JP2007115560A - Anisotropic conductive film and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an anisotropic conductive film capable of inter-terminal connection excellent in connection reliability and insulating properties compatible with connection of fine circuits at low cost, as well as an anisotropic conductive film with conductive particles regularly arrayed. <P>SOLUTION: The manufacturing method of the anisotropic conductive film comprises a process of discharging conductive particles on a face of base material or on a face of an insulating adhesive applied on a base material with the use of a nozzle having a fine opening and regularly arraying the conductive particles, and the anisotropic conductive film is obtained by the above method. <P>COPYRIGHT: (C)2007,JPO&INPIT

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), the conductive film located in the middle of the insulating adhesive when the anisotropic conductive film is pressure-bonded. Particles easily flow out of the terminal. As a result, conductive particles are present at high density between adjacent terminals, resulting in problems in maintaining insulation such as insufficient insulation between terminals and leakage or short-circuiting.
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.

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

  Therefore, a method of regularly arranging conductive particles is being studied. For example, NEDO's venture company-supported regional consortium R & D (SME creation base type) 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. .

  Further, as disclosed in Patent Document 15 and the like, a method of arranging conductive particles only in a specific region by applying an electrostatic attractive force or repulsive force to charged conductive particles has also been proposed. However, in this method, there is a problem in particle control because of the aggregation of particles due to liquid crosslinking due to moisture present in the gas phase.

  On the other hand, as disclosed in Patent Document 16, a method using a magnetic field has also been proposed, but this method uses cylindrical conductive particles having a double structure of a conductive magnetic film and an insulating shell as resin. This is different from the present invention which provides an anisotropic conductive film in which conductive particles are regularly arranged in a specific region.

JP 59-120436 A JP-A-60-84718 JP-A-60-191228 JP-A-61-55809 JP-A 61-274394 Japanese Patent Laid-Open No. 61-287974 JP 62-244142 A 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-A-61-78069 JP 2002-075580 A Patent No. 3048773

  The main object of the present invention is to provide a method capable of inexpensively manufacturing an anisotropic conductive film that enables connection between terminals excellent in connection reliability and insulation even when connecting fine circuits. And Another object of the present invention is to provide an anisotropic conductive film in which conductive particles are regularly arranged.

As a result of intensive studies in view of the problems of the prior art, the present inventor has found that the above object can be achieved by a production method having a specific process, and has completed the present invention.

  That is, this invention provides the invention which concerns on each following item.

1. The step of discharging conductive particles using a nozzle having a fine opening and arranging the conductive particles regularly on the surface of the base material or on the surface of the base material coated with the insulating adhesive. A method for producing an anisotropic conductive film, comprising:

2. Item 2. The method for producing an anisotropic conductive film according to Item 1, further comprising a step of applying an insulating adhesive onto the particle adhesion surface after discharging the conductive particles.

3. Item 3. The method for producing an anisotropic conductive film according to Item 1 or 2, wherein the conductive particles discharged from the nozzle having the fine opening are dispersed in an insulating adhesive.

4). Item 4. The method for producing an anisotropic conductive film according to Item 3, wherein the insulating adhesive in which the conductive particles are dispersed is discharged by an inkjet method.

5. Any one of Items 1 to 4, wherein the conductive particles are composed of particles or metal particles having a metal film containing nickel and gold on the surface of a central core made of a polymer core material, and the average particle diameter is 2 to 10 μm. A method for producing the anisotropic conductive film according to claim 1.

6). An anisotropic conductive film in which conductive particles are regularly arranged, obtained by the production method according to any one of Items 1 to 5.

  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. In addition, it is possible to connect the terminals with excellent connection reliability and insulation. Further, lateral conduction due to the connection between the conductive particles can be prevented, and the terminals can be efficiently conducted with a small number of conductive particles, so that it can be manufactured at low cost.

The present invention is characterized in that conductive particles are regularly arranged on a substrate or a substrate coated with an insulating adhesive by using a nozzle having a fine opening to regularly arrange the conductive particles. It is a manufacturing method of an electroconductive film, In addition, the manufacturing method which has the process of applying an insulating adhesive agent further on the particle adhesion surface after discharging the said electroconductive particle is also included. Details of the production method of the present invention will be described below.

2 to 4 exemplify the outline of the anisotropic conductive film and the method for producing the same according to the present invention, which will be described in order. FIG. 2 shows an example in which an insulating adhesive in which conductive particles are dispersed is discharged on a base material using a nozzle having a fine opening, and the conductive particles are regularly arranged, and then further insulated on the particle adhesion surface. It is an example which shows the anisotropic conductive film which coated the adhesive, and its manufacturing method. In FIG. 3, the insulating adhesive in which the conductive particles are dispersed is discharged on a base material coated with the insulating adhesive in advance using a nozzle having a fine opening, and the conductive particles are regularly arranged. It is an example which shows an anisotropic conductive film and its manufacturing method. FIG. 4 shows an arrangement in which conductive particles are regularly arranged by discharging an insulating adhesive in which conductive particles are dispersed using a nozzle having fine openings on a substrate that has been coated with an insulating adhesive in advance. This is an example showing an anisotropic conductive film in which an insulating adhesive is further applied to the particle adhesion surface and a method for producing the same.

  As a method of discharging an insulating adhesive in which conductive particles are dispersed from a nozzle having the fine opening, it is preferable to adopt an ink jet method. By adopting the ink jet method, it becomes possible to freely set the discharge area and discharge pattern of the insulating adhesive in which the conductive particles are dispersed, thereby realizing the regular arrangement of the conductive particles that is the object of the present invention. be able to. Inkjet methods include a piezo jet type using a piezoelectric element and a bubble jet (registered trademark) type using an electrothermal transducer as an energy generating element, and any type can be used.

The insulating adhesive used in the present invention is not particularly limited, and examples thereof include a thermoplastic material used for an adhesive sheet and the like, a material that exhibits curability by heat and light, and the like. 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. The insulating adhesive applied on the substrate and the insulating adhesive for dispersing the conductive particles may be the same type, or different types and different compositions of the insulating adhesive.
The coating thickness of the insulating adhesive on the substrate should correspond 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 inevitably from the diameter of the conductive particles. Becomes a large thickness. For example, in the connection between the LCD panel and TCP or FPC, a thickness of about 10 to 20 μm is preferable. Moreover, if the peelability at the time of this press-bonding is good, there is no particular limitation on the substrate to be used, but in general, a film made of polyethylene terephthalate (PET) subjected to a release treatment is used.

  The conductive particles dispersed in the insulating adhesive are not particularly limited as long as they are conductive particles. For example, various metals such as nickel, iron, copper, aluminum, tin, lead, chromium, cobalt, silver and gold Or metal alloys, metal oxides, carbon, graphite, glass, ceramics, and plastic particles whose surfaces are coated with metal. However, in consideration of connection of a fine circuit and long-term connection reliability, it is more preferable that the surface of the polymer core material is provided with a metal coating such as gold or nickel.

  The thickness of the metal film is not particularly limited, but if it is too thin, the conductivity becomes unstable, and conversely if it is too thick, particle deformation becomes difficult or aggregation occurs, so about 0.01 to 1 μm is preferable. . The method for forming this metal film is, of course, better to form uniformly in consideration of the adhesion and conductivity between the film and the polymer core material that is the central core. Electroless plating or the like is preferable.

In addition, there is no particular limitation on the resin composition of the polymer core material. For example, polymer polymers such as epoxy resin, urethane resin, melamine resin, phenol resin, acrylic resin, polyester resin, styrene resin, and styrene butadiene copolymer are used. Can be used. These can be used alone or in combination of two or more.

Although there is no restriction | limiting in particular about the particle size of the electroconductive particle used by this invention, Preferably it is an average particle diameter of 2-10 micrometers. Considering discharging conductive particles from a nozzle having a fine opening, problems such as nozzle clogging are less likely to occur as the particle size is smaller. However, if the conductive particles are less 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. It is extremely difficult to apply the coating with the current technology, and in fact, it is impossible to stably connect fine circuits. On the contrary, with particles exceeding 10 μm, it is possible to uniformly coat the metal without aggregation, but when connecting a fine circuit, the electrical insulation between the terminals cannot be maintained, so the number of particles is Not much can be blended and there is a limit to improving connection reliability. Furthermore, problems such as nozzle clogging tend to occur, which is not preferable. For example, in the connection between a liquid crystal display panel and an FPC (flexible circuit board), which is the main application of the anisotropic conductive film, particularly in the connection of a fine pitch circuit having a pitch of about 50 μm, an average particle size of about 3 to 5 μm is preferable. Needless to say, it is preferable that the particle size distribution is sharper, and it is more preferable if the average particle size is within ± 10%.

There are no particular restrictions on the blending amount of the conductive particles dispersed in the insulating adhesive, and the blending amount is such that nozzle clogging does not occur, and is adjusted as appropriate according to the particle size of the conductive particles used, the pitch and pattern of the circuit to be connected. Just do it. Moreover, there is no restriction | limiting in particular about the method to disperse | distribute electroconductive particle to an insulating adhesive agent, What is necessary is just to select an appropriate method from a well-known technique according to the property of an insulating adhesive agent and electroconductive particle, and these compounding quantities.

The usage example of the anisotropic conductive film produced with the manufacturing method of this invention is shown in FIG. For example, the pressure bonding is performed on the LCD panel by heat and pressure, the substrate is peeled off, TCP is placed, and the paper is temporarily fixed by pressure. Furthermore, the main pressure bonding can be performed by heating and pressurizing, and the terminals can be efficiently conducted.

The features of the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited to the examples. In addition, evaluation of the anisotropic conductive film in this invention was performed as follows.

(1) Observation of particle arrangement state The arrangement state of particles adhered on the substrate was observed using a fluorescence microscope (Olympus Optical Co., Ltd.).

(2) Conductivity An anisotropic conductive film is placed on a 1.1 mm thick ITO glass on which an indium oxide / tin oxide conductive film having a sheet resistance of 30Ω is formed on the entire surface, and 80 ° C., 0.5 MPa, 3 seconds. Then, the surface PET film was peeled off, and the TCP was further pressure-bonded from above at 180 ° C. and 3 MPa for 15 seconds. TCP consists of a polyimide base material and copper foil, and is Sn-plated on the surface after circuit processing. Using the connected samples, the connection resistance values of adjacent terminals on the TCP were measured.

<Example 1>
Using a homomixer, 5.0 wt% of conductive particle micropearl AU (average particle size 5 μm, manufactured by Sekisui Chemical Co., Ltd.) was dispersed in an epoxy insulating adhesive to prepare a conductive particle dispersion. Next, droplets of the conductive particle dispersion liquid were ejected in the form of dots at equal intervals of 40 μm in length and width on the PET film substrate subjected to the release treatment by an ink jet method, and then dried at a temperature of 65 ° C. for 3 minutes. Further, an epoxy insulating adhesive was applied thereon so that the thickness on the substrate after drying was 10 μm to 15 μm, and dried at 65 ° C. for 10 minutes to obtain an anisotropic conductive film. As a result of observing the anisotropic conductive film with a fluorescence microscope, it can be confirmed that the conductive particle groups are regularly arranged at equal intervals of 30 μm, and each conductive particle group is composed of two to three particles. It had been. As a result of evaluating the conductivity of the obtained anisotropic conductive film, the connection resistance value between adjacent terminals was as good as 2Ω or less for all terminals.

<Example 2>
An epoxy insulating adhesive was applied on the PET film substrate so that the thickness after drying was 10 to 15 μm, and dried at 65 ° C. for 3 minutes. Then, on the PET film substrate coated with this insulating adhesive, droplets were ejected at equal intervals by the same conductive particle dispersion and inkjet method as in Example 1, and then dried at 65 ° C. for 10 minutes. An anisotropic conductive film was obtained. As a result of observing the anisotropic conductive film with a fluorescence microscope, it can be confirmed that the conductive particle groups are regularly arranged at equal intervals of 30 μm, and each conductive particle group is composed of two to three particles. It had been. As a result of evaluating the conductivity of the obtained anisotropic conductive film, the connection resistance value between adjacent terminals was as good as 2Ω or less for all terminals.

<Example 3>
Using an ultrasonic cleaner, 5.0 wt% of conductive particle micropearl AU (average particle diameter 5 μm, manufactured by Sekisui Chemical Co., Ltd.) was dispersed in an epoxy insulating adhesive to prepare a conductive particle dispersion. An epoxy insulating adhesive was applied on the PET film substrate so that the thickness after drying was 5 μm, and dried at 65 ° C. for 2 minutes. On top of that, droplets of the conductive particle dispersion were ejected in the form of dots at equal intervals of 30 μm in length and width by an inkjet method, and then dried at 65 ° C. for 3 minutes. Further, on this, an epoxy insulating adhesive was applied so that the thickness on the dried substrate was 10 to 15 μm, and dried at 65 ° C. for 10 minutes to obtain an anisotropic conductive film. As a result of observing the anisotropic conductive film with a fluorescence microscope, it can be confirmed that the conductive particle groups are regularly arranged at equal intervals of 20 μm, and each conductive particle group is composed of two to three particles. It had been. As a result of evaluating the conductivity of the obtained anisotropic conductive film, the connection resistance value between adjacent terminals was as good as 2Ω or less for all terminals.

Sectional drawing which shows an example of the conventional anisotropic conductive film and its connection method Schematic which shows an example of the anisotropic conductive film of this invention, and its manufacturing method Schematic which shows an example of the anisotropic conductive film of this invention, and its manufacturing method Schematic which shows an example of the anisotropic conductive film of this invention, and its manufacturing method Schematic which shows the usage example of the anisotropic conductive film created with the manufacturing method of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base material 2 Conductive particle 3 Insulating adhesive 4 LCD panel 5 TCP
6 terminals

Claims (6)

The step of discharging conductive particles using a nozzle having a fine opening and arranging the conductive particles regularly on the surface of the base material or on the surface of the base material coated with the insulating adhesive. A method for producing an anisotropic conductive film, comprising: The method for producing an anisotropic conductive film according to claim 1, further comprising a step of coating an insulating adhesive on the particle adhesion surface after discharging the conductive particles. The manufacturing method of the anisotropic conductive film of Claim 1 or 2 with which the electrically-conductive particle discharged from the nozzle which has the said fine opening part is disperse | distributed to the insulating adhesive agent. The method for producing an anisotropic conductive film according to claim 3, wherein the insulating adhesive in which the conductive particles are dispersed is discharged by an inkjet method. The conductive particles are composed of particles or metal particles having a metal film containing nickel and gold on the surface of a central core made of a polymer core material, and the average particle diameter is 2 to 10 µm. A method for producing the anisotropic conductive film according to claim 1. An anisotropic conductive film in which conductive particles are regularly arranged, obtained by the production method according to claim 1.

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