HK1261545B - Anisotropic conductive film - Google Patents

Description

Anisotropic conductive film

Technical Field

The present invention relates to an anisotropic conductive film.

Background Art

Anisotropic conductive films, which consist of conductive particles dispersed in an insulating resin binder, are widely used when mounting electronic components such as IC chips on substrates. With the recent trend toward narrower bump pitches associated with the high-density mounting of electronic components, there is a strong demand for anisotropic conductive films that can enhance the ability to capture conductive particles on the bumps and prevent short circuits.

To meet these requirements for anisotropic conductive films, various methods for regularly aligning conductive particles have been investigated. Known techniques include, for example, covering a stretched film with conductive particles and biaxially stretching the film to achieve a single-layer arrangement of the conductive particles (Patent Document 1); or utilizing magnetism to hold conductive particles in a substrate and then transferring them to an adhesive film to achieve a predetermined arrangement (Patent Document 2).

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent No. 5147048;

Patent Document 2: Japanese Patent No. 4887700.

Summary of the Invention

Problems to be solved by the invention

However, the biaxial stretching method makes it difficult to precisely arrange the conductive particles in a predetermined position, and omissions often occur in the arrangement of conductive particles. The transfer method can arrange the conductive particles more precisely than the biaxial stretching method, but it is difficult to completely eliminate omissions of conductive particles across the entire surface of the anisotropic conductive film.

Furthermore, anisotropic conductive film products are typically manufactured in lengths exceeding 5 meters. Therefore, it is difficult and unrealistic to produce an anisotropic conductive film with no missing conductive particles along its entire length. For example, if even a single missing conductive particle is considered an out-of-specification defective product, the product yield rate decreases, increasing manufacturing costs. Furthermore, if missing conductive particles are noticeable in the product, the stability of the anisotropic conductive connection becomes problematic.

Therefore, an object of the present invention is to provide an anisotropic conductive film having omissions in a predetermined regular arrangement of conductive particles for anisotropic conductive connection in substantially the same manner as an anisotropic conductive film having no omissions.

Solutions to Problems

The present inventors have discovered that even when there are omissions in the predetermined regular arrangement of the conductive particles, no problems arise in the anisotropic conductive connection in the following cases (A) to (C).

(A) If there are continuous omissions in the predetermined regular arrangement of conductive particles, poor conduction is likely to occur. This tendency is particularly strong when there are continuous omissions in the long side direction of the anisotropic conductive film. However, even if there are continuous omissions in the long side direction of the anisotropic conductive film, as long as the number of consecutive omissions is less than the predetermined number corresponding to the connection object, poor conduction is unlikely to occur.

(B) When anisotropic conductive film is used on FOG (film on glass) or other materials where the bumps are relatively large, the maximum bump width is generally around 200 μm. Therefore, if there are more than 10 conductive particles within a 200 μm range in the long side direction of the anisotropic conductive film, there will be no substantial connection problems even if there are omissions in the regular arrangement of the conductive particles.

(C) In the case of anisotropic conductive film used for bumps at specific locations (for example, there are bump rows at both ends in the short side direction) and in the case of COG (chip on glass) where the area of each bump is relatively small, when the both ends in the short side direction of the anisotropic conductive film are aligned with the terminal rows of the chip, as long as the locations where conductive particles are continuously omitted by a predetermined number or more (that is, the locations where they are significantly omitted at a level that becomes a problem in actual use) are not present along the both ends in the short side direction of the anisotropic conductive film, even if the conductive particles are continuously omitted by a predetermined number or more in the central portion in the short side direction, it is unlikely that problems will occur in the connection.

The present invention is conceived based on these insights and provides an anisotropic conductive film having a length of more than 5m, having a regularly arranged area in which conductive particles are regularly arranged in an insulating resin adhesive, and within the regularly arranged area, there is no in-specification area where conductive particles are continuously omitted for more than a predetermined number of places, and the anisotropic conductive film exists with a predetermined width in the short side direction and a predetermined length or more in the long side direction of the anisotropic conductive film.

The structure of the anisotropic conductive film of the present invention enables substantially the same anisotropic conductive connection as an anisotropic conductive film without omissions, even if there are omissions in the regular arrangement of conductive particles. In other words, the structure allows the amount of conductive particles to be reduced without degrading the properties of the anisotropic conductive film. Therefore, the anisotropic conductive film of the present invention can reduce the amount of metal used in the conductive particles, not only reducing manufacturing costs but also lowering environmental impact or helping to mitigate the specifications of anisotropic conductive film products (improving manufacturing yield). To achieve stable conductive properties with the minimum number of conductive particles required for anisotropic connection, it is preferable to make the regularly arranged area and the within-specification area consistent. Furthermore, areas where more than a predetermined number of conductive particles are continuously omitted, i.e., areas outside the specification, may exist, as long as this does not significantly impair the effects of the present invention.

In particular, an anisotropic conductive film for a large number of bumps, such as COG (chip on glass), where each bump area is relatively small, is provided in which at least the end regions along the short side of the anisotropic conductive film have within-specification regions.

In addition, as an anisotropic conductive film for FOG (film on glass) with a relatively large bump area, a method is provided in which 10 or more conductive particles are present in a region of 200 μm in the longitudinal direction arbitrarily selected across the entire width of the anisotropic conductive film.

The present invention also provides a method for producing an anisotropic conductive film, comprising cutting a wide roll (original and reverse) of an anisotropic conductive film in which conductive particles are regularly arranged in an insulating resin adhesive into an anisotropic conductive film having a length of 5 m or more in a longitudinal direction in a manner that does not include any out-of-specification portions where the conductive particles are continuously omitted from the regular arrangement by a predetermined number or in a manner that makes the out-of-specification portions be at desired positions in the short side direction of the film.

The present invention further provides a method for producing an anisotropic conductive film. The method involves removing out-of-specification areas where conductive particles are continuously omitted for a predetermined number or more from an anisotropic conductive film having an insulating resin binder, and then joining the removed anisotropic conductive film to produce an anisotropic conductive film having a length of 5 m or greater. A length of 5 m or greater facilitates installation and verification in anisotropic connection equipment used for continuous production. This reduces the verification burden when replacing anisotropic conductive film used in conventional anisotropic connection structures.

The present invention also provides a method for manufacturing a connection structure, wherein a first electronic component having a terminal array and a second electronic component having a terminal array are thermocompressed with an anisotropic conductive film interposed therebetween, thereby anisotropically connecting the terminal arrays of the first and second electronic components to each other, wherein the anisotropic conductive film has a regular arrangement region in which conductive particles are regularly arranged in an insulating resin adhesive.

As the anisotropic conductive film, an anisotropic conductive film is used, wherein there is no area within the specification arrangement area where conductive particles are continuously omitted for a predetermined number or more, and the anisotropic conductive film is formed with a predetermined width in the short side direction and a predetermined length in the long side direction of the anisotropic conductive film.

Align the area within the specification with the terminal array of the electronic component.

In this manufacturing method, when the first electronic component and the second electronic component each have a plurality of terminal rows, and the within-specification regions are formed in parallel in the anisotropic conductive film,

It is preferred that the area between adjacent specification areas be aligned with the area between terminal rows.

Effects of the Invention

According to the method for manufacturing an anisotropic conductive film of the present invention, it is possible to extract areas that are practically problem-free from anisotropic conductive films that have previously been judged to be defective due to the omission of conductive particles, thereby producing an anisotropic conductive film. Furthermore, according to the method for manufacturing a connection structure of the present invention, even if the anisotropic conductive film used to manufacture the connection structure has areas that have been judged to be problematic due to the omission of conductive particles, if there are no areas within the specification where a predetermined number or more of conductive particles are continuously missing, and the anisotropic conductive film is provided with a predetermined width in the short direction and a predetermined length in the long direction, the within-specification area can be aligned with the terminal array of the electronic component. This improves the yield rate of the anisotropic conductive film manufacturing without compromising the reliability of the anisotropic conductive connection.

BRIEF DESCRIPTION OF THE DRAWINGS

[ Fig. 1] Fig. 1 is a plan view illustrating the arrangement of conductive particles in an anisotropic conductive film 1A according to an embodiment.

[ Fig. 2] Fig. 2 is a plan view illustrating the arrangement of conductive particles in an anisotropic conductive film 1B of the embodiment.

[ Fig. 3] Fig. 3 is a plan view illustrating the arrangement of conductive particles in an anisotropic conductive film 1C according to an embodiment.

[ FIG. 4] FIG. 4 is a plan view showing the positions of portions where the arrangement of conductive particles in the anisotropic conductive film for COG is out of specification.

[ Fig. 5] Fig. 5 is a cross-sectional view of an anisotropic conductive film 1a according to an embodiment.

[ Fig. 6] Fig. 6 is a cross-sectional view of an anisotropic conductive film 1b of an embodiment.

[ Fig. 7] Fig. 7 is a cross-sectional view of an anisotropic conductive film 1c according to an embodiment.

[ Fig. 8] Fig. 8 is a cross-sectional view of an anisotropic conductive film 1d according to an embodiment.

[ Fig. 9] Fig. 9 is a cross-sectional view of an anisotropic conductive film 1e according to an embodiment.

[Fig. 10] Fig. 10 is a schematic diagram showing the bump arrangement of an evaluation IC.

DETAILED DESCRIPTION

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. In addition, in each figure, the same reference numerals represent the same or equivalent components.

<Anisotropic Conductive Film>

(Overall structure of anisotropic conductive film)

The anisotropic conductive film of the present invention comprises regions in which conductive particles are regularly arranged within an insulating resin binder (regularly arranged regions). Preferably, the conductive particles are separated from one another and arranged in a regular pattern (e.g., a grid pattern) when viewed from above. A single regularly arranged region may extend across the entire surface of the anisotropic conductive film, or multiple groups of conductive particles may be arranged across the entire surface as separate regularly arranged regions.

The anisotropic conductive film of the present invention has a regularly arranged area, which can accurately detect and grasp the omission of conductive particles in the regularly arranged area of the conductive particles. With respect to the anisotropic conductive film of the present invention, within such a regularly arranged area, there is no within-specification area where the conductive particles are continuously omitted for more than a predetermined number of times, and the within-specification area exists with a predetermined width in the short side direction of the anisotropic conductive film and a predetermined length in the long side direction of the anisotropic conductive film. In addition, when a plurality of conductive particle groups are arranged as regularly arranged areas separated from each other on the entire surface of the anisotropic conductive film, in each regularly arranged area, the within-specification area exists with a predetermined width in the short side direction of the anisotropic conductive film and a predetermined length in the long side direction of the anisotropic conductive film.

Regarding the within-specification area, the short-side direction of the anisotropic conductive film corresponds to the long-side direction of the terminal in a typical anisotropic conductive connection structure. This improves the ability of the conductive particles aligned along the short-side direction of the anisotropic conductive film to be captured by the terminal, and the anisotropic conductive connection conditions are relatively easily mitigated. Consequently, when the entire short-side direction of the anisotropic conductive film is pressed against the connection tool to facilitate anisotropic conductive connection, the pressing width condition along the short-side direction of the anisotropic conductive film can also be mitigated. Specifically, the upper limit of the "predetermined width" along the short-side direction of the anisotropic conductive film is preferably 95% or less, more preferably 90% or less of the short-side direction of the anisotropic conductive film. Meanwhile, the lower limit is preferably 10% or more, more preferably 20% or more. Furthermore, the "predetermined width" of the anisotropic conductive film in the short-side direction is preferably located outside the center of the short-side direction of the anisotropic conductive film, that is, at the ends (either end portions), to facilitate anisotropic connection with IC chips such as conventional COGs and similar terminal layouts. The widths of the respective within-specification regions at the two end portions can be the same or different to accommodate the desired terminal layout.

On the other hand, regarding the within-specification area, the term "above a predetermined length" in the long direction of the anisotropic conductive film (i.e., the short direction of the terminals in a typical anisotropic conductive connection structure) means, based on an anisotropic conductive connection structure (e.g., a small, approximately 10 mm square component such as a camera module), that the length should be 5 mm or longer, preferably 10 mm or longer, and more preferably 20 mm or longer (equivalent to 0.4% of the length of an anisotropic conductive film of 5 m). Furthermore, for large anisotropic conductive connection structures (e.g., large displays of 80 inches or more), the regularly arranged area can be 2000 mm or longer.

In addition, regarding the area within the specification, the longer the upper limit of "above a predetermined length" in the long side direction of the anisotropic conductive film, the higher the quality of the anisotropic conductive film itself, so it is preferred. Therefore, there is no special limit on the upper limit of "above a predetermined length", but from the perspective of image inspection when performing quality management of the anisotropic conductive film, if it is limited to a certain length, it will be easier to manage quality information. For example, if it is separated by a certain length, it will be easy to compare the data of each length. In addition, there is also the advantage of simply not having a large amount of image data. As an example of the upper limit of "above a predetermined length", if it is less than 1000m, preferably less than 500m, more preferably less than 350m, and more preferably less than 50m, it will become easier to process or manage the image data during inspection.

Furthermore, from the perspective of stable connection, it is preferable to make the within-specification region infinitely equal to, and even identical to, the regularly arranged region. Furthermore, as long as this does not significantly impair the effects of the present invention, portions (out-of-specification portions) where a predetermined number or more of the conductive particles are continuously omitted may exist within the regularly arranged region. Furthermore, outside the regularly arranged region of the anisotropic conductive film, blank regions where no conductive particles are present, or random arrangement regions where the conductive particles are randomly arranged, may exist.

In order to ensure stable productivity of the connected structure formed by the anisotropic conductive connection, the film length of the anisotropic conductive film of the present invention is preferably 5 m or longer, more preferably 10 m or longer, and even more preferably 50 m or longer. On the other hand, if the film length is too long, the labor required for equipment installation and transportation, as well as the cost of equipment modification, will increase. Therefore, it is preferably 5000 m or shorter, more preferably 1000 m or shorter, and even more preferably 500 m or shorter. The film width is not particularly limited, but is, for example, 0.5 to 5 mm.

Since the anisotropic conductive film is longer than its width, it is preferably wound onto a reel as a roll. A roll can also be made by joining multiple anisotropic conductive films. A connecting tape can be used to connect the anisotropic conductive films. The thickness of the connecting tape is not particularly limited, but excessive thickness can adversely affect resin extrusion or blocking, so it is preferably 10 to 40 μm.

(Configuration of conductive particles)

As a regular arrangement of conductive particles, for example, a square lattice arrangement can be cited, as in the anisotropic conductive film 1A shown in FIG1 . In addition, as a regular arrangement of conductive particles, a lattice arrangement such as a rectangular lattice, a rhombus lattice, or a hexagonal lattice can be cited. A column of particles in which conductive particles are arranged linearly at predetermined intervals and arranged side by side at predetermined intervals can also be cited. Furthermore, as in the anisotropic conductive film 1B shown in FIG2 , the conductive particles 2 can be arranged such that the conductive particles 2 occupy a plurality of vertices among the vertices of a regular polygon (a regular hexagon in this embodiment) in which the regular polygons are arranged side by side without gaps, so that a trapezoidal repeating unit 5 consisting of the conductive particles 2a, 2b, 2c, and 2d can be identified. Furthermore, the trapezoidal repeating unit is an example of a regular arrangement of conductive particles, which can be either an isolated arrangement or a collection of a plurality of repeating units forming an isolated regular arrangement region of conductive particles. Here, the repeating unit 5 is a repeating unit of the configuration of conductive particles formed by sequentially connecting the centers of the closest conductive particles 2. Due to the repetition of a predetermined regularity, the repeating unit 5 extends across one side of the anisotropic conductive film. The configuration shape of the conductive particles in the repeating unit 5 itself is not particularly limited. However, if the repeating unit 5 is configured so that the conductive particles 2 occupy a portion of a regular polygon, it is easy to understand the configuration of the conductive particles, and thus it is easy to determine whether any conductive particles are missing from the predetermined configuration. In addition, if the configuration of the conductive particles is easy to understand, various operations in the manufacture of the anisotropic conductive film or in product inspection such as indentation inspection after connecting electronic components using the anisotropic conductive film become easier, which can shorten the time and thus reduce the number of working hours.

The lattice axis or arrangement axis of the conductive particles 2 can be parallel to or intersecting the longitudinal direction of the anisotropic conductive film and can be determined based on the width of the connected terminals, the terminal pitch, etc. For example, in the case of an anisotropic conductive film for fine pitch, as shown in FIG1 , the lattice axis L1 of the conductive particles 2 is tilted relative to the longitudinal direction of the anisotropic conductive film 1A, and the angle θ formed between the longitudinal direction (the short side of the film) of the terminal 10 connected to the anisotropic conductive film 1A and the lattice axis L1 is preferably 6° to 84°, and more preferably 11° to 74°.

(Conductive particles)

Conductive particles 2 can be appropriately selected from known conductive particles used in anisotropic conductive films. Examples include metal particles of nickel, copper, silver, gold, palladium, and the like; and metal-coated resin particles obtained by coating the surface of resin particles such as polyamide and polybenzoguanamine with a metal such as nickel. The size of the conductive particles is preferably 1 μm to 30 μm, more preferably 1 μm to 10 μm, and even more preferably 2 μm to 6 μm.

The average particle size of the conductive particles 2 can be measured using an imaging or laser particle size distribution analyzer. Alternatively, the average particle size can be determined by observing the anisotropic conductive film from above and measuring the particle size. In this case, preferably 200 or more particles are measured, more preferably 500 or more particles are measured, and even more preferably 1000 or more particles are measured.

The surfaces of the conductive particles 2 are preferably coated with an insulating coating or insulating particle treatment. Such a coating should be selected so as to be difficult to peel from the surface of the conductive particles 2 and not cause problems with anisotropic bonding. Alternatively, protrusions may be provided on the entire or a portion of the surface of the conductive particles 2. The height of the protrusions is preferably within 20% of the conductive particle diameter, and more preferably within 10%.

(Shortest interparticle distance of conductive particles)

The shortest interparticle distance of the conductive particles is preferably more than 0.5 times the average particle size of the conductive particles. If the distance is too short, it is easy to cause a short circuit due to contact between the conductive particles. The upper limit of the distance between adjacent conductive particles can be determined by corresponding bump shape or bump spacing. As an example, if it is set to capture more than 10 conductive particles, it is less than 50 times the average particle size, and preferably less than 40 times. More preferably less than 30 times.

(Number density of conductive particles)

From the perspective of reducing the production cost of the anisotropic conductive film, the number density of the conductive particles is preferably 50,000 particles/ ^mm² or less, more preferably 35,000 particles/ ^mm² or less, and even more preferably 30,000 particles/ ^mm² or less. On the other hand, if the number density of the conductive particles is too low, there is a concern that the conductive particles may not be sufficiently captured by the terminals, resulting in poor conduction. Therefore, a number density of 30 particles/ ^mm² or more is sufficient, preferably 300 particles/ ^mm² or more, more preferably 500 particles/ ^mm² or more, and even more preferably 800 particles/ ^mm² or more is sufficient.

(Insulating resin adhesive)

As the insulating resin binder 3, a suitable selection of known thermopolymerizable compositions, photopolymerizable compositions, and photothermal polymerizable compositions used as insulating resin binders in anisotropic conductive films can be used. Examples of thermopolymerizable compositions include thermoradical polymerizable resin compositions containing an acrylate compound and a thermal radical polymerization initiator; thermocationic polymerizable resin compositions containing an epoxy compound and a thermal cationic polymerization initiator; and thermoanionic polymerizable resin compositions containing an epoxy compound and a thermal anionic polymerization initiator. Examples of photopolymerizable compositions include photoradical polymerizable resin compositions containing an acrylate compound and a photoradical polymerization initiator. In particular, multiple polymerizable compositions may be used in combination if no problems arise. Examples of combined use include the combination of a thermocationic polymerizable composition and a thermoradical polymerizable composition.

Here, the photopolymerization initiator may contain multiple photopolymerization initiators that react to light of different wavelengths. This allows different wavelengths to be used for photocuring the resin constituting the insulating resin layer during the manufacture of the anisotropic conductive film and for photocuring the resin used to bond electronic components during anisotropic connection.

When insulating resin binder 3 is formed using a photopolymerizable composition, all or part of the photopolymerizable compound contained in insulating resin binder 3 can be photocured by photocuring during the manufacture of the anisotropic conductive film. This photocuring maintains or fixes the arrangement of conductive particles 2 in insulating resin binder 3, offering the potential for suppressing short circuits and improving capture. Furthermore, by adjusting the photocuring conditions, the viscosity of the insulating resin layer during the anisotropic conductive film manufacturing process can be adjusted.

The amount of the photopolymerizable compound in the insulating resin adhesive 3 is preferably 30% by mass or less, more preferably 10% by mass or less, and even more preferably less than 2% by mass. This is because too much photopolymerizable compound increases the thrust required for press-fitting during anisotropic conductive connection.

On the other hand, the thermopolymerizable composition contains a thermopolymerizable compound and a thermopolymerization initiator. However, the thermopolymerizable compound may also function as a photopolymerizable compound. Furthermore, the thermopolymerizable composition may contain a photopolymerizable compound separately from the thermopolymerizable compound and a photopolymerization initiator. Preferably, the thermopolymerizable compound and the photopolymerization initiator are separately from the thermopolymerizable compound. For example, a thermal cationic polymerization initiator may be used as the thermopolymerizable initiator, an epoxy resin may be used as the thermopolymerizable compound, a photoradical initiator may be used as the photopolymerization initiator, or an acrylate compound may be used as the photopolymerizable compound. The insulating adhesive 3 may also comprise a cured product of any of these polymerizable compositions.

As the acrylate compound used as the thermally or photopolymerizable compound, conventionally known thermally polymerizable (meth)acrylate monomers can be used, for example, monofunctional (meth)acrylate monomers and difunctional or higher-functional (meth)acrylate monomers.

In addition, the epoxy compound used as the polymerizable compound preferably forms a three-dimensional network structure and imparts good heat resistance and adhesion, and is used in combination with a solid epoxy resin and a liquid epoxy resin. Here, a solid epoxy resin refers to an epoxy resin that is solid at room temperature. In addition, a liquid epoxy resin refers to an epoxy resin that is liquid at room temperature. In addition, room temperature refers to the temperature range of 5 to 35°C as specified in JIS Z8703. In the present invention, two or more epoxy compounds can be used in combination. In addition, an oxetane compound can also be used in combination in addition to the epoxy compound.

The solid epoxy resin is not particularly limited as long as it is compatible with the liquid epoxy resin and is solid at room temperature. Examples of the solid epoxy resin include bisphenol A epoxy resin, bisphenol F epoxy resin, multifunctional epoxy resin, dicyclopentadiene epoxy resin, novolac phenol epoxy resin, biphenyl epoxy resin, and naphthalene epoxy resin. One of these epoxy resins can be used alone, or two or more can be used in combination. Among these, bisphenol A epoxy resin is preferably used.

The liquid epoxy resin is not particularly limited as long as it is liquid at room temperature. Examples thereof include bisphenol A epoxy resin, bisphenol F epoxy resin, novolac phenol epoxy resin, and naphthalene epoxy resin. These can be used alone or in combination of two or more. In particular, bisphenol A epoxy resin is preferably used from the viewpoints of film adhesiveness and flexibility.

Examples of thermal radical polymerization initiators include organic peroxides and azo compounds. In particular, organic peroxides that do not generate nitrogen that causes bubbles can be preferably used.

The amount of the thermal radical polymerization initiator used is preferably 2 to 60 parts by mass, more preferably 5 to 40 parts by mass, based on 100 parts by mass of the (meth)acrylate compound, because curing may be poor if too little, and product life may be shortened if too much.

As the thermal cationic polymerization initiator, an initiator known as a thermal cationic polymerization initiator for epoxy compounds can be used. For example, iodonium salts, sulfonium salts, quaternary phosphonium salts, ferrocenes, etc. that generate oxygen by heat can be used. In particular, aromatic sulfonium salts that show good latency with respect to temperature can be preferably used.

The amount of the thermal cationic polymerization initiator used tends to be insufficient in curing if too little, and tends to be shortened in product life if too much. Therefore, the amount is preferably 2 to 60 parts by mass, more preferably 5 to 40 parts by mass, based on 100 parts by mass of the epoxy compound.

As anionic polymerization initiators, commonly used known curing agents can be used. Examples include organic acid dihydrazides, dicyandiamide, amino compounds, polyamideamine compounds, cyanate compounds, phenolic resins, acid anhydrides, carboxylic acids, tertiary amino compounds, imidazoles, Lewis acids, Brønsted acid salts, polythiol curing agents, urea resins, melamine resins, isocyanate compounds, and blocked isocyanate compounds. These can be used alone or in combination of two or more. Among these, microcapsule-type latent curing agents comprising a modified imidazole core coated with polyurethane are preferred.

The thermopolymerizable composition preferably contains a film-forming resin. The film-forming resin is, for example, a high molecular weight resin having an average molecular weight of 10,000 or more. From the perspective of film formation, the average molecular weight is preferably about 10,000 to 80,000. Examples of the film-forming resin include phenoxy resins, polyester resins, polyurethane resins, polyester polyurethane resins, acrylic resins, polyimide resins, butyral resins, and the like. These resins can be used alone or in combination of two or more. Among these, phenoxy resins can be suitably used from the perspectives of film formation and connection reliability.

To adjust the melt viscosity, the thermopolymerizable composition may contain an insulating filler. Examples include silica powder and alumina powder. The insulating filler preferably has a particle size of 20 to 1000 nm, and the amount incorporated is preferably 5 to 50 parts by mass per 100 parts by mass of the thermopolymerizable compound (photopolymerizable compound) such as the epoxy compound. Furthermore, the composition may contain fillers other than the insulating filler, softeners, accelerators, antioxidants, colorants (pigments, dyes), organic solvents, and ion trapping agents.

In addition, stress buffers, silane coupling agents, inorganic fillers, etc. may be added as needed. Examples of stress buffers include hydrogenated styrene-butadiene block copolymers and hydrogenated styrene-isoprene block copolymers. Examples of silane coupling agents include epoxies, methacryloyloxys, aminos, vinyls, mercapto/sulfides, and urea compounds. Examples of inorganic fillers include silica, talc, titanium oxide, calcium carbonate, and magnesium oxide.

The insulating resin adhesive 3 can be formed by coating a coating composition containing the aforementioned resin, drying it, or further curing it, or by pre-forming it into a film using a known method. The insulating resin adhesive 3 can also be obtained by laminating resin layers as needed. Furthermore, the insulating resin adhesive 3 is preferably formed on a release film such as a release-treated polyethylene terephthalate film.

(Viscosity of insulating resin adhesive)

The minimum melt viscosity of the insulating resin binder 3 can be appropriately determined depending on the anisotropic conductive film production method, etc. For example, when the anisotropic conductive film production method employs a method in which conductive particles are retained in a predetermined arrangement on the surface of the insulating resin binder and then press-fitted into the insulating resin binder, the minimum melt viscosity of the insulating resin binder 3 is preferably 1100 Pa·s or higher from the perspective of film formability. In particular, since film formation can be performed at 40-80°C, the viscosity of the insulating resin binder 3 at 60°C is preferably 3000-20000 Pa·s. Furthermore, as described later, recesses 3b are formed around the exposed portions of the conductive particles 2 pressed into the insulating resin adhesive 3, as shown in FIG5 or FIG6 , or recesses 3c are formed directly above the conductive particles 2 pressed into the insulating resin adhesive 3, as shown in FIG7 . From this perspective, the minimum melt viscosity of the insulating resin adhesive 3 may be 1500 Pa·s or higher, preferably 2000 Pa·s or higher, more preferably 3000 to 15000 Pa·s, and even more preferably 3000 to 10000 Pa·s. For example, this minimum melt viscosity can be determined using a rotational rheometer (manufactured by TA Instruments) at a constant temperature increase rate of 10°C/min and a measurement pressure of 5 g, using a measuring plate with an 8 mm diameter. Furthermore, when the step of press-fitting the conductive particles 2 into the insulating resin adhesive 3 is performed at 40 to 80°C, the viscosity of the insulating resin adhesive 3 at 60°C is preferably 3,000 to 20,000 Pa·s from the perspective of forming the recesses 3b or 3c, as described above. This measurement is performed using the same method as for the minimum melt viscosity, and the value at 60°C can be extracted for determination.

By ensuring that the viscosity of the resin constituting the insulating resin adhesive 3 is high as described above, when the anisotropic conductive film is used, when the conductive particles 2 are sandwiched between opposing connection objects such as electronic components and heated and pressurized, the conductive particles 2 within the anisotropic conductive film can be prevented from flowing due to the flow of the melted insulating resin adhesive 3. Furthermore, when the amount of resin around or directly above the conductive particles is substantially zero, or reduced relative to the surrounding area, as in recesses 3b and 3c, the pressing force applied to the conductive particles is easily transmitted from the connection tool, thereby effectively holding the conductive particles between the terminals and improving the conductive characteristics and the ability to capture the conductive particles.

(Thickness of insulating resin adhesive)

The thickness La of the insulating resin adhesive 3 is preferably 1 μm to 60 μm, more preferably 1 μm to 30 μm, and even more preferably 2 μm to 15 μm. Furthermore, the ratio (La/D) of the thickness La of the insulating resin adhesive 3 to the average particle size D of the conductive particles 2 is preferably 0.6 to 10. If the thickness La of the insulating resin adhesive 3 is too large, the conductive particles may become dislocated during anisotropic conductive connection, reducing the ability of the terminals to capture the conductive particles. This tendency is significant when La/D exceeds 10. Therefore, La/D is more preferably 8 or less, and even more preferably 6 or less. Conversely, if the thickness La of the insulating resin adhesive 3 is too small, such that La/D is less than 0.6, it becomes difficult for the insulating resin adhesive 3 to maintain the conductive particles in a predetermined dispersion or arrangement. In particular, when the terminals to be connected are high-density COG terminals, the ratio (La/D) of the thickness La of the insulating adhesive layer 4 to the particle size D of the conductive particles 2 is preferably 0.8 to 2.

(Method of embedding conductive particles in insulating resin adhesive)

The embedding state of the conductive particles 2 in the insulating resin adhesive 3 is not particularly limited. However, when anisotropic conductive connection is made by sandwiching an anisotropic conductive film between opposing components and applying heat and pressure, as shown in Figures 5 and 6 , it is preferable to partially expose the conductive particles 2 from the insulating resin adhesive 3, forming recesses 3b around the exposed portions of the conductive particles 2 relative to a tangent plane 3p taken along the insulating resin adhesive surface 3a at the center between adjacent conductive particles 2. Alternatively, as shown in Figure 7 , recesses 3c are formed relative to the same tangent plane 3p in the portion of the insulating resin adhesive directly above the conductive particles 2 pressed into the insulating resin adhesive 3, thereby creating undulations on the surface of the insulating resin adhesive 3 directly above the conductive particles 2. The presence of recesses 3b as shown in Figure 5 reduces the resistance experienced by the conductive particles 2 from the insulating resin adhesive 3 compared to a case without recesses 3b, as opposed to flattening of the conductive particles 2 that occurs when the conductive particles 2 are sandwiched between opposing electrodes of electronic components and subjected to heat and pressure. This facilitates the holding of the conductive particles 2 between the opposing electrodes, further improving conductivity. Furthermore, by forming recesses 3c (Figure 7) on the surface of the resin immediately above the conductive particles 2 within the resin constituting the insulating resin binder 3, the pressure applied during heating and pressing is more easily concentrated on the conductive particles 2, compared to a case without recesses 3c. This allows the conductive particles 2 to be more easily held between the electrodes, thereby improving conductivity.

In order to facilitate the effects of the recesses 3 b and 3 c described above, the ratio (Le/D) of the maximum depth Le of the recesses 3 b ( FIG. 5 and FIG. 6 ) around the exposed portion of the conductive particles 2 to the average particle diameter D of the conductive particles 2 is preferably less than 50%, more preferably less than 30%, and even more preferably 20 to 25%. The ratio (Ld/D) of the maximum diameter Ld of the recesses 3 b ( FIG. 5 and FIG. 6 ) around the exposed portion of the conductive particles 2 to the average particle diameter D of the conductive particles 2 is preferably 150% or less, more preferably 100 to 130%. The ratio (Lf/D) of the maximum depth Lf of the recesses 3 c ( FIG. 7 ) in the resin directly above the conductive particles 2 to the average particle diameter D of the conductive particles 2 is greater than 0, and preferably less than 10%, and more preferably 5% or less.

Furthermore, the diameter Lc of the exposed portion of the conductive particle 2 can be made smaller than the average particle diameter D of the conductive particle 2. This allows the conductive particle 2 to be exposed at a single point on the top 2t of the conductive particle 2, or the conductive particle 2 can be completely buried in the insulating resin binder 3, making the diameter Lc zero. From the perspective of ease of positional adjustment of the conductive particles when embedding the conductive particles in the insulating resin layer by press-fitting the conductive particles, it is preferable to keep the diameter Lc within 15%.

(Position of Conductive Particles in the Thickness Direction of the Insulating Resin Adhesive)

In order to facilitate the effect of the above-mentioned recess 3 b, the ratio (Lb/D) of the distance Lb of the deepest part of the conductive particles 2 from the tangential plane 3 p (hereinafter referred to as the embedding amount) to the average particle diameter D of the conductive particles 2 (hereinafter referred to as the embedding rate) is preferably 60% or more and 105% or less.

(Insulating adhesive layer)

In the anisotropic conductive film of the present invention, the insulating adhesive layer 4 may be laminated on the insulating resin binder 3 in which the conductive particles 2 are arranged.

When the insulating resin adhesive 3 is formed with the aforementioned recessed portion 3b, the insulating adhesive layer 4 can be laminated on either the surface of the insulating resin adhesive 3 having the recessed portion 3b, as in the anisotropic conductive film 1d shown in FIG8 , or on the surface opposite the surface having the recessed portion 3b, as in the anisotropic conductive film 1e shown in FIG9 . The same applies when the insulating resin adhesive 3 is formed with the recessed portion 3c. When the anisotropic conductive film is used to anisotropically connect electronic components, the insulating adhesive layer 4 can be laminated to fill gaps formed by the electrodes or bumps of the electronic components, thereby improving adhesion.

Furthermore, when laminating the insulating adhesive layer 4 on the insulating resin adhesive 3, regardless of whether the insulating adhesive layer 4 is located on the surface where the recesses 3b and 3c are formed, it is preferred that the insulating adhesive layer 4 be located on the side of the electronic component, such as the IC chip, that is being pressed by the tool (in other words, the insulating resin adhesive 3 be located on the side of the electronic component, such as the substrate, that is placed on the stage). This prevents the unintended movement of the conductive particles and improves their capture efficiency.

The insulating adhesive layer 4 can be used as the insulating adhesive layer in the known anisotropic conductive film, or the viscosity can be adjusted to a lower level using the same resin as the insulating resin adhesive 3 described above. The greater the difference in the minimum melt viscosity between the insulating adhesive layer 4 and the insulating resin adhesive 3, the easier it is to fill the gaps formed by the electrodes or bumps of the electronic components with the insulating adhesive layer 4, thereby improving the adhesion between the electronic components. In addition, the greater the difference, the smaller the amount of resin movement of the insulating resin adhesive 3 during anisotropic conductive connection, so the capture of conductive particles on the terminal becomes easier to improve. In actual use, the minimum melt viscosity ratio of the insulating adhesive layer 4 to the insulating resin adhesive 3 is preferably greater than 2, more preferably greater than 5, and even more preferably greater than 8. On the other hand, if this ratio is too large, there is a concern that the resin will be squeezed out or blocked when the long anisotropic conductive film is made into a roll, so in actual use, it is preferably less than 15. More specifically, the preferred minimum melt viscosity of the insulating adhesive layer 4 satisfies the above ratio and is 3000 Pa·s or less, more preferably 2000 Pa·s or less, and particularly preferably 100 to 2000 Pa·s.

The insulating adhesive layer 4 can be formed by coating a coating composition containing the same resin as that forming the insulating resin binder 3 and then drying or curing it, or by forming it into a film in advance using a known method.

The thickness of the insulating adhesive layer 4 is not particularly limited, but is preferably 4 to 20 μm, or preferably 1 to 8 times the diameter of the conductive particles.

In addition, the minimum melt viscosity of the entire laminated anisotropic conductive film, which is a combination of the insulating resin adhesive 3 and the insulating adhesive layer 4, also depends on the ratio of the thickness of the insulating resin adhesive 3 and the insulating adhesive layer 4. However, in actual use, it can be below 8000 Pa·s, and for the convenience of filling between bumps, it can be 200 to 7000 Pa·s, preferably 200 to 4000 Pa·s.

(Third insulating resin layer)

A third insulating resin layer may be provided on the opposite side of the insulating adhesive layer 4, sandwiching the insulating resin adhesive 3. For example, the third insulating resin layer can function as an adhesive layer. Similar to the insulating adhesive layer 4, it may be provided to fill gaps formed by electrodes or bumps of electronic components.

The resin composition, viscosity, and thickness of the third insulating resin layer may be the same as or different from those of the insulating adhesive layer 4. The minimum melt viscosity of the anisotropic conductive film that bonds the insulating resin adhesive 3, the insulating adhesive layer 4, and the third insulating resin layer is not particularly limited, but may be 8000 Pa·s or less, 200 to 7000 Pa·s, or even 200 to 4000 Pa·s.

Furthermore, if necessary, an insulating filler such as silica particles, alumina, or aluminum hydroxide may be added not only to the insulating resin binder 3 but also to the insulating adhesive layer 4. The amount of the insulating filler added is preferably 3 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the resin constituting these layers. This prevents the anisotropic conductive film from melting during anisotropic conductive connection, and prevents the conductive particles from being unnecessarily moved by the molten resin.

<Method for Manufacturing Anisotropic Conductive Film>

(Overview of the Manufacturing Method)

In the present invention, a wide roll of anisotropic conductive film is first obtained or produced, in which conductive particles are regularly arranged in an insulating adhesive. Next, the roll of anisotropic conductive film is examined for omissions from the regular arrangement of the conductive particles. The roll is then cut into anisotropic conductive film of a predetermined width, excluding the region containing the out-of-specification portions, to ensure that the regularly arranged conductive particles are not continuously omitted for a predetermined number of times (a first embodiment). Alternatively, the wide roll is cut longitudinally to a predetermined width, such that the out-of-specification portions are located at desired positions along the short side of the film (a second embodiment). Alternatively, in the first embodiment, the anisotropic conductive film after the out-of-specification portions have been removed (i.e., the remaining anisotropic conductive film, or the remaining anisotropic conductive film after the out-of-specification portions have been removed) is joined to produce an anisotropic conductive film having a length of 5 m or greater.

The method for producing the initial anisotropic conductive film before removing the aforementioned region is not particularly limited. For example, a transfer mold for arranging the conductive particles in a predetermined arrangement can be prepared. The conductive particles are then filled into the concave portion of the transfer mold. An insulating resin binder 3 formed on a release film is then applied to the mold, and pressure is applied to press the conductive particles 2 into the insulating resin binder 3, thereby transferring the conductive particles 2 to the insulating resin binder 3. Alternatively, an insulating adhesive layer 4 can be further laminated on the conductive particles 2. In this manner, an anisotropic conductive film can be obtained.

Alternatively, an anisotropic conductive film can be produced by filling the recesses of a transfer mold with conductive particles, then covering them with an insulating resin binder. The conductive particles are then transferred from the transfer mold to the surface of the insulating resin binder, and the conductive particles on the insulating resin binder are then pressed into the insulating resin binder. The amount of conductive particles embedded (Lb) can be adjusted by adjusting the pressure and temperature during this press-in process. Furthermore, the shape and depth of the recesses 3b and 3c can be adjusted by adjusting the viscosity of the insulating resin binder during press-in, the speed of press-in, and the temperature. For example, when manufacturing an anisotropic conductive film 1a having recesses 3b as shown in FIG5 , or an anisotropic conductive film 1c having recesses 3c as shown in FIG7 , the viscosity of the insulating resin adhesive at 60°C is preferably 3000 Pa·s or higher, more preferably 4000 Pa·s or higher, and even more preferably 4500 Pa·s or higher, depending on the shape and depth of the recesses. The viscosity is preferably 20000 Pa·s or lower, more preferably 15000 Pa·s or lower, and even more preferably 10000 Pa·s or lower, depending on the shape and depth of the recesses. Furthermore, the temperature during press-in is 40-80°C, and more preferably 50-60°C.

In addition, as a transfer mold, in addition to filling the recessed portions with the conductive particles, a slight adhesive may be applied to the top surface of the convex portion to allow the conductive particles to adhere to the top surface.

These transfer molds can be produced using known techniques such as machining, photolithography, and printing.

Furthermore, as a method for arranging the conductive particles in a predetermined arrangement, a method using a biaxially stretched film may be used instead of the method using the transfer side.

(Correspondence to missing areas)

In the first embodiment of the anisotropic conductive film manufacturing method of the present invention, whether the anisotropic conductive film is used in a connection structure with relatively small bump areas (an example of this is a COG connection where the terminals are arranged in isolation) or in a connection structure with relatively large bump areas (an example of this is a FOG connection where the long side of the effective area is the same as the film width and the terminals are not arranged in isolation), in an anisotropic conductive film where the conductive particles are regularly arranged in a plan view, preferably where the conductive particles are regularly arranged and spaced apart from each other in a plan view, out-of-specification areas where a predetermined number of consecutive areas of missing conductive particles are removed from the area where the conductive particles are regularly arranged (regular arrangement area). In other words, the area where the missing areas are merely scattered and do not cause problems with the conductive stability after the connection is considered to be within the specification area and is not subject to removal. The range within which this problem does not occur varies depending on the connection object. However, as an example, when using an anisotropic conductive film for FOG, even if 1 to 20 conductive particles are omitted consecutively, or 1 to 209 particles are omitted depending on the situation, there is little chance of problems with conduction stability. The number 209 consecutively omitted conductive particles has the following meaning. Specifically, under the typical anisotropic conductive connection conditions (connection area of 0.4 ^μm² ) for an increased connection area of FOG, where the anisotropic conductive film is 2 mm wide and the terminal to be connected is 200 μm wide, arranging the conductive particles in a 15×15 square grid would ideally require 225 conductive particles to be present within the 0.4 ^μm² connection area. However, assuming 209 conductive particles are omitted, this means that 16 conductive particles are present within the terminal area, the minimum number of particles captured within the 0.4 ^μm² connection area. Here, the number of trapped conductive particles, 16, is set to a value between 11 and 20, the lower limit of the preferred number of trapped particles (described later). Therefore, this value is considered suitable for identifying conditions that easily ensure stable conduction. This means that the number of trapped conductive particles (16 in this case) exceeds the number of conductive particles along the lattice arrangement axis (as mentioned above, the number of conductive particles along the lattice arrangement axis in this case is 15). This means that the number of conductive particles trapped in a terminal exceeds the total number of lattice axes in a particular direction, resulting in trapped conductive particles present in at least two lattice arrangement axes in the same direction. This capture of conductive particles arranged along at least two lattice axes allows for a certain degree of separation between the positions of the conductive particles captured by the terminal, allowing comparison of the pressure balance. This completes the conditions for determining whether the conductive particles are properly pressed into the connection. Furthermore, when used in COG applications, problems with conduction stability are less likely to occur if the number of consecutively missed particles is between 1 and 20. Problems are even less likely to occur if the number is 15 or less, and particularly 10 or less.

In addition, regarding omissions within the specification area, there can also be allowable omissions within the specification area that do not hinder the connection. The size of such allowable omissions can be judged based on the gap between the terminals. This is a method other than the above-mentioned judgment based on the number of consecutive omissions. For example, the omissions in the long side direction of the membrane (the width direction of the terminal) are preferably less than the total of the gap between the terminals (that is, so that the omission does not span two terminals). In addition, it is preferred that the omissions in the short side direction of the membrane (the long side direction of the terminal) are separated by a distance greater than 50% of the terminal length. In this way, there are conductive particles that can be captured in an area that is at least less than 50% of the terminal length. If there are omissions like this, it can be expected that the conductive performance can be allowed in general anisotropic connections. In addition, in the case of assuming such omissions, the size of the omission can be considered as a rectangle formed by the longest distance between the conductive particles in the directions parallel to the long side direction and the short side direction of the membrane. Considering this, the permissible size of the gap in the case of fine-pitch terminals such as COG is, as an example, preferably 80 μm or less in the long-side direction (the width of the terminal), more preferably 30 μm or less, and even more preferably 10 μm or less. Furthermore, in the short-side direction (the long side of the terminal), it is desirable to retain at least 50% of the terminal length for the captured area. Therefore, as an example, it is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 40 μm or less. Furthermore, in the case of FOG (fog) with wider terminals, the gap in the long-side direction (the width of the terminal) is preferably 400 μm or less, and more preferably 200 μm or less. The effective connection area is in the short-side direction, so it should be less than 50%, preferably less than 30%. Depending on the terminal layout, the above values can be appropriately combined. This is because the present invention is not limited to standard COG or FOG.

As shown in Figure 1, when the missing portions 2X are discontinuous and independent, or when the missing portions 2X are connected in a number less than a predetermined number, they are dispersed. In contrast, when there is a portion 2Y in which the missing portions 2X are continuous for a predetermined number or more and are removed as an out-of-specification portion, the anisotropic conductive film is cut along its longitudinal direction to remove the strip-shaped region R containing the portion 2Y. While Figure 1 shows three consecutive missing portions as an out-of-specification portion, this number is merely an example.

The presence or absence of such omissions can be observed using an imaging device such as an optical microscope, a metallurgical microscope, or a CCD camera. Furthermore, by combining an imaging device with an image analysis and processing system (e.g., WinROOF, Mitani Shoji Co., Ltd.), the dispersion state of the conductive particles in the anisotropic conductive film 1A can be determined and their positions can be pinpointed. As an example, an imaging device with a maximum output pixel count (H) x (V) of 648 x 494 and a frame rate of 30 to 60 fps can be used.

For anisotropic conductive films used in connection structures (such as FOGs) with relatively large individual bump areas, as shown in Figure 3, it is preferable to cut the entire roll so that at least 10 conductive particles are present in any region S, 200 μm long along the longitudinal direction of the anisotropic conductive film, across the full width W of the anisotropic conductive film 1C. In other words, at any location along the full length of the anisotropic conductive film, at least 10 conductive particles are present within a 200 μm length. This is because the maximum bump width in typical FOG connections is approximately 200 μm. Furthermore, the bump length (or tool width) in typical FOG connections is 0.3 to 4 mm, so the full width W of the anisotropic conductive film after cutting is preferably within 4 mm.

From the perspective of increasing the number of conductive particles captured by the terminal in order to improve the reliability of the connection, the more preferred number of conductive particles present in region S is 11 or more, more preferably 20 or more. There is no particular limit to the upper limit. However, if the number of conductive particles present in region S is too large and the number of conductive particles captured on the terminal during anisotropic conductive connection is too large, the thrust required for the pressing fixture used in the anisotropic conductive connection will also increase excessively. In this case, there is a concern that the degree of pressing into each other of the anisotropically connected structures obtained by continuous anisotropic connection is too different. Therefore, the number of conductive particles present in region S is preferably 50 or less, more preferably 40 or less, and more preferably 35 or less.

On the other hand, in the second embodiment of the method for manufacturing an anisotropic conductive film of the present invention, the entire roll of an anisotropic conductive film for a connection structure (COG, etc.) in which each bump area is relatively small can be cut in such a manner that a predetermined number or more of continuous out-of-specification portions 2X where conductive particles are omitted relative to the regular arrangement do not exist at the end portion 1P in the short side direction of the anisotropic conductive film 1A, thereby ensuring that even if conductive particles are omitted, there are no out-of-specification portions at the end portion 1P of the anisotropic conductive film after cutting, and preferably ensuring that conductive particles 2 are present in the predetermined arrangement.

Here, the width of the end portion 1P of the anisotropic conductive film 1A in the short-side direction is preferably within 20% of the width of the anisotropic conductive film 1A in the short-side direction, and more preferably within 30%. This is because, in the connection of electronic components using anisotropic conductive films, the terminal array of the electronic component is generally located within a strip-shaped area within 20% of the width in the short-side direction, and more preferably within 30% of the width from the edge extending along the long-side direction of the anisotropic conductive film. Furthermore, the size of the end portion 1P may differ between the left and right ends depending on the terminal layout of the connected electronic component.

Furthermore, as shown in Figure 4, in a COG-connected IC chip or other electronic component 12, where bumps (terminals) 10 are arranged in two rows, even if, within the regularly arranged region (regular arrangement region) of the anisotropic conductive film 1 used for this connection, there are out-of-specification locations where the conductive particles are continuously missing a predetermined number or more, if the in-specification region Q, where no out-of-specification locations exist, is formed with a predetermined width in the short-side direction of the anisotropic conductive film 1 and a predetermined length in the long-side direction of the anisotropic conductive film 1, the in-specification region Q is aligned with the terminal rows 11. In other words, the region R of the anisotropic conductive film 1 containing the out-of-specification locations is aligned with the region between the two terminal rows 11 (i.e., the region where no terminals are to be connected), thereby anisotropically conductively connecting the opposing electronic components 12 via the anisotropic conductive film 1. The present invention also includes a connection structure that achieves anisotropic conductive connection through such alignment. Furthermore, Figure 4 shows the distance from the end of the electronic component 12 to the inner end of the bump 10. This distance preferably overlaps with the width of the area Q within the specification. In the case of COG, when bonding the film to the glass, alignment can be performed by moving the stage supporting the glass or by moving the film side. This alignment method is not limited to COG and can also be applied to the manufacture of FOG or other connection structures. The present invention includes a method for manufacturing a connection structure including such steps.

More specifically, usually, the length L10 of each terminal 10 in the long side direction is generally 30 to 300 μm, and the distance L11 between two rows of terminal rows 11 ranges from 100 to 200 μm in smaller electronic components such as IC chips with a relatively small short side of the outer shape having multiple rows of bumps (for example, 3 rows arranged in an alternating manner), and ranges from 1000 to 2000 μm in larger electronic components such as IC chips with a relatively long short side of the outer shape. Therefore, in the anisotropic conductive film 1, the width LR of the region R including the out-of-specification portion is within the width of the distance L11 between adjacent terminal rows 11. If the width LQ of the within-specification region Q has the length L10 in the long side direction of the terminal 10, there will be no problem with the COG connection. In addition, even if the width LR of the region R of the anisotropic conductive film exceeds the distance L11 between the terminal rows, and the region R partially overlaps with the terminal row 11, as long as the number of conductive particles captured at each terminal 10 through the anisotropic conductive connection is preferably more than 10, more preferably more than 13, there will be no problem in actual use. For example, when the size of the terminal 10 is 100μ×20μm, the interval L11 of the terminal column 11 is 1000μm, and the number density of the conductive particles in the area Q within the specification of the anisotropic conductive film 1 is 32,000 pieces/ ^mm2 , even if the area R of the anisotropic conductive film overlaps with the terminal 10, as long as the overlapping width is within 50% of the length L10 of the terminal 10, there is no problem in actual use and COG connection can be performed.

(Cutting of anisotropic conductive film)

In the method for manufacturing an anisotropic conductive film of the present invention, in order to improve the productivity of the anisotropic conductive film, a long piece of the anisotropic conductive film is produced with a certain width. The film is then inspected for missing conductive particles using the aforementioned inspection method, preferably also for defective portions such as aggregates. The film is then cut so that these portions are not included in the anisotropic conductive film of a predetermined width. Alternatively, the film is cut into an anisotropic conductive film of a predetermined width so that the missing portions or defective portions such as aggregates are included in the anisotropic conductive film and are positioned at desired locations along the short side of the anisotropic conductive film. This results in an anisotropic conductive film with substantially no missing portions. During the manufacturing process of the anisotropic conductive film, marking may be performed to record the defective portions.

(Bonding of anisotropic conductive films)

In the method for producing an anisotropic conductive film of the present invention, the remaining anisotropic conductive film after cutting out the region including the predetermined missing portion is joined, thereby providing an anisotropic conductive film including the missing portion and not causing any problem in practical use.

According to the present invention, an anisotropic conductive film can be obtained inexpensively, which is wound on a reel and has no continuous omissions of more than a predetermined number of conductive particles along the long side direction over the entire length of the long anisotropic conductive film with a length of more than 5 m and less than 5000 m. In particular, for COG applications, an anisotropic conductive film can be obtained in which there are no omissions of conductive particles at the end 1P of the width in the short side direction of the film over the entire length of the long anisotropic conductive film with a length of more than 5 m and less than 5000 m.

＜Connection structure＞

The anisotropic conductive film of the present invention is preferably used for anisotropically conductively connecting a first electronic component such as an FPC, IC chip, or IC module to a second electronic component such as an FPC, rigid substrate, ceramic substrate, glass substrate, or plastic substrate using heat or light. Furthermore, IC chips or IC modules can be stacked to anisotropically conductively connect the first electronic components. The resulting connection structure also forms part of the present invention.

As a method for connecting electronic components using anisotropic conductive film, for example, to improve connection reliability, it is preferable to temporarily adhere the interface of the anisotropic conductive film on the side where the conductive particles are located in the film thickness direction to a second electronic component such as a wiring substrate. The temporarily adhered anisotropic conductive film is then thermocompressed from the first electronic component side, carrying a first electronic component such as an IC chip. Alternatively, light curing can be used for connection. Furthermore, in this connection, it is preferable to align the long sides of the electronic component's terminals 10 with the short sides of the anisotropic conductive films 1A and 1B to improve connection efficiency.

Example

Hereinafter, the present invention will be described in detail using examples, but the present invention is not limited to these examples.

＜Preparation of COG transfer master sheet＞

First, the master disc used in the examples was prepared as follows. Specifically, a 2 mm thick nickel plate was prepared, and cylindrical protrusions (outer diameter 4 μm, height 4 μm, center-to-center distance 6 μm) were formed in a hexagonal lattice pattern on a 50 cm square area of the plate, resulting in a transfer master disc with an area density of 32,000 protrusions/ ^mm² .

(Production of film master)

Next, a polyethylene terephthalate substrate film having a width of 50 cm and a thickness of 50 μm was prepared. A photocurable resin composition containing 100 parts by mass of an acrylate resin (M208, Toagosei Co., Ltd.) and 2 parts by mass of a photopolymerization initiator (IRGACURE 184, BASF Japan Co., Ltd.) was applied to the substrate film to a thickness of 30 μm.

The resulting photocurable resin composition film was pressed against a nickel transfer master from its convex surface and irradiated with light from a high-pressure mercury lamp (1000 mJ) from the substrate film side, forming a photocurable resin layer in which the convex portions of the transfer master were transferred as concave portions. This operation was repeated continuously while aligning the substrate film in its longitudinal direction, resulting in a film-like master with a length of approximately 10 m, in which the convex portions of the transfer master were transferred as concave portions. The resulting film-like master had concave portions arranged in a hexagonal lattice pattern corresponding to the convex pattern of the transfer master.

We selected 1,000 random 1 ^mm² areas from the resulting film master and counted the number of concave portions in each area using an optical microscope. We then divided the total number of concave portions in each area by the total area of the area to calculate the surface density of the concave portions. The surface density of the concave portions was 32,000/ ^mm² , the same as the surface density of the convex pattern on the transfer master.

<Fabrication of anisotropic conductive films for COG>

(Filling of film-like master with conductive particles)

Metal-coated resin particles (Sekisui Chemical Co., Ltd., AUL703, average particle size 3μm) were prepared as conductive particles and were repeatedly spread onto the surface of a film master. The particles were then wiped with a cloth to fill the recessed areas of the film master, which had been cut at 30cm intervals along its length. The cuts were made at five locations, including the starting and ending points, and three locations in the middle between them. To prevent any conductive particles from filling the resin mold, the number of particles spread and the number of times the particles were spread were adjusted to create areas where the conductive particles were omitted.

(Production of Film for Insulating Resin Layer and Film for Second Insulating Resin Layer)

To determine a suitable resin blend for COG, the resin compositions shown in Table 1 were mixed and coated onto a release-treated PET film. After drying, insulating resin layer films (4 μm thick) were prepared using insulating adhesives A1 to A4, and a second insulating resin layer film (14 μm thick) was prepared using insulating adhesive B, each with a size of 20 × 30 cm.

[Table 1]

(Transfer of conductive particles to insulating resin layer)

On a cut film master disc filled with conductive particles according to predetermined conditions, the insulating resin layer film was aligned and placed so that its longitudinal length was uniform and its width direction encompassed the vicinity of the film master disc's center. Pressing was performed at 60°C and 0.5 MPa to transfer the conductive particles. The insulating resin layer film was then peeled from the film master disc, and the conductive particles on the insulating resin layer film were pressed into the insulating resin layer film using pressure (pressing conditions: 60-70°C, 0.5 MPa). Furthermore, a second insulating resin layer film was laminated to cover the conductive particle transfer surface. This process was repeated at five locations on the cut film master disc, producing anisotropic conductive films (ACF1-ACF4) with embedded conductive particles as shown in Figure 8. In this case, the embedding of the conductive particles was controlled by the press-in conditions. The embedded state of the conductive particles was observed at five points in a group on the film master prepared in this manner and cut at 30 cm along its longitudinal direction. Concavities were observed around the exposed portions of the embedded conductive particles or directly above the embedded conductive particles in all groups, as shown in Table 2. Furthermore, ACF4 failed to maintain its film shape during the indentation of the conductive particles. Therefore, ACFs 1-3 are suitable for COG applications. Furthermore, the embedded state of the conductive particles was confirmed before lamination with insulating adhesive B. For ACFs 1-3, images acquired by a CCD image sensor were observed using image analysis software (WinROOF, Mitani Shoji Co., Ltd.) to confirm the presence of conductive particle omissions. The results revealed a combination of five or fewer consecutive omissions in the longitudinal direction of the film (within the maximum interparticle distance of 33 μm, less than the total of 38 μm for the bump width and interbump gap, described later), and seven or fewer omissions in the width direction (within the maximum interparticle distance of 45 μm). The rectangular area of 33 μm in the film length direction and 38 μm in the film width direction can be considered as an allowable omission. Therefore, any size smaller than this is considered an allowable omission. In addition, omissions in the width direction exist when the bump length is 50 μm or more.

[Table 2]

(Fabrication of anisotropic conductive film for COG considering the omission of conductive particles)

Next, the films were slit with a width of 1.8 mm to reflect the "conductive particle omission conditions" shown in Table 3 for Examples 1 to 4 and Comparative Example 1 (see Figures 4 and 10: LQ [μm], LR [μm], LQ/W [%], LR/W [%]). If this was not achieved, the fabrication procedures for ACF1 to ACF3 were repeated for each of the Examples and Comparative Examples, adjusting the amount of conductive particles dispersed. Three types of anisotropic conductive films were then produced. The anisotropic conductive films of each Example and Comparative Example were slit with a width of 1.8 mm so that the LR (the width of the out-of-specification region (a region lacking conductive particles)) was located at the center of the film. The out-of-specification region includes a rectangular region with a permissible omission of 33 μm in the film's longitudinal direction and 38 μm in the film's width, a rectangular region with either side larger and lacking conductive particles, or a region containing the permissible omission region with a width less than 50 μm.

[Table 3]

<Evaluation 1 (in the case of COG)>

The following experiments/evaluations were conducted on the conductive properties (initial conductivity and conductive reliability) of connection structures obtained by COG connection using the three types of anisotropic conductive films produced in Examples 1 to 4 and Comparative Example 1, respectively.

(Initial continuity)

As electronic components for COG connections, the following evaluation ICs (see Figure 10) and glass substrates were used. The anisotropic conductive film to be evaluated was sandwiched between the ICs and the glass substrates, and heat and pressure were applied (180°C, 60 MPa, 5 seconds) to produce each connection. In this case, the long side of the anisotropic conductive film was aligned with the short side of the bumps, and the connection was performed so that a pair of within-specification regions of the anisotropic conductive film were located at either end of the short side of the IC chip. The on-resistance of the resulting connection structure was measured using a digital multimeter (34401A, AGILENT TECHNOLOGIES Co., Ltd.) using the four-terminal method (JIS K7194). For practical use, a value of 2Ω or less is ideal.

(Conduction reliability)

The connected structure subjected to the initial on-resistance measurement was placed in a thermostatic chamber at 85°C and 85% humidity for 500 hours, and the on-resistance was measured again. For practical use, a resistance of 5Ω or less is preferred.

(Evaluation IC)

IC size: 1.6mm (width) × 30.0mm (length) × 0.2mm (thickness)

Gold bump: 15μm (height) × 20μm (width) × 100μm (length)

(With an inter-bump gap of 18 μm, 1000 gold bumps are arranged along the longitudinal direction of the IC at each end in the width direction of the IC. The distance between the gold bumps is 1000 μm.)

FIG10 is a plan view of an evaluation IC 100 viewed from the side with bumps formed. Reference numeral 101 denotes a bump, and G denotes the gap between bumps. Reference numeral 102 denotes the distance between the bumps. Regions A and B enclosed by dashed lines correspond to the within-specification area of the anisotropic conductive film, while region C sandwiched between them corresponds to the non-specification area of the anisotropic conductive film (an area without conductive particles). Reference numeral V denotes the distance between the short-side edge of the IC chip and the end of the bump.

(Glass substrate)

Glass material: CORNING 1737F

Appearance: 30mm×50mm

Thickness 0.5mm

Terminal ITO wiring

(Evaluation Criteria)

For the tested connection structures, those with an initial on-resistance of 2Ω or less for all terminals and an on-resistance of 5Ω or less after the conduction reliability test were rated "good." Those with other resistances (even if there was a single bump outside these ranges) were rated "poor." The results are shown in Table 3.

As shown in Table 3, the connection structures produced using the three types of anisotropic conductive films in Examples 1 to 4 had good conduction characteristics. However, in Comparative Example 1, the within-specification area was too small, so the conduction characteristics were evaluated as poor.

Furthermore, it was found that even if a portion of the terminal contains an omission region, as long as the number of conductive particles captured by the terminal is at least 10, preferably at least 13, there is no problem in practical use. The omission region can also be located within the terminal arrangement, but it was also found that the degree of this varies depending on the terminal area, so appropriate adjustments can be made (Example 4). Based on the above examples, it was found that the proportion of the in-spec region of the film width should be at least 13%, preferably at least 20%, and even more preferably at least 33%.

<Fabrication of FOG Transfer Master, FOG Film Master, and FOG-compatible Anisotropic Conductive Film>

By replacing the insulating resin adhesive in Table 1 with the adhesive in Table 4 and repeating the COG-compatible anisotropic conductive film production process, except for selecting conditions that resulted in the conductive particles being left out, FOG transfer masters, FOG film masters, and finally anisotropic conductive films (ACF5 to ACF8 (see Table 5)) were produced, each with conductive particles embedded in the configuration shown in Figure 8. In this case, the embedding state of the conductive particles was controlled by the press-in conditions. As shown in Table 5, recesses were observed around the exposed portions of the embedded conductive particles or directly above them. This was confirmed before laminating with insulating adhesive D. Furthermore, ACF8 failed to maintain its film shape during press-in of the conductive particles. Therefore, it was determined that ACF5 to ACF7 are suitable for FOG applications.

Furthermore, for ACFs 5 to 7, images acquired with a CCD image sensor were observed using image analysis software (WinROOF, Mitani Shoji Co., Ltd.) to confirm the absence of conductive particles. The results revealed a state where at least 10 conductive particles were consistently absent within 200 μm in the film's longitudinal direction (the width of the terminal) (Example 5), and a state where only 1 to 2 conductive particles were absent (Comparative Example 2).

[Table 4]

[Table 5]

(Fabrication of anisotropic conductive film for FOG to prevent the loss of conductive particles)

Next, a set of five anisotropic conductive films (ACF5-7) cut into 20 x 30 cm pieces were cut into 2 mm widths. Five randomly selected locations (a total of 25 locations across the five pieces) were used to prepare an anisotropic conductive film for Example 5, in which at least 10 conductive particles were present within a 20 mm region of the film (200 μm in the longitudinal direction of the film (the width of the terminal). The same procedure was repeated, except that only one or two conductive particles were present in each region, to prepare an anisotropic conductive film for Comparative Example 2.

<Evaluation 2 (in the case of FOG)>

The following experiments/evaluations were conducted on the conductive properties (initial conductivity and conductivity reliability) of connection structures obtained by performing FOG connection using the three types of anisotropic conductive films produced in Example 5 and Comparative Example 2, respectively.

(Initial continuity)

As electronic components for FOG connections, the following evaluation FPCs and glass substrates were used. The anisotropic conductive film to be evaluated was cut and clamped so that 25 randomly selected locations were positioned between the evaluation FPCs and the glass substrates. Heat and pressure were applied (180°C, 4.5 MPa, 5 seconds) to produce each evaluation connection. In this case, the connection was made so that the long side of the anisotropic conductive film aligned with the short side of the bumps. The resulting connection structure was measured for on-resistance using a digital multimeter (34401A, AGILENT TECHNOLOGIES Co., Ltd.) using the four-terminal method (JIS K7194). For practical use, a value of 2Ω or less is ideal.

(Conduction reliability)

The connected structure subjected to the initial on-resistance measurement was placed in a thermostatic chamber at 85°C and 85% humidity for 500 hours, and the on-resistance was measured again. For practical use, a resistance of 5Ω or less is preferred.

(Evaluation FPC)

8μm thick, 400μm pitch Cu wiring (L/S=200/200) was formed on a 38μm thick polyimide substrate with tin plating.

(Glass substrate)

Glass material: CORNING 1737F

Appearance: 30mm×50mm

Thickness 0.5mm

Terminal ITO wiring

(Evaluation results)

The connection structures tested were evaluated as "good" if their initial on-resistance was 2Ω or less and their on-resistance after the on-resistance reliability test was 5Ω or less; otherwise, they were evaluated as "poor." The results showed that the connection structures fabricated using the three anisotropic conductive films of Example 5 had good on-resistance. On the other hand, the connection structure fabricated using the anisotropic conductive film of Comparative Example 2 had an out-of-specification region within the regular arrangement region compared to Example 5, resulting in a poor on-resistance evaluation.

Industrial applicability

The anisotropic conductive film of the present invention has conductive particles regularly arranged within a regular arrangement region of an insulating resin adhesive, with a length of at least 5 m. Furthermore, within the regular arrangement region, there are no areas within the specification where more than a predetermined number of conductive particles are continuously omitted. Furthermore, the anisotropic conductive film has a predetermined width in the short direction of the anisotropic conductive film and a predetermined length in the long direction of the anisotropic conductive film. Therefore, even if there are omissions in the regular arrangement of conductive particles, the film can be used for anisotropic conductive connection in much the same way as an anisotropic conductive film without omissions. The film is useful as a low-cost bonding member for anisotropic conductive connections.

Label Description

1. 1A, 1B, 1C anisotropic conductive film; 1P the end of the width in the short side direction of the anisotropic conductive film; 2. 2a, 2b, 2c, 2d conductive particles; 2t the top of the conductive particles; 2X the omission of conductive particles; 2Y the omission of the continuous portion; 3 insulating resin adhesive; 3a the surface of the insulating resin adhesive in the center between adjacent conductive particles; 3b, 3c recessed portions; 3p the tangent plane; 4 insulating adhesive layer; 5 repeating unit; 10 bumps, terminals; 11 terminal array; 12 electronic components; D the average particle size of the conductive particles; L1 the lattice axis; La the thickness of the insulating resin adhesive; Q the area within the specifications; R the area including the parts outside the specifications; S any area.

Claims (15)

1. An anisotropic conductive film having a length of 5 m or more, comprising a regularly arranged region in which conductive particles are regularly disposed in an insulating resin adhesive, wherein within this regularly arranged region there is no region with a predetermined number or more of continuously missing conductive particles, and the anisotropic conductive film has a predetermined width in the short side direction and a predetermined length or more in the long side direction. A continuous omission of a predetermined number of conductive particles refers to an omission of conductive particles at a level that would pose a problem in practical use. Within the specified area, there are locations where continuous omissions in the membrane length direction and continuous omissions in the membrane width direction are combined by a number of omissions that is less than the predetermined number. 2. The anisotropic conductive film as claimed in claim 1, wherein the regularly configured region is consistent with the region within the specification. 3. The anisotropic conductive film as described in claim 1, wherein there are out-of-specification portions where a predetermined number or more conductive particles are continuously missing. 4. The anisotropic conductive film as described in claim 1, wherein, in a region arbitrarily selected along the long side direction of 200 μm across the full width of the anisotropic conductive film, there are more than 10 conductive particles. 5. The anisotropic conductive film as claimed in claim 1, wherein at least the end region along the short side direction of the anisotropic conductive film has an in-specification region. 6. The anisotropic conductive film as claimed in claim 1, wherein an insulating adhesive layer is laminated on the insulating resin adhesive on which the conductive particles are disposed. 7. The anisotropic conductive film according to any one of claims 1 to 6, wherein the anisotropic conductive film is a roll wound onto a spool. 8. A method for manufacturing an anisotropic conductive film, comprising cutting a wide roll of an anisotropic conductive film in which conductive particles are regularly arranged in an insulating resin adhesive along its length, either in a manner that excludes any portion of conductive particles that is continuously omitted from the regular arrangement or in a manner that positions the portion of the non-standard particles at a desired location along the short side of the film, to produce an anisotropic conductive film with a length of 5 m or more. A continuous omission of a predetermined number of conductive particles refers to an omission of conductive particles at a level that would pose a problem in practical use. Within the specified area, there are locations where continuous omissions in the membrane length direction and continuous omissions in the membrane width direction are combined by a number of omissions that is less than the predetermined number. 9. A method for manufacturing an anisotropic conductive film, comprising: removing portions of an anisotropic conductive film from which conductive particles are regularly arranged in a symmetrical configuration region having an insulating resin adhesive; bonding the removed anisotropic conductive film to form an anisotropic conductive film with a length of 5 m or more. The continuous omission of a predetermined number of conductive particles refers to the omission of conductive particles at a level that would cause problems in practical use. 10. A method for manufacturing a connecting structure, wherein the connecting structure is press-fitted with a first electronic component having terminal rows and a second electronic component having terminal rows via an anisotropic conductive film, thereby anisotropically conductively connecting the terminal rows of the first electronic component and the second electronic component to each other, wherein the anisotropic conductive film has a dimensionally configured area in which conductive particles are regularly arranged in an insulating resin adhesive, wherein... As an anisotropic conductive film, it is used in a region within a specification where there is no continuous omission of a predetermined number of conductive particles within the specified configuration area. The anisotropic conductive film is formed with a predetermined width in the short side direction and a predetermined length in the long side direction. A continuous omission of a predetermined number of conductive particles refers to an omission of conductive particles at a level that would pose a problem in practical use. Align this area within the specification with the terminal blocks of the electronic components. Within the specified area, there are locations where continuous omissions in the membrane length direction and continuous omissions in the membrane width direction are combined by a number of omissions that is less than the predetermined number. 11. The method for manufacturing a connecting structure as claimed in claim 10, wherein, When the first electronic component and the second electronic component each have multiple terminal rows, and these are formed side-by-side within a specified region in an anisotropic conductive film, Align the area between adjacent specification areas with the area between terminal rows. 12. A connection structure for anisotropically conductively connecting a first electronic component and a second electronic component via an anisotropic conductive film as described in any one of claims 1 to 6. 13. A method for manufacturing a connecting structure, wherein a first electronic component and a second electronic component are anisotropically electrically connected by an anisotropic conductive film as described in any one of claims 1 to 6. 14. A method for manufacturing an anisotropic conductive film, comprising cutting a wide roll of an anisotropic conductive film in which conductive particles are regularly arranged in an insulating resin adhesive, such that it does not contain any portions of conductive particles that are continuously omitted from the regular arrangement, or in such a way that the portions of the non-standard arrangement are located at a desired position in the short side direction of the film, to produce an anisotropic conductive film with a length of 5 m or more. A continuous omission of a predetermined number of conductive particles refers to an omission of conductive particles at a level that would pose a problem in practical use. The anisotropic conductive film has an insulating adhesive layer laminated on the insulating resin adhesive on which the conductive particles are disposed. Within the specified area, there are locations where continuous omissions in the membrane length direction and continuous omissions in the membrane width direction are combined by a number of omissions that is less than the predetermined number. 15. A method for manufacturing an anisotropic conductive film, comprising: removing portions of an anisotropic conductive film from which conductive particles are regularly arranged in a symmetrical configuration region having an insulating resin adhesive; bonding the removed anisotropic conductive film to form an anisotropic conductive film with a length of 5 m or more. The continuous leakage of conductive particles exceeding a predetermined number refers to the leakage of conductive particles at a level that would cause problems in practical use. The anisotropic conductive film has an insulating adhesive layer laminated on top of the insulating resin adhesive containing the conductive particles. Within the specified area, there are locations where continuous omissions in the membrane length direction and continuous omissions in the membrane width direction are combined by a number of omissions that is less than the predetermined number.