Method for manufacturing circuit board

Abstract

This method for manufacturing a circuit board comprises: a resist layer formation step for forming, on at least one surface of a circuit board, a resist layer containing palladium particles and a dispersant that covers the palladium particles; an exposure step for exposing the resist layer; a resist pattern formation step for developing the resist layer exposed in the exposure step and forming a resist pattern in the resist layer; a heating step for heating the substrate in which the resist pattern is formed in the resist layer; and a wiring layer formation step for forming an electroconductive wiring layer on the exposed substrate after the resist pattern formation step.

Description

Circuit board manufacturing method

[0001] The present invention relates to a method for manufacturing a circuit board.

[0002] Various methods for producing circuit boards having fine wiring have been investigated. As an example of a method for producing a circuit board, a full additive method has been disclosed, which includes the steps of roughening the surface of an adhesive layer formed on a substrate and applying a catalyst containing a palladium compound to the surface, treating the catalyst with acid to activate the catalyst, heat-treating the substrate obtained in the previous step to fix the catalyst to the surface of the adhesive layer, forming a resist layer on the heat-treated adhesive layer, forming a resist pattern on the resist layer by exposure and development, treating the catalyst again with acid, and electroless plating the substrate obtained in the previous step to form a conductor circuit.

[0003] Japanese Patent Application Publication No. 5-21932

[0004] However, the full additive method involves many steps and requires multiple pieces of equipment and many chemicals before fine wiring can be formed on a substrate.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a circuit board that can manufacture a circuit board having fine wiring with fewer steps than the number of steps required in the conventional full additive method.

[0006] The present invention is as follows: [1] A method for producing a circuit board according to the present invention includes a resist layer forming step of forming a resist layer containing palladium particles and a dispersant that covers the palladium particles on at least one surface of a substrate, an exposure step of exposing the resist layer to light, a resist pattern forming step of developing the resist layer exposed in the exposure step to form a resist pattern in the resist layer, a heating step of heating the substrate on which the resist pattern has been formed on the resist layer, and a wiring layer forming step of forming a conductive wiring layer on the substrate exposed after the resist pattern forming step.

[0007] [2] The resist layer may contain a photosensitive base material and a photopolymerization initiator.

[0008] [3] The amount of palladium particles contained in the resist layer may be 0.4 parts by mass or more and 3.3 parts by mass or less with respect to 100 parts by mass of the photosensitive base agent.

[0009] [4] The photosensitive base material may be a photosensitive urethane resin.

[0010] According to the present invention, it is possible to provide a method for manufacturing a circuit board that can manufacture a circuit board having fine wiring with fewer steps than the number of steps required in the conventional full additive method.

[0011] FIG. 1 is a schematic diagram for explaining a resist layer forming step in the method for manufacturing a circuit board according to an embodiment; FIG. 2 is a schematic diagram for explaining an exposure step in the method for manufacturing a circuit board according to an embodiment; FIG. 3 is a schematic diagram for explaining a resist pattern forming step in the method for manufacturing a circuit board according to an embodiment; FIG. 4 is a schematic diagram for explaining a heating step in the method for manufacturing a circuit board according to an embodiment; FIG. 5 is a schematic diagram for explaining a wiring layer forming step in the method for manufacturing a circuit board according to an embodiment; and FIG. 6 is a schematic diagram showing masks used in Examples and Comparative Examples.

[0012] Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following content. The present invention can be carried out with appropriate modifications within the scope of its gist.

[0013] 1A to 1E, a method for manufacturing a circuit board according to an embodiment will be described. The method for manufacturing a circuit board includes (a) a resist layer forming step, (b) an exposure step, (c) a resist pattern forming step, (d) a heating step, and (e) a wiring layer forming step.

[0014] 1A, a resist layer 12 is formed on one surface of a substrate 10. In this step, a process of forming a resist layer using a negative dry film will be described as an example.

[0015] First, a negative dry film is placed on the substrate 10. Next, the negative dry film and the substrate 10 are heated and pressed together using, for example, a laminator. This forms a resist layer 12 on the substrate 10. The heating and pressing conditions are, for example, 30°C to 100°C, 0.1 MPa to 1.0 MPa, and 5 seconds to 60 seconds. The heating and pressing may be performed in a reduced pressure atmosphere. The thickness of the negative dry film is appropriately selected depending on the thickness of the wiring layer to be formed on the substrate 10.

[0016] The substrate 10 may be any substrate on which the resist layer 12 can be formed, and examples thereof include flexible printed wiring boards, film-like substrates, substrates on which circuits are formed, and insulating substrates such as FR4. Examples of film-like substrates include polyimide films, polyethylene terephthalate films (PET films), and liquid crystal films (LCP films).

[0017] The resist layer 12 is composed of a resist material containing palladium particles 121 and a dispersant (not shown) that coats the palladium particles 121. The average particle size of the palladium particles 121 is preferably 1 nm to 100 nm, more preferably 1 nm to 75 nm, and even more preferably 1 nm to 30 nm. This increases the surface area of ​​the palladium particles contained in the resist layer 12, thereby improving the activation efficiency of the palladium particles. The dispersant that coats the palladium particles 121 is composed of a compound that can bond with the palladium particles 121, such as a nitrogen-containing compound containing nitrogen in its terminal functional group and / or a compound having an unsaturated bond. The bond between the palladium particles 121 and this compound can be, for example, a coordinate bond, an ionic bond, or a covalent bond, with a coordinate bond being preferred from the perspective of dispersibility. An example of the nitrogen-containing compound is a polymer having an ammonium group in its terminal functional group. An example of the compound having an unsaturated bond is polyethylene glycol alkyl ether acrylate. The particle size of the palladium particles 121 can be measured from a transmission electron microscope (TEM) image.

[0018] From the viewpoint of facilitating the formation of the wiring layer 18 on the substrate 10, the amount of palladium particles 121 contained in the resist material is 0.4 parts by mass or more and 3.3 parts by mass or less, and preferably 1.0 parts by mass or more and 3.0 parts by mass or less, relative to 100 parts by mass of a photosensitive main agent described below. This allows the palladium particles 121 to adhere to the surface of the substrate 10 exposed after development in the resist pattern formation step described below. The amount of palladium particles 121 can be measured using an ICP optical emission spectrometer.

[0019] The resist material constituting the resist layer 12 further includes a photosensitive base agent and a photopolymerization initiator. Examples of the photosensitive base agent contained in the resist material include photosensitive urethane resins. Examples of photosensitive urethane resins include resins having an ester bond and an unsaturated bond in the main chain of the same molecule, anionic groups at the side chains and / or terminals, and unsaturated bond groups at the side chains. The number-average molecular weight of the photosensitive urethane resin is preferably 2,000 or more and 500,000 or less from the viewpoints of facilitating the formation of the resist layer 12 on the substrate 10, achieving a uniform thickness of the resist layer 12, and enhancing the heat resistance and water resistance of the resist layer 12. The number-average molecular weight of the photosensitive urethane resin can be measured by gel permeation chromatography using polymethyl methacrylate as a standard sample.

[0020] The amount of unsaturated bonds contained in the main chain of the photosensitive urethane resin is preferably 0.40 mmol / g or more and 2.20 mmol / g or less from the viewpoint of improving the strength and heat resistance of the cured resist layer 12. The amount of unsaturated bonds is calculated by dividing the number of moles of unsaturated dibasic acid by the quantity (g) of the obtained photosensitive urethane resin. The unsaturated dibasic acid is an acid component used in synthesizing the polyol that constitutes the photosensitive urethane resin.

[0021] The amount of anionic groups contained in the photosensitive urethane resin is preferably 0.60 mmol / g or more and 1.50 mmol / g or less from the viewpoints of improving the development accuracy of the resist layer 12, uniformly mixing the photosensitive urethane resin with other materials contained in the resist material of the resist layer 12, and uniformly thicknessing the resist layer 12. Examples of anionic groups include functional groups that generate anions, such as carboxyl groups and sulfonic acid groups. Carboxyl groups are preferred from the viewpoint of improving the development accuracy of the resist layer 12. The amount of anionic groups is calculated by measuring the acid value of the obtained photosensitive urethane resin and dividing the acid value by the molecular weight of KOH. The acid value of the photosensitive urethane resin is preferably 33 mgKOH / g or more and 85 mgKOH / g or less. The acid value of the photosensitive urethane resin can be measured according to the method described in JIS K 0070.

[0022] From the viewpoint of obtaining a fine resist pattern, the amount of unsaturated bonds in the side chains of the photosensitive urethane resin is preferably 0.10 mmol / g or more and 0.90 mmol / g or less. This amount of unsaturated bonds is calculated by dividing the number of moles of unsaturated bond groups by the quantity (g) of the obtained photosensitive urethane resin. This unsaturated bond group is an unsaturated bond group contained in a compound having both an unsaturated bond group and a functional group containing at least one active hydrogen in the molecule.

[0023] The photosensitive urethane resin can be obtained, for example, by mixing and reacting (a) a polyol having an ester bond and an unsaturated bond in the main chain, (b) a compound having both a functional group containing at least one active hydrogen atom and at least one anionic group in the molecule, (c) a polyisocyanate, and (d) a compound having both a functional group containing at least one active hydrogen atom and an unsaturated bond group in the molecule. Examples of the functional group containing active hydrogen include a carboxyl group and a hydroxyl group. The photosensitive urethane resin can be synthesized using a known synthesis method.

[0024] Examples of the polyol (a) include polyester polyols having unsaturated bonds in the main chain. Polyester polyols are obtained by reacting an acid component with a polyol component. Examples of the acid component include unsaturated dibasic acids such as dimethyl maleate, dimethyl fumarate, maleic acid dichloride, and maleic anhydride. Examples of the polyol component include 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. Examples of the compound (b) include (i) dimethylolpropanoic acid, (ii) dimethylolbutanoic acid, and (iii) compounds obtained by free radical reaction of a monomer containing a hydroxyl group and an unsaturated group with a monomer containing a carboxyl group and an unsaturated group. Examples of the polyisocyanate (c) include tolylene diisocyanate, xylene diisocyanate, methylene diisocyanate, hexane diisocyanate, and isophorone diisocyanate. Examples of the compound (d) include glycerin monoallyl ether, glycerin monoacrylate, and glycerin monomethacrylate.

[0025] Examples of photopolymerization initiators contained in the resist material include bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 1,2-octanedione, 1-[4-(phenylthio)phenyl-, 2-(O-benzoyloxime)], and the like. From the viewpoint of curability, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide are preferred. The photopolymerization initiator may be used alone or in combination with two or more photopolymerization initiators. The amount of photopolymerization initiator contained in the resist material is preferably 2 to 20 parts by weight, more preferably 6 to 16 parts by weight, per 100 parts by weight of the photosensitive base material, from the viewpoint of enhancing reactivity with the photosensitive base material and enhancing adhesion between the resist layer 12 and the substrate 10.

[0026] Furthermore, the resist material constituting the resist layer 12 may further contain an acrylate monomer in order to facilitate the processability of the resist material. Examples of acrylate monomers include urethane acrylate monomers and epoxy acrylate monomers. Examples of urethane acrylate monomers include aliphatic urethane acrylate monomers containing one or more acrylate groups per molecule. Examples of epoxy acrylate monomers include modified epoxy acrylate monomers containing one or more acrylate groups per molecule, fatty acid-modified epoxy acrylate monomers containing one or more acrylate groups per molecule, and amine-modified bisphenol A-type epoxy acrylate monomers containing one or more acrylate groups per molecule. The acrylate monomer may be composed of one type of acrylate monomer or two or more types of acrylate monomers. From the viewpoint of ensuring the hardening of the resist material and improving the accuracy of development of the resist layer 12, the amount of acrylate monomer contained in the resist material is preferably 10 parts by mass or more and 70 parts by mass or less, more preferably 30 parts by mass or more and 60 parts by mass or less, and even more preferably 30 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the photosensitive main agent.

[0027] (b) Exposure Step As shown in FIG. 1B , the resist layer 12 is exposed to light. Specifically, in order to form a resist pattern in the resist layer 12, the resist layer 12 is exposed to light through a mask 14 having openings 14 a. The resist layer 12 exposed through the openings 14 a corresponds to the portions other than the wiring and other metal portions to be formed. The resist layer 12 not exposed through the mask 14 corresponds to the wiring and other metal portions to be formed. The wavelength of the light 16 used during exposure may be any wavelength that can form a resist pattern in the resist layer 12, and is, for example, 200 nm or more and 500 nm or less. The exposure conditions may be any conditions that can form a resist pattern in the resist layer 12, and may be, for example, a high-pressure mercury lamp with an integrated light dose of 50 mJ / cm. ２ More than 1500mJ / cm ２ The following conditions are included:

[0028] (c) Resist Pattern Formation Step As shown in FIG. 1C , the exposed resist layer 12 is developed to form a resist pattern 12p in the resist layer 12. Specifically, when the resist layer 12 is exposed through a mask 14 and developed, only the resist layer 12 not exposed by light 16 dissolves in the developer. At this time, palladium particles 121 adhere to the surface of the substrate 10 exposed by the dissolution of the resist layer 12. These palladium particles 121 serve as a scaffolding for forming a wiring layer 18 on the exposed surface of the substrate 10 in the subsequent wiring layer formation step. Note that the developer used in development may be any solution capable of developing the exposed resist layer 12, such as an alkaline aqueous solution such as a sodium carbonate solution. Here, the resist pattern 12p refers to the resist layer 12 that has a shape corresponding to the outline of the opening 14a after exposure and development.

[0029] 1D , the substrate 10 having the resist pattern 12p formed on the resist layer 12 is heated using a heater 20. This activates the palladium particles 121 adhering to the exposed surface of the substrate 10 and causes them to be fixed to the surface of the substrate 10. From the viewpoint of activating the palladium particles 121 and fixing them to the surface of the substrate 10, the heating temperature and time are, for example, 200° C. or higher and 280° C. or lower, and 2 minutes or longer and 30 minutes or shorter, and preferably 200° C. or higher and 260° C. or lower, and 10 minutes or longer and 20 minutes or shorter.

[0030] (e) Wiring Layer Formation Step As shown in FIG. 1E, a conductive wiring layer 18 is formed on the exposed substrate 10. The wiring layer 18 can be formed, for example, by electroless plating. The electroless plating conditions may be any conditions that allow the wiring layer 18 to be formed on the substrate 10, such as immersing the substrate 10 in a copper-containing electroless plating solution for 1 minute to 30 minutes. The copper-containing electroless plating solution used here may be, for example, an aqueous solution containing copper ions, a complexing agent, and a reducing agent. Examples of complexing agents include Rochelle salt and sodium salt of ethylenediaminetetraacetic acid. Examples of reducing agents include formaldehyde, a formaldehyde precursor, or a derivative thereof.

[0031] The thickness of the wiring layer 18 formed by electroless plating may be further increased by electrolytic plating. The conditions for electrolytic plating may be any as long as the thickness of the wiring layer 18 can be further increased. For example, the substrate 10 having the wiring layer 18 formed by electroless plating is immersed in an electrolytic plating solution for 1 minute to 60 minutes, and a current of 0.05 A / dm ２ 10.0A / dm or more ２ The treatment conditions are as follows: The electrolytic plating solution used here may be, for example, a copper sulfate plating solution, a copper pyrophosphate plating solution, or a copper cyanide plating solution.

[0032] The thickness of the wiring layer 18 may be thinner than the thickness of the resist pattern 12p, thicker than the thickness of the resist pattern 12p, or the same as the thickness of the resist pattern 12p.

[0033] 1E, another wiring layer may be formed on the surface of the resist pattern 12p and the surface of the wiring layer 18 through the steps (a) to (e) described above. This allows the circuit to be multi-layered in the thickness direction of the substrate 10. Alternatively, a substrate on which another circuit is formed may be laminated via an adhesive sheet on the surface of the resist pattern 12p and the surface of the wiring layer 18. This method also allows the circuit to be multi-layered in the thickness direction of the substrate 10.

[0034] A circuit board can be obtained through the above steps (a) to (e). Furthermore, the circuit board manufacturing method of this embodiment eliminates the steps required in conventional full-additive circuit board manufacturing methods: laminating an adhesive layer on a substrate, roughening the surface of the adhesive layer, applying a catalyst containing a palladium compound to the roughened surface, and activating the catalyst by treating it with acid. Furthermore, reducing the number of steps in the circuit board manufacturing method allows for a reduction in the amount of equipment and chemicals required.

[0035] The resist material constituting the resist layer 12 in the (a) resist layer formation step may be any material capable of forming a resist pattern by exposure and development, and examples thereof include positive resist materials and negative resist materials. Examples of resist materials include resist liquid and dry films formed in film form. When forming a resist layer on the substrate 10 using a resist liquid, the resist liquid is applied to the substrate 10 using, for example, a coater. Next, the applied resist liquid is heated using a heater to harden the resist liquid. This forms the resist layer 12 on the substrate 10. Here, a positive resist material dissolves in a developer when exposed to light, but does not dissolve in a developer when not exposed to light. A negative resist material does not dissolve in a developer when exposed to light, but dissolves in a developer when not exposed to light.

[0036] Furthermore, the method for manufacturing a circuit board according to this embodiment includes a resist layer formation step of forming a resist layer using a negative dry film of a negative resist material, but may also include a resist layer formation step of forming a resist layer by changing this negative resist material to a positive resist material.

[0037] Furthermore, if the palladium particles 121 can be left on the surface of the substrate 10 exposed by developing the resist layer 12, various photoetching steps can be appropriately selected in the manufacturing method of the circuit board of this embodiment.

[0038] Furthermore, in the method for manufacturing a circuit board of this embodiment, a method for forming a circuit on only one side of the substrate 10 has been described, but circuits may also be formed on both sides of the substrate 10 through the same processing steps as those described above.

[0039] The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples. In the examples and comparative examples, the parts by mass refer to the parts by mass of the solid content only, excluding volatile components such as solvents.

[0040] Example 1 Preparation of Negative Resist Material 100 parts by mass of a photosensitive urethane resin as a photosensitive base agent, 40 parts by mass of Ebecryl-1039 (manufactured by Daicel Allnex Corporation) as an acrylate monomer, 12 parts by mass of Omnirad TPO-H (manufactured by BASF) as a photopolymerization initiator, and 1.5 parts by mass of CP-018T6 (manufactured by Nissan Chemical Industries, Ltd.) as a liquid containing palladium particles and a dispersant were placed in a container and mixed using a mixer to obtain a negative resist material. Hereinafter, the negative resist material will be simply referred to as the resist material.

[0041] This resist material contained 0.45 parts by mass of palladium particles per 100 parts by mass of photosensitive urethane resin. The amount of palladium particles was determined as follows. First, the resist material was applied to the surface of a release-treated PET film (PI3811, manufactured by Lintec Corporation) using a comma coater to a dry thickness of 25 μm, and then dried to form a resist layer on the PET film surface. Next, 0.5 g of the resist layer collected from the PET film on which the resist layer was formed was added to an acidic solution and dissolved to obtain a measurement sample. The amount of palladium particles contained in the obtained measurement sample was then measured using an ICP optical emission spectrometer (ICPE-9800 series, manufactured by Shimadzu Corporation). The drying conditions for forming the resist layer on the PET film were 160°C and 5 minutes. Furthermore, a mixed solution containing 0.5 ml of 97% by mass sulfuric acid, 5 ml of 61% by mass nitric acid, and 44.5 ml of pure water was used as the acidic solution.

[0042] The photosensitive urethane resin used in preparing the resist material was synthesized according to the following procedure. A 2-liter flask equipped with a stirrer, thermometer, and condenser was charged with 365 g of adipic acid, 245 g of maleic anhydride, and 661 g of 1,6-hexanediol, and the mixture was heated to 130°C with stirring. The temperature was then raised to 210°C over 4 hours, and the mixture was allowed to react for 2 hours while maintaining the temperature at 210°C. During this time, 134 g of condensed water was removed from the reaction system. The mixture was then cooled to 100°C, and 0.11 g of hydroquinone was added to obtain a polyester polyol having unsaturated bonds in its main chain. The amount of unsaturated bonds in the main chain of the resulting polyester polyol was 2.20 mmol / g, and the OH value was 59.5 mgKOH / g.

[0043] Next, a 5-liter flask equipped with a stirrer, thermometer, and condenser was charged with 1,000 g of polyester polyol, 170 g of glycerin monomethacrylate (NOF Corporation, Blenmer® GLM), 275 g of dimethylolbutanoic acid, and 650 g of isophorone diisocyanate, and 698 g of toluene was added to achieve a resin content of 75%. The reaction was then carried out at 100°C until all NCO groups were removed, after which 1,397 g of methyl ethyl ketone was added to obtain a photosensitive urethane resin solution with a resin content of 50%. The resulting photosensitive urethane resin had an unsaturated bond content of 1.05 mmol / g in the main chain, an anionic group (carboxyl group) content of 0.89 mmol / g, and an acid value of 50 mgKOH / g.

[0044] [Circuit Board Manufacturing] (Resist Layer Formation Process) Using a comma coater, the resist material was applied to a polyimide film (Kapton 100EN-C, manufactured by Toray DuPont Co., Ltd.) to a dry thickness of 25 μm, and then dried to form a resist layer on one side of the polyimide film. The drying conditions were 160°C and 5 minutes. In this example, to protect the surface of the resist layer, a PET film (PI3811, manufactured by Lintec Corporation) that had been subjected to a release treatment was bonded to the surface of the resist layer so that the surface came into contact with the release-treated surface of the PET film. The bonding conditions were 0.5 MPa, 50°C, and 30 seconds.

[0045] (Exposure Step) The resist layer was exposed through a mask using an ultra-high pressure mercury lamp (USH-250BY, manufactured by Ushio Lighting Co., Ltd.) with an accumulated light amount of 300 mJ / cm ２ The mask was exposed from the PET film side until the light reached a wavelength of 365 nm. A mask with a pattern of 100 μm / 100 μm L / S was used. The mask with this pattern is shown in FIG. 2. Here, L represents a light-shielding portion that blocks light when exposed, and S represents an opening that allows light to pass through.

[0046] (Resist Pattern Formation Step) After exposure, the PET film was peeled off from the resist layer formed on one side of the polyimide film. Next, the exposed resist layer surface was sprayed with a 1% by mass aqueous solution of sodium carbonate at 30°C for 60 seconds for development. After development, it was confirmed that a resist pattern had been formed on the resist layer. The nozzle pressure during spraying was 0.18 MPa.

[0047] (Heating Step) The polyimide film having the resist pattern formed on the resist layer was dried in a dryer at 240° C. for 15 minutes.

[0048] (Wiring Layer Formation Step) The polyimide film obtained in the heating step was immersed for 10 minutes in a plating bath containing an electroless plating solution (Uemura Kogyo Co., Ltd., Thru-Cup PMK, copper concentration 2.5 g / L) at a liquid temperature of 40° C., and then removed from the plating bath. A laminate was obtained in which an electroless plating layer having a thickness of 0.2 μm was formed on the polyimide film surface exposed by development.

[0049] Next, the laminate on which the electroless plating layer of 0.2 μm thickness was formed was immersed in a plating bath containing an electrolytic plating solution (Top Lucina SF, manufactured by Okuno Chemical Industries Co., Ltd.) at a liquid temperature of 25° C., and the laminate was subjected to a current of 2 A / dm ２ Electrolytic plating was performed for 30 minutes at 1000 kJ / min. This resulted in a laminate in which a 12 μm-thick electroplated layer was formed on the electroless plated layer. The thickness of the electroplated layer was measured using a micrometer. No wiring layer was observed on the surface of the resist layer on which the resist pattern was formed, confirming that a circuit board could be obtained by the method of this example.

[0050] (Example 2) (Preparation of Resist Material) A resist material was prepared using the same materials as used in the preparation of the resist material in Example 1, except that the amount of CP-018T6 (manufactured by Nissan Chemical Industries, Ltd.) was changed to 7.5 parts by mass. The resist material thus prepared contained 2.25 parts by mass of palladium particles per 100 parts by mass of photosensitive urethane resin.

[0051] [Manufacturing of Circuit Board] The circuit board of Example 2 was manufactured using the same materials as those used in manufacturing the circuit board of Example 1, under the same conditions as those used in manufacturing the circuit board of Example 1. In the circuit board of Example 2, as in the circuit board of Example 1, a wiring layer was formed on the surface of the polyimide film exposed by development, and no wiring layer was observed on the surface of the resist layer on which the resist pattern was formed.

[0052] (Example 3) (Preparation of Resist Material) A resist material was prepared using the same materials as used in the preparation of the resist material in Example 1, except that the amount of CP-018T6 (manufactured by Nissan Chemical Industries, Ltd.) was changed to 10.5 parts by mass. The resist material thus prepared contained 3.15 parts by mass of palladium particles per 100 parts by mass of photosensitive urethane resin.

[0053] [Manufacturing of Circuit Board] The circuit board of Example 3 was manufactured using the same materials as those used in manufacturing the circuit board of Example 1, under the same conditions as those used in manufacturing the circuit board of Example 1. In the circuit board of Example 3, as in the circuit board of Example 1, a wiring layer was formed on the surface of the polyimide film exposed by development, and no wiring layer was observed on the surface of the resist layer on which the resist pattern was formed.

[0054] Comparative Example 1 Preparation of Resist Material A resist material was prepared using the same materials as used in the preparation of the resist material in Example 1, except that the amount of CP-018T6 (manufactured by Nissan Chemical Industries, Ltd.) was changed to 0.75 parts by mass. The resist material thus prepared contained 0.23 parts by mass of palladium particles per 100 parts by mass of photosensitive urethane resin.

[0055] [Manufacturing of Circuit Board] The circuit board of Comparative Example 1 was manufactured using the same materials and under the same conditions as those used in manufacturing the circuit board of Example 1. In the wiring layer forming step, no wiring layer was formed on the surface of the polyimide film exposed by development, and a circuit board could not be obtained.

[0056] (Comparative Example 2) (Preparation of Resist Material) The same materials as used in the preparation of the resist material in Example 1 were used, except that the amount of CP-018T6 (manufactured by Nissan Chemical Industries, Ltd.) was changed to 15.0 parts by mass, and the same amounts of materials as used in the preparation of the resist material in Example 1 were added to prepare a resist material. Note that because the viscosity of the prepared resist material was low, it was not possible to form a resist layer on the surface of the PET film in the same manner as in Example 1. For this reason, 0.5 g of a sample for measuring the amount of palladium particles was collected from the resist material after volatilizing the solvent. Then, measurements were made under the same measurement conditions as in Example 1. As a result of the measurement, 4.5 parts by mass of palladium particles were contained per 100 parts by mass of the photosensitive urethane resin.

[0057] [Manufacturing of Circuit Board] The circuit board of Comparative Example 2 was manufactured using the same materials and under the same conditions as those used in manufacturing the circuit board of Example 1. In the resist layer forming step, a resist layer could not be formed on the polyimide film due to the low viscosity of the resist material.

[0058] Comparative Example 3 (Preparation of Resist Material) A resist material was prepared without adding CP-018T6 (manufactured by Nissan Chemical Industries, Ltd.). Except for CP-018T6 (manufactured by Nissan Chemical Industries, Ltd.), the same materials as those used in the preparation of the resist material in Example 1 were used, and the same amounts of the materials used in the preparation of the resist material in Example 1 were added.

[0059] [Manufacturing of Circuit Board] The circuit board of Comparative Example 3 was manufactured using the same materials and under the same conditions as those used in manufacturing the circuit board of Example 1. In the wiring layer forming step, no wiring layer was formed on the surface of the polyimide film exposed by development, and a circuit board could not be obtained.

[0060] The results of the examples and comparative examples show that when the amount of palladium particles contained in the resist layer is 0.4 parts by mass or more and 3.3 parts by mass or less per 100 parts by mass of photosensitive urethane resin, a wiring layer can be formed on the surface of the polyimide film exposed by development.

[0061] As described above, according to the method for manufacturing a circuit board according to this embodiment, a circuit board having fine wiring can be manufactured with fewer steps than the number of steps required in the conventional full additive method.

[0062] The present invention allows various embodiments and modifications without departing from the broad spirit and scope of the present invention. Furthermore, the above-described embodiments are intended to explain the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and within the scope of the meaning of the invention equivalent thereto are considered to be within the scope of the present invention.

[0063] This application is based on Japanese Patent Application No. 2023-198800, filed on November 24, 2023. The specification, claims, and drawings of Japanese Patent Application No. 2023-198800 are incorporated herein by reference.

[0064] (Appendix) Various aspects of the present disclosure are collectively described below as appendices. (Appendix 1) A method for manufacturing a circuit board, comprising: a resist layer forming step of forming a resist layer containing palladium particles and a dispersant that covers the palladium particles on at least one surface of a substrate, an exposure step of exposing the resist layer to light, a resist pattern forming step of developing the resist layer exposed in the exposure step to form a resist pattern in the resist layer, a heating step of heating the substrate on which the resist pattern has been formed on the resist layer, and a wiring layer forming step of forming a conductive wiring layer on the substrate exposed after the resist pattern forming step.

[0065] (Supplementary Note 2) The method for manufacturing a circuit board according to Supplementary Note 1, wherein the resist layer contains a photosensitive base material and a photopolymerization initiator.

[0066] (Appendix 3) The method for producing a circuit board according to Appendix 2, wherein the amount of palladium particles contained in the resist layer is 0.4 parts by mass or more and 3.3 parts by mass or less with respect to 100 parts by mass of the photosensitive base material.

[0067] (Supplementary Note 4) The method for manufacturing a circuit board according to Supplementary Note 2 or Supplementary Note 3, wherein the photosensitive base material is a photosensitive urethane resin.

[0068] 10 substrate, 12 resist layer, 12p resist pattern, 14 mask, 14a opening, 16 light, 18 wiring layer, 20 heater, 121 palladium particles.

Claims

1. A method for manufacturing a circuit board, comprising: a resist layer forming step of forming a resist layer containing palladium particles and a dispersing agent that covers the palladium particles on at least one surface of a substrate; an exposure step of exposing the resist layer; a resist pattern forming step of developing the resist layer exposed in the exposure step to form a resist pattern in the resist layer; a heating step of heating the substrate on which the resist pattern has been formed on the resist layer; and a wiring layer forming step of forming a conductive wiring layer on the substrate exposed after the resist pattern forming step.

2. The method for manufacturing a circuit board according to claim 1, wherein the resist layer contains a photosensitive base material and a photopolymerization initiator.

3. The method for manufacturing a circuit board according to claim 2, wherein the amount of palladium particles contained in the resist layer is 0.4 parts by mass or more and 3.3 parts by mass or less per 100 parts by mass of the photosensitive base material.

4. The method for manufacturing a circuit board according to claim 2 or 3, wherein the photosensitive base material is a photosensitive urethane resin.

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