Method for manufacturing wiring board

Abstract

To provide a manufacturing method of a wiring board capable of suppressing reduction in durability of a solid electrolyte film.SOLUTION: A manufacturing method of a wiring board 80 includes the steps of: preparing an insulative base material B containing resin; roughening a surface B2 of a portion where a wiring layer C is provided; depositing metal particles M onto a surface of the base material, thereby forming a seed layer 20 containing the metal on the base material; disposing an electrolyte film 13 between a positive electrode 11 and the seed layer which is a negative electrode, bringing the electrolyte film into contact with the seed layer, applying a voltage between the positive electrode and the seed layer, and reducing metal ions contained in the electrolyte film, thereby depositing a metal film F on the seed layer; forming a cut from a surface of the metal film to a boundary between the roughened portion and a non-roughened portion on the surface of the base material; and physically removing, from the base material, portions which are positioned in the non-roughened portion on the base material of the metal film and the seed layer.SELECTED DRAWING: Figure 1A

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a wiring board. [Background technology]

[0002] Conventionally, when manufacturing electronic circuit boards and the like, a metal film is formed on the surface of a substrate to form a metal circuit pattern (for example, Patent Document 1). Patent Document 1 discloses a technique for precipitating a metal by reducing metal ions, and forming a metal film made of the precipitated metal on the surface of a conductor pattern layer of a resin substrate.

[0003] In the technology disclosed in Patent Document 1, a voltage is applied between the conductive pattern layer, which serves as the anode and cathode, using a power supply unit while a solid electrolyte membrane (hereinafter also referred to as electrolyte membrane) is pressed against the surface of the conductive pattern layer of the resin substrate. The application of voltage by the power supply unit reduces metal ions contained in the electrolyte membrane on the surface of the conductive pattern layer. Therefore, metal is precipitated on the surface of the conductive pattern layer, and a metal coating can be formed on the surface of the conductive pattern layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-125087 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, a portion of the surface of the resin substrate where the conductor pattern layer is not formed cannot become a cathode, and therefore a metal film is not formed on this portion. Therefore, when a voltage is applied between the anode and the conductor pattern layer, a step is generated between the portion where the metal film is formed and the portion where the metal film is not formed. Since the electrolyte membrane is pressed against the surface of the conductor pattern layer of the resin substrate, the electrolyte membrane deforms to conform to the step. As the metal film on the surface of the conductor pattern layer grows, the step also becomes larger, and therefore, when the electrolyte membrane conforms to the step, it may be locally plastically deformed, which may reduce the durability of the electrolyte membrane.

[0006] 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 wiring board capable of suppressing a decrease in durability of a solid electrolyte membrane. [Means for solving the problem]

[0007] In view of the above-mentioned problems, a method for manufacturing a wiring board according to the present invention is a method for manufacturing a wiring board including a substrate and a wiring layer having a predetermined wiring pattern provided on a surface of the substrate, the method comprising the steps of: preparing an insulating substrate containing a resin as the substrate; roughening a surface of a portion of the substrate on which the wiring layer is to be provided; forming a seed layer containing a metal on the surface of the substrate by depositing metal particles generated by a target source on the surface of the substrate; disposing a solid electrolyte film between an anode and the seed layer which is a cathode, bringing the solid electrolyte film into contact with the seed layer, and applying a voltage between the anode and the seed layer to reduce metal ions contained in the solid electrolyte film, thereby forming a metal coating on the seed layer; forming a cut in the metal coating and the seed layer from the surface of the metal coating toward a boundary between a roughened portion and a non-roughened portion on the surface of the substrate; and physically removing from the substrate a portion of the metal coating and the seed layer where the cut is formed, the portion of the metal coating and the seed layer which is located in the non-roughened portion of the substrate.

[0008] In the method for manufacturing a wiring board according to the present invention, the surface of the portion of the substrate on which the wiring layer is provided is roughened, so that the surface roughness of the portion on which the wiring layer is provided is rougher than that of the other portions of the substrate. In other words, the roughened portion has irregularities, and the surface area of ​​the roughened portion is larger than that of the other portions. In this method, after roughening the surface of the substrate, metal particles generated by the target source are deposited on the substrate surface, thereby forming a seed layer with a flat surface on the substrate surface. At this time, the seed layer enters the recesses of the roughened portion of the substrate surface, and contacts the substrate with a surface area larger than that of the other portions. Therefore, the adhesion strength between the portion of the substrate on which the wiring layer is provided and the seed layer is higher than the adhesion strength between the portion of the substrate on which the wiring layer is not provided and the seed layer. In this method, the solid electrolyte film is brought into contact with the flat seed layer to form a metal film on the seed layer, so that local deformation of the solid electrolyte film can be suppressed, and thus the durability deterioration of the solid electrolyte film can be suppressed. Finally, the portions of the metal coating and the seed layer that are located in the non-roughened portion of the substrate are physically removed from the substrate, thereby forming a wiring layer of a predetermined wiring pattern on the surface of the substrate.

[0009] In a preferred embodiment, in the roughening step, the surface of the portion on which the wiring layer is to be provided is roughened by a laser.

[0010] According to this aspect, the surface of the portion where the wiring layer is to be provided is roughened by the laser, so that a finer wiring pattern can be realized compared to the case where the surface is roughened by using a chemical solution such as permanganate. Also, heat is applied to the resin of the substrate by the laser in the atmosphere, so that functional groups of the oxide of the resin are generated, and the functional groups are attached to the surface of the roughened portion of the substrate. The metal particles generated by the target source are bonded to the functional groups generated from the resin of the substrate, so that the adhesive strength between the roughened portion of the substrate surface and the seed layer can be increased.

[0011] A preferred embodiment includes a step of irradiating the surface of the base material with oxygen plasma after the step of roughening and before the step of forming the seed layer.

[0012] Since the surface area of ​​the roughened portion of the surface of the substrate is larger than the surface area of ​​the other portions, according to this embodiment, more oxygen-containing functional groups are attached to the surface of the roughened portion of the substrate, and the metal particles generated by the target source bond to the functional groups attached to the surface of the substrate, thereby increasing the adhesive strength between the surface of the roughened portion of the substrate and the seed layer.

[0013] In a preferred embodiment, the step of forming the seed layer includes a step of using copper as the target source, and depositing copper particles as the metal particles on the surface of the substrate by sputtering to form a copper-containing seed layer on the surface of the substrate, and after the step of forming the metal coating, a step of applying heat to the substrate, the seed layer, and the metal coating until the resin of the substrate softens, thereby performing a heat treatment.

[0014] Since the surface area of ​​the roughened portion of the substrate surface is larger than the surface area of ​​the other portions, according to this aspect, more copper particles coming from the target source are deposited on the surface of the roughened portion of the substrate. When copper particles are deposited on the surface of the substrate by sputtering, a gap is formed between the copper particles and the surface of the substrate. According to this aspect, heat is applied to the substrate, seed layer, and metal coating to perform heat treatment until the resin of the substrate softens, so that the resin softened by the heat treatment enters the gap formed between the copper particles and the surface of the substrate. Since more copper particles are deposited on the surface of the roughened portion of the substrate, the contact area between the copper particles and the softened resin is increased, and the adhesion strength between the surface of the roughened portion of the substrate and the seed layer can be increased.

[0015] In a preferred embodiment, the step of forming the notches and the step of removing are carried out after the step of carrying out the heat treatment.

[0016] According to this aspect, after the heat treatment, a cut is formed in the metal coating and the seed layer from the surface of the metal coating toward the boundary between the roughened portion and the non-roughened portion on the surface of the substrate. In this way, the heat treatment increases the adhesion strength between the surface of the roughened portion of the substrate and the seed layer, and the cut is formed in the metal coating and the seed layer. Therefore, when the cut is formed, the seed layer can be prevented from peeling off from the surface of the roughened portion of the substrate. Since the seed layer is strongly adhered to the surface of the roughened portion of the substrate, only the portion of the metal coating and the seed layer where the cut is formed that is located in the non-roughened portion of the substrate can be removed from the substrate. Effect of the Invention

[0017] According to the present invention, it is possible to suppress a decrease in durability of a solid electrolyte membrane. [Brief description of the drawings]

[0018] [Figure 1A] 1A to 1C are cross-sectional views illustrating steps for manufacturing a wiring board according to a first embodiment of the present invention, where (a) shows a step of preparing a base material, (b) shows a step of roughening, and (c) shows a step of forming a seed layer. [Figure 1B] 5A to 5F are cross-sectional views illustrating the steps of manufacturing a wiring board according to the first embodiment of the present invention, where (d) shows a step of forming a metal film, (e) shows a step of forming a notch, and (f) shows a removal step. [Figure 1C] FIG. 4 is a cross-sectional view illustrating a process for manufacturing the wiring board according to the first embodiment of the present invention, where (g) shows the manufactured wiring board. [Diagram 2] 4 is a cross-sectional view showing a film formation apparatus used in manufacturing the wiring board according to the first embodiment, illustrating a state in which the solid electrolyte film is separated from the seed layer. FIG. [Diagram 3] 1 is a cross-sectional view showing a film formation apparatus used in manufacturing a wiring board according to a first embodiment, illustrating a state in which a solid electrolyte film is in contact with a seed layer. [Figure 4A] 5A to 5C are cross-sectional views illustrating steps for manufacturing a wiring board according to a second embodiment of the present invention, where (a) shows a step of preparing a base material, (b) shows a step of roughening, and (b-1) shows a step of irradiating oxygen plasma. [Figure 4B] 5A to 5E are cross-sectional views illustrating the steps of manufacturing a wiring board according to a second embodiment of the present invention, where (c) shows a step of forming a seed layer, (d) shows a step of forming a metal film, and (e) shows a step of forming a notch. [Figure 4C] 5A to 5G are cross-sectional views illustrating steps for manufacturing a wiring board according to a second embodiment of the present invention, where (f) shows a removing step, and (g) shows the manufactured wiring board. [Figure 5A] 11A to 11C are cross-sectional views illustrating steps for manufacturing a wiring board according to a third embodiment of the present invention, where (a) shows a step of preparing a base material, (b) shows a step of roughening, and (b-1) shows a step of irradiating oxygen plasma. [Figure 5B] 11A to 11D are cross-sectional views illustrating the steps of manufacturing a wiring board according to a third embodiment of the present invention, where (c) shows a step of forming a seed layer, (d) shows a step of forming a metal film, and (d-1) shows a step of performing heat treatment. [Figure 5C] 11A to 11G are cross-sectional views illustrating the steps of manufacturing a wiring board according to a third embodiment of the present invention, where (e) shows a step of forming a notch, (f) shows a removing step, and (g) shows the manufactured wiring board. [Figure 6] 1 is a diagram illustrating an embodiment of the present invention, showing the peel strength of each test specimen manufactured by changing the manufacturing conditions of the wiring board. [Figure 7] This is to explain an embodiment of the present invention, and shows the peel strength ratio of each test piece manufactured by changing the type of plasma irradiated onto the substrate as the manufacturing condition of the wiring board. [Figure 8] FIG. 1 illustrates an embodiment of the present invention, in which (a) shows a planar photograph of a test specimen, and (b) shows the peel strength of each test specimen manufactured by switching the order of the heat treatment step and the incision forming step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] First Embodiment A method for manufacturing a wiring board 80 according to the first embodiment will be described with reference to Fig. 1A to Fig. 3. The manufacturing method of this embodiment can be applied to the manufacture of a wiring board 80 including a base material B and a wiring layer C having a predetermined wiring pattern provided on a surface B1 of the base material B, as shown in Fig. 1C(g).

[0021] [Preparation process] 1A(a), in the manufacturing method of the wiring board 80 of the present embodiment, a step of preparing an insulating base material B containing a resin is carried out as the base material B. As the resin constituting the base material B, for example, a thermoplastic resin such as epoxy resin, ABS resin, AS resin, AAS resin, PS resin, EVA resin, PMMA resin, PBT resin, PET resin, PPS resin, PA resin, POM resin, PC resin, PP resin, PE resin, PI resin (polyimide), polymer alloy resin containing elastomer and PP, modified PPO resin, PTFE resin, ETFE resin, etc. can be used. As the base material B, for example, a base material made of glass epoxy resin, a flexible film-like base material such as polyimide resin, etc. can be used.

[0022] [Roughening process] Next, as shown in FIG. 1A(b), in the manufacturing method according to the present embodiment, a step of roughening the surface B2 of the surface B1 of the base material B, where the wiring layer C is provided, is carried out. Specifically, in this step, the base material B is placed in a laser irradiation device (not shown), and a laser 30 is irradiated from a laser light source (not shown) provided in the laser irradiation device toward the surface B1 of the base material B. The surface B2 of the portion where the wiring layer C is provided is irradiated with the laser 30 so that a predetermined pattern corresponding to the wiring pattern of the wiring board 80 is formed on the surface B1 of the base material B, and the surface B2 is roughened. As a result, unevenness is formed on the surface B2 of the roughened portion of the surface B1 of the base material B. It is preferable to roughen the surface B2 of the portion where the wiring layer C is provided of the base material B so that the arithmetic mean roughness Ra is 0.1 μm to 0.5 μm. This is because the larger the Ra, the higher the adhesion strength between the base material B and metal particles (e.g., copper particles) described later, but on the other hand, the surface area of ​​the metal particles (e.g., copper particles) present on the surface B2 of the base material B becomes larger, and the conductive path becomes longer, resulting in a larger transmission loss. In communications such as 5G and 6G, lower transmission loss is required, so in this case, it is more preferable to roughen the surface B2 so that the arithmetic mean roughness Ra of the surface B2 is 0.1 μm to 0.2 μm. In this process, for example, a mask member (not shown) having a shape corresponding to the wiring pattern of the wiring board 80 may be placed on the surface B1 of the base material B, and the surface B1 of the base material B may be roughened using a chemical solution such as permanganate. When the surface B1 of the base material B is roughened by the laser 30, a finer wiring pattern can be realized compared to when the surface B1 of the base material B is roughened using a chemical solution such as permanganate. Furthermore, when heat is applied to the resin of the base material B by the laser 30 in the atmosphere, functional groups of oxides of the resin are generated, and the functional groups are attached to the surface B2 of the roughened portion of the surface B1 of the base material B. The functional groups are generated when heat is applied to the resin of the base material B by the laser 30 in the atmosphere, particularly in an oxygen atmosphere, and examples of the functional groups include a hydroxyl group (-OH), a carboxyl group (-COOH), and an aldehyde group (-COH).

[0023] [Seed layer formation process] Next, as shown in FIG. 1A(c), a step of forming a seed layer 20 containing a metal on the surface B1 of the substrate B is performed by depositing metal particles M generated by a target source (not shown) on the surface B1 of the substrate B. Specifically, in this step, the substrate B manufactured through the roughening step is attached to a transport device (not shown), and the substrate B is transported to a position where the surface B1 of the substrate B faces the target source (not shown). Thereafter, in this step, metal particles M (e.g., copper particles) generated by the target source are deposited on the surface B2 of the roughened portion of the substrate B and the surface B3 of the unroughened portion. In detail, on the surface B2 of the roughened portion of the substrate B, the metal particles M flying from the target source enter the recesses formed on the surface B2, and after the recesses are filled with the metal particles M, the metal particles M are deposited so as to cover the protrusions formed on the surface B2. On the other hand, on the surface B3 of the unroughened portion of the substrate B, the metal particles M flying from the target source are uniformly deposited. In this way, the metal particles M are deposited on the surface B1 of the base material B (i.e., the surface B2 of the roughened portion of the base material B and the surface B3 of the unroughened portion), thereby forming a seed layer 20 of a predetermined thickness. The seed layer 20 has a flat surface 21 facing a target source. Examples of a method for forming the seed layer 20 include physical vapor deposition (PVD) such as sputtering, vacuum deposition, or ion plating. The material of the seed layer 20 is preferably one that can bond with the functional group generated in the above-mentioned roughening step. For example, when the seed layer 20 is formed as a single layer of a type of metal, the material may be copper, silver, nickel, or the like. When the seed layer 20 is formed by laminating a plurality of metals, the material may be titanium on the side of the base material B and copper on the side of the metal film F described later. When copper is selected as the material of the seed layer 20, it is preferable to form the seed layer 20 so that the crystal grain size of the copper is in the range of 1 nm to 1 μm. The crystal grain size of the copper can be measured by observing the cross section of the copper film using a transmission electron microscope (TEM).

[0024] As described above, in the manufacturing method according to the present embodiment, the surface B2 of the surface B1 of the base material B on which the wiring layer C is provided is roughened, so that the surface roughness of the surface B2 of the surface B1 of the base material B on which the wiring layer C is provided is rougher than that of the other portions. That is, the surface area of ​​the surface B2 of the roughened portion of the base material B is larger than the surface area of ​​the other portions. The metal particles M generated by the target source enter the recesses of the roughened portion of the surface B1 of the base material B. Therefore, the seed layer 20 contacts the base material B with a larger surface area on the surface B2 of the roughened portion of the base material B than on the surface B3 of the other portions. As a result, the adhesion strength between the surface B2 of the surface B2 of the surface B1 of the base material B on which the wiring layer C is provided and the seed layer 20 can be made higher than the adhesion strength between the surface B3 of the other portions of the surface B1 of the base material B and the seed layer 20. Furthermore, the metal particles M generated by the target source collide with the surface B1 of the base material B and are bonded to functional groups generated from the resin of the base material B. Therefore, the adhesion strength between the surface B2 of the roughened portion of the base material B and the seed layer 20 can be made higher than the adhesion strength between the surface B3 of the other portion and the seed layer 20.

[0025] [Metal coating process] 1B(d), a step of forming a metal coating F is performed. In this step, the metal coating F is formed on the surface 21 of the seed layer 20 using the film forming apparatus 1 shown in FIGS. 2 and 3. The metal coating F is formed to a thickness of, for example, 1 μm or more and 100 μm or less.

[0026] First, the configuration of the film forming apparatus 1 will be described. The film forming apparatus 1 is a film forming apparatus (plating apparatus) that forms a metal film F by solid-phase electrodeposition, and is used when forming the metal film F on the surface 21 of the seed layer 20. In this embodiment, for convenience of explanation, the positional relationship of the components of the film forming apparatus 1 is specified on the premise that a solid electrolyte membrane 13 (hereinafter also referred to as an electrolyte membrane) is arranged below the anode 11, and a substrate B is further arranged below that. However, as long as the metal film F can be formed on the surface 21 of the seed layer 20 formed on the substrate B, the positional relationship is not limited to this, and for example, the film forming apparatus 1 in FIG. 2 may be upside down.

[0027] As shown in FIG. 2, the film forming apparatus 1 includes a metal anode 11, an electrolyte membrane 13 disposed between the anode 11 and a seed layer 20 which is a cathode, and a power supply unit 14 which applies a voltage between the anode 11 and the seed layer 20.

[0028] In this embodiment, the film forming apparatus 1 further includes a container 15, which contains the anode 11 and a solution L (hereinafter, referred to as metal solution L) containing ions of a metal (e.g., Cu) that is a material of the metal coating F. Specifically, a container space 15c that contains the metal solution L is formed between the anode 11 and the electrolyte membrane 13, and the contained metal solution L flows from one side of the container 15 to the other side.

[0029] 2, when the anode 11 and the electrolyte membrane 13 are disposed apart from each other, the anode 11 is plate-shaped and may be either a soluble anode made of the same material as the metal film F (e.g., Cu), or an anode made of a material insoluble in the metal solution L (e.g., Ti). On the other hand, although not shown, when the anode 11 and the electrolyte membrane 13 are in contact with each other, the anode 11 may be an anode made of a porous body through which the metal solution L permeates and which supplies metal ions to the electrolyte membrane 13.

[0030] The electrolyte membrane 13 is not particularly limited as long as it can be impregnated (contains) metal ions therein by contacting it with the above-mentioned metal solution L and can precipitate metal derived from the metal ions on the surface 21 of the seed layer 20, which is the cathode, when a voltage is applied. The thickness of the electrolyte membrane 13 is, for example, about 5 μm to about 200 μm. Examples of materials for the electrolyte membrane 13 include fluorine-based resins such as Nafion (registered trademark) manufactured by DuPont, hydrocarbon-based resins, polyamic acid resins, and resins having a cation exchange function such as Selemion (CMV, CMD, CMF series) manufactured by Asahi Glass Co., Ltd.

[0031] The metal solution L is a liquid containing the metal of the metal coating F in an ionic state. Examples of the metal include Cu, Ni, Ag, and Au. The metal solution L is prepared by dissolving (ionizing) these metals in an acid such as nitric acid, phosphoric acid, succinic acid, sulfuric acid, or pyrophosphoric acid.

[0032] Furthermore, the film forming apparatus 1 of this embodiment includes, at the upper portion of the container 15, a lifting device 70 for lifting and lowering the container 15. The lifting device 70 may be any device capable of lifting and lowering the container 15, and may be configured, for example, by a hydraulic or pneumatic cylinder, an electric actuator, a linear guide, a motor, or the like.

[0033] The container 15 is provided with a supply port 15a through which the metal solution L is supplied and a discharge port 15b through which the metal solution L is discharged. The supply port 15a and the discharge port 15b are connected to the tank T via pipes 50 and 52, respectively. The metal solution L pumped from the tank T by the pump P flows into the container 15 from the supply port 15a, is discharged from the discharge port 15b, and returns to the tank T. A pressure regulating valve 54 is provided downstream of the discharge port 15b, and the metal solution L in the container 15 can be pressurized to a predetermined pressure by the pressure regulating valve 54 and the pump P. Therefore, during film formation, the electrolyte membrane 13 presses the surface 21 of the seed layer 20 due to the liquid pressure of the metal solution L. As a result, the metal film F can be formed on the seed layer 20 while the surface 21 of the seed layer 20 is uniformly pressurized by the electrolyte membrane 13.

[0034] The film forming apparatus 1 of this embodiment includes a metal pedestal 110 on which the base material B on which the seed layer 20 is formed is placed, and the metal pedestal 110 is electrically connected to the negative electrode of the power supply unit 14. The positive electrode of the power supply unit 14 is electrically connected to the anode 11 built into the container 15. Specifically, the film forming apparatus 1 includes a conductive member 56 that contacts a part (specifically, an end) of the seed layer 20 during the formation of the metal film F so as to conduct the negative electrode of the power supply unit 14 and the seed layer 20. The conductive member 56 is a metal plate that covers a part of the edge of the seed layer 20, and a part of the conductive member 56 is bent so as to contact the metal pedestal 110. As a result, the metal pedestal 110 is electrically connected to the seed layer 20 via the conductive member 56. The conductive member 56 is detachable from the base material B on which the seed layer 20 is formed.

[0035] Next, a description will be given of a process for forming the metal coating F using the film forming apparatus 1. In this process, the electrolyte membrane 13 is disposed between the anode 11 and the seed layer 20, which is the cathode, and the electrolyte membrane 13 is brought into contact with the seed layer 20. A voltage is applied between the anode 11 and the seed layer 20 to reduce metal ions contained in the electrolyte membrane 13, thereby forming the metal coating F on the seed layer 20.

[0036] First, in the film formation process, as shown in Fig. 2, the substrate B on which the seed layer 20 is formed and the conductive member 56 are placed at predetermined positions on the metal pedestal 110. Then, as shown in Fig. 3, the container 15 is lowered to a predetermined height by the lifting device 70.

[0037] When the metal solution L is pressurized by the pump P, the electrolyte membrane 13 is pressed against the surface 21 of the seed layer 20, and the pressure of the metal solution L in the container 15 is set to a constant pressure by the pressure regulating valve 54. That is, the electrolyte membrane 13 can uniformly press the surface 21 of the seed layer 20 with the regulated liquid pressure of the metal solution L in the container 15.

[0038] In this pressed state, a voltage is applied between the anode 11 and the seed layer 20 to reduce the metal ions contained in the electrolyte membrane 13, and metal derived from the metal ions is deposited on the surface 21 of the seed layer 20. Furthermore, due to the application of the voltage, the metal ions of the metal solution L in the container 15 continue to be reduced at the cathode, so that a metal film F is formed on the surface 21 of the seed layer 20.

[0039] When the metal coating F is formed to a predetermined thickness, the application of voltage between the anode 11 and the seed layer 20 is stopped, and the pump P stops pressurizing the metal solution L. Then, the lifting device 70 is used to raise the container 15 to a predetermined height (see FIG. 2), and the substrate B with the metal coating F formed thereon as shown in FIG. 1B(d) is removed from the metal pedestal 110.

[0040] [Process of forming the notches] Next, as shown in FIG. 1B(e), a step of forming an incision 24 is performed on the metal coating F and the seed layer 20 from the surface F1 of the metal coating F toward the boundary B4 between the surface B2 of the roughened portion and the surface B3 of the unroughened portion on the surface B1 of the base material B, or the vicinity thereof. Specifically, in this step, the base material B on which the seed layer 20 and the metal coating F are formed is placed in a laser irradiation device (not shown), and a laser 32 is irradiated toward the surface F1 of the metal coating F from a laser light source (not shown) provided in the laser irradiation device. The laser 32 forms an incision 24 in the metal coating F and the seed layer 20 from the surface F1 of the metal coating F to the surface B1 of the base material B or the vicinity thereof. It is preferable that the incision 24 reaches the surface B1 of the base material B, but it is not necessary that the incision 24 reaches the surface B1 of the base material B as long as the second seed layer portion 20B and the second metal coating portion FB can be removed from the base material B in the removing step described later.

[0041] In the step of forming the incisions 24, when both the material of the metal coating F and the seed layer 20 are copper, it is preferable to perform laser processing on the metal coating F and the seed layer 20 with a short pulse to an ultrashort pulse, which is a non-thermal processing with little thermal effect, while forming the incisions in the metal coating F and the seed layer 20, so as not to melt the resin of the base material B. The number of times of laser irradiation is determined according to the thickness of the metal coating F and the seed layer 20, and the thicker the thickness, the more the number of times of laser irradiation needs to be increased. For example, when the thickness of the metal coating F and the seed layer 20 of copper or the like is 20 μm, the laser irradiation is performed under the conditions of a green laser (wavelength 532 nm), an output of 1 W, a pulse width of 20 ps (picoseconds), and a frequency of 30 kHz. By forming the incisions 24, the seed layer 20 is separated into a first seed layer portion 20A located on the surface B2 of the roughened portion of the base material B and a second seed layer portion 20B located on the surface B3 of the unroughened portion of the base material B. Further, the metal coating F is separated into a first metal coating portion FA located on the first seed layer portion 20A and a second metal coating portion FB located on the second seed layer portion 20B. Note that the method for forming the incisions 24 is not limited to the laser, and a physical cutting tool (cutting machine) such as a rotary blade cutter or a straight blade cutter may also be used.

[0042] [Removal process] Next, as shown in FIG. 1B(f), a step of physically removing from the base material B the part of the metal coating F and the seed layer 20 where the incision 24 is formed, which is located in the part of the base material B that is not roughened, is performed. That is, in this step, the second metal coating part FB and the second seed layer part 20B of the metal coating F and the seed layer 20 are physically removed from the surface B3 of the part of the base material B that is not roughened. As a method of removing, a physical method may be used, for example, a peeling member such as an adhesive tape 90, a film, or a magnet, or a compressible gas such as compressed air (not shown) may be used. Here, as described above, the seed layer 20 contacts the base material B with a larger surface area on the surface B2 of the roughened part of the base material B than the surface B3 of the other part, so that the adhesion strength between the surface B2 of the roughened part and the seed layer 20 is higher than the adhesion strength between the surface B3 of the other part and the seed layer 20. Furthermore, the metal particles M generated by the target source collide with the surface B1 of the substrate B and bond with functional groups generated from the resin of the substrate B, so that the adhesion strength between the surface B2 of the roughened portion of the substrate B and the seed layer 20 is higher than the adhesion strength between the surface B3 of the other portion and the seed layer 20. For this reason, as shown in the figure, an adhesive tape 90 is attached to the surface F1 of the metal coating F, and then the tape 90 is pulled up, so that only the second metal coating portion FB and the second seed layer portion 20B are removed from the surface B3 of the unroughened portion of the substrate B. Meanwhile, the first metal coating portion FA and the first seed layer portion 20A remain on the surface B2 of the roughened portion of the substrate B to form the wiring layer C. As a result, as shown in FIG. 1B(g), a wiring board 80 can be obtained in which a wiring layer C of a predetermined wiring pattern is formed on the surface B1 of the substrate B.

[0043] As described above, according to the manufacturing method of this embodiment, the seed layer 20 having the flat surface 21 is formed on the surface B1 of the base material B. Therefore, the electrolyte membrane 13 can be brought into contact with this flat surface 21 to form the metal coating F on the surface 21 of the seed layer 20, thereby suppressing local deformation of the electrolyte membrane 13. Therefore, even when the formation of the metal coating F is repeated, a decrease in the durability of the electrolyte membrane 13 can be suppressed.

[0044] <Second embodiment> Next, a method for manufacturing a wiring board 80 according to a second embodiment will be described with reference to Figures 4A and 4B. The manufacturing method according to the second embodiment differs from the manufacturing method according to the first embodiment in that it includes a step of irradiating the surface B1 of the base material B with oxygen plasma 40 after the step of roughening the base material B (Figure 4A(b)) and before the step of forming the seed layer 20 (Figure 4A(c)). Below, the differences will be mainly described, and the same members and parts as those in the above-mentioned embodiment will be denoted by the same reference numerals and detailed description thereof will be omitted.

[0045] [Oxygen plasma irradiation process] As shown in FIG. 4A(b-1), in this embodiment, after the step of roughening the substrate B (FIG. 4A(b)), the surface B1 of the substrate B (i.e., the surface B2 of the roughened portion and the surface B3 of the unroughened portion of the substrate B) is irradiated with oxygen plasma 40. Specifically, in this step, the substrate B manufactured through the roughening step is attached to a conveying device (not shown), and the substrate B is conveyed to a position where the surface B1 of the substrate B faces an oxygen plasma generating source (not shown). Thereafter, in this step, the surface B2 of the roughened portion of the substrate B and the surface B3 of the unroughened portion of the substrate B are irradiated with oxygen plasma 40 generated by the oxygen plasma generating source, and a functional group containing oxygen (for example, a hydroxyl group (-OH), a carboxyl group (-COOH), an aldehyde group (-COH)) is attached to the surface B1 of the substrate B. Since the surface area of ​​surface B2 of the roughened portion of surface B1 of substrate B is larger than the surface area of ​​surface B3 of the other portion, more oxygen-containing functional groups are attached to surface B2 of the roughened portion of substrate B. As described above, the application of heat by laser 30 to the resin of substrate B in the atmosphere generates oxide functional groups of the resin, but according to this embodiment, more oxygen-containing functional groups can be attached.

[0046] Thereafter, the step of forming the seed layer 20 described above is carried out. The metal particles M generated by the target source collide with the surface B1 of the base material B, and thereby bond to functional groups attached to the surface B1 of the base material B (i.e., the surface B2 of the roughened portion of the base material B and the surface B3 of the non-roughened portion). Therefore, the adhesion strength between the surface B2 of the roughened portion of the base material B and the seed layer 20 can be made higher than the adhesion strength between the surface B3 of the other portion and the seed layer 20.

[0047] <Third embodiment> Next, a method for manufacturing a wiring board 80 according to a third embodiment will be described with reference to Figures 5A to 5C. The manufacturing method according to the third embodiment differs from the manufacturing method according to the second embodiment in that it includes a step of performing heat treatment (Figure 5B(d-1)) after the step of forming a metal film F (Figure 5B(d)), and in that the steps of forming and removing the notches are performed after the step of performing the heat treatment. Below, the differences will be mainly described, and the same members and parts as those in the above-mentioned embodiment will be denoted by the same reference numerals and detailed description thereof will be omitted.

[0048] [Heat treatment process] In this embodiment, prior to the step of performing heat treatment, a step of forming a seed layer 20 is carried out as shown in FIG. 5A(c). In this step, copper is used as a target source, and copper particles as metal particles M are deposited on the surface B1 of the base material B by sputtering to form a copper-containing seed layer 20 on the surface B1 of the base material B. Next, as shown in FIG. 5B(d), a step of forming a metal film F on the surface 21 of the seed layer 20 is carried out using a film forming apparatus 1. The steps of forming the seed layer 20 and forming the metal film F have been described in the first embodiment, and therefore, description of these steps will be omitted in this embodiment.

[0049] As shown in FIG. 5B(d-1), in this embodiment, after the step of forming the metal film F, a step of applying heat to the substrate B, the seed layer 20, and the metal film F until the resin of the substrate B is softened is performed to perform a heat treatment. Specifically, in this step, the substrate B on which the seed layer 20 and the metal film F are formed is attached to a conveying device (not shown), and the substrate B is placed inside a heating device 100 such as an electric furnace. After that, the substrate B is heated for a certain period of time, for example, in an oxygen atmosphere, at a temperature at which the resin of the substrate B is softened but not at which copper, which is the material of the seed layer 20 and the metal film F, is softened. The heat treatment is preferably performed at a temperature in the range of 120°C to 350°C in accordance with the Tg (glass transition temperature) of the resin, at which the resin applied to the substrate B is softened. In particular, when an epoxy resin is selected as the material of the substrate B, the heat treatment is preferably performed at a temperature in the range of 120°C to 200°C, at which the epoxy resin is softened. Here, when copper particles are deposited on the surface B1 of the base material B by sputtering, a gap is formed between the copper particles and the surface B1 of the base material B. According to the present embodiment, heat is applied to the base material B, the seed layer 20, and the metal coating F until the resin of the base material B is softened, and the resin softened by the heat treatment enters the gap formed between the copper particles and the surface B1 of the base material B. Since more copper particles are deposited on the surface B2 of the roughened portion of the base material B, the contact area between the copper particles and the softened resin increases. Therefore, the adhesion strength between the surface B2 of the roughened portion of the base material B and the seed layer 20 can be made higher than the adhesion strength between the surface B3 of the non-roughened portion of the base material B and the seed layer 20. In addition, when the material of the metal coating F is copper, the base material B on which the seed layer 20 and the metal coating F are formed is heat-treated for a certain period of time in a temperature range of 120°C to 200°C, thereby increasing the above-mentioned adhesion strength and alleviating the internal stress of the metal coating F generated when the metal coating F is formed.

[0050] In the present embodiment, the heat treatment is performed by placing the base material B on which the seed layer 20 and the metal coating F are formed inside a heating device 100 such as an electric furnace. However, the heat treatment may be performed using a laser irradiation device (not shown). Specifically, the base material B on which the seed layer 20 and the metal coating F are formed is placed in a laser irradiation device (not shown), and a laser is irradiated from a laser light source (not shown) provided in the laser irradiation device toward the surface F1 of the metal coating F. More specifically, the surface of the first metal coating part FA, which becomes the wiring layer C, of ​​the surface F1 of the metal coating F is irradiated with a laser. The heat applied by the laser is transmitted through the first metal coating part FA and the first seed layer part 20A to reach the surface B2 of the roughened part of the base material B. This makes it possible to soften the resin on the surface B2 of the roughened part of the base material B. When the heat treatment is performed using a laser irradiation device (not shown), it is possible to suppress the heat from being transmitted to the surface B3 of the unroughened part of the base material B, compared to when the heat treatment is performed using a heating device 100 such as an electric furnace. This makes it possible to increase the difference in adhesion strength between the seed layer 20 and surface B2 of the roughened portion of the substrate B and the adhesion strength between the seed layer 20 and surface B3 of the non-roughened portion of the substrate B. Therefore, in the subsequent removal step, the second metal coating portion FB and the second seed layer portion 20B can be easily peeled off from surface B3 of the non-roughened portion of the substrate B.

[0051] In the manufacturing method according to the present embodiment, the step of forming the incision (FIG. 5B(e)) and the step of removing the incision (FIG. 5B(f)) are performed after the step of performing the heat treatment (FIG. 5(d-1)). Therefore, the incision 24 can be formed in the metal coating film F and the seed layer 20 in a state in which the adhesion strength between the surface B2 of the roughened portion of the base material B and the seed layer 20 is made higher than the adhesion strength between the surface B3 of the non-roughened portion of the base material B and the seed layer 20 by the heat treatment. Therefore, when the incision 24 is formed, it is possible to prevent the seed layer 20 (i.e., the first seed layer portion 20A) from peeling off from the surface B2 of the roughened portion of the base material B. Since the first seed layer portion 20A is strongly adhered to the surface B2 of the roughened portion of the base material B, only the second metal coating portion FB and the second seed layer portion 20B can be removed from the base material out of the portions of the metal coating film F and the seed layer 20 in which the incision 24 is formed. EXAMPLES

[0052] The invention is illustrated by the following examples.

[0053] [Example 1] A glass epoxy substrate (ABF substrate manufactured by Ajinomoto Co., Ltd.) was prepared as a substrate for film formation, which was made by impregnating a layer of glass fiber cloth with epoxy resin. Next, the above-mentioned roughening process was carried out by irradiating the prepared substrate with a laser in the atmosphere. In this process, a LodeStone device manufactured by Esi Corporation was used to irradiate the laser under the following conditions: wavelength 515 nm, pulse width 0.8 ps, beam diameter φ10 μm, output 0.15 W, repetition frequency 100 KHz, scanning speed 500 mm / s, overlap 5 μm. As a result, a substrate was obtained with an arithmetic mean roughness Ra=0.20 μm, compared to the arithmetic mean roughness Ra=0.05 μm of the surface of the substrate before roughening.

[0054] Next, the roughened substrate was irradiated with the above-mentioned plasma. In this process, a high-speed sputtering device manufactured by Shimadzu Corporation was used, and plasma was irradiated under the conditions of Ar / H2 plasma: RF1750W×60 sec., O2 plasma: RF2100W×180 sec. Thereafter, the above-mentioned process of forming a seed layer was carried out on the substrate irradiated with the above-mentioned plasma. In this process, a high-speed sputtering device manufactured by Shimadzu Corporation was used, copper was selected as the target source, and a copper seed layer with a thickness of 600 nm was formed.

[0055] Next, a copper film was formed using the film forming apparatus 1 (FIGS. 2 and 3) according to the first embodiment. CuSO4 (1M) / H2SO4 (0.2M) was used as the metal solution, and a Cu plate was used as the anode. The film forming conditions were as follows: the temperature of the metal solution was 42°C, the solid electrolyte film was adhered to the substrate, the metal solution was pressurized to 1 kN, and the film forming speed was 1.5 μm / min, and a copper film having a thickness of 10 μm was formed.

[0056] Next, the above-mentioned step of heat treatment was performed on the substrate on which the copper seed layer and copper film were formed. In this step, an electric furnace was used to perform heat treatment under the conditions of 200°C x 60 min in an oxygen atmosphere. Next, the above-mentioned step of forming an incision was performed on the substrate on which the copper seed layer and copper film were formed after the heat treatment. In this step, a laser was used to irradiate the copper film and the copper seed layer with a laser from the surface of the copper film toward the boundary between the surface of the roughened portion and the surface of the unroughened portion on the surface of the substrate, forming an incision. Finally, the above-mentioned step of removing was performed. In this step, an adhesive tape was attached to the surface of the copper film, and the tape was peeled off to create a wiring board as a test specimen. The width of the wiring board as the test specimen was 5 mm.

[0057] [Example 2] The specimen of Example 2 differs from the specimen of Example 1 in that it was manufactured by carrying out a heat treatment process using a laser irradiation device. In this process, the surface of the first metal coating portion, which is to become the wiring layer, of the surface of the copper coating was irradiated with a laser. Specifically, the laser was irradiated for 1 minute under the following conditions: output 20 W, scanning speed 50 mm / s, wavelength 532 nm, pulse width 15 ps (picoseconds), beam diameter about φ19 μm (beam diameter after defocusing about φ5 mm), pulse frequency 200 KHz (step 0.25 μm). The other manufacturing conditions were the same as those of Example 1.

[0058] [Example 3] The specimen of Example 3 differs from the specimen of Example 1 in that the step of irradiating the roughened base material with plasma was omitted. The other manufacturing conditions were the same as those of Example 1.

[0059] [Example 4] The specimen of Example 4 differs from the specimen of Example 2 in that the step of irradiating the roughened base material with plasma was omitted. The other manufacturing conditions were the same as those of Example 2.

[0060] [Example 5] The specimen of Example 5 differs from the specimen of Example 1 in that the roughened base material was irradiated with oxygen plasma in the plasma irradiation step. The other manufacturing conditions were the same as those of Example 1.

[0061] [Comparative Example 1] The specimen of Comparative Example 1 differs from the specimen of Example 1 in that a copper seed layer was formed by electroless plating in the step of forming a seed layer on the substrate. The other manufacturing conditions were the same as those of Example 1.

[0062] [Comparative Example 2] The specimen of Comparative Example 2 differs from the specimen of Example 2 in that a copper seed layer was formed by electroless plating in the step of forming a seed layer on the substrate. The other manufacturing conditions were the same as those of Example 2.

[0063] [Comparative Example 3] The specimen of Comparative Example 3 differs from the specimen of Example 1 in that the roughened substrate was irradiated with hydrogen plasma in the plasma irradiation step. The other manufacturing conditions were the same as those of Example 1.

[0064] [Comparative Example 4] The specimen of Comparative Example 4 differs from the specimen of Example 1 in that a heat treatment step was performed after the step of forming and removing the incisions. The other manufacturing conditions were the same as those of Example 1.

[0065] [Comparative Example 5] The specimen of Comparative Example 4 differs from the specimen of Example 1 in that a heat treatment step was performed after the step of forming and removing the incisions, and that both ends of the specimen were cut by 1 mm to create a specimen with a width of 3 mm. The other manufacturing conditions were the same as those of Example 1.

[0066] [Checking the film formation status] The adhesion strength of the seed layer to the substrate of the wiring board manufactured as described above was measured by a peel test (Shimadzu Corporation EZ test). In the measurement of peel strength, the substrate of the test specimen was attached to a fixed plate, and the copper seed layer and copper film of the test specimen chucked by the device were peeled off in a 90° direction to the substrate. Specifically, the copper film was pulled while sliding the fixed plate. Here, if the adhesion strength of the copper film to the substrate of the test specimen was 0.5 kN / m or less, it was determined that the adhesion strength was insufficient, and if the adhesion strength was greater than 0.5 kN / m, it was determined that the adhesion strength was good. The above 0.5 kN / m is a value generally used as a threshold value of adhesion strength of wiring boards. The results are shown in Figs. 6 to 8.

[0067] [Results / Discussion] FIG. 6 is an explanatory diagram of an embodiment of the present invention, and shows the peel strength of each test specimen manufactured by changing the manufacturing conditions of the wiring board. FIG. 6 shows the manufacturing conditions of Examples 1 to 4 and Comparative Examples 1 to 2, and the peel strength of each test specimen. As is clear from FIG. 6, all of the test specimens according to Examples 1 to 4 obtained peel strengths exceeding the threshold value of 0.5 kN / m, which was a good result. For the test specimens of Examples 3 and 4, it is considered that the copper particles generated by the target source collided with the surface of the substrate and bonded with the functional groups generated from the resin of the substrate, thereby increasing the adhesive strength between the surface of the roughened portion of the substrate and the seed layer. For the test specimens of Examples 1 and 2, it is considered that the functional groups containing oxygen were attached more to the surface of the roughened portion of the substrate, and the adhesive strength between the surface of the roughened portion of the substrate and the seed layer was further increased. For the test specimens of Comparative Examples 1 and 2, it is considered that the copper seed layer was formed by electroless plating, and therefore the copper ions penetrated into the resin of the substrate when the seed layer was formed, resulting in a very high peel strength. In this case, although the peel strength between the substrate and the seed layer exceeds the threshold value (0.5 kN / m), copper ions remain inside the resin, undesirably reducing the insulating properties of the substrate.

[0068] FIG. 7 is for explaining an embodiment of the present invention, and shows the peel strength ratio of each test specimen manufactured by changing the type of plasma irradiated to the substrate as the manufacturing condition of the wiring board. As is clear from FIG. 7, when the roughened substrate was irradiated with H2+O2 plasma (Example 1) and O2 plasma (Example 5), a higher peel strength was obtained than when the substrate was not irradiated with plasma. On the other hand, when the roughened substrate was irradiated with H2 plasma (Comparative Example 3), a lower peel strength was obtained than when the substrate was not irradiated with plasma. With respect to the test specimens of Examples 1 and 5, it is considered that more oxygen-containing functional groups were attached to the surface of the roughened portion of the substrate, and the adhesive strength between the surface of the roughened portion of the substrate and the seed layer was further increased. On the other hand, with respect to the test specimen of Comparative Example 3, it is considered that by irradiating the surface of the roughened substrate with H2 plasma, the oxygen atoms of the functional groups generated from the resin of the substrate reacted, and the functional groups attached to the surface of the substrate were removed from the surface of the substrate.

[0069] FIG. 8 is an explanatory diagram of an embodiment of the present invention, in which (a) shows a planar photograph of a test specimen, and (b) shows the peel strength of each test specimen manufactured by switching the order of the heat treatment step and the incision forming step. As shown in FIG. 8(b), the test specimen (5 mm width) according to Example 1 obtained a peel strength exceeding the threshold value of 0.5 kN / m, which was a good result. On the other hand, the test specimen (5 mm width) according to Comparative Example 4 has a peel strength below the threshold value of 0.5 kN / m. In contrast, the test specimen (3 mm width) according to Comparative Example 5 obtained a peel strength equivalent to that of the test specimen of Example 1. From Comparative Examples 4 and 5, it is considered that the test specimens produced by carrying out the heat treatment step after the incision forming step and the removal step have a lower peel strength at both ends (1 mm width) than at the center (3 mm width). This is believed to be because the cuts are formed in the copper film and the copper seed layer before the heat treatment (i.e., before the adhesive strength between the seed layer and the resin is increased), and both ends (1 mm wide) of the copper seed layer float (peel off) from the substrate when the cuts are formed. In contrast, in Example 1, the cuts are formed in the copper film and the seed layer in a state in which the adhesive strength between the surface of the roughened portion of the substrate and the seed layer is increased by the heat treatment, and therefore it is believed that the seed layer does not peel off from the surface of the roughened portion of the substrate when the cuts are formed. [Explanation of symbols]

[0070] 11: anode, 13: solid electrolyte film, 20: seed layer, 24: notch, 30: laser, 40: oxygen plasma, 80: wiring board, B: base material, B1: surface, B2: surface of portion where wiring layer is provided, B4: boundary, C: wiring layer, M: metal particle, F: metal film, F1: surface

Claims

1. A method for manufacturing a wiring board including a base material and a wiring layer having a predetermined wiring pattern provided on a surface of the base material, the method comprising the steps of: preparing an insulating base material containing a resin as the base material; roughening a surface of the base material at a portion on which the wiring layer is to be provided; forming a metal-containing seed layer on a surface of the substrate by depositing metal particles produced by a target source onto the surface of the substrate; a step of disposing a solid electrolyte membrane between an anode and the seed layer which is a cathode, bringing the solid electrolyte membrane into contact with the seed layer, and applying a voltage between the anode and the seed layer to reduce metal ions contained in the solid electrolyte membrane, thereby forming a metal coating on the seed layer; forming a cut in the metal coating and the seed layer from a surface of the metal coating toward a boundary between a roughened portion and a non-roughened portion on a surface of the substrate; and physically removing, from the substrate, portions of the metal film and the seed layer in which the notches are formed, the portions being located in non-roughened portions of the substrate.

2. 2. The method for manufacturing a wiring board according to claim 1, wherein in the roughening step, the surface of the portion on which the wiring layer is to be provided is roughened by a laser.

3. 3. The method for manufacturing a wiring board according to claim 2, further comprising the step of irradiating the surface of the base with oxygen plasma after the step of roughening and before the step of forming the seed layer.

4. In the step of forming the seed layer, copper is used as the target source, and copper particles as the metal particles are deposited on the surface of the base material by sputtering to form a copper-containing seed layer on the surface of the base material; 4. The method for manufacturing a wiring board according to claim 3, further comprising, after the step of forming the metal film, a step of performing a heat treatment by applying heat to the substrate, the seed layer, and the metal film until the resin of the substrate softens.

5. 5. The method for manufacturing a wiring board according to claim 4, wherein the step of forming the cut and the step of removing are performed after the step of performing the heat treatment.

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