Abstract:
Provided is a substrate, wherein wire-breaking of a plurality of signal lines can be detected, circuit configuration can be simplified, and processing load accompanying wire-breaking detection processing can be minimized. This substrate is a multi-layer structured FPC substrate ( 203 ), having a plurality of layers (L 1 -L 4 ) insulated from each other. In this FPC substrate ( 203 ), a signal line ( 302 ) is provided on each of the plurality of layers (L 1 -L 4 ). A dummy line ( 303 ) is provided, by being bent from one layer among the plurality of layers (L 1 -L 4 ) towards a layer other than the one of the layers, on both the one of the layers and the layer other than the one of the layers.

Description:
TECHNICAL FIELD 
       [0001]    The present invention particularly relates to a substrate and a mobile terminal device for detecting wire-breaking of a signal line. 
       BACKGROUND ART 
       [0002]    In recent years, there has been mainly used a folding mobile terminal device in which multiple casings are openably connected via hinges. In such a mobile terminal device, in many cases, each function block and a control circuit are arranged over multiple casings for an optimum arrangement of each function block in the casings and integration of the control circuit for operating each function block. Therefore, various signals need to be sent between the casings and there are provided signal lines and power supply lines for connecting circuit substrates arranged in the respective casings. In the mobile terminal device having an open/close mechanism with which the signal lines are provided, there is a problem that the signal lines or power supply lines are easily broken at a portion movable along with the open/close. Therefore, it is important to detect and report that the signal lines or power supply lines can be broken in order to prevent an abrupt failure or abrupt poor operation. 
         [0003]    There is conventionally known a device for detecting and reporting that a signal line can be broken (Patent Literature 1, for example). Patent Literature 1 discloses that release of a flexible print (described as “FPC” below) substrate or wire-breaking of an internal wiring is detected and its result is reported to a liquid crystal device. Specifically, two detection lines for detecting release or wire-breaking are formed separately from a control signal line in the FPC substrate arranged between a liquid crystal panel and a liquid crystal driver substrate. In Patent Literature 1, the voltage values of the two detection lines are subjected to OR, respectively, to detect wire-breaking and to display alarm information on the liquid crystal panel. In this way, Patent Literature 1 is to detect and report wire-breaking of the control signal line for connecting the liquid crystal panel as a display function block and the liquid crystal driver. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         PL1 
         Japanese Patent Application Laid-Open No. 2008-15287 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0006]    However, Patent Literature 1 is directed for detecting wire-breaking of a signal line in one function block, and as many wire-breaking detection circuits shown in Patent Literature 1 as function blocks need to be provided for detecting wire-breaking of each signal line in multiple function blocks. Thus, in Patent Literature 1, there is a problem that a wire-breaking detection circuit is complicated and a processing load on the wire-breaking detection processing increases. 
         [0007]    It is an object of the present invention to provide a substrate and a mobile terminal device capable of detecting wire-breaking of multiple signal lines, simplifying a circuit structure and restricting a processing load on the wire-breaking detection processing. 
       Solution to Problem 
       [0008]    A substrate according to the present invention is a multilayer structured substrate having multiple mutually-insulated layers, and comprises signal lines provided in the respective layers, and dummy lines bent from one layer among the layers toward a layer other than the one layer and provided in both the one of the layers and the layer other than the one of the layers. 
         [0009]    A mobile terminal device according to the present invention comprises a first casing, a second casing, a multilayer structured substrate that connects the first casing and the second casing and has multiple mutually-insulated layers, signal lines provided in the respective layers, dummy lines that travel between the first casing and the second casing and are bent from one layer among the layers toward a layer other than the one layer to be provided in both the one of the layers and the layer other than the one of the layers, a wire-breaking detection section that detects wire-breaking of the dummy line, and an alarm section that, when the wire-breaking detection section detects wire-breaking of the dummy line, gives an alarm about the wire-breaking of a signal line of the one layer or the layer other than the one layer. 
       Advantageous Effects of Invention 
       [0010]    According to the present invention, it is possible to detect wire-breaking of multiple signal lines and to simplify a circuit structure, thereby restricting a processing load on a wire-breaking detection processing. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  is a perspective view of an open state of a mobile terminal device according to Embodiment 1 of the present invention; 
           [0012]      FIG. 2  is a plan view of an open state of the mobile terminal device according to Embodiment 1 of the present invention; 
           [0013]      FIG. 3  is a plan view of essential sections of the mobile terminal device according to Embodiment 1 of the present invention; 
           [0014]      FIG. 4  is side vide of a FPC substrate according to Embodiment 1 of the present invention; 
           [0015]      FIG. 5  is a plan view of essential sections of a mobile terminal device according to Embodiment 2 of the present invention; and 
           [0016]      FIG. 6  is a plan view of essential sections of a mobile terminal device according to Embodiment 3 of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0017]    Embodiments of the present invention will be described below in detail with reference to the drawings. 
       Embodiment 1 
       [0018]      FIG. 1  is a perspective view of an open state of mobile terminal device  100  according to Embodiment 1 of the present invention.  FIG. 2  is a plan view of an open state of mobile terminal device  100 . 
         [0019]    As shown in  FIG. 1 , mobile terminal device  100  comprises first casing  101 , second casing  102  and hinge section  103 . 
         [0020]    First casing  101  has operation section  110 , first circuit substrate  201 , and connector  204 . Second casing  102  has display section  120 , second circuit substrate  202 , and connector  205 . Each constituent will be described below in detail. 
         [0021]    First casing  101  is substantially box-shaped, and is connected with second casing  102  rotatably in X1 or X2 (see  FIG. 1 ) direction via hinge section  103 . First casing  101  has first circuit substrate  201  therein. First casing  101  has operation section  110  that is operated by a user and enables e-mails to be transmitted and received, or digital television broadcast to be viewed. 
         [0022]    Second casing  102  is substantially box-shaped, and is connected with first casing  101  rotatably in X1 or X2 direction via hinge section  103 . Second casing  102  has second circuit substrate  202  therein. Second casing  102  has display section  120  that displays characters and the like input by operation section  110  or images and the like of digital television broadcast received by mobile terminal device  100 . 
         [0023]    Hinge section  103  rotatably connects first casing  101  and second casing  102  in X1 or X2 direction. Hinge section  103  has FPC substrate  203  therein. 
         [0024]    First circuit substrate  201  has connector  204  connected with FPC substrate  203 . First circuit substrate  201  is electrically connected with second circuit substrate  202  via connector  204 , FPC substrate  203  and connector  205 . The circuit structure of first circuit substrate  201  will be described later. 
         [0025]    Second circuit substrate  202  has connector  205  connected with FPC substrate  203 . Second circuit substrate  202  is electrically connected with first circuit substrate  201  via connector  205 , FPC substrate  203  and connector  204 . First circuit substrate  201 , second circuit substrate  202  and FPC substrate  203  may not be separately formed, first circuit substrate  201  and FPC substrate  203  may be integrally formed, and second circuit substrate  202  and FPC substrate  203  may be separately formed. First circuit substrate  201  and FPC substrate  203  may be separately formed and second circuit substrate  202  and FPC substrate  203  may be integrally formed. When first circuit substrate  201  and FPC substrate  203  are integrally formed, connector  204  may not he required. When second circuit substrate  202  and FPC substrate  203  are integrally formed, connector  205  may not be required. 
         [0026]    A structure of essential sections of mobile terminal device  100  will be described below in detail with reference to  FIG. 3 .  FIG. 3  is a plan view of essential sections of mobile terminal device  100 . In  FIG. 3 , like reference numerals are denoted to the same constituents as those of  FIGS. 1 and 2 , and an explanation thereof will be omitted. In  FIG. 3 , an explanation of first casing  101 , second casing  102  and hinge section  103  will be omitted for convenience of description. 
         [0027]    First circuit substrate  201  has circuit section  301 . First circuit substrate  201  prints and forms first signal line  302  and first dummy line  303  therein. First circuit substrate  201  prints and forms second signal line  304  and second dummy line  305  therein. First circuit substrate  201  has resistor  306  and resistor  307 . 
         [0028]    Second circuit substrate  202  prints and forms first signal line  302  and second signal line  304  therein. Second circuit substrate  202  prints and forms first dummy line  303  and second dummy line  305  therein. Second circuit substrate  202  has a plurality of different function blocks (not shown). First signal line  302 , first dummy line  303 , second signal line  304  and second dummy line  305  may not be printed and formed, and may be separately formed from second circuit substrate  202  and may be formed in any method. The function block is configured of a camera, IrDA, or an electronic component necessary for operating LCD. 
         [0029]    FPC substrate  203  is made of a flexible material. FPC substrate  203  forms first signal line  302 , first dummy line  303 , second signal line  304 , and second dummy line  305  therein. FPC substrate  203  is provided with insulation sections that insulate first signal line  302 , first dummy line  303 , second signal line  304  and second dummy line  305  mutually and from outside. 
         [0030]    Circuit section  301  is electrically connected to first signal line  302 , first dummy line  303 , second signal line  304  and second dummy line  305 . Circuit section  301  supplies power to the function blocks, which are the connection destinations of first signal line  302  and second signal line  304 . Circuit section  301  outputs a control signal to first signal line  302  and second signal line  304  for controlling the operations of the function blocks, which are the connection destinations of first signal line  302  and second signal line  304 . Circuit section  301  has a constant current source that supplies a constant current to first dummy line  303  and second dummy line  305 . Circuit section  301  detects wire-breaking of first dummy tine  303  and second dummy line  305 . A wire-breaking detection method will be described later. 
         [0031]    First signal line  302  connects circuit section  301  with the function block (not shown) provided in second casing  102 . First signal line  302  is printed and formed in first circuit substrate  201 , is formed in FPC substrate  203  by hinge section  103 , and is printed and formed in second circuit substrate  202 . First signal line  302  is formed as a continuous signal line over first circuit substrate  201 , FPC substrate  203  and second circuit substrate  202 . 
         [0032]    First dummy line  303  is electrically connected at one end to circuit section  301 . First dummy line  303  is extended from one end connected with circuit section  301  toward second casing  102 , travels between first circuit substrate  201  and second circuit substrate  202 , and is earthed at the other end on a ground section of first circuit substrate  201  via resistor  306 . First dummy line  303  is provided at the horizontally outer sides of first signal line  302 . The horizontally outer sides of first signal line  302  mean the upper side and the lower side of first signal line  302  in  FIG. 3 . First dummy line  303  has folding section  303   a  in second circuit substrate  202 . First dummy line  303  is formed as a continuous dummy line over first circuit substrate  201 , FPC substrate  203  and second circuit substrate  202 . 
         [0033]    Second signal line  304  connects circuit section  301  with the function block (not shown) provided in second casing  102 . First signal line  302  is printed and formed in first circuit substrate  201 , is formed in FPC substrate  203  by hinge section  103 , and is printed and formed in second circuit substrate  202 . Second signal line  304  is formed as a continuous signal line over first circuit substrate  201 , FPC substrate  203  and second circuit substrate  202 . 
         [0034]    Second dummy line  305  is electrically connected at one end to circuit section  301 . Second dummy line  305  is extended from one end connected with circuit section  301  toward second casing  102 , travels between first circuit substrate  201  and second circuit substrate  202 , and is earthed at the other end on the ground section of first circuit substrate  201  via resistor  307 . Second dummy line  305  is provided at the horizontally outer sides of second signal line  304 . The horizontally outer sides of second signal line  304  mean the upper side and the lower side of second signal line  304  in  FIG. 3 . Second dummy line  305  has folding section  305   a  in second circuit substrate  202 . Second dummy line  305  is formed as a continuous dummy line over first circuit substrate  201 , FPC substrate  203  and second circuit substrate  202 . 
         [0035]    A structure of FPC substrate  203  will be described below with reference to  FIG. 4 .  FIG. 4  is a side view of FPC substrate  203 . 
         [0036]    FPC substrate  203  is multilayer structured as shown in  FIG. 4 . Specifically, FPC substrate  203  has a four-layer structure of first layer L 1 , second layer L 2 , third layer L 3  and fourth layer L 4 . The insulation sections (not shown) mutually isolate first layer L 1  and second layer L 2 , second layer L 2  and third layer L 3 , and third layer L 3  and fourth layer L 4 . First dummy line  303  is extended from first circuit substrate  201  toward second circuit substrate  202  in first layer L 1 . Since first dummy line  303  is bent downward in the middle of first layer L 1 , is bent toward first circuit substrate  201  in second layer L 2 , so that first dummy line  303  is extended from second circuit substrate  202  toward first circuit substrate  201  in second layer L 2 . Since first dummy line  303  is bent downward in the middle of second layer L 2 , is bent toward second circuit substrate  202  in third layer L 3 , so that first dummy line  303  is extended from first circuit substrate  201  toward second circuit substrate  202  in third layer L 3 . Since first dummy line  303  is bent downward in the middle of third layer L 3 , is bent toward first circuit substrate  201  in fourth layer L 4 , so that first dummy line  303  is extended from second circuit substrate  202  toward first circuit substrate  201  in fourth layer L 4 . First dummy line  303  formed in first layer L 1  and first dummy line  303  formed in second layer L 2  are arranged to be at the horizontally outer sides of first signal line  302 . First dummy line  303  formed in third layer L 3  and first dummy line  303  formed in fourth layer L 4  are arranged to be at the horizontally outer sides of first signal line  302 . In this way, first dummy line  303  travels between first circuit substrate  201  and second circuit substrate  202 , and is formed as a continuous dummy line from first layer L 1  to fourth layer L 4 . The layers of FPC substrate  203  are not limited to four layers, and may employ any number of layers. 
         [0037]    With multilayer structured FPC substrate  203 , signal lines that connect different function blocks from those of circuit section  301  can be provided in each of first layer L 1  to fourth layer L 4 . In this way, multiple signal lines and first dummy lines  303  connected with multiple function blocks are grouped as a group of wirings, thereby detecting and alarming wire-breaking. 
         [0038]    Second dummy line  305  is formed in the same structure as  FIG. 4 , and its explanation will be omitted. 
         [0039]    The explanation of the structure of mobile terminal device  100  terminates. 
         [0040]    A method for detecting wire-breaking of FPC substrate  203  will be described below with reference to  FIG. 3 . 
         [0041]    Circuit section  301  supplies a constant current from the constant current source to first dummy line  303  and second dummy line  305 . Circuit section  301  monitors the voltages of first dummy line  303  and second dummy line  305 , and detects a change in voltage. For example, circuit section  301  A/D converts the detected voltage value and compares the voltage value after the conversion with a threshold, thereby detecting a change in voltage. The voltage change detection is not limited to the above method, and may employ various methods. For example, when circuit section  301  has an A/D conversion function, resistor  306  and resistor  307  may be deleted, and circuit section  301  may apply a bias to first dummy line  303  and second dummy line  305  thereby to detect a change in voltage. 
         [0042]    In a normal state in which first dummy line  303  and second dummy line  305  are not broken, the voltages of first dummy line  303  and second dummy line  305  detected by circuit section  301  are within a certain predefined range. 
         [0043]    In this state, when first dummy line  303  is broken, the voltage of first dummy line  303  detected by circuit section  301  is out of the predefined range. Therefore, circuit section  301  detects that the voltage of first dummy line  303  is out of the predefined range, and thereby detects the wire-breaking of first dummy line  303 . 
         [0044]    Similarly, when second dummy line  305  is broken, the voltage of second dummy line  305  detected by circuit section  301  is out of the predefined range. Thus, circuit section  301  detects that the voltage of second dummy line  305  is out of the predefined range, and thereby detects the wire-breaking of second dummy line  305 . 
         [0045]    When circuit section  301  detects the wire-breaking of first dummy line  303 , mobile terminal device  100  displays and alarms, on display section  120 , that first signal line  302  can be broken. When circuit section  301  detects the wire-breaking of second dummy line  305 , mobile terminal device  100  displays and alarms, on display section  120 , that second signal line  304  can be broken. At this time, mobile terminal device  100  can display a different alarm per function block. Thereby, the user can quickly grasp a portion where wire-breaking can possibly occur. 
         [0046]    A stress along with the open/close operation of first casing  101  and second casing  102  is more easily applied to the outside of FPC substrate  203  than to the inside thereof. Therefore, typically first dummy line  303  is more easily broken than first signal line  302 . Similarly, typically second dummy line  305  is more easily broken than second signal line  304 . Thus, an alarm is given when the wire-breaking of first dummy line  303  is detected or when the wire-breaking of second dummy line  305  is detected, and thus the user can previously take a countermeasure such as repair before first signal line  302  or second signal line  304  is broken. 
         [0047]    In the present embodiment, two first dummy lines  303  and two second dummy lines  305  may be arranged. In this case, for each of first dummy lines  303  and second dummy lines  305 , the outer dummy line may be for alarm display and the inner dummy line may be for power supply stop. In this case, an alarm is given when only the outer dummy line is broken, and the power supply can be stopped when the outer dummy line is broken and further the inner dummy line is broken. Thereby, an alarm and a power supply can be stopped per function block. For example, when a signal line of the function block of the camera can be broken, the power supply to the function block of the camera is stopped and the power supply to the function block of the phone can be continued. Consequently, mobile terminal device  100  cannot use the camera function but can continuously use the call function. 
         [0048]    As described above, according to the present embodiment, wire-breaking can be detected per function blocks and the circuit structure can be simplified, thereby restricting the processing load on the wire-breaking detection processing. According to the present embodiment, the first circuit substrate and the second circuit substrate are connected via the FPC substrate, thereby further reducing more manufacture cost than use of a coaxial line. According to the present embodiment, by giving an alarm when wire-breaking of a dummy line is detected, repair is possible before a signal line is broken, thereby avoiding an abrupt disabled state due to wire-breaking of a signal line. 
         [0049]    In the present embodiment, two signal lines are provided, but any number of signal lines may be employed depending on the number of function blocks mounted on the mobile terminal device. In the present embodiment, one signal line is associated with one dummy line for arrangement, but the present embodiment is not limited thereto, and multiple signal lines and one dummy line may be associated and arranged, and one signal line and multiple dummy lines may be associated and arranged. 
       Embodiment 2 
       [0050]      FIG. 5  is a plan view of essential sections of mobile terminal device  100  according to Embodiment 2 of the present invention. 
         [0051]    Mobile terminal device  100  shown in  FIG. 5  is such that first signal line  302 , first dummy line  303 , second signal line  304 , second dummy line  305 , resistor  306  and resistor  307  are deleted from mobile terminal device  100  according to Embodiment 1 shown in  FIG. 3 , first signal line  502 , first dummy line  503 , second signal line  504 , second dummy line  505 , third signal line  506 , third dummy line  507 , resistor  508 , resistor  509  and resistor  510  are added thereto, and circuit section  501  is provided instead of circuit section  301 . In  FIG. 5 , like reference numerals are denoted to the same constituents as those of  FIG. 3 , and an explanation thereof will be omitted. In the present embodiment, a perspective view of the open state of mobile terminal device  100  is the same as  FIG. 1  and the plan view of the open state of mobile terminal device  100  is the same as  FIG. 2 , and thus an explanation thereof will be omitted. In the present embodiment, the structure of the FPC substrate is the same as  FIG. 4 , and thus an explanation thereof will be omitted. 
         [0052]    First circuit substrate  201  has circuit section  501 . First circuit substrate  201  prints and forms first signal line  502  and first dummy line  503  therein. First circuit substrate  201  prints and forms second signal line  504  and second dummy line  505  therein. First circuit substrate  201  prints and forms third signal line  506  and third dummy line  507  therein. First circuit substrate  201  has resistor  508 , resistor  509  and resistor  510 . First signal line  502 , first dummy line  503 , second signal line  504 , second dummy line  505 , third signal line  506  and third dummy line  507  may not be printed and formed, and may be formed separately from first circuit substrate  201  and may be formed in any method. 
         [0053]    Second circuit substrate  202  prints and forms first signal line  502  and first dummy line  503  therein. Second circuit substrate  202  prints and forms second signal line  504  and second dummy line  505  therein. Second circuit substrate  202  prints and forms third signal line  506  and third dummy line  507  therein. Second circuit substrate  202  has a plurality of different function blocks (not shown). First signal line  502 , first dummy line  503 , second signal line  504 , second dummy line  505 , third signal line  506  and third dummy line  507  may not be printed and formed, and may be formed separately from second circuit substrate  202  and may be formed in any method. 
         [0054]    FPC substrate  203  is made of a flexible material. FPC substrate  203  forms first signal line  502 , first dummy line  503 , second signal line  504 , second dummy line  505 , third signal line  506  and third dummy line  507  therein. FPC substrate  203  is provided with insulation sections that insulate first signal line  502 , first dummy line  503 , second signal line  504 , second dummy line  505 , third signal line  506  and third dummy line  507  mutually and from outside. 
         [0055]    Circuit section  501  is electrically connected to first signal line  502 , first dummy line  503 , second signal line  504 , second dummy line  505 , third signal line  506  and third dummy line  507 . Circuit section  501  supplies power to the function blocks, which are the connection destinations of first signal line  502 , second signal line  504  and third signal line  506 . Circuit section  501  outputs a control signal to first signal line  502 , second signal line  504  and third signal line  506  for controlling the operations of the function blocks, which are the connection destinations of first signal line  502 , second signal line  504  and third signal line  506 . Circuit section  501  has a constant current source that supplies a constant current to first dummy line  503 , second dummy line  505  and third dummy line  507 . Circuit section  501  detects wire-breaking of first dummy line  503 , second dummy line  505  and third dummy line  507 . A wire-breaking detection method will be described later. 
         [0056]    First signal line  502  connects circuit section  501  and the function block (not shown) provided in second casing  102 . First signal line  502  is printed and formed in first circuit substrate  201 , is formed in FPC substrate  203  by hinge section  103 , and is printed and formed in second circuit substrate  202 . First signal line  502  is formed as a continuous signal line over first circuit substrate  201 , FPC substrate  203  and second circuit substrate  202 . 
         [0057]    First dummy line  503  is electrically connected at one end to circuit section  501 . First dummy line  503  is extended from one end connected with circuit section  501  toward second casing  102 , travels between first circuit substrate  201  and second circuit substrate  202 , and is earthed at the other end to the ground section of first circuit substrate  201  via resistor  510 . First dummy line  503  is provided at the horizontally outer sides of first signal line  502 . The horizontally outer sides of first signal line  502  mean the upper side and the lower side of first signal line  502  in FIGS. First dummy line  503  has folding section  503   a  in second circuit substrate  202 . First dummy line  503  is formed as a continuous dummy line over first circuit substrate  201 , FPC substrate  203  and second circuit substrate  202 . 
         [0058]    Second signal line  504  connects circuit section  501  and the function block (not shown) provided in second casing  102 . Second signal line  504  is printed and formed in first circuit substrate  201 , is formed in FPC substrate  203  by hinge section  103 , and is printed and formed in second circuit substrate  202 . Second signal line  504  is formed as a continuous signal line over first circuit substrate  201 , FPC substrate  203  and second circuit substrate  202 . 
         [0059]    Second dummy line  505  is electrically connected at one end to circuit section  501 . Second dummy line  505  is extended from one end connected with circuit section  501  toward second casing  102 , travels between first circuit substrate  201  and second circuit substrate  202 , and is earthed at the other end to the ground section of first circuit substrate  201  via resistor  509 . Second dummy line  505  is provided at the horizontally outer sides of second signal line  504 . The horizontally outer sides of second signal line  504  mean the upper side and the lower side of second signal line  504  in  FIG. 5 . Second dummy line  505  has folding section  505   a  in second circuit substrate  202 . Second dummy line  505  is formed as a continuous dummy line over first circuit substrate  201 , FPC substrate  203  and second circuit substrate  202 . Second dummy line  505  is arranged more inside than first dummy line  503 . 
         [0060]    Third signal line  506  connects circuit section  501  and the function block (not shown) provided in second casing  102 . Third signal line  506  is printed and formed in first circuit substrate  201 , is formed in FPC substrate  203  by hinge section  103 , and is printed and formed in second circuit substrate  202 . Third signal line  506  is formed as a continuous signal line over first circuit substrate  201 , FPC substrate  203  and second circuit substrate  202 . 
         [0061]    Third dummy line  507  is electrically connected at one end to circuit section  501 . Third dummy line  507  is extended from one end connected with circuit section  501  toward second casing  102 , travels between first circuit substrate  201  and second circuit substrate  202 , and is earthed at the other end to the ground section of first circuit substrate  201  via resistor  508 . Third dummy line  507  is provided at the horizontally outer sides of third signal line  506 . The horizontally outer sides of third signal line  506  mean the upper side and the lower side of third signal line  506  in  FIG. 5 . Third dummy line  507  has folding section  507   a  in second circuit substrate  202 . Third dummy line  507  is formed as a continuous dummy line over first circuit substrate  201 , FPC substrate  203  and second circuit substrate  202 . Third dummy line  507  is arranged more inside than first dummy line  503  and second dummy line  505 . 
         [0062]    A method for detecting wire-breaking of FPC substrate  203  will be described below with reference to  FIG. 5 . 
         [0063]    Circuit section  501  supplies a constant current from the constant current source to first dummy line  503 , second dummy line  505  and third dummy line  507 . Circuit section  501  monitors the voltages of first dummy line  503 , second dummy line  505  and third dummy line  507 , and detects a change in voltage. For example, circuit section  501  A/D converts the detected voltage value and compares the voltage value after the conversion with a threshold, thereby detecting a change in voltage. The voltage change detection is not limited to the above method, and may employ various methods. For example, when circuit section  501  has an A/D conversion function, resistor  508 , resistor  509  and resistor  510  may be deleted, and circuit section  501  may apply a bias to first dummy line  503 , second dummy line  505  and third dummy line  507  thereby to detect a change in voltage. 
         [0064]    In a normal state where any of first dummy line  503 , second dummy line  505  and third dummy line  507  is not broken, the voltages of first dummy line  503 , second dummy line  505  and third dummy line  507  detected by circuit section  501  are within a certain predefined range. 
         [0065]    In this state, when first dummy line  503  is broken, the voltage of first dummy line  503  detected by circuit section  501  is out of the predefined range. Thus, circuit section  501  detects that the voltage of first dummy line  503  is out of the predefined range, and thereby detects the wire-breaking of first dummy line  503 , 
         [0066]    Similarly, when second dummy line  505  is broken, the voltage of second dummy line  505  detected by circuit section  501  is out of the predefined range. Therefore, circuit section  501  detects that the voltage of second dummy line  505  is out of the predefined range, and thereby detects the wire-breaking of second dummy line  505 . 
         [0067]    Similarly, when third dummy line  507  is broken, the voltage of third dummy line  507  detected by circuit section  501  is out of the predefined range. Thus, circuit section  501  detects that the voltage of third dummy line  507  is out of the predefined range, and thereby detects the wire-breaking of third dummy line  507 . 
         [0068]    When circuit section  501  detects the wire-breaking of first dummy line  503  and does not detect the wire-breaking of the second dummy line, mobile terminal device  100  displays and alarms, on display section  120 , that only first signal line  502  can be broken. When circuit section  501  detects the wire-breaking of second dummy line  505 , mobile terminal device  100  decides that first signal line  502  is broken, and displays and alarms, on display section  120 , that second signal line  504  can be broken. When circuit section  501  detects the wire-breaking of third dummy line  507 , mobile terminal device  100  decides that first signal line  502  and second signal line  504  are broken, and displays and alarms, on display section  202 , that third signal line  506  can be broken. At this time, mobile terminal device  100  can display a different alarm per function block. Thereby, the user can quickly grasp a portion where wire-breaking can occur. 
         [0069]    A stress along with the open/close operation of first casing  101  and second casing  102  is more easily applied to the outside of FPC substrate  203  than to the inside thereof. Therefore, typically first dummy line  503  is more easily broken than first signal line  502 . Similarly, typically second dummy line  505  is more easily broken than second signal line  504 . Similarly, typically third dummy line  507  is more easily broken than third signal line  506 . Thus, an alarm is given when the wire-breaking of first dummy line  503  is detected, when the wire-breaking of second dummy line  505  is detected, or when the wire-breaking of third dummy line  507  is detected, and thus the user can previously take a countermeasure such as repair before first signal line  502 , second signal line  504  or third signal line  506  is broken. 
         [0070]    In  FIG. 5 , the function block connected to second signal line  504  is more frequently used, that is more important than the function block connected to first signal tine  502 . For example, it is assumed that the function block connected with first signal line  502  is a camera or IrDA and the function block connected with second signal line  504  is display section  120  and a control circuit that controls display section  120 . Thereby, fewer failures due to wire-breaking occur in a function block with higher importance. 
         [0071]    Similarly, in  FIG. 5 , the function block connected with third signal line  506  is more frequently used, that is more important than the function block connected with second signal line  504 . For example, it is assumed that the function block connected with second signal line  504  is display section  202  and the control circuit that controls display section  202 , and the function block connected with third signal line  506  is the control circuit that controls the call function of the phone. Thereby, fewer failures due to wire-breaking occur in a function block with higher importance. 
         [0072]    In the present embodiment, two first dummy lines  503 , two second dummy line  505  and two third dummy lines  507  may be arranged. In this case, for each of first dummy lines  503 , second dummy lines  505  and third dummy lines  507 , the outer dummy line may be for wire-breaking detection and the inner dummy line may be for power supply stop. For example, when the wire-breaking of second dummy line  505  is detected, the power supply to the function block connected with first signal line  502  is stopped, and an alarm is given that second signal line  504  can be broken. When the wire-breaking of third dummy line  507  is detected, the power supply to the function block connected with first signal line  502  and the function block connected with second signal line  504  is stopped, and an alarm is given that third signal line  506  can be broken. 
         [0073]    As described above, according to the present embodiment, in addition to the effects of Embodiment 1, a signal line and a dummy line of a function block with higher importance are arranged inside the FPC substrate, thereby reducing wire-breaking of a signal line of a function block with higher importance. 
         [0074]    In the present embodiment, a function block with higher importance is selected depending on use frequency, but the present embodiment is not limited thereto, and a function block with higher importance may be selected based on user&#39;s manual setting, or a function block with higher importance may be arbitrarily selected. In the present embodiment, two signal lines are employed, but any number of signal lines may be employed depending on the number of function blocks mounted on the mobile terminal device. In the present embodiment, one signal line and one dummy line are associated and arranged, but the present embodiment is not limited thereto, and multiple signal lines and one dummy line may be arranged in association with each other, or one signal line and multiple dummy lines may be arranged in association with each other. 
       Embodiment 3 
       [0075]      FIG. 6  is a plan view of essential sections of mobile terminal device  100  according to Embodiment 3 of the present invention. 
         [0076]    Mobile terminal device  100  shown in  FIG. 6  is such that first signal line  302 , first dummy line  303 , second signal line  304 , second dummy line  305 , resistor  306  and resistor  307  are deleted from mobile terminal device  100  according to Embodiment 1 shown in  FIG. 3 , and signal line  602 , first dummy line  603 , second dummy line  604  and resistor  605  are added thereto and circuit section  601  is provided instead of circuit section  301 . In  FIG. 6 , like reference numerals are denoted to the same constituents as those of  FIG. 3  and an explanation thereof will be omitted. In the present embodiment, a perspective view of the open state of mobile terminal device  100  is the same as  FIG. 1  and the plan view of the open state of mobile terminal device  100  is the same as  FIG. 2 , and thus an explanation thereof will be omitted. In the present embodiment, the structure of the FPC substrate is the same as  FIG. 4 , and thus an explanation thereof will be omitted. 
         [0077]    First circuit substrate  201  has circuit section  601 . First circuit substrate  201  prints and forms signal line  602 , first dummy line  603  and second dummy line  604  therein. First circuit substrate  201  has resistor  605 . Signal line  602 , first dummy line  603  and second dummy line  604  may not be printed and formed, and may be formed separately from first circuit substrate  201  and may be formed in any method. 
         [0078]    Second circuit substrate  202  prints and forms signal line  602  therein. Second circuit substrate  202  prints and forms first dummy line  603  and second dummy line  604  therein. Second circuit substrate  202  has a function block (not shown). Signal line  602 , first dummy line  603  and second dummy line  604  may not be printed and formed, and may be formed separately from second circuit substrate  202  and may be formed in any method. 
         [0079]    FPC substrate  203  is made of a flexible material, FPC substrate  203  forms signal line  602 , first dummy line  603  and second dummy line  604  therein. FPC substrate  203  is provided with insulation sections that insulate signal line  602 , first dummy line  603  and second dummy line  604  mutually and from outside. 
         [0080]    Circuit section  601  is electrically connected with signal line  602 , first dummy line  603  and second dummy line  604 . Circuit section  601  supplies power to the function block, which is the connection destination of signal line  602 . Circuit section  601  outputs a control signal to signal line  602  for controlling the operation of the function block, which are the connection destination of signal line  602 . Circuit section  601  has a constant current source that supplies a constant current to first dummy line  603  and second dummy line  604 . Circuit section  601  detects wire-breaking of first dummy line  603  and second dummy line  604 . A wire-breaking detection method will be described later. 
         [0081]    Signal line  602  connects circuit section  601  with the device (not shown) provided in second casing  102 . Signal line  602  is printed and formed in first circuit substrate  201 , is formed in FPC substrate  203  by hinge section  103 , and is printed and formed in second circuit substrate  202 . Signal line  602  is formed as a continuous signal line over first circuit substrate  201 , FPC substrate  203  and second circuit substrate  202 . 
         [0082]    First dummy line  603  is electrically connected at one end to circuit section  601 . First dummy line  603  is extended from one end connected with circuit section  601  toward second casing  102 , travels between first circuit substrate  201  and second circuit substrate  202 , and is earthed at the other end on the ground section of first circuit substrate  201  via resistor  605 . First dummy line  603  is provided at the horizontally outer sides of signal line  602  and second dummy line  604 . The horizontally outer sides of signal line  602  mean the upper side and the lower side of signal line  602  in  FIG. 6 . The horizontally outer sides of second dummy line  604  mean the upper side and the lower side of second dummy line  604  in  FIG. 6 . First dummy line  603  has folding section  603   a  in second circuit substrate  202 . First dummy line  603  is formed as a continuous dummy line over first circuit substrate  201 , FPC substrate  203  and second circuit substrate  202 . 
         [0083]    Second dummy line  604  is electrically connected at one end to circuit section  601 . Second dummy line  604  is extended from one end connected with circuit section  601  toward second casing  102 , travels between first circuit substrate  201  and second circuit substrate  202 , and is earthed at the other end to the ground section of first circuit substrate  201  via resistor  605 . Second dummy line  604  is provided at the horizontally outer sides of signal line  602 . Second dummy line  604  has folding section  604   a  in second circuit substrate  202 . Second dummy line  604  is formed as a continuous dummy line over first circuit substrate  201 , FPC substrate  203  and second circuit substrate  202 . 
         [0084]    A method for detecting wire-breaking of FPC substrate  203  will be described below with reference to  FIG. 6 . 
         [0085]    Circuit section  601  supplies a constant current from the constant current source to first dummy line  603  and second dummy line  604 . Circuit section  601  monitors the voltages of first dummy line  603  and second dummy line  604  and detects a change in voltage. For example, circuit section  601  A/D converts the detected voltage value and compares the voltage value after the conversion with a threshold, thereby detecting a change in voltage. The voltage change detection is not limited to the above method, and may employ various methods. For example, when circuit section  601  has an A/D conversion function, resistor  605  may be deleted and circuit section  601  may apply a bias to first dummy line  603  and second dummy line  604  thereby to detect a change in voltage. 
         [0086]    In a normal state in which first dummy line  603  and second dummy line  604  are not broken, the voltages of first dummy line  603  and second dummy line  604  detected by circuit section  601  are within a certain predefined range. 
         [0087]    In this state, when first dummy line  603  is broken, the voltage of first dummy line  603  detected by circuit section  601  is out of the predefined range. Thus, circuit section  601  detects that the voltage of first dummy line  603  is out of the predefined range, thereby detecting the wire-breaking of first dummy line  603 . 
         [0088]    Similarly, when second dummy line  604  is broken, the voltage of second dummy line  604  detected by circuit section  601  is out of the predefined range. Therefore, circuit section  601  detects that the voltage of second dummy line  604  is out of the predefined range, thereby detecting the wire-breaking of second dummy line  604 . 
         [0089]    When circuit section  601  detects the wire-breaking of first dummy line  603 , mobile terminal device  100  displays and alarms, on display section  120 , that signal line  602  can be broken. When circuit section  601  detects the wire-breaking of second dummy line  604 , mobile terminal device  100  stops power supplying by circuit section  601  to signal line  602 . Thereby, the power supply to the function block connected to signal line  602  can be stopped. 
         [0090]    A stress along with the open/close operation of first casing  101  and second casing  102  is more easily applied to the outside of FPC substrate  203  than to the inside thereof. Thus, typically second dummy line  604  is more easily broken than signal line  602 . Similarly, typically first dummy line  603  is more easily broken than second dummy line  604 . Thus, an alarm is given when the wire-breaking of first dummy line  603  is detected, and thus a countermeasure such as repair can be taken before the power supply to the function block connected with signal line  602  stops due to the wire-breaking of second dummy line  604 . The power supply by signal line  602  is stopped when the wire-breaking of second dummy line  604  is detected, thereby preventing mobile terminal device  100  from continuously being used in a failure or poor operation state. 
         [0091]    As described above, according to the present embodiment, by giving an alarm when the wire-breaking of the dummy line is detected, repair is possible before the signal line is broken, thereby preventing an abrupt disabled state due to the wire-breaking of the signal line. According to the present embodiment, the first circuit substrate and the second circuit substrate are connected via the FPC substrate, thereby further reducing more manufacture cost than use of a coaxial line. 
         [0092]    In the present embodiment, one signal line is provided, but any number of signal lines may be employed depending on the number of devices mounted on the mobile terminal device. In the present embodiment, one signal line is associated with two dummy lines for arrangement, but the present embodiment is not limited thereto, and multiple signal lines may be associated with two dummy lines for arrangement or one signal line may be associated with three or more dummy lines for arrangement. 
         [0093]    The dummy lines are formed via the second circuit substrate in Embodiment 1 to Embodiment 3 described above, but the present invention is not limited thereto and the dummy lines may not necessarily routed through the second circuit substrate as long as they route through the hinge section. That is, if it is possible to detect that the signal lines can be broken in the FPC substrate due to the open/close of the casings, the dummy lines may be arbitrarily arranged. The FPC substrate is multilayer structured in Embodiment 1 to Embodiment 3 described above, but the present invention is not limited thereto and the FPC substrate may have a single-layer structure. An alarm for wire-breaking is displayed on the display section in Embodiment 1 to Embodiment 3 described above, but the present invention is not limited thereto, and an alarm for wire-breaking may be given by use of any report section such as vibration or speech. The circuit section that detects wire-breaking is provided in the first circuit substrate in Embodiment 1 to Embodiment 3 described above, but the present invention is not limited thereto and the circuit section that detects wire-breaking may be provided in the second circuit substrate. 
         [0094]    The disclosed contents of Specification, Drawings and Abstract contained in Japanese Patent Application 2009-270035 filed on Nov. 27, 2009 are all incorporated in the present application. 
       INDUSTRIAL APPLICABILITY 
       [0095]    The substrate and mobile terminal device according to the present invention are particularly suitable for detecting wire-breaking of a signal line.