JP2008208431A - Electroforming mold, method of manufacturing electroforming mold and method of manufacturing electroformed component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroforming mold by which a plurality of electroformed components different in thickness are manufactured without dividing the electroforming mold and each of components has an electrode on the bottom surface, and to provide a method of manufacturing the electroforming mold. <P>SOLUTION: The electroforming mold 101 includes a conductive layer 2, many resin layers which is formed on the conductive layer, an intermediate conductive film 5a interposed among the many resin layers, and a plurality of cavities having side walls each surrounded by the resin, wherein the plurality of the cavities comprises a first cavity C1 having a depth penetrating through the whole many resin layers, a second cavity C2 having a depth penetrating through a partial layers in the many resin layers and a switching cavity S having a stepwise structure in every many resin layers, the conductive layer 2 is exposed on the bottom surface of the first cavity C1, the intermediate conductive film 5a is exposed on the bottom surface of the second cavity C2, the conductive layer 2 is exposed on the bottom surface of the switching cavity S, and the intermediate conductive film 5a is exposed on each resin layer having the stepwise structure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electroforming mold used in an electroforming method, a manufacturing method thereof, and a manufacturing method of an electroformed part using the electroforming mold.

  The electroforming method is suitable for mass production and is used for manufacturing various parts. For example, a watch is manufactured by depositing a conductive film on a resin surface to which the original shape is transferred (see, for example, Patent Document 1). A heat press molding method is known as a transfer method to the original resin (see, for example, Patent Document 1). The hot press molding method is a method in which the resin is heated to a temperature equal to or higher than the glass transition point and softened, and the original shape is transferred to the resin by pressing the original. In the hot press molding method, the original shape can be transferred to a resin with dimensional accuracy on the order of nanometers.

In recent years, a mold using a silicon process has been used as a mold for manufacturing a component or mold having a minute shape. As a method for producing an electroforming mold using a silicon process, there is known a method (UV-LIGA method) in which a resist pattern is used as an electroforming mold with ultraviolet light used in a semiconductor exposure apparatus (for example, patent document). 2). The electroforming mold produced by the UV-LIGA method has no electrode on the side wall of the mold, and the electroformed product is deposited from the bottom surface of the mold. Therefore, even if a high aspect ratio structure is produced by the electroforming method, A good part free from bubbles and defects can be formed inside the casting. In addition, as described in Patent Document 2, by forming a plurality of component shapes on a single mask, various types of components can be manufactured at once, making it suitable for high-mix low-volume production. Is the method.
JP-A-52-60241 JP 2006-64575 A

  However, in Patent Document 1, an electrode is obtained by forming electrodes on all surfaces (hereinafter referred to as electroformed surfaces) on which electroforming of a resin whose shape has been transferred (hereinafter referred to as a transfer resin mold). Therefore, when electroforming is performed, the electroformed product is deposited on the entire surface on which the electrode of the electroforming mold is formed. Therefore, in order to take out the timepiece hand, it is necessary to remove unnecessary portions. In addition, when producing electroformed parts with a high aspect ratio, if electroforming is performed simultaneously from the mold side and the mold bottom, the electric field concentrates on the opposite side of the mold side to the mold bottom, that is, the mold top surface. It is easy to increase the electroforming speed on the mold upper surface side of the mold side surface. Therefore, the electroformed product deposited from the side surface of the die is connected to the upper surface portion of the die, and a gap is formed inside the electroformed product. Therefore, there is a problem that the strength and mold transferability of the electroformed part are lowered.

  In Patent Document 2, since the electrode can be formed only on the bottom surface of the electroforming mold, it is possible to manufacture an electroformed part having no gap inside the electroformed product. However, in Patent Document 2, various types of parts can be electroformed at the same time. However, since photoresists having the same thickness are used as molds, in order to obtain parts having different thicknesses, parts having the same thickness can be combined with each other. There is a problem that it is necessary to obtain a predetermined thickness by consolidating into one section and making the amount of polishing different for each section, and a step of dividing the electroforming mold for each section before polishing.

  The present invention has been made in view of the above-described problems, and it is possible to manufacture a plurality of parts having different thicknesses without dividing the electroforming mold, and to provide an electroforming mold having an electrode on the bottom surface of each part and a manufacturing method thereof. The purpose is to provide.

  In order to achieve the above object, the present invention provides a conductor, a multilayer resin formed on the conductor, an intermediate conductive film sandwiched between the multilayer resins, and a sidewall by the resin. A plurality of cavities surrounded by a plurality of cavities, wherein the plurality of cavities include a first cavity having a depth over the whole layer of the multilayer resin and a depth over a part of the layers of the multilayer resin. The second cavity and a third cavity having a step-like structure for each of the multilayer resins, and the conductor is exposed on the bottom surface of the first cavity, and the second cavity The intermediate conductive film is exposed at the bottom surface of the cavity, the conductor is exposed at the bottom surface of the third cavity, and the intermediate conductive film is formed on each layer of the resin having the stepped structure. The exposed electroforming mold was used.

  The present invention also provides an electroforming mold comprising a plurality of the second cavities, wherein the intermediate conductive film exposed to the third cavities is connected to a plurality of bottom surfaces of the second cavities. did.

  Moreover, the present invention is an electroforming mold in which a plurality of the first cavities and the second cavities are arranged.

  In the present invention, the resin has at least three layers or more and the depth of the second cavity is at least two types.

  Furthermore, the present invention is a method of manufacturing the above electroforming mold, wherein a first photoresist forming step of forming a first photoresist on a conductor, a soluble portion and an insoluble portion in the first photoresist are provided. A first exposure step to be formed; an intermediate conductive film forming step for forming an intermediate conductive film on the insoluble portion formed in the first exposure step; and a second photo on the first photoresist and the intermediate conductive film. A second photoresist forming step for forming a resist; a second exposure step for forming a soluble portion and an insoluble portion in the second photoresist and / or the first photoresist; the first exposure step; The electroforming mold manufacturing method includes a developing process for removing the soluble portion formed in the second exposure process.

  Also, the present invention provides an electroforming method in which the thickness of the first photoresist is a difference between the maximum thickness and the minimum thickness of components to be formed.

  In addition, the present invention provides an electroforming manufacturing method in which the intermediate conductive film forming step, the second photoresist forming step, and the second exposure step are repeated a plurality of times before the developing step is performed. did.

  Furthermore, the present invention is a method of manufacturing an electroformed part that produces an electroformed part using the above electroforming mold, the electroforming process for performing electroforming on the electroforming mold, and the unnecessary formation formed in the electroforming process A polishing step for removing the electroformed product, and the polishing step further controls the thickness of the parts formed on the electroforming mold without separating and dividing the electroforming mold that has been electroformed. It was set as the manufacturing method of the electroformed part which obtains different parts.

  Further, the present invention provides an electroformed component manufacturing method including a current density adjusting step of making the current density constant when the electroformed product contacts the intermediate conductive film in the electroforming step.

  In the present invention, since the second photoresist is applied onto the smooth first photoresist and the intermediate conductive film, the thickness of the second photoresist can be easily controlled. It becomes easy to define by the thickness of the first photoresist and the second photoresist, and cavities of parts having different thicknesses can be formed in one electroforming mold. In addition, the conductive layer is exposed in the deep cavity and the stepped cavity, the intermediate conductive film is provided on the first photoresist, the shallow cavity is formed thereon, and the intermediate layer is also formed on the step of the stepped cavity. By disposing the conductive film, the electroformed product can be grown only from the bottom in the shallow cavity. Therefore, parts having different thicknesses and no gaps inside can be formed in a single polishing step without dividing the electroforming mold.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a diagram for explaining an example of an electroforming mold and a manufacturing method thereof according to the present invention, and shows an example of an electroforming mold for manufacturing two types of parts having different thicknesses by an electroforming method.

  FIG. 1A is a diagram illustrating a first photoresist deposition process in which a first photoresist 3 is deposited on a substrate 1 on which a conductive layer 2 as a conductor is formed. As shown in FIG. 1A, after forming a conductive layer 2 on a substrate 1, a first photoresist 3 is deposited. The thickness of the substrate 1 is several tens of μm to several mm, and may be any thickness that can maintain the strength of the electroforming mold 101 in the electroforming process described later. The thickness of the conductive layer 2 is from several tens of nm to several μm, and may be any thickness as long as conduction can be obtained in an electroforming process described later. The thickness of the first photoresist 3 is several μm to several mm, and is almost the same as the difference in thickness between the thick part and the thin part of each part to be manufactured.

  As the material of the substrate 1, a material generally used in a silicon process such as glass or silicon, or a metal material such as stainless steel or aluminum (Al) is used. The material of the conductive layer 2 is gold (Au), silver (Ag), nickel (Ni), or the like. Chromium (Cr), titanium (Ti), or the like may be formed between the conductive layer 2 and the substrate 1 as an anchor metal (not shown) for enhancing the adhesion of the conductive layer 2. When the material of the substrate 1 is a metal, the substrate 1 itself becomes a conductor, and thus the conductive layer 2 is not always necessary. The first photoresist 3 is a negative photoresist. The first photoresist 3 may be a chemically amplified photoresist. When a high aspect ratio structure is manufactured, it is desirable to use a chemically amplified photoresist based on an epoxy resin as the first photoresist 3.

  The formation method of the conductive layer 2 is a sputtering method, a vacuum evaporation method, or the like. As a method for depositing the first photoresist 3, spin coating, dip coating, spray coating, or a sheet-like photoresist film may be attached to the substrate 1. Alternatively, a plurality of sheet-like photoresist films may be stacked to form the first photoresist 3 having a desired thickness.

  FIG. 1B is a view for explaining a first exposure step for forming the insoluble part 3a and the soluble part 3b. After depositing the first photoresist 3, as shown in FIG. 1B, the first photoresist 3 is irradiated with exposure light 999 through a mask 10 to form insoluble portions 3a and soluble portions 3b. In order to form the insoluble portion 3a and the soluble portion 3b, ultraviolet light is exposed through a photomask. When the first photoresist 3 is a chemical amplification type, PEB (Post Exposure Bake) is performed after exposure.

  Next, FIG. 1C is a diagram for explaining an intermediate conductive film forming step for forming the intermediate conductive film 5 a on the first photoresist 3. After the exposure process of the first photoresist 3 described with reference to FIG. 1B, the intermediate conductive film 5a is formed without developing the first photoresist 3. The thickness of the intermediate conductive film 5a is several nm to several μm, and may be any thickness as long as conduction can be obtained in an electroforming process described later. The material of the intermediate conductive film 5a is gold (Au), silver (Ag), nickel (Ni), copper (Cu), etc., and the adhesion of the intermediate conductive film 5a between the intermediate conductive film 5a and the insoluble portion 3a. Chromium (Cr), titanium (Ti), or the like may be formed as an anchor metal (not shown) for strengthening. The intermediate conductive film 5a is deposited using a vapor deposition method such as a sputtering method or a vacuum evaporation method, or a wet method such as electroless plating, and is patterned by a lift-off method or an etching method.

  Next, FIG. 1D is a diagram for explaining a second photoresist deposition process for depositing the second photoresist 6 on the intermediate conductive film 5a. The thickness of the second photoresist 6 is several μm to several mm, and is almost the same as the thickness of the thin part among the parts to be manufactured. Alternatively, the thickness of the second photoresist 6 may be a thickness obtained by adding the amount of removal of the second photoresist 6 in the polishing step described later in addition to the thickness of the thin component among the components to be manufactured. . The second photoresist 6 may be a negative type or a positive type. The second photoresist 6 may be a chemically amplified photoresist. In the case of producing a high aspect ratio structure, it is desirable to use a chemically amplified photoresist based on an epoxy resin as the second photoresist 6. The material of the second photoresist 6 is preferably the same as the first photoresist 3 because it can be developed with the same developer in the development process described later, but is different from the first photoresist 3. May be.

  The second photoresist 6 may be deposited by spin coating, dip coating, spray coating, or a sheet-like photoresist film. Alternatively, a plurality of sheet-like photoresist films may be stacked to form the second photoresist 6 having a desired thickness.

  Next, FIG.1 (e) is a figure explaining the 2nd exposure process which forms the insoluble part 6a, the soluble part 6b, and the insoluble part 3c. In order to form the insoluble part 6a, the soluble part 6b, and the insoluble part 3c, ultraviolet light is exposed through a photomask. When the second photoresist 6 is a chemically amplified type, PEB (Post Exposure Bake) is performed after exposure. The photomask P1 is positioned so as to cover a part of the second photoresist 6 and the soluble portion 3b that has not been exposed in the first exposure process described with reference to FIG. The photomask P2 is aligned so as to cover a part of the second photoresist 6 and the intermediate conductive film 5a. The photomask P3 is aligned so as to cover a part of the photoresist 6, a part of the intermediate conductive film 5a, and the insoluble part 3b.

  Next, FIG. 1 (f) is a diagram for explaining a developing process for removing the soluble portions 3b and 6b. The development is performed by immersing the first photoresist 3 and the second photoresist 6 in a developing solution. The electroforming mold 101 in which the first cavity C1, the second cavity C2, and the switching cavity S as the third cavity are formed is obtained by the development process.

  Next, a procedure for manufacturing an electroformed part using the electroforming mold 101 manufactured by the above manufacturing method will be described with reference to FIGS.

  FIG. 2 is a diagram for explaining an electroforming process using the electroforming mold 101. The electroforming liquid 22 is filled in the electroforming tank 21, and the electroforming mold 101 and the electrode 23 are immersed in the electroforming liquid 22. The electroforming liquid 22 varies depending on the metal to be deposited. For example, when nickel is deposited, an aqueous solution containing nickel sulfamate hydrate is used. The material of the electrode 23 is substantially the same material as the metal to be deposited. When nickel is deposited, nickel is used, and a nickel plate or a nickel basket with a nickel ball is used as the electrode 23. The material deposited by the production method of the present invention is not limited to nickel. The present invention is applicable to all materials that can be electroformed, such as copper (Cu), cobalt (Co), and tin (Sn). The conductive layer 2 of the electroforming mold 101 is connected to the power source V. When electrons are supplied through the conductive layer 2 by the voltage of the power source V, metal is gradually deposited from the conductive layer 2. The deposited metal grows in the thickness direction of the substrate 1.

  FIG. 3 is a diagram for explaining a process for producing the electroformed component 100 using the electroforming mold 101. By the electroforming process described with reference to FIG. 2, the electroformed product 100 a is deposited from the conductive layer 2 as shown in FIG. That is, the electroformed product 100a is deposited in the first cavity C1 and the switching cavity S where the conductive layer 2 is exposed on the surface. At this time, since no current flows through the intermediate conductive film 5a, the electroformed product 100a does not precipitate in the second cavity C2 on the intermediate conductive film 5a.

  Next, FIG. 3B is a diagram showing a state in which the electroformed product 100a has grown by the thickness of the insoluble portions 3a and 3c of the first photoresist 3. Until this time, since no current flows through the intermediate conductive film 5a, the electroformed product 100a does not precipitate in the second cavity C2 on the intermediate conductive film 5a.

  FIG. 3C is a diagram showing a state in which the electroformed product 100a has grown up to the middle of the thickness up to the insoluble portion 6a of the second photoresist 6. When the electroformed product 100a grows beyond the thickness of the first photoresist 3 from the state described in FIG. 3B, the electroformed product 100a grows in the lateral direction in addition to the thickness direction in the switching cavity S. The electroformed product 100a contacts the intermediate conductive film 5a. When the electroformed product 100a comes into contact with the intermediate conductive film 5a, a current also flows through the intermediate conductive film 5a. Therefore, the electroformed product 100a starts to deposit on the intermediate conductive film 5a, and the electroformed product 100a also enters the second cavity C2. The casting 100a begins to grow from the bottom surface of the second cavity C2.

  When the electroformed product 100a comes into contact with the intermediate conductive film 5a, the area to be electroformed increases. In the case of a constant voltage power supply, the current value increases, and in the case of a constant current power supply, the voltage value increases. Since the physical property values such as Young's modulus, stress, and hardness of the electroformed product 100a are greatly affected by the current density, these physical property values of the electroformed product 100a may become unstable. Therefore, in order to stabilize the physical properties of the electroformed product 100a, a current density adjusting step is performed in which the voltage and current of the power source are changed so that the current density becomes constant at the moment when the electroformed product 100a contacts the intermediate conductive film 5a. May be.

  Next, FIG.3 (d) is a figure which shows the state which deposited the electrocast 100a to desired thickness. At this time, as shown in FIG. 3D, the relative heights of the respective surfaces of the electroformed product 100a in the first cavity C1, the second cavity C2, and the switching cavity S are substantially the same. It is. This is because when the electroformed product in the first cavity C1 and the switching cavity S grows to the vicinity of the bottom surface of the second cavity C2, the electroformed product 100a in the second cavity C2 starts to grow. Because. Therefore, the amount of projection d1 of the electroformed product 100a from the surface of the electroforming mold 101 can be reduced.

  Next, FIG.3 (e) is a figure explaining the grinding | polishing process which arrange | equalizes the relative height of the electroformed product 100a of each cavity. After depositing the electroformed product 100a to a desired height, the relative heights of the electroformed products 100a of the respective cavities are aligned by a polishing process. A grinding step may be performed before the polishing step. In the electroforming process, when the thickness of the electroformed product 100a can be controlled, the polishing process may not be performed.

  Next, as shown in FIG. 3 (f), the electroformed product 100a is taken out from the electroforming mold 101, and electroformed parts PA1 and PA2 having different thicknesses are obtained. The electroformed product 100a taken out from the switching cavity S can also be used as the electroformed component PA3 having a multi-stage structure. The electroformed product 100a may be taken out by dissolving the insoluble portion 3a and the insoluble portion 6a with an organic solvent, or physically peeling the electroformed product 100a by applying a force that separates the electroformed product 100a from the substrate 1. When the conductive layer 2 and the intermediate conductive film 5a are attached to the electroformed product 100a, the conductive layer 2 and the intermediate conductive film 5a are removed using a method such as wet etching or polishing. If there is no problem even if the conductive layer 2 and the intermediate conductive film 5a are attached due to the function of the component, the conductive layer 2 and the intermediate conductive film 5a may not be removed. When the conductive layer 2 and the intermediate conductive film 5a are necessary for the function of the component, the conductive layer 2 and the intermediate conductive film 5a are not removed.

  As described above, according to the method for manufacturing an electroforming mold of the present invention, the first photoresist 3 in the first stage which is smooth and the second photoresist 6 in the second stage are applied on the intermediate conductive film 5a. It is easy to control the thickness of the second-stage second photoresist 6, and it is easy to define the thicknesses of parts having different thicknesses by the thickness of the first photoresist 3 and the second photoresist 6. Thus, cavities of parts having different thicknesses can be formed in one electroforming mold.

  Further, the conductive layer 2 is exposed in the first cavity C1 and the switching cavity S for thick parts, and an intermediate conductive film 5a is provided on the first photoresist 3 in the first stage, and for the thin parts thereon. By forming the second cavity C2 and disposing the intermediate conductive film 5a also on the step of the switching cavity S, the electroformed product 100a can be grown only from the bottom in the second cavity C2. . Therefore, parts having different thicknesses and no gaps inside can be formed in a single polishing step without dividing the electroforming mold.

  Heretofore, the electroforming mold 101 for producing two types of parts having different thicknesses, the manufacturing method thereof, and the manufacturing method of the parts using the electroformed mold 101 have been described, but FIG. 1 (f). Before the developing process described above, the intermediate photoresist film forming process described with reference to FIG. 1C to the second photoresist forming process described with reference to FIG. Different parts can be manufactured.

  FIG. 4 is a diagram showing an example of an electroforming mold capable of manufacturing three types of parts having different thicknesses as a modified example of the present invention. As shown in FIG. 4, in the electroforming mold 102, an intermediate conductive film 5b is further formed on the surface of the second photoresist 6 with respect to the electroforming mold 101, and a third cavity is formed on the intermediate conductive film 5b. A tee C3 is formed. As a result, the electroformed product 100a deposited in the first cavity C1, the electroformed product 100a deposited in the second cavity C2, and the electroformed product 100a deposited in the third cavity C3 have a thickness of each other. It can be used as an electroformed part having three different thicknesses. Further, the electroformed product 100a taken out from the switching cavity S of the electroforming mold 102 can be used as an electroformed component having a three-stage structure.

  FIG. 5 is a cross-sectional view showing an example of an electroforming mold having a plurality of first cavities C1, second cavities C2, and switching cavities S as another modification of the present invention. The electroforming mold 103 shown in FIG. 5 can be formed simply by changing the shapes of the mask 10 and the photomask P in the manufacturing process described with reference to FIG.

  Moreover, FIG. 6 is sectional drawing which shows the example of the electroforming mold which has one common switching cavity S with respect to a pair of 2nd cavity C2, as another modification of this invention. As shown in FIG. 6, in this electroforming mold 104, the intermediate conductive film 5a of the switching cavity S is connected to the intermediate conductive film 5a on the bottom surface of each of the pair of second cavities C2. Therefore, a plurality of second cavities C2 can be energized by one switching cavity S, and the number of switching cavities S in the mold can be reduced. Many C1 and 2nd cavity C2 can be arrange | positioned. FIG. 6 shows an example in which two cavities C2 are connected to one switching cavity S. However, two or more second cavities C2 are connected by two-dimensional wiring. It is possible to energize the cavity C2.

It is sectional drawing explaining the example of the electroforming mold which concerns on this invention, and its manufacturing method. It is a figure explaining the electroforming process using the electroforming mold which concerns on this invention. It is sectional drawing explaining the process of producing an electroformed component using the electroforming mold which concerns on this invention. It is sectional drawing which shows the modification of the electroforming mold which concerns on this invention. It is sectional drawing which shows the other modification of the electroforming mold which concerns on this invention. It is sectional drawing which shows the other modification of the electroforming mold which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Conductive layer 3 First photoresist 3a, 3c Insoluble part 3b Soluble part 5a Intermediate conductive film 6 Second photoresist 6a Insoluble part 6b Soluble part 101, 102, 103, 104 Electroforming mold C1 First cavity C2 Second cavity S Switching cavity PA1, PA2, PA3 Electroformed parts

Claims (9)

A conductor and a multilayer resin formed on the conductor;
An intermediate conductive film sandwiched between the multilayer resins;
A plurality of cavities each surrounded by a side wall by the resin;
The plurality of cavities include a first cavity having a depth over the entire layer of the multilayer resin, a second cavity having a depth over a part of the multilayer resin, and the multilayer cavity. It consists of a third cavity with a stepped structure for each resin,
The conductor is exposed on the bottom surface of the first cavity, the intermediate conductive film is exposed on the bottom surface of the second cavity, and the conductor is exposed on the bottom surface of the third cavity. And the intermediate conductive film is exposed on each layer of the resin having the stepped structure.   The plurality of second cavities are provided, and the intermediate conductive film exposed to the third cavity is connected to the bottom surfaces of the plurality of second cavities. The electromold described.   The electroforming mold according to claim 1 or 2, wherein a plurality of the first cavities and the second cavities are arranged.   The electroforming mold according to claim 2 or 3, wherein the resin has at least three layers and the depth of the second cavity is at least two kinds. A method for producing the electroforming mold according to any one of claims 1 to 4,
A first photoresist forming step of forming a first photoresist on the conductor;
A first exposure step of forming a soluble portion and an insoluble portion in the first photoresist;
An intermediate conductive film forming step of forming an intermediate conductive film on the insoluble portion formed in the first exposure step;
A second photoresist forming step of forming a second photoresist on the first photoresist and the intermediate conductive film;
A second exposure step of forming a soluble part and an insoluble part in the second photoresist and / or the first photoresist;
A method for producing an electroforming mold, comprising: a developing step for removing the soluble portion formed by the first exposure step and the second exposure step.   6. The method of manufacturing an electroforming mold according to claim 5, wherein the thickness of the first photoresist is a difference between the maximum thickness and the minimum thickness of components to be formed.   7. The intermediate conductive film forming step, the second photoresist forming step, and the second exposure step are repeated a plurality of times before performing the developing step. The manufacturing method of the electroforming mold as described in 2. An electroformed component manufacturing method for producing an electroformed component using the electroforming mold according to any one of claims 1 to 4,
An electroforming process for electroforming the electroforming mold;
It consists of a polishing process to remove unnecessary electroformed products formed in the electroforming process,
The polishing step further controls the thickness of the parts formed on the electroforming mold without separating and dividing the electroforming mold that has been electroformed to obtain parts having different thicknesses. A manufacturing method for parts.   9. The process for producing an electroformed part according to claim 8, wherein the electroforming step includes a current density adjusting step for making the current density constant when the electroformed product comes into contact with the intermediate conductive film. Method.

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