Abstract:
A plasma display apparatus has an electronic circuit module including a rigid substrate attached to a chassis thereof and a flexible substrate partially overlapped with the rigid substrate. The rigid substrate has chips and the flexible substrate has a first portion with apertures for exposing the chips and bonding pads and a second portion positioned on the outside of the rigid substrate. Bonding wires connect terminals of the chips with the bonding pads of the flexible substrate. A reinforcing pattern or a dummy pattern is provided in at least the first portion of the flexible substrate. The reinforcing pattern provides for rigidity for the first portion of the flexible substrate for accurate positioning of the bonding pads relative to the chips.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a plasma display apparatus. 
     2. Description of the Related Art 
     A plasma display apparatus (PDP) comprises a plasma display panel having two glass substrates disposed in opposition, and a driving and controlling circuit part. One of the glass substrates has a plurality of parallel address electrodes, and the other glass substrate has a plurality of sustain electrodes disposed in parallel to each other and perpendicular to the address electrodes. The sustain electrodes include X electrodes and Y electrodes disposed alternately. Display cells are formed between two adjacent X electrode and Y electrode. The circuit part is disposed on the external surface of one of the glass substrates of the plasma display panel, and includes several rigid substrates. A flexible substrate is used for connecting electrodes of the plasma display panel and the rigid substrate. 
     The plasma display apparatus is disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 11-327503, and No. 11-327458. 
     Since the flexible substrate is flexible, it is necessary to use the flexible substrate at a curved portion. However, the flexible substrate is expensive, and the price thereof is two times the cost of a normal rigid substrate. Further, since the flexible substrate is used at the bent portion, warpage or breakage is apt to occur. Examples in which reinforcing patterns are provided at the peripheries of flexible substrates are disclosed in Japanese Unexamined Patent Publication (Kokai) No. 61-131492 and Japanese Unexamined Utility Model Publication (Kokai) No. 6-45364. 
     In the plasma display apparatus, the flexible substrate is used as a composite substrate or an electronic circuit module in which the flexible substrate is coupled and adhered to the rigid substrate. Therefore, the portion of the flexible substrate superimposed or the rigid substrate has no problem of warpage or breakage, which is likely to occur in an individual flexible substrate. 
     However, at the portion of superimposed portion between the rigid substrate and the flexible substrate, the rigid substrate holds bare chips, and the flexible substrate has apertures for exposing the bare chips and bonding pads, so that terminals of the bare chips and the bonding pads of the flexible substrate are connected together with bonding wires. In carrying out wire bonding, it is not possible to achieve wire bonding if there is a deviation between the position of the terminals of the bare chips and the position of the bonding pads of the flexible substrate. In many cases, the positional deviation occurs due to degradation in the precision of the size of the flexible substrate, particularly the degradation in the precision of the size around the aperture of the flexible substrate. The precision of the size around the aperture of the flexible substrate is degraded due to thermal contraction in the wire bonding at the time of connecting the flexible substrate to the rigid substrate. 
     Therefore, conventionally, the outer shape of the flexible substrate is designed to have a relatively large size, in particular, a relatively large size has been used for the width from the aperture of the flexible substrate to the outer edge thereof, thereby to try to prevent the degradation in the positional precision at the peripheral region of the aperture of the flexible substrate. 
     However, since the flexible substrate is expensive, the increase in the size of the outer shape of the flexible substrate leads to an increase in cost. Therefore, it has been desired to avoid occurrence of a positional deviation between the position of the terminals of the bare chip and the position of the bonding pads of the flexible substrate, without increasing the size of the outer shape of the flexible substrate. 
     Further, the flexible substrate is easily broken at a position that is brought into contact with the outer edge of the rigid substrate. Further, the flexible substrate is broken or distorted at a position on the outside of the rigid substrate. Further, as a high voltage is used in the plasma display apparatus, it has been desired to reduce the inductance of the conductor patterns of the flexible substrate. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a plasma display apparatus in which a satisfactory wire bonding can be carried out without increasing the size of the outer shape of a flexible substrate. 
     It is another object of the present invention to provide a plasma display apparatus capable of preventing occurrence of breakage or warpage of a flexible substrate. 
     It is still another object of the present invention to provide a plasma display apparatus capable of reducing the inductance of conductor patterns of a flexible substrate. 
     According to one aspect of the present invention, there is provided a plasma display apparatus comprising a plasma display panel having a plurality of electrodes for emission of light, an electronic circuit module including a rigid substrate having at least one chip, and a flexible substrate coupled to the rigid substrate and having a first portion with an aperture for exposing the chip and bonding pads and a second portion positioned on the outside of the rigid substrate, bonding wires connecting terminals of the chip with the bonding pads of the flexible substrate, and a reinforcing pattern provided in at least the first portion of the flexible substrate. 
     In this structure, the reinforcing pattern is provided in at least the first portion of the flexible substrate coupled to the rigid substrate. The reinforcing pattern is formed with a metal material that is the same as the metal material of conductor patterns. When the flexible substrate is connected to the rigid substrate or when the flexible substrate is wire bonded, a metal material does not thermally contract as easily as a resin that constitutes the flexible substrate. Therefore, a positional deviation does not occur easily. As a result, even when a distance from the aperture of the flexible substrate to the outer edge is decreased thereby relatively decreasing the size of the outer shape of the flexible substrate, the positional precision at portions around the aperture of the flexible substrate is not degraded. As the size of the outer shape of the flexible substrate can be made relatively small, it is possible to achieve a cost reduction. 
     According to another aspect of the present invention, there is provided a plasma display apparatus comprising a plasma display panel having a plurality of electrodes for emission of light, an electronic circuit module including a rigid substrate, and a flexible substrate coupled to the rigid substrate and having conductor patterns electrically connected to the electrodes of the plasma display panel, and a reinforcing pattern provided in a layer of the flexible substrate separate from a layer on which the conductor patterns exist. 
     In this structure, since the reinforcing pattern is provided in the layer of the flexible substrate separate from the layer on which conductor patterns exist, it is possible to prevent occurrence of breakage or warpage of the flexible substrate. Further, when a high voltage is applied to the conductor patterns of the flexible substrate, an eddy current is generated in the reinforcing pattern disposed opposite to the conductor patterns, based on an electromagnetic inductance. As a result, it is possible to reduce the inductance of the conductor patterns. Consequently, it is possible to obtain satisfactory display characteristics. 
     Preferably, the reinforcing pattern is provided at a position overlapping with the conductor patterns. For example, the reinforcing pattern is provided as a conductor film that extends along the outer edge of the rigid substrate. Although the flexible substrate is weak at a portion that is brought into contact with the outer edge of the rigid substrate, the flexible substrate is not easily broken as this flexible substrate is reinforced with the reinforcing pattern. Alternatively, the reinforcing pattern is provided as a completely covering conductor film on the portion of the flexible substrate positioned on the outside of the rigid substrate. Alternatively, the reinforcing pattern is provided as a conductor film including conductor strips provided corresponding to the individual conductor strips of the conductor patterns. As a result, the flexible substrate is not easily deformed, and the conductor patterns of the flexible substrate are not broken. 
     According to still another aspect of the present invention, there is provided a plasma display apparatus comprising a plasma display panel having a plurality of electrodes for emission of light, an electronic circuit module including a rigid substrate, and a flexible substrate coupled to the rigid substrate and having conductor patterns electrically connected to the electrodes of the plasma display panel, and a dummy pattern provided on the rigid substrate. 
     In this structure, when a high voltage is applied to conductor patterns of the flexible substrate, an eddy current is generated in the dummy pattern disposed opposite to the conductor patterns, based on an electromagnetic inductance. As a result, it is possible to reduce the inductance of the conductor patterns. Consequently, it is possible to obtain satisfactory display characteristics. 
     According to still another aspect of the present invention, there is provided a plasma display apparatus comprising a plasma display panel having a plurality of electrodes for emission of light, an electronic circuit module including a rigid substrate, and a flexible substrate coupled to the rigid substrate and having conductor patterns electrically connected to the electrodes of the plasma display panel, and an electric part having a first portion fixed to the flexible substrate and a second portion fixed to the rigid substrate. 
     In this structure, the electric part is disposed extending over the rigid substrate and the flexible substrate, thereby to electrically interconnect the rigid substrate and the flexible substrate. Therefore, it is possible to decrease the number of wires connecting the rigid substrate and the flexible substrate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more apparent from the following description of the preferred embodiments, with reference to the accompanying drawings, in which: 
     FIG. 1 is a perspective view showing a plasma display apparatus according to an embodiment of the present invention; 
     FIG. 2 is a cross-sectional view of the plasma display apparatus shown in FIG. 1; 
     FIG. 3 is a diagram showing electrodes and sustain pulse generating circuits of the plasma display apparatus shown in FIG.  1  and FIG. 2; 
     FIG. 4 is a plan view showing an example of the electronic circuit module; 
     FIG. 5 is a cross-sectional view of the electronic circuit module shown in FIG. 4; 
     FIG. 6 is a plan view showing an example of a conventional electronic circuit module; 
     FIG. 7 is a plan view showing a modified example of the electronic circuit module shown in FIG. 4; 
     FIG. 8 is a view showing in detail conductor patterns of the flexible substrate of the electronic circuit module shown in FIG. 7; 
     FIG. 9 is a perspective view showing another example of the electronic circuit module; 
     FIG. 10 is a perspective view showing still another example of the electronic circuit module; 
     FIG. 11 is a perspective view showing still another example of the electronic circuit module; 
     FIG. 12 is a perspective view showing a part of the flexible substrate shown in FIG. 11; 
     FIG. 13 is a view showing a modified example of the reinforcing patterns shown in FIG. 12; 
     FIG. 14 is a cross-sectional view of the flexible substrate taken along the line XIV—XIV in FIG. 13; 
     FIG. 15 is a view showing a modified example of the reinforcing patterns shown in FIG. 12; 
     FIG. 16 is a cross-sectional view of the flexible substrate taken along the line XVI—XVI in FIG. 15; 
     FIG. 17 is a view showing an example in which a dummy pattern is provided in the rigid substrate; and 
     FIG. 18 is a view showing an example in which electric parts are provided extending over the flexible substrate and the rigid substrate. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will be explained below with reference to the drawings. 
     FIG. 1 is a perspective view showing a plasma display apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the plasma display apparatus shown in FIG.  1 . FIG. 3 is a view showing electrodes and sustain pulse generating circuits of the plasma display apparatus shown in FIGS. 1 and 2. 
     In FIGS. 1 and 2, the plasma display apparatus  10  comprises a plasma display panel  16  including glass substrates  12  and  14  disposed opposite to each other, a chassis  18  provided on one of the glass substrates  12 , and a driving and controlling circuit part  19  provided on the chassis  18 . In FIGS. 1 and 2, the circuit part  19  includes electronic circuit modules  20  and  21 . Each of the electronic circuit modules  20  and  21  includes a rigid substrate  22  and a flexible substrate  24  coupled and adhered to the rigid substrate  22 . 
     FIG. 3 is a view showing electrodes  26  and  28  provided on the plasma display panel  16  (the glass substrates  12  and  14 ) and circuit portions included in the circuit device  19 . The glass substrate  12  has a plurality of address electrodes  26  disposed in parallel with each other. The glass substrate  14  has a plurality of sustain electrodes  28  extending in parallel with each other and perpendicular to the address electrodes  26 . Partitions  29  are formed between two adjacent address electrodes  26  in parallel with the address electrodes  26 . 
     The sustain electrodes  28  include X electrodes  28   x  and Y electrodes  28   y  disposed alternately. That is, the sustain electrodes  28  include a first x electrode  28   x , a first Y electrode  28   y , a second x electrode  28   x , a second Y electrode  28   y , a third x electrode  28   x , a third Y electrode  28   y , a fourth x electrode  28   x , a fourth Y electrode  28   y , and so on, in this order from the top. 
     The circuit part  19  includes an address pulse generating circuit  30 , X electrode sustain pulse generating circuits  32  and  34 , Y electrode sustain pulse generating circuits  36  and  38 , a scanning circuit  40 , a power source circuit  42 , and a control circuit (not shown) connected to these circuits. The address pulse generating circuit  30  supplies driving pulses to the address electrodes  26 . The sustain pulse generating circuit  32  supplies driving pulses to odd number X electrodes  28   x , and the sustain pulse generating circuit  34  supplies driving pulses to even number X electrodes  28   x . The sustain pulse generating circuits  36  and  38  supply driving pulses to the Y electrodes  28   y  via the scanning circuit  40 . 
     In this plasma display apparatus  10 , the side of the glass substrate  14  is the display side. Display cells are formed between the adjacent X electrode  28   x  and Y electrode  28   y . In one display cell, a high write voltage pulse is applied to between the address electrode  26  and the Y electrode  28   y  to generate a priming by discharge, and then a sustain voltage pulse is applied to between the X electrode  28   x  and the Y electrode  28   y  to sustain the discharge, to thereby emit light at the display cell. 
     FIG. 4 is a plan view showing an example of the electronic circuit module  21 . FIG. 5 is a cross-sectional view of the electronic circuit module  21  of FIG.  4 . The rigid substrate  22  of the electronic circuit module  21  shown in FIGS. 1 to  5  includes the scanning circuit  40 , which includes bare chips  44  and conductor patterns  46  connected to the bare chips  44 . 
     The flexible substrate  24  has two resin layers and conductor patterns  46  sandwiched between the two resin layers. The flexible substrate  24  has a first portion  24   a  overlapping with and adhered to the rigid substrate  22 , and a second portion  24   b  positioned on the outside of the rigid substrate  22 . The second portion  24   b  is curved and connected to the electrodes  28   y  of the plasma display panel  16 , as shown in FIG.  2 . 
     The flexible substrate  24  has apertures  48  allowing the bare chips  44  to be exposed therethrough, and bonding pads  50  provided at the ends of the conductor patterns  46  close to the bare chips  44 . Bonding wires  52  connect terminals  44   a  of the bare chips  44  with the bonding pads  50 . FIG. 4 shows the state before the wire bonding is carried out, and FIG. 5 shows the state after the wire bonding is carried out. In the wire bonding, the terminals  44   a  of the bare chips  44  and the bonding pads  50  of the flexible substrate  24  must be positioned accurately. 
     In FIGS. 4 and 5, a reinforcing pattern  54  is provided at the peripheral region of the flexible substrate  24 , without interfering with the wiring areas of signal lines. The reinforcing pattern  54  is not connected electrically. The reinforcing pattern  54  is preferably provided at least in the first portion  24   a  of the flexible substrate  24  near the apertures  48 . The reinforcing pattern  54  is made of the same metal as that of the conductor patterns  46  in the form of a conductor line. By the provision of the reinforcing pattern  54 , it is possible to prevent subtle deformation of portions of the flexible substrate  24  surrounding the aperture  48  due to thermal contraction or humidity change, even if the width from the aperture  48  to the outer edge of the flexible substrate  24  is decreased. Therefore, it becomes possible to secure positional precision of the bonding pads  50  with respect to the terminals of the bare chips  44 . As a result, it is possible to achieve cost reduction, by decreasing the size of the shape of the relatively expensive flexible substrate  24 . 
     It is possible to provide the reinforcing pattern  54  not only in a single layer of the flexible substrate  24  but also in a plurality of layers of the flexible substrate  24 . For providing the reinforcing patterns  54  in a plurality of layers of the flexible substrate  24 , it is preferable that the reinforcing pattern  54  in one layer and the reinforcing patterns  54  in another layer are formed at the same position and in the same pattern areas with each other so that it becomes possible to minimize a difference between expansion on the front surface side and expansion on the rear surface side of the flexible substrate  24  attributable to variations in temperature and humidity, to restrict warpage and breakage. 
     FIG. 6 is a plan view showing an example of a conventional electronic circuit module  21 X. The electronic circuit module  21 X comprises a rigid substrate  22 X and a flexible substrate  24 X. In the conventional electronic circuit module  21 X having no reinforcing pattern  54 , it is necessary to take a relatively large width D from an aperture  48  of the flexible substrate  24 X to the outer edge thereof, in order to secure positional precision of a bonding pad  50  with respect to a terminal of a bare chip  44 . When the width D is small, it is difficult to obtain a size precision necessary for wire bonding. 
     In the present invention, there is significance in the point that the reinforcing pattern  54  is provided in at least the first portion  24   a  of the flexible substrate  24  (a portion of the flexible substrate  24  that is adhered to the rigid substrate  22 ). When a flexible substrate is individually used, there is a case in which a reinforcing pattern may be provided in the peripheral region of the flexible substrate in order to obtain reinforcement. However, in the structure where the flexible substrate  24  is adhered to the rigid substrate  22 , it is not necessary to provide a reinforcing pattern in the flexible substrate  24  only for the purpose of obtaining reinforcement, since the rigid substrate  22  has sufficient strength and rigidity. The reinforced pattern  54  of the present invention is provided for the purpose of reducing the size of the outer shape of the flexible substrate  24  and obtaining size precision necessary for wire bonding. 
     FIG. 7 is a plan view showing a modified example of the electronic circuit module  21  shown in FIG.  4 . In this example, one side of the aperture  48  of the flexible substrate  24  is open to the outer edge, and the outer edge of the flexible substrate  24  is discontinuous at the aperture  48 . A reinforcing pattern  54  is provided along the periphery of the flexible substrate  24  and the periphery of the aperture  48 . With this arrangement, the reinforcing pattern  54  can make the flexible substrate  22  rigid without interfering with the wiring area of the signal lines. Therefore, it is possible to minimize a size variation based on the provision of the reinforcing pattern  54  near bonding pads  50  that particularly require size precision. As a result, it becomes possible to further decrease the size of the outer shape of the flexible substrate  24  and to obtain the size precision necessary for wire bonding. This leads to a reduction in cost. 
     FIG. 8 is a view showing, in detail, conductor patterns of the flexible substrate  24  of the electronic circuit module  21 . The basic structure of the electronic circuit module  21  shown in FIG. 8 is similar to that of the electronic circuit module  21  shown in FIG.  7 . FIG. 8 shows a state that a resin layer on the upper side of the flexible substrate  24  is removed, and the conductor patterns  46  of the flexible substrate  24  are visible. The conductor patterns  46  include first and second conductor patterns  46   a  and  46   b  located on the upper and lower sides of the intermediate resin layer. The first conductor patterns  46   a  are connected to bonding pads  50  connected to the first bare chip  44  and extend along the upper surface of the intermediate resin layer. The second conductor patterns  46   b  are connected to the bonding pad  50  connected to the adjacent, second bare chip  44  and extend along the lower surface of the intermediate resin layer. The second conductor patterns  46   b  change their course onto the upper surface of the intermediate layer via through-holes  24   h  in the intermediate position of the flexible substrate  24 , and extend along the upper surface of the intermediate resin layer. After the through-holes  24   h , the first and second conductor patterns  46   a  and  46   b  are disposed alternately one by one on the upper surface of the intermediate resin layer. After the through-holes  24   h , there are no conductor patterns on the lower surface of the intermediate resin layer. 
     In the conductor patterns  46 , a dummy conductor pattern can be provided as a reinforcing pattern on the lower surface of the intermediate resin layer, since there are no conductor patterns on the lower surface of the intermediate resin layers after the through-holes  24   h.    
     FIG. 9 is a perspective view showing another example of the electronic circuit module. In FIG. 9, the reinforcing pattern  56  is provided on the layer of the flexible substrate  24  which is different from the layer on which the conductor patterns  46  exist. The reinforcing pattern  56  is not connected electrically. In FIG. 9, the conductor patterns  46  are formed on the upper surface of the flexible substrate  24 , and are not visible. The reinforcing pattern  56  is formed as a conductor film that extends long along the external edge of the rigid substrate  22  on the lower surface of the flexible substrate  24 . As shown in FIG. 2, the flexible substrate  24  is bent to the greater extent near the outer edge of the rigid substrate  22 , and is brought into contact with the outer edge of the rigid substrate  22 . Therefore, this flexible substrate is a portion which might be easily damaged. The reinforcing pattern  56  reinforces the portion of the flexible substrate  24  that could be easily damaged. 
     FIG. 10 is a perspective view showing still another example of the electronic circuit module. In FIG. 10, the reinforcing pattern  56  is provided as an wholly covering film on the layer of the flexible substrate  24  separate from the layer on which the conductor patterns  46  exist. In FIG. 10, the conductor patterns  46  are formed on the upper surface of the flexible substrate  24 , and are not visible. The reinforcing pattern  56  is formed as a conductor film adhered to a portion that is brought into contact with the outer edge of the rigid substrate  22  and a portion of the flexible substrate  24  positioned on the outside of the rigid substrate  22 . 
     When the conductor patterns  46  are formed as shown in FIG. 8, the first and second conductor patterns  46   a  and  46   b  are disposed alternately one by one on the upper surface of the intermediate resin layer after the through-holes  24   h . There are no conductor patterns on the lower surface of the intermediate resin layers after the through-holes  24   h . Therefore, it is possible to provide with the reinforcing pattern  56  by adhesion to the whole lower surface of the intermediate resin layer that has no conductor patterns. The reinforcing pattern  56  reinforces the portion of the flexible substrate  24  that is easily damaged. 
     FIG. 11 is a perspective view showing still another example of an electronic circuit module. In FIG. 11, the reinforcing pattern  56  is provided on the layer of the flexible substrate  24  separate from the layer on which the conductor patterns  46  exist. In FIG. 11, the conductor patterns  46  are not visible. The reinforcing pattern  56  is formed as a conductor film including conductor portions provided corresponding to individual conductor portions of the conductor patterns  46 , at a portion that is brought into contact with the outer edge of the rigid substrate  22  and a portion of the flexible substrate  24  positioned on the outside of the rigid substrate  22 . In this case as well, the first and second conductor patterns  46   a  and  46   b  are disposed alternately one by one on the upper surface of the intermediate resin layer after the through-holes  24   h . There are no conductor patterns on the lower surface of the intermediate resin layers after the through-holes  24   h . Therefore, it is possible to provide the reinforcing pattern  56  on the lower surface of the intermediate resin layer that has no conductor patterns. With this arrangement, the areas of the front and back patterns of the flexible substrate  24  become uniform, and it becomes possible to restrict warpage and breakage. 
     FIG. 12 is a perspective view showing a part of the flexible substrate  24  shown in FIG.  11 . The conductor patterns  46  exist on the upper surface of the flexible substrate  24 , and the reinforcing pattern  56  exists on the lower surface of the flexible substrate  24 . It is preferable that the reinforcing pattern  56  is formed at the same position as the conductor patterns  46  and in the same pattern area as that of the conductor pattern  46 .  58  denotes a current that flows through the conductor patterns  46 . When the current  58  flows through the conductor patterns  46 , an eddy current  60  is induced in the reinforcing pattern  56  due to electromagnetic inductance based on a high voltage applied to the conductor patterns  46 . This eddy current  60  flows in a direction opposite to the direction of the current  58  that flows through the conductor patterns  46 . As a result, it is possible to reduce the inductance of the conductor patterns  46 , and to obtain satisfactory display characteristics of a glass panel (the display part). It is also possible to reduce the inductance based on the eddy current in the case of the pattern in the form of the wholly covering film, as shown in FIG.  10 . 
     FIG. 13 is a view showing a modified example of the reinforcing pattern shown in FIG.  12 . FIG. 14 is a cross-sectional view of the flexible substrate  24  taken along the line XIV—XIV in FIG.  13 . Conductor patterns  46  and the reinforcing pattern  56  are formed at the same positions, and the width of each conductor pattern  46  is smaller than the width of each reinforcing pattern  56 . When the width of the reinforcing pattern  56  is made equal to or larger than the width of the conductor pattern  46  by cutting out a portion of the conductor pattern with a low current density, it is possible to expect the effect of low inductance. 
     FIG. 15 is a view showing a modified example of the reinforcing pattern shown in FIG.  12 . FIG. 16 is a cross-sectional view of the flexible substrate  24  taken along the line XVI—XVI in FIG. 15. A plurality of conductor patterns  46  are disposed as one set. Each one set of the conductor patterns  46  is formed to have a small width, and the conductor patterns  46  are disposed close to each other. Reinforcing pattern  56  is provided for each one set of the conductor patterns  46 . With this arrangement, it is possible to expect the effect of low inductance. 
     FIG. 17 is a view showing an example where a dummy pattern is provided on the rigid substrate. The flexible substrate  24  has conductor patterns  46  and the above-described reinforcing pattern  56  (not shown). The rigid substrate  22  has a dummy pattern  62 . It is preferable that the dummy pattern  62  is formed in the form of the covering film having a large area. In this structure, the patterns are formed based on a method of achieving a reduction in inductance on the flexible substrate  24 , and the dummy pattern  62  is provided by adhesion to the rigid substrate  22  on a wide area. This makes it possible to reduce inductance by utilizing more effectively the eddy current  60 . 
     FIG. 18 is a view showing an example where electric parts are provided straddling both on the flexible substrate  24  and the rigid substrate  22 . The first foot pattern  64  is provided on the flexible substrate  24 , and the second foot pattern  66  is provided on the rigid substrate  22 . A first portion of each electric part (electronic part)  68  is fixed to each first foot pattern  64 , and a second portion of each electric part (electronic part)  68  is fixed to each second foot pattern  66 . In the case of carrying out soldering by reflow, it is possible to avoid failure in applying a soldering paste due to a difference in the heights of the two substrates, by adjusting a paste volume to be coated onto the two substrates. The electric parts (electronic parts)  68  are disposed to extend over the rigid substrate  22  and the flexible substrate  24 , thereby to electrically connect between the rigid substrate  22  and the flexible substrate  24 . As a result, it is possible to decrease the number of wires to be applied between the rigid substrate  22  and the flexible substrate  24 . Based on this mounting method, it becomes possible to electrically connect between various kinds of substrates through parts. It is also possible to improve the wiring efficiency on mutual substrates, and to decrease the area of the substrates. 
     As explained above, according to the present invention, it is possible to restrict occurrence of warpage, breakage and tearing, and to decrease the cost of substrates while decreasing the areas of the substrates. Further, it is possible to obtain a plasma display apparatus with satisfactory electrical characteristics.