Abstract:
A tape carrier package that is capable of preventing a short between adjacent pads in boning the tape carrier package mounted with an integrated circuit onto a liquid crystal panel and a print wiring substrate. In the package, a base film is mounted with an integrated circuit. Input pads are connected to the integrated circuit to input an external input signal to the integrated circuit. Each of output pads has a first portion extended to the integrated circuit, and a second portion extended to the first portion to have a narrower line width than the first portion.

Description:
BACKGROUND OF THE INVENTION 
     This application claims the benefit of Korean patent application number P2000-0866, filed Feb. 23, 2000 which is hereby incorporated by reference for all purposes as if fully set forth herein. 
     1. Field of the Invention 
     This invention relates to an apparatus for mounting an integrated circuit in a liquid crystal display, and more particularly to a tape carrier package that reduces the possibility of a short between adjacent pads when bonding the tape carrier package to a liquid crystal panel and/or a printed wiring substrate. Also, the present invention is related to a method of fabricating such a tape carrier package. 
     2. Description of the Related Art 
     Generally, an active matrix liquid crystal display uses thin film transistors (TFTs) as switching devices to display natural-looking moving pictures. Since such a liquid crystal display can be made into a smaller-size device than a cathode ray tube, it is commercially viable for use a monitor such as a portable television, lap-top personal computer or other consumer device. 
     The active matrix liquid crystal display displays a picture corresponding to video signals such as television signals on a pixel (or picture element) matrix having pixels arranged at each intersection between gate lines and data lines. Each pixel includes a liquid crystal cell for controlling a transmitted light quantity in accordance with a voltage level of a data signal from a data line. A TFT (thin film transistor) is installed at an intersection between a gate line and a data line to switch a data signal to be transferred to the liquid crystal cell in response to a scanning signal (i.e., a gate pulse) from the gate line. 
     Such a liquid crystal display requires a number of integrated circuits (ICs) connected to the data lines and the gate lines to apply data signals and scanning signals to the data lines and the gate lines, respectively. The ICs are installed between the print wiring board (PWB) and the liquid crystal panel to apply signals supplied from the PWB to the data lines and the gate lines. IC mounting methods include chip on board, hereinafter referred to as “COB”, tape automated bonding, hereinafter referred to as “TAB”, and a chip on glass, hereinafter referred to as “COG”. (Other methods are also possible). The COB system is mainly used for monochromatic liquid crystal displays having a pixel pitch of more than 300 μm. As shown in FIG. 1, in this COB system, ICs  8  are mounted on a PWB  6  and a heat-seal connector  10  connects the PWB  6  and a glass substrate  3  in a liquid crystal panel  2 . In this case, a back light unit  4  used as a light source is provided between the liquid crystal panel  2  and the PWB  6 . As shown in FIG. 2, in the TAB system, ICs  14  are mounted on a tape carrier package (TCP)  12 . The TCP  12  is connected between the PWB  6  and the liquid crystal panel  3 . As shown in FIG. 3, in the COG system, an IC chip  20  is directly mounted on a glass substrate  17  in a liquid crystal panel  16 . 
     The above-mentioned TAB IC mounting method has been widely employed because it can widen an effective area of the panel and has a relatively simple mounting process. 
     As shown in FIG. 4, the TCP  12  employed in the TAB system includes a base film  22  on which is mounted an IC  14 . The base film  22  is also provided with input and output pads  24  and  26  connected to input and output pins of the IC  14 . The input and output pads  24  and  26  have a two-layer structure in which copper(Cu) is plated with tin(Sn) for preventing oxidation. Line widths of the input pads  24  are set to be larger than those of the output pads  26 . As shown in FIG. 5, the input pads  24  of the base film  22  are connected, via an anisotropic conductive film (ACF)  30 , to pads  28  on the PWB  6 . The output pads  26  are also connected via the ACF  30  to pads  28  on the liquid crystal panel  2 . 
     However, the IC mounting method employing the TAB system has a problem in that a conductive alien substance produced from a cutting process of TCP  12  may generate a short between the pads  28  on the liquid crystal panel  2  or the PWB  6  and the pads  24  and  26  of the base film  22 , respectively as shown in FIG.  5 . More specifically, the TCP  12  is formed on a flexible polyimide film roll (FPFR)  32  and then is cut into the shape shown by the dashed line  40  in FIG.  6 . In this case, the input and output pads  24  and  26  extend outside of a cutting line  40 . At this time, as seen from FIG.  7 A and FIG. 7B, the input pads  24  have the same line width at the inside and outside of the cutting line  40 . The output pads  24  also have the same line width inside and outside of the cutting line  40 . In FIG.  7 A and FIG. 7B, a bonding layer  27  functions to adhere the input and output pads  24  and  26  on the base film  22 . An extension of the input and output pads  24  and  26  into a dummy area outside of the cutting line  40  aims at electrically testing whether or not there is a defect in the IC  14 , the pads  24 ,  26  and/or the interconnection pattern between the IC  14  and the pads  24 ,  26 , before the base film  22  has been cut. After the test, the base film  22  and the input and output pads  24  and  26  are cut along the cutting line  40 . At this time, a portion of the input and output pads  24  and  26  on the cutting line  40  may come off due to friction between a cutter (not shown) and the input and output pads  24  and  26 . A conductive alien substance  42  generated in this manner is adhered to the TCP  12  by static electricity such that the material  42  is loaded into a pad bonding equipment (not shown) along with the TCP  12 . This conductive alien substance  42  is interposed between the pads  28  of the PWB  6  or the liquid crystal panel  2  and the input and output pads  24  and  26  as shown in FIG. 5 during the pad bonding process, which causes an insulation breakdown of the ACF  30 . As a result, the pads  28  on the adjacent PWB  6  or liquid crystal panel  2  and/or the input and output pads  24 ,  26  are short-circuited due to the conductive alien substance  42 . Particularly, as line widths of the input and output pads  24  and  26  on the cutting line  40  are relatively wide, so too is the size of the conductive alien substance  42 . Since a distance between panels in a high-resolution liquid crystal display is narrow, a conductive alien substance  42  with a small size also may cause a short between panels in such a high-resolution liquid crystal display. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a tape carrier package that reduces the possibility of a short between adjacent pads. 
     A further object of the present invention is to provide a method of fabricating a tape carrier package that reduces the possibility of a short between adjacent pads. 
     In order to achieve these and other objects of the invention, a tape carrier package according to one aspect of the present invention includes a base film for mounting an integrated circuit; input pads connected to the integrated circuit and output pads connected to the integrated circuit, each of the output pads including a first portion adjacent to the integrated circuit and a second portion extended from the first portion, wherein the second portion has a narrower line width than the first portion. 
     A method of fabricating a tape carrier package according to another aspect of the present invention includes the steps of forming input pads at the inside of a coating line of the tape carrier package on a base film; forming output pads including a first portion connected to an integrated circuit on the base film, a second portion positioned at the cutting line and having a narrower line with than the first portion, and a third portion extending from the second portion and having a wider line width than the second portion; mounting the integrated circuit on the base film; connecting the input pads and the first portions; to the integrated circuit and the base film along the cutting line. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects of the invention will be apparent from the following detailed description of preferred embodiments of the present invention with reference to the accompanying drawings, in which: 
     FIG. 1 is a side view showing an integrated circuit mounting method employing the conventional chip on board system; 
     FIG. 2 is a side view showing an integrated circuit mounting method employing the conventional tape automated bonding system; 
     FIG. 3 is a side view showing an integrated circuit mounting method employing the conventional chip on glass system; 
     FIG. 4 is a perspective view showing the structure of the tape carrier package shown in FIG. 2; 
     FIG. 5 is a plan view showing a connection between the input and output pads of the tape carrier package shown in FIG.  2  and the pads on a liquid crystal panel or a printed wiring board shown in; 
     FIG. 6 is a plan view showing the tape carrier package of FIG. 2 in an uncut state; 
     FIG. 7A is a cross sectional view of the input pads taken along lines A-A′ and B-B′ of FIG. 6; 
     FIG. 7B is a cross sectional view of the input pads taken along a line C-C′ of FIG. 6; 
     FIG. 8 is a perspective view of a tape carrier package according to an embodiment of the present invention; 
     FIG. 9 is a plan view showing the tape carrier package of FIG. 8 in an uncut state; 
     FIG. 10A is a cross sectional view of the input pads taken along the line D-D′ of FIG. 9; 
     FIG. 10B is a cross sectional view of the input pads taken along the line E-E′ of FIG. 9; 
     FIG. 10C is a cross sectional view of the input pads taken along the line F-F′ of FIG. 9; and 
     FIG. 10D is a cross sectional view of the input pads taken along the line G-G′ of FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG.  8  and FIG. 9, there is shown a tape carrier package (TCP) according to an embodiment of the present invention. The TCP includes ICs  58  mounted on a center portion of a base film  52 , input pads  54  provided only at the inside of a cutting line  60  of the base film  52 , and output pads  56  having a body  56   a  and a neck  56   b  that have a different line width from each other. In a process of fabricating a liquid crystal display, the input pads  54  of the TCP are connected, via an ACF (not shown), to the pads on the PWB (not shown). The input pads  54  are provided only at the inside base film area of the cutting line  68  as shown in FIGS. 8 and 9. In other words, the input pads  54  do not extend outside of the cutting line  60 , but are formed only inside of the cutting line  60 . The input pads  54  preferably extend to the edge of the cutting line  60  as shown in FIG.  8 . Alternatively, a small space may be left between the cutting line  60  and the edge of the input pads  54  as shown in FIG.  9 . 
     The output pads  56  are connected, via the ACF, to the signal line pads (not shown) on a liquid crystal panel. As shown in FIG. 9, each output pad  56  consists of a body  56   a  with a wide line width, neck  56   b  with a narrow line width, and a dummy part  55  that is cut away when the TCP is being cut from the FPFR  62 . The body  56   a  is positioned at the inside base film area of the cutting line  60  while the neck  56   b  is positioned at a cutting line  60 . The dummy part  55  extends from the neck  56   b  and is positioned at an outside area of the cutting line  60 . In this case, the dummy part  55  has the same line width as the body  56   a.  However, it is also possible to form dummy part  55  that have wider or narrower line widths than the body  56   a.  Such input and output pads  54  and  56  have a two-layer structure in which copper(Cu) is plated with tin(Sn) for preventing oxidation. Also show in FIGS. 10A-C is an optional bonding film  57 , which adheres the pads  54 ,  56  to the base film  52 . 
     The neck  56   b  can be formed with a width of approximately 30% of the width of the body  56   a  when the output pads  56  have a pitch of approximately 70 microns. In this case, the defect ratio of the output pads (or wiring) is below 50%. However, the width of the neck  56   b  of the output pad  56  is preferably about 30.30 microns when the body  56   a  has a width of approximately 35.30 microns. This is because the neck  56   b  may be bent when it has a width of 20 microns. 
     The dummy parts  55  of the output pads  56  and the input pads  54  formed on the FPFR  62  contact probes of a tester (not shown) in an uncut state. In this state, a test is performed for judging whether or not there is a defect in the ICs, the pads  54 ,  56  and/or the interconnection pattern between the pads  54 ,  56  and the ICs in the TCP. Because the input pads  54  are relatively wider and longer than the output pads  56 , it is possible to connect the probes of the tester to the input pads  54  without the need for extensions of the input pads  54  past the cutting line  60 . However, because the output pads  56  are relatively shorter and narrower than the input pads  54 , it is necessary to include the dummy parts  55  to provide sufficient space to connect the probes of the tester to the output pads  56 . 
     After the test has been completed, the base film  52  and the necks  56   b  of the output pads  56  are cut along the cutting line  60 . At this time, since the input pads  54  do not exist on the cutting line  60  and the necks  56   a  are set to have a small line width, friction between the pads  56  and the cutter is greatly reduced. Accordingly, the generation of a conductive alien substance during the cutting can be prevented. The TCP cut in this manner is loaded into a pad bonding equipment (not shown). Upon pad bonding, the input and output pads  54 ,  56  of the TCP are opposed to the PWB and the liquid crystal panel  2  with the ACF therebetween. Subsequently, the input pads  54  and the pads on the PWB, or the output pads  56  and the pads on the liquid crystal panel  2  is pressurized in a state of heating the ACF. At this point, the input and output pads  54  and  56  of the TCP and the PWB or the pads on the liquid crystal panel  2  are electrically connected to each other by conductive particles within the ACF. Accordingly, a conductive alien substance is not generated, or a conductive alien substance with a very small size is generated in the cutting process, so that the chance of a short among the pads  54 ,  56 , including the pads on the PWB, is greatly reduced. 
     As described above, according to the present invention, the pads are provided at the inner base film area of the cutting line or provided on the cutting line in such a manner to have a narrow line width, so that it is possible to minimize a conductive alien substance generated during the cutting. Accordingly, the TCP according to the present invention can greatly reduce the chance of a short between pads from being generated when the TCP is bonded to a PWB or liquid crystal panel. 
     Although the present invention has been illustrated explained by the embodiments shown in the drawings described above, it should be understood by one of ordinary skill in the art that the invention is not limited to the embodiments, described above but rather that various changes or modifications thereof are possible without departing from the spirit of the invention. Accordingly, the scope of the invention shall be limited only by the appended claims and their equivalents.