JP2004047335A - Terminal connection structure and flexible board using same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a terminal connection structure of electronic equipment using an anisotropic conductor layer and a flexible substrate capable of improving utilization rate of a conductor particle, by the above, augmentation of resistance rate of the terminal connection is prevented, and reliability of the terminal connection can be improved. <P>SOLUTION: A groove 11 obliquely traversing the terminal is arranged and installed at terminal faces of respective terminals 1 existing at a connecting part of the flexible substrate. Especially, the depth of the groove 11 is set to be slightly smaller than the diameter of the conductor particle 1, and the breadth of the groove 11 is set to be larger than the diameter of the conductor particle 3. In a connected state after being thermally compression-bonded, the conductor particles 3 of a sufficient number remain in the groove 11. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a terminal connection structure for an electronic device using an anisotropic conductive layer, and a flexible substrate used for the structure. Further, the present invention relates to a flat panel display device having such a terminal connection structure.
[0002]
[Prior art]
As a technique for connecting terminals having fine pitches, there is a technique using an anisotropic conductive layer. In particular, in a flat display device such as a liquid crystal display device, an anisotropic conductive layer is used for connecting a terminal group on a display panel to a terminal group on a flexible substrate connected to an external drive system. An anisotropic conductive layer is a layer of conductive particles dispersed in a thermosetting or thermoplastic resin layer. This realizes conduction (for example, Japanese Patent Application Laid-Open No. 10-077460). As the anisotropic conductive layer used for assembling the flat panel display device, an anisotropic conductive film (ACF) supplied as a tape-like or strip-like film is generally used for convenience in the working process (for example, JP-A-8-114810).
[0003]
Hereinafter, the configuration of the flat panel display device, particularly, the configuration of the liquid crystal display device will be described.
[0004]
2. Description of the Related Art Flat display devices such as liquid crystal display devices are rapidly expanding their markets to notebook PCs, liquid crystal monitors, home televisions, and the like because they can achieve thinness, light weight, and low power consumption.
[0005]
These flat panel display devices include a display panel body in which pixels are arranged to form an image display area, and a drive circuit system for inputting image signals and other drive signals to the display panel body. A display panel main body constituting a display area of a flat panel display device usually includes a plurality of pixels between two insulating substrates, the degree of light transmission or reflection of which can be adjusted according to external control. It is. An electrode region, a color filter, and the like are formed on one surface of each insulating substrate by a number of processing steps, and then a cell structure sandwiching a liquid crystal material or the like, that is, a display panel body is formed.
[0006]
The input of the drive signal from the drive circuit system to the display panel main body is performed through a printed wiring board such as a flexible wiring board connected to a peripheral portion of the display panel main body. Generally, a plurality of drive IC chips for controlling an input signal at a predetermined timing and generating an output signal are arranged on a peripheral portion of a display panel main body, and an input from the drive circuit system to each drive IC chip is a flexible wiring board or the like. Done through.
[0007]
There is a COG (Chip On Glass) system in which the drive IC chip is mounted directly on the peripheral portion of the display panel body, but one drive IC called a tape carrier package (hereinafter, referred to as TCP) is provided. A method using a small-sized flexible board on which a chip is mounted is often used.
[0008]
The TCP is often referred to as a branch wiring board, and a plurality of TCPs includes one printed wiring board (hereinafter referred to as a PCB) on the drive circuit system side, that is, a main wiring board, and a peripheral portion of a display panel body. It is arranged to bridge between and connect. As a result, output of each drive IC chip from the main wiring board (PCB) and output from each drive IC chip to the display panel main body are realized. Here, the PCB is a wiring board for performing output from the drive circuit system or a wiring board on which a drive circuit system such as a controller IC is mounted.
[0009]
The input side edge of each TCP is mounted at the position of the output pad group of the PCB, so that the input terminal group of each TCP and the corresponding output pad group on the PCB are electrically connected. Similarly, the output side edge of the TCP is directly mounted on the peripheral edge of the display panel main body, whereby the output terminal group of the TCP is electrically connected to the connection pad group on the peripheral edge of the display panel main body. .
[0010]
In the past, when mounting the input side edge portion of the TCP on the PCB, it was generally performed by soldering, but in recent years, an anisotropic conductive layer has been used. This is to cope with the fact that the pitch between terminals has become smaller due to the higher definition of the flat panel display device, or to improve work efficiency.
[0011]
In any case, since the terminals connected by the ACF are formed by patterning a metal film or the like, the terminals form rectangular or strip-like projections, and the upper surface has a flat surface with no difference in elevation.
[0012]
However, in the thermocompression bonding process of connecting such terminals via the ACF, the conductive particles originally in the region of the terminal surface are flushed out of the edge of the terminal surface region together with the molten resin. . In this way, the conductive particles located along the edge of the terminal surface area and outside thereof do not contribute to the connection between the terminals at all. Therefore, the resistance of the terminal connection is increased by the amount of the conductive particles being pushed away in this manner.
[0013]
Therefore, in Japanese Patent Application Laid-Open No. 2001-343903, the terminal is made of a sintered metal particle to increase the surface roughness of the terminal surface, and the ten-point surface roughness Rz is set to be equal to or smaller than the diameter of the conductive particles, and It is disclosed that the height Ra is larger than the diameter of the conductive particles.
[0014]
[Problems to be solved by the invention]
However, if the surface roughness is to be increased in this manner, there is a problem that the manufacturing cost of the terminal increases and the thickness of the terminal increases. In particular, when the surface roughness is increased by such a method, the flow of the conductive particles may be extremely deteriorated, and uniform pressure bonding may be difficult. Further, depending on the height distribution of the surface irregularities, the proportion of the conductive particles buried in the large irregularities may increase.
[0015]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and in a terminal connection structure of an electronic device using an anisotropic conductive layer and a flexible substrate used for the same, easily and reliably improves the utilization rate of conductive particles. Accordingly, it is possible to provide a device capable of preventing an increase in the resistivity of the terminal connection and improving the reliability of the terminal connection.
[0016]
[Means for Solving the Problems]
A flexible substrate of the present invention includes a flexible insulating substrate, an output-side wiring group extending toward one edge of the insulating substrate, and an anisotropic conductive film extending from an end of the output-side wiring group. And an output-side terminal group connected to an external terminal group through a flexible substrate, wherein the surface of each terminal of the output-side terminal group has a surface on which the movement of the conductive particles during melt flow of the anisotropic conductive film is performed. The restricting grooves are arranged so as to extend from the center or the vicinity of the center line of the terminal to the edge of the terminal.
[0017]
According to the above configuration, it is possible to improve the utilization efficiency of the conductive particles, prevent an increase in the resistivity of the terminal connection, and improve the reliability of the terminal connection.
[0018]
The terminal connection structure of the present invention electrically connects a first terminal on a flexible first substrate and a second terminal on a second substrate via an anisotropic conductive film. In the terminal connection structure for mechanical connection, grooves are arranged on the terminal surface of the first or second terminal, and the grooves have a depth smaller than the diameter of the conductive particles and a width smaller than the diameter of the conductive particles. It is characterized by being large.
[0019]
Preferably, the groove extends from a center or near a center line of the terminal to around an edge of the terminal. More preferably, it extends to the edge.
[0020]
With such a configuration, at the time of thermocompression bonding, the conductive particles are collected at the location of the groove and flow out to the edge of the terminal together with the molten resin by an appropriate amount, and a large number of conductive particles remain in the groove. You can do so. Therefore, thermocompression bonding can be performed uniformly and easily, and the utilization efficiency of the conductive particles can be sufficiently improved.
[0021]
Preferably, the groove is appropriately curved or meandering.
[0022]
With such a configuration, at the time of thermocompression bonding, it is possible to control the flow of the molten resin containing the conductive particles to an optimal state, so that the optimal amount of the molten resin flows out of the portion on the terminal surface. In addition, a sufficient amount of conductive particles can be left on the terminal surface.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
A flat panel display according to an embodiment of the present invention will be described with reference to FIGS.
[0024]
FIG. 1 is a schematic perspective view showing the surface shape of a TCP output terminal. FIG. 2 is a schematic cross-sectional view showing a state in which the output terminal of the TCP is connected to the connection pad of the display panel via the ACF. FIG. 3 is a schematic horizontal sectional view showing the distribution of the conductive particles of the ACF in such a terminal connection structure. FIG. 4 schematically shows the entire appearance of the flat panel display device without a frame or the like.
[0025]
The flat display device of the embodiment is, for example, an XGA-TFT type normally white mode light transmission type liquid crystal display device having a diagonal dimension of 13.3 inches. In the example of FIG. 4, one insulating substrate protrudes along two long sides and one short side of the rectangular display panel main body 4 to form a peripheral portion 41 for connection. An elongated drive input PCB 7 is arranged along each peripheral edge 41, and a plurality of rectangular TCPs 5 are arranged so as to bridge between the peripheral edge 41 of the display panel main body 4 and the drive input PCB 7. .
[0026]
The output end portion 5a of each TCP 5 is attached to the corresponding input pad portion of the peripheral portion 41 via the ACF 2 and is electrically connected. The input end 5b of each TCP 5 is connected to the output pad of the drive input PCB 7 via the ACF.
[0027]
As shown in FIG. 1, the output terminals 11 arranged at the output end 5a of the TCP 5 are arranged with grooves 11 provided on the terminal surface. The output-side terminals 1 are strip-shaped metal patterns provided on the base film 55 of the TCP 5, and are arranged at a constant pitch. The grooves 11 extend linearly so as to obliquely cross the output side terminals 1 and are arranged at substantially constant intervals.
[0028]
In order to provide the groove 11 on the terminal surface, for example, when forming the output side terminal 1, after forming a solid metal pattern by plating operation or the like, the entire surface can be scratched. After this scratching, a resist pattern is provided, and each output side terminal 1 is created by patterning.
[0029]
As shown in FIG. 2, the output terminal 1 of the TCP 5 and the connection pad 6 on the peripheral portion 41 of the display panel main body 4 are connected via the ACF. The depth of the groove 11 is slightly smaller than the diameter of the conductive particles 3, and the width of the groove 11 is considerably larger than the diameter of the conductive particles 3. For example, the diameter of the conductive particles 3 is 3 to 6 μm, the depth of the groove 11 is smaller than 2 to 4 μm, and the width of the groove 11 is 6 to 10 μm.
[0030]
Further, as shown in FIGS. 2 and 3, the conductive particles 3 in the ACF 2 are substantially in the groove 11 at a portion sandwiched between the output terminal 1 of the TCP 5 and the connection pad 6 of the display panel main body 4. Are distributed so as to concentrate on By the conductive particles 3 gathered in the grooves 11, electrical connection between the butted terminals is achieved.
[0031]
In order to perform such terminal connection, for example, after attaching to a predetermined portion of the peripheral portion 41 of the strip-shaped ACF2 display panel 4, the TCP5 is positioned and arranged, and then the TCP5 is heated using a heater tool. Thermocompression bonding in which the output end 5a is pressed. With the heating and pressing in the thermocompression bonding step, the molten resin partially flows out along the groove 11 from a region on the terminal surface, that is, a region to be sandwiched. Further, with the flow of the molten resin, the conductive particles 3 in the ACF 2 are once collected in the groove 11, and a part of the conductive particles 3 flows from the groove 11 to the region 15 between the adjacent terminals, and It is distributed around the point along the edge 1a.
[0032]
Since the grooves 11 are arranged obliquely across the output terminals 1, an appropriate resistance is given to the flow of the molten resin and the conductive particles 3 along the grooves 11 in the thermocompression bonding step. Thereby, during the thermocompression bonding process, an appropriate flow of the molten resin is performed by the time the resin is cured or the pressing operation is completed, and a sufficient number of conductive particles 3 remain in the grooves 11 to contribute to terminal connection. I do. Moreover, since the grooves 11 are arranged so as to be distributed substantially uniformly, the conductive particles 3 are also distributed almost uniformly in the terminal surface.
[0033]
Hereinafter, Modifications 1 to 4 will be described with reference to FIGS.
[0034]
In Modification Example 1 shown in FIG. 5, on the terminal surface of the output terminal 1 of the TCP 5, linear grooves 11 'starting from near the center line of the terminal and extending to the edge 1a of the terminal are arranged. Even with the groove having such a shape, substantially the same effect as in the case of the above embodiment can be obtained. That is, the flow of the molten resin from the vicinity of the center line of the terminal to the edge thereof is appropriately assisted, and a sufficient number of conductive particles can be left in the groove.
[0035]
In the modification 2 shown in Fig. 6, a meandering groove 11 "that obliquely crosses the terminal is provided on the terminal surface of the output terminal 1 of the TCP 5. That is, in the same configuration as in the above embodiment, the groove is formed. It is curved and meandering in a wavy line.
[0036]
According to the melt viscosity of the molten resin, the heat flow property, the density of the conductive particles, etc., by appropriately applying such meandering, the flow of the resin and the flow of the conductive particles in the thermocompression bonding process are optimized. be able to.
[0037]
In other words, for the groove provided obliquely across the terminal surface, the degree of slanting is appropriately adjusted, and the degree of flow of the molten resin and the conductive particles can be optimized by appropriately forming the groove in a meandering manner. .
[0038]
In Modification 3 shown in FIG. 7, the surface of the conductive particles 3 ′ in the ACF 2 is covered with the small protrusions 31 in the same configuration as that of the embodiment. Since the flow of the conductive particles is regulated by such small projections 31, the amount of the conductive particles that escape to the inter-terminal region 15 is reduced, and the electric resistance of the inter-terminal connection can be further reduced.
[0039]
Such conductive particles with small projections can be provided, for example, by sintering fine conductive particles on the surface of spherical conductive particles.
[0040]
Alternatively, it can be created by the following method. First, spherical polymer particles having a uniform diameter and size distribution are prepared by an ordinary method. Next, the surface of the spherical polymer particles is covered with a low-melting-point polymer, and then the fine polymer particles are mixed while applying moderate heating, and fused to the surface of the spherical polymer particles serving as a core. Then, the surface of the polymer particles with small projections is plated with gold and then covered with a thin insulating coating layer.
[0041]
Further, after the particles soluble in a solvent are embedded in the surface of the spherical polymer particles, the particles are dissolved and removed, whereby irregularities or small projections can be provided on the surface.
[0042]
Modification 4 shown in FIG. 8 is the same as Modification 3 except that no groove is provided on the terminal surface. That is, in the same configuration as the conventional terminal connection, the surface of the conductive particles 3 ′ in the ACF 2 is covered with the small protrusion 31. By using such conductive particles with small projections, even if there is no groove on the terminal surface, the flow of the conductive particles to the inter-terminal region 15 can be restricted to some extent, and a decrease in terminal connection resistance can be prevented. be able to. Depending on the melt viscosity of the molten resin, the thermocompression bonding conditions, and the like, a sufficient effect can be obtained by using the conductive particles 3 ′ with small projections as the conductive particles of the ACF 2 in this manner.
[0043]
In the above-described embodiment and the modified example, the groove is provided in the output side terminal of the TCP. However, the groove may be provided in the connection pad of the display panel main body. Although the connection between the TCP 5 and the PCB 7 has not been described, a similar groove may be provided in a terminal of the TCP or a pad of the PCB when the connection is performed by the ACF.
[0044]
Further, in the above-described embodiment and modified examples, the terminal has been described as having a strip shape. However, the same is true even if the terminal has a rectangular shape close to a square, a circular shape, or the like. In this case, a groove extending from the center of the terminal to the edge can be appropriately provided. This groove can also be provided at an angle to the edge or in a curved or meandering manner.
[0045]
The grooves may be provided in a mesh shape such as a vertical or horizontal lattice shape or a spider web shape. In this case, the flow which makes the distribution of the resin and the conductive particles uniform in the terminal surface is promoted, and the effect of suppressing the flow of the conductive particles is obtained by the groove extending in parallel with the edge of the terminal. In some cases, by providing only parallel grooves on the edge of the terminal, the effect of suppressing the flow of conductive particles can be obtained.
[0046]
In the above-described embodiment and modified examples, TCP is connected to the connection pad of the display panel main body via the ACF. However, when the liquid crystal display device is a polycrystalline silicon TFT type or the like, a simple flexible wiring (FPC) is used. There may be. The same applies to a flat display device other than the liquid crystal display device, for example, an organic EL type.
[0047]
The present invention is not limited to the flat display device, but can be applied to any terminal connection structure that connects terminals having a fine pitch using an anisotropic conductive layer. The anisotropic conductive layer is not limited to the one supplied in the form of a film.
[0048]
【The invention's effect】
It is possible to improve the utilization rate of the conductive particles, thereby preventing an increase in the resistivity of the terminal connection and improving the reliability of the terminal connection.
[Brief description of the drawings]
FIG. 1 is a schematic partial cross-sectional perspective view showing a surface shape of an output terminal of a TCP according to an embodiment.
FIG. 2 is a schematic cross-sectional perspective view showing a terminal connection structure at a peripheral portion of the flat display device according to the example, which is cut in a terminal longitudinal direction.
FIG. 3 is a schematic horizontal cross-sectional view showing distribution of conductive particles in a terminal connection structure of the flat panel display according to the example.
FIG. 4 is a schematic external perspective view showing the entire flat display device without a frame or the like.
FIG. 5 is a schematic partial cross-sectional perspective view corresponding to FIG. 1, showing a surface shape of an output terminal of a TCP according to a first modification.
FIG. 6 is a schematic partial cross-sectional perspective view corresponding to FIG. 1 and illustrating a surface shape of an output-side terminal of a flexible substrate according to a second modification.
FIG. 7 is a laminated sectional perspective view corresponding to FIG. 2, schematically showing a terminal connection structure according to Modification 3.
FIG. 8 is a laminated sectional perspective view corresponding to FIG. 2, schematically showing a terminal connection structure according to Modification Example 4.
[Explanation of symbols]
1 TCP output terminal 11 Groove on output terminal 1 15 Terminal area 2 ACF (anisotropic conductive film)
3 Conductive Particles 41 Peripheral Edge 5a of Display Panel Main Body Output End 55 of TCP Base Film of TCP

Claims (8)

A flexible insulating substrate;
An output-side wiring group extending toward one edge of the insulating substrate;
In a flexible substrate extending from an end of the output-side wiring group and including an output-side terminal group connected to an external terminal group via an anisotropic conductive film,
On the surface of each terminal of the output side terminal group, a groove for regulating movement of conductive particles during melt flow of the anisotropic conductive film is formed from the center or near the center line of the terminal. A flexible substrate, which is arranged to extend to an edge. Terminal connection structure for electrically and mechanically connecting a first terminal on a flexible first substrate and a second terminal on a second substrate via an anisotropic conductive film At
A terminal connection structure, wherein grooves are arranged on a terminal surface of the first or second terminal, and a depth of the groove is smaller than a diameter of the anisotropic conductive film. The terminal connection structure according to claim 2, wherein the groove extends from a center portion or a vicinity of a center line of the terminal to an edge of the terminal. The terminal connection structure according to claim 2, wherein a width of the groove is larger than a diameter of the conductive particle. The terminal connection structure according to claim 3, wherein the groove extends obliquely with respect to an edge of the terminal. The terminal connection structure according to claim 3, wherein the groove is curved or meandering. Terminal connection structure for electrically and mechanically connecting a first terminal on a flexible first substrate and a second terminal on a second substrate via an anisotropic conductive film At
4. The terminal connection structure according to claim 2, wherein the surface of the conductive particles in the anisotropic conductive layer is covered with small projections. 5. Terminal connection structure for electrically and mechanically connecting a first terminal on a flexible first substrate and a second terminal on a second substrate via an anisotropic conductive film At
A terminal connection structure, wherein the surface of the conductive particles in the anisotropic conductive layer is covered with small projections.

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