JP4789738B2 - Anisotropic conductive film - Google Patents

Description

  In the electrical connection of a fine pattern, the present invention is excellent in electrical connectivity of electrodes having a small area, and is difficult to cause a dielectric breakdown (short) between fine wirings, so that sufficient heat cannot be supplied at the time of connection. Even if it exists, it is related with the anisotropic conductive film in which the connection which gives high insulation reliability is possible.

  Anisotropic conductive film is a film in which conductive particles are dispersed in an insulating adhesive. Connection between a liquid crystal display and a semiconductor chip or TCP, connection between FPC and TCP, connection between FPC and printed wiring board. It is a connecting member used for simple operation. For example, it is widely used for connecting a liquid crystal display of a notebook personal computer or a mobile phone and a control IC. Recently, a semiconductor chip is directly applied to a printed circuit board or a flexible wiring board. It is also used for flip chip mounting (Patent Documents 1, 2, and 3).

In recent years, the dimensions of connected wiring patterns and electrode patterns have been increasingly miniaturized in this field. In many cases, the width of wirings and electrodes is miniaturized to a level of a few tens of μm. On the other hand, the average particle diameter of the conductive particles that have been used so far was particles of several μm to 10 μm level, which is the same level as the line width of the wiring or electrode. Then, when the dimension of the electrode pattern to be connected is reduced, in the anisotropic conductive film in which the conductive particles are randomly dispersed and arranged, there is a deviation in the distribution of the conductive particles. It is unavoidable as a probability theory that it is arranged at a position where no exists and is not electrically connected.
In order to solve this problem, it is effective to disperse smaller conductive particles in the film at a high density. However, when the size of the conductive particles is reduced, the surface area increases rapidly and secondary aggregation easily occurs. As a result, if the density of the conductive particles is lowered to maintain the insulation, a wiring pattern or an electrode pattern that is not connected is generated. It has been considered difficult to cope with miniaturization while maintaining (Patent Document 4).

  Furthermore, in order to realize high-density mounting centering on a small liquid crystal panel, a method of mounting an IC chip face down on a glass substrate and connecting with an anisotropic conductive film is used. In this case, an anisotropic conductive film is sandwiched between the glass chip and the IC chip that are aligned so that the electrodes face each other, and connected by applying pressure from the back of the IC chip while applying heat. Is done. As a result, the IC chip and the glass substrate are electrically connected, and the sealing effect of the anisotropic conductive film can prevent moisture from entering between the connection areas, thereby maintaining connection reliability. . However, at the outer periphery of the IC chip, the anisotropic conductive film is difficult to be supplied with sufficient heat from the IC chip, so the curing reaction may be insufficient or unreacted, Since the effect is low and it is easy to absorb water, there is a problem that the wiring on the glass substrate is corroded, and a device for the wiring material (Patent Document 5) and further a protective resin is formed around the IC chip (Patent Document 6). ) And other improvements have been made. However, in recent years, since a high voltage is applied between the wirings or the wirings have a narrow pitch, the insulation reliability due to the corrosion of the wirings is insufficient, and further improvement is required.

Japanese Patent Laid-Open No. 03-107888 Japanese Patent Laid-Open No. 04-366630 JP-A-61-195179 JP 09-31176 A Japanese Patent Laid-Open No. 11-223825 JP 05-333359 A

  In the electrical connection of a fine pattern, the present invention is excellent in electrical connectivity of electrodes having a small area, and is difficult to cause a dielectric breakdown (short) between fine wirings, so that sufficient heat cannot be supplied at the time of connection. Even if it exists, it aims at provision of the anisotropic conductive film in which the connection which gives high insulation reliability is possible.

As a result of intensive studies to solve the above problems, the present inventors have first determined that the distance between particles is a specific average value and a specific value for a problem corresponding to miniaturization while maintaining connection reliability. It has been found that the conductive particles are arranged as a single layer on the surface layer of the insulating adhesive so as to have a standard deviation, so that it can meet the above-mentioned purpose, and the skeleton of the present invention is made.
Next, the interface layer is provided with a thermosetting resin layer that does not contain a latent curing agent, and a thermosetting resin layer that contains a latent curing agent is laminated at a specific film thickness ratio. It has been found that even if it is a part where it is difficult to supply heat, it provides high insulation reliability and high connection reliability of the thermosetting resin. This discovery is easily anticipated by those skilled in the art in view of the fact that, in the past, it has been said that a high curing rate is required using a thermosetting resin in order to exhibit high connection reliability and insulation reliability. It was impossible.

That is, the present invention is as follows.
1) At least the two layers of the first layer containing the thermosetting resin (A) and the latent curing agent, and the second layer containing the thermosetting resin (B) but not containing the latent curing agent. In the anisotropic conductive film having the conductivity by pressing in the thickness direction, wherein the second layer is the outermost layer and the conductive particles are arranged in a single layer, (1) the center of the conductive particles The average distance is not less than 2 μm and not more than 20 μm, the coefficient of variation is not less than 0.05 and less than 0.5, and (2) the thickness of the second layer relative to the thickness of the first layer is not less than 0.01 and not more than 0.00. An anisotropic conductive film characterized by being less than 25.
2) The anisotropic conductive film as described in 1) above, wherein the thermosetting resin (A) contained in the first layer is an epoxy resin.
3) A circuit connection method for electrically connecting an electrode of an IC chip and an electrode of a circuit board, wherein the anisotropic conductive film according to the above 1) or 2) is in contact with the circuit board on the second layer side. A circuit connection method characterized in that it is sandwiched between an IC chip and a circuit board in a larger area than the chip and is pressurized while supplying heat from the IC chip side.
4) A connection structure connected by the method described in 3) above.

  The anisotropic conductive adhesive film of the present invention is excellent in electrical connection of electrodes with a small area in electrical connection of a fine pattern, and is less likely to cause dielectric breakdown (short) between fine wirings. Even in a region where heat is difficult to be supplied, there is an effect of enabling connection that provides high insulation reliability.

The present invention will be specifically described below.
The present invention provides at least the two layers of a first layer containing a thermosetting resin (A) and a latent curing agent, and a second layer containing a thermosetting resin (B) and no latent curing agent. It is composed of
First, the first layer will be described.
As the thermosetting resin (A) used in the first layer, a resin that crosslinks by reacting with a latent curing agent by heating is used. As such a thermosetting resin (A), an epoxy resin, a phenol resin, an acrylate, a urethane resin, etc. are used, for example. For each thermosetting resin, a latent curing agent suitable for it is used. For example, if the acrylate has a reactive double bond at the molecular end, the latent curing agent generates a radical by heating. A latent curing agent such as peroxide is used.

In the present invention, it is preferable to use an epoxy resin as the thermosetting resin (A) because of high connection reliability.
Examples of the epoxy resin used here include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, tetramethylbisphenol A type epoxy resin, biphenol type epoxy resin, naphthalene type epoxy resin, and resorcin type epoxy. Resin, fluorene type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, bisphenol A novolak type epoxy resin, aliphatic ether type epoxy resin, etc. glycidyl ether type epoxy resin, glycidyl ether ester type epoxy resin, glycidyl ester type There are epoxy resins, glycidylamine type epoxy resins, hydantoin type epoxy resins, alicyclic epoxides, etc. These epoxy resins are urethane modified. , Rubber-modified, it may be a modified epoxy resin such as silicone-modified. Glycidyl ether type epoxy resins are preferable, and naphthalene type epoxy resins, bisphenol A type epoxy resins, and bisphenol F type epoxy resins are more preferable.

  As the latent curing agent when using an epoxy resin as the thermosetting resin (A), boron compound, hydrazide, tertiary amine, imidazole, dicyandiamide, carboxylic acid anhydride, thiol, isocyanate, boron complex salt and derivatives thereof Can be used. Of these, adduct-type curing agents such as amine adducts and imidazole adducts are preferable because they balance the stability and curability. Adduct-type curing agents are obtained by reacting primary or secondary amines or imidazoles with epoxy resins, isocyanate compounds, urea compounds, and the like. Among the latent curing agents, a microcapsule type latent curing agent is particularly preferable because of its excellent stability in the presence of a solvent. The microcapsule-type curing agent is a material in which the surface of the curing agent is stabilized with a resin film, etc., and the resin film is destroyed by the temperature and pressure during connection work, the curing agent diffuses outside the microcapsule, and the epoxy resin and react. Among the microcapsule-type latent curing agents, a latent curing agent obtained by microencapsulating an adduct-type curing agent such as an amine adduct or an imidazole adduct is more preferable because of excellent balance between stability and curability.

In order to obtain the high curability of the thermosetting resin, the latent curing agent is preferably used in an amount of 1 to 100 parts by mass with respect to 100 parts by mass of the thermosetting resin (A). More preferably, it is 4-60 mass parts, More preferably, it is 8-40 mass parts, More preferably, it is 10-30 mass parts, and a water absorption rate can be restrained low by this.
In the first layer, polyester resin, acrylic rubber, SBR, NBR, silicone resin, polyvinyl butyral resin, polyurethane resin, polyacetal resin, urea resin, xylene resin for the purpose of imparting adhesiveness, stress relaxation during curing, etc. It is preferable to contain a polymer component such as a polyamide resin, a polyimide resin, a rubber containing a functional group such as a carboxyl group, a hydroxyl group, a vinyl group or an amino group, or an elastomer. These polymer components preferably have a molecular weight of 10,000 to 3,000,000, more preferably 50,000 to 1,500,000. The content of the polymer component is preferably 100% by mass or less, more preferably 2 to 80% by mass with respect to the thermosetting resin.

The first layer preferably contains a film-forming polymer. As the film-forming polymer, a phenoxy resin having excellent long-term connection reliability is preferable. As the phenoxy resin used here, bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, bisphenol A bisphenol F mixed type phenoxy resin, bisphenol A bisphenol S mixed type phenoxy resin, fluorene ring-containing phenoxy resin, caprolactone modified bisphenol A type Examples include phenoxy resin. 10-200 mass% is preferable with respect to a thermosetting resin, and, as for content of a film-forming polymer | macromolecule, 30-150 mass% is still more preferable.
The first layer can further contain insulating particles, fillers, softeners, accelerators, anti-aging agents, colorants, flame retardants, thixotropic agents, and the like. Furthermore, it is preferable to contain a coupling agent from an adhesive viewpoint. As the coupling agent, a silane coupling agent containing a ketimine group, a vinyl group, an acrylic group, an amino group, an epoxy group and an isocyanate group is preferable from the viewpoint of improving adhesiveness.
When mixing each component of a 1st layer, a solvent can be used as needed. Examples of the solvent include methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, ethyl acetate, butyl acetate, ethylene glycol monoalkyl ether acetate, propylene glycol monoalkyl ether acetate, and the like. A plurality of solvents can be used in combination.
In the present invention, the first layer may be composed of a plurality of layers.
The thickness of the first layer is preferably 5 μm or more and less than 50 μm.

Next, the second layer will be described.
As a thermosetting resin (B) used for a 2nd layer, an epoxy resin, a phenol resin, an acrylate, a urethane resin etc. are used, for example.
In the present invention, it is preferable to use an epoxy resin as the thermosetting resin (B) because of high connection reliability.
Examples of the epoxy resin used here include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, tetramethylbisphenol A type epoxy resin, biphenol type epoxy resin, naphthalene type epoxy resin, and resorcin type epoxy. Resin, fluorene type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, bisphenol A novolak type epoxy resin, aliphatic ether type epoxy resin, etc. glycidyl ether type epoxy resin, glycidyl ether ester type epoxy resin, glycidyl ester type There are epoxy resins, glycidylamine type epoxy resins, hydantoin type epoxy resins, alicyclic epoxides, etc. These epoxy resins are urethane modified. , Rubber-modified, it may be a modified epoxy resin such as silicone-modified. Glycidyl ether type epoxy resins are preferable, and naphthalene type epoxy resins, bisphenol A type epoxy resins, and bisphenol F type epoxy resins are more preferable. Furthermore, a liquid epoxy resin is preferable in order to express the sticking property to the substrate. The liquid epoxy resin is an epoxy resin having fluidity at 25 ° C.

In the present invention, it is preferable to use the same kind of resin for the thermosetting resin (A) and the thermosetting resin (B) in order to maintain high adhesion between the layers.
The second layer used in the present invention preferably contains a coupling agent for the purpose of improving adhesiveness. As the coupling agent, a silane coupling agent containing a ketimine group, a vinyl group, an acrylic group, an amino group, an epoxy group and an isocyanate group is preferable from the viewpoint of improving adhesiveness.
In the second layer, the amount of the coupling agent used is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the thermosetting resin (B) in order to obtain high adhesiveness. More preferably, it is 0.2-4 mass parts, More preferably, it is 0.3-3 mass parts.
The second layer is provided with polyester resin, acrylic rubber, SBR, NBR, silicone resin, polyvinyl butyral resin, polyurethane resin, polyacetal resin, urea resin, xylene resin for the purpose of imparting adhesiveness, stress relaxation during curing, etc. It is preferable to contain a polymer component such as a polyamide resin, a polyimide resin, a rubber containing a functional group such as a carboxyl group, a hydroxyl group, a vinyl group or an amino group, or an elastomer. These polymer components preferably have a molecular weight of 10,000 to 3,000,000, more preferably 50,000 to 1,500,000. The content of the polymer component is preferably 100% by mass or less, more preferably 2 to 80% by mass with respect to the thermosetting resin.

The second layer preferably contains a film-forming polymer. As the film-forming polymer, a phenoxy resin having excellent long-term connection reliability is preferable. As the phenoxy resin used here, bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, bisphenol A bisphenol F mixed type phenoxy resin, bisphenol A bisphenol S mixed type phenoxy resin, fluorene ring-containing phenoxy resin, caprolactone modified bisphenol A type Examples include phenoxy resin. The content of the film-forming polymer is preferably 0.1 to 50 times, more preferably 0.5 to 25 times that of the thermosetting resin.
The second layer can further contain insulating particles, fillers, softeners, accelerators, anti-aging agents, colorants, flame retardants, thixotropic agents, and the like.
When mixing each component of a 2nd layer, a solvent can be used as needed. Examples of the solvent include methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, ethyl acetate, butyl acetate, ethylene glycol monoalkyl ether acetate, propylene glycol monoalkyl ether acetate, and the like. A plurality of solvents can be used in combination.

In the present invention, the second layer does not contain a latent curing agent for curing the thermosetting resin (B). The latent curing agent here means a curing agent having a function of curing the thermosetting resin (B) at the time of connection, and includes a curing agent that has already reacted with the thermosetting resin (B) before connection. Not.
In the present invention, the second layer may further comprise a plurality of layers.
In the present invention, other layers may be further formed in addition to the first layer and the second layer. The thickness of the other layer is preferably less than 0.25 with respect to the thickness of the first layer.
When other layers are further formed, at least the second layer needs to be formed in the outermost layer, and thereby high insulation reliability is obtained even in a region where sufficient heat is difficult to be supplied at the time of connection. It is done.

In the present invention, the thickness of the second layer relative to the thickness of the first layer is 0.01 or more and less than 0.25. Preferably they are 0.02 or more and less than 0.20, More preferably, they are 0.04 or more and less than 0.18, More preferably, they are 0.05 or more and less than 0.16. By making the thickness of the second layer with respect to the thickness of the first layer 0.01 or more and less than 0.25, it has high adhesiveness and high insulation even if it is difficult to supply sufficient heat at the time of connection. Reliability can be obtained. Furthermore, when the thickness of the second layer with respect to the thickness of the first layer is 0.05 or more and less than 0.16, an anisotropic conductive film having high heat resistance and small performance variation can be obtained.
The thickness of the second layer is preferably 0.1 μm or more and less than 5 μm. More preferably, it is 0.2 μm or more and less than 4 μm, more preferably 0.4 μm or more and less than 3.5 μm, and still more preferably 0.5 μm or more and less than 3 μm. By setting the thickness of the second layer to 0.1 μm or more and less than 5 μm, it is possible to obtain high insulation reliability even in a portion that has high adhesiveness and is difficult to supply sufficient heat at the time of connection.

The anisotropic conductive film of the present invention contains conductive particles in order to absorb variations in the electrode height of an IC chip or a circuit board. As the conductive particles, metal particles, particles made of carbon, particles obtained by coating a polymer core material with a metal thin film, or the like can be used.
As the metal particles, for example, a simple substance such as gold, silver, copper, nickel, aluminum, zinc, tin, lead, solder, indium, palladium, etc., or two or more of these metals are combined in a layered or inclined manner. Particles are exemplified.
Particles with a polymer core coated with a metal thin film include epoxy resin, styrene resin, silicone resin, acrylic resin, polyolefin resin, melamine resin, benzoguanamine resin, urethane resin, phenol resin, polyester resin, divinylbenzene crosslinked product, NBR , SBR and other polymer core materials combined with one or more polymers, gold, silver, copper, nickel, aluminum, zinc, tin, lead, solder, indium, palladium, etc. The particle | grains which metal-coated by plating etc. in combination of 2 or more types are illustrated. The thickness of the metal thin film is preferably 0.005 μm or more and 1 μm or less, and more preferably 0.01 μm or more and 0.5 μm or less from the viewpoint of connection stability and particle aggregation. It is preferable in terms of connection stability that the metal thin film is uniformly coated. Particles obtained by further insulating coating the surfaces of these conductive particles can also be used.

The average particle diameter of the conductive particles is preferably in the range of 0.5 μm or more and less than 10 μm from the viewpoints of both conductivity and insulation and particle aggregability. More preferably, they are 1 micrometer or more and less than 7 micrometers, More preferably, they are 1.5 micrometers or more and less than 6 micrometers, More preferably, they are 2 micrometers or more and less than 5.5 micrometers, More preferably, they are 2.5 micrometers or more and less than 5 micrometers. The standard deviation of the particle diameter of the conductive particles is preferably as small as possible, and is preferably 50% or less of the average particle diameter. More preferably, it is 20% or less, More preferably, it is 10% or less, More preferably, it is 5% or less.
The content of the conductive particles is preferably 0.1% by volume or more and less than 20% by volume with respect to the anisotropic conductive film of the present invention. More preferably, it is 0.13 volume% or more and less than 15 volume%, More preferably, it is 0.15 volume% or more and less than 10 volume%, More preferably, it is 0.2 volume% or more and less than 5 volume%, More preferably, it is 0.25 volume. % Or more and less than 3% by volume. In the region where the content of the conductive particles is 0.1% by volume or more and less than 20% by volume, it is easy to achieve both conductivity between opposing electrodes and insulation between adjacent electrodes. Furthermore, by making the content less than 5% by volume, high insulation reliability can be easily obtained even at a site where it is difficult to supply sufficient heat during connection.

In the anisotropic conductive film of the present invention, the conductive particles are arranged in a single layer in order to secure the conductivity in the thickness direction and the insulation in the plane direction (hereinafter often referred to as anisotropic conductivity) at a high level. . Here, being arranged in a single layer means that the height of the center of the conductive particles in the anisotropic conductive film does not vary beyond the diameter of the conductive particles.
In the anisotropic conductive film of the present invention, the conductive particles are present in the second layer or in the vicinity of the interface between the second layer and the other layers, so that the arranged conductive particles move greatly during connection. Since it can suppress, it is preferable.

  The anisotropic conductive film of the present invention has high anisotropic conductivity because the conductive particles are arranged at a specific center distance and the center distance is arranged with a specific coefficient of variation. . That is, the anisotropic conductive adhesive film of the present invention has an average distance between centers of the conductive particles of 2 μm or more and 20 μm or less. By setting the distance between the centers to be 2 μm or more, the insulation in the plane direction, that is, the insulation between adjacent electrodes can be maintained at a high level. On the other hand, by setting the center-to-center distance to 20 μm or less, it is possible to obtain a conductive particle density capable of maintaining the electrical conductivity in the thickness direction, that is, the electrical connectivity between the connection electrodes, and high performance as an anisotropic conductive adhesive film. Demonstrate. The average distance between the centers of the conductive particles is preferably 2.5 μm to 18 μm, more preferably 3 μm to 16 μm, still more preferably 3.5 μm to 15 μm, and still more preferably 4 μm to 13 μm. The variation coefficient of the distance between the centers of the conductive particles is a value obtained by dividing the standard deviation of the distance between the centers of the conductive particles by the average value. In the present invention, it is 0.05 or more and less than 0.5. Preferably they are 0.07 or more and less than 0.45, More preferably, they are 0.09 or more and less than 0.4, More preferably, they are 0.1 or more and less than 0.35, More preferably, they are 0.12 or more and less than 0.3. By setting the coefficient of variation to 0.05 or more, it is possible to stably connect semiconductor chips with different electrode patterns without causing flow of conductive particles during connection that adversely affects the electrical connectivity between connection electrodes. On the other hand, by setting it to less than 0.5, the variation in the number of conductive particles trapped between the connection electrodes can be kept small, the variation in connection resistance between the electrodes is small, and a stable connection is obtained. It is done.

The anisotropic conductive film of the present invention may be formed on a release sheet. Examples of the release sheet include films such as polyesters such as polyethylene, polypropylene, polystyrene, PET, and PEN, nylon, vinyl chloride, and polyvinyl alcohol. Preferred resins for the release sheet include polypropylene and PET. The release sheet is preferably subjected to surface treatment such as fluorine treatment, silicone treatment or alkyd treatment.
The anisotropic conductive film of the present invention is produced, for example, by the following method.
That is, first, a conductive particle array sheet in which conductive particles arranged in a single layer are fixed on a sheet with an adhesive is manufactured. In order to produce an array sheet, for example, an adhesive is preferably applied on a stretchable sheet so as to have a film thickness of 10 μm or less, and conductive particles are filled thereon. Thereafter, the conductive particles that have not reached the pressure-sensitive adhesive layer are removed by air blowing or the like, thereby forming a single conductive particle layer in which the conductive particles are densely packed. If necessary, the conductive particles arranged in a single layer are embedded in the adhesive. The filling rate defined by the ratio of the projected area of the conductive particles to the total area at this time is preferably 60% or more and 90% or less. More preferably, they are 65% or more and 88% or less, More preferably, they are 68% or more and 85% or less. The filling factor greatly affects the coefficient of variation of the distance between the centers of the conductive particles, which is an important factor in the present invention.

Next, the sheet on which the conductive particles are fixed is drawn at a desired draw ratio so that each conductive particle has a desired center-to-center distance with a coefficient of variation necessary for the present invention. As a result, an array sheet of conductive particles arranged on the substrate is obtained.
Examples of the stretchable sheet include sheets of polyester such as polyethylene, polypropylene, polystyrene, PET, and PEN, nylon, vinyl chloride, and polyvinyl alcohol. Examples of the adhesive include urethane resin, acrylic resin, urea resin, melamine resin, phenol resin, vinyl acetate, chloroprene and the like.
Stretching is so-called biaxial stretching in which both longitudinal stretching and lateral stretching are performed, and can be performed by a known method. Examples of the method include a method of pulling between two or four sides of the film with a clip or the like, and a method of stretching by changing the rotation speed of the roll while sandwiching between two or more rolls. The stretching may be simultaneous biaxial stretching in which the machine direction and the transverse direction are stretched simultaneously, or may be sequential biaxial stretching in which the other is stretched after stretching in one direction. Simultaneous biaxial stretching is preferred because it is difficult to cause disorder in the arrangement of the conductive particles during stretching. In order to perform stretching with high accuracy, it is preferable to soften a stretchable film. Depending on the stretchable sheet used, for example, it is preferable to perform stretching at 70 ° C. or more and less than 250 ° C. More preferably, it is 75 degreeC or more and less than 200 degreeC, More preferably, it is 80 degreeC or more and less than 160 degreeC, More preferably, it is 85 degreeC or more and less than 145 degreeC. If the stretching temperature is too high, the adhesive force of the pressure-sensitive adhesive is reduced, the arrangement of the conductive particles is disturbed, and the coefficient of variation in the distance between the centers of the conductive particles is increased.

Next, for example, on the release sheet, a solution in which each component of the first layer and the second layer is uniformly mixed is applied, the solvent is dried, and the first layer and the second layer on the release sheet Get.
Next, the first layer is stacked on the conductive particle side of the array sheet, the conductive particles are embedded in the first layer using a heat roll or the like, the stretchable sheet is peeled off, and then the second layer is stacked and laminated. In particular, the anisotropic conductive film of the present invention can be obtained. After embedding the conductive particles in the second layer, the first layer may be laminated, or after embedding in another layer, the first layer and the second layer are laminated so that the second layer becomes the outermost layer. It doesn't matter. Furthermore, for example, after forming a single conductive particle layer in which conductive particles are closely packed on a stretchable sheet, a solution in which the components of the second layer are uniformly mixed is applied, and the solvent is dried. Later, the anisotropic conductive film of the present invention can be obtained by stretching and then laminating the first layer.
The anisotropic conductive film of the present invention is obtained by the above method and the like. Generally, an anisotropic conductive film is slit to a desired width and wound up in a reel shape.

The anisotropic conductive film of the present invention is used, for example, to electrically connect an electrode of an IC chip and an electrode of a circuit board.
As a circuit connection method of the present invention, a circuit board such as a glass substrate in which a circuit and an electrode are formed by ITO wiring, metal wiring, etc., and an IC chip in which an electrode is formed at a position that makes a pair with the electrode of the circuit board are prepared. Then, the anisotropic conductive film of the present invention is attached to the position where the IC chip on the glass substrate is arranged so that the second layer side is the circuit board side. Here, the area of the anisotropic conductive film is preferably slightly larger than the IC chip. The width and length of the anisotropic conductive film are more preferably 100.05% to 150% of the width and length of the IC chip, respectively. More preferably, it is 100.1%-120%. By making it one size larger, it is possible to suppress defects due to defective attaching positions of the anisotropic conductive film. Next, the glass substrate and the IC chip are aligned so that the respective electrodes make a pair with each other, and then thermocompression bonded. The thermocompression bonding is preferably performed at a temperature range of 80 ° C. to 250 ° C. for 1 second to 30 minutes. The pressure to be applied is preferably 0.1 MPa to 50 MPa with respect to the chip surface.
Supply of heat when performing thermocompression bonding is performed from the IC chip side in order to prevent performance degradation of the glass substrate. When supplying heat also from a glass substrate, it is preferable that the temperature of a glass substrate is less than 80 degreeC.
By the above method, the connection structure of the present invention is obtained.

The invention is explained in more detail by means of examples.
[Example 1]
100 parts by mass of phenoxy resin (manufactured by InChem, trade name: PKHC, weight average molecular weight 43000, the same shall apply hereinafter), bisphenol A type liquid epoxy resin (manufactured by Asahi Kasei Chemicals Co., Ltd., trade name: AER 2603, same shall apply hereinafter) Mixture of capsule type latent curing agent and liquid epoxy resin (manufactured by Asahi Kasei Chemicals Co., Ltd., trade name: NOVACURE 3941, hereinafter referred to as NOVACURE) 50 parts by mass, silane coupling agent (manufactured by Nihon Unicar Co., Ltd., trade name A-187) The same applies hereinafter) 1 part by mass and 500 parts by mass of ethyl acetate were mixed to obtain varnish A.
The varnish A was applied onto a release sheet made of 50 μm PET film subjected to a release treatment using a blade coater, and the solvent was dried and removed at 70 ° C. to obtain a resin film A. It was 20 micrometers as a result of measuring the film thickness of the resin film A using the photoelectric digital length measuring machine (The Nikon company make, brand name: Digimicro MH-15M / TC-101, and the same below).

Varnish B was obtained by mixing 100 parts by mass of a phenoxy resin, 100 parts by mass of a bisphenol A type liquid epoxy resin, 0.8 parts by mass of a silane coupling agent, and 600 parts by mass of ethyl acetate. The varnish B was applied onto a release sheet made of 38 μm PET film which had been subjected to mold release treatment using a blade coater, and the solvent was dried and removed at 70 ° C. to obtain a resin film B having a thickness of 0.5 μm.
An acrylic polymer diluted with ethyl acetate to a resin content of 5% by mass using a blade coater was applied onto a 100 μm unstretched copolymerized polypropylene film and dried at 80 ° C. for 10 minutes to form an adhesive layer having a thickness of 1 μm. The acrylic polymer used here was 62 parts by mass of methyl acrylate, 30.6 parts by mass of 2-ethylhexyl acrylate, and 7 parts by mass of 2-hydroxyethyl acrylate in 233 parts by mass of ethyl acetate. The weight average molecular weight obtained by polymerizing 0.2 parts by mass of nitrile for 30 hours at 65 ° C. in a nitrogen gas stream is 950,000. The weight average molecular weight was measured by gel permeation chromatography (GPC).

On this pressure-sensitive adhesive, conductive particles having an average particle size of 4 μm (trade name: Micropearl AU204, manufactured by Sekisui Chemical Co., Ltd.) were filled on one side, and conductive particles that did not reach the pressure-sensitive adhesive were eliminated by air blowing. As a result, a single-layer conductive particle layer having a filling rate of 60% was formed.
Next, the polypropylene film on which the conductive particles are fixed with an adhesive is stretched to 2.0 times at 135 ° C. at a rate of 10% / second in both longitudinal and lateral directions using a test biaxial stretching apparatus. The array sheet A was obtained by cooling to room temperature.
Next, the resin film A was overlapped on the conductive particle side of the array sheet A and laminated under the conditions of 60 ° C. and 0.3 MPa to embed the conductive particles in the resin film A, and then the polypropylene film and the adhesive were peeled off.

Next, the resin film B was overlapped on the conductive particle side and laminated under the conditions of 50 ° C. and 0.1 MPa to obtain an anisotropic conductive film A. The ratio of the thickness of the second layer (resin film B) to the thickness of the first layer (resin film A) of the anisotropic conductive film A is 0.025, and the content of the conductive particles is anisotropic conductive film A. It was 1.9 volume% with respect to.
As a result of observing the anisotropic conductive film A with a microscope (manufactured by Keyence Corporation, trade name: VHX-100, the same applies hereinafter), the conductive particles are in focus at the same focal point. It was arranged in a single layer. Moreover, from the image obtained with the microscope, the result of calculating the average value of the center-to-center distance of the conductive particles and the coefficient of variation thereof using image processing software (trade name: A image-kun, manufactured by Asahi Kasei Corporation). The average value was 9.8 μm, and the coefficient of variation was 0.42. As the distance between the centers of the conductive particles, the length of a side of a triangle formed by Deloni triangulation using the center point of each particle was used, and the observation of the conductive particles was performed for particles within 0.06 mm ² .

  Next, the chip size is 1.6 mm × 16.1 mm, bare chip 1 in which 20 μm × 100 μm gold bumps are arranged at a pitch of 30 μm, bare chip 2 in which gold bumps of 25 μm × 100 μm are arranged at a pitch of 40 μm, and 16 μm × 90 μm An ITO glass substrate having a bare chip 3 in which gold bumps are arranged at a pitch of 25 μm and a connection pitch corresponding to each bare chip is prepared, and 1.8 mm × 18 mm so as to cover the IC chip connection positions of the three types of ITO glass substrates. The anisotropic conductive film A is peeled off and bonded to the second layer side PET film release sheet, and thermocompression bonded under the conditions of 70 ° C., 0.5 MPa, 2 seconds, and the first layer side PET film release is performed. After the sheet is peeled off, the bare chip corresponding to each ITO glass substrate is flip chip bonder (Toray Engineering Co., Ltd.) Alignment is performed using a formula company FC2000 (the same applies hereinafter), reaches 180 ° C after 2 seconds with constant heat, and then pressurizes and pressurizes at 4 MPa for 20 seconds under the condition of constant temperature, and connects the bare chip to the ITO glass substrate. As a result, a connection structure was obtained.

From each IC chip and ITO glass substrate, a daisy chain circuit having 32 joints and a comb-shaped electrode having 20 pairs of combs are formed, and connection resistance measurement and insulation resistance measurement are performed. Indicates that continuity is established and all connections are made. On the other hand, the insulation resistances of the comb electrodes were all 10 ⁹ Ω or more, and no short circuit occurred between adjacent electrodes.
Further, a connection reliability test was performed using the connection structure connected using the bare chip 2. That is, as a result of conducting a connection reliability test for 500 hours in an environment of 60 ° C. and 90% relative humidity by applying a voltage of 30 V to the insulation resistance measurement unit, there is no abnormality in both insulation resistance and conduction resistance. There was no corrosion, no metal deposition, and no floating or peeling of the IC chip from the substrate. Further, when a connection reliability test was conducted for up to 1000 hours, a slight amount of metal was observed on the ITO wiring portion outside the IC chip, but no abnormality occurred in both the insulation resistance and the conduction resistance.

[Example 2]
A 50 μm PET film release sheet obtained by releasing the varnish A prepared in Example 1 was applied using a blade coater, and the solvent was dried and removed at 70 ° C. to obtain a resin film C having a film thickness of 18 μm.
Varnish D was obtained by mixing 100 parts by mass of phenoxy resin, 10 parts by mass of bisphenol A liquid epoxy resin, 0.7 parts by mass of silane coupling agent, and 240 parts by mass of methyl ethyl ketone.
The pressure-sensitive adhesive formed on the unstretched copolymerized polypropylene film prepared in Example 1 was filled with conductive particles having an average particle size of 3 μm (trade name: Micropearl AU203, manufactured by Sekisui Chemical Co., Ltd.) and air blown. Conductive particles that did not reach the adhesive were excluded. As a result, a conductive particle layer having a filling rate of 70% was formed. Furthermore, varnish D was applied onto the conductive particle layer using a blade coater, and varnish D entered the gap between the conductive particles of the conductive particle layer. Furthermore, the solvent was removed by drying at 70 ° C. to obtain a multilayer film D in which a resin film D having a thickness of 10 μm containing conductive particles was formed on a polypropylene film and an adhesive.

Next, this multilayer film D was stretched up to 2.5 times at 135 ° C. at a rate of 10% / second in both longitudinal and lateral directions using a test biaxial stretching apparatus, and gradually cooled to room temperature, and an array sheet D was obtained.
When the cross section of the array sheet D was observed using a scanning electron microscope (manufactured by Hitachi, Ltd .: S-4700, hereinafter the same), the thickness of the resin film D was 1.5 μm.
Further, the resin film C is stacked on the resin film D side, laminated under the conditions of 50 ° C. and 0.1 MPa, the polypropylene film and the adhesive are peeled off, and the resin film B created in Example 1 is further stacked. Lamination was performed under the conditions of 50 ° C. and 0.1 MPa to obtain an anisotropic conductive film C.
The ratio of the thickness of the second layer (resin film D + resin film B) to the thickness of the first layer (resin film C) of the anisotropic conductive film C is 0.11, and the content of conductive particles is anisotropic conductive. 1.1% by volume of the conductive film C.

As a result of observing the anisotropic conductive film C with a microscope, the conductive particles were in focus at the same focal point, and therefore, the anisotropic conductive film C was arranged in a single layer in the anisotropic conductive film A. Also, as a result of obtaining the average value of the center-to-center distance of the conductive particles and the coefficient of variation thereof from the image obtained by the microscope using the image processing software, the average value was 8.5 μm and the coefficient of variation was 0.25. It was. As the distance between the centers of the conductive particles, the length of a side of a triangle formed by Deloni triangulation using the center point of each particle was used, and the observation of the conductive particles was performed for particles within 0.06 mm ² .
Next, as in Example 1, the connection resistance measurement and the insulation resistance measurement were performed using the three types of bare chips. As a result, there was no abnormality. Further, as in Example 1, the bare chip 3 was used. When the connection reliability test was performed using the connection structure, the insulation resistance and the conduction resistance were not abnormal even after 1000 hours had passed, and further, corrosion of the electrodes, metal deposition, and floating of the IC chip from the substrate There was no occurrence of peeling.

[Comparative Example 1]
An anisotropic conductive film was prepared in the same manner as in Example 1 except that the resin film B was not laminated, and a connection reliability test using a connection structure using the bare chip 2 in the same manner as in Example 1. As a result, the insulation resistance decreased to 10 ⁷ Ω or less in 300 hours, and metal deposition was observed on the ITO wiring part outside the IC chip, which was found to be the cause of dielectric breakdown.
Since the anisotropic conductive film used in Comparative Example 1 does not have the second layer, the insulation reliability of the portion where sufficient heat is difficult to be supplied at the time of connection was low.

[Comparative Example 2]
An anisotropic conductive film E was prepared in the same manner as in Example 1 except that the film thickness of the resin film B was changed to 6 μm. The ratio of the thickness of the second layer (resin film B) to the thickness of the first layer (resin film A) of the anisotropic conductive film E was 0.33. Next, as a result of conducting a connection reliability test using the connection structure using the bare chip 2 in the same manner as in Example 1, the daisy chain circuit cannot be conducted in 20 hours. Peeling was observed. In the anisotropic conductive film used in Comparative Example 2, the connection reliability was inferior because the second layer was too thick.

[Comparative Example 3]
100 parts by mass of a phenoxy resin, 30 parts by mass of a bisphenol A type liquid epoxy resin, 0.8 parts by mass of a silane coupling agent, 30 parts by mass of conductive particles (trade name: Micropearl AU203, manufactured by Sekisui Chemical Co., Ltd.), The varnish F was obtained by mixing 240 parts by mass of methyl ethyl ketone. The varnish F was applied onto a release sheet made of 38 μm PET film which had been subjected to mold release treatment using a blade coater, and the solvent was dried and removed at 70 ° C. to obtain a resin film F having a thickness of 3 μm.
Next, the resin film F and the resin film A obtained in Example 1 are laminated using a heat roll, and the PET film release sheet on the resin film F side is further peeled off. Then, the resin film B obtained in Example 1 is removed. Were laminated using a heat roll to obtain an anisotropic conductive film F. The ratio of the thickness of the second layer (resin film F + resin film B) to the thickness of the first layer (resin film A) of the anisotropic conductive film F was 0.18.
The anisotropic conductive film F was observed with a microscope, and the average value of the center-to-center distance of the conductive particles and the coefficient of variation thereof were obtained from the obtained image using image processing software. The average value was 9.1 μm. The coefficient of variation was 0.62. As the distance between the centers of the conductive particles, the length of a side of a triangle formed by Deloni triangulation using the center point of each particle was used, and the observation of the conductive particles was performed for particles within 0.06 mm ² .
Next, as in Example 1, the connection resistance measurement was performed using three types of bare chips. As a result, no current flowed through the daisy chain of the connection structure using the bare chips 1 and 3, and the electrical connection was made. As a result, it was found that it cannot be used as a connection material.

  The anisotropic conductive adhesive film of the present invention is excellent in electrical connection of electrodes with a small area in electrical connection of a fine pattern, and is less likely to cause dielectric breakdown (short) between fine wirings. Even a portion where heat is difficult to be supplied has high insulation reliability and can be suitably used in electrical connection applications of fine patterns.

Claims (4)

  A first layer containing a thermosetting resin (A) and a latent curing agent, and a second layer containing a thermosetting resin (B) but not containing a latent curing agent, are composed of at least the two layers. In the anisotropic conductive film having conductivity by pressing in the thickness direction, wherein the second layer is the outermost layer and the conductive particles are arranged in a single layer, (1) Distance between centers of the conductive particles Is an average of 2 μm or more and 20 μm or less, its coefficient of variation is 0.05 or more and less than 0.5, and (2) the second layer is thicker than the first layer by 0.01 to less than 0.25 An anisotropic conductive film characterized by being:   The anisotropic conductive film according to claim 1, wherein the thermosetting resin (A) contained in the first layer is an epoxy resin.   A circuit connection method for electrically connecting an electrode of an IC chip and an electrode of a circuit board, wherein the anisotropic conductive film according to claim 1 or 2 is in contact with the circuit board on the second layer side, and more than the IC chip. A circuit connection method characterized by sandwiching an IC chip and a circuit board in a large area and applying pressure while supplying heat from the IC chip side.   A connection structure connected by the method according to claim 3.