KR0123045B1 - Adhesive compositions - Google Patents

Abstract

The present invention is related to flexible printing circuit board and aqueous adhesive composition for coverlay film characterized by comprising 10-50 wt% of acrylonitrile, 30-80 wt% of alkyl acryl ester having 1-12 of carbon atom, 1-10 wt% of hydroxyethylacrylate or hydroxyethylmetacrylate, 50-80 wt% of water dispersive acryl copolymer consisting of 1-10 wt% of glycidylacrylate or glycidylmethacrylate, 5-20 wt% of aqueous epoxy compound having 2 or more epoxy group within one molecule, 1-10 wt% of melamine formaldehyde resin and 5-30 wt% of aromatic bromine compound.

Description

Aqueous adhesive composition for flexible printed circuit boards and coverlay films

The present invention is used in the manufacture of flexible printed circuit boards and coverlay films, and relates to an aqueous adhesive composition having excellent flowability, excellent adhesion, heat resistance, chemical resistance, solvent resistance, electrical insulation, flexibility, and storage properties. Specifically, 10-50% by weight of acrylonitrile, 30-80% by weight of alkylacrylic ester having an alkyl group having 1-12 carbon atoms, 1-10% by weight of hydroxyethyl acrylate or hydroxyethyl methacrylate, glyci 50-80% by weight of water-dispersible acrylic copolymer composed of 1-10% by weight of diacrylate or glycidyl methacrylate and 5-20% by weight of water-soluble epoxy compound having two or more epoxy groups in one molecule, melamine formaldehyde Aqueous adhesive composition for flexible printed circuit board and coverlay film comprising 1-10% by weight of resin and 5-30% by weight of aromatic bromine compound It relates.

Recently, the trend of miniaturization, high integration, simplicity, and high performance has been prominent in the electric and electronic industries. To satisfy these demands, the development of flexible printed circuit boards having good flexibility and integrating circuits is absolutely required. The flexible printed circuit board is flexible and can be folded in accordance with the internal structure of the product. Since it is made of a very thin material, the flexible printed circuit board can take a sufficient role as a circuit board while taking up little space.

In general, a flexible printed circuit board is coated with an adhesive on a film such as a polyimide resin, a polyester resin, a polyamideimide resin, a polyetherimide resin, which are basic substrates, and then a conductor such as a copper foil or an aluminum foil is adhered thereto, and a metal It is manufactured by printing a circuit and etching metal foil using screen printing and dry film photoresist on the conductor surface. The above-mentioned film is used as a substrate of a flexible printed circuit board because it is excellent in thermal, mechanical and electrical properties. In addition, the coverlay film is applied to the film of the same material as the original in order to protect the printed circuit, semi-cured and then the film or paper having a releasability as a protective sheet to the adhesive surface, and in use release film or release paper Remove and protect by covering the printed circuit surface on the flexible printed circuit board.

Adhesives used in the manufacture of flexible printed circuit boards and coverlay films require properties such as heat resistance, chemical resistance, solvent resistance, electrical insulation, and flexibility. Especially in the case of coverlays, the adhesive flows out of the film during lamination processing. It should be small, fill the gaps between the circuits well, and have a long shelf life in the semi-cured state. Shelf life should be at least 3 months at room temperature and 6 months at 5 ℃.

On the other hand, since flexible printed circuit boards and coverlays are used in electrical and electronic products, flame retardancy is required. Since copper foil and polyimide films have flame retardancy among the substrates of flexible printed circuit boards, the flame retardance of adhesives affects the flame retardance of the entire substrate. The impact is very large.

Conventionally used adhesives for flexible printed circuit boards include acrylonitrile-butadiene rubber, butyral resin, nylon / epoxy resin, acrylonitrile-butadiene rubber / phenolic resin, acrylonitrile-butadiene resin / epoxy resin, crosslinkable There are acrylic rubbers, acrylic rubbers and epoxy watches, and these adhesives do not satisfy all of the above properties. For example, nylon / epoxy adhesives have good adhesion but have poor electrical insulation at high temperatures. Acrylonitrile-butadiene / phenolic adhesives have good adhesion but poor chemical and heat resistance, and acrylonitrile-butadiene having a carboxyl group. Epoxy resin adhesives have excellent adhesion, chemical resistance, and electrical insulation, but their heat resistance is weak, and the adhesion and flexibility are significantly reduced when they are heated. A relatively good adhesive is an acrylic rubber / epoxy adhesive, which must be used as a solution of flammable organic solvents such as methyl ethyl ketone, toluene, acetone, and ethanol. This is accompanied by a removal process, and at this time, there is a high risk of work due to the organic solvent, it is harmful to the health of workers.

From this point of view, the development of an aqueous adhesive is required, and the development of an emulsion polymerization adhesive acrylic adhesive having adhesive strength, electrical insulation, flexibility, heat resistance, and integrity and proper flow required in a coverlay film is required.

Accordingly, it is an object of the present invention to provide an aqueous adhesive composition for a flexible printed circuit board and a coverlay film having excellent flow strength, excellent adhesive strength, heat resistance, chemical resistance, insulation, solvent resistance, flexibility, and storage properties as a cost-effective formulation.

In order to achieve the above object as well as another object easily expressed in the present invention, 50-80% by weight of water-dispersible acrylic copolymer, 5-20% by weight of water-soluble epoxy compound having two or more epoxy groups in one molecule, melamine form 1-10% by weight of aldehyde resin and 5-30% by weight of aromatic bromine compound are prepared. The water-dispersible acrylic copolymer in the adhesive composition is 10-50% by weight of acrylonitrile and alkyl having 1-12 carbon atoms. 30-80 weight% of acrylic ester, 1-10 weight% of hydroxyethyl acrylate or hydroxyethyl methacrylate, and 1-10 weight% of glycidyl acrylate or glycidyl methacrylate are polymerized and used.

The water-dispersible acrylic copolymer provides flexibility and adhesion while forming the main component of the adhesive. 50-80% by weight of the acrylic copolymer is included in the total adhesive component, but less than 50% by weight is more than 80% by weight, the flexibility is lowered heat resistance.

By using acrylonitrile as a main component of the water-dispersible acrylic copolymer, the adhesive has resistance to organic chemicals such as acetone and methylene chloride, and has adhesive strength to copper plates and gives rigidity to the resin.

Acrylonitrile uses 10-50% by weight of the total monomer components of the acrylic copolymer. If it is less than 10% by weight, the adhesion is insufficient, and if it is more than 50% by weight, the flexibility is insufficient. In addition to acrylonitrile, the alkylacryl ester having 1 to 12 carbon atoms as a main component of the copolymer provides adhesiveness to the adhesive and at the same time has flexibility, which is a required characteristic of the adhesive for flexible printed circuit boards. Alkyl acrylate is used 30-80% by weight of the total monomer components, less than 30% by weight lacks the adhesive strength, if it exceeds 80% by weight lacks flexibility. The acrylic copolymer copolymerizes glycidyl acrylate or glycidyl methacrylate having an oxirane group to react with epoxy compound and melamine formaldehyde resin to have high crosslinking density, heat resistance and rigidity. In the copolymer, 1-10% by weight is used. If it is less than 1% by weight, the tensile strength and chemical resistance after heat treatment are weakened. Hydroxyacrylate or hydroxymethacrylate is a hydrophilic monomer, which helps to disperse the monomer during emulsion polymerization of acrylic and improves the adhesive strength of the adhesive, and is used in 1-10% by weight of the total acrylic copolymer. If it is less than 1% by weight, a stable acryl emulsion cannot be obtained and if it is more than 10% by weight, the soldering heat resistance is lowered.

The aqueous dispersion of the acrylic copolymer having the composition of the monomers as described above is prepared by a common fusion polymerization method. Potassium-persulfate (hereinafter referred to as KPS) is used as the polymerization initiator, and the acrylic monomer is mixed with distilled water and added dropwise to an aqueous solution at 70 ° C. in which the polymerization initiator is dissolved for 3-4 hours. After the addition of the monomer, the aging is proceeded again at 70 ℃ for 3-4 hours, the reaction is terminated and cooled to room temperature. Filter the aggregates using a filter and adjust the pH to 7-10 with amine or the like.

Examples of the water-soluble epoxy compound having two or more epoxy groups in one molecule include epoxide compounds having a hydrophilic ether bond in molecules such as ethylene glycol diglycidyl ether and polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, and diglycerol. The epoxy compound which has an ether bond and an alcohol group is preferable among molecules, such as polyglycidyl ether and sorbitol polyglycidyl ether. The water-soluble epoxy compound improves the adhesive strength of the adhesive, and imparts stiffness and heat resistance of the adhesive by reacting with a carboxyl group of the acrylic copolymer to form a crosslinked structure. If the content of the water-soluble epoxy compound having two or more epoxy groups in one molecule is less than 5% by weight, the heat resistance and the adhesive strength are lowered, and if it exceeds 20% by weight, the flexibility is lowered.

Since the melamine formaldehyde resin has a multifunctional group, the crosslinking density can be played out, thereby reinforcing the stiffness and heat resistance of the pressure-sensitive adhesive. If the melamine formaldehyde resin is less than 1% by weight, the Young's resistance is lowered, and if it exceeds 10% by weight, the flexibility is lowered.

Aromatic bromine compound is used in the form of milky white emulsion, it is effective to add a flame retardancy to the adhesive is effective to add 5-30% by weight. If the amount of the aromatic bromine compound is less than 5% by weight, flame retardancy is insufficient, and if it exceeds 30% by weight, the adhesive strength of the adhesive is lowered.

The adhesive prepared by the above composition is an aqueous adhesive having a viscosity of 100-2000 cps, and is applied on the heat-resistant base film to have a thickness of 20-50 μ after drying and dried at 80-120 ° C. for 1-20 minutes, and then the thickness is 5- 80μ rolled copper foil, electrolytic copper foil, aluminum foil, etc. are laminated, pressed using a metal roll or heat-resistant rubber roll heated to 100-150 ° C. at a pressure of 3-60 Kg / cm 2 and then subjected to 3-48 hours at 80-200 ° C. It hardens and a flexible copper clad laminated board is obtained. In the case of a coverlay film, instead of attaching a copper plate, a release-treated film or paper is attached and semi-cured at 80-120 ° C. for 5-30 minutes. The coverlay film is printed on the circuit of the flexible copper clad laminate, then laminated thereon, and bonded by press for 30-90 minutes at a pressure of 10-60Kg / cm2 at 160-180 ° C to produce a flexible printed circuit board.

The following examples and comparative examples further illustrate the invention but do not limit the scope of the invention.

The physical property evaluation method in an Example and a comparative example is as follows.

1. Adhesive strength

Adhesion strength between copper foil and heat resistant film is measured according to ICP-FC-240B. The measurement conditions are measured after being left for 48 hours at a temperature of 20 ° C. and a relative humidity of 65%, or after floating on a lead melt at 260 ° C. for 30 seconds.

2. Flame retardant

The adhesive layer is applied on the polyimide film to a thickness of 25μ, heat treated at 150 ° C for 5 hours and tested for flame retardancy according to UL-94 standard. The characteristics were divided into four levels of V-0, V-1, V-2, and HB. (V-0 is the most flame retardant, in the order of V-1, V-2, HB.)

3. soldering heat resistance

Plot the wiring surface on the lead melt at 260 ℃ for 60 seconds and observe the appearance.

4. Chemical resistance

According to JISC6481, the test piece is immersed in acetone and methylene chloride at room temperature for 15 minutes, and then taken out to observe the appearance.

5. Flexibility

Bend the specimen under a load of 500 g and measure the number of bends until the conductor is not energized.

6. Insulation resistance

According to JISC6481, after leaving for 96 hours at a temperature of 20 DEG C and a relative humidity of 65%, the volume resistance is measured.

Example 1

30 weight% of acrylonitrile, 60 weight% of ethyl acrylate, 5 weight% of glycidyl methacrylate, and 5 weight% of hydroxyethyl methacrylate were mixed with distilled water to prepare a monomer mixture. KRS is dissolved in distilled water as a polymerization initiator and the temperature is raised to 70 ° C. While stirring this aqueous solution, the monomer mixture prepared in advance was added dropwise for 3.5 hours, and then aged for 4.5 hours. After the reaction is completed, the temperature is cooled to room temperature, and the aggregates are removed using a filter. The solid content of the final acrylic copolymer aqueous dispersion is 50% and adjusted to pH 7.0-10.0 with an amine base.

To 100 g of the resin component of the acrylic copolymer aqueous solution, 7.5 g of diethylene glycol diglycidyl ether (equivalent ratio: 170 WPE, viscosity: 1500 cps), which is a water-soluble epoxy compound, is added and melamine formaldehyde resin (trade name: CYMEL303, American Sinami) 5.0 g of Desa (AMERICAN CYANAMID Co., Ltd.) is added, and 20.0 g of aromatic bromine compound (trade name: Fran B-80EM, manufactured by Daehwa Chemical, 50 wt% of solids) in emulsion form is added to form an adhesive having a viscosity of 450 cps.

Using this adhesive, apply on 50μ thick polyimide film (trade name: KAPTON, manufactured by DUPONT), dry at 120 ℃ for 5 minutes, laminate 35μ thick electrolytic copper foil, and use metal roll or rubber roll. Lamination is carried out at a temperature of 140 ° C. and a pressure of 5 kg / cm 2. Thereafter, the post-coating for 10 hours at 130 ℃ to completely cure the adhesive layer.

A coverlay film sheet was obtained by applying onto a 50 μm-thick polyimide film using an adhesive of the same composition, drying at 120 ° C. for 10 minutes, and attaching a release treated polyester film to the adhesive side.

After printing the circuit on the flexible copper-clad laminate, a coverlay film from which the release film was removed is pasted onto the printed circuit, and then bonded to the printed circuit by using a press at a temperature and pressure of 160 ° C. and 30 Kg / cm ² to produce a flexible printed circuit board. As a result of evaluating the characteristics of the manufactured flexible printed circuit board, the adhesive strength is 1.8Kg / cm at the normal state (20 ℃, 65% relative humidity) and 1.3Kg / cm after the heat treatment (260 ℃, 30 seconds). . Flame retardancy measured by UL-94 method was V-0 level, good soldering heat resistance and chemical resistance, flexural strength is 1300 times and insulation resistance is 10 ¹⁷ Ω.

Example 2

32 wt% acrylonitrile, 60 wt% butyl acrylate, 5 wt% glycidyl acrylate, and 3 wt% hydroxyethyl acrylate were mixed together with distilled water to prepare a monomer mixture, and copolymerized in the same manner as in Example 1. To prepare an aqueous dispersion of an acrylic copolymer having a solid content of 45% by weight.

The water-soluble epoxy compound is composed of 8.0 g of sorbitol tetraglycidyl ether (equivalent ratio: 170 WPE, viscosity: 6000 cps) and melamine formaldehyde resin (trade name: CYMEL325, American Cinnamic Co., Ltd.). Co., Ltd.) 2.0g is mixed and 18.0g of aromatic bromine compound (Fran B-80EM, 50% by weight of solids) is added. This adhesive was applied and processed in the same manner as in Example 1 to prepare a flexible printed circuit board.

As a result of evaluation of specificity, the adhesive strength was 1.7Kg / cm (normal state: 20 ° C, relative humidity 65%), 1.3Kg / cm, and (after heat treatment: 260 ° C, 30 seconds). The flame retardancy according to UL-94 standard was V-0 level, and the chemical resistance and heat resistance were good, the bending resistance was 1500 times, and the insulation resistance was 10 ¹⁷ Ω.

Example 3

A monomer mixture was prepared by mixing 30% by weight of acrylonitrile, 60% by weight of butyl acrylate, 5% by weight of glycidyl acrylate, and 5% by weight of hydroxyethyl acrylate with distilled water and copolymerizing in the same manner as in Example 1. To prepare an aqueous dispersion of an acrylic copolymer having a solid content of 50%.

To 100 g of the resin component of the acrylic copolymer aqueous solution, the water-soluble epoxy compound was added 8.0 g of sorbitol tetraglycidyl ether (equivalent ratio: 170 WPE, viscosity: 6000 cps) and 2.0 g of melamine formaldehyde resin (CYMEL 327), and aromatic bromine 50 g of a compound (Fran B-80EM, 50 weight% of solid content) is added. The adhesive is applied and processed in the same manner as in Example 1 to prepare a flexible printed circuit board.

As a result of evaluating the properties, the tensile strength was 1.5Kg / cm (normal state: 20 ℃ relative humidity: 65%), 1.3Kg / cm (after heat resistance: 260 ℃, 30 seconds). It is at V-0 level, has good chemical resistance and heat resistance, bend resistance is 1400 times, and insulation resistance is 10 ¹⁷ Ω.

Comparative Example 1

A monomer mixture was prepared by mixing 32% by weight of acrylonitrile, 65% by weight of butyl acrylate, 2.5% by weight of glycidyl acrylate, and 0.05% by weight of hydroxyethyl acrylate with distilled water and copolymerizing in the same manner as in Example 1. To prepare an aqueous dispersion of an acrylic copolymer having a solid content of 50% by weight.

An aqueous dispersion of the acrylic copolymer was blended in the same manner as in Example 1 to prepare an adhesive to prepare a flexible printed circuit board.

As a result of evaluating the properties, the adhesive strength was 0.9Kg / cm (normal state: 20 ° C, relative humidity 65%), 0.4Kg / cm, and (after heat treatment: 260 ° C, 30 seconds). The flame retardancy according to UL-94 standard was V-0 level, and the chemical resistance is good, but when the heat resistance is evaluated, there is a problem of falling off the adhesive surface, the bending resistance is 1300 times, and the insulation resistance is 10 ¹⁷ Ω. The reason why the adhesive strength was lowered as compared with Example 1 was because the content of hydroxyethylate was less than the proper amount.

Comparative Example 2

12% by weight of acrylonitrile, 70% by weight of butyl acrylate, 3.0% by weight of glycidyl acrylate, and 15.0% by weight of hydroxyethyl acrylate were mixed with distilled water to prepare a monomer mixture, and copolymerized in the same manner as in Example 1. To prepare an aqueous dispersion of an acrylic copolymer having a solids content of 40% by weight.

An aqueous dispersion of the acrylic copolymer was blended in the same manner as in Example 1 to prepare an adhesive, thereby manufacturing a flexible printed circuit board.

As a result of evaluating the properties, the adhesive strength was 1.3Kg / cm (normal state: 20 ° C, relative humidity 65%), 0.4Kg / cm, and (after heat treatment: 260 ° C, 30 seconds). The flame retardancy according to UL-94 standard was V-0 level, and the chemical resistance is good, but when the heat resistance is evaluated, there is a problem of falling off the adhesive surface, the bending resistance is 1100 times, and the insulation resistance is 1017Ω. The reason why the heat resistance was lowered as compared with Example 1 was because the content of hydroxyethyl acrylate exceeded an appropriate amount.

Comparative Example 3

32 wt% acrylonitrile, 60 wt% butyl acrylate, 5 wt% glycidyl acrylate, and 3 wt% hydroxyethyl acrylate were mixed together with distilled water to prepare a monomer mixture, and copolymerized in the same manner as in Example 1. To prepare an aqueous dispersion of an acrylic copolymer having a solid content of 45% by weight.

8.0 g of sorbitol tetraglycidyl ether (equivalent ratio: 170 WPE, viscosity: 6000 cps) and melamine formaldehyde resin (product name: CYMEL325, manufactured by AMERICAN CYANAMID Co.) with respect to 100 g of the resin component of the acrylic copolymer aqueous dispersion. To the mixture was added 6.0 g of an aromatic bromine compound (trade name: Fran B-80EM, solid content 50% by weight).

This adhesive was applied and processed in the same manner as in Example 1 to prepare a flexible printed circuit board.

As a result of evaluation of the properties, the adhesive strength was 1.6Kg / cm (normal state: 20 ℃, relative humidity 65%), 1.3Kg / cm, (after heat treatment: 260 ℃, 30 seconds) and flame retardancy according to UL-94 standard It is HB level, has good chemical resistance and heat resistance, is 1500 times of bending resistance and insulation resistance is 10 ¹⁷ Ω. The reason why the flame retardancy is lowered is that the content of the aromatic bromine compound is insufficient.

[Comparative Example 4]

32 wt% acrylonitrile, 60 wt% butyl acrylate, 5 wt% glycidyl acrylate, and 3 wt% hydroxyethyl acrylate were mixed together with distilled water to prepare a monomer mixture, and copolymerized in the same manner as in Example 1. To prepare an aqueous dispersion of an acrylic copolymer having a solid content of 45% by weight.

8.0 g of sorbitol tetraglycidyl ether (equivalent ratio: 170 WPE, viscosity: 6000 cps) and melamine formaldehyde resin (product name: CYMEL325, manufactured by AMERICAN CYANAMID Co.) with respect to 100 g of the resin component of the acrylic copolymer aqueous dispersion. To the mixture, 80.0 g of an aromatic bromine compound (trade name: Fran B-80EM, 50 wt% solids) is added.

This adhesive was applied and processed in the same manner as in Example 1 to prepare a flexible printed circuit board.

As a result of evaluating the properties, the adhesive strength was 0.8Kg / cm (steady state: 20 ℃, relative humidity 65%), 0.7Kg / cm, (after heat treatment: 260 ℃, 30 seconds). V-0 level, good chemical resistance, but heat resistance is falling off the adhesive surface, bend resistance 800 times, insulation resistance is 10 ¹⁷ Ω. The reason why the adhesion, heat resistance, and flex resistance did not reach the required level is because too much aromatic bromine compound was added.

Claims (2)

50-80 wt% of water-dispersible acrylic copolymer, 5-20 wt% of water-soluble epoxy compound having two or more epoxy groups in one molecule, 1-10 wt% of melamine formaldehyde resin, and 5-30 wt% of aromatic bromine compound. An aqueous adhesive composition for a flexible printed circuit board and coverlay film. The method of claim 1, wherein the water-dispersible acrylic copolymer is 10-50% by weight of acrylonitrile, 30-80% by weight of alkylacrylic ester having an alkyl group having 1-12 carbon atoms, hydroxyethyl acrylate or hydroxyethyl methacryl. An aqueous adhesive composition for a flexible printed circuit board and a coverlay film, characterized in that the composition consists of a rate of 1-10% by weight and 1-10% by weight of glycidyl acrylate or glycidyl methacrylate.