HK1240406B - Anisotropic conductive film and connection method - Google Patents

Description

Anisotropic conductive film and connection method

Technical Field

The present invention relates to an anisotropic conductive film and a connection method.

Background Art

Conventionally, as a means for connecting electronic components to substrates, a tape-shaped connection material (for example, anisotropic conductive film (ACF)) obtained by applying a release film with a thermosetting resin containing conductive particles dispersed therein has been used.

The anisotropic conductive film is used, for example, for connecting a COF (Chip on Film) to a rigid substrate (eg, a PWB (Printed Wiring Board)) (FOB: Flex on Board, rigid-flex board bonding).

To improve the solderability of mounted components such as IC chips and capacitors, these rigid substrates are sometimes treated with an anti-rust treatment using an organic solderability preservative (OSP). Examples of such prefluxes include imidazole-based prefluxes.

However, the above-mentioned substrate subjected to rust prevention treatment has a problem in that the adhesion of the anisotropic conductive film is reduced.

Therefore, in order to provide stable connection reliability for the connection of the above-mentioned rust-proof treated substrate, a circuit connection material has been proposed, which contains a curing agent that generates free radicals, a free radical polymerizing substance, a phosphate ester and conductive particles, and when the total weight of the circuit connection material excluding the conductive particles is 100 parts by weight, the proportion of the phosphate ester therein is in the range of 0.5 parts by weight to 2.5 parts by weight (for example, refer to Patent Document 1).

However, in this proposed technology, although the insulation between adjacent terminals is excellent, the long-term electrical conductivity between the connection terminals is insufficient.

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent Application Laid-Open No. 2009-277769.

Summary of the Invention

Problems to be solved by the invention

The present invention aims to solve the aforementioned problems and achieve the following objectives. Specifically, the present invention aims to provide an anisotropic conductive film and a joint using the same, wherein the anisotropic conductive film exhibits excellent insulation between adjacent terminals and long-term electrical conductivity between connected terminals, even when connecting substrates that have undergone rust prevention treatment.

Means for solving problems

The means for solving the above-mentioned problems are as follows.

<1> An anisotropic conductive film, characterized by comprising the following layers:

a conductive particle-containing layer containing conductive particles, a thermosetting resin, and a curing agent; and

The thermoplastic layer contains an acid component.

<2> The anisotropic conductive film according to <1>, wherein the acid component is a phosphate compound.

<3> The anisotropic conductive film according to any one of <1> to <2>, wherein the melt viscosity of the conductive particle-containing layer is higher than the melt viscosity of the thermoplastic layer.

<4> A connection method for connecting a terminal of a first circuit component to a terminal of a second circuit component, characterized by comprising the following steps:

a first disposing step of disposing the anisotropic conductive film according to any one of <1> to <3> on the terminal of the first circuit component so that the thermoplastic layer is in contact with the terminal of the first circuit component;

a second disposing step of disposing the second circuit component on the anisotropic conductive film; and

a heating and pressurizing step of heating and pressurizing the second circuit component by a heating and pressurizing member;

The terminals of the first circuit member are subjected to rust prevention treatment using a rust preventive agent.

Effects of the Invention

According to the present invention, the above-mentioned problems in the past can be solved and the above-mentioned objectives can be achieved. An anisotropic conductive film and a joint body using the anisotropic conductive film can be provided, wherein the anisotropic conductive film has excellent insulation between adjacent terminals and long-term conductivity between connecting terminals even when connecting substrates that have been rust-proofed.

BRIEF DESCRIPTION OF THE DRAWINGS

[Fig. 1A] Fig. 1A is a schematic cross-sectional view (part 1) for explaining an example of the connection method of the present invention.

[Fig. 1B] Fig. 1B is a schematic cross-sectional view (part 2) for explaining an example of the connection method of the present invention.

[Fig. 1C] Fig. 1C is a schematic cross-sectional view (part 3) for explaining an example of the connection method of the present invention.

[Fig. 1D] Fig. 1D is a schematic cross-sectional view (part 4) for explaining an example of the connection method of the present invention.

[Fig. 1E] Fig. 1E is a schematic cross-sectional view (part 5) for explaining an example of the connection method of the present invention.

DETAILED DESCRIPTION

(Anisotropic Conductive Film)

The anisotropic conductive film of the present invention includes at least a conductive particle-containing layer and a thermoplastic layer, and further includes other components as needed.

<Conductive Particle-Containing Layer>

The conductive particle-containing layer contains at least conductive particles, a thermosetting resin, and a curing agent, and further contains other components as needed.

<<Conductive Particles>>

The conductive particles are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include metal particles and metal-coated resin particles.

The metal particles are not particularly limited and can be appropriately selected depending on the intended purpose, and examples thereof include nickel, cobalt, silver, copper, gold, palladium, and solder (solder). These may be used alone or in combination of two or more.

Among these, nickel, silver, and copper are preferred. To prevent surface oxidation, these metal particles may also be coated with gold or palladium on their surfaces. Furthermore, particles coated with metal protrusions or organic insulating films on their surfaces may also be used.

The metal-coated resin particles are not particularly limited, as long as they are particles in which the surface of the resin particles is coated with a metal. Suitable selections may be made depending on the intended purpose. Examples include particles in which the surface of the resin particles is coated with at least one of nickel, silver, solder, copper, gold, and palladium. Furthermore, particles having metallic protrusions or an organic insulating coating applied to the surface may also be used. When low-resistance connections are desired, particles in which the surface of the resin particles is coated with silver are preferred.

The method for coating the resin particles with metal is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include chemical plating and sputtering.

The material of the resin particles is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include styrene-divinylbenzene copolymers, benzoguanamine resins, cross-linked polystyrene resins, acrylic resins, and styrene-silica composite resins.

The conductive particles may be conductive particles as long as they are conductive during anisotropic conductive connection. For example, particles having an insulating film applied to the surface of metal particles are also conductive particles as long as the particles deform during anisotropic conductive connection to expose the metal particles.

The average particle size of the conductive particles is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 1 μm to 50 μm, more preferably 2 μm to 25 μm, and particularly preferably 2 μm to 10 μm.

The average particle size is an average value of particle sizes measured for 10 randomly selected conductive particles.

The particle size can be measured, for example, by observation using a scanning electron microscope.

The content of the conductive particles in the conductive particle-containing layer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.5% by mass to 10% by mass, and more preferably 1% by mass to 5% by mass.

<<Thermosetting resin>>

The thermosetting resin is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include epoxy resins and polymerizable acrylic compounds.

Epoxy resin

The epoxy resin is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin, modified epoxy resins thereof, alicyclic epoxy resins, etc. These may be used alone or in combination of two or more.

-Polymerizable acrylic compounds-

The polymerizable acrylic compound is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include polyethylene glycol diacrylate, phosphate ester acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, isobutyl acrylate, tert-butyl acrylate, isooctyl acrylate, bisphenoxyethanol fluorene diacrylate, 2-acryloyloxyethyl succinate, lauryl acrylate, stearyl acrylate, isobornyl acrylate, tricyclodecane dimethanol dimethacrylate, cyclohexyl acrylate, tris(2-hydroxyethyl)isocyanurate triacrylate, tetrahydrofurfuryl acrylate, diglycidyl phthalate acrylate, ethoxylated bisphenol A dimethacrylate, bisphenol A epoxy acrylate, urethane acrylate, epoxy acrylate, and the like, as well as their corresponding methacrylates. These may be used alone or in combination of two or more.

The content of the thermosetting resin in the conductive particle-containing layer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 20% by mass to 60% by mass, and more preferably 30% by mass to 50% by mass.

<<Curing Agent>>

The curing agent is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include imidazoles, organic peroxides, anionic curing agents, and cationic curing agents.

Examples of the imidazoles include 2-ethyl-4-methylimidazole and the like.

Examples of the organic peroxide include lauroyl peroxide, butyl peroxide, benzyl peroxide, dilauroyl peroxide, dibutyl peroxide, peroxydicarbonate, and benzoyl peroxide.

Examples of the anionic curing agent include organic amines.

Examples of the cationic curing agent include sulfonium salts, onium salts, and aluminum chelate agents.

Among these, organic peroxides are preferred, and dilauroyl peroxide is more preferred, from the viewpoint of excellent storage stability.

The combination of the thermosetting resin and the curing agent is not particularly limited and may be appropriately selected depending on the intended purpose. However, a combination of the epoxy resin and the cationic curing agent, or a combination of the polymerizable acrylic compound and the organic peroxide is preferred.

The content of the curing agent in the conductive particle-containing layer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 1% by mass to 15% by mass, and more preferably 2% by mass to 10% by mass.

<<Other ingredients>>

As said other component contained in the said electroconductive particle containing layer, a film-forming resin, a filler, etc. are mentioned, for example.

-Film-forming resin-

The film-forming resin is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include phenoxy resins, unsaturated polyester resins, saturated polyester resins, urethane resins, butadiene resins, polyimide resins, polyamide resins, and polyolefin resins. One of these film-forming resins may be used alone, or two or more may be used in combination. Among these, phenoxy resins are preferred from the perspectives of film-forming properties, processability, and connection reliability.

Examples of the phenoxy resin include resins synthesized from bisphenol A and epichlorohydrin.

As the phenoxy resin, a suitably synthesized resin may be used, or a commercially available product may be used.

The content of the film-forming resin in the conductive particle-containing layer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 20% by mass to 60% by mass, and more preferably 30% by mass to 50% by mass.

-filler-

The filler is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include alumina, silica, talc, mica, kaolin, zeolite, barium sulfate, and calcium carbonate.

The content of the filler in the conductive particle-containing layer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.5% by mass to 15% by mass, and more preferably 1% by mass to 10% by mass.

It is preferable that the conductive particle-containing layer does not contain an acid component. Examples of the acid component include the acid components described below.

The average thickness of the conductive particle-containing layer is not particularly limited and can be appropriately selected, but is preferably 10 μm to 50 μm, and more preferably 20 μm to 40 μm.

Here, the said average thickness is the average value when measuring the thickness of five places of the said conductive particle-containing layer at random.

<Thermoplastic Layer>

The thermoplastic layer contains at least an acid component and, if necessary, other components.

The thermoplastic layer is a layer that exhibits plasticity due to heat.

The thermoplastic layer may contain a compound having a reactive functional group such as an epoxy resin or a polymerizable acrylic compound, but in this case, it does not contain a curing agent for curing the compound.

<<Acid Component>>

The acid component is not particularly limited as long as it is an acidic component and can be appropriately selected according to the purpose. Examples of the acidic group in the acid component include: a phosphate group, a carboxyl group, a sulfo group, etc. Examples of the compound having an acidic group include: (meth)acrylates having an acidic group, etc.

The acid component may be rosin (abietic acid). The rosin generates acid when melted.

Among these, phosphoric acid ester compounds are preferred because they have strong acidity and can easily remove the rust inhibitor. Examples of the phosphoric acid ester compounds include phosphoric acid ester type acrylates.

The content of the acid component in the thermoplastic layer is not particularly limited and can be appropriately selected depending on the intended purpose, but is preferably 1% to 10% by mass, and more preferably 2% to 6% by mass. If the content is less than 1% by mass, removal of the rust inhibitor may be insufficient; if it exceeds 10% by mass, it may be difficult to achieve a balanced blend with other components of the thermoplastic layer.

<<Other ingredients>>

Examples of the other components in the thermoplastic layer include film-forming resins and other resins.

-Film-forming resin-

The film-forming resin is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include the film-forming resins exemplified in the description of the conductive particle-containing layer.

The content of the film-forming resin in the thermoplastic layer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0% by mass to 20% by mass, and more preferably 0% by mass to 10% by mass.

-Other resins-

The aforementioned other resin is not particularly limited, as long as it is a resin other than the aforementioned film-forming resin, and can be appropriately selected depending on the intended purpose. Examples include epoxy resins and polymerizable acrylic compounds. Since these are commonly used components in anisotropic conductive films, they can also be used as materials for the aforementioned thermoplastic layer in the anisotropic conductive film of the present invention. However, when the aforementioned thermoplastic layer contains these compounds having reactive functional groups, the aforementioned thermoplastic layer typically does not contain a curing agent for curing them.

The content of the other resin in the thermoplastic layer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 60% by mass to 99% by mass, and more preferably 80% by mass to 97% by mass.

The average thickness of the thermoplastic layer is not particularly limited and can be appropriately selected, but is preferably 1 μm to 10 μm, more preferably 2 μm to 7 μm. An average thickness within the preferred range is advantageous in terms of easier control of fluidity and less residual angle at the connection portion after crimping.

Here, the average thickness is an average value of thicknesses measured at five random locations on the thermoplastic layer.

The melt viscosity of the conductive particle-containing layer is preferably greater than the melt viscosity of the thermoplastic layer from the perspective of facilitating the removal of the thermoplastic layer from between the connection terminals. As for the ratio of the melt viscosities, the melt viscosity of the conductive particle-containing layer is preferably 10 times or more, more preferably 15 to 70 times, and particularly preferably 20 to 70 times the melt viscosity of the thermoplastic layer from the perspective of facilitating the removal of the thermoplastic layer from between the connection terminals.

The melt viscosity is measured using a rheometer (manufactured by HAAKE) for example. The measurement is performed using each layer. The measurement is performed at a temperature in the flow region, and the result obtained when the set temperature during viscosity measurement is 85°C is defined as the melt viscosity.

(Connection method)

The connection method according to the present invention includes at least a first placement step, a second placement step, and a heating and pressurizing step, and further includes other steps as necessary.

The above-mentioned connection method is a method of connecting the terminal of the first circuit component and the terminal of the second circuit component.

<First Circuit Component and Second Circuit Component>

As the above-mentioned first circuit component and the above-mentioned second circuit component, there is no special limitation as long as they are circuit components having terminals and being the objects of anisotropic conductive connection using the above-mentioned anisotropic conductive film. They can be appropriately selected according to the purpose, for example: plastic substrates with terminals, Flex-on-Board (flexible and hard board bonding, FOB), Flex-on-Flex (flexible boards bonded to each other, FOF), etc.

The material of the terminal is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include Cu, Au-plated Cu, Ni and Au-plated Cu, and Sn-plated Cu.

The material and structure of the plastic substrate with terminals are not particularly limited and can be appropriately selected depending on the intended purpose. Examples include rigid substrates with terminals and flexible substrates with terminals. Examples of rigid substrates with terminals include glass epoxy substrates with copper wiring. Examples of flexible substrates with terminals include polyimide substrates with copper wiring.

The shapes and sizes of the first circuit member and the second circuit member are not particularly limited and can be appropriately selected according to the intended purpose.

The first circuit component and the second circuit component may be the same circuit component or different circuit components.

The terminals of the first circuit member are subjected to rust prevention treatment using a rust preventive agent.

It is preferable that the terminals of the second circuit member are not subjected to rust prevention treatment using a rust preventive agent.

The rust preventive is not particularly limited and can be appropriately selected depending on the intended purpose. The rust preventive is generally referred to as a pre-flux or an OSP (Organic Solderability Preservative).

The rust preventive agent contains, for example, at least an imidazole compound, copper ions, and an organic acid. Examples of the imidazole compound include benzimidazole, etc. The benzimidazole may have a substituent.

The rust inhibitor is preferably water-soluble.

The method of the rust prevention treatment is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a method of immersing the circuit component to be treated in the rust preventive agent or an aqueous solution of a diluted rust preventive agent.

By performing the above-mentioned rust-proofing treatment, the terminals and circuit parts on the circuit components are protected.

<First Arrangement Process>

The first placement step is not particularly limited as long as it is a step of placing the anisotropic conductive film of the present invention on the terminal of the first circuit member so that the thermoplastic layer is in contact with the terminal of the first circuit member, and can be appropriately selected depending on the purpose.

<Second Arrangement Process>

The second disposing step is not particularly limited as long as it is a step of disposing the second circuit member on the anisotropic conductive film, and can be appropriately selected depending on the intended purpose.

<Heating and Pressing Process>

The heating and pressing step is not particularly limited as long as it is a step of heating and pressing the second circuit member by a heating and pressing member, and can be appropriately selected depending on the purpose. For example, heating and pressing can be performed by a heating and pressing member.

Examples of the heating and pressurizing member include a pressurizing member having a heating mechanism, etc. Examples of the heating and pressurizing member having a heating mechanism include a heating tool, etc.

The heating temperature is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 140°C to 200°C.

The pressurization pressure is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.1 MPa to 80 MPa.

The heating and pressurizing time is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the time may be 0.5 seconds to 120 seconds.

Here, an example of the connection method of the present invention is described with reference to the drawings.

1A to 1E are schematic cross-sectional views for explaining an example of the connection method of the present invention.

First, as shown in Fig. 1A, a first circuit component 1 is prepared. The first circuit component 1 includes a substrate 1A and terminals 1B located on the substrate 1A. Terminals 1B are subjected to a rust-proofing treatment using a rust-proofing agent 1C.

Next, as shown in Figure 1B, an anisotropic conductive film 2 is placed on the first circuit component 1. The anisotropic conductive film 2 is formed by laminating a thermoplastic layer 2A and a conductive particle-containing layer 2B. It should be noted that the anisotropic conductive film 2 is placed on the first circuit component 1 so that the thermoplastic layer 2A contacts the terminal 1B of the first circuit component 1. It should be noted that the conductive particle-containing layer 2B contains conductive particles 2C. At this point, as shown in Figure 1C, the acid component in the thermoplastic layer 2A removes the rust inhibitor 1C from the terminal 1B.

Next, as shown in FIG1D , a second circuit component 3 is disposed on the conductive particle-containing layer 2B of the anisotropic conductive film 2. The second circuit component 3 includes a substrate 3A and terminals 3B located on the substrate 3A. The second circuit component 3 is disposed on the conductive particle-containing layer 2B of the anisotropic conductive film 2 so that the terminals 3B are in contact with the conductive particle-containing layer 2B.

Next, as shown in FIG1E , the first circuit component 1 and the second circuit component 3 are connected by heating and pressurizing the second circuit component 3. At this point, since the rust inhibitor 1C is not present on the terminal 1B, good connectivity is achieved. Furthermore, during heating and pressurization, the thermoplastic layer 2A is squeezed out from at least between the terminal 1B and the terminal 3B. Therefore, the acid component in the thermoplastic layer 2A does not degrade the terminal 1B or the terminal 3B (e.g., corrode, dissolve, migrate, etc.).

Therefore, according to the connection method of the present invention, even when substrates subjected to rust-proofing treatment are connected, a connection with excellent insulation between adjacent terminals and long-term conductivity between the connection terminals can be achieved.

It should be noted that, in the above description based on Figures 1A to 1E , Figure 1C shows an embodiment in which the rust preventative agent 1C is removed. However, the connection method of the present invention is not limited to this embodiment. For example, even if the rust preventative agent is not removed from the terminal during the first placement step, it can be removed from the terminal during the heating and pressurizing step. The connection method of the present invention also includes such embodiments.

Example

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

(Example 1)

<Fabrication of Anisotropic Conductive Film>

<<Production of the First Layer>>

A first layer composition was prepared by uniformly mixing 55 parts by mass of a bisphenol F epoxy resin (Mitsubishi Chemical Corporation, trade name: jER-4004P), 25 parts by mass of a difunctional acrylic monomer (Shin-Nakamura Chemical Co., Ltd., trade name: A-200), 20 parts by mass of a urethane acrylate (Shin-Nakamura Chemical Co., Ltd., trade name: U-2PPA), and 4 parts by mass of a phosphate ester acrylate (Nippon Kayaku Co., Ltd., trade name: PM-2) using a conventional method. The resulting composition was applied to a release polyester film and dried with hot air at 70°C for 3 minutes to produce a first layer with an average thickness of 5 μm.

<<Production of the Second Layer>>

A second layer composition was prepared by uniformly mixing 45 parts by mass of a phenoxy resin (trade name: YP50, manufactured by Nippon Steel Chemical Co., Ltd.), 20 parts by mass of a bifunctional acrylic monomer (trade name: A-200, manufactured by Shin-Nakamura Chemical Co., Ltd.), 20 parts by mass of a urethane acrylate (trade name: U-2PPA, manufactured by Shin-Nakamura Chemical Co., Ltd.), 5 parts by mass of a silica filler (average particle size 5 μm, trade name: Aerosil RY200, manufactured by Nippon Aerosil Co., Ltd.), 5 parts by mass of dilauroyl peroxide (trade name: PEROYL L, manufactured by NOF Corporation), and 3 parts by mass of nickel-plated resin particles with an average particle size of 10 μm using a conventional method. The resulting composition was applied to a release polyester film and dried by blowing hot air at 70°C for 5 minutes to produce a second layer having an average thickness of 30 μm.

The first layer and the second layer were bonded together using a laminator to obtain a double-layer anisotropic conductive film.

(Example 2)

An anisotropic conductive film was produced in the same manner as in Example 1, except that the average thickness of the first layer was 3 μm and the average thickness of the second layer was 32 μm.

(Example 3)

An anisotropic conductive film was produced in the same manner as in Example 1, except that the composition of the first layer was changed to the composition shown in Table 1.

(Example 4)

An anisotropic conductive film was produced in the same manner as in Example 1, except that the composition of the first layer, and the average thickness of the first layer and the average thickness of the second layer were changed as shown in Table 1.

(Example 5)

An anisotropic conductive film was produced in the same manner as in Example 1, except that the composition of the first layer was changed as shown in Table 1.

(Example 6)

An anisotropic conductive film was produced in the same manner as in Example 1, except that the composition of the first layer was changed as shown in Table 1.

(Comparative Example 1)

An anisotropic conductive film was produced in the same manner as in Example 1, except that the composition of the first layer was changed as shown in Table 1.

(Comparative Example 2)

An anisotropic conductive film was produced in the same manner as in Example 1, except that the composition of the first layer, and the average thickness of the first layer and the average thickness of the second layer were changed as shown in Table 1.

(Comparative Example 3)

A second layer composition was prepared by uniformly mixing 45 parts by mass of a phenoxy resin (trade name: YP50, manufactured by Nippon Steel Chemical Co., Ltd.), 20 parts by mass of a bifunctional acrylic monomer (trade name: A-200, manufactured by Shin-Nakamura Chemical Co., Ltd.), 20 parts by mass of a urethane acrylate (trade name: U-2PPA, manufactured by Shin-Nakamura Chemical Co., Ltd.), 4 parts by mass of a phosphate ester acrylate (trade name: PM-2, manufactured by Nippon Kayaku Co., Ltd.), 5 parts by mass of a silica filler (average particle size 5 μm, trade name: Aerosil RY200, manufactured by Nippon Aerosil Co., Ltd.), 5 parts by mass of dilauroyl peroxide (trade name: PEROY L, manufactured by NOF Corporation), and 3 parts by mass of nickel-plated resin particles with an average particle size of 10 μm. The resulting composition was applied to a release polyester film and dried by blowing hot air at 70°C for 5 minutes to produce an anisotropic conductive film with an average thickness of 35 μm.

<Production of Joint>

As the first circuit component, a PWB (printed wiring board) (evaluation substrate manufactured by Dexerials Corporation, 200 μm P, Cu 35 μm t - rust-proofed, FR-4 substrate) was used.

As the second circuit component, a COF (chip on film) package (evaluation substrate manufactured by Dexerials Corporation, 200 µm P, Cu 8 µm t-Sn plating, 38 µm t-S'perflex substrate) was used.

The first circuit member and the second circuit member were connected using the produced anisotropic conductive film.

It should be noted that the first circuit component used was a component that had passed through a reflow furnace with a top temperature of 250° C. three times.

First, an anisotropic conductive film cut to a width of 2.0 mm was attached to the first circuit component in such a way that the first layer was in contact with the terminals of the first circuit component. After the second circuit component was aligned thereon, it was crimped using a heated and pressurized tool (buffer material 250 μmt - silicone rubber, 2.0 mm width) under the crimping conditions of 170°C - 3 MPa - 5 seconds to produce a joint.

<Measurement of Melt Viscosity>

The melt viscosities of the first and second layers in the Examples and Comparative Examples were measured using a rheometer (manufactured by HAAKE). The measurements were performed on each layer before laminating the first and second layers using a laminator. The measurements were performed at a temperature within the flow range, with the set temperature for the viscosity measurement set at 85°C. The results are shown in Table 1.

<THB evaluation>

The resulting bonded products were subjected to THB evaluation. They were exposed to a 60°C, 95% RH environment and a 50V DC voltage was applied for 250 hours. After the test, the presence of insulation degradation due to corrosion and migration was confirmed, and the evaluation was performed according to the following criteria. The results are shown in Table 1.

[Evaluation Criteria]

○: Insulation resistance value is 1.0×10 ⁹ Ω or more

△: Insulation resistance value is 1.0×10 ⁸ Ω or more and less than 1.0×10 ⁹ Ω

×: Insulation resistance value is less than 1.0×l0 ⁸ Ω.

<Measurement of On-Resistance>

The connection resistance of the prepared bonded structure was measured initially and after 500 hours at 85°C and 85% RH, using a four-terminal method with a current of 1 mA flowing, and evaluated according to the following evaluation criteria. The results are shown in Table 1.

[Evaluation Criteria]

○: Less than 0.3Ω

△: 0.3Ω or more and less than 0.6Ω

×: 0.6Ω or more.

[Table 1]

The unit of the compounding amounts shown in Table 1 is part by mass.

jER-4004P: Bisphenol F epoxy resin, manufactured by Mitsubishi Chemical Corporation

YP-70: Bisphenol A/F type epoxy phenoxy resin, manufactured by Nippon Steel Chemical Co., Ltd.

YP-50: Bisphenol A epoxy phenoxy resin, manufactured by Nippon Steel Chemical Co., Ltd.

A-200: Bifunctional acrylic monomer, manufactured by Shin-Nakamura Chemical Co., Ltd.

U-2PPA: Urethane acrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.

PM-2: Phosphate ester acrylate, manufactured by Nippon Kayaku Co., Ltd.

KE-604: Rosin, manufactured by Arakawa Chemical Industries, Ltd.

PEROYL L: Dilauroyl peroxide, manufactured by NOF Corporation

Aerosil RY200: Silica filler, manufactured by Japan AEROSIL Co., Ltd.

In Examples 1 to 6, the insulation between adjacent terminals and the long-term conductivity between the connection terminals were excellent.

In Comparative Example 1, although the first layer contained an acid component, it contained a curing component and a curing agent rather than a thermoplastic layer, resulting in insufficient insulation resistance. This is believed to be because after the assembly was fabricated, the first layer was not extruded from the terminal, and the acid component in the first layer damaged the terminal, causing migration.

Comparative Example 2 showed insufficient on-resistance. This is probably because the first layer, although a thermoplastic layer, did not contain an acid component and therefore could not remove the rust inhibitor on the terminals. As a result, the rust inhibitor reduced the connectivity between the terminals.

Comparative Example 3 had insufficient insulation resistance. This is presumably because the acid component damaged the terminals and caused migration of the terminals after the joint was produced.

Industrial applicability

The anisotropic conductive film of the present invention has excellent insulation between adjacent terminals and long-term conductivity between connecting terminals even when connecting rust-proofed substrates, and is therefore suitable for connecting rust-proofed substrates to other substrates.

Explanation of symbols

1　　First circuit component

1A Base material

1B terminal

1C Rust inhibitor

2. Anisotropic conductive film

2A Thermoplastic layer

2B Conductive particle-containing layer

2C Conductive particles

3. Second circuit component

3A Base material

3B terminal

Claims (4)

1. An anisotropic conductive film, characterized in that it comprises the following layer: The conductive particles contain a layer comprising conductive particles, a thermosetting resin, and a curing agent; and Thermoplastic layer, which contains acidic components, The melt viscosity of the conductive particle layer is greater than that of the thermoplastic layer. 2. The anisotropic conductive film according to claim 1, wherein the acid component is a phosphate ester compound. 3. A connection method for connecting the terminals of a first circuit component to the terminals of a second circuit component, characterized in that it comprises the following steps: The first configuration step involves configuring the anisotropic conductive film as described in claim 1 or 2 on the terminals of the first circuit component in such a manner that the thermoplastic layer contacts the terminals of the first circuit component. The second configuration step involves configuring the second circuit component on the anisotropic conductive film; and The heating and pressurizing process involves heating and pressurizing the second circuit component using a heating and pressurizing component. The terminals of the first circuit component are subjected to rust prevention treatment based on rust inhibitor. 4. A junction wherein the terminals of a first circuit component and the terminals of a second circuit component are connected via a cured anisotropic conductive film as described in claim 1 or 2.