JP4766943B2 - CIRCUIT ADHESIVE SHEET AND METHOD FOR MANUFACTURING THE SAME - Google Patents

Description

  The present invention relates to a circuit adhesive sheet and a connection structure excellent in low temperature and short time connectivity.

Until now, regarding a circuit adhesive sheet for connecting a fine circuit, various compositions and circuit adhesive sheet configurations have been studied in order to ensure connectivity and prevent a short circuit.
For example, a method of laminating a curing agent layer containing a curing agent that generates radicals upon heating and a radical polymerizable substance and a conductive particle layer containing conductive particles and radical polymerizable substances that do not contain a curing agent that generates radicals upon heating. (Refer to Patent Document 1), a method of laminating an adhesive resin layer containing an inorganic filler and an adhesive layer mainly composed of an adhesive resin composition in order to adjust the thermal expansion coefficient to ensure connection reliability (Patent Document 1) 2), or a method of blending fine rubber particles in the adhesive composition in order to reduce thermal stress during connection and ensure reliability (see Patent Document 3), connection reliability due to elongation of adhesive resin In order to suppress the deterioration of the property, a method using a conductive particle plated with gold and a small diameter encapsulated latent curing agent (see Patent Document 4), a layer containing conductive particles and a layer not containing conductive particles The layers to prevent shorting between adjacent circuits, (see Patent Documents 5 and 6) how to ensure connectivity, etc. are known.

However, in the conventional technology that alleviates thermal stress during connection, mismatch in thermal expansion coefficient, etc., sufficient curing cannot be obtained under conditions such as lower temperature and shorter time, and initial connectivity and connection reliability are reduced. It was not satisfactory.
On the other hand, at the time of crimping, the adhesive resin must be removed from the connecting portion to ensure the connectivity, so there is a limit to blending a highly reactive curing agent to ensure sufficient connectivity. there were. In general, as a method for producing a circuit adhesive sheet, a method of adding a curable resin and a curing agent to a solvent in advance and drying the solvent to form a sheet is used, but a highly reactive curing agent is used. When it was used, the storage stability was lowered due to the presence of the solvent, so that it was not satisfactory in ensuring electrical connection, adhesion strength, and storage stability. Further, even in the prior art such as improvement in connection reliability by the type and configuration of conductive particles, connection reliability cannot be ensured in the case of low temperature and short time connection.

Japanese Patent Laid-Open No. 10-273630 Japanese Patent Laid-Open No. 10-226769 Japanese Patent Laid-Open No. 11-50032 Japanese Patent No. 2586154 JP-A-6-45024 JP 2003-49152 A

  The present invention relates to a circuit adhesive sheet that has good storage stability and can be connected in a low temperature for a short time without impairing the adhesive strength and electrical connectivity between adjacent circuits of a fine circuit, its manufacturing method, and use thereof An object of the present invention is to provide a finely connected structure.

As a result of intensive studies to solve the above problems, the present inventor uses a circuit adhesive sheet characterized in that the curing agent concentration forms a specific distribution state in the film thickness direction of the circuit sheet. It has been found that the above problem can be solved.
That is, the present invention is as follows.

(1) A circuit adhesive sheet containing at least a curing agent and a curable insulating resin , the curing agent is included over the entire circuit adhesive sheet, and along the thickness direction from one surface of the circuit adhesive sheet. A circuit adhesive sheet, wherein the concentration of the curing agent in a region of 1/3 times the thickness of the sheet is 1.1 to 10 times the concentration of the curing agent in other regions.
(2) It contains at least two kinds of curing agents having different reactivity with the curable insulating resin, and reacts most in the region of 1/3 times the sheet thickness along the thickness direction from one surface of the circuit adhesive sheet. The circuit adhesive sheet according to (1) above, which contains a highly curing agent.
(3) The above (1), wherein at least one of the curing agents is a solid curing agent, and an average particle diameter thereof is 1/50 to 1/3 times the sheet thickness of the circuit adhesive sheet. Or the circuit adhesive sheet as described in (2).
(4) The circuit adhesive sheet according to the above (1) to (3), wherein conductive particles having an average particle diameter 1/10 to 1 times the average film thickness of the circuit adhesive sheet are blended.

(5) A circuit adhesive sheet is obtained by transferring a solid curing agent present in a dispersed state on a smooth plate to an adhesive sheet containing at least a curing agent and a curable insulating resin. The manufacturing method of the circuit adhesive sheet as described in said (1)-(4).
(6) An adhesive layer is provided on a biaxially stretchable film to form a laminate, and a solid curing agent is adhered onto the laminate to produce a solid curing agent-attached film, and the solid curing agent is adhered. The film is biaxially stretched and held within a range of 50% to 1000%, and the solid curing agent is transferred to an adhesive sheet comprising at least a curing agent and a curable insulating resin. The method for producing a circuit adhesive sheet according to any one of (1) to (4) above, comprising a step of producing a circuit adhesive sheet having a high region.
(7) A micro-connection structure characterized in that an electronic circuit component and a circuit board are connected by bringing a surface having a high curing agent concentration of the circuit adhesive sheet according to any one of (1) to (4) into contact with the circuit board side. How to connect the body.
(8) A fine connection structure comprising an electronic circuit component and a circuit board connected by the connection method of the fine connection structure according to (7).

  The circuit adhesive sheet of the present invention has good storage stability and can ensure good connectivity when it is pressure-bonded at a low temperature for a short time. Moreover, the fine connection structure obtained by using the circuit adhesive sheet of the present invention has good insulating properties between adjacent connection terminals and good electrical connectivity between the connected connection terminals.

Hereinafter, the present invention will be specifically described.
As the curable insulating resin used for the circuit adhesive sheet of the present invention, thermosetting resin, photocurable resin, light and thermosetting resin, electron beam curable resin, and the like can be used. In view of ease of handling, it is preferable to use a thermosetting insulating resin. As the thermosetting resin, an epoxy resin, an acrylic resin, or the like can be used, and an epoxy resin is particularly preferable.

  The epoxy resin is a compound having two or more epoxy groups in one molecule, and is preferably a compound having a glycidyl ether group, a glycidyl ester group or an alicyclic epoxy group, or a compound obtained by epoxidizing a double bond in the molecule. . Specifically, bisphenol A type epoxy resin, bisphenol F type epoxy resin, naphthalene type epoxy resin, novolac phenol type epoxy resin, or modified epoxy resins thereof can be used.

  Any curing agent can be used for the circuit adhesive sheet of the present invention as long as it can cure the curable insulating resin. When a thermosetting resin is used as the curable insulating resin, a curing agent that reacts with the thermosetting resin at 100 ° C. or higher is preferable. When an epoxy resin is used as the curable resin, the curing agent is preferably a latent curing agent from the viewpoint of storage stability. For example, an imidazole curing agent, a capsule-type imidazole curing agent, a cationic curing agent, a radical A system curing agent, a Lewis acid curing agent, an amine imide curing agent, a polyamine salt curing agent, a hydrazide curing agent, and the like can be used. From the viewpoint of storage stability and low-temperature reactivity, capsule-type imidazole curing agents are preferred. It is also preferable to use a microcapsule type curing agent in which a highly reactive curing agent is encapsulated in a microcapsule or the like made of resin or ceramics and coated with a thermoplastic resin or wax.

In the present invention, the entire circuit adhesive sheet contains a curing agent, and the concentration of the curing agent is in the region of 1/3 times the sheet thickness along the thickness direction from one surface of the circuit adhesive sheet. It is characterized by being 1.1 to 10 times the concentration of the curing agent in the other region.
In the circuit adhesive sheet of the present invention, there is a distribution in the curing agent concentration in the film thickness direction, and the insulating resin on the connection surface can be effectively eliminated at the time of crimping, compared with a structure in which the curing agent is uniformly blended. It is possible to effectively impart connectivity with a smaller amount of curing agent.

  The curing agent used in the present invention may have a concentration distribution using one kind of curing agent, but two or more curing agents having different reactivity with respect to the curable resin used in the present invention are used. It is preferable that the most reactive curing agent is contained in a region within 1/3 times the average film thickness along the thickness direction from one surface of the circuit adhesive sheet.

It is preferable that at least one of the curing agents used in the present invention is a solid curing agent.
Examples of the solid curing agent include an amine adduct curing agent (reaction product of an imidazole compound and an epoxy resin), a hydrazide curing agent, a dicyandiamide curing agent, and a composite curing agent in which two or more thereof are combined. is there. From the viewpoint of storage stability, it is preferable to coat the solid curing agent with a thermoplastic resin, wax or the like.

The solid curing agent preferably has an average particle size of 1/50 or more and 1/3 or less of the average film thickness of the circuit adhesive sheet of the present invention, and is 1/20 or more and 1/10 or less. More preferably. From the viewpoint of curability, it is preferably 1/50 or more, and from the viewpoint of connectivity, it is preferably 1/3 or less.
The average particle diameter of the curing agent can be measured with an airflow dispersion type laser particle size distribution meter (manufactured by JOEL, HELOS).

  In the present invention, the high reactivity of the curing agent with respect to the curable resin means that the reaction start temperature between the curing agent and the curable resin is low or the reaction rate is high. Regarding the reaction start temperature, when two kinds of curing agents having different reactivities are compared, the curing agent having high reactivity is preferably 10 ° C. or more lower than the curing agent having low reactivity, and is 20 ° C. or more lower. Is more preferable. The reaction start temperature can be measured by DSC or the like after mixing the curable resin and the curing agent used in the present invention in an average blending amount.

  The reaction rate can be measured using a method such as Arrhenius plot after measuring the reaction rate under conditions where the temperature is changed. The reaction rate is preferably 10% or more, more preferably 20% or more. For example, a curing agent that has not been encapsulated to enhance storage stability is more reactive than that encapsulated.

  In addition, the usual manufacturing method often employs a method in which a curing agent is blended in an insulating adhesive solution in advance, but in this case, the influence of the solvent cannot be ignored, and curing in the insulating adhesive solution is performed. Because of concerns such as the reaction between the agent and the curable resin, there is a limit to the potential imparting method that can be used. In addition, there is a limitation on the type of curing agent due to the concern about the reaction between the curing agent and the curable resin due to heating during solvent drying. In the method for producing a circuit adhesive sheet of the present invention, a method of transferring a curing agent in a dry manner to an insulating adhesive sheet that already contains no solvent is also possible. Therefore, there are few restrictions on the potential imparting material and the configuration which can be used for the solvent, and the effect can be exhibited.

Next, the circuit adhesive sheet of the present invention will be described.
The thickness of the circuit adhesive sheet is preferably 2 μm or more and 40 μm or less, and more preferably 5 μm or more and 30 μm or less. 2 μm or more is preferable from the viewpoint of mechanical connection strength, and 40 μm or less is preferable from the viewpoint of preventing an excessive amount of the insulating resin flowing out due to the flow of the insulating resin during connection.

In the circuit adhesive sheet of the present invention, the position where the curing agent particles are present with respect to the thickness direction of the circuit adhesive sheet can be measured by a laser microscope capable of measuring the displacement in the focal direction. At the same time, the number of curing agent particles can be measured. When the displacement in the focal direction is measured using the laser microscope, the displacement measurement resolution is preferably 0.1 μm or less, and particularly preferably 0.01 μm or less.
When mix | blending electroconductive particle with the circuit adhesive sheet of this invention, the average particle diameter of electroconductive particle has preferable 1/10 to 1 time of the sheet | seat thickness of a circuit adhesive sheet.

Next, the manufacturing method of a circuit adhesive sheet is demonstrated.
As a method for producing the circuit adhesive sheet of the present invention, a method of dispersing and dispersing a curing agent on a smooth plate and transferring the dispersed curing agent to an adhesive sheet containing at least a curable resin can be used. .
As a method of spraying the curing agent particles, it is preferable to disperse the curing agent particles after removing the charge. For example, the static elimination treatment is performed by grounding the particle outlet of the spraying device. As the smooth plate used at this time, a glass plate, a Teflon (registered trademark) plate, a metal plate, or the like can be used.

In order to prevent the migration and aggregation of the curing agent particles, it is preferable to form an adhesive layer on a smooth plate, and in order to facilitate the transfer of the curing agent particles to the adhesive sheet, a weak adhesive layer is provided. Is preferred. As the pressure-sensitive adhesive, a natural rubber-based, synthetic rubber-based, or silicone-based pressure-sensitive adhesive can be used. The thickness of the adhesive layer is preferably in the range of 1 μm to 10 μm, and more preferably in the range of 2 μm to 5 μm. When the thickness of the adhesive layer is too thin, the adhesive effect is insufficient, and when it is too thick, the transfer is insufficient. In the case of continuous processing, it is preferable to transfer on a smooth plate using a film on which an adhesive layer is formed.
In the circuit adhesive sheet of the present invention, a part of some curing agent particles may be exposed from one surface of the circuit adhesive sheet.

  As a more preferable production method of the circuit adhesive sheet of the present invention, an adhesive layer is formed on a biaxially stretchable film or sheet, a single layer of curing agent particles is arranged thereon, and they are stretched. There is a method in which the curing agent particles are dispersed and arranged and transferred to an adhesive sheet made of at least a curing agent and a curable insulating resin in a stretched state.

  As the biaxially stretchable film or sheet, a known resin film or the like can be used, but a polyethylene resin, a polypropylene resin, a polyester resin, a polyvinyl butyral resin, a polyvinyl alcohol resin, a polyvinylidene chloride resin or the like can be used alone or in combination. It is preferable to use a flexible and stretchable resin film such as a coalescence or a rubber sheet such as nitrile rubber, butadiene rubber, or silicone rubber. Polypropylene resin and polyester resin are particularly preferable. The shrinkage after stretching is preferably 10% or less.

  As a method for arranging and fixing the curing agent particles in a single layer on a biaxially stretchable film or sheet, a known method can be used. For example, a method in which an adhesive layer containing at least a thermoplastic resin is formed on the biaxially stretchable film, and hardener particles are brought into contact with the adhesive layer, and a single layer is applied by applying a load with a rubber roll or the like. Can be taken. In this case, a method of repeating the adhesion-roll operation several times is preferable for filling without gaps. In the case of spherical hardener particles, the closest packing is the most stable structure, so that it can be filled relatively easily. Alternatively, an adhesive is formed on the biaxially stretchable film to form an adhesive layer, and the curing agent particles are adhered on the adhesive layer. If necessary, the adhesion may be repeated several times, and dispersed in a single layer. Can be used.

  The thickness of the adhesive layer is preferably in the range of 1/50 to 3 times the average particle size of the curing agent particles used, and more preferably in the range of 1/10 to 2 times. From the viewpoint of holding the curing agent particles during adhesion of the curing agent particles and during stretching, the thickness of the adhesive layer is preferably 1/50 or more of the average particle diameter of the curing agent particles, from the viewpoint of particle transfer to the adhesive sheet after stretching. 3 times or less is preferable. As a method for forming the adhesive layer, a method in which a pressure-sensitive adhesive dispersed or dissolved in a solvent or water is applied by a known method such as a gravure coater, a die coater, a knife coater, or a bar coater and dried. When a hot-melt type pressure-sensitive adhesive is used, it can be roll-coated without a solvent.

  As the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer, a known one can be used, but when biaxial stretching is performed while heating, it is preferable to use a non-thermal crosslinkable pressure-sensitive adhesive. Specifically, natural rubber latex adhesives, synthetic rubber latex adhesives, synthetic resin emulsion adhesives, silicone adhesives, ethylene-vinyl acetate copolymer adhesives, etc. may be used alone or in combination. Can do.

  In adhering the curing agent particles to the adhesive layer, it is preferable to dispose the curing agent particles in a single layer with almost no gap (dense filling). As the method of dense packing, the above-described method of dispersing and arranging the curing agent particles on the biaxially stretchable film can be used. In addition, close packing shall mean filling so that the average particle | grain space | interval between the filled hardening | curing agent particles may be 1/2 or less of an average particle diameter. More preferably, the average particle interval between the filled particles is 1/5 or less of the average particle size.

  As a method of stretching a biaxially stretchable film in which hardener particles are arranged in a single layer, a known method can be used, but a biaxial stretching device is preferably used from the viewpoint of uniform dispersion alignment. From the viewpoint of particle spacing, the degree of stretching is preferably 50% or more and 1000% or less, and more preferably 50% or more and 300% or less. In addition, 100% stretching means that the length of the portion stretched along the stretching direction is 100% of the length before stretching. The stretching direction is arbitrary, but biaxial stretching with a stretching angle of 90 ° is preferable, and simultaneous stretching is preferable. In the case of biaxial stretching, the degree of stretching in each direction may be the same or different.

  The film thickness of the biaxially stretched film is preferably 1/10 to 1 times the total thickness of the adhesive sheet to be transferred and the base film of the adhesive sheet, and 1/5 to 1/2. It is particularly preferred that From the viewpoint of handling properties of the stretched film, it is preferably 1/10 or more, and from the viewpoint of transfer of the curing agent particles to the stretched adhesive sheet, it is preferably 1 time or less.

As the biaxial stretching apparatus, a simultaneous biaxial continuous stretching apparatus is preferable.
As the simultaneous biaxial continuous stretching apparatus, a known one can be used, but a tenter type stretching machine that continuously stretches by fixing the long side with a chuck fitting and simultaneously stretching the distance in the vertical and horizontal directions is preferable. As a method for adjusting the degree of stretching, a screw method or a pantograph method can be used, but a pantograph method is more preferable from the viewpoint of accuracy of adjustment. When stretching while heating, it is preferable to provide a preheating zone before the stretched portion and a heat setting zone behind the stretched portion. Preferably, the biaxially stretchable film is a long film, and the adhesive sheet is also a long adhesive sheet. In the present specification, the term “long” means that the length is 10 m or more. If a long adhesive sheet is used, a connection structure can be produced continuously, which is efficient.

The adhesive sheet is an adhesive layer comprising a curing agent and a curable insulating resin, and this adhesive sheet is usually formed on a peelable base film (holding film). For this reason, the circuit adhesive sheet obtained is normally formed on a peelable base film. In the present specification, the laminate of the circuit adhesive sheet and the base film may be referred to as a circuit adhesive sheet.
The circuit adhesive sheet of the present invention may be a single-layer sheet comprising at least a curing agent and a curable insulating resin, and further includes a resin sheet that does not include conductive particles and includes at least an insulating resin. It may be a multilayered sheet.

  The circuit adhesive sheet of the present invention may contain a thermoplastic resin or the like in addition to the curing agent and the curable insulating resin. By blending a thermoplastic resin, it can be easily formed into a sheet. In this case, the blending amount is preferably 200 parts by mass or less, particularly preferably 100 parts by mass or less, based on 100 parts by mass of the components including the curing agent and the curable insulating resin.

  Thermoplastic resins that can be blended with the curable insulating resin of the present invention include phenoxy resin, polyvinyl acetal resin, polyvinyl butyral resin, alkylated cellulose resin, polyester resin, acrylic resin, styrene resin, urethane resin, polyethylene terephthalate resin, etc. Yes, one kind selected from them may be used, or two or more kinds of resins may be used in combination. Among these resins, a resin having a polar group such as a hydroxyl group or a carboxyl group is preferable from the viewpoint of adhesive strength. Moreover, it is preferable that a thermoplastic resin contains 1 or more types of thermoplastic resins whose glass transition temperature is 80 degreeC or more.

Conductive particles can be blended in the circuit adhesive sheet of the present invention.
The average particle diameter of the conductive particles blended in the circuit adhesive sheet of the present invention is preferably in the range of 1/10 to 1 times the film thickness of the circuit adhesive sheet.
In the present invention, the average particle diameter of the conductive particles means the average diameter of the conductive particles.

  The blending amount of the conductive particles in the circuit adhesive sheet is preferably 0.5 parts by mass to 20 parts by mass with respect to 100 parts by mass of the components including the curing agent and the curable insulating resin. It is particularly preferable that the amount is 10 parts by mass. 20 parts by mass or less is preferable from the viewpoint of insulation, and 0.5 parts by mass or more is preferable from the viewpoint of electrical connectivity.

As the conductive particles, it is preferable to use at least one selected from resin particles coated with noble metal, metal particles coated with noble metal, metal particles, alloy particles coated with noble metal, and alloy particles.
As the resin particles coated with the noble metal, it is preferable to use those obtained by coating spherical particles such as polystyrene, benzoguanamine, and polymethyl methacrylate with nickel and gold in this order.

Resin particles coated with a noble metal can be formed using softer resin particles according to the hardness of the fine connection terminal (bump) to be connected.
When the bump hardness to be connected is less than 50 Hv in terms of Vickers hardness, it is preferable to use flexible resin particles such as polymethacrylate resin. Moreover, when bump hardness is 50 Hv or more, it is preferable to use hard resin particles, such as a benzoguanamine resin.

  As the metal particles coated with the noble metal, it is preferable to use a metal particle such as nickel or copper coated with a noble metal such as gold, palladium or rhodium on the outermost layer. As a coating method, a thin film forming method such as a vapor deposition method or a sputtering method, a coating method using a dry blend method, a wet method such as an electroless plating method or an electrolytic plating method can be used. From the viewpoint of mass productivity, the electroless plating method is preferable.

As the metal particles, those selected from metals such as silver, copper and nickel are preferably used. The alloy particles preferably have a melting point of 150 ° C. or more and 500 ° C. or less, and more preferably low melting point alloy particles having a melting point of 150 ° C. or more and 350 ° C. or less. When the melting point is 500 ° C. or less, a metal bond can be formed between the connection terminals, which is preferable from the viewpoint of connection reliability. Moreover, it is preferable that melting | fusing point is 150 degreeC or more from a viewpoint of heat-resistant connection reliability.
As the alloy particles coated with the noble metal, for example, alloy particles composed of two or more kinds selected from gold, silver, copper, nickel, tin, zinc, bismuth, indium, etc. are coated with the noble metal using the above method or the like. Can be used.

  As the alloy particles, for example, alloy particles composed of two or more selected from gold, silver, copper, nickel, tin, zinc, bismuth, indium and the like are preferable. When alloy particles having a melting point of 150 ° C. or higher and 500 ° C. or lower are used, it is preferable to coat the particle surface with a flux or the like in advance. It is preferable to use a so-called flux because the surface oxides can be removed. As the flux, fatty acids such as abietic acid can be used.

  The ratio of the average particle size to the maximum particle size of the conductive particles is preferably 2 or less, and more preferably 1.5 or less. The particle size distribution of the conductive particles is preferably narrower, and the geometric standard deviation of the particle size distribution of the conductive particles is preferably 1.2 to 2.5, and preferably 1.2 to 1.4. Is particularly preferred. When the geometric standard deviation is the above value, the variation in particle size is reduced. Usually, when a certain gap exists between two terminals to be connected, it is considered that the conductive particles function more effectively as the particle diameters become uniform.

  The geometric standard deviation of the particle size distribution is a value obtained by dividing the σ value of the particle size distribution (particle size value of 84.13% cumulative) by the particle size value of 50% cumulative. When the particle size distribution (logarithm) is set on the horizontal axis of the particle size distribution graph and the cumulative value (%, cumulative number ratio, logarithm) is set on the vertical axis, the particle size distribution is almost linear, and the particle size distribution is lognormal distribution. Follow. The cumulative value indicates the number ratio of particles having a certain particle size or less with respect to the total number of particles, and is expressed in%. The sharpness of the particle size distribution is expressed by the ratio of σ (the cumulative particle size value of 84.13%) and the average particle size (the cumulative particle size value of 50%). The σ value is an actual measurement value or a read value from the plot value of the graph.

The average particle size and particle size distribution can be measured using a known method and apparatus, and a wet particle size distribution meter, a laser particle size distribution meter, or the like can be used. Alternatively, the average particle size and particle size distribution may be calculated by observing the particles with an electron microscope or the like.
The average particle diameter of the conductive particles is preferably 1/10 to 1 times the sheet thickness of the circuit adhesive sheet, more preferably 1/10 to 1/2 times, still more preferably 1/10 to 1/3 times. .

In the circuit adhesive sheet of the present invention, an additive may be blended with the above components.
In order to improve the adhesion between the circuit adhesive sheet and the adherend, a coupling agent can be blended as an additive. As the coupling agent, a silane coupling agent, a titanium coupling agent, an aluminum coupling agent, or the like can be used, and a silane coupling agent is preferable. Examples of the silane coupling agent include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-mercaptotrimethoxysilane, γ-aminopropyltrimethoxysilane, β-aminoethyl-γ- Aminopropyltrimethoxysilane, γ-ureidopropyltrimethoxysilane, and the like can be used.

  The blending amount of the coupling agent is preferably 0.01 parts by mass to 1 part by mass with respect to 100 parts by mass of the components including the curing agent and the curable insulating resin. 0.01 mass part or more is preferable from a viewpoint of adhesive improvement, and 1 mass part or less is preferable from a reliability viewpoint.

  Furthermore, an ion scavenger can be blended as an additive in order to prevent insulation deterioration due to ionic components in the circuit adhesive sheet during moisture absorption. As the ion scavenger, an organic ion exchanger, an inorganic ion exchanger, an inorganic ion adsorbent, and the like can be used, but an inorganic ion exchanger excellent in heat resistance is preferable. As the inorganic ion exchanger, zirconium compounds, zirconium bismuth compounds, antimony bismuth compounds, and magnesium aluminum compounds can be used. There are cation type, anion type, and both ion types as ion types to be exchanged, but metal ions (cations) that cause ion migration directly, increase electrical conductivity, and cause generation of metal ions. Both anions are preferred because both anions can be exchanged.

The average particle size of the ion scavenger to be blended is preferably 0.01 μm or more and 5 μm or less, and more preferably 0.01 μm or more and 1 μm or less.
The compounding amount of the ion scavenger is preferably 0.01 to 3 parts by mass with respect to 100 parts by mass of the resin component. When the blending amount is less than 0.01 parts by mass, the ion trapping effect is insufficient, and 3 parts by mass or less is preferable from the viewpoint of electrical connection.

  Next, the connection method of the present invention in which an electronic circuit component having fine connection terminals and a circuit board having a corresponding circuit are electrically connected with a circuit adhesive sheet will be described. In the connection method, the electronic circuit component and a circuit board having a corresponding circuit are electrically connected using the circuit adhesive sheet of the present invention.

The circuit adhesive sheet of the present invention is connected by bringing the surface having a high curing agent concentration into contact with the circuit board side having a relatively low wiring height, and thermocompression bonding from the circuit component side having a relatively high wiring height. It is preferable.
By disposing the surface having a high curing agent concentration on the circuit board surface having a relatively low wiring height, the connection strength can be further increased and the reliability can be increased.

The film thickness of the circuit adhesive sheet is preferably 1 to 2 times the sum of the connected wiring heights. From the viewpoint of the mechanical strength of the fine connection structure, it is preferably 1 or more, and from the viewpoint of preventing excessive resin from protruding due to the resin flow of the circuit adhesive sheet during connection, it is preferably 2 or less.
In the present invention, the circuit adhesive sheet is an adhesive layer comprising a curing agent and a curable insulating resin, and this adhesive sheet is usually formed on a peelable base film (holding film). For this reason, the circuit adhesive sheet obtained is normally formed on a peelable base film.
In the present specification, the laminate of the circuit adhesive sheet and the base film may be referred to as a circuit adhesive sheet.

The present invention also relates to a fine connection structure connected by the fine connection method.
The material of the circuit board constituting the finely connected structure of the present invention may be an organic substrate or an inorganic substrate. As the organic substrate, a polyimide film substrate, a polyamide film substrate, a polyethersulfone film substrate, a rigid substrate obtained by impregnating a glass cloth with an epoxy resin, a rigid substrate obtained by impregnating a glass cloth with a bismaleimide-triazine resin, or the like may be used. it can. As the inorganic substrate, a silicon substrate, a glass substrate, an alumina substrate, an aluminum nitride substrate, or the like can be used. The wiring material of the wiring board is inorganic wiring materials such as indium tin oxide and indium zinc oxide, metal wiring materials such as gold-plated copper, chromium-copper, aluminum and gold bumps, and metal materials such as aluminum and chromium indium tin oxide. A composite wiring material covering an inorganic wiring material such as an object can be used.

As an application to which the circuit adhesive sheet of the present invention is applied, or as an electronic circuit component constituting the fine connection structure of the present invention, a wiring board connection application of a display device such as a liquid crystal display device, a plasma display device, an electroluminescence display device, etc. These devices can be used for mounting electronic components such as LSIs, wiring board connecting portions of other devices, and mounting electronic components such as LSIs. Among the display devices, it is preferably used for plasma display devices and electroluminescence display devices that require reliability.
Next, the present invention will be described with reference to examples and comparative examples.

[Example 1]
Acetic acid containing 35 g of phenoxy resin (glass transition temperature 98 ° C., number average molecular weight 14000), 28 g of bisphenol A type epoxy resin (epoxy equivalent 190, 25 ° C. viscosity, 14000 mPa · S), 0.4 g of γ-glycidoxypropyltrimethoxysilane Dissolve in a mixed solvent of ethyl-toluene (mixing ratio 1: 1) to obtain a 50% solid content solution.
37 g of a liquid epoxy resin containing microcapsule-type latent imidazole curing agent (average size of microcapsules 4 μm, active temperature 125 ° C., curing agent content 12 g) was blended and dispersed in the 50% solid content solution. Then, it apply | coated on the 50-micrometer-thick polyethylene terephthalate film (base film), air-dried at 60 degreeC for 10 minute (s), and obtained the film-form adhesive sheet of 20-micrometer-thickness. The concentration of the curing agent in the adhesive sheet was 11.9% by weight, and the average content was 2.62 g / m ² .

The microcapsule-type latent imidazole curing agent is contained in a non-stretched polyethylene film having a thickness of 40 μm coated with a nitrile rubber latex-methyl methacrylate graft copolymer adhesive as a pressure-sensitive adhesive layer in a thickness of 3 μm. As a hardener more reactive than liquid epoxy resin, amine adduct with average particle size of 4.0μm (adduct of epoxy resin and imidazole, softening point 105 ° C, true density 1.21g / cm ³ ) with almost no gap, single layer coating did. That is, the curing agent particles were sprayed so as to be almost spread on the film, and excess curing agent particles were scraped off with a scrubber made of soft rubber. By repeating this operation twice, a hardener particle-adhered film coated with a single layer without a gap was obtained.

This film was fixed using 10 chucks in the vertical and horizontal directions using a biaxial stretching device (X6H-S manufactured by Toyo Seiki, pantograph type corner stretching type biaxial stretching device), and then a speed of 20% / sec. And stretched 100% and fixed. Then, after laminating the adhesive sheet on the stretched film, it was peeled off to obtain a circuit adhesive sheet.
Almost all of the used curing agent particles were transferred to the circuit adhesive sheet.

Using a laser microscope (Keyence Co., VK9500, shape measurement resolution 0.01 μm) capable of measuring the displacement in the focal direction by randomly selecting 100 of the curing agent particles in the obtained circuit adhesive sheet, the circuit The distance from the surface of the adhesive sheet was measured. As a result, all of the transferred curing agent was present in the adhesive sheet in the region of 1/3 of the sheet thickness in the sheet thickness direction from the transfer surface. The amount of the hardener transferred was 1.2 g / m ² , and the hardener concentration in the adhesive sheet in the region of 1/3 of the sheet thickness from the transfer surface to the sheet thickness direction was 24.4% by weight. It was 2.05 times the density of the other region.

[Example 2]
37 g of phenoxy resin (glass transition temperature 98 ° C., number average molecular weight 14000), 37 g of naphthalene type epoxy resin (epoxy equivalent 136, semi-solid), 0.06 g of γ-ureidopropyltrimethoxysilane were mixed with ethyl acetate-toluene mixed solvent (mixed) To a 50% solid content solution.
A liquid epoxy resin containing a microcapsule-type latent imidazole curing agent (average particle diameter of microcapsule 5 μm, active temperature 125 ° C., curing agent content 8.6 g) is mixed and dispersed in the above-mentioned 50% solid content solution. Then, it apply | coated on the 50-micrometer-thick polyethylene terephthalate film, and air-dried at 60 degreeC for 15 minute (s), and obtained the film-form adhesive sheet of 20-micrometer-thickness.
The concentration of the curing agent in the adhesive sheet was 8.56% by weight, and the average content was 1.88 g / m ² .

1,3-bis (hydrazinoethyl) having an average particle diameter of 5 μm was applied to 3 μm of the same nitrile rubber latex-methyl methacrylate graft copolymer adhesive as in Example 1 on an unstretched polyethylene film having a thickness of 45 μm. A curing agent particle-adhered film was obtained in which -5-isopropylhydantoin (melting point: 120 ° C., true specific gravity: 1.33) was applied by a method similar to that of Example 1 with almost no gap.
The film was stretched by 200% in the vertical and horizontal directions and fixed in the same manner as in Example 1 using a biaxial stretching apparatus. Then, after laminating the adhesive sheet on the stretched film, it was peeled off to obtain a circuit adhesive sheet.

Using a laser microscope (Keyence Corporation, VK9500, shape measurement resolution 0.01 μm) capable of measuring the displacement in the focal direction by randomly selecting 100 of the curing agent particles of the obtained circuit adhesive sheet. The distance from the sheet surface was measured. As a result, all of the transferred curing agent was present in the adhesive sheet in the region of 1/3 of the sheet thickness in the sheet thickness direction from the transfer surface. The amount of the curing agent transferred was 0.73 g / m ² , and the concentration of the curing agent in the adhesive sheet in the region of 1/3 of the sheet thickness from the transfer surface to the sheet thickness direction was 16.84% by weight. It was 1.97 times the concentration of the curing agent in the other region.

[Example 3]
20 g of phenoxy resin (glass transition temperature 45 ° C., number average molecular weight 12000), 23 g of phenoxy resin (glass transition temperature 98 ° C., number average molecular weight 14000), 26 g of naphthalene type epoxy resin (epoxy equivalent 136, semi-solid), γ-glycid 0.1 g of xylpropyltriethoxysilane is dissolved in a mixed solvent of ethyl acetate-toluene (mixing ratio 1: 1) to obtain a 50% solid content solution. Liquid epoxy resin containing microcapsule type latent imidazole curing agent (average particle size of microcapsule 4 μm, active temperature 125 ° C., curing agent content 10.3 g) 31 g, gold-plated plastic particles 5 g of average particle size 3.0 μm Is dispersed in the 50% solid content solution. Then, it apply | coated on the 50-micrometer-thick polyethylene terephthalate film, and air-dried at 60 degreeC for 15 minute (s), and obtained the film-form adhesive sheet of 20-micrometer-thickness.
The concentration of the curing agent in the adhesive sheet was 10.26% by weight, and the average content was 2.26 g / m ² .

By the same method as in Example 1, a hardener particle-adhered film coated with a single layer with almost no gap was obtained. This film was stretched and fixed by 250% in the vertical and horizontal directions using a biaxial stretching apparatus in the same manner as in Example 1. Then, after laminating the adhesive sheet on the stretched film, it was peeled off to obtain a circuit adhesive sheet.
Using a laser microscope (Keyence Corporation, VK9500, shape measurement resolution 0.01 μm) capable of measuring the displacement in the focal direction by randomly selecting 100 of the curing agent particles of the obtained circuit adhesive sheet. The distance from the sheet surface was measured. As a result, all of the transferred curing agent was present in the adhesive sheet in the region of 1/3 of the sheet thickness in the sheet thickness direction from the transfer surface. The amount of the hardener transferred was 0.4 g / m ² , and the hardener concentration in the adhesive sheet in the region of 1/3 of the sheet thickness from the transfer surface to the thickness direction of the sheet was 14.85 wt%. It was 1.44 times the concentration of the curing agent in the other region.

[Comparative Example 1]
Acetic acid containing 35 g of phenoxy resin (glass transition temperature 98 ° C., number average molecular weight 14,000), bisphenol A type epoxy resin (epoxy equivalent 190, viscosity at 25 ° C., 14000 mPa · S) 28 g, and γ-glycidoxypropyltrimethoxysilane 0.3 g Dissolve in a mixed solvent of ethyl-toluene (mixing ratio 1: 1) to obtain a 50% solid content solution.
37 g of a liquid epoxy resin containing microcapsule-type latent imidazole curing agent (average size of microcapsules 5 μm, active temperature 125 ° C., curing agent content 12 g) was mixed and dispersed in the 50% solid content solution.
Then, it apply | coated on the 50-micrometer-thick polyethylene terephthalate film, and air-dried for 15 minutes at 60 degreeC, and obtained the film-form circuit adhesive sheet of 20-micrometer-thickness. The concentration of the curing agent in the circuit adhesive sheet was 11.9% by weight, and the average content was 2.62 g / m ² .

[Comparative Example 2]
42 g of phenoxy resin (glass transition temperature 45 ° C., number average molecular weight 12000), 32 g of naphthalene type epoxy resin (epoxy equivalent 136, semi-solid), 0.06 g of γ-ureidopropyltrimethoxysilane were mixed with ethyl acetate-toluene mixed solvent (mixed) To a 50% solid content solution.
Liquid epoxy resin containing microcapsule type latent imidazole curing agent (average particle size of microcapsule 5 μm, active temperature 125 ° C., curing agent content 8.6 g) 26 g, gold-plated plastic particles 6 having an average particle size of 3.0 μm 0.0 g was mixed and dispersed in the 50% solid content solution.
Then, it apply | coated on the 50-micrometer-thick polyethylene terephthalate film, and air-dried for 15 minutes at 60 degreeC, and obtained the film-form circuit adhesive sheet of 20-micrometer-thickness. The concentration of the curing agent in the circuit adhesive sheet was 8.1% by weight, and the average content was 1.85 g / m ² .

(Connection resistance measurement method)
Two hundred indium tin oxide (ITO, sheet resistance 25Ω) wires having a wiring width of 80 μm and a wiring pitch of 200 μm are formed on a glass substrate having a thickness of 1.1 mm, and aluminum wiring (including 1 part by weight of titanium, 5000 μm) is formed on the wiring. ). A circuit adhesive sheet having a width of 2 mm is temporarily stretched on this substrate, and after pressurizing at 80 ° C., 0.3 MPa for 3 seconds using a 2.5 mm-width crimping head, the polyethylene terephthalate base film is peeled off. A flexible printed wiring board (material polyimide resin, thickness 25 μm) having 200 circuits in which a copper wiring having a wiring width of 100 μm, a wiring pitch of 200 μm, and a thickness of 18 μm is plated with nickel of 1 μm and gold of 0.02 μm is placed at the wiring position. In addition, after temporary connection, pressure bonding with 5 MPa is performed at 160 ° C. for 5 seconds. After crimping, the resistance between the connection terminals is measured with a four-terminal resistance meter. The average resistance value at 20 measurement points is defined as the connection resistance value.

(Environmental testing)
In the same manner as the connection resistance value measuring method, the glass substrate and the flexible printed wiring board are crimped and connected using a circuit adhesive sheet. After pressure bonding, the pressure-bonded substrate is held at 60 ° C. and 95% relative humidity for 250 hours and then taken out and left in a 25 ° C. and 50% relative humidity environment for 1 hour. Thereafter, the connection resistance value is measured in the same manner as the connection resistance value measuring method, and is set as the connection resistance value after the environmental test. The flexible printed wiring board of the same board | substrate is cut | disconnected to width 10mm, and 90 degree peel strength is measured using an Instron (SHIMADU AGS-50A). The pulling speed is 50 mm / min. Those having a peel strength of 7.84 N / cm or more are indicated by ○, and those having a peel strength of less than 7.84 N / cm are indicated by ×.

(Storability)
The circuit adhesive sheet is stored in a thermostatic chamber at 35 ° C. for 3 days, and then crimped and connected in the same manner as in the connection resistance measurement method. The peel strength is measured in the same manner as in the environmental test, and the peel strength is 7.84 N / The thing of cm or more is set as (circle) and the thing below 7.84 N / cm is set as x.

The results are shown in Table 1.
In this embodiment, the connection resistance value measurement method shows initial electrical connectivity.
In the environmental test, the connection resistance value indicates the reliability of electrical connectivity, and the peel strength indicates the reliability of adhesive strength.
In Table 1, Examples 1-3 have shown that a connection resistance value and the resistance value after an environmental test are low, and electrical connectivity is favorable. From the fact that the peel strength is high even after the environmental test, it can be seen that the adhesive strength is high. Moreover, since the peel strength after storage maintains the strength before storage, it can be seen that the storage stability is good.
As shown in Table 1, in Examples 1 and 2, no conductive particles were present, but it was possible to connect by contact by biting between metal electrodes.
In addition, the pressure-bonding condition of (connection resistance value measuring method) is 160 ° C., 5 seconds, and 5 MPa pressure, but 170-190 ° C., 10-15 seconds, 5 MPa pressure is a common condition. , Low temperature, short time.

  The circuit adhesive sheet of the present invention is excellent as a connection material for high-definition display devices and the like that are excellent in low temperature, short-time connectivity and connection reliability and require fine circuit connection.

Claims (8)

A circuit adhesive sheet comprising at least a curing agent and a curable insulating resin , the curing agent is included over the entire circuit adhesive sheet, and the thickness of the sheet is increased along the thickness direction from one surface of the circuit adhesive sheet. A circuit adhesive sheet, wherein the concentration of the curing agent in the region of 1/3 is 1.1 to 10 times the concentration of the curing agent in the other region .   Highest reactivity in the region of 1/3 times the sheet thickness along the thickness direction from one surface of the circuit adhesive sheet, including at least two curing agents having different reactivity with the curable insulating resin The circuit adhesive sheet according to claim 1, further comprising a curing agent.   The at least 1 type of hardening | curing agent is a solid hardening | curing agent, The average particle diameter is 1/50 time or more and 1/3 time or less of the sheet | seat thickness of a circuit adhesive sheet, The claim 1 or 2 characterized by the above-mentioned. Circuit adhesive sheet.   The circuit adhesive sheet according to any one of claims 1 to 3, wherein conductive particles having an average particle diameter 1/10 to 1 times the average film thickness of the circuit adhesive sheet are blended. 2. A circuit adhesive sheet is obtained by transferring a solid curing agent present in a dispersed state on a smooth plate to an adhesive sheet containing at least a curing agent and a curable insulating resin. The manufacturing method of the circuit adhesive sheet in any one of -4.   An adhesive layer is provided on a biaxially stretchable film to form a laminate, and a solid curing agent is deposited on the laminate to produce a solid curing agent-attached film. % To 1000% biaxially stretched and held, and by transferring the solid curing agent to an adhesive sheet comprising at least a curing agent and a curable insulating resin, a region having a high curing agent concentration is formed. The method for producing a circuit adhesive sheet according to claim 1, further comprising a step of producing a circuit adhesive sheet having the circuit adhesive sheet.   The connection of the fine connection structure characterized by connecting the electronic circuit component and a circuit board by making the surface with a high hardening | curing agent density | concentration of the circuit adhesive sheet in any one of Claims 1-4 contact a circuit board side. Method.   An electronic circuit component and a circuit board, which are connected by the connection method of the fine connection structure according to claim 7, and a fine connection structure.