JP5796232B2 - Conductive particles, anisotropic conductive materials, and connection structures - Google Patents

Description

  The present invention relates to conductive particles having carbon particles as core particles and an anisotropic conductive material in which the conductive particles are dispersed in an insulating adhesive.

  An anisotropic conductive material in which conductive particles are dispersed in an insulating adhesive is used as a wiring material. As the conductive particles, resin particles having a uniform particle diameter are used as core particles, and the surface thereof is used. In addition, a material plated with a metal such as nickel or gold, or a particle made only of a metal such as nickel is used. Among them, the former is mainly used for glass substrates such as LCD panels for fine pitch connection, and the latter is used for PWB (Printed Wiring Board), COF (Chip On Film), TCP (Tape Carrier Package), etc. It is used for connection with FPC (Flexible Printed Circuits), or for connection between a glass substrate and a FPC using a wiring material having high surface oxidation properties such as ITO and IZO.

  However, if particles made of only metal are used as conductive particles of an anisotropic conductive material, the metal particles have a higher specific gravity than the resin composition constituting the insulating adhesive, and thus settle in the anisotropic conductive material. It is easy to cause agglomeration of particles caused by sedimentation, causing problems such as a short circuit between wires connected by an anisotropic conductive material.

  On the other hand, conductive particles with resin particles as core particles have a lighter specific gravity than conductive particles made only of metal, so dispersibility in anisotropic conductive materials is improved, but wiring using anisotropic conductive materials There is a problem in that the indentation of the conductive particles is not sufficiently developed at the time of connection between them, so that the connection state cannot be confirmed, and thus the connection reliability cannot be improved.

  In addition, as the conductive particles of the anisotropic conductive material, carbon particles are used as core particles, and the surface thereof is subjected to metal plating. In particular, a plurality of protrusions are provided on the surface of the conductive particles, It has been proposed to reduce the connection resistance by concentrating the load on the protruding portion when the conductive particles and the wiring are pressed together so that the conductive particles bite into the wiring at the protruding portion (Patent Document 1).

Japanese Patent No.2823799

  However, as described in Patent Document 1, when tar is attached to carbon particles to form graphitized protrusions by firing, the carbon particles are likely to aggregate, and therefore anisotropically blended as conductive particles The conductive material has a problem that it easily causes a short circuit between wirings.

  In contrast, the present invention provides conductive particles that have good dispersibility in anisotropic conductive materials and have a high effect of biting into wiring, and anisotropy using such conductive particles. An object is to provide a conductive material.

  The present inventor uses anisotropically conductive carbon particles that are substantially free of surface irregularities as the core particles, and uses a metal plating layer having irregularities as the outer shell. It has been found that the dispersibility of the conductive particles in the conductive material is sufficiently increased and the effect of the conductive particles in the wiring is increased, thereby ensuring high connection reliability.

  That is, the present invention is a conductive particle in which carbon particles having substantially no surface unevenness are coated with a plating layer, and the surface unevenness ratio of the particles is expressed by T / D (where D is the particle plane Conductivity in which the surface irregularity ratio of the conductive particles is 0.01 to 0.6 when the diameter of the inscribed circle with respect to the outline of the particle in the projected view and T is the maximum distance between the outline and the inscribed circle) Provide particles.

  In addition, the present invention provides an anisotropic conductive material in which the above-described conductive particles are dispersed in an insulating adhesive, and the anisotropic conductive material is disposed between opposing terminals, and the terminals are added. An anisotropic conductive connection method for connecting by pressing and an anisotropic conductive connection body connected by the anisotropic conductive material are provided.

Since the conductive particles of the present invention have carbon particles as core particles and have a specific gravity smaller than that of metal particles, the dispersibility of the conductive particles in the anisotropic conductive material is good.
Moreover, since the electroconductive particle of this invention has surface unevenness | corrugation, since it is excellent in the penetration effect to the wiring of an electroconductive particle, high connection reliability can be ensured.

  Further, the surface irregularities are formed by a plating layer that is an outer shell of the carbon particles, and the carbon particles themselves have substantially no surface irregularities, so that the carbon particles themselves have surface irregularities. Aggregation of carbon particles does not occur. Therefore, the conductive particles of the present invention have good dispersibility in the anisotropic conductive material despite having carbon particles as core particles and surface irregularities.

  Therefore, the anisotropic conductive material using the conductive particles of the present invention and the anisotropic conductive connection method using the same exhibit high connection reliability without causing an unnecessary short circuit.

FIG. 1 is an explanatory diagram of a method for measuring the surface roughness ratio.

Hereinafter, the present invention will be specifically described.
The conductive particles of the present invention have carbon particles as core particles, the surfaces of which are coated with a plating layer serving as an outer shell, and irregularities are formed on the surfaces of the conductive particles.

Here, the carbon particles have substantially no surface unevenness, that is, the surface unevenness ratio (T / D) is zero.
In this surface unevenness ratio (T / D), as shown in FIG. 1, D is a diameter D of a circle 2 inscribed in the outline 1 in a projection view in which conductive particles are projected onto a plane, and T is The maximum value of the distance between the circumscribed circle 1 and the inscribed circle 2, that is, the distance between the most protruding portion as surface irregularities and the inscribed circle 2. Here, it is assumed that the inscribed circle 2 is in contact with the circumscribed circle 1 at least at three points. As a projection view of the conductive particles, a scanning electron microscope image (approximately 4000 times magnification) of the conductive particles can be used. Further, “substantially no surface unevenness” means that the surface unevenness ratio (T / D) is less than 0.001.

  The carbon particles are not particularly limited as long as they are substantially free of surface irregularities, and may have a true spherical shape, a disc shape, a column shape, or the like, but a true spherical shape is preferable.

  Such carbon particles can be obtained by firing resin particles such as benzoguanamine / formaldehyde condensate and phenol resin.

  In the present invention, the aggregation of carbon particles is reduced by using carbon particles having substantially no surface irregularities as described above. Therefore, agglomeration of conductive particles that occurs when carbon particles having surface irregularities are made conductive particles of anisotropic conductive material is reduced, and unnecessary shorts between wirings connected by anisotropic conductive material are eliminated. Can do.

On the other hand, surface unevenness is formed on the plating layer as the outer shell of the carbon particles so that the surface unevenness ratio (T / D) is 0.01 to 0.6, preferably 0.05 to 0.25. In this case, it is preferable that the protrusions forming the surface irregularities cover 30% or more of the surface area of the conductive particles.
By such surface irregularities, the effect of the conductive particles biting into the wiring can be improved, and the connection reliability can be improved. On the other hand, if the surface unevenness ratio (T / D) is too small, a sufficient biting effect cannot be obtained. On the other hand, if the surface unevenness ratio is too large, the unevenness of the surface of the conductive particles becomes severe, and when used for connecting electrodes and the like, This is not preferable because the contact area with the electrode becomes small and the connection resistance value varies.

  As a method for forming surface irregularities in the plating layer, for example, in accordance with the description in the examples of Japanese Patent Application Laid-Open No. 2007-324138, fine particles that become the core material of surface protrusions are attached to the core particles, and the core particles are covered with the fine particles. Thus, an electroless plating layer may be formed.

  Examples of the metal forming the plating layer include a nickel layer, a copper layer, and a palladium layer. A gold layer may be formed on the outermost surface of the plating layer.

  The overall particle size of the conductive particles composed of the carbon particles and the plating layer as described above depends on the wiring member connected by the conductive particles, but is usually preferably 1 to 30 μm, and 1 to 10 μm. More preferably. If the particle size of the conductive particles is excessively small, the surface irregularities of the connection terminals are sunk, and the connection between the terminals cannot be performed. On the other hand, when the particle size of the conductive particles is excessively large, the wiring member is easily deformed and it is difficult to maintain a normal connection state.

  In the anisotropic conductive material of the present invention, the above-described conductive particles are dispersed in an insulating adhesive.

  Insulating adhesives can take various forms as well as known anisotropic conductive materials, such as film-forming resins, liquid epoxy compounds (curing components) or acrylic monomers (curing components), curing agents, silanes, and the like. It can comprise a coupling agent or the like.

  Examples of the film-forming resin include phenoxy resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, urethane resin, butadiene resin, polyimide resin, polyamide resin, polyolefin resin, and the like. be able to. Among these, a phenoxy resin can be preferably used from the viewpoint of film forming property, workability, and connection reliability.

  Examples of the liquid epoxy compound include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, novolac type epoxy compounds, modified epoxy compounds thereof, alicyclic epoxy compounds, and the like. Can do. In this case, examples of the curing agent include anionic curing agents such as polyamines and imidazoles, cationic curing agents such as sulfonium salts, and latent curing agents such as phenolic curing agents.

  Examples of the acrylic monomer include ethyl (meth) acrylate. In this case, examples of the curing agent (radical polymerization initiator) include organic peroxides and azobisbutyronitrile.

  Examples of the silane coupling agent include an epoxy silane coupling agent and an acrylic silane coupling agent. These silane coupling agents are mainly alkoxysilane derivatives.

  In the binder resin composition, a filler, a softener, an accelerator, an anti-aging agent, a colorant (pigment, dye), an organic solvent, an ion catcher agent, and the like can be blended as necessary.

  If the content of the conductive particles in the anisotropic conductive material of the present invention is too small, the conduction reliability is lowered, and if it is too much, the anisotropic conductivity is lowered, preferably 0.1 to 20% by mass, more preferably Is 0.2 to 10% by mass.

  In addition, the anisotropic conductive material may have a paste shape, a film shape, or the like. In particular, examples of the film-like anisotropic conductive material include an anisotropic conductive film in which a coating film of an anisotropic conductive material is formed on a release film.

  As in the case of conventional anisotropic conductive materials, the anisotropic conductive material of the present invention is disposed as a coating film or a film between terminals to be connected such as a flexible substrate, a rigid substrate, and an electronic component, and the terminals are added. It can be used for anisotropic conductive connection that electrically and mechanically connects between terminals by heating, UV irradiation, etc. while pressing, thereby producing an anisotropic conductive connection body having high connection reliability. It becomes possible. The present invention also includes such a connection body.

  Hereinafter, the present invention will be specifically described by way of examples.

Example 1
(1) Manufacture of carbon particles (core particles) True spherical resin particles (“Epester GP70” manufactured by Nippon Shokubai Co., Ltd.) consisting of an average particle size of 7 μm of benzoguanamine / formaldehyde condensate are treated at 1000 ° C. for 10 hours under an inert gas atmosphere. Sintering produced spherical carbon particles having an average particle size of 5 μm.

(2) Production of conductive particles The carbon particles obtained in (1) were used as core particles, and surface irregularities were formed on the surfaces of the core particles as described below in Example 1 of JP-A-2007-324138. A plating layer was formed to produce conductive particles.

(2-1) Electroless Plating Pretreatment Step 10 g of carbon particles were subjected to alkali degreasing with an aqueous sodium hydroxide solution, acid neutralization, and sensitizing with a tin dichloride solution. Thereafter, electroless plating pretreatment for activation with a palladium dichloride solution was performed, and after filtering and washing, substrate fine particles having palladium adhered to the particle surfaces were obtained.

(2-2) Core material compounding process
The substrate fine particles obtained in (2-1) were stirred and dispersed in 300 ml of deionized water for 3 minutes. Thereafter, 1 g of metallic nickel particles having an average particle size of 0.05 μm was added to the aqueous solution as a core material over 3 minutes to obtain nickel particle-attached carbon particles.

(2-3) Electroless nickel plating
(2-3-1) Electroless plating first stage process
The nickel particle-attached carbon particles obtained in (2-2) were further diluted with 1200 ml of water, and 4 ml of a plating stabilizer was added. Thereafter, 120 ml of a mixed solution of nickel sulfate 450 g / l, sodium hypophosphite 150 g / l, sodium citrate 116 g / l, and plating stabilizer 6 ml is passed through this metering pump at an addition rate of 81 ml / min. Added. Then, it stirred until pH became stable and it confirmed that foaming of hydrogen stopped.

(2-3-2) Late stage of electroless plating Next, 650 ml of a mixed solution of nickel sulfate 450 g / l, sodium hypophosphite 150 g / l, sodium citrate 116 g / l, and plating stabilizer 35 ml was added to 27 ml / The addition was made through a metering pump at an addition rate of minutes. Then, it stirred until pH became stable and it confirmed that foaming of hydrogen stopped.

Next, the plating solution was filtered, and the filtrate was washed with water and then dried with a vacuum dryer at 80 ° C. to obtain nickel-plated carbon particles.
Thereafter, the surface was further plated with gold by a displacement plating method to obtain conductive fine particles having surface irregularities.

(3) Manufacture of anisotropic conductive film As thermosetting binder, 50 parts by weight of microcapsule amine curing agent (Asahi Kasei Chemicals, trade name NovaCure HX3941HP), liquid epoxy resin (Japan Epoxy Resin, trade name) EP828) 14 parts by weight, phenoxy resin (trade name YP50, manufactured by Toto Kasei Co., Ltd.) 35 parts by weight, silane coupling agent (trade name KBE403, manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part by weight, and the conductive particles obtained in (2) Is mixed and dispersed so that the volume ratio of the conductive particles is 10%, and is applied to a PET film which has been subjected to a release treatment with silicone so as to have a thickness of 35 μm. Manufactured.

(4) Manufacture of anisotropic conductive connector COF (50 μm pitch, Cu 8 μm thickness-Sn plating, 38 μm thickness-Sperflex substrate) manufactured by Sony Chemical & Information Device and PWB manufactured by Sony Chemical & Information Device Co., Ltd. (50 μm pitch, Cu 35 μm thickness—Au plating, FR-4 base material) and these were connected using the anisotropic conductive film prepared in (3). In this case, first, an anisotropic conductive film is slit to a width of 1.5 mm, this is attached to the PWB, and the COF is aligned and disposed thereon, and a cushioning material 250 μm thick silicone rubber, 1.5 mm width heating Using a tool, an anisotropic conductive connector was manufactured by heating and pressing under pressure bonding conditions of 190 ° C. and 3 MPa for 10 seconds.

Example 2
Conductive particles having surface irregularities in the same manner as in Example 1 except that metal nickel particles having an average particle size of 0.5 μm were used instead of metal nickel particles having an average particle size of 0.05 μm in the core material compounding step. Got.
Moreover, the anisotropic conductive film was manufactured similarly to Example 1 using this electroconductive particle, and also the connection body was manufactured using the anisotropic conductive film.

Example 3
Conductive particles having surface irregularities were obtained in the same manner as in Example 1 except that metal nickel particles having an average particle diameter of 1 μm were used instead of metal nickel particles having an average particle diameter of 0.05 μm in the core material compounding step. Obtained.
Moreover, the anisotropic conductive film was manufactured similarly to Example 1 using this electroconductive particle, and also the connection body was manufactured using the anisotropic conductive film.

Example 4
Conductive particles having surface irregularities were obtained in the same manner as in Example 2 except that electroless copper plating was performed instead of electroless nickel plating.
Moreover, the anisotropic conductive film was manufactured similarly to Example 1 using this electroconductive particle, and also the connection body was manufactured using the anisotropic conductive film.

Example 5
Conductive fine particles having surface irregularities were obtained in the same manner as in Example 2 except that electroless palladium plating was performed instead of electroless nickel plating.
Moreover, the anisotropic conductive film was manufactured similarly to Example 1 using this electroconductive particle, and also the connection body was manufactured using the anisotropic conductive film.

Comparative Example 1
Spherical carbon with an average particle size of 5 μm is calcined at 1000 ° C. for 10 hours in an inert gas atmosphere with true spherical resin particles (“Eposter GP70” manufactured by Nippon Shokubai Co., Ltd.) having an average particle size of 7 μm of benzoguanamine / formaldehyde condensate Particles were prepared, tar was attached to the surface of the spherical carbon particles according to Japanese Patent No. 2823799, and carbon particles having protrusions graphitized by firing were prepared.
Conductive particles having surface irregularities were obtained in the same manner as in Example 1 except that the carbon particles having protrusions were not subjected to the electroless plating pretreatment step and the core material composite step.
Moreover, the anisotropic conductive film was manufactured similarly to Example 1 using this electroconductive particle, and also the connection body was manufactured using the anisotropic conductive film.

Comparative Example 2
True spherical conductive particles were obtained in the same manner as in Example 1 except that the core material composite step was not performed after the electroless plating pretreatment step on the carbon particles.
Moreover, the anisotropic conductive film was manufactured similarly to Example 1 using this electroconductive particle, and also the connection body was manufactured using the anisotropic conductive film.

Comparative Example 3
True spherical particles (“Epester GP50”; manufactured by Nippon Shokubai Co., Ltd.) consisting of a monodispersed volume average particle size of benzoguanamine / melamine / formaldehyde condensate of 5 μm are the main particles. After adding 0.1 part by mass of monodisperse spherical particles having a monodisperse volume average particle size of 0.5 μm and 30 parts by mass of an acrylic dispersion medium, the mixture is mixed by ultrasonic waves to adhere fine particles to the main particles, The mixture was heated and melted at 0 ° C. to obtain resin particles having protrusions on the surface by a general wet external addition method.
Then, except having not performed the core substance compounding process, it carried out similarly to Example 1, and metal-plated the resin particle, and obtained the electroconductive particle which has surface unevenness | corrugation.
Moreover, the anisotropic conductive film was manufactured similarly to Example 1 using this electroconductive particle, and also the connection body was manufactured using the anisotropic conductive film.

Comparative Example 4
The surface was the same as in Example 2 except that true spherical particles (“Eposter GP50”; manufactured by Nippon Shokubai Co., Ltd.) having an average particle diameter of 5 μm monodispersed benzoguanamine / melamine / formaldehyde condensate were used as core particles. Conductive particles having irregularities were obtained.

Comparative Example 5
Conductive particles having surface irregularities were obtained in the same manner as in Example 2 except that metal nickel particles having an average particle diameter of 5 μm were used as core particles instead of carbon particles.
Moreover, the anisotropic conductive film was manufactured similarly to Example 1 using this electroconductive particle, and also the connection body was manufactured using the anisotropic conductive film.

Evaluation (a) Surface roughness ratio, (b) Aggregation of core particles, (c) Connection resistance of connection body, (d) Insulation property of connection body, (e) Particle indentation of connection body was tested and evaluated as follows. did. These results are shown in Table 1.

(A) Surface unevenness ratio Core particles and conductive particles produced using the core particles were photographed using a scanning electron microscope (4000 times magnification), respectively, and the surface unevenness ratio was determined on the image by the method described above. .

(B) Aggregation of core particles For the core particles of Example 1, Comparative Example 1 and Comparative Example 3, a particle size distribution meter (“Sheath Flow Electric Resistance Type Particle Size Distribution Meter SD2000”, manufactured by Sysmex Corporation) was used, and orifice diameter: 50 μm The ratio of the aggregated particles was measured with a dispersion liquid: methanol. In this case, the number of measured particles was about 10000 pcs (particle counts), and those having a particle size distribution larger than 7 μm were regarded as aggregated particles.
○: Less than 10% aggregated particles ×: 10% or more aggregated particles

(C) Connection resistance of connection body Using the 4-terminal method, the connection resistance of each connection body when the current of 1 mA was applied was set to 500 hours at 85 ° C and 85% RH immediately after the connection body was manufactured. It was measured later.

(D) Insulating property of the connection body,
About each connection body, the insulation resistance between adjacent terminals was measured on 20V conditions, and the following reference | standard evaluated.
○: 10 ⁸ Ω or more △: 10 ⁷ Ω or more and less than 10 ⁸ Ω ×: less than 10 ⁷ Ω In practice, it is desired that the evaluation is ○.

(E) Particle Indentation For each connected body, particles captured on the terminal were observed from the COF side using a microscope (Olympus Industrial Inspection Microscope MX51), and evaluated according to the presence or absence of the indentation according to the following criteria.
○: Among 10 observation points, there are 5 or more observation points where indentations are observed. ×: Among 10 observation points, there are less than 5 observation points where indentations are observed.

  From the results in Table 1, when carbon particles are used as core particles, as in Comparative Example 1, if protrusions are provided on the carbon particles, the core particles are likely to aggregate. As a result, the insulating property of the anisotropic conductive material is inferior, and when the projections are not provided on the carbon particles as in Comparative Example 2, the carbon particles are less likely to agglomerate. In the case where the surface unevenness is not provided, the connection resistance becomes high. On the other hand, if the carbon particle is not provided with protrusions as in Examples 1 to 5 and the surface plating layer is provided with unevenness, the carbon particles are aggregated. It can be seen that the insulating property of the anisotropic conductive material is good, the connection resistance is low, the particle indentation is observed, and the conduction reliability is increased.

  On the other hand, when resin particles are used as core particles as in Comparative Examples 3 and 4, the core particles do not aggregate, but are easily charged when the core particles are resin particles, and the aggregate increases due to charging. Therefore, it can be seen that the dispersibility is deteriorated, the insulating property is lowered, and further, when the protrusion is provided on the resin particle as in Comparative Example 3, the particle indentation is not generated and the connection reliability is poor.

  In addition, when the metal particles are core particles as in Comparative Example 5, when they are blended in the anisotropic conductive material, the particle specific gravity is large, so that the particle dispersibility due to the sedimentation of the particles is reduced and anisotropic. It can be seen that the insulating property of the conductive conductive material is lowered.

1 circumscribed circle 2 inscribed circle D diameter of inscribed circle T maximum value of distance between circumscribed circle and inscribed circle

Claims (5)

An anisotropic conductive material in which conductive particles are dispersed in an insulating adhesive,
The conductive particles are conductive particles having surface protrusions prepared by attaching metallic nickel fine particles to true spherical carbon particles substantially free of surface irregularities and coating the fine particles together with an electroless plating layer. Yes,
The surface roughness ratio of the particle is T / D (where D is the diameter of the inscribed circle with respect to the outline of the particle in the projection onto the plane of the particle, and T is the maximum value of the distance between the outline and the inscribed circle) An anisotropic conductive material in which the surface unevenness ratio of the conductive particles is 0.21 to 0.51. As the plating layer, the anisotropic conductive material according to claim 1 Symbol mounting having a nickel layer, a copper layer or palladium layer. The anisotropic conductive material according to claim 1 or 2, which is formed into a film shape. The anisotropic conductive connection method which arrange | positions the anisotropic conductive material in any one of Claims 1-3 between the terminals which oppose, and pressurizes and connects between terminals. The anisotropic conductive connection body connected using the anisotropic conductive material in any one of Claims 1-3 .

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