Primer composition for electroless plating, laminate, and method for manufacturing the same.

Abstract

To provide a primer composition for electroless plating that can give a primer layer having sufficient coating strength without compromising the reactivity with electroless plating liquid.SOLUTION: A primer composition for electroless plating according to the present invention includes a phenoxy resin (A), and 25-65 pts.mass of a melamine resin (B) with respect to 100 pts.mass of the phenoxy resin (A).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a primer composition for electroless plating, a laminate, and a method for producing the same.

Background Art

[0002] Techniques for forming metal plating on an insulating substrate such as a resin substrate are used in the production of conductive films for electromagnetic shielding, decorative plating for imparting design, and electronic components such as integrated circuits and resistors. In particular, when manufacturing a printed wiring board used in electronic devices, a technique for forming plating is used when forming a conductive wiring pattern on an insulating substrate.

[0003] At that time, in order to improve the adhesion between the insulating substrate and the plating layer, it has been studied to impart an anchor effect by performing etching (roughening) to form fine irregularities on the surface of the insulating substrate. However, this etching not only complicates the process but also has a problem that transmission loss tends to increase due to the skin effect in high-frequency compatible devices for 5G.

[0004] On the other hand, methods for adhering an insulating substrate and a plating layer without performing etching have been studied. For example, a method is known in which a primer layer containing an electroless plating catalyst is formed on the surface of an insulating substrate and then a plating layer is formed (see Patent Document 1).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The formation of a plating layer on the surface of an insulating substrate is usually carried out by first forming a primer layer on the surface of the insulating substrate, and then bringing the primer layer into contact with an electroless plating solution or the like. These processes are usually performed roll-to-roll. However, if the coating strength of the primer layer is insufficient, the surface of the primer layer tends to become uneven, and the primer layer may peel off from the insulating substrate (causing delamination), or the surface of the primer layer may be scratched due to friction with the roll. Therefore, it is desirable to increase the coating strength of the primer layer. It is also desirable to increase the coating strength of the primer layer described in Patent Document 1 even further.

[0007] However, if the strength of the primer layer is increased too much, the surface becomes too hard, reducing its reactivity with the electroless plating solution and making it impossible to form a uniform plating layer. Furthermore, if the strength of the primer layer is increased too much, the adhesion to the insulating substrate may also be impaired.

[0008] This invention has been made in view of these circumstances, and aims to provide a primer composition for electroless plating, a laminate, and a method for manufacturing it that can provide a primer layer having sufficient coating strength without reducing reactivity or adhesion to the electroless plating solution. [Means for solving the problem]

[0009] The electroless plating primer composition of the present invention comprises a phenoxy resin (A) and 25 to 65 parts by mass of melamine resin (B) per 100 parts by mass of the phenoxy resin (A).

[0010] The laminate of the present invention comprises an insulating substrate, a primer layer disposed on the insulating substrate and containing a cured product of the electroless plating primer composition of the present invention, and a metal plating layer disposed on the primer layer.

[0011] The present invention provides a method for manufacturing a laminate, comprising the steps of: applying the electroless plating primer composition of the present invention to the surface of an insulating substrate, then drying and curing it to form a primer layer; and forming a metal plating layer on the primer layer by electroless plating. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a primer composition for electroless plating, a laminate, and a method for manufacturing it that can impart a primer layer having sufficient coating strength without reducing reactivity with the electroless plating solution. [Modes for carrying out the invention]

[0013] The inventors investigated the composition of a primer composition that can cure well in a short time and impart a cured product with high coating strength, and found that a combination of phenoxy resin (A) and melamine resin (B) is effective. Furthermore, they found that by adjusting the content of melamine resin (B) to a predetermined range, good reactivity and adhesion with electroless plating solutions can also be maintained.

[0014] The reason for this is not clear, but it is speculated that the following occurs: Phenoxy resin (A) not only has a tough structure but also contains many hydroxyl groups in its molecule. Therefore, the hydroxyl groups of phenoxy resin (A) can react with the methylol groups of melamine resin (B), etc., to form a high-density crosslinked structure, resulting in a cured product with high surface hardness. On the other hand, if the amount of melamine resin (B) is too high, the surface hardness of the cured product becomes too high, making it difficult for the palladium catalyst, which acts as a reaction nucleus with the electroless plating solution, to be exposed on the surface, or making it difficult to stably retain the palladium catalyst when it is applied to the cured product of the primer composition, thus impairing the reactivity of the electroless plating solution. In addition, if the cured product becomes too hard, its adhesiveness is also easily impaired. In contrast, by appropriately adjusting the content of melamine resin (B), a cured product with appropriate strength can be obtained, thereby suppressing the above-mentioned problems. Such a primer composition is suitable for the process of forming a plating film using roll-to-roll.

[0015] Furthermore, by adding epoxy resin (C) and resolphenol resin (D) to the above components, the adhesion of the cured primer composition can be further enhanced. Specifically, the methylol hydroxyl groups or phenolic hydroxyl groups of resolphenol resin (D) react with the epoxy groups of epoxy resin (C), not only facilitating the curing of epoxy resin (C), but also generating hydroxyl groups during the reaction process (ring-opening reaction). This is thought to effectively improve adhesion to the insulating substrate.

[0016] The composition of the primer composition of the present invention will be described in detail below.

[0017] 1. Primer composition The primer composition of the present invention comprises a phenoxy resin (A) and a melamine resin (B).

[0018] 1-1. Phenoxy resin (A) Phenoxy resin (A) is a polymer having a polyhydroxypolyether structure obtained by polyaddition reaction of polyfunctional phenols and polyfunctional glycidyl ethers (preferably bisphenols and epichlorohydrin).

[0019] The weight-average molecular weight (Mw) of phenoxy resin (A) is typically 10,000 to 200,000, preferably 20,000 to 100,000, and more preferably 30,000 to 80,000. When the Mw of phenoxy resin (A) is above a certain level, it is easier to obtain a cured primer composition with high coating strength, and when it is below a certain level, the viscosity of the primer composition does not increase excessively, and handling is not easily impaired. The Mw of phenoxy resin (A) can be determined by performing gel permeation chromatography (GPC) using tetrahydrofuran (THF) as the solvent and expressing it as a value equivalent to standard polystyrene.

[0020] The secondary hydroxyl equivalent of the phenoxy resin (A) is not particularly limited, but is preferably 240 g / eq or more, more preferably 250 to 290 g / eq. When the secondary hydroxyl equivalent of the phenoxy resin (A) is within the above range, since it contains a large amount of hydroxyl groups, it is not only easier to react with the melamine resin (B), but also easier to further enhance the adhesion to the insulating base material.

[0021] The phenoxy resin (A) may have an epoxy group in the molecule. The epoxy equivalent of the phenoxy resin (A) is preferably 5000 g / eq or more, more preferably 6500 g / eq or more. The epoxy equivalent can be measured according to JIS K7236.

[0022] Examples of the phenoxy resin (A) include bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, bisphenol S type phenoxy resin, copolymer type phenoxy resin of bisphenol A type and bisphenol F type (bisphenol AF type phenoxy resin), bisphenol E type phenoxy resin, naphthalene type phenoxy resin, novolac type phenoxy resin, biphenyl type phenoxy resin, cyclopentadiene type phenoxy resin, etc. The phenoxy resin (A) can be used alone or in combination of two or more.

[0023] Examples of commercially available products of the phenoxy resin (A) include jER4250 (manufactured by Mitsubishi Chemical Corporation, bisphenol A type phenoxy resin / bisphenol F type phenoxy resin mixed type, epoxy equivalent 7500 - 8900 g / eq), YX7200B35 (manufactured by Mitsubishi Chemical Corporation, phenoxy resin containing biphenyl skeleton and cyclohexane skeleton, epoxy equivalent: 9000 g / eq), 1256 (manufactured by Mitsubishi Chemical Corporation, bisphenol A skeleton-containing phenoxy resin, epoxy equivalent: 7,800 g / eq), YX6954BH35 (manufactured by Mitsubishi Chemical Corporation, bisphenol acetophenone skeleton-containing phenoxy resin, epoxy equivalent: 13000 g / eq), etc.

[0024] Since the phenoxy resin (A) contains many hydroxyl groups in the molecule, it can react well (curing reaction) with the melamine resin (B). As a result, the cured product of the primer composition containing these has high coating film strength.

[0025] The content of the phenoxy resin (A) is preferably 20 to 65% by mass, more preferably 30 to 60% by mass, based on the non-volatile components of the primer composition. When the content of the phenoxy resin (A) is above a certain level, it can react sufficiently with the melamine resin (B) for curing, so the cured product of the primer composition can have high coating film strength. In this specification, the non-volatile components refer to the components constituting the composition other than the solvent.

[0026] 1-2. Melamine resin (B) The melamine resin (B) can function as a curing agent that reacts with the hydroxyl groups contained in the phenoxy resin (A) to cure the phenoxy resin (A).

[0027] Such a melamine resin (B) can be melamine, a methylolated melamine derivative obtained by condensing melamine and formaldehyde, a compound obtained by reacting methylolated melamine with a lower alcohol to partially or completely etherify it, or a mixture thereof. The melamine resin (B) may be either a monomer or a condensate composed of dimers or higher multimers.

[0028] Examples of the lower alcohol used for etherification include methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, and isobutanol. That is, the melamine resin (B) has functional groups such as alkoxymethyl groups such as imino groups, methylol groups, methoxymethyl groups, and butoxymethyl groups. Specifically, it includes imino group type methylated melamine resins, methylol group type melamine resins, methylol group type methylated melamine resins, and fully alkylated type methylated melamine resins. Among them, methylolated melamine resins are preferred.

[0029] Examples of commercially available melamine resin (B) include Nikalac MW-100LM, Nikalac MW-30, Nikalac MW-30M, Nikalac MW-22, Nikalac MW-22A, Nikalac MS-11, and Nikalac MX-750 from Sanwa Chemical Co., Ltd.; Cymel 300, Cymel 301, and Cymel 350 from Mitsui Cyanamid Co., Ltd.; and U-VAN 703 from Mitsui Chemicals, Inc. Melamine resin (B) may be used alone or in combination of two or more types.

[0030] In addition to the self-condensation of melamine resin (B), the reaction (curing reaction) between hydroxyl groups contained in phenoxy resin (A) and melamine resin (B) proceeds easily, thus improving the coating strength of the cured product of the primer composition.

[0031] The content of melamine resin (B) is 25 to 65 parts by mass per 100 parts by mass of phenoxy resin (A). When the content of melamine resin (B) is 25 parts by mass or more per 100 parts by mass of phenoxy resin (A), the phenoxy resin (A) and melamine resin (B) can be sufficiently cured, so the cured product of the primer composition has high coating strength and excellent abrasion resistance. When the content of melamine resin (B) is 65 parts by mass or less per 100 parts by mass of phenoxy resin (A), the cured product of the primer composition does not become too hard and can have appropriate flexibility. As a result, the reactivity with the electroless plating solution in the subsequent process is less likely to decrease, and the adhesion is less likely to be impaired. From a similar viewpoint, the content of melamine resin (B) is preferably 30 to 60 parts by mass, and more preferably 35 to 55 parts by mass, per 100 parts by mass of phenoxy resin (A).

[0032] 1-3. Other ingredients The primer composition of the present invention may further contain other components as needed. For example, the primer composition of the present invention preferably further contains an epoxy resin (C) and a resolphenol resin (D) in order to further enhance adhesive strength and adhesive reliability.

[0033] 1-3-1. Epoxy resin (C) The epoxy resin (C) is a resin having epoxy groups, excluding the phenoxy resin (A) mentioned above. The epoxy resin (C) preferably includes a bifunctional epoxy resin having two or more epoxy groups in its molecule, and more preferably includes a polyfunctional epoxy resin having three or more epoxy groups in its molecule. A polyfunctional epoxy resin having three or more epoxy groups in its molecule has many reaction sites with, for example, resolphenol resin (D), resulting in many hydroxyl groups being generated by ring-opening of the epoxy groups, thus particularly enhancing adhesion. The epoxy resin (C) may be used alone or in combination of two or more types.

[0034] Examples of epoxy resins (C) include epoxy resins having aromatic rings (aromatic epoxy resins) such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol AF type epoxy resin, bixylenol type epoxy resin, trisphenol type epoxy resin, naphthol novolac type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, tert-butyl-catechol type epoxy resin, naphthalene type epoxy resin, anthracene type epoxy resin, biphenyl type epoxy resin, cyclopentadiene type epoxy resin, tetraphenylethane type epoxy resin, and aminophenol type epoxy resin; alicyclic epoxy resins such as cyclohexanedimethanol type epoxy resin; and aliphatic epoxy resins such as trimethylol type epoxy resin.

[0035] Among these, aromatic epoxy resins are preferred from the standpoint of making it easier to improve adhesive reliability. For example, polyfunctional aromatic epoxy resins having three or more epoxy groups in the molecule include naphthalene-type tetrafunctional epoxy resins, cresol novolac-type epoxy resins, phenol novolac-type epoxy resins, trisphenol-type epoxy resins, bisphenol A-type epoxy resins, bisphenol AF-type epoxy resins, and tetraphenylethane-type epoxy resins. Examples of commercially available products include "jER1031S" (tetraphenylethane-type epoxy resin) and "157S70" (bisphenol novolac-type epoxy resin).

[0036] The epoxy resin (C) may be a liquid epoxy resin or a solid epoxy resin. From the viewpoint of easily increasing the strength of the coating film, a solid epoxy resin is preferred. Note that "liquid" means that it is liquid at 20°C; "solid" means that it is solid at 20°C.

[0037] The epoxy equivalent of epoxy resin (C) is not particularly limited, but is preferably less than 5000 g / eq. On the other hand, the epoxy equivalent of phenoxy resin (A) is preferably 5000 g / eq or more. Thus, phenoxy resin (A), like epoxy resin (C), may have epoxy groups in its molecule, but in this specification, they can be distinguished by their epoxy equivalent.

[0038] The epoxy equivalent of epoxy resin (C) is preferably 50 to 3000 g / eq, more preferably 100 to 1000 g / eq, and even more preferably 140 to 300 g / eq, from the viewpoint of reactivity. When the epoxy equivalent is within the above range, sufficient curing is possible without impairing the coatability of the primer composition. The epoxy equivalent can be measured by the same method as described above.

[0039] The weight-average molecular weight (Mw) of epoxy resin (C) is not particularly limited, but is preferably 1000 or less. The Mw of epoxy resin (C) is the weight-average molecular weight on a standard polystyrene basis, measured by GPC, as described above.

[0040] 1-3-2. Resolephenol resin (D) The resolphenol resin (D) can function as a polyaddition-type epoxy resin curing agent for the epoxy resin (C). That is, at least one of the phenolic OH group and methylol group of the resolphenol resin (D) can undergo an addition reaction with the epoxy group of the epoxy resin (C). This can result in a primer composition with good adhesive reliability.

[0041] Examples of resolphenol resins (D) include phenol type, cresol type, alkyl type, bisphenol A type, or copolymers thereof. Examples of commercially available resolphenol resins (D) include Phenolite TD-447 (manufactured by DIC Corporation, cresol type).

[0042] The total amount of epoxy resin (C) and resolphenol resin (D) is preferably 25 to 85 parts by mass, more preferably 30 to 80 parts by mass, and even more preferably 35 to 65 parts by mass, per 100 parts by mass of phenoxy resin (A). When the above total amount is above a certain level, it is easier to further improve the adhesive strength and adhesive reliability of the cured product of the primer composition.

[0043] Furthermore, the total amount of epoxy resin (C) and resolphenol resin (D) may be set according to the content of melamine resin (B). For example, if the melamine resin (B) content is high, the total amount of epoxy resin (C) and resolphenol resin (D) may also be increased from the viewpoint of improving adhesion and adhesive reliability. That is, the content ratio of the total amount of epoxy resin (C) and resolphenol resin (D) to melamine resin (B) is, for example, 50 / 50 to 60 / 40. If the content ratio of melamine resin (B) is above a certain level, it is easier to further increase the coating strength of the cured product of the primer composition; if it is below a certain level, it is easier to further increase the adhesive strength and adhesive reliability of the cured product of the primer composition; and if the content ratio is below a certain level, the coating strength of the cured product is less likely to be impaired.

[0044] The content of resolphenol resin (D) is preferably 40 to 60% by mass relative to the total amount of epoxy resin (C) and resolphenol resin (D). When the content of resolphenol resin (D) is within the above range, the curing reaction of epoxy resin (C) and the reaction between epoxy resin (C) and phenoxy resin (A) are more easily promoted, which tends to increase the adhesive strength and adhesive reliability of the cured product.

[0045] 1-3-3. Palladium catalyst The primer composition of the present invention may further contain a palladium catalyst. The palladium catalyst is preferably in the form of palladium particles and can function as a nucleating agent for electroless plating. The palladium catalyst may be dispersed in a dispersant.

[0046] The average particle diameter of palladium particles is not particularly limited, but can be, for example, 2 to 10 nm. The average particle diameter of palladium particles can be calculated by measuring the diameters of any 10 particles using a transmission electron microscope and taking the number average of these measurements (as a number-based average diameter).

[0047] The palladium catalyst content is preferably 1 to 30% by mass, and more preferably 1 to 5% by mass, relative to the non-volatile components of the primer composition. When the palladium catalyst content is above a certain amount, the adhesion between the resulting primer layer and the electroless plating film is easily enhanced, while when it is below a certain amount, the coating properties and dispersion stability are less likely to be impaired.

[0048] 1-3-4. Solvent The primer composition of the present invention may further contain a solvent (dispersion medium) for dispersing the palladium catalyst. The solvent is preferably one that can disperse the palladium catalyst or its dispersion, and may be, for example, water or an aprotic polar solvent.

[0049] Examples of aprotic polar solvents include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and γ-butyrolactone.

[0050] In addition, it may contain alcohols such as methanol and ethanol; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; glycol ethers such as ethylene glycol monomethyl ether and ethylene glycol monobutyl ether; aromatic carboxylic acid esters such as methyl benzoate, ethyl benzoate, and methyl salicylate; aromatic hydrocarbons such as toluene and xylene; glycol ether esters such as methyl cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, methyl carbitol acetate, and butyl carbitol acetate; and alkanol esters such as ethyl acetate and butyl acetate.

[0051] 1-3-5. Silica particles When the primer composition of the present invention contains a palladium catalyst, it is preferable that the primer composition further contains silica particles. The silica particles may primarily have the function of enhancing the stability of the palladium catalyst.

[0052] As silica particles, in addition to untreated silica particles, hydrophilic silica particles and hydrophobic silica particles can be used. The shape of the silica particles is not limited and may be spherical silica or crushed silica.

[0053] Among silica particles, hydrophobic silica particles are preferred because they easily suppress aggregation between silica particles and further enhance the dispersion stability of the palladium catalyst. Hydrophobic silica particles are obtained by surface treatment of silica particles. As surface treatment agents for silica particles, for example, silane coupling agents such as β-ethyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane, or treatment agents such as silicone oil can be used. Examples of hydrophobic silica particles include organosilica sols such as methanol silica, IPA-ST, NPC-ST-30, MEK-ST, PMA-ST, and MIBK-ST manufactured by Nissan Chemical Industries, Ltd.

[0054] The average particle diameter of silica particles is preferably 10 to 100 nm, more preferably 10 to 50 nm. The average particle diameter can be measured by the cumulant method using a dynamic light scattering measuring instrument. Alternatively, it can be measured using a transmission electron microscope and calculated as the number-based average diameter.

[0055] The silica particle content is not particularly limited, but can be, for example, 1 to 30% by mass relative to the non-volatile components of the primer composition. This can further enhance the stability of the palladium catalyst.

[0056] 1-4. Manufacturing method The primer composition of the present invention can be prepared by any method, for example, by mixing the above components.

[0057] The palladium catalyst may be added in particulate form or in a dispersed state (as a dispersion) using a dispersant.

[0058] 2. Laminate The laminate of the present invention comprises an insulating substrate, a primer layer containing a cured product of the primer composition of the present invention, and a metal plating layer.

[0059] (Insulating substrate) The insulating substrate may be a resin substrate or an inorganic substrate such as ceramics or glass. Examples of materials that make up the resin substrate include polyester, (meth)acrylic resin, polycarbonate, polystyrene, polyvinyl chloride, polyamide, polyimide (e.g., MPI), polyetherimide, polyacetal, polyetheretherketone (PEEK), cyclic polyolefin (COC), polyolefin, polyphenylene sulfide (PPS), polysulfone, phenolic resin, liquid crystalline polymer (LCP), and fluororesin. Examples of ceramics that make up the inorganic substrate include alumina.

[0060] In particular, when the laminate is a printed circuit board, especially a printed circuit board used in high-frequency devices such as 5G, the insulating substrate is more preferably a low dielectric constant insulating substrate (low dielectric substrate). Examples of low dielectric substrate materials include low dielectric constant resins and glass such as polyimide (MPI), polyetheretherketone (PEEK), cyclic polyolefin (COC), polyphenylene sulfide (PPS), liquid crystalline polymer (LCP), and fluororesin, and polyphenylene sulfide (PPS) is preferred.

[0061] The thickness of the insulating substrate is not particularly limited, but can be, for example, 12.5 to 50 μm.

[0062] (Primer layer) The primer layer comprises a cured product of the primer composition of the present invention.

[0063] The thickness of the primer layer is not particularly limited, as long as it is sufficient to ensure adhesive strength between the metal plating layer and the insulating substrate, but it is preferable that it be thinner than the thickness of the metal plating layer. In particular, since the cured product of the primer composition of the present invention exhibits good adhesive strength, the thickness of the primer layer can be made sufficiently thin. Specifically, the thickness of the primer layer may be, for example, 0.05 to 0.5 μm.

[0064] (Metal plating layer) The metal plating layer is a layer obtained by bringing the surface of the primer layer into contact with an electroless plating solution, and contains metals such as copper, platinum, gold, silver, nickel, chromium, cobalt, and tin. The metal plating layer preferably contains a metal selected from the group consisting of copper, platinum, gold, silver, and nickel, and more preferably contains copper or an alloy thereof.

[0065] The thickness of the metal plating layer can be set appropriately depending on the application, but for example, when used in printed circuit boards, it may be 0.01 to 50 μm, preferably 0.1 to 10 μm, and more preferably 0.1 to 2 μm.

[0066] The metal plating layer may be patterned into a predetermined shape. The patterned metal plating layer can function, for example, as a wiring pattern on a printed circuit board.

[0067] The laminate of the present invention can be used in circuit formation substrates used in electronic circuits and integrated circuits, organic EL elements, organic transistors, flexible printed circuit boards, transparent electrodes used in RFID, touch panels, and electromagnetic shielding materials. In particular, it can be suitably used in applications requiring durability at high temperatures, and can be used in applications generally referred to as copper-clad laminates (CCL), such as flexible printed circuit boards (FPC), tape-bonded (TAB), chip-on-film (COF), and printed wiring boards (PWB).

[0068] 3. Method for manufacturing the laminate The laminate of the present invention can be obtained by 1) applying the primer composition of the present invention to the surface of an insulating substrate, then drying and curing it to form a primer layer, and 2) applying electroless plating to the surface of the primer layer to form a metal plating layer.

[0069] Regarding step 1) The primer composition of the present invention is applied to the surface of an insulating substrate.

[0070] The method for applying the primer composition is not particularly limited and can be carried out by methods such as gravure printing, flexographic printing, inkjet printing, dipping, spraying, spin coating, roll coating, reverse coating, and screen printing.

[0071] Next, the applied primer composition is dried and cured to obtain a primer layer.

[0072] Drying and curing can be carried out by heating. The heating temperature should be sufficient to allow the reaction between the phenoxy resin (A) and the melamine resin (B) in the primer composition to proceed sufficiently, for example, 60 to 400°C, preferably 80 to 150°C. The heating time depends on the heating temperature, but for example, it can be about 0.1 to 60 minutes, preferably 10 to 30 minutes.

[0073] Regarding step 2) Next, the surface of the primer layer on the insulating substrate is brought into contact with the electroless plating solution to form an electroless plating film (metal plating layer).

[0074] From the viewpoint of efficiently performing electroless plating, it is preferable that a palladium catalyst be present on the surface of the primer layer. As described above, the palladium catalyst may be included in the primer composition beforehand, or it may be further applied to the surface of the primer layer by contacting it with a solution containing the palladium catalyst. From the viewpoint of effectively increasing reactivity with the electroless plating solution, it is preferable that the palladium catalyst be included in the primer composition beforehand.

[0075] The electroless plating solution may contain the above-mentioned metal, a reducing agent, and water and / or a water-soluble organic solvent. The conditions for electroless plating can be set according to the composition of the electroless plating solution. For example, the temperature of the electroless copper plating bath can usually be around 25 to 45°C. The processing time depends on the application, but for example, when forming a metal plating layer with a thickness of about 0.3 to 0.4 μm, it can be about 10 to 20 minutes.

[0076] The metal plating layer may be formed in a patterned manner (full additive method) or thinly formed over the entire surface of the primer layer (semi-additive method).

[0077] For example, when forming a patterned metal plating layer, a plating resist corresponding to the desired pattern is formed on the surface of a primer layer, and the areas where the plating resist is not formed are electrolessly plated to form the metal plating layer. Subsequently, the plating resist is dissolved and removed with a chemical solution to obtain the patterned metal plating layer (desired conductive pattern) (fully additive method).

[0078] Alternatively, if a thin metal plating layer is formed over the entire surface of the primer layer, a second metal plating layer may be further formed in a pattern on the metal plating layer in step 3) described later (semi-additive method).

[0079] Regarding step 3) As described above, a thin metal plating layer (seed layer) formed by electroless plating over the entire surface of the primer layer may be formed on the surface of the seed layer, a plating resist corresponding to the desired pattern may be formed, and the areas where the plating resist is not formed may be electroplated to further form a second metal plating layer. Subsequently, the plating resist can be dissolved and removed with a chemical solution, and the unnecessary parts can be further etched to obtain a metal plating layer formed in a pattern (desired conductive pattern).

[0080] Thus, printed circuit boards as laminates can be manufactured using semi-additive or fully additive methods. This allows for the formation of fine-pitch wiring patterns.

[0081] These processes are typically carried out using a roll-to-roll method, as described above. The primer composition of the present invention can be sufficiently cured in a relatively short time even in such a roll-to-roll manufacturing process (step 1 above). This allows for the formation of a primer layer with sufficient coating strength, resistance to scratches caused by friction with the rolls, and excellent abrasion resistance. Furthermore, the primer layer has neither excessive coating strength nor excessive flexibility, resulting in excellent reactivity when in contact with an electroless plating solution (step 2 above). This enables the formation of a uniform metal plating layer.

[0082] Thus, by using the primer composition of the present invention, good adhesion between the insulating substrate and the metal plating layer can be achieved without etching the surface of the insulating substrate, thus minimizing the occurrence of the skin effect. Therefore, the laminate of the present invention can be suitably used in printed wiring boards (PWBs) used in high-frequency devices. [Examples]

[0083] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited in any way thereto.

[0084] 1. Materials of the primer composition <Material> (1) Base resin • jER4250 (manufactured by Mitsubishi Chemical Corporation, mixed type of bisphenol A phenoxy resin / bisphenol F phenoxy resin, secondary hydroxyl group equivalent: 270 g / eq, epoxy equivalent: 7500-8900 g / eq, Mw: 60,000) • Teisaresin SG-80H (manufactured by Nagase ChemteX Corporation, acrylic acid ester / glycidyl methacrylate / acrylonitrile copolymer, epoxy equivalent 9100 g / eq, Mw: 350,000, Tg: 11℃) • Urethane-modified polyester copolymer (manufactured by Toyobo Co., Ltd., Byron UR-3200)

[0085] (2) Melamine resin • U-VAN 703 (manufactured by Mitsui Chemicals, melamine resin)

[0086] (3) Epoxy resin jER1031S (manufactured by Mitsubishi Chemical Corporation, tetraphenylethane type epoxy resin, epoxy equivalent 200g / eq, Mw: 800, solid)

[0087] (4) Resolephenol resin • Phenolite TD-447 (manufactured by DIC Corporation, resol-type phenolic curing agent, cresol-modified type)

[0088] (5) Palladium catalyst • Pd nanopowder (ML-001N manufactured by Iox Corporation, average particle size 5nm)

[0089] (6) Silica particles (catalyst stabilizer) • PMA-ST (manufactured by Nissan Chemical Corporation, silica particles, average particle size 12 nm)

[0090] 2. Preparation and evaluation of primer compositions [Examples 1-3, Comparative Examples 1-7] (Preparation of primer composition) A primer composition was prepared by mixing each component to achieve the composition shown in Table 1.

[0091] (Formation of primer layer) A 50 μm thick polyphenylene sulfide (PPS) film was prepared as an insulating substrate. The primer composition shown in Table 1 was applied to one side of this film using a bar coater, dried in a drying oven at 120°C for 5 minutes, and then cured by heating at 150°C for 30 minutes to form a 0.5 μm thick primer layer.

[0092] (Electroless plating) The film with the primer layer described above was immersed in an electroless plating bath and electroless plating was performed. The electroless copper plating bath used was Surupap PSY (Cu concentration 2-3 g / L) manufactured by Uemura Kogyo Co., Ltd. The electroless plating was performed at 35°C for 10 minutes to achieve a plating thickness of 0.2 μm.

[0093] [evaluation] The abrasion resistance of the primer layer, the reactivity of electroless Cu plating, and the adhesion of the plating during the lamination process were evaluated using the following methods.

[0094] (1) Scratch resistance A laminate of PPS film and primer layer was cut to a size of 200 mm x 30 mm to serve as a test specimen. The surface hardness of the primer layer of this test specimen was measured using a rubbing tester (JSPS-type friction tester) with Bencot (a registered trademark of Asahi Kasei Corporation). The abrasion resistance was then evaluated based on the following criteria. ○: No wounds are formed. △: 3 or fewer scratches ×: More than 3 scratches A score of △ or higher was considered good.

[0095] (2) Reactivity of electroless Cu plating The sheet resistance of the plated layer surface obtained by electroless plating was measured using a surface resistance meter. Then, the electroless Cu plating reactivity was evaluated based on the following criteria. ○: Sheet resistance value is 0.25Ω / □ or less △: Sheet resistance value greater than 0.25Ω / □ and less than or equal to 0.9Ω / □ ×: Sheet resistance value exceeds 0.9Ω / □ If the result is △ or higher, it is judged that the plating layer has been formed uniformly and the electroless plating reactivity is good.

[0096] (3) Adhesiveness (Initial adhesion) The adhesion of the plated layer of the resulting laminate was measured using a 90° peel test. Specifically, the test was performed at room temperature with a peel rate of 25 mm / min. An adhesive strength of 5 N / cm or higher was considered good.

[0097] (Adhesion reliability) The resulting laminate was stored in an atmospheric oven at 150°C for 168 hours. Subsequently, the adhesive strength of the plating layer was evaluated using the same method and criteria as described above.

[0098] The evaluation results of the primer compositions of Examples 1-3 and Comparative Examples 1-7 are shown in Table 1.

[0099] [Table 1]

[0100] As shown in Table 1, the primer compositions of Examples 1 to 3, which contain at least phenoxy resin (A) and a predetermined amount of melamine resin (B), can form a primer layer with high surface hardness and exhibit good reactivity with electroless plating solutions. Furthermore, they also exhibit good adhesion.

[0101] In contrast, the primer compositions of Comparative Examples 1 and 3, which contain little or no melamine resin (B), exhibit poor curing, resulting in low coating strength and low abrasion resistance. Furthermore, the palladium catalyst is less exposed, leading to low reactivity with the electroless plating solution. On the other hand, the primer composition of Comparative Example 2, which contains a high amount of melamine resin (B), exhibits high coating strength, but the coating is too hard, resulting in low reactivity with the electroless plating solution.

[0102] Furthermore, as shown in Table 1, the primer layers of Comparative Examples 4 and 5, which used acrylic resin as the base resin, exhibited low abrasion resistance and reactivity with electroless plating solutions; and the primer layers of Comparative Examples 6 and 7, which used polyester urethane resin, exhibited low adhesion. [Industrial applicability]

[0103] According to the present invention, it is possible to provide a primer composition for electroless plating that can impart a primer layer having sufficient coating strength without reducing reactivity with the electroless plating solution. Therefore, it is suitable for laminates used to obtain printed circuit boards, particularly printed circuit boards used in high-frequency devices such as 5G.

Claims

1. A phenoxy resin (A) with an epoxy equivalent of 5000 g / eq or more, The phenoxy resin (A) comprises 25 to 65 parts by mass of melamine resin (B) per 100 parts by mass of the phenoxy resin (A), Primer composition for electroless plating.

2. A phenoxy resin (A) and The phenoxy resin (A) is mixed with 25 to 65 parts by mass of melamine resin (B) per 100 parts by mass, Epoxy resin (C) and Includes resolphenol resin (D), A primer composition for electroless plating.

3. The total amount of the epoxy resin (C) and the resolphenol resin (D) is 30 to 80 parts by mass per 100 parts by mass of the phenoxy resin (A). The electroless plating primer composition according to claim 2.

4. The epoxy resin (C) is a polyfunctional epoxy resin having three or more epoxy groups in its molecule. The electroless plating primer composition according to claim 2 or 3.

5. The epoxy resin (C) is a solid epoxy resin. A primer composition for electroless plating according to any one of claims 2 to 4.

6. Phenoxy resin (A) and The phenoxy resin (A) is mixed with 25 to 65 parts by mass of melamine resin (B) per 100 parts by mass, Including a palladium catalyst, Primer composition for electroless plating.

7. Further containing silica particles, The electroless plating primer composition according to claim 6.

8. Insulating substrate and A primer layer disposed on the insulating substrate, comprising a cured product of the electroless plating primer composition according to any one of claims 1 to 7, A metal plating layer disposed on the primer layer and including, Laminated structure.

9. The insulating substrate includes a low dielectric constant resin selected from the group consisting of polyimide, polyetheretherketone, cyclic polyolefin, polyphenylene sulfide, liquid crystalline polymer, and fluororesin. The laminate according to claim 8.

10. A step of applying the electroless plating primer composition according to any one of claims 1 to 7 to the surface of an insulating substrate, and then drying and curing it to form a primer layer, The process of forming a metal plating layer on the primer layer by electroless plating. including, A method for manufacturing laminates.

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