JP2006024551A - Method of manufacturing anisotropic conductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an anisotropic conductive film for enabling terminal connection with excellent connection reliability and insulation property at low cost regardless of connection between minute circuits, connection between a minute part and a minute circuit or the like. <P>SOLUTION: In the method of manufacturing an anisotropic conductive film in which conductive particles are regularly arranged in a specific region, magnetic recording is performed in a specific region of a magnetic medium in advance, the conductive particles of magnetic substance are captured in this specific region and then the conductive particles regularly arranged in the specific region are fixed not to move. <P>COPYRIGHT: (C)2006,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 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. .

  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.

  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 a resin binder. The present invention is different from the present invention in which the conductive particles are arranged only 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 61-78069 A Japanese Patent Laid-Open No. 2002-075580 Patent No. 3048773

  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 in a specific region, wherein magnetic recording is performed in advance on a specific region of a magnetic medium, and then the conductive particles that are magnetic materials are A method for producing an anisotropic conductive film, characterized by having a step of capturing in a specific region,
(2) The method for producing an anisotropic conductive film according to (1), including a step of fixing so that the conductive particles regularly arranged in a specific region do not move after capture,
(3) The method for producing an anisotropic conductive film according to (1) or (2), comprising a step of covering and fixing the conductive particles with an insulating adhesive after capture,
It is.

  According to the manufacturing method of the present invention, it is possible to obtain an anisotropic conductive film in which conductive particles are regularly arranged only in a specific region, so that connection between fine circuits, connection between minute portions and minute circuits is possible. Even if it is, 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 less conductive Since the terminals can efficiently conduct between the terminals, it can be manufactured at low cost.

  The present invention is a method for producing an anisotropic conductive film, comprising the steps of performing magnetic recording only in a specific region of a magnetic medium in advance and then capturing the conductive particles as a magnetic material only in the specific region. In addition, the manufacturing method includes a step of fixing the conductive particles regularly arranged in a specific region after capturing so as not to move.

  An example of the production method of the present invention will be described with reference to FIGS. For example, a magnetic recording area and a non-recording area are created by magnetic recording only a specific area of the magnetic medium using a magnetic recording apparatus. By spreading conductive particles, which are magnetic materials, on the magnetic medium magnetically recorded only in the specific region, the conductive particles adhere only to the magnetic recording region, and the conductive particles can be captured only in the specific region.

  As a method of magnetic recording only in a specific area, for example, an arbitrary waveform generator generates a pulsed electric signal at an arbitrary frequency, and the magnetic recording apparatus converts the electric signal into a magnetic signal to a magnetic medium. There is a method of creating a magnetic recording area and a non-recording area by magnetic recording. The ratio of the magnetic recording area to the non-recording area can be easily changed by adjusting the pulse width per wavelength in the pulse signal, and the size of each area can be magnetically recorded on a magnetic medium by a magnetic recording device. Adjustment is possible by setting the frequency set by the arbitrary waveform generator with respect to the traveling speed at the time. As the magnetic recording device, a cassette tape recorder or a video cassette recorder can be used. By selecting the magnetic recording device and the magnetic medium, the specific area can be freely adjusted such as a band shape or an island shape.

  Alternatively, a vertical stripe pattern can be drawn at an arbitrary width and interval, and an electric signal obtained by video recording can be used in place of an electric signal generated by an arbitrary waveform generator. The ratio and width of the magnetic recording area and the non-recording area can be adjusted by the width and interval of the vertical stripe pattern. For example, when the signal is input from the video signal side using a video recorder, a regular magnetic recording area with a constant interval can be formed.

  As another method, for example, a titanium oxide sol is applied to a substrate such as a film and then baked. Next, after performing electroless plating while performing UV irradiation using a mask that is open only at a portion corresponding to a specific region, magnetic recording can be performed only on the specific region by magnetization. These methods are listed as methods for magnetic recording only in a specific area, but are not limited thereto.

  The method of spraying the conductive particles that are magnetic materials is not particularly limited as long as it is a method that can capture the conductive particles that are magnetic materials on the magnetic medium, for example, a method of immersing the magnetic medium in a tank in which the conductive particles are flowed, Examples include a method of spraying conductive particles by spraying, a method of dropping a dispersion in which conductive particles are dispersed, and a method of immersing a magnetic medium in a dispersion in which conductive particles are dispersed. Regardless of wet type or dry type. Further, a step of removing the conductive particles excessively attached to the magnetic medium may be added.

  Conductive particles captured only in a specific region of the magnetic medium can be transferred onto another substrate. There is no particular limitation on the method for transferring onto another substrate as long as the conductive particles captured only in a specific region can be transferred as they are, and the captured conductive particles are transferred to a substrate having adhesiveness. It can be transferred by contact.

  Although there is no restriction | limiting in particular as said base material, For example, 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. When 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 are transferred.

  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.

  The magnetic medium is not particularly limited as long as it can capture magnetic particles in the magnetically recorded region. One type of magnetic substance alone, a composite of two or more kinds of magnetic substances, and a non-magnetic base material are magnetic. Any compound of the body can be used. In addition, an adhesive material can be applied on the magnetic medium in order to improve the trapping property of the conductive particles. As this adhesive material, if the insulating adhesive used later has adhesiveness, it 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 tackiness may be different from the insulating adhesive.

  The conductive particles that are magnetic materials are not particularly limited as long as they have electrical conductivity and magnetism. , Metal alloys of these and various metals such as copper, aluminum, tin, lead, chromium, silver, gold, or particles made of metal alloys, metal oxides, carbon, graphite, glass, ceramics, polymers, etc. The surface coated with a ferromagnetic metal or ferromagnetic alloy can be applied, but in consideration of connection reliability and application to fine circuit connections, a polymer core material with a ferromagnetic metal coating Is desirable.

  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, a sharper particle size distribution is preferable, and it is preferably within ± 10% of the average particle size.

  The process of fixing the conductive particles regularly arranged in a specific area after capturing does not prevent the insulating adhesive from filling between terminals other than the conductive particles during the main pressure bonding of heating and pressurization. There is no particular limitation as long as the conductive particles can be fixed so that they do not move. For example, after applying a thermosetting insulating adhesive to the magnetic medium that has captured the conductive particles and heating it to such an extent that curing does not proceed sufficiently, further insulating bonding A method that utilizes the difference in the degree of curing of the insulating adhesive, such as applying an agent. There are no particular restrictions on the insulating adhesive applied in two steps, the same or different.

 The step of fixing the conductive particles may be performed when the conductive particles are transferred from the magnetic medium to the substrate. For example, there is a method in which a thin insulating adhesive is applied to a substrate and heated to such an extent that curing does not proceed sufficiently, and then the conductive particles captured on the magnetic medium are transferred. There are no particular restrictions on the method of transferring the conductive particles captured on the magnetic medium. The method of transferring by applying pressure, the method of transferring using the adhesiveness of the insulating adhesive, the transfer by applying magnetic force from the back side of the substrate And the like.

In the present invention, it is desirable to further include a step of coating the conductive particles with an insulating adhesive after capturing. The method is not particularly limited, but a method such as coating, spraying, or casting the insulating adhesive is not particularly limited. Can be used.
The thickness of the insulating adhesive only needs to 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 has a thickness larger than the diameter of the conductive particles. For example, when the LCD panel is connected to TCP or FPC, a thickness of about 10 to 20 μm is preferable.

  The insulating adhesive 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, and the like. Can be 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.

  An example of using the anisotropic conductive film manufactured by the above method is shown in FIG. After fixing the conductive particles 13 with the insulating adhesive 20 heated to such an extent that the curing does not proceed sufficiently, and further covering the insulating adhesive 20, for example, the substrate 15 is temporarily pressure-bonded onto the LCD panel 4 by heating and pressing. Is peeled off, TCP5 is placed, and temporarily fixed by pressurization. Further, the main pressure bonding is performed by heating and pressurization. However, since the conductive particles are fixed, it is difficult to flow out of the terminals, and the terminals can be efficiently conducted between the terminals.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

 Using a multifunction synthesizer 1946 (manufactured by NF Circuit Block) as an arbitrary waveform generator, a square wave with a frequency of 1 kHz, a duty (ratio of the pulse width to the entire waveform) of 5%, and an amplitude of 25 mV is generated, and the tape recorder MD-F350 ( Electric signal was input from the microphone terminal of Sharp Corporation. Since the tape running speed of this tape recorder is 48 mm / sec, one cycle of the square wave generated by the above arbitrary waveform generator is 48 μm, of which the magnetic recording area is 2.4 μm. This electric signal was converted into a magnetic signal by a tape recorder and input to an audio cassette tape MG1-46 (manufactured by Hitachi Maxell).

  When the audio cassette tape magnetically recorded only in a specific area is immersed in an ethanol solution in which 0.1% by weight of micropearl AU, 5 μm (manufactured by Sekisui Chemical Co., Ltd.) is dispersed as conductive particles, the width of the audio cassette tape is reduced. A band of approximately 700 μm composed of conductive particles is arranged in a half region in a direction perpendicular to the traveling direction, and the conductive particles are aligned at intervals of 48 μm in a direction parallel to the traveling direction in each row. Observed. In the band shape of about 700 μm, the conductive particles were continuous, and the width of the band was composed of 3 to 4 conductive particles. On the other hand, randomly attached conductive particles were observed in the area of the audio cassette tape that was not magnetically recorded.

 In order to prevent the conductive particles arranged on the cassette tape from moving, an insulating adhesive is applied on the cassette tape to a thickness of 5 to 10 μm after drying, and curing is performed at a temperature of 120 ° C. for 30 seconds. Immobilized. Furthermore, after apply | coating an insulating adhesive agent on this, it dried at 65 degreeC for 10 minute (s), and obtained the anisotropic conductive film of thickness 15-20 micrometers.

 The obtained anisotropic conductive film was placed on a 1.1 mm thick ITO glass on which an indium oxide / tin oxide conductive film having a sheet resistance of 30Ω was formed on the entire surface, and conditions of 80 ° C., 0.5 MPa, and 3 seconds. And pressure bonding was performed by heating and pressing. Thereafter, the cassette tape was peeled off, and the TCP was heated and pressed under the conditions of 180 ° C., 3 MPa, and 15 seconds from the top to perform main pressure bonding. TCP is made of a polyimide base material and copper foil, and is Sn-plated on the surface after circuit processing. Evaluation was performed using connected samples. The connection resistance value between adjacent terminals was as good as 2Ω or less for all terminals.

 Using a device similar to that of Example 1, a square wave having a frequency of 2 kHz, a duty (ratio of the pulse width to the entire waveform) of 10%, and an amplitude of 25 mV is generated, and from a microphone terminal of a tape recorder MD-F350 (manufactured by Sharp Corporation). An electrical signal was input. One cycle of the square wave under this condition is 24 μm, of which the magnetic recording area is 2.4 μm. This electric signal was similarly input to the audio cassette tape.

  Similarly, when ethanol in which conductive particles are dispersed is dropped onto the audio cassette tape, a band of about 700 μm composed of conductive particles is perpendicular to the running direction in a half region with respect to the width direction of the audio cassette tape. Two rows were arranged in the direction, and it was observed that the conductive particles were arranged at intervals of 24 μm in the direction parallel to the running direction in each row. In the band shape of about 700 μm, the conductive particles were almost continuous, and the width of the band was composed of 1 to 3 conductive particles. On the other hand, randomly attached conductive particles were observed in the area of the audio cassette tape that was not magnetically recorded.

Hereinafter, as a result of fixing the conductive particles by the same method as in Example 1 and evaluating the obtained anisotropic conductive film, the connection resistance value between adjacent terminals was as good as 2Ω or less for all terminals.

 Using a device similar to that in Example 1, a square wave having a frequency of 3 kHz, a duty (ratio of the pulse width to the entire waveform) of 15%, and an amplitude of 25 mV is generated, and from the microphone terminal of the tape recorder MD-F350 (manufactured by Sharp Corporation). An electrical signal was input. One cycle of the square wave under this condition is 16 μm, of which the magnetic recording area is 2.4 μm. This electric signal was similarly input to the audio cassette tape.

  Similarly, when the audio cassette tape is immersed in an ethanol solution in which conductive particles are dispersed, a band of about 700 μm composed of conductive particles is formed in the half direction with respect to the width direction of the audio cassette tape. Two rows were arranged in the vertical direction, and in each row, it was observed that the conductive particles were aligned at intervals of 16 μm in the direction parallel to the running direction. In the band shape of about 700 μm, the conductive particles were almost continuous, and the width of the band was composed of 1 to 3 conductive particles. On the other hand, randomly attached conductive particles were observed in the area of the audio cassette tape that was not magnetically recorded.

Hereinafter, as a result of fixing the conductive particles by the same method as in Example 1 and evaluating 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 The figure which shows the manufacturing method which is one Example of this invention The figure which shows the magnetic medium which magnetic-recorded only to the specific area | region of this invention Sectional drawing which shows a mode that the electroconductive particle was supplemented to the magnetic-recording area | region of this invention 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 Magnetic medium 11a Magnetic recording area 11b Non-recording area 12 Conductive particle 13 Adhesive layer 14 Base material 20 Insulating adhesive

Claims (3)

A method for producing an anisotropic conductive film in which conductive particles are regularly arranged in a specific region, wherein magnetic recording is performed in advance on a specific region of a magnetic medium, and then the conductive particles as a magnetic material are placed in the specific region. A method for producing an anisotropic conductive film, comprising a step of capturing. The manufacturing method of the anisotropic conductive film of Claim 1 which has the process of fixing so that the electrically-conductive particle regularly arrange | positioned to a specific area | region may not move after capture | acquisition. The method for producing an anisotropic conductive film according to claim 1, further comprising a step of covering and fixing the conductive particles with an insulating adhesive after capturing.

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