JP7459048B2 - conductive adhesive composition - Google Patents

Description

The present invention relates to a conductive adhesive composition.

As a means for electrically connecting an electronic component and a substrate, use of a conductive adhesive composition in which a conductive filler is dispersed can be mentioned. As such a conductive adhesive composition, for example, Patent Document 1 describes a thermoplastic resin composition that has excellent mechanical strength and heat resistance, and also has excellent electrical properties such as conductivity and antistatic property. Amorphous thermoplastic resin (component A), crystalline thermoplastic resin (component B), conductive carbon black (component C), and a specific surface area lower than that of the conductive carbon black of component C. Thermoplastic resin compositions are described that consist of large conductive carbon black or hollow carbon fibrils.

However, depending on the application, a conductive adhesive composition that can provide isotropic conductivity is required, but the conductivity of the thermoplastic resin composition described in Patent Document 1 is anisotropic, and is not isotropic. If a high amount of conductive filler is added in order to achieve this, there is a risk that adhesiveness will be impaired.

Additionally, in recent years, conductive adhesive compositions used to connect heat-sensitive components such as electronic components, such as electrodes of piezoelectric films, are required to be processable at low temperatures, particularly at temperatures below 120°C. has been done. In response to such problems, Patent Document 2 discloses an anisotropic conductive film that connects terminals of a first electronic component and a terminal of a second electronic component in an anisotropic manner, the film-forming resin and , an anisotropic conductive film containing a curable resin, a curing agent, and conductive particles, the film-forming resin containing a crystalline resin and an amorphous resin is disclosed. Further, Patent Document 3 discloses an anisotropic conductive film that connects a terminal of a first electronic component and a terminal of a second electronic component in an anisotropic conductive manner, the film comprising a crystalline resin and an amorphous resin. , conductive particles, and the crystalline resin contains a crystalline resin that has the same bond that characterizes the resin as the bond that characterizes the resin that the amorphous resin has. A conductive film is disclosed. However, both are anisotropic conductive films.

Furthermore, 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. is disclosed, and it is disclosed that (f) conductive particles can be further included in order to impart conductivity or anisotropic conductivity.

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

Japanese Patent Application Publication No. 2003-96317 JP2014-102943A Japanese Patent Application Publication No. 2014-60025 International Publication No. 2009/038190

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

In order to solve the above problems, the conductive adhesive composition of the present invention comprises a crystalline thermoplastic resin (A) having a melting point of 90°C or higher, a carboxyl group-modified polyester resin (B), and a urethane-modified polyester resin (C). ), 50 to 300 parts by mass of a dendrite-shaped conductive filler is contained per 100 parts by mass of the resin component containing at least .

The crystalline thermoplastic resin (A) may be a crystalline polyester resin.

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

The glass transition point of the above urethane modified polyester resin (C) may be 80 to 120°C.

The content of the crystalline thermoplastic resin (A) may be 50 to 70 parts by mass per 100 parts by mass of the resin component.

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

The content of the urethane-modified polyester resin (C) may be 15 to 35 parts by mass per 100 parts by mass of the resin component.

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 can be obtained.

FIG. 2 is a schematic cross-sectional view showing a sample used for measuring 85° C. creep strength and tensile shear adhesive strength. FIG. 3 is a schematic cross-sectional view showing a sample used for measuring 90° peel strength. FIG. 2 is a schematic cross-sectional view for explaining a method of measuring surface resistivity _R1 . FIG _{. 2} is a schematic cross-sectional view for explaining a method of measuring connection resistivity R2.

The following describes in more detail the embodiments of the present invention.

The conductive adhesive composition according to the present embodiment contains 50 to 300 parts by mass of a dendrite-shaped conductive filler per 100 parts by mass of a resin component containing at least a crystalline thermoplastic resin (A) having a melting point of 90°C or higher, a carboxyl group-modified polyester resin (B), and a urethane-modified polyester resin (C). Here, a crystalline resin is a polymeric substance that has a crystalline portion when solidified, and such a crystalline resin usually exhibits a clear endothermic peak rather than a stepwise change in endothermic amount in the differential scanning calorimetry (hereinafter also referred to as "DSC") curve obtained during the temperature rise process of differential scanning calorimetry (DSC). The melting point (Tm) of the crystalline resin refers to the peak top temperature of the endothermic peak. In this specification, the differential scanning calorimetry is performed using a differential scanning calorimeter (e.g., manufactured by Seiko Electronics Co., Ltd., product name "DSC220 type"), and the measurement conditions are as follows: air is introduced at a flow rate of 10 mL/min, the temperature is maintained at 25° C., and the temperature is then increased at 10° C./min to 200° C. In addition, in this specification, the crystalline thermoplastic resin (A) does not include the carboxyl group-modified polyester resin (B) and the urethane-modified polyester resin (C).

The crystalline thermoplastic resin (A) is not particularly limited, but includes, for example, polyester (PEs), polyethylene (PE), polypropylene (PP), polyamide (PA), polyimide (PI), polycarbonate (PC), polyacetal ( POM), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), etc., and these may be used alone or in a mixture of two or more. . Among these, polyester resins are preferred 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 the number average molecular weight is within the above range, the viscosity becomes appropriate and it is easy to form a coating such as an electrode of a piezoelectric film. In this specification, the number average molecular weight is a value measured using gel permeation chromatography (for example, measuring device: "Iliance HPLC System" manufactured by Waters Corporation, column: "KF-806L" manufactured by Shodex) using tetrahydrofuran as the solvent and converted into standard polystyrene.

The melting point of the crystalline thermoplastic resin (A) is not particularly limited as long as it is 90°C or higher, but it is preferably 90 to 140°C, more preferably 90 to 130°C. Considering the usage conditions of electronic components and substrates connected using the conductive adhesive composition according to the present embodiment, it is desirable that the adhesiveness is maintained at 85°C or lower, and the melting point of the crystalline thermoplastic resin (A) is When the temperature is 90°C or higher, creep deformation at 85°C is difficult to occur and excellent adhesiveness is easily obtained. Moreover, when the melting point of the crystalline thermoplastic resin (A) is 140° C. or lower, it is difficult to gel even when dissolved in an organic solvent at room temperature, and excellent processability is easily obtained.

The carboxyl group-modified polyester resin (B) may be crystalline or amorphous, but is preferably amorphous. An amorphous resin is a polymeric substance that does not have crystalline parts when solidified, and the differential scanning calorimetry curve obtained during the heating process of DSC for such an amorphous resin is usually clear. It does not show any endothermic peak.

The glass transition point of the carboxyl group-modified polyester resin (B) is not particularly limited, but is preferably 10 to 30°C, more preferably 14 to 30°C. Here, in this specification, the glass transition point means the temperature at the inflection point of a differential scanning calorimetry curve obtained by differential scanning calorimetry. When the glass transition point is within the above range, it is easy to obtain excellent low-temperature processability and flexibility, and excellent results are obtained in both the 85°C creep strength test and the 90° peel strength test for evaluating adhesion. Cheap.

The number average molecular weight of the carboxyl group-modified polyester resin (B) is not particularly limited, but is preferably 10,000 to 30,000, and more preferably 14,000 to 20,000. When the number average molecular weight is within the above range, excellent flexibility is easily obtained, and excellent results are also easily obtained in the 90° peel strength test for evaluating adhesion.

The acid value of the carboxyl group-modified polyester resin (B) is not particularly limited, but is preferably 10 to 25 mgKOH/g, and more preferably 15 to 20 mgKOH/g. When the acid value is within the above range, excellent flexibility is easily obtained, and excellent results are also easily obtained in the 90° peel strength test for evaluating adhesion.

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

The glass transition point of the urethane-modified polyester resin (C) is not particularly limited, but is preferably 70 to 120°C, more preferably 75 to 110°C, and even more preferably 80 to 110°C. When the glass transition point is within the above range, it is easy to obtain excellent low-temperature processability and flexibility, and excellent results are obtained in both the 85°C creep strength test and the 90° peel strength test for evaluating adhesion. Cheap.

The number average molecular weight of the urethane-modified polyester resin (C) is not particularly limited, but is preferably from 10,000 to 50,000, more preferably from 20,000 to 45,000. When the number average molecular weight is within the above range, excellent flexibility is likely to be obtained, and excellent results are also likely to be obtained in a 90° peel strength test for evaluating adhesiveness.

The resin component of the conductive adhesive composition of the present embodiment may include the above-mentioned crystalline thermoplastic resin (A), carboxyl group-modified polyester resin (B), urethane-modified polyester resin, within a range that does not impair the purpose of the present invention. Resins other than (C) may be included.

The content of the crystalline thermoplastic resin (A) in 100 parts by mass of the resin component is not particularly limited, but is preferably from 50 to 70 parts by mass, more preferably from 50 to 60 parts by mass. When the content ratio is within the above range, excellent results are likely to be obtained in the 85° C. creep strength test for evaluating adhesiveness.

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

The content of the urethane-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 20 to 30 parts by mass. When the content ratio is within the above range, excellent results are likely to be obtained in the 85° C. creep strength test for evaluating adhesiveness.

The content of the conductive filler is 50 to 300 parts by weight, preferably 50 to 280 parts by weight, and more preferably 50 to 250 parts by weight, based on 100 parts by weight of the resin component. When the content is 50 parts by mass or more, isotropic conductivity is easily obtained, and when the content 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 has a dendrite shape, 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 conductivity, silver-coated copper particles, silver-coated copper alloy particles, and silver-coated nickel particles are preferable. Here, the dendrite shape refers to a shape having one or more dendrites protruding from the particle surface, and the dendrites may be only main branches without branches, or branch parts branch from the main branch. The shape may be a planar shape or a three-dimensionally grown shape.

The silver-coated copper particles may have copper particles and a silver-containing layer coating the copper particles, the silver-coated copper alloy particles may have copper alloy particles and a silver-containing layer coating the copper alloy particles, and the silver-coated nickel particles may have nickel particles and a silver-containing layer coating the nickel particles. The copper alloy particles may have a nickel content of 0.5 to 20% by mass and a zinc content of 1 to 20% by mass. The nickel and zinc may be contained within the above ranges, with the balance being copper, and the remaining copper may contain inevitable impurities.

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

The average particle size of the conductive filler is not particularly limited, but is preferably 1 to 20 μm, and more preferably 3 to 15 μm. When the average particle size 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 size means the particle size (primary particle size) at an integrated value of 50% in the particle size distribution obtained by the laser diffraction scattering method.

The hardness of the composition can be adjusted by appropriately blending silica, urethane beads, etc. into the conductive adhesive composition of this embodiment, depending on 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 made soft.

In addition to the above components, the conductive adhesive composition of this embodiment may contain antioxidants, pigments, dyes, tackifying resins, plasticizers, UV absorbers, defoamers, leveling adjusters, fillers, flame retardants, etc., within the scope of the invention.

The conductive adhesive composition of this embodiment can be manufactured by kneading in accordance with a conventional method using a commonly used mixer such as a Banbury mixer, a kneader, or a roll.

The conductive adhesive composition of one embodiment can be suitably used as an electrode for a piezoelectric film or as an adhesive for heat-sensitive electronic components.

The conductive adhesive composition of the present embodiment may be formed into a film by coating a release-treated film of polyethylene terephthalate or the like to a desired thickness to form a conductive adhesive film. In addition, for the purpose of protecting the conductive adhesive film, a release film may be provided on one or both sides thereof.

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

Each component was mixed according to the formulation shown in Table 1 below to prepare a conductive adhesive composition. This was coated on a release-treated polyethylene terephthalate (PET) film (release film 18) to produce a conductive adhesive film with a thickness of 60 μm. 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°C, Mn=22000
・Crystalline thermoplastic resin 2: Crystalline polyester, Tm=92°C, Mn=36000
・Crystalline thermoplastic resin 3: Crystalline polyester, Tm=85°C, Mn=19000
・Amorphous thermoplastic resin 1: Amorphous polyester, Tg=65°C, Mn=16000
・Carboxyl group-modified polyester resin: Tg = 15°C, Mn = 16000, acid value = 18mgKOH/g
・Urethane modified polyester resin 1: Tg = 84°C, Mn = 40000
・Urethane modified polyester resin 2: Tg=106°C, Mn=25000
- Conductive filler 1: dendrite-shaped silver-coated copper particles, average particle diameter 5 μm, silver coating amount 10% by mass
・Conductive filler 2: Spherical, silver-coated copper particles, average particle diameter 5 μm
・Urethane beads: “Dynamic Beads UCN-5050 Clear” manufactured by Dainichiseika Kagyo Co., Ltd.

The adhesive properties (85°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.

- 85°C creep strength: sample 1 in which copper foil 12 is laminated on PET film 10 via double-sided tape 11, and aluminum vapor-deposited surface of aluminum vapor-deposited film 13 on PET film 10 via double-sided tape 11 is the surface. A laminated sample 2 was prepared, and each sample was cut to have a size of 50 mm x 20 mm. Then, the conductive adhesive film 14 made of the conductive adhesive composition obtained above and having a thickness of 60 μm was cut into a size of 20 mm x 5 mm, laminated on the copper foil 12 of sample 1, and heated to After press-bonding at 100° C. and a pressure of 0.5 MPa for 30 seconds, the release film 18 was peeled off. 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 bonded together and connected by press-bonding at a temperature of 100° C. and a pressure of 0.5 MPa for 30 seconds. Grasp the non-adhesive end of sample 1 and hang it in an air oven. After attaching a weight of 500 ± 2 g to the non-adhesive end of sample 2, heat it at 85°C to remove the sample. The time taken for Sample 1 and Sample 2 to separate at the bonded location was measured. Those whose time until separation was 500 hours or more were considered to have excellent adhesiveness.

- 90° peel strength (N/5mm): Sample 3 in which copper foil 12 was laminated on glass epoxy substrate 15 via double-sided tape 11 and aluminum vapor-deposited film 13 were prepared, and the size of each was 5mm x It was cut to a length of 70 mm. Then, as shown in FIG. 2, the conductive adhesive film 14 obtained above was cut into a size of 5 mm x 50 mm, and laminated on the copper foil 12 of sample 3 at a temperature of 100°C and a pressure of 0. After pressing for 30 seconds at .5 MPa, the release film 18 was peeled off. Then, the aluminum-deposited surface of the aluminum-deposited film 13 and the conductive adhesive film 14 were bonded together 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 off using a tensile tester (PT-200N manufactured by Minebea Co., Ltd.) at a tensile speed of 120 mm/min and at a peeling direction of 90 degrees (in the direction of the arrow in Figure 2). The average value of the load was taken as the measured value. Those having a 90° peel strength of 3.5 N/5 mm or more were considered to have excellent adhesive properties.

・Tensile shear adhesive strength (N/20mm): Sample 1 and sample 2 were bonded and connected using conductive adhesive film 14 in the same manner as the 85°C creep strength, and tensile shear adhesive strength manufactured by Shimadzu Corporation was prepared in accordance with JIS K6850. A tensile test was conducted using test "AGS-X50S" at a tensile speed of 200 mm/min, and the maximum load at break was measured. If it was 60N/20mm or more, it was considered to have excellent adhesiveness.

・Surface resistivity (Ω/□): As shown in FIG. 3, cubic-shaped electrodes A and B (electrode area: 1 cm ² (each side = 1 cm), electrodes Surface: gold plating treatment) was placed. At this time, the interval between electrodes A and B was 10 mm. A load of 4.9 N was applied to each electrode in the vertical direction, and the resistance value between electrodes A and B was measured using a two-terminal method, and the value 1 minute after the start of the measurement was taken as the surface resistivity _R1 .

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

In all cases, the measurement atmosphere temperature was room temperature (18 to 28°C), and the average values were shown in Table 1, with the number of tests being n=5. If the resistance value is 10Ω/□ or less, it can be judged that the conductivity is excellent. At this time, it was also evaluated whether the electrical connection was anisotropic or isotropic, and if it was anisotropic, the evaluation of surface resistivity _R1 was blanked (-).

As shown in Table 1, Examples 1 to 7 were excellent in adhesive properties (85°C creep strength, 90° peel strength, and tensile shear adhesive strength), surface resistivity, and connection resistivity.

Comparative Example 1 is an example in which a crystalline thermoplastic resin having a melting point of 85°C was used instead of the crystalline thermoplastic resin (A), and the 85°C creep strength was poor.

Comparative Example 2 is an example in which an amorphous thermoplastic resin was used instead of the carboxyl group-modified polyester resin (B), and the 90° peel strength was poor.

Comparative Example 3 was an example that did not contain the urethane-modified polyester resin (C) and had poor creep strength at 85°C.

Comparative Example 4 was an example in which the content of the conductive filler was less than the lower limit, and the surface resistivity and the connection resistivity with the aluminum vapor-deposited surface were poor.

Comparative Example 5 is an example in which the content of the conductive filler exceeds the upper limit, and the 85°C creep strength and 90° peel strength were poor.

Comparative Example 6 is an example in which the conductive filler has a spherical shape, the electrical connection is anisotropic, and the connection resistivity with the aluminum vapor deposition surface and the connection resistivity with the copper foil surface are poor.

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

Claims (6)

A conductive adhesive composition comprising 50 to 300 parts by mass of a dendrite-shaped conductive filler per 100 parts by mass of a resin component containing at least a crystalline thermoplastic resin (A) having a melting point of 90°C or more and 140°C or less, a carboxyl group-modified polyester resin (B ), and a urethane-modified polyester resin (C), wherein the crystalline thermoplastic resin (A) is a crystalline polyester . The conductive adhesive composition according to claim 1 , wherein the carboxyl group-modified polyester resin (B) has a glass transition point of 10 to 30°C. The conductive adhesive composition according to claim 1 or 2 , wherein the urethane-modified polyester resin (C) has a glass transition point of 80 to 120°C. The conductive adhesive composition according to any one of claims 1 to 3 , wherein the content of the crystalline thermoplastic resin (A) is 50 to 70 parts by mass in 100 parts by mass of the resin component. The conductive adhesive composition according to any one of claims 1 to 4 , wherein the content of the carboxyl group-modified polyester resin (B) is 15 to 35 parts by mass in 100 parts by mass of the resin component. The conductive adhesive composition according to any one of claims 1 to 5 , wherein the content of the urethane-modified polyester resin (C) is 15 to 35 parts by mass in 100 parts by mass of the resin component.

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