Anisotropic conductive film, bonding method using same, and bonded body

Abstract

To provide an anisotropic conductive film which facilitates production, enables long-term storage, does not have an adverse impact on the peripheral environment, and can efficiently connect a terminal of an electronic component in a short time.SOLUTION: An anisotropic conductive film is composed of a single layer film or a multilayer film, wherein all the layers constituting the anisotropic conductive film contain polyolefin having crystallinity; at least one layer constituting the anisotropic conductive film is composed of a resin composition in which conductive particles are dispersed in the polyolefin; and the polyolefin contained in the layer arranged on the outermost layer is modified polyolefin including a monomer unit having at least one functional group selected from the group consisting of an anhydrous carboxylic acid group, a carboxyl group, an epoxy group and a hydroxyl group.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an anisotropic conductive film for connecting circuit boards having a plurality of opposing terminals and a method for manufacturing the same. The present invention also relates to a film roll formed by winding the anisotropic conductive film and a method for storing the same. The present invention also relates to an electronic component having an anisotropic conductive film fixed to a terminal and a method for storing the same. Furthermore, the present invention also relates to a connection method and a bonded body using the anisotropic conductive film. [Background technology]

[0002] Anisotropic conductive films (ACFs) are functional adhesive materials that have undergone technological advances in step with the miniaturization of circuit boards. When connecting circuit boards with multiple opposing terminals, applying heat and pressure through the ACF allows electrical connection between the opposing terminals while maintaining insulation between adjacent terminals. ACFs are essentially films with conductive particles dispersed in an insulating resin. Figure 1 is a schematic diagram showing an assembly 10 formed by joining circuit boards 2 and 2' using ACF 1. A metal terminal 3 on circuit board 2 and a metal terminal 3' on circuit board 2' are electrically connected via conductive particles 4. Meanwhile, insulating resin 5 is present between the conductive particles 4, maintaining insulation between adjacent terminals. Since its commercialization in 1977, ACFs have been widely used in fields such as flat panel displays, and considerable research has been conducted to address the need for fine-pitch connections, which is required for increasingly high-resolution displays.

[0003] Anisotropic conductive films currently available on the market can be broadly divided into two types: those based on epoxy resin and those based on (meth)acrylate resin. Both resins are thermosetting resins that harden when heated. When epoxy resins are used, anionic ring-opening polymerization using an imidazole-based curing agent has traditionally been used, but in recent years, ring-opening polymerization using cationic species has often been used. On the other hand, when (meth)acrylate resins are used, peroxides are used as radical initiators to add-polymerize double bonds. In either case, the curing conditions are 130 to 170°C for approximately 5 seconds (see, for example, Patent Documents 1 to 3).

[0004] However, when using such thermosetting resins, the film contains a resin with reactive functional groups and a curing agent to harden it. Therefore, the curing reaction proceeds slowly even at room temperature or below, rendering the product unusable after a certain period of time. Anisotropic conductive films, which can be cured at relatively low temperatures and in a short time, are typically stored at temperatures below 5°C and have a warranty period of five months after manufacture. They are also shipped refrigerated, resulting in significant costs, including temperature control during transportation. Furthermore, temperature control is required by the customer, and quality issues can occur due to condensation upon opening, necessitating the limitations and strict management required by thermosetting resins.

[0005] Patent Document 4 describes an anisotropic conductive film containing a crystalline resin, an amorphous resin of the same type, and conductive particles. The inclusion of the crystalline resin is said to enable bonding in a short time due to crystallization upon cooling. Furthermore, since the film does not contain a curing agent and the resin does not crosslink during the curing reaction, the anisotropic conductive film is said to be able to be stored for a long period of time. The anisotropic conductive film in Patent Document 4 is manufactured by applying a varnish containing the above-mentioned raw materials to a substrate film. The inclusion of the same amorphous resin is said to result in a smooth anisotropic conductive film. DSC measurement of the anisotropic conductive film indicates that a crystallinity level of approximately 1.0 to 6.0 J / g is preferable when the heat generated during cooling is approximately 1.0 to 6.0 J / g. In the examples of Patent Document 4, an anisotropic conductive film is obtained by dissolving a crystalline polyester resin, an amorphous polyester resin, and a polyurethane elastomer in a solvent, dispersing silver-plated resin particles in the solution, applying the solution to a PET film, and drying the solution. The anisotropic conductive film is then heated at 120°C and 2 MPa for 3 seconds and pressed to obtain a bonded assembly. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 9-115335 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-320455 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-111092 [Patent Document 4] Japanese Patent Application Laid-Open No. 2014-60025 Summary of the Invention [Problem to be solved by the invention]

[0007] When a thermosetting resin such as those described in Patent Documents 1 to 3 is used, the storage stability of the anisotropic conductive film is insufficient. On the other hand, in the case of an anisotropic conductive film using a crystalline resin such as that described in Patent Document 4, although the storage stability problem can be solved, the time required for connection is still insufficient, and further speed-up is required. Furthermore, the anisotropic conductive films described in Patent Documents 1 to 4 all have complicated manufacturing processes, and the use of organic solvents during production raises concerns about adverse effects on the surrounding environment. Therefore, an anisotropic conductive film that solves these problems has been desired. [Means for solving the problem]

[0008] The present invention provides an anisotropic conductive film consisting of a single-layer film or a multilayer film, wherein all layers constituting the anisotropic conductive film contain a crystalline polyolefin, at least one layer constituting the anisotropic conductive film is made of a resin composition in which conductive particles are dispersed in the polyolefin, and the polyolefin contained in the layer arranged as the outermost layer is a modified polyolefin containing a monomer unit having at least one functional group selected from the group consisting of a carboxylic acid anhydride group, a carboxyl group, an epoxy group, and a hydroxyl group.

[0009] In this case, the polyolefin contained in all the layers preferably has a crystallization enthalpy (ΔHc) of 20 to 200 J / g when measured with a differential scanning calorimeter (DSC) at a temperature decrease rate of 10°C / min. It is also preferable that the polyolefin is polypropylene or polyethylene. It is also preferable that the modified polyolefin contains 0.01 to 2 mol% of the monomer unit having the functional group relative to the total monomer units. An anisotropic conductive film formed by melt extrusion is also a preferred embodiment of the present invention.

[0010] In a preferred embodiment, the anisotropic conductive film is a single-layer film, and the single-layer film is made of a resin composition in which conductive particles are dispersed in the modified polyolefin.

[0011] In another preferred embodiment, the anisotropic conductive film is a two-layer film, one layer of which is made of a resin composition in which conductive particles are dispersed in the modified polyolefin, and the other layer of which is made of a resin containing the modified polyolefin but not containing conductive particles.

[0012] In another preferred embodiment, the anisotropic conductive film is a three-layer or more film consisting of one or more inner layers and two outer layers, at least one inner layer being made of a resin composition in which conductive particles are dispersed in the polyolefin, and both outer layers being made of a resin containing the modified polyolefin but not containing conductive particles. In this case, it is preferable that the polyolefin contained in at least one of the inner layers is an unmodified polyolefin that does not contain a monomer unit having the functional group.

[0013] When the anisotropic conductive film is a two-layer film or a three-layer or more film, an anisotropic conductive film formed by melt co-extrusion is a preferred embodiment of the present invention.

[0014] The anisotropic conductive film is preferably produced by melt extrusion molding at a temperature exceeding the melting points (Tm) of all the polyolefins contained in the film.

[0015] A preferred embodiment of the present invention is a film roll formed by winding the anisotropic conductive film without a support film. A preferred embodiment of the present invention is also a film roll formed by winding a multilayer structure including the anisotropic conductive film and a support film. Furthermore, a preferred embodiment of the present invention is also a method for storing the film roll, characterized in that the film roll is stored at a temperature of 15°C or higher for one month or more.

[0016] A preferred embodiment of the present invention is a connection method for anisotropically conductively connecting terminals of a first electronic component and a second electronic component, the connection method comprising the steps of: a placement step of placing the anisotropic conductive film between the two terminals; a melting step of heating the polyolefin while pressing it from one terminal side with a heating and pressing member to melt the polyolefin; a cooling step of cooling the polyolefin while continuing the pressing; and a depressurizing step of releasing the pressing force, in this order. In this case, it is preferable that in the placement step, the anisotropic conductive film is fixed to one terminal before the other terminal is placed.

[0017] Furthermore, a preferred embodiment of the present invention is a joined body comprising a first electronic component having a terminal, a second electronic component having a terminal, and a molten and solidified anisotropic conductive film interposed between the first electronic component and the second electronic component to electrically connect both terminals, wherein the anisotropic conductive film is the anisotropic conductive film described above.

[0018] Furthermore, a preferred embodiment of the present invention is an electronic component having the above-mentioned anisotropic conductive film fixed to a terminal, the terminal not being electrically connected to the terminal of another electronic component, and storing the electronic component at a temperature of 15°C or higher for one month or more. [Effects of the Invention]

[0019] The anisotropic conductive film of the present invention is easy to manufacture and can be stored for a long period of time. Furthermore, the manufacturing method of the present invention allows the anisotropic conductive film to be easily manufactured without adversely affecting the surrounding environment. Furthermore, the connection method of the present invention allows the terminals of electronic components to be connected efficiently in a short time. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a cross-sectional view showing a bonded body 10 in which circuit boards 2 and 2' are bonded together using an anisotropic conductive film 1. FIG. [Figure 2] 1 is a cross-sectional view of an anisotropic conductive film 1 having a single layer structure obtained in Example 1. FIG. [Figure 3] 1 is a cross-sectional view of a two-layer anisotropic conductive film 1 obtained in Example 3. FIG. [Figure 4] 1 is a cross-sectional view of an anisotropic conductive film 1 having a three-layer structure obtained in Example 4. FIG. [Figure 5] FIG. 1 shows a state in which an anisotropic conductive film 1 is placed on a terminal 7, and a Ni plate 8 is further placed on top of that, when measuring connection resistance. [Figure 6] FIG. 1 is a diagram showing a state in which a terminal 7 and a Ni plate 8 are joined using an anisotropic conductive film 1 when measuring connection resistance. [Figure 7] FIG. 7 is a schematic cross-sectional view taken along the line AA′ in FIG. [Figure 8] FIG. 10 is a diagram showing a method for measuring the resistance between adjacent terminals 7' located on opposite sides of the joint. DETAILED DESCRIPTION OF THE INVENTION

[0021] The anisotropic conductive film of the present invention is an anisotropic conductive film consisting of a single-layer film or a multilayer film, and all of the constituent layers contain a crystalline polyolefin. This allows for quick and easy bonding of terminals of electronic components by crystallizing the heated and molten resin as it cools. Furthermore, since the resin shrinks during crystallization, a force acts to draw the opposing terminals closer together, sandwiching conductive particles between the terminals and securing them in a secure contact state.

[0022] The polyolefin contained in all the layers preferably has a crystallization enthalpy (ΔHc) of 20 to 200 J / g when measured with a differential scanning calorimeter (DSC) at a temperature drop rate of 10°C / min. If ΔHc is small, the shrinkage rate associated with crystallization decreases and the crystallization rate also decreases, making connection failure more likely to occur and reducing productivity. ΔHc is more preferably 30 J / g or more, and even more preferably 40 J / g or more. The crystallization enthalpy (ΔHc) is calculated from the area of ​​the exothermic peak observed when the resin is melted using a differential scanning calorimeter (DSC) and then cooled at a temperature drop rate of 10°C / min. A more specific measurement method is as described in the examples.

[0023] Polyolefins have a low dielectric constant, which is advantageous because it can reduce signal transmission loss when transmitting high-frequency electrical signals. This tendency becomes particularly pronounced as the frequency increases, and this will become increasingly important as digital technology advances. Furthermore, while many conventional anisotropic conductive films use thermosetting resins, which have had problems with storage stability, this film does not have this problem. The anisotropic conductive film of the present invention does not require a chemical reaction during bonding and does not contain a curing agent, so it can be stored at room temperature for long periods of time.

[0024] The crystalline polyolefin used in the present invention is preferably polypropylene or polyethylene. Here, polypropylene refers to a polymer containing more than 50% by mass of propylene units, and polyethylene refers to a polymer containing more than 50% by mass of ethylene units. Polyethylene and polypropylene may be copolymerized with a comonomer. Examples of such comonomers include α-olefins other than ethylene and propylene, vinyl esters such as vinyl acetate, vinyl chloride, unsaturated carboxylic acids such as (meth)acrylic acid, unsaturated carboxylic acid esters such as methyl (meth)acrylate, and unsaturated carboxylic anhydrides such as maleic anhydride. Furthermore, polypropylene may be copolymerized with ethylene, and polyethylene may be copolymerized with propylene. The form of copolymerization is also not limited, and may be any of random copolymerization, block copolymerization, and graft copolymerization.

[0025] The melting point (Tm) of the polyolefin is preferably 100 to 180°C. If the melting point is too low, the heat resistance of the resulting bonded body will decrease, and the crystallinity will also decrease. The melting point is more preferably 110°C or higher, and even more preferably 120°C or higher. On the other hand, if the melting point is too high, high temperatures will be required for bonding, which may increase the elongation of the base material forming the electrical circuit, causing pitch misalignment between terminals and may also have a thermally adverse effect on the electrical circuit. The melting point is more preferably 170°C or lower. The melting point (Tm) is the temperature at the apex of the endothermic peak observed when heating at a rate of 10°C / min (second run) using a differential scanning calorimeter (DSC). More specific measurement methods are as described in the Examples.

[0026] At least one layer constituting the anisotropic conductive film of the present invention is made of a resin composition in which conductive particles are dispersed in polyolefin. The conductive particles are sandwiched between two opposing terminals and come into contact with each other, thereby electrically connecting the two terminals. Meanwhile, the presence of polyolefin between the conductive particles prevents conduction between adjacent terminals connected to the same electronic component.

[0027] The conductive particles used in the present invention may be metal powder, metal-plated resin particles, carbon fiber, etc. Metal powders have an electrical resistivity of 1×10 at 20° C. -4 Metal powders with a resistivity of less than Ω·cm are preferred, including powders of silver (Ag), copper (Cu), nickel (Ni), palladium (Pd), tungsten (W), tin (Sn), and alloys containing these metals.

[0028] When metal-plated resin particles are used as conductive particles, spherical particles synthesized by emulsion polymerization or suspension polymerization can be used as the resin particles. Among them, monodisperse particles produced by seed polymerization are preferably used. Resin particles after polymerization can also be classified and used. Various resins can be used, such as acrylic resin, styrene resin, divinylbenzene resin, benzoguanamine resin, and epoxy resin. Metals used for plating include various metals that can be electrolessly plated on plastic, such as silver (Ag), copper (Cu), nickel (Ni), gold (Au), tungsten (W), and palladium (Pd). Preferably, the electrical resistivity at 20°C is 1×10 -4 Metals with a resistance less than Ω·cm are used.

[0029] The conductive particles preferably have a particle size (diameter) of 1 to 30 μm, and can be selected appropriately depending on the terminal dimensions, application, etc. If the particle size is too small, there is a risk of variations in connection reliability between terminals. The particle size is more preferably 1.5 μm or more, and even more preferably 2 μm or more. On the other hand, if the particle size is too large, it becomes difficult to arrange the particles between terminals, and there is a risk of reduced connection reliability; this tendency becomes more pronounced as the terminal dimensions become smaller. The particle size is more preferably 20 μm or less, and even more preferably 10 μm or less.

[0030] The preferred amount of conductive particles in the resin composition is 1 to 50% by mass, and is adjusted as appropriate depending on the terminal dimensions, application, etc. The preferred amount of particles differs between metal powder and metal-plated resin particles. If the particle content is too low, it may be difficult to arrange the particles between terminals, which may result in reduced connection reliability. In the case of metal powder, the content is more preferably 3% by mass or more, and even more preferably 5% by mass or more. In the case of metal-plated resin particles, the content is more preferably 2% by mass or more, and even more preferably 2.5% by mass or more. If the particle content is too high, there is a risk of short-circuiting between adjacent terminals. In the case of metal powder, the content is more preferably 30% by mass or less, and even more preferably 20% by mass or less. In the case of plated resin particles, the content is more preferably 20% by mass or less, and even more preferably 10% by mass or less.

[0031] A resin composition in which conductive particles are dispersed in a polyolefin can be produced by melt-kneading the two. Various melt-kneading means such as a twin-screw extruder, a single-screw extruder, a kneader, or a Banbury mixer can be used, but a twin-screw extruder is preferred because it allows for uniform dispersion. The temperature during melt-kneading is set to a temperature higher than the melting point (Tm) of the polyolefin. In this case, it is preferable to set the temperature 10 to 150°C higher than Tm. The resin composition after melt-kneading is preferably pelletized and then subjected to the subsequent molding process.

[0032] In the anisotropic conductive film of the present invention, the polyolefin contained in the layer disposed as the outermost layer is a modified polyolefin containing a monomer unit having at least one functional group selected from the group consisting of a carboxylic anhydride group, a carboxyl group, an epoxy group, and a hydroxyl group. When the anisotropic conductive film has a single-layer or two-layer structure, all layers correspond to the outermost layer, and when it has a three-layer structure, both outer layers except the middle layer correspond to the outermost layer. In other words, the layer having the surface that will come into direct contact with the terminal during bonding is the outermost layer. When the polyolefin contained in the layer disposed as the outermost layer is a modified polyolefin, good adhesion between the terminal and the anisotropic conductive film is obtained.

[0033] The modified polyolefin contains a monomer unit having at least one functional group selected from the group consisting of a carboxylic acid anhydride group, a carboxyl group, an epoxy group, and a hydroxyl group. These functional groups contribute to providing good adhesion to metal materials. Examples of monomers having a carboxylic acid anhydride group include maleic anhydride and itaconic anhydride, with maleic anhydride being particularly preferred. Polyolefins graft-polymerized with maleic anhydride are ideal. Examples of monomers having a carboxyl group include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, and unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid. Some or all of the carboxyl groups in the modified polyolefin may form metal salts, such as sodium salts or zinc salts. Examples of monomers having an epoxy group include glycidyl acrylate and glycidyl methacrylate. Examples of monomer units having a hydroxyl group include vinyl alcohol units. Vinyl alcohol units can be obtained by copolymerizing vinyl acetate and then saponifying the copolymer.

[0034] The modified polyolefin preferably contains 0.01 to 2 mol % of the monomer units having the functional group relative to the total monomer units. By containing a certain amount or more of the monomer units having the functional group, good adhesion to metal terminals can be achieved. If the content of the monomer units is too low, adhesion may be reduced. The content of the monomer units is more preferably 0.02 mol % or more, and even more preferably 0.05 mol % or more. On the other hand, if the content of the monomer units is too high, the melting point and crystallinity may decrease, which may result in reduced heat resistance and reduced electrical conductivity of the bonded product. The content of the monomer units is more preferably 1 mol % or less, and even more preferably 0.5 mol % or less. In the case of a layer made of a resin composition containing an unmodified polyolefin and a modified polyolefin, the monomer units having the functional group relative to the total monomer units of both polyolefins may be contained in the above-mentioned ratio.

[0035] The total thickness of the anisotropic conductive film of the present invention is adjusted depending on the terminal dimensions and application, and is not particularly limited, but is preferably 10 to 100 μm. If the film thickness is less than 10 μm, handling of the film becomes difficult, making it difficult to stably produce a homogeneous film. The film thickness is more preferably 15 μm or more, and even more preferably 20 μm or more. On the other hand, if the film thickness exceeds 100 μm, a large amount of polyolefin must be flowed in the joining process, which may result in poor connection. The film thickness is more preferably 80 μm or less, and even more preferably 60 μm or less.

[0036] In a preferred embodiment of the present invention, the anisotropic conductive film is a single-layer film. The single-layer film is made of a resin composition in which conductive particles are dispersed in a modified polyolefin. Because of its simple layer structure, it is easy to manufacture. Furthermore, it is suitable when the wiring thickness of both terminals to be joined is small and the difference in level with the substrate is small.

[0037] In another preferred embodiment of the present invention, the anisotropic conductive film is a two-layer film. One layer is made of a resin composition in which conductive particles are dispersed in a modified polyolefin, and the other layer is made of a resin containing the modified polyolefin but not containing conductive particles. By including conductive particles only in one layer, it is possible to achieve uniform distribution in the plane direction even with a small absolute amount of conductive particles. This film is suitable for use when the layer containing conductive particles contacts a terminal with a thin wiring thickness and a small step with the substrate, and the layer not containing conductive particles contacts a terminal with a thick wiring thickness and a large step with the substrate. For example, this film is suitable for connecting a display substrate having a thin-film transparent electrode such as ITO formed on a glass substrate to a flexible flat cable having a relatively thick copper wire electrode.

[0038] In another preferred embodiment of the present invention, the anisotropic conductive film is a film with three or more layers. It is composed of one or more inner layers and two outer layers, with at least one inner layer made of a resin composition in which conductive particles are dispersed in polyolefin, and both outer layers made of a resin containing modified polyolefin but not conductive particles. By including conductive particles only in the inner layer, it is possible to achieve uniform distribution in the surface direction even if the absolute amount of conductive particles is reduced. This is suitable when the wiring thickness of both terminals to be joined is large and there is a large difference in level with the substrate. By including modified polyolefin in the two outer layers, adhesion to the terminals is improved.

[0039] In this case, it is preferable that the polyolefin contained in at least one of the inner layers is an unmodified polyolefin that does not contain a monomer unit having the functional group. Generally, unmodified polyolefins have higher crystallinity and a faster crystallization rate than modified polyolefins, allowing for faster and greater shrinkage during bonding, thereby improving connection reliability. Furthermore, unmodified polyolefins are less expensive, which is effective in reducing costs, and there is no problem with the adhesion between the layer containing the modified polyolefin and the layer containing the unmodified polyolefin. For example, in the case of a three-layer film, it is preferable that the inner layer is made of a resin composition containing unmodified polyolefin and conductive particles.

[0040] The anisotropic conductive film of the present invention is preferably produced by melt extrusion molding. Furthermore, when the anisotropic conductive film of the present invention is a multilayer film, it is preferably produced by melt coextrusion molding. Conventional anisotropic conductive films are produced by dissolving a thermosetting resin in an organic solvent, dispersing conductive particles in a varnish, applying the varnish to a substrate film, and then drying the varnish. However, this method complicates the production process, and the use of organic solvents raises concerns about adverse effects on the surrounding environment. In contrast, the anisotropic conductive film of the present invention can be produced by melt extrusion molding, which simplifies the production process and eliminates the risk of adverse effects on the surrounding environment. Furthermore, while conventional methods have made it difficult to produce multilayer films, the present invention employs melt coextrusion molding, making it possible to easily produce multilayer films.

[0041] When producing the anisotropic conductive film of the present invention, melt extrusion is preferably performed at a temperature exceeding the melting point (Tm) of all polyolefins contained in the film. In this case, melt extrusion is more preferably performed at a temperature 10 to 150°C higher than the melting point (Tm). A film can be continuously produced by melting the raw resin in an extruder and extruding it through a T-die. Alternatively, the raw resin can be melted in an extruder and then extruded through a cylindrical die for inflation molding. Furthermore, a multilayer film can be easily produced by extruding it through a T-die using multiple extruders. In this case, a feedblock method in which the layers are joined before the T-die or a multi-manifold method in which the layers are joined within the T-die can be employed. The surface of the anisotropic conductive film thus obtained may be modified by corona treatment or plasma treatment to improve adhesion to terminals.

[0042] The anisotropic conductive film thus obtained is slit to a specified width using a slitter. The film width is adjusted depending on the dimensions of the terminals to be connected, etc. The film width is usually 0.5 to 20 mm. If the film width is too narrow, it becomes difficult to handle. The film width is preferably 1 mm or more, and more preferably 1.5 mm or more. On the other hand, if the film width is too wide, it becomes difficult to connect terminals in a narrow area. The film width is preferably 10 mm or less, and more preferably 5 mm or less. The slit film is taken up into a roll. Because the film width is narrow, it is preferable to wind it around a core with a flange that corresponds to its width.

[0043] The anisotropic conductive film of the present invention contains polyolefin as a main component, so it does not stick to other films and has sufficient strength on its own. Therefore, it does not require a support film as in the past. A preferred embodiment of the present invention is a film roll formed by winding the anisotropic conductive film without a support film. In this form, it can be transported and stored for long periods at room temperature.

[0044] On the other hand, a film roll formed by winding a multilayer structure including the anisotropic conductive film and a support film is also a preferred embodiment. As mentioned above, although a support film is not necessarily required to produce the anisotropic conductive film in the present invention, many current production processes use bonding devices that assume the presence of a support film. Therefore, a support film is required to use the anisotropic conductive film of the present invention without modifying such bonding devices. In this case, laminating the anisotropic conductive film with the support film allows it to be used with conventional bonding devices. Furthermore, when the anisotropic conductive film is thin, the presence of a support film can improve its handleability. In this case, the anisotropic conductive film can be attached to the support film by extrusion coating directly onto the support film from a T-die. Alternatively, an anisotropic conductive film layer and a base film layer with low adhesive strength can be co-extruded. Alternatively, the anisotropic conductive film can be attached to the support film via a temporary adhesive.

[0045] Such a film roll of the present invention can be stored for one month or more at a temperature of 15° C. or higher. The storage temperature may be 20° C. or higher, or 25° C. or higher. The storage period may be two months or more, six months or more, or one year or more.

[0046] A preferred embodiment of the present invention is a connection method for anisotropically conductively connecting a terminal of a first electronic component and a terminal of a second electronic component, characterized in that the connection method comprises, in this order: a placement step of placing the anisotropic conductive film between the two terminals; a melting step of heating and pressing from one terminal side with a heating and pressing member to melt the polyolefin; a cooling step of cooling while continuing to press; and a depressurizing step of releasing the pressure.

[0047] In the placement step, the anisotropic conductive film is placed between both terminals, and the terminals to be connected are aligned so that they overlap. In the melting step, the polyolefin is melted by heating while being pressed from one terminal side with a heating and pressing member. In order to reduce the thermal impact on the electronic component and melt it in a short time, it is preferable to heat the resin in a spot for a short time using a pulse heat press. It is preferable that the maximum temperature of the molten resin is 10 to 100°C higher than the melting point (Tm) of the polyolefin. Furthermore, the time from the start of heating to the end of heating is preferably 5 seconds or less, more preferably 3 seconds or less. The pressure is usually 0.5 to 20 MPa.

[0048] In the cooling process, the resin is cooled while the pressure is continued. By continuing the pressure during cooling, the resin can be solidified while maintaining electrical connection between the terminals and the conductive particles. Following the cooling process, a decompression process is performed in which the pressure is released. Here, releasing the pressure is referred to as press-out. The lower the resin temperature during press-out, the more reliably the terminals can be connected. On the other hand, the higher the press-out temperature, the shorter the press-out time, which shortens the cooling process and improves production efficiency. Even if the press-out temperature exceeds the melting point (Tm) of the resin, the subsequent shrinkage caused by crystallization of the resin allows for connection of the terminals (Example 5). This is an advantage derived from the crystallinity of polyolefins. It was confirmed that when an amorphous resin is used, poor connection occurs even when the resin is cooled to a temperature lower than the deflection temperature under load (Comparative Example 2). From the viewpoint of reliable terminal connection, the press-out temperature is preferably Tm+20°C or lower, more preferably Tm or lower, and even more preferably Tm-20°C or lower. The time from stopping heating to pressing out is preferably within 10 seconds, more preferably within 5 seconds, even more preferably within 2 seconds, and particularly preferably within 1 second. Although the pulse heat press used in the examples of the present application is not provided with a cooling means, the cooling rate can be further increased by air cooling or water cooling.

[0049] As described above, the connection method of the present invention can shorten the time required for the melting, cooling, and depressurizing steps, i.e., the time from the start of heating to press-out, thereby improving productivity compared to conventional methods. The time from the start of heating to press-out is preferably within 12 seconds, more preferably within 7 seconds, even more preferably within 4 seconds, and particularly preferably within 3 seconds.

[0050] It is also preferable to first fix an anisotropic conductive film to one terminal in the placement step and then place the other terminal. In this case, one electronic component can be distributed with the anisotropic conductive film of the present invention fixed to its terminal. That is, it is possible to distribute an electronic component having an anisotropic conductive film fixed to its terminal, with the terminal not electrically connected to the terminal of another electronic component. For example, if an anisotropic conductive film is fixed to the terminal of a flexible flat cable (FFC) in advance, it becomes easier to join it to the terminal of another electronic component. In this case, a preferred method of fixing the anisotropic conductive film is to lightly fuse the film by heating and pressing at a relatively low temperature or low pressure. Such an electronic component having the anisotropic conductive film of the present invention fixed thereto can be stored for one month or more at a temperature of 15°C or higher. The storage temperature may be 20°C or higher, or 25°C or higher. The storage period may be two months or more, six months or more, or one year or more.

[0051] The bonded body thus formed comprises a first electronic component having a terminal, a second electronic component having a terminal, and a molten and solidified anisotropic conductive film that is interposed between the first electronic component and the second electronic component and electrically connects the terminals of both components. [Example]

[0052] The present invention will be described in more detail below with reference to examples. The analytical and evaluation methods used in the examples were as follows.

[0053] (1) Crystallization enthalpy (ΔHc) Using a Hitachi High-Technologies Corporation differential scanning calorimeter "DSC7000," the crystallization enthalpy (ΔHc: J / g) was calculated from the area of ​​the exothermic peak observed immediately after heating to 200°C at a rate of 10°C / min and then cooling to 0°C at a rate of 10°C / min.

[0054] (2) Melting point (Tm) Using a Hitachi High-Technologies Corporation differential scanning calorimeter "DSC7000," the sample was heated to 200°C at a rate of 10°C / min (1st run), immediately followed by cooling to 0°C at a rate of 10°C / min, and then immediately heated again to 200°C at a rate of 10°C / min (2nd run). The melting point (Tm: °C) was determined from the temperature at the apex of the endothermic peak observed during the second run.

[0055] (3) Connection resistance As shown in Figure 5, a flexible flat cable (FFC) 6 was prepared by laminating eight 0.6 mm wide, 10 cm long, and 36 μm thick Cu wires in parallel on a polyester resin substrate film with 0.4 mm spacing. Terminals (3 mm long) 7 and 7', which do not have a substrate film, are provided at both ends of the FFC. The Cu wires of terminals 7 and 7' are Sn-plated. The FFC 6 was placed on a Teflon sheet (not shown). An anisotropic conductive film 1 measuring 3 mm wide, 10 mm long, and 40 μm thick was placed on one terminal 7 of the FFC 6, and a Ni plate 8 measuring 2 mm wide, 10 mm long, and 75 μm thick was then placed on top of that. The two components were then bonded by applying heat and pressure from the Ni plate 8 side. The bonding was performed using a pulse heat press machine "TCW-315 / NA-112" manufactured by Nippon Avionics Co., Ltd. The tip dimensions were 10 mm x 4 mm. The bonding conditions were a set temperature of 250°C, pressure of 4 MPa, temperature rise time of 1 second, and hold time of 1 second. Tests were conducted by changing the timing at which the load was stopped, i.e., the temperature at the time of press-out. Figure 6 shows the appearance after bonding, and Figure 7 shows the A-A' cross section of Figure 6. In this test, the excess molten resin flows out through the gaps between the Cu wires, so the surface of the Cu wire is hardly covered with resin.

[0056] When the temperature change over time was measured by inserting an 80 μm diameter thermocouple between the terminal 7 and the anisotropic conductive film 1, the temperature reached 185°C approximately 1 second after heating began and remained at approximately 190±5°C for approximately 1 second until heating was stopped. After heating was stopped, the temperature reached 150°C 0.5 seconds later, 130°C 1 second later, 110°C 2 seconds later, 90°C 3 seconds later, and 60°C 8 seconds later. There was almost no difference in the temperature profile even when the anisotropic conductive film 1 was configured differently.

[0057] Using the specimens bonded as described above, the resistance between adjacent terminals 7' located on the opposite side of the bonded portion was measured. A clip-type lead was connected to a Hioki EE RM3544 resistance meter, and the contact probe 9 was clamped by the clip and measured using the four-terminal method (Figure 8). The resistance of one conductor of the FFC6 used in the evaluation was calculated to be 78 mΩ based on the copper resistivity, cross-sectional area, and length. Therefore, since this measurement measured the resistance of two conductors, a measured resistance of approximately 160 mΩ can be determined to indicate a satisfactory electrical connection between the two terminals. Two FFC6 samples were measured, and resistance was measured at a total of seven locations between eight conductors. Resistance was measured at 23°C for a total of 14 locations, and the maximum (Max), minimum (Min), and average (Av) values ​​were obtained.

[0058] Similarly, the connection resistance at 100°C was measured using a similarly joined sample. Instead of contact probes, 0.3 mm diameter enameled copper wire was soldered to each of two adjacent terminals, and the enameled copper wire was pulled out of the hot air circulating oven and clamped with a clip. The internal temperature of the oven was raised to 100°C, and then the connection resistance was measured in the oven at 100°C 5 minutes later. Two FFC6 samples were measured, with one measurement taken at each location, and the average value was obtained.

[0059] (4) Adhesive strength Using the same flexible flat cable (FFC) as used in "(3) Connection Resistance" above, a 3 mm wide, 10 mm long, and 40 μm thick anisotropic conductive film (ACFC) was placed on the terminal section consisting of Sn-plated Cu wire, and then an aluminum plate measuring 30 mm wide, 60 mm long, and 0.3 mm thick was placed on top of that. The bonding was then performed by applying heat and pressure from the aluminum plate side. The bonding was performed using a pulse heat press (TCW-315 / NA-112) manufactured by Nippon Avionics Co., Ltd. The tip dimensions were 10 mm x 4 mm. The bonding conditions were a set temperature of 250°C, a pressure of 4 MPa, a heating time of 1 second, and a holding time of 1 second. The maximum temperature of the ACFC during heating was approximately 190°C. The opposite side of the bonded portion of the resulting FFC sample was gripped with a chuck and pulled perpendicular to the aluminum plate at a speed of 5 mm / min. The adhesive strength was measured by a 90° peel test. The test was performed at various press-out temperatures.

[0060] The resins used in the following examples are as follows: Maleic anhydride modified polypropylene (MAn-PP) "Admer QF551" manufactured by Mitsui Chemicals, Inc. MFR (JIS K7210-1, 230°C, load 2.16 kg): 6 g / 10 min Melting point (Tm): 139℃ Crystallization enthalpy (ΔHc): 62 J / g Maleic anhydride content: 0.15 mol% Unmodified polypropylene (PP: random copolymer) Sun Allomer Co., Ltd. "PC630S" MFR (JIS K7210-1, 230℃, load 2.16kg): 7g / 10 minutes Melting point (Tm): 147℃ Crystallization enthalpy (ΔHc): 71 J / g ABS "Stylac 321" manufactured by Asahi Kasei Corporation MVR (JIS K7210, 220°C, load 98N): 7cm 3 / 10 minutes Melting point (Tm): None (amorphous) Crystallization enthalpy (ΔHc): zero (amorphous) Deflection temperature under load (JIS K7191, flatwise, bending stress 1.8 MPa): 77°C

[0061] The conductive particles used in the following examples are as follows: ·Ni powder "NIE03PB" manufactured by High Purity Chemical Laboratory Co., Ltd. Particle size: 3~5μm Conductive resin particles Nippon Chemical Industry Co., Ltd. "55NR5.0-KSGD" Three-dimensionally cross-linked resin particles with a particle diameter of 5 μm, plated with Ni

[0062] Example 1 Pellets of maleic anhydride-modified polypropylene "Admer QF551" were dry-blended with Ni powder "NIE03PB" to achieve a Ni powder content of 8% by mass. The mixture was then melt-kneaded using a twin-screw extruder (screw diameter 25 mm, L / D = 41) at a cylinder temperature of 190°C and a throughput of 5 kg / h. The mixture was then extruded into strands and cut to produce composition pellets. The resulting composition pellets were fed into a single-screw extruder (screw diameter 20 mm, L / D = 25), melt-kneaded at a cylinder temperature of 180°C, extruded through a T-die, and withdrawn at a speed of 0.8 m / min to obtain a 40 μm-thick single-layer anisotropic conductive film 1. A cross-sectional schematic diagram of this anisotropic conductive film 1 is shown in Figure 2. The resulting anisotropic conductive film 1 consists of a single layer of a composition containing maleic anhydride-modified polypropylene 51 and Ni powder 4. Using this anisotropic conductive film 1, bonding was performed according to the method described above at a press-out temperature of 60°C (8 seconds after heating was stopped), and the connection resistance and adhesive strength were measured. The results are summarized in Table 1.

[0063] Example 2 A 40 μm-thick single-layer anisotropic conductive film was produced in the same manner as in Example 1, except that conductive resin particles "55NR5.0-KSGD" were used in place of the Ni powder in Example 1, and the content was changed to 3.5 mass %, and the connection resistance and adhesive strength were measured. The results are summarized in Table 1.

[0064] Example 3 A multilayer film manufacturing apparatus equipped with three single-screw extruders (screw diameter 32 mm, L / D = 30) was used. Pellets of the composition containing the maleic anhydride-modified polypropylene produced in Example 1 and Ni powder were fed into the first extruder, while pellets of "Admer QF551," a maleic anhydride-modified polypropylene without Ni powder, were fed into the second and third extruders. All extruders were melt-kneaded at a cylinder temperature of 180°C. After melt-kneading, the mixture was extruded through a T-die and withdrawn at a speed of 5 m / min to obtain a 40 μm-thick multilayer anisotropic conductive film. The output of the first extruder was double that of the second and third extruders, so that the layer derived from the first extruder was 20 μm thick, and the layers derived from the second and third extruders were each 10 μm thick. However, because both the second and third extruders extruded the same resin, a single layer of 20 μm was formed. A cross-sectional schematic diagram of the resulting anisotropic conductive film 1 is shown in Figure 3. An anisotropic conductive film 1 having a two-layer structure was obtained, which had a layer (20 μm) of a composition containing maleic anhydride-modified polypropylene 51 and Ni powder 4 and a layer (20 μm) of maleic anhydride-modified polypropylene 51 not containing Ni powder. Using this anisotropic conductive film 1, the connection resistance and adhesive strength were measured in the same manner as in Example 1. The results are summarized in Table 1.

[0065] Example 4 Pellets of unmodified polypropylene "PC630S" were dry-blended with Ni powder "NIE03PB" to a Ni powder content of 8% by mass. Then, composition pellets were produced using the same twin-screw extruder as in Example 1 under the same conditions. Using the same multilayer film production apparatus as in Example 3, the resulting composition pellets were fed into the second extruder, and pellets of maleic anhydride-modified polypropylene "Admer QF551" not containing Ni powder were fed into the first and third extruders. Both extruders were melt-kneaded at a cylinder temperature of 180°C. After melt-kneading, the mixture was extruded through a T-die and withdrawn at a speed of 5 m / min to obtain a 40 μm-thick multilayer anisotropic conductive film. The output of the second extruder was double that of the first and third extruders, so that the inner layer derived from the first extruder had a thickness of 20 μm, and the outer layers derived from the first and third extruders each had a thickness of 10 μm. A cross-sectional schematic diagram of the resulting anisotropic conductive film 1 is shown in FIG. 4. An anisotropic conductive film 1 having a three-layer structure was obtained in which a layer (10 μm) of maleic anhydride-modified polypropylene 51 containing no Ni powder, a layer (20 μm) of a composition containing unmodified polypropylene 52 and Ni powder 4, and a layer (10 μm) of maleic anhydride-modified polypropylene 51 containing no Ni powder 4 were arranged in this order. The connection resistance and adhesive strength of this anisotropic conductive film 1 were measured in the same manner as in Example 1. The results are summarized in Table 1.

[0066] Example 5 Using the anisotropic conductive film obtained in Example 1, the connection resistance and adhesive strength were measured in the same manner as in Example 1, except that the press-out temperature was 150°C (0.5 seconds after heating was stopped). The results are summarized in Table 1.

[0067] Comparative Example 1 The composition pellets containing unmodified polypropylene and Ni powder obtained in Example 4 were fed into the same single-screw extruder as in Example 1, and a 40 μm-thick single-layer anisotropic conductive film was obtained under the same conditions as in Example 1. The connection resistance and adhesive strength of the obtained anisotropic conductive film were measured in the same manner as in Example 1. The results are summarized in Table 1.

[0068] Comparative Example 2 Pellets of ABS "Stylac 321" were dry-blended with Ni powder "NIE03PB" so that the Ni powder content was 8% by mass. Then, composition pellets were produced using the same twin-screw extruder and under the same conditions as in Example 1. The resulting composition pellets were fed into the same single-screw extruder as in Example 1, melt-kneaded at a cylinder temperature of 180°C, extruded through a T-die, and withdrawn at a speed of 0.8 m / min to obtain a 40 μm-thick single-layer anisotropic conductive film. The connection resistance and adhesive strength of the resulting anisotropic conductive film were measured in the same manner as in Example 1. The results are summarized in Table 1. In Table 1, "open" indicates that no continuity was observed between adjacent terminals 7', resulting in an open circuit. If some of the measurement points were "open," the average resistance value obtained at the remaining measurement points was used.

[0069] Comparative Example 3 Using the anisotropic conductive film obtained in Comparative Example 2, the connection resistance and adhesive strength were measured in the same manner as in Example 1, except that the press-out temperature was set to 110°C (2 seconds after heating was stopped). The results are summarized in Table 1.

[0070] [Table 1]

[0071] As can be seen from Table 1, in Examples 1 to 5, sufficient electrical connection was achieved at the joint, as well as sufficient adhesive strength. It was particularly surprising that good electrical conductivity was achieved even when the press-out was performed at a temperature (150°C) higher than the melting point of the resin (139°C), as in Example 5. It is believed that the large crystallization enthalpy and rapid crystallization rate contribute to ensuring electrical conductivity and significantly contribute to speeding up the joining process. Although not described as an example above, the inventors confirmed that when the anisotropic conductive film obtained in Example 1 was used and heating and pressure were stopped at around 190°C, sufficient electrical connection could not be achieved. Furthermore, electrical connection could be maintained even in a high-temperature environment of 100°C. The resistance value was higher in the measurement at 100°C than in the measurement at 23°C, due to the increase in electrical resistivity caused by the increase in measurement temperature. On the other hand, as shown in Comparative Example 1, when unmodified polypropylene was used, the adhesive strength was insufficient. Furthermore, as shown in Comparative Example 3, when amorphous ABS resin was used and press-out was performed at a temperature higher than the deflection temperature under load, electrical connection could not be achieved. Furthermore, as shown in Comparative Example 2, even when amorphous ABS resin was used and press-out was performed at a temperature lower than the deflection temperature under load, non-conductive terminals were included, and the reliability of the electrical connection was insufficient. [Explanation of symbols]

[0072] 1 Anisotropic conductive film 2, 2' circuit board 3, 3' metal terminal 4 Conductive particles (Ni powder) 5. Resin 51 Maleic anhydride modified polypropylene 52 Unmodified polypropylene 6 FFC 7, 7' terminals 8 Ni plate 9 Contact Probe 10 zygote

Claims

1. An anisotropic conductive film made of a single layer film or a multilayer film for connecting circuit boards having a plurality of opposing terminals, all layers constituting the anisotropic conductive film contain crystalline polyolefin, At least one layer constituting the anisotropic conductive film is made of a resin composition in which conductive particles are dispersed in the polyolefin, the polyolefin contained in the layer disposed on the outermost layer is a modified polyolefin containing a monomer unit having at least one functional group selected from the group consisting of a carboxylic anhydride group, a carboxyl group, an epoxy group, and a hydroxyl group; and An anisotropic conductive film characterized in that the polyolefin contained in all of the layers has a crystallization enthalpy (ΔHc) of 20 to 200 J / g when measured at a temperature decrease rate of 10°C / min using a differential scanning calorimeter (DSC).

2. 2. The anisotropic conductive film according to claim 1, wherein the polyolefin is polypropylene or polyethylene.

3. 3. The anisotropic conductive film according to claim 1, wherein the modified polyolefin contains 0.01 to 2 mol % of the monomer units having the functional group relative to the total monomer units.

4. 4. The anisotropic conductive film according to claim 1, which is obtained by melt extrusion molding.

5. The anisotropic conductive film is a single-layer film, 5. The anisotropic conductive film according to claim 1, wherein the single-layer film is made of a resin composition in which conductive particles are dispersed in the modified polyolefin.

6. The anisotropic conductive film is a two-layer film, one layer is made of a resin composition in which conductive particles are dispersed in the modified polyolefin, 5. The anisotropic conductive film according to claim 1, wherein the other layer is made of a resin containing the modified polyolefin and not containing conductive particles.

7. The anisotropic conductive film is a film having three or more layers, It is composed of one or more inner layers and two outer layers, At least one inner layer is made of a resin composition in which conductive particles are dispersed in the polyolefin, 5. The anisotropic conductive film according to claim 1, wherein both of the two outer layers are made of a resin that contains the modified polyolefin and does not contain conductive particles.

8. 8. The anisotropic conductive film according to claim 7, wherein the polyolefin contained in at least one of the inner layers is an unmodified polyolefin that does not contain a monomer unit having the functional group.

9. 9. The anisotropic conductive film according to claim 6, which is obtained by melt coextrusion molding.

10. The method for producing an anisotropic conductive film according to any one of claims 1 to 9, wherein the film is melt-extruded at a temperature exceeding the melting points (Tm) of all polyolefins contained in the film.

11. A film roll obtained by winding the anisotropic conductive film according to any one of claims 1 to 9 without using a support film.

12. A film roll obtained by winding a multilayer structure comprising the anisotropic conductive film according to any one of claims 1 to 9 and a support film.

13. 13. The method for storing a film roll according to claim 11 or 12, wherein the film roll is stored at a temperature of 15°C or higher for one month or longer.

14. A connection method for anisotropically conductively connecting a terminal of a first electronic component and a terminal of a second electronic component, comprising: a placement step of placing the anisotropic conductive film according to any one of claims 1 to 9 between both terminals; a melting step of melting the polyolefin by heating while pressing it from one terminal side with a heating and pressing member; A cooling step of cooling the product while continuing to press it; and A connection method characterized in that a decompression step for releasing the pressure is carried out in this order.

15. 15. The connection method according to claim 14, wherein in the arranging step, an anisotropic conductive film is fixed to one of the terminals beforehand, and then the other terminal is arranged.

16. a first electronic component having a terminal, a second electronic component having a terminal, and a melt-solidified anisotropic conductive film interposed between the first electronic component and the second electronic component to electrically connect the terminals of both components; A bonded body, wherein the anisotropic conductive film is the anisotropic conductive film according to any one of claims 1 to 9.

17. 10. An electronic component having a terminal to which the anisotropic conductive film according to claim 1 is fixed, wherein the terminal is not electrically connected to the terminal of another electronic component.

18. The method for storing electronic components according to claim 17, wherein the electronic components are stored at a temperature of 15°C or higher for one month or longer.

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