KR102580259B1 - Conductive adhesive composition - Google Patents

Abstract

The present invention provides a conductive adhesive composition that can be processed at 120°C or lower and has isotropic conductivity and excellent adhesiveness. For 100 parts by mass of the resin component containing at least (A) a crystalline thermoplastic resin with a melting point of 100°C or higher, (B) an amorphous thermoplastic resin, and (C) a carboxyl group-modified polyester resin, 50 to 50 parts by mass of a dendrite-shaped conductive filler is added. It is set as a conductive adhesive composition containing 300 parts by mass.

Description

Conductive adhesive composition

The present invention relates to a conductive adhesive composition.

As a means of electrically connecting an electronic component and a board, use of a conductive adhesive composition in which a conductive filler is dispersed may be used. As such a conductive adhesive composition, for example, Patent Document 1 describes an amorphous ( Non-crystalline thermoplastic resin (component A), crystalline thermoplastic resin (component B), conductive carbon black (component C), and conductive carbon black or hollow carbon blood with a larger specific surface area than the conductive carbon black of component C. A thermoplastic resin composition consisting of Brill is described.

However, depending on the application, a conductive adhesive composition that provides isotropic conductivity is required. The thermoplastic resin composition described in Patent Document 1 has anisotropic conductivity, and a conductive filler is added to make it isotropic. If the mixture was mixed at a high level, there was a risk that the adhesiveness would be impaired.

In addition, in recent years, conductive adhesive compositions used for connecting heat-vulnerable members such as electronic components, for example, electrodes of piezoelectric films, etc. are required to be capable of processing at low temperatures, especially at temperatures of 120°C or lower. Regarding this problem, Patent Document 2 discloses an anisotropic conductive film that anisotropically conductively connects a terminal of a first electronic component to a terminal of a second electronic component, and contains a film forming resin, a curable resin, a curing agent, and conductive particles. And an anisotropic conductive film in which the film-forming resin contains a crystalline resin and an amorphous resin is disclosed. In addition, Patent Document 3 describes an anisotropic conductive film for anisotropically conductively connecting a terminal of a first electronic component and a terminal of a second electronic component, containing a crystalline resin, an amorphous resin, and conductive particles, and the crystalline resin An anisotropic conductive film is disclosed, which is characterized in that it contains a crystalline resin having a bond that characterizes the resin and is identical to the bond that characterizes the resin possessed by the amorphous resin. However, they are all anisotropic conductive films.

In addition, Patent Document 4 discloses an adhesive composition containing (a) a crystalline polyester resin having a melting point of 40°C to 80°C, (b) a radically polymerizable compound, and (c) a radical polymerization initiator, and is conductive. Alternatively, in order to provide anisotropic conductivity, (f) conductive particles may be further included.

However, as described above, in order to obtain isotropic conductivity, it is necessary to mix a high level of conductive filler, and there is room for further improvement in terms of both adhesion and isotropic conductivity.

Japanese Patent Publication No. 2003-96317 Japanese Patent Publication No. 2014-102943 Japanese Patent Publication No. 2014-60025 International Publication No. 2009/038190

The present invention was made in consideration of the above, and its purpose is to provide a conductive adhesive composition that can be processed at low temperatures of 120°C or lower and has isotropic conductivity and excellent adhesive properties.

In order to solve the above problems, the conductive adhesive composition of the present invention includes a resin component containing at least (A) a crystalline thermoplastic resin with a melting point of 100°C or higher, (B) an amorphous thermoplastic resin, and (C) a carboxyl group-modified polyester resin. With respect to 100 parts by mass, 50 to 300 parts by mass of dendrite-shaped conductive filler is contained.

The crystalline thermoplastic resin (A) is preferably a crystalline polyester, and the amorphous thermoplastic resin (B) is preferably an amorphous polyester.

The conductive filler may be one or two types selected from the group consisting of copper particles, silver particles, gold particles, nickel particles, silver-coated copper particles, silver-coated copper alloy particles, and silver-coated nickel particles.

The glass transition point of the carboxyl group-modified polyester resin (C) may be 10 to 30°C.

The glass transition point of the amorphous thermoplastic resin (B) may be 50 to 120°C.

The content ratio ((A)/(B)) of the crystalline thermoplastic resin (A) and the amorphous thermoplastic resin (B) may be 60/40 to 90/10 in mass ratio.

The content of the carboxyl group-modified polyester resin (C) in 100 parts by mass of the resin component can be 15 to 35 parts by mass.

According to the conductive adhesive composition according to the present invention, processing at a low temperature of 120°C or lower is possible, and isotropic conductivity and excellent adhesiveness are obtained.

[Figure 1] A schematic cross-sectional view showing a sample used for measurement of 70°C creep strength and tensile shear adhesive strength.
[Figure 2] A schematic cross-sectional view showing a sample used for measurement of 90° peel strength.
[Figure 3] A schematic cross-sectional view for explaining a method of measuring surface resistivity R ₁ .
[FIG. 4] It is a schematic cross-sectional view for illustrating a method of measuring connection resistance R ₂ .

Hereinafter, embodiments of the present invention will be described in more detail.

The conductive adhesive composition according to the present embodiment is based on 100 parts by mass of a resin component containing at least (A) a crystalline thermoplastic resin with a melting point of 100°C or higher, (B) an amorphous thermoplastic resin, and (C) a carboxyl group-modified polyester resin. , shall contain 50 to 300 parts by mass of dendrite-shaped conductive filler. Here, a crystalline resin is a polymer material that has a crystal portion when solidified, and such a crystalline resin is usually obtained during the temperature increase process of differential scanning calorimetry (hereinafter also referred to as “DSC”). The differential scanning calorimetry curve shows a clear endothermic peak rather than a step-like change in endothermic amount. The melting point (Tm) of the crystalline resin refers to the temperature of the peak top in the endothermic peak. Additionally, an amorphous resin is a polymer material that does not have a crystalline portion when solidified, and the differential scanning calorimetry curve obtained during the temperature increase process of DSC for such an amorphous resin usually does not show a clear endothermic peak. In this specification, the differential scanning calorimetry is measured using a differential scanning calorimeter (e.g., manufactured by Seiko Denshi Kogyo Co., Ltd., brand name "DSC220 type"), and the measurement conditions are air. It is introduced at a flow rate of 10 mL/min, maintained at 25°C, and then raised to 200°C at 10°C/min. In addition, in this specification, the carboxyl group-modified polyester resin (C) is not included in the crystalline thermoplastic resin (A) or the amorphous thermoplastic resin (B).

The crystalline thermoplastic resin (A) is not particularly limited, but includes, for example, polyester (PEs), polyethylene (PE), polypropylene (PP), polyamide (PA), polyimide (PI), and polycarbonate (PC). , polyacetal (POM), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), etc. These may be used individually, or two or more types may be used. You may use it as a mixture. Among these, polyester is preferable from the viewpoint of processability at low temperatures of 120°C or lower.

The number average molecular weight of the crystalline thermoplastic resin (A) is not particularly limited, but is preferably 8,000 to 30,000, and more preferably 10,000 to 25,000. When it is 8000 or more and 30000 or less, the viscosity becomes appropriate and it is easy to form a film such as an electrode of a piezoelectric film. In this specification, the number average molecular weight is measured using gel permeation chromatography (e.g., measuring device: “lliance HPLC system” manufactured by Waters Corporation, column: “KF-806L” manufactured by Shodex), and the solvent is tetra. The value is measured using hydrofuran and converted to standard polystyrene.

The melting point of the crystalline thermoplastic resin (A) is not particularly limited as long as it is 100°C or higher, but is preferably 100 to 140°C, more preferably 110 to 140°C, and still more preferably 110 to 130°C. From the usage situation of the electronic component and the board connected using the conductive adhesive composition according to the present embodiment, it is preferable that the adhesiveness is maintained at 70 ° C. or lower, and the melting point of the crystalline thermoplastic resin (A) is 100 ° C. or higher. , creep deformation at 70°C is unlikely to occur, and excellent adhesion is easy to obtain. In addition, when the temperature is 140°C or lower, it is difficult to gel even if dissolved in an organic solvent at room temperature, and excellent processability is easily obtained.

The amorphous thermoplastic resin (B) is not particularly limited, but examples include polyester (PEs), polyvinyl chloride (PVC), polystyrene (PS), polymethyl methacrylate (PMMA), and acrylonitrile butadiene styrene ( ABS), polycarbonate (PC), polyethersulfone (PES), polyetherimide (PEI), polyamideimide (PAI), etc. These may be used individually or in a mixture of two or more types. You can also use it as . Among these, polyester is preferable from the viewpoint of processability at low temperatures of 120°C or lower.

The number average molecular weight of the amorphous thermoplastic resin (B) is not particularly limited, but is preferably 10,000 to 30,000, and more preferably 12,000 to 25,000.

The glass transition point (Tg) of the amorphous thermoplastic resin (B) is not particularly limited, but is preferably 50 to 120°C, and more preferably 60 to 100°C. When the temperature is 50°C or higher, excellent adhesiveness, especially excellent peel adhesion, is easy to be obtained, and when it is 120°C or lower, flexibility is excellent and it is easy to apply to applications such as films.

Here, in this specification, the glass transition point means the temperature of the inflection point of the differential scanning calorimetry curve obtained by differential scanning calorimetry.

The carboxyl group-modified polyester resin (C) may be crystalline or amorphous, but is preferably amorphous.

The glass transition point of the carboxyl group-modified polyester resin (C) is not particularly limited, but is preferably 10 to 30°C, and more preferably 14 to 30°C.

The number average molecular weight of the carboxyl group-modified polyester resin (C) is not particularly limited, but is preferably 10,000 to 30,000, and more preferably 14,000 to 20,000.

The acid value of the carboxyl group-modified polyester resin (C) is not particularly limited, but is preferably 10 to 25 mgKOH/g, and more preferably 15 to 20 mgKOH/g.

The resin component of the conductive adhesive composition of the present embodiment includes other than the above-mentioned crystalline thermoplastic resin (A), amorphous thermoplastic resin (B), and carboxyl group-modified polyester resin (C), as long as it does not impair the purpose of the present invention. Resin may be included.

The content ratio ((A)/(B)) of the crystalline thermoplastic resin (A) and the amorphous thermoplastic resin (B) is not particularly limited, but is preferably 60/40 to 90/10 in mass ratio, and 70/30. It is more preferable that it is ~90/10. When the content ratio is within the above range, excellent results are likely to be obtained in a 70°C creep test to evaluate adhesiveness.

The content ratio of the crystalline thermoplastic resin (A) in 100 parts by mass of the resin component is not particularly limited, but is preferably 40 to 70 parts by mass, more preferably 45 to 65 parts by mass, and even more preferably 50 to 60 parts by mass. .

The content ratio of the amorphous thermoplastic resin (B) in 100 parts by mass of the resin component is not particularly limited, but is preferably 15 to 35 parts by mass, more preferably 15 to 30 parts by mass, and even more preferably 15 to 25 parts by mass. .

The content ratio of the carboxyl group-modified polyester resin (C) in 100 parts by mass of the resin component is not particularly limited, but is preferably 15 to 35 parts by mass, more preferably 15 to 30 parts by mass, and even more preferably 20 to 30 parts by mass. do. When the content ratio is within the above range, excellent results are likely to be obtained in the 90° peel test for evaluating adhesiveness.

The content of the conductive filler is 50 to 300 parts by mass, preferably 50 to 280 parts by mass, and more preferably 50 to 250 parts by mass, per 100 parts by mass of the resin component. When it is 50 parts by mass or more, isotropic conductivity can easily be obtained, and when it is 300 parts by mass or less, it is easy to achieve both conductivity and adhesiveness.

The conductive filler is not particularly limited as long as it is in the form of a dendrite, but examples include copper particles, silver particles, gold particles, nickel particles, silver-coated copper particles, silver-coated copper alloy particles, and silver-coated nickel particles, which can reduce costs. From the viewpoint of hyperconductivity, silver-coated copper particles, silver-coated copper alloy particles, and silver-coated nickel particles are preferable. Here, the dendrite shape refers to a shape that has one or more dendritic protrusions protruding from the surface of the particle. The dendrite may be only a main branch without branches, and the branch portions branch from the main branch to form a planar or three-dimensional shape. It can also be a shape that grows into an enemy.

The silver-coated copper particles may have copper particles and a silver-containing layer that covers the copper particles, and the silver-coated copper alloy particles may have copper alloy particles and a silver-containing layer that covers the copper alloy particles, and the silver-coated nickel particles may have copper alloy particles and a silver-containing layer that covers the copper alloy particles. The particles may have nickel particles and a silver-containing layer covering the nickel particles. Additionally, the copper alloy particles may have a nickel content of 0.5 to 20 mass% and a zinc content of 1 to 20 mass%. Nickel and zinc are contained within the above-mentioned range, the remainder is made of copper, and the remainder of copper may contain unavoidable impurities.

The silver coating amount is preferably 1 to 30% by mass, and more preferably 3 to 20% by mass, in proportion to the silver-coated copper particles, silver-coated copper alloy particles, or silver-coated nickel particles. If the silver coating amount is 1% by mass or more, excellent conductivity can be easily obtained, and if the silver coating layer is 30% by mass or less, the cost can be reduced compared to silver particles while maintaining excellent conductivity.

The average particle diameter of the conductive filler is not particularly limited, but is preferably 1 to 20 μm, and more preferably 3 to 15 μm. When the thickness is 1 μm or more, excellent dispersibility is easily obtained, and when it is 20 μm or less, excellent conductivity is easily obtained. Here, in this specification, the average particle diameter means the particle diameter (primary particle diameter) at 50% of the integrated value in the particle size distribution obtained by the laser diffraction scattering method.

The hardness of the composition can be adjusted by appropriately mixing silica, urethane beads, etc. in the conductive adhesive composition of this embodiment according to the required physical properties. By blending silica, the conductive adhesive composition can be made hard, and by blending urethane beads, the conductive adhesive composition can be softened.

In addition to the above-mentioned components, the conductive adhesive composition of the present embodiment contains antioxidants, pigments, dyes, tackifying resins, plasticizers, ultraviolet absorbers, anti-foaming agents, leveling regulators, fillers, and flame retardants within the range that does not impair the purpose of the present invention. etc. can be combined.

The conductive adhesive composition of this embodiment can be produced by kneading according to a conventional method using a commonly used mixer such as a Banbury mixer, kneader, or roll.

The conductive adhesive composition of one embodiment can be suitably used as an electrode for a piezoelectric film (piezo film) or as an adhesive for electronic components that are sensitive to heat.

The conductive adhesive composition of the present embodiment may be formed into a film by coating a film made of polyethylene terephthalate or the like that has been subjected to mold release treatment to a desired thickness, thereby forming a conductive adhesive film. Additionally, for the purpose of protecting the conductive adhesive film, a release film may be provided on one side or both sides.

<Example>

Examples of the present invention are shown below, but the present invention is not limited to the examples below. In the following, mixing ratios, etc. are based on mass unless otherwise specified.

Each component was mixed according to the formulation shown in Table 1 below, and a conductive adhesive composition was prepared. This was coated on a polyethylene terephthalate (PET) film (release film 18) that had been subjected to release treatment, and a conductive adhesive film with a film thickness of 60 μm was produced. Details of the compounds listed in the table are as follows, where Tm represents the melting point, Tg represents the glass transition point, and Mn represents the number average molecular weight.

·Crystalline thermoplastic resin 1: Crystalline polyester, Tm=120℃, Mn=22000

·Crystalline thermoplastic resin 2: Crystalline polyester, Tm=95℃, Mn=20000

·Amorphous thermoplastic resin: Amorphous polyester, Tg=65℃, Mn=16000

·Carboxyl group-modified polyester resin: Tg=15℃, Mn=16000, acid value=18mgKOH/g

Conductive filler 1: dendrite-shaped silver-coated copper particles, average particle diameter 5 μm, silver coating amount 10 mass%

Conductive filler 2: spherical, silver-coated copper particles, average particle diameter 5㎛

・Urethane beads: “Dynamic Beads UCN-5050 Clear” manufactured by Dainichi Seika Kogyo Co., Ltd.

・Silica: “Ssilohovic 200” manufactured by Fuji Silicia Chemical Co., Ltd.

The adhesiveness (70°C creep strength, 90° peel strength, and tensile shear adhesive strength), surface resistivity, and connection resistivity of the obtained conductive adhesive composition were measured, and the results are shown in Table 1. The measurement method is as shown below.

Creep strength at 70°C: Sample 1 in which copper foil 12 was laminated on PET film 10 through double-sided tape 11, and aluminum deposition film 13 on PET film 10 through double-sided tape 11. ) Sample 2 was prepared so that the aluminum deposition surface was the surface, and each sample was cut to a size of 50 mm x 20 mm. Then, the conductive adhesive film 14 with a film thickness of 60 μm made of the conductive adhesive composition obtained above was cut to a size of 20 mm x 5 mm and laminated on the copper foil 12 of Sample 1, at a temperature of 100°C. After pressing at a pressure of 0.5 MPa for 30 seconds, the release film 18 was peeled. Then, as shown in FIG. 1, the aluminum-deposited surface of the aluminum-deposited film 13 of Sample 2 and the conductive adhesive film 14 were adhered and connected by press-bonding at a temperature of 100° C. and a pressure of 0.5 MPa for 30 seconds. The end of Sample 1 on the non-adhered side is grasped and hung in an air oven, and a weight of 500 ± 2 g is attached to the non-adhered end of Sample 2, followed by heating at 70°C, and Sample 1 The time until sample 2 and sample 2 were separated from the adhesive point was measured. Those with a separation time of 500 hours or more were considered to have excellent adhesiveness.

・90° peel strength (N/5 mm): Sample 3, in which copper foil 12 was laminated through double-sided tape 11, and aluminum vapor deposition film 13 were prepared on a glass epoxy substrate 15, and each It was cut to a size of 5 mm x 70 mm. As shown in FIG. 2, the conductive adhesive film 14 obtained above was cut to a size of 5 mm After pressing for 30 seconds, the release film 18 was peeled. Then, the aluminum-deposited surface of the aluminum-deposited film 13 and the conductive adhesive film 14 were adhered and connected by press-bonding at a temperature of 100° C. and a pressure of 0.5 MPa for 30 seconds. The aluminum vapor-deposited film 13 connected to Sample 3 was peeled using a tensile tester (PT-200N manufactured by Minebea Co., Ltd.) at a tensile speed of 120 mm/min and a peeling direction of 90 degrees (arrow direction in FIG. 2), The average value of the load until failure was taken as the measured value.

· Tensile shear adhesive strength (N/20 mm): 70°C Similar to the creep strength, Sample 1 and Sample 2 are bonded and connected with a conductive adhesive film 14, in accordance with JIS K6850, manufactured by Shimadzu Seisakusho Co., Ltd. Using the tensile test "AGS-X50S", a pulling test was performed at a tensile speed of 200 mm/min, and the maximum load at breakage was measured. Those with a thickness of 60 N/20 mm or more were considered to have excellent adhesiveness.

Surface resistivity (Ω/□): As shown in FIG. 3, on the conductive adhesive film 14 produced above, cubic-shaped electrodes A and B (electrode area: 1 cm2 (each side = 1 cm), electrodes Surface: plating treatment) was installed. At this time, the spacing between electrodes A and B was 10 mm. A load of 4.9 N was applied to each electrode in the vertical direction, the resistance value between the AB electrodes was measured using the two-terminal method, and the value 1 minute after the start of the measurement was taken as the surface resistivity R ₁ .

·Connection resistance: The connection resistance with the aluminum vapor deposition surface and the connection resistance with the copper foil surface were measured. Specifically, as shown in FIG. 4, an aluminum vapor deposition film 17 is prepared by forming an aluminum vapor deposition layer 16 on a PET film 10, and a conductive film with a thickness of 60 μm is formed of the conductive adhesive composition obtained above. The adhesive film 14 was transferred to the aluminum deposition film 17 by pressing at a temperature of 100°C and a pressure of 0.5 MPa for 30 seconds, and the release film 18 was peeled off. Then, among the cube-shaped electrodes C and D (electrode area: 1 cm2 (each side = 1 cm), electrode surface: plating), electrode C was mounted on the conductive adhesive film 14, and electrode D was placed on an aluminum vapor-deposited film ( 17) It was mounted on the table. Otherwise, the connection resistance value R ₂ between CD electrodes was measured in the same manner as the surface resistivity. In addition, the connection resistance with the copper foil surface was measured in the same manner as above except that copper foil was used instead of the aluminum vapor deposition film 17 and the electrode D was mounted on the copper foil.

In all cases, the measurement ambient temperature was room temperature (18 to 28°C), and the average value with the number of tests set to n = 5 is shown in Table 1. A resistance value of 10Ω/□ or less can be judged to have excellent conductivity. At this time, it was also evaluated whether the electrical connection was anisotropic or isotropic, and for those that were anisotropic, the surface resistivity R ₁ was evaluated as blank (-).

[Table 1]

As shown in Table 1, Examples 1 to 5 were all excellent in adhesion (70°C creep strength, 90° peel strength, and tensile shear adhesive strength), surface resistivity, and connection resistivity.

Comparative Example 1 was an example that did not contain the carboxyl group-modified polyester resin (C), and the 90° peel strength was inferior.

Comparative Example 2 is an example in which only the carboxyl group-modified polyester resin (C) was used, and the creep strength at 70°C was inferior.

Comparative Example 3 is an example in which a spherical conductive filler was used, and isotropic conductivity was not obtained. Additionally, the connection resistance was inferior to either the aluminum vapor deposition surface or the copper foil surface.

In Comparative Example 4, the melting point of the crystalline thermoplastic resin was outside the predetermined range, and the creep strength at 70°C was poor.

1: Sample
2: Sample
3: Sample
10: PET film
11: Double-sided tape
12: Copper foil
13: Aluminum deposition film
14: Conductive adhesive film
15: Glass epoxy substrate
16: Aluminum deposition layer
17: Aluminum deposition film
18: Release film
A, B, C, D: Electrodes

Claims (7)

(A) a crystalline thermoplastic resin with a melting point of 100℃ or higher; (B) an amorphous thermoplastic resin with a glass transition point of 50∼120℃; and (C) a carboxyl group-modified polyester resin with a glass transition point of 10∼30℃. Containing 50 to 300 parts by mass of a dendrite-shaped conductive filler, based on 100 parts by mass of the resin component containing at least
In 100 parts by mass of the resin components, the content of component (A) is 40 to 70 parts by mass, the content of component (B) is 15 to 35 parts by mass, and the content of component (C) is 15 to 35 parts by mass,
A conductive adhesive composition further containing urethane beads or silica. According to paragraph 1,
A conductive adhesive composition wherein the crystalline thermoplastic resin (A) is a crystalline polyester, and the amorphous thermoplastic resin (B) is an amorphous polyester. According to claim 1 or 2,
A conductive adhesive composition wherein the conductive filler is one or two or more selected from the group consisting of copper particles, silver particles, gold particles, nickel particles, silver-coated copper particles, silver-coated copper alloy particles, and silver-coated nickel particles. ◈Claim 4 was abandoned upon payment of the setup registration fee.◈ According to claim 1 or 2,
A conductive adhesive composition wherein the content ratio ((A)/(B)) of the crystalline thermoplastic resin (A) and the amorphous thermoplastic resin (B) is 60/40 to 90/10 in mass ratio. ◈Claim 5 was abandoned upon payment of the setup registration fee.◈ According to claim 1 or 2,
A conductive adhesive composition wherein the content of the carboxyl group-modified polyester resin (C) is 15 to 35 parts by mass based on 100 parts by mass of the resin component. delete delete

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