Method for manufacturing a circuit board

Abstract

A method for manufacturing a circuit substrate includes the following steps: a resist layer forming step of forming a resist layer containing palladium particles and a dispersant covering 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 is formed in the resist layer; and a wiring layer forming step of forming a wiring layer having conductivity on the substrate exposed after the resist pattern forming step.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a circuit board. Background Technology

[0002] Various methods for manufacturing circuit boards with fine wiring were investigated. As an example of a method for manufacturing a circuit board, a fully additive method was disclosed, which includes the following steps: roughening the surface of an adhesive layer formed on a substrate and applying a catalyst containing a palladium compound to the surface; activating the catalyst by treating it with an acid; 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 in the resist layer by exposure and development; treating the catalyst again with an acid; and electrolessly plating the substrate obtained in the previous step to form a conductive circuit.

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 5-21932 Summary of the Invention

[0004] The problem that the invention aims to solve However, the total additive process involves many steps, requiring multiple pieces of equipment and numerous chemicals, until the microwires are formed on the substrate.

[0005] The present invention was made in view of the above circumstances. That is, the object of the present invention is to provide a method for manufacturing a circuit board that can manufacture a circuit board with fine wiring using fewer steps than the conventional all-additive method.

[0006] Methods for solving problems The present invention is described below.

[0007] [1] The method for manufacturing the circuit board involved in this invention includes the following steps: The resist layer forming process forms a resist layer comprising palladium particles and a dispersant covering the palladium particles on at least one side of a substrate; The exposure process involves exposing the aforementioned resist layer to light; The resist pattern forming process involves developing the resist layer that has been exposed in the aforementioned exposure process to form a resist pattern in the resist layer. The heating process involves heating the substrate in which the aforementioned resist pattern has been formed in the aforementioned resist layer; and The wiring layer formation process forms a conductive wiring layer on the substrate exposed after the aforementioned resist pattern formation process.

[0008] [2] The aforementioned resist layer may contain a photosensitive agent and a photopolymerization initiator.

[0009] [3] The amount of palladium particles contained in the aforementioned resist layer may be more than 0.4 parts by mass and less than 3.3 parts by mass relative to 100 parts by mass of the aforementioned photosensitive main agent.

[0010] [4] The aforementioned photosensitive main agent can be a photosensitive polyurethane resin.

[0011] Invention Effects According to the present invention, a method for manufacturing a circuit board can be provided, which can manufacture a circuit board with fine wiring using fewer steps than the conventional all-additive method. Attached Figure Description

[0012] [ Figure 1A [This is a schematic diagram illustrating the resist layer formation process in the method for manufacturing a circuit board according to the embodiments.]

[0013] [ Figure 1B [This is a schematic diagram illustrating the exposure process of the manufacturing method of the circuit board according to the embodiment.]

[0014] [ Figure 1C [This is a schematic diagram illustrating the resist patterning process in the method for manufacturing a circuit board according to the embodiments.]

[0015] [ Figure 1D [This is a schematic diagram illustrating the heating process in the method for manufacturing a circuit board according to the embodiment.]

[0016] [ Figure 1E [This is a schematic diagram illustrating the wiring layer formation process in the manufacturing method of the circuit board according to the embodiment.]

[0017] [ Figure 2 This is a schematic diagram illustrating the masks used in the embodiments and comparative examples. Detailed Implementation

[0018] The following describes in detail specific embodiments of the present invention (hereinafter referred to as embodiments). These embodiments are examples used to illustrate the present invention and are not intended to limit the invention to the following content. The present invention can be implemented with appropriate modifications within its scope.

[0019] [Manufacturing method of circuit board] Reference Figures 1A to 1E The method for manufacturing the circuit board according to the embodiment will be described.

[0020] The manufacturing method of the circuit board includes (a) a resist layer formation process, (b) an exposure process, (c) a resist pattern formation process, (d) a heating process, and (e) a wiring layer formation process.

[0021] (a) Resist layer formation process like Figure 1A As shown, a resist layer 12 is formed on one side of the substrate 10. In this process, the process of forming the resist layer using a negative dry film will be described as an example.

[0022] First, a negative dry film is applied to the substrate 10. Next, the negative dry film and the substrate 10 are heated and pressurized simultaneously, for example, using a laminator. This forms a resist layer 12 on the substrate 10. The heating and pressurizing conditions are, for example, 30°C to 100°C, 0.1 MPa to 1.0 MPa, and 5 seconds to 60 seconds. Heating and pressurizing can also be performed under a reduced pressure atmosphere. The thickness of the negative dry film can be appropriately selected based on the thickness of the wiring layer formed on the substrate 10.

[0023] The substrate 10 can be any substrate capable of forming the resist layer 12. Examples include flexible printed wiring boards, film substrates, substrates with circuits formed, and insulating substrates such as FR4. Examples of film substrates include polyimide films, polyethylene terephthalate films (PET films), and liquid crystal films (LCP films).

[0024] The resist layer 12 is composed of a resist material containing palladium particles 121 and a dispersant (not shown) covering 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 activity efficiency of the palladium particles. The dispersant covering the palladium particles 121 is composed of a compound capable of bonding with the palladium particles 121. Examples include nitrogen-containing compounds with nitrogen in their terminal functional groups and / or compounds having unsaturated bonds. The bonding between the palladium particles 121 and this compound can be, for example, coordination bonding, ionic bonding, or covalent bonding; from a dispersibility viewpoint, coordination bonding is preferred. Examples of nitrogen-containing compounds include polymers with ammonium groups in their terminal functional groups. Examples of compounds having unsaturated bonds include, for example, polyethylene glycol alkyl ethers of acrylic acid. It should be noted that the particle size of palladium 121 can be determined by images obtained from a transmission electron microscope (TEM).

[0025] Regarding the amount of palladium particles 121 contained in the resist material, from the viewpoint of facilitating the formation of the wiring layer 18 on the substrate 10, it is preferably 0.4 parts by mass to 3.3 parts by mass, and more preferably 1.0 parts by mass to 3.0 parts by mass, relative to the photosensitive main agent 100 parts by mass described later. This allows the palladium particles 121 to adhere to the surface of the substrate 10 exposed after development in the resist patterning process described later. It should be noted that the amount of palladium particles 121 can be determined using an ICP emission spectroscopy analyzer.

[0026] The resist material constituting the resist layer 12 also includes a photosensitive main agent and a photopolymerization initiator. Examples of photosensitive main agents included in the resist material include photosensitive polyurethane resins. Examples of photosensitive polyurethane resins include resins having ester bonds and unsaturated bonds in the main chain within the same molecule, having anionic groups in the side chains and / or at the ends, and having unsaturated bond groups in the side chains. From the viewpoints of facilitating the formation of the resist layer 12 on the substrate 10, ensuring uniform thickness of the resist layer 12, and improving the heat resistance and water resistance of the resist layer 12, the number average molecular weight of the photosensitive polyurethane resin is preferably 2000 or more and 500,000 or less. It should be noted that, regarding the number average molecular weight of the photosensitive polyurethane resin, polymethyl methacrylate can be used as a standard sample, and the determination can be performed using gel permeation chromatography.

[0027] From the viewpoint of improving the strength and heat resistance of the cured resist layer 12, the amount of unsaturated bonds in the main chain of the photosensitive polyurethane resin is preferably 0.40 mmol / g or more and 2.20 mmol / g or less. This amount of unsaturated bonds can be calculated by dividing the molar number of unsaturated diacids by the amount (g) of the resulting photosensitive polyurethane resin. The unsaturated diacid is the acid component used in the synthesis of the polyol constituting the photosensitive polyurethane resin.

[0028] From the viewpoints of improving the development accuracy of the resist layer 12, ensuring uniform mixing of other materials contained in the resist material of the resist layer 12 with the photosensitive polyurethane resin, and achieving uniform thickness of the resist layer 12, the amount of anionic groups contained in the photosensitive polyurethane resin is preferably 0.60 mmol / g or more and 1.50 mmol / g or less. Examples of anionic groups include carboxyl groups and sulfonic acid groups, which are functional groups that generate anions. From the viewpoint of improving the development accuracy of the resist layer 12, carboxyl groups are preferred. It should be noted that the amount of anionic groups can be calculated by measuring the acid value of the obtained photosensitive polyurethane resin and dividing that acid value by the molecular weight of KOH. Preferably, the acid value of the photosensitive polyurethane resin is 33 mg KOH / g or more and 85 mg KOH / g or less. The acid value of the photosensitive polyurethane resin can be determined based on the method described in JIS K 0070.

[0029] From the viewpoint of obtaining fine resist patterns, the amount of unsaturated bonds in the side chains of the photosensitive polyurethane resin is preferably 0.10 mmol / g or more and 0.90 mmol / g or less. This amount of unsaturated bonds can be calculated by dividing the molar number of unsaturated bond groups by the amount (g) of the resulting photosensitive polyurethane resin. The unsaturated bond group is an unsaturated bond group contained in a compound having at least one functional group containing an active hydrogen atom and an unsaturated bond group within the molecule.

[0030] Photosensitive polyurethane resins can be obtained, for example, by mixing and reacting a compound having (a) an ester bond and an unsaturated bond in its main chain, (b) a compound having at least one functional group containing an active hydrogen and at least one anionic group in its molecule, (c) a polyisocyanate, and (d) a compound having at least one functional group containing an active hydrogen and an unsaturated bond in its molecule. Examples of functional groups containing active hydrogen include carboxyl groups and hydroxyl groups. Furthermore, known synthetic methods can be used to synthesize photosensitive polyurethane resins.

[0031] As a polyol in (a), examples include polyester polyols having unsaturated bonds in the main chain. Polyester polyols can be obtained by reacting an acid component with a polyol component. Examples of acid components include unsaturated dicarboxylic acids such as dimethyl maleate, dimethyl fumarate, maleic dichloro, and maleic anhydride. Examples of polyol components include 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. As a compound in (b), examples include (i) dimethylolpropionic acid, (ii) dimethylolbutyric acid, and (iii) compounds obtained by radically reacting a monomer containing hydroxyl and unsaturated groups with a monomer containing carboxyl and unsaturated groups. As a polyisocyanate in (c), examples include toluene diisocyanate, dimethyl phthalate diisocyanate, methylene diisocyanate, hexane diisocyanate, and isophorone diisocyanate. Examples of compounds that can be classified as (d) include glyceryl monoallyl ether, glyceryl monoacrylate, and glyceryl monomethacrylate.

[0032] Examples of photopolymerization initiators included in the resist material include bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, and 1-[4-(phenylthio)phenyl-1,2-octanedione-2-(O-benzoyl oxime)]. From the viewpoint of curability, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and 2,4,6-trimethylbenzoyl diphenylphosphine oxide are preferred. Regarding the photopolymerization initiator, one photopolymerization initiator can be used alone, or two or more photopolymerization initiators can be used in combination. Regarding the amount of photopolymerization initiator included in the resist material, from the viewpoint of improving reactivity with the photosensitizing agent and improving the adhesion between the resist layer 12 and the substrate 10, it is preferably 2 to 20 parts by mass relative to 100 parts by mass of the photosensitive agent, more preferably 6 to 16 parts by mass.

[0033] Furthermore, from the viewpoint of facilitating the processability of the resist material, the resist material constituting the resist layer 12 may also include acrylate monomers. Examples of acrylate monomers include, for example, urethane acrylate monomers and epoxy acrylate monomers. Examples of urethane acrylate monomers include, for example, aliphatic urethane acrylate monomers containing one or more acrylate groups per molecule. Examples of epoxy acrylate monomers include, for example, 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 consist of one type of acrylate monomer or two or more types of acrylate monomers. Regarding the amount of acrylate monomer contained in the resist material, from the viewpoint of ensuring reliable curing of the resist material and improving the accuracy of development of the resist layer 12, it 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.

[0034] (b) Exposure process like Figure 1B As shown, the resist layer 12 is exposed. Specifically, in order to form a resist pattern in the resist layer 12, the resist layer 12 is exposed through a mask 14 having an opening 14a. The resist layer 12 exposed through the opening 14a corresponds to the portion other than the metal portion such as wiring to be formed. The resist layer 12 not exposed through the mask 14 corresponds to the metal portion such as wiring to be formed. The wavelength of the light 16 used during exposure only needs to be a wavelength that can form a resist pattern in the resist layer 12, for example, 200 nm or more and 500 nm or less. As for the exposure conditions, it is sufficient to form a resist pattern in the resist layer 12. For example, a high-pressure mercury lamp can be used and the cumulative light intensity can be set to 50 mJ / cm. 2 Above 1500mJ / cm 2 The following conditions apply.

[0035] (c) Resist pattern formation process like Figure 1CAs shown, the exposed resist layer 12 is developed, forming a resist pattern 12p within it. Specifically, if the resist layer 12 is exposed and developed through a mask 14, only the resist layer 12 not exposed to light 16 dissolves in the developing solution. 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 support, forming a wiring layer 18 on the exposed surface of the substrate 10 in a subsequent wiring layer formation process. It should be noted that the developing solution used during development can be any solution capable of developing the exposed resist layer 12; for example, an alkaline aqueous solution such as sodium carbonate solution can be used. 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.

[0036] (d) Heating process like Figure 1D As shown, the substrate 10, in which the resist pattern 12p is formed in the resist layer 12, is heated using the heater 20. This activates the palladium particles 121 adhering to the exposed surface of the substrate 10, fixing them onto the surface of the substrate 10. From the viewpoint of activating the palladium particles 121 to fix them onto the surface of the substrate 10, the heating temperature and time are, for example, 200°C to 280°C and 2 minutes to 30 minutes, preferably 200°C to 260°C and 10 minutes to 20 minutes.

[0037] (e) Wiring layer formation process like Figure 1E As shown, a conductive wiring layer 18 is formed on the exposed substrate 10. The wiring layer 18 can be formed, for example, by electroless plating. As a condition for electroless plating, it is sufficient that the wiring layer 18 can be formed on the substrate 10; for example, immersing the substrate 10 in an electroless plating solution containing copper for 1 minute to 30 minutes is an example. As a copper-containing electroless plating solution used at this time, an aqueous solution containing copper ions, a complexing agent, and a reducing agent is an example. As a complexing agent, examples include Rochelle salt and sodium salt of ethylenediaminetetraacetic acid. As a reducing agent, examples include formaldehyde, formaldehyde precursors, or derivatives thereof.

[0038] It should be noted that the thickness of the wiring layer 18 formed without electroplating can also be further increased by electroplating. The conditions for electroplating are simply those that can further increase the thickness of the wiring layer 18. For example, the following conditions can be given: immersing the substrate 10 having the wiring layer 18 formed without electroplating in an electroplating solution for 1 minute to 60 minutes at a concentration of 0.05 A / dm². 2 Above 10.0A / dm 2The following processing is performed. Examples of electroplating solutions used at this time include copper sulfate plating solution, copper pyrophosphate plating solution, and copper cyanide plating solution.

[0039] In addition, the thickness of the wiring layer 18 can be thinner than the thickness of the resist pattern 12p, thicker than the thickness of the resist pattern 12p, or the same thickness as the resist pattern 12p.

[0040] Alternatively, it can also be achieved through the processes described in (a) to (e) above. Figure 1E Other wiring layers are formed on the surface of the resist pattern 12p and the surface of the wiring layer 18. This allows for multilayering of the circuitry in the thickness direction of the substrate 10. Alternatively, a substrate with other circuitry can be formed by laminating the surface of the resist pattern 12p and the surface of the wiring layer 18 using an adhesive sheet. This method also allows for multilayering of the circuitry in the thickness direction of the substrate 10.

[0041] Through the processes described in (a) to (e) above, a circuit board can be obtained. Furthermore, the circuit board manufacturing method according to this embodiment eliminates the need for steps essential in conventional fully additive circuit board manufacturing methods: laminating an adhesive layer on the 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. Additionally, because the number of processes in the circuit board manufacturing method is reduced, the number of equipment and the amount of chemicals can be reduced.

[0042] It should be noted that, in the resist layer formation process (a), the resist material constituting the resist layer 12 can be any material capable of forming a resist pattern by exposure and development. For example, positive resist materials and negative resist materials can be used. The form of the resist material can be, for example, a liquid resist or a dry film already formed into a film. When forming a resist layer on the substrate 10 using a liquid resist, for example, a coating machine is used to coat the substrate 10 with the liquid resist. Next, the coated liquid resist is heated using a heater to cure it. Thus, a resist layer 12 is formed on the substrate 10. Here, the positive resist material dissolves in the developer when exposed to light, and does not dissolve in the developer if not exposed to light. The negative resist material does not dissolve in the developer if exposed to light, and dissolves in the developer if not exposed to light.

[0043] In addition, the method for manufacturing a circuit board in this embodiment includes a resist layer forming step that uses a negative dry film of a negative resist material to form a resist layer, but may also include a resist layer forming step that changes the negative resist material to a positive resist material to form a resist layer.

[0044] Furthermore, as long as palladium particles 121 remain on the surface of the substrate 10 exposed by developing the resist layer 12, various photolithography processes can be appropriately selected in the circuit board manufacturing method of this embodiment.

[0045] Furthermore, in the manufacturing method of the circuit board in this embodiment, a method for forming a circuit on only one side of the substrate 10 has been described. However, on the other hand, a circuit can also be formed on both sides of the substrate 10 through the same processing steps as described above.

[0046] Example The present invention will now be described in more detail using examples. The present invention is not limited to any of the examples described below. Furthermore, in the examples and comparative examples, parts by mass represent the parts by mass of the solid components obtained after removing volatile components such as solvents.

[0047] (Example 1) (Preparation of negative resist materials) 100 parts by weight of photosensitive polyurethane resin as the main photosensitive agent, 40 parts by weight of Ebecryl-1039 (manufactured by DAICEL-ALLNEX LTD.) as the acrylate monomer, 12 parts by weight of Omnirad TPO-H (manufactured by BASF) as the photopolymerization initiator, and 1.5 parts by weight of CP-018T6 (manufactured by Nissan Chemical Co.) as a liquid containing palladium particles and a dispersant were added to a container and mixed using a mixer to obtain a negative photoresist material. Hereinafter, the negative photoresist material will be simply referred to as the photoresist material.

[0048] The resist material contains 0.45 parts by mass of palladium particles relative to 100 parts by mass of the photosensitive polyurethane resin. The amount of palladium particles was determined as follows. First, using a comma coater, the resist material was coated onto the surface of a PET film (LINTEC Corporation, PI3811) that had undergone a release treatment, to a thickness of 25 μm after drying. The film was 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 with the resist layer formed was added to an acidic solution to dissolve it, obtaining a test sample. Then, the amount of palladium particles contained in the obtained test sample was determined using an ICP emission spectrometer (Shimadzu Corporation, ICPE-9800 series). The drying conditions for forming the resist layer on the PET film were set to 160°C for 5 minutes. The acidic solution used was a mixed solution containing 0.5 ml of 97% sulfuric acid, 5 ml of 61% nitric acid, and 44.5 ml of pure water.

[0049] The photosensitive polyurethane resin used in the preparation of the photoresist material was synthesized through the following steps. 365 g of adipic acid, 245 g of maleic anhydride, and 661 g of 1,6-hexanediol were added to a 2-liter flask equipped with a stirrer, thermometer, and condenser, and heated to 130°C while stirring. After 4 hours, the temperature was raised to 210°C and maintained at 210°C for 2 hours. During this time, 134 g of condensation 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 with unsaturated bonds in its main chain. The obtained polyester polyol had an unsaturated bond content of 2.20 mmol / g in its main chain and an OH value of 59.5 mg KOH / g.

[0050] Next, 1000g of polyester polyol, 170g of glycerol monomethacrylate (manufactured by Nippon Oil Co., Ltd., BLEMMER (registered trademark) GLM), 275g of dimethylolbutyric acid, and 650g of isophorone diisocyanate were added to a 5-liter flask equipped with a stirrer, thermometer, and condenser. Toluene (698g) was then added to achieve a resin composition of 75%. The reaction was then carried out at 100°C until the NCO groups disappeared. Then, 1397g of methyl ethyl ketone was added to obtain a photosensitive polyurethane resin solution with a resin composition of 50%. The obtained photosensitive polyurethane 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 mg KOH / g.

[0051] [Circuit board manufacturing] (Resist layer formation process) Using a comma coating machine, the photoresist material was coated onto a polyimide film (manufactured by DU PONT-TORAY CO., LTD., Kapton 100EN-C) to a dried thickness of 25 μm. After drying, the film was allowed to dry, forming a photoresist layer on one side of the polyimide film. The drying conditions were set to 160°C for 5 minutes. In this embodiment, to protect the surface of the photoresist layer, the PET film was laminated onto the surface of the photoresist layer by contacting the release-treated surface of a PET film (manufactured by LINTEC, PI3811). The lamination conditions were set to 0.5 MPa, 50°C, and 30 seconds.

[0052] (Exposure process) Exposure is performed on the photoresist layer through a mask. An ultra-high pressure mercury lamp (USHIO LIGHTING, INC., USH-250BY) is used to expose the PET film from the side until the cumulative light intensity reaches 300 mJ / cm². 2The wavelength of the light used for exposure was set to 365 nm. A mask with a pattern of 100 μm / 100 μm L / S was used. This patterned mask is shown below. Figure 2 In this context, L represents the light-blocking part that blocks light during exposure. S represents the opening that allows light to pass through.

[0053] (Resist pattern formation process) After exposure, the PET film is peeled off from the resist layer formed on one side of the polyimide film. Next, a 1% sodium carbonate aqueous solution at 30°C is sprayed onto the exposed resist layer surface for 60 seconds for development. After development, a resist pattern is confirmed to have formed within the resist layer. The nozzle pressure during spraying is set to 0.18 MPa.

[0054] (Heating process) The polyimide film with a resist pattern formed in the resist layer was dried using a dryer. The drying conditions were set to 240°C for 15 minutes.

[0055] (Wiring layer formation process) In a plating bath containing an electroless plating solution (THRU-CUP PMK, manufactured by Uemura Kogyo Co., Ltd., copper concentration 2.5 g / L) at a temperature of 40°C, the polyimide film obtained in the heating process was immersed for 10 minutes and then removed from the plating bath. A laminate with an electroless plating layer of 0.2 μm thickness was obtained on the surface of the polyimide film exposed by development.

[0056] Next, the laminate with a non-electroplated layer of 0.2 μm thickness is immersed in a plating bath containing an electroplating solution (TOP LUCINA SF) at a temperature of 25°C, at a flow rate of 2 A / dm. 2 An electroplating process was performed for 30 minutes. This resulted in a laminate with an electroplated layer of 12 μm thickness formed on the non-electroplated layer. The thickness of the electroplated layer was measured using a micrometer. It should be noted that no wiring layer was observed on the surface of the resist layer with the resist pattern, confirming that a circuit board can be obtained using the method of this embodiment.

[0057] (Example 2) (Preparation of corrosion-resistant materials) The amount of CP-018T6 (manufactured by Nissan Chemical Co., Ltd.) was changed to 7.5 parts by mass. Otherwise, the same materials as those used in the preparation of the resist material in Example 1 were used, and the same amount of materials as those used in the preparation of the resist material in Example 1 were added. The prepared resist material contained 2.25 parts by mass of palladium particles relative to 100 parts by mass of the photosensitive polyurethane resin.

[0058] [Circuit board manufacturing] The circuit board of Example 2 was manufactured using the same materials as the circuit board of Example 1 and under the same manufacturing conditions as the circuit board of Example 1. Similar to the circuit board of Example 1, the circuit board of Example 2 has a wiring layer formed on the surface of the polyimide film exposed by development, and the wiring layer is not visible on the surface of the resist layer where the resist pattern is formed.

[0059] (Example 3) (Preparation of corrosion-resistant materials) The amount of CP-018T6 (manufactured by Nissan Chemical Co., Ltd.) was changed to 10.5 parts by mass. Otherwise, the same materials as those used in the preparation of the resist material in Example 1 were used, and the same amount of materials as those used in the preparation of the resist material in Example 1 were added. The prepared resist material contained 3.15 parts by mass of palladium particles relative to 100 parts by mass of the photosensitive polyurethane resin.

[0060] [Circuit board manufacturing] The circuit board of Example 3 was manufactured using the same materials as the circuit board of Example 1 and under the same manufacturing conditions as the circuit board of Example 1. Similar to the circuit board of Example 1, the circuit board of Example 3 had a wiring layer formed on the surface of the polyimide film exposed by development, and the wiring layer was not visible on the surface of the resist layer where the resist pattern was formed.

[0061] (Comparative Example 1) (Preparation of corrosion-resistant materials) The amount of CP-018T6 (manufactured by Nissan Chemical Co., Ltd.) was changed to 0.75 parts by mass. Otherwise, the same materials as those used in the preparation of the resist material in Example 1 were used, and the same amount of materials as those used in the preparation of the resist material in Example 1 were added. The prepared resist material contained 0.23 parts by mass of palladium particles relative to 100 parts by mass of the photosensitive polyurethane resin.

[0062] [Circuit board manufacturing] The circuit board of Comparative Example 1 was manufactured using the same materials as those used in the manufacture of the circuit board of Example 1, and under the same manufacturing conditions as those used in the manufacture of the circuit board of Example 1. However, in the wiring layer formation process, a wiring layer was not formed on the surface of the polyimide film exposed by developing, and a circuit board was not obtained.

[0063] (Comparative Example 2) (Preparation of corrosion-resistant materials) The amount of CP-018T6 (manufactured by Nissan Chemical Co., Ltd.) was changed to 15.0 parts by mass. Otherwise, the same materials used in the preparation of the resist material in Example 1 were used, and the same amount of materials used in the preparation of the resist material in Example 1 were added. It should be noted that because the prepared resist material had low viscosity, a resist layer was not formed on the PET film surface as in Example 1. Therefore, the 0.5 g sample used to determine the amount of palladium particles was collected from the resist material after the solvent had evaporated. The determination was then performed under the same conditions as described in Example 1. The result showed that the resist contained 4.5 parts by mass of palladium particles relative to 100 parts by mass of the photosensitive polyurethane resin.

[0064] [Circuit board manufacturing] The circuit board of Comparative Example 2 was manufactured using the same materials as those used in the manufacture of the circuit board of Example 1, and under the same manufacturing conditions as those used in the manufacture of the circuit board of Example 1. During the resist layer formation process, due to the low viscosity of the resist material, a resist layer could not be formed on the polyimide film.

[0065] (Comparative Example 3) (Preparation of corrosion-resistant materials) The photoresist material was prepared without the addition of CP-018T6 (manufactured by Nissan Chemical Co., Ltd.). Except for CP-018T6 (manufactured by Nissan Chemical Co., Ltd.), the same materials used in the preparation of the photoresist material of Example 1 were used, and the same amount of materials were added as used in the preparation of the photoresist material of Example 1.

[0066] [Circuit board manufacturing] The circuit board of Comparative Example 3 was manufactured using the same material as the circuit board of Example 1 and under the same manufacturing conditions. However, in the wiring layer formation process, a wiring layer was not formed on the surface of the polyimide film exposed by developing, and a circuit board was not obtained.

[0067] As can be seen from the results of the examples and comparative examples, by making the amount of palladium particles contained in the resist layer more than 0.4 parts by mass and less than 3.3 parts by mass relative to 100 parts by mass of the photosensitive polyurethane resin, a wiring layer can be formed on the surface of the polyimide film exposed by development.

[0068] According to the circuit board manufacturing method of this embodiment, a circuit board with fine wiring can be manufactured with fewer processes than that of the conventional all-additive method.

[0069] Various embodiments and modifications are possible with respect to the present invention without departing from its broad spirit and scope. Furthermore, the embodiments described above are illustrative and do not limit the scope of the invention. That is, the scope of the invention is defined not by the embodiments, but by the claims. Moreover, various modifications implemented within the scope of the claims and their equivalents are considered to be within the scope of the invention.

[0070] This application is based on Japanese Patent Application No. 2023-198800, filed on November 24, 2023. The description, claims, and drawings of Japanese Patent Application No. 2023-198800 are incorporated herein by reference.

[0071] (Postscript) The various methods of this public document are summarized and recorded below as appendices.

[0072] (Note 1) A method for manufacturing a circuit board includes the following steps: The resist layer forming process forms a resist layer comprising palladium particles and a dispersant covering the palladium particles on at least one side of a substrate; The exposure process involves exposing the aforementioned resist layer to light; The resist pattern forming process involves developing the resist layer that has been exposed in the aforementioned exposure process to form a resist pattern in the resist layer. The heating process involves heating the substrate in which the aforementioned resist pattern has been formed in the aforementioned resist layer; and The wiring layer formation process forms a conductive wiring layer on the substrate exposed after the aforementioned resist pattern formation process.

[0073] (Note 2) The method for manufacturing a circuit board as described in Appendix 1, wherein the aforementioned resist layer comprises a photosensitive agent and a photopolymerization initiator.

[0074] (Note 3) In the method for manufacturing a circuit board as described in Appendix 2, the amount of palladium particles contained in the aforementioned resist layer is 0.4 parts by mass or more and 3.3 parts by mass or less relative to 100 parts by mass of the aforementioned photosensitive main agent.

[0075] (Note 4) The method for manufacturing a circuit board as described in Appendix 2 or Appendix 3, wherein the aforementioned photosensitive main agent is a photosensitive polyurethane resin.

[0076] Explanation of reference numerals in the attached figures 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 the following steps: The resist layer forming process involves forming a resist layer comprising palladium particles and a dispersant covering the palladium particles on at least one side of a substrate. The exposure process involves exposing the resist layer to light. The resist pattern forming process involves developing the resist layer that has been exposed in the exposure process to form a resist pattern in the resist layer. The heating process involves heating the substrate in which the resist pattern is formed in the resist layer; and The wiring layer forming process forms a conductive wiring layer on the substrate exposed after the resist pattern forming process.

2. The method for manufacturing a circuit board as described in claim 1, wherein, The resist layer contains a photosensitive agent and a photopolymerization initiator.

3. The method for manufacturing a circuit board as described in claim 2, wherein, The amount of palladium particles contained in the resist layer is between 0.4 and 3.3 parts by mass relative to 100 parts by mass of the photosensitive main agent.

4. The method for manufacturing a circuit board as described in claim 2 or 3, wherein, The photosensitive main agent is a photosensitive polyurethane resin.

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