JP2002075580A - Manufacturing method for anisotropic conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for an anisotropic conductive film allowing electrode connection with excellent connection reliability and insulating characteristics even when a circuit connection pitch is very fine. SOLUTION: This manufacturing method for the anisotropic conductive film having conductive particles arranged only in a specific area includes a process for forming the area, which is used for concentrating the conductive particles, on a base material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing an anisotropic conductive film used for connecting electrodes of various electronic components.

[0002]

2. Description of the Related Art A thin film having conductivity only in a thickness direction and electrically insulated in a direction crossing the thickness direction is an anisotropic conductive film (ACF; Anisotropi).
c Conductive film), which is used for interconnecting electric circuit elements. For example, a method of mounting a driver IC on a liquid crystal display panel is a tape carrier package (TCP; Tape carrier P).
TBA for connecting the package) with an anisotropic conductive film
(Tape Automated Bonding) method has been put to practical use. Also, in COG (Chip On Glass) for connecting an IC directly to a glass substrate, an anisotropic conductive film is used for the connection.

An anisotropic conductive film is made of ITO (Indum-Tin-) which is used as a transparent electrode of a liquid crystal display device.
Oxide) is suitable for connection of electrodes that cannot be soldered. In addition, the soldering or the method using a conductive adhesive must form the connection member only in the conductive circuit portion. However, since the anisotropic conductive film can obtain conductivity only in the necessary portions, the density is high and the definition is high. It is suitable for fine circuit connection that is becoming more and more advanced.

As disclosed in Japanese Patent Application Laid-Open No. 61-78069 and the like, an anisotropic conductive film is a film in which conductive particles are uniformly dispersed in an insulating adhesive, and is positioned between an IC electrode and a substrate electrode. Then, the conductive particles in the anisotropic conductive film are pressed against each other by pressing the anisotropic conductive film, so that only the overlapping electrodes are electrically connected.

In such an anisotropic conductive film, metal fine particles or resin fine particles whose surface is covered with metal are used as conductive particles, and a thermosetting epoxy resin or the like is used as an adhesive. .

[0006] In recent years, the circuit connection pitch has been miniaturized, and a problem of lateral conduction has occurred in the conventional anisotropic conductive film.
When the anisotropic conductive film is pressed, the conductive particles flow out of the electrodes, and as a result, the conductive particles exist at a high density between adjacent electrodes, or the insulation between the electrodes becomes insufficient, Problems such as leaks and short-circuits occur in maintaining insulation. FIG. 2 shows this state.

As shown in FIG. 2, when the anisotropic conductive film 4 is pressed, the conductive particles 3 flow out of the electrode 2.
High density exists between adjacent electrodes. as a result,
Leaks and shorts occur, particularly when the connection pitch becomes finer.

In order to prevent lateral conduction, it is conceivable to reduce the mixing ratio of conductive particles in the anisotropic conductive film. However, when the mixing ratio of conductive particles is reduced, the connection area between the conductive particles and the electrodes is reduced. As a result, the connection resistance increases.

[0009]

SUMMARY OF THE INVENTION In view of the above, the present invention provides a method of manufacturing an anisotropic conductive film which enables electrode connection with excellent connection reliability and insulation even if the circuit connection pitch is fine. The purpose is to provide.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a method for producing an anisotropic conductive film in which conductive particles are arranged only in a specific region, and a method for arranging conductive particles in a concentrated manner on a substrate. It is a method of manufacturing an anisotropic conductive film including a step of forming a region. Hereinafter, the present invention will be described in detail.

The inventor of the present invention has found that the cause of insufficient insulation between electrodes or leakage or short-circuit is that conductive particles flow out of the electrodes due to pressure bonding and exist at high density between adjacent electrodes. Therefore, as shown in FIG. 1, if the conductive particles 3 do not exist at a high density between the adjacent electrodes, the conductive particles 3 flow out of the electrodes 2 by press bonding, and the insulation between the electrodes is insufficient. And no more leaks or shorts. The present invention has been completed after intensive studies based on this finding.

[0012] The production method of the present invention is characterized in that it has a step of forming a region for arranging conductive particles on the substrate in a concentrated manner. Examples of the substrate include a substrate having an adhesive layer, an electrode substrate, and the like. The substrate having the pressure-sensitive adhesive layer can be produced, for example, by applying a thin material having tackiness on the substrate. When the conductive particles are adhered, it is possible to prevent the conductive particles from moving due to vibration or an external force in the next step after the conductive particles are sprayed.

If the adhesive used later has adhesiveness, the adhesive material can be used as a sticky material by applying the adhesive thinly. When the agent is diluted with a solvent or the like, if it shows tackiness before it is completely dried, it can be similarly used as a tacky material. The adhesive material may be different from the adhesive to be used later, and if the substrate itself has adhesiveness, it is not necessary to separately apply an adhesive material.

As a method of forming a region for arranging conductive particles on the substrate in a concentrated manner, for example, a method using a mask having an opening, an electrostatic attraction to charged conductive particles, Alternatively, a method of applying a repulsive force may be used. As a method using a mask having the above-mentioned opening,
For example, as shown in FIG. 3, the base material 7 is covered with a mask 5 in which only the region corresponding to the electrode is open, so that the conductive particles 3 can be sprayed only in the region corresponding to the electrode. The mask may be in close contact with the substrate or may be provided separately from the substrate. The mask is not particularly limited, and examples thereof include a mask in which an opening is formed by etching a metal thin film with photolithography or the like, and a mask in which a hole is formed in a resin film with a laser or the like. Further, a screen mesh or the like may be used as the mask.

As a method of applying electrostatic attraction or repulsion to the charged conductive particles, for example, as shown in FIG. 4, an electrode substrate is used as a base material, and a voltage is applied to the electrode 2. Apply. When the charged conductive particles 3 are dropped from above, for example, when the charging of the conductive particles 3 is negative, a positive voltage is applied to the electrode 2 to cause an attractive force to act, thereby causing the conductive particles 3 It can be arranged on the electrode in a concentrated manner. The conductive particles are charged by repeated collision with the inner wall of the pipe during spraying. For example, depending on the gas to be used, gold-plated conductive particles collide with the SUS pipe and become negatively charged. The voltage applied to the electrode is preferably about 500 V to 5 kV, more preferably 1.5 to 2.5 kV.

As a method of applying electrostatic attraction or repulsion to charged conductive particles, for example, a mask having an opening is formed of a conductive material, and the mask itself is charged with the same charge as the conductive particles. By applying a polarity voltage, a repulsive force acts on the conductive particles, and the conductive particles can be concentrated and arranged in a region outside the mask.

In order to manufacture an anisotropic conductive film, a region for arranging conductive particles in a concentrated manner is formed on a substrate, and then the conductive particles are sprayed on the substrate. By dispersing the conductive particles on the substrate on which the region for arranging the conductive particles is formed, the conductive particles can be disposed only in a specific region on the substrate.

As a method for dispersing the conductive particles, for example, spraying or vibration can be used to efficiently disperse the conductive particles. When a mask having an opening is installed on a substrate having an adhesive layer, in a state where the mask is installed on the substrate, the conductive particles are brought into contact with the adhesive layer,
The adhesive may be adhered only to the opening by adhesive force, or after the conductive particles are scattered, the conductive particles may be pressed into the adhesive layer of the opening by a press or the like and fixed. Thereafter, by removing the mask, a state in which the conductive particles are densely packed in the specific region can be obtained.

In the production method of the present invention, after the conductive particles are sprayed on the substrate, the conductive particles may be further transferred onto a different substrate. For example, after the conductive particles are sprayed on an electrode substrate or the like, the conductive particles may be transferred to a substrate having an adhesive layer.

After the conductive particles are sprayed, an adhesive is applied on the substrate to which the conductive particles have adhered. An anisotropic conductive film in which conductive particles are arranged only in a specific region can be obtained by forming an adhesive layer on a substrate to which conductive particles are adhered while controlling the thickness. In the obtained anisotropic conductive film, the surface of the conductive particles may be exposed on the anisotropic conductive film.

The obtained anisotropic conductive film is pressure-bonded onto the electrode, the base material is peeled off, and then the electrode to be connected is heated and pressure-bonded to the opposite side, so that only the connection portion is formed as shown in FIG. Conductive particles can be disposed on the surface of the substrate. In some cases, the conductive particles may flow out of the electrode during thermocompression bonding. In such a case, by setting the initial arrangement state of the conductive particles as narrow as possible, the outflow of the conductive particles to the outside of the electrode can be reduced.

When an electrode substrate is used as the substrate,
The adhesive layer may be formed directly on the electrode substrate, and then the conductive particles may be sprayed. Further, an adhesive layer may be formed thereon and the conductive particles may be peeled off from the electrode substrate.

The region where the conductive particles are arranged does not necessarily have to coincide with the electrode position. For example, when the distance between the electrodes is large, even if the conductive particles exist between the electrodes, the conductive particles existing between the electrodes may be used. If the particles and the conductive particles existing on the electrode do not come into contact with each other, no leak or the like occurs, so that there is no problem.

The conductive particles used in the present invention are not particularly limited, and examples thereof include metal fine particles and synthetic resin fine particles coated with metal. The adhesive used in the present invention is not particularly limited, and examples thereof include a thermoplastic material used for an adhesive sheet or the like, and a material that is curable by heat or light. Above all, a curable material is preferable because of its excellent heat resistance and moisture resistance after connection. Particularly, a material used as an epoxy-based adhesive is preferably used because it cures in a short time and has excellent adhesiveness.

According to the production method of the present invention, it is possible to obtain an anisotropic conductive film in which conductive particles are concentrated on the electrodes, so that there is no leak or the like between adjacent electrodes even in electrode connection at a fine pitch. Electrode connections can be made.

[0026]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

(Example 1) A having a thickness of 30 μm was used as a mask.
1 was prepared in which openings having a diameter of 30 μm were formed on one surface at intervals of 30 μm. An epoxy-based adhesive was thinly applied on a polypropylene film, and the above mask was attached. A suitable amount of micropearl AU, 5 μm (manufactured by Sekisui Chemical Co., Ltd.) as conductive particles was placed on the attached mask, and vibration was applied by a vibration device. Thereafter, when the mask was peeled off, the conductive particles were present only at positions corresponding to the mask openings. Subsequently, an epoxy adhesive was applied to form an adhesive film.

The obtained adhesive film was applied with a line width of 30 μm.
m, space 30 μm stripe-shaped ITO pattern / pressed on glass substrate so that conductive particles are positioned on ITO, peeled off polypropylene film, and sandwiched adhesive film with similar ITO pattern / glass on opposite side Place the substrate, align with the ITO pattern,
The upper and lower ITO patterns were connected to each other via an adhesive film by thermocompression bonding. Upper and lower connected ITO
As a result of measuring the connection resistance, it was 1Ω or less. On the other hand, the insulation resistance between adjacent ITOs was 1 × 10 ¹¹ Ω or more. Therefore, it was found that the obtained adhesive film functions as an anisotropic conductive film.

(Example 2) An ITO / glass substrate having a stripe pattern of 15 μm in space and 15 μm in space was prepared. A thin epoxy-based adhesive was applied on a polypropylene film, and adhered to the ITO / glass substrate. Then, while maintaining a state where a voltage of −2.5 kV was applied to the ITO pattern, a predetermined amount of micropearl AU, 5 μm (manufactured by Sekisui Chemical Co., Ltd.) was measured as conductive particles,
Using compressed air, it was sprayed on a polypropylene film via a SUS pipe. As a result, the conductive particles adhered almost in a line only to the position corresponding to the space of the ITO pattern on the polypropylene film. An epoxy adhesive was applied on the film to obtain an adhesive film.

The obtained adhesive film was prepared with a line width of 15 μm.
m, space 15 μm stripe-shaped ITO pattern / Glass substrate, pressure-bonded so that the positions of the conductive particles coincide with ITO, peel off the polypropylene film, and sandwich the adhesive film with the same ITO pattern / glass on the opposite side. The substrate was placed, the alignment was performed using an ITO pattern, and the upper and lower ITO patterns were connected to each other via an adhesive film by heat compression. Upper and lower connected I
As a result of measuring the TO connection resistance, it was 1 Ω or less. On the other hand, the insulation resistance between adjacent ITOs was 1 × 10 ¹¹ Ω or more. Therefore, it was found that it functions as an anisotropic conductive film.

(Example 3) A voltage of -2 kV was applied to the ITO pattern / glass substrate used in Example 2, and the state was maintained. Micropearl AU, 5 µm (manufactured by Sekisui Chemical Co., Ltd.) was used as conductive particles. Quantitative measurement, using compressed air,
It was sprayed directly onto the ITO pattern / glass substrate via a SUS pipe. As a result, the conductive particles were arranged almost in a line only in the space of the ITO pattern.

Next, a thin polypropylene film coated with an epoxy-based adhesive was uniformly and once adhered to the substrate on which the conductive particles were arranged, with the adhesive surface facing the conductive particles, and then peeled off. As a result, the conductive particles were transferred to the adhesive surface. An epoxy adhesive was applied to the surface of the transferred conductive particles to obtain an adhesive film.

The obtained adhesive film was coated with a line width of 15 μm.
m, space 15 μm stripe-shaped ITO pattern / pressed on glass substrate so that the position of conductive particles coincided with the position of ITO, peeled off the polypropylene film, and placed the same ITO pattern on the opposite side with an adhesive film in between / The glass substrate was placed, alignment was performed using an ITO pattern, and the upper and lower ITO patterns were connected to each other via an adhesive layer by heat compression. Upper and lower connected IT
As a result of measuring the O connection resistance, it was 1Ω or less. on the other hand,
The insulation resistance between adjacent ITOs was 1 × 10 ¹¹ Ω or more. Therefore, it was found that the adhesive film functions as an anisotropic conductive film.

(Comparative Example 1) An epoxy adhesive was diluted with a solvent (1,4-dioxane, methyl ethyl ketone), and micropearl A was prepared as conductive particles in the obtained solution.
U, 5 μm (manufactured by Sekisui Chemical Co., Ltd.) was added to a concentration of 15% by volume, and the mixture was stirred and dispersed in the solution. Thereafter, the solution was applied on a polypropylene film to obtain an adhesive film. The obtained adhesive film was subjected to a line width of 15
μm, space 15μm stripe-patterned ITO pattern / glass substrate is adhered, the polypropylene film is peeled off, and the same ITO pattern / glass substrate is placed on the opposite side with the adhesive layer in between, and aligned with the ITO pattern. Then, the upper and lower ITO patterns were connected to each other via an adhesive film by heat compression. When the resistance was measured by connecting to ITO in the same manner as in Example 2, the upper and lower and adjacent ITO had a resistance of 1Ω or less. Therefore, it was found that a leak occurred between adjacent electrodes.

[0035]

According to the present invention, since the conductive particles are concentrated in a specific region, the anisotropic conductive film can perform electrode connection without leakage between adjacent electrodes even in electrode connection at a fine pitch. Can be manufactured.

[Brief description of the drawings]

FIG. 1 is a view showing that conductive particles do not exist between adjacent electrodes.

FIG. 2 is a view showing that an anisotropic conductive film is pressed, conductive particles flow out of an electrode, and conductive particles exist between adjacent electrodes at a high density.

FIG. 3 is a diagram showing how to spread conductive particles using a mask having openings.

FIG. 4 is a diagram showing that a positive voltage is applied to an electrode to apply negative voltage to conductive particles that are negatively charged, thereby causing the conductive particles to be dispersed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Electrode 3 Conductive particle 4 Anisotropic conductive film 5 Mask 6 Adhesive layer 7 Base material 8 Adhesive layer

Claims (4)

[Claims] 1. A method of manufacturing an anisotropic conductive film in which conductive particles are arranged only in a specific region, comprising a step of forming a region for arranging conductive particles on a substrate in a concentrated manner. A method for producing an anisotropic conductive film, comprising: 2. The method for producing an anisotropic conductive film according to claim 1, further comprising the step of transferring conductive particles onto different substrates. 3. The anisotropic method according to claim 1, wherein the step of forming a region for arranging the conductive particles on the substrate in a concentrated manner is performed by using a mask having an opening. A method for manufacturing a conductive film. 4. The step of forming a region for arranging conductive particles in a concentrated manner on a substrate is performed by applying electrostatic attraction or repulsion to charged conductive particles. The method for producing an anisotropic conductive film according to claim 1 or 2, wherein: