Method for manufacturing printed wiring board

Abstract

The present invention provides a two-sided connection planar semi-additive method laminate and a printed wiring board using the same. The two-sided connection planar semi-additive method laminate does not require surface roughening using chromic acid, permanganic acid, formation of a surface modification layer using an alkali, or the like, and does not use a vacuum device, and can form a wiring having high adhesion of a substrate and a conductor circuit, less undercut, good design reproducibility, and a good rectangular cross-sectional shape as a circuit wiring. The present invention is completed by finding that a through hole penetrating both sides is formed in a laminate in which a silver particle layer (M1) and a copper layer (M2) having a thickness of 0.1 μm to 2 μm are sequentially layered on both surfaces of an insulating substrate (A), a copper or nickel layer is formed on the surface of the through hole, a pattern resist is formed on the conductive silver particle layer (M1), and copper is electroplated, thereby forming a two-sided connection printed wiring board having a good rectangular cross-sectional shape as a circuit wiring with good design reproducibility.

Description

Technical Field

[0001] The present invention relates to a planar semi-additive laminate for electrically connecting two sides of a substrate and a printed wiring board using the same. Background Technology

[0002] Printed wiring boards (PCBs) are metal layers with circuit patterns formed on the surface of an insulating substrate. In recent years, with the miniaturization and weight reduction requirements of electronic devices, there is a need for thinner PCBs (films) and more precise circuit wiring. Previously, a subtractive method was widely used to manufacture circuit wiring: etching resist with a circuit pattern formed on the surface of a copper layer on an insulating substrate, and etching the copper layer in areas where no circuitry is needed to form the copper wiring. However, in this subtractive method, copper residue at the bottom edge of the wiring is prone to remain. If the distance between wirings becomes shorter due to the high density of the wiring, problems such as short circuits and lack of insulation reliability between wirings arise. Furthermore, if further etching is performed to prevent short circuits and improve insulation reliability, the etching solution can spread into the lower part of the resist, causing lateral etching, resulting in a thinner wiring width. Especially when areas with different wiring densities are mixed together, fine wirings in areas with low wiring density may disappear if etched. Furthermore, the cross-sectional shape of the wiring obtained by the subtractive method is not rectangular, but becomes a trapezoidal or triangular shape with the bottom edge extending towards the substrate. Therefore, it becomes a wiring with a different width in the thickness direction, which also presents a challenge as an electrical transmission path.

[0003] A semi-additive method has been proposed as a way to fabricate micro-wiring circuits to solve these problems. In the semi-additive method, a conductive seed layer is first formed on an insulating substrate, and then a resist is plated onto the non-circuit-forming portion of the seed layer. After the wiring portion is formed by electroplating through the conductive seed layer, the resist is peeled off, and the seed layer of the non-circuit-forming portion is removed, thereby forming a micro-wiring circuit. According to this method, since the plating is deposited along the shape of the resist, the cross-sectional shape of the wiring can be rectangular. Furthermore, since wiring of the target width can be deposited regardless of the density of the pattern, it is suitable for forming micro-wiring circuits.

[0004] In semi-addition processes, methods for forming conductive seed layers on insulating substrates using electroless copper plating and electroless nickel plating with palladium catalysts are known. In these methods, for example, when using deposited films, to ensure adhesion between the film substrate and the copper plating film, a surface roughening process called desmearing roughening is performed using a strong reagent such as permanganate. The plating film forms from the resulting voids, thereby utilizing an anchoring effect to ensure adhesion between the insulating substrate and the plating film. However, if the substrate surface is roughened, issues arise such as difficulty in forming fine wiring and deterioration of high-frequency transmission characteristics. Therefore, the degree of roughening has been investigated, but with low roughening, the required adhesion strength between the formed wiring and the substrate cannot be obtained.

[0005] On the other hand, techniques for forming conductive seed crystals by electroless nickel plating on polyimide films are also known. In this case, the polyimide film is immersed in a strong alkali, thereby opening the ring-shaped imide rings on the surface and making the film surface hydrophilic. At the same time, a water-permeable modified layer is formed, and a palladium catalyst is permeated into this modified layer for electroless nickel plating, thereby forming a nickel seed layer (for example, see Patent Document 1). In this technique, nickel plating is formed from the outermost modified layer of the polyimide to obtain adhesion strength. However, since this modified layer is in a state of open imide rings, there is a problem that the film surface becomes a physically and chemically fragile structure.

[0006] In contrast, as a method that does not involve surface roughening or forming a modified layer on the surface, it is also known to form conductive seed crystals such as nickel or titanium on an insulating substrate by sputtering (for example, see Patent Document 2). This method can form a seed layer without roughening the substrate surface, but it has the following problems: it requires expensive vacuum equipment, requires a large initial investment, the size and shape of the substrate are limited, and the process is cumbersome and has low productivity.

[0007] As a solution to the problems of sputtering methods, a method has been proposed that utilizes a coating layer of conductive ink containing metal particles as a conductive seed layer (for example, see Patent Document 3). This technology discloses a method of coating a conductive ink containing metal particles with a particle size of 1 to 500 nm onto an insulating substrate made of a film or sheet, subjecting it to heat treatment, thereby fixing the metal particles in the coated conductive ink as a metal layer onto the insulating substrate to form a conductive seed layer, and then performing plating on this conductive seed layer.

[0008] Patent document 3 proposes a pattern formation method using a semi-additive process. In the embodiments, it describes using a substrate with a copper conductive seed layer formed by coating conductive ink containing dispersed copper particles and heat-treating it as the substrate for the semi-additive process. A photosensitive resist is formed on the conductive seed layer. After exposure and development, copper electroplating is used to thicken the pattern formation area. After the resist is peeled off, the copper conductive seed layer is etched away. Furthermore, in the ongoing research on forming printed circuit boards using a semi-additive process, a substrate with a thin copper foil or copper-plated film as conductive seed crystals on an insulating substrate is used as the substrate for the semi-additive process.

[0009] Thus, as with the combination of a copper conductive seed layer and a copper circuit pattern, when the conductive seed layer and the conductive layer of the circuit pattern are formed of the same metal, it is known that when the conductive seed layer of the non-patterned portion is removed, the conductive layer of the circuit pattern is also etched at the same time. Therefore, the circuit pattern becomes thinner and finer, and the surface roughness of the circuit conductive layer also increases. This is a problem that should be solved when manufacturing high-density wiring and high-frequency transmission wiring.

[0010] Regarding these issues, the inventors have invented a technique in which a substrate on which a conductive silver particle layer is formed on the surface of an insulating substrate is used as a substrate for a semi-additive process. This prevents the circuit pattern from becoming thinner or thinner during the seed layer etching process, resulting in a printed wiring board with excellent design reproducibility and a smooth circuit layer surface. (Non-Patent Literature 1, 2)

[0011] This technology can form circuits on both sides, but when forming holes in a substrate with conductive silver particle layers on both sides of an insulating substrate to connect the circuits on both sides, if the conventional two-sided electrical connection process using electroless copper plating is performed, the conductive silver particle layer (M1) may be damaged and cannot be used as a plating seed during the micro-etching process to remove the palladium catalyst adsorbed on the conductive seed layer. In addition, forming a copper plating film on the silver particle layer (M1) will cause the conductive seed layer used for circuit pattern formation to become a copper layer. Therefore, as mentioned above, the refinement and thinning of the circuit pattern in the seed layer etching process becomes a problem.

[0012] Existing technical documents

[0013] Patent documents

[0014] Patent Document 1: International Publication No. 2009 / 004774;

[0015] Patent Document 2: Japanese Patent Application Publication No. 9-136378;

[0016] Patent document 3: Japanese Patent Application Publication No. 2010-272837;

[0017] Non-patent literature 1: Akira Murakawa, Norimasa Fukasawa, Wataru Fujikawa, Jun Shiraha: "Copper patterning technique using a semi-additive method based on silver nanoparticles", Proceedings of the 28th Symposium on Microelectronics, pp. 285-288, 2018.

[0018] Non-Patent Literature 2: Akira Murakawa, Shota Shinbayashi, Norimasa Fukasawa, Wataru Fujikawa, Jun Shiraha: “Copper Wiring Formation Using a Semi-Additive Method with Silver as Seed Layer”, Proceedings of the 33rd Spring Conference of the Institute of Electronics and Equipment, 11B2-03, 2019. Summary of the Invention

[0019] The problem that the invention aims to solve

[0020] The problem to be solved by the present invention is to provide a planar semi-additive laminate for two-sided connection and a printed wiring board using the same. The planar semi-additive laminate for two-sided connection does not require surface roughening with chromic acid or permanganate, or surface modification layer formation with alkali, and does not require a vacuum device. It can form wiring with high adhesion between the substrate and conductor circuit, low undercut, good design reproducibility, and good rectangular cross-sectional shape as circuit wiring.

[0021] Methods for solving problems

[0022] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that by forming a through hole through both sides of a laminate in which a silver particle layer (M1) and a copper layer (M2) with a thickness of 0.1 μm to 2 μm are sequentially stacked on both surfaces of an insulating substrate (A), a copper or nickel layer is formed on the surface of the through hole and the formed copper or nickel is replaced with silver to form a substrate, a pattern resist is formed on the conductive silver particle layer (M1), and the two sides of the substrate are electrically connected by electroplating copper and a circuit pattern is formed. In this way, it is possible to form a printed wiring board with high adhesion between the substrate and the conductor circuit, low undercut, good design reproducibility, and a good rectangular cross-sectional shape for circuit wiring without complex surface roughening, surface modification layer formation, or vacuum equipment. This invention is thus completed.

[0023] That is, the present invention provides the following:

[0024] 1. A method for manufacturing a printed wiring board, characterized in that it comprises:

[0025] Step 1: A through hole is formed on both sides of the laminate. A silver particle layer (M1) and a copper layer (M2) are sequentially stacked on the two surfaces of the insulating substrate (A) of the laminate, and the thickness of the copper layer (M2) is 0.1μm to 2μm.

[0026] Step 2: Apply an electroless plating catalyst to the substrate having the above-mentioned through holes and to the surface of the through holes.

[0027] Step 3: Etch the copper layer (M2) to expose the conductive silver particle layer (M1);

[0028] Step 4: A copper or nickel layer is formed on the surface of the through hole and on the silver particle layer (M1) by electroless plating.

[0029] Step 5 involves replacing the copper or nickel formed on the surface of the through hole and on the silver particle layer (M1) with silver.

[0030] Step 6: A patterned resist is formed on the silver plating layer (M3) formed on the conductive silver particle layer (M1).

[0031] Step 7: The two sides of the substrate are electrically connected by electroplating copper, and a conductive layer (M4) of circuit pattern is formed.

[0032] Step 8: The pattern resist is stripped off, and the silver particle layer (M1) of the non-circuit pattern formation part is removed using an etching solution.

[0033] 2. A method for manufacturing a printed wiring board, characterized in that it comprises:

[0034] Step 1: A through hole is formed on both sides of the laminate. A silver particle layer (M1) and a copper layer (M2) are sequentially stacked on the two surfaces of the insulating substrate (A) of the laminate, and the thickness of the copper layer (M2) is 0.1μm to 2μm.

[0035] Step 2: Apply an electroless plating catalyst to the substrate having the above-mentioned through holes and to the surface of the through holes.

[0036] Step 3: Etch the copper layer (M2) to expose the conductive silver particle layer (M1);

[0037] Step 4: A copper or nickel layer is formed on the surface of the through hole by electroless plating;

[0038] Step 5 involves replacing the copper or nickel formed on the surface of the aforementioned through-hole with silver;

[0039] Step 6: A patterned resist is formed on the conductive silver particle layer (M1).

[0040] Step 7: The two sides of the substrate are electrically connected by electroplating copper, and a conductive layer (M4) of circuit pattern is formed.

[0041] Step 8: The pattern resist is stripped off, and the silver particle layer (M1) of the non-circuit pattern formation part is removed using an etching solution.

[0042] 3. A method for manufacturing a printed wiring board, characterized in that it comprises:

[0043] Step 1: A through hole is formed on both sides of the laminate. A silver particle layer (M1) and a peelable capping layer (RC) are sequentially laminated on both surfaces of the insulating substrate (A) of the laminate.

[0044] Step 2: Apply an electroless plating catalyst to the surface of the substrate having the above-mentioned through holes;

[0045] Step 3 involves peeling off the aforementioned peelable capping layer (RC) to expose the conductive silver particle layer (M1).

[0046] Step 4: A copper or nickel layer is formed on the surface of the through hole and the silver particle layer (M1) by electroless plating.

[0047] Step 5: Replace the copper or nickel formed on the surface of the through hole and the silver particle layer (M1) with silver.

[0048] Step 6: A patterned resist is formed on the silver plating layer (M3) formed on the conductive silver particle layer (M1).

[0049] Step 7: The two sides of the substrate are electrically connected by electroplating copper, and a conductive layer (M4) of circuit pattern is formed.

[0050] Step 8: The pattern resist is stripped off, and the silver particle layer (M1) of the non-circuit pattern formation part is removed using an etching solution.

[0051] 4. A method for manufacturing a printed wiring board, characterized in that it comprises:

[0052] Step 1: A through hole is formed on both sides of the laminate. A silver particle layer (M1) and a peelable capping layer (RC) are sequentially laminated on both surfaces of the insulating substrate (A) of the laminate.

[0053] Step 2: Apply an electroless plating catalyst to the surface of the substrate having the above-mentioned through holes;

[0054] Step 3 involves peeling off the aforementioned peelable capping layer (RC) to expose the conductive silver particle layer (M1).

[0055] Step 4: A copper or nickel layer is formed on the surface of the through hole by electroless plating;

[0056] Step 5: Replace the copper or nickel formed on the surface of the through hole with silver;

[0057] Step 6: A patterned resist is formed on the conductive silver particle layer (M1).

[0058] Step 7: The two sides of the substrate are electrically connected by electroplating copper, and a conductive layer (M4) of circuit pattern is formed.

[0059] Step 8: The pattern resist is stripped off, and the silver particle layer (M1) of the non-circuit pattern formation part is removed using an etching solution.

[0060] 5. A method for manufacturing a semi-additive laminate as described in any one of 1 to 4, characterized in that a primer layer (B) is further laminated between the insulating substrate (A) and the silver particle layer (M1).

[0061] 6. A method for manufacturing a printed wiring board as described in any one of 1 to 5, characterized in that the thickness of the copper or nickel layer formed on the surface of the through hole is 0.1 to 1 μm.

[0062] 7. The method for manufacturing a printed wiring board as described in any one of 1 to 4, wherein the silver particles constituting the silver particle layer (M1) are coated with a polymeric dispersant.

[0063] 8. The method for manufacturing a printed wiring board as described in 5, wherein in the method for manufacturing a printed wiring board as described in 4, the primer layer (B) is a layer composed of a resin having a reactive functional group [X], the polymeric dispersant has a reactive functional group [Y], and the reactive functional group [X] and the reactive functional group [Y] can form bonds with each other through a reaction.

[0064] 9. The method for manufacturing a printed wiring board as described in 6, wherein the reactive functional group [Y] is a basic nitrogen atom group.

[0065] 10. The method for manufacturing a printed wiring board as described in 7, wherein the polymeric dispersant having the above-mentioned reactive functional group [Y] is selected from one or more polyalkylene imides and polyalkylene imides having a polyoxyalkylene structure containing an ethylene oxide unit.

[0066] 11. The method for manufacturing a printed wiring board as described in any one of 5 to 8, wherein the reactive functional group [X] is selected from one or more groups selected from the group consisting of ketone, acetoacetyl, epoxy, carboxyl, N-alkanol, isocyanate, vinyl, (meth)acryloyl, and allyl.

[0067] Invention Effects

[0068] By using the printed wiring board manufacturing method of the present invention, it is possible to design and manufacture two-sided connected printed wiring boards with high reproducibility, smooth surfaces, and good rectangular cross-sectional shapes on various smooth substrates without using a vacuum device. Therefore, by using the technology of the present invention, high-density, high-performance printed wiring boards with multilayering capable of handling high-frequency transmission can be provided at low cost, resulting in high industrial applicability in the field of printed wiring. Furthermore, the printed wiring board manufacturing method of the present invention can be used not only for conventional printed wiring boards but also for various electronic components with patterned metal layers on the substrate surface, such as connectors, electromagnetic wave shielding, RFID antennas, and film capacitors. Attached Figure Description

[0069] Figure 1 This is a process diagram of fabricating a printed wiring board using a laminated body with a semi-additive method as described in Embodiment 1 or 3.

[0070] Figure 2 This is a process diagram of fabricating a printed wiring board using a laminated body with a semi-additive method as described in Embodiment 2 or 4. Detailed Implementation

[0071] The method for manufacturing the printed wiring board of the present invention is characterized by having:

[0072] Step 1: A through hole is formed on both sides of the laminate. A silver particle layer (M1) and a copper layer (M2) are sequentially stacked on the two surfaces of the insulating substrate (A) of the laminate, and the thickness of the copper layer (M2) is 0.1μm to 2μm.

[0073] Step 2: Apply an electroless plating catalyst to the substrate having the above-mentioned through holes and to the surface of the through holes.

[0074] Step 3: Etch the copper layer (M2) to expose the conductive silver particle layer (M1);

[0075] Step 4: A copper or nickel layer is formed on the surface of the through hole and on the silver particle layer (M1) by electroless plating.

[0076] Step 5 involves replacing the copper or nickel formed on the surface of the through hole and on the silver particle layer (M1) with silver.

[0077] Step 6: A patterned resist is formed on the silver plating layer (M3) formed on the conductive silver particle layer (M1).

[0078] Step 7: The two sides of the substrate are electrically connected by electroplating copper, and a conductive layer (M4) of circuit pattern is formed.

[0079] Step 8: The pattern resist is stripped off, and the silver particle layer (M1) of the non-circuit pattern formation part is removed using an etching solution.

[0080] Furthermore, the method for manufacturing the printed wiring board of the present invention is characterized by having:

[0081] Step 1: A through hole is formed on both sides of the laminate. A silver particle layer (M1) and a copper layer (M2) are sequentially stacked on the two surfaces of the insulating substrate (A) of the laminate, and the thickness of the copper layer (M2) is 0.1μm to 2μm.

[0082] Step 2: Apply an electroless plating catalyst to the substrate having the above-mentioned through holes and to the surface of the through holes.

[0083] Step 3: Etch the copper layer (M2) to expose the conductive silver particle layer (M1);

[0084] Step 4: A copper or nickel layer is formed on the surface of the through hole by electroless plating;

[0085] Step 5 involves replacing the copper or nickel formed on the surface of the aforementioned through-hole with silver;

[0086] Step 6: A patterned resist is formed on the conductive silver particle layer (M1).

[0087] Step 7 involves electrically connecting the two sides of the substrate by electroplating copper and forming a conductive layer (M4) with a circuit pattern.

[0088] Furthermore, a more preferred embodiment of the method for manufacturing the printed wiring board of the present invention is characterized in that a primer layer (B) is further provided between the insulating substrate layer (A) and the conductive silver particle layer (M1).

[0089] Materials used as the aforementioned insulating substrate (A) include, for example: polyimide resin, polyamide-imide resin, polyamide resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyethylene naphthalate resin, polycarbonate resin, acrylonitrile-butadiene-styrene (ABS) resin, polyarylate resin, polyacetal resin, acrylic resins such as poly(meth)acrylate, polyvinylidene fluoride resin, polytetrafluoroethylene resin, polyvinyl chloride resin, polyvinylidene chloride resin, vinyl chloride resin grafted with acrylic resin, polyvinyl alcohol resin, polyethylene resin, polypropylene resin, urethane resin, cycloolefin resin, polystyrene, liquid crystal polymer (LCP), polyetheretherketone (PEEK) resin, polyphenylene sulfide (PPS), polyphenylene sulfone (PPSU), cellulose nanofibers, silicon, silicon carbide, gallium nitride, sapphire, ceramics, glass, diamond-like carbon (DLC), alumina, etc.

[0090] Alternatively, a resin substrate containing a thermosetting resin and an inorganic filler can be suitably used as the aforementioned insulating substrate (A). Examples of the aforementioned thermosetting resin include, for instance, epoxy resin, phenolic resin, unsaturated imide resin, cyanate ester resin, isocyanate ester resin, and benzo[a]benzene resin. Examples of suitable inorganic fillers include azircon resins, oxetine resins, amino resins, unsaturated polyester resins, allyl resins, dicyclopentadiene resins, silicone resins, triazine resins, and melamine resins. Conversely, examples of inorganic fillers include silica, alumina, talc, mica, aluminum hydroxide, magnesium hydroxide, calcium carbonate, aluminum borate, and borosilicate glass. One or more of these thermosetting resins and inorganic fillers can be used.

[0091] The insulating substrate (A) can be any of the following: a planar flexible material, a rigid material, or a rigid-flexible material. More specifically, the insulating substrate (A) can be a commercially available material formed into a film, sheet, or plate, or a material obtained by forming a planar shape from a solution, melt, or dispersion of the aforementioned resin. Furthermore, the insulating substrate (A) can be a substrate formed by depositing the aforementioned resin material on a conductive material such as a metal, or a substrate formed by laminating the aforementioned resin material onto a printed wiring board with a circuit pattern.

[0092] In the method for manufacturing the printed wiring board of the present invention, the silver particle layer (M1) mentioned above is used as the plating substrate layer when the conductive layer (M4) which is described later as a wiring pattern is formed by the plating process.

[0093] The silver particles constituting the silver particle layer (M1) may contain metal particles other than silver within the range that allows the plating process described later to be carried out normally. However, from the viewpoint of further improving the etching removeability of the non-circuit forming part described later, the proportion of metal particles other than silver is preferably 5 parts by mass or less, more preferably 2 parts by mass or less, relative to 100 parts by mass of silver.

[0094] As a method for forming the silver particle layer (M1) on both sides of the planar insulating substrate (A), for example, a method of coating both sides of the insulating substrate (A) with a silver particle dispersion can be cited. There are no particular limitations on the coating method of the silver particle dispersion as long as it can effectively form the silver particle layer (M1), and various coating methods can be appropriately selected according to the shape, size, rigidity, and flexibility of the insulating substrate (A) used. Specific coating methods include, for example: gravure printing, offset printing, flexographic printing, pad printing, gravure offset printing, letterpress printing, letterpress reversal printing, screen printing, micro-touch printing, reverse printing, pneumatic doctor blade coating, doctor blade coating, air knife coating, extrusion coating, impregnation coating, transfer roller coating, contact coating, cast coating, spray coating, inkjet coating, die coating, spin coating, rod coating, dip coating, etc. At this time, the silver particle layer (M1) can be formed on both sides of the insulating substrate (A) at the same time, or it can be formed on one side of the insulating substrate (A) and then on the other side.

[0095] To improve the coatability of the silver particle dispersion and enhance the adhesion of the conductive layer (M4) of the circuit pattern formed during the plating process to the substrate, the aforementioned insulating substrate (A) and the primer layer (B) formed on the insulating substrate (A) can be surface-treated before coating with the silver particle dispersion. As for the surface treatment method for the insulating substrate (A), there are no particular limitations as long as increasing the surface roughness does not pose a problem for the formation of the micro-pitch pattern or signal transmission loss caused by the rough surface; any suitable method can be selected. Examples of such surface treatment methods include, for instance, UV treatment, gas-phase ozone treatment, liquid-phase ozone treatment, corona treatment, and plasma treatment. These surface treatment methods can be performed using one method or by combining two or more methods.

[0096] After the silver particle dispersion is applied to the insulating substrate (A) or the primer layer (B), the coating film is dried, thereby evaporating the solvent contained in the silver particle dispersion and forming the silver particle layer (M1) on the insulating substrate (A) or the primer layer (B).

[0097] The drying temperature and time can be appropriately selected based on the heat resistance temperature of the substrate and the type of solvent used in the metal particle dispersion (described later). A range of 20 to 350°C is preferred, and the time is preferably in the range of 1 to 200 minutes. Furthermore, in order to form a silver particle layer (M1) with excellent adhesion on the substrate, a drying temperature in the range of 0 to 250°C is more preferable.

[0098] To reduce the resistance of the silver particle layer and improve the adhesion between the insulating substrate (A) or the primer layer (B) and the silver particle layer (M1), the insulating substrate (A) with the silver particle layer (M1) or the insulating substrate (A) with the primer layer (B) may be further annealed after drying, as needed. The annealing temperature and time can be appropriately selected based on the heat resistance of the substrate, the required resistance, and the production rate, and can be carried out for 1 minute to 2 weeks within the range of 60 to 350°C. Furthermore, it is preferable to carry out the annealing for 1 minute to 2 weeks within the temperature range of 60 to 180°C, and more preferably for approximately 1 minute to 5 hours within the temperature range of 180 to 350°C.

[0099] During the drying process described above, air supply may or may not be specifically provided. Furthermore, drying can be carried out in the atmosphere, under a displacement atmosphere of inert gases such as nitrogen or argon, or under a gas flow, or even under a vacuum.

[0100] In addition to natural drying at the coating site, the coated film can also be dried in a dryer such as a blower or a constant-temperature dryer. Furthermore, when the insulating substrate (A) is a roll film or sheet, it can be continuously moved within a designated non-heated or heated space after the coating process for drying and firing. Examples of heating methods for this drying and firing include ovens, hot air drying furnaces, infrared drying furnaces, laser irradiation, microwaves, and light irradiation (flash irradiation devices). These heating methods can be used individually or in combination.

[0101] The amount of the metal particle layer (M1) formed on the insulating substrate (A) or the primer layer (B) is preferably 0.01 to 30 g / m². 2 The range is more preferably 0.01~10 g / m 2 The range is specified. Furthermore, considering that the formation of the conductive layer (M4) performed by the plating process described later becomes easier, and the removal of the seed layer performed by the etching process described later becomes easier, a concentration of 0.05~5 g / m is further preferred. 2 The range.

[0102] The amount of silver particle layer (M1) formed can be confirmed using well-known analytical methods such as fluorescence X-ray diffraction, atomic absorption spectrometry, and ICP.

[0103] Furthermore, in the process of exposing the circuit pattern to the resist layer using active light, in order to suppress the reflection of active light from the silver particle layer (M1), the silver particle layer (M1) may contain light-absorbing pigments or dyes such as graphite or carbon, anthocyanin compounds, phthalocyanine compounds, dithiol metal complexes, naphthoquinone compounds, diimonium compounds, and azo compounds as light absorbers, within a range that allows the formation of the silver particle layer (M1), enables the normal implementation of the electroplating process described later, and ensures the etch removeability described later. These pigments or dyes can be appropriately selected according to the wavelength of the active light used. Furthermore, one or more of these pigments or dyes may be used. Moreover, to include these pigments or dyes in the silver particle layer (M1), these pigments or dyes can be added to the silver particle dispersion described later.

[0104] The silver particle dispersion used to form the silver particle layer (M1) is formed by dispersing silver particles in a solvent. There are no particular limitations on the shape of the silver particles, as long as the silver particle layer (M1) is formed well; various shapes of silver particles, such as spherical, lenticular, polyhedral, plate-like, rod-like, and linear, can be used. These silver particles can be of a single shape or a combination of two or more different shapes.

[0105] When the silver particles are spherical or polyhedral in shape, their average particle size is preferably in the range of 1 to 20,000 nm. Furthermore, when forming fine circuit patterns, considering the ability to further improve the homogeneity of the silver particle layer (M1) and the removability using the etching solution (described later), the average particle size is more preferably in the range of 1 to 200 nm, and even more preferably in the range of 1 to 50 nm. It should be noted that the "average particle size" of the nano-sized particles is the volume average value measured by dynamic light scattering method after diluting the metal particles with a good dispersing solvent. In this measurement, "Nanotrac UPA-150" manufactured by MICROTRAC can be used.

[0106] On the other hand, when the silver particles have shapes such as lens-shaped, rod-shaped, or wire-shaped, their short axis 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.

[0107] The silver particles mentioned above are preferably made of silver particles as the main component. However, as long as it does not hinder the plating process described later, or does not impair the removability of the silver particle layer (M1) described later using the etching solution, a portion of the silver constituting the silver particles can be replaced with other metals, or mixed with metal components other than silver.

[0108] Examples of metals that can be substituted or mixed include one or more metallic elements selected from the group consisting of gold, platinum, palladium, ruthenium, tin, copper, nickel, iron, cobalt, titanium, indium, and iridium.

[0109] The ratio of the metal replaced or mixed with the silver particles is preferably 5% by mass or less in the silver particles, and more preferably 2% by mass or less from the viewpoint of the plating properties of the silver particle layer (M1) and the removability by the etching solution.

[0110] The silver particle dispersion used to form the silver particle layer (M1) is made by dispersing silver particles in various solvents. The particle size distribution of the silver particles in the dispersion can be uniformly monodisperse, or it can be a mixture of particles within the above-mentioned average particle size range.

[0111] The solvent used in the dispersion of the silver particles can be an aqueous medium or an organic solvent. Examples of aqueous media include distilled water, ion-exchanged water, pure water, ultrapure water, and mixtures of the above water with organic solvents.

[0112] Examples of organic solvents that can be mixed with water 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.

[0113] In addition, examples of organic solvents used alone include: alcohol compounds, ether compounds, ester compounds, ketone compounds, etc.

[0114] Examples of alcohol or ether solvents that can be used as solvents include: methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, heptanol, hexanol, octanol, nonanol, decanol, undecylol, dodecanol, tridecanol, tetradecanol, pentadecylol, stearyl alcohol, allyl alcohol, cyclohexanol, terpineol, terpineol, dihydroterpineol, 2-ethyl-1,3-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, and dipropylene glycol. 1,2-Butanediol, 1,3-Butanediol, 1,4-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, Tripropylene glycol monobutyl ether, etc.

[0115] Examples of ketone solvents include acetone, cyclohexanone, and methyl ethyl ketone. Examples of ester solvents include ethyl acetate, butyl acetate, 3-methoxybutyl acetate, and 3-methoxy-3-methylbutyl acetate. Furthermore, other organic solvents include hydrocarbon solvents such as toluene, particularly hydrocarbon solvents with 8 or more carbon atoms.

[0116] Examples of nonpolar solvents that can be used as hydrocarbon solvents with 8 or more carbon atoms include octane, nonane, decane, dodecane, tridecane, tetradecane, cyclooctane, xylene, mesitylene, ethylbenzene, dodecylbenzene, tetrahydronaphthalene, and trimethylbenzenecyclohexane. These solvents can be used in combination with other solvents as needed. Furthermore, they can also be used in combination with solvents such as mineral oil and naphtha as mixed solvents.

[0117] There are no particular limitations as long as the solvent described above allows for stable dispersion of the silver particles and good formation of the silver particle layer (M1) on the insulating substrate (A) or the primer layer (B) formed on the insulating substrate (A) as described later. Furthermore, one or more solvents may be used.

[0118] Regarding the silver particle content in the aforementioned silver particle dispersion, as long as the various coating methods described above are used, the amount of the silver particle layer (M1) formed on the aforementioned insulating substrate (A) is 0.01~30 g / m². 2 The viscosity can be adjusted appropriately within a range to achieve optimal coating adaptability that matches the various coating methods described above. Preferably, the range is 0.1 to 50% by mass, and more preferably, it is 0.5 to 20% by mass.

[0119] The aforementioned silver particle dispersion preferably exhibits long-term dispersion stability by preventing the silver particles from agglomerating, fusing, or precipitating in the aforementioned solvents, and preferably contains a dispersant for dispersing the silver particles in the aforementioned solvents. As such a dispersant, a dispersant having functional groups that coordinate with the metal particles is preferred; examples include dispersants having functional groups such as carboxyl, amino, cyano, acetoacetyl, phosphorus-containing groups, thiols, cyanothiols, and glycine groups.

[0120] As the dispersant mentioned above, commercially available or separately synthesized low or high molecular weight dispersants can be used, as long as they are appropriately selected according to the purpose, such as the solvent for dispersing the metal particles and the type of the insulating substrate (A) on which the metal particle dispersion is coated. For example, suitable dispersants include: dodecyl mercaptan, 1-octyl mercaptan, triphenylphosphine, dodecylamine, polyethylene glycol, polyvinylpyrrolidone, polyethyleneimine, polyvinylpyrrolidone; fatty acids such as myristic acid, caprylic acid, and stearic acid; and polycyclic hydrocarbon compounds with carboxyl groups such as cholic acid, glycyrrhizic acid, and pinoresinic acid. Here, when forming a silver particle layer (M1) on the primer layer (B) described later, from the viewpoint of improving the adhesion between the two layers, it is preferable to use a compound having a reactive functional group [Y] that can form a bond with the reactive functional group [X] of the resin used in the primer layer (B) described later.

[0121] Examples of compounds having the reactive functional group [Y] include compounds having amino, amide, alkanolamide, carboxyl, carboxylic anhydride, carbonyl, acetoacetyl, epoxy, alicyclic epoxy, oxobutane ring, vinyl, allyl, (meth)acryloyl, (terminated) isocyanate, (alkoxy)silyl, silsesquioxane compounds, etc. In particular, from the viewpoint of further improving the adhesion between the primer layer (B) and the metal particle layer (M1), the aforementioned reactive functional group [Y] is preferably a basic nitrogen atom group. Examples of such basic nitrogen atom groups include imino, primary amino, secondary amino, etc.

[0122] The aforementioned basic nitrogen atom groups can be present singly or in multiples in the dispersant molecule 1. By containing multiple basic nitrogen atoms in the dispersant, a portion of the basic nitrogen atom groups contributes to the dispersion stability of the metal particles due to their interaction with the metal particles, while the remaining basic nitrogen atom groups contribute to improved adhesion to the aforementioned insulating substrate (A). Furthermore, when a resin having a reactive functional group [X] is used in the primer layer (B) described later, the basic nitrogen atom groups in the dispersant can form bonds with the reactive functional group [X], which can further improve the adhesion of the conductive layer (M4) of the circuit pattern described later on the aforementioned insulating substrate (A), and is therefore preferred.

[0123] Regarding the aforementioned dispersant, considering the stability and coatability of the silver particle dispersion and the ability to form a silver particle layer (M1) exhibiting good adhesion on the aforementioned insulating substrate (A), the dispersant is preferably a polymeric dispersant. As such a polymeric dispersant, polyalkylene imides such as polyethyleneimine and polypropyleneimine, or compounds formed by adding polyoxyalkylene to the aforementioned polyalkylene imides, are preferred.

[0124] The compound formed by adding polyoxyalkylene to the above-mentioned polyalkylene imide can be a compound formed by combining polyethylene imide and polyoxyalkylene in a straight chain, or it can be a compound formed by branching polyoxyalkylene onto the side of the main chain composed of the above-mentioned polyethylene imide.

[0125] Specific examples of compounds formed by adding polyoxyalkylene to the aforementioned polyalkylene imide include: block copolymers of polyethyleneimine and polyethylene oxide; compounds that incorporate a polyethylene oxide structure by adding ethylene oxide to a portion of the imino group present in the main chain of polyethyleneimine; and compounds formed by reacting the amino group of the polyalkylene imide, the hydroxyl group of the polyethylene oxide glycol, and the epoxy group of the epoxy resin.

[0126] Commercially available products of the aforementioned polyalkylene imides include, for example, “PAO2006W,” “PAO306,” “PAO318,” and “PAO718” from the “EPOMIN (registered trademark) PAO series” manufactured by Nippon Shokubai Co., Ltd.

[0127] The number average molecular weight of the above-mentioned polyalkylimide is preferably in the range of 3,000 to 30,000.

[0128] The amount of the dispersant used 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. In addition, from the viewpoint of being able to form a silver particle layer (M1) with good adhesion on the insulating substrate (A) or the primer layer (B) described later, it is preferably in the range of 0.1 to 10 parts by mass relative to 100 parts by mass of the silver particles. Furthermore, from the viewpoint of being able to improve the plating properties of the silver particle layer (M1), it is more preferably in the range of 0.1 to 5 parts by mass.

[0129] There are no particular limitations on the method for manufacturing the aforementioned silver particle dispersion; various methods can be used. For example, silver particles manufactured using a gas-phase method such as low-vacuum gas-phase evaporation can be dispersed in a solvent, or a silver particle dispersion can be directly prepared by reducing silver compounds in a liquid phase. Regardless of whether a gas-phase or liquid-phase method is used, the solvent composition of the dispersion during manufacturing and the dispersion during coating can be appropriately changed as needed by replacing or adding solvents. Among gas-phase and liquid-phase methods, the liquid-phase method is particularly suitable from the perspective of dispersion stability and simplicity of the manufacturing process. For example, a liquid-phase method can be used to manufacture the dispersion by reducing silver ions in the presence of the aforementioned polymeric dispersant.

[0130] In the above-mentioned dispersion of silver particles, surfactants, leveling agents, viscosity modifiers, film-forming aids, defoamers, preservatives and other organic compounds can be added as needed.

[0131] Examples of the aforementioned surfactants include, for instance, nonionic surfactants such as polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl ether, polyoxyethylene styrene phenyl ether, polyoxyethylene sorbitan tetraoleate, and polyoxyethylene-polyoxypropylene copolymer; anionic surfactants such as fatty acid salts like sodium oleate, alkyl sulfate salts, alkylbenzene sulfonates, alkyl sulfosuccinates, naphthalene sulfonates, polyoxyethylene alkyl sulfates, sodium alkyl sulfonates, and sodium alkyl diphenyl ether sulfonates; and cationic surfactants such as alkylamine salts, alkyl trimethylammonium salts, and alkyl dimethyl benzylammonium salts.

[0132] As the leveling agent mentioned above, general leveling agents can be used, such as silicone compounds, acetylene glycol compounds, fluorine compounds, etc.

[0133] As viscosity modifiers, common thickeners can be used, such as acrylic polymers that can be thickened by adjusting to alkalinity, synthetic rubber latex, urethane resins that can be thickened by molecular association, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, polyvinyl alcohol, hydrogenated castor oil, amide wax, oxidized polyethylene, metal soaps, dibenzyl sorbitol, etc.

[0134] As the aforementioned film-forming aids, general film-forming aids can be used, such as anionic surfactants like sodium dioctyl sulfosuccinate, hydrophobic nonionic surfactants like sorbitan monooleate, polyether-modified siloxanes, and silicone oils.

[0135] As the aforementioned defoamer, general defoamers can be used, such as silicone-based defoamers, nonionic surfactants, polyethers, higher alcohols, polymeric surfactants, etc.

[0136] As the aforementioned preservatives, common preservatives can be used, such as: isothiazolin-based preservatives, triazine-based preservatives, imidazole-based preservatives, pyridine-based preservatives, azole-based preservatives, pyrithione-based preservatives, etc.

[0137] Furthermore, as a more preferred embodiment of the semi-additive laminate used in the manufacturing method of the printed wiring board of the present invention, a laminate having a primer layer (B) further between the insulating substrate layer (A) and the conductive silver particle layer (M1) can be listed. The semi-additive laminate with this primer layer can further improve the adhesion of the conductive layer (M4) of the circuit pattern to the insulating substrate (A), and is therefore preferred.

[0138] The aforementioned primer layer (B) can be formed by applying a primer to a portion or the entire surface of the aforementioned insulating substrate (A) and removing solvents such as aqueous media and organic solvents contained in the primer. Here, the primer is used to improve the adhesion of the conductive layer (M4) to the insulating substrate (A) and is a liquid composition formed by dissolving or dispersing various resins described later in a solvent.

[0139] As for the method of applying the primer to the insulating substrate (A), there are no particular limitations as long as the primer layer (B) can be formed well. Various coating methods can be appropriately selected according to the shape, size, rigidity, and flexibility of the insulating substrate (A). Specific coating methods include, for example: gravure printing, offset printing, flexographic printing, pad printing, gravure offset printing, letterpress printing, letterpress reversal printing, screen printing, micro-touch printing, reverse printing, pneumatic doctor blade coating, doctor blade coating, air knife coating, extrusion coating, impregnation coating, transfer roller coating, contact coating, cast coating, spray coating, inkjet coating, mold coating, spin coating, rod coating, dip coating, etc.

[0140] Furthermore, as for the method of coating the primer on both sides of the insulating substrate (A) in the form of a film, sheet, or plate, there are no particular limitations as long as the primer layer (B) can be formed well, and the coating method exemplified above can be appropriately selected. In this case, the primer layer (B) can be formed on both sides of the insulating substrate (A) simultaneously, or it can be formed on one side of the insulating substrate (A) and then on the other side.

[0141] To improve the coatability of the primer and enhance the adhesion of the conductive layer (M4) of the aforementioned circuit pattern to the substrate, the insulating substrate (A) may be surface-treated before applying the primer. The same surface treatment method used for forming the silver particle layer (M1) on the insulating substrate (A) can be employed for the surface treatment of the insulating substrate (A).

[0142] As a method for forming a primer layer (B) by applying the primer to the surface of an insulating substrate (A) and then removing the solvent contained in the coating layer, a common method is to use a dryer to dry the substrate and allow the solvent to evaporate. The drying temperature can be set to a range that allows the solvent to evaporate without adversely affecting the insulating substrate (A); it can be room temperature drying or heated drying. Specifically, the drying temperature is preferably in the range of 20 to 350°C, more preferably in the range of 60 to 300°C. Furthermore, the drying time is preferably in the range of 1 to 200 minutes, more preferably in the range of 1 to 60 minutes.

[0143] Regarding the aforementioned drying process, air supply may or may not be required. Furthermore, drying can be carried out in the atmosphere, under a displacement atmosphere or flow such as nitrogen or argon, or under a vacuum.

[0144] When the insulating substrate (A) is a single film, sheet, or plate, drying can be carried out either naturally at the coating site or in a dryer such as a blower or a constant temperature dryer. Furthermore, when the insulating substrate (A) is a roll film or sheet, drying can be carried out by continuously moving the roll within a designated non-heated or heated space after the coating process.

[0145] The thickness of the primer layer (B) can be appropriately selected according to the specifications and uses of the printed wiring board manufactured using the present invention. From the viewpoint of further improving the adhesion between the insulating substrate (A) and the conductive layer (M4) of the circuit pattern, it is preferably in the range of 10nm to 30μm, more preferably in the range of 10nm to 1μm, and even more preferably in the range of 10nm to 500nm.

[0146] When the dispersant for the aforementioned metal particles is a substance having a reactive functional group [Y], the resin forming the primer layer (B) is preferably a resin having a reactive functional group [X] that is reactive to the reactive functional group [Y]. Examples of the aforementioned reactive functional group [X] include, for example, amino, amide, alkanolamide, ketone, carboxyl, carboxylic anhydride, carbonyl, acetoacetyl, epoxy, alicyclic epoxy, oxetane ring, vinyl, allyl, (meth)acryloyl, (terminated)isocyanate, (alkoxy)silyl, etc. Alternatively, silsesquioxane compounds may be used as the compounds forming the primer layer (B).

[0147] In particular, when the reactive functional group [Y] in the above-mentioned dispersant is a basic nitrogen atom group, from the viewpoint of further improving the adhesion of the conductive layer (M4) on the above-mentioned insulating substrate (A), the resin forming the primer layer (B) is preferably a resin having ketone, carboxyl, carbonyl, acetoacetyl, epoxy, alicyclic epoxy, alkanolamide, isocyanate, vinyl, (meth)acryloyl, or allyl as reactive functional groups [X].

[0148] Examples of resins used to form the primer layer (B) include: urethane resins, acrylic resins, core-shell composite resins with urethane resin as the shell and acrylic resin as the core, epoxy resins, imide resins, amide resins, melamine resins, phenolic resins, urea-formaldehyde resins, and capped isocyanates such as polyvinyl alcohol and polyvinylpyrrolidone obtained by reacting capping agents such as phenol with polyisocyanates. It should be noted that core-shell composite resins with urethane resin as the shell and acrylic resin as the core can be obtained, for example, by polymerizing acrylic monomers in the presence of urethane resin. Furthermore, one or more of these resins can be used.

[0149] Of the resins used to form the primer layer (B), those that generate a reducing compound by heating are preferred from the viewpoint of further improving the adhesion of the conductive layer (M4) to the insulating substrate (A). Examples of such reducing compounds include phenolic compounds, aromatic amine compounds, sulfur compounds, phosphoric acid compounds, and aldehyde compounds. Among these reducing compounds, phenolic compounds and aldehyde compounds are preferred.

[0150] When a resin that generates reducing compounds upon heating is used in a primer, reducing compounds such as formaldehyde and phenol will be generated during the heating and drying process when forming the primer layer (B). Specific examples of resins that generate reducing compounds upon heating include: resins polymerized from monomers containing N-alkanol (meth)acrylamide; core-shell composite resins with a urethane resin as the shell and a resin polymerized from monomers containing N-alkanol (meth)acrylamide as the core; urea-formaldehyde-methanol condensates; urea-melamine-formaldehyde-methanol condensates; poly(N-alkoxyhydroxymethyl (meth)acrylamide); formaldehyde adducts of poly(meth)acrylamide; melamine resins; and phenolic resins, phenol-terminated isocyanates, etc., which generate phenolic compounds upon heating. Among these resins, from the viewpoint of improving adhesion, core-shell composite resins with urethane resin as the shell and a resin polymerized from monomers containing N-alkanol (meth)acrylamide as the core, melamine resin, and phenol-terminated isocyanate are preferred.

[0151] It should be noted that in this invention, "(meth)acrylamide" means one or both of "methacrylamide" and "acrylamide", and "(meth)acrylic acid" means one or both of "methacrylic acid" and "acrylic acid".

[0152] Resins that generate reducing compounds through heating can be obtained by polymerizing monomers with functional groups that generate reducing compounds through heating using polymerization methods such as free radical polymerization, anionic polymerization, and cationic polymerization.

[0153] Monomers having functional groups that generate reducing compounds upon heating include, for example, N-alkanolyl vinyl monomers, specifically including: N-hydroxymethyl (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, N-propanol (meth)acrylamide, etc.

[0154] In addition, when manufacturing the resin that generates a reducing compound by heating, various other monomers such as (meth)acrylates can be copolymerized together with monomers having functional groups that generate a reducing compound by heating.

[0155] When the aforementioned terminated isocyanate is used as the resin for forming the primer layer (B), the primer layer (B) is formed by the self-reaction between isocyanate groups to form urea diketone bonds, or by the formation of bonds between isocyanate groups and functional groups of other components. These bonds can be formed before or after coating the metal particle dispersion, either by heating.

[0156] Examples of the aforementioned capped isocyanates include substances having functional groups formed by capping the isocyanate group with a capping agent.

[0157] The aforementioned capped isocyanate preferably has the above-mentioned functional groups in the range of 350~600 g / mol per mole of capped isocyanate.

[0158] From the viewpoint of improving adhesion, the aforementioned functional groups are preferably 1 to 10 per molecule of the aforementioned capped isocyanate, and more preferably 2 to 5.

[0159] Furthermore, from the viewpoint of improving adhesion, the number average molecular weight of the above-mentioned capped isocyanate is preferably in the range of 1,500 to 5,000, and more preferably in the range of 1,500 to 3,000.

[0160] Furthermore, from the viewpoint of further improving adhesion, it is preferable that the aforementioned end-capped isocyanate has an aromatic ring. Examples of such aromatic rings include phenyl and naphthyl groups.

[0161] It should be noted that the above-mentioned capped isocyanates can be manufactured by reacting some or all of the isocyanate groups of the isocyanate compound with a capping agent.

[0162] Examples of isocyanate compounds that can serve as raw materials for the aforementioned end-capped isocyanates include, for example, polyisocyanate compounds with aromatic rings such as 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, crude diphenylmethane diisocyanate, phenylene diisocyanate, toluene diisocyanate, and naphthalene diisocyanate; aliphatic polyisocyanate compounds or polyisocyanate compounds with alicyclic structures such as hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, phenylenediamine diisocyanate, and tetramethylphenylenediamine diisocyanate. Additionally, examples of the biuret, isocyanurate, and adduct forms of the aforementioned polyisocyanate compounds can also be cited.

[0163] In addition, as the aforementioned isocyanate compound, examples can also be given of compounds obtained by reacting the polyisocyanate compound described above with compounds having hydroxyl or amino groups.

[0164] When introducing an aromatic ring into the aforementioned end-capped isocyanate, a polyisocyanate compound having an aromatic ring is preferred. Furthermore, among polyisocyanate compounds having an aromatic ring, 4,4'-diphenylmethane diisocyanate, toluene diisocyanate, isocyanurate form of 4,4'-diphenylmethane diisocyanate, and isocyanurate form of toluene diisocyanate are preferred.

[0165] Examples of end-capping agents used in the manufacture of the aforementioned end-capped isocyanates include: phenolic compounds such as phenol and cresol; lactam compounds such as ε-caprolactam, δ-valeronactam, and γ-butyrolactam; oxime compounds such as formamide oxime, acetaldehyde oxime, acetone oxime, methyl ethyl ketone oxime, methyl isobutyl ketone oxime, and cyclohexanone oxime; 2-hydroxypyridine, butyl cellosolve, propylene glycol monomethyl ether, benzyl alcohol, methanol, ethanol, n-butanol, isobutanol, dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, acetylacetone, butanethiol, dodecyl mercaptan, acetanilide, acetamide, succinimide, maleimide, imidazole, 2-methylimidazole, urea, thiourea, ethylhexene, diphenylaniline, aniline, carbazole, ethyleneimide, polyethyleneimide, 1H-pyrazole, 3-methylpyrazole, and 3,5-dimethylpyrazole. Preferably, the capping agent is capable of dissociating and generating isocyanate groups by heating in the range of 70 to 200°C, and more preferably, it is capable of dissociating and generating isocyanate groups by heating in the range of 110 to 180°C. Specifically, phenolic compounds, lactam compounds, and oxime compounds are preferred, especially phenolic compounds, which become reducing compounds when the capping agent is desorbed by heating.

[0166] Examples of methods for manufacturing the aforementioned capped isocyanate include: mixing a pre-manufactured isocyanate compound with the capping agent and reacting the mixture; or mixing the capping agent with raw materials used to manufacture the isocyanate compound and reacting the mixture.

[0167] More specifically, the above-mentioned end-capped isocyanate can be manufactured by reacting the above-mentioned polyisocyanate compound with a compound having hydroxyl or amino groups to produce an isocyanate compound with isocyanate groups at the end, and then mixing the above-mentioned isocyanate compound with the above-mentioned end-capping agent and reacting it.

[0168] The content of the end-capped isocyanate obtained by the above method in the resin forming the primer layer (B) is preferably in the range of 50 to 100% by mass, and more preferably in the range of 70 to 100% by mass.

[0169] Examples of the melamine resins mentioned above include: mono- or polyhydroxymethyl melamine obtained by adding 1 to 6 moles of formaldehyde to 1 mole of melamine; etherifications (degree of etherification arbitrary) of (poly)hydroxymethyl melamines such as trimethoxyhydroxymethyl melamine, tributoxyhydroxymethyl melamine, and hexamethoxyhydroxymethyl melamine; and urea-melamine-formaldehyde-methanol condensates.

[0170] In addition to the method described above using a resin that generates a reducing compound through heating, methods involving adding a reducing compound to the resin can also be cited. In this case, examples of the added reducing compounds include: phenolic antioxidants, aromatic amine antioxidants, sulfur-based antioxidants, phosphoric acid antioxidants, vitamin C, vitamin E, sodium ethylenediaminetetraacetate, sulfites, hypophosphite, hydrazine, formaldehyde, sodium borohydride, dimethylamineborane, phenol, etc.

[0171] In this invention, the method of adding reducing compounds to resin may result in a decrease in electrical properties due to the final residue of low molecular weight components and ionic compounds. Therefore, it is more preferable to use a resin that generates reducing compounds by heating.

[0172] Furthermore, as a preferred resin for forming the aforementioned primer layer (B), resins containing compounds having an aminotriazine ring can be cited as examples. The aforementioned compound having an aminotriazine ring can be a low molecular weight compound or a resin with a higher molecular weight.

[0173] As the aforementioned low molecular weight compounds containing an aminotriazine ring, various additives containing an aminotriazine ring can be used. Examples of commercially available products include: 2,4-diamino-6-vinyltriazine ("VT" manufactured by Shikoku Kasei Corporation), "VD-3" and "VD-4" (compounds containing an aminotriazine ring and a hydroxyl group) manufactured by Shikoku Kasei Corporation, and "VD-5" (compound containing an aminotriazine ring and an ethoxysilyl group) manufactured by Shikoku Kasei Corporation. These compounds can be used as additives by adding one or more of them to the resin forming the primer layer (B).

[0174] The amount of the low molecular weight compound having an aminotriazine ring used is preferably 0.1 to 50 parts by mass relative to 100 parts by mass of the resin, and more preferably 0.5 to 10 parts by mass.

[0175] As for the aforementioned resins containing an aminotriazine ring, resins in which an aminotriazine ring is introduced into the polymer chain of the resin via covalent bonds can also be suitably used. Specifically, aminotriazine-modified phenolic varnish resins can be cited as an example.

[0176] The aforementioned aminotriazine-modified phenolic varnish resin is a phenolic varnish resin formed by the combination of an aminotriazine ring structure and a phenolic structure via a methylene group. This aminotriazine-modified phenolic varnish resin can be obtained, for example, by co-condensing aminotriazine compounds such as melamine, benzoguanidine, and acetylguanidine with phenolic compounds such as phenol, cresol, butylphenol, bisphenol A, phenylphenol, naphthol, and resorcinol, and formaldehyde, in the presence of a weakly basic catalyst such as an alkylamine, or in the absence of a catalyst, near neutrality; or by reacting alkyl ethers of aminotriazine compounds such as methylated melamine with the aforementioned phenolic compounds.

[0177] The aforementioned aminotriazine-modified phenolic varnish resin preferably does not contain hydroxymethyl groups. Furthermore, the aforementioned aminotriazine-modified phenolic varnish resin may contain molecules that are generated as byproducts during its manufacturing process, such as molecules where only the aminotriazine structure is methylene-bound or molecules where only the phenol structure is methylene-bound. It may also contain a small amount of unreacted raw materials.

[0178] Examples of phenolic structures include, for example, phenol residues, cresol residues, butylphenol residues, bisphenol A residues, phenylphenol residues, naphthol residues, and resorcinol residues. Furthermore, the term "residue" here refers to a structure formed by the removal of at least one hydrogen atom from a carbon atom bound to an aromatic ring. For example, in the case of phenol, it refers to hydroxyphenyl.

[0179] Examples of triazine structures derived from aminotriazine compounds such as melamine, benzoguanamine, and acetylguanidine can be cited as examples.

[0180] One or more of the phenolic and triazine structures described above can be used. Furthermore, considering the potential for improved adhesion, a phenolic residue is preferred as the phenolic structure, and a structure derived from melamine is preferred as the triazine structure.

[0181] In addition, considering the ability to further improve the adhesion, the hydroxyl value of the above-mentioned aminotriazine modified phenolic varnish resin is preferably 50 mg KOH / g or more and 200 mg KOH / g or less, more preferably 80 mg KOH / g or more and 180 mg KOH / g or less, and even more preferably 100 mg KOH / g or more and 150 mg KOH / g or less.

[0182] The above-mentioned aminotriazine modified phenolic varnish resin can be used in combination with one or more of the same resin.

[0183] Furthermore, when using aminotriazine-modified phenolic varnish resin as the above-mentioned compound having an aminotriazine ring, it is preferable to use epoxy resin in conjunction.

[0184] Examples of epoxy resins mentioned above include: bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, cresol phenolic varnish type epoxy resin, phenolic varnish type epoxy resin, bisphenol A phenolic varnish type epoxy resin, alcohol ether type epoxy resin, tetrabromobisphenol A type epoxy resin, naphthalene type epoxy resin, phosphorus-containing epoxy compounds having a structure derived from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivatives, epoxy resins having a structure derived from dicyclopentadiene derivatives, and epoxides of epoxidized soybean oil and other oils. One or more of these epoxy resins may be used.

[0185] Among the aforementioned epoxy resins, from the perspective of further improving adhesion, bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, cresol phenolic varnish type epoxy resin, phenolic varnish type epoxy resin, and bisphenol A phenolic varnish type epoxy resin are preferred, and bisphenol A type epoxy resin is particularly preferred.

[0186] In addition, considering the ability to further improve the adhesion, the epoxy equivalent of the epoxy resin is preferably 100g / equivalent or more and 300g / equivalent or less, more preferably 120g / equivalent or more and 250g / equivalent or less, and even more preferably 150g / equivalent or more and 200g / equivalent or less.

[0187] When the primer layer (B) is a layer containing aminotriazine-modified phenolic varnish resin and epoxy resin, from the viewpoint of further improving adhesion, the molar ratio [(x) / (y)] of the phenolic hydroxyl group (x) in the aminotriazine-modified phenolic varnish resin to the epoxy group (y) in the epoxy resin is preferably 0.1 to 5 and less, more preferably 0.2 to 3 and less, and even more preferably 0.3 to 2 and less.

[0188] When forming a layer containing an aminotriazine-modified phenolic varnish resin and an epoxy resin as the aforementioned primer layer (B), a primer resin composition containing the aforementioned compound having an aminotriazine ring and an epoxy resin is used.

[0189] Furthermore, in the primer resin composition used to form the primer layer (B) containing the above-mentioned aminotriazine-modified phenolic varnish resin and epoxy resin, other resins such as urethane resin, acrylic resin, end-capped isocyanate resin, melamine resin, and phenolic resin may also be added as needed. One of these other resins may be used, or two or more may be used in combination.

[0190] From the viewpoint of coatability and film-forming properties, the primer used to form the above-mentioned primer layer (B) is preferably composed of 1 to 70% by mass of the above-mentioned resin, and more preferably 1 to 20% by mass.

[0191] Furthermore, various organic solvents and aqueous media can be cited as solvents that can be used in the aforementioned primers. Examples of organic solvents include toluene, ethyl acetate, methyl ethyl ketone, and cyclohexanone, while examples of aqueous media include water, organic solvents mixed with water, and mixtures thereof.

[0192] Examples of organic solvents that can be mixed with water 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.

[0193] Furthermore, the resin forming the primer layer (B) may, as needed, have functional groups such as alkoxysilyl, silanol, hydroxyl, and amino groups that facilitate crosslinking reactions. Regarding the crosslinking structure formed using these functional groups, the crosslinking structure can be formed before the subsequent step of forming the silver particle layer (M1), or it can be formed after the step of forming the silver particle layer (M1). When forming the crosslinking structure after the step of forming the silver particle layer (M1), the crosslinking structure can be formed in the primer layer (B) before forming the conductive layer (M4), or it can be formed in the primer layer (B) after forming the conductive layer (M4), for example, by curing.

[0194] In the aforementioned primer layer (B), known substances such as pH adjusters (primarily crosslinking agents), film-forming aids, leveling agents, thickeners, hydrophobic agents, and defoamers may be added as needed.

[0195] Examples of crosslinking agents include metal chelating compounds, polyamine compounds, aziridine compounds, metal salt compounds, and isocyanate compounds. Examples of thermal crosslinking agents that form a crosslinked structure by reacting at relatively low temperatures of around 25–100°C include melamine-based compounds and epoxy compounds. Thermal crosslinking agents, such as zozoline compounds, carbodiimide compounds, and terminally capped isocyanate compounds, are used to form crosslinked structures by reacting at relatively high temperatures above 100°C, as well as various photocrosslinking agents. When using the above-mentioned aminotriazine-modified phenolic varnish resin and epoxy resin as the primer layer (B), it is preferable to use a polycarboxylic acid as the crosslinking agent in the primer resin composition. Examples of such polycarboxylic acids include trimellitic anhydride, pyromellitic anhydride, maleic anhydride, and succinic acid. One or more of these crosslinking agents can be used. Furthermore, among these crosslinking agents, trimellitic anhydride is preferred from the perspective of further improving adhesion.

[0196] The amount of the crosslinking agent used varies depending on the type, but from the viewpoint of improving the adhesion of the conductive layer (M4) to the substrate, it is preferably in the range of 0.01 to 60 parts by mass relative to the total 100 parts by mass of the resin contained in the primer, 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.

[0197] When using the aforementioned crosslinking agent, the crosslinked structure can be formed before the subsequent step of forming the silver particle layer (M1), or it can be formed after the step of forming the silver particle layer (M1). When forming the crosslinked structure after the step of forming the silver particle layer (M1), the crosslinked structure can be formed on the primer layer (B) before forming the conductive layer (M4), or it can be formed on the primer layer (B) after forming the conductive layer (M4), for example, by curing.

[0198] In this invention, the method of forming the silver particle layer (M1) on the primer layer (B) is the same as the method of forming the silver particle layer (M1) on the insulating substrate (A).

[0199] In addition, regarding the primer layer (B), in order to improve the coatability of the silver particle dispersion and the adhesion of the conductive layer (M4) to the substrate, it can be surface treated before coating the silver particle dispersion, just like the insulating substrate (A).

[0200] From the viewpoint that the copper layer (M2) stacked on the conductive silver particle layer is to be efficiently exposed without damaging the silver particle layer (M1) in the process of etching the copper layer (M2) to expose the conductive silver particle layer (M1) in the process described later in step 3, the thickness of the copper layer (M2) is preferably 0.1 μm to 2 μm, and more preferably 0.5 μm to 1.5 μm.

[0201] As a method for stacking the copper layer (M2) onto the conductive silver particle layer (M1), it can be formed on the conductive silver particle layer (M1) by a dry or wet copper plating method.

[0202] Examples of dry copper plating methods include vacuum evaporation, ion plating, and sputtering. Examples of wet copper plating methods include electroless copper plating using the aforementioned silver particle layer (M1) as a plating catalyst, electroplating, and combinations of electroless and electroplating. Electroplating increases the plating deposition rate, thus improving manufacturing efficiency.

[0203] There are no particular limitations on the copper plating method used to form a copper layer (M2) on the aforementioned silver particle layer (M1). It can be formed by vacuum evaporation, ion plating, or sputtering as dry plating methods, or by electroless copper plating, electroplating, or a combination of electroless and electroplating as wet plating methods. In addition, it can be formed by combining dry and wet plating methods. In all cases, commonly known copper plating methods can be appropriately used.

[0204] Preferably, the copper plating is performed by forming a copper layer (M2) of the same thickness on the silver particle layer (M1) on both surfaces of the insulating substrate (A).

[0205] In the process of forming the copper layer (M2) by the above-described copper plating method, the surface of the silver particle layer (M1) can be surface-treated as needed. Examples of such surface treatments include cleaning with acidic or alkaline cleaning solutions, corona treatment, plasma treatment, UV treatment, gas-phase ozone treatment, liquid-phase ozone treatment, and treatment using surface treatment agents, all without damaging the resist pattern formed on the surface of the silver particle layer (M1). These surface treatments can be performed using one method or a combination of two or more methods.

[0206] In the semi-additive laminate of the present invention, the silver plating implemented to ensure the conductivity of both sides of the substrate can also be manufactured using a substrate on which a conductive silver particle layer (M1) and a release capping layer (RC) are sequentially laminated on both surfaces of an insulating substrate (A).

[0207] The aforementioned peelable capping layer (RC) is stacked on the aforementioned silver particle layer (M1). Therefore, when manufacturing the semi-additive laminate of the present invention, in the process of forming through holes through both sides described later, organic and inorganic debris (smear) is prevented from adhering to the surface of the silver particle layer (M1). In addition, in the process of making the inner wall surface of the formed through holes conductive, electroless plating catalyst is prevented from adhering to the conductive silver particle layer (M1), thus protecting the silver particle layer (M1).

[0208] As for the raw material of the above-mentioned peelable cover layer (RC), there are no particular limitations as long as the purpose of protecting the above-mentioned conductive silver particle layer (M1) can be achieved in the pretreatment step of the step of using conductive seed crystals for electroplating copper for forming circuit pattern layer as described later in the manufacturing method of the printed wiring board of the present invention. Various commercially available resin films can be used, and polyethylene, polypropylene, and polyethylene terephthalate films can be used appropriately.

[0209] The aforementioned peelable cover (RC) can also be used on films containing a silicone layer for improving peelability, such as those made of polyethylene, polypropylene, or polyethylene terephthalate.

[0210] From the viewpoints of membrane processability, the protective properties of the aforementioned silver particle layer (M1), and the ease of forming through-holes in the substrate, the thickness of the peelable capping layer (RC) used in this invention is preferably 10 to 100 μm, more preferably 15 to 70 μm.

[0211] The release capping layer (RC) used in this invention can be laminated onto the silver particle layer (M1) after the silver particle layer (M1) is coated. For example, when the silver particle layer (M1) is coated using a roller coater, the release capping layer (RC) can be laminated by winding it up together during take-up.

[0212] Alkali-soluble resins can also be used as raw materials for the release coating (RC) of the present invention. There are no particular limitations on the alkali-soluble resin as long as it can be developed in an alkaline developer; commonly known alkali-soluble resins can be used, such as amide-imide resins and resins having alkali-soluble functional groups such as carboxyl groups and phenolic hydroxyl groups. Regarding the alkali-soluble resin, a resin solution can be coated onto the silver particle layer (M1) to form a film, or a pre-filmed resin can be used. When using a film-formed resin, for example, as described above, the silver particle layer (M1) can be coated using a roller coater, and the release coating (RC) can be laminated by winding it up together during take-up.

[0213] Step 1 of the manufacturing method of the printed wiring board of the present invention is as follows: forming a through hole through both surfaces of a laminate in which a silver particle layer (M1) and a copper layer (M2) are sequentially stacked on both surfaces of an insulating substrate (A) and the copper layer (M2) has a thickness of 0.1 μm to 2 μm, or a laminate in which a primer layer (B) is further stacked between the insulating substrate (A) and the silver particle layer (M1).

[0214] In addition, step 1 of a preferred manufacturing method of the semi-additive laminate of the present invention is the following step: forming a through hole through both surfaces of a laminate in which a silver particle layer (M1) and a release cap layer (RC) are sequentially laminated on both surfaces of an insulating substrate (A), or a laminate in which a primer layer (B) is further laminated between the insulating substrate (A) and the silver particle layer (M1).

[0215] In step 1, as a method for forming the through hole in the laminate having the copper layer (M2), any known and commonly used method can be appropriately selected. For example, methods such as drilling, laser processing, processing methods that combine laser processing of the opening of the copper layer with reagent etching of the insulating substrate using oxidizing agents, alkaline reagents, acidic reagents, etc., and processing methods that combine etching of the hole pattern of the copper foil using resist with reagent etching of the insulating substrate using oxidizing agents, alkaline reagents, acidic reagents, etc.

[0216] Furthermore, in step 1, as a method for forming the through hole in a laminate having the aforementioned peelable cover layer (RC), any known and commonly used method can be appropriately selected, such as drilling or laser processing.

[0217] The hole diameter formed in the above-mentioned hole-opening process is preferably in the range of 0.01~1mm, more preferably in the range of 0.02~0.5mm, and even more preferably in the range of 0.03~0.1mm.

[0218] Organic and inorganic debris (smear) generated during hole drilling can cause poor plating adhesion, reduced plating bonding, and damage to the plating appearance during the subsequent two-sided electrical connection and conductive layer (M4) plating processes. Therefore, it is preferable to remove the debris (smear). Examples of methods for removing smear include: dry treatment such as plasma treatment and backsputtering; cleaning treatment using aqueous solutions of oxidizing agents such as potassium permanganate; cleaning treatment using aqueous solutions of alkalis or acids; and wet treatment using organic solvents.

[0219] Step 2 of the method for manufacturing the printed wiring board of the present invention is the following step: applying an electroless plating catalyst to the surface of the laminate with through holes formed in step 1 above.

[0220] In step 4 of the method for manufacturing the printed wiring board of the present invention, as a method for forming a copper or nickel layer on the surface of the through hole, electroless copper plating or electroless nickel plating is preferably performed. Various known and conventional electroless copper plating and electroless nickel plating methods can be used, and electroless plating using a palladium catalyst is particularly suitable. In step 2 of the method for manufacturing the printed wiring board of the present invention, as a method for imparting a palladium catalyst onto the substrate, various known and conventional methods can be used, for example, simply using the sensitizer-activator method or the catalyst-accelerator method.

[0221] Step 3 of the method for manufacturing a semi-additive laminate of the present invention comprises the following steps: etching the copper layer (M2) to remove the catalyst applied to the copper layer (M2), and exposing the conductive silver particle layer (M1) used to form the conductive layer (M4) as a seed layer in the printed wiring board manufacturing process.

[0222] In step 3, the reagent used to etch away the 0.1μm~2μm thick copper layer (M2) stacked on the conductive silver particle layer (M1) is not particularly limited as long as it can efficiently etch the copper layer (M2) without damaging the underlying silver particle layer (M1). Commonly known copper micro-etching solutions or soft etching solutions can be used. As the etching solution for the copper layer (M2), aqueous solutions of persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate, or sulfuric acid-hydrogen peroxide aqueous solutions can be used.

[0223] The concentration of the aqueous solution of persulfate or the aqueous solution of sulfuric acid-hydrogen peroxide can be appropriately selected according to the thickness of the copper layer (M2) of the semi-additive laminate used to manufacture the printed wiring board and the design of the manufacturing apparatus. In the process used, it is preferable to set the etching rate of the copper layer to be less than 2 μm / min. From the viewpoint of efficiently removing the copper layer (M2) and preventing damage to the conductive silver particle layer (M1) as the substrate layer, it is more preferable to set the etching rate to be 0.1 μm / min to 1.5 μm / min.

[0224] Step 4 of the method for manufacturing a semi-additive laminate of the present invention is the following step: electroless copper plating or electroless nickel plating is performed using a plating catalyst applied to the surface of the through hole of the substrate via steps 2 and 3 above, thereby forming a copper layer or a nickel layer on the surface of the through hole.

[0225] From the viewpoint of efficiently and reliably replacing the copper or nickel layer with a silver layer in step 5 and ensuring the conductivity of the replaced silver layer, the copper or nickel layer formed on the surface of the through-hole in step 4 is preferably 0.1 μm to 1 μm thick. In the electroless copper or nickel plating process of the present invention, depending on the plating conditions, sometimes the silver particle layer (M1) exposed in step 3 above functions as an electroless plating catalyst, and electroless copper or nickel plating is also deposited on the silver particle layer (M1). However, the copper or nickel layer formed on the silver particle layer (M1) can also be replaced with a silver layer by the replacement silver plating in step 5.

[0226] The replacement silver plating in step 5 of this invention can be performed using any known and commonly used plating method, and commercially available electroless replacement silver plating processes can be appropriately used.

[0227] In the method for manufacturing the printed wiring board of the present invention, in step 6, a pattern resist for the circuit pattern is formed on the silver plating layer (M3) or the conductive silver particle layer (M1) formed on the silver particle layer (M1). In step 4, if a copper layer or a nickel layer is formed on the silver particle layer (M1), the pattern resist for the circuit pattern is formed on the displacement silver plating layer formed on the silver particle layer (M1) in step 5.

[0228] In step 6, the process of forming the patterned resist, in order to improve the adhesion with the resist layer, the surface of the aforementioned silver particle layer (M1) or the replacement silver plating layer may undergo surface treatments such as cleaning with acidic or alkaline cleaning solutions, corona treatment, plasma treatment, UV treatment, gas phase ozone treatment, liquid phase ozone treatment, or treatment with surface treatment agents before forming the resist. These surface treatments may be performed using one method or by combining two or more methods.

[0229] As for the above-mentioned treatment using surface treatment agents, for example, the following methods can be used: the method described in Japanese Patent Application Publication No. 7-258870, which uses a rust inhibitor composed of a triazole compound, a silane coupling agent, and an organic acid; the method described in Japanese Patent Application Publication No. 2000-286546, which uses an organic acid, a benzotriazole rust inhibitor, and a silane coupling agent; the method described in Japanese Patent Application Publication No. 2002-363189, which uses a substance with a structure formed by combining nitrogen-containing heterocycles such as triazoles and thiadiazoles with silanes such as trimethoxysilyl and triethoxysilyl via organic groups having sulfide (sulfide) bonds; and the method described in WO2013 / 186941, which uses... Methods for treating silane compounds having a triazine ring and an amino group; methods for treating imidazole silane compounds obtained by reacting a formyl imidazole compound with an aminopropyl silane compound, as described in Japanese Patent Application Publication No. 2015-214743; methods for treating with azole silane compounds, as described in Japanese Patent Application Publication No. 2016-134454; methods for treating with an aromatic compound having an amino and an aromatic ring in one molecule, a polybasic acid having two or more carboxyl groups, and a solution containing halide ions, as described in Japanese Patent Application Publication No. 2017-203073; methods for treating with a surface treatment agent containing a triazole silane compound, as described in Japanese Patent Application Publication No. 2018-16865, etc.

[0230] In the method for manufacturing the printed wiring board of the present invention, in order to form a metallic pattern on the surface, the pattern is exposed to a photosensitive resist using a photomask or a direct exposure machine with active light. The exposure amount can be set appropriately as needed. The latent image formed on the photosensitive resist by exposure is removed using a developing solution, thereby forming a patterned resist.

[0231] Examples of developers include 0.3-2% by mass dilute alkaline aqueous solutions such as sodium carbonate or potassium carbonate. Surfactants, defoamers, and small amounts of organic solvents to promote development can be added to these dilute alkaline aqueous solutions. Alternatively, by immersing the exposed substrate in the developer or by spraying the developer onto the resist using a sprayer, a pattern resist with the patterned areas removed can be formed.

[0232] When forming patterned resist, resist residues such as skirts at the interface between the cured resist and the substrate, and resist deposits remaining on the substrate surface can be removed by using plasma deslagging treatment or commercially available resist residue removers.

[0233] As the photosensitive resist used in this invention, commercially available resist inks, liquid resists, and dry film resists can be used, as long as they are appropriately selected according to the resolution of the target pattern, the type of exposure machine used, the type of reagent used in the subsequent plating process, pH, etc.

[0234] Examples of commercially available resist inks include: "Mounting Resist MA-830" and "Etching Resist X-87" manufactured by Taiyo Ink Manufacturing Co., Ltd.; etching and plating resists from NAZDAR Corporation; and the "Etching Resist PLAS FINE PER" series and "Mounting Resist PLAS FINE PPR" series manufactured by Moyo Chemical Industry Co., Ltd. Additionally, examples of electrodeposition resists include the "Eagle" and "Pepper" series from Dow Chemical Company. Furthermore, examples of commercially available dry films include: the "Photec" series manufactured by Hitachi Chemical Co., Ltd.; the "ALPHO" series manufactured by Nikko-Materials Co., Ltd.; the "Sunfort" series manufactured by Asahi Kasei Corporation; and the "Riston" series manufactured by DuPont.

[0235] For efficient manufacturing of printed circuit boards, dry film resists are readily available, especially in the case of forming microcircuits, where semi-additive dry films are sufficient. Commercially available dry films for this purpose include, for example: Nikko Materials Co., Ltd.'s "ALFO LDF500" and "NIT2700", Asahi Kasei Corporation's "Sunfort UFG-258", Hitachi Chemical Co., Ltd.'s "RD series (RD-2015, 1225)" and "RY series (RY-5319, 5325)", and DuPont's "PlateMaster series (PM200, 300)".

[0236] In the manufacturing process of the printed wiring board of the present invention, when forming a circuit pattern on a substrate, the conductive silver particle layer (M1) or a displacement silver plating layer formed on the conductive silver particle layer (M1) is used as the cathode electrode for copper electroplating. The silver particle layer (M1) or displacement silver plating layer exposed by development as described above is then subjected to a copper electroplating process. This allows the through-holes of the laminate to be connected by copper plating, while simultaneously forming a conductive layer (M4) of the circuit pattern. (Step 6 of the printed wiring board manufacturing method of the present invention)

[0237] Before forming the conductive layer (M4) using the aforementioned copper electroplating method, surface treatment may be performed on the surface of the silver particle layer (M1) or the replacement silver plating layer formed on the conductive silver particle layer (M1), as needed. Examples of such surface treatments include cleaning with acidic or alkaline cleaning solutions, corona treatment, plasma treatment, UV treatment, gas-phase ozone treatment, liquid-phase ozone treatment, and treatment using surface treatment agents, provided that the resist pattern formed on the surface of the silver particle layer (M1) or the conductive silver particle layer (M1) is not damaged. These surface treatments can be performed using one method or in combination of two or more methods.

[0238] When forming a conductive layer (M4) with a circuit pattern on an insulating substrate using the semi-additive method of the present invention, annealing can be performed after plating to alleviate the stress of the plating and improve the adhesion. Annealing can be performed before the etching process described later, after the etching process, or both before and after the etching process.

[0239] The annealing temperature can be appropriately selected within the range of 40 to 300°C, depending on the heat resistance of the substrate and the intended use. A range of 40 to 250°C is preferred, and a range of 40 to 200°C is more preferable to suppress oxidative degradation of the coating. Furthermore, within the temperature range of 40 to 200°C, the annealing time can be from 10 minutes to 10 days, while annealing at temperatures exceeding 200°C can be from 5 minutes to 10 hours. Additionally, a rust inhibitor can be appropriately applied to the coating surface during annealing.

[0240] In step 7 of the method for manufacturing the printed wiring board of the present invention, after the conductive layer (M4) is formed by plating in step 6, the pattern resist formed using the photosensitive resist is peeled off, and the silver particle layer (M1) of the non-patterned area or the silver particle layer (M1) of the non-patterned area and the replacement silver plating layer are removed using an etching solution. The removal of the pattern resist can be performed under the recommended conditions described in the catalog, instruction manual, etc., of the photosensitive resist used. Furthermore, as the resist stripping solution used for removing the pattern resist, a commercially available resist stripping solution or a 1.5-3% by mass aqueous solution of sodium hydroxide or potassium hydroxide set at 45-60°C can be used. The resist can be removed by immersing the substrate on which the conductive layer (M4) with the above-mentioned circuit pattern is formed in the stripping solution, or by spraying the stripping solution using a sprayer or the like.

[0241] Furthermore, the etching solution used to remove the silver particle layer (M1) and the replacement silver plating layer from the non-patterned areas is preferably selectively etched only the silver particle layer (M1) and the replacement silver plating layer, without etching the copper forming the conductive layer (M4). A mixture of carboxylic acid and hydrogen peroxide can be used as such an etching solution.

[0242] Examples of the aforementioned carboxylic acids include, for instance, acetic acid, formic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, heptadecanic 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, benzenehexacarboxylic acid, silicic acid, pyruvic acid, lactic acid, malic acid, citric acid, fumaric acid, maleic acid, aconitic acid, glutaric acid, adipic acid, and amino acids. One or more of these carboxylic acids can be used. Among these carboxylic acids, acetic acid is preferred as the primary carboxylic acid for ease of manufacture and operation as an etching solution.

[0243] It is believed that if a mixture of carboxylic acid and hydrogen peroxide is used as the etching solution, peroxycarboxylic acid will be generated through the reaction of hydrogen peroxide and carboxylic acid. It is speculated that the generated peroxycarboxylic acid inhibits the dissolution of copper constituting the conductive layer (M4) and preferentially dissolves silver constituting the silver particle layer (M1).

[0244] As for the mixing ratio of the above-mentioned carboxylic acid and hydrogen peroxide, considering the ability to suppress the dissolution of the copper conductive layer (M4), the preferred ratio is 2 to 100 moles of hydrogen peroxide relative to 1 mole of carboxylic acid, and more preferably 2 to 50 moles of hydrogen peroxide.

[0245] The mixture of the aforementioned carboxylic acid and hydrogen peroxide is preferably an aqueous solution prepared by diluting with water. Furthermore, considering the ability to suppress the effect of temperature rise in the etching solution, the content ratio of the mixture of the aforementioned carboxylic acid and hydrogen peroxide in the aqueous solution is preferably in the range of 2 to 65% by mass, more preferably in the range of 2 to 30% by mass.

[0246] The water used for dilution is preferably water that has had ionic substances and impurities removed, such as ion-exchanged water, pure water, or ultrapure water.

[0247] In the above etching solution, a protective agent can be further added to protect the conductive layer (M4) of the copper and inhibit its dissolution. A azole compound is preferably used as the protective agent.

[0248] Examples of the aforementioned azole compounds include, for example, imidazole, pyrazole, triazole, and tetraazole. azole, thiazole, selenazole diazole, thiadiazole, Triazole, thiatriazole, etc.

[0249] Specific examples of the aforementioned azole compounds include, for instance, 2-methylbenzimidazole, aminotriazole, 1,2,3-benzotriazole, 4-aminobenzotriazole, 1-diaminomethylbenzotriazole, aminotetrazole, phenyltetrazole, 2-phenylthiazole, benzothiazole, etc. One or more of these azole compounds may be used.

[0250] The concentration of the above-mentioned azole compound in the etching solution is preferably in the range of 0.001 to 2% by mass, and more preferably in the range of 0.01 to 0.2% by mass.

[0251] In addition, in the above-mentioned etching solution, it is preferable to add polyalkylene glycol as a protective agent in order to suppress the dissolution of the copper conductive layer (M4).

[0252] Examples of the aforementioned polyalkylene glycols include, for example, water-soluble polymers such as polyethylene glycol, polypropylene glycol, and polyoxyethylene-polyoxypropylene block copolymers. Polyethylene glycol is preferred. Furthermore, the number average molecular weight of the polyalkylene glycol is preferably in the range of 200 to 20,000.

[0253] The concentration of the aforementioned polyalkylene glycol in the etching solution is preferably in the range of 0.001 to 2% by mass, and more preferably in the range of 0.01 to 1% by mass.

[0254] In the above etching solution, additives such as sodium salts, potassium salts, and ammonium salts of organic acids can be added as needed to suppress pH fluctuations.

[0255] In the manufacturing method of the printed wiring board of the present invention, the removal of the silver particle layer (M1) of the non-pattern forming part and the replacement silver plating layer can be performed by the following method: after forming the conductive layer (M4), the pattern resist formed by the photosensitive resist is peeled off, and the peeled substrate is immersed in the etching solution or the etching solution is sprayed onto the substrate using a sprayer or the like.

[0256] When using an etching apparatus to remove the silver particle layer (M1) of the non-patterned portion and replace the silver plating layer, for example, the etching solution can be prepared in such a way that all the components of the etching solution are in a predetermined composition and then supplied to the etching apparatus, or each component of the etching solution can be supplied to the etching apparatus separately and the components can be mixed in the apparatus to form a predetermined composition.

[0257] The above-mentioned etching solution is preferably used in a temperature range of 10~35°C. Especially when using an etching solution containing hydrogen peroxide, it is preferable to use it in a temperature range below 30°C to suppress the decomposition of hydrogen peroxide.

[0258] After removing the silver particle layer (M1) using the aforementioned etching solution, in order to prevent the silver components dissolved in the etching solution from adhering to and remaining on the printed circuit board, a further cleaning operation can be performed in addition to water rinsing. During the cleaning operation, a cleaning solution that dissolves silver oxide, silver sulfide, and silver chloride but hardly dissolves silver is preferably used. Specifically, an aqueous solution containing thiosulfate or tris(3-hydroxyalkyl)phosphine, or an aqueous solution containing mercaptocarboxylic acid or its salt, is preferably used as the cleaning reagent.

[0259] Examples of the aforementioned thiosulfates include, for example, ammonium thiosulfate, sodium thiosulfate, and potassium thiosulfate. Examples of the aforementioned tris(3-hydroxyalkyl)phosphine include, for example, tris(3-hydroxymethyl)phosphine, tris(3-hydroxyethyl)phosphine, and tris(3-hydroxypropyl)phosphine. One of these thiosulfates or tris(3-hydroxyalkyl)phosphines may be used, or two or more may be used in combination.

[0260] The concentration of the aqueous solution containing thiosulfate can be set appropriately according to the process time and the characteristics of the cleaning equipment used. It is preferably in the range of 0.1% to 40% by mass, and from the viewpoint of cleaning efficiency and reagent stability during continuous use, it is more preferably in the range of 1% to 30% by mass.

[0261] Furthermore, the concentration of the aqueous solution containing the above-mentioned tris(3-hydroxyalkyl)phosphine can be appropriately set according to the process time, the characteristics of the cleaning device used, etc., and is preferably in the range of 0.1 to 50% by mass. From the viewpoint of cleaning efficiency and reagent stability during continuous use, it is more preferably in the range of 1 to 40% by mass.

[0262] Examples of the aforementioned thiocarboxylic acids include, for example, thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, thiomalic acid, cysteine, and N-acetylcysteine. Additionally, examples of salts of the aforementioned thiocarboxylic acids include, for example, alkali metal salts, ammonium salts, and amine salts.

[0263] The concentration of the aqueous solution of mercaptocarboxylic acid or its salt 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 viewpoint of cleaning efficiency and process cost when performing large-scale processing.

[0264] As a method for performing the above-mentioned cleaning operation, examples include: immersing the printed circuit board obtained by etching away the silver particle layer (M1) of the non-patterned portion in the cleaning reagent; or spraying the cleaning reagent onto the printed circuit board using a sprayer or the like. Regarding the temperature of the cleaning reagent, it can be used at room temperature (25°C), but for the purpose of stable cleaning without being affected by outdoor temperature, the temperature can be set to 30°C, for example.

[0265] In addition, the process of removing the silver particle layer (M1) of the non-patterned area using etching solution and the cleaning operation can be repeated as needed.

[0266] As described above, after the silver particle layer (M1) and the replacement silver plating layer of the non-patterned portion are removed using the above-mentioned etching solution, the printed wiring board of the present invention can be further cleaned as needed to further improve the insulation of the non-patterned portion. In 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.

[0267] Examples of cleaning using the alkaline permanganate solution include: immersing the printed circuit board obtained by the above method in an alkaline permanganate solution set at 20-60°C; and spraying the alkaline permanganate solution onto the printed circuit board using a sprayer or similar device. To improve the wettability of the alkaline permanganate solution on the substrate surface and increase cleaning efficiency, the printed circuit board can be treated by contacting it with a water-soluble organic solvent containing alcohol hydroxyl groups before cleaning. Examples of such organic solvents include methanol, ethanol, n-propanol, and isopropanol. One or more of these organic solvents can be used.

[0268] The concentration of the alkaline permanganate solution can be selected appropriately as needed. Preferably, 0.1 to 10 parts by mass of potassium permanganate or sodium permanganate are dissolved in 100 parts by mass of a 0.1 to 10% by mass aqueous solution of potassium hydroxide or sodium hydroxide. From the viewpoint of cleaning efficiency, it is more preferable to dissolve 1 to 6 parts by mass of potassium permanganate or sodium permanganate in 100 parts by mass of a 1 to 6% by mass aqueous solution of potassium hydroxide or sodium hydroxide.

[0269] When performing the cleaning with alkaline permanganate solution, it is preferable to treat the cleaned printed circuit board with a neutralizing and reducing liquid after cleaning with the alkaline permanganate solution. Examples of such neutralizing and reducing liquids include, for example, 0.5-15% by mass dilute sulfuric acid or an aqueous solution containing an organic acid. Examples of such organic acids include, formic acid, acetic acid, oxalic acid, citric acid, ascorbic acid, and methionine.

[0270] The cleaning using alkaline permanganate solution can be performed after the cleaning to prevent the silver components dissolved in the etching solution from adhering to and remaining on the printed wiring board, or the cleaning using alkaline permanganate solution can be performed alone instead of the cleaning to prevent the silver components dissolved in the etching solution from adhering to and remaining on the printed wiring board.

[0271] Furthermore, the printed wiring board obtained using the manufacturing method of the present invention can be appropriately laminated with a cover film on the circuit pattern, formed with a solder mask layer, and nickel-gold plating, nickel-palladium-gold plating, or palladium-gold plating as the final surface treatment of the circuit pattern, as needed.

[0272] The printed wiring board manufacturing method of the present invention described above enables the manufacture of substrates with smooth surface circuit patterns on various smooth substrates, exhibiting high adhesion, excellent design reproducibility, and a good rectangular cross-sectional shape, without the use of vacuum equipment. Therefore, by using the semi-additive laminate of the present invention, high-density, high-performance printed wiring board substrates and printed wiring boards of various shapes and sizes can be readily provided at low cost, resulting in high industrial applicability in the field of printed wiring boards. Furthermore, by using the laminate, it is possible not only to manufacture printed wiring boards but also to manufacture various components with patterned metal layers on the surface of planar substrates, such as connectors, electromagnetic wave shielding, RFID antennas, and film capacitors.

[0273] Example

[0274] The present invention will now be described in detail using examples.

[0275] [Manufacturing Example 1: Manufacturing of Primer (B-1)]

[0276] In a nitrogen-purged container equipped with a thermometer, a nitrogen inlet tube, and a stirrer, 100 parts by mass of polyester polyol (a polyester polyol obtained by reacting 1,4-cyclohexanediethanol, neopentyl glycol, and adipic acid), 17.6 parts by mass of 2,2-dimethylolpropionic acid, 21.7 parts by mass of 1,4-cyclohexanediethanol, 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 with isocyanate groups at the end.

[0277] Next, 13.3 parts by mass of triethylamine were added to the above urethane prepolymer solution to neutralize the carboxyl groups present in the urethane prepolymer. Then, 380 parts by mass of water were added and stirred thoroughly to obtain an aqueous dispersion of the urethane prepolymer.

[0278] To the aqueous dispersion of the urethane prepolymer obtained above, 8.8 parts by mass of a 25% by mass ethylenediamine aqueous solution were added and stirred to induce chain elongation in the urethane prepolymer. Next, curing and solvent removal were performed to obtain an aqueous dispersion of urethane resin (30% by mass of non-volatile components). The weight-average molecular weight of the above urethane resin is 53,000.

[0279] Next, 140 parts by mass of deionized water and 100 parts by mass of the aqueous dispersion of the urethane resin obtained above were added to a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet pipe, a thermometer, a dropping funnel for adding the monomer mixture, and a dropping funnel for adding the polymerization catalyst. The temperature was raised to 80°C while nitrogen was being introduced. Then, while stirring and maintaining the temperature inside the reaction vessel at 80°C, 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-butoxymethacrylamide, along with 20 parts by mass of a 0.5% by mass ammonium persulfate aqueous solution, were added dropwise over 120 minutes through separate dropping funnels.

[0280] After the addition was complete, the mixture was stirred for another 60 minutes at the same temperature. The temperature inside the reaction vessel was then 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 core-shell composite resin, i.e., a primer layer resin composition, with the aforementioned urethane resin as the shell layer and an acrylic resin such as methyl methacrylate as the core layer. Next, isopropanol and deionized water were added to this aqueous dispersion at a mass ratio of 7 / 3 (isopropanol to water) and a non-volatile content of 2% by mass, and mixed to obtain primer (B-1).

[0281] [Manufacturing Example 2: Manufacturing of Primer (B-2)]

[0282] In a reaction flask equipped with a reflux condenser, thermometer, and stirrer, 200 parts by weight of water and 350 parts by weight of methanol were added to 600 parts by weight of formalin containing 37% by weight of formaldehyde and 7% by weight of methanol. Next, 25% by weight of sodium hydroxide aqueous solution was added to the aqueous solution to adjust the pH to 10, and then 310 parts by weight of melamine was added. The liquid temperature was raised to 85°C, and a hydroxymethylation reaction was carried out for 1 hour.

[0283] Then, formic acid was added and the pH was adjusted to 7, followed by cooling to 60°C to allow for etherification (a second-order reaction). At a turbidity temperature of 40°C, a 25% by mass sodium hydroxide aqueous solution was added to adjust the pH to 9, stopping the etherification reaction (reaction time: 1 hour). Residual methanol was removed under reduced pressure at 50°C (methanol removal time: 4 hours) to obtain a primer resin composition containing melamine resin with 80% by mass of non-volatile components. Next, methyl ethyl ketone was added to this resin composition for dilution and mixing, thereby obtaining a primer (B-2) with 2% by mass of non-volatile components.

[0284] [Manufacturing Example 3: Manufacturing of Primer (B-3)]

[0285] In a reaction vessel equipped with a thermometer, a nitrogen inlet tube, a stirrer, and purged with nitrogen, 9.2 parts by mass of 2,2-dimethylolpropionic acid, 57.4 parts by mass of polymethylene polyphenyl polyisocyanate (Millionate MR-200 manufactured by Tosoh Corporation), and 233 parts by mass of methyl ethyl ketone were added, and the reaction was carried out at 70°C for 6 hours to obtain an isocyanate compound. Next, 26.4 parts by mass of phenol were supplied to the reaction vessel as a capping agent, and the reaction was carried out at 70°C for 6 hours. Then, the mixture was cooled to 40°C to obtain a solution of capped isocyanate.

[0286] Next, 7 parts by mass of triethylamine were added to the obtained isocyanate solution at 40°C to neutralize the carboxyl groups of the isocyanate. Water was added and the mixture was stirred thoroughly. Methyl ethyl ketone was then removed by distillation to obtain a primer resin composition containing 20% ​​by mass of the non-volatile component, which is composed of the isocyanate and water. Methyl ethyl ketone was then added to this resin composition for dilution and mixing to obtain a primer (B-3) with 2% by mass of the non-volatile component.

[0287] [Manufacturing Example 4: Manufacturing of Primer (B-4)]

[0288] 35 parts by weight of phenolic varnish resin (PHENOLITE TD-2131 manufactured by DIC Corporation, hydroxyl equivalent 104 g / equivalent), 64 parts by weight of epoxy resin (EPICLON 850-S manufactured by DIC Corporation; bisphenol A type epoxy resin, epoxy equivalent 188 g / equivalent), and 1 part by weight of 2,4-diamino-6-vinyltriazine (VT manufactured by Shikoku Kasei Corporation) were mixed and diluted with methyl ethyl ketone to a non-volatile component of 2% by weight to obtain primer (B-4).

[0289] [Manufacturing Example 5: Manufacturing of Primer (B-5)]

[0290] 35 parts by weight of phenolic varnish resin (PHENOLITE TD-2131 manufactured by DIC Corporation, hydroxyl equivalent 104 g / equivalent), 64 parts by weight of epoxy resin (EPICLON 850-S manufactured by DIC Corporation; bisphenol A type epoxy resin, epoxy equivalent 188 g / equivalent), and 1 part by weight of silane coupling agent with triazine ring (VD-5 manufactured by Shikoku Kasei Corporation) were mixed and diluted with methyl ethyl ketone to a non-volatile component of 2% by weight to obtain primer (B-5).

[0291] [Manufacturing Example 6: Manufacturing of Primer (B-6)]

[0292] In a flask equipped with a thermometer, condenser, distillation column, and stirrer, 750 parts by mass of phenol, 75 parts by mass of melamine, 346 parts by mass of 41.5% formalin, and 1.5 parts by mass of triethylamine were added. The mixture was heated to 100°C while being exothermic. After reacting at 100°C under reflux for 2 hours, water was removed under normal pressure, and the temperature was raised to 180°C for another 2 hours. Unreacted phenol was then removed under reduced pressure to obtain an aminotriazine-modified phenolic varnish resin. The hydroxyl equivalent was 120 g / equivalent.

[0293] The above-obtained aminotriazine phenolic varnish resin (65 parts by weight) and epoxy resin (“EPICLON 850-S” manufactured by DIC Corporation; bisphenol A type epoxy resin, epoxy equivalent 188 g / equivalent) were mixed and then diluted with methyl ethyl ketone to a non-volatile component concentration of 2% by weight, thereby obtaining the primer composition (B-6).

[0294] [Manufacturing Example 7: Manufacturing of Primer (B-7)]

[0295] The aminotriazine phenolic varnish resin obtained in Manufacturing Example 6 was mixed with 52 parts by weight of epoxy resin (“EPICLON 850-S” manufactured by DIC Corporation; bisphenol A type epoxy resin, epoxy equivalent 188 g / equivalent), and then diluted with methyl ethyl ketone to a non-volatile component of 2% by weight, thereby obtaining the primer composition (B-7).

[0296] [Manufacturing Example 8: Manufacturing of Primer (B-8)]

[0297] The amounts of aminotriazine phenolic varnish resin and epoxy resin were changed from 48 parts by mass to 39 parts by mass and from 52 parts by mass to 61 parts by mass, respectively. Otherwise, the same procedure as in Manufacturing Example 7 was followed to obtain a primer composition (B-8) with 2% by mass of non-volatile components.

[0298] [Manufacturing Example 9: Manufacturing of Primer (B-9)]

[0299] The amounts of aminotriazine phenolic varnish resin and epoxy resin were changed from 48 parts by mass to 31 parts by mass and from 52 parts by mass to 69 parts by mass, respectively. Otherwise, the same procedure as in Manufacturing Example 8 was followed to obtain a primer composition (B-9) with 2% by mass of non-volatile components.

[0300] [Manufacturing Example 10: Manufacturing of Primer (B-10)]

[0301] In manufacturing example 7, 47 parts by weight of aminotriazine phenolic varnish resin and 52 parts by weight of epoxy resin (“EPICLON 850-S” manufactured by DIC Corporation; bisphenol A type epoxy resin, epoxy equivalent 188 g / equivalent) were further mixed with 1 part by weight of trimellitic anhydride, and then diluted and mixed with methyl ethyl ketone to a non-volatile component of 2% by weight, thereby obtaining primer (B-10).

[0302] [Manufacturing Example 11: Manufacturing of Primer (B-11)]

[0303] In a reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet pipe, thermometer, and dropping funnel, add 350 parts by weight of deionized water and 4 parts by weight of surfactant ("Latemul E-118B" manufactured by Kao Corporation: 25% by weight of active ingredient), and heat to 70°C while blowing in nitrogen.

[0304] Under stirring, a portion (5 parts by mass) of the monomer preemulsion was added to the reaction vessel, followed by 0.1 parts by mass of potassium persulfate. Polymerization was carried out for 60 minutes while maintaining the temperature inside the reaction vessel at 70°C. The monomer preemulsion was obtained by mixing a vinyl monomer mixture consisting of 47.0 parts by mass of methyl methacrylate, 5.0 parts by mass of glycidyl methacrylate, 45.0 parts by mass of n-butyl acrylate, and 3.0 parts by mass of methacrylic acid, 4 parts by mass of surfactant (Aqualon KH-1025 manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.: 25 parts by mass of active ingredient), and 15 parts by mass of deionized water.

[0305] Next, while maintaining the temperature inside the reaction vessel at 70°C, the remaining monomer pre-emulsion (114 parts by mass) and 30 parts by mass of an aqueous solution of potassium persulfate (1.0% by mass of active ingredient) were added dropwise over 180 minutes using different dropping funnels. After the addition was completed, the mixture was stirred at this temperature for 60 minutes.

[0306] The temperature inside the reaction vessel was cooled to 40°C. Then, deionized water was used to achieve a non-volatile component content of 10.0% by mass, followed by filtration through a 200-mesh filter cloth to obtain the primer resin composition used in this invention. Next, water was added to the resin composition for dilution and mixing to obtain a primer (B-11) with a non-volatile component content of 5% by mass.

[0307] [Preparation Example 1: Preparation of Silver Particle Dispersion]

[0308] A compound formed by the addition of p-ethylene imine to polyethylene oxide was used as a dispersant to disperse silver particles with 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 deionized water, thereby preparing a dispersion containing silver particles and a dispersant. Next, deionized water, ethanol, and a surfactant were added to the obtained dispersion to prepare a 5% by mass silver particle dispersion.

[0309] [Preparation Example 2: Preparation of Copper Etching Solution]

[0310] A copper etching solution was prepared by mixing sulfuric acid (37.5 g / L) and hydrogen peroxide (13.5 g / L) in ion-exchanged water.

[0311] Electroless silver plating baths for preparation examples (3) to (5) were prepared based on Japanese Patent Application Publication No. 2000-300875.

[0312] [Preparation Example 3: Preparation of Electroless Silver Plating Bath (1)]

[0313] Silver methanesulfonate 10 g / L (calculated as silver), methanesulfonic acid 100 g / L, 1,4-bis(2-hydroxyethylthio)ethane 25 g / L, pH 0.5, bath temperature 40℃

[0314] [Preparation Example 4: Preparation of Electroless Silver Plating Bath (2)]

[0315] Silver nitrate 5 g / L (based on silver), 1,4-bis(2-hydroxyethylthio)butane 40 g / L

[0316] 2,2'-(Ethylene dithio)diethanethiol 90 g / L, pH 3.0 (adjusted with dilute nitric acid)

[0317] Bath temperature 25℃

[0318] [Preparation Example 5: Preparation of Electroless Silver Plating Bath (3)]

[0319] Silver oxide 1 g / L (calculated as silver), p-toluenesulfonic acid 30 g / L, tartaric acid 50 g / L

[0320] 2,2'-(Ethylene dithio)diethanethiol 45 g / L, thiourea 20 g / L, β-naphthol polyoxyethylene ether (EO15) 5 g / L, pH 6.5 (adjusted with NaOH), bath temperature 70℃

[0321] [Preparation Example 6: Preparation of Etching Solution for Silver]

[0322] Add 2.6 parts by mass of acetic acid to 47.4 parts by mass of water, and further add 50 parts by mass of 35% hydrogen peroxide to prepare silver etching solution (1). The molar ratio of hydrogen peroxide to carboxylic acid (hydrogen peroxide / carboxylic acid) of the silver etching solution (1) is 13.6, and the content ratio of the mixture of hydrogen peroxide and carboxylic acid in the silver etching solution (1) is 22.4% by mass.

[0323] (Example 1)

[0324] (Process 1)

[0325] On the surface of a polyimide film ("Kapton 100EN-C" manufactured by Toray DuPont, Inc.; 25 μm thick) serving as the insulating substrate, a benchtop miniature coating machine ("KPrinting Proofer" manufactured by RK Print Coat Instruments) was used to apply a dried silver particle layer of 0.5 g / m². 2 The silver particle dispersion obtained in Example 1 was prepared by coating the film. Next, it was dried at 160°C for 5 minutes using a hot air dryer. Further, the film was flipped over and the same procedure was performed to achieve a silver particle layer of 0.5 g / m². 2 The silver particle dispersion obtained in Example 1 was coated onto the polyimide film and dried at 160°C for 5 minutes using a hot air dryer, thereby forming silver particle layers on both surfaces of the polyimide film. The resulting film substrate was then fired at 250°C for 5 minutes, and the conductivity of the silver particle layers was confirmed using a testing machine.

[0326] The polyimide film with conductive silver particle layers on both surfaces obtained above was fixed to a polyethylene frame and immersed 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 an electroless copper plating film (M2; thickness 0.2μm) on both surfaces. Next, a 100μm diameter through-hole was formed at the connection position of the solid GND on the back side of the transmission characteristic evaluation terminal of the microstrip line with a wiring length of 100mm and an impedance of 50Ω.

[0327] (Step 2: Apply palladium catalyst to the through-hole)

[0328] The prepreg solution for electroless plating (“OPC-SAL-M”, manufactured by Okuno Pharmaceutical Co., Ltd.) was diluted with water to a ratio of 260 g / L and kept at 25°C. The membrane with through holes formed therein was immersed in the liquid for 1 minute.

[0329] The pre-impregnation solution (OPC-SAL-M, manufactured by Okuno Pharmaceutical Co., Ltd.) and the Sn-Pd colloidal catalyst solution (OPC-90 Catalyst, manufactured by Okuno Pharmaceutical Co., Ltd.) were diluted with water at a ratio of 260 g / L and 30 mL / L, respectively, and maintained at 25°C. The pre-impregnation treated object was immersed in the solution for 5 minutes, followed by rinsing with running water for 2 minutes.

[0330] The activation solutions (“OPC-505 Accelerator A”, manufactured by Okuno Pharmaceutical Co., Ltd.) and the activation solution (“OPC-505 Accelerator B”, manufactured by Okuno Pharmaceutical Co., Ltd.) were diluted with water at concentrations of 100 mL / L and 8 mL / L, respectively, and kept at 30°C. The substrate to be plated after the catalyst compound application process was immersed in this solution for 5 minutes, followed by a 2-minute water rinse to apply palladium catalyst to the inner wall of the through-hole and the two copper surfaces.

[0331] (Process 3)

[0332] The copper in the obtained film was removed using the sulfuric acid-hydrogen peroxide copper etching solution prepared in Preparation Example 2, so as to expose the conductive silver particle layer (M1).

[0333] (Process 4: Electroless copper plating)

[0334] The obtained film substrate was immersed in an electroless copper plating solution (Circuposit 6550 manufactured by Rohm and Haas Electronic Materials Co., Ltd.) at 35°C for 25 minutes to form an electroless copper plating layer (0.5 μm thick) on the conductive silver particle layer (M1) on the inner wall of the through hole and on both surfaces.

[0335] (Process 5: Electroless displacement silver plating)

[0336] The electroless silver plating solution prepared in Preparation Example 3 was set to 40°C. The film prepared above was immersed in the solution for 3 minutes while shaking, and the copper plating layer formed on the inner wall of the through hole and the silver particle layer (M1) was replaced and plated to form a silver plating layer (M3).

[0337] (Step 6)

[0338] On the silver-plated layer (M1) thus obtained, a dry film resist (Photec RD-1225 manufactured by Hitachi Chemical Co., Ltd.; resist film thickness 25μm) is laminated at 100°C using a roller laminator. Then, a microstrip line pattern with a wiring length of 100mm and an impedance of 50Ω, as well as a terminal pad pattern for the via connected to GND for the measurement probe, are exposed on the resist using a direct exposure digital imaging device (Nuvogo1000R manufactured by Orbotech Co., Ltd.). Next, development is performed using a 1% sodium carbonate aqueous solution, thereby forming the microstrip line pattern and the patterned resist where the probe terminal pads are removed on the silver-plated layer (M3), exposing the silver-plated layer (M1) on the polyimide film.

[0339] (Step 7)

[0340] Next, the silver-plated layer (M3) surface of the substrate with the patterned resist was set as the cathode, and phosphorus-containing copper was used as the anode. Electroplating was performed for 41 minutes using an electroplating solution containing copper sulfate (copper sulfate 60 g / L, sulfuric acid 190 g / L, chloride ion 50 mg / L, additive (Copper Gleam ST-901 manufactured by Rohm and Haas Electronic Materials Co., Ltd.)) at a current density of 2 A / dm2. This formed an 18 μm thick circuit pattern layer on the microstrip pattern and probe terminal pads where the resist was removed by copper electroplating. Then, the film with the copper-patterned metal was immersed in a 3% by mass sodium hydroxide aqueous solution set at 50°C to remove the patterned resist.

[0341] (Step 8)

[0342] Next, the film obtained above was immersed in the silver etchant obtained in Preparation Example 3 at 25°C for 30 seconds to remove the silver plating layer (M3) and the silver particle layer (M1) other than the circuit pattern, thereby obtaining a printed wiring board. Regarding the cross-sectional shape of the circuit forming part (microstrip line and probe terminal part) of the fabricated printed wiring board, the wiring height and wiring width were not reduced, and it exhibited a rectangular shape without undercut, which is a circuit pattern layer with a smooth surface.

[0343] (Example 2)

[0344] In step 1, the immersion time in the electroless copper plating solution is changed from 10 minutes to 25 minutes to create a laminate with a copper layer of 0.5 μm on both surfaces of the insulating substrate (A), forming a through hole that penetrates both surfaces. Then, steps 2 to 8 are performed in the same manner as in Example 1 to obtain a printed wiring board. Regarding the cross-sectional shape of the circuit forming part (microstrip line and probe terminal part) of the fabricated printed wiring board, the wiring height and wiring width are not reduced, and it presents a rectangular shape without undercut, which is a circuit pattern layer with a smooth surface.

[0345] (Example 3)

[0346] The dried silver particle layer was reduced from 0.5 g / m 2 Change to 0.8g / m 2 In addition, following the same procedure as in Example 1, silver particle layers were formed on both surfaces of the polyimide film, and the film was fired at 250°C for 5 minutes. The conductivity of the silver particle layers was confirmed using a testing machine. The polyimide film with conductive silver particle layers on both surfaces obtained in this way was fixed to a copper frame. The surface of the silver particle layer was set as the cathode, and phosphorus copper was used as the anode. Electroplating was performed for 2.5 minutes at a current density of 2A / dm2 using an electroplating solution containing copper sulfate (copper sulfate 60g / L, sulfuric acid 190g / L, chloride ion 50mg / L, additive (Copper Gleam ST-901 manufactured by Rohm and Haas Electronic Materials Co., Ltd.)). This produced a laminate with a silver particle layer (M1) and a 1μm thick copper layer (M2) formed on both surfaces of the polyimide film, which serves as the insulating substrate (A), forming a through hole that penetrates both surfaces. Then, following the same procedure as in Example 1, steps 2 to 8 were performed to obtain a printed wiring board. Regarding the cross-sectional shape of the circuit forming part (microstrip line and probe terminal part) of the printed wiring board, the wiring height and wiring width are not reduced, and it presents a rectangular shape without undercut, which is a circuit pattern layer with a smooth surface.

[0347] (Example 4)

[0348] On the surface of the polyimide film ("Kapton 100EN-C" manufactured by Toray DuPont, Inc., 25 μm thick), the primer (B-1) obtained in Manufacturing Example 1 was applied to a dried thickness of 120 nm using a benchtop small coater ("K PrintingProofer" manufactured by RK Print Coat Instruments). The film was then dried at 80°C for 5 minutes using a hot air dryer. Furthermore, the film was flipped over, and the same procedure was repeated to apply the primer (B-1) obtained in Manufacturing Example 1 to a dried thickness of 120 nm. The film was then dried at 80°C for 5 minutes using a hot air dryer, thereby forming primer layers on both surfaces of the polyimide film.

[0349] The insulating substrate (A) was changed from a polyimide film to the polyimide obtained above, in which a primer layer was formed on both surfaces of the polyimide film. Otherwise, the process was the same as in Example 2, to fabricate a laminate having a primer (B-1) layer, a conductive silver particle layer (M1), and a 0.5 μm copper layer on both surfaces of the insulating substrate (A), forming through-holes penetrating both surfaces. Then, the process was repeated in the same manner as in Example 2, performing steps 2 to 8, thereby obtaining a printed wiring board. Regarding the cross-sectional shape of the circuit forming portion (microstrip line and probe terminal portion) of the fabricated printed wiring board, the wiring height and width were not reduced, and it exhibited a rectangular shape without undercut, with a smooth surface circuit pattern layer.

[0350] (Example 5)

[0351] In Example 4, the silver particle layer was increased from 0.5 g / m². 2 Change to 0.8g / m 2 The plating time was changed from 2.5 minutes to 4.5 minutes. Otherwise, copper plating was performed in the same manner as in Example 3, thereby creating a laminate with a primer layer (B), a conductive silver particle layer (M1), and a 2μm thick copper layer (M2) formed on both surfaces of a polyimide film serving as an insulating substrate (A). Through-holes were formed penetrating both surfaces. Then, steps 2 to 8 were performed in the same manner as in Example 4, thereby obtaining a printed wiring board. Regarding the cross-sectional shape of the circuit forming portion (microstrip line and probe terminal portion) of the fabricated printed wiring board, the wiring height and width were not reduced, and it exhibited a rectangular shape without undercut, with a smooth surface circuit pattern layer.

[0352] (Examples 6-8)

[0353] In Examples 1-3, a 38 μm thick polyester re-peelable adhesive tape (manufactured by Panac Co., Ltd., Panaprotect HP / CT) was laminated onto the silver particle layer (M1) as a peelable cover layer (RC) instead of forming a copper layer (M2). Otherwise, the process was the same as in Examples 1-3, resulting in a laminate with conductive silver particle layers (M1) on both surfaces of an insulating substrate (A), and further having through holes connecting the two surfaces of the insulating substrate. The conductivity of the through holes was ensured by the silver layer. For this laminate, through holes were formed on both surfaces using a drill bit, as in Examples 1-3. Then, steps 2-8 were performed, as in Examples 1-3, thereby obtaining a printed wiring board. Regarding the cross-sectional shape of the circuit forming portion (microstrip line and probe terminal portion) of the fabricated printed wiring board, the wiring height and width were not reduced, and it exhibited a rectangular shape without undercut, resulting in a smooth surface circuit pattern layer.

[0354] (Examples 9 and 10)

[0355] In Examples 4 and 5, a 38 μm thick polyester re-peelable adhesive tape (manufactured by Panac Co., Ltd., Panaprotect HP / CT) was laminated onto the silver particle layer (M1) as a peelable cover layer (RC) instead of forming the copper layer (M2). Otherwise, in the same manner as in Examples 4 and 5, a laminate containing a primer layer (B), a conductive silver particle layer (M1), and a copper layer (M2) was formed on both surfaces of an insulating substrate (A). For this laminate, through-holes were formed on both surfaces using a drill bit, in the same manner as in Examples 4 and 5. Then, in the same manner as in Examples 4 and 5, steps 2 to 8 were performed to obtain a printed wiring board. Regarding the cross-sectional shape of the circuit forming portion (microstrip line and probe terminal portion) of the fabricated printed wiring board, the wiring height and wiring width were not reduced, and it exhibited a rectangular shape without undercut, resulting in a smooth surface circuit pattern layer.

[0356] (Examples 11-15)

[0357] The 100μm diameter through-holes formed using a drill were changed to 70μm diameter through-holes formed using a laser. Otherwise, the same procedures as in Examples 1-5 were performed, from steps 1 to 8, to obtain a printed wiring board. Regarding the cross-sectional shape of the circuit forming portion (microstrip line and probe terminal portion) of the fabricated printed wiring board, the wiring height and width were not reduced, and it exhibited a rectangular shape without undercut, forming a circuit pattern layer with a smooth surface.

[0358] (Examples 16-20)

[0359] The 100μm diameter through-holes formed using a drill were changed to 70μm diameter through-holes formed using a laser. Otherwise, the same procedures as in Examples 6-10 were followed, performing steps 1-8 to obtain a printed wiring board. Regarding the cross-sectional shape of the circuit forming portion (microstrip line and probe terminal portion) of the fabricated printed wiring board, the wiring height and width were not reduced, and it exhibited a rectangular shape without undercut, forming a circuit pattern layer with a smooth surface.

[0360] (Examples 21 and 22)

[0361] In Example 5, the thickness of the electroless copper plating layer formed on the conductive silver particle layer (M1) on both surfaces in step 4 was changed from 0.5 μm to 0.7 μm (Example 21) and 1 μm (Example 22), respectively. The replacement silver plating bath was changed to the plating bath of Preparation Example 4 and Preparation Example 5, respectively. Otherwise, steps 1 to 8 were performed in the same manner as in Example 5, thereby obtaining a printed wiring board. Regarding the cross-sectional shape of the circuit forming part (microstrip line and probe terminal part) of the fabricated printed wiring board, the wiring height and wiring width were not reduced, and it exhibited a rectangular shape without undercut, which is a circuit pattern layer with a smooth surface.

[0362] (Examples 23-39)

[0363] The type of insulating substrate, the type of primer used for the primer layer and its drying conditions, the amount of silver in the silver particle layer, the type of cover layer for the silver particle layer, the through-hole formation method, the thickness of the copper plating film replaced by silver plating, and the type of replacement silver plating solution are changed as shown in Table 1 or 2. Otherwise, the operation is the same as in Examples 1 to 22 to obtain a printed wiring board. Regarding the cross-sectional shape of the circuit forming part (microstrip line and probe terminal part) of the printed wiring board, the wiring height and wiring width are not reduced, and it presents a rectangular shape without undercut, which is a circuit pattern layer with a smooth surface.

[0364] (Example 40)

[0365] In Example 5, the electroless copper plating in step 4 was replaced with electroless nickel plating. In the electroless nickel plating, the film after step 3 was immersed in an electroless nickel plating solution (ICP NiCORON GM(NP) manufactured by Okuno Pharmaceutical Co., Ltd.) set at 80°C for 1.5 minutes, thereby forming an electroless nickel plating layer (0.2 μm thick) on the inner wall of the through hole.

[0366] The obtained film was treated for 10 minutes using a displacement silver plating process (DAIN SILVER EL manufactured by Daiwa Kasei Corporation) set at 25°C, which replaced the nickel plating layer formed on the inner wall of the through hole with a silver plating layer (M3).

[0367] In step 6, a resist pattern is formed on the silver particle layer (M1) instead of forming the resist on the silver plating layer (M3) on the silver particle layer (M1). Then, the same operation as in Example 5 is performed to obtain a printed wiring board. Regarding the cross-sectional shape of the circuit forming part (microstrip line and probe terminal part) of the fabricated printed wiring board, the wiring height and wiring width are not reduced, and it presents a rectangular shape without undercut, which is a circuit pattern layer with a smooth surface.

[0368] (Example 41)

[0369] In Example 40, the electroless nickel plating solution in step 4 was changed from "ICP NiCORON GM(NP)" to TOP CHEM ALLOY 66-LF (manufactured by Okuno Pharmaceutical Co., Ltd.) set at 60°C, and immersed for 2.5 minutes, thereby forming an electroless nickel plating layer (thickness 0.2 μm) on the inner wall of the through hole and the silver particle layer (M1).

[0370] The obtained film was treated for 10 minutes using a displacement silver plating process (DAIN SILVER EL manufactured by Daiwa Chemical Co., Ltd.) set at 25°C, which replaced the nickel plating layer formed on the inner wall of the through hole and the silver particle layer (M1) with a silver plating layer (M3).

[0371] In step 6, a resist pattern is formed on the displacement silver plating layer (M3) formed on the silver particle layer (M1). Then, the same operation as in Example 39 is performed to obtain a printed wiring board. Regarding the cross-sectional shape of the circuit forming part (microstrip line and probe terminal part) of the printed wiring board, the wiring height and wiring width are not reduced, and it presents a rectangular shape without undercut, which is a circuit pattern layer with a smooth surface.

[0372] (Comparative Example 1)

[0373] A commercially available 25μm thick polyimide substrate FCCL ("Upisel N-BE1310YSB" manufactured by UBE EXSYMO Co., Ltd.) with a roughened copper foil of 3μm thickness on both sides as the plating substrate was used instead of the polyimide film with silver particle layers formed on both sides. Otherwise, the same procedure as in Examples 1 to 22 was followed to form through holes through both sides. MacDermid's black hole process (hole forming - carbon adsorption treatment - etching) was performed to attach carbon to the surface of the through holes. The copper foil surface with attached carbon was removed by etching with the sulfuric acid-hydrogen peroxide aqueous solution prepared in Preparation Example 2. Thus, a substrate with copper foil on both surfaces of the insulating substrate (A) was obtained, which further has through holes connecting the two sides of the insulating substrate, and the conductivity of the surface of the through holes is ensured by carbon.

[0374] Subsequently, a patterned resist is formed on the surface of the copper foil instead of the silver particle layer (M1). Otherwise, the same procedure as in Examples 1 to 22 is followed to form a conductor circuit layer with a copper microstrip line of 18 μm thickness and a probe terminal pad pattern on the copper foil plating substrate.

[0375] Next, the copper seed crystal was removed by immersion in a sulfuric acid-hydrogen peroxide-based flash etchant used in the etching of the copper seed crystal. As a result, the conductive layer (M4) of the microstrip line was etched, the film thickness decreased by about 3 μm, the wiring width also decreased by about 6 μm, and the cross-sectional shape could not maintain a rectangle but became a "trapezoidal" shape. In addition, the surface of the copper conductive layer became rough due to etching, and the smoothness was reduced.

[0376] (Comparative Example 2)

[0377] A polyimide film ("Kapton 100EN-C", manufactured by Toray DuPont, Inc.; thickness 25 μm) was used as the plating substrate to replace the polyimide film with silver particle layers formed on both sides. This was obtained by sputtering nickel / chromium (30 nm thickness, nickel / chromium mass ratio = 80 / 20) on both sides, sputtering 70 nm copper, and then performing a 1 μm thick copper electroplating treatment. Otherwise, the same procedure as in Comparative Example 1 was followed to form a conductor circuit layer with a copper microstrip line and probe terminal pad pattern on the copper foil plating substrate.

[0378] Next, the copper seed crystal was removed by immersion in a sulfuric acid-hydrogen peroxide-based flash etchant used in the etching of the copper seed crystal. As a result, the conductive layer (M4) of the microstrip line was etched, resulting in a film thickness reduction of approximately 1 μm and a reduction in wiring width of more than 2 μm. Furthermore, the cross-sectional shape could no longer maintain a rectangle and became trapezoidal. Additionally, the surface of the copper conductive layer became rough due to etching, reducing its smoothness. Moreover, in areas outside the conductive layer (M4) pattern, only the copper layer was removed; the nickel / chromium layer remained.

[0379] [Confirmation of the presence or absence of undercut and the cross-sectional shape of the wiring section]

[0380] The cross-section of the comb-shaped electrode portion of the printed wiring board obtained above was magnified to 500 to 10,000 times using a scanning electron microscope (JSM7800 manufactured by Nippon Electron Ltd.) to confirm the presence or absence of undercut and the cross-sectional shape of the comb-shaped electrode portion.

[0381] The surface roughness of the printed wiring board was observed using a laser microscope (manufactured by Keynes, VK-9710) to confirm its smoothness. A surface roughness Rz of 3 μm or less was evaluated as smooth (smoothness: 〇), while a surface roughness Rz greater than 3 μm was evaluated as rough (smoothness: ×). Furthermore, when the difference between the designed width of the wiring obtained from the resist used to form the wiring and the width of the upper surface of the formed wiring was 2 μm or less, it was evaluated as lateral etching being suppressed and the rectangular shape being maintained (rectangularity: 〇). A difference greater than 2 μm was evaluated as the rectangular shape not being maintained (rectangularity: ×), as shown in Tables 1 to 3.

[0382] [Table 1]

[0383]

[0384] [Table 2]

[0385]

[0386] [Table 3]

[0387]

[0388] Symbol Explanation

[0389] 1: Insulating substrate

[0390] 2: Silver Particle Layer

[0391] 3: Covering layer (copper layer or strippable cover layer)

[0392] 4: Through hole (through hole)

[0393] 5: Catalyst for electroless plating

[0394] 6: Electroless copper plating or electroless nickel plating

[0395] 7: Replace the silver plating layer

[0396] 8: Pattern resist

[0397] 9: Conductive layer (electrolytic copper plating layer)

[0398] (1a) Semi-additive method using laminates (structure of embodiment 1)

[0399] (1b) Process 1: Formation of through hole (through hole)

[0400] (1c) Step 2: Electroless plating catalyst application

[0401] (1d) Process 3: Exposure of the conductive silver particle layer

[0402] (1e) Process 4: Electroless copper plating or electroless nickel plating on the surface of the through-hole and the surface of the silver particle layer.

[0403] (1f) Process 5: Replacement silver plating of copper or nickel plating layer

[0404] (1g) Process 6: Pattern resist formation

[0405] (1h) Process 7: Formation of a conductive layer based on electroplated copper

[0406] (1i) Step 8: Pattern resist stripping

[0407] (1i) Process 8: Removal of silver seed crystals

[0408] (2a) Semi-additive method using laminates (structure of embodiment 2)

[0409] (2b) Process 1: Formation of through hole (through hole)

[0410] (2c) Step 2: Electroless plating with catalyst preparation

[0411] (2d) Process 3: Exposure of the conductive silver particle layer

[0412] (2e) Step 4: Electroless copper plating or electroless nickel plating on the surface of the through hole

[0413] (2f) Process 5: Replacement silver plating of copper or nickel plating layer

[0414] (2g) Process 6: Pattern resist formation

[0415] (2h) Step 7: Formation of a conductive layer based on electroplated copper

[0416] (2i) Step 8: Pattern resist stripping

[0417] (2i) Process 8: Removal of silver seed crystals.

Claims

1. A method for manufacturing a printed wiring board, characterized in that, have: Step 1: Forming through holes on both sides of the laminate, wherein a silver particle layer M1 and a copper layer M2 are sequentially stacked on the two surfaces of the insulating substrate A of the laminate, and the thickness of the copper layer M2 is 0.1μm to 2μm. Step 2: Apply an electroless plating catalyst to the substrate having the through hole and the surface of the through hole. Step 3: Etch the copper layer M2 to expose the conductive silver particle layer M1; Step 4: A copper or nickel layer is formed on the surface of the through hole and on the silver particle layer M1 by electroless plating. Step 5 involves replacing the copper or nickel formed on the surface of the through hole and on the silver particle layer M1 with silver. Step 6: A patterned resist is formed on the silver plating layer M3 formed on the conductive silver particle layer M1; Step 7: The two sides of the substrate are electrically connected by electroplating copper, and a conductive layer M4 with a circuit pattern is formed. Step 8: Remove the pattern resist and use an etching solution to remove the silver particle layer M1 of the non-circuit pattern forming part.

2. A method for manufacturing a printed wiring board, characterized in that, have: Step 1: Forming through holes on both sides of the laminate, wherein a silver particle layer M1 and a copper layer M2 are sequentially stacked on the two surfaces of the insulating substrate A of the laminate, and the thickness of the copper layer M2 is 0.1μm to 2μm. Step 2: Apply an electroless plating catalyst to the substrate having the through hole and the surface of the through hole. Step 3: Etch the copper layer M2 to expose the conductive silver particle layer M1; Step 4: A copper or nickel layer is formed on the surface of the through hole by electroless plating; Step 5: Replace the copper or nickel formed on the surface of the through hole with silver; Step 6: A patterned resist is formed on the conductive silver particle layer M1; Step 7: The two sides of the substrate are electrically connected by electroplating copper, and a conductive layer M4 with a circuit pattern is formed. Step 8: Remove the pattern resist and use an etching solution to remove the silver particle layer M1 of the non-circuit pattern forming part.

3. A method for manufacturing a printed wiring board, characterized in that, have: Step 1: A through hole is formed on both sides of the laminate. A silver particle layer M1 and a peelable cover layer RC are sequentially stacked on both surfaces of the insulating substrate A of the laminate. Step 2: Apply an electroless plating catalyst to the surface of the substrate having the through holes; Step 3: Peel off the peelable cover layer RC to expose the conductive silver particle layer M1. Step 4: A copper or nickel layer is formed on the surface of the through hole and the silver particle layer M1 by electroless plating. Step 5: Replace the copper or nickel formed on the surface of the through hole and the silver particle layer M1 with silver. Step 6: A patterned resist is formed on the silver plating layer M3 formed on the conductive silver particle layer M1; Step 7: The two sides of the substrate are electrically connected by electroplating copper, and a conductive layer M4 with a circuit pattern is formed. Step 8: Remove the pattern resist and use an etching solution to remove the silver particle layer M1 of the non-circuit pattern forming part.

4. A method for manufacturing a printed wiring board, characterized in that, have: Step 1: A through hole is formed on both sides of the laminate. A silver particle layer M1 and a peelable cover layer RC are sequentially stacked on both surfaces of the insulating substrate A of the laminate. Step 2: Apply an electroless plating catalyst to the surface of the substrate having the through holes; Step 3: Peel off the peelable cover layer RC to expose the conductive silver particle layer M1. Step 4: A copper or nickel layer is formed on the surface of the through hole by electroless plating; Step 5: Replace the copper or nickel formed on the surface of the through hole with silver; Step 6: A patterned resist is formed on the conductive silver particle layer M1; Step 7: The two sides of the substrate are electrically connected by electroplating copper, and a conductive layer M4 with a circuit pattern is formed. Step 8: Remove the pattern resist and use an etching solution to remove the silver particle layer M1 of the non-circuit pattern forming part.

5. The method for manufacturing a printed wiring board according to any one of claims 1 to 4, characterized in that, A primer layer B is further laminated between the insulating substrate A and the silver particle layer M1.

6. The method for manufacturing a printed wiring board according to any one of claims 1 to 4, characterized in that, The thickness of the copper or nickel layer formed on the surface of the through hole is 0.1 to 1 μm.

7. The method for manufacturing a printed wiring board according to any one of claims 1 to 4, wherein the silver particles constituting the silver particle layer M1 are coated with a polymeric dispersant.

8. The method for manufacturing a printed wiring board according to claim 5, wherein, The silver particles constituting the silver particle layer M1 are coated with a polymeric dispersant. The primer layer B is a layer composed of a resin having a reactive functional group [X]. The polymeric dispersant has a reactive functional group [Y]. The reactive functional groups [X] and [Y] can form bonds with each other through a reaction.

9. The method for manufacturing a printed wiring board according to claim 8, wherein the reactive functional group [Y] is a basic nitrogen atom group.

10. The method for manufacturing a printed wiring board according to claim 8, wherein the polymeric dispersant having the reactive functional group [Y] is one or more selected from the group consisting of polyalkylene imides and polyalkylene imides having a polyoxyalkylene structure containing ethylene oxide units.

11. The method for manufacturing a printed wiring board according to claim 8, wherein the reactive functional group [X] is selected from one or more of the group consisting of ketone, acetoacetyl, epoxy, carboxyl, N-alkanol, isocyanate, vinyl, (meth)acryloyl, and allyl.

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