JP2007186593A - Anisotropic conductive film and electronic/electric instrument using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anisotropic conductive film which can reduce dispersion in splice resistance between terminals and electronic/electric instruments using the anisotropic film. <P>SOLUTION: The anisotropic conductive film comprises an insulating adhesive film and electroconductive particles fixed to the insulating adhesive film. In the film, the electroconductive particles are regularly arranged in two or more rows in the planar view of a film surface of the insulating adhesive film, express the regularity of higher order equal to or more than secondary order, when the film surface of the insulating adhesive film is photographed in the planar view and enlarged images are analyzed by Fourier transform, and arrangement spaces of the electroconductive particles are 10-300 μm. Electronic/electric instruments using the anisotropic film are provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an anisotropic conductive film and electronic / electrical equipment.

  In recent years, the need for fine circuit connection such as connection between a liquid crystal display (LCD) and a tape carrier package (TCP) and connection between a TCP and a printed circuit board (PCB) has increased. As the connection method, a method using an anisotropic conductive film in which conductive particles are dispersed in an insulating adhesive film is used.

In this method, an anisotropic conductive film is sandwiched between terminals to be connected and heated and pressed to maintain electrical insulation between adjacent terminals in the plane direction and to electrically conduct between upper and lower terminals.
More specifically, when the anisotropic conductive film is sandwiched between the vertically opposed terminals, the conductive particles are sandwiched between the upper and lower terminals, and an electrical connection is formed.
On the other hand, since the conductive particles are not in contact between terminals adjacent in the plane direction, electrical insulation is ensured.

  As an arrangement pattern of the conductive particles in the anisotropic conductive film, for example, a method of forming a dense region of conductive particles at the top of an equilateral triangle without gaps has been proposed (see, for example, Patent Document 1). .

JP 2003-208931 A

However, the technique of Patent Document 1 has room for improvement in the following points.
In Patent Document 1, as a method of arranging conductive particles, a metal mask having a through-hole in a necessary portion is brought into contact with a sticky adhesive in a planar manner, and the conductive particles are sprinkled from above the metal mask to remove excess conductivity. The particles are removed, and the metal mask is removed to produce a connection member. Alternatively, it is possible that the conductive particles can be sprayed from above the metal mask by a liquid crystal spacer spraying device or can be manufactured by a silk screen printing method. However, in any method, in the follow-up experiment by the inventor, the problem of missing teeth that the conductive particles are not arranged at a predetermined location, and conversely, a plurality of particles aggregate although the conductive particles are arranged at the predetermined location. As a result, problems such as a large number of conductive particles gathering in one place are likely to occur, and it is difficult to realize precise arrangement. In other words, theoretically, it should be possible to improve the performance of anisotropic conductive films by arranging conductive particles, especially to reduce variation in connection resistance between terminals, but the actual conductive particle arrangement technology is still insufficient. As a result, it is difficult to produce an anisotropic conductive film with good performance because the intended arrangement cannot be realized while the arrangement is intended. Further, when the technique for evaluating the arrangement of the conductive particles is insufficient, it is judged that the quality of the arrangement control cannot be determined, which is also a factor that delays the solution of the above problem.

  An object of the present invention is to provide an anisotropic conductive film capable of suppressing variation in connection resistance between terminals, and further to provide an electronic / electrical device using the anisotropic conductive film.

  This inventor examined the method of determining the quality of the arrangement | sequence of an electroconductive particle for the performance improvement of the anisotropic conductive film characterized by the arrangement | sequence of an electroconductive particle. As a result of intensive studies, it is possible to suitably determine the quality of the array by Fourier transforming and analyzing the photograph of the conductive particle array by image analysis. As a result of the regularity of the conductive particle array, anisotropic conduction of the preferable conductive particle array is possible. It has been found that a conductive film can be obtained.

The present invention
(1) An anisotropic conductive film having an insulating adhesive film and conductive particles fixed to the insulating adhesive film, wherein the conductive particles are film surfaces of the insulating adhesive film. When viewed in plan, when arranged in a plurality of rows regularly, characterized in that when an enlarged photograph taken in plan view of the film surface of the insulating adhesive film is subjected to image analysis by Fourier transform, An anisotropic conductive film according to (2) (1), characterized in that each row shows secondary or higher order regularity, and the conductive particles are arranged at intervals of 10 μm to 300 μm. Electronic / electrical equipment comprising electronic / electrical parts electrically connected by a conductive film,
(3) In the electronic / electrical device according to (2), the electronic / electrical component includes a semiconductor device, a printed circuit board, a liquid crystal display (LCD) panel, a plasma display panel (PDP), an electroluminescence (EL) panel, Electronic and electrical equipment characterized by field emission display (FED) panels and tape carrier packages,
(4) In the electronic / electrical device according to (2) or (3), the electronic / electrical device is an image display module, a computer, a television, a measuring device, or a communication device.・ Electrical equipment,
It is.

ADVANTAGE OF THE INVENTION According to this invention, the anisotropic conductive film and electronic / electrical equipment which can suppress the dispersion | variation in the connection resistance between terminals are provided.

The method for evaluating the anisotropic conductive film in the present inventor will be described below.
First, the photograph which expanded the film surface of the anisotropic conductive film with the optical microscope is image | photographed. An anisotropic conductive film is desirable because it is easier to observe the state before being bonded to various devices. However, if necessary, remove the anisotropic conductive film after being bonded to various devices from the device, or if part of the device is transparent, it will not be a problem if you observe the optical microscope while it is still bonded to the device. No. In addition, this micrograph needs to be the image which planarly viewed the film surface instead of the cross section of an anisotropic conductive film.

In the case of a digital camera, the obtained photograph is directly used as image data. However, if the photograph is an ordinary silver salt film, it needs to be converted into digital data by reading it with a scanner. The image format is not particularly specified as long as it can be processed by image analysis software described later.

The image data of the conductive particle arrangement of the obtained anisotropic conductive film is subjected to Fourier transform processing using image analysis software to obtain a Fourier transform image. The reason why the Fourier transform is used for evaluating the regular arrangement of the conductive particles is that the Fourier transform is used in waveform analysis and the like and is an extremely useful tool for detecting the regularity of various events. . In patents related to conventional conductive particle array anisotropic conductive films, the evaluation method for quantifying and determining the regular array property of the obtained conductive particles is not clearly described, and therefore, even though it is called a regular array, it is actually Had no way to quantitatively judge the regularity of the conductive particles, so there was no way to judge the performance quantitatively. This is useful for making it easier to judge. The image analysis software is not particularly specified, and is not particularly specified as long as the image can be Fourier transformed to display a Fourier transform image. An important point in the observation of the Fourier transform image is that not only the primary peak, but also that a peak exhibiting higher order regularity is observed, and the arrangement interval of the conductive particles indicated by the peak is It is a point which needs to confirm that it is the space | interval of 10-300 micrometers which is the width | variety requested | required with a normal anisotropic conductive film. In the case where a peak indicating secondary or higher order regularity is not observed, it is determined that the conductive particles in the anisotropic conductive film are insufficiently arranged in the plane of the film. In particular, when the primary peak does not appear, the conductive particles are judged to be randomly arranged, and are out of the scope of this patent. Also, when the array width is less than 10 μm, it is difficult to reduce the variation in connection resistance between wirings compared to the case of random array, and when it exceeds 300 μm, conduction at the wiring connection part may be insufficient. There is sex.

An analysis example is shown as an example of the present invention. The anisotropic conductive film in which the conductive particles are regularly arranged was arranged by the method shown in the specification of Japanese Patent Application No. 2005-86343. Optical microscope images were stored in bitmap format and used for image analysis. Scion Image (manufactured by Scion Corporation) was used as the image analysis software used for the Fourier transform. An analysis example is shown in FIG. FIG. 1 is a plane direction optical micrograph of conductive particles and a Fourier transform processed image thereof. In the case of non-arrangement, not only the secondary but even the primary peak cannot be observed, whereas in the case of relatively good arrangement, higher-order peaks of the second or higher order are observed, and the distance between the conductive particles in the vertical direction is also horizontal. Both directions are known to be 29 μm. The above analysis is merely an example, and there is no limitation on the method of arranging conductive particles, the format of image data, the type of image analysis software, and the like. In short, it has been found that an anisotropic conductive film that can confirm the regular arrangement of conductive particles by analyzing the waveform by Fourier transform processing will greatly improve connection reliability compared to conventional films. This is within the scope of this patent.

  In the present invention, there is no limitation on the arrangement or the like in the thickness direction of the film, but more preferably at least some of the conductive particles are exposed from the surface of the insulating adhesive film. It is preferable. By exposing at least some of the conductive particles from the surface of the insulating adhesive film, friction is generated between the conductive particles and the terminals when the upper and lower terminals are connected. Therefore, when connecting the upper and lower terminals, the conductive particles are less likely to flow in the space between the terminals adjacent in the plane direction. This is because, by reducing the number of conductive particles flowing in the space between the terminals adjacent in the plane direction, it is possible to prevent a short circuit between the terminals adjacent in the plane direction.

The conductive particles used in the present invention are not particularly limited as long as they have conductivity. Ferromagnetic metals such as nickel, iron, cobalt, cobalt ferrite, aluminum Heusler alloy, magnetite, yttrium iron garnet, metal alloys of these with various metals such as copper, aluminum, tin, lead, chromium, silver, gold, or Conductive substances such as metal alloys, metal oxides, carbon, graphite, etc. as relatively flexible polymer core materials such as epoxy resin, urethane resin, melamine resin, phenol resin, acrylic resin, polyester resin, styrene resin, styrene A polymer produced by coating the surface of one or a combination of two or more of polymers such as butadiene copolymers is preferably used.

  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 the average particle diameter is preferably 2 μm to 50 μm. In the case of 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, but there is a problem that the particles are likely to aggregate. This is because it tends to be difficult to apply.

  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. 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 thickness of the insulating adhesive to be applied only needs to correspond to an amount sufficient to satisfy the space between the 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. Become. For example, a thickness of about 10 μm to 20 μm is preferable for the connection between the LCD panel and TCP or FPC, and a thickness of about 20 to 400 μm is preferable for the connection between the semiconductor chip and the circuit board.

In the present invention, as an electronic / electrical component manufactured using the anisotropic conductive film having the above characteristics, a semiconductor device, a printed circuit board, a liquid crystal display (LCD) panel, a plasma display panel (PDP) An electroluminescence (EL) panel, a field emission display (FED) panel, and a tape carrier package can be exemplified.
Furthermore, it is preferable that the electronic / electrical device is any one of an image display module, a computer, a television, a measuring device, and a communication device.

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 this embodiment.
In the embodiment, the multi-function synthesizer 1946 (manufactured by NF Circuit Block) is used for the arbitrary waveform generator, “video cassette recorder HV-S550” (manufactured by Mitsubishi Electric) is used for the magnetic recording device, and “ “Video tape HG120” (manufactured by TDK) and “Micropearl AU 5 μm” (manufactured by Sekisui Chemical Co., Ltd.) were used as the conductive particles. Moreover, the anisotropic conductive film in the present invention was evaluated as follows.

(1) Observation of particle arrangement state The state of particles arranged on a magnetic medium was observed using a fluorescence microscope (Olympus Optical Co., Ltd.) to obtain a micrograph.

(2) Image Analysis Image analysis was performed using a Scion Image (manufactured by Scion Corporation) running on Windows (registered trademark). Image analysis was performed by Fourier transforming an image of 128 × 128 pixels. It was determined whether or not a higher-order peak higher than the second order was present, and the sequence interval indicated by the peak was measured.

(3) 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 value of 30Ω is formed on the entire surface, and 80 ° C., 0.5 MPa, After pre-bonding under the conditions of seconds, the PET film on the surface was peeled off, and the TCP was further pressure-bonded under conditions of 180 ° C., 3 MPa, 15 seconds from the top. TCP consists of a polyimide base material and copper foil, and is Sn-plated on the surface after circuit processing. The terminal width (dimension along the longitudinal direction of the anisotropic conductive film) is 20 μm, and the terminal length (dimension along the short side of the anisotropic conductive film) is 1000 μm. Here, the number of terminals was 20. Using the connected samples, the connection resistance values of adjacent terminals on the TCP were measured. All terminals were measured and averaged.

(4) Connection resistance between terminals Using the sample created in the above (3), the resistance value between terminals that should have no conduction was measured. In the combination of terminals that should not have continuity, the combination of adjacent terminals was selected and measured, and the average value was shown.

<Example 1>
A square wave having a frequency of 200 kHz, a duty of 1.0%, and an amplitude of 20 V was generated from the arbitrary waveform generator and directly input to the video head of the magnetic recording apparatus. This electric signal was converted into a magnetic signal by a video head and input to a video tape. Since the relative speed between the tape and the video head of the magnetic recording apparatus is 5.8 m / sec, one cycle of the square wave generated by the above arbitrary waveform generating apparatus is 29 μm, of which the magnetic recording area is 0.29 μm.
Using an ultrasonic cleaner, 0.10 wt% of conductive particles Micropearl AU 5 μm (manufactured by Sekisui Chemical Co., Ltd.) was dispersed in ethanol for 3 minutes, and a video tape magnetically recorded under the above conditions was immersed for 3 minutes. After pulling up, in order to prevent aggregation due to the movement of particles during the volatilization of ethanol, it was dried at room temperature with a magnet placed under the videotape.
Next, the conductive particles regularly arranged in the specific region as described above are transferred and fixed on the substrate so as not to move. An insulating adhesive is applied on a polyethylene terephthalate (PET) film substrate that has been subjected to a release treatment so that the thickness after drying becomes 10 μm to 15 μm, and is dried at a temperature of 65 ° C. for 10 minutes. The conductive particles trapped in were transferred and fixed onto the substrate by applying pressure from above to obtain an anisotropic conductive film.

<Comparative Example 1>
Thickness after drying on polyethylene terephthalate (PET) film base material mixed with insulating adhesive and conductive particle micropearl AU5μm (manufactured by Sekisui Chemical Co., Ltd.) for 20 minutes using a three-one motor. Was coated with an insulating adhesive so that the thickness became 10 μm to 15 μm, and dried at a temperature of 65 ° C. for 10 minutes to obtain an anisotropic conductive film.

Table 1 shows the evaluation results of the anisotropic conductive films of Examples and Comparative Examples.

Explanatory drawing about the correlation between the arrangement of conductive particles and the Fourier transform image

Claims (4)

An anisotropic conductive film having an insulating adhesive film and conductive particles fixed to the insulating adhesive film, wherein the conductive particles are viewed from above the film surface of the insulating adhesive film. When the enlarged photograph taken by viewing the film surface of the insulating adhesive film in plan view is subjected to image analysis by Fourier transform, it is arranged in a plurality of rows regularly. An anisotropic conductive film, wherein the anisotropic conductive film exhibits secondary and higher order regularity and has an arrangement interval of the conductive particles of 10 μm to 300 μm. An electronic / electrical device having electronic / electrical components electrically connected by the anisotropic conductive film according to claim 1. 3. The electronic / electrical device according to claim 2, wherein the electronic / electrical component is a semiconductor device, a printed circuit board, a liquid crystal display (LCD) panel, a plasma display panel (PDP), an electroluminescence (EL) panel, a field emission display. Electronic and electrical equipment characterized by (FED) panels and tape carrier packages. 4. The electronic / electrical device according to claim 2, wherein the electronic / electrical device is any one of an image display module, a computer, a television, a measuring device, and a communication device.

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