JP7225505B2 - conductive adhesive composition - Google Patents

Description

The present invention relates to conductive adhesive compositions.

Use of a conductive adhesive composition in which a conductive filler is dispersed may be used as means for electrically connecting an electronic component and a substrate. As such a conductive adhesive composition, for example, Patent Document 1 discloses a thermoplastic resin composition that is excellent in mechanical strength and heat resistance and also in electrical properties such as conductivity and antistatic properties. specific surface area than the amorphous thermoplastic resin (component A), the crystalline thermoplastic resin (component B), the conductive carbon black (component C), and the conductive carbon black of component C Thermoplastic resin compositions consisting of conductive carbon black or hollow carbon fibrils with a high .lambda.

However, depending on the application, there is a demand for a conductive adhesive composition that provides isotropic conductivity. Therefore, if a large amount of conductive filler is blended, there is a risk that the adhesiveness will be impaired.

In recent years, conductive adhesive compositions used for connecting heat-sensitive members such as electronic components, for example, electrodes of piezoelectric films, are required to be capable of being processed at low temperatures, particularly at temperatures of 120 ° C. or less. It is In response to such a problem, Patent Document 2 discloses an anisotropic conductive film for anisotropically conductively connecting a terminal of a first electronic component and a terminal of a second electronic component, , an anisotropic conductive film containing a curable resin, a curing agent, and conductive particles, wherein the film-forming resin contains a crystalline resin and an amorphous resin. Further, Patent Document 3 discloses an anisotropic conductive film for anisotropically conductively connecting a terminal of a first electronic component and a terminal of a second electronic component, comprising a crystalline resin and an amorphous resin. , and conductive particles, and the crystalline resin contains a crystalline resin having 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.

Further, Patent Document 4 describes 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 mix a large amount of conductive filler, and there is room for further improvement in terms of compatibility between adhesion and isotropic conductivity.

JP-A-2003-96317 JP 2014-102943 A JP 2014-60025 A WO2009/038190

The present invention has been made in view of the above, and it is an object of the present invention to provide a conductive adhesive composition that can be processed at a low temperature of 120° C. or less and has both isotropic conductivity and excellent adhesiveness. aim.

In order to solve the above problems, the conductive adhesive composition of the present invention comprises (A) a crystalline thermoplastic resin having a melting point of 100° C. or higher and (B) an amorphous resin having a glass transition point of 50 to 120° C. 50 to 300 parts by mass of a dendritic conductive filler with respect to 100 parts by mass of a resin component containing at least a thermoplastic resin and (C) a carboxyl group-modified polyester resin having a glass transition point of 10 to 30°C. , the content of component (A) in 100 parts by mass of the resin component 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 70 parts by mass. It shall be 35 parts by mass .

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

The conductive filler is one or two 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. can do.

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. be able to.

The content of the carboxyl group-modified polyester resin (C) can be 15 to 35 parts by mass in 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 less is possible, and isotropic conductivity and excellent adhesiveness are obtained.

FIG. 3 is a schematic cross-sectional view showing a sample used for measuring 70° C. creep strength and tensile shear bond strength. It is a schematic cross-sectional view showing a sample used for measuring 90° peel strength. FIG. 4 is a schematic cross-sectional view for explaining a method for measuring surface resistivity _R1 . It is a schematic cross section for explaining a method of measuring connection resistivity _R2 .

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

The conductive adhesive composition according to the present embodiment contains at least (A) a crystalline thermoplastic resin having a melting point of 100° C. or higher, (B) an amorphous thermoplastic resin, and (C) a carboxyl group-modified polyester resin. 50 to 300 parts by mass of the dendrite-shaped conductive filler is contained with respect to 100 parts by mass of the resin component. Here, the crystalline resin is a polymeric substance that has a crystalline portion when solidified. A differential scanning calorimetry curve obtained in the process shows a distinct endothermic peak instead of a stepwise endothermic change. The melting point (Tm) of the crystalline resin means the peak top temperature of the endothermic peak. In addition, an amorphous resin is a polymeric substance that does not have a crystalline portion when solidified. , does not show a distinct endothermic peak. In this specification, differential scanning calorimetry is measured using a differential scanning calorimeter (for example, manufactured by Seiko Instruments Inc., trade name "DSC220"), and the measurement conditions are air flow rate After flowing in at 10 mL/min and maintaining at 25° C., the temperature is raised to 200° C. at 10° C./min. In this specification, the crystalline thermoplastic resin (A) and the amorphous thermoplastic resin (B) do not include the carboxyl group-modified polyester resin (C).

The crystalline thermoplastic resin (A) is not particularly limited, but examples include polyesters (PEs), polyethylene (PE), polypropylene (PP), polyamide (PA), polyimide (PI), polycarbonate (PC), polyacetal ( POM), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS) and the like, and these may be used singly or as a mixture of two or more. Among these, from the viewpoint of workability at a low temperature of 120° C. or less, polyester is preferable.

Although the number average molecular weight of the crystalline thermoplastic resin (A) is not particularly limited, it is preferably 8,000 to 30,000, more preferably 10,000 to 25,000. When it is 8,000 or more and 30,000 or less, the viscosity is moderate, and it is easy to form a film such as an electrode of a piezoelectric film. In the present specification, the number average molecular weight is measured by gel permeation chromatography (e.g., measuring device: "lliance HPLC system" manufactured by Waters Corporation, column: "KF-806L" manufactured by Shodex), and the solvent is tetrahydrofuran. Measured by standard polystyrene conversion.

The melting point of the crystalline thermoplastic resin (A) is not particularly limited as long as it is 100°C or higher, but it is preferably 100 to 140°C, more preferably 110 to 140°C, and 110 to 130°C. is more preferred. It is desirable that the adhesiveness is maintained at 70 ° C. or less from the usage conditions of the electronic component and the substrate that are connected using the conductive adhesive composition according to the present embodiment, and the melting point of the crystalline thermoplastic resin (A) is When the temperature is 100° C. or higher, creep deformation at 70° C. is less likely to occur, and excellent adhesiveness can be easily obtained. Further, when the temperature is 140° C. or lower, gelation is unlikely to occur even when dissolved in an organic solvent at room temperature, and excellent workability can be easily obtained.

Examples of the amorphous thermoplastic resin (B) include, but are not limited to, polyesters (PEs), polyvinyl chloride (PVC), polystyrene (PS), polymethylmethacrylate (PMMA), acrylonitrile butadiene styrene (ABS). , polycarbonate (PC), polyethersulfone (PES), polyetherimide (PEI), polyamideimide (PAI), etc., and these may be used alone, or two or more may be used as a mixture. good too. Among these, from the viewpoint of workability at a low temperature of 120° C. or less, polyester is preferable.

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

Although the glass transition point (Tg) of the amorphous thermoplastic resin (B) is not particularly limited, it is preferably 50 to 120°C, more preferably 60 to 100°C. When the temperature is 50°C or higher, excellent adhesiveness, particularly, excellent peeling adhesive strength can be easily obtained.

Here, in the present specification, the glass transition point means the temperature at 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.

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

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

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

The resin component of the conductive adhesive composition of the present embodiment includes the above-mentioned crystalline thermoplastic resin (A), amorphous thermoplastic resin (B), carboxyl group-modified A resin other than the polyester resin (C) may be contained.

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

The content 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 50 to 70 parts by mass. It is more preferably 60 parts by mass.

The content 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 15 parts by mass. More preferably, it is up to 25 parts by mass.

The content 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 20 to 30 parts by mass. It is more preferably 30 parts by mass. When the content 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, more preferably 50 to 250 parts by mass, based on 100 parts by mass of the resin component. When it is 50 parts by mass or more, isotropic conductivity is easily 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 has a dendrite shape, and examples thereof include copper particles, silver particles, gold particles, nickel particles, silver-coated copper particles, silver-coated copper alloy particles, and silver-coated nickel particles. From the viewpoint of conductivity, silver-coated copper particles, silver-coated copper alloy particles, and silver-coated nickel particles are preferable. Here, the term “dendritic shape” refers to a shape having one or more dendrites protruding from the particle surface. It may have a planar shape or a shape grown three-dimensionally.

The silver-coated copper particles may have copper particles and a silver-containing layer covering the copper particles, and the silver-coated copper alloy particles are composed of the copper alloy particles and the silver-containing layer covering the copper alloy particles. 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. Nickel and zinc may be included within the above ranges, the balance may be copper, and the balance copper may contain unavoidable impurities.

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

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

The conductive adhesive composition of the present embodiment can be appropriately blended with silica, urethane beads, or the like depending on the physical properties required to adjust the hardness of the composition. By blending silica, the conductive adhesive composition can be hardened, and by blending urethane beads, the conductive adhesive composition can be softened.

In addition to the above components, the conductive adhesive composition of the present embodiment may contain antioxidants, pigments, dyes, tackifying resins, plasticizers, ultraviolet absorbers, and anti-oxidants, as long as the objects of the present invention are not impaired. Foaming agents, leveling modifiers, fillers, flame retardants and the like can be blended.

The conductive adhesive composition of the present embodiment can be prepared by kneading according to 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 (piezo film) or as an adhesive for heat-sensitive electronic components.

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

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

According to the composition shown in Table 1 below, each component was mixed to prepare a conductive adhesive composition. This was coated on a release-treated polyethylene terephthalate (PET) film (release film 18) to prepare a conductive adhesive film with a thickness of 60 μm. The details of the compounds described in the table are as follows, where Tm represents the melting point, Tg the glass transition point, and Mn the number average molecular weight.
・Crystalline thermoplastic resin 1: crystalline polyester, Tm = 120°C, Mn = 22000
- Crystalline thermoplastic resin 2: crystalline polyester, Tm = 95 ° C., Mn = 20000
- Amorphous thermoplastic resin: amorphous polyester, Tg = 65 ° C., Mn = 16000
· Carboxyl group-modified polyester resin: Tg = 15 ° C., Mn = 16000, acid value = 18 mgKOH / g
- Conductive filler 1: dendrite-shaped silver-coated copper particles, average particle size 5 μm, silver coating amount 10% by mass
・ Conductive filler 2: spherical, silver-coated copper particles, average particle size 5 μm
・Urethane beads: Dainichiseika Kogyo Co., Ltd. “Dynamic Beads UCN-5050 Clear”
・ Silica: “Silophobic 200” manufactured by Fuji Silysia Chemical Co., Ltd.

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

・70°C creep strength: Sample 1, in which copper foil 12 is laminated on PET film 10 via double-sided tape 11, and the aluminum vapor-deposited surface of aluminum vapor-deposited film 13 on PET film 10 via double-sided tape 11 are the surfaces. Sample 2 laminated in the above manner was prepared, and each sample size was cut to 50 mm×20 mm. Then, the conductive adhesive film 14 having a thickness of 60 μm made of the conductive adhesive composition obtained above was cut into a size of 20 mm × 5 mm and laminated on the copper foil 12 of the sample 1. After pressing for 30 seconds at 100° C. and a pressure of 0.5 MPa, the release film 18 was peeled off. Then, as shown in FIG. 1, the aluminum vapor-deposited surface of the aluminum vapor-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. Grasp the end of sample 1 on the non-bonded side and hang it in an air oven, attach a weight of 500 ± 2 g to the end of sample 2 on the non-bonded side, heat at 70 ° C., and sample The time required for Sample 1 and Sample 2 to separate at the adhesion point was measured. Those whose time until separation was 500 hours or more were judged to be excellent in adhesiveness.

・90° peel strength (N/5mm): Sample 3, in which copper foil 12 is laminated via double-sided tape 11 on glass epoxy substrate 15, and aluminum deposition film 13 are prepared, and each size is 5 mm × It was cut to be 70 mm. Then, as shown in FIG. 2, the conductive adhesive film 14 obtained above was cut to a size of 5 mm×50 mm, laminated on the copper foil 12 of the sample 3, and the temperature was 100° C. and the pressure was 0. After press bonding at 5 MPa for 30 seconds, the release film 18 was peeled off. Then, the aluminum vapor-deposited surface of the aluminum vapor-deposited film 13 and the conductive adhesive film 14 were adhered to each other and connected by pressing 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 with a tensile tester (PT-200N manufactured by Minebea Co., Ltd.) at a tensile speed of 120 mm/min and in a peeling direction of 90 degrees (the direction of the arrow in FIG. 2). The average value of the load was used as the measured value.

・Tensile shear bond strength (N/20mm): Similar to the 70°C creep strength, sample 1 and sample 2 were adhered and connected with a conductive adhesive film 14, and in compliance with JIS K6850, Shimadzu Co., Ltd. tensile strength Using the test "AGS-X50S", a tensile test was performed at a tensile speed of 200 mm/min to measure the maximum load at break. Those having a strength of 60 N/20 mm or more were considered to be excellent in adhesiveness.

・^Surface resistivity (Ω/□): As shown in FIG. surface: gold-plated) was placed. At this time, the distance between the electrodes A and B was set to 10 mm. A load of 4.9 N was applied to _each electrode in the vertical direction, and the resistance value between the A and B electrodes was measured by the two-probe method.

- Connection resistivity: The connection resistivity with the aluminum deposition surface and the connection resistivity with the copper foil surface were measured. Specifically, as shown in FIG. 4, an aluminum vapor deposition film 17 having an aluminum vapor deposition layer 16 formed on a PET film 10 is prepared, and a 60 μm-thick conductive film made of the conductive adhesive composition obtained above is prepared. 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, of the cubic electrodes C and D (electrode area: 1 cm ² (each side = 1 cm), electrode surface: gold-plated), the electrode C is placed on the conductive adhesive film 14, and the electrode D is placed on the aluminum deposition film. 17. Other than that, the connection resistance value _R2 between the CD electrodes was measured in the same manner as the surface resistivity. The connection resistivity with the copper foil surface was measured in the same manner as described above except that copper foil was used instead of the aluminum deposited film 17 and the electrode D was placed on the copper foil.

Table 1 shows the average values obtained by setting the ambient temperature for measurement to room temperature (18 to 28° C.) and the number of tests to be n=5. If the resistance value is 10Ω/□ or less, it can be judged that the conductivity is excellent. At this time, whether the electrical connection was anisotropic or isotropic was also evaluated, and the evaluation of the surface resistivity _R1 of the anisotropic one was blank (-).

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

Comparative Example 1 is an example containing no carboxyl group-modified polyester resin (C), and was inferior in 90° peel strength.

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

Comparative Example 3 is an example in which spherical conductive fillers were used, and isotropic conductivity was not obtained. Moreover, the connection resistivity was inferior to both the aluminum deposition surface and the copper foil surface.

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

Reference Signs List 1...Sample 2...Sample 3...Sample 10...PET film 11...Double-sided tape 12...Copper foil 13...Aluminum deposition film 14...Conductive adhesion Film 15...Glass epoxy substrate 16...Aluminum deposition layer 17...Aluminum deposition film 18...Releasing films A, B, C, D...Electrodes

Claims (5)

(A) a crystalline thermoplastic resin having a melting point of 100° C. or higher, (B) an amorphous thermoplastic resin having a glass transition point of 50 to 120° C., and (C) a carboxyl group having a glass transition point of 10 to 30° C. Containing 50 to 300 parts by mass of a dendrite-shaped conductive filler with respect to 100 parts by mass of a resin component containing at least a modified polyester resin ,
The content of component (A) in 100 parts by mass of the resin component 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. Part by mass, conductive adhesive composition. 2. The conductive adhesive composition according to claim 1, wherein said crystalline thermoplastic resin (A) is a crystalline polyester and said amorphous thermoplastic resin (B) is an amorphous polyester. The conductive filler is one 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. Item 3. The conductive adhesive composition according to Item 1 or 2. 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. 4. The conductive adhesive composition according to any one of 1 to 3 . The conductive adhesive composition according to any one of claims 1 to 4 , wherein the content of the carboxyl group-modified polyester resin (C) is 15 to 35 parts by mass in 100 parts by mass of the resin component.

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