Abstract:
This drive chip has a configuration that is provided with: a base main body; two terminal groups that are respectively disposed along the base main body sides in the longitudinal direction of the base main body, said sides facing each other; a narrow-pitch section in one terminal group wherein terminals are disposed in a zigzag manner in two or more rows, said narrow-pitch section having a narrow terminal pitch in the longitudinal direction; a rough pitch section in the one terminal group, said rough pitch section having a terminal pitch in the longitudinal direction wider than that of the narrow pitch section; and a dummy bump that is disposed between the two terminal groups, said dummy bump being disposed parallel to the rough pitch section.

Description:
TECHNICAL FIELD 
     The present invention relates to drive chips, and to display apparatuses provided with drive chips. 
     BACKGROUND ART 
     Conventionally, liquid crystal display devices are used as medium- to small-size display devices for use in portable information terminals and the like. A liquid crystal display device incorporates a drive chip for driving a liquid crystal panel, and to make the liquid crystal display device slim, the drive chip is mounted directly on the liquid crystal panel on a COG (chip-on-glass) basis. In a COG process, typically, an ACF (anisotropic conductive film) is held between a drive chip and a liquid crystal panel, and these are compression-bonded together at high temperature so that the drive chip and the liquid crystal panel are electrically connected together. 
     Today, increasingly slim liquid crystal display devices are sought, and accordingly increasingly slim drive chips are sought. Inconveniently, however, making a drive chip slim causes it to sag under heat during compression bonding. This may lead to defective electrical connection between the drive chip and the liquid crystal panel. 
     Patent Document 1 identified below discloses a drive chip comprising: a base body including a face having a first end portion and a second end portion parallel to the longer sides and a third end portion and a fourth end portion parallel to the shorter sides perpendicular to the longer sides; a number of input terminals formed in the first end portion along the longer sides of the base body; a number of first output terminals arranged in the second end portion along the longer sides; and dummy terminals formed between the input terminals and the first output terminals. Here, the dummy terminals are formed in one or more rows along the longer sides. 
     LIST OF CITATIONS 
     Patent Literature 
     
         
         Patent Document 1: Japanese Patent Application Publication No. 2005-203758 
       
    
     SUMMARY OF THE INVENTION 
     Technical Problem 
     Inconveniently, however, according to Patent Document 1, dummy terminals are arranged in one or more rows in the direction of the longer sides of the drive chip, and thus a sufficient area for circuitry cannot be secured without increasing the size of the drive chip; this makes it difficult to secure a sufficient area for circuitry. 
     An object of the present invention is to provide a drive chip that makes it possible to secure a sufficient area for circuitry and simultaneously to prevent defective connection by suppressing a warp. Another object of the present invention is to provide a display device incorporating such a drive chip. 
     Means for Solving the Problem 
     To achieve the above objects, according to one aspect of the present invention, a drive chip includes: a base body; two groups of terminals arranged respectively along opposite sides of the base body in its lengthwise direction; a narrow-pitch portion in which, with respect to one of the groups whose terminals are arranged in two or more rows in a staggered formation, terminals are arranged at a narrow lengthwise-direction pitch; a rough-pitch portion in which, with respect to said one group of terminals, terminals are arranged at a broader lengthwise-direction pitch than in the narrow-pitch portion; and a bump provided between the two groups of terminals, in the rough-pitch portion. 
     Advantageous Effects of the Invention 
     According to the present invention, a dummy bump provided on a drive chip suppresses a sag in the drive chip under heat during compression-bonding in a COG process. As a result, the drive chip and a liquid crystal panel are kept parallel to each other, and thus defective electrical connection between the drive chip and the liquid crystal panel is prevented. Moreover, owing to the dummy bump being provided in a rough-pitch portion which is not crowded with circuitry, it is possible to secure a sufficient area for circuitry without increasing the size of the drive chip. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an exploded perspective view showing a liquid crystal display device according to one embodiment of the present invention; 
         FIG. 2  is a plan view of a drive chip according to a first embodiment of the present invention; 
         FIG. 3  is a widthwise-direction sectional view of a drive chip in a liquid crystal display device incorporating a drive chip according to the first embodiment; 
         FIG. 4  is a widthwise-direction sectional view of a drive chip in a liquid crystal display device incorporating a drive chip of a comparative example; 
         FIG. 5  is a plan view of a drive chip according to a second embodiment of the present invention; 
         FIG. 6  is a plan view of another drive chip according to the second embodiment of the present invention; and 
         FIG. 7  is a plan view of a drive chip according to a third embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described below with reference to the accompanying drawings. 
       FIG. 1  is an exploded perspective view showing a liquid crystal display device according to one embodiment of the present invention. In  FIG. 1 , the liquid crystal display device  10  is depicted as lying horizontally with its display surface pointing up. 
     The liquid crystal display device  10  is for use as a display in televisions and computers. The liquid crystal display device  10  includes a backlight chassis  11 , light source units  12 , a light guide plate  13 , an optical sheet  14 , a panel frame  15 , a liquid crystal panel  16  with a drive chip  20  mounted on it, and a bezel  17 . The backlight chassis  11 , the light source units  12 , the light guide plate  13 , and the optical sheet  14 , when assembled together, constitute a unit which is referred to as a backlight device  18 . 
     The backlight chassis  11  is a box-shaped member which serves as a base for mounting on it (housing in it) the components of the backlight device  18 , namely the light source units  12 , the light guide plate  13 , the optical sheet  14 , etc. As the material for the backlight chassis  11 , to obtain satisfactory rigidity and heat dissipation, it is preferable to use SECC (sheet steel) or Al to name a few. 
     The light source units  12  each include LEDs (light-emitting diodes) as point light sources and an LED board on which the LEDs are mounted. As light sources, instead of LEDs, fluorescent lamps or the like as linear light sources may be used. On the LED board, a plurality of LEDs are arranged at predetermined intervals along one side of the light guide plate  13 . The light source units  12  are arranged to constitute an edge-lit construction. In a large-size liquid crystal display device, with consideration given to heat dissipation and mechanical strength, used as the LED board is typically a metal board of Al or the like. 
     As a means for fastening the light source units  12  to the backlight chassis  11 , it is possible to use screws or adhesive. Although, in  FIG. 1 , two light source units  12  are arranged along opposite side faces of the light guide plate  13 , it is also possible to arrange a light source unit  12  along only one side face of the light guide plate  13 , or additionally arrange a light source unit  12  along another side face of the light guide plate  13 . In short, a light source unit  12  can be arranged along at least one side face of the light guide plate  13 . Here, each such side face faces LEDs, and serves as a light entry portion (light entry surface) through which light from the LEDs enters the light guide plate  13 . 
     The light guide plate  13  has a pair of main faces (a top and a bottom face) and a plurality of side faces (in  FIG. 1 , four faces) formed between them. The light guide plate  13  is a member which converts the light from the LEDs that has entered it through an end face (side face) into planar light and which then emits the planar light through the top face. As the material for the light guide plate  13 , it is preferable to use, from the viewpoint of thickness reduction and weight reduction, resin such as acrylic resin or PC (polycarbonate). 
     The optical sheet  14  collectively refers to one, or a combination of more than one, out of a diffuser sheet, a lens sheet, a luminance enhancement sheet, etc. The optical sheet  14  is laid over the light guide plate  13 , and serves to shine light evenly on the liquid crystal panel  16 . Thus, a crease or a sag in the sheet results in degraded display quality. 
     The panel frame  15  is a picture frame-shaped member which holds the liquid crystal panel  16  in such a way that it does not make contact with the optical sheet  14 . As the material for the panel frame  15 , it is preferable to use resin such as PC. The panel frame  15  also serves to suppress a warp or a sag. 
     The liquid crystal panel  16  is a member composed of two transparent substrates with a liquid crystal element held between them. While the liquid crystal element is driven under the control of the drive chip  20 , the liquid crystal panel  16  is illuminated by the backlight device  18  and thereby an image is displayed. 
     The drive chip  20  includes a base body, a plurality of input terminals, and a plurality of output terminals, and is mounted on the liquid crystal panel  16  on a COG basis. The drive chip  20  converts image data fed in from the outside into a drive signal fit for the driving of the liquid crystal panel  16 , and feeds the drive signal to the liquid crystal panel with optimal timing. 
     The bezel  17  is a picture frame-shaped member which holds and secures the liquid crystal panel  16  in position, and is placed over the box-shaped backlight chassis  11  as if a lid. As the material for the bezel  17 , it is possible to use SECC or AL, or, for weight reduction, PC, ABS resin, CFRP (carbon fiber-reinforced plastic), or the like. For further weight reduction, by use of any of these materials, the bezel  17  may be molded integrally with a housing (unillustrated) as an outer casing. 
     In the liquid crystal display device  10  structured as described above, the drive chip  20  is devised to be distinctive of the present invention. Now, embodiments of the drive chip  20  will be described in detail. 
     &lt;First Embodiment&gt; 
       FIG. 2  is a plan view of a drive chip according to a first embodiment of the present invention. As one embodiment of the drive chip  20  described previously, a drive chip  201  according to the first embodiment has a base body  202 , a group of input terminals  203 , a group of output terminals  204 , and a dummy bump  205 . 
     The base body  202  is an electrically insulating member of which the face on which the groups of terminals are arranged is rectangular in shape. The base body  202  has, for example, a thickness of 0.2 mm or less and a length of 1.5 mm or more in its widthwise direction (i.e., the direction along shorter sides). Inside the base body  202  is provided a semiconductor element (unillustrated) for converting an image signal fed in from the outside into a drive signal necessary for driving. 
     The group of input terminals  203  and the group of output terminals  204  are two groups of terminals arranged respectively along opposite sides of the base body  202  in its lengthwise direction (i.e., the direction along longer sides). In the group of input terminals  203 , rectangular terminals  203   a  are formed at equal intervals in one row, in a straight formation. The group of input terminals  203  may comprise two or more rows. 
     In the group of output terminals  204 , rectangular terminals  204   a , which are smaller than input terminals, are formed in two rows, in a staggered formation. In a central part of the group of output terminals  204  in the lengthwise direction, to secure an area for circuitry, the terminals  204   a  are arranged at a broader lengthwise-direction pitch than elsewhere (than in narrow-pitch portions  204   b  and  204   d , which will be described later), and this part is referred to as a rough-pitch portion  204   c . On the other hand, on both sides of the rough-pitch portion  204   c , no area for circuitry needs to be secured, and thus the terminals  204   a  are arranged densely, at a narrower pitch than in the rough-pitch portion  204   c;  these parts are referred to as narrow-pitch portions  204   b  and  204   d . The group of output terminals  204  may comprise three or more rows. 
     The arrangement formations of the group of input terminals  203  and the group of output terminals  204  may be switched so that the group of input terminals  203  is arranged in a staggered formation and the group of output terminals is arranged in a straight formation. The groups of terminals  203  and  204  may both be arranged in a staggered formation, or in a straight formation in two or more rows. 
     The dummy bump  205  is a bump that is electrically connected to nowhere. The dummy bump  205  is arranged approximately at the center of the base body  202 . That is, the dummy bump  205  is arranged between the group of input terminals  203  and the group of output terminals  204 , in the rough-pitch portion  204   c . The height (thickness) of the dummy bump  205  is equal to the height (thickness) of the group of input terminals  203  and the group of output terminals  204 . The dummy bump  205  has a larger area than each of the terminals  203   a  and  204   a . Instead of the dummy bump  205 , a functional bump that is electrically connected to somewhere may be provided. 
       FIG. 3  is a widthwise-direction sectional view of the drive chip  201  in a liquid crystal display device incorporating the drive chip  201  according to the first embodiment. By use of a liquid crystal panel  16  having conductor lines  30  formed on it, an ACF (anisotropic conductive film)  31  is held between the drive chip  201  and the liquid crystal panel  16 , and these are compression-bonded together under heat by a COG process so that the groups of terminals  203  and  204  are electrically connected to the conductor lines  30 . In  FIG. 3 , the ACF  31  is schematically depicted by a large number of electrically conductive particles contained in it. The dummy bump  205  is compression-bonded to the liquid crystal panel  16  via the ACF  31 . 
       FIG. 4  is a widthwise-direction sectional view of a drive chip in a liquid crystal display device incorporating a drive chip of a comparative example. Compared with the drive chip  201  of the first embodiment, the drive chip  100  of the comparative example has no dummy bump  205 . 
     As described above, the base body has a thickness as small as 0.2 mm or less, and has a widthwise-direction dimension as large as 1.5 mm or more; thus, the drive chip  100  sags in the widthwise direction under heat during compression bonding in the COG process, and the liquid crystal panel  16  sags in the opposite direction so as to be warped backward. As a result, a gap larger than is supposed to be appears between the liquid crystal panel  16  and, in particular, the terminals  204   a  in an outer row in the group of output terminals  204 ; thus, there, the electrically conductive particles in the ACF  31  do not have satisfactory particle flatness, resulting in defective electrical connection between the drive chip  100  and the liquid crystal panel  16 . 
     By contrast, in the liquid crystal display device incorporating the drive chip  201  according to the first embodiment, owing to the provision of the dummy bump  205 , the sag in the drive chip  201  under heat during compression bonding in the COG process is suppressed. As a result, the drive chip  201  and the liquid crystal panel  16  are kept parallel to each other (see  FIG. 3 ); accordingly, the electrically conductive particles in the ACF  31  in contact with all the terminals  203   a  and  204   a  have satisfactory particle flatness, and thus defective electrical connection between the drive chip  201  and the liquid crystal panel  16  is prevented. 
     Moreover, in the drive chip  201  according to the first embodiment, the dummy bump  205  is provided in the rough-pitch portion  204   c , which is not crowded with circuity. Thus, it is possible to secure a sufficient area for circuitry without increasing the size of the drive chip  201 . 
     &lt;Second Embodiment&gt; 
       FIG. 5  is a plan view of a drive chip according to a second embodiment of the present invention. As another embodiment of the drive chip  20  described previously, a drive chip  206  according to the second embodiment has two dummy bumps  205  each like the one in the first embodiment. Otherwise, such parts as find their counterparts in the first embodiment are identified by common reference signs, and will not be discussed in detail. 
     As shown in  FIG. 5 , the two dummy bumps  205  are arranged approximately at the center of the base body  202 , side by side in the lengthwise direction. That is, the two dummy bumps  205  are arranged between the group of input terminals  203  and the group of output terminals  204 , in the rough-pitch portion  204   c.    
       FIG. 6  is a plan view of another drive chip according to the second embodiment of the present invention. As yet another embodiment of the drive chip  20  described previously, another drive chip  207  according to the second embodiment has three dummy bumps  205  each like the one in the first embodiment. As shown in  FIG. 6 , the three dummy bumps  205  are arranged approximately at the center of the base body  202 , in a row in the lengthwise direction. That is, the three dummy bumps  205  are arranged between the group of input terminals  203  and the group of output terminals  204 , in the rough-pitch portion  204   c.    
     In the second embodiment, four or more dummy bumps  205  may be provided. In this way, a drive chip according to the second embodiment is provided with a plurality of dummy bumps  205 , and this makes it possible to secure a sufficient area for circuitry and simultaneously to prevent, more reliably, defective electrical connection between the drive chip and the liquid crystal panel  16 . As in the first embodiment, the dummy bumps  205  may be replaced with functional bumps. 
     &lt;Third Embodiment&gt; 
       FIG. 7  is a plan view of a drive chip according to a third embodiment of the present invention. As still another embodiment of the drive chip  20  described previously, a drive chip  208  according to the third embodiment has a rough-pitch portion  204   c  arranged in an end part of the group of output terminals  204  in the lengthwise direction. Otherwise, such parts as find their counterparts in the first embodiment are identified by common reference signs, and will not be discussed in detail. 
     As shown in  FIG. 7 , a dummy bump  205  is arranged near an end part of the base body  202  in the lengthwise direction. That is, the dummy bump  205  is arranged between the group of input terminals  203  and the group of output terminals  204 , in the rough-pitch portion  204   c  in a row. 
     Even in a case as described above where the rough-pitch portion  204   c  is arranged near an end part of the base body  202 , by arranging the dummy bump  205  in the rough-pitch portion  204   c , it is possible to secure a sufficient area for circuitry and simultaneously to prevent defective electrical connection between the drive chip and the liquid crystal panel  16 . As in the first embodiment, the dummy bump  205  may be replaced with a functional bump. In the third embodiment, as in the second embodiment, a plurality of dummy bumps  205  may be provided. 
     INDUSTRIAL APPLICABILITY 
     Drive chips according to the present invention find application in display devices such as liquid crystal display devices, and are suitably used, in particular, in medium- to small-size liquid crystal display devices for use in portable information terminals and the like. 
     LIST OF REFERENCE SIGNS 
     
         
         
           
               10  liquid crystal display device 
               11  backlight chassis 
               12  light source unit 
               13 ,  21 ,  31 ,  41  light guide plate 
               14  optical sheet 
               15  panel frame 
               16  liquid crystal panel 
               17  bezel 
               18  backlight device 
               30  conductor line 
               31  ACF 
               201 ,  206 - 208  drive chip 
               202  base body 
               203  input terminal 
               203   a ,  204   a  terminal 
               204  output terminal 
               204   b ,  204   d  narrow-pitch portion 
               204   c  rough-pitch portion 
               205  dummy bump