the main extension axis S, which is in parallel with the longitudinal direction X of the base  310 . 
     Each of the wirings  340  of the beacon  200  is formed by forming a wiring portion  320  extending in the direction P perpendicular to the main extension axis S and a conductor portion  330  extending in the same direction P on the wiring portion  320 . In addition to the wirings  340  in the direction P, the beacon  200  includes the wirings  350  extending in the direction Q in parallel with the main extension axis S. The conductor portions  330  are not formed on the wirings  350  extending in the direction Q. Extending the conductor portions  330  in the direction P perpendicular to the main extension axis S less hinders the extension of the base  310  than extending the conductor portions  330  in the direction Q in parallel with the main extension axis S (see the above description made with reference to  FIG. 6A  to  FIG. 7B , as needed). Thus, the conductor portions  330  of the beacon  200  less hinders the extension of the base  310 . 
     Since the conductor portions  330  are formed on the wiring portions  320 , the resistance of the wirings  340  is maintained low. The electricity storage elements  500  are connected to these wirings  340  having low resistance. Since the wirings  340  including the conductor portions  330  extend in the direction P perpendicular to the main extension axis S, even when the beacon  200  is extended along the main extension axis S, a crack that increases the resistance of the wirings  340  is not easily caused in any one of the conductor portions  330  (see the above description made with reference to  FIGS. 10A to 11B , as needed). Thus, even when the beacon  200  is extended, change of the characteristics of the wiring board  300  is reduced. As a result, since increase of the voltage drop is reduced, change of the amount of power supplied to the load portion  600  is reduced. Namely, even when the beacon  200  is extended, since change of the characteristics of the wiring board  300  is reduced, change of the characteristics of the beacon  200  is reduced. Therefore, the beacon  200  stably operates. 
     In addition, since the electricity storage elements  500  of the beacon  200  are formed side by side in the direction P, the base  310  has a smaller size in its longitudinal direction X than that of the above beacon  200 A including the electricity storage elements  500  formed side by side in the direction Q. Namely, the beacon  200  has a smaller size than the above beacon  200 A. As a result, the beacon  200  may be installed and mounted on a more variety of devices or wearable terminals. 
     The electricity storage elements  500  of the beacon  200  may be arranged and connected differently from what is illustrated in  FIG. 22 . 
       FIG. 23  illustrates a beacon according to a first variation of the second embodiment. More specifically, FIG.  23  is a schematic plan view of a main portion of a beacon according to a first variation of the second embodiment. 
     This beacon  200   a  illustrated in  FIG. 23  includes a pair of wiring portions  320 , each extending in a direction P perpendicular to a main extension axis S and a plurality of wiring portions (protruding wirings)  360  each protruding from one wiring portion  320  to the other wiring portion  320  (along a direction Q). The wiring portions  320  and the protruding wirings  360  are connected to each other. The protruding wirings  360  protruding from one wiring portion  320  are arranged to face the respective protruding wirings  360  protruding from the other wiring portion  320 . One wiring portion  320  and the protruding wirings  360  connected thereto are spaced apart from the other wiring portion  320  and the protruding wirings  360  connected thereto with a gap  361 , which is in the form of a crank course. 
     The protruding wirings  360  are formed by printing conductive paste on a base  310 . For example, the protruding wirings  360  are printed on the base  310  simultaneously with the wiring portions  320  (and wirings  350 ). 
     Conductor portions  330  are made of metal material or carbon material having lower resistivity than the wiring portions  320 , and the conductor portions  330  are formed on the respective wiring portions  320 . A wiring portion  320  and a conductor portion  330  thereon form a wiring  340  extending in the direction P. 
     For example, the conductor portions  330  are not formed on the wirings  350  that connect a power supply portion  400  and a load portion  600  and that extend in the direction Q nor on the protruding wirings  360  that protrude from the wirings  340 . 
     The beacon  200   a  includes at least one electricity storage element  500  such as a chip capacitor (seven electricity storage elements  500  in  FIG. 23  as an example). Two electricity storage elements  500  are each connected between protruding wirings  360  that face each other and that are arranged between the pair of wirings  340 . Each one of the other electricity storage elements  500  is connected between a protruding wiring  360  and a wiring  350  that face each other. 
     For example, an individual electricity storage element  500  has a rectangular planar shape. An electricity storage element  500  having a rectangular planar shape is arranged and connected between protruding wirings  360  facing each other or between a protruding wiring  360  and a wiring  350  facing each other, in such a manner that the longitudinal direction of the electricity storage element  500  is in the direction P, as illustrated in  FIG. 23 . If the electricity storage elements  500  are arranged in this way, even when the beacon  200   a  is bent and extended along the main extension axis S, the extension is not hindered by the electricity storage elements  500  as much as it is by those having its longitudinal direction in the direction Q. 
       FIG. 24  is a beacon according to a second variation of the second embodiment. More specifically,  FIG. 24  is a schematic plan view of a main portion of a beacon according to a second variation of the second embodiment. 
     This beacon  200   b  illustrated in  FIG. 24  is obtained by forming two sets of the electricity storage elements  500  illustrated in  FIG. 23  in parallel with each other. 
     Namely, in the beacon  200   b , between a pair of wirings  340  that is connected to one wiring  350  extending in the direction Q and that extends in the direction P, another wiring  340  that is connected to the other wiring  350  extending in the direction Q and that extends in the direction P is formed. In addition, in the beacon  200   b , between facing wirings  340 , protruding wirings  360  are formed with a gap  361  in the form of a crank course, as in the above example in  FIG. 23 . In addition, an electricity storage element  500  is formed between protruding wirings  360  or between a protruding wiring  360  and a wiring  350 . 
     With the beacon  200   b  having the above structure, the capacitance or the quantity of charges accumulated is increased by increasing the number of electricity storage elements  500 . As a result, a sufficient amount of power supplied to the load portion  600  is ensured. 
     In addition, the electricity storage elements  500  are connected to the low-resistance wirings  340  including the conductor portions  330 . In addition, since the wirings  340  extend in the direction P, even when the beacon  200   b  is extended along the main extension axis S, a crack is not easily caused in any one of the conductor portions  330 . Thus, the resistance of the corresponding wiring  340  is not easily increased. Therefore, even when the number of electricity storage elements  500  is increased, the increase of the wiring length and the increase of the resistance thereby are prevented. 
       FIG. 25  illustrates a beacon according to a third variation of the second embodiment. More specifically,  FIG. 25  is a schematic plan view of a main portion of a beacon according to a third variation of the second embodiment. 
     While this beacon  200   c  illustrated in  FIG. 25  is similar to the beacon  200   a  illustrated in  FIG. 23 , these beacons are different in that the beacon  200   c  includes more electricity storage elements  500 . 
     Namely, the beacon  200   c  includes additional electricity storage elements  500  each arranged and connected between a protruding wiring  360  protruding from one wiring  340  and the other wiring  340 , in addition to the electricity storage elements  500  illustrated in  FIG. 23 . 
     With the beacon  200   c  having the above structure, by arranging electricity storage elements  500  more densely, more electricity storage elements  500  are arranged. Accordingly, since the capacitance or the quantity of charges accumulated is increased, a sufficient amount of power supplied to the load portion  600  is ensured. 
     While  FIGS. 22 to 25  illustrate examples in which no conductor portion  330  is formed on the wirings  350  and the protruding wirings  360  extending in the direction Q, conductor portions  330  may be formed on these wirings  350  and protruding wirings  360 . By forming the conductor portions  330 , the resistance of the wirings  350  and the protruding wirings  360  is reduced. However, when the beacon is extended along the main extension axis S, a crack that increases the resistance is caused relatively easily in the conductor portions  330  formed on the wirings  350  and the protruding wirings  360 . Thus, when such a crack is caused in a conductor portion  330 , the characteristics of the wiring board  300  and the beacon  200 ,  200   a ,  200   b , or  200   c  including the wiring board  300  could change. Unless a crack that increases the resistance of a wiring  350  and a protruding wiring  360  is caused in a conductor portion  330 , the beacon  200 ,  200   a ,  200   b , or  200   c  including the wiring board  300  including the low-resistivity wirings  350 , protruding wirings  360 , and wirings  340  represents good characteristics. 
     The conductor portions  330  of the wirings  340  (or of the wirings  340 , wirings  350  and protruding wirings  360 ) may have any one of various planar shapes other than a rectangular planar shape. 
       FIGS. 26A and 26B  illustrate examples of a conductor portion according to the second embodiment. 
     For example, as illustrated by a solid line in  FIG. 26A , an end portion  331  of a conductor portion  330  extending in the direction P is widened in the direction Q perpendicular to the direction P so that the planar shape of the conductor portion  330  will be a T shape. In the case of the conductor portion  330  having a rectangular planar shape indicated by a dotted line in  FIG. 26A , when a crack is caused in a location as illustrated by a chained line  336  (corresponding to a diagonal line), the path of the current flowing through the conductor portion  330  in the direction P is divided by the crack. As a result, the resistance of the corresponding wiring  340  including the conductor portion  330  is increased. In contrast, in the case of the conductor portion  330  whose planar shape is a T shape as indicated by the solid line in  FIG. 26A , unless a crack is caused in a location illustrated by a thick solid line  337  and the path of the current flowing through the conductor portion  330  in the direction P is divided, the resistance of the corresponding wiring  340  including the conductor portion  330  is not increased. If the planar shape of the conductor portion  330  is formed to have a T shape, the range of the direction of the crack that does not increase the resistance of the corresponding wiring  340  is more widened, the range of the direction (angle) in which the corresponding wiring  340  extends is more widened, or the range of the main extension axis S is more widened, compared with the conductor portion  330  having a rectangular planar shape. 
     For example, as illustrated by a solid line in  FIG. 26B , an end portion  332  of a conductor portion  330  extending in the direction P may be widened in the direction Q perpendicular to the direction P so that the planar shape of the conductor portion  330  will be an L shape. Namely, in the case of the conductor portion  330  having a rectangular planar shape as illustrated by a dotted line in  FIG. 26B , when a crack is caused in a location as illustrated by a chained line  336  (corresponding to a diagonal line), the path of the current flowing through the conductor portion  330  is divided. As a result, the resistance of the corresponding wiring  340  including the conductor portion  330  is increased. In contrast, in the case of the conductor portion  330  whose planar shape is an L shape as indicated by a solid line in  FIG. 26B , unless a crack is caused in a location as illustrated by a thick solid line  337  and the path of the current flowing through the conductor portion  330  is divided, the resistance of the wiring  340  is not increased. If the planar shape of the conductor portion  330  is formed to have an L shape, the range of the direction of the crack that does not increase the resistance of the corresponding wiring  340  is more widened, the range of the direction in which the corresponding wiring  340  extends is more widened, or the range of the main extension axis S is more widened, compared with the conductor portion  330  having a rectangular planar shape. 
     While the above description has been made with examples in which the planar shape of a conductor portion  330  is T or L shape, the same advantageous effects are obtained by forming the planar shape to be Japanese katakana character “e,” which looks similar to the English letter “H” rotated by 90 degrees, or Japanese katakana character “ko,” which looks similar to a square without the left side. 
       FIG. 27  illustrates an example of a wiring board according to the second embodiment. More specifically,  FIG. 27  is a schematic plan view of a main portion of a wiring board according to the second embodiment. 
       FIG. 27  illustrates an example of a wiring board  300  including wirings  340  each including a wiring portion  320  and a conductor portion  330  as illustrated in  FIG. 26A or 26B  on the wiring portion  320 . An individual wiring  340  is formed by forming a conductor portion  330  whose planar shape is a T shape or an L shape on the corresponding wiring portion  320  connected to a wiring  350 . For example, an electricity storage element  500  is arranged and connected between wirings  340  or between a wiring  340  and a wiring  350 . A beacon may be formed by using the wiring board  300  having this structure. 
       FIGS. 28A and 28B  illustrate examples of a conductor portion according to the second embodiment. 
     For example, a conductor portion  330  extending in the direction P is formed to have a planar shape as illustrated by a solid line in  FIG. 28A . In  FIG. 28A , the width of the conductor portion  330  gradually increases from its center portion  333  towards its two end portions  334  in the direction P. In other words, the conductor portion  330  extending in the direction P is formed to have a planar shape so that the width of the conductor portion  330  gradually decreases from the two end portions  334  towards the center portion  333 . 
     With the conductor portion  330  having this planar shape, too, the same advantageous effects as described above are obtained. In the case of the conductor portion  330  having a rectangular planar shape indicated by a dotted line in  FIG. 28A , if a crack is caused in a location indicated by a chained line  336 , the resistance of the corresponding wiring  340  is increased. However, in the case of the conductor portion  330  having the widened planar shape, the direction of a crack that does not increase the resistance of the corresponding wiring  340  is widened to a location indicated by a thick solid line  337 . 
     In addition, for example, the range of the direction in which the corresponding wiring  340  extends is more widened, and the range of the main extension axis S is more widened, compared with the conductor portion  330  having a rectangular planar shape. In addition, by gradually increasing the width of the conductor portion  330  from the center portion  333  to the two end portions  334  so that the sides near the center portion  333  in the direction Q are bent in a concave shape, formation of a flexion point and stress concentration at a flexion point are prevented. Thus, occurrence of a crack is prevented. In addition, in the case of the conductor portion  330  indicated by a solid line in  FIG. 28A , space for arranging electricity storage elements  500  is ensured beside the center portion  333  in the direction Q. 
     In addition, for example, the conductor portion  330  may be formed to have a planar shape as indicated by a solid line in  FIG. 28B . In  FIG. 28B , the width of the conductor portion  330  gradually increases from the center portion  333  towards its two end portions  334  in the direction P. In addition, the width of the conductor portion  330  gradually increases from the center portion  333  towards its two end portions  334  in the direction Q. In other words, the conductor portion  330  is formed to have a planar shape so that the width of the conductor portion  330  gradually decreases from the end portions  334  in the directions P and Q towards the center portion  333 . 
     With this conductor portion  330 , too, the same advantageous effects as described above are obtained. In the case of the conductor portion  330  indicated by a dotted line in  FIG. 28B , if a crack is caused in a location indicated by a chained line  336 , the resistance of the corresponding wiring  340  is increased. However, in the case of the conductor portion  330  having the widened planar shape, the direction of a crack that does not increase the resistance of the corresponding wiring  340  is widened to a location indicated by a thick solid line  337 . In addition, for example, the range of the direction in which the corresponding wiring  340  extends is more widened, and the range of the main extension axis S is more widened, compared with the conductor portion  330  indicated by the dotted line in  FIG. 28B . In addition, in the case of the conductor portion  330  indicated by the solid line in  FIG. 28B , space for arranging electricity storage elements  500  is ensured beside the center portion  333  in the directions P and Q. As in the example in  FIG. 28A , by gradually increasing the width of the conductor portion  330  from the center portion  333  to the end portions  334  in the directions P and Q so that the sides near the center portion  333  in the directions P and Q are bent in a concave shape and so that a flexion point is not formed, stress concentration is prevented. Thus, occurrence of a crack is prevented. 
       FIGS. 29A and 29B  illustrate other examples of the wiring board according to the second embodiment. More specifically,  FIGS. 29A and 29B  are schematic plan views of main portions of other examples of the wiring board according to the second embodiment. 
       FIG. 29A  is an example of the wiring board  300  including a wiring  340  including a wiring portion  320  and a conductor portion  330  as illustrated in  FIG. 28A  on the wiring portion  320 . Two areas are ensured on the wiring portion  320  beside the conductor portion  330  in the direction Q, and two electricity storage elements  500  are connected to the wiring portion  320  on the respective areas. Each of the two electricity storage elements  500  is connected to another wiring  370 . A beacon may be formed by using the wiring board  300  having this structure. 
       FIG. 29B  illustrates an example of the wiring board  300  including a wiring  340  including a wiring portion  320  and a conductor portion  330  as illustrated in  FIG. 28B  on the wiring portion  320 . Four areas are ensured on the wiring portion  320  beside the conductor portion  330  in the directions P and Q, and four electricity storage elements  500  are connected to the wiring portion  320  on the respective areas. Each of the four electricity storage elements  500  is connected to another wiring  370 . A beacon may be formed by using the wiring board  300  having this structure. 
     A wiring board may be formed by mounting one or two of the above power supply portion  400 , electricity storage elements  500 , and load portion  600  on the base  310 . For example, a wiring board may be formed by mounting at least one electricity storage element  500  on the base  310 , without mounting the power supply portion  400  and the load portion  600 . 
     Next, a third embodiment will be described. 
     The above beacons  200 ,  200   a ,  200   b ,  200   c , etc. according to the second embodiment may be installed in or mounted on various kinds of electronic apparatus. 
       FIG. 30  illustrates an example of an electronic apparatus according to the third embodiment. 
     The beacon  200  as illustrated in  FIG. 22  will be described as an example of the beacon according to the third embodiment. For example, the beacon  200  may be installed in a lighting equipment or mounted on a wearable terminal.  FIG. 30  schematically illustrates how the beacon  200  is installed in or mounted on an electronic apparatus  800  such as a lighting equipment or a wearable terminal. The beacon  200  may be first extended in accordance with deformation of the electronic apparatus  800  and next installed in or mounted on the electronic apparatus  800 . However, for convenience,  FIG. 30  illustrates the beacon  200  that has not been extended yet. 
     The beacon  200  illustrated in  FIG. 30  includes: a wiring board  300  having extensibility; and a power supply portion  400 , electricity storage elements  500 , and a load portion  600  mounted on the wiring board  300 . For example, the base  310  of the wiring board  300  of the beacon  200  has a longitudinal direction X in parallel with a main extension axis S. The wiring board  300  includes wirings  340 , each of which includes a wiring portion  320  and a conductor portion  330  formed thereon and extends in a direction P, and wirings  350 , each of which extends in a direction Q perpendicular to the direction P. A plurality of (four, for example) electricity storage elements  500  are connected to the wirings  340  extending in the direction P. The load portion  600  includes: a control unit  610  including electronic components  611  to  613 ; and a wireless communication module  620 . The wiring board  300  further includes a wiring  380  on which the electronic components  611  to  613  and the wireless communication module  620  of the load portion  600  are implemented. A part of the wiring  380 , for example, a wiring  381  connecting the electronic components  611  and  612  and extending in the direction P, includes a wiring portion  381   a  and a conductor portion  381   b  formed thereon. The same structure as that of the wirings  340  is adopted for this part. 
     In the beacon  200 , electric charges discharged from the power supply portion  400  are transmitted to the electricity storage elements  500  via the wirings  350  and  340 . The electric charges are temporarily accumulated in the electricity storage elements  500 . After a certain quantity of electric charges is accumulated, the electric charges are transmitted from the electricity storage elements  500  to the load portion  600  via the wirings  350  and  340 . For example, the control unit  610  (the electronic components  611  to  613 ) monitors the quantity of electric charges accumulated in the electricity storage elements  500 . After the certain quantity of electric charges is accumulated, the control unit  610  supplies the electric charges from the electricity storage elements  500  to the wireless communication module  620  via the wirings  340 ,  350 , and  380 . When receiving the electric charges, the wireless communication module  620  transmits predetermined information to the outside of the electronic apparatus  800 . 
     The information transmitted from the beacon  200  of the electronic apparatus  800  is received by a receiving apparatus  900  (a terminal) outside the electronic apparatus  800  such as a smartphone, a tablet, a personal computer, or a wearable terminal. The receiving apparatus  900  uses the received information for various services. For example, the information is used for a location information service in which the receiving apparatus  900  is provided with its current location and is guided to its destination. As another example, the information is used for a monitoring service in which a source transmitting information about the beacon  200  is searched for. 
     The above description has been made by using, as an example, the electronic apparatus  800  including the beacon  200 . However, an electronic apparatus using one of the other beacons  200   a ,  200   b ,  200   c , etc. may be realized in the same way. 
     In addition, other than a beacon, the above wiring board having extensibility may be used for any one of various kinds of electronic apparatus such as computers (personal computers, supercomputers, servers, etc.), smartphones, mobile phones, tablet terminals, sensors, cameras, audio devices, measuring devices, inspection devices, and manufacturing devices. In this case, the wiring board may be used for connecting electronic components or connecting electronic apparatuses by using a connector, other than for mounting electronic components. 
     According to the disclosed technique, even when a base is extended in its longitudinal direction and a crack is caused thereby, the resistance is not changed by the crack. Namely, a wiring board representing stable characteristics is obtained. In addition, an electronic apparatus that includes the wiring board and that stably operates is obtained. 
     All examples and conditional language provided herein are intended for the pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventor to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although one or more embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.