JPH10273628A - Film-like adhesive and production of circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a film-like adhesive having high reactivity and long pot life in the film-like adhesive formed between electrodes of two circuit boards and satisfactorily used for connecting both electrodes in a liquid crystal panel, etc. SOLUTION: This film-like adhesive is composed of two layers of a first adhesive layer containing an epoxy resin (A) and an epoxy resin curing agent and a second adhesive layer containing an epoxy resin (B), and the epoxy resin (A) has longer gel time than that of the epoxy resin (B) and the second adhesive layer contains no epoxy resin curing agent or contains the epoxy resin curing agent in an amount smaller than that in the first adhesive layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film adhesive which is formed between electrodes of two circuit boards in a liquid crystal panel or the like, and is good for connecting both electrodes.

[0002]

2. Description of the Related Art Along with bonding two circuit boards together,
As a circuit connecting member for obtaining electrical continuity between these electrodes, a styrene-based or polyester-based thermoplastic material,
A film adhesive composed of a thermosetting substance such as an epoxy-based or silicone-based substance and conductive particles is generally known.

[0003]

When joining using this film adhesive, it is necessary to join at as low a temperature as possible in order not to expose the electronic parts to be joined to high temperatures. In addition, there is a demand for joining in a short time in order to improve productivity. In order to lower the temperature and shorten the bonding time, it is necessary to apply a thermosetting resin and a curing agent having higher reactivity. However, since the curable substance and the curing agent are contained in the same system, the higher the reactivity, the more easily the curable substance and the curing agent react, and the shorter the pot life, the higher the reactivity. There is. For this reason, it is necessary to devise measures such as extending the pot life by using a hardening agent imparted with microcapsules or the like.However, even when a curing agent imparted with microcapsules or the like is used, the epoxy reaction does not occur. When the reactivity is very high, the pot life is shortened, so that there is still a limit in increasing the reactivity. An object of the present invention is to provide a film adhesive having higher reactivity than the conventional one and having the same pot life as the conventional one.

[0004]

According to the present invention, there is provided a film adhesive comprising a first adhesive layer containing an epoxy resin (A) and an epoxy resin curing agent, and a second adhesive layer containing an epoxy resin (B). The epoxy resin (A) has a longer gel time than the epoxy resin (B), and the second adhesive layer contains no epoxy resin curing agent or is harder than the first adhesive layer. It is characterized in that the mixing amount is small. Conductive particles can be mixed into at least one of the adhesive layers so as to exhibit anisotropic conductivity. As the conductive particles, those having an average particle size of 2 to 18 μm can be used, and the content of the conductive particles is 100 parts (by volume) of the adhesive resin composition.
Is preferably 0.1 to 20 parts (volume). The method for manufacturing a circuit board according to the present invention includes a first circuit member having a first connection terminal, a second circuit member having a second connection terminal, and a first connection terminal and a second connection terminal. The film-like adhesive of the present invention is interposed between the first connection terminal and the second connection terminal arranged opposite to each other, and the first connection terminal arranged oppositely by applying heat and pressure. The second connection terminal is electrically connected.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The epoxy resin used in the present invention will be described. Epoxy resin is a bisphenol type epoxy resin derived from epichlorohydrin and bisphenol A or F, AD, etc., an epoxy novolak resin derived from epichlorohydrin and phenol novolak or cresol novolak, or a naphthalene-based epoxy resin having a skeleton containing a naphthalene ring, Various epoxy compounds having two or more glycidyl groups in one molecule, such as glycidylamine, glycidyl ether, biphenyl, and alicyclic, can be used alone or in combination of two or more. These epoxy resins use impurity ions (N
a +, Cl-) and hydrolyzable chlorine etc.
It is preferable to use a high-purity product reduced in order to prevent electron migration.

[0006] Epoxy resin curing agents include polyaddition type curing agents such as polyamines, polymercaptans, polyphenols and acid anhydrides, and catalytic curing agents include imidazole, hydrazide, boron trifluoride-amine complexes and sulfonium. There are salts, amine imides, diamino maleonitriles, melamines and derivatives thereof, polyamine salts, dicyandiamides and the like, and modified products thereof, and these can be used alone or as a mixture of two or more. Catalytic curing agents are anionic or cationically polymerizable, and are preferred because they can easily obtain rapid curing properties and require little consideration of chemical equivalents. Tertiary amines and imidazoles are mainly used as anionic polymerization type catalyst-type curing agents. Epoxy resins containing tertiary amines or imidazoles can be heated for several tens of seconds at a medium temperature of about 160 to 200 ° C.
The pot life is relatively long because it is cured by heating for several hours. As the cationic polymerization type catalyst-type curing agent, a photosensitive onium salt that cures a resin by irradiation with energy rays, for example, an aromatic diazonium salt, an aromatic sulfonium salt, or the like is mainly used. In addition to energy ray irradiation, aliphatic sulfonium salts and the like are also activated by heating to cure the epoxy resin. This type of curing agent is preferred because it has the characteristic of fast curing. Since these hardeners are coated with a polymer substance such as polyurethane or polyester, or a metal thin film such as Ni or Cu and an inorganic substance such as calcium silicate and microencapsulated, the pot life is extended. Preferred.

The gel time is the time required for the curable resin to gel under certain curing conditions. The higher the reactivity between the curable resin and the curing agent, the shorter the gel time. It is a guide. Although the value changes considerably depending on the amounts of the curable resin and the curing agent, the measurement temperature, and the like, as long as the gel time is measured under the same measurement conditions, the reactivity between the curable resin and the curing agent can be compared. Here, an example of the measurement of the gel time is shown. 5 parts by weight of a catalytic curing agent is blended with 100 parts by weight of the epoxy resin, and 100 mg of this is dropped on a hot plate adjusted to a temperature of 140 ° C., and the time until gelation is defined as gel time.

As the conductive particles, Au, Ag, Ni,
There are metal particles such as Cu and solder, carbon, and the like, and the conductive layer described above may be formed by coating the above conductive layer with non-conductive glass, ceramic, plastic, or the like.
In the case of plastic core or hot melt metal particles,
Heat and pressure are preferable because they have deformability, so that the contact area with the electrode increases during connection and reliability is improved. The conductive particles are added in an amount of 0.1 to 100 parts (volume) of the adhesive resin component.
Depending on the application, it can be used in a wide range of 1 to 30 parts (volume)
In order to prevent a short circuit in a circuit due to excessive conductive particles, 0.1 to 20 parts (by volume) is more preferable.

The connection of the electrodes using the connection material (film adhesive) obtained in the present invention will be described. In this method, an adhesive composition (film-like adhesive) is formed between opposing electrodes on a substrate, and the electrodes are connected by heating and pressing to obtain contact between the two electrodes and adhesion between the substrates. As a substrate on which electrodes are formed, inorganic materials such as semiconductors, glass, and ceramics, organic materials such as polyimide and polycarbonate, and combinations of these composite materials such as glass / epoxy can be used.

The connection material (film adhesive) of the present invention can also be used, for example, when a semiconductor chip is adhered and fixed with a substrate and an adhesive film by a face-down method and both electrodes are electrically connected. That is, a first circuit member having a first connection terminal, and a second circuit member having a second connection terminal, the first connection terminal and the second connection terminal are arranged facing each other, The connection material (film adhesive) of the present invention is interposed between the first connection terminal and the second connection terminal that are arranged to face each other, and heated and pressurized, and the first connection terminal and the second connection that are arranged to face each other. The circuit board can be manufactured by electrically connecting the terminals.

[0011] Such circuit members include chip parts such as semiconductor chips, resistor chips, and capacitor chips.
A board such as a printed board is used. These circuit members are usually provided with a large number of connection terminals (in some cases, a single connection terminal may be provided), and at least one set of the circuit members is arranged so that at least a part of the connection terminals provided on the circuit members are opposed to each other. Then, an adhesive is interposed between the opposed connection terminals and heated and pressed to electrically connect the opposed connection terminals to form a circuit board. By heating and pressurizing at least one set of circuit members, the connection terminals arranged to face each other can be electrically connected by direct contact or via conductive particles of an anisotropic conductive adhesive.

In the present invention, the amount of the epoxy resin curing agent in the adhesive layer containing the highly reactive epoxy resin (B) is appropriately adjusted according to the required pot life without considering the reactivity of the system. it can. Since heat and pressure are applied when electronic components are joined using this film adhesive, an adhesive layer containing an epoxy resin (B), an adhesive layer not containing an epoxy resin curing agent, an epoxy resin (A) and The adhesive layers containing the epoxy resin curing agent melt and mix with each other. Considering that the layer containing the epoxy resin (A) is mixed with the adhesive layer containing no epoxy resin curing agent and the layer containing the epoxy resin (B), if the amount of the epoxy resin curing agent is increased in advance, Since a sufficient amount of epoxy resin curing agent is supplied to react the epoxy resin (B), high reactivity can be obtained.

[0013]

【Example】

Example 1 Bisphenol A type phenoxy resin (average molecular weight: 20,000) 6 from bisphenol A and epichlorohydrin
0 g was prepared by a general method, and this was mixed in a weight ratio of toluene (boiling point 110.6 ° C., SP value 8.90) / ethyl acetate (boiling point 77.1 ° C., SP value 9.10) = 50/50. It was dissolved in a solvent to obtain a solution having a solid content of 40%. Bisphenol A type liquid epoxy resin (manufactured by Yuka Shell Epoxy Co., Ltd., trade name: Epicoat 828) 50 parts (parts by weight,
The same applies hereinafter), bisphenol A type phenoxy resin 50
Parts and 7.5 parts of a cationic thermal polymerization initiator (trade name: San-Aid SI60 manufactured by Sanshin Chemical Co., Ltd.), and 3 parts of conductive particles (volume, adhesive resin composition 100) Parts (volume)) and disperse, thickness 8
A 0 μm fluororesin film was applied using a coating device, and dried with hot air at 75 ° C. for 10 minutes to obtain a conductive adhesive layer 1 having a thickness of 9 μm. 50 parts of epoxidized polybutadiene resin (trade name Eporide PB4700-02, manufactured by Daicel Chemical Industries, Ltd.), bisphenol A
50 parts of a mold phenoxy resin are mixed, and 3 parts of conductive particles are further mixed and dispersed with respect to 100 parts (volume) of the adhesive resin composition by volume, using a coating apparatus on a 80 μm-thick fluororesin film. The conductive adhesive layer 2 having a thickness of 9 μm was obtained by applying and drying with hot air at 75 ° C. for 10 minutes. The conductive adhesive layer 1 and the conductive adhesive layer 2 were laminated with a roll laminator while heating to 40 ° C., thereby obtaining a film adhesive having an adhesive layer thickness of 18 μm.

Embodiment 2 The thickness of the conductive adhesive layer 1 is 17 μm and the conductive adhesive layer 2
A film-like adhesive was obtained in the same manner as in Example 1 except that the thickness was 1 μm.

Example 3 Example 1 was repeated except that the amount of the cationic thermal polymerization initiator to be mixed into the conductive adhesive layer 1 was 20 parts, the thickness was 1 μm, and the thickness of the conductive adhesive layer 2 was 17 μm. A film adhesive was obtained in the same manner as described above.

Example 4 The thickness of the conductive adhesive layer 1 is 33 μm and the conductive adhesive layer 2
A film-like adhesive was obtained in the same manner as in Example 1 except that the thickness was 2 μm.

Example 5 Example 1 was repeated except that the amount of the cationic thermal polymerization initiator to be mixed into the conductive adhesive layer 1 was 20 parts, the thickness was 2 μm, and the thickness of the conductive adhesive layer 2 was 33 μm. A film adhesive was obtained in the same manner as described above.

Example 6 A film adhesive was obtained in the same manner as in Example 1 except that 2.5 parts of a cationic thermal polymerization initiator was added to the conductive adhesive layer 2.

Example 7 In place of the epoxidized polybutadiene resin contained in the conductive adhesive layer 2, a naphthalene-based epoxy resin (naphthalene diol-based epoxy resin, trade name HP-4032, manufactured by Dainippon Ink and Chemicals, Inc.) was used. Otherwise in the same manner as in Example 1, a film adhesive was obtained.

Example 8 The resin blended in the conductive adhesive layer 1 was bisphenol A
A film-like adhesive was obtained in the same manner as in Example 1 except that 100 parts of a phenoxy resin was used and an anionic thermal polymerization initiator (imidazole, manufactured by Kanto Chemical Co., Ltd.) was used instead of the cationic thermal polymerization initiator contained. Was. The gel times of the epoxy resin and the cationic thermal polymerization initiator used in Example 1 are shown in Table 1.

Table 1 Gel time at 140 ° C. Epoxy resin Cationic Anionic Thermal polymerization initiator Thermal polymerization Initiator ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Epicoat 828 12 seconds-Epolide PB47006 6 seconds-HP4032 6 seconds 8 seconds ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Comparative Example 1 25 parts of an epoxidized polybutadiene resin (trade name: Eporide PB4700, manufactured by Daicel Chemical Industries, Ltd.), 25 parts of a bisphenol A liquid epoxy resin (trade name: Epicoat 828, manufactured by Yuka Shell Epoxy Co., Ltd.), and 50 parts of bisphenol A-type phenoxy resin and 5 parts of a cationic thermal polymerization initiator (trade name: San-Aid SI60, manufactured by Sanshin Chemical Co., Ltd.) were further blended and dispersed by 3% by volume of conductive particles to obtain a thickness. An 80 μm fluororesin film was applied using a coating device, and dried with hot air at 75 ° C. for 10 minutes to obtain a film adhesive having an adhesive layer thickness of 18 μm.

Comparative Example 2 A film adhesive was obtained in the same manner as in Example 1 except that the amount of the cationic thermal polymerization initiator contained in the conductive adhesive layer 1 was changed to 2.5 parts.

Comparative Example 3 A film adhesive was obtained in the same manner as in Example 1 except that 5 parts of a cationic thermal polymerization initiator was added to the conductive adhesive layer 2.

Circuit Connection Using the film adhesive described above, a line width of 50 μm was used.
A flexible circuit board (FPC) having 500 copper circuits having a pitch of 100 μm and a thickness of 18 μm is placed at 150 ° C.
Heating and pressurizing was performed at 20 MPa for 20 seconds, and the connection was made over a width of 2 mm. At this time, after the adhesive surface of the film adhesive is pasted on one FPC in advance, it is temporarily connected by heating and pressing at 70 ° C. and 0.5 MPa for 5 seconds, and then the fluororesin film is peeled off and the other side is removed. FPC. Further, the above-mentioned FPC and glass (surface resistance 20 Ω / port) on which a thin layer of indium oxide (ITO) was formed were heated and pressed at 170 ° C. and 3 MPa for 20 seconds, and were connected over a width of 2 mm. At this time, a temporary connection was made to the ITO glass in the same manner as described above.

Measurement of Connection Resistance After connecting the circuits, the resistance value between the adjacent circuits of the FPC including the above-mentioned connection portion was initially and for 500 hours kept in a thermo-hygrostat at 85 ° C. and 85% RH. It was measured with a meter.
Resistance value is the average of 150 points of resistance between adjacent circuits (x + 3σ)
Indicated by

Measurement of Adhesive Strength at Connections The adhesiveness between the adhesive used for the FPC and each adhesive composition was evaluated by measuring the adhesive force per 1 cm by a 90-degree peeling method according to JIS-z0237. . The used FPC is #
7100 (Toray Industries, Inc., trade name) was used as an adhesive. Then, using this FPC, a circuit connection squad was prepared and measured. As a measuring device, Tensilon UTM-4 manufactured by Toyo Baldwin Co., Ltd. (peeling speed 50 mm / min, 25 ° C.) was used. Table 2 shows the results. Measurement of adhesive strength of connection part The adhesiveness between the adhesive used for FPC and each adhesive composition is 1 cm.
The contact force per contact was measured and evaluated by a 90-degree peeling method according to JIS-z0237. The FPC used was prepared using # 7100 (Toray Industries, Inc., trade name) as an adhesive. Then, using this FPC, a circuit connection squad was prepared and measured. The measuring device was Tensilon UTM-4 manufactured by Toyo Baldwin Co., Ltd. (peeling speed 50 mm
/ Min, 25 ° C). Table 2 shows the results.

Examples 1 to 5 and 7, in which the naphthalene type epoxy resin and the epoxidized polybutadiene, which are epoxy resins having a shorter gel time than the bisphenol-A type epoxy resin, are in a layer containing no epoxy resin curing agent.
In No. 8, a good pot life was obtained. Also, even if there is a small amount of epoxy resin curing agent in the layer containing naphthalene type epoxy resin and epoxidized polybutadiene,
Although the pot life was slightly shortened, a pot life that could be used practically was obtained. However, when the amount of the epoxy resin curing agent contained in the layer containing the naphthalene type epoxy resin and the epoxidized polybutadiene is more than 2.5 parts, the pot life becomes extremely short as in Comparative Examples 1 and 3.

Table 2 接 続 Connection resistance value at the time of preparation (Ω) Adhesive strength (N / m) Pot life ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Example 1 1.9 800 14 Day Example 2 2.1 700 12 days Example 3 2.4 780 10 days Example 4 1.9 700 14 days Example 5 2.6 750 10 days Example 6 3.0 810 9 days Example 7 2 0.3 790 10 days Example 8 1.9 850 9 days Comparative Example 1 3.3 600 1 day Comparative Example 2 500 or more 220 * Comparative Example 3 4.3 650 1 day ━━━━━━━━━━━━━━━━━━━━━━━ *: Insufficient reaction

[0030]

As described in detail above, according to the present invention, it has become possible to provide a film-like adhesive having a high reaction and a long pot life. Further, according to the present invention, it is possible to manufacture a circuit board having excellent reliability.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H05K 3/38 H05K 3/38 E (72) Inventor Itsuo Watanabe 48 Tsudai, Tsukuba-shi, Ibaraki Pref.

Claims (5)

[Claims] 1. An epoxy resin (A) comprising two layers, a first adhesive layer containing an epoxy resin (A) and an epoxy resin curing agent, and a second adhesive layer containing an epoxy resin (B). Has a longer gel time than the epoxy resin (B).
A film-like adhesive characterized in that no epoxy resin curing agent is mixed in the adhesive layer or the amount of the epoxy resin curing agent is smaller than that of the first adhesive layer. 2. The film-like adhesive according to claim 1, wherein conductive particles are mixed into at least one of the adhesive layers to exhibit anisotropic conductivity. 3. The film adhesive according to claim 2, wherein the average particle size of the conductive particles is 2 to 18 μm. 4. The content of the conductive particles is 0.1 to 20 parts (volume) based on 100 parts (volume) of the adhesive resin composition.
The film adhesive according to any one of claims 1 to 3, wherein 5. A first circuit member having a first connection terminal and a second circuit member having a second connection terminal are arranged with the first connection terminal and the second connection terminal facing each other. The film-like adhesive according to any one of claims 1 to 4 is interposed between the first connection terminal and the second connection terminal arranged opposite to each other, and the first connection terminal arranged opposite to each other by heating and pressing. A method of manufacturing a circuit board for electrically connecting a second connection terminal to a circuit board.