JP7616018B2 - Method for manufacturing a wiring board - Google Patents

Description

The present invention relates to a method for manufacturing a wiring board, and in particular to a method for manufacturing a wiring board that includes a substrate and a wiring layer having a predetermined wiring pattern provided on the surface of the substrate, the wiring layer having a seed layer of a predetermined pattern corresponding to the wiring pattern provided on the surface of the substrate, and a metal layer provided on the seed layer.

A method has been used in which a solid electrolyte membrane is placed between an anode and a seed layer or the like provided on the surface of a substrate or base material facing the anode, in such a state that the solid electrolyte membrane is in contact with the substrate or seed layer, and a liquid containing metal ions from a metal solution is allowed to seep out toward the outer surface of the solid electrolyte membrane while a voltage is applied between the anode and the substrate or seed layer or the like corresponding to the cathode, forming a metal layer in which the metal ions are reduced on the substrate or seed layer.

For example, Patent Document 1 discloses a film formation method in which a metal film (metal layer) is formed on a substrate by using a solution storage unit in which a storage space containing a metal solution containing metal ions is provided between an anode and a solid electrolyte membrane placed above the anode, placing a substrate above the anode via a solid electrolyte membrane, and applying a voltage between the anode and the substrate corresponding to the cathode. In this film formation method, the solid electrolyte membrane is placed above the anode, thereby preventing the metal solution from flowing downward from the solution storage unit when the solid electrolyte membrane is replaced, as in the method in which the solid electrolyte membrane is placed below the anode. When a voltage is applied, the liquid containing metal ions in the metal solution in the storage space seeps out onto the upper surface side of the solid electrolyte membrane, and the metal ions are reduced and precipitated on the surface of the substrate. This forms a metal film on the surface of the substrate. In particular, the metal solution in the storage space is pressurized to form a convex shape of the solid electrolyte membrane, and the surface of the substrate is pressed against the solid electrolyte membrane from above before applying a voltage, thereby forming a uniform metal film.

JP 2018-150599 A

On the other hand, in a method for manufacturing a wiring board comprising a substrate and a wiring layer of a predetermined wiring pattern provided on the surface of the substrate, the wiring layer having a seed layer of a predetermined pattern corresponding to the wiring pattern provided on the surface of the substrate, and a metal layer provided on the seed layer, when a metal solution containing metal ions and a solid electrolyte film are used to form a metal layer in which metal ions are reduced on the seed layer, it is desirable to selectively form the metal layer in a direction perpendicular to the surface of the seed layer that is approximately parallel to the surface of the substrate so that adjacent wires in the wiring layer of the wiring pattern do not become conductive to each other and cause a short circuit. However, in this case, a problem occurs in which the metal layer is formed isotropically in the line width direction of the side surface of the seed layer. Furthermore, such a problem becomes more pronounced when the metal solution in the storage space is pressurized as described above.

The present invention was made in consideration of these points, and its purpose is to provide a method for manufacturing a wiring board that can suppress electrical conduction between adjacent wiring patterns in a wiring layer.

In order to solve the above problems, the present invention provides a method for producing a wiring board, comprising: an insulating base material; and a wiring layer having a predetermined wiring pattern provided on a surface of the base material, the wiring layer having a seed layer of a predetermined pattern corresponding to the wiring pattern provided on the surface of the base material; and a metal layer provided on the surface of the seed layer, the method comprising the steps of: preparing a base material with a seed layer, the base material and the seed layer provided on the surface of the base material; and disposing the seed layer above the solid electrolyte membrane in a solution containing section provided between an anode and a solid electrolyte membrane disposed thereover and having a containing space for containing a metal solution containing metal ions therein, the seed layer being disposed so that a surface of the seed layer faces the anode and is in contact with an upper surface of the solid electrolyte membrane. and a forming step of applying a voltage between the anode and the seed layer corresponding to the cathode in a state in which the seed layer-bearing substrate is disposed by the disposing step, thereby causing a liquid containing the metal ions of the metal solution to seep out from the accommodation space to an upper surface of the solid electrolyte membrane and reducing the metal ions in the liquid on the surface of the seed layer to form a film, thereby forming the metal layer, wherein in the forming step, a current density of a current flowing between the anode and the seed layer and a film formation time for applying the voltage are set to a current density and a film formation time required to form the metal layer to a target thickness, and in the forming step, an amount of the liquid seeping out is set to 0.0021 g/ ^cm2 or less per 1 μm of the target thickness of the metal layer.

Furthermore, the method for manufacturing a wiring board of the present invention is a method for manufacturing a wiring board comprising an insulating base material and a wiring layer having a predetermined wiring pattern provided on the surface of the base material, the wiring layer having a seed layer of a predetermined pattern corresponding to the wiring pattern provided on the surface of the base material, and a metal layer provided on the surface of the seed layer, the method comprising the steps of: preparing a base material with a seed layer comprising the base material and the seed layer provided on the surface of the base material; and preparing a substrate with a seed layer, the seed layer being provided on the surface of the base material; and preparing a substrate with a seed layer, the seed layer being provided on the surface of the base material, the seed layer being provided on the surface of the base material, the substrate being provided with a seed layer ... The method includes a step of arranging the substrate with the seed layer so that the anode and the seed layer corresponding to the cathode are in contact with each other, and a step of forming the metal layer by applying a voltage between the anode and the seed layer corresponding to the cathode while the substrate with the seed layer is arranged by the step of arranging, thereby causing a liquid containing the metal ions of the metal solution to seep out from the storage space to the upper surface side of the solid electrolyte membrane, and reducing the metal ions in the liquid on the surface of the seed layer to form a film, and forming the metal layer, wherein the metal layer is formed in the step of forming the metal layer such that the average value of the ratio of the width Ws of the metal layer in the line width direction of the side surface of the seed layer to the thickness Tf of the metal layer in the direction perpendicular to the surface of the seed layer is 0.70 or less.

The present invention makes it possible to suppress electrical conduction between adjacent wiring patterns in a wiring layer.

4 is a flowchart of a method for manufacturing a wiring board according to the first embodiment. 1A to 1C are schematic diagrams showing the steps of a method for manufacturing a wiring board according to a first embodiment, in which (a) to (c) are schematic diagrams showing the cross section, front surface, and back surface of a substrate with a seed layer in a preparation process, respectively. 5A to 5C are schematic process diagrams illustrating the method for manufacturing the wiring board according to the first embodiment, and are schematic cross-sectional views illustrating a liquid supplying step. 5A to 5C are schematic process diagrams illustrating the method for manufacturing the wiring board according to the first embodiment, and are schematic cross-sectional views illustrating a placement step. 5A to 5C are schematic process diagrams illustrating a method for manufacturing a wiring board according to the first embodiment, and are schematic cross-sectional views illustrating a formation process. 2A is a schematic enlarged cross-sectional view of the wiring board shown in FIG. 2D, and FIG. 2B is a schematic top view of the wiring board shown in FIG. 2A. This is a table showing cross-sectional photographs of five wires (wire 1 to wire 5) selected from the line-and-space wiring pattern of the wiring layer of the wiring board manufactured in each of Examples 1 to 3, together with the lateral thickening amount of the metal layer (left) and the lateral thickening amount of the metal layer (right) calculated for each wire. 1 is a table showing a cross-sectional photograph of one wire selected from the line-and-space wiring patterns of the wiring boards manufactured in each of Example 4 and Comparative Examples 1 to 11. 1 is a graph showing the relationship between the amount of liquid seeping out per 1 μm of target thickness of the metal layer and the amount of lateral expansion of the metal layer, calculated for Example 4 and Comparative Examples 1 to 11. 1 is a graph showing the average weight of pure water collected by a micropipette measured using a weighing scale, and the average weight of pure water collected by a micropipette measured using a Kimwipe. 1 is a graph showing the relationship between the surface area of the seed layer and the amount of liquid exuded. 11 is a graph showing the relationship between the pressure applied to the metal solution in the storage space and the amount of liquid seeping out.

Below, the method for manufacturing a wiring board according to an embodiment of the present invention will be described broadly in terms of a first aspect and a second aspect. In the embodiment, unless otherwise specified, "upper" refers to the direction opposite to the vertical direction, and "lower" refers to the same direction as the vertical direction. Furthermore, "upper surface" refers to the surface facing the opposite direction to the vertical direction, and "lower surface" refers to the surface facing the same direction as the vertical direction. Furthermore, "line width direction" refers to the line width direction of the wiring of the wiring pattern, which is parallel to the surface of the substrate and perpendicular to the extension direction of the wiring.

A. First Aspect A method for manufacturing a wiring board according to the first aspect will be outlined by first illustrating a first embodiment. FIG. 1 is a flow chart of the method for manufacturing a wiring board according to the first embodiment. FIGS. 2A to 2D are schematic process diagrams showing the method for manufacturing a wiring board according to the first embodiment. FIGS. 2A(a) to 2A(c) are schematic diagrams showing the cross section, front surface, and back surface of a substrate with a seed layer in a preparation step. FIGS. 2B to 2D are schematic cross-sectional views showing the liquid supply step, the arrangement step, and the formation step, respectively. FIG. 3(a) is a schematic cross-sectional view of an enlarged view of the wiring board shown in FIG. 2D, and FIG. 3(b) is a schematic top view of the wiring board shown in FIG. 3(a).

In the method for manufacturing a wiring board according to the first embodiment, first, as shown in FIG. 1 and FIG. 2A(a)-(c), a seed layer-attached substrate 1 is prepared, which includes an insulating substrate 2, a seed layer 4 provided on the surface 2f of the substrate 2, a conductor layer 6 provided on the back surface 2r of the substrate 2, and via conductors 8 filled in via holes 2h that penetrate from the location of the seed layer 4 on the surface 2f of the substrate 2 to the back surface 2r (preparation step S1). The seed layer 4 has a predetermined line and space according to a predetermined fine line and space wiring pattern, and has a surface 4f that is parallel to the surface 2f of the substrate 2 and a side surface 4s that is perpendicular to the surface 2f of the substrate 2. The conductor layer 6 is provided over the entire back surface 2r of the substrate 2. The via conductors 8 electrically connect the seed layer 4 and the conductor layer 6.

Next, as shown in FIG. 1 and FIG. 2B, a film forming apparatus 100 for forming a metal layer by solid electrolytic deposition (SED) is prepared, which includes a housing 15 having an opening 15a at the top and an anode 13 at the bottom of the accommodation space G, and a solution accommodation section 20 including a solid electrolyte membrane 17 arranged at the top of the housing 15 so as to cover and seal the opening 15a of the housing 15. Then, in the film forming apparatus 100, a metal solution L containing metal ions is supplied to the accommodation space G of the solution accommodation section 20 (liquid supply process S2). In the film forming apparatus 100, a solid electrolyte membrane 17 having a predetermined metal ion permeability is used as the solid electrolyte membrane 17.

The housing 15 is provided with a supply port 15f and a discharge port 15d for the metal solution L. The storage space G of the solution storage section 20 is sealed by the housing 15 and the solid electrolyte membrane 17 except for the supply port 15f and the discharge port 15d, and stores the metal solution L together with the anode 13. The supply port 15f and the discharge port 15d are connected to the tank 101 via piping. In the film forming apparatus 100, a pump 102 and a pressure adjustment valve 103 are provided upstream of the supply port 15f and downstream of the discharge port 15d, respectively. By using the pump 102, the metal solution L sent out from the tank 101 can be supplied to the storage space G through the supply port 15f and returned to the tank 101 by discharging it from the storage space G through the discharge port 15d. By using the pump 102 and the pressure adjustment valve 103, the liquid pressure of the metal solution L in the storage space G can be adjusted. In the liquid supply step S2, with the storage space G of the housing 15 sealed with the solid electrolyte membrane 17, the pump 102 is used to supply the metal solution L from the tank 101 through the supply port 15f to the storage space G while discharging the air in the storage space G to the outside through the exhaust port 15d, thereby filling the storage space G with the metal solution L. Then, by using the pump 102 and the pressure adjustment valve 103, the liquid pressure of the metal solution L in the storage space G at the position on the solid electrolyte membrane 17 side of the metal solution L in the storage space G is adjusted to atmospheric pressure. This keeps the upper surface 17t of the solid electrolyte membrane 17 flat.

Next, as shown in FIG. 1 and FIG. 2C, the seed layer-attached substrate 1 is arranged above the solid electrolyte membrane 17 in the solution accommodating section 20, which has an accommodating space G between the anode 13 and the solid electrolyte membrane 17 arranged above it, so that the surface 4f of the seed layer 4 faces the anode 13 and contacts the upper surface 17t of the solid electrolyte membrane 17 (arrangement step S3). At this time, as shown in FIG. 2C, the seed layer-attached substrate 1 is held by a holding jig 200 attached to a lifting device (not shown), or, although not shown, the seed layer-attached substrate 1 is not held by a jig and is simply placed on the upper surface 17t of the solid electrolyte membrane 17, thereby adjusting the contact pressure at which the surface 4f of the seed layer 4 presses against the contact surface of the upper surface 17t of the solid electrolyte membrane 17 to be equal to or less than the pressure due to the weight of the seed layer-attached substrate 1 alone.

Next, as shown in FIG. 1 and FIG. 2D, in a state where the substrate 1 with the seed layer is arranged by the arrangement step S3, the anode 13 and the conductor layer 6 of the substrate 1 with the seed layer are connected to the positive and negative electrodes of the power supply unit 104, respectively, to apply a voltage between the anode 13 and the seed layer 4 corresponding to the cathode. In this case, the metal ions move as a liquid from the anode 13 side toward the seed layer 4 (cathode) side, accompanied by other components of the metal solution. As a result, the liquid containing the metal ions and other components of the metal solution seeps out from the accommodation space G to the upper surface 17t side of the solid electrolyte membrane 17, and the metal ions in the liquid are reduced on the surface 4f of the seed layer 4 to form a film. In this way, the metal layer 5 is formed on the surface 4f of the seed layer 4 by solid-phase electrodeposition (formation step S4).

In the formation step S4, the current density of the current flowing between the anode 13 and the seed layer 4 and the film formation time for applying the voltage are set to the current density and film formation time required for forming the metal layer 5 to a uniform target thickness over the entire surface 4f of the seed layer 4 by depositing an amount of metal ions corresponding to the amount of electricity determined by the product of the current density and the film formation time only in a direction perpendicular to the surface on the surface 4f of the seed layer 4 (the current density and film formation time required for forming the metal layer 5 to the target thickness). As described above, in the film formation device 100, a solid electrolyte membrane 17 having a predetermined metal ion permeability is used. Furthermore, in the liquid supply step S2, the liquid pressure at the position of the metal solution L on the solid electrolyte membrane 17 side of the accommodation space G is adjusted to atmospheric pressure, and in the arrangement step S3, the contact pressure at which the surface 4f of the seed layer 4 presses the contact surface of the upper surface 17t of the solid electrolyte membrane 17 is adjusted to be equal to or less than the pressure due to the weight of the seed layer-attached substrate 1 alone. As a result, in the forming step S4, the amount of liquid containing metal ions seeping out from the accommodation space G onto the upper surface 17t side of the solid electrolyte membrane 17 is set to 0.0021 g/ ^cm2 or less per 1 μm of the target thickness of the metal layer 5.

As a result of the above, as shown in FIG. 2D and FIGS. 3(a) and (b), a wiring board 10 is manufactured, which includes an insulating base material 2, a wiring layer 9 having a wiring pattern of a predetermined fine line and space provided on the surface 2f of the base material 2, the wiring layer 9 having a seed layer 4 of a predetermined line and space corresponding to the wiring pattern provided on the surface 2f of the base material 2, and a metal layer 5 provided on the surface 4f of the seed layer 4.

In the method for manufacturing a wiring board according to the first embodiment, in the formation step S4, the amount of liquid containing metal ions seeping out from the accommodation space G to the upper surface 17t side of the solid electrolyte film 17 is set to 0.0021 g/ ^cm2 or less per 1 μm of the target thickness of the metal layer 5. In this way, the amount of liquid containing metal ions seeping out is suppressed, so that the liquid containing metal ions can be suppressed from flowing around from the surface 4f of the seed layer 4 to the side surface 4s. Therefore, the amount of metal ions in the liquid that are supplied to the side surface 4s of the seed layer 4 and reduced can be reduced. Therefore, the deposition of metal ions in the line width direction of the side surface 4s of the seed layer 4 is suppressed, and the metal ions can be selectively deposited in a direction perpendicular to the surface 4f of the seed layer 4. As a result, as shown in Figures 3(a) and (b), the metal layer 5 can be formed so that the average ratio (lateral thickening amount of the metal layer 5) of the width Ws of the metal layer 5 in the line width direction of the side 4s of the seed layer 4 to the thickness Tf of the metal layer 5 in the direction perpendicular to the surface 4f of the seed layer 4 is 0.70 or less.

Therefore, according to the method for manufacturing a wiring board according to the first aspect, for example, as in the first embodiment, it is possible to suppress the formation of a metal layer in the line width direction of the side surface of the seed layer, and to selectively form a metal layer on the surface of the seed layer in a direction perpendicular to the surface. This makes it possible to suppress electrical conduction between adjacent wirings in the wiring pattern of the wiring layer.

Next, we will explain in detail each component of the wiring board manufacturing method according to the first aspect.

1. Preparation Step In the preparation step, a base material with a seed layer is prepared, the base material including an insulating base material and the seed layer provided on a surface of the base material.

The substrate with a seed layer is not particularly limited as long as it comprises an insulating substrate and a seed layer, but may further comprise a conductor layer provided on the back surface of the substrate, and a via conductor that is filled in a via hole that penetrates from the seed layer on the front surface of the substrate to the back surface of the substrate and electrically connects the seed layer and the conductor layer, as in the substrate with a seed layer according to the first embodiment, and the surface of the substrate may be exposed in the space of the seed layer. By connecting the conductor layer to the negative electrode of the power supply unit, a voltage can be applied between the seed layer corresponding to the anode and the cathode. In addition, the substrate with a seed layer may further comprise a conductive underlayer provided on the front surface of the substrate, the seed layer is provided on the surface of the underlayer, and the surface of the underlayer is exposed in the space of the seed layer. By connecting the underlayer to the negative electrode of the power supply unit, a voltage can be applied between the seed layer corresponding to the anode and the cathode.

The substrate is not particularly limited as long as it is insulating, but for example, a substrate made of glass epoxy resin, a substrate in the form of a flexible film such as polyimide resin, a substrate made of glass, etc. are preferred, and among these, glass epoxy resin is particularly preferred. In addition, when a substrate made of resin is used as the substrate, for example, a thermoplastic resin such as 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, polymer alloy resin containing elastomer and PP, modified PPO resin, PTFE resin, ETFE resin, etc., or a thermosetting resin such as phenol resin, melamine resin, amino resin, unsaturated polyester resin, polyurethane, diallyl phthalate, silicone resin, alkyd resin, etc., a resin obtained by adding a cyanate resin to an epoxy resin, or a liquid crystal polymer, etc. can be used.

The seed layer has a predetermined pattern according to the wiring pattern of the wiring layer, and has a surface that is approximately parallel to the surface of the substrate, and a side surface that connects the surface of the seed layer and the surface of the substrate. The pattern of the seed layer is not particularly limited as long as it is a predetermined pattern according to the wiring pattern of the wiring layer, and examples thereof include lines and spaces. The line width (line width)/space width (line interval width) of the line and space of the seed layer is not particularly limited, but is preferably, for example, 100 μm or more and 500 μm or less/100 μm or more and 500 μm or less. When the line width/space width is a fine width in such a range, the effect of suppressing the conduction between adjacent wirings of the wiring layer wiring pattern becomes significant. The line width/space width is the line width/line interval of the seed layer when the wiring substrate is viewed in a plan view. The line width and space width of the seed layer may be formed to the same dimension or different dimensions.

The seed layer is not particularly limited as long as it is conductive and can be formed by reducing metal ions on the surface by applying a voltage between the anode and the seed layer, but examples include those containing metal. As the seed layer, a layer on which a natural oxide film does not form on the surface or a layer that does not contain oxides in the entire layer is preferable. As the material for the seed layer, for example, silver, copper, gold, palladium, platinum, etc. are preferable, and among them, silver, copper, etc. can be used. As the material for the seed layer, for example, one or more types selected from the group consisting of silver, copper, gold, palladium, and platinum can be used.

The thickness of the seed layer is not particularly limited, but is preferably, for example, 10 μm or more and 50 μm or less. This is because by making the seed layer thicker than 10 μm, it is possible to effectively prevent a metal layer from being formed in the line width direction of the side surface of the seed layer. In addition, by making the seed layer thicker than 50 μm, it is possible to reduce the material costs and processing costs required for forming the seed layer, thereby obtaining cost benefits.

The seed layer is formed, for example, by a method of disposing and solidifying an ink containing metal particles on the surface of an insulating substrate or a base layer. The method of disposing the ink on the surface of the insulating substrate or base layer is not particularly limited, and various printing methods such as screen printing, inkjet printing, and transfer printing can be used. The method of solidifying the ink disposed on the surface of the insulating substrate or base layer is not particularly limited, and examples thereof include a method of sintering the metal particles contained in the ink, and a method of solidifying the ink by heating or drying. When the seed layer is formed by sintering, sintering is performed at a temperature below the heat resistance temperature of the substrate (for example, about 250°C or less when a substrate made of glass epoxy resin is used). The seed layer can also be formed without using ink, for example, by a deposition method or a sputtering method.

The underlayer is not particularly limited as long as it has conductivity, but for example, a layer containing an oxide on the surface is preferable. Examples of the layer containing an oxide on the surface include a layer with a natural oxide film formed on the surface and a layer containing an oxide throughout the layer, but a layer with a natural oxide film formed on the surface is preferable. The natural oxide film refers to an oxide film that is naturally formed on the surface of a material when the material is left in the air. When the underlayer is a layer on which a natural oxide film is formed on the surface, it is preferable to form the underlayer, for example, from silicide. The term "silicide" refers to a compound composed of metal and silicon. As the silicide, it is preferable to use a transition metal silicide (a silicide composed of a transition metal and silicon). The material of the underlayer is not particularly limited, but for example, transition metal silicides such as ZrSi ₂ and WSi ₂ , metal oxides such as ITO (indium tin oxide), Ti, alloys containing Ti, alloys containing Cr such as stainless steel, conductive resins, etc. are preferable, and among them, transition metal silicides such as ZrSi ₂ and WSi ₂ are preferable. The thickness of the underlayer is not particularly limited, but is preferably, for example, 20 nm to 300 nm. The underlayer is formed by a sputtering method, a deposition method such as a PVD (physical vapor deposition) method or a CVD (chemical vapor deposition) method, a plating method, or the like.

2. Arrangement Step In the arrangement step, the base material with the seed layer is arranged above the solid electrolyte membrane in a solution accommodation section having an accommodation space for accommodating a metal solution containing metal ions between an anode and a solid electrolyte membrane arranged thereover, such that a surface of the seed layer faces the anode and is in contact with an upper surface of the solid electrolyte membrane.

The solution storage section is not particularly limited as long as it has a storage space between the anode and the solid electrolyte membrane, but examples include the solution storage section according to the first embodiment, which is composed of a housing with an opening at the top and an anode at the bottom, and a solid electrolyte membrane placed on the top of the housing so as to cover and seal the opening of the housing.

The metal solution in the storage space is a solution containing the metal contained in the metal layer described below in the form of metal ions. The metal of the metal ions is not particularly limited, but examples thereof include copper, nickel, silver, and gold. The metal solution is not particularly limited as long as the metal of the metal ions is dissolved in an acid such as nitric acid, phosphoric acid, succinic acid, nickel sulfate, and pyrophosphoric acid, but an example is an aqueous solution of copper sulfate.

The liquid pressure of the metal solution in the accommodation space needs to be adjusted to a liquid pressure that allows the amount of liquid seepage to be 0.0021 g/cm ² or less per 1 μm of the target thickness of the metal layer in the formation process. The liquid pressure of the metal solution in the accommodation space is not particularly limited as long as it is such a liquid pressure, but for example, a liquid pressure that makes the liquid pressure at the upper end of the solid electrolyte in the metal solution in the accommodation space as close to atmospheric pressure as possible is preferable, and among them, a liquid pressure that makes the liquid pressure at the upper end of the solid electrolyte in the metal solution in the accommodation space become atmospheric pressure is preferable. This is because the driving force for exuding the liquid is reduced by the liquid pressure of the metal solution, so that the amount of liquid seepage in the formation process can be easily set to the above range. Note that when adjusting the liquid pressure of the metal solution in the accommodation space, it is necessary to take into consideration that the metal solution in the accommodation space is pressurized through the solid electrolyte membrane by the contact pressure of the surface of the seed layer pressing the contact surface of the upper surface of the solid electrolyte membrane, and the liquid pressure of the metal solution in the accommodation space changes.

The concentration of metal ions in the metal solution in the storage space must be adjusted to a concentration that allows the formation of a metal layer due to the current density of the current flowing between the anode and the seed layer in the formation process. If the concentration of metal ions in the metal solution is too low relative to the current density, components other than metal ions are reduced on the surface of the seed layer in the formation process, making it impossible to form a metal layer. From this perspective, when the metal solution is a copper (II) sulfate aqueous solution, the concentration of copper ions (Cu ²⁺ ) (metal ions in the metal solution) in the copper (II) sulfate aqueous solution is preferably, for example, 0.15 mol/L or more.

The solid electrolyte membrane is not particularly limited as long as it can be impregnated with a liquid containing metal ions by contacting it with a metal solution, and can be made to seep out to the upper surface by moving the liquid containing metal ions through the internal permeation channels by applying a voltage, and can precipitate metal derived from the metal ions by reducing the metal ions on the surface of the seed layer. The thickness of the solid electrolyte membrane is, for example, about 5 μm to about 200 μm. Examples of materials for the solid electrolyte membrane include fluororesins such as Nafion (registered trademark) manufactured by DuPont, hydrocarbon resins, polyamic acid resins, and resins with cation exchange functions such as Selemion (CMV, CMD, CMF series) manufactured by Asahi Glass Co., Ltd. In addition, it is necessary to use a solid electrolyte membrane having a predetermined metal ion permeability that can adjust the amount of liquid seeping out per 1 μm of the target thickness of the metal layer to a predetermined value or less in the formation process. The metal ion permeability of the solid electrolyte membrane is determined by the diameter of the permeation channels of the solid electrolyte membrane.

The contact pressure at which the surface of the seed layer presses the contact surface of the upper surface of the solid electrolyte membrane needs to be adjusted to a pressure that allows the amount of liquid seepage to be 0.0021 g/ ^cm2 or less per 1 μm of the target thickness of the metal layer in the formation process. The contact pressure is not particularly limited as long as it is such a pressure, but it is preferable that it is as small as possible, for example, it is preferable that it is less than the pressure due to only the weight of the base material with the seed layer, and in particular 0 (zero). This is because the metal solution in the storage space is not unnecessarily pressurized through the solid electrolyte membrane by the contact pressure, making it easy to keep the amount of liquid seepage within the above range in the formation process.

3. Forming step In the forming step, in a state where the base material with the seed layer is arranged by the arranging step, a voltage is applied between the anode and the seed layer corresponding to the cathode, so that the liquid containing the metal ions of the metal solution is exuded from the accommodation space to the upper surface side of the solid electrolyte membrane, and the metal ions in the liquid are reduced on the surface of the seed layer to form a film, thereby forming the metal layer. Furthermore, the current density of the current flowing between the anode and the seed layer and the film formation time for applying the voltage are set to the current density and film formation time required to form the metal layer to a target thickness. The amount of exudation of the liquid (the amount of the liquid exuding from the accommodation space to the upper surface side of the solid electrolyte membrane) is set to 0.0021 g/ ^cm2 or less per 1 μm of the target thickness of the metal layer.

Here, "the current density and deposition time required to form a metal layer to a target thickness" refers to the current density and deposition time required to deposit an amount of metal ions corresponding to the amount of electricity determined by the product of the current density and deposition time on the surface of the seed layer only in the direction perpendicular to the surface of the seed layer, thereby forming a metal layer with a uniform target thickness over the entire surface of the seed layer. And, "the amount of liquid exuded per 1 μm of the target thickness of the metal layer" refers to the amount obtained by dividing the amount of liquid exuded per 1 ^cm2 of the surface area of the seed layer in the formation process by the target thickness [μm] of the metal layer, when the current density and deposition time in the formation process are the current density and deposition time required to form a metal layer to the target thickness.

The amount of liquid seepage per 1 μm of the target thickness of the metal layer is not particularly limited as long as it is 0.0021 g/cm2 ^{or less} as described above, but 0.0018 g/cm2 ^or less is preferable, and 0.00026 g/cm2 or ^less is particularly preferable. This is because the effect of selectively forming a metal layer on the surface of the seed layer is improved.

There are no particular limitations on the method for adjusting the amount of liquid seepage per 1 μm of the target thickness of the metal layer to below these predetermined values. For example, a method may be used in which a solid electrolyte membrane having a predetermined metal ion permeability is appropriately selected and used, and the liquid pressure at the upper end of the solid electrolyte in the metal solution in the storage space is adjusted to a predetermined value or less to adjust the amount of liquid seepage per 1 μm of the target thickness of the metal layer.

As the formation process, similar to the formation process according to the second embodiment described below, a process of forming the metal layer such that the average lateral expansion amount of the metal layer is 0.70 or less is preferable, and the smaller the lateral expansion amount of the metal layer, the more preferable. As the formation process, a process of forming a metal layer such that the average lateral expansion amount of the metal layer is 0.30 or less is more preferable, and among these, a process of forming a metal layer such that the average lateral expansion amount of the metal layer is 0.20 or less is more preferable, and a process of forming a metal layer such that the average lateral expansion amount of the metal layer is 0 (zero) is particularly preferable. This is because the effect of suppressing conduction between adjacent wirings in the wiring pattern of the wiring layer is remarkable.

The current density of the current flowing between the anode and the seed layer by applying a voltage between the anode and the seed layer is not particularly limited. For example, when the metal solution is an aqueous solution of copper (II) sulfate, the current density is preferably 5 mA/cm2 or ^more and 400 mA/cm2 or ^less .

4. Manufacturing Method of Wiring Board The manufacturing method of a wiring board according to the first aspect is a method for manufacturing a wiring board including an insulating base material and a wiring layer having a predetermined wiring pattern provided on a surface of the base material, the wiring layer having a seed layer of a predetermined pattern corresponding to the wiring pattern provided on the surface of the base material, and a metal layer provided on the surface of the seed layer, the method including the preparing step, the arranging step, and the forming step.

In the formation process, a metal layer is formed on the surface of the seed layer to form a wiring layer of a predetermined wiring pattern having a seed layer of a predetermined pattern provided on the surface of the substrate and a metal layer provided on the surface of the seed layer.

The wiring pattern of the wiring layer is not particularly limited, but may be, for example, a line and space. The line width (line width)/space width (line interval width) of the line and space of the wiring layer is not particularly limited, but is usually determined by the line width/space width of the seed layer and the line width (line width) of the metal layer.

B. Second Aspect A method for manufacturing a wiring board according to a second aspect is a method for manufacturing a wiring board comprising an insulating base material and a wiring layer having a predetermined wiring pattern provided on the surface of the base material, the wiring layer having a seed layer having a predetermined pattern corresponding to the wiring pattern provided on the surface of the base material, and a metal layer provided on the surface of the seed layer, the method comprising a preparation step, a disposition step, and a formation step. The preparation step and the disposition step are the same as the preparation step and the disposition step according to the first aspect. In the formation step, in a state in which the base material with the seed layer is disposed by the disposition step, a voltage is applied between the anode and the seed layer corresponding to the cathode, so that a liquid containing the metal ions of the metal solution seeps out from the accommodation space to the upper surface side of the solid electrolyte membrane, and the metal ions in the liquid are reduced on the surface of the seed layer to form a film, thereby forming the metal layer. The metal layer is formed so that the average value of the ratio of the width Ws of the metal layer in the line width direction of the side surface of the seed layer to the thickness Tf of the metal layer in the direction perpendicular to the surface of the seed layer (sometimes abbreviated as "lateral thickening of the metal layer" in this specification) is 0.70 or less. According to the method for manufacturing a wiring board of the second aspect, since the metal layer can be selectively formed on the surface of the seed layer in the direction perpendicular to the surface, it is possible to suppress conduction between adjacent wirings in the wiring pattern of the wiring layer.

Here, "the average value of the ratio of the width Ws of the metal layer in the line width direction of the side of the seed layer to the thickness Tf of the metal layer in the direction perpendicular to the surface of the seed layer (average value of the lateral expansion of the metal layer)" refers to the average of the ratio of the width Ws of the metal layer in the line width direction of the side of the seed layer to the thickness Tf of the metal layer in the direction perpendicular to the surface of the seed layer in a cross section perpendicular to the extension direction of the wiring, calculated at five or more different points of the wiring pattern. "The thickness Tf of the metal layer in the direction perpendicular to the surface of the seed layer" refers to, for example, the average value of the thickness of the metal layer that exists in the direction perpendicular to the surface from the surface of the seed layer in a cross section perpendicular to the extension direction of the wiring. "The width Ws of the metal layer in the line width direction of the side of the seed layer" refers to, for example, the average value of the width (dimension in the line width direction) of the metal layer that exists in the line width direction of the side of the seed layer in a cross section perpendicular to the extension direction of the wiring.

The formation process is not particularly limited as long as it is a process of forming a metal layer so that the average lateral expansion amount of the metal layer is 0.70 or less, and the smaller the lateral expansion amount of the metal layer, the better. However, a process of forming a metal layer so that the average lateral expansion amount of the metal layer is 0.30 or less is preferable, and among these, a process of forming a metal layer so that the average lateral expansion amount of the metal layer is 0.20 or less is preferable, and a process of forming a metal layer so that the average lateral expansion amount of the metal layer is 0 (zero) is particularly preferable. This is because the effect of suppressing conduction between adjacent wirings in the wiring pattern of the wiring layer is remarkable.

In the forming step, similarly to the forming step according to the first embodiment, the current density of the current flowing between the anode and the seed layer and the film-forming time for applying the voltage are set to the current density and film-forming time required to form the metal layer to a target thickness, and the amount of seepage of the liquid (the amount of the liquid seeping out from the storage space to the upper surface side of the solid electrolyte membrane) is preferably set to 0.0021 g/ ^cm2 or less per 1 μm of the target thickness of the metal layer, similarly to the forming step according to the first embodiment. Furthermore, the amount of seepage of the liquid per 1 μm of the target thickness of the metal layer is preferably 0.0018 g/cm2 or ^less , and particularly preferably 0.00026 g/cm2 or ^less , as in the forming step according to the first embodiment.

In the formation process, a metal layer is formed on the surface of the seed layer to form a wiring layer of a predetermined wiring pattern having a seed layer of a predetermined pattern provided on the surface of the substrate and a metal layer provided on the surface of the seed layer. The wiring pattern of the wiring layer is the same as the wiring pattern of the wiring layer according to the first embodiment.

The manufacturing method for the wiring board according to the embodiment will be explained in more detail below with examples and comparative examples.

1. Confirmation of the Effect of the Amount of Seepage of Liquid In the method for manufacturing a wiring board according to the first embodiment described above, the effect of the present invention was confirmed when the amount of seepage of the liquid per 1 μm of target thickness of the metal layer was changed.

[Example 1]
The method for manufacturing a wiring board according to the first embodiment was carried out. In this method, first, in a preparation step, a substrate with a seed layer for evaluation was prepared as follows.

(Substrate with seed layer for evaluation)
Insulating substrate: Kyoden substrate Thickness of seed layer: 18 μm
Line width/space width of seed layer: 100 μm to 500 μm/100 μm to 500 μm (The seed layer has a pattern including three different line widths/space widths (100 μm/100 μm, 300 μm/300 μm, and 500 μm/500 μm).)

Next, in the liquid supplying step, a film forming apparatus for upward film formation was prepared, which had a solution storage section consisting of a housing with an opening at the top and an anode located on the bottom surface of the storage space, and a solid electrolyte membrane described below that was placed on the top of the housing so as to cover and seal the opening of the housing. Then, in the film forming apparatus, the metal solution L described below was supplied to the storage space of the solution storage section.

(Solid electrolyte membrane)
Type: A
Material: Nafion (registered trademark) manufactured by DuPont

(Metal solution)
Type: Copper (II) sulfate aqueous solution Copper sulfate concentration: 1 mol/L (sulfuric acid concentration: 0.2 mol/L)

Next, in the placement step, the substrate with the seed layer for evaluation was placed above the solid electrolyte membrane in the solution storage section so that the surface of the seed layer faced the anode and was in contact with the upper surface of the solid electrolyte membrane. In this case, the substrate with the seed layer was simply placed on the upper surface of the solid electrolyte membrane without being held by a jig, so that the contact pressure with which the surface of the seed layer pressed against the contact surface of the upper surface of the solid electrolyte membrane was the pressure due only to the weight of the substrate with the seed layer.

Next, in the formation process, a voltage was applied between the anode and the seed layer corresponding to the cathode, with the substrate with the seed layer for evaluation placed in the placement process. This caused the liquid containing the metal ions and other components of the metal solution to seep out from the storage space to the upper surface of the solid electrolyte membrane by the upward film formation method, and the metal ions in the liquid were reduced on the surface of the seed layer to form a film. In this way, a metal layer was formed on the surface of the seed layer. At this time, the formation conditions of the metal layer were as follows. Specifically, the target thickness of the metal layer was set to the target thickness below, and the current density of the current flowing between the anode and the seed layer and the film formation time for applying the voltage were set to the current density and film formation time required to form the metal layer to the target thickness below.

(Conditions for forming metal layer)
Film formation temperature: room temperature Target thickness of metal layer: 20 μm
Current density: 25mA/ ^cm2
Film formation time: 47 min

By the above steps, a wiring board was manufactured that had an insulating base material and a wiring layer with a predetermined line-and-space wiring pattern provided on the surface of the base material, the wiring layer having a seed layer and a metal layer.

[Example 2]
Except for changing the type of the solid electrolyte membrane to B, a wiring board was manufactured by carrying out the same manufacturing method as in Example 1.

[Example 3]
Except for changing the type of solid electrolyte film to C, a wiring board was manufactured by carrying out the same manufacturing method as in Example 1.

[Calculation of the amount of liquid seeping out per 1 μm of target thickness of metal layer]
In the formation process of each of Examples 1 to 3, the amount of liquid seeping out from the accommodation space to the upper surface side of the solid electrolyte membrane was calculated by the following procedure.

(Procedure for calculating the amount of seepage of liquid)
Step 1: Place an empty beaker on a precision balance.
Step 2: Place a dry Kimwipe in the beaker and weigh it.
Step 3: In the formation step, a metal layer is formed by solid phase electrodeposition.
Step 4: After the formation step, the exudate liquid (the exudate liquid adhering to the substrate with the seed layer for evaluation and the liquid adhering to the solid electrolyte membrane) is wiped off with a Kimwipe.
Step 5: Place the wiped Kimwipe into the beaker used in step 2 and measure its weight.
Step 6: The amount of exudation [g/cm ² ] is calculated by dividing the weight difference [g] between the weight measured in step 2 and the weight measured in step 5 by the surface area [cm ² ] of the seed layer.

Then, the amount of liquid seepage calculated by the above procedure was divided by the target thickness of the metal layer to calculate the amount of liquid seepage per 1 μm of the target thickness of the metal layer. Table 1 below shows the amount of liquid seepage and the amount of liquid seepage per 1 μm of the target thickness of the metal layer.

[Calculation of the average lateral thickness of the metal layer]
For the line-and-space wiring patterns of the wiring boards manufactured in each of Examples 1 to 3, the ratio of the width Ws of the metal layer in the line width direction of the side of the seed layer to the thickness Tf of the metal layer in the direction perpendicular to the extension direction of the wiring (lateral expansion of the metal layer) was calculated at five or more different locations of the wiring pattern, and the ratio was averaged to calculate the average lateral expansion of the metal layer.

Specifically, first, five arbitrary wirings (wiring 1 to wiring 5) were selected from the line-and-space wiring pattern of the wiring board manufactured in each example. Next, a cross-sectional photograph perpendicular to the extension direction of each selected wiring was taken. Then, using the cross-sectional photograph, the ratio of the width Ws of the metal layer in the line width direction of the left side of the seed layer to the thickness Tf of the metal layer in the direction perpendicular to the surface of the seed layer (lateral thickening amount of the metal layer (left)) and the ratio of the width Ws of the metal layer in the line width direction of the right side of the seed layer to the thickness Tf of the metal layer in the direction perpendicular to the surface of the seed layer (lateral thickening amount of the metal layer (right)) were calculated for the left and right side of the seed layer in the cross section perpendicular to the extension direction of each wiring, except for the part where the cross-sectional photograph was unclear and the thickness Tf or width Ws of the metal layer could not be measured. Next, the lateral thickening amount of the metal layer (left) and the lateral thickening amount of the metal layer (right) calculated for the five selected wirings were summed up, and the average value of the lateral thickening amount of the metal layer was calculated by dividing the sum by the number of data.

Figure 4 shows cross-sectional photographs of five wires (wire 1 to wire 5) selected from the line-and-space wiring pattern of the wiring layer of the wiring board manufactured in each of Examples 1 to 3, along with the lateral expansion amount of the metal layer calculated for each wire (left) and the lateral expansion amount of the metal layer (right). Table 1 below shows the average lateral expansion amount of the metal layer calculated for the line-and-space wiring pattern of the wiring layer of the wiring board manufactured in each of Examples 1 to 3.

[evaluation]
As shown in Table 1 and Figure 4 above, when the amount of liquid exuded per 1 μm of the target thickness of the metal layer was 0.0021 g/ ^cm2 or less, the average lateral expansion amount of the metal layer was 0.70 or less. When the amount of liquid exuded per 1 μm of the target thickness of the metal layer was 0.0018 g/ ^cm2 or less, the average lateral expansion amount of the metal layer was 0.30 or less. When the amount of liquid exuded per 1 μm of the target thickness of the metal layer was 0.00026 g/cm2 or ^less , the average lateral expansion amount of the metal layer was 0.20 or less.

For comparison, the seed layer-attached substrate and metal solution used in each of Examples 1 to 3 were used, and the seed layer-attached substrate was directly immersed in the metal solution to perform immersion plating to form a metal layer on the surface of the seed layer under the same metal layer formation conditions as in Examples 1 to 3, thereby producing a wiring board in which the wiring layer has a seed layer and a metal layer. As a result, the lateral thickening amounts of the metal layer for five wirings selected in the wiring pattern of the wiring layer were "0.95", "0.99", "0.95", "0.95", and "0.99", respectively, with the average value being approximately 1. It was confirmed that with normal immersion plating, the metal layer is formed isotropically in the direction perpendicular to the surface of the seed layer and in the line width direction on the side.

2. Confirmation of the effect of the upward film formation method As in the first embodiment, in the film formation device for upward film formation, a method (upper film formation method) was implemented in which a liquid containing metal ions and other components of the metal solution was allowed to seep out from the storage space to the upper side of the solid electrolyte membrane, and the metal ions in the liquid were reduced on the surface of the seed layer to form a film, and in the film formation device for downward film formation described below, a method (lower film formation method) was implemented in which a liquid containing metal ions and other components of the metal solution was allowed to seep out from the storage space to the lower side of the solid electrolyte membrane, and the metal ions in the liquid were reduced on the surface of the seed layer to form a film. From these results, the effect of the upward film formation method was confirmed.

[Example 4]
A wiring board was manufactured by carrying out the same method as in Example 1, except that the following substrate with a seed layer for evaluation was used as the substrate with a seed layer, the type of solid electrolyte membrane was changed to D, the following metal solution was used as the metal solution, and the conditions for forming the metal layer were as follows.

(Substrate with seed layer for evaluation)
Insulating substrate: Kyoden substrate Thickness of seed layer: 18 μm
Line width/space width of seed layer: 100 μm to 500 μm/100 μm to 500 μm (The seed layer has a pattern including three different line widths/space widths (100 μm/100 μm, 300 μm/300 μm, and 500 μm/500 μm).)

(Metal solution)
Type: Copper (II) sulfate aqueous solution Copper sulfate concentration: 1 mol/L (sulfuric acid concentration: 0.2 mol/L)

(Conditions for forming metal layer)
Film formation temperature: room temperature Target thickness of metal layer: 20 μm
Current density: 25mA/ ^cm2
Film formation time: 47 min

[Comparative Example 1]
Except for changing the type of solid electrolyte film to E, a wiring board was manufactured by carrying out the same manufacturing method as in Example 4.

[Comparative Example 2]
Except for changing the type of solid electrolyte film to F, a wiring board was manufactured by carrying out the same manufacturing method as in Example 4.

[Comparative Example 3]
Except for changing the type of solid electrolyte film to G, a wiring board was manufactured by carrying out the same manufacturing method as in Example 4.

[Comparative Example 4]
Except for changing the type of solid electrolyte film to H, a wiring board was manufactured by carrying out the same manufacturing method as in Example 4.

[Comparative Example 5]
Except for changing the type of solid electrolyte film to I, a wiring board was manufactured by carrying out the same manufacturing method as in Example 4.

[Comparative Example 6]
First, in the preparation step, a substrate with a seed layer for evaluation similar to that of Example 4 was prepared as a substrate with a seed layer. Next, in the liquid supply step, a film forming apparatus for lower film formation was prepared, which was equipped with a solution storage section composed of a housing having an opening at the bottom and an anode arranged on the upper surface of the storage space, and a solid electrolyte membrane arranged at the bottom of the housing so as to cover and seal the opening of the housing. In this case, as the solid electrolyte membrane, a solid electrolyte membrane similar to that of Example 4 was used, except that the type was J. Then, in the film forming apparatus, a metal solution L similar to that of Example 4 was supplied to the storage space of the solution storage section.

Next, in the placement step, the substrate with the seed layer for evaluation was placed below the solid electrolyte membrane in the solution storage section so that the surface of the seed layer faced the anode and was in contact with the lower surface of the solid electrolyte membrane.

Next, in the formation process, with the substrate with the seed layer for evaluation placed in the placement process, a voltage was applied between the anode and the seed layer corresponding to the cathode. This caused the liquid containing the metal ions and other components of the metal solution to seep out from the storage space to the underside of the solid electrolyte membrane by the downward film formation method, and the metal ions in the liquid were reduced on the surface of the seed layer to form a film. In this way, a metal layer was formed on the surface of the seed layer. At this time, the conditions for forming the metal layer were the same as in Example 4.

By the above steps, a wiring board was manufactured that had an insulating base material and a wiring layer with a predetermined line-and-space wiring pattern provided on the surface of the base material, the wiring layer having a seed layer and a metal layer.

[Comparative Example 7]
A wiring board was manufactured by carrying out the same manufacturing method as in Comparative Example 6, except that the type of solid electrolyte film was changed to K.

[Comparative Example 8]
Except for changing the type of solid electrolyte membrane to L, a wiring board was manufactured by carrying out the same manufacturing method as in Comparative Example 6.

[Comparative Example 9]
Except for changing the type of solid electrolyte membrane to M, a wiring board was manufactured by carrying out the same manufacturing method as in Comparative Example 6.

[Comparative Example 10]
Except for changing the type of solid electrolyte film to N, a wiring board was manufactured by carrying out the same manufacturing method as in Comparative Example 6.

[Comparative Example 11]
A wiring board was manufactured by carrying out the same manufacturing method as in Comparative Example 6, except that the type of solid electrolyte film was changed to O (O-).

[Calculation of the amount of liquid seeping out per 1 μm of target thickness of metal layer]
In the formation process of each of Example 4 and Comparative Examples 1 to 11, the amount of liquid seeping out from the accommodation space onto the upper or lower side of the solid electrolyte membrane was calculated using the same procedure as in the above section "1. Confirmation of the effect of the amount of liquid seeping out [Calculation of the amount of liquid seeping out per 1 μm of target thickness of the metal layer]". Next, the amount of liquid seeping out calculated using the above procedure was divided by the target thickness of the metal layer to calculate the amount of liquid seeping out per 1 μm of target thickness of the metal layer. Table 2 below shows the amount of liquid seeping out and the amount of liquid seeping out per 1 μm of target thickness of the metal layer.

[Calculation of lateral thickness of metal layer]
At any one point of the line-and-space wiring pattern of the wiring board manufactured in each of the examples of Example 4 and Comparative Examples 1 to 11, the ratio of the width Ws of the metal layer in the line width direction of the side of the seed layer to the thickness Tf of the metal layer in the direction perpendicular to the surface of the seed layer in the cross section perpendicular to the extension direction of the wiring (lateral thickening of the metal layer) was calculated. Specifically, first, any one wiring was selected from the line-and-space wiring pattern of the wiring board manufactured in each example. Next, a cross-sectional photograph perpendicular to the extension direction of the selected one wiring was taken. Then, using the cross-sectional photograph, the ratio of the width Ws of the metal layer in the line width direction of the side of the seed layer to the thickness Tf of the metal layer in the direction perpendicular to the surface of the seed layer (lateral thickening of the metal layer) was calculated for one of the left and right side portions of the seed layer in the cross section perpendicular to the extension direction of the wiring. FIG. 5 is a table showing a cross-sectional photograph of one wiring selected from the line-and-space wiring pattern of the wiring board manufactured in each of the examples of Example 4 and Comparative Examples 1 to 11. Table 2 below shows the lateral expansion amount of the metal layer calculated at one location of one wire selected from the line-and-space wiring pattern of the wiring board manufactured in each of Example 4 and Comparative Examples 1 to 11. Fig. 6 is a graph showing the relationship between the amount of liquid seepage per 1 µm of the target thickness of the metal layer and the lateral expansion amount of the metal layer calculated for Example 4 and Comparative Examples 1 to 11.

[evaluation]
As shown in Table 2, Figures 5 and 6 above, in the upward film-forming method, when the amount of liquid seepage per 1 μm of the target thickness of the metal layer is about 0.001 g/cm ² or less, the lateral expansion of the metal layer is significantly reduced to 0, and it was confirmed that the metal layer is selectively formed in the direction perpendicular to the surface of the seed layer. On the other hand, in the downward film-forming method, regardless of the amount of liquid seepage per 1 μm of the target thickness of the metal layer, the lateral expansion of the metal layer is about 1, and it was confirmed that the metal layer is formed isotropically in the direction perpendicular to the surface of the seed layer and in the line width direction of the side. This is thought to be because, in the downward film-forming method, the liquid containing the metal ions of the metal solution is caused to seep out from the storage space to the lower side of the solid electrolyte membrane, so that the liquid is easily supplied to the side of the seed layer.

3. Reference: Evaluation of accuracy of the method for calculating the amount of exuded liquid The accuracy of the method for calculating the amount of exuded liquid was evaluated according to the procedure in the above section "1. Confirmation of the effect of the amount of exuded liquid [Calculation of the amount of exuded liquid per 1 μm of target thickness of metal layer]." Specifically, the evaluation was performed according to the following procedure.

Step 1: Collect 60 μL of pure water using a micropipette and drop it into a beaker.
Step 2: The weight of the pure water dropped into the beaker is measured using a scale.
Step 3: Steps 1 and 2 are repeated 10 times, and the weights of the pure water collected by the micropipette measured on the weighing scale are averaged to evaluate the variation in the weight of the pure water collected by the micropipette.
Step 4: Take 60 μL of pure water with a micropipette and drop it onto the Kyoden substrate.
Step 5: Wipe off the pure water dropped onto the Kyoden substrate with a Kimwipe whose weight has been measured in advance.
Step 6: Measure the weight of the Kimwipe that has been wiped.
Step 7: The weight of the collected pure water is calculated from the weight difference between the previously measured weight of the Kimwipe and the weight measured in step 6.
Step 8: Repeat steps 4 to 7 ten times, and calculate the average weight of the pure water collected by the micropipette measured with the Kimwipe to evaluate the variation in the measurement method for the weight of pure water measured with the Kimwipe.

Figure 7 is a graph showing the average weight of pure water collected by the micropipette measured using a weighing scale, and the average weight of pure water collected by the micropipette measured using a Kimwipe. As shown in Figure 7, there is almost no difference between the average weight of pure water collected by the micropipette measured using a weighing scale, and the average weight of pure water collected by the micropipette measured using a Kimwipe, so it was confirmed that there is no problem with the accuracy of the method for calculating the amount of liquid seepage using the above procedure.

4. Reference: Confirmation of the Relationship Between the Surface Area of the Seed Layer and the Amount of Exuded Liquid The method for manufacturing a wiring board according to the embodiment was carried out by changing the surface area of the seed layer, and the relationship between the surface area of the seed layer and the amount of exudation of the liquid containing metal ions of the metal solution that exuded from the accommodation space to the upper surface side of the solid electrolyte membrane was confirmed. Fig. 8 is a graph showing the relationship between the surface area of the seed layer and the amount of exuded liquid.

5. Reference: Confirmation of the relationship between the pressure applied to pressurize the metal solution and the amount of liquid seeping out Using the solution storage unit according to the embodiment, the pressure applied to pressurize the metal solution in the storage space was changed to confirm the relationship between the pressure applied to pressurize the metal solution in the storage space and the amount of liquid containing metal ions in the metal solution seeping out from the storage space to the upper surface side of the solid electrolyte membrane. Fig. 9 is a graph showing the relationship between the pressure applied to pressurize the metal solution in the storage space and the amount of liquid seeping out.

The above describes in detail the method for manufacturing a wiring board according to an embodiment of the present invention, but the present invention is not limited to the above embodiment, and various design changes can be made without departing from the spirit of the present invention described in the claims.

REFERENCE SIGNS LIST 1 Substrate with seed layer 2 Insulating substrate 2f Front surface 2r Back surface 4 Seed layer 4f Front surface 4s Side surface 5 Metal layer 6 Conductor layer 8 Via conductor 9 Wiring layer 10 Wiring substrate 100 Film forming device 13 Anode 15 Housing 15a Opening 15f Supply port 15d Discharge port 17 Solid electrolyte membrane 17t Top surface 20 Solution storage section G Storage space L Metal solution 101 Tank 102 Pump 103 Pressure adjustment valve 200 Holding jig

Claims (6)

A method for manufacturing a wiring board comprising an insulating base material and a wiring layer having a predetermined wiring pattern provided on a surface of the base material, the wiring layer having a seed layer having a predetermined pattern corresponding to the wiring pattern provided on the surface of the base material, and a metal layer provided on the surface of the seed layer, the method comprising the steps of:
a preparation step of preparing a substrate with a seed layer, the substrate including the substrate and the seed layer provided on a surface of the substrate;
a placement step of placing the base material with the seed layer above the solid electrolyte membrane in a solution storage section, the solution storage section having a storage space for storing a metal solution containing metal ions between an anode and a solid electrolyte membrane placed thereon, such that a surface of the seed layer faces the anode and contacts an upper surface of the solid electrolyte membrane;
a forming step of applying a voltage between the anode and the seed layer corresponding to a cathode in a state in which the base material with a seed layer is disposed in the disposing step, thereby causing a liquid containing the metal ions of the metal solution to seep out from the accommodation space to an upper surface side of the solid electrolyte membrane, and reducing the metal ions in the liquid on a surface of the seed layer to form a film, thereby forming the metal layer;
In the forming step, the current density of the current flowing between the anode and the seed layer and the film formation time for applying the voltage are set to the current density and film formation time required to form the metal layer to a target thickness,
A method for manufacturing a wiring board, wherein in the forming step, an amount of seepage of the liquid is 0.0021 g/cm ² or less per 1 μm of the target thickness of the metal layer. 2 . The method for manufacturing a wiring board according to claim 1 , wherein in the forming step, the amount of the seepage of the liquid is set to 0.0018 g/cm ² or less per 1 μm of the target thickness of the metal layer. 3. The method for manufacturing a wiring board according to claim 2, wherein in the forming step, the amount of the seepage of the liquid is set to 0.00026 g/ ^cm2 or less per 1 μm of the target thickness of the metal layer. A method for manufacturing a wiring board comprising: an insulating base material; and a wiring layer having a predetermined wiring pattern provided on a surface of the base material, the wiring layer having a seed layer having a predetermined pattern corresponding to the wiring pattern provided on the surface of the base material; and a metal layer provided on the surface of the seed layer, the method comprising the steps of:
a preparation step of preparing a substrate with a seed layer, the substrate including the substrate and the seed layer provided on a surface of the substrate;
a placement step of placing the base material with the seed layer above the solid electrolyte membrane in a solution storage section, the solution storage section having a storage space for storing a metal solution containing metal ions between an anode and a solid electrolyte membrane placed thereon, such that a surface of the seed layer faces the anode and contacts an upper surface of the solid electrolyte membrane;
a forming step of applying a voltage between the anode and the seed layer corresponding to a cathode in a state in which the base material with a seed layer is disposed in the disposing step, thereby causing a liquid containing the metal ions of the metal solution to seep out from the accommodation space to an upper surface side of the solid electrolyte membrane, and reducing the metal ions in the liquid on a surface of the seed layer to form a film, thereby forming the metal layer;
A method for manufacturing a wiring substrate, characterized in that, in the formation process, the metal layer is formed so that the average ratio of the width Ws of the metal layer in the line width direction of the side of the seed layer to the thickness Tf of the metal layer in the direction perpendicular to the surface of the seed layer is 0.70 or less. The method for manufacturing a wiring board according to claim 4, characterized in that in the formation process, the metal layer is formed so that the average ratio of Ws to Tf is 0.30 or less. The method for manufacturing a wiring board according to claim 5, characterized in that in the formation process, the metal layer is formed so that the average ratio of Ws to Tf is 0.20 or less.

Images