Abstract:
Disclosed is a flexible circuit board connection structure that has a simple configuration, is inexpensive, and has superior connection reliability. The connection structure is a structure connecting a first flexible circuit board  40  and a second flexible circuit board  50  and is characterized in that a first through-hole  45  and a second through-hole  46  are formed in the first flexible circuit board  40 , the second flexible circuit board  50  is inserted through the first through-hole  45  from the first surface  48  side of the first flexible circuit board  40  to the second surface  49  side of the same, and the second flexible circuit board  50 , which has been inserted through to the second surface  49  side of the first flexible circuit board  40 , is soldered to the first flexible circuit board  40  from the first surface  48  side of the first flexible circuit board  40  via the second through-hole  46.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a display device and a connection structure of a flexible circuit board. 
       BACKGROUND ART 
       [0002]    Display devices, as represented by portable terminal equipment such as cellular phones, PDAs, or the like, and televisions, personal computer displays, or the like, are equipped internally with numerous electronic components. These electronic components are connected to one another electrically by a circuit board or the like. In recent years, as display devices have been miniaturized and made more light-weight, attempts have been made to reduce as much as possible the space occupied by the circuit board. In order to attain such space reduction, there has been an adoption of flexible circuit boards that are capable of being freely bent and folded (Patent Document 1). 
         [0003]    The aforementioned Patent Document 1 discloses a structure for connection between flexible circuit boards. 
         [0004]    Specifically, this is a substrate connection structure for inserting a flexible substrate into an insertion hole provided in a fixed substrate having a wiring pattern, and then for soldering and fixing. The aforementioned flexible substrate is provided with a slant part formed of dimensions that become progressively larger than an aperture width of an insertion hole of the aforementioned fixed substrate in order from front to back along the insertion direction, an attachment part formed of dimensions smaller than the aforementioned aperture width of the insertion hole and positioned to the rear of the tilted part, and a stopper part formed of dimensions larger than the aforementioned aperture width of the insertion hole and positioned to the rear of the attachment part. In the flexible substrate connection structure, the aforementioned attachment part engages with the insertion hole of the aforementioned fixed substrate, and the wiring patterns of both aforementioned substrates are soldered and fixed together. 
       RELATED ART DOCUMENT 
     Patent Documents 
       [0000]    
       
         Patent Document 1: Japanese Utility Model Application Laid-Open Publication No. H4-87675. 
       
     
       PROBLEMS TO BE SOLVED BY THE INVENTION 
       [0006]    When flexible circuit boards are connected together by soldering, normally the soldering iron is held in one hand, and the other hand holds the solder wire. Thus, there frequently are difficulties during positioning of the soldering location by hand. Thus, often the terminal to be soldered is positioned, and then a double-sided tape, fixing tape, or a jig is used to fix the position of the soldering location. However, the double-sided tape or fixing tape used for positioning by this procedure results in increased cost, and thus this procedure is preferably not used. 
         [0007]    The non-tape type fixing procedure of the aforementioned Patent Document 1 fixes the flexible circuit board to the insertion hole of the fixed substrate. However, when stress is applied to the inserted flexible circuit board, connection stress concentrates at the soldered part, and there are instances where cracks are generated in the solder and the connection fails. In order to prevent the occurrence of such failure, a means becomes necessary such as attachment of double-sided tape or gluing together or the like so that the concentrated stress can be endured, and this results in increased cost. 
       SUMMARY OF THE INVENTION 
       [0008]    Based on the aforementioned circumstances, an object of the present invention is to provide a flexible circuit board connection structure that has a simple structure, is inexpensive, and has excellent connection reliability. A further object of the present invention is to provide a display device that is equipped with such a connection structure. 
       MEANS FOR SOLVING THE PROBLEMS 
       [0009]    In order to solve the aforementioned problems, the flexible circuit board connection structure of the present invention is a connection structure between a first flexible circuit board and a second flexible circuit board where a first through-hole and a second through-hole are formed in the aforementioned first flexible circuit board, the aforementioned second flexible circuit board is inserted into the aforementioned first through-hole from a first surface side of the aforementioned first flexible circuit board to a second surface side, and the aforementioned second flexible circuit board inserted to the aforementioned second surface side of the aforementioned first flexible circuit board is soldered and connected to the aforementioned first flexible circuit board from the aforementioned first surface side of the aforementioned first flexible circuit board through the aforementioned second through-hole. 
         [0010]    According to this type of connection structure, two through-holes are provided, the second flexible circuit board is inserted into the first through-hole, and this inserted second flexible circuit board is connected to the first flexible circuit board through the second through-hole. Thus, although stress can concentrate at the first through-hole (i.e., part into which the substrate is inserted) when stress is applied to the second flexible circuit board, there is no generation of cracks or the like at the solder part due to concentration of stress at the second through-hole (i.e., a soldered part), and connection failures become unlikely. Thus, there is no need for adoption of measures such as attachment of fixing tape or the like, and due to the connection structure being a simple structure providing two through-holes in the substrate, there is no accompanying cost increase. 
         [0011]    In the aforementioned connection structure, the aforementioned first flexible circuit board may have, on at least the aforementioned first surface side, a first-side terminal, the aforementioned second flexible circuit board may have, on at least its first surface side, a second-side terminal, and the aforementioned second-side terminal may be disposed opposing the aforementioned second surface side of the aforementioned first flexible circuit board, while the aforementioned second-side terminal may be soldered and connected to the aforementioned first-side terminal of the aforementioned first flexible circuit board through the aforementioned second through-hole. 
         [0012]    Due to soldering and connecting of the second-side terminal and the first-side terminal together in this manner through the second through-hole, reliability of the connection becomes extremely high. 
         [0013]    Moreover, in a state where the aforementioned second flexible circuit board is inserted into the aforementioned first through-hole, the aforementioned first-side terminal of the aforementioned first flexible circuit board may be superimposed on the aforementioned second-side terminal of the aforementioned second flexible circuit board. 
         [0014]    If a configuration is adopted such that the first-side terminal is superimposed on the second side-terminal in the state where the second flexible circuit board is inserted into the first through-hole, positioning is accomplished by inserting the second flexible circuit board into the first through-hole, and thus the work of positioning becomes greatly simplified. 
         [0015]    Moreover, the aforementioned first through-holes may be disposed on the aforementioned first flexible circuit board in a zigzag pattern, and the aforementioned second-side terminals may be disposed on the aforementioned second flexible circuit board in a zigzag pattern. 
         [0016]    For terminals disposed in a zigzag pattern in this manner, it becomes possible to easily perform the positioning required for connection. 
         [0017]    Moreover, the hole width of the aforementioned first through-hole may be approximately the same as a substrate width of the aforementioned second flexible circuit board. 
         [0018]    Due to approximate matching of the hole width and the substrate width in this manner, it becomes possible to achieve positioning for connection by passing the second flexible circuit board into the first through-hole. 
         [0019]    Moreover, a protuberance may be provided in the aforementioned second flexible circuit board; the aforementioned protuberance may restrict insertion of the aforementioned second flexible circuit board into the aforementioned first through-hole to a certain amount. 
         [0020]    Due to providing of the protuberance in this manner, the amount of insertion is restricted, and positioning in the direction of insertion becomes simplified. 
         [0021]    Moreover, a protuberance projecting in the width direction of the aforementioned second flexible circuit board may be formed in the aforementioned second flexible circuit board, and the width of the substrate of the aforementioned second flexible circuit board including the aforementioned protuberance may be larger than hole width of the aforementioned first through-hole. 
         [0022]    Due to providing of the protuberance in this manner, the amount of insertion is restricted, and positioning in the direction of insertion becomes simplified. 
         [0023]    Moreover, a solder attachment land may be formed on the protuberance where the solder attachment land may be formed within the aforementioned first through-hole of the aforementioned first flexible circuit board and may be positioned overlapping the aforementioned protuberance of the second flexible circuit board inserted into the aforementioned first through-hole, and the aforementioned solder attachment lands may be fixed by soldering. 
         [0024]    Due to addition of the soldering connection to the second through-hole in this case, and due to reinforcing connection and fixing by this solder attachment land, even when an external stress is applied to one of the substrates so that stress would occur at the solder connection part, there is resistance to failure such as the generation of cracks or the like at the solder part. 
         [0025]    The aforementioned solder connection may be performed so as to bridge at least one part of the aforementioned second insertion-hole. 
         [0026]    When a solder connection is performed in the form of bridging at least one part of the second insertion-hole in this manner, connections are performed between the ends of the hole (i.e., at two locations), and it thus becomes possible to strengthen this solder connection itself. 
         [0027]    Next, in order to solve the aforementioned problems, the display device of the present invention is a display device having a touch panel and including: a main control part for performing display control; a touch panel control part for performing control of the touch panel; a first flexible circuit board connected to the aforementioned main control part; and a second flexible circuit board connected to the aforementioned touch panel control part; where the aforementioned first flexible circuit board and the aforementioned second flexible circuit board are connected together by the aforementioned connection structure. 
         [0028]    If the aforementioned connection structure is achieved in a display device provided with a touch panel in this manner by connection together of flexible circuit boards relating to the touch panel control and display control, the display device is resistant to connection failure, and it becomes possible to inexpensively provide a highly reliable display device. 
         [0029]    Next, in order to solve the aforementioned problems, the display device of the present invention is a display device having a backlight and including: a main control part for performing display control; a backlight control part for control of the backlight; a first flexible circuit board connected to the aforementioned main control part; and a second flexible circuit board connected to the aforementioned backlight control part; where the aforementioned first flexible circuit board and the aforementioned second flexible circuit board are connected together by the aforementioned connection structure. 
         [0030]    If the aforementioned connection structure is achieved by a display device provided with a backlight in this manner by connection together of flexible circuit boards relating to the backlight control and display control, the display device is resistant to connection failure, and it becomes possible to inexpensively provide a highly reliable display device. 
         [0031]    Furthermore, the aforementioned main control part may perform display control of a liquid crystal panel. 
         [0032]    There is high demand for reduced weight for this type of liquid crystal display device, and by adopting the connection structure for flexible circuit boards in the manner of the present invention, it is possible to contribute to the further reduction of weight of liquid crystal display devices. 
       EFFECTS OF THE INVENTION 
       [0033]    According to the present invention, it becomes possible to provide a flexible circuit board connection structure that has excellent connection reliability and is inexpensive and has a simple structure. Moreover, the present invention makes it possible to provide a display device equipped with such a connection structure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]      FIG. 1  is a block diagram showing the schematic structure of a liquid crystal display device that is an embodiment of the present invention. 
           [0035]      FIG. 2  is a top view showing a flexible circuit board connection structure provided in the liquid crystal display device of  FIG. 1 . 
           [0036]      FIG. 3  is a cross-sectional drawing showing a flexible circuit board connection structure provided in the liquid crystal display device of  FIG. 1 . 
           [0037]      FIG. 4  is a drawing for explanation of the operation of the flexible circuit board connection structure provided for the liquid crystal display device of  FIG. 1 . 
           [0038]      FIG. 5  is a top view showing a first modified example of the connection structure of the flexible circuit board. 
           [0039]      FIG. 6  is a drawing for explanation of the operation of the connection structure of  FIG. 5 . 
           [0040]      FIG. 7  is a top view showing a second modified example of the connection structure of the flexible circuit board. 
           [0041]      FIG. 8  is a cross-sectional view along the line A-A in  FIG. 7 . 
           [0042]      FIG. 9  is a drawing for explanation of the operation of the connection structure of  FIG. 7 . 
           [0043]      FIG. 10  is a top view showing a third modified example of the connection structure of the flexible circuit board. 
           [0044]      FIG. 11  is a cross-sectional drawing showing a comparative example of the connection structure of the flexible circuit board. 
           [0045]      FIG. 12  is a cross-sectional drawing showing a comparative example of the connection structure of the flexible circuit board. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0046]    An embodiment of the present invention will be explained using  FIGS. 1 to 4 . 
         [0047]    An example of a liquid crystal display device (display device)  1  of the present invention is shown, and this liquid crystal display device  1  is equipped with a liquid crystal panel  11 , a backlight  12 , and a touch panel  13 . This liquid crystal display device  1  is suitable for use, for example, as a small-scale display device of a cellular phone or the like. 
         [0048]    The liquid crystal panel  11  retains a liquid crystal layer sandwiched between a pair of substrates. Voltage applied to the liquid crystal layer by an external main control part  10  is controlled for each pixel, and display control is performed based on such control. This liquid crystal panel  11  and the main control part  10  are connected by the main flexible circuit board  40 , and the main flexible circuit board  40  can be retained while being folded over. Thus, the liquid crystal display device  1  is advantageous, for example, in the construction of a small-scale display of a cellular phone monitor or the like. 
         [0049]    The backlight  12  provides the liquid crystal panel  11  with illumination light for display. The supply of electrical power is controlled by an external backlight control part  20  in order to adjust lighting. This backlight  12  and the backlight control part  20  are connected together by the flexible circuit board  22 , and the backlight control part  20  is connected to the main flexible circuit board  40  through the backlight flexible circuit board  50  so that signals can be exchanged with the main control part  10 . These flexible circuit boards  22  and  50  can be contained within the display device by being folded over in the same manner as the main flexible circuit board  40 . 
         [0050]    The touch panel  13  is an input device and includes a transparent panel for sensing coordinates. Data input or the like is performed by the use of a touch pen, finger, or the like to touch the display face of this panel. The inputted data are transmitted to the touch panel control part  30 , and based on these data, the display information displayed by the liquid crystal panel  11  is determined. This touch panel  13  and the touch panel control part  30  are connected together by the flexible circuit board  32 , and the touch panel control part  30  is connected to the main flexible circuit board  40  through the touch panel flexible circuit board  60  so that signals can be exchanged with the main control part  10 . These flexible circuit boards  32  and  60  can be contained within the display device by being folded over in the same manner as the main flexible circuit board  40 . 
         [0051]    The flexible circuit boards of the present embodiment in this manner are connected together, and this connection is achieved specifically by soldering connections. The connection structure between flexible circuit boards provided for the liquid crystal display device  1  will be explained below in detail. 
         [0052]    Due to the progress of high density mounting of electronic display equipment such as those of cellular phones or the like, and due to demand for weight reduction, highly flexible circuit boards have been adopted that, due to flexibility, have a high degree of freedom of mounting. In the aforementioned manner, the present embodiment adopts flexible circuit boards  22  and  32 , a main flexible circuit board  40 , a backlight flexible circuit board  50 , a touch panel flexible circuit board  60 , or the like. Moreover, the flexible circuit boards of the present embodiment are connected together, and signals can be exchanged between the various control parts  10 ,  20 , and  30 . A connection structure for connection together of the flexible circuit boards in this manner is exemplified by the connection structure between the main flexible circuit board  40  (first flexible circuit board) and the backlight flexible circuit board  50  or the touch panel flexible circuit board  60  (second flexible circuit board, sometimes generally referred to hereinafter as the flexible circuit board  50  ( 60 )) shown in  FIGS. 2 through 4 . 
         [0053]    As illustrated, the main flexible circuit board  40  and the flexible circuit board  50  ( 60 ) are connected together by the solder part  90 . Two through-holes  45  and  46  are formed in the main flexible circuit board  40 . Among these through-holes, the flexible circuit board  50  ( 60 ) is inserted into the first through-hole  45 , and the flexible circuit board  50  ( 60 ) is soldered and connected to the main flexible circuit board  40  at the second through-hole  46 . 
         [0054]    On the main flexible circuit board  40 , a connection terminal (first-side terminal)  42  is formed for providing connection to the flexible circuit board  50  ( 60 ) at the front surface (first surface)  48  side of the substrate  41  of the main flexible circuit board  40 . On the other hand, on the flexible circuit board  50  ( 60 ), a connection terminal (second-side terminal)  52  ( 62 ) is formed on the front surface (first surface)  58  ( 68 ) side of the substrate  51  ( 61 ) of the flexible circuit board  50  ( 60 ) for providing a connection to the main flexible circuit board  40 . Then the flexible circuit board  50  ( 60 ) is inserted from the front surface  48  side of the main flexible circuit board  40  toward the rear surface (second surface)  49  side. A reference numeral  59  ( 69 ) is assigned to the rear surface (second surface) side of the flexible circuit board  50  ( 60 ). Moreover, the connection terminal  42  is linearly shaped and has a structure that is separated by the second through-hole  46 . 
         [0055]    The inserted flexible circuit board  50  ( 60 ) has a distal-end side distal end part (inserted part)  51   a  ( 61   a ) separated by the first through-hole  45  from a proximal-end side proximal end part  51   b  ( 61   b ). Through the second through-hole  46 , the connection terminal  52  ( 62 ) formed in the front surface  48  side of the distal end part  51   a  ( 61   a ) of the flexible circuit board  50  ( 60 ) is soldered and connected to the connection terminal  42  of the front surface  48  side of the main flexible circuit board  40 . That is to say, the connection terminal  42  and the connection terminal  52  ( 62 ) are soldered and connected together from the front surface  48  side of the main flexible circuit board  40  through the second through-hole  46 . 
         [0056]    When such a soldering connection is to be performed, as shown in  FIG. 4 , the flexible circuit board  50  ( 60 ) is inserted into the first through-hole  45 , and the distal end part  51   a  ( 61   a ) is led to the rear surface  49  side of the main flexible circuit board  40  so that the rear surface  49  faces the connection terminal  52  ( 62 ). Then, the flexible circuit board  50  ( 60 ) is inserted until the connection terminal  52  ( 62 ) opposes the second through-hole  46  of the main flexible circuit board  40 , and both flexible circuit boards  40  and  50  ( 60 ) are positioned together. 
         [0057]    Due to insertion of the flexible circuit board  50  ( 60 ) into the first through-hole  45  at this time, the flexible circuit board  50  ( 60 ) is positioned and fixed with respect to the first through-hole  45 , and this eliminates mispositioning between both flexible circuit boards  40  and  50  ( 60 ). In particular, since the width of the substrate of the flexible circuit board  50  ( 60 ) is approximately the same as the hole width of the first through-hole  45  according to the present embodiment, it is quite difficult for mispositioning to occur. 
         [0058]    Moreover, in the state in which the flexible circuit board  50  ( 60 ) is inserted into the first through-hole  45  in this manner (i.e., a state in which both flexible circuit boards  40  and  50  ( 60 ) are positioned together), the connection terminal  42  of the main flexible circuit board  40  and the connection terminal  52  ( 62 ) of the flexible circuit board  50  ( 60 ) overlap as viewed from above the substrates. Due to the connection terminal  42  of the main flexible circuit board  40  being separated linearly by the second through-hole  46 , the connection terminal  52  ( 62 ) of the flexible circuit board  50  ( 60 ) exposed through the second through-hole  46  becomes positioned collinearly with the connection terminal  42  of the main flexible circuit board  40 . Then the connection structure shown in  FIGS. 1 to 3  is provided by soldering of each of the connection terminals  42  and  52  ( 62 ), collinearly arranged in this manner, through the second through-hole  46  from the front surface  48  side of the main flexible circuit board  40 . 
         [0059]    The solder connection is performed in the form of bridging at least one part of the second insertion-hole  46 . That is to say, the connection terminal  42  of the main circuit board  40  that has been separated by the second through-hole  46  is extended in order to form a connection. 
         [0060]    A liquid crystal display device  1  and a connection structure of the flexible circuit boards of the liquid crystal display device  1  of the present embodiment have been explained above. The operation and effect of the connection structure will be explained next. 
         [0061]    According to the aforementioned connection structure, two through-holes are arranged in the main flexible circuit board  40 , the flexible circuit board  50  ( 60 ) is inserted into the first through-hole  45 , and the inserted flexible circuit board  50  ( 60 ) is connected to the main flexible circuit board  40  through the second through-hole  46 . Thus, when stress is applied to the flexible circuit board  50  ( 60 ), although stress can concentrate at the first through-hole  45  (i.e., the part where the substrate is inserted), due to the difficulty of stress concentrating at the second through-hole  46  (i.e., the soldered part), there is no generation of cracking or the like at the solder part, and connection failure is inhibited. As a result, there is no need to adopt measures such as attaching fixing tape or the like, and the structure of the connection is simply formed by providing two through-holes in the main flexible circuit board  40 . Thus, the connection is not accompanied by increased cost. 
         [0062]    The main flexible circuit board  40  has at least the connection terminal  42  on the front surface  48  side, and the flexible circuit board  50  ( 60 ) has at least the connection terminal  52  on the front surface  58  side of the flexible circuit board  50  ( 60 ). The connection terminal  52  ( 62 ) is disposed facing the rear surface  49  of the main flexible circuit board  40 , and the connection terminal  52  ( 62 ) is soldered and connected to the connection terminal  42  of the main flexible circuit board  40  through the second through-hole  46 . In this manner, the flexible circuit board  50  ( 60 ) is inserted into the first through-hole  45 , and the connection terminal  52  ( 62 ) and the connection terminal  42  are soldered and connected together through the second through-hole  46 , and thus, these connections become highly reliable. 
         [0063]    In the state in which the flexible circuit board  50  ( 60 ) is inserted into the first through-hole  45 , the connection terminal  42  of the main flexible circuit board  40  overlaps the connection terminal  52  ( 62 ) of the flexible circuit board  50  ( 60 ). In the state in which the flexible circuit board  50  ( 60 ) is inserted into the first through-hole  45 , due to the formation of a structure where the connection terminal  42  overlaps the connection terminal  52  ( 62 ) in this manner, positioning together of both substrates is accomplished by insertion of the flexible circuit board  50  ( 60 ) into the first through-hole  45 , and the work required for such positioning together becomes very simple. 
         [0064]    Moreover, the hole width of the first through-hole  45  is roughly the same as the substrate width of the flexible circuit board  50  ( 60 ). Thus, by insertion of the flexible circuit board  50  ( 60 ) into the first through-hole  45 , it becomes possible to achieve positioning together for the connection. 
         [0065]    Moreover, a solder part  90  is formed over at least part of the second insertion-hole  46 . Due to connections being performed at holes at both ends (i.e., at two locations), the solder connection itself becomes strengthened. That is to say, when soldering is performed by the solder part  190  by simply overlapping substrates  140  and  150  as shown in  FIG. 11 , the resultant connection occurs at one edge, and the necessity arises of fixing the connection by use of double-sided tape  161 . Moreover, if a single through-hole  245  is provided in a first flexible circuit board  240  as shown in  FIG. 12 , if a second flexible circuit board  250  is inserted into the through-hole  245 , and if a soldering connection is made by a solder part  290  at this insertion part, then this results in a connection at one end, and the reliability of the connection becomes low. 
       Modified Examples 
       [0066]    Several modified examples of the present embodiment will be explained next. 
         [0067]    In the first modified example shown in  FIGS. 5 and 6 , a protuberance is provided in the flexible circuit board  50  ( 60 ). Specifically, at the width-direction edge parts of the substrate  51  ( 61 ), protuberances  53  ( 63 ) are formed that project in the width direction. The width of the flexible circuit board  50  ( 60 ), including these protuberances  53  ( 63 ), is made larger than the hole width of the first through-hole  45 . 
         [0068]    Due to providing of the protuberances  53  ( 63 ) in this manner, the amount of insertion of the flexible circuit board  50  ( 60 ) into the first through-hole  45  of the main flexible circuit board  40  is restricted, and this results in achievement of simple positioning together in the insertion direction. 
         [0069]    Next, in a second modified example shown in  FIG. 7  through  FIG. 9 , the connection terminals  42  of the main flexible circuit board  40  are disposed in a zigzag pattern as viewed from above the substrate  41 , and the first through-holes  46  are similarly disposed in a zigzag pattern as viewed from above. Connection terminals  52  ( 62 ) are also disposed on the flexible circuit board  50  ( 60 ) in a zigzag pattern as viewed from above. 
         [0070]    When the connection terminals  42  and  52  ( 62 ) are disposed in a zigzag pattern in this manner, by adoption of a connection structure similar to that of the aforementioned embodiment, it is possible to easily perform positioning together for the connection. That is to say, although positioning together frequently becomes difficult when using a zigzag pattern of connection terminals, by adoption of the connection structure of the present embodiment, positioning together can be performed reliably even when the terminals are disposed in a zigzag pattern. Due to placement of the terminals in the zigzag pattern, even when the number of terminals is increased and the terminal pitch is narrowed, solder bridging seldom occurs, and current leakage is seldom generated. 
         [0071]    Next, in a third modified example shown in  FIG. 10 , protuberances  53  ( 63 ) are arranged on the flexible circuit board  50  ( 60 ) in a manner similar to the aforementioned first modified example. Solder attachment lands  53   a  ( 63   a ) are formed on these protuberances  53  ( 63 ), and solder attachment lands  47  are formed in the first through-hole  45  of the main flexible circuit board  40  at positions of overlap with the protuberances  53  ( 63 ) of the flexible circuit board  50  ( 60 ) inserted into the aforementioned first through-hole  45 . The solder attachment lands  53   a  ( 63   a ) and  47  are fixed together by solder parts  95 . 
         [0072]    In this case, a solder connection is added to the second through-hole  46 , and connection and fixing are performed strongly by the solder attachment land parts. Thus, even when external stress is applied to either of the substrates  40  and  50  ( 60 ), stress tends not to be applied to the solder connection part, and the solder part is resistant to the occurrence of failure such as the generation of cracking or the like. 
         [0073]    Although embodiments of the present invention have been indicated above, the present invention is not limited by the embodiments explained by the aforementioned description and figures, and for example, embodiments such as the following are included in the technical scope of the present invention. 
         [0074]    (1) According to the aforementioned embodiments, connection structures have been explained for connection between a main flexible circuit board  40  and a backlight flexible circuit board  50 , and between a main flexible circuit board  40  and a touch panel flexible circuit board  60 . However, the connection structure of the present invention may be adopted for connection between other types of flexible circuit boards. For example, if a connection is needed between a backlight flexible circuit board and a touch panel flexible circuit board, the connection structure of the present invention may be adopted for connection between such substrates. 
         [0075]    (2) Although according to the aforementioned embodiments, a display device was indicated that was utilized by a cellular phone, the flexible circuit board connection structure of the present invention may be adopted for any display device, as exemplified by display devices used for computer monitors, display devices used for television receivers, or the like. 
       DESCRIPTION OF REFERENCE CHARACTERS 
       [0000]    
       
         
           
               1  liquid crystal display device (display device) 
               10  main control part 
               11  liquid crystal panel (display panel) 
               12  backlight 
               13  touch panel 
               20  backlight control part 
               30  touch panel control part 
               40  main flexible circuit board (first flexible circuit board) 
               41  substrate 
               42  connection terminal (first-side terminal) 
               45  first through-hole 
               46  second through-hole 
               47  solder attachment land 
               48  front surface (first surface) 
               49  rear surface (second surface) 
               50  backlight flexible circuit board (second flexible circuit board) 
               51  substrate 
               51   a  distal end part (inserted part) 
               51   b  proximal end part (non-inserted part) 
               52  connection terminal (second-side terminal) 
               53  protuberance 
               53   a  solder attachment land 
               58  front surface (first surface) 
               59  rear surface (second surface) 
               60  touch panel flexible circuit board (second flexible circuit board) 
               61  substrate 
               61   a  distal end part (inserted part) 
               61   b  proximal end part (non-inserted part) 
               62  connection terminal (second-side terminal) 
               63  protuberance 
               63   a  solder attachment land 
               68  front surface (first surface) 
               69  rear surface (second surface) 
               90  solder part 
               95  solder part