JPH09291259A - Low-temperature heating curable type anisotropic electroconductive adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-temperature heating curable type anisotropic electroconductive adhesive, capable of mutually connecting circuits at a low temperature of <=150 deg.C heating temperature in a short time of <=15sec heating time and excellent in connection reliability and shelf life. SOLUTION: This low-temperature heating curable type anisotropic electroconductive adhesive contains 0.1-5vol.% electroconductive particles in the low-temperature heating curable type anisotropic electroconductive adhesive consisting essentially of (A) 4-20 pts.wt. vinyl ester resin, (B) 4-20 pts.wt. polyfunctional acrylate, (C) 10-50 pts.wt. monoacrylate having a bonding functional group, (D) 0.1-5 pts.wt. organic peroxide and (E) 10-80 pts.wt. carboxyl- modified styrene-ethylene-butene-styrene copolymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electrical connection between minute circuits, and more particularly to LCD (liquid crystal display).
And FPC (flexible printed circuit board) connection, FPC and PCB (printed circuit board) connection, heat curing used for fine connection materials used for micro joining between semiconductor IC and IC mounting board, etc. Type anisotropic conductive adhesive, especially heating temperature 150 ° C or less, heating time 15
The present invention relates to a low-temperature heat-curable anisotropically conductive adhesive that can be connected at a relatively low temperature of less than a second and a short time, has excellent connection reliability, and has excellent storage stability.

[0002]

2. Description of the Related Art With the recent miniaturization and thinning of electronic devices, the necessity of connecting minute circuits to each other, connecting minute parts to minute circuits, etc. has been dramatically increasing. As a new material, for example, an adhesive or an anisotropic conductive adhesive containing conductive particles in an adhesive film is used with the progress of the solder joining technique. In this method, an anisotropic conductive adhesive containing a predetermined amount of conductive particles is sandwiched between the circuits to be connected, and thermocompression bonding is performed at a predetermined temperature, pressure, and time to electrically connect and bond the circuits. At the same time, the insulation is secured between the adjacent circuits. Further, in recent years, miniaturization and miniaturization of circuit members to be connected have been further advanced, and damage due to heat during bonding and dimensional change due to thermal expansion and contraction have become problems that cannot be ignored. Therefore, there is a strong demand for an anisotropic conductive adhesive that can be connected at a lower temperature and is excellent in reliability and connection stability.

Adhesive resins that have been used in conventional anisotropically conductive adhesives are roughly classified into those that heat and melt to bond (thermoplastic resins) and those that undergo a curing reaction by heating (bonding to heat). Curable resin). Anisotropic conductive adhesives using a thermoplastic resin as the adhesive resin are disclosed in, for example, JP-A Nos. 62-154746 and 62-1098.
78, 61-77278, 61-77279), it is necessary to control the heating temperature at the time of bonding to be equal to or higher than the melting temperature of the resin, but it may be possible to connect at a relatively low temperature depending on the adhesive resin used. Moreover, since no chemical reaction is involved, connection can be made in a short time. Therefore, it is possible to suppress the damage of the adherend due to heat to a low level. However, when the circuits are connected using these adhesives, the heat resistance, moisture resistance, and chemical resistance of the connection parts are limited due to the properties of the adhesive resin, and there are problems with connection reliability and stability. It was

An anisotropic conductive adhesive using a thermosetting resin as the adhesive resin is disclosed in, for example, JP-A-61-74205,
In JP-A-1-113480, JP-A-6-52715, and JP-A-7-268303), it is necessary to set the heating temperature for bonding to the same temperature as the curing temperature of the thermosetting resin used. Further, in order to obtain sufficient adhesive strength and connection reliability, it is necessary to allow the curing reaction to proceed sufficiently,
It is necessary to keep the heating state for a certain time or longer. This type of anisotropic conductive adhesive is currently the mainstream because it has excellent heat resistance, chemical resistance, and moisture resistance after being sufficiently cured by heating. However, this type of anisotropic conductive adhesive has drawbacks such as thermal damage to an adherend and dimensional change due to thermal expansion and contraction due to the above-mentioned restrictions in use.

As an anisotropic conductive adhesive using a thermoplastic resin, there is one having a styrene-butadiene-styrene block copolymer as a main component. Those containing a styrene-butadiene-styrene block copolymer as a main component have been widely used because they can set the adhesion temperature to a relatively low temperature and have heat resistance based on the styrene block. However, since this styrene-butadiene-styrene block copolymer does not have an adhesive functional group, it has a drawback of low adhesive strength. As a method for improving this drawback, introduction of an adhesive functional group has been attempted. For example, it has been proposed that a carboxylated styrene-ethylene-butene-styrene-block copolymer and a styrene-butadiene-styrene-block copolymer are used in combination to impart adhesiveness based on a carboxyl group (Japanese Patent Laid-Open No. H11 (1999) -135242). No. 5-247424). However, in this method, a thermoplastic resin having an adhesive functional group and an ordinary thermoplastic resin are used only in a compatible manner, and although the adhesive strength is improved, a thermosetting anisotropic conductive adhesive is used. It has not reached the level of connection reliability. Further, as a method of using an adhesive functional group, a method in which a carboxylated styrene-ethylene-butene-styrene-block copolymer and an acrylic acid-acrylate copolymer are used in combination (JP-A-5-27996).
44) and a method of using a polyester resin having a carboxyl group (JP-A-5-159622). A method in which a thermoplastic resin having a carboxyl group and a thermosetting resin are used in combination (JP-A-1-309206, 5-
No. 21094), but none of them has low temperature connectivity and reliability.

On the other hand, as an anisotropic conductive adhesive having low-temperature connectivity, conductive particles are dispersed in an adhesive resin containing a cationically polymerizable substance and a sulfonium salt (JP-A-7-90237). ) Or a reactive adhesive such as an epoxy resin and a conductive particle dispersed in a 4- (dialkylamino) pyridine derivative (JP-A-4-189883) have been proposed, but the storability of the adhesive resin is also proposed. There is a problem such as corrosion of the connected circuit terminals.

[0007]

SUMMARY OF THE INVENTION The present invention has a heating temperature of 1
The present invention provides a low temperature heat-curable anisotropically conductive adhesive that can connect circuits at a relatively low temperature in a short time of 50 ° C. or less and a heating time of 15 seconds or less, and that is excellent in connection reliability and storage stability.

[0008]

[Means for Solving the Problems]

(A) 4 to 20 parts by weight of vinyl ester resin, (B) 4 to 20 parts by weight of polyfunctional acrylate, (C) 10 to 50 parts by weight of monoacrylate having an adhesive functional group, (D) organic peroxide 0. 1 to 5 parts by weight, and (E) carboxyl-modified styrene-ethylene-butene-styrene copolymer 10
A low-temperature heat-curable anisotropic conductive adhesive containing 0.1 to 5 volume% of conductive particles in a low-temperature heat-curable adhesive consisting of -80 parts by weight. In particular, the vinyl ester resin is a bisphenol type vinyl ester of the formula (1) or a phenol novolac type vinyl ester of the formula (2),

[0009]

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[0010]

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The polyfunctional acrylate is triacrylate,
It is preferable to use a monoacrylate having a carboxyl group or a hydroxyl group as the adhesive functional group.

The vinyl ester resin used in the present invention is a reaction product of a general epoxy resin with acrylic acid or methacrylic acid, a reaction product of glycidyl methacrylate with a polyhydric phenol, or a derivative thereof. However, in particular, a structure represented by the formula (1) or the formula (2) and having a theoretical molecular weight of 500 to 2,000 is preferable. Further, the vinyl ester resin in which -R in formula (1) or formula (2) is hydrogen is excellent in curability and therefore excellent in low temperature connectivity. These vinyl ester resins may be used alone or in combination with those having different structures, molecular weights and the like. Further, in order to facilitate the handling of the vinyl ester resin, it is possible to use it by diluting it with a styrene monomer, an acrylate monomer, various solvents or the like to adjust the viscosity. Also, in order to ensure the storage stability of this vinyl ester resin, the low temperature connectivity when a polymerization inhibitor such as quinones, polyhydric phenols, phenols, etc. is made into a low temperature heat curing type anisotropic conductive adhesive in advance You may add in the range which does not lower. The blending amount of vinyl ester resin is
The amount is 4 to 20 parts by weight, but if it is less than 4 parts by weight, there arises a problem in connection reliability, and if it exceeds 20 parts by weight, the adhesive strength decreases.

Examples of the polyfunctional acrylate used in the present invention include tripropylene glycol diacrylate, pentaerythritol diacrylate monostearate, trimethylolpropane triacrylate, isocyanuric acid ethylene oxide modified triacrylate, and trimethylolpropane ethylene oxide. Examples thereof include modified triacrylate, dipentaerythritol hexaacrylate, pentaerythritol tetraacrylate and the like, and these may be used alone or in combination. Among these, triacrylate having a good curing reactivity is preferable. These polyfunctional acrylates may be premixed with the vinyl ester resin described above.
In addition, various polymerization inhibitors may be added if necessary. The compounding amount of the polyfunctional acrylate is 4 to 20.
If the amount is less than 4 parts by weight, low temperature curability will occur, and if it exceeds 20 parts by weight, the adhesive strength will be reduced.

Examples of the monoacrylate having an adhesive functional group used in the present invention include β-methacryloyloxyethyl hydrogen phthalate, β-methacryloyloxyethyl hydrogen succinate and β.
-Acryloyloxyethyl hydrogen succinate, 2-hydroxy-1,3-dimethacryloxypropane, 2-hydroxy-1-acryloxy-3-methacryloxypropane and the like can be mentioned. As the adhesive functional group, a hydroxyl group and a carboxyl group are preferable because they have excellent adhesiveness to a wide range of materials. The compounding amount of the monoacrylate having an adhesive functional group is 10 to 50 parts by weight, but if it is less than 10 parts by weight, the adhesiveness is lowered, and if it exceeds 50 parts by weight, the connection reliability is lowered.

As the organic peroxide used in the present invention, commercially available peroxides can be used.
In particular, by using the one having a half-life temperature of 90 to 150 ° C. for 1 minute, it is possible to achieve both low temperature connectivity and storage stability of the anisotropic conductive adhesive of the present invention. Examples of the organic peroxide include t-butylperoxy-2-ethylhexanate, t-hexylperoxy-2-ethylhexanate, 1,1-bis (t-butylperoxy)-
Examples include 3,3,5-trimethylcyclohexane, 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, bis (4-t-butylcyclohexyl) peroxydicarbonate and the like. It is also possible to add various polymerization inhibitors to these peroxides in advance in order to improve the storage stability. Further, it may be diluted with a solvent or the like and used to facilitate the work of dissolving it in the resin. If the one-minute half-life temperature is less than 90 ° C, the adhesive will have a problem in storability, and if it exceeds 150 ° C, low-temperature curing will be difficult. The blending amount of the organic peroxide is 0.1 to 5 parts by weight, but if it is less than 0.1 parts by weight, there arises a problem in low temperature curability, and if it exceeds 5 parts by weight, the storage stability is deteriorated.

The carboxyl-modified styrene-ethylene-butene-styrene copolymer (hereinafter referred to as carboxyl-modified SEBS) used in the present invention has a molecular weight of 1
The styrene component (S) and the ethylene-butene (E) may be used.
Weight ratio (S / EB) with component B) is 10/90 to 50 /
Fifty can be used. In particular, the fluidity of the carboxyl-modified SEBS during heating affects the adhesive strength and the connection resistance value during bonding, so the melt flow rate (JI
SK 7210) is 1g / 10 minutes (200 ℃,
It is preferably 5 kg or more. Carboxyl modified SE
The content of a carboxyl group in BS may be one or more in one molecule in both or one of the S component and the EB component.
The compounding amount of the carboxyl-modified SEBS is 10 to 80 parts by weight, but if it is less than 10 parts by weight, the adhesive strength is lowered, and 8
If the amount exceeds 0 parts by weight, the connection reliability decreases. The conductive particles used in the present invention include, for example, various metals (for example, Fe, Ni, Co, Cr, Sn, Mo, Pb, Z).
n, Ag, etc.), metal alloys, metal oxides, carbon, graphite, plastic particles having a metal layer formed on their surfaces, and the like. The particle size and material of these conductive particles can be appropriately selected depending on the pitch and pattern of the circuit to be adhesively connected, the thickness and material of the circuit terminals, and the like. The compounding amount of the conductive particles is 0.1 to 5 parts by weight, but if it is less than 0.1 part by weight, the number of the conductive particles existing on the connection terminal becomes small, so that the connection reliability is deteriorated and 5 parts by weight. If it exceeds the area, short-circuit troubles easily occur between adjacent terminals when connecting a fine circuit.

Further, in the anisotropic conductive adhesive of the present invention,
An appropriate amount of coupling agent may be added if necessary. The purpose of adding the coupling agent is to improve the adhesiveness of the adhesive interface of the anisotropic conductive adhesive, improve the adhesive strength, heat resistance and moisture resistance, and improve the connection reliability. As the coupling agent, a silane coupling agent can be particularly preferably added and used, and examples thereof include epoxysilane type, mercaptosilane type, and acrylsilane type. For example, β- (3,4-epoxycyclohexyl) )
Ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane and the like can be used.

The low temperature heat-curable anisotropically conductive adhesive of the present invention comprises a vinyl ester resin excellent in heat resistance, chemical resistance, connection reliability and low temperature curability, and a polyfunctional acrylate excellent in low temperature rapid curing, adhesiveness. The monoacrylate having a functional group and the carboxyl-modified SEBS, which has excellent adhesiveness, are cured together as a unit by radicals generated by heating from organic peroxides, so it is extremely low temperature as a heat-curable anisotropic conductive adhesive. It is possible to bond in a short time,
Furthermore, the adhesive property is also excellent. Therefore, the connection reliability is excellent in combination with the conductive action of the conductive particles added to the anisotropic conductive adhesive. Moreover, as an organic peroxide, 1
By combining with one having a half-life temperature of 90 to 150 ° C. for a minute, both low temperature curability and storage stability can be achieved.

[0013]

The present invention will be described below with reference to examples and comparative examples. Examples and Comparative Examples 1. Preparation of Adhesive Resin Formulation The raw materials shown in Table 1 were dissolved in toluene at the proportions (parts by weight) shown in Table 2 so that they would be the same nonvolatile, and an adhesive resin formulation solution was obtained. 2. Conductive particles Ni / Au-plated polystyrene particles having an average particle size of 5 μm were added to the above adhesive resin composition solution at a volume fraction of 1% of nonvolatile components.
And added for 30 minutes. 3. Preparation of Anisotropic Conductive Adhesive The composition obtained in the above 2 was subjected to a release treatment of 50 μm.
m cast on polyethylene terephthalate film,
The film was dried in an oven at 40 ° C. for 5 minutes to obtain a film-shaped anisotropic conductive adhesive having a thickness of 15 μm. 4. Evaluation method The film-like anisotropic conductive adhesive of the above 3 was cut into a width of 2 mm. After sticking this on 1.1 mm thick ITO glass (surface resistance 30 Ω / □) at 80 ° C. for 3 seconds at 5 kg / cm ² , the polyethylene terephthalate film was peeled off, and a Cu circuit of 100 μm pitch and 35 μm thickness was formed. 60
A 75 μm flexible printed wiring board (FPC) made of polyimide is attached on the adhesive, and the heating temperature is 140 ° C. or 150 ° C., the heating time is 15 seconds, and the pressure is 30 k.
Connection was made by heating and pressurizing at g / cm ² . Adhesive strength of the obtained circuit connection product (measurement of 90 ° peeling strength, peeling speed 50 mm / min), connection resistance value, connection reliability (temperature 8
5 ° C., 85% humidity, connection resistance after standing for 100 hours),
Table 3 shows the evaluation results of the storability (25 ° C, connection resistance value when used after being left for 1 week).

In Examples 1 to 3, anisotropic conductive adhesives were prepared using monoacrylates having various adhesive functional groups. Both heating time 15 seconds, heating temperature 1
It can be seen that low-temperature connection is possible under heating conditions of 50 ° C. or lower, and that the adhesiveness and connection reliability are good.
Also, since the connection resistance value is stable even after being used after being left for 1 week at a temperature of 25 ° C., it can be understood that there is no problem in storability. Examples 4 to 6 are cases where various vinyl ester resins and various polyfunctional acrylates were used. Examples 1-3
It can be seen that it has excellent connection characteristics similar to. In Example 7, the carboxyl-modified SEBS was changed to one having a large melt flow rate. Connection resistance values are Examples 1 to 6
It is lower than that of, and it is understood that the connection stability is further excellent. Examples 8 and 9 use various organic peroxides. It can be seen that there is no problem in connection characteristics in either case. Example 10 is a case where a carboxyl-modified SEBS having a melt flow rate of 1 g / 10 minutes (200 ° C., 5 kg) or less is used. The connection resistance value is higher than those of the other examples. This is presumably because the carboxyl-modified SEBS of this example had poorer fluidity at this heating temperature than the other ones, and thus the conductive particles blended and the object to be connected could not be sufficiently contacted.

On the other hand, Comparative Example 1 is a case where the monoacrylate having an adhesive functional group is not added, Comparative Example 2 is a case where the carboxyl-modified SEBS is not added, and Comparative Example 3 is a case where the organic peroxide is not added. . The adhesive strength is Examples 1 to 1
It is lower than 0, and it is understood that there is a problem in connection reliability. In particular, the result of Comparative Example 3 is that the adhesive resin does not cure because the adhesive resin contains no organic peroxide, and the connection performance is extremely poor. In Comparative Example 4, the vinyl ester resin is 4
This is the case when the amount is less than parts by weight. It can be seen that the connection reliability has a problem as compared with the embodiment. Comparative Example 5 is a case where the vinyl ester resin exceeds 20 parts by weight. It can be seen that although the connection resistance value is good, the adhesive strength is low and there is a problem. Comparative Example 6 is a case where the polyfunctional acrylate is less than 4 parts by weight. In particular, since the adhesive strength and the connection resistance value in the low temperature range are not good, it is considered that there is a problem in the curability in the low temperature range. Comparative Example 7 is a case where the polyfunctional acrylate exceeds 20 parts by weight. It can be seen that the adhesive strength is low as a whole and there is a problem. In Comparative Example 8, when the monoacrylate having the adhesive functional group exceeds 50 parts by weight, Comparative Example 9
Is the case where the carboxyl-modified SEBS exceeds 80 parts by weight. It turns out that there is a problem in connection reliability in both cases. Comparative Example 10 is a case where the organic peroxide exceeds 5 parts by weight. It can be seen that there is a problem with the storability because the connection resistance value when used at 25 ° C. for 1 week is high.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

[0018]

According to the present invention, a heating temperature of 150 ° C.
Hereafter, the circuits can be connected to each other at a low temperature in a short time of 15 seconds or less, and an anisotropic conductive adhesive having excellent connection reliability and storability can be obtained, which is extremely useful.

Claims (5)

[Claims] 1. (A) 4 to 20 parts by weight of vinyl ester resin, (B) 4 to 20 parts by weight of polyfunctional acrylate, (C)
10 to 50 parts by weight of monoacrylate having an adhesive functional group, 0.1 to 5 parts by weight of (D) organic peroxide, and (E)
Low temperature heat-curable adhesive containing 0.1 to 5 volume% of conductive particles in a low-temperature heat-curable adhesive containing 10 to 80 parts by weight of a carboxyl-modified styrene-ethylene-butene-styrene copolymer as an essential component. Type anisotropic conductive adhesive. 2. The low temperature heat-curable anisotropically conductive adhesive according to claim 1, wherein the vinyl ester resin (A) is a bisphenol type vinyl ester of the formula (1) or a phenol novolac type vinyl ester of the formula (2). . Embedded image Embedded image 3. The low temperature heat-curable anisotropically conductive adhesive according to claim 1, wherein the polyfunctional acrylate (B) is triacrylate. 4. The low temperature heat-curable anisotropically conductive adhesive according to claim 1, wherein (C) the adhesive functional group is a monoacrylate having a carboxyl group or a hydroxyl group. 5. The low-temperature heat-curable anisotropically conductive adhesive according to claim 1, wherein the (D) organic peroxide has a half-life temperature of 90 to 150 ° C. for 1 minute.