JPS63245484A - Adhesive composition - Google Patents

Abstract

PURPOSE:To prepare the title compsn. which is free from the occurrence of air bubbles at the connections, excellent in connection reliability, and suitable for use in the connection of circuits, by mixing an insulating adhesive component, a plated particle having a particular particle diameter, a finely divided dry-process silica, and a metal deactivator in a predetermined volume ratio. CONSTITUTION:99.8-75vol.% insulating adhesive component (A) (e.g., styrene- vinyl copolymer or rosin) is mixed with 0.1-15vol.% plated particle (B) having a particle diameter of 0.5-50mum (e.g., nickel-plated styrene particle), 0.05-5vol.% dry-process silica (C) having a particle diameter of 0.1mum or less, and 0.05-5vol.% metal deactivator (D) (e.g., 3-amino-1,2,4-triazole) to prepare an intended adhesive compsn. It is pref.. that component (C) be a dry-process silica having a BET specific surface area of at least 40m<2>/g. Circuits connected with the aforesaid adhesive compsn. is advantagenous in that not only it is free from the occurrence of air bubbles but also the deterioration of the adhesive can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an adhesive composition, and more particularly to an adhesive composition for circuit connection with excellent connection reliability.

[Conventional technology]

Connecting circuits where connection terminals are arranged facing each other at a fine pitch, such as connecting integrated circuits to wiring boards, connecting display elements to wiring boards, and connecting electrical circuits to leads. As a method, a predetermined amount of conductive filler is contained in an insulating adhesive, which is interposed between circuits to be connected, and conductivity can be obtained in the thickness direction of the circuit by applying heat or pressure. At the same time, a method is known in which a film-like material or adhesive (hereinafter collectively referred to as a connecting member) for connecting fine circuits is used, which can provide insulation between adjacent circuits.

For example, according to Japanese Patent Application Laid-Open No. 51-20941, conductive particles such as carbon or metal particles are mixed into a non-conductive adhesive, and in order to further improve the insulating properties in the plane direction, Although attempts have been made to mix insulating particles with small particle sizes, no consideration has been given to connection reliability, which is an important property for connection materials.

Since the connecting member is a bulk connecting material for a multi-point circuit, the reliability of the connecting part is the most important characteristic.

[Problem that the invention seeks to solve]

As a result of various studies on improving connection reliability, the present inventors found that by using particles (for example, plated particles) in which a thin metal layer is formed on a polymer core as conductive particles, We proposed that the connection reliability would be significantly improved compared to the case of using conventional metal particles (patent application 1986-31).
No. 088).

According to this proposal, reliability could be improved by approximating the thermal expansion coefficients of the conductive particles and the adhesive and by increasing the contact area of the conductive particles with the circuit surface.

When we conducted various studies on the reliability of microcircuit connectors using connecting members made of conductive plating particles, we found that air bubbles were sometimes generated at the connections during high-temperature processing, and the reliability of these air bubbles was poor. A problem arose in that it decreased. That is, it is considered that the generation of air bubbles in the circuit connection portion reduces the effective bonding area, leading to a decrease in connection reliability. Here, the target microcircuit has a wiring density of, for example, 5 wires/double to 20 wires/double, and the circuit width in this case is usually 100 μm or less.
The connection area of the electrodes is extremely small.

Regarding the above-mentioned bubble generation phenomenon at the circuit connection part, since it occurs particularly prominently in connection members using plating particles,
The cause of this appears to be the plating particles. Therefore, when we consider the manufacturing process of plated particles, we find that most of them are wet process 1, as described below. In other words, the general plating method for microparticles is
First, the nuclei are subjected to surface treatments such as hydrophilization with surfactants and surface roughening with acids or alkalis as necessary under wet conditions, and then a plating catalyst such as palladium chloride is applied to the nuclei surfaces. Next, it is manufactured through a process of immersing it in an electroless plating solution to form a plating layer, followed by washing and drying.

Here, regarding the plating particles, in order to enable connection of fine circuits, it is necessary to maintain insulation from adjacent circuits, so the particle size needs to be approximately 50 μm or less in maximum diameter. As described above, since the plated particles have a small particle size and a large surface area, they have the property of easily adsorbing various substances.

Furthermore, as mentioned above, most of the plating particle manufacturing process is wet, so it is difficult to completely remove plating solution residue, moisture, and foaming elements such as air bubbles from the plating particles. However, methods such as washing the plated particles with a low boiling point solvent or drying them in vacuum have not been completely effective.

In other words, circuit connections using connection members containing foamed elements adsorbed to plating particles fail in reliability evaluation tests such as thermal shock tests, high-temperature high-temperature tests, and high-temperature heating tests.
The foaming elements adsorbed to the plating particles expand or aggregate at high temperatures and grow into large bubbles.
Alternatively, reliability was unsatisfactory because these foam elements accelerated deterioration of the adhesive.

[Problem that the invention seeks to solve]

The present invention has been made in view of the above problems. That is, the present invention aims to solve the above-mentioned problems and to provide an adhesive composition that does not generate bubbles at the connection part of the circuit of the connection body and is suppressed from deterioration. be.

[Means for solving problems]

The adhesive composition of the present invention is characterized by comprising the following (a) to (d).

(a) Insulating adhesive component 99.8 to 75% by volume (b)
Plated particles with a particle size of 0.5-50 μm 0.1-15% by volume (c) Dry process silica with a particle size of 0.1 μm or less 0605-
5% by volume (iv) Metal deactivator 0.05-5% by volume Below, the present invention will be described in detail.

The adhesive component (a) used in the present invention can basically be applied to thermoplastic adhesives exhibiting insulating properties, and adhesives that can be cured by heat, light, electron beams, moisture, anaerobic conditions, etc. However, thermoplastic, thermosetting, and photocurable materials are particularly suitable because they are easy to handle. In addition, various adjusting agents such as tackifiers, crosslinking agents, anti-aging agents, and dispersants may be used in these adhesives.

The base materials used in these adhesives are shown by way of example only and not limitation, such as ethylene-vinyl acetate copolymer, modified ethylene-vinyl acetate copolymer, polyethylene, ethylene-propylene copolymer, Ethylene-acrylic acid copolymer, ethylene-acrylic ester copolymer, ethylene-acrylate copolymer, acrylic ester rubber, polyisobutylene, adduct polypropylene, polyvinyl butyral, acrylonitrile-butadiene copolymer 1 ．． Styrene-butadiene block copolymer, styrene-isoprene block copolymer, styrene-ethylene-butylene block copolymer, polybutadiene, ethyl cellulose, phenoxy resin, polyester, epoxy resin, polyamide, polyvinyl ether, polyurethane, polyisoprene, silicone rubber,
Synthetic polymer compounds such as polychloroprene, synthetic rubbers,
Examples include natural polymer compounds such as natural rubber. These can be used alone or in combination of two or more.

Examples of the tackifier include dicyclopentadiene resin, rosin, modified rosin, terpene resin, xylene resin, terpene-phenol resin, alkylphenol resin, coumaron-indene resin, etc., and these may be used alone or in combination as necessary. Two or more types are used in combination.

Typical examples of the tackiness modifier include various plasticizers such as dioctyl phthalate.

The crosslinking agent is used when it is necessary to increase the cohesive force of the polymer, and examples thereof include polyfunctional substances that react with functional groups of the polymer, such as polyisocyanates, melamine resins, Examples include urea resins, phenol resins, amines, acid anhydrides, peroxides, etc. Furthermore, benzophenone, benzoquinone, etc. may be used as a sensitizer in the case of photocuring.

These may be used alone or in combination of two or more, if necessary.

The anti-aging agent is used when it is necessary to increase the stability of the adhesive against heat, oxygen, light, etc., and includes, for example, stabilizers such as metal soaps, and antioxidants such as alkylphenols. , benzophenone-based, benzotriazole-based, and other ultraviolet absorbers, which may be used alone or in combination of two or more, if necessary.

The dispersant may be used to improve the dispersibility of conductive particles. Examples of this include surfactants, which can be used singly or in combination of nonionic, cationic, anionic, and amphoteric agents.

In addition, various coupling agents and chelating agents can also be used by adding them to the adhesive component.

The plated particles (b) in the present invention have a particle size of 0.
．． A material having a diameter of 5 to 50 μm is used. Particle size is 0.5μm
If it is less than 50 μm, the surface area of the particles will be large and the amount of adsorption of the foaming element will increase, which is undesirable. If it exceeds 50 μm, the probability that particles will exist between adjacent circuits will increase when the circuits are minute, resulting in insufficient insulating properties in the plane direction. This is not desirable because

For these reasons, the preferred range of particle size is 1 to 30μ.
It is m.

The particle size here refers to the average particle size according to the following formula.

D-Σnd/Σnn n indicates the number of particles having a particle size of d. Methods for measuring these particle sizes include commonly used electron microscopes, optical microscopes, Coulter counters, and light scattering methods.

The shape of the plating particles is not particularly limited as long as the average particle size is within the above range, but in order to improve the reliability of the connection part, it is preferable to have a shape with as small an aspect ratio as possible, such as a spherical shape or a conical shape.

The plating particles preferably have a conductive coating layer formed on the surface of the core material by plating.

As the core material, polymeric substances such as rubber and plastic, conductive substances such as Ni and Cu carbon, and non-conductive substances such as mica and glass can be used.
These core materials may be completely solid bodies, hollow bodies, foam bodies, aggregates, etc., and these can be used alone or in combination.

Various electrically conductive materials can be used as the metal for the coating layer, but Nis Ags^u1Sns is preferably used from the viewpoint of electrical conductivity and corrosion resistance.
Cus Pb, and these can be used alone or in combination.

Although the thickness of the coating layer is not particularly limited, it is preferably about 0.01 to 5 μm. As the coating method, the above-mentioned electroless plating method is suitable, but sputtering method or vapor deposition method may also be used.

In the present invention, the amount of the plated particles in the adhesive is 0.1 to 15% by volume. If it is less than 0.1% by volume, it is difficult to obtain satisfactory conductivity, and if it exceeds 10% by volume, the chances of particles connecting in the plane direction increase, resulting in a decrease in insulation with adjacent circuits.

For these reasons, the preferable addition amount is 0.5 to IO volume %.

The dry process silica (c) used in the present invention will be explained. Silica has silicon dioxide (Sin2) as its main component, and is a material commonly used as a filler for rubber etc. It is generally referred to as white carbon, and its manufacturing methods include dry method and wet method. It is broadly divided into. Such silica has conventionally been used for purposes such as thickening liquids to impart a thixotropic effect, reinforcing rubber-like elastic bodies, and maintaining the fluidity of powdered substances. Silica applicable to the present invention is obtained by a dry process such as thermal decomposition of silicon halide, thermal decomposition of silicic acid-containing substances, and thermal decomposition of organosilicon compounds. According to the dry method,
High purity products (generally 99% or higher purity) can be obtained, and products whose internal structure does not change when heated below the melting point can be obtained. Therefore, it is necessary to use dry process silica as a raw material for adhesives used as connection members for electronics, which are extremely sensitive to impurities and require stable connection characteristics.

The amount of dry process silica added is 0.05 to the adhesive composition.
~5% by volume. If it is less than 0.05% by volume, the ability to adsorb the foam element will be insufficient, and if it exceeds 5% by volume, the adhesion to the circuit will be insufficient, which is not preferable.

The dry process silica used in the present invention preferably has a particle size of 0.1 μm or less and a BET method slope surface area of 0rrf/g or more, and further has a silanol group (-3
Hydrophilic materials containing tOH) are particularly preferably used.

It is preferable that the particle size is smaller because the surface area of the particles becomes larger, and if the BET method slope surface area is On ('g or more), the foaming element will be well adsorbed, so the amount of dry process silica added may be small. There is no adverse effect such as a decrease in the adhesion of the connecting member to the circuit.The reason why hydrophilicity is preferable is that the majority of the foamed element is water or a hydrophilic substance.

An example of such dry process silica is Degu
Aerosil, a product name of SSA and Nippon Aerosil, and Cab-O-3i I, Do, a product of Cabot.
w Corning product name DCFine 5il
ica and Franso1 company's product name Frans
il etc. are commercially available. In principle, the metal deactivator (d) used in the present invention is one that deactivates the metal by reacting with the metal to form a complex and prevents the acceleration of deterioration of the metal or the adhesive in contact with the metal. Generally applicable.

Examples of such metal deactivators include aromatic amines, acid amides, hydrazides, and azoles.

Among these, triazole compounds having nitrogen-containing groups such as amine groups, nitro groups, and azo groups are more preferably used as metal deactivators for improving connection reliability, which is the objective of the present invention. Alternatively, benzotriazole compounds can be mentioned.

Specific examples thereof are given for purposes of illustration only and not by way of limitation:
For example, 3-amino-1,2,4-)lyazole, 4
-amino-1,2,4-)riazole, 3-benzyl-
5-amino-1,2,4-triazole, l-benzyl-3-amino-5-phenyl-1,2,4-1-riazole, 1,4-diphenylendoanilinodihydrotriazole, 3,5-diamino -1,2,4-) riazole, 3,5-bis(4-aminophenyl)-1,2゜4
-triazole, 4-salicylideneimino-3゜5-diphenyl-1,2,4-triazole, 3- (N-salicyloyl)amino-1,2,4-triazole, 3-
[N-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionylcoamino-1,2,4-1-riazole, 5-amino-3-(p-nitrohensyl)-
1,2,4-triazole, 12.4-1-riazole-5-azo-4-(N,N-diethyl)aniline, 1゜2.4-triazole-5-azu-4'-(N-methyl- N-benzyl)aniline, 3-(,4-N-ethyl-
N-pendylaminophenylazo)-2,3-dimethyltriazolium, 1,4-dimethyl-2-amino-5-
+4- (benzyl-ethylamino)phenylazo l-
1,2,4-triazolium, 3,5-bis(4-(N
, N-diethylamino)phenylazo)-1,2,4-
Triazole, 1,4-dimethyl-3,5-bis[(4
-(diethylamino)phenyl)azo) 1. 2゜4-triazolium, 1,4-dimethyl-3,5-bis(4-(N-methyl-N-β-methoxyethylamino)
phenylazo)-1,2,,l-)riazolium, 1.
2. 4-) Riazole-5-azo-3'-(2'-
Examples include phenyl)indole, 3-((1-ethyl-2-phenylindol-3-yne)azo-1,2,4-triazole, and the like.

In the present invention, the metal deactivator is used in an adhesive composition in an amount of 0.05 to 5% by volume. At this time, this metal deactivator can be used alone or in combination of two or more types, and if this value is less than 0.05 volume %, the effect of preventing metal deterioration of the adhesive will be small, and if it exceeds 5 volume %. Since the compatibility between the adhesive and the adhesive decreases, a bleed phenomenon becomes more likely to occur, and in both cases, the reliability of the connected circuit decreases.

As a method for producing an adhesive made of the above composition, components (B) to (D) may be mixed and dispersed in the adhesive component (A) in sequence, and the order and method of mixing are not particularly limited.

For example, in the case of a liquid adhesive, this composition is used by coating it on one or the other circuit to be connected to form a connecting member layer, removing the solvent as necessary, and then applying the adhesive to the other circuit. It may be connected to the circuit using methods such as heating and pressurizing.

Alternatively, a connecting member layer is formed by coating and drying on a peelable film base material, and the adhesive composition is formed into a film-like material, and then this film-like material is inserted between circuits to be connected. A method of connecting circuits in the same manner as described above can be suitably used.

[Effect]

Although the functional relationship of the components of the adhesive composition according to the present invention is not necessarily clear, it can be considered as follows.

First, the insulating adhesive component (a) acts as a bonding material for the circuits to be connected, and the plating particles (b) can be used to create electrical connections between connected circuits and between adjacent circuits (by selecting the particle size and amount added). Provides insulation in the surface direction).

The particle size of dry process silica (c) is smaller than that of plated particles, that is, the surface area is significantly larger than that of plated particles, so moisture adsorbed to the plated particles is difficult to remove by normal means. adsorbs foam elements. The particle size of the silica that has adsorbed the foamed elements is sufficiently smaller than that of the plated particles, so the foamed elements are more finely divided and dispersed in the connecting member than when they are adsorbed to the plated particles. The presence of this material reduces the occurrence of bubbles at circuit connections. Furthermore, the foaming elements are likely to chemically bond with the silanol groups on the silica surface (for this reason, the foaming elements are difficult to dissociate), so it is thought that the foaming elements exist in a form that is more difficult to foam.

The metal deactivator (d) is a substance that accelerates the deterioration of the adhesive contained in the foaming element (for example, residual metal from the plating solution),
Deterioration of the adhesive is prevented by inactivating the plating particles by chelate bonding with metals such as coating metals and connection circuits.

〔Example〕

Hereinafter, the present invention will be explained in detail based on Examples, but the present invention is not limited thereto.

Example 1 (1) Preparation of plated particles Polystyrene particles with an average particle diameter of 10 μm were dispersed in water,
After activation treatment with palladium chloride was performed at room temperature, it was dispersed in an electroless nickel plating solution (Blue Schumer, trade name manufactured by Nippon Kanigen Co., Ltd.), and plated at 90° C. for 1 hour with stirring. It was confirmed by cross-sectional observation using an electron microscope that the thickness of the nickel plating at this time was 0.2 μm. Further, the specific gravity was 2.0.

(2) Preparation of adhesive composition Trublen T-406 (
Styrene-butadiene-styrene broth polymer (trade name manufactured by Asahi Kasei Corporation) and Ys Volista S-1
45 (terpene phenol, trade name manufactured by Yasushi Oil Co., Ltd.) at a solid content weight ratio of 70:30.
% toluene) was prepared. In the adhesive solution of (a), Aerosil 200 (
Product name manufactured by Nippon Aerosil Co., Ltd., BET method surface area 00
m/g, particle size 0.012 μm, specific gravity 2.2, purity 99.
8%) was added in an amount of 1% by volume, and mark CDA-1 (3-(N-salicyloyl)) was added as a metal deactivating agent (d).
Amino-1,2,4-triazole, trade name manufactured by Adeka Argus, specific gravity 1.0] was added in an amount of 0.5% by volume. After the above mixture was thoroughly stirred, the plated particles (b) prepared in (1) were added to the mixture at a concentration of 2% by volume.

The amounts added in (b), (c), and (d) above indicate the amounts added to the solid content of the adhesive (a), and the composition consisting of (a) to (d) is further stirred, An adhesive composition of the present invention was obtained.

Applying the above adhesive composition onto a separator (thermoplastic polyester film subjected to silicone release treatment) using a roll coater so that the thickness after drying is 15 μm,
The solvent toluene was removed by drying at 100° C. for 10 minutes to obtain a membrane-like connection member.

(3) Circuit connection line width Q, lmm, pitch 0.2mm, thickness 18μ
A connecting member cut to a length of 1100 mm while being glued was placed on a flexible circuit board CF P C) with 100 mm of copper circuits, and was heated at 150℃ - 2 kg/ca.
! -5 seconds of heating and pressurization was performed to obtain an FPC with a connecting member.

After that, the separator was peeled off, and the circuit was aligned with a transparent conductive glass (indium oxide circuit, glass thickness 0.5 mm) having a circuit with the same pitch as the FPC under a microscope. A circuit connection structure was obtained by heating and pressurizing.

(4) Evaluation The connected structure obtained above was divided into two parts, and the connection state was observed and a high temperature storage test was performed.

Observation of the connection state involves observing the connection part under a microscope from the transparent conductive glass side while raising the temperature to check the temperature at which air bubbles are generated at the circuit connection part.
It is stored for a long time in an atmosphere of 5℃-85%RH, and the bubbles and corrosion in the connection parts are observed over time using a microscope, and changes in connection resistance are also tracked.The goal is to have no abnormalities for more than 1500 hours. .

In the case of this example, no bubbles were observed in the connection state up to 150°C, and even in the high-temperature test,
At 0 hours, no bubbles or corrosion were generated, there was little change in connection resistance, and no circuit oven occurred. The contents and evaluation results of these compositions are shown in Table 1, and it was found that excellent connection reliability could be obtained. Furthermore, in this example, since the adhesive was thermoplastic, the circuit connection operation was easy.

Examples 2 to 5 and Comparative Examples 1 to 2 The blending amounts of the compositions were changed as shown in Table 1, and the other operations were carried out in the same manner as in Example 1, and the results are shown in Table 1.

This result shows that in Examples 2 to 5, no bubbles were observed in the temperature increase test even at 150°C, and no abnormality was observed in the high temperature test for the target 1500 hours, indicating that the connection reliability was good. I found out that there is.

On the other hand, in Comparative Example 1, no dry process silica (c) was added to the composition, but bubbles were generated at 120'C in the temperature rise test, and bubbles were also generated at 750'C in the high temperature test. , a circuit open has occurred. In addition, Comparative Example 2 is a case where metal deactivator (d) is not added, but
Although the bubble generation temperature in the temperature increase test was good at 150° C. or higher, corrosion was observed at the end of the circuit after 750 hours in the high temperature test. Therefore, an open circuit occurred at the circuit connection after 1000 hours of processing.

Examples 6 to 8 The same procedure as in Example 1 was carried out except that the grade of the dry process silica of Example 1 was changed as shown in Table 1, and the results are shown in Table 1.

The silica used was Aerosil 0X50 in Example 6.
(Product name manufactured by Nippon Aerosil Co., Ltd., BET method specific surface area 50
n? /g, particle size 0.05 μm), and in Example 7, Aerosil 380 (trade name, manufactured by Nippon Aerosil Co., Ltd., BET
In Example 8, Cab-O-3il (Cabot
company product name, BET method specific surface area 200rd/g, particle size 0
．． 02 μm). The specific gravity of these silicas is 2.2
It is.

The results are shown in Table 1, and it can be seen that good reliability was obtained in all cases, and that dry process silica with various properties was applicable.

Examples 9 to 10 The same procedure as in Example 8 was carried out except that the type of metal deactivator used in Example 8 was changed as shown in Table 1, and the results are shown in Table 1.

In Example 9, benzotriazole, a first class reagent, and in Example 10, Mark 0DA-6 (decamethylene dicarboxylic acid disalicyloyl hydrazide, trade name, manufactured by Adeka Argus) were used after being dissolved in methyl ethyl ketone. These results also showed excellent connection reliability as shown in Table 1.

Examples 11-12 The adhesive used in Example 1 was changed to a thermosetting type, and the plated particles were coated with a film thickness of 0.01 μm on the surface of the particles used in Example 1.
An adhesive composition was obtained in the same manner as in Example 1, except that an adhesive composition plated with Au was used.

The materials used for the adhesive were Niball 1032, Trill rubber (product name manufactured by Nippon Zeon Co., Ltd.), and Hytanol 2400 (
Alkylphenol, Hitachi Chemical Co., Ltd. product name), Epicoat 1001 (bisphenol type epoxy resin,
(Product name manufactured by Yuka Shell Epoxy Co., Ltd.), Curesol 2E4
MZ (2-ethyl-4-methylimidazole, trade name of Shikoku Kasei Kogyo Co., Ltd.). After connecting the circuit by heating and pressurizing as in Example 1, post-curing was performed at 130° C. for 30 minutes. As shown in Table 1, the evaluation results of this product showed excellent connection reliability.

In addition, the circuit connectors in Examples 11 and 12 had particularly excellent adhesiveness to the circuit because the adhesive was a thermosetting type.

[Effects of the Invention] The circuit connection body using the adhesive composition of the present invention has no air bubbles in the connection part, and deterioration of the adhesive is suppressed, so connection reliability is significantly improved. Its industrial value is extremely large.

Claims (1)

[Claims] 1. An adhesive composition comprising the following (a) to (d). (a) Insulating adhesive component: 99.8-75% by volume (b) Plating particles with a particle size of 0.5-50 μm: 0.1-15
Volume % (c) Dry method silica with particle size of 0.1 μm or less 0.05 to 5
Volume % (d) Metal deactivator 0.05 to 5 volume % 2. BET method specific surface area of dry method silica is 40 m^2/g
The adhesive composition according to claim 1, which is the above.