JP2005019274A - Manufacturing method of anisotropic conductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an anisotropic conductive film in which terminal connection excellent in connection reliability and insulation becomes possible at a low cost by arranging regularly conductive particles only in a specified region. <P>SOLUTION: This manufacturing method of an anisotropic conductive film has a process in which, using a roll 11 of which the protruded part is worked so as to become a desired arrangement pattern, the conductive particles are captured on the surface of the roll 11 when passing through paste 13 dispersed with the conductive particles, then only the conductive particles captured on the protruded part are regularly transferred on the substrate 14 using liquid as a binder. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides an anisotropic conductive film that can be used for electrical connection between minute circuits, for example, a connection between a liquid crystal display (LCD) and a flexible circuit board, a micro junction between a semiconductor IC and an IC mounting board, and the like. It is about the method.
[0002]
[Prior art]
With the recent miniaturization 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.
[0003]
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.
[0004]
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.
[0005]
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.
[0006]
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 pressure-bonded, 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.
[0007]
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 connections between intended terminals, which increases production costs. It was connected to.
[0008]
Therefore, a method of regularly arranging conductive particles has been studied. For example, NEDO's venture company-supported regional consortium R & D (SME creation foundation type) Fine pitch compatible anisotropic conductive material R & D 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. .
[0009]
[Patent Document 1]
JP 59-120436 A [Patent Document 2]
Japanese Laid-Open Patent Publication No. 60-84718 [Patent Document 3]
Japanese Laid-Open Patent Publication No. 60-191228 [Patent Document 4]
Japanese Laid-Open Patent Publication No. 61-55809 [Patent Document 5]
Japanese Laid-Open Patent Publication No. 61-274394 [Patent Document 6]
Japanese Laid-Open Patent Publication No. 61-287974 [Patent Document 7]
Japanese Laid-Open Patent Publication No. Sho 62-244142 [Patent Document 8]
Japanese Laid-Open Patent Publication No. 63-153534 [Patent Document 9]
Japanese Laid-Open Patent Publication No. 63-305591 [Patent Document 10]
Japanese Laid-Open Patent Publication No. 64-47084 [Patent Document 11]
Japanese Laid-Open Patent Publication No. 64-81878 [Patent Document 12]
Japanese Laid-Open Patent Publication No. 1-446549 [Patent Document 13]
JP-A-1-251787 [Patent Document 14]
Japanese Patent Laid-Open No. 61-78069 [0010]
[Problems to be solved by the invention]
INDUSTRIAL APPLICABILITY The present invention can inexpensively manufacture an anisotropic conductive film that enables terminal connection with excellent connection reliability and insulation even when the connection is between minute circuits, the connection between minute portions and minute circuits, or the like. It aims to provide a method.
[0011]
[Means for Solving the Problems]
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, wherein the conductive particles are applied to the convex portions of a roll obtained by processing the convex portions so as to have a desired arrangement pattern. A method for producing an anisotropic conductive film comprising a step of transferring conductive particles onto a substrate after capturing.
(2) The method for producing an anisotropic conductive film according to (1), wherein the conductive particles are in a paste form dispersed in a liquid.
(3) The manufacturing method of the anisotropic conductive film of (1)-(2) which has an adhesion layer in the said base material.
(4) The method for producing an anisotropic conductive film according to (1) to (3), comprising a step of coating the conductive particles with an insulating adhesive after transfer.
It is.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
An example of the manufacturing method of the present invention will be described with reference to FIGS. In order to regularly arrange the conductive particles 17 on the base material 14, the roll 11 having a convex portion processed so as to have a desired arrangement pattern is used, and the surface of the roll is placed in the paste 13 in which the conductive particles are dispersed. After the conductive particles are captured on the roll surface by dipping, only the conductive particles captured on the convex portions are transferred onto the substrate using the liquid 19 as a binder. In order to fix the conductive particles transferred to the base material, a step of coating the conductive particles with an insulating adhesive after the transfer may be included. The transfer method using a roll is simple and highly productive. In addition, since expensive conductive particles are regularly arranged, lateral conduction due to the connection between the conductive particles can be prevented, and the efficiency is reduced with fewer conductive particles. Since the terminals can be electrically connected, it can be manufactured at a low cost from the viewpoint of materials.
[0013]
The usage example of the anisotropic conductive film manufactured by the said system is shown in FIG. After the conductive particles 17 are coated with the insulating adhesive 20, for example, temporary bonding is performed on the LCD panel 4 by heating and pressing, the base material 14 is peeled off, the TCP 5 is placed, and temporary fixing is performed by pressing. Further, the main pressure bonding is performed by heating and pressurization. However, 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 conducted efficiently.
[0014]
Although there is no restriction | limiting in particular as the said base material 14, The base material which has an adhesion layer 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 process after the conductive particles 17 are transferred.
[0015]
If the insulating adhesive used later has adhesiveness, the adhesive material can be used as an adhesive material by thinly applying the insulating adhesive. In addition, when the insulating adhesive 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.
[0016]
The protrusion 18 processed into a roll can capture one or more conductive particles, and there is a particular limitation as long as the captured conductive particles have an interval that does not contact the conductive particles captured by the adjacent convex portions. And can be processed into a convex shape such as a circle, a quadrangle, and an irregular shape. The pattern of the convex portions may be adapted to the circuit design, or may be a pattern in which the convex portions are arranged at a constant interval such as a staggered lattice so as to be applicable to any circuit. The number of conductive particles that can be captured by the convex portions is preferably 2 or more. If it is a convex part which can capture two or more, it can have conductivity if one or more conductive particles can be captured even if all of the captured conductive particles are not transferred onto the substrate. When the roll surface is immersed in the paste 13 in which the conductive particles are dispersed, the conductive particles adhere to portions other than the convex portions, but the convex portions are controlled by controlling the force with which the roll contacts the substrate. It is possible to transfer only the conductive particles of the convex portion to the base material without bringing the other parts into contact with the base material.
[0017]
In order to regularly capture the conductive particles on the convex portions of the roll processed into a desired arrangement pattern, the liquid 19 in which the conductive particles are dispersed in advance is a diluted or concentrated insulating adhesive used later or conductive particles. If it is a material which does not melt | dissolve, there will be no restriction | limiting in particular, Water and various organic solvents can be used.
[0018]
The conductive particles 17 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 apply metal coating to
[0019]
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.
[0020]
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.
[0021]
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.
[0022]
The particle size 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.
[0023]
The particle diameter of the conductive particles is not particularly limited, but it is preferably 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%.
[0024]
The insulating adhesive 20 for fixing the conductive particles transferred onto the substrate is not particularly limited. For example, a thermoplastic material used for an adhesive sheet or the like, a material that exhibits curability by heat or light, or the like. Is mentioned. 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.
[0025]
There is no restriction | limiting in particular in the method of apply | coating the insulating adhesive agent for fixing electroconductive particle, Systems, 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 terminals other than the conductive particles at the time of the main pressure bonding of 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.
[0026]
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.
[0027]
【The invention's effect】
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 in the case of connection between minute circuits, connection between minute parts and minute circuits, 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.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a conventional anisotropic conductive film and a connection method thereof. FIG. 2 is a view showing a manufacturing method according to an embodiment of the present invention. FIG. 4 is a cross-sectional view showing an example of the anisotropic conductive film of the present invention and its connection method.
DESCRIPTION OF SYMBOLS 1 Base material 2 Conductive particle 3 Insulating adhesive 4 LCD panel 5 TCP
6 Terminal 11 Roll 12 Roll 13 after supplementing conductive particles Paste 14 Substrate 15 Substrate 16 after transfer of conductive particles Back roll 17 Conductive particles 18 Roll protrusion 19 Liquid 20 Insulating adhesive

Claims (4)

A method for producing an anisotropic conductive film in which conductive particles are regularly arranged only in a specific region, and the conductive particles are captured by the convex portions of a roll in which the convex portions are processed so as to have a desired arrangement pattern. Then, the manufacturing method of the anisotropic conductive film characterized by having the process of transferring electroconductive particle on a base material. The method for producing an anisotropic conductive film according to claim 1, wherein the conductive particles are in a paste form dispersed in a liquid. The manufacturing method of the anisotropic conductive film of Claim 1 or 2 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 3, further comprising a step of coating the conductive particles with an insulating adhesive after transfer.

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