FILM FORMING APPARATUS FOR METAL FILM

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese patent application JP 2023-191134 filed on Nov. 8, 2023, the entire content of which is hereby incorporated by reference into this application.

BACKGROUND
Technical Field

The present disclosure relates to a film forming apparatus for a metal film.

Background Art

Conventionally, metal films have been formed by depositing metal on a surface of a substrate by electroplating (for example, JP 2016-125087 A). A film forming apparatus disclosed in JP 2016-125087 A includes a container (housing) that houses a plating solution. An opening is formed in the container and is sealed by an electrolyte membrane. The film forming apparatus further includes a pressing mechanism that presses the substrate by the electrolyte membrane with the hydraulic pressure of the plating solution.

Here, when forming the metal film on the surface of the substrate, voltage is applied between an anode and the substrate while the substrate is being pressed with the hydraulic pressure of the electrolyte membrane. In this manner, the metal film in a predetermined pattern can be formed on a base layer. When forming the metal film in a predetermined pattern on the substrate, use of a masking member shown in JP 2016-108586 A is also expected.

SUMMARY

However, in a case where a mask portion of the masking member shown in JP 2016-108586 A is made of a rubber material, at the time of film forming, rubber particles (rubber powder) of the mask portion adhere to the surface of an electrolyte membrane when the masking member is pressed by the electrolyte membrane. When slightly stretched due to the hydraulic pressure of a plating solution, the electrolyte membrane partially covers a penetrating portion formed in the mask portion. As a result, at the time of film forming, the movement of metal ions from the penetrating portion toward a substrate is hindered by the rubber particles adhering to the electrolyte membrane. This makes it difficult to form a metal film in a predetermined pattern corresponding to the shape of the penetrating portion.

The present disclosure has been made in view of the foregoing and provides a film forming apparatus for a metal film capable of accurately forming a metal film in a predetermined pattern using a masking member having a mask portion made of a rubber material.

In view of the aforementioned problem, a film forming apparatus for a metal film according to the present disclosure is a film forming apparatus for a metal film that forms the metal film in a predetermined pattern on a surface of a substrate by electroplating, and includes: a container having an opening formed at a position opposing the substrate, the opening covered by an electrolyte membrane with a plating solution contained in the container; a pressing mechanism configured to press the substrate by the electrolyte membrane with a hydraulic pressure of the plating solution contained in the container; an anode disposed inside the container at a position opposing the electrolyte membrane; and a masking member disposed between the electrolyte membrane and the substrate, the masking member having a penetrating portion in the predetermined pattern formed therein, in which the masking member includes a mask portion made of a rubber material and having the penetrating portion formed therein, and a contact prevention member made of a resin material is disposed on an opposing surface, which opposes the electrolyte membrane, of surfaces of the mask portion, the contact prevention member being configured to prevent contact between the mask portion and the electrolyte membrane.

According to the present disclosure, at the time of film forming, the masking member is contacted between the electrolyte membrane and the substrate, and the substrate is pressed by the electrolyte membrane via the masking member with the hydraulic pressure of the plating solution contained in the container. When voltage is applied between the anode and the substrate with such a state, metal ions contained in the plating solution contained in the container pass through the electrolyte membrane and moisture of the plating solution exudes from the electrolyte membrane as a leachate. In this manner, the penetrating portion formed in the mask portion is filled with the leachate, with the elastically deformed mask portion closely adhering to the surface of the substrate, and pressurization is performed. With such a state, metal ions of the plating solution pass through the penetrating portion, and the passing metal ions turn into metal to be deposited on the surface of the substrate. As a result, the metal film in a predetermined pattern corresponding to the penetrating portion can be formed on the surface of the substrate.

Here, even when the electrolyte membrane deforms toward the mask portion with the hydraulic pressure of the plating solution, since the contact prevention member made of a resin material is disposed on the opposing surface, which opposes the electrolyte membrane, of the surfaces of the mask portion, the electrolyte membrane can be prevented from contacting the opposing surface of the mask portion. In this manner, rubber particles derived from the rubber material of the mask portion can be prevented from adhering to the electrolyte membrane. As a result, even when the electrolyte membrane is deformed with the hydraulic pressure of the plating solution, since the movement of metal ions is not hindered by the rubber particles in a portion, which covers the penetrating portion of the mask portion, of the electrolyte membrane, the metal film in a predetermined pattern can be accurately formed.

In an embodiment, the contact prevention member is a cover sheet disposed on the opposing surface so as to cover the penetrating portion, and a plurality of openings is formed in the cover sheet at a position where at least the penetrating portion is covered, the plurality of openings allowing the plating solution to penetrate therethrough.

According to this embodiment, since the cover sheet is disposed on the opposing surface so as to cover the penetrating portion, adhesion of the rubber particles to the electrolyte membrane can be suppressed. In addition, since the cover sheet is disposed so as to cover the penetrating portion of the mask portion, sagging of the electrolyte membrane deformed due to the hydraulic pressure of the plating solution or the like can be suppressed. Further, the hydraulic pressure of the plating solution can be uniformly exerted on the mask portion via the electrolyte membrane and the cover sheet. This allows the mask portion to uniformly deform, so that the sealing property between the mask portion and the substrate can be stably secured. Further, since a plurality of openings, through which the plating solution penetrates, is formed at a position where at least the penetrating portion is covered, the leachate exuded from the electrolyte membrane passes through the openings of the cover sheet and is supplied to the penetrating portion. As a result, at the time of film forming, since the metal ions move within the leachate filled in the penetrating portion, the metal film corresponding to the pattern of the penetrating portion can be stably formed on the surface of the substrate.

In another embodiment, the mask portion includes a first portion facing the electrolyte membrane and a second portion facing the substrate, and the masking member includes a mesh portion woven with a wire, the mesh portion being disposed between the first portion and the second portion and retaining the first portion and the second portion.

According to this embodiment, since the mesh portion is sandwiched between the first portion facing the electrolyte membrane and the second portion facing the substrate, the force exerted on the mesh portion due to the hydraulic pressure of the plating solution can be uniformly dispersed in the second portion. This allows the second portion to uniformly deform, so that the sealing property between the mask portion and the substrate can be stably secured. Further, since the openings of a mesh in the mesh portion are formed at the position of the penetrating portion, the leachate exuded from the electrolyte membrane passes through the openings of the mesh in the mesh portion. As a result, the metal derived from the metal ions can be stably deposited on the surface of the substrate. Since the first and the second portions can be continuously formed via the openings of the mesh in the mesh portion, the mask portion can be stably retained in the mesh portion.

In an embodiment, the cover sheet is a sheet in a mesh woven with a wire, and each of the openings of the mesh in the cover sheet is larger than an opening of a mesh in the mesh portion.

According to this embodiment, since the opening of the mesh in the cover sheet is larger than the opening of the mesh in the mesh portion, the leachate exuded from the electrolyte membrane can be smoothly supplied to the penetrating portion of the mask portion through the openings of the cover sheet. In this manner, the metal film in a stable pattern can be formed.

In further another embodiment, the contact prevention member is a resin film that covers the opposing surface.

According to this embodiment, since the resin film covers the opposing surface of the mask portion, adhesion of the rubber particles to the electrolyte membrane can be suppressed, and the leachate (plating solution) exuded from the electrolyte membrane is smoothly supplied to the penetrating portion of the mask portion. In this manner, the metal film in a desired pattern can be stably formed.

According to the present disclosure, a metal film in a predetermined pattern can be accurately formed using a masking member having a mask portion made of a rubber material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view showing an example of a film forming apparatus for a metal film according to an embodiment of the present disclosure;

FIG. 2 is a schematic perspective view showing a cover sheet, a masking member, and a substrate on which a metal film is formed that are shown in FIG. 1;

FIG. 3 is a schematic cross-sectional view for explaining film forming using the film forming apparatus shown in FIG. 1;

FIG. 4 is an enlarged cross-sectional view of a main portion for explaining forming of a metal film using the film forming apparatus shown in FIG. 3;

FIG. 5 is a schematic perspective view showing a modification of the masking member shown in FIG. 3;

FIG. 6 is an enlarged cross-sectional view of the main portion for explaining forming of the metal film using the film forming apparatus shown in FIG. 5; and

FIG. 7 is an enlarged cross-sectional view for explaining forming of a metal film using a masking member according to a comparative example.

DETAILED DESCRIPTION

A film forming apparatus 1 for a metal film according to an embodiment of the present disclosure will be described. FIG. 1 is a schematic cross-sectional view showing an example of the film forming apparatus for a metal film according to the embodiment of the present disclosure.

As shown in FIG. 1, the film forming apparatus 1 is a film forming apparatus configured to form a metal film F in a predetermined pattern P on a substrate B by electroplating, with a masking member 60 sandwiched between an electrolyte membrane 13 and the substrate B. Specifically, the film forming apparatus 1 includes an anode 11, the electrolyte membrane 13, and a power supply 14 that applies voltage between the anode 11 and the substrate B.

The film forming apparatus 1 includes a container 15 that contains the anode 11 and a plating solution L, a mount base 40 on which the substrate B is mounted, and the masking member 60. At the time of film forming, the masking member 60 is mounted on the mount base 40, together with the substrate B. The electrolyte membrane 13 is disposed between the masking member 60 and the anode 11.

The film forming apparatus 1 includes a linear motion actuator 70 that raises and lowers the container 15. For convenience of explanation, the present embodiment is based on the premise that the electrolyte membrane 13 is disposed below the anode 11, and the masking member 60 and the substrate B are disposed further below. However, as long as the metal film F can be formed on the surface of the substrate B, the positional relations are not limited to those described above.

The substrate B functions as a cathode. The substrate B is a plate-like substrate. In the present embodiment, the substrate B is a rectangular board. An opposing surface, which opposes the electrolyte membrane 13 (screen mask 62), of the surfaces of the substrate B, is a film forming surface functioning as the cathode. As long as the substrate B functions as the cathode (i.e., a conductive surface), the material of the substrate B is not particularly limited. The substrate B may be made of a metal material, such as aluminum or copper.

In the present embodiment, as shown in FIG. 2, since the pattern (wiring pattern) P is formed from the metal film F, a substrate with a base layer Bb of copper or the like formed on a surface of an insulating board Ba of resin or the like is used as the substrate B. In this case, after forming the metal film F, the base layer Bb excluding a portion where the metal film F was formed is removed by etching or the like. In this manner, the pattern P with the metal film F can be formed on the surface of the insulating board Ba.

The anode 11 is, as an example, a non-porous anode (for example, having no pores) made of the same metal as that of the metal film. The anode 11 has a block-like or a plate-like shape. Examples of the material of the anode 11 may include copper. The anode 11 is dissolved when voltage is applied by the power supply 14. However, when the film is formed only with metal ions of the plating solution L, the anode 11 is insoluble in the plating solution L. The anode 11 is electrically connected to a positive electrode of the power supply 14. A negative electrode of the power supply 14 is electrically connected to the substrate B via the mount base 40.

The plating solution L is a solution containing metal in an ionic form of the metal film to be formed. Examples of the metal may include copper, nickel, gold, silver, or iron. The plating solution L is a solution with these metals dissolved (ionized) with acid such as a nitric acid, a phosphoric acid, a succinic acid, a sulfuric acid, or a pyrophosphoric acid. Examples of solvent of the solution may include water or alcohol. When the metal is copper, for example, examples of the plating solution L may include an aqueous solution containing copper sulfate, copper pyrophosphate, and the like.

The electrolyte membrane 13 is a membrane that can be impregnated with (contain) the metal ions together with the plating solution L by being contacted with the plating solution L. The electrolyte membrane 13 is a flexible membrane. The material of the electrolyte membrane 13 is not particularly limited as long as the metal ions of the plating solution L can be moved to the substrate B side when voltage is applied by the power supply 14. Examples of the material of the electrolyte membrane 13 may include a fluorine-based resin having an ion-exchange function, such as Nafion® manufactured by Du Pont Corporation. The film thickness of the electrolyte membrane 13 may be in a range of 20 μm to 200 μm and may be in a range of 20 μm to 60 μm.

The container 15 is made of material insoluble in the plating solution L. A storing space 15a that stores the plating solution L is formed in the container 15. The anode 11 is disposed in the storing space 15a of the container 15. An opening 15d is formed on the substrate B side of the storing space 15a. The opening 15d of the container 15 is covered with the electrolyte membrane 13. Specifically, a peripheral edge of the electrolyte membrane 13 is sandwiched between the container 15 and a frame 17. In this manner, the plating solution L in the storing space 15a can be sealed with the electrolyte membrane 13.

As shown in FIG. 1 and FIG. 3, the linear motion actuator 70 raises and lowers the container 15 so that the electrolyte membrane 13 and the masking member 60 are flexibly contacted and separated. In the present embodiment, the mount base 40 is fixed and the container 15 is raised and lowered by the linear motion actuator 70. The linear motion actuator 70 is an electric actuator and converts a rotational motion of a motor into a linear motion by means of a ball screw or the like. However, in place of the electric actuator, a hydraulic or a pneumatic actuator may be used.

In the container 15, a supply flow path 15b for supplying the plating solution L to the storing space 15a is formed. Further, in the container 15, a discharge flow path 15c for discharging the plating solution L from the storing space 15a is formed. The supply flow path 15b and the discharge flow path 15c are holes communicating with the storing space 15a. The supply flow path 15b and the discharge flow path 15c are formed sandwiching the storing space 15a therebetween. The supply flow path 15b is fluidly connected to a liquid supply pipe 51. The discharge flow path 15c is fluidly connected to a liquid discharge pipe 52.

The film forming apparatus 1 further includes a liquid tank 90, the liquid supply pipe 51, the liquid discharge pipe 52, and a pump 80. As shown in FIG. 1, the liquid tank 90 contains the plating solution L. The liquid supply pipe 51 connects the liquid tank 90 and the container 15. The liquid supply pipe 51 is provided with the pump 80. The pump 80 supplies the plating solution L from the liquid tank 90 to the container 15. The liquid discharge pipe 52 connects the liquid tank 90 and the container 15. The liquid discharge pipe 52 is provided with a pressure regulating valve 54. The pressure regulating valve 54 adjusts a pressure (hydraulic pressure) of the plating solution L in the storing space 15a to a predetermined pressure.

In the present embodiment, the plating solution L is sucked into the liquid supply pipe 51 from the liquid tank 90 by driving the pump 80. The sucked plating solution L is pumped through the supply flow path 15b to the storing space 15a. The plating solution L in the storing space 15a is returned to the liquid tank 90 via the discharge flow path 15c. In this manner, the plating solution L circulates inside the film forming apparatus 1.

Further, by continuing driving the pump 80, the hydraulic pressure of the plating solution L in the storing space 15a can be maintained at a predetermined pressure by means of the pressure regulating valve 54. The pump 80 is for pressing, via a cover sheet 30A, the masking member 60 by means of the electrolyte membrane 13 on which the hydraulic pressure of the plating solution L is exerted. However, as long as the masking member 60 can be pressed by the electrolyte membrane 13, the pressing mechanism is not particularly limited. In place of the pump 80, an ejection mechanism including a piston and a cylinder that eject the plating solution L may be adopted.

The mount base 40 is made of a conductive material (e.g., metal) as an example. A recess 41 is formed in the mount base 40. The recess 41 is a portion recessed from an opposing surface of the mount base 40 for housing the substrate B.

The masking member 60 includes a frame 61 and the screen mask 62. The frame 61 supports a peripheral edge 62a of the screen mask 62 on the electrolyte membrane 13 side relative to the frame 61. Specifically, the peripheral edge 62a of the screen mask 62 is securely fixed to the frame 61. In the present embodiment, the screen mask 62 has a rectangular outer shape. Therefore, the frame 61 has a rectangular frame-like shape. The material of the frame 61 is not particularly limited, as long as the shape of the masking member 60 can be retained. Examples of the material of the frame 61 may include a metal material such as stainless steel or a resin material such as a thermoplastic resin. The frame 61 is formed by, for example, stamping a metal plate and has a thickness of around 1 mm to 3 mm.

A penetrating portion 68 corresponding to the predetermined pattern P of the metal film F is formed in the screen mask 62. The screen mask 62 includes a mesh portion 64 and a mask portion 65. The screen mask 62 is a mask having a flexibility of around 50 μm to 400 μm. The screen mask 62 is supported on a surface, which is on the substrate B side, of the surfaces of the frame 61.

A peripheral edge of the mesh portion 64 is securely fixed to the frame 61. The mesh portion 64 is stretched so as to cover an opening of the frame 61 with a predetermined tension. The mesh portion 64 has a plurality of openings 64c, 64c, . . . formed in a grid pattern. Specifically, as shown in FIG. 4, the mesh portion 64 is a mesh-like portion (mesh) in which a plurality of oriented wires 64a, 64b is woven so as to intersect with each other. The plurality of wires 64a, 64a is arranged at intervals from each other, and the plurality of wires 64b, 64b intersecting with the plurality of wires 64a, 64a is arranged at intervals from each other. As a result, the plurality of openings 64c, 64c, . . . is formed in a grid pattern in the mesh portion 64. The material of the wires 64a, 64b is not particularly limited as long as the wires have corrosion resistance against the plating solution L. Examples of the material of the wires 64a, 64b may include a resin material such as a polyester resin. Other than those described above, the mesh portion 64 may be made of a resin material such as an acrylic resin, a vinyl acetate resin, a polyvinyl chloride resin, a polypropylene resin, a polyethylene resin, a polystyrene resin, a polycarbonate resin, a polyimide resin, or a urethane resin, as long as the wires can be formed.

The mask portion 65 is retained by the sheet-like mesh portion 64. The penetrating portion 68 corresponding to the predetermined pattern P is formed in the mask portion 65. The mask portion 65 is a portion that closely adheres to the substrate B by being pressed by the electrolyte membrane 13 at the time of film forming. The material of the mask portion 65 is not particularly limited as long as it can closely adhere to the substrate B. Examples of the material of the mask portion 65 may include a rubber material such as silicone rubber (PMDS) or ethylene propylene diene rubber (EPDM). The hardness of the rubber material may be equal to or smaller than HS100, or equal to or smaller than HS50 in Shore A hardness.

The mask portion 65 is made of an elastic material that is compressively elastically deformed by being pressed by the electrolyte membrane 13. In order to secure the adhesion to the substrate B, the deformation amount in the thickness direction (pressing direction) of the mask portion 65 due to the pressing by means of the electrolyte membrane 13 may be in a range of 5 to 20% of the thickness of the mask portion before deformation. The screen mask 62 having the predetermined pattern P can be manufactured by a typical silk screen manufacturing technique using an emulsion. Therefore, the detailed description of the method for manufacturing the screen mask 62 will be omitted.

As shown in FIG. 4, the mask portion 65 includes a first portion 65a facing the electrolyte membrane 13 and a second portion 65b facing the substrate B. The mesh portion 64 is a portion that is disposed between the first portion 65a and the second portion 65b and that retains the first portion 65a and second portion 65b. That is, the mesh portion 64 is sandwiched between the first portion 65a and the second portion 65b, and the first portion 65a and the second portion 65b are coupled via the openings 64c of the mesh portion 64. The force exerted on the mesh portion 64 due to the hydraulic pressure of the plating solution L at the time of film forming can be uniformly dispersed in the second portion 65b. As a result, the deformation of the second portion 65b can be made uniform, so that the sealing property between the mask portion 65 and the substrate B can be stably secured.

Further, on an opposing surface 65c, which opposes the electrolyte membrane 13, of the surfaces of the mask portion 65, the cover sheet 30A for preventing contact between the mask portion 65 and the electrolyte membrane 13 is disposed. The cover sheet 30A corresponds to a “contact prevention member” in the present disclosure. In the present embodiment, the cover sheet 30A may have flexibility, the structure of which is not limited as long as the plating solution L exuded from the electrolyte membrane 13 can be supplied to the penetrating portion 68 of the mask portion 65, and may be a sheet member made of resin (resin material) with openings formed corresponding to the shape of the pattern P of the penetrating portion 68. In the present embodiment, a plurality of openings 31c, through which the plating solution L penetrates, is formed in the cover sheet 30A at a position where at least the penetrating portion 68 is covered. Examples of the cover sheet 30A as such may include a sponge-like resin sheet or a resin sheet with a plurality of openings (through-holes) formed therein. Since the resin material is a synthetic resin produced through polymerization reaction or the like, the particles do not adhere to the electrolyte membrane 13. Examples of the resin material as such may include an acrylic resin, a vinyl acetate resin, a polyvinyl chloride resin, a polypropylene resin, a polyethylene resin, a polystyrene resin, a polycarbonate resin, a polyimide resin, a urethane resin, or a polyester resin. Other than those described above, the resin material may be super engineering plastic such as a liquid crystal polymer.

The cover sheet 30A may be a sheet in a mesh woven with wires 31a, 31b. The plurality of opening 31c, 31c, . . . is formed in a grid pattern in the cover sheet 30A. Specifically, as shown in FIG. 2 and FIG. 4, the cover sheet 30A is a portion (mesh) in a mesh woven with the plurality of oriented wires 31a, 31b intersecting with each other. The plurality of wires 31a, 31a is arranged at intervals from each other, and the plurality of wires 31b, 31b intersecting with the plurality of wires 31a, 31a is arranged at intervals from each other. As a result, the plurality of opening 31c, 31c, . . . is formed in a grid pattern in the cover sheet 30A. The wires 31a, 31b are made of the aforementioned resin material. The openings 31c of the mesh in the cover sheet 30A are larger than the openings of the mesh in the mesh portion 64. Specifically, the intervals between the wires 31a, 31a (wires 31b, 31b) are greater than the intervals between the wires 64a, 64a (64b, 64b).

Referring to FIG. 1 to FIG. 4, a method for film forming using the film forming apparatus 1 will be described. First, a disposing step is performed. In this step, as shown in FIG. 1, the substrate B is disposed on the mount base 40. Specifically, the substrate B is housed in the recess 41 of the mount base 40. In the present embodiment, with the substrate B housed in the recess 41, the surface of the substrate B projects from the opposing surface (surface opposing the electrolyte membrane 13) of the mount base 40. As a result, the mask portion 65 of the masking member 60 can be uniformly contacted to the surface of the substrate B. In doing so, the alignment of the substrate B relative to the anode 11 attached to the container 15 may be adjusted and the temperature of the substrate B may be adjusted.

Next, the masking member 60 is disposed in the mount base 40. In doing so, the masking member 60 is housed such that the surface of the substrate B is housed within an internal space 69 of the frame 61 of the masking member 60. Specifically, as shown in FIG. 4, the surface (surface of the base layer Bb) of the substrate B is covered with the mask portion 65 of the masking member 60. Further, as shown in FIG. 2, the cover sheet 30A is disposed so as to cover the opposing surface 65c of the mask portion 65.

Next, a pressing step is performed. In this step, the substrate B is pressed by the electrolyte membrane 13, via the cover sheet 30A and the screen mask 62, with the hydraulic pressure of the plating solution L that has contacted the electrolyte membrane 13. First, the linear motion actuator 70 is actuated, thereby lowering the container 15 toward the cover sheet 30A and the masking member 60 from the state shown in FIG. 1 to the state shown in FIG. 3.

Then, the pump 80 is actuated, thereby supplying the plating solution L to the storing space 15a of the container 15. Since the liquid discharge pipe 52 is provided with the pressure regulating valve 54, the hydraulic pressure of the plating solution L in the storing space 15a is maintained at a predetermined pressure. As a result, as shown in FIG. 4, the electrolyte membrane 13 deforms toward the internal space 69 of the frame 61 due to the hydraulic pressure of the plating solution L, so that the screen mask 62 can be sandwiched between the electrolyte membrane 13 and the substrate B. Further, the masking member 60 can be pressed by the electrolyte membrane 13 on which the hydraulic pressure of the plating solution L is exerted.

As shown in FIG. 4, such pressing allows the screen mask 62 to closely adhere to the surface of the substrate B. Since the mask portion 65 is made of a rubber material, the mask portion 65 is compressively elastically deformed due to the hydraulic pressure of the plating solution L, so that the adhesion between the mask portion 65 and the substrate B is improved. Further, when the pressing by means of the electrolyte membrane 13 is continued, the penetrating portion 68 formed in the screen mask 62 is filled with a leachate (plating solution) La exuded from the electrolyte membrane 13 swollen with the plating solution L and pressurization is performed.

Next, as shown in FIG. 4, a film forming step is performed. In this step, the metal film F is formed while keeping the pressing state by means of the electrolyte membrane 13 in the pressing step. Specifically, voltage is applied between the anode 11 and the substrate B. This causes the metal ions contained in the plating solution L to pass through the electrolyte membrane 13. The metal ions that have passed through the electrolyte membrane 13 move to the surface of the substrate B via the leachate La and are reduced on the surface of the substrate B. As a result, the metal ions of the plating solution L pass through the penetrating portion 68 and the passing metal ions are deposited on the surface of the substrate B. In this manner, as shown in FIG. 2, the metal film F in the predetermined pattern P corresponding to the shape of the penetrating portion 68 can be formed on the surface of the substrate B.

In the film forming apparatus, when the cover sheet 30A is not used as the contact prevention member, the mask portion 65 is directly pressed by the electrolyte membrane 13 at the time of film forming as shown in FIG. 7, and thus, rubber particles C of the mask portion 65 adhere to the surface of the electrolyte membrane 13. When the electrolyte membrane 13 slightly stretches due to the hydraulic pressure of the plating solution L, a portion, to which the rubber particles C adhere, of the electrolyte membrane 13 deforms so as to enter the penetrating portion 68 formed in the mask portion 65. As a result, at the time of film forming, the movement of the metal ions from the penetrating portion 68 toward the substrate B is hindered by the rubber particles C that have adhered to the electrolyte membrane 13. This makes it difficult to form the metal film F in the predetermined pattern P corresponding to the shape of the penetrating portion 68 as shown in FIG. 7. In particular, when the metal film F is repeatedly formed, since the electrolyte membrane 13 stretches due to the hydraulic pressure repeatedly exerted, such a phenomenon becomes noticeable.

However, in the present embodiment, as shown in FIG. 4, the cover sheet (contact prevention member) 30A made of a resin material is disposed on the opposing surface 65c, which opposes the electrolyte membrane 13, of the surfaces of the mask portion 65. Thus, even when the electrolyte membrane 13 deforms toward the mask portion 65 due to the hydraulic pressure of the plating solution L, direct contact of the electrolyte membrane 13 with the opposing surface 65c of the mask portion 65 can be avoided. In this manner, the rubber particles derived from the rubber material of the mask portion 65 can be prevented from adhering to the electrolyte membrane 13. As a result, even when the electrolyte membrane 13 deforms due to the hydraulic pressure of the plating solution L, in the portion, which covers the penetrating portion 68 of the mask portion 65, of the electrolyte membrane 13, the movement of the metal ions is not hindered by the rubber particles. Thus, as compared to the case shown in FIG. 7, the metal film F in the predetermined pattern P can be accurately formed on the substrate B.

In particular, in the present embodiment, since the cover sheet 30A is disposed so as to cover the penetrating portion 68 of the mask portion 65, sagging or the like of the electrolyte membrane 13 deformed due to the hydraulic pressure of the plating solution L can be suppressed. Further, the hydraulic pressure can be uniformly exerted on the mask portion 65 via the electrolyte membrane 13 and the cover sheet 30A. As a result, since the mask portion 65 can be uniformly deformed, the sealing property between the mask portion 65 and the substrate B can be stably secured.

Further, since the plurality of openings 31c, through which the plating solution L penetrates, is formed in the cover sheet 30A at a position covering the penetrating portion 68, the leachate (plating solution) La exuded from the electrolyte membrane 13 is made to pass through the openings 31c of the cover sheet 30A and is enabled to be stably supplied to the penetrating portion 68. As a result, the metal film F corresponding to the pattern of the penetrating portion 68 can be stably formed on the surface of the substrate B.

Further, since the openings 31c of the mesh in the cover sheet 30A are larger than the openings 64c of the mesh in the mesh portion 64, the leachate La exuded from the electrolyte membrane 13 can be smoothly supplied through the openings of the cover sheet 30A to the penetrating portion 68 of the mask portion 65. In this manner, the metal film F corresponding to the pattern of the penetrating portion 68 can be stably formed on the surface of the substrate B.

Thereafter, the linear motion actuator 70 raises the container 15 to detach the substrate B from the electrolyte membrane 13 and the substrate B is removed from the mount base 40. Note that when a wire is manufactured with the metal film F, the conductive base layer Bb formed on the surface of the insulating board Ba of the substrate B may be etched so as to maintain a portion where the metal film F is formed.

With reference to FIG. 5 and FIG. 6, the film forming apparatus according to a modification will be described below. In the film forming apparatus of FIG. 1 to FIG. 4, the cover sheet 30A is used as the contact prevention member preventing the contact between the mask portion 65 and the electrolyte membrane 13, on the opposing surface that opposes the electrolyte membrane 13. In this modification, the mask portion 65 is provided with a resin film 30B as the contact prevention member in place of the cover sheet 30A.

In the present embodiment, the resin film 30B made of a resin material (synthetic resin) is formed so as to cover the opposing surface 65c, which opposes the electrolyte membrane 13, of the surfaces of the mask portion 65. The resin film 30B may have flexibility and is formed on the opposing surface 65c of the mask portion 65 in such a manner as described below. As one of the film forming methods, the resin film 30B may be formed on the opposing surface 65c of the mask portion 65 such that the opposing surface 65c of the mask portion 65 is coated with emulsion in which synthetic resin particles are dispersed in a liquid and is dried, for example. As another film forming method, the resin film 30B may be formed on the opposing surface 65c of the mask portion 65 such that the opposing surface 65c of the mask portion 65 is coated with an uncured resin and the coated resin is subjected to polymerization reaction. As further another film forming method, the resin film 30B may be formed by affixing, to the opposing surface 65c of the mask portion 65, a resin film in which a through-hole in the same shape as that of the predetermined pattern P is formed.

Examples of the resin of the resin film 30B may include a fluorocarbon resin such as polytetrafluoroethylene (PTFE), Poly Vinylidene DiFluoride (PVDF), Poly Chloro Tri Fluoro Ethylene (PCTFE), or perfluoroalkoxy-fluororesin (PFA). With the use of a fluorocarbon resin for the resin film 30B, the friction on the surface of the resin film 30B can be reduced. As a result, even when the electrolyte membrane 13 presses the mask portion 65 and stretches at the time of film forming repeatedly performed, the electrolyte membrane 13 can be prevented from being damaged by the resin film 30B.

Alternatively, examples of the resin of the resin film 30B may include polyether resin such as polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), or polyethylene naphthalate (PEN). With the use of a polyether resin for the resin film 30B, the flexibility of the resin film 30B can be improved. Therefore, even when the electrolyte membrane 13 presses the mask portion 65 and stretches at the time of film forming repeatedly performed, the electrolyte membrane 13 can be prevented from being damaged by the resin film 30B.

In the case of this modification also, as shown in FIG. 6, since the resin film 30B is disposed on the opposing surface 65c of the mask portion 65, adhesion of the rubber particles of the mask portion 65 to the electrolyte membrane 13 can be suppressed. Further, the leachate La exuded from the electrolyte membrane 13 is directly supplied to the penetrating portion 68 of the mask portion 65. In this manner, the metal film F in the desired pattern P can be stably formed.

EXAMPLE

A mask portion with a penetrating portion formed therein was formed on both sides of an LCP resin mesh portion having a wire diameter of 20 μm and 420 mesh, using silicone rubber. In this manner, a masking member having the mesh portion and the masking portion was produced. Note that of the thickness of the mask portion, the thickness of a first portion was 30 μm and the thickness of a second portion was 20 μm. Note that the penetrating portion included three types of widths of 100 μm, 250 μm, and 500 μm. Then, a cover sheet in an LCP resin mesh having a wire diameter of 20 μm and 420 mesh was prepared.

Next, a copper (Cu) substrate in a square having a thickness of 0.9 mm and one side length of 7.8 cm was prepared. The substrate was subjected to cathode electrolytic degreasing at 55° C. for 1 minute using an IC-200RM manufactured by JCU Corporation, and was then washed with pure water for 1 minute. Further, the substrate was immersed in a 10% dilute sulfuric acid at room temperature for 1 minute to be subjected to acid cleaning, and was then washed with pure water for 1 minute.

Thereafter, as shown in FIG. 4, a metal film having a thickness of 5 μm was formed on the surface of the substrate by solid electro deposition (SED) using a device having the same configuration as that of the film forming apparatus including the cover sheet. Specifically, prior to the film forming, the masking member was pressurized together with the cover sheet by the electrolyte membrane under conditions of pressurization of 0.6 MPa for 24 hours, and then, the film was formed under the following conditions. The film forming conditions were: film forming temperature: 42° C., plating solution: 1 mol/l copper sulfate+0.2 mol/l sulfuric acid, anode: phosphorus-containing copper plate, inter-electrode distance of anode-cathode: 2 mm, pressurization: 0.6 MPa, film forming area: 38 cm²/substrate size 61.4 cm², and current: 7 ASD.

As a comparative example, as shown in FIG. 7, film forming was performed without providing the mesh of the example under the same conditions as those of the example. The defects of the example and the comparative example in film forming were examined. As a result, no defect was found in the metal film of the example, while eight defects were found in the metal film of the comparative example. When the electrolyte membrane of the comparative example was examined, rubber particles of the mask portion adhered to the electrolyte membrane, which was confirmed to be the cause of the defects in the metal film.

The embodiment of the present disclosure has been described in detail above, but the present disclosure is not limited to the aforementioned embodiment, and various design changes can be made within the scope without departing from the spirit of the present disclosure described in the scope of the claims.

FILM FORMING APPARATUS FOR METAL FILM

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