JP2006339613A - Wiring connection structure and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring connection structure and a liquid crystal display device contriving the simplification and sharing of a wiring structure, an improvement in the workability in wiring connection and an improvement in reliability of connection. <P>SOLUTION: In the present invention, an ACF (anisotropic conductive film) with such a constitution that conductive particles are dispersed to a resin binder is arranged over an element connection region and an FPC wiring region, and an element provided with a connection terminal is electrically connected with the wiring of the element connection region on the ACF on the element connection region through the ACF. An FPC film is connected with the connection wiring in the wiring region for FPC on the ACF on the wiring region for FPC. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wiring portion connection structure applied to a liquid crystal display device and the like, and more particularly, to a technique that enables an element such as a driving IC mounted on a substrate and a flexible printed board to be connected without a gap.

In general, a liquid crystal display device includes a liquid crystal panel in which liquid crystal is sealed between upper and lower transparent substrates, a driver circuit thereof, and a circuit board electrically connected to the video signal processing device. A driver circuit is generally configured as a flexible connection board that connects a liquid crystal panel and a circuit board with a driving IC and power supply components mounted on a film board on which a predetermined wiring pattern is formed. It is.
As a connection method between a flexible connection board and a circuit board, in recent years, in order to improve the resolution of the liquid crystal screen, the pitch interval of the connection lead of the circuit board and the pitch interval of the electrodes of the connection board tend to be finely formed. In addition, a TAB (Tape Automated Bonding) mounting method using an ACF (Anisotropic Conductive Film) is widely applied to the connection between the connection board and the printed circuit board.
The ACF is formed by dispersing conductive particles in an adhesive resin binder and is usually formed in a tape shape. And this ACF tape is affixed on the connection lead of a circuit board, is affixed on an ACF tape in the state which aligned the connection board | substrate with the printed circuit board, and a connection board | substrate and a printed circuit board are heated, and is attached. First, the binder resin is softened by crimping, and the electrodes of the connection board and the connection leads of the circuit board are electrically connected through the conductive particles during compression, and the binder resin is cured by further heating. Thus, the connection board and the circuit board are fixed to complete the connection.

5 and 6 show an example of a general liquid crystal display device provided with a driving IC.
In the liquid crystal display device of this example, a driving IC 103 is mounted on one substrate 102 of a pair of substrates 101 and 102 sandwiching a liquid crystal layer by COG (Chip On Glass) mounting or the like. It is necessary to connect one transparent electrode and the other transparent electrode of the substrate to be paired with the driving IC 103, and the substrate 102 is formed in such a manner that the lead wiring is extended by a transparent conductive material such as indium tin oxide (ITO). By forming it above, the driving IC 103 and each transparent electrode are connected.
Further, it is necessary to connect a flexible printed circuit board (FPC) 106 for connecting an electric circuit for supplying a driving signal to the driving IC 103. Conventionally, as shown in FIG. The connection wiring 104b is formed of a transparent conductive material, the driving IC 103 is connected to one end of the connection wiring 104b (the end closer to the inside of the substrate 102), and the other end of the connection wiring 104b. The ACF film 107 is sandwiched between (the end near the outer peripheral edge of the substrate) and the FPC 106 and heated and pressed to electrically connect the connection wiring 104b and the wiring 106a of the FPC 106 through the conductive particles in the ACF film 107. Connected.

By the way, the present inventors are provided with a pair of substrates facing each other with a liquid crystal layer interposed therebetween. The drive IC is mounted on the substrate, and the drive IC and the flexible printed wiring board are connected to the substrate on which the drive IC is mounted. A connection wiring is formed, a driving IC is connected to the end of the connection wiring, an ACF film is disposed in the vicinity of the driving IC, and the connection wiring and the flexible printed wiring board are electrically connected via the ACF film. A patent application has been filed for a liquid crystal display device having a structure in which the ends of the wiring pattern of the flexible printed wiring board are extended to the vicinity of the driving IC and the driving IC and the flexible printed wiring board are electrically connected. (See Patent Document 1)
Japanese Patent Laid-Open No. 2004-61979

  As a structure obtained by further developing the connection structure using the COG mounting and the ACF film, the present inventors arrange the ACF film 111 for COG on the side of the lead wiring area close to the display area of the substrate 102 as shown in FIG. A structure in which an ACF film 112 for FPC is placed on 110 and slightly outside of the previous ACF film 111, the driving IC is connected to the ACF film 111 by crimping, and the FPC is connected to the ACF film 112 by pressing. The wiring connection structure is simplified.

In the conventional liquid crystal display device shown in FIGS. 5 and 6, the FPC 106 is disposed between the driving IC 103 and the ACF film 107, but the gap 110 is necessarily between the driving IC 103 and the ACF film 106. Therefore, the arrangement efficiency is poor in terms of narrowing the frame of the liquid crystal display device.
Further, even when the structure shown in FIG. 7 is adopted, since the crossing in the operation of attaching the ACF films 111 and 112 on the substrate 110 inevitably occurs about ± 0.3 mm, the ACF films 111 and 112 should be at least 0. It is necessary to paste them at a distance of about 0.6 mm, and even at least a width of about 0.6 mm has become a useless area that cannot be ignored in downsized electronic devices such as mobile phones.

In this way, the crossing at the time of pasting is required to be at least about ± 0.3 mm when the connection terminal 121 of the driving IC 120 is pressed against the ACF film 111 and joined as shown in FIGS. Compared with the case where the connection terminal is pressed against the ACF film 107 and joined, the comparison between the connection terminal 121 of the driving IC and the connection terminal of the FPC 106 has a large difference in terminal size and gap, and the pressing pressure and temperature Since the desirable conditions such as are different from each other, after pressing and connecting the driving IC 120 with the pressure head 123 shown in FIG. 8, the pressure head 124 having another size and different pressure shown in FIG. The FPC 106 must be crimped and connected to the ACF film 107, and it is inevitably a little clear in consideration of interference and clearance between both heads. Due to the fact that there is a need to provide a lance.
Note that the ACF film 111 for the connection terminal 121 of the driving IC 120 and the ACF film 107 for the FPC 106 are provided separately, whereas the connection terminal 121 of the driving IC 120 has a pitch number of 10 μm, The portion has a pitch of about 0.1 to 1 mm, the size and pitch of the terminals are different, and naturally the pressing force against the ACF film is also different, so the viscosity of the resin constituting the ACF film is different, and the heat treatment temperature is also caused by them. This is because they are different and need to be prepared as separate ACF films.

The present invention has been made in view of the above circumstances, and by simplifying and sharing the wiring structure by allowing the wiring connection directly under the element and the wiring connection directly under the FPC to be performed by one ACF, It is another object of the present invention to provide a wiring connection structure capable of improving workability during wiring connection and improving connection reliability.
In addition, the present invention simplifies and shares the wiring structure in the liquid crystal substrate by sharing the wiring connection directly below the liquid crystal driving element and the wiring connection directly below the FPC so that it can be performed by one ACF. An object of the present invention is to provide a liquid crystal display device capable of improving workability during wiring connection and improving connection reliability.

  The present invention has been made in view of the above circumstances, and an element connection region and an FPC wiring region are provided on a substrate apart from each other, and conductive particles are provided in a resin binder across the element connection region and the FPC wiring region. An ACF film having a dispersed configuration is arranged, and an element having a connection terminal on the ACF film on the element connection region is electrically connected to the wiring in the element connection region via the ACF film. The FPC film is placed on the ACF film on the FPC wiring area and is electrically connected to the connection wiring in the FPC wiring area via the ACF film. It is characterized by being installed.

The liquid crystal display device of the present invention is a liquid crystal display device comprising a pair of substrates facing each other with a liquid crystal layer interposed therebetween, and wirings provided on the surface of each substrate on the liquid crystal layer side. Is wired in the driving element connection region of the one substrate, and an FPC wiring region is formed on the peripheral edge portion of the substrate so as to be separated from the driving element connection region. The driving element connection region and the FPC wiring region ACF film having a structure in which conductive particles are dispersed in a resin binder is disposed over both areas, and the driving element is connected to the ACF film on the driving element connection area, and the connection terminal is connected to the ACF film. The FPC film is placed on the ACF film on the FPC wiring area, and the wiring portion is connected to the ACF film. Characterized by comprising installed while connected to the connection wiring of the FPC wiring region by.
In any of the above structures, the wiring connection directly under the element and the wiring connection directly under the FPC can be shared by one ACF, and the wiring structure can be simplified and shared, and two ACF films can be used. In addition, it is possible to improve workability at the time of wiring connection and improve connection reliability. In addition, compared to the case where separate ACF films are arranged, there is no need to apply pressure bonding under different conditions when heating and pressure bonding, so there is no need to provide a clearance when pressure bonding ACF films. The flexible printed circuit board can be arranged as close as possible.

The present invention is characterized in that the pitch and thickness of the connection terminal portion of the element are different from the pitch and thickness of the wiring portion of the FPC film.
The above-described structure can be applied even when the pitch and thickness of the connection terminal portion of the element and the wiring portion of the ACF film are different.

  In the present invention, the connection terminal of the element is connected by thermocompression bonding to the wiring of the driving element connection region on the substrate through the conductive particles of the ACF film, and the wiring portion of the FPC film is connected to the wiring of the ACF film. It is characterized by being connected by thermocompression bonding to the connection wiring of the drive element connection region on the substrate via conductive particles.

The present invention is characterized in that the binder is made of an epoxy resin or an acrylic resin, the binder thickness is 20 to 25 μm, and the elastic modulus of the binder is 1.0 to 3.0 GPa.
If the thickness of the binder made of the resin is in the above range and the elastic modulus is in the above range, there is no problem even if the connecting terminal of the element and the electrode of the flexible printed board have a structure with different pitches and sizes. Can be connected without any problems.

The present invention is characterized in that the binder is made of epoxy resin or acrylic resin, the binder has a thickness of 20 to 25 μm, and the diameter of the conductive particles dispersed and blended in the binder is in the range of 3 to 5 μm. .
If the thickness of the binder made of the resin is in the above range and the diameter of the conductive particles is in the above range, the connection terminal of the element and the electrode of the flexible printed circuit board have a structure in which the pitch and size are different. Can be connected without any problem.

In the present invention, the binder is made of an epoxy resin or an acrylic resin, the binder thickness is 20 to 25 μm, and the density of conductive particles dispersed and blended in the binder is in the range of 1 million particles / mm ^{3 to} 7.5 million particles / mm ³ . It is characterized by being made.
If the thickness of the binder made of the resin is in the above range and the density of the conductive particles is in the above range, the connection terminal of the element and the electrode of the flexible printed circuit board have a structure with different pitches and sizes. Can be connected without any problem.

According to the present invention, the wiring connection directly under the element and the wiring connection directly under the FPC can be shared by one ACF, and by using one ACF film, the conventional structure in which two ACF films are used. In comparison, the wiring structure can be simplified and shared. Compared to the conventional structure in which two ACF films are installed and individually crimped and connected, the workability at the time of wiring connection can be improved by crimping one ACF film, and when one ACF film is crimped By improving the conditions, it is possible to improve the connection reliability.
In addition, compared to the case of disposing different ACF films, there is no need to press-bond under different conditions when heat-bonding is performed, so the clearance necessary for pressure-bonding ACF films separately is provided. There is no need, and the device and the flexible printed circuit board can be arranged as closely as possible. Further, by adopting a structure in which the element and the flexible printed board are attached to the substrate of the liquid crystal display device, it contributes to narrowing and downsizing of the liquid crystal display device substrate.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments described below. Further, in the following drawings, the scale of each component is described in a different scale for each component so that it can be easily shown in the drawing.
FIG. 1 is a perspective view illustrating a schematic configuration of the liquid crystal display device according to the first embodiment, and FIG. 2 is a cross-sectional view taken along line II-II of the liquid crystal display device of FIG.
In the figure, reference numeral 1 denotes a liquid crystal cell. The liquid crystal cell 1 is formed by superposing two transparent substrates 2 and 3 so as to form a cell gap therebetween and injecting them between the substrates 2 and 3. The liquid crystal 5 thus formed has a basic structure in which the substrates 2 and 3 are surrounded and sandwiched by the sealing material 6 formed on the peripheral portion on the opposite surface side. 1 and 2, the substrate 2 positioned on the lower side is larger than the upper substrate 3, and a driving element connection region 7 and an FPC wiring region 8, which will be described later, are formed on the projecting portion 2 a of the substrate 2. The driving element (driving IC) 9 is mounted in the driving element connection area 7 and the flexible printed circuit board (FPC) 10 is connected to the FPC wiring area 8 to constitute the liquid crystal display device A.

The liquid crystal driving circuit provided in the liquid crystal cell 1 used in this embodiment is not particularly limited, and may be either a simple matrix type or an active matrix type. For example, a TFT-type circuit configuration in which a thin film transistor is arranged for each pixel that divides a display area and a source line and a gate line for driving control are arranged vertically and horizontally, or a plurality of strip-like electrodes are provided on one substrate side The present invention can be applied to any simple matrix type configuration in which a plurality of strip electrodes are arranged on the other substrate side. The liquid crystal cell 1 can be applied to any configuration of a transmission type, a reflection type, and a transflective type.
In the liquid crystal cell 1 of this embodiment, a plurality of wiring lines S for a liquid crystal driving circuit are formed in the display area of the liquid crystal cell 1, and these wiring lines S are formed so as to extend outward from the display area. It is drawn out to the upper surface side of the overhanging portion 2 a, and is densely arranged as the extended wiring 11 in the elongated driving element connection region 7 partitioned along the edge 3 a of the substrate 3 in the overhanging portion 2 a. In the drive element connection region 7, a necessary number of extended wirings 11 are aligned and formed so as to match the alignment pitch of connection terminals such as bumps of the drive element 9. Since these extension wirings 11 are preferably formed by extending the circuit wiring for driving the liquid crystal constituting a part of the liquid crystal cell 1 as it is, they are usually formed from a transparent conductive film such as ITO. A conductive film such as metal wiring may be separately formed on the substrate 2.

  Next, the outer end portion of the upper surface of the overhanging portion 2a of the substrate 2 (the end portion on the opposite side of the upper surface of the overhanging portion 2a from the substrate 3 side) has the same length as the driving element connection region 7 described above. An FPC wiring area 8 having a width is formed, and a plurality of strip-like connection wirings 15 are formed in the FPC wiring area 8 at a pitch that matches a pitch of a wiring portion 25 described later formed on the flexible printed circuit board 10. They are arranged in parallel to each other. These connection wirings 15 are usually formed of a transparent conductive film such as ITO like the extension wirings 11, but a conductive film such as a metal wiring is separately formed on the projecting portion 2 a of the substrate 2. But it ’s okay.

Then, the ACF film 16 is mounted so as to straddle the plurality of extended wires 11 arranged in the previous drive element connection region 7 and the plurality of connection wires 15 arranged in the FPC wiring region 8, A plurality of connection terminals 9 a on one side of the drive element 9 are electrically connected to the ACF film 16 on the drive element connection region 7, on the ACF film 16 on the wiring region 8, and the drive element connection region A plurality of connection terminals 9 b on the other side of the drive element 9 are electrically connected to a portion closer to 7. The driving element 9 has a main body 9A which is chip-shaped and includes a functional element such as a semiconductor, and has a plurality of connection terminals such as bumps at a pitch of about 20 μm to 50 μm on one side and the other side thereof. 9a and 9b are protrudingly formed.
These connection terminals 9a and 9b are formed to have a surface area of about 1000 to 8000 μm ² size, a height of about 9 μm to ²⁰ μm, and a distance between terminals of about 8 μm to 20 μm, for example, one side of the main body 9A Several tens to several hundreds are formed.

The ACF film 16 has a structure in which a large number of conductive particles are dispersed inside a binder made of an epoxy resin or an acrylic resin.
FIG. 3 shows an example of the conceptual structure of the ACF film 16 used in this form. The ACF film 16 in this form has an upper and lower two-layer structure composed of a base layer 20 and a dispersion layer 21, and the base layer 20 has dispersed conductive particles. The dispersion layer 21 has a density of about 1 million particles / mm ^{3 to} 7.5 million particles / mm ³ of conductive particles 22 having a particle diameter of about ³ μm to 5 μm. The binder 23 is dispersed and blended.
The two-layer structure as described above is preferable because the fluidity of the binder is improved and the conductive particles are easily dispersed uniformly in the binder.

The ACF film 16 as a whole has a thickness of, for example, about 20 μm to 25 μm, the base layer 20 has a thickness of, for example, about 9 μm to 15 μm, and the dispersion layer 21 has a thickness of, for example, about 10 μm to 14 μm.
If the ACF film 16 is too thick, the resin tends to be too much and the contact resistance tends to increase. On the other hand, if the ACF film 16 is too thin, there is a problem that the binder will flow too much and the conductive particles cannot be retained. .

The resin binder constituting the ACF film 16 preferably has an elastic modulus of, for example, about 1.0 to 3.0 GPa (at 30 ° C.) and 0.05 GPa or less (at 150 ° C.). Further, the crystallization temperature Tg of the binder is preferably in the range of 100 to 150 ° C.
When the elastic modulus is 1 GPa or less at 30 ° C., the connection resistance increases. Moreover, in the case of 3 GPa or more, the adhesiveness of the ACF film 16 is lowered. In addition, when the crystallization temperature Tg of the binder is less than 100 ° C., the tendency to react by temporary fixing becomes strong, so that handling is difficult, and when the Tg exceeds 150 ° C., the reaction temperature is too high. The temperature must be increased and handling becomes difficult.

  The drive element 9 pressurizes the connection terminals 9a and 9b in a heated state with respect to the ACF film 16, and causes the plurality of connection terminals 9a and 9b to enter the binder of the ACF film 16 to thereby form a plurality of connection terminals. 9a is electrically connected to the extension wiring 11 through the plurality of conductive particles 22, and the plurality of connection terminals 9b are electrically connected to the connection wiring 15 through the conductive particles 22, and then the binder is heated by heating. The connection terminals 9a and 9b are bonded to the wirings 11 and 15 by being fluidized and solidified.

Next, an ACF film 16 is extended and formed on the wiring 15 outside the portion where the driving element 9 is joined in the protruding portion 2a of the substrate 2 so as to reach the end of the substrate 2 as it is. The wiring part 25 of the flexible printed circuit board 10 is joined on the ACF film 16.
The flexible printed board 10 is formed by forming a plurality of wiring portions 25 made of a copper foil, a plating layer, or the like at a predetermined pitch on a base material layer made of polyimide.
As a specific structure of these wiring parts 25, the following laminated structure can be illustrated. For example, a laminated structure of an adhesive layer, a copper foil, a Th plated layer, a Ni plated layer, and an Au plated layer, a laminated structure of an adhesive layer, a copper foil, a Th plated layer, and a lead or lead-free plated layer, an adhesive layer and a copper foil Examples include a laminated structure of lead or lead-free plating layers, a laminated structure of copper foil, Th layer, Ni plating layer, and Au plating layer, and a laminated structure of copper foil and lead- or lead-free plating layer.
In the flexible printed circuit board 10, the pitch of the wiring part 25 is about 0.06 mm to 4 mm, the width of the wiring part at the end of the flexible printed circuit board (conductor terminal width) is about 0.03 mm to 1 mm, and the thickness is about 10 μm to 80 μm. The space between each conductor of the wiring part 25 is about 0.03 mm to 2 mm.

As described above, the pitch, width, and height of the connection terminals 9b of the drive element 9 are on the order of several μm to several hundred μm, and the pitch and width of the wiring portion 25 of the flexible printed circuit board 10 are 0. Since it is in the range of about 1 mm to several mm, the size of each other is in a different order. Conventionally, connection of terminals and conductors having different orders as described above has been difficult to obtain a good pressure-bonding property with a single ACF film. However, if the ACF film 16 has the structure described above, In addition to the type and thickness of the resin binder, the size of the conductive particles is good, and since the ACF film 16 having a conductive particle dispersion state in an appropriate range is used, the connection terminals 9a having different sizes and pitches, 9b and the wiring part 25 can be shared by using one ACF film 16, and any part can be pressure-bonded with good bondability.
For example, conventionally, when the connecting terminals of the driving element 9 have a pitch and width of the order of several tens of micrometers, and the pitch of the wiring portion of the flexible printed circuit board is about 0.1 mm to 0.6 mm and the width, the ACF film is used for pressure bonding. In this case, terminals and wiring portions having different pitches and widths cannot be pressure-bonded with the same ACF film. However, by using the ACF film 16 as described above, both of them can be bonded together. Good joint reliability and strength can be achieved even when pressure is shared.

In addition, since the base of the connection terminal 9b of the drive element 9 and the base of the wiring portion 25 of the flexible printed board 10 are both made of the same ACF film 16, the pressure bonding between the connection terminal 9b and the wiring portion 25 is the same pressure. Be able to do with the head.
FIG. 4 shows this state. By using the pressure head 26 having the pressing surfaces 26a and 26b adjacent to each other through the stepped portion, the driving element 9 and the flexible printed circuit board 10 are pressed at the same time, thereby one ACF film. Thus, the drive element 9 and the flexible printed circuit board 10 having different pitches and sizes can be simultaneously bonded by pressure bonding.
Thereby, even if the connection terminal 9b of the drive element 9 and the wiring part 25 of the flexible printed circuit board 10 are brought as close as possible, the same pressure head 26 can be crimped without any trouble. It is possible to dispose the portion and the crimped joint portion of the wiring portion 25 of the flexible printed circuit board 10 closer than ever, and, for example, the joint portion can be joined with a gap of about 0.2 mm. It has a feature that it can provide a joining structure with no wasteful space.

On the other hand, in the conventional structure, the connection portion of the connection terminal of the driving element 9 and the wiring portion of the flexible printed circuit board are joined with a structure using separate ACF films. There is a problem that a clearance of about ± 0.3 mm is required at the time of pressing and pressure bonding, and a wasteful space is created only in the clearance, and the area of the protruding portion of the substrate 2 cannot be reduced. If the structure of this embodiment is adopted, the overhanging portion 2a of the substrate 2 can be made smaller than before. Therefore, the liquid crystal display device A of this embodiment has a preferable feature in terms of space saving when used in a small electronic device such as a mobile phone whose size is being pushed down.
For example, conventionally, when separate ACF films are used for the drive element connection area and the flexible printed circuit board connection area, it is about 0.6 mm to several mm from the position control of the pressure head for pressure bonding the both. Although a clearance is absolutely necessary, by using this form of structure and sharing an ACF film, a useless space can be narrowed to a gap of about 0.2 mm. As a result, the structure of the present embodiment can be downsized by about 0.4 mm to several mm, but the internal structure of the mobile phone is expected to reduce the size of the liquid crystal display device even if it is only a fraction of a mm. Because it is rare, the effect is great.

  In addition, since two types of ACF films that have been conventionally used can be unified, one type of ACF film can be shared, and the required cost of the ACF film can be reduced to about ½. Furthermore, if two types of ACF films are stored as in the prior art, the binder is cured with time depending on the type of binder resin, so the storage and maintenance of the ACF film itself is complicated, and depending on the type of binder resin However, the storage period of two types of ACF films had to be managed, but since the ACF film can be unified into one type, storage of the ACF film itself becomes easy, and the manufacturing process of the structure using the ACF film 16 Contributes to simplification.

  In the above embodiments, the example in which the present invention is applied to the connecting portion between the driving element 9 such as the driving IC of the liquid crystal display device and the flexible printed board 10 has been described. However, the structure of the present invention is not limited to this. It can be widely applied to the case where an element having a plurality of connection terminals and the wiring portion of the flexible printed circuit board are joined on the substrate, and particularly the size and pitch of the connection terminal on the element side and the wiring portion of the flexible printed circuit board. Needless to say, the present invention can be widely applied to connection structures in general when the size and pitch are different.

A first wiring group having a width of 27 μm and a pitch of 42 μm made of ITO formed on a glass substrate, and a second wiring group having a width of 0.08 mm and a pitch of 0.16 mm made of ITO formed on the edge of the glass substrate. On the other hand, an ACF film having a thickness of 24 μm was disposed so as to straddle the first wiring group and the second wiring group.
A liquid crystal driving IC having 808 metal pads having a height of 15 μm, such as a width of 27 μm and a pitch of 42 μm, is installed on the ACF film on the first wiring group, and the width on the ACF film on the second wiring group. A flexible printed circuit board provided with a wiring portion having a pitch of 0.08 mm and a pitch of 0.16 mm was placed, and a pressure head was pressed from above with a pressure of 10 MPa, and heated to 200 ° C. for bonding. This pressure head has a structure having a step on the pressing surface, and employs a structure capable of heating while pressing the liquid crystal driving IC and the flexible printed circuit board simultaneously with a uniform pressure.
Here, the end portion of the liquid crystal driving IC and the end portion of the flexible printed circuit board were joined with a gap of 0.2 mm.

The ACF film used here has a total thickness of 24 μm made of epoxy resin, a base layer thickness of 12 μm in the portion without conductive particles, a thickness of 12 μm in the portion of the dispersed layer in which the conductive particles are dispersed, and 3.1 million conductive particles having a particle size of 4 μm. A material dispersed at a density of / mm ³ was used. The elastic modulus of the epoxy resin binder was 2.6 GPa (30 ° C.).
The driving IC and the flexible printed circuit board were bonded to the wiring group by 50 pieces, and a high-temperature and high-humidity energization test was performed on the driving IC through the wiring portion of the flexible printed circuit board. All of them worked as usual.
Therefore, it has been found that the wiring connection structure allows the connection terminal of the driving IC and the wiring portion of the flexible printed circuit board to be joined with one ACF film.

Next, an ACF film having an ACF film thickness of 35 μm was prepared and subjected to the above test. However, 100% display failure due to poor connection terminal conduction occurred.
This seems to be because the ACF film was too thick and the conductive particles could not contact the wiring in the above-described pressure bonding.
An ACF film having an ACF film thickness of 15 μm was prepared and subjected to the above-described test. However, 100% of display defects due to poor connection terminal connection occurred. This is presumably because the ACF film was too thin and the binder part flowed too much in the above-described pressure bonding, and the conductive particles were not satisfactorily held by the binder.

50 drive ICs were bonded in the same manner as described above using an ACF film having a layer thickness of 22 μm, an average conductive particle diameter of 4 μm, and a conductive particle density of 2 million particles / mm ³ , and using different resin binder elastic modulus. When the test was conducted and the current test was conducted, 100% display failure was caused by the connection terminal failure with the binder having an elastic modulus of 0.5 GPa, and 100% display failure was caused by the connection terminal connection failure even with the binder of 3.3 GPa. It occurred.
On the other hand, connection failure did not occur in the sample using the binder resin of 1.0 GPa, the sample using the binder resin of 2.0 GPa, and the sample using the binder resin of 3.0 GPa. This is presumed to be due to the following reason.
In the sample having an elastic modulus of 0.5 GPa, it seems that the fluidity of the binder was too good and a problem occurred in the adhesion of the ACF film. In addition, it is considered that a sample having an elastic modulus of 3.0 GPa has a short circuit between terminals due to aggregation of conductive particles.

When a layer thickness of the ACF film is 22 μm, and the conductive particle density is 2 million particles / mm ³ , a joining test similar to the above is performed using different conductive particle diameters to be used. 100% display failure was caused by connection terminal connection failure in the sample using, and 100% display failure was caused by connection terminal connection failure even in the sample using conductive particles having an average of 6 μm.
On the other hand, connection failure did not occur between the sample using conductive particles having an average diameter of 3 μm and the sample using conductive particles having an average of 5 μm.
This is presumed to be due to the following reason. When the conductive particles are 2 μm, it is considered that the connection failure occurred because the variation in the bump height of the drive element (drive IC) could not be absorbed. Further, when the conductive particles are 6 μm, the conductive particles are short-circuited between the bumps of the driving IC, which causes a problem.

From the above test results, it was found that when the binder is made of an epoxy resin or an acrylic resin and the binder thickness is 20 to 25 μm, the elastic modulus of the binder is preferably in the range of 1.0 to 3.0 GPa.
Moreover, when the said binder consists of an epoxy resin or an acrylic resin, and the said binder thickness is 20-25 micrometers, it turned out that the diameter of the electroconductive particle disperse-blended with the said binder is the range of 3 micrometers-5 micrometers.
Further, when the binder is made of an epoxy resin or an acrylic resin and the binder thickness is 20 to 25 μm, the density of the conductive particles dispersed and blended in the binder is in the range of 1 million particles / mm ^{3 to} 7.5 million particles / mm ³ . Was found to be preferred.

  The present invention can be widely applied to a structure in which an element and a flexible printed board are connected to another board by wiring. For example, the structure of the present invention is applied to a connecting structure part of a driving IC and a flexible printed board of a liquid crystal display device. Of course, it can be widely applied to connection wiring portions of other general structures.

FIG. 1 is a perspective view of a liquid crystal display device showing a first embodiment of the present invention. 2 is a partial cross-sectional view taken along line II-II of the liquid crystal display device of FIG. FIG. 3 is a cross-sectional view of an ACF film incorporated in the liquid crystal display device. FIG. 4 is an explanatory view showing a state in which the structure of the present invention is manufactured with one pressure head. FIG. 5 is a perspective view showing an example of a conventional liquid crystal display device. 6 is a partial cross-sectional view taken along the line IX-IX of the liquid crystal display device shown in FIG. FIG. 7 is a plan view showing a connection area of a driving IC and a connection area of a flexible printed board of a conventional liquid crystal display device. FIG. 8 is an explanatory view showing a state in which a driving IC is connected to wiring on a substrate through an ACF film in a conventional liquid crystal display device. FIG. 9 is an explanatory view showing a state in which a flexible printed board is connected to wiring on the board via an ACF film in a conventional liquid crystal display device.

Explanation of symbols

A liquid crystal display device,
1 liquid crystal cell,
A few substrates,
5 Liquid crystal,
6 Sealing material,
7 Drive element connection area,
8 FPC wiring area,
9 Drive element (drive IC),
9a, 9b connection terminal,
10 Flexible printed circuit board,
11 Extension wiring,
15 Wiring section,
16 ACF film,
20 base layer,
21 dispersion layer,
22 conductive particles,
23 binder,
25 Wiring section,
26 pressure head,

Claims (12)

  An element connection region and an FPC wiring region are provided apart from each other on the substrate, and an ACF film having a configuration in which conductive particles are dispersed in a resin binder is disposed across the device connection region and the FPC wiring region. On the ACF film on the connection area, an element having a connection terminal is installed in a state where the connection terminal is electrically connected to the wiring of the element connection area via the ACF film, and the FPC wiring A wiring connection structure, wherein an FPC film is installed on an ACF film on a region in a state where the wiring portion is electrically connected to the connection wiring of the FPC wiring region via the ACF film.   The wiring connection structure according to claim 1, wherein the pitch and thickness of the connection terminal portion of the element are different from the pitch and thickness of the wiring portion of the FPC film.   The connection terminal of the element is connected by thermocompression bonding to the wiring of the driving element connection region on the substrate through the conductive particles of the ACF film, and the wiring portion of the FPC film is connected through the conductive particles of the ACF film. The wiring connection structure according to claim 1, wherein the wiring connection structure is connected to the connection wiring in the drive element connection region on the substrate by thermocompression bonding.   4. The binder according to claim 1, wherein the binder is made of an epoxy resin or an acrylic resin, the binder thickness is 20 to 25 [mu] m, and the elastic modulus of the binder is 1.0 to 3.0 GPa. The wiring connection structure according to the above.   The binder is made of an epoxy resin or an acrylic resin, the binder thickness is 20 to 25 µm, and the diameter of the conductive particles dispersed and blended in the binder is 3 µm to 5 µm. Wiring connection structure in any one of. The binder is made of epoxy resin or acrylic resin, the binder thickness is 20 to 25 μm, and the density of the conductive particles dispersed and blended in the binder is in the range of 1 million particles / mm ^{3 to} 7.5 million particles / mm ^3. The wiring connection structure according to any one of claims 1 to 3.   A liquid crystal display device comprising a pair of substrates opposed to each other with a liquid crystal layer interposed therebetween, and wirings provided on the surface of each substrate on the liquid crystal layer side, wherein each wiring is used for driving the one substrate An FPC wiring area is formed on the periphery of the substrate and spaced from the driving element connection area, and the driving element connection area and the FPC wiring area extend over both areas. An ACF film having a structure in which conductive particles are dispersed in a resin binder is disposed, and a driving element is connected to the driving element on the ACF film on the driving element connection region, and the connection terminal is connected to the driving element via the ACF film. The FPC film is installed on the ACF film on the FPC wiring area, and the wiring portion is connected to the FPC wiring area via the ACF film. The liquid crystal display device characterized by comprising installed in a state of the connection to the connection wiring.   The liquid crystal display device according to claim 7, wherein the pitch and thickness of the connection terminal portion of the driving element are different from the pitch and thickness of the wiring portion of the FPC film.   The connection terminal of the driving element is connected by thermocompression bonding to the wiring of the driving element connection region on the substrate through the conductive particles of the ACF film, and the wiring portion of the FPC film is connected to the conductive particles of the ACF film. The liquid crystal display device according to claim 7, wherein the liquid crystal display device is connected by thermocompression bonding to a connection wiring in a drive element connection region on the substrate via a substrate.   The binder according to any one of claims 7 to 9, wherein the binder is made of an epoxy resin or an acrylic resin, the binder thickness is 20 to 25 µm, and the elastic modulus of the binder is 1.0 to 3.0 GPa. A liquid crystal display device according to claim 1.   The binder is made of an epoxy resin or an acrylic resin, the binder thickness is 20 to 25 µm, and the diameter of the conductive particles dispersed and blended in the binder is 3 µm to 5 µm. A liquid crystal display device according to any one of the above. The binder is made of epoxy resin or acrylic resin, the binder thickness is 20 to 25 μm, and the density of the conductive particles dispersed and blended in the binder is in the range of 1 million particles / mm ^{3 to} 7.5 million particles / mm ^3. The liquid crystal display device according to claim 7, wherein the liquid crystal display device is a liquid crystal display device.

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