Laminate for semi-additive process, printed wiring board, method for manufacturing laminate for semi-additive process, and method for manufacturing printed wiring board

Abstract

[Problem] To obtain a laminate for a semi-additive process in which, even with a step for forming an aperture in a substrate for a semi-additive process and forming a conductive seed layer as well as an additional conductive seed layer on the surface of the aperture, interconnects with a satisfactorily smooth and rectangular shape can be formed without retaining a metallic layer of the same type as the conductive layer of a pattern circuit on the conductive seed layer during circuit formation. [Solution] A laminate for a semi-additive process according to the present invention comprises: an insulating substrate; a first conductive seed layer with an aperture formed on at least one side of the insulating substrate; a second conductive seed layer formed on the inner surface of the aperture in the first conductive seed layer and electrically connected to the first conductive seed layer; and a cover layer covering the aperture, wherein the first conductive seed layer and the second conductive seed layer are formed from a metallic material, and the second conductive seed layer is formed from a different type of metallic material than the first conductive seed layer.

Description

Laminate for semi-additive process, printed wiring board, method for manufacturing laminate for semi-additive process, and method for manufacturing printed wiring board

[0001] The present invention relates to a planar laminate for semi-additive processes used to electrically connect both surfaces of a substrate, a printed wiring board, a method for manufacturing a laminate for semi-additive processes, and a method for manufacturing a printed wiring board.

[0002] Printed wiring boards are formed by forming a metal layer of a patterned circuit on the surface of an insulating substrate. In recent years, demands for smaller and lighter electronic products have led to demands for thinner printed wiring boards and finer circuit wiring. Conventionally, subtractive methods have been widely used to manufacture circuit wiring. This involves forming an etching resist of a patterned circuit shape on the surface of a copper layer formed on an insulating substrate, and then etching away the copper layer in areas where no circuit is needed to form copper wiring. However, the subtractive method tends to leave copper at the base of the wiring. As the distance between wiring lines becomes shorter due to increased density of the circuit wiring, problems such as short circuits and poor insulation reliability between wiring lines have been encountered. Furthermore, further etching to prevent short circuits or improve insulation reliability has been problematic, as the etching solution finds its way under the resist, causing side etching and resulting in a narrower wiring width. In particular, when regions with different wiring densities are mixed, there has been a problem in that fine wiring lines in low-density regions disappear as etching progresses. Furthermore, the surface of the wiring obtained by the subtractive method is not smooth, and the trapezoidal or triangular shape has a wide base toward the substrate, resulting in wiring with varying widths in the thickness direction, which poses problems as an electrical transmission path.

[0003] The semi-additive process has been proposed as a method for solving these problems and fabricating fine wiring circuits. In the semi-additive process, a conductive seed layer is formed on an insulating substrate, and a plating resist is formed on the seed layer in areas where no circuit is to be formed. After forming wiring sections by electrolytic plating through the conductive seed layer, the resist is peeled off, and the seed layer in the areas where no circuit is to be formed is removed to form fine wiring. This process deposits plating along the shape of the resist, making it possible to smooth the surface shape of the wiring and form a rectangular cross-section. Furthermore, it is possible to deposit wiring of the desired width regardless of the density of the pattern, making it suitable for forming fine wiring.

[0004] In the semi-additive process, a conductive seed layer is formed on an insulating substrate by electroless copper plating or electroless nickel plating using a palladium catalyst. In these methods, for example, when a build-up film is used, the substrate surface is roughened using a strong chemical such as permanganic acid, known as desmear roughening, to ensure adhesion between the film substrate and the copper plating film. The plating film is formed from the resulting voids, utilizing the anchor effect to ensure adhesion between the insulating substrate and the plating film. However, roughening the substrate surface makes it difficult to form fine wiring and also leads to problems such as deterioration of high-frequency transmission characteristics. For this reason, attempts have been made to reduce the degree of roughening, but there has been a problem that the necessary adhesion strength between the formed wiring and the substrate cannot be obtained when the roughening level is low.

[0005] Meanwhile, a technique for forming a conductive seed layer by electroless nickel plating on a polyimide film is also known. In this technique, the polyimide film is immersed in a strong alkali to open the imide rings in the surface layer, making the film surface hydrophilic, and at the same time, a water-permeable modified layer is formed. A palladium catalyst is then impregnated into the modified layer, and electroless nickel plating is performed to form a nickel seed layer (see, for example, Patent Document 1). In this technique, nickel plating is formed from within the modified layer on the outermost polyimide surface, thereby achieving adhesion strength. However, because the modified layer is in a state where the imide rings are opened, the surface layer of the film has a physically and chemically weak structure.

[0006] In contrast to this, a method of forming a conductive seed of nickel, titanium, or the like on an insulating substrate by sputtering is also known as a method of roughening the surface or of not forming a modified layer on the surface (see, for example, Patent Document 2). This method makes it possible to form a seed layer without roughening the substrate surface, but has problems such as the need to use an expensive vacuum device, requiring a large initial investment, limitations on the size and shape of the substrate, and a complicated process with low productivity.

[0007] As a method for solving the problems of the sputtering method, a method has been proposed in which a coating layer of a conductive ink containing metal particles is used as a conductive seed layer (see, for example, Patent Document 3). This technology discloses a technique in which a conductive ink in which metal particles having a particle diameter of 1 to 500 nm are dispersed is coated on an insulating substrate made of a film or sheet, and heat treatment is performed to fix the metal particles in the coated conductive ink as a metal layer on the insulating substrate, thereby forming a conductive seed layer, and further plating is performed on the conductive seed layer.

[0008] Patent Document 3 proposes pattern formation by a semi-additive method, and in the examples it describes that a substrate on which a conductive ink having copper particles dispersed therein is applied and heat-treated to form a copper conductive seed layer is used as a substrate for the semi-additive method, a photosensitive resist is formed on the conductive seed layer, exposure and development are carried out, and the pattern formation portion is thickened by electrolytic copper plating, and after peeling off the resist, the copper conductive seed layer is etched away. Also, in the case of printed wiring board formation by the semi-additive method that has been studied in the past, a substrate in which a thin copper foil or copper plating film is provided as a conductive seed on an insulating substrate is used as a substrate for the semi-additive method.

[0009] When the conductive seed layer and the conductive layer of the pattern circuit are formed from the same metal, as in the case of a combination of a copper conductive seed layer and a copper pattern circuit, it is known that when the conductive seed layer in the non-pattern forming area is removed, the conductive layer of the pattern circuit is also etched at the same time, resulting in the pattern circuit becoming narrower and thinner and increasing the surface roughness of the circuit conductive layer, which has been a problem that needs to be solved in the manufacture of high-density wiring and wiring for high-frequency transmission.

[0010] In response to these problems, Non-Patent Documents 1 and 2 invent a technology for forming a printed wiring board having a smooth circuit layer surface with good design reproducibility, in which a substrate having a conductive silver particle layer formed on the surface of an insulating substrate is used as a substrate for a semi-additive process, and in which thinning or thinning of the pattern circuit does not occur in the seed layer etching step.

[0011] International Publication No. 2009 / 004774 Japanese Patent Application Laid-Open No. 9-136378 Japanese Patent Application Laid-Open No. 2010-272837

[0012] Akira Murakawa, Norimasa Fukazawa, Wataru Fujikawa, Jun Shiraga: "Copper pattern formation technology using semi-additive method with silver nanoparticles as a base layer", Proceedings of the 28th Microelectronics Symposium, pp. 285-288, 2018. Akira Murakawa, Shota Shinbayashi, Norimasa Fukazawa, Wataru Fujikawa, Jun Shiraga: "Copper wiring formation using semi-additive method with silver as a seed layer", Proceedings of the 33rd Japan Institute of Electronics Packaging Spring Conference, 11B2-03, 2019.

[0013] The techniques of Non-Patent Documents 1 and 2 allow for circuit formation not only on one side but also on both sides, but when a process of forming holes in a semi-additive substrate having conductive silver particle layers on both sides of an insulating substrate and forming a conductive seed layer using a conductive material is carried out to connect the circuits on both sides, the conductive material is formed not only in the hole parts but also on the silver particle layer. If the conductive seed layer and the conductive layer of the pattern circuit are formed from the same metal, as described above, when the conductive seed layer in the non-pattern forming parts is removed, the conductive layer of the pattern circuit is also etched at the same time, which is known to result in the pattern circuit becoming narrower and thinner and the surface roughness of the circuit conductive layer increasing, and this has been a problem that needed to be solved in the manufacture of high-density wiring and wiring for high-frequency transmission.

[0014] The problem that the present invention aims to solve is to obtain a laminate for semi-additive processing that has a smooth surface and is capable of forming good rectangular wiring without retaining a metal layer of the same type as the conductive layer of the pattern circuit on the conductive seed layer during circuit formation, even after undergoing the steps of forming openings in a substrate for semi-additive processing and forming a conductive seed layer and a further conductive seed layer on the surface of the openings.

[0015] As a result of intensive research aimed at solving the above-mentioned problems, the inventors have discovered that a laminate for semi-additive processes comprising an insulating base material, a first conductive seed layer having an opening formed on at least one surface of the insulating base material, a second conductive seed layer formed on the inner surface of the opening of the first conductive seed layer and electrically connected to the first conductive seed layer, and a cover layer covering the opening, wherein the first conductive seed layer and the second conductive seed layer are made of different metal materials, can form wiring with a good rectangular shape during circuit formation. The present invention is based on this finding. Specifically, the gist of the present invention is as follows.

[0016] [1] A laminate for semi-additive processes comprising: an insulating substrate; a first conductive seed layer having an opening formed on at least one surface of the insulating substrate; a second conductive seed layer formed on the inner surface of the opening of the first conductive seed layer and electrically connected to the first conductive seed layer; and a cover layer covering the opening, wherein the first conductive seed layer and the second conductive seed layer are made of a metal material, and the second conductive seed layer is made of a metal material different from that of the first conductive seed layer. [2] The laminate for semi-additive processes according to [1], wherein the metal material constituting the first conductive seed layer is silver and the metal material constituting the second conductive seed layer is copper. [3] The laminate for semi-additive processes according to [1] or [2], wherein a primer layer is formed between the insulating substrate and the first conductive seed layer. [4] A printed wiring board using the laminate for semi-additive processes according to any one of [1] to [3]. [5] A method for producing the semi-additive construction laminate according to any one of [1] to [3], comprising the steps of: forming an opening in a substrate having a first conductive seed layer on at least one surface of the insulating substrate; forming a second conductive seed layer made of a metal different from that of the first conductive seed layer on the surface of the first conductive seed layer and the inner surface of the opening; and forming a cover layer to cover the opening. [6] A method for producing the semi-additive construction laminate according to [5], wherein the opening is formed in a state in which a protective layer is formed on the first conductive seed layer. [7] A method for producing the semi-additive construction laminate according to [6], wherein the protective layer is a peelable cover layer. [8] A method for producing the semi-additive construction laminate according to [5] or [6], wherein the protective layer is made of the same metal material as the metal material forming the second conductive seed layer.[9] A method for producing a printed wiring board using a semi-additive laminate obtained by the production method according to any one of [5] to [8], comprising the steps of: removing a portion of the second conductive seed layer on the first conductive seed layer of the semi-additive laminate to expose a surface of the first conductive seed layer; removing a cover layer covering the opening; forming a plating resist on a portion of the exposed first conductive seed layer; forming a pattern circuit section on the second conductive seed layer and the exposed first conductive seed layer by electroplating; peeling off the plating resist to expose the first conductive seed layer; and removing the exposed first conductive seed layer.

[10] The method for producing a printed wiring board according to [9], wherein the metal material constituting the first conductive seed layer is silver and the metal material constituting the second conductive seed layer is copper.

[11] The method for producing a printed wiring board according to [9] or

[10] , wherein a primer layer is provided between the insulating substrate and the first conductive seed layer.

[0017] According to the present invention, it is possible to provide a laminate for semi-additive processes, which has a smooth surface and is capable of forming wiring with a good rectangular shape, without retaining a metal layer of the same type as the conductive layer of the pattern circuit on the conductive seed layer during circuit formation, even after undergoing the steps of forming an opening in a substrate for semi-additive processes and forming a conductive seed layer on the surface of the opening, and a further conductive seed layer on the surface of the opening, and a printed wiring board using the same.

[0018] Fig. 1 is a cross-sectional view showing a manufacturing process for a printed wiring board according to the present invention. Fig. 2 is a cross-sectional view showing a manufacturing process for a printed wiring board according to the present invention. Fig. 3 is a cross-sectional view showing a manufacturing process for a printed wiring board according to the present invention. Fig. 4 is a cross-sectional view showing a manufacturing process for a printed wiring board according to the present invention.

[0019] The laminate for semi-additive manufacturing according to the present invention comprises an insulating substrate; a first conductive seed layer having an opening formed on at least one surface of the insulating substrate; a second conductive seed layer formed on the inner surface of the opening of the first conductive seed layer and electrically connected to the first conductive seed layer; and a cover layer covering the opening, wherein the first conductive seed layer and the second conductive seed layer are made of a metal material, and the second conductive seed layer is made of a metal material different from that of the first conductive seed layer.

[0020] Furthermore, the method for manufacturing a laminate for semi-additive processes according to the present invention includes the steps of: forming an opening in a substrate for semi-additive processes having a first conductive seed layer on at least one surface of an insulating substrate; forming a second conductive seed layer made of a metal different from that of the first conductive seed layer on the surface of the first conductive seed layer and on the inner surface of the opening; and forming a cover layer to cover the opening.

[0021] Furthermore, a method for manufacturing a printed wiring board using the semi-additive laminate of the present invention includes the steps of: forming an opening in a semi-additive substrate having a first conductive seed layer on at least one surface of an insulating substrate; forming a second conductive seed layer made of a metal different from that of the first conductive seed layer on the surface of the first conductive seed layer and on the inner surface of the opening; and forming a cover layer to cover the opening.

[0022] The method for manufacturing a printed wiring board using the semi-additive method laminate according to the present invention preferably further comprises the steps of removing a portion of the second conductive seed layer on the first conductive seed layer to expose the surface of the first conductive seed layer; removing the cover layer that covers the opening; forming a plating resist on a portion of the exposed first conductive seed layer; forming a pattern circuit portion on the second conductive seed layer and the exposed first conductive seed layer by electroplating; peeling off the plating resist to expose the first conductive seed layer; and removing the exposed first conductive seed layer.

[0023] Here, it is preferable that the metal material constituting the first conductive seed layer is silver and the metal material constituting the second conductive seed layer is copper. It is also preferable that a primer layer is provided between the insulating substrate and the first conductive seed layer. In the present invention, the term "opening" refers collectively to vias and through-holes. It is also preferable that the electrolytic plating method is an electrolytic copper plating method.

[0024] Examples of materials for the insulating substrate include polyimide resin, polyamideimide resin, polyamide resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, polycarbonate resin, acrylonitrile-butadiene-styrene (ABS) resin, polyarylate resin, polyacetal resin, acrylic resin such as poly(methyl meth)acrylate, polyvinylidene fluoride resin, polytetrafluoroethylene resin, polyvinyl chloride resin, polyvinylidene chloride resin, vinyl chloride resin graft copolymerized with acrylic resin, polyvinyl alcohol resin, polyethylene resin, polypropylene resin, urethane resin, cycloolefin resin, polystyrene, liquid crystal polymer (LCP), polyether ether ketone (PEEK) resin, polyphenylene sulfide (PPS), polyphenylene sulfone (PPSU), cellulose nanofiber, silicon, silicon carbide, gallium nitride, sapphire, ceramics, glass, diamond-like carbon (DLC), and alumina.

[0025] Furthermore, a resin substrate containing a thermosetting resin and an inorganic filler can also be suitably used as the insulating substrate. Examples of the thermosetting resin include epoxy resins, phenolic resins, unsaturated imide resins, cyanate resins, isocyanate resins, benzoxazine resins, oxetane resins, amino resins, unsaturated polyester resins, allyl resins, dicyclopentadiene resins, silicone resins, triazine resins, and melamine resins. Examples of the inorganic filler include silica, alumina, talc, mica, aluminum hydroxide, magnesium hydroxide, calcium carbonate, aluminum borate, and borosilicate glass. These thermosetting resins and inorganic fillers can be used alone or in combination of two or more. Substrates containing a thermoplastic resin and an inorganic filler can also be suitably used. The thermoplastic resin and inorganic filler can also be used alone or in combination of two or more.

[0026] The insulating substrate may be in the form of a planar flexible material, a rigid material, or a rigid-flexible material. More specifically, a commercially available material formed into a film, sheet, or plate shape may be used, or a material formed by applying and drying a solution, melt, or dispersion of the above-mentioned resin to a planar shape may be used. The insulating substrate may also be a substrate formed from a solution, melt, or dispersion of the above-mentioned resin on a conductive material such as metal, or a substrate formed by laminating the above-mentioned resin material on a printed wiring board on which a pattern circuit is formed.

[0027] When a printed wiring board is manufactured using the laminate for semi-additive processes of the present invention, the first conductive seed layer serves as a plating base layer when a pattern circuit layer that will become the pattern wiring described below is formed by a plating process.

[0028] The metal material constituting the first conductive seed layer can be various conductive substances such as gold, platinum, palladium, aluminum, tin, copper, nickel, titanium, indium, and iridium, as long as the plating process and etching process described below can be carried out without any problems. Among these, silver is preferably used because it has the highest electrical conductivity.

[0029] When silver is selected as the metal material constituting the first conductive seed layer, metal materials other than silver can be contained to the extent that the plating process described below can be carried out without problems. However, the proportion of metal materials other than silver is preferably 5 parts by mass or less, and more preferably 2 parts by mass or less, per 100 parts by mass of silver, as this can further improve the etching removability of the non-circuit forming parts described below.

[0030] The method for forming the first conductive seed layer on both sides of the planar insulating substrate is not particularly limited, and examples thereof include a method of applying a conductive particle dispersion to both sides of the insulating substrate. The method for applying the particle dispersion is not particularly limited as long as the first conductive seed layer can be successfully formed, and various application methods may be appropriately selected depending on the shape, size, and rigidity of the insulating substrate used. Specific application methods include, for example, gravure printing, offset printing, flexography, pad printing, gravure offset printing, letterpress printing, letterpress reversal printing, screen printing, microcontact printing, reverse printing, air doctor coating, blade coating, air knife coating, squeeze coating, impregnation coating, transfer roll coating, kiss coating, cast coating, spray coating, inkjet printing, die coating, spin coating, bar coating, and dip coating. In this case, the first conductive seed layer may be formed on both sides of the insulating base material at the same time, or may be formed on one side of the insulating base material and then formed on the other side.

[0031] The insulating substrate and the primer layer formed on the insulating substrate, which will be described later, may be surface-treated before applying the conductive particle dispersion liquid in order to improve the coatability of the conductive particle dispersion liquid and the adhesion of the pattern circuit layer formed in the plating process to the substrate. The surface treatment method for the insulating substrate is not particularly limited, and various methods may be appropriately selected, as long as the surface roughness does not increase, causing problems in fine-pitch pattern formation or signal transmission loss due to the rough surface. Examples of such surface treatment methods include UV treatment, gas-phase ozone treatment, liquid-phase ozone treatment, corona treatment, and plasma treatment. These surface treatment methods can be performed by one method or by a combination of two or more methods.

[0032] After the conductive particle dispersion liquid is applied onto the insulating substrate or the primer layer, the coating film is dried, whereby the solvent contained in the conductive particle dispersion liquid volatilizes, and the first conductive seed layer is formed on the insulating substrate or the primer layer.

[0033] The drying temperature and time may be appropriately selected depending on the heat resistance temperature of the substrate used and the type of solvent used in the conductive particle dispersion liquid described below, but are preferably in the range of 20 to 350° C. and the drying time in the range of 1 to 200 minutes. In addition, in order to form a first conductive seed layer having excellent adhesion on the substrate, the drying temperature is more preferably in the range of 0 to 250° C.

[0034] The insulating substrate on which the first conductive seed layer is formed, or the insulating substrate on which the primer layer is formed, may be further annealed, if necessary, after the drying process described above, for the purpose of reducing the electrical resistance of the first conductive seed layer or improving the adhesion between the insulating substrate or the primer layer and the first conductive seed layer. The annealing temperature and time can be appropriately selected depending on the heat resistance temperature of the substrate used, the required electrical resistance, productivity, etc., and may be performed in the range of 60 to 350°C for 1 minute to 2 weeks. Furthermore, in the temperature range of 60 to 180°C, a time of 1 minute to 2 weeks is preferred, and in the range of 180 to 350°C, a time of about 1 minute to 5 hours is preferred.

[0035] The drying may be performed with or without air blowing, and may be performed in the air, in an atmosphere substituted with an inert gas such as nitrogen or argon, under an air flow, or in a vacuum.

[0036] The coating film can be dried naturally at the coating site, or in a dryer such as a blower or a constant temperature dryer. Furthermore, when the insulating substrate is a roll film or roll sheet, drying and baking can be carried out by continuously moving the roll material in an installed non-heated or heated space following the coating process. Examples of heating methods for drying and baking include ovens, hot air drying furnaces, infrared drying furnaces, laser irradiation, microwaves, and light irradiation (flash irradiation devices). These heating methods can be used alone or in combination.

[0037] The thickness of the first conductive seed layer formed on the insulating substrate or the primer layer may be appropriately selected depending on the specifications and applications of the printed wiring board manufactured using the present invention. Specifically, the thickness is preferably in the range of 1 nm to 5 μm, and more preferably in the range of 1 nm to 3 μm. Furthermore, the thickness is more preferably in the range of 10 nm to 1 μm, because this facilitates the formation of a conductive layer in the plating step described below and the seed layer removal step by etching described below.

[0038] The details of the components constituting the first conductive seed layer can be confirmed using known and commonly used analytical techniques such as X-ray fluorescence, atomic absorption spectrometry, and ICP.

[0039] Furthermore, in the process of exposing a pattern circuit to actinic light on a resist layer (described later), in order to suppress reflection of actinic light from the first conductive seed layer, the first conductive seed layer may contain a light-absorbing pigment or dye such as graphite or carbon, a cyanine compound, a phthalocyanine compound, a dithiol metal complex, a naphthoquinone compound, a diimmonium compound, or an azo compound, as long as the first conductive seed layer can be formed, the electrolytic plating (described later) can be performed without problems, and the etching removability (described later) can be ensured. These pigments or dyes may be selected appropriately depending on the wavelength of the actinic light to be used. These pigments or dyes may be used alone or in combination of two or more. Furthermore, to incorporate these pigments or dyes into the first conductive seed layer, these pigments or dyes may be blended into the conductive particle dispersion (described later).

[0040] The conductive particle dispersion used to form the first conductive seed layer is a dispersion of conductive particles in a solvent. The shape of the conductive particles is not particularly limited as long as it satisfactorily forms the first conductive seed layer, and conductive particles of various shapes, such as spherical, lenticular, polyhedral, tabular, rod-like, and wire-like shapes, can be used. These conductive particles can be used alone or in combination of two or more different shapes.

[0041] When the conductive particles are spherical or polyhedral in shape, the average particle diameter is preferably in the range of 1 to 20,000 nm. Furthermore, when forming a fine pattern circuit, the uniformity of the first conductive seed layer is further improved, and the removability by the etching solution described below can also be further improved. Therefore, the average particle diameter is more preferably in the range of 1 to 200 nm, and even more preferably in the range of 1 to 50 nm. The "average particle diameter" of nanometer-sized particles is the volume average value measured by diluting the conductive particles with a good dispersion solvent and using a dynamic light scattering method. A "Nanotrac UPA-150" manufactured by Microtrac Corporation can be used for this measurement.

[0042] On the other hand, when the conductive particles have a shape such as a lens shape, a rod shape, or a wire shape, the minor axis thereof is preferably in the range of 1 to 200 nm, more preferably in the range of 2 to 100 nm, and even more preferably in the range of 5 to 50 nm.

[0043] The conductive particles are preferably composed mainly of silver particles, but a part of the silver constituting the conductive particles may be replaced with another metal, or a metal component other than silver may be mixed in, as long as this does not interfere with the plating step described below or does not impair the removability of the first conductive seed layer by an etching solution described below.

[0044] The metal to be substituted or mixed includes one or more metal elements selected from the group consisting of gold, platinum, palladium, ruthenium, aluminum, tin, copper, nickel, iron, cobalt, titanium, indium and iridium.

[0045] The ratio of the metal substituted or mixed with the silver particles is preferably 5 mass% or less in the silver particles, and more preferably 2 mass% or less from the viewpoint of the plating properties of the first conductive seed layer and removability by an etching solution.

[0046] The silver particle dispersion used to form the first conductive seed layer is prepared by dispersing silver particles in various solvents, and the particle size distribution of the silver particles in the dispersion may be monodisperse and uniform, or may be a mixture of particles having an average particle size within the above-mentioned range.

[0047] The solvent used for the dispersion of silver particles may be an aqueous medium or an organic solvent, such as distilled water, ion-exchanged water, pure water, ultrapure water, or a mixture of water and an organic solvent that is miscible with water.

[0048] Examples of the water-miscible organic solvent include alcohol solvents such as methanol, ethanol, n-propanol, isopropanol, ethyl carbitol, ethyl cellosolve, and butyl cellosolve; ketone solvents such as acetone and methyl ethyl ketone; alkylene glycol solvents such as ethylene glycol, diethylene glycol, and propylene glycol; polyalkylene glycol solvents such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; lactam solvents such as N-methyl-2-pyrrolidone, etc. When the organic solvent is used alone, examples of the organic solvent include alcohol compounds, ether compounds, ester compounds, and ketone compounds.

[0049] Examples of the alcohol solvent or ether solvent include methanol, ethanol, n-propanol, isopropyl alcohol, n-butanol, isobutyl alcohol, sec-butanol, tert-butanol, heptanol, hexanol, octanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol, stearyl alcohol, allyl alcohol, cyclohexanol, terpineol, terpineol, dihydroterpineol, 2-ethyl-1,3-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-dimethyl-2,3-dimethyl- ... , 4-butanediol, 2,3-butanediol, glycerin, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, propylene glycol monopropyl ether, dipropylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, and tripropylene glycol monobutyl ether.

[0050] Examples of the ketone solvent include acetone, cyclohexanone, methyl ethyl ketone, etc. Examples of the ester solvent include ethyl acetate, butyl acetate, 3-methoxybutyl acetate, 3-methoxy-3-methyl-butyl acetate, etc. Other organic solvents include hydrocarbon solvents such as toluene, particularly hydrocarbon solvents having 8 or more carbon atoms.

[0051] Examples of the hydrocarbon solvent having 8 or more carbon atoms include nonpolar solvents such as octane, nonane, decane, dodecane, tridecane, tetradecane, cyclooctane, xylene, mesitylene, ethylbenzene, dodecylbenzene, tetralin, and trimethylbenzenecyclohexane, which can be used in combination with other solvents as needed. Furthermore, mixed solvents such as mineral spirits and solvent naphtha can also be used in combination.

[0052] The solvent is not particularly limited as long as it stably disperses silver particles and allows the first conductive seed layer to be favorably formed on the insulating substrate or a primer layer formed on the insulating substrate, which will be described later. The solvents can be used alone or in combination of two or more.

[0053] The content of silver particles in the silver particle dispersion is 0.01 to 30 g / m when the amount of the first conductive seed layer formed on the insulating substrate is 0.01 to 30 g / m using the various coating methods described above. ２ The content of the coating agent may be suitably adjusted to fall within the range of 0.1 to 50% by mass, and the content may be adjusted to have a viscosity suitable for optimum coating suitability according to the various coating methods described above. However, the content is preferably in the range of 0.1 to 50% by mass, and more preferably in the range of 0.5 to 20% by mass.

[0054] The silver particle dispersion preferably maintains dispersion stability for a long period of time in the various solvents described above without causing aggregation, fusion, or precipitation of the silver particles, and preferably contains a dispersant for dispersing the silver particles in the various solvents described above. Such a dispersant is preferably a dispersant having a functional group that coordinates with the metal particles, such as a carboxyl group, an amino group, a cyano group, an acetoacetyl group, a phosphorus atom-containing group, a thiol group, a thiocyanato group, or a glycinato group.

[0055] The dispersant can be a commercially available or independently synthesized low-molecular-weight or high-molecular-weight dispersant. It can be appropriately selected depending on the intended purpose, such as the solvent for dispersing the metal particles and the type of insulating substrate to which the metal particle dispersion is applied. Examples of suitable dispersants include dodecanethiol, 1-octanethiol, triphenylphosphine, dodecylamine, polyethylene glycol, polyvinylpyrrolidone, polyethyleneimine, and polyvinylpyrrolidone; fatty acids such as myristic acid, octanoic acid, and stearic acid; and polycyclic hydrocarbon compounds having a carboxyl group such as cholic acid, glycyrrhizic acid, and apicic acid. When forming a first conductive seed layer on a primer layer (described below), it is preferable to use a compound having a reactive functional group [Y] capable of forming a bond with a reactive functional group [X] of the resin used in the primer layer (described below), since this improves the adhesion between the two layers.

[0056] Examples of compounds having a reactive functional group [Y] include compounds having an amino group, an amide group, an alkylolamide group, a carboxyl group, a carboxyl anhydride group, a carbonyl group, an acetoacetyl group, an epoxy group, an alicyclic epoxy group, an oxetane ring, a vinyl group, an allyl group, a (meth)acryloyl group, a (blocked) isocyanate group, an (alkoxy)silyl group, and the like, and silsesquioxane compounds. In particular, the reactive functional group [Y] is preferably a basic nitrogen atom-containing group, since this can further improve the adhesion between the primer layer and the first conductive seed layer. Examples of the basic nitrogen atom-containing group include an imino group, a primary amino group, and a secondary amino group.

[0057] The basic nitrogen atom-containing group may be present in one or more per dispersant molecule. By containing multiple basic nitrogen atoms in the dispersant, some of the basic nitrogen atom-containing groups contribute to the dispersion stability of the metal particles through interaction with the metal particles, and the remaining basic nitrogen atom-containing groups contribute to improving adhesion to the insulating substrate. Furthermore, when a resin having a reactive functional group [X] is used in the primer layer described below, the basic nitrogen atom-containing group in the dispersant can form a bond with this reactive functional group [X], which is preferable, thereby further improving adhesion.

[0058] The dispersant is preferably a polymer dispersant because it provides stability and coatability to the dispersion of silver particles and can form a first conductive seed layer that exhibits good adhesion on the insulating substrate. Preferred polymer dispersants include polyalkyleneimines such as polyethyleneimine and polypropyleneimine, and compounds in which polyoxyalkylene is added to the polyalkyleneimines.

[0059] The compound in which a polyoxyalkylene is added to the polyalkyleneimine may be a compound in which the polyethyleneimine and the polyoxyalkylene are bonded in a linear chain, or a compound in which the polyoxyalkylene is grafted onto a side chain of the main chain made of the polyethyleneimine.

[0060] Specific examples of the compound in which a polyoxyalkylene is added to the polyalkyleneimine include a block copolymer of polyethyleneimine and polyoxyethylene, a compound in which a polyoxyethylene structure is introduced by addition reaction of ethylene oxide with some of the imino groups present in the main chain of polyethyleneimine, and a compound in which an amino group of a polyalkyleneimine, a hydroxyl group of a polyoxyethylene glycol, and an epoxy group of an epoxy resin are reacted with each other.

[0061] Commercially available polyalkyleneimines include "PAO2006W," "PAO306," "PAO318," and "PAO718" from the "Epomin (registered trademark) PAO series" manufactured by Nippon Shokubai Co., Ltd.

[0062] The number average molecular weight of the polyalkyleneimine is preferably in the range of 3,000 to 30,000.

[0063] The amount of the dispersant required to disperse the silver particles is preferably in the range of 0.01 to 50 parts by mass relative to 100 parts by mass of the silver particles. Furthermore, the amount is preferably in the range of 0.1 to 10 parts by mass relative to 100 parts by mass of the silver particles, since this allows a first conductive seed layer exhibiting good adhesion to be formed on the insulating substrate or on a primer layer described below. Furthermore, the amount is more preferably in the range of 0.1 to 5 parts by mass, since this allows for improved plating properties of the first conductive seed layer.

[0064] The method for producing the silver particle dispersion is not particularly limited, and various methods can be used for production. For example, silver particles produced using a gas phase method such as low-vacuum gas evaporation may be dispersed in a solvent, or a silver compound may be reduced in a liquid phase to directly prepare a silver particle dispersion. In both the gas phase and liquid phase methods, the solvent composition of the dispersion during production and the dispersion during coating can be changed as needed by solvent exchange or solvent addition. Of the gas phase and liquid phase methods, the liquid phase method is particularly preferred due to the stability of the dispersion and the simplicity of the production process. For example, the liquid phase method can be used to produce a silver particle dispersion by reducing silver ions in the presence of the polymer dispersant.

[0065] The dispersion of silver particles may further contain organic compounds such as surfactants, leveling agents, viscosity modifiers, film-forming aids, antifoaming agents, and preservatives, if necessary.

[0066] Examples of the surfactant include nonionic surfactants such as polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene styrylphenyl ether, polyoxyethylene sorbitol tetraoleate, and polyoxyethylene-polyoxypropylene copolymer; anionic surfactants such as fatty acid salts such as sodium oleate, alkyl sulfate ester salts, alkylbenzenesulfonates, alkyl sulfosuccinates, naphthalenesulfonates, polyoxyethylene alkyl sulfates, sodium alkanesulfonates, and sodium alkyldiphenylethersulfonates; and cationic surfactants such as alkylamine salts, alkyltrimethylammonium salts, and alkyldimethylbenzylammonium salts.

[0067] As the leveling agent, a general leveling agent can be used, and examples thereof include silicone-based compounds, acetylene diol-based compounds, and fluorine-based compounds.

[0068] As the viscosity modifier, a general thickener can be used, and examples thereof include acrylic polymers that can be thickened by adjusting the alkalinity, synthetic rubber latex, urethane resins that can be thickened by molecular association, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, polyvinyl alcohol, hydrated castor oil, amide wax, oxidized polyethylene, metal soaps, and dibenzylidene sorbitol.

[0069] As the film-forming aid, a general film-forming aid can be used, and examples thereof include anionic surfactants such as dioctyl sulfosuccinate sodium salt, hydrophobic nonionic surfactants such as sorbitan monooleate, polyether-modified siloxane, and silicone oil.

[0070] As the defoaming agent, a general defoaming agent can be used, and examples thereof include silicone-based defoaming agents, nonionic surfactants, polyethers, higher alcohols, and polymer-based surfactants.

[0071] As the preservative, a common preservative can be used, and examples thereof include isothiazolinone-based preservatives, triazine-based preservatives, imidazole-based preservatives, pyridine-based preservatives, azole-based preservatives, and pyrithione-based preservatives.

[0072] A more preferred embodiment of the semi-additive laminate of the present invention is a laminate further comprising a primer layer between the insulating substrate layer and the first conductive seed layer. A semi-additive laminate provided with this primer layer is preferred because it can further improve the adhesion of the pattern circuit layer to the insulating substrate.

[0073] The primer layer can be formed by applying a primer to a part or the entire surface of the insulating substrate and then removing the solvent contained in the primer, such as an aqueous medium, an organic solvent, etc. Here, the primer is used for the purpose of improving the adhesion of the pattern circuit layer to the insulating substrate, and is a liquid composition in which various resins described below are dissolved or dispersed in a solvent.

[0074] The method for applying the primer to the insulating substrate is not particularly limited as long as a primer layer can be well formed, and various application methods may be appropriately selected depending on the shape, size, rigidity, etc. of the insulating substrate to be used. Specific application methods include, for example, gravure printing, offset printing, flexography, pad printing, gravure offset printing, letterpress printing, letterpress reversal printing, screen printing, microcontact printing, reverse printing, air doctor coater, blade coater, air knife coater, squeeze coater, impregnation coater, transfer roll coater, kiss coater, cast coater, spray coater, inkjet printing, die coater, spin coater, bar coater, and dip coater.

[0075] The method for applying the primer to both surfaces of the insulating substrate in the form of a film, sheet, or plate is not particularly limited as long as a primer layer can be formed satisfactorily, and any of the application methods exemplified above may be appropriately selected. In this case, the primer layer may be formed simultaneously on both surfaces of the insulating substrate, or may be formed on one surface of the insulating substrate and then formed on the other surface.

[0076] The insulating substrate may be surface-treated before the primer is applied in order to improve the coatability of the primer and the adhesion of the pattern circuit layer to the substrate. As a surface treatment method for the insulating substrate, the same surface treatment method as that used when forming the first conductive seed layer on the insulating substrate described above can be used.

[0077] A typical method for forming a primer layer by applying the primer to the surface of an insulating substrate and then removing the solvent contained in the coating layer is, for example, drying using a dryer to volatilize the solvent. The drying temperature may be set within a range that allows the solvent to volatilize and does not adversely affect the insulating substrate, and may be room temperature drying or heat drying. Specifically, the drying temperature is preferably in the range of 20 to 350°C, more preferably 60 to 300°C. The drying time is preferably in the range of 1 to 200 minutes, more preferably 1 to 60 minutes.

[0078] The drying may be performed with or without air blowing, and may be performed in the air, in a substituted atmosphere such as nitrogen or argon, under an air flow, or under vacuum.

[0079] When the insulating substrate is a sheet film, sheet, or plate, drying can be carried out by natural drying at the coating site, or by air drying or in a dryer such as a constant temperature dryer. When the insulating substrate is a roll film or roll sheet, drying can be carried out by continuously moving the roll material in an installed non-heated or heated space following the coating step.

[0080] The film thickness of the primer layer may be appropriately selected depending on the specifications and applications of the printed wiring board produced using the present invention. However, the thickness is preferably in the range of 10 nm to 30 μm, more preferably in the range of 10 nm to 5 μm, and even more preferably in the range of 10 nm to 3 μm, because this can further improve the adhesion between the insulating base material and the pattern circuit layer.

[0081] When the resin forming the primer layer is a resin having a reactive functional group [X] that is reactive with the reactive functional group [Y], which is used as the dispersant for the metal particles, the resin preferably has a reactive functional group [X] that is reactive with the reactive functional group [Y]. Examples of the reactive functional group [X] include an amino group, an amide group, an alkylolamide group, a keto group, a carboxyl group, a carboxyl anhydride group, a carbonyl group, an acetoacetyl group, an epoxy group, an alicyclic epoxy group, an oxetane ring, a vinyl group, an allyl group, a (meth)acryloyl group, a (blocked) isocyanate group, and an (alkoxy)silyl group. A silsesquioxane compound can also be used as the compound forming the primer layer.

[0082] In particular, when the reactive functional group [Y] in the dispersant is a basic nitrogen atom-containing group, the adhesion of the conductive layer on the insulating substrate can be further improved. Therefore, it is preferable that the resin forming the primer layer has, as the reactive functional group [X], a keto group, a carboxyl group, a carbonyl group, an acetoacetyl group, an epoxy group, an alicyclic epoxy group, an alkylolamide group, an isocyanate group, a vinyl group, a (meth)acryloyl group, or an allyl group.

[0083] Examples of resins that form the primer layer include urethane resins, acrylic resins, core-shell composite resins with a urethane resin shell and an acrylic resin core, epoxy resins, imide resins, amide resins, melamine resins, phenolic resins, urea-formaldehyde resins, blocked isocyanate polyvinyl alcohol obtained by reacting a polyisocyanate with a blocking agent such as phenol, and polyvinylpyrrolidone. Core-shell composite resins with a urethane resin shell and an acrylic resin core can be obtained, for example, by polymerizing an acrylic monomer in the presence of a urethane resin. These resins can be used alone or in combination of two or more.

[0084] Among the resins for forming the primer layer, resins that generate a reducing compound upon heating are preferred because they can further improve the adhesion of the conductive layer to the insulating substrate. Examples of the reducing compound include phenol compounds, aromatic amine compounds, sulfur compounds, phosphoric acid compounds, and aldehyde compounds. Among these reducing compounds, phenol compounds and aldehyde compounds are preferred.

[0085] When a resin that generates a reducing compound upon heating is used in a primer, the resin generates reducing compounds such as formaldehyde and phenol during the heat drying process when forming the primer layer. Specific examples of resins that generate reducing compounds upon heating include resins obtained by polymerizing a monomer containing N-alkylol(meth)acrylamide, core-shell composite resins having a urethane resin as the shell and a resin obtained by polymerizing a monomer containing N-alkylol(meth)acrylamide as the core, urea-formaldehyde-methanol condensates, urea-melamine-formaldehyde-methanol condensates, poly-N-alkoxymethylol(meth)acrylamide, formaldehyde adducts of poly(meth)acrylamide, and melamine resins, which generate formaldehyde upon heating; and resins that generate phenolic compounds upon heating, such as phenolic resins and phenol-blocked isocyanates. Among these resins, from the viewpoint of improving adhesion, core-shell type composite resins having a urethane resin as the shell and a resin obtained by polymerizing a monomer containing N-alkylol(meth)acrylamide as the core, melamine resins, and phenol-blocked isocyanates are preferred.

[0086] In the present invention, "(meth)acrylic" refers to either or both of "methacrylic" and "acrylic."

[0087] The resin that generates a reducing compound when heated can be obtained by polymerizing a monomer having a functional group that generates a reducing compound when heated by a polymerization method such as radical polymerization, anionic polymerization, or cationic polymerization.

[0088] Examples of the monomer having a functional group that generates a reducing compound upon heating include N-alkylol vinyl monomers, and specific examples thereof include N-methylol(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-ethoxymethyl(meth)acrylamide, N-propoxymethyl(meth)acrylamide, N-isopropoxymethyl(meth)acrylamide, N-n-butoxymethyl(meth)acrylamide, N-isobutoxymethyl(meth)acrylamide, N-pentoxymethyl(meth)acrylamide, N-ethanol(meth)acrylamide, and N-propanol(meth)acrylamide.

[0089] Furthermore, when producing the resin that generates a reducing compound when heated, various other monomers such as alkyl (meth)acrylates can also be copolymerized together with the monomer having a functional group that generates a reducing compound when heated.

[0090] When the blocked isocyanate is used as the resin for forming the primer layer, a primer is formed by forming a uretdione bond through a self-reaction between isocyanate groups or by forming a bond between an isocyanate group and a functional group of another component. The bond formed in this case may be formed before the metal particle dispersion is applied, or may not be formed before the metal particle dispersion is applied and may be formed by heating after the metal particle dispersion is applied.

[0091] The blocked isocyanate may be one having a functional group formed by blocking an isocyanate group with a blocking agent.

[0092] The blocked isocyanate preferably has the functional group in an amount of 350 to 600 g / mol per mole of the blocked isocyanate.

[0093] From the viewpoint of improving adhesion, the blocked isocyanate preferably has 1 to 10 functional groups, more preferably 2 to 5 functional groups, in one molecule.

[0094] From the viewpoint of improving adhesion, the number average molecular weight of the blocked isocyanate is preferably in the range of 1,500 to 5,000, and more preferably in the range of 1,500 to 3,000.

[0095] Furthermore, from the viewpoint of further improving adhesion, the blocked isocyanate preferably has an aromatic ring, such as a phenyl group or a naphthyl group.

[0096] The blocked isocyanate can be produced by reacting a part or all of the isocyanate groups of an isocyanate compound with a blocking agent.

[0097] Examples of isocyanate compounds that can be used as raw materials for the blocked isocyanate include polyisocyanate compounds having an aromatic ring, such as 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, crude diphenylmethane diisocyanate, phenylene diisocyanate, tolylene diisocyanate, and naphthalene diisocyanate; and aliphatic polyisocyanate compounds or polyisocyanate compounds having an alicyclic structure, such as hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate. Also included are biuret forms, isocyanurates, adducts, and the like of the above-mentioned polyisocyanate compounds.

[0098] Further, examples of the isocyanate compound include those obtained by reacting the polyisocyanate compounds exemplified above with a compound having a hydroxyl group or an amino group.

[0099] When an aromatic ring is introduced into the blocked isocyanate, it is preferable to use a polyisocyanate compound having an aromatic ring. Among the polyisocyanate compounds having an aromatic ring, 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, an isocyanurate of 4,4'-diphenylmethane diisocyanate, and an isocyanurate of tolylene diisocyanate are preferred.

[0100] Examples of the blocking agent used in producing the blocked isocyanate include phenolic compounds such as phenol and cresol; lactam compounds such as ε-caprolactam, δ-valerolactam and γ-butyrolactam; oxime compounds such as formamide oxime, acetaldoxime, acetone oxime, methyl ethyl ketoxime, methyl isobutyl ketoxime and cyclohexanone oxime; 2-hydroxypyridine, butyl cellosolve, propylene glycol monomethyl ether, benzyl alcohol, methanol, Examples of the blocking agent include ethanol, n-butanol, isobutanol, dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, acetylacetone, butyl mercaptan, dodecyl mercaptan, acetanilide, acetic acid amide, succinimide, maleimide, imidazole, 2-methylimidazole, urea, thiourea, ethylene urea, diphenylaniline, aniline, carbazole, ethyleneimine, polyethyleneimine, 1H-pyrazole, 3-methylpyrazole, and 3,5-dimethylpyrazole. Among these, blocking agents capable of dissociating to generate an isocyanate group upon heating in the range of 70 to 200°C are preferred, and blocking agents capable of generating an isocyanate group upon heating in the range of 110 to 180°C are more preferred. Specifically, phenol compounds, lactam compounds, and oxime compounds are preferred, and phenol compounds are particularly preferred because they become reducing compounds when the blocking agent is eliminated by heating.

[0101] Examples of the method for producing the blocked isocyanate include a method of mixing the isocyanate compound produced in advance with the blocking agent and allowing them to react, and a method of mixing the blocking agent with raw materials used in the production of the isocyanate compound and allowing them to react.

[0102] More specifically, the blocked isocyanate can be produced by reacting the polyisocyanate compound with a compound having a hydroxyl group or an amino group to produce an isocyanate compound having an isocyanate group at its terminal, and then mixing and reacting the isocyanate compound with the blocking agent.

[0103] The content of the blocked isocyanate obtained by the above method in the resin forming the primer layer is preferably in the range of 50 to 100% by mass, more preferably in the range of 70 to 100% by mass.

[0104] Examples of the melamine resin include mono- or polymethylolmelamine in which 1 to 6 moles of formaldehyde are added to 1 mole of melamine; etherified (poly)methylolmelamines (with any degree of etherification), such as trimethoxymethylolmelamine, tributoxymethylolmelamine, and hexamethoxymethylolmelamine; and urea-melamine-formaldehyde-methanol condensates. In addition to the method using a resin that generates a reducing compound upon heating, as described above, a method of adding a reducing compound to the resin can also be used. Examples of the reducing compound to be added in this case include phenolic antioxidants, aromatic amine antioxidants, sulfur-based antioxidants, phosphoric acid-based antioxidants, vitamin C, vitamin E, sodium ethylenediaminetetraacetate, sulfites, hypophosphorous acid, hypophosphites, hydrazine, formaldehyde, sodium borohydride, dimethylamine borane, and phenol.

[0105] In the present invention, the method of adding a reducing compound to a resin may ultimately result in residual low-molecular-weight components or ionic compounds, which may deteriorate the electrical properties. Therefore, a method using a resin that generates a reducing compound when heated is more preferable.

[0106] A preferred example of a resin for forming the primer layer is one containing a compound having an aminotriazine ring. The compound having an aminotriazine ring may be a low molecular weight compound or a higher molecular weight resin.

[0107] The low-molecular-weight compound having an aminotriazine ring can be any of various additives having an aminotriazine ring. Commercially available products include 2,4-diamino-6-vinyl-s-triazine ("VT" manufactured by Shikoku Chemical Industry Co., Ltd.), "VD-3" and "VD-4" manufactured by Shikoku Chemical Industry Co., Ltd. (compounds having an aminotriazine ring and a hydroxyl group), and "VD-5" manufactured by Shikoku Chemical Industry Co., Ltd. (compound having an aminotriazine ring and an ethoxysilyl group). These can be used as additives by adding one or more types to the resin that forms the primer layer.

[0108] The amount of the low-molecular-weight compound having an aminotriazine ring used is preferably 0.1 parts by mass or more and 50 parts by mass or less, and more preferably 0.5 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the resin.

[0109] As the resin having an aminotriazine ring, a resin in which an aminotriazine ring is introduced into the polymer chain by a covalent bond can also be suitably used, specifically, an aminotriazine-modified novolak resin.

[0110] The aminotriazine-modified novolac resin is a novolac resin in which an aminotriazine ring structure and a phenol structure are bonded via a methylene group. The aminotriazine-modified novolac resin can be obtained, for example, by co-condensing an aminotriazine compound such as melamine, benzoguanamine, or acetoguanamine with a phenol compound such as phenol, cresol, butylphenol, bisphenol A, phenylphenol, naphthol, or resorcinol and formaldehyde at approximately neutral pH in the presence of a weak alkaline catalyst such as an alkylamine or without a catalyst, or by reacting an alkyl ether of an aminotriazine compound such as methyl-etherified melamine with the phenol compound.

[0111] The aminotriazine-modified novolak resin preferably contains substantially no methylol groups. The aminotriazine-modified novolak resin may contain molecules in which only aminotriazine structures are methylene-linked, molecules in which only phenol structures are methylene-linked, or the like, which are produced as by-products during the production of the aminotriazine-modified novolak resin. Furthermore, the aminotriazine-modified novolak resin may contain a small amount of unreacted raw materials.

[0112] Examples of the phenol structure include a phenol residue, a cresol residue, a butylphenol residue, a bisphenol A residue, a phenylphenol residue, a naphthol residue, and a resorcinol residue. The term "residue" as used herein refers to a structure in which at least one hydrogen atom bonded to a carbon atom of an aromatic ring has been removed. For example, in the case of phenol, this refers to a hydroxyphenyl group.

[0113] Examples of the triazine structure include structures derived from aminotriazine compounds such as melamine, benzoguanamine, and acetoguanamine.

[0114] The phenol structure and the triazine structure can be used alone or in combination of two or more thereof. In addition, the phenol structure is preferably a phenol residue, and the triazine structure is preferably a structure derived from melamine, because these structures can further improve adhesion.

[0115] The hydroxyl value of the aminotriazine-modified novolak resin is preferably from 50 mgKOH / g to 200 mgKOH / g, more preferably from 80 mgKOH / g to 180 mgKOH / g, and even more preferably from 100 mgKOH / g to 150 mgKOH / g, because this can further improve adhesion.

[0116] The aminotriazine-modified novolak resins can be used alone or in combination of two or more.

[0117] When an aminotriazine-modified novolak resin is used as the compound having an aminotriazine ring, it is preferable to use an epoxy resin in combination.

[0118] Examples of the epoxy resin include bisphenol A type epoxy resins, bisphenol F type epoxy resins, biphenyl type epoxy resins, cresol novolac type epoxy resins, phenol novolac type epoxy resins, bisphenol A novolac type epoxy resins, alcohol ether type epoxy resins, tetrabromobisphenol A type epoxy resins, naphthalene type epoxy resins, phosphorus-containing epoxy compounds having a structure derived from a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivative, epoxy resins having a structure derived from a dicyclopentadiene derivative, epoxidized products of fats and oils such as epoxidized soybean oil, etc. These epoxy resins can be used alone or in combination of two or more.

[0119] Among the above epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, biphenyl type epoxy resins, cresol novolac type epoxy resins, phenol novolac type epoxy resins, and bisphenol A novolac type epoxy resins are preferred because they can further improve adhesion, and bisphenol A type epoxy resins are particularly preferred.

[0120] Furthermore, the epoxy equivalent of the epoxy resin is preferably 100 g / equivalent or more and 300 g / equivalent or less, more preferably 120 g / equivalent or more and 250 g / equivalent or less, and even more preferably 150 g / equivalent or more and 200 g / equivalent or less, because this can further improve adhesion.

[0121] When the primer layer is a layer containing an aminotriazine-modified novolac resin and an epoxy resin, the molar ratio [(x) / (y)] of the phenolic hydroxyl group (x) in the aminotriazine-modified novolac resin to the epoxy group (y) in the epoxy resin is preferably 0.1 or more and 5 or less, more preferably 0.2 or more and 3 or less, and even more preferably 0.3 or more and 2 or less, in order to further improve adhesion.

[0122] When a layer containing an aminotriazine-modified novolak resin and an epoxy resin is formed as the primer layer, a primer resin composition containing the compound having an aminotriazine ring and the epoxy resin is used.

[0123] Furthermore, the primer resin composition used to form the primer layer containing the aminotriazine-modified novolac resin and the epoxy resin may contain other resins as needed, such as urethane resins, acrylic resins, blocked isocyanate resins, melamine resins, phenolic resins, etc. These other resins may be used alone or in combination of two or more.

[0124] The primer used to form the primer layer preferably contains the resin in an amount of 1 to 70% by mass, more preferably 1 to 20% by mass, from the viewpoints of coatability and film-forming properties.

[0125] Examples of solvents that can be used for the primer include various organic solvents and aqueous media. Examples of the organic solvents include toluene, ethyl acetate, methyl ethyl ketone, and cyclohexanone. Examples of the aqueous media include water, organic solvents that are miscible with water, and mixtures thereof.

[0126] Examples of the water-miscible organic solvent include alcohol solvents such as methanol, ethanol, n-propanol, isopropanol, ethyl carbitol, ethyl cellosolve, and butyl cellosolve; ketone solvents such as acetone and methyl ethyl ketone; alkylene glycol solvents such as ethylene glycol, diethylene glycol, and propylene glycol; polyalkylene glycol solvents such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; and lactam solvents such as N-methyl-2-pyrrolidone.

[0127] Furthermore, the resin forming the primer layer may have a functional group that contributes to a crosslinking reaction, such as an alkoxysilyl group, a silanol group, a hydroxyl group, or an amino group, as necessary. The crosslinked structure formed using these functional groups may already be formed before the subsequent step of forming a first conductive seed layer, or may be formed after the step of forming the first conductive seed layer. When the crosslinked structure is formed after the step of forming the first conductive seed layer, the crosslinked structure may be formed in the primer layer before forming the pattern circuit layer, or the crosslinked structure may be formed in the primer layer after forming the pattern circuit layer, for example, by aging to promote the reaction.

[0128] If necessary, known substances such as a crosslinking agent, a pH adjuster, a film-forming aid, a leveling agent, a thickener, a water repellent, and an antifoaming agent may be appropriately added to the primer layer.

[0129] Examples of the crosslinking agent include metal chelate compounds, polyamine compounds, aziridine compounds, metal salt compounds, and isocyanate compounds. These include thermal crosslinking agents that react at relatively low temperatures of about 25 to 100°C to form a crosslinked structure, and thermal crosslinking agents that react at relatively high temperatures of 100°C or higher to form a crosslinked structure, such as melamine compounds, epoxy compounds, oxazoline compounds, carbodiimide compounds, and blocked isocyanate compounds, as well as various photocrosslinking agents. When the aminotriazine-modified novolac resin and epoxy resin are used in the primer layer, it is preferable to use a polycarboxylic acid as the crosslinking agent in the primer resin composition. Examples of the polycarboxylic acid include trimellitic anhydride, pyromellitic anhydride, maleic anhydride, and succinic acid. These crosslinking agents can be used alone or in combination of two or more. Among these crosslinking agents, trimellitic anhydride is preferred because it can further improve adhesion.

[0130] The amount of the crosslinking agent used varies depending on the type, but from the viewpoint of improving the adhesion of the pattern circuit layer to the substrate, it is preferably in the range of 0.01 to 60 parts by mass, more preferably in the range of 0.1 to 10 parts by mass, and even more preferably in the range of 0.1 to 5 parts by mass, relative to 100 parts by mass of the total of the resins contained in the primer.

[0131] When the crosslinking agent is used, a crosslinked structure may already be formed before the subsequent step of forming a first conductive seed layer, or the crosslinked structure may be formed after the step of forming the first conductive seed layer. When the crosslinked structure is formed after the step of forming the first conductive seed layer, the crosslinked structure may be formed in the primer layer before forming the pattern circuit layer, or the crosslinked structure may be formed in the primer layer by, for example, aging after forming the pattern circuit layer.

[0132] In the present invention, the method for forming the first conductive seed layer on the primer layer is the same as the method for forming the first conductive seed layer on the insulating substrate.

[0133] Furthermore, similarly to the insulating substrate, the primer layer may be subjected to a surface treatment before the silver particle dispersion is applied thereto, for the purposes of improving the coatability of the silver particle dispersion and improving the adhesion of the pattern circuit layer to the substrate.

[0134] As a method for forming the first conductive seed layer on both sides of the planar insulating substrate, a method may also be used in which the first conductive seed layer is formed on a temporary substrate and then transferred onto the insulating substrate.

[0135] Since the temporary substrate needs to be finally peeled off after the first conductive seed layer is transferred onto the insulating substrate, it is preferable to select a temporary substrate that can be easily peeled off at the interface between the temporary substrate and the first conductive seed layer. For example, examples of polymer films include aromatic polyesters such as polyethylene terephthalate, polybutylene terephthalate (PBT), polyethylene naphthalate, and polybutylene naphthalate; fluorine-based resins such as polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, vinylidene fluoride resin, trifluorochloroethylene resin, trifluorochloroethylene-ethylene copolymer, tetrafluoroethylene-perfluorodioxol copolymer, vinyl fluoride resin, and polyvinylidene fluoride; polymethylpentene (TPX), polypropylene (PP) [including biaxially oriented polypropylene (OPP) and non-axially oriented polypropylene (CPP)], and polyethylene (PE) [high density polyethylene]. Polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) and other olefin resins; polystyrene (PS); polyvinyl chloride (PVC), polyimide, polyimide resins such as transparent polyimide; polyamide resins such as polyamideimide and polyamide; polycarbonate, acrylonitrile-butadiene-styrene (ABS) resin, polymer alloys of ABS and polycarbonate, acrylic resins such as poly(meth)methyl acrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polycarbonate, polyethylene, polypropylene, polyurethane, liquid crystal polymer (LCP), polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polyphenylene sulfone (PPSU), epoxy resins, etc. Among them, aromatic polyester, polyethylene, olefin resin, fluorine-based resin, polyimide resin, LCP, polyphenylene sulfide can be used as the temporary substrate.

[0136] Metals such as copper, aluminum, aluminum alloys, titanium, stainless steel, beryllium copper, phosphor bronze, nickel, nichrome, nickel alloys, tin, zinc, lead, gold, zinc, lead, tantalum, molybdenum, niobium, iron, and silver can be used as the temporary substrate. In addition, silicon, ceramics, glass, and the like can be suitably used as the inorganic substrate.

[0137] The shape of the temporary substrate is not particularly limited, but using a film-like or sheet-like temporary substrate provides good handling. The film thickness of the temporary substrate is usually preferably in the range of 1 to 5,000 μm, more preferably in the range of 1 to 300 μm, more preferably in the range of 1 to 200 μm, more preferably in the range of 1 to 100 μm, and even more preferably in the range of 1 to 50 μm. Since the temporary substrate is no longer needed after the first conductive seed layer is transferred onto the insulating substrate, it is preferable that the temporary substrate be thin enough not to impair workability from a cost perspective.

[0138] The formation of the first conductive seed layer on the temporary substrate may be appropriately adjusted with reference to the method for forming the first conductive seed layer on the insulating substrate described above. Furthermore, when manufacturing a laminate for semi-additive processing having a configuration in which a primer layer is provided between the insulating substrate and the first conductive seed layer, the first conductive seed layer may be formed on the temporary substrate, and then a primer layer may be formed on the first conductive seed layer. The method for forming the primer layer may be appropriately adjusted by adjusting the method for forming the primer layer on the insulating substrate described above.

[0139] As a method for transferring the first conductive seed layer, or the first conductive seed layer and primer layer onto the insulating substrate, the surface of the first conductive seed layer or primer layer on the temporary substrate can be bonded to the insulating substrate using heat and pressure. For example, a thermal lamination method, a thermal roll transfer method, a pressing method, a vacuum pressing method, etc. can be suitably used.

[0140] In the laminate for semi-additive processes of the present invention, a peelable cover layer can be laminated as a protective layer on the first conductive seed layer.

[0141] By laminating the peelable cover layer on the first conductive seed layer, it is possible to prevent organic and inorganic debris (smear) generated during the process of forming openings in the first conductive seed layer described below in the method for producing a printed wiring board of the present invention from adhering to the surface of the first conductive seed layer.

[0142] The material for the peelable cover layer is not particularly limited as long as the purpose of protecting the first conductive seed layer is achieved in the method for manufacturing the printed wiring board of the present invention, and various commercially available resins and metal films can be used, but polyethylene, polypropylene, and polyethylene terephthalate films are preferably used.

[0143] The peelable cover layer may be a film of polyethylene, polypropylene, polyethylene terephthalate, or the like, having a silicone layer thereon to improve peelability.

[0144] The peelable cover layer may be a film of polyethylene, polypropylene, polyethylene terephthalate, or the like, and may be adhesive so as to have sufficient adhesion to the first conductive seed layer to withstand the processes described below.

[0145] The film thickness of the peelable cover layer used in the present invention is preferably 10 to 100 μm, more preferably 15 to 70 μm, from the viewpoints of film handling, protection of the first conductive seed layer, and ease of forming through holes in the substrate.

[0146] The release cover layer used in the present invention can be laminated on the first conductive seed layer after coating the first conductive seed layer. For example, when the first conductive seed layer is coated using a roll coater, the release cover layer can be laminated by winding the first conductive seed layer together with the first conductive seed layer.

[0147] When the first conductive seed layer is formed on an insulating substrate by the transfer method, the temporary substrate can be used as a release cover layer.

[0148] An alkali-soluble resin may also be used as the material for the release cover layer of the present invention. The alkali-soluble resin is not particularly limited as long as it can be developed with an alkaline developer, and known and commonly used resins can be used, such as amide-imide resins and resins having alkali-soluble functional groups such as carboxyl groups and phenolic hydroxyl groups. The alkali-soluble resin may be formed into a film by coating a resin solution onto the first conductive seed layer, or a film may be used in advance. When a film is used, the first conductive seed layer can be coated with a roll coater, and the release cover layer can be wound up together with the first conductive seed layer during winding, as described above, for example.

[0149] In the laminate for semi-additive processes of the present invention, a protective layer made of the same metal material as the second seed layer can be laminated on the first conductive seed layer.

[0150] By laminating the protective layer on the first conductive seed layer, it is possible to prevent organic and inorganic dust (smear) generated during the process of forming through holes penetrating both sides, which will be described later, in the method for manufacturing a printed wiring board of the present invention from adhering to the surface of the first conductive seed layer.

[0151] Furthermore, by constructing the protective layer from the same metal material as the metal material that constitutes the second conductive seed layer, when the second conductive seed layer is formed, the second conductive seed layer and the protective layer are integrated, and as a whole they function as a second conductive seed layer.

[0152] The thickness of the protective layer is not particularly limited as long as the step of forming an opening in the first conductive seed can be carried out well and the subsequent step of removing a portion of the second conductive seed can be carried out without any problems. However, from the viewpoint of the efficiency of the process of forming an opening, the thickness is preferably in the range of 0.1 to 10 μm, and from the viewpoint of the efficiency of the process of removing a portion of the second conductive seed in the subsequent step, the thickness is preferably in the range of 0.2 to 3 μm.

[0153] The protective layer made of the metal can be formed on the first conductive seed layer by a known or commonly used dry or wet plating method. When the first conductive seed is formed by the above-mentioned transfer method, a temporary substrate for transfer may be made of the same metal as the second conductive seed and attached to an insulating substrate, and the temporary substrate may be used as a metal protective layer.

[0154] The metal material constituting the second conductive seed layer can be various conductive substances such as gold, platinum, palladium, aluminum, tin, copper, nickel, titanium, indium, and iridium, as long as the plating process and etching process described below can be carried out without problems. However, if the type or mixture is different from that of the first conductive seed layer, a metal with a different composition must be selected.

[0155] (Manufacturing Process of Laminate for Semi-Additive Process) The manufacturing process of the laminate for semi-additive process according to the present invention will be described with reference to FIGS. 1 and 2. FIG.

[0156] In step (1), a substrate is prepared in which a circuit 12 (copper or the like) is formed on an insulating base material (base) 10.

[0157] Next, in step (2), an insulating substrate 13 (e.g., prepreg or interlayer insulating material), a primer layer 14, and a first conductive seed layer 16 (e.g., silver) are formed on the substrate in this order. The insulating substrate 13, primer layer 14, and first conductive seed layer 16 may be formed one layer at a time or all at once. Although not shown, a protective layer (e.g., a resin or metal film) may be optionally provided on the surface of the first conductive seed layer 16. In the example process shown in FIG. 1 , the primer layer 14 and the first conductive seed layer 16 are formed on one side of the substrate 10, but the primer layer and the conductive seed layer may be formed on both sides of the substrate.

[0158] In step (3), via processing (laser or the like) is performed on the first conductive seed layer 16 (or any protective layer) to form vias (openings) 18. A known and commonly used method may be appropriately selected as the method for forming the vias (openings), and examples include drilling, laser processing, and processing methods that combine laser processing with chemical etching of an insulating substrate using an oxidizing agent, alkaline chemical, acidic chemical, or the like. In the illustrated example, so-called blind vias are used, but through-holes can also be formed.

[0159] The hole diameter of the holes formed by the drilling process is preferably in the range of 0.01 to 1 mm, more preferably in the range of 0.01 to 0.5 mm, and even more preferably in the range of 0.02 to 0.1 mm.

[0160] Organic and inorganic debris (smear) generated during drilling can cause poor plating deposition, reduced plating adhesion, and impaired plating appearance in the plating process for forming electrical connections between both surfaces and conductive layers, as described below, so it is preferable to remove the debris (desmear). Desmearing methods include, for example, dry processes (dry desmear) such as plasma treatment and reverse sputtering, and wet processes (wet desmear) such as cleaning with an aqueous solution of an oxidant such as potassium permanganate, cleaning with an aqueous solution of an alkali or acid, and cleaning with an organic solvent.

[0161] In step (4), electroless copper plating is performed on the entire surface including the inside of the via (opening) 18 to form a second conductive seed layer 20 (copper).

[0162] Next, in step (5) as shown in Fig. 2, a cover layer 22 is formed on the entire surface. In the illustrated example, the cover layer 22 is an etching resist, and the etching resist is formed by attaching a film-like material, but the cover layer 22 can also be formed by applying a liquid material.

[0163] In the step (5) of forming the cover layer 22, the surface of the second conductive seed layer 20 may be subjected to a surface treatment such as cleaning treatment with an acidic or alkaline cleaning solution, corona treatment, plasma treatment, UV treatment, gas-phase ozone treatment, liquid-phase ozone treatment, or treatment with a surface treatment agent before forming the cover layer 22, in order to improve adhesion to the cover layer 22. These surface treatments can be performed by one method or by a combination of two or more methods.

[0164] Examples of the treatment with the surface treatment agent include a treatment method using a rust inhibitor comprising a triazole compound, a silane coupling agent, and an organic acid, as described in JP-A-7-258870; a treatment method using an organic acid, a benzotriazole rust inhibitor, and a silane coupling agent, as described in JP-A-2000-286546; a treatment method using a substance having a structure in which a nitrogen-containing heterocycle such as triazole or thiadiazole and a silyl group such as a trimethoxysilyl group or a triethoxysilyl group are bonded via an organic group having a thioether (sulfide) bond, as described in JP-A-2002-363189; and a treatment method using a compound having a structure in which a triazine ring and an amino group are bonded via an organic group having a thioether (sulfide) bond, as described in WO2013 / 186941. a method of treating with a silane compound having a group; a method of treating with an imidazole silane compound obtained by reacting a formyl imidazole compound with an aminopropyl silane compound, as described in JP 2015-214743 A; a method of treating with an azole silane compound, as described in JP 2016-134454 A; a method of treating with a solution containing an aromatic compound having an amino group and an aromatic ring in one molecule, a polybasic acid having two or more carboxyl groups, and a halide ion, as described in JP 2017-203073 A; a method of treating with a surface treatment agent containing a triazole silane compound, as described in JP 2018-16865 A, and the like can be used.

[0165] In step (6), the cover layer 22 is patterned. When a negative etching resist is used as the cover layer, the exposed portion becomes insoluble in the subsequent developer, and the unexposed portion dissolves in the developer and is removed. After removal, the cover layer 22 that covers the opening is formed.

[0166] In step (6), the cover layer 22 is exposed to actinic light in a pattern by passing it through a photomask or by using a direct exposure machine. The exposure dose may be appropriately set as needed. The latent image formed in the photosensitive resist by exposure is removed using a developer, thereby patterning the cover layer 22.

[0167] Examples of the developer include a dilute aqueous alkali solution of 0.3 to 2% by mass of sodium carbonate, potassium carbonate, or the like. A surfactant, an antifoaming agent, or a small amount of an organic solvent to promote development may be added to the dilute aqueous alkali solution. Furthermore, development is carried out by immersing the exposed substrate in the developer or by spraying the developer onto the resist with a spray or the like, and this development can form a patterned resist in which the pattern-forming portion has been removed.

[0168] When forming the cover layer 22, resist residues such as footings formed at the boundary between the hardened resist and the substrate and resist deposits remaining on the surface of the substrate may be removed by plasma descum treatment or by using a commercially available resist residue remover.

[0169] The cover layer 22 used in the present invention can be a commercially available resist ink, liquid resist, or dry film resist, and can be selected appropriately depending on the desired pattern resolution, the type of exposure machine used, the type of chemical solution used in the subsequent plating process, pH, etc.

[0170] Examples of commercially available resist inks include "Plating Resist MA-830" and "Etching Resist X-87" manufactured by Taiyo Ink Mfg. Co., Ltd.; etching resist and plating resist from NAZDAR; and "Etching Resist PLAS FINE PER" series and "Plating Resist PLAS FINE PPR" series manufactured by GOO Chemical Industry Co., Ltd. Examples of electrodeposition resists include "Eagle Series" and "Peper Series" manufactured by The Dow Chemical Company. Examples of commercially available dry films include "Photec" series manufactured by Resonac Inc.; "ALPHO" series manufactured by Nikko Materials Co., Ltd.; "Sunfort" series manufactured by Asahi Kasei Corporation; and "Riston" series manufactured by DuPont.

[0171] To efficiently manufacture printed wiring boards, it is convenient to use a dry film resist, and particularly when forming fine circuits, a dry film for semi-additive processing may be used. Commercially available dry films for this purpose include, for example, "ALFO LDF500" and "NIT2700" manufactured by Nikko Materials Co., Ltd., "Sunfort UFG-258" manufactured by Asahi Kasei Corporation, "RD Series (RD-2015, 1225)" and "RY Series (RY-5319, 5325)" manufactured by Resonac Co., Ltd., and "PlateMaster Series (PM200, 300)" manufactured by DuPont.

[0172] In step (6), the diameter of the cover layer 22 after patterning is preferably set to a ratio of 1.05 to 3.0, more preferably 1.05 to 2.5, and even more preferably 1.05 to 2.0, where the diameter of the via (opening) 18 is taken as 1. If the diameter of the cover layer 22 after patterning is too small, it may be difficult to cover the via (opening) 18, and if the diameter of the cover layer 22 after patterning is too large, it may be difficult to improve the wiring density. Note that if the patterns of the via (opening) 18 and the cover layer 22 are not perfect circles, the above ratio can be set based on the diameters of the circles inscribed in each of them.

[0173] In this manner, the laminate for semi-additive processes of the present invention can be produced.

[0174] In the above steps (5) and (6), a manufacturing example using a resist is shown as a method for forming a cover layer that covers the opening, but in the present invention, this is not particularly limited, and the cover layer can be formed using any known or commonly used material and method as long as it functions as a cover layer that covers the opening when the second conductive seed layer described below is etched and can be removed thereafter.

[0175] (Printed Wiring Board Manufacturing Process) The manufacturing process for a printed wiring board using the semi-additive process laminate according to the present invention will be described with reference to Figures 2 to 4. In step (7), the portion of the second conductive seed layer 20 that is not covered by the cover layer 22 is removed by etching to expose the first conductive seed layer 16. Etching is carried out under conditions that do not etch the underlying first conductive seed layer 16, for example, using a sulfuric acid-hydrogen peroxide or persulfate-based etching solution, with the temperature, concentration, and etching time appropriately adjusted.

[0176] When removing the second conductive seed layer, a physical removal process may be performed other than chemical etching using a chemical solution, as long as the seed function of the first conductive seed layer is not impaired. For example, a wet blasting process may be performed in which an aqueous solution mixed with an abrasive is sprayed with air.

[0177] In step (8), the cover layer 22 is removed by immersion in a stripping solution such as sodium hydroxide.

[0178] In step (9), a plating resist 24 is formed on the entire surface. In the illustrated example, the plating resist 24 is formed by attaching a film-like resist, but it can also be formed by applying a liquid resist.

[0179] In the step of forming the plating resist 24 in step (9), for the same purpose as in step (5), the surface of the first conductive seed layer 16 may be subjected to a surface treatment such as cleaning treatment with an acidic or alkaline cleaning solution, corona treatment, plasma treatment, UV treatment, gas-phase ozone treatment, liquid-phase ozone treatment, or treatment with a surface treatment agent before forming the plating resist 24. These surface treatments may be performed by one method or by a combination of two or more methods.

[0180] In step (10), the plating resist 24 is patterned so that the resist remains in the non-circuit forming areas. If the plating resist 24 is a negative type, the exposed areas will be insoluble in the subsequent developer, and the unexposed areas will dissolve in the developer and be removed.

[0181] In step (11), the entire surface is subjected to electrolytic plating such as electrolytic copper plating to form a pattern circuit 26. Note that it is possible to employ filling plating, which plates up the inside of the via (opening) 18 to the same height as the wiring, or conformal plating only on the inner wall of the via (opening) 18.

[0182] In step (11), the first conductive seed layer 16 is used as a cathode electrode for electrolytic copper plating, and the first conductive seed layer 16 exposed by development is treated by electrolytic copper plating, thereby connecting the vias (openings) 18 of the laminate with copper plating and simultaneously forming a pattern circuit layer.

[0183] Before forming the pattern circuit 26 by electrolytic copper plating, the surface of the first conductive seed layer 16 may be subjected to a surface treatment, if necessary. Examples of this surface treatment include cleaning treatment with an acidic or alkaline cleaning solution, corona treatment, plasma treatment, UV treatment, gas-phase ozone treatment, liquid-phase ozone treatment, and treatment with a surface treatment agent, provided that the surface of the first conductive seed layer 16 and the formed patterned plating resist 24 are not damaged. These surface treatments can be performed by one method or by a combination of two or more methods.

[0184] In step (11), when forming the pattern circuit 26, annealing may be performed after plating for the purpose of relieving stress in the plating film and improving adhesion. Annealing may be performed before the etching step described below, after the etching step, or before or after the etching.

[0185] The annealing temperature may be selected appropriately within the range of 40 to 300°C depending on the heat resistance of the substrate used and the intended use, but a range of 40 to 250°C is preferred, and a range of 40 to 200°C is more preferred for the purpose of suppressing oxidative degradation of the plating film. Furthermore, the annealing time is preferably 10 minutes to 10 days when the temperature range is 40 to 200°C, and about 5 minutes to 10 hours when annealing at temperatures above 200°C. When annealing the plating film, a rust inhibitor may be applied to the plating film surface as appropriate.

[0186] In step (12), the plating resist 24 is stripped by immersion in a stripping solution such as sodium hydroxide.

[0187] In step (13), the first conductive seed layer 16 is etched using a chemical solution that does not etch the pattern circuit 26, such as an organic acid.

[0188] By repeating the above steps, a multilayer board with the required number of layers can be formed. Also, although the above example assumes a rigid board, similar steps can be carried out on both sides of a flexible board.

[0189] In step (12), the plating resist 24 is stripped, and then, in step (13), the first conductive seed layer 16 in the non-pattern-forming portion is removed with an etching solution. The plating resist 24 may be stripped under the recommended conditions described in the catalog, specifications, etc. of the photosensitive resist used. The resist stripper used to strip the plating resist 24 may be a commercially available resist stripper or a 1.5 to 3 mass % aqueous solution of sodium hydroxide or potassium hydroxide set at 45 to 60°C. The plating resist 24 may be stripped by immersing the substrate on which the pattern circuit 26 is formed in the stripper or by spraying the stripper with a spray or the like.

[0190] Furthermore, the etching solution used to remove the first conductive seed layer 16 in the non-pattern formation areas is preferably one that selectively etches only the first conductive seed layer 16 and does not etch the copper that forms the pattern circuit 26. An example of such an etching solution is a mixture of carboxylic acid and hydrogen peroxide.

[0191] Examples of the carboxylic acid include acetic acid, formic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, oleic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, oxalic acid, malonic acid, succinic acid, benzoic acid, salicylic acid, phthalic acid, isophthalic acid, terephthalic acid, gallic acid, mellitic acid, cinnamic acid, pyruvic acid, lactic acid, malic acid, citric acid, fumaric acid, maleic acid, aconitic acid, glutaric acid, adipic acid, and amino acids. These carboxylic acids can be used alone or in combination of two or more. Among these carboxylic acids, acetic acid is preferably used primarily because it is easy to produce and handle as an etching solution.

[0192] When a mixture of carboxylic acid and hydrogen peroxide is used as an etching solution, it is believed that the hydrogen peroxide reacts with the carboxylic acid to produce percarboxylic acid (peroxycarboxylic acid), which is presumed to preferentially dissolve the silver constituting the first conductive seed layer 16 while suppressing the dissolution of the copper constituting the pattern circuit 26.

[0193] The mixing ratio of the mixture of carboxylic acid and hydrogen peroxide is preferably in the range of 2 to 100 moles of hydrogen peroxide per mole of carboxylic acid, more preferably in the range of 2 to 50 moles of hydrogen peroxide, since this can suppress dissolution of the copper pattern circuit 26.

[0194] The mixture of carboxylic acid and hydrogen peroxide is preferably an aqueous solution diluted with water, and the content of the mixture of carboxylic acid and hydrogen peroxide in the aqueous solution is preferably in the range of 2 to 65 mass %, more preferably in the range of 2 to 30 mass %, since this can suppress the effect of a temperature rise in the etching solution.

[0195] The water used for the dilution is preferably water from which ionic substances and impurities have been removed, such as ion-exchanged water, pure water, or ultrapure water.

[0196] The etching solution may further contain a protective agent to protect and inhibit dissolution of the pattern circuit 26. An azole compound is preferably used as the protective agent.

[0197] Examples of the azole compound include imidazole, pyrazole, triazole, tetrazole, oxazole, thiazole, selenazole, oxadiazole, thiadiazole, oxatriazole, and thiatriazole.

[0198] Specific examples of the azole compound include 2-methylbenzimidazole, aminotriazole, 1,2,3-benzotriazole, 4-aminobenzotriazole, 1-bisaminomethylbenzotriazole, aminotetrazole, phenyltetrazole, 2-phenylthiazole, benzothiazole, etc. These azole compounds can be used alone or in combination of two or more.

[0199] The concentration of the azole compound in the etching solution is preferably in the range of 0.001 to 2% by mass, more preferably in the range of 0.01 to 0.2% by mass.

[0200] Furthermore, it is preferable to add polyalkylene glycol as a protective agent to the etching solution, since this can prevent the copper pattern circuit 26 from dissolving.

[0201] Examples of polyalkylene glycols include water-soluble polymers such as polyethylene glycol, polypropylene glycol, and polyoxyethylene-polyoxypropylene block copolymers. Among these, polyethylene glycol is preferred. The number-average molecular weight of the polyalkylene glycol is preferably in the range of 200 to 20,000.

[0202] The concentration of the polyalkylene glycol in the etching solution is preferably in the range of 0.001 to 2% by mass, more preferably in the range of 0.01 to 1% by mass.

[0203] In order to suppress fluctuations in pH, additives such as sodium salts, potassium salts, and ammonium salts of organic acids may be added to the etching solution as needed.

[0204] In step (13), the first conductive seed layer 16 can be removed by immersing the substrate in an etching solution after forming the pattern circuit 26, or by spraying the etching solution onto the substrate with a spray or the like.

[0205] When using an etching apparatus to remove the first conductive seed layer 16 in the non-pattern forming portion, for example, all components of the etching solution may be prepared to have a predetermined composition and then supplied to the etching apparatus, or each component of the etching solution may be supplied separately to the etching apparatus and mixed within the apparatus to prepare the predetermined composition.

[0206] The etching solution is preferably used in a temperature range of 10 to 35°C. In particular, when an etching solution containing hydrogen peroxide is used, it is preferably used in a temperature range of 30°C or less, since this can suppress decomposition of hydrogen peroxide.

[0207] After the first conductive seed layer 16 has been removed with an etching solution, a cleaning operation may be performed in addition to rinsing with water to prevent silver components dissolved in the etching solution from adhering to and remaining on the printed wiring board. For the cleaning operation, a cleaning solution that dissolves silver oxide, silver sulfide, and silver chloride but hardly dissolves silver is preferably used. Specifically, it is preferable to use an aqueous solution containing thiosulfate or tris(3-hydroxyalkyl)phosphine, or an aqueous solution containing mercaptocarboxylic acid or a salt thereof, as the cleaning chemical.

[0208] Examples of thiosulfates include ammonium thiosulfate, sodium thiosulfate, potassium thiosulfate, etc. Examples of the tris(3-hydroxyalkyl)phosphines include tris(3-hydroxymethyl)phosphine, tris(3-hydroxyethyl)phosphine, tris(3-hydroxypropyl)phosphine, etc. These thiosulfates or tris(3-hydroxyalkyl)phosphines can be used either individually or in combination of two or more.

[0209] When an aqueous solution containing a thiosulfate is used, its concentration may be appropriately set depending on the process time, the characteristics of the cleaning device to be used, and the like. The concentration is preferably in the range of 0.1 to 40 mass %, and more preferably in the range of 1 to 30 mass % from the viewpoints of cleaning efficiency and stability of the chemical solution during continuous use.

[0210] Furthermore, when an aqueous solution containing tris(3-hydroxyalkyl)phosphine is used, its concentration may be appropriately set depending on the process time, the characteristics of the cleaning device to be used, and the like, but is preferably in the range of 0.1 to 50 mass %, and more preferably in the range of 1 to 40 mass % from the viewpoints of cleaning efficiency and stability of the chemical solution during continuous use.

[0211] Examples of mercaptocarboxylic acids include thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, thiomalic acid, cysteine, N-acetylcysteine, etc. Examples of salts of mercaptocarboxylic acids include alkali metal salts, ammonium salts, amine salts, etc.

[0212] When an aqueous solution of mercaptocarboxylic acid or a salt thereof is used, the concentration is preferably in the range of 0.1 to 20% by mass, and more preferably in the range of 0.5 to 15% by mass from the viewpoints of cleaning efficiency and process costs when treating a large amount.

[0213] Examples of methods for carrying out the above-mentioned cleaning operation include a method of immersing the printed wiring board obtained by etching away the first conductive seed layer 16 in the non-pattern forming portion in a cleaning solution, a method of spraying the cleaning solution onto the printed wiring board with a spray, etc. The temperature of the cleaning solution can be set at room temperature (25°C), but it may also be set at a temperature of, for example, 30°C, since this allows for stable cleaning treatment without being affected by the outside air temperature.

[0214] Furthermore, the step of removing the first conductive seed layer 16 from the non-pattern forming area with an etching solution and the cleaning operation can be repeated as necessary.

[0215] In the method for producing a printed wiring board of the present invention, after removing the first conductive seed layer 16 from the non-pattern-forming portion with an etching solution as described above, a cleaning operation may be further performed as necessary to further improve the insulation of the non-pattern-forming portion. For this cleaning operation, for example, an alkaline permanganate solution obtained by dissolving potassium permanganate or sodium permanganate in an aqueous solution of potassium hydroxide or sodium hydroxide can be used.

[0216] Cleaning using an alkaline permanganate solution can be performed by immersing the printed wiring board obtained by the above method in an alkaline permanganate solution set to 20 to 60°C, or by spraying the alkaline permanganate solution onto the printed wiring board using a spray or the like. Prior to cleaning, the printed wiring board may be treated by contacting it with a water-soluble organic solvent having an alcoholic hydroxyl group in order to improve the wettability of the alkaline permanganate solution to the substrate surface and improve cleaning efficiency. Examples of such organic solvents include methyl alcohol, ethyl alcohol, n-propyl alcohol, and isopropyl alcohol. These organic solvents can be used alone or in combination of two or more.

[0217] The concentration of the alkaline permanganate solution may be appropriately selected as needed, but is preferably one in which 0.1 to 10 parts by mass of potassium permanganate or sodium permanganate is dissolved in 100 parts by mass of a 0.1 to 10% by mass aqueous solution of potassium hydroxide or sodium hydroxide, and from the viewpoint of cleaning efficiency, more preferably one in which 1 to 6 parts by mass of potassium permanganate or sodium permanganate is dissolved in 100 parts by mass of a 1 to 6% by mass aqueous solution of potassium hydroxide or sodium hydroxide.

[0218] When cleaning with an alkaline permanganate solution is performed, it is preferable to treat the cleaned printed wiring board with a solution having a neutralizing / reducing effect after cleaning with the alkaline permanganate solution. Examples of the solution having a neutralizing / reducing effect include an aqueous solution containing 0.5 to 15% by mass of dilute sulfuric acid or an organic acid. Examples of the organic acid include formic acid, acetic acid, oxalic acid, citric acid, ascorbic acid, and methionine.

[0219] The cleaning with the alkaline permanganate solution may be carried out after cleaning for the purpose of preventing silver components dissolved in the etching solution from adhering to and remaining on the printed wiring board, or alternatively, only cleaning with the alkaline permanganate solution may be carried out instead of cleaning for the purpose of preventing silver components dissolved in the etching solution from adhering to and remaining on the printed wiring board.

[0220] Furthermore, the printed wiring board obtained by the method for producing a printed wiring board of the present invention may be appropriately and optionally subjected to lamination of a coverlay film on the pattern circuit, formation of a solder resist layer, and nickel / gold plating, nickel / palladium / gold plating, or palladium / gold plating as a final surface treatment of the pattern circuit.

[0221] The method for producing a printed wiring board using the semi-additive laminate of the present invention described above makes it possible to produce double-sided and via-connected circuit boards that have high adhesion, good design reproducibility, and a pattern circuit with a smooth surface and a good rectangular cross-sectional shape on various smooth substrates. Therefore, by using the method for producing a printed wiring board using the semi-additive laminate of the present invention, high-density, high-performance substrates for printed wiring boards and printed wiring boards of various shapes and sizes can be provided efficiently at low cost, and the method has high industrial applicability in the field of printed wiring boards. Furthermore, by using the laminate, not only printed wiring boards but also various components having a patterned metal layer on a planar substrate surface, such as connectors, electromagnetic wave shields, antennas for RFID and the like, and film capacitors, can be produced.

[0222] The present invention will be described in more detail below using examples and comparative examples. In the following examples and comparative examples, "parts" and "%" are all based on mass.

[0223] [Production Example 1: Production of Primer] In a nitrogen-substituted vessel equipped with a thermometer, a nitrogen gas inlet tube, and a stirrer, 100 parts by mass of polyester polyol (a polyester polyol obtained by reacting 1,4-cyclohexanedimethanol, neopentyl glycol, and adipic acid), 17.6 parts by mass of 2,2-dimethylolpropionic acid, 21.7 parts by mass of 1,4-cyclohexanedimethanol, and 106.2 parts by mass of dicyclohexylmethane-4,4'-diisocyanate were reacted in a mixed solvent of 178 parts by mass of methyl ethyl ketone to obtain a urethane prepolymer solution having an isocyanate group at its terminal.

[0224] Next, 13.3 parts by mass of triethylamine was added to the urethane prepolymer solution to neutralize the carboxyl groups of the urethane prepolymer, and 380 parts by mass of water was then added and thoroughly stirred to obtain an aqueous dispersion of the urethane prepolymer.

[0225] To the aqueous dispersion of the urethane prepolymer obtained above, 8.8 parts by weight of a 25% by weight ethylenediamine solution was added and stirred to chain-extend the urethane prepolymer. Subsequently, aging and desolvation were performed to obtain an aqueous dispersion of a urethane resin (non-volatile content: 30% by weight). The weight-average molecular weight of the urethane resin was 53,000.

[0226] Next, 140 parts by mass of deionized water and 100 parts by mass of the aqueous dispersion of the urethane resin obtained above were placed in a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, a dropping funnel for dropping the monomer mixture, and a dropping funnel for dropping the polymerization catalyst, and the temperature was raised to 80°C while blowing in nitrogen. Thereafter, with stirring, a monomer mixture consisting of 60 parts by mass of methyl methacrylate, 30 parts by mass of n-butyl acrylate, and 10 parts by mass of N-n-butoxymethylacrylamide, and 20 parts by mass of a 0.5% by mass aqueous ammonium persulfate solution were added dropwise from separate dropping funnels over 120 minutes while maintaining the temperature inside the reaction vessel at 80°C.

[0227] After the dropwise addition was completed, the mixture was stirred at the same temperature for an additional 60 minutes, and then the temperature inside the reaction vessel was cooled to 40°C. The mixture was diluted with deionized water to a non-volatile content of 20% by mass, and then filtered through a 200-mesh filter cloth to obtain an aqueous dispersion of a resin composition for a primer layer, which is a core-shell composite resin having the urethane resin as the shell layer and an acrylic resin made from methyl methacrylate or the like as a raw material as the core layer. Next, isopropyl alcohol and deionized water were added to and mixed with this aqueous dispersion so that the mass ratio of isopropanol to water was 7 / 3 and the non-volatile content was 2% by mass, thereby obtaining a primer.

[0228] Preparation Example 1: Preparation of Silver Particle Dispersion A dispersion containing silver particles and a dispersant was prepared by dispersing silver particles having an average particle size of 30 nm in a mixed solvent of 45 parts by mass of ethylene glycol and 55 parts by mass of ion-exchanged water using a compound obtained by adding polyoxyethylene to polyethyleneimine as a dispersant. Next, ion-exchanged water, ethanol, and a surfactant were added to the resulting dispersion to prepare a 5% by mass silver particle dispersion.

[0229] Preparation Example 2: Preparation of silver etching solution A silver etching solution was prepared by adding 2.6 parts by mass of acetic acid to 47.4 parts by mass of ion-exchanged water, and then adding 50 parts by mass of 35% by mass of hydrogen peroxide water. The molar ratio of hydrogen peroxide to carboxylic acid (hydrogen peroxide / carboxylic acid) in this silver etching solution was 13.6, and the content of the mixture of hydrogen peroxide and carboxylic acid in the silver etching solution was 22.4% by mass.

[0230] Preparation Example 3: Preparation of copper etching solution A copper etching solution was prepared by mixing 37.5 g / L of sulfuric acid and 13.5 g / L of hydrogen peroxide with ion-exchanged water.

[0231] Example 1 The primer obtained in Production Example 1 was applied to the surface of a polyimide film ("Kapton 100EN-C" manufactured by DuPont-Toray Co., Ltd.; thickness: 25 μm) serving as an insulating substrate using a small desktop coater ("K Printing Profer" manufactured by RK Print Coat Instruments Co., Ltd.) so that the thickness after drying would be 300 nm, and then dried for 5 minutes using a hot air dryer at 80°C. Furthermore, the film was turned over, and the primer obtained in Production Example 1 was applied to the surface in the same manner as above so that the thickness after drying would be 300 nm, and then dried for 5 minutes using a hot air dryer at 80°C, thereby forming primer layers on both surfaces of the polyimide film.

[0232] The silver particle dispersion obtained in Preparation Example 1 was applied to the polyimide film having primer layers on both surfaces thereof using a small desktop coater (RK Printing Profer, manufactured by RK Print Coat Instruments) so that the silver particle layer after drying was 0.5 g / m ２ The film was then dried at 160°C for 5 minutes using a hot air dryer. The film was then turned over, and the silver particle dispersion obtained in Preparation Example 1 was applied in the same manner as above so that the silver particle layer was 0.5 g / m ２The resulting polyimide film was dried at 160° C. for 5 minutes using a hot air dryer to form silver particle layers on both surfaces of the polyimide film. The film substrate thus obtained was baked at 250° C. for 5 minutes, and then the conductivity of the silver particle layer was confirmed with a tester to obtain a polyimide film having the primer and the first conductive seed layer (silver particle layer) on both surfaces of the polyimide.

[0233] On the polyimide film obtained above having first conductive seed layers on both surfaces, a 38 μm thick polyester removable adhesive tape (Panaprotect HP / CT, manufactured by Panac Corporation) was laminated as a peelable cover layer using a roll laminator (VA-770, manufactured by Taisei Laminator Co., Ltd.), thereby producing a laminate for semi-additive processing in which the first conductive seed layer and the peelable cover layer were sequentially laminated on both surfaces of the polyimide film, which is an insulating substrate.

[0234] On the peelable cover layer of the laminate, CO ２ A via with a diameter of 50 μm was formed using a laser processing machine (manufactured by Via Mechanics Co., Ltd.). Smears generated by the via processing were then removed by plasma treatment, and the peelable cover layer was peeled off to expose the first conductive seed layer. Next, the entire surface, including the inside of the via, was subjected to electroless copper plating (immersion in an electroless copper plating solution ("Circuposit 6550" manufactured by Rohm and Haas Electronic Materials Co., Ltd.) at 35° C. for 10 minutes) to form a copper layer, which was a second conductive seed layer.

[0235] Next, as a cover layer, an etching resist (Photec RY-3110 manufactured by Resonac Corporation, resist film thickness 25 μm) was formed on the entire surface using a roll laminator (VA-770 manufactured by Taisei Laminator Co., Ltd.) under conditions of 100°C, and then a pattern was exposed using an exposure device (manufactured by Oak Manufacturing Co., Ltd.) equipped with a high-pressure mercury lamp in a design that could protect the via portion, and development was carried out at 30°C with a 1 mass % sodium carbonate aqueous solution to remove the etching resist other than that on the via.

[0236] Subsequently, the electroless copper-plated portions not covered with the etching resist were removed by etching using the sulfuric acid / hydrogen peroxide-based copper etching solution prepared in Preparation Example 3, and then the substrate was immersed in a 3 mass % aqueous sodium hydroxide solution at 50°C to strip the etching resist.

[0237] A plating resist (Photec RY-5125 manufactured by Resonac Corporation, resist film thickness 15 μm) was formed on the entire surface using a roll laminator (VA-770 manufactured by Taisei Laminator Co., Ltd.) at 100°C, and then pattern exposure was performed using an exposure device equipped with a high-pressure mercury lamp (manufactured by Oak Manufacturing Co., Ltd.), and development was performed at 30°C with a 1 mass % sodium carbonate aqueous solution, thereby removing the plating resist from the via and wiring portions.

[0238] The first conductive seed layer and the surface of the second conductive seed layer formed on the surface of the opening were placed on the cathode, phosphorous copper was used as the anode, and an electrolytic plating solution containing copper sulfate (copper sulfate 60 g / L, sulfuric acid 190 g / L, chloride ions 50 mg / L, additive (Coppergleam ST-901 manufactured by Rohm and Haas Electronic Materials Co., Ltd.) was used, with a current density of 2.4 A / dm ２ After electrolytic copper plating was performed for 30 minutes at 50° C. to plate up the via portion and the wiring portion to the same height, the plating resist was stripped by immersion in a 3 mass % aqueous sodium hydroxide solution at 50° C. Finally, the laminate obtained above was immersed in the silver etching solution obtained in Preparation Example 2 at 25° C. for 30 seconds to remove the first conductive seed layer other than the conductive layer pattern, thereby obtaining a printed wiring board.

[0239] Example 2 A printed wiring board was obtained through the same steps as in Example 1, except that no primer layer was provided.

[0240] Example 3 A printed wiring board was obtained through the same steps as in Example 1, except that no peelable cover layer was provided and the peeling step of the peelable cover layer was not carried out.

[0241] (Example 4) In Example 1, instead of forming a 38 μm thick Panaprotect HP / CT as a peelable cover layer on a polyimide film having first conductive seed layers on both surfaces, the first conductive seed layer was placed as the cathode, phosphorous copper was used as the anode, and an electroplating solution containing copper sulfate (copper sulfate 60 g / L, sulfuric acid 190 g / L, chloride ions 50 mg / L, additive (Coppergleam ST-901 manufactured by Rohm and Haas Electronic Materials Co., Ltd.) was used, at a current density of 2.0 A / dm ２ A laminate was obtained through the same steps as in Example 1, except that a copper layer having a thickness of 2 μm was formed on the first conductive layer by electrolytic copper plating at 800 K for 2.5 minutes.

[0242] From above the copper layer of the laminate, CO ２ A via with a diameter of 100 μm was formed using a laser processing machine (manufactured by Via Mechanics Co., Ltd.). Smears generated by the via processing were then removed by wet desmearing using permanganic acid. Next, the entire surface, including the interior of the via, was subjected to electroless copper plating (immersion in an electroless copper plating solution ("Circuposit 6550" manufactured by Rohm and Haas Electronic Materials Co., Ltd.) at 35° C. for 10 minutes) to form a copper layer serving as a second conductive seed layer.

[0243] After forming the copper layer as the second conductive seed layer, the copper-plated portions not covered with the etching resist were removed by etching using the sulfuric acid / hydrogen peroxide-based copper etching solution prepared in Preparation Example 3, in the same manner as in Example 1, and a printed wiring board was obtained in the same manner as in Example 1.

[0244] Example 5 In Example 4, the type of the first conductive seed layer was changed to aluminum, and an aluminum layer having a thickness of 500 nm was formed by vapor deposition, followed by the same steps as in Example 4 to obtain a laminate. Aluminum etching was performed using a mixed acid Al etching solution (manufactured by Kanto Chemical Co., Inc.).

[0245] (Comparative Example 1) After forming a copper layer as the second conductive seed layer of the laminate, a conductive layer pattern was formed using a plating resist without going through the step of removing the electroless copper plating using an etching resist, and a printed wiring board was obtained through the same steps as in Example 1, except that etching was performed using the sulfuric acid / hydrogen peroxide-based copper etching solution prepared in Preparation Example 3.

[0246] [Evaluation method 1: Smoothness of wiring surface] The surface shape of the wiring of the printed wiring board obtained above was confirmed by magnifying it 1,000 times using a scanning electron microscope (JEOL Ltd. "JSM7600F") to observe the surface of the wiring. ⊚: The wiring surface shape was smooth. ◯: The wiring surface shape was partially smooth. ×: The wiring surface shape was not smooth.

[0247] [Evaluation Method 2: Rectangularity of Wiring Cross Section] After resin sealing and polishing were performed so that the cross section of the wiring of the printed wiring board obtained above could be observed, the cross section was confirmed using a scanning electron microscope ("JSM7600F" manufactured by JEOL Ltd.) at a magnification of 5,000 times. ○: The cross section was rectangular. ×: The cross section was not rectangular.

[0248]

[0249] 10: Insulating substrate (base) 12: Circuit 13: Insulating substrate 14: Primer layer 16: First conductive seed layer 18: Via (opening) 20: Second conductive seed layer 22: Cover layer 24: Plating resist 26: Pattern circuit

Claims

1. A laminate for a semi-additive process comprising: an insulating substrate; a first conductive seed layer having an opening formed on at least one surface of the insulating substrate; a second conductive seed layer formed on the inner surface of the opening in the first conductive seed layer and electrically connected to the first conductive seed layer; and a cover layer covering the opening, wherein the first conductive seed layer and the second conductive seed layer are made of a metal material, and the second conductive seed layer is made of a metal material different from that of the first conductive seed layer.

2. The laminate for semi-additive processing according to claim 1, wherein the metal material constituting the first conductive seed layer is silver and the metal material constituting the second conductive seed layer is copper.

3. The laminate for semi-additive manufacturing according to claim 1, which has a primer layer between the insulating substrate and the first conductive seed layer.

4. A printed wiring board using the laminate for semi-additive processes according to any one of claims 1 to 3.

5. A method for producing a laminate for semi-additive manufacturing according to any one of claims 1 to 3, comprising the steps of: forming an opening in an insulating substrate having a first conductive seed layer on at least one surface of the substrate; forming a second conductive seed layer made of a metal different from that of the first conductive seed layer on the surface of the first conductive seed layer and on the inner surface of the opening; and forming a cover layer to cover the opening.

6. The method for producing a laminate for semi-additive processing according to claim 5, wherein the opening is formed in a state where a protective layer is formed on the first conductive seed layer.

7. The method for producing a laminate for semi-additive processing according to claim 6, wherein the protective layer is a peelable cover layer.

8. The method for producing a laminate for semi-additive processing according to claim 6, wherein the protective layer is made of the same metal material as the metal material forming the second conductive seed layer.

9. A method for manufacturing a printed wiring board using a laminate for semi-additive manufacturing obtained by the manufacturing method described in claim 5 or 6, comprising the steps of: removing a portion of the second conductive seed layer on the first conductive seed layer of the laminate for semi-additive manufacturing to expose the surface of the first conductive seed layer; removing the cover layer that covers the opening; forming a plating resist on a portion of the exposed first conductive seed layer; forming a pattern circuit section on the second conductive seed layer and the exposed first conductive seed layer by electrolytic plating; peeling off the plating resist to expose the first conductive seed layer; and removing the exposed first conductive seed layer.

10. The method for producing a printed wiring board according to claim 9, wherein the metal material constituting the first conductive seed layer is silver, and the metal material constituting the second conductive seed layer is copper.

11. The method for producing a printed wiring board according to claim 9 or 10, wherein a primer layer is provided between the insulating substrate and the first conductive seed layer.

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