JP3113306B2 - Polyvinyl acetal resin and adhesive containing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for producing a copper-clad laminate, which has a low viscosity for adhering a metal copper foil for a printed circuit to a substrate.
The present invention also relates to an adhesive having excellent adhesive strength and solder heat resistance, and a polyvinyl acetal resin contained in the adhesive.

[0002]

2. Description of the Related Art Conventionally, copper-clad laminates for printed circuits have been prepared by applying an adhesive to one side of a copper foil and drying it to form an adhesive-coated copper foil. The base material surface impregnated with the thermosetting resin is overlapped so as to be in contact with each other, and these are integrated by heating and pressure bonding. As the adhesive, a polyvinyl acetal resin, a phenol resin, a melamine Adhesives containing thermosetting resins such as resins and epoxy resins have been used.

[0003] The copper-clad laminate obtained as described above is
A printed circuit is provided by etching a copper foil portion, and a circuit component is attached to the circuit by soldering, which is used for various electronic devices.

[0004] This copper-clad laminate is made by bonding a metal copper foil and a non-conductive substrate, and it is needless to say that the bonding is required to be strong, but it is further required that the bonding be performed by etching. Copper-clad laminates with even better heat resistance due to the tendency to immerse them in a high-temperature molten solder bath when attaching circuit components to the remaining copper foil part, especially the recent immersion time has been increasing. Boards have come to be required.

In response to such a demand, an adhesive mainly composed of a polyvinyl acetal resin having a specific composition, for example, an acetoacetal-butyl acetal mixed polyvinyl acetal resin having a degree of polymerization of 1500 to 2500, wherein an acetoacetal portion and a butyl acetal The ratio to the acetal portion is 3: 7 to 7: 3 by weight, and the vinyl alcohol portion is 14:14.
To 21% by weight, a vinyl acetate portion of 3% by weight or less, and an acrylic acid portion of 0.1 to 1.9% by weight.
JP-A-98306), an acetoacetal-butylacetal mixed polyvinyl acetal resin having a degree of polymerization of 1500 to 2500, wherein the ratio of the acetoacetal portion to the butylacetal portion is 3: 7 to 7: 3 by weight, and vinyl alcohol is used. 14 to 21% by weight, less than 4% by weight of vinyl acetate, 0.1 to 1.5% of maleic acid
An adhesive (Japanese Patent Application Laid-Open No. 58-98307) containing a weight percent of polyvinyl acetal resin as a main component has been proposed.

[0006] However, adhesives obtained using these polyvinyl acetal resins have various properties due to their high viscosity, although the heat resistance and the adhesive strength of the copper-clad laminate to which the copper foil is adhered using the adhesive are good. There's a problem.

[0007] The above problems are that a small amount of a high-viscosity adhesive is applied to a thin and flexible copper foil of, for example, about 30 to 40 microns, so that application workability is low and uniform application is difficult. Also, the adhesive is applied on one side of the copper foil and on the rough side having an innumerable number of fine projections having a height of about 10 microns electrodeposited on the surface, so that the adhesive having a high viscosity is It is difficult to penetrate into the deep portion of the fine void, which is a concave portion between the convex portions, and the adhesiveness between the rough surface of the copper foil and the adhesive tends to be insufficient.

Further, an adhesive having a high viscosity has difficulty in handling such as transportation, measurement and mixing.

In order to avoid such a problem, even if the adhesive is diluted with a solvent or heated to increase the temperature of the adhesive to reduce the viscosity of the adhesive, the adhesive is applied. Neither is a preferable method because it involves problems such as requiring more heat energy and time for drying the adhesive and shortening the pot life of the adhesive.

[0010]

DISCLOSURE OF THE INVENTION The present invention has been made in view of such prior art, and a polyvinyl acetal resin having a low viscosity of an adhesive and having excellent adhesive strength and solder heat resistance has been developed. Adhesive containing a conductive resin and a solvent,
Another object is to provide a polyvinyl acetal resin to be contained in the adhesive.

[0011]

As a result of various studies, the present inventors have found that a carboxy-modified acetoacetal-butylacetal mixed polyvinyl acetal resin having a specific composition and an adhesive containing the polyvinyl acetal resin achieve the object. Thus, the present invention was completed.

That is, the gist of the present invention is as follows.

(1) An acetoacetal unit (A), a butyl acetal unit (B), a vinyl alcohol unit (C), a fatty acid vinyl ester unit (D) and a unit (E) having a carboxyl group bonded as a side chain. The average degree of polymerization is 1500 to 2500, the ratio of (A) and (B) is 3: 7 to 7: 3 by weight, the ratio of (C) is (A),
14 to 21% by weight based on the total basis of (B), (C), (D) and (E), and the proportion of (D) is 5 based on the same basis as (C).
-13% by weight, and the proportion of carboxyl groups bonded as side chains to (E) is 0.1-5% by weight on the same basis as (C).
Carboxy modified acetoacetal-butyl acetal mixture
Printed circuit copper foil containing synthetic polyvinyl acetal resin
Bonding adhesive, and (2) according to claim 1, wherein the polyvinyl cell Atar resin, copper foil bonding adhesive for printed circuit containing a thermosetting resin and a solvent, and (3) according to claim 1 or
(4) an adhesive-coated copper foil obtained by applying the adhesive according to (2);
A copper foil is connected to the substrate by the adhesive according to claim 1 or 2.
Copper-clad laminate for printed circuit formation characterized by being attached
Board.

Hereinafter, the present invention will be described in detail. In this specification, the acetoacetal-butyl acetal mixed polyvinyl acetal resin is an acetoacetal unit (A) obtained by allowing both acetaldehyde and butylaldehyde to coexist in the reaction system during the acetalization reaction.
And a butyl acetal unit (B).

The carboxy-modified acetoacetal-butylacetal mixed polyvinyl acetal resin of the present invention (hereinafter sometimes abbreviated as carboxy-modified mixed polyvinyl acetal resin) will be described below.

The average degree of polymerization of the carboxy-modified mixed polyvinyl acetal resin of the present invention is 1500 to 2500, preferably
1600-2300. If the average degree of polymerization is less than 1500, both the adhesive strength and the solder heat resistance are insufficient.If the average polymerization degree exceeds 2500, the viscosity of the adhesive containing the resin increases, and especially the coating workability and handleability are reduced, and the solderability is reduced. There is little improvement in heat resistance.

The ratio of (A) to (B) in the carboxy-modified mixed polyvinyl acetal resin of the present invention (measured by an infrared spectrophotometer) is 3: 7 to 7: 3 by weight.
Preferably, it is 6: 4 to 4: 6. This weight ratio is 3: 7
If it is less than 7, the soldering heat resistance of the adhesive is insufficient, and 7:
If it exceeds 3, the solvent solubility of the resin may decrease, or the resin may become hard and brittle, causing cracks in the adhesive layer after being applied and dried on the copper foil. The degree of acetalization of the resin [total of (A) and (B)] is preferably 65% by weight or more, and 70% by weight, as long as (C), (D) and (E) satisfy the respective ranges. The above is desirable.

The proportion of the vinyl alcohol unit (C) remaining without being acetalized in the resin of the present invention is expressed by units (A),
(B), (C), (D) and (E) is 14 to 21 wt% with respect to the total basis, if less than 14 wt%, the reactivity with the thermosetting resin blended in the adhesive is low, The curing reaction tends to be insufficient. On the other hand, when the content exceeds 21% by weight, the solubility in an organic solvent decreases.

One of the features of the carboxy-modified mixed polyvinyl acetal resin of the present invention is that the ratio having fatty acid vinyl ester units (D) is higher than that of the polyvinyl acetal resin conventionally used as a component of the adhesive for copper foil. That is.

Conventionally, the fatty acid vinyl ester unit is
Since the solder heat resistance of the adhesive layer is reduced, it has been considered that the lower the ratio, the better. However, in the adhesive containing the carboxy-modified mixed polyvinyl acetal resin and the thermosetting resin of the present invention, even if the ratio of the fatty acid vinyl ester unit of the polyvinyl acetal resin is high, the conventional soldering hardly reduces solder heat resistance. An adhesive having a lower viscosity than the adhesive can be obtained.

The proportion of the carboxy-modified mixed polyvinyl acetal resin of the present invention having the unit (D) is 5 to 13% by weight, preferably 7 to 12% by weight on the same basis as the (C). this
When the proportion of (D) is less than 5% by weight, the decrease in viscosity of the adhesive is small, and when it exceeds 13% by weight, the solder heat resistance decreases.
Vinyl acetate is preferred as the fatty acid vinyl ester.
The proportion having the above fatty acid vinyl ester unit is determined by adding an aqueous solution of caustic soda to the resin dissolved in ethyl alcohol and heating to hydrolyze the ester portion to produce fatty acid soda (the remaining caustic soda is dissolved in sulfuric acid. Sum), and then, as an internal standard substance, a fatty acid different from the fatty acid of the fatty acid vinyl ester unit (D) (in the case of vinyl acetate, propionic acid is used), and phosphoric acid, and the mixture is formed by gas chromatography to decompose the fatty acid soda. The amount of the fatty acid is determined, and the amount of the fatty acid can be calculated and calculated.

The ratio of the carboxyl group in the carboxy-modified mixed polyvinyl acetal resin of the present invention is such that the carboxyl group (in terms of COOH) corresponds to the units (A), (B), (C),
The weight percentage based on the total basis of (D) and (E) is shown, and the ratio is required to be 0.1 to 5% by weight, and preferably 0.5 to 2.5% by weight. If the proportion of carboxyl groups is less than 0.1% by weight, the adhesion to metals and the like is not sufficient, and if it exceeds 5% by weight, both the normal adhesive strength and the solder heat resistance tend to decrease and are uneconomical. .

The amount of the carboxyl group contained in the resin was determined by converting the carboxyl group into a sodium salt and converting the sodium quantified using an atomic absorption spectrophotometer into a carboxyl group.

Next, a method for producing the carboxy-modified mixed polyvinyl acetal resin of the present invention will be described.

The carboxy-modified mixed polyvinyl acetal resin of the present invention is obtained by using one or more carboxy-modified PVA having a carboxyl group as a side chain by using both acetaldehyde and butyl aldehyde in a medium containing an acid catalyst. It is obtained by acetalization.

The above carboxy-modified PVA can be obtained by a known method, for example, a method described in JP-B-46-7605, JP-A-57-94002, or the like. Specifically, for example, one or more fatty acid vinyl esters (vinyl acetate, vinyl propionate, vinyl formate, etc.)
And unsaturated monocarboxylic acids (acrylic acid, methacrylic acid, crotonic acid, etc.), ethylenically unsaturated dicarboxylic acids (maleic acid, fumaric acid, itaconic acid, etc.), ethylenically unsaturated dicarboxylic anhydrides (maleic anhydride) , Alkyl (meth) acrylate [methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, ethylhexyl (meth) acrylate],
It can be obtained by a method of saponifying a copolymer resin with one or more kinds of (meth) acrylonitrile.

Further, a monomer having a side chain which is converted into a carboxyl group by reacting with one or more kinds of fatty acid vinyl esters and an acid used as a catalyst in performing an acetalization reaction [eg, acrylamide, methacrylamide And the like.) Modified PVA obtained by saponifying one or more copolymer resins with carboxy-modified PVA
Can be used as

The carboxy-modified PVA includes, in addition to a vinyl alcohol unit, a fatty acid vinyl ester unit and a unit having a carboxyl group (including a group having a side chain which is converted into a carboxyl group by reacting with an acid), a fatty acid It is also possible to use PVA in which units of other monomers copolymerizable with the vinyl ester have been added to the PVA by about 10% by weight or less by copolymerization. Other monomers copolymerizable with the fatty acid vinyl ester include, for example, a monomer having a glycidyl group (allyl glycidyl ether,
Glycidyl (meth) acrylate), monomers having a halogen atom (such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride), olefins (such as ethylene and propylene), and alkyl vinyl ethers.

The carboxyl group in the carboxy-modified PVA may be in the form of an acid, salt, acid amide, alkyl ester or a combination thereof.

The carboxy-modified PVA used as a raw material PVA to obtain the carboxy-modified mixed polyvinyl acetal resin of the present invention has a ratio having a carboxyl group, a structure of a carboxyl unit, a form of a carboxyl group, and a ratio having a fatty acid vinyl ester unit. Alternatively, two or more kinds having different average polymerization degrees may be used in combination.

As raw materials, two or more carboxy-modified PVAs
When used in combination, the combination is selected so that the carboxy-modified mixed polyvinyl acetal resin of the present invention is obtained, and as long as the carboxy-modified mixed polyvinyl acetal resin of the present invention is obtained, the carboxy-modified PVA used as a raw material is used. The respective properties, for example, the average degree of polymerization, the ratio having a carboxyl group, and the ratio having a fatty acid vinyl ester unit are not limited.

The carboxy-modified polyvinyl acetal resin of the present invention is preferably obtained by using only carboxy-modified PVA as a raw material PVA. A mixed resin with a resin is also included. This mixed resin may be used alone or in combination of two or more of the above resins. However, in the acetalization reaction, carboxy-modified PVA and uncarboxy-modified PVA are used as raw material PVA.
It is preferable to use a method obtained by acetalization reaction in the presence of both A.

Ratio (weight ratio) of carboxy-modified mixed polyvinyl acetal resin and non-carboxy-modified mixed polyvinyl acetal resin in the above mixed resin
Is from 9: 1 to 1: 9, preferably from 8: 2 to 2: 8.

The carboxy-modified PVA used as a raw material for obtaining the carboxy-modified mixed polyvinyl acetal resin of the present invention is preferably PVA obtained by saponifying a copolymer resin of vinyl acetate and acrylamide or maleic acid.

The carboxy-modified mixed polyvinyl acetal resin of the present invention is not limited to the production method and conditions, and may be, for example, one obtained by using an organic solvent, water or a mixture thereof as a medium in the acetalization reaction. , Dissolution method, precipitation method,
Examples include those obtained by a homogeneous method or a method combining these methods.

The acetalization reaction is carried out in the presence of an acid catalyst. As the acid catalyst, an inorganic acid is usually used, and examples thereof include hydrochloric acid, sulfuric acid and nitric acid. Of these, hydrochloric acid is preferred.

For the neutralization of the acid catalyst at the end of the acetalization reaction, hydroxides, carbonates and the like of alkali metals and alkaline earth metals can be used. However, if the resin containing this salt is contained in the adhesive, it may cause a decrease in the insulating property of the adhesive layer.Therefore, as a neutralizing agent for the acid catalyst, ethylene oxide, alkylene oxide such as propylene oxide may be used. Use is preferred.

Next, the adhesive of the present invention will be described.

The adhesive of the present invention contains one or more of the above-mentioned carboxy-modified acetoacetal-butylacetal mixed polyvinyl acetal resin, one or more thermosetting resins, and a solvent. .

The thermosetting resin contained in the adhesive of the present invention includes, for example, phenolic resins and amino resins. Examples of the phenolic resin include a soluble phenol / formalin resin, among which are a novolak type and a resol type. Also, modified phenolic resins are included.

As the amino resin, for example, a modified melamine resin such as a melamine resin or a butylated melamine resin can be used.

The content ratio (weight ratio) of the carboxy-modified mixed polyvinyl acetal resin and the thermosetting resin in the adhesive of the present invention is preferably from 1: 4 to 4: 1, and from 2: 3 to 4:
A range of 3: 2 is desirable.

Examples of the solvent contained in the adhesive of the present invention include ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, methanol, ethanol, and the like.
Examples include alcohols such as isopropanol and butanol, aromatics such as toluene and xylene, esters such as methyl acetate and ethyl acetate, and solvents can be used alone or in combination of two or more. The ratio of the solvent to be contained can be arbitrarily selected.

The adhesive of the present invention may contain, as desired, isocyanate, soluble polyurethane, and various additives as components other than the carboxy-modified polyvinyl acetal resin, the thermosetting resin and the solvent. Examples of the above-mentioned various additives include known stabilizers, antioxidants, and catalysts.

The adhesive of the present invention can be obtained by mixing, dissolving and dispersing, in a solvent, a carboxy-modified mixed polyvinyl acetal resin, a thermosetting resin and, if desired, substances other than these two resins. After the resin is dissolved and dispersed in the solvent used separately,
The method of mixing in a liquid state is preferable for obtaining a uniform adhesive. Further, the adhesive of the present invention can be obtained by an apparatus or a method usually used for producing an adhesive, a paint or the like.

[0046]

The present invention will be described below with reference to examples and comparative examples. Unless otherwise specified, “parts” and “%”
Each represents parts by weight and% by weight.

Example 1 (Production of carboxy-modified mixed polyvinyl acetal resin) In a reactor equipped with a stirrer, a reflux condenser and a thermometer, 490 parts of methanol and 6 parts of 35% hydrochloric acid were charged, and further modified with acrylamide copolymer. PVA (average degree of polymerization 1730, residual vinyl acetate unit 16%, acrylamide content 4.7%)
100 parts were added with stirring. Next, 41 parts of acetaldehyde and 38 parts of butyl aldehyde were added thereto, and a mixed acetalization reaction was performed at a temperature of 60 ° C. for 6 hours with stirring to obtain a methanol solution of a carboxy-modified mixed polyvinyl acetal resin. After the solution was cooled and neutralized with ethylene oxide, water was added with stirring to carry out a precipitation operation of the resin, followed by washing and drying to obtain a white powdery carboxy-modified mixed polyvinyl acetal resin.

The composition of the obtained resin was 16.4% of vinyl alcohol unit, 8.4% of vinyl acetate unit, and 1.6% of carboxyl group content. The acetoacetal unit and butyl acetal in the resin were measured using an infrared spectrophotometer. The ratio with the unit (weight ratio) is 5: 5, and the degree of acetalization is 72.7.
%Met.

The viscosity of a 5% solution obtained by dissolving the resin in a mixed solvent of equal weights of ethanol and toluene has a viscosity at 20 ° C.
It was 58cps. (Manufacture of adhesive)

8 parts of the carboxy-modified mixed polyvinyl acetal resin produced above was mixed with a mixed organic solvent [methyl ethyl ketone / methanol / xylene / toluene = 50 /
17/17/17 (weight ratio)] After dissolving in 72 parts, 80 parts of this solution and a phenol resin solution (resin content 60%, Gunei Chemical Industry Co., Ltd.)
(Product name: PL-2205) 20 parts were mixed to form an adhesive. The viscosity of the adhesive at 20 ° C. was 4,700 cps. (Production of copper clad laminate and measurement of physical properties)

The adhesive produced as described above was applied to the roughened surface of a metallic copper foil (thickness: 35 μm) at a solid content of 35 g / m ^2.
And dried naturally in a hot air dryer at 140 ° C. for 3 minutes to produce an adhesive-coated copper foil. The adhesive-coated surface of the copper foil was placed in contact with the upper surface of several sheets of phenolic resin-impregnated paper, and these were heat-pressed for 1 hour at a temperature of 160 ° C. and a pressure of 75 kg / cm ² to be integrated. One copper-clad laminate was obtained. 25 × 10
It was cut into 0 mm to obtain a test piece for measuring physical properties. Using this test piece, the normal state (20 ° C.) adhesive strength and the solder heat resistance (260 ° C.) were measured. The measuring method was based on JIS C-6485. Table 2 shows the results
Shown in

The adhesive obtained in the examples has a low viscosity,
Application and measurement on the copper foil surface were easy, and the adhesive-coated surface of the adhesive-coated copper foil was uniform.

Examples 2 to 13 and Comparative Examples 1 to 11 Carboxy-modified mixed polyvinyl acetal resin and non-carboxy-modified mixed polyvinyl acetal in the same manner as in Example 1 except that the production conditions were changed as shown in Table 1. A resin (Comparative Example 1) was obtained. Table 2 shows the properties of the obtained resin. In the same manner as in Example 1, an adhesive containing the above-mentioned mixed polyvinyl acetal resin was produced, and a copper-clad laminate bonded using the adhesive was produced, and the physical properties of the copper-clad laminate were measured. Table 2 shows the results.

The adhesives obtained in Examples 2 to 13 had a low viscosity, were easy to apply and measure on the copper foil surface, and had a uniform adhesive-coated surface of the adhesive-coated copper foil. On the other hand, the adhesives obtained in Comparative Examples 2, 3 and 10 had high viscosities, were difficult to apply and measure, and had uneven application thickness on the application surface and lacked uniformity.

[0055]

[Table 1]

[0056]

[Table 2]

[0057]

The adhesive of the present invention containing the carboxy-modified mixed polyvinyl acetal resin, the thermosetting resin and the solvent of the present invention has a low viscosity, is excellent in coating workability, handleability, and uniformity of the coating film. Moreover, the copper-clad laminate bonded using this adhesive has excellent normal-state adhesive strength and solder heat resistance.

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Claims (4)

(57) [Claims] An acetoacetal unit (A), a butyl acetal unit (B), a vinyl alcohol unit (C), a fatty acid vinyl ester unit (D), and a unit (E) having a carboxyl group bonded as a side chain. The average degree of polymerization is 1500 to 2500, the ratio of (A) and (B) is 3: 7 to 7: 3 by weight, and the ratio of (C) is (A), (B).
14 to 2 with respect to the total standard of (C), (D) and (E)
1% by weight, the proportion of (D) is 5 to 13% by weight based on (C), and the proportion of carboxyl groups bonded as side chains to (E) is 0.1 to 5% by weight based on (C). Carboki which is%
Modified acetoacetal-butylacetal mixed polyvinyl
Connection for copper foil bonding of printed circuits containing nil acetal resin
Adhesive. 2. An adhesive for bonding a copper foil of a printed circuit, comprising the polyvinyl acetal resin, the thermosetting resin and the solvent according to claim 1 . 3. Applying the adhesive according to claim 1 or 2
Adhesive-coated copper foil. 4. The method according to claim 1, wherein a copper foil is provided on the substrate.
Printed circuit type characterized by being adhered by an adhesive
Copper clad laminate for forming.