CN204689937U - Anisotropic conductive film and connection structural bodies - Google Patents

Abstract

The utility model provides an anisotropic conductive film and a connecting structure. In the anisotropic conductive film (11), 70% or more of the conductive particles (P) in the conductive adhesive layer (13) are separated from other adjacent conductive particles (P). Therefore, when the circuit members (2), (3) are connected, the aggregation between the adjacent conductive particles (P), (P) is suppressed, and the connection between the bump electrodes (6), (6) and the circuit can be well ensured. Insulation between electrodes (8), (8). In addition, in the anisotropic conductive film (11), the thickness of the conductive adhesive layer (13) is greater than or equal to 0.6 times and less than 1.0 times the average particle diameter of the conductive particles (P). As a result, the fluidity of the conductive particles (P) during crimping is suppressed, the capture efficiency of the conductive particles (P) between the bump electrodes (6) and the circuit electrodes (8) can be improved, and the circuit member (2) can be ensured. , (3) connection reliability.

Description

Anisotropic conductive film and bonded structure

technical field

The utility model relates to an anisotropic conductive film and a connecting structure.

Background technique

Conventionally, for example, in the connection between a liquid crystal display and a tape carrier package (TCP), a connection between a flexible printed circuit board (FPC) and a TCP, or a connection between an FPC and a printed wiring board, an adhesive film in which conductive particles are dispersed has been used. Anisotropic conductive film. Also, when mounting a semiconductor silicon chip on a substrate, so-called chip-on-glass (COG) in which a semiconductor silicon chip is directly mounted on a substrate is performed instead of conventional wire bonding, and an anisotropic conductive film is also used here.

In recent years, along with the development of electronic equipment, higher density of wiring and higher functionality of circuits have been advanced. As a result, there is a need for a bonded structure in which the distance between the connection electrodes is, for example, 15 μm or less, and the bump electrodes of the connection member are also gradually reduced in area. In order to obtain stable electrical connection in bump connection with a reduced area, it is necessary to interpose a sufficient number of conductive particles between the bump electrode and the circuit electrode on the substrate side.

In response to such a problem, for example, in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 6-45024) and Patent Document 2 (Japanese Patent Application Publication No. 2003-49152), reduction in the diameter of conductive particles in an anisotropic conductive film is carried out. On the other hand, the method of increasing the particle density is a method of using an anisotropic conductive film having a two-layer structure of an adhesive layer containing conductive particles and an insulating adhesive layer. In addition, for example, in Patent Document 3 (Japanese Patent Laid-Open No. 2010-027847 ) and Patent Document 4 (Japanese Patent Laid-Open No. 2012-191015 ), the substrate is provided with a barrier to prevent the flow of conductive particles in the anisotropic conductive film. Walls and protrusions improve the capture efficiency of conductive particles between bump electrodes and circuit electrodes. Furthermore, Patent Document 5 (Japanese Unexamined Patent Application Publication No. 2011-109156 ) discloses a bonded structure in which the average particle diameter and the like of conductive particles are segregated on the substrate side at a constant ratio.

Utility model content

However, in the conventional method described above, secondary aggregation of conductive particles occurs between bump electrodes or between circuit electrodes, and the distribution of conductive particles becomes dense, which may impair insulation. In addition, the flow of the anisotropic conductive film may fluctuate during bonding, and there may be problems such as peeling due to uneven filling of resin between substrates and a decrease in connection resistance.

This utility model is made in order to solve the above-mentioned problems, and its purpose is to provide an anisotropic conductive film and an anisotropic conductive film capable of ensuring both the connection reliability between opposing circuit members and the insulation between electrodes in the circuit members. Connection structure.

In order to solve the above-mentioned problems, the anisotropic conductive film according to the present invention is characterized by comprising a conductive adhesive layer including an adhesive layer in which conductive particles are dispersed, and a conductive adhesive layer laminated on the conductive adhesive layer. An insulating adhesive layer comprising an adhesive layer in which conductive particles are not dispersed, the thickness of the conductive adhesive layer is greater than or equal to 0.6 times and less than 1.0 times the average particle diameter of the conductive particles, and in the conductive adhesive layer , forming a state where more than 70% of the conductive particles are separated from other adjacent conductive particles.

In this anisotropic conductive film, 70% or more of the conductive particles in the conductive adhesive layer are separated from other adjacent conductive particles. Therefore, aggregation between adjacent conductive particles is suppressed at the time of circuit member connection, and insulation between electrodes in a circuit member can be ensured favorably. In addition, in the anisotropic conductive film, the thickness of the conductive adhesive layer is equal to or greater than 0.6 times and less than 1.0 times the average particle diameter of the conductive particles. Thereby, the fluidity of the conductive particles is suppressed at the time of crimping, and the capture efficiency of the conductive particles between the electrodes of the opposing circuit members can be improved. Therefore, connection reliability between circuit members can be ensured.

In addition, in the conductive adhesive layer, it is preferable that the conductive particles are not exposed on the surface opposite to the insulating adhesive layer, and the conductive adhesive layer exists between the conductive particles and the surface of the conductive adhesive layer. The thickness is greater than 0 μm and less than or equal to 1 μm. In this case, when the anisotropic conductive film is disposed on the circuit member, it is possible to prevent gaps from being generated between the circuit member and the anisotropic conductive film due to unevenness of the conductive particles.

In addition, it is preferable that the average particle diameter of the conductive particles is greater than or equal to 2.5 μm and less than or equal to 6.0 μm. By satisfying this range, securing of connection reliability between opposing circuit members and securing of insulation between electrodes in the circuit members can be more suitably achieved. The average particle diameter of the conductive particles may be greater than or equal to 2.7 μm, or greater than or equal to 3.0 μm. In addition, the average particle diameter of the conductive particles may be equal to or less than 5.5 μm, or may be equal to or less than 5.0 μm.

In addition, it is preferable that the particle density of the conductive particles is greater than or equal to 5000 particles/mm ² and less than or equal to 50000 particles/mm ² . In this case, when the anisotropic conductive film is disposed on the circuit member, it is possible to prevent gaps from being generated between the circuit member and the anisotropic conductive film due to unevenness of the conductive particles.

In addition, it is preferable that the thickness of the conductive adhesive layer is greater than or equal to 1.5 μm and less than or equal to 6.0 μm. By satisfying this range, securing of connection reliability between opposing circuit members and securing of insulation between electrodes in the circuit members can be more suitably achieved. In addition, it is preferable that the total thickness of the conductive adhesive layer and the insulating adhesive layer is greater than or equal to 5.0 μm and less than or equal to 30 μm.

In addition, the conductive particles preferably contain nickel. Nickel is a strong magnetic substance and has sufficient electrical conductivity. Therefore, a state where the conductive particles are separated from other conductive particles can be easily formed by applying a method such as a magnetic field.

In addition, the connection structure according to the present invention is characterized in that the first circuit member provided with the bump electrodes and the second circuit member provided with the circuit electrodes corresponding to the bump electrodes are connected through the cured product of the above-mentioned anisotropic conductive film. connected circuit components.

According to this bonded structure, in the conductive adhesive layer of the anisotropic conductive film, 70% or more of the conductive particles are separated from other adjacent conductive particles. Therefore, aggregation between adjacent conductive particles is suppressed at the time of circuit member connection, and insulation between electrodes in a circuit member can be ensured favorably. In addition, in this bonded structure, the thickness of the conductive adhesive layer of the anisotropic conductive film is 0.6 times or more and less than 1.0 times the average particle diameter of the conductive particles. Thereby, the fluidity of the conductive particles is suppressed at the time of crimping, and the capture efficiency of the conductive particles between the electrodes of the opposing circuit members can be improved. Therefore, connection reliability between circuit members can be ensured.

In addition, the total thickness of the conductive adhesive layer and the insulating adhesive layer in the anisotropic conductive film before curing, and the distance from the mounting surface of the first circuit member to the mounting surface of the second circuit member are preferably The difference is greater than or equal to 0 μm and less than or equal to 10 μm. Thereby, the gap between the circuit members 2 and 3 can be satisfactorily filled with the anisotropic conductive adhesive layer. The difference may be greater than or equal to 0.5 μm and less than or equal to 8.0 μm, or may be greater than or equal to 1.0 μm and less than or equal to 5.0 μm.

Description of drawings

FIG. 1 is a schematic cross-sectional view showing one embodiment of a connection structure according to the present invention.

Fig. 2 is a schematic cross-sectional view showing one embodiment of an anisotropic conductive film used in the bonded structure shown in Fig. 1 .

Fig. 3 is a schematic cross-sectional view showing a manufacturing process of the bonded structure shown in Fig. 1 .

Fig. 4 is a schematic cross-sectional view showing a step subsequent to Fig. 3 .

FIG. 5 is a schematic view showing a manufacturing process of the anisotropic conductive film shown in FIG. 2 .

FIG. 6 is a schematic view showing the state of the magnetic field application step.

7 is a schematic cross-sectional view showing the state of the anisotropic conductive film after a magnetic field application step and a drying step.

FIG. 8 is a schematic cross-sectional view showing a lamination step subsequent to FIG. 7 .

Detailed ways

Hereinafter, preferred embodiments of the anisotropic conductive film and bonded structure according to the present invention will be described in detail with reference to the drawings.

[Constitution of connection structure]

FIG. 1 is a schematic cross-sectional view showing one embodiment of a connection structure according to the present invention. As shown in the figure, the bonded structure 1 is constituted by including a first circuit member 2 and a second circuit member 3 facing each other, and a cured product 4 of an anisotropic conductive film connecting these circuit members 2 and 3 .

The first circuit member 2 is, for example, a tape carrier package (TCP), a printed wiring board, a semiconductor silicon chip, or the like. The first circuit member 2 has a plurality of bump electrodes 6 on the mounting surface 5 a side of the main body 5 . Bump electrode 6 is formed in a rectangular shape in, for example, a plan view, and has a thickness of, for example, greater than or equal to 3 μm and less than 18 μm. The material for forming the bump electrodes 6 is, for example, Au or the like, which is easier to deform than the conductive particles P contained in the cured product 4 of the anisotropic conductive film. In addition, an insulating layer may be formed in a portion where bump electrode 6 is not formed on mounting surface 5 a.

The second circuit member 3 is, for example, a glass substrate, a plastic substrate, a flexible printed circuit board (FPC), a ceramic wiring board, etc., in which a circuit is formed of ITO, IZO, or metal used in a liquid crystal display. As shown in FIG. 1 , the second circuit member 3 has a plurality of circuit electrodes 8 corresponding to the bump electrodes 6 on the mounting surface 7 a side of the main body 7 . Like the bump electrodes 6 , the circuit electrodes 8 are formed in a rectangular shape in plan view, for example, and have a thickness of, for example, about 100 nm. The surface of the circuit electrode 8 is made of one or more selected from, for example, gold, silver, copper, tin, ruthenium, rhodium, palladium, osmium, iridium, platinum, indium tin oxide (ITO), and indium zinc oxide (IZO). Composed of 2 or more materials. In addition, on the mounting surface 7a, an insulating layer may be formed in a portion where the circuit electrode 8 is not formed.

The cured product 4 of the anisotropic conductive film is a layer formed using the anisotropic conductive film 11 (see FIG. 2 ) described later, and has a first region 9 formed by curing the conductive adhesive layer 13, and The second region 10 formed by curing the insulating adhesive layer 14 . In this embodiment, the first region 9 is located on the second circuit member 3 side, and the second region 10 is located on the first circuit member 2 side. In addition, in this embodiment, for convenience of description, the layer in which the conductive particles P are dispersed is called a conductive adhesive layer, and the layer in which the conductive particles P are not dispersed is called an insulating adhesive layer. The adhesive component itself is non-conductive.

Conductive particles P are in a state of being segregated on the second circuit member 3 side, and are interposed between bump electrodes 6 and circuit electrodes 8 in a state of being slightly flattened and deformed by crimping. Thereby, the electrical connection between the bump electrode 6 and the circuit electrode 8 is realized. In addition, between the adjacent bump electrodes 6, 6 and between the adjacent circuit electrodes 8, 8, the state where the conductive particles P are separated is formed, and the adjacent bump electrodes 6, 6 and the adjacent circuit electrodes are realized. Electrical insulation between circuit electrodes 8,8.

[Structure of Anisotropic Conductive Film]

Fig. 2 is a schematic cross-sectional view showing one embodiment of an anisotropic conductive film used in the bonded structure shown in Fig. 1 . As shown in the figure, the anisotropic conductive film 11 passes through the release film 12, the conductive adhesive layer 13 including the adhesive layer in which the conductive particles P are dispersed, and the adhesive layer including the conductive particles P not dispersed. Insulative adhesive layers 14 are stacked to form layers.

The release film 12 is formed of, for example, polyethylene terephthalate (PET), polyethylene, polypropylene, or the like. The release film 12 may contain arbitrary fillers. In addition, the surface of the release film 12 may be subjected to mold release treatment, plasma treatment, or the like.

The adhesive layers forming the conductive adhesive layer 13 and the insulating adhesive layer 14 each contain a curing agent, a monomer, and a film-forming material. When using an epoxy resin monomer, examples of the curing agent include imidazole-based, hydrazide-based, boron trifluoride-amine complexes, sulfonium salts, amine imides, polyamine salts, dicyandiamide, etc. . When the curing agent is coated with a polyurethane-based or polyester-based polymer and microencapsulated, it is suitable because the pot life is prolonged. On the other hand, when an acrylic monomer is used, examples of the curing agent include substances that decompose by heating to generate free radicals, such as peroxide compounds and azo compounds.

When using an epoxy monomer, the curing agent is appropriately selected according to the target joining temperature, joining time, storage stability, and the like. As for the curing agent, from the viewpoint of high reactivity, it is preferable that the gelation time with the epoxy resin composition is less than or equal to 10 seconds at a predetermined temperature, and from the viewpoint of storage stability, it is preferable to store it at a constant temperature of 40°C. There was no change in the gel time with the epoxy resin composition after storage in the tank for 10 days. From such a point of view, the curing agent is preferably a sulfonium salt.

When using acrylic monomers, the curing agent is appropriately selected according to the target connection temperature, connection time, storage stability, etc. In terms of high reactivity and storage stability, an organic peroxide or an azo compound having a half-life of 10 hours at a temperature of 40° C. or higher and a half-life of 1 minute at a temperature of 180° C. or less is preferable, and a half-life of 10 hours is more preferable. Organic peroxides or azo compounds with a temperature greater than or equal to 60°C and a half-life of 1 minute at a temperature less than or equal to 170°C. These curing agents may be used alone or in combination, and decomposition accelerators, inhibitors, and the like may be used in combination.

When using any of epoxy monomers and acrylic monomers, in order to obtain a sufficient reaction rate when the connection time is 10 seconds or less, the amount of the curing agent is preferably based on the amount of the monomer described later. It is 0.1-40 mass parts with the total 100 mass parts of the film-forming material mentioned later, More preferably, it is 1-35 mass parts. When the compounding quantity of a hardening|curing agent is less than 0.1 mass part, sufficient reaction rate cannot be obtained, and it tends to be difficult to obtain favorable adhesive strength and small connection resistance. On the other hand, when the compounding quantity of a hardening|curing agent exceeds 40 mass parts, there exists a tendency for the fluidity|fluidity of an adhesive to fall, or connection resistance to rise, or the storage stability of an adhesive to fall.

In addition, when using epoxy resin monomers as monomers, bisphenol-type epoxy resins derived from epichlorohydrin and bisphenol A, bisphenol F, bisphenol AD, etc. can be used; Epoxy novolac resins derived from phenol novolac and cresol novolac; glycidylamine, glycidyl ether, various epoxy resins having two or more glycidyl groups in one molecule of biphenyl, alicyclic, etc. compounds etc.

When using an acrylic monomer, it is preferable that a radically polymerizable compound has the functional group which polymerizes by a radical. As such a radically polymerizable compound, (meth)acrylate, a maleimide compound, a benzene derivative, etc. are mentioned. In addition, the radically polymerizable compound may be used in any state of a monomer or an oligomer, or may be used in admixture of a monomer and an oligomer. These monomers may be used alone or in combination of two or more.

The film-forming material is a polymer that functions to facilitate handling of a low-viscosity composition containing the aforementioned curing agent and monomer. By using a film-forming material, it is possible to suppress easy cracking, cracking, or stickiness of the film, and to obtain an anisotropic conductive film 11 that is easy to handle.

As a film-forming material, thermoplastic resins are suitably used, and examples thereof include phenoxy resins, polyvinyl formal resins, polystyrene resins, polyvinyl butyral resins, polyester resins, polyamide resins, xylene resins, and polyurethane resins. , polyacrylic resin, polyester polyurethane resin, etc. Furthermore, these polymers may contain siloxane bonds and fluorine substituents. These resins can be used individually or in mixture of 2 or more types. Among the above-mentioned resins, phenoxy resins are preferably used from the viewpoints of adhesive strength, compatibility, heat resistance, and mechanical strength.

The larger the molecular weight of the thermoplastic resin, the easier it is to obtain film-forming properties, and the melt viscosity that affects the fluidity of the anisotropic conductive film can be set in a wide range. The molecular weight of the thermoplastic resin is preferably 5,000 to 150,000, particularly preferably 10,000 to 80,000 in weight average molecular weight. When the weight average molecular weight is 5,000 or more, good film-forming properties are easily obtained, and when the weight average molecular weight is 150,000 or less, good compatibility with other components is easily obtained.

In addition, in the present invention, the weight average molecular weight refers to a value measured using a calibration curve obtained from standard polystyrene by gel permeation chromatography (GPC) under the following conditions.

(measurement conditions)

Device: GPC-8020 manufactured by Tosoh Corporation

Detector: RI-8020 manufactured by Tosoh Corporation

Column: Gelpack GLA160S+GLA150S manufactured by Hitachi Chemical Co., Ltd.

Sample concentration: 120mg/3mL

Solvent: THF

Injection volume: 60μL

Pressure: 2.94×10 ⁶ Pa (30kgf/cm ² )

Flow: 1.00mL/min

In addition, based on the total amount of the curing agent, monomer, and film-forming material, the content of the film-forming material is preferably 5% to 80% by weight, more preferably 15% to 70% by weight. When it is 5% by weight or more, good film-forming properties are easily obtained, and when it is 80% by weight or less, the curable composition tends to exhibit good fluidity.

In addition, the adhesive layer forming the conductive adhesive layer 13 and the insulating adhesive layer 14 may further contain fillers, softeners, accelerators, anti-aging agents, colorants, flame retardants, thixotropic agents, Coupling agent and phenolic resin, melamine resin, isocyanate, etc.

When a filler is contained, further improvement in connection reliability can be expected. The maximum diameter of the filler is preferably smaller than the particle diameter of the conductive particles, and the content of the filler is preferably 5 to 60 parts by volume relative to 100 parts by volume of the adhesive layer. When it exceeds 60 parts by volume, the effect of improving reliability may be saturated, and when it is less than 5 parts by volume, the effect of addition is small.

Regarding the conductive particles P, in the conductive adhesive layer 13, more than 70% of the conductive particles P are separated from other adjacent conductive particles P. Such a dispersed state is formed by a magnetic field application step described later. As the conductive particles P, particles containing nickel are suitably used from the viewpoint of dispersing in the magnetic field application step. It is generally known that iron, cobalt, and nickel are ferromagnetic substances and are magnetized by an external magnetic field. Among them, it is meaningful to use nickel because it can achieve both electrical conductivity and dispersibility by application of a magnetic field. Moreover, in order to obtain the storage stability of the electroconductive particle P, the surface layer of the electroconductive particle P may be platinum-type noble metals, such as gold and silver, instead of nickel. In addition, the surface of nickel may be coated with noble metals such as Au. Furthermore, a material obtained by coating non-conductive glass, ceramics, plastic, etc. with a conductive substance such as the above metal can also be used. In this case, a nickel layer can also be provided to form a multilayer structure.

In addition, since the magnetism of nickel is influenced by the concentration of phosphorus contained in the nickel plating layer, it is preferable to adjust the magnetism required for the dispersion of the conductive particles P by the magnetic field as appropriate. The magnetism of the conductive particles P can be measured by saturation magnetization, for example, with a vibrating sample magnetometer (VSM: Vibrating Sample Magnetmeter). In order to disperse the conductive particles P by an external magnetic field, it is preferable that the saturation magnetization is in the range of 5.0 emu/g to 50 emu/g in the VSM measurement. When it is less than 5.0 emu/g, dispersion of the conductive particles P may not be performed even if a magnetic field is applied. On the other hand, when it exceeds 50 emu/g, the magnetization of the conductive particles P becomes too large, the conductive particles P are bonded in the thickness direction of the conductive adhesive layer 13, and the dispersibility of the conductive particles P may decrease.

The average particle diameter of the conductive particles P is preferably greater than or equal to 2.5 μm and less than or equal to 6.0 μm. When the average particle size of the conductive particles P is less than 2.5 μm, it is difficult to disperse the conductive particles P well in the conductive adhesive layer 13 due to the problem of the coating accuracy of the release film 12, and the average particle size of the conductive particles P exceeds When it is 6.0 micrometers, the insulation between the adjacent circuit electrodes 8 and 8 of the bonded structure 1 may fall. In order to obtain good dispersibility of the conductive particles P, the average particle diameter of the conductive particles P is more preferably equal to or greater than 2.7 μm, further preferably equal to or greater than 3 μm. On the other hand, from the viewpoint of ensuring insulation between adjacent circuit electrodes 8 and 8 of the bonded structure 1, the average particle diameter of the conductive particles P is more preferably 5.5 μm or less, and still more preferably 5 μm or less.

It is preferable that the compounding quantity of the electroconductive particle P is 1 volume part - 100 volume parts with respect to 100 volume parts of components other than the electroconductive particle P of the electroconductive adhesive layer. From the viewpoint of preventing the short circuit of the adjacent circuit electrodes 8 and 8 caused by the excessive presence of the conductive particles P, the compounding amount of the conductive particles P is more preferably 10 parts by volume to 50 parts by volume. Furthermore, it is preferable that the average particle diameter of the conductive particles is in the range of 2.5 μm or more and 6.0 μm or less, and the particle density of the conductive particles is 5000 particles/mm ² or more and 50000 particles/mm ² or less. In this case, the dispersion|distribution of the electrically-conductive particle P, and the insulation between adjacent circuit electrodes 8 and 8 can be made compatible more suitably.

Regarding the relationship between the average particle diameter of the conductive particles P and the thickness of the conductive adhesive layer 13 , the thickness of the conductive adhesive layer 13 is preferably greater than or equal to 0.6 times and less than 1.0 times the average particle diameter of the conductive particles P. When the thickness of conductive adhesive layer 13 is less than 0.6 times the average particle diameter of conductive particles P, the particle density of conductive particles P decreases, and poor connection between bump electrodes 6 and circuit electrodes 8 may occur. In addition, when the thickness of the conductive adhesive layer 13 is greater than or equal to 1.0 times the average particle diameter of the conductive particles P, adjacent conductive particles P, P aggregate, and there is a possibility that adjacent circuit electrodes 8, 8 short circuits. In order to obtain better dispersibility, the thickness of the conductive adhesive layer 13 is preferably 0.7 times or more and 0.9 times or less with respect to the average particle diameter of the conductive particles P. In addition, the thickness of the conductive adhesive layer 13 is preferably greater than or equal to 1.5 μm and less than or equal to 6.0 μm.

As a result of satisfying such a relationship, a part of the conductive particle P protrudes toward the insulating adhesive layer 14, and the boundary S between the insulating adhesive layer 14 and the conductive adhesive layer 13 is located between adjacent conductive particles. P, the interval part of P. Moreover, electroconductive particle P is not exposed to the surface (namely, the surface by the release film 12 side) opposite to the insulating adhesive layer 14 of the electroconductive adhesive layer 13, and an opposite surface forms a flat surface. The thickness of the conductive adhesive layer 13 present between the conductive particles P and the surface of the conductive adhesive layer 13 is preferably greater than 0 μm and less than or equal to 1 μm.

The boundary S between the insulating adhesive layer 14 and the conductive adhesive layer 13 can be confirmed by cross-sectional observation of the anisotropic conductive film 11 . Considering the compositional difference between the insulating adhesive layer 14 and the conductive adhesive layer 13, the insulating adhesive can also be judged based on the difference in the observed image in processing/observation devices such as FIB, SEM, and TEM. The boundary S between the layer 14 and the conductive adhesive layer 13 .

When the insulating adhesive layer 14 and the conductive adhesive layer 13 are hardly compatible with each other, the boundary S can be confirmed as an interface. The composition of the insulating adhesive layer 14 and the conductive adhesive layer 13 is similar, and when the interface disappears in the lamination process described later, the insulating adhesive layer 14 and the conductive adhesive layer 13 may be mixed together. A boundary layer form is observed.

On the other hand, the thickness of the insulating adhesive layer 14 can be set suitably. The total thickness of the conductive adhesive layer 13 and the insulating adhesive layer 14 is, for example, 5 μm to 30 μm. In addition, the sum of the thicknesses of the conductive adhesive layer 13 and the insulating adhesive layer 14 is generally equal to the thickness from the mounting surface 5a of the first circuit member 2 to the mounting surface 7a of the second circuit member 3 in the bonded structure 1. The difference in distance is preferably 0 μm to 10 μm. From the viewpoint of filling between the circuit members 2 and 3 with the cured product 4 of the anisotropic conductive film, the above-mentioned difference is preferably 0.5 μm to 8.0 μm, more preferably 1.0 μm to 5.0 μm.

When the difference is less than 0 μm, there is a possibility that the space between the first circuit member 2 and the second circuit member 3 cannot be filled with the cured product 4 of the anisotropic conductive film, which may cause a decrease in connection reliability after peeling and humidity resistance tests. On the other hand, if the difference exceeds 10 μm, the resin is not sufficiently removed when the first circuit member 2 and the second circuit member 3 are crimped, and conduction between the bump electrodes 6 and the circuit electrodes 8 may not be obtained.

[Manufacturing method of bonded structure]

Fig. 3 is a schematic cross-sectional view showing a manufacturing process of the bonded structure shown in Fig. 1 . When forming the bonded structure 1, first, the release film 12 is peeled off from the anisotropic conductive film 11, and the anisotropic conductive film 11 is laminated so that the conductive adhesive layer 13 side faces the mounting surface 7a. On the second circuit member 3. Next, as shown in FIG. 4 , the first circuit member 2 is arranged on the second circuit member 3 on which the anisotropic conductive film 11 is laminated so that the bump electrodes 6 face the circuit electrodes 8 . Then, the first circuit member 2 and the second circuit member 3 are pressed in the thickness direction while heating the anisotropic conductive film 11 .

As a result, the adhesive component of the anisotropic conductive film 11 flows, the distance between the bump electrode 6 and the circuit electrode 8 is shortened, and the conductive particle P is stuck, the conductive adhesive layer 13 and the insulating adhesive The adhesive layer 14 is cured. By curing the conductive adhesive layer 13 and the insulating adhesive layer 14, the bump electrode 6 is electrically connected to the circuit electrode 8 and the adjacent bump electrodes 6 and 6 are connected to the adjacent circuit electrode 8. , 8 are electrically insulated to form a cured product 4 of an anisotropic conductive film, and the bonded structure 1 shown in FIG. 1 is obtained. In the obtained bonded structure 1, the cured product 4 of the anisotropic conductive film can sufficiently prevent the time-dependent change in the distance between the bump electrode 6 and the circuit electrode 8, and can also ensure long-term reliability of electrical characteristics. .

In addition, the heating temperature of the anisotropic conductive film 11 is preferably higher than or equal to the temperature at which polymerization active species are generated in the curing agent and polymerization of the polymerization monomer is initiated. The heating temperature is, for example, 80°C to 200°C, preferably 100°C to 180°C. In addition, the heating time is, for example, 0.1 second to 30 seconds, preferably 1 second to 20 seconds. When the heating temperature is lower than 80°C, the curing rate becomes slow, and when it exceeds 200°C, undesired side reactions tend to proceed. In addition, when the heating time is less than 0.1 second, the curing reaction does not proceed sufficiently, and when it exceeds 30 seconds, the productivity of the cured product decreases, and undesired side reactions tend to proceed.

[Manufacturing method of anisotropic conductive film]

FIG. 5 is a schematic view showing a manufacturing process of the anisotropic conductive film shown in FIG. 2 . In the example shown in the figure, the long release film 12 is conveyed at a predetermined speed by the delivery roller 21 and the winding roller 22 . On the transport path of the release film 12, a coater 23 for coating an adhesive paste W as a material for forming the conductive adhesive layer 13 is arranged, and the adhesive paste W in which the conductive particles P are dispersed is coated by the coater 23. The paste W is coated on the release film 12 (coating step). The thickness of the adhesive paste W coated on the peeling film 12 by the coater 23 varies with time depending on the ratio of the solvent contained in the resin composition, and is preferably less than 1.6 times the average particle diameter of the conductive particles P.

The viscosity of the adhesive paste W may vary depending on the application and the application method, but usually it is preferably 10 mPa·s to 10000 mPa·s. From the viewpoint of suppressing separation of complexes in the adhesive paste W and improving compatibility, it is more preferably 50 mPa·s to 5000 mPa·s. In addition, in order to improve the appearance of the anisotropic conductive film 11, it is preferably 100 mPa·s to 3000 mPa·s. When it exceeds 10000 mPa·s, the dispersion of conductive particles P in the subsequent magnetic field application step may be suppressed, and when it is less than 10 mPa·s, the compound of adhesive paste W may be separated.

The method of applying the adhesive paste W is not limited to the above method, and a known method can be used. Examples include spin coating, roll coating, bar coating, dip coating, micro gravure coating, curtain coating, die coating, spray coating, blade coating, kneader coating, flow coating, Screen printing method, casting method, etc. Bar coating, die coating, and micro gravure coating are suitable for producing the anisotropic conductive film 11 , and micro gravure coating is particularly suitable from the viewpoint of film thickness accuracy.

On the back stage side of the coater 23, a pair of magnets 24 and 25 are arrange|positioned up and down facing each other so that the peeling film 12 may be pinched|interposed. In the present embodiment, as shown in FIG. 6 , the magnet 24 arranged on the upper side has an N pole, and the magnet 25 arranged on the lower side has an S pole. Therefore, when the release film 12 is conveyed between the magnets 24 and 25, the conductive particles P in the adhesive paste W are magnetized, and the conductive particles P and P are separated in the in-plane direction of the adhesive paste W due to the repulsive force. state (magnetic field application process).

In addition, in order to maintain the separated state of the conductive particles P in the magnetic field application step, the adhesive paste W is dried by hot air or the like while the release film 12 passes between the magnets 24 and 25 (drying step). Thereby, the viscosity of adhesive agent paste W rises, and as shown in FIG. Peel off the film 12 on. In addition, the thickness of the adhesive paste W decreases through the drying process, and by making the thickness of the adhesive paste W less than 1.6 times the average particle diameter of the conductive particles P as described above, the conductive adhesive layer 13 can be made The thickness is greater than or equal to 0.6 times and less than 1.0 times the average particle diameter of the conductive particles P.

In addition, the drying temperature of the adhesive paste W is preferably, for example, 20°C to 80°C. In addition, the conveyance speed of the release film 12 is preferably, for example, 30 mm/s to 160 mm/s. For example, when using the conductive particle P whose average particle diameter is 3 micrometers, it is preferable that the thickness of the adhesive paste W is 5 micrometers - 10 micrometers. When the conveying speed of the release film 12 is less than the above range, the adhesive paste W may dry before the conductive particles P are separated, and the dispersion may be insufficient. When the conveyance speed of the peeling film 12 exceeds the said range, application of a magnetic field will be finished before drying, and there exists a possibility that electroconductive particle P may re-aggregate. In addition, when the thickness of the adhesive paste W is less than the above range, the gap of the coater 23 may be insufficient, and the number of conductive particles P in the conductive adhesive layer 13 may be insufficient, and the thickness of the adhesive paste W exceeds In the case of the said range, the gap of the coater 23 is too large, and the number of the electroconductive particle P in the electroconductive adhesive bond layer 13 may become excessive.

After the conductive adhesive layer 13 is formed, as shown in FIG. 8 , the separately produced insulating adhesive layer 14 is laminated on the conductive adhesive layer 13 (lamination step). Thus, the anisotropic conductive film 11 shown in FIG. 2 is obtained. In addition, for lamination of the insulating adhesive layer 14, a hot roll laminator can be used, for example. In addition, not limited to lamination, an adhesive paste as a material of the insulating adhesive layer 14 may be applied on the conductive adhesive layer 13 and dried.

From the above description, in the anisotropic conductive film 11 , 70% or more of the conductive particles P are separated from other adjacent conductive particles P in the conductive adhesive layer 13 . Therefore, when the first circuit member 2 and the second circuit member 3 are connected, the aggregation between the adjacent conductive particles P and P is suppressed, and the gap between the adjacent bump electrodes 6 and 6 and the adjacent circuit can be well ensured. Insulation between electrodes 8,8. In addition, in the anisotropic conductive film 11 , the thickness of the conductive adhesive layer 13 is equal to or greater than 0.6 times and less than 1.0 times the average particle diameter of the conductive particles P. Thereby, the flow of the conductive particles P is suppressed at the time of pressure bonding, and the capture efficiency of the conductive particles P between the bump electrodes 6 and the circuit electrodes 8 can be improved. Therefore, connection reliability between the first circuit member 2 and the second circuit member 3 can be ensured.

In the conventional manufacturing method, although conductive particles spaced apart from adjacent conductive particles were dispersed, most conductive particles were in contact with adjacent conductive particles and aggregated. On the other hand, in this manufacturing method, the state where almost all conductive particles are separated from adjacent conductive particles is maintained.

Therefore, according to the manufacturing method of the anisotropic conductive film 11 according to the present embodiment, it can be confirmed that the conductive particles P can be easily formed by applying a magnetic field to the adhesive paste W coated on the release film 12. The state of being separated from other conductive particles P by repulsion. Moreover, in the manufacturing method of the anisotropic conductive film 11, the adhesive paste W is applied so that the thickness of the adhesive paste W may become smaller than 1.6 times of the average particle diameter of the conductive particle P in a coating process. Accordingly, when the adhesive paste W is dried, the thickness of the conductive adhesive layer 13 can be made equal to or greater than 0.6 times and less than 1.0 times the average particle diameter of the conductive particles P. Therefore, the anisotropic conductive film 11 exhibiting the above effects can be easily obtained.

Example

Hereinafter, examples and comparative examples of the present invention will be described.

(Example 1)

In a 3000mL 3-necked flask equipped with a serpentine cooling tube, a calcium chloride tube, and a Teflon stirring rod connected to a stirring motor, 45 g of 4,4'-(9-fluorenylidene)-diphenol ( Sigma-Aldrich Japan Co., Ltd.), and 50 g of 3,3',5,5'-tetramethylbiphenol diglycidyl ether (manufactured by Mitsubishi Chemical Corporation: YX-4000H) were dissolved in 1000 mL of N-methylpyrrolidone. Prepare a reaction solution. 21 g of potassium carbonate was added thereto, and stirred while heating to 110° C. with a mantle heater. After stirring for 3 hours, the reaction solution was dropped into a beaker containing 1000 mL of methanol, and the generated precipitate was collected by suction filtration. The filtered precipitate was further washed 3 times with 300 mL of methanol to obtain 75 g of phenoxy resin a.

Then, the molecular weight of the phenoxy resin a was measured using a high performance liquid chromatograph GP8020 manufactured by Tosoh Corporation (column: Gelpak GLA150S and GLA160S manufactured by Hitachi Chemical Co., Ltd., solvent: tetrahydrofuran, flow rate: 1.0 mL/min). As a result, Mn=15769, Mw=38045, and Mw/Mn=2.413 in terms of polystyrene.

Next, when forming the adhesive paste for the conductive adhesive layer, 50 parts by mass of bisphenol A epoxy resin (manufactured by Mitsubishi Chemical Corporation: jER828) as an epoxy compound was blended in solid content. The components include 5 parts by mass of 4-hydroxyphenylmethylbenzylsulfonium hexafluoroantimonate as a curing agent, and 50 parts by mass of phenoxy resin a as a film-forming material in terms of solid content. In addition, regarding the conductive particles, a nickel layer with a thickness of 0.2 μm was provided on the surface of the particles with polystyrene as the core to produce conductive particles with an average particle diameter of 3.3 μm and a specific gravity of 2.5, and 80 parts by mass of the conductive particles were blended into the resin composition. Then, it was coated on a PET resin film with a thickness of 50 μm using a coater, and a magnetic field was applied while drying the resin composition to obtain a conductive adhesive layer with a thickness of 2.7 μm.

Next, when forming the adhesive paste for the insulating adhesive layer, 45 parts by mass of bisphenol F-type epoxy resin (manufactured by Mitsubishi Chemical Corporation: jER807) as an epoxy compound was blended in terms of solid content. 5 parts by mass of 4-hydroxyphenylmethylbenzylsulfonium hexafluoroantimonate as a curing agent, and 55 parts by mass of phenoxy resin b with Mw50000 and Tg70°C as a film-forming material in terms of solid content. Then, it was applied on a PET resin film with a thickness of 50 μm using a coater, and dried with hot air at 70° C. for 5 minutes to obtain an insulating adhesive layer with a thickness of 16 μm. Then, the conductive adhesive layer and the insulating adhesive layer were heated to 40° C. and bonded together using a hot roll laminator to obtain the anisotropic conductive film according to Example 1.

(Example 2)

Except having made the thickness of the electroconductive adhesive layer into 2.1 micrometers, it carried out similarly to Example 1, and produced the anisotropic electroconductive film which concerns on Example 2.

(Example 3)

In addition to the use of conductive particles with a thickness of 0.2 μm on the surface of particles with polystyrene as the core, a nickel layer, an average particle size of 3.6 μm, and a specific gravity of 2.5, and the point that the thickness of the conductive adhesive layer is 3.1 μm. In the same manner as in Example 1, the anisotropic conductive film according to Example 3 was produced.

(Example 4)

In addition to the use of conductive particles with a thickness of 0.2 μm on the surface of particles with polystyrene as the core, an average particle size of 4.1 μm, and a specific gravity of 2.4, and the point of making the thickness of the conductive adhesive layer 3.4 μm, it is the same as In the same manner as in Example 1, the anisotropic conductive film according to Example 4 was produced.

(Example 5)

In addition to the use of conductive particles with a thickness of 0.2 μm on the surface of particles with polystyrene as the core, a nickel layer, an average particle size of 5.1 μm, and a specific gravity of 2.3, and the point that the thickness of the conductive adhesive layer is 3.9 μm. In the same manner as in Example 1, the anisotropic conductive film according to Example 5 was produced.

(comparative example 1)

The anisotropic conductive film according to Comparative Example 1 was produced in the same manner as in Example 1 except that the thickness of the conductive adhesive layer was 1.8 μm.

(comparative example 2)

An anisotropic conductive film related to Comparative Example 2 was produced in the same manner as in Example 1 except that the thickness of the conductive adhesive layer was 3.5 μm.

(comparative example 3)

The anisotropic conductive film according to Comparative Example 3 was produced in the same manner as in Example 1 except that the application of a magnetic field was not performed.

(calculation of the density of conductive particles in the anisotropic conductive film)

Regarding the anisotropic conductive films of Examples 1 to 5 and Comparative Examples 1 to 3, the number of conductive particles per 2500 μm ² (50 μm×50 μm) was actually measured at 20 places with a metal microscope, and the average value was converted to 1 mm ² .

(Evaluation of Monodispersity Rate of Conductive Particles)

Regarding the anisotropic conductive films of Examples 1 to 5 and Comparative Examples 1 to 3, the monodispersity rate of the conductive particles (conductive particles existing in a state (monodisperse state) separated from other adjacent conductive particles) was evaluated. ratio). The monodispersity ratio was calculated using monodispersity ratio (%)=(the number of conductive particles in a monodisperse state in 2500 μm ² /the number of conductive particles in 2500 μm ² )×100. In the actual measurement of the conductive particles, observation was performed at a magnification of 200 times using a metal microscope.

Table 1 is a table showing the results of evaluation tests related to the dispersibility of conductive particles in the anisotropic conductive film. As shown in the table, in the anisotropic conductive films related to Examples 1 to 5, the conductive particle density of 19,000 particles/ ^mm2 or more was maintained, and the monodispersity rate exceeded 80%, and good monodispersity was obtained. sex. On the other hand, in the anisotropic conductive film related to Comparative Example 1, the average particle diameter of the conductive adhesive layer relative to the conductive particles became too thin, and although the monodispersity rate was 85%, the conductive particle density was 9000%. pieces/mm ² degree.

In addition, in the anisotropic conductive film according to Comparative Example 2, the conductive adhesive layer was too thick with respect to the average particle size of the conductive particles, and although the density of the conductive particles was as high as 35,000 particles/mm ² , the monodispersity rate was only 14%. In addition, in the anisotropic conductive film according to Comparative Example 3, the monodispersity rate was about 34% as a result of not applying a magnetic field.

(Creation of connection structure)

As the first circuit member, prepare an IC chip with a linear arrangement structure in which bump electrodes are arranged in a row (outer shape 2mm×20mm, thickness 0.55mm, size of bump electrodes 100μm×30μm, distance between bump electrodes 8μm, bump electrodes Electrode thickness 15 μm). In addition, as a second circuit member, a glass substrate (manufactured by Corning Incorporated: #1737, 38 mm x 28 mm, thickness 0.3 mm) was prepared in which an ITO wiring pattern (pattern width 21 μm, inter-electrode pitch 17 μm) was formed.

The connection of the IC chip and the glass substrate used a thermocompression bonding apparatus consisting of a stage (150mm×150mm) including a ceramic heater and a tool (3mm×20mm). First, the release film on the conductive adhesive layer of the anisotropic conductive film (2.5mm×25mm) involved in Examples 1 to 5 and Comparative Examples 1 to 3 was peeled off, and at 80°C, 0.98MPa (10kgf/cm ² ) under the condition of heating and pressing for 2 seconds, the surface on the side of the conductive adhesive layer was pasted on the glass substrate.

Next, after peeling off the release film on the insulating adhesive layer of the anisotropic conductive film and aligning the bump electrodes of the IC chip and the circuit electrodes of the glass substrate, the actual measurement of the anisotropic conductive film is the highest. It heated and pressurized for 5 seconds under conditions of reaching a temperature of 170° C. and a pressure of 70 MPa in terms of area on the bump electrodes, and bonded the insulating adhesive layer on the IC chip.

(Evaluation of capture rate of conductive particles and resistance characteristics)

Regarding the bonded structures obtained using the anisotropic conductive films of Examples 1 to 5 and Comparative Examples 1 to 3, the capture rate of conductive particles between the bump electrode and the circuit electrode, and the degree of contact between the bump electrode and the circuit electrode were evaluated. The resistance value between electrodes, and the insulation resistance between adjacent circuit electrodes. The capture rate is the ratio of the density of the conductive particles on the bump electrode to the density of the conductive particles in the anisotropic conductive film, and the capture rate (%)=(average of the number of conductive particles on the bump electrode/bump The electrode area/the number of conductive particles per unit area of the anisotropic conductive film)×100 was calculated.

In addition, the evaluation of resistance value was implemented by the four-probe measurement method, and the average value measured at 14 places was used. In the evaluation of insulation resistance, a voltage of 50 V was applied to the bonded structures obtained using the anisotropic conductive films of Examples 1 to 5 and Comparative Examples 1 to 3, and the insulation resistance between circuit electrodes at a total of 1440 locations was collectively measured. . Regarding the insulation resistance, the case where it was greater than 10 ⁸ Ω was judged as A, and the case where it was less than or equal to 10 ⁸ Ω was judged as B.

Table 2 is a table showing the results of evaluation tests related to the capture rate of conductive particles and resistance characteristics in bonded structures using the anisotropic conductive film. As shown in the table, in the bonded structures according to Examples 1 to 5, the capture rate of conductive particles was about 50%, and both the resistance value and the insulation resistance were good. On the other hand, in the bonded structure according to Comparative Example 1, the density of conductive particles was low, so the capture rate of conductive particles was equivalent to that of Examples 1-5, but the resistance value was higher than that of Examples 1-5. Moreover, in Comparative Examples 2 and 3, since the monodispersity rate of electroconductive particle was low, insulation resistance fell compared with Examples 1-5.

Table 1

Table 2

Claims (15)

1. An anisotropic conductive film, characterized in that it possesses: a conductive adhesive layer comprising an adhesive layer dispersed with conductive particles, and an insulating adhesive layer laminated on the conductive adhesive layer and comprising an adhesive layer in which the conductive particles are not dispersed, The thickness of the conductive adhesive layer is greater than or equal to 0.6 times and less than 1.0 times the average particle diameter of the conductive particles, In the conductive adhesive layer, 70% or more of the conductive particles are separated from other adjacent conductive particles. 2. The anisotropic conductive film according to claim 1, wherein in the conductive adhesive layer, the conductive particles are not exposed on the surface opposite to the insulating adhesive layer. A thickness of the conductive adhesive layer present between the conductive particles and the surface of the conductive adhesive layer is greater than 0 μm and less than or equal to 1 μm. 3 . The anisotropic conductive film according to claim 1 , wherein the average particle diameter of the conductive particles is greater than or equal to 2.5 μm and less than or equal to 6.0 μm. 4 . The anisotropic conductive film according to claim 3 , wherein the average particle diameter of the conductive particles is greater than or equal to 2.7 μm. 5 . The anisotropic conductive film according to claim 3 , wherein the average particle diameter of the conductive particles is greater than or equal to 3.0 μm. 6 . The anisotropic conductive film according to claim 3 , wherein the average particle diameter of the conductive particles is less than or equal to 5.5 μm. 7. The anisotropic conductive film according to claim 3, wherein the average particle diameter of the conductive particles is less than or equal to 5.0 μm. 8 . The anisotropic conductive film according to claim 3 , wherein the density of the conductive particles is greater than or equal to 5000 particles/mm ² and less than or equal to 50000 particles/mm ² . 9 . The anisotropic conductive film according to claim 1 , wherein the thickness of the conductive adhesive layer is greater than or equal to 1.5 μm and less than or equal to 6.0 μm. 10. The anisotropic conductive film according to claim 1, wherein the total thickness of the conductive adhesive layer and the insulating adhesive layer is greater than or equal to 5.0 μm and less than or equal to 30 μm. 11. The anisotropic conductive film according to claim 1, wherein the conductive particles contain nickel. 12. A bonded structure, characterized in that the first circuit member provided with bump electrodes and the first circuit member provided with corresponding The second circuit member of the circuit electrode of the bump electrode is connected. 13. The bonded structure according to claim 12, wherein the total thickness of the conductive adhesive layer and the thickness of the insulating adhesive layer in the anisotropic conductive film before curing is , and the distance from the mounting surface of the first circuit member to the mounting surface of the second circuit member is greater than or equal to 0 μm and less than or equal to 10 μm. 14. The bonded structure according to claim 13, wherein the difference is greater than or equal to 0.5 μm and less than or equal to 8.0 μm. 15. The bonded structure according to claim 13, wherein the difference is greater than or equal to 1.0 μm and less than or equal to 5.0 μm.