JP2005209454A - Manufacturing method of anisotropic conductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an anisotropic conductive film which enables a terminal connection with excellent connection reliability and insulation property even in connecting minute circuits to each other, or connecting a minute part to the minute circuit. <P>SOLUTION: On the manufacturing method of the anisotropic conductive film, particles 13 are made to be captured in holes of a porous plate 12, on which holes with a diameter smaller than that of conductive particles are distributed with a distance same as the distance of an intended pattern to be distributed, and afterwards, the conductive particles are transferred on a base material. If necessary, a process of shaking off particles other than those captured in the holes of the porous plate is included. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention provides an anisotropic conductive film that can be used for electrical connection between fine circuits, for example, connection between a liquid crystal display (LCD) and a flexible circuit board, micro-bonding between a semiconductor IC and an IC mounting board, and the like. It is about the method.

  With the recent downsizing and thinning of electronic devices, the need for connections between minute circuits and connections between minute parts and minute circuits has increased dramatically. With progress, anisotropic conductive adhesives and films are used as new materials (see, for example, Patent Documents 1 to 13). In particular, it has recently been applied to the connection between an LCD panel that cannot be handled by soldering and a TCP (tape carrier package) equipped with a driver IC, and has become an indispensable connection material for LCDs.

  In this method, as shown in FIG. 1, an anisotropic conductive film is sandwiched between members to be connected and heated and pressed to maintain electrical insulation between adjacent terminals in the plane direction, and between the upper and lower terminals. Then, it is electrically connected. The anisotropic conductive film has been widely used for such applications because of the lack of heat resistance of the adherend and conventional connections such as soldering that cause electrical shorts between adjacent terminals in fine circuits. This is because the method is not applicable.

  As disclosed in Patent Document 14 and the like, generally, an anisotropic conductive film is a film in which conductive particles are uniformly dispersed in an insulating adhesive, and alignment is performed between an IC electrode and a substrate electrode to perform anisotropic conduction. By crimping the film, the conductive particles in the anisotropic conductive film are brought into pressure contact so that only the overlapping electrodes are electrically connected.

  This anisotropic conductive film uses plastic particles, etc. whose surfaces are plated with nickel, gold, etc. as the conductive particles, and the insulating adhesive is classified into a thermoplastic type and a thermosetting type. However, recently, an epoxy resin-based thermosetting type having excellent reliability is being used more widely than a thermoplastic type.

In recent years, the circuit connection pitch has been miniaturized, and the problem of lateral conduction has occurred in the conventional anisotropic conductive film. As shown in FIG. 1, when the conductive particles 2 are dispersed in the insulating adhesive 3, when the anisotropic conductive film is crimped, the conductive particles located in the middle of the insulating adhesive are outside the terminal. As a result, conductive particles exist at a high density between adjacent terminals, resulting in insufficient insulation between terminals, leakage, short circuit, etc. Occurs.
In order to prevent lateral conduction, it is conceivable to reduce the mixing rate of the conductive particles in the anisotropic conductive film, but if the mixing rate of the conductive particles is reduced, the connection area between the conductive particles and the terminal decreases, There was a problem that connection resistance became high.

In addition to product quality problems, conductive particles are generally very expensive at several thousand yen per gram, and many of them are not used for the connection between intended terminals, which increases production costs. It was connected to.

For this reason, a method of regularly arranging conductive particles has been studied. For example, NEDO's venture company-supported regional consortium R & D (SME creation base type) R & D on anisotropic conductive materials for fine pitches, crimping There has been proposed a method in which a hole is formed in a resin film that does not melt at a temperature, conductive particles are embedded therein, and then sandwiched with a resin that melts the top and bottom. In this method, two techniques of photolithography and laser are used for the lattice holes for regularly arranging the conductive particles. However, such a method requires the production of a special metal mask for forming regular holes and a laser irradiation device, and a fine device can be obtained, but the manufacturing device is expensive. .

JP 59-120436 A JP-A-60-84718 JP-A-60-191228 JP-A 61-55809 JP-A 61-274394 JP-A 61-287974 JP-A 62-244142 JP-A-63-153534 JP-A 63-305591 JP-A 64-47084 JP-A-64-81878 JP-A-1-46549 JP-A-1-251787 JP 61-78069 A

  INDUSTRIAL APPLICABILITY The present invention can inexpensively produce an anisotropic conductive film that enables terminal connection with excellent connection reliability and insulation even when connecting fine circuits, connecting minute parts and fine circuits, and the like. It aims to provide a method.

That is, the present invention
(1) A method for producing an anisotropic conductive film in which conductive particles are regularly arranged only in a specific region, and a perforated plate having pores smaller than the particle diameter of the conductive particles at the same interval as a desired arrangement pattern A method for producing an anisotropic conductive film, comprising the step of capturing particles in the pores and then transferring the conductive particles onto a substrate.
(2) The method for producing an anisotropic conductive film according to (1), further including a step of dropping particles other than those captured by the holes of the porous plate while the conductive particles are captured.
(3) The method for producing an anisotropic conductive film according to (1) or (2), wherein the conductive particles are captured by the porous plate by setting the opposite side where the conductive particles are present across the porous plate to a reduced pressure state.
(4) The manufacturing method of the anisotropic conductive film of (1)-(3) which has an adhesion layer in the said base material.
(5) The method for producing an anisotropic conductive film according to (1) to (4), comprising a step of coating the conductive particles with an insulating adhesive after transfer.
It is.

  According to the manufacturing method of the present invention, an anisotropic conductive film in which conductive particles are regularly arranged can be obtained. Therefore, even if the connection between fine circuits, the connection between a minute part and a minute circuit, etc. Terminal connection with excellent connection reliability and insulation is possible, and since expensive conductive particles are regularly arranged, lateral conduction due to the connection between the conductive particles can be prevented, and terminals can be efficiently made with fewer conductive particles. Since it can conduct between, it can manufacture at low cost.

In the present invention, particles are trapped in holes of a perforated plate having holes smaller than the particle diameter of the conductive particles at the same interval as a desired arrangement pattern in which the conductive particles are to be arranged, and then the conductive particles are transferred onto the substrate. This is a method for producing an anisotropic conductive film, and if necessary, includes a step of dropping particles other than those trapped in the holes of the perforated plate.
An example of the production method of the present invention will be described with reference to FIGS. A porous plate 12 having holes 16 smaller than the particle diameter of the conductive particles is attached to the container 11 so as to have a desired arrangement pattern, and the conductive particles are put into the container lower tank 11a. The porous plate 12 captures the conductive particles 13 by putting the container upper tank 11b on the opposite side where the conductive particles 13 are present across the porous plate 12 into a reduced pressure state. When capturing the conductive particles 13, a step of dropping the conductive particles attached to the porous plate 12 or the captured conductive particles by aggregation or the like may be provided. The captured conductive particles 13 are transferred onto the base material having the adhesive layer 14. In order to fix the conductive particles 13 transferred to the base material 15, a step of coating the conductive particles 13 with an insulating adhesive after transfer may be included. This method, which can capture only the amount of expensive conductive particles required by a simple method and arrange them regularly, can prevent lateral conduction due to the connection between the conductive particles, and can efficiently conduct between terminals with few conductive particles. Therefore, it is a highly productive method that can be manufactured at a low cost from the viewpoint of materials.

  The pore diameter of the porous plate 12 having the pores 16 smaller than the particle diameter of the conductive particles 13 is not particularly limited as long as it is smaller than the particle diameter of the conductive particles 13, but when the pore diameter is too close to the particle diameter, the conductive particles 13 are captured. May be caught between the holes 16 and may not be transferred to the base material 15. In addition, if it is too small, the conductive particles 13 cannot be captured efficiently, so that the pore diameter is preferably 0.3D to 0.9D with respect to the diameter D of the conductive particles. The shape of the hole is not particularly limited as long as one particle can be captured per hole and the conductive particles to be captured do not contact each other, and can be processed into a circular shape, a polygonal shape, an indefinite shape, or the like. The hole pattern may be adapted to the circuit design, or may be a pattern arranged at regular intervals such as a staggered lattice so as to be applicable to any circuit. The material of the perforated plate is not particularly limited as long as it has a strength capable of capturing conductive particles. Metal materials such as iron, stainless steel, copper and aluminum, organic materials such as polyethylene, polystyrene and polypropylene, and composite materials combining these materials Can be used.

As a method for capturing the conductive particles 13, as described above, a method of capturing the conductive particles by suction with the container upper tank 11b on the opposite side where the conductive particles 13 exist across the porous plate 12 being in a reduced pressure state, However, there is no particular limitation as long as the method can selectively capture the conductive particles 13 in the holes of the porous plate 12. In order to capture the conductive particles 13 efficiently, the container 11 may be vibrated, or the lower part of the container may be made of a porous material and air may be blown from the lower part to make the conductive particles flow. At that time, it is preferable to use dehumidified dry air in order to prevent adhesion between the conductive particles.

When capturing the conductive particles 13, the step of dropping the conductive particles adhering to the conductive particles captured by the perforated plate 12 or agglomeration is to drop only the particles other than the captured particles without dropping the captured conductive particles. There is no particular limitation as long as it is a method to be used, and an air blower or a scraper can be used. At that time, for example, if the container upper tank 11b on the opposite side where the conductive particles 13 exist across the perforated plate 12 is in a reduced pressure state, the captured particles are applied. Is preferable because it can be prevented from falling off.

  The method for transferring the captured conductive particles 13 onto the substrate having the adhesive layer 14 is not particularly limited as long as the captured regularly arranged conductive particles can be transferred as they are. Transfer can be performed by bringing the captured conductive particles 13 into contact with the adhesive layer 14 or the like. Transfer to the base material 15 can be facilitated by releasing the force to capture the conductive particles, but if the conductive particles are difficult to come off the hole, air or pins from the opposite side where the conductive particles are captured The transfer can be facilitated by applying a force to the conductive particles.

Although there is no restriction | limiting in particular as the said base material 15, The base material which has the adhesion layer 14 can be used. The base material having the adhesive layer can be produced, for example, by thinly applying an adhesive material on the base material. If there is adhesiveness, it is possible to prevent the conductive particles from moving due to vibration or external force in the next step after the conductive particles 13 are transferred.

  As the above-mentioned adhesive material, if the insulating adhesive 20 used later has adhesiveness, it can be used as an adhesive material by thinly applying the insulating adhesive. Further, when the insulating adhesive 20 is diluted with a solvent or the like, it can be used as a material having adhesiveness as long as it exhibits adhesiveness before being completely dried. The material having adhesiveness may be different from the insulating adhesive. Furthermore, if the base material itself has adhesiveness, it is not necessary to apply an adhesive material separately.

  The conductive particles 13 used in the present invention are not particularly limited as long as they have conductivity, and various metals and metals such as nickel, iron, copper, aluminum, tin, lead, chromium, cobalt, silver, and gold Alloys, metal oxides, carbon, graphite, glass and ceramics, polymer particles with metal coated surfaces, etc. can be applied, but considering the reliability of connection and application to fine circuit connection, polymer core material It is desirable to have a metal coating on the surface.

  Here, the polymer core material is not particularly limited in composition and the like. For example, one of the polymers such as epoxy resin, urethane resin, melamine resin, phenol resin, acrylic resin, polyester resin, styrene resin, styrene butadiene copolymer is used. A single species or a combination of two or more species may be used.

  Although there is no particular limitation on the metal coating applied to the surface of the polymer core material, a nickel and gold coating that is usually applied is desirable in consideration of the stability of conduction.

  Although there is no restriction | limiting in particular in the thickness of a film, Since there exists a problem of becoming easy to produce aggregation when too thick, about 0.01-0.2 micrometer is desirable. In addition, in the method of forming the coating, it is needless to say that the coating is uniformly formed in consideration of the adhesion and conductivity between the coating and the polymer core material. desirable.

  The particle diameter and blending amount of the conductive particles can be selected appropriately depending on the pitch and pattern of the circuit to be connected, the thickness and material of the circuit terminal, and the like.

  The particle diameter of the conductive particles is not particularly limited, but is desirably 2 to 15 μm on average. If it is smaller than 2 μm, it is possible to mix a large number of conductive particles in order to obtain high connection reliability with fine circuit connection, but uniformly coat the polymer core material without agglomeration. Is extremely difficult with the current technology, and it is actually difficult to stably connect fine circuits. On the other hand, if it is larger than 15 μm, it is possible to uniformly coat the metal without agglomeration. However, when a fine circuit is connected, the electrical insulation between the terminals cannot be maintained. Can not be blended too much, and there is a limit to improving connection reliability. For example, in the connection between the LCD panel and TCP or FPC, particularly in the connection of a very fine pitch circuit having a pitch of about 50 μm, an average particle size of about 3 to 5 μm is desirable. Needless to say, it is preferable that the particle size distribution is sharp, and it is more preferable if the average particle size is within ± 10%.

The insulating adhesive 20 for fixing the conductive particles 13 transferred onto the substrate is not particularly limited. For example, a thermoplastic material used for an adhesive sheet or the like, or a material that is curable by heat or light. Etc. Especially, since it is excellent in heat resistance and moisture resistance by making it harden | cure after a connection, a curable material is preferable. In particular, a material used as an epoxy-based adhesive is preferably used from the viewpoint of curing in a short time and excellent adhesiveness. In the case of using a curable resin, it is necessary to melt and flow when used as an anisotropic conductive film. Therefore, the state in which the conductive particles are fixed is preferably a semi-cured state.

The method for applying the insulating adhesive 20 for immobilizing the conductive particles 13 is not particularly limited, and methods such as coating, spraying, and casting can be used.
The thickness of the insulating adhesive is not particularly limited as long as it corresponds to an amount sufficient to satisfy the space between the terminals other than the conductive particles during the main pressure bonding of the heat and pressure, and the thickness is necessarily larger than the diameter of the conductive particles. It becomes. For example, in the connection between the LCD panel and TCP or FPC, a thickness of 10 to 20 μm is preferable.

  After the conductive particles are fixed with the insulating adhesive, the locations where the conductive particles exist are inevitably distributed to the substrate side according to this method. Conductive particles located in the middle of the insulating adhesive are likely to flow out of the terminal during the main pressure bonding of heating and pressurization, but since they are biased toward the substrate side, the flow out of the terminal is reduced and efficient. Can be conducted between the terminals.

FIG. 4 shows an example of using the anisotropic conductive film manufactured by the above method. After the conductive particles 13 are coated with the insulating adhesive 20, for example, the pressure bonding is performed on the LCD panel 4 by heat and pressure, the base material 15 is peeled off, the TCP 5 is placed, and temporarily fixed by pressure. Further, the main pressure bonding is performed by heat and pressure. Since the conductive particles are present in one of the insulating adhesives, it is difficult for the conductive particles to flow out of the terminals, and the terminals can be efficiently connected to each other.

Sectional drawing which shows an example of the conventional anisotropic conductive film and its connection method The figure which shows the manufacturing method which is one Example of this invention The figure which shows a mode that electroconductive particle is transcribe | transferred to the adhesion layer of a base material. Sectional drawing which shows an example of the anisotropic conductive film of this invention, and its connection method

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base material 2 Conductive particle 3 Insulating adhesive 4 LCD panel 5 TCP
6 Terminal 11 Container 11a Container lower tank 11b Container upper tank 12 Perforated plate 13 Conductive particle 14 Adhesive layer 15 Base material 16 Hole 17 Conductive particle 20 Insulating adhesive

Claims (5)

A method for producing an anisotropic conductive film in which conductive particles are regularly arranged only in a specific region, wherein the pores of the perforated plate have pores smaller than the particle diameter of the conductive particles at the same interval as a desired arrangement pattern. A method for producing an anisotropic conductive film comprising a step of transferring conductive particles onto a substrate after capturing the particles. The method for producing an anisotropic conductive film according to claim 1, further comprising a step of dropping particles other than those captured in the holes of the perforated plate in a state where the conductive particles are captured. The method for producing an anisotropic conductive film according to claim 1 or 2, wherein the conductive particles are captured by the porous plate by setting the opposite side where the conductive particles are present across the porous plate to a reduced pressure state. The manufacturing method of the anisotropic conductive film as described in any one of Claims 1-3 which has an adhesion layer in the said base material. The method for producing an anisotropic conductive film according to any one of claims 1 to 4, further comprising a step of coating the conductive particles with an insulating adhesive after the transfer.

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