JPH04314391A - Adhesive for fabricating printed circuit board by additive process - Google Patents

Abstract

PURPOSE:To enhance electric corrosion resistance by using an adhesive containing high-purity acrylonitrile-butadiene rubber with a certain amount or less of metal ionized impurities, alkylphenol resin, epoxy resin, and cation reactive optical initiator which bridges glycidyl methacrylate and epoxy resin in the rubber as essential components. CONSTITUTION:By producing high-purity acrylonitrile-butadiene rubber without using Na<+> ions or other metallic ionized substances, it is possible to keep the amount of metal ionized impurities to 50ppm or less. As alkylphenol resin, P phenol or P phenylphenol is used. As a cation reactive optical initiator which simultaneously bridges glycidyl methacrylate and epoxy resin, a cation compound such as triphenyl sulfonium salt can be used.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet curing adhesive for additive printed wiring boards that has excellent electrical corrosion resistance and can be cured at low temperatures and in a short time.

0002

2. Description of the Related Art As is well known, printed wiring boards produced by the additive method are those in which necessary wiring patterns are formed on an adhesive-coated insulating substrate by electroless plating. For example, an adhesive layer containing a plating catalyst is provided on an insulating substrate such as a laminate containing a plating catalyst and cured at a temperature of 160° C. or higher for about 1 hour. Next, after masking with a plating resist, the surface of the adhesive layer in the circuit forming portion is selectively chemically roughened using an oxidizing etching solution such as chromium sulfuric acid as a pretreatment for electroless plating. Then, after a neutralization and water washing process, it is immersed in an electroless copper plating solution to deposit copper on the circuit portion, thereby forming a wiring pattern.

[0003] Adhesives for printed wiring boards produced by such an additive method generally contain acrylonitrile butadiene rubber, which has excellent adhesion to deposited copper plating, or acrylonitrile butadiene rubber containing carboxyl groups at both ends, and Adhesives that contain thermosetting resin components such as alkylphenol resins or epoxy resins to ensure heat resistance, and inorganic fillers as appropriate to reinforce and chemically roughen the adhesive coating. agents have been proposed.

[0004] For example, Japanese Patent Publication No. 48-24250, Japanese Patent Publication No. 9843-1983, and Japanese Patent Publication No. 45-9996 disclose techniques related to such adhesives.
Publication No. 16391, Special Publication No. 16391, Special Publication No. 52-
31539, Japanese Unexamined Patent Publication No. 51-28668, etc.

[0005]

[Problems to be Solved by the Invention] In recent years, with the miniaturization and weight reduction of electronic devices, there has been a demand for higher wiring densities, and as a result, the spacing between through holes has become narrower. As a result, the electric field generated between adjacent wiring conductors or conductors on the inner wall of the through hole activates impurity ions in the insulating base material that supports the conductor and various processing solutions remaining inside, causing a migration phenomenon between the conductors. Insulation deterioration due to this will progress more easily.

[0006] Therefore, in order to perform high-density wiring, only the width of the conductor must be reduced, which has put a limit on high-density wiring.

On the other hand, in order to achieve high-density wiring, mechanical properties such as dimensional stability, warping, and twisting of printed wiring board substrates have also become important. From now on, it will be affected by the heat added to the process of manufacturing printed wiring boards, such as curing of adhesives, curing of plating resists, and annealing after electroless plating.

[0008] For this reason, it is necessary to develop a technology that allows materials for printed wiring boards to be cured at low temperatures and in a short time.

The present invention was developed as a result of intensive studies on these problems, and is suitable for high-density wiring that has excellent electrical corrosion resistance, is effective against insulation deterioration on the surface of an insulated substrate, and can be cured at low temperatures and in a short time. The present invention provides an adhesive for printed wiring boards using an additive method.

0010

[Means for Solving the Problems] The adhesive for additive printed wiring boards of the present invention comprises (A) a high-purity acrylonitrile having glycidyl methacrylate in the molecule and having a metal ionic impurity content of 50 ppm or less; butadiene rubber, (B) an alkylphenol resin, (C) an epoxy resin, and (D) a cationic photoinitiator that simultaneously crosslinks glycidyl methacrylate and the epoxy resin in the high-purity acrylonitrile butadiene rubber. It is characterized by being contained as an essential component.

The acrylonitrile butadiene rubber containing glycidyl methacrylate used in the present invention is obtained by copolymerizing acrylonitrile butadiene with glycidyl methacrylate.

The content of glycidyl methacrylate is not particularly limited, but it is preferably 2% by weight or more.

[0013] Ordinary acrylonitrile butadiene rubber is generally produced by emulsion polymerization, but polymerization residues such as a surfactant used as an emulsifier or a coagulant cause K+, Na+, Mg+, SO4 2-, C
The total amount of metal ionic impurities such as l-, etc. reaches several percent.

[0014] The high purity acrylonitrile butadiene rubber used in the present invention is manufactured using a manufacturing process that uses as little of these ionic substances as possible. As a result, K
+, Na+, Ma+, SO4 2-, Cl-,
The total amount of each ion can be 50 ppm or less.

The amount of high purity acrylonitrile butadiene rubber containing glycidyl methacrylate in the solid content of the adhesive excluding organic solvents is in the range of 10 to 60 parts by weight. If it is less than 10 parts by weight, the adhesive strength with deposited copper tends to decrease, and if it is more than 60 parts by weight, heat resistance will deteriorate.

Examples of the alkylphenol resin include P-phenol, P-phenylphenol, P-cumylphenol, or alkylphenol, butylphenol, Sec-butylphenol, or octylphenol. A P-substituted alkylphenol such as P-substituted alkylphenol is used.

[0017] The blending amount thereof is in the range of 2 to 20 parts by weight based on the solid content excluding the organic solvent. If it is less than 2 parts by weight, the crosslinking with the acrylonitrile butadiene rubber will be insufficient, resulting in a decrease in heat resistance, and if it is more than 20 parts by weight, the adhesive strength with the precipitated plated copper will decrease.

The epoxy resin is not particularly limited, and bisphenol A type epoxy resins, novolac type epoxy resins, alicyclic epoxy resins, etc. can be used.

[0019] The blending amount thereof is in the range of 20 to 70 parts by weight based on the solid content excluding the organic solvent. If it is less than 20 parts by weight, the heat resistance and electrolytic corrosion resistance will decrease, and if it is more than 70 parts by weight, the adhesive force with the deposited plated copper will decrease.

As the cationic photoinitiator for simultaneously crosslinking glycidyl methacrylate and the epoxy resin, a cationic compound such as a triphenylsulfonium salt can be used.

As the cationic compound of the triphenylsulfonium salt, triphenylsulfone hexafluoroantimonate and triphenylsulfone hexafluorophosphate can be used.

[0022] The blending amount thereof is in the range of 0.1 to 5 parts by weight based on the solid content excluding the organic solvent. If it is less than 0.1 parts by weight, the reaction between glycidyl methacrylate and the epoxy resin upon irradiation with ultraviolet light will be insufficient, and if it is more than 5 parts by weight, there will remain a photoinitiator that does not contribute to the ultraviolet curing reaction, so it is unnecessary.

In the present invention, the adhesive may contain a plating catalyst for electroless plating.

[0024] As the plating catalyst, it is possible to use a plating catalyst in which elements of Groups 8 and 2B of the Periodic Table of the Elements are adsorbed on an inorganic or organic substance as a metal chloride compound, and then reduced to a metal.

The amount of the plating catalyst contained in the adhesive is preferably in the range of 1 to 15 parts by weight. If it is less than 1 part by weight, the plating precipitation properties will be reduced, and if it is more than 15 parts by weight, the insulation resistance will be reduced.

[0026] Further, in the adhesive of the present invention, an inorganic filler may be appropriately blended. The inorganic filler is one that easily creates irregularities in the chemical roughening process and improves adhesiveness. For example, finely powdered silica, aluminum hydroxide, zirconium silicate, silica, calcium carbonate, talc, etc. can be used.

Each component of the above adhesive is kneaded and mixed in an organic solvent to form a solution mixture. As the organic solvent used at this time, one or more of toluene, methyl ethyl ketone, xylene, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether acetate, or ethyl acetate can be used.

The insulating substrate on which the adhesive according to the present invention is used is not particularly limited, and may include phenolic resin-based or epoxy resin-based resin laminates, substrates made of inorganic or organic composites, etc. is used.

[0029] As a method of applying the adhesive to the insulating base material, a roll coating method, a curtain coating method, a dipping method, or a method of laminating a dry film adhesive and the insulating base material can be used. The thickness of the adhesive coating is approximately 10 to 50 μm.

After applying the adhesive to the insulating substrate, the adhesive is cured by ultraviolet irradiation. The amount of UV irradiation at this time is
It is in the range of 0.3 to 5 J/cm2. 0.3J/cm
If it is less than 2, the adhesive will not be completely cured and the
2 or more, the adhesive coating changes color to yellowish brown, which is not preferable. The amount of UV irradiation is adjusted by the lamp wattage, conveyor speed, or lamp irradiation distance.

[0031] When depositing electroless plating, the surface of the adhesive is chemically roughened to give it a shape suitable for adhesion.

As the treatment liquid used for chemical roughening, chromic acid-sulfuric acid, chromic acid-sulfuric acid-sodium fluoride, hydrofluoroboric acid-dichromic acid, etc. can be used. As the electroless plating bath, one that can form a general copper plating film is used.

[0033] Holes for mounting electronic components and holes for conduction in the wiring board are made using a punch press or an NC drill machine.

The pattern is formed by screen printing a plating resist or by curing a photomask with ultraviolet rays and developing it.

These plating resists are formed before or after the chemical roughening process.

[0036]

[Operation] Ordinary adhesives for additive wiring boards use acrylonitrile butadiene rubber as a main component, which has excellent adhesion to deposited copper plating.

[0037] This acrylonitrile butadiene rubber is
Since it does not have a reactive group that can be cured by ultraviolet irradiation, a method of crosslinking by blending a phenol resin has usually been used.

Therefore, in order to cure the adhesive, 160
This requires more than one hour at a temperature of .degree. C. or higher, which is not desirable in terms of manufacturing cost or mechanical properties of the substrate.

Furthermore, ordinary acrylonitrile butadiene rubber is unfavorable in terms of electrical corrosion resistance because it contains a large amount of ionic impurities that are mixed in during the manufacturing process.

In the present invention, glycidyl methacrylate is added to acrylonitrile butadiene rubber, and at the same time, ionic impurities are reduced, and at the same time, an epoxy resin, a phenol resin, and a photoinitiator are blended.

[0041] As a result, it is possible to provide an adhesive for additive printed wiring boards which is cured by ultraviolet rays at low temperatures and in a short time, and at the same time has excellent electrolytic corrosion resistance.

[0042]

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

Example 1 [Composition] High purity acrylonitrile butadiene rubber containing glycidyl methacrylate (glycidyl methacrylate content 6% by weight, total amount of ionic impurities 12p)
pm, Nippon Zeon Co., Ltd.)...30 parts by weight Alkylphenol resin Hytanol 2400 (
Hitachi Chemical Co., Ltd. product name)
...10 parts by weight Epoxy resin UVR-6400 (trade name manufactured by Union Carbide)...
・・・・・・・・・45 parts by weight Photoinitiator UVI-6
970 (Triphenylsulfone hexafluoroantimonate, trade name manufactured by Union Carbide) 1 part by weight
Plating catalyst Cat#11 (product name manufactured by Hitachi Chemical Co., Ltd.)...
......4 parts by weight Filler Micropax 20A (product name manufactured by Hakusui Chemical Co., Ltd.)...
......10 parts by weight of these materials were dissolved in MEK solvent using a laikai machine and a stirrer,
An adhesive solution having a solid content of 30% by weight was prepared. This adhesive solution was applied onto a release-treated PET film using a roll coater and dried to give an adhesive film thickness of about 30 μm.

[0044] This adhesive-coated film was used as a glass epoxy resin laminate (manufactured by Hitachi Chemical Co., Ltd., trade name LE-16).
Heat and pressure lamination was performed on both sides of 8).

[0045] Next, ultraviolet rays were irradiated at 1 J/cm2 to obtain an adhesive-coated insulating substrate. A plating photoresist SR-3000 (trade name, manufactured by Hitachi Chemical Co., Ltd.) was laminated onto this substrate, and a comb for evaluating electrolytic corrosion resistance with line/space of 0.2 mm/0.2 mm was formed by UV irradiation and solvent development. A mold pattern and a test pattern consisting of a 10 mm line width and a 25 mm square for measuring peel strength and soldering heat resistance were prepared.

Next, chromic acid solution (55 g of CrO3,
The adhesive surface of the patterned portion was selectively roughened by immersing it in 220 ml of concentrated sulfuric acid diluted with water to make a total volume of 1 liter at 40° C. for 15 minutes, followed by washing with water and neutralization.

Next, electroless copper plating solution (Hitachi Chemical Co., Ltd.
Co., Ltd. (trade name: CC-41) to deposit 35 μm of copper plating, and then annealing was performed at 160° C. for 60 minutes to obtain a test pattern for an additive printed wiring board.

[0048] In the electrolytic corrosion resistance test, DC 100V was continuously applied between the circuits under heating and humidification at 85°C and 85% RH, and the insulation resistance was examined at predetermined intervals. In addition, in order to prevent water droplets from directly adhering between the circuits under the above test environment, a solder resist was printed on the entire surface in advance to protect the film formation before the test.

Peel strength and soldering heat resistance are determined according to JIS-C
-6481. Table 1 shows the results of these tests.

Example 2 [Composition] High purity acrylonitrile butadiene rubber containing glycidyl methacrylate (glycidyl methacrylate content: 8% by weight, total amount of ionic impurities: 10 ppm, manufactured by Nippon Zeon Co., Ltd.)...40 parts by weight
Alkylphenol resin Hytanol 2400
(Product name manufactured by Hitachi Chemical Co., Ltd.)
...5 parts by weight Epoxy resin UVR-640
0 (trade name manufactured by Union Carbide Company)・1 part by weight Photoinitiator UVI-6970 (triphenylsulfone hexafluoroantimonate, trade name manufactured by Union Carbide Company)・・・・・・・・・・・・・・・1 part by weight
Plating catalyst Cat #11 (trade name manufactured by Hitachi Chemical Co., Ltd.)...4 parts by weight Filler Hygilite H-42
M (trade name manufactured by Showa Denko K.K.): 10 parts by weight An adhesive solution was prepared from a composition consisting of these in the same manner as described in Example 1, and a test pattern for an additive printed wiring board was obtained. The test results are shown in Table 1.

Example 3 [Composition] High purity acrylonitrile butadiene rubber containing glycidyl methacrylate (glycidyl methacrylate content 6% by weight, total ionic impurities 12 ppm, manufactured by Nippon Zeon Co., Ltd.)...40 parts by weight
Alkylphenol resin Hytanol 2400
(Product name manufactured by Hitachi Chemical Co., Ltd.)
...5 parts by weight Epoxy resin DEN-438 (
Down Chemical Co., Ltd. (trade name): 30 parts by weight Photoinitiator UVI-6950 (triphenylsulfone hexafluorophore, Union Carbide Co., Ltd. trade name): 1 part by weight Plating catalyst Cat #11 (trade name manufactured by Hitachi Chemical Co., Ltd.)・
...4 parts by weight Filler Micropax 20A (trade name manufactured by Hakusui Kagaku Co., Ltd.) ...15 parts by weight An adhesive solution was prepared from a composition consisting of these in the same manner as described in Example 1, and additive A test pattern of printed wiring board was obtained. The test results are shown in Table 1.

Comparative Example 1 [Composition] Non-methacrylic acid glycidyl acrylonitrile butadiene rubber Nipol 1042 (total ionic impurities 150 ppm, manufactured by Nippon Zeon Co., Ltd., trade name) 40 weight Part Alkylphenol resin Hytanol 2400
(Product name manufactured by Hitachi Chemical Co., Ltd.)
...20 parts by weight Epoxy resin Epicoat 1
001 (trade name manufactured by Yuka Shell Co., Ltd.)...20 parts by weight
Epoxy curing agent Imidazole 2EMz (trade name manufactured by Shikoku Kasei Co., Ltd.) - 0.1 part by weight Plating catalyst Cat #11 (trade name manufactured by Hitachi Chemical Co., Ltd.) - 5 parts by weight Filler Micropax 20A (white water Chemical company product name)...
...15 parts by weight of the composition was laminated onto an insulating base material in the same manner as in Example 1. Then 1
The adhesive was cured at 70° C. for 1 hour to produce an adhesive-attached insulating substrate. Example 1 Using this insulating substrate with adhesive
A test pattern was obtained in the same manner. The test results are shown in Table 1.

[0053]

[Table 1]

[0054]

[Effects of the Invention] As explained above, the adhesive composition of the present invention provides an adhesive for additive printed wiring boards that can be cured at low temperatures and in a short time by ultraviolet irradiation, and has excellent electrical corrosion resistance. be able to.

Claims (3)

[Claims] 1. In an additive printed wiring board in which a necessary circuit pattern is formed by electroless plating, an adhesive consisting of the following components is used. A. High purity acrylonitrile butadiene rubber having glycidyl methacrylate in the molecule and having a metal ionic impurity content of 50 ppm or less B. Alkylphenol resin C. Epoxy resin D. Cation-reactive photoinitiator that simultaneously crosslinks glycidyl methacrylate and epoxy resin in high-purity acrylonitrile butadiene rubber 2. Of the solid content excluding organic solvents, 10 to 60 parts by weight of high purity acrylonitrile butadiene rubber containing glycidyl methacrylate, 2 to 20 parts by weight of alkylphenol resin, and 20 to 70 parts by weight of epoxy resin. 2. The additive method printed wiring board adhesive according to claim 1, wherein the cationic reactive photoinitiator that simultaneously crosslinks glycidyl methacrylate and the epoxy resin in the high purity acrylonitrile butadiene rubber is in the range of 0.1 to 5 parts by weight. agent. 3. The additive method printed wiring board adhesive according to claim 1, wherein a cationic compound of triphenylsulfonium salt is used as a cation-reactive photoinitiator for simultaneously crosslinking glycidyl methacrylate and an epoxy resin.