JP2022066011A - Film deposition method of metal plating film and film deposition apparatus - Google Patents

Abstract

To provide a film deposition method of a metal plating film capable of suppressing a breakage of a porous film, and a film deposition apparatus.SOLUTION: A film deposition method of a metal plating film according to the invention in which the metal plating film is deposited on a surface of a metal base material by a solid phase replacing type electroless plating method, includes: a preparation step of preparing a film deposition apparatus that has a housing that has at least a bottom wall and a side wall surrounding the bottom wall and an accommodation space arranged therein, a metal base material arranged on a bottom inside the housing, a porous film arranged on the surface of the metal base material, and an electroless plating liquid accommodated in the accommodation space; and a deposition step of depositing the metal plating film on the surface of the metal base material by using the film deposition apparatus, and precipitating on the surface of the metal base material by reducing a metal ion derived from the electroless plating liquid contained inside the porous film.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a metal plating film forming method and a film forming apparatus for forming a metal plating film on the surface of a metal substrate by a solid phase substitution type electroless plating method.

In recent years, in a method of forming a metal plating film on the surface of an object to be plated such as a metal base material or wiring of electronic industrial parts, the use of a large amount of plating liquid and its waste liquid have become problems. Therefore, from the viewpoint of manufacturing cost and environmental load, a solid phase method such as a solid phase electrodeposition method (SED: Solid Electro Deposition) or a solid phase electroless deposition method (SELD: Solid Electroless Deposition) is used.

In the solid phase electrodeposition method, a porous membrane such as a solid electrolyte membrane is placed between an anode and a base material serving as a cathode, the porous membrane is brought into contact with the surface of the base material, and the anode and the base material are used. This is a method of forming a metal plating film made of metal on the surface of a base material by applying a voltage between them and precipitating metal ions contained inside the porous film on the surface of the base material. On the other hand, the solid phase electroless method includes a solid phase substitution type electroless plating method and a solid phase reduction type electroless plating method. In the solid-phase electroless plating method, a substituted electroless plating solution containing ions of a first metal and a second metal (or a metal substrate) having a higher ionization tendency than the first metal are plated. A porous film is installed between the second metal). In this configuration, the ions of the first metal that have passed through the porous membrane cause a redox reaction due to the difference in ionization tendency between the second metal, which is the base metal, and the metals. As a result, the ions of the first metal are deposited on the surface of the second metal to form a metal plating film made of the first metal on the surface of the second metal. Further, in the solid phase reduction electroless plating method, a porous film is installed between the reduction electroless plating solution containing metal ions and the metal substrate. In this configuration, the metal ions that have passed through the porous film cause a redox reaction with the reducing agent contained in the reduced electroless plating solution. This is a method of forming a metal plating film on the surface of a metal substrate by precipitating metal ions on the surface of the metal substrate.

In the solid phase method such as the solid phase electrodeposition method and the solid phase electroless method, the amount of the plating solution used and the amount of the waste liquid thereof are small, so that the manufacturing cost and the environmental load can be reduced. In the conventional solid phase method, for example, as in the method for forming a metal plating film described in Patent Document 1, a porous film such as a solid electrolyte film seals the open end of a housing containing a plating solution. A film forming apparatus may be used that is attached to the film and has a structure in which the porous film is narrowed by a housing.

Japanese Unexamined Patent Publication No. 2016-23338

In the film forming apparatus having the above-mentioned structure used in the conventional solid-phase method, the porous film may be damaged due to the porous film being narrowed by the housing. In addition, the weight of the plating solution may damage the porous film. If the porous film is damaged, the plating solution leaks and the metal plating film cannot be formed. Such a problem becomes remarkable when the film forming apparatus becomes large.

The present invention has been made in view of these points, and an object of the present invention is to provide a method for forming a metal plating film and a film forming apparatus capable of suppressing damage to the porous film.

In order to solve the above problems, the method for forming a metal plating film of the present invention is a method for forming a metal plating film on the surface of a metal substrate by a solid phase displacement type electroless plating method. A housing having at least a bottom wall and a side wall surrounding the bottom wall and having a storage space inside, a metal base material arranged on the bottom surface inside the housing, and a metal base material on the surface of the metal base material. A preparatory step for preparing a film forming apparatus having the porous film arranged in the above-mentioned accommodating space and the electroless plating solution accommodated in the accommodating space, and the above-mentioned film forming apparatus are used and included inside the above-mentioned porous film. It is provided with a film forming step of forming a metal plating film on the surface of the metal substrate by precipitating the metal ions derived from the electroless plating solution on the surface of the metal substrate. It is a feature.

According to the method for forming a metal plating film of the present invention, damage to the porous film can be suppressed.

Further, the film forming apparatus of the present invention is a film forming apparatus for forming a metal plating film on the surface of a metal substrate by a solid phase displacement type electroless plating method, and surrounds at least the bottom wall and the bottom wall. A housing having a side wall and an accommodation space provided inside, a metal base material arranged on the inner bottom surface of the housing, and a porous film arranged on the surface of the metal base material, and the above-mentioned accommodation. It is characterized by being provided with a non-electrolytic plating solution housed in a space.

According to the film forming apparatus of the present invention, damage to the porous film can be suppressed.

According to the present invention, damage to the porous membrane can be suppressed.

(A) to (c) are schematic process sectional views showing a method for forming a metal plating film according to the first embodiment. (A) and (b) are schematic process sectional views which show the film forming method of the metal plating film which concerns on 2nd Embodiment. It is a schematic sectional drawing which shows the film-forming apparatus which concerns on 3rd Embodiment. (A) to (c) are schematic process sectional views showing a method for forming a metal plating film according to Example 1. Example 1 (using PTFE housing x with porous membrane) and Comparative Example 1 (using PTFE housing x without porous membrane) and Example 2 (using aluminum housing x with porous membrane) and Comparative Example 2 (aluminum). It is a graph which shows the average of the weight change before and after the film formation of 60 metal base materials in the case of using a manufacturing housing × without a porous film). Example 1 (using PTFE housing x with porous membrane) and Comparative Example 1 (using PTFE housing x without porous membrane) and Example 2 (using aluminum housing x with porous membrane) and Comparative Example 2 (aluminum). It is a graph which shows the average of the surface roughness Ra of the gold plating film of 60 metal base materials in the case of using a manufacturing housing × without a porous film).

Hereinafter, embodiments relating to the method for forming a metal plating film and the film forming apparatus of the present invention will be described. First, the first embodiment and the second embodiment will be illustrated and described about the outline of the film forming method of the metal plating film and the film forming apparatus according to the embodiment.

(First Embodiment)
The method for forming a metal plating film according to the first embodiment is a method for forming a metal plating film on the surface of a metal substrate by a solid phase displacement type electroless plating method, and the film forming apparatus according to the first embodiment. Is a film forming apparatus for using the film forming method according to the first embodiment. 1A to 1C are schematic process sectional views showing a method for forming a metal plating film according to the first embodiment.

In the method for forming a metal plating film according to the first embodiment, first, as shown in FIG. 1A, the film forming apparatus 1 according to the first embodiment is prepared (preparation step). The film forming apparatus 1 has a side wall 2sw that surrounds the bottom wall 2bw and the bottom wall 2bw, and has a housing 2 provided with a rectangular pillar-shaped accommodation space 2S having a rectangular bottom surface 2bs inside, and a bottom surface 2bs inside the housing 2. The flat metal base material 4 arranged in the above, the porous film 6 having a rectangular shape in a plan view and arranged on the surface 4s of the metal base material 4, and the surface 6s of the porous film 6 are arranged. Further, the float material 8 which is flat and has a rectangular shape in a plan view and the electroless gold plating solution L (electrolytic plating solution) accommodated in the accommodation space 2S are provided. The film forming apparatus 1 further includes a lid 10 that closes the opening 2h facing the bottom wall 2bw of the housing 2. The metal base material 4, the porous film 6, and the float material 8 are arranged in order in the vertical direction on the bottom surface 2bs inside the housing 2, are housed in the storage space 2S of the housing 2, and are electroless gold plating solutions. Immersed in L. The metal base material 4 has a nickel plating film 4n provided on the surface of a copper substrate 4c by electroless plating. The porous film 6 is not fixed anywhere and is arranged on the surface 4ns (surface 4s of the metal substrate 4) of the nickel plating film 4n of the metal substrate 4. The electroless gold plating solution contains at least a gold compound and a complexing agent. The density of the float material 8 is 1.09 times or more and 1.65 times or less the density of the electroless gold plating solution L, and the weight of the float material 8 is larger than the weight of the porous film 6. The housing 2 is made of aluminum (a metal serving as a sacrificial anode). The lid 10 is made of the same material as the housing 2.

Next, as shown in FIG. 1 (b), the film forming apparatus 1 is charged into the inner 20N of the atmospheric atmosphere held at 80 ° C. in the constant temperature bath 20. As a result, the housing 2 of the film forming apparatus 1 is uniformly heated to heat the electroless gold plating solution L, and heat convection is generated in the electroless gold plating solution L.

Next, as shown in FIG. 1 (c), the electroless gold plating solution L contained inside the porous film 6 is generated by using the film forming apparatus 1 to generate heat convection in the electroless gold plating solution L. By reducing the gold ions (metal ions) derived from the metal base material 4, the gold ions (metal ions) are deposited on the surface 4ns (surface 4s of the metal base material 4) of the nickel plating film 4n of the metal base material 4. As a result, a gold plating film M (metal plating film) is formed on the surface 4ns of the nickel plating film 4n of the metal substrate 4 (depositioning step).

According to the first embodiment, the gold plating film M can be formed by reducing and precipitating gold ions derived from the electroless gold plating solution L contained inside the porous film 6 not fixed to the housing 2. .. Therefore, the damage of the porous film 6 used in the solid phase substitution type electroless plating method can be suppressed.

Further, according to the first embodiment, the film forming apparatus 1 further includes the float material 8, and the density of the float material 8 is 1.09 times or more the density of the electroless gold plating solution L (electroless plating solution). It is 1.65 times or less, and the weight of the float material 8 is larger than the weight of the porous film 6. Therefore, when the gold ions derived from the electroless gold plating solution L contained inside the porous film 6 are reduced to precipitate on the surface 4ns of the nickel plating film 4n of the metal substrate 4, the float material 8 is absent. It is possible to make a simple vibration with an amplitude of 0.2 mm or less in the vertical direction while contacting the inner side surface 2ss of the housing 2 by the thermal convection of the electrolytic gold plating solution L. Specifically, the float material 8 is simply placed at a position separated from the surface 6s of the porous film 6 by an amplitude of 0.2 mm or less in the vertical direction as the center of vibration, and has an amplitude of 0.2 mm or less in the vertical direction. By vibrating, the float material 8 can be repeatedly contacted and separated from the surface 6s of the porous film 6. As a result, gold derived from the electroless gold plating solution L contained inside the porous film 6 in a state where the porous film 6 is brought close to the surface 4ns of the nickel plating film 4n of the metal substrate 4 without being in close contact with the surface 4ns. By reducing the ions, it can be deposited on the surface 4ns of the nickel plating film 4n of the metal substrate 4. As a result, damage to the porous film 6 due to adhesion to the metal substrate 4 can be suppressed, and a uniform gold plating film M can be formed.

Further, according to the first embodiment, the housing 2 is made of aluminum (a metal serving as a sacrificial anode). Therefore, when gold ions derived from the electroless gold plating solution L contained inside the porous film 6 are reduced to precipitate on the surface 4ns of the nickel plating film 4n of the metal substrate 4, the nickel of the copper substrate 4c is deposited. The back surface 4cr (the back surface 4r of the metal base material 4) on which the plating film 4n is not provided is in contact with the bottom surface 2bs of the housing 2 made of aluminum, which has a higher ionization tendency than copper and nickel. As a result, a local battery is formed between the nickel plating film 4n and the housing 2, and a local anode reaction of the housing 2 occurs in this local battery. As a result of the electrons generated by this reaction flowing from the housing 2 to the nickel plating film 4n via the copper substrate 4c, a local cathode reaction of gold ions on the surface 4ns of the nickel plating film 4n is induced. Along with this, the gold and nickel substitution reaction on the surface 4ns of the nickel plating film 4n is promoted, so that a more uniform and thick gold plating film M can be formed. Further, the film forming apparatus 1 further has a lid 10 for closing the opening 2h of the housing 2, and since the lid 10 is made of aluminum, the substitution reaction between gold and nickel is remarkably promoted and is more uniform. A thick gold plating film M can be formed.

(Second Embodiment)
The method for forming a metal plating film according to the second embodiment is a method for forming a metal plating film on the surface of a metal substrate by a solid phase displacement type electroless plating method, and the film forming apparatus according to the second embodiment. Is a film forming apparatus for using the film forming method according to the second embodiment. 2A and 2B are schematic process sectional views showing a method for forming a metal plating film according to a second embodiment.

In the method for forming a metal plating film according to the second embodiment, first, as shown in FIG. 2A, the film forming apparatus 1 according to the second embodiment is prepared (preparation step). The film forming apparatus 1 has a side wall 2sw that surrounds the bottom wall 2bw and the bottom wall 2bw, and has a housing 2 having a rectangular pillar-shaped accommodation space 2S having a rectangular bottom surface 2bs inside, and a bottom surface 2bs inside the housing 2. The flat metal base material 4 arranged in the metal base material 4, the porous film 6 having a rectangular shape in a plan view arranged on the surface 4s of the metal base material 4, and the electroless gold plating housed in the storage space 2S. It is provided with a liquid L (electroless plating liquid). The film forming apparatus 1 further has a lid 10 that closes the opening 2h facing the bottom wall 2bw of the housing 2. The metal base material 4 and the porous film 6 are arranged in order in the vertical direction on the bottom surface 2bs inside the housing 2, are housed in the storage space 2S of the housing 2, and are immersed in the electroless gold plating solution L. ing. The metal base material 4 has a nickel plating film 4n provided on the surface of a copper substrate 4c by electroless plating. The porous film 6 is not fixed anywhere and is arranged on the surface 4ns (surface 4s of the metal substrate 4) of the nickel plating film 4n of the metal substrate 4. The electroless gold plating solution contains at least a gold compound and a complexing agent. The temperature of the electroless gold plating solution is set to 80 ° C. The housing 2 is made of PTFE (polytetrafluoroethylene). The lid 10 is made of the same material as the housing.

Next, as shown in FIG. 2B, the film forming apparatus 1 is used to reduce the gold ions (metal ions) derived from the electroless gold plating solution L contained inside the porous film 6. It is deposited on the surface 4ns (surface 4s of the metal substrate 4) of the nickel plating film 4n of the metal substrate 4. As a result, a gold plating film M (metal plating film) is formed on the surface 4ns of the nickel plating film 4n of the metal substrate 4 (depositioning step).

According to the second embodiment, the gold plating film M can be formed by reducing and precipitating the gold ions derived from the electroless gold plating solution L contained inside the porous film 6 not fixed to the housing 2. .. Therefore, the damage of the porous film 6 used in the solid phase substitution type electroless plating method can be suppressed.

Subsequently, the details of the film forming method of the metal plating film and the configuration of the film forming apparatus according to the embodiment will be described.

1. 1. Method for forming a metal plating film The method for forming a metal plating film according to an embodiment is a method for forming a metal plating film on the surface of a metal substrate by a solid phase displacement type electroless plating method. Therefore, it has a preparation process and a film formation process. Hereinafter, the preparation process and the film forming process will be described in detail.

(1) Preparation process In the preparation process, a film forming apparatus is prepared. The film forming apparatus has at least a bottom wall and a side wall surrounding the bottom wall, and has a housing provided with a storage space inside, a metal base material arranged on the bottom surface inside the housing, and the metal base material. It has a porous film arranged on the surface of the above and an electroless plating solution accommodated in the accommodation space.

a. Housing The material constituting the housing is not particularly limited, but may be, for example, metal, resin, or the like. The housing is preferably made of a metal serving as a sacrificial anode. This is because a more uniform and thick metal plating film can be formed. The metal serving as the sacrificial anode is not particularly limited as long as it is a metal having a higher ionization tendency than the metal constituting the metal base material. For example, the metal base material has a nickel plating film provided on the surface of the copper substrate. In some cases, aluminum, iron and the like are preferable.

Since the electroless plating solution described later is stored in the storage space inside the housing, oxidation of the plating solution can be suppressed. Therefore, it is not necessary to add an oxidation inhibitor to the electroless plating solution. Further, by sealing the electroless plating solution in the housing, hydrogen can be easily eutectoided in the plating film, and as a result, the solder wettability can be improved.

As the film forming apparatus, it is preferable that the film forming apparatus further has a lid for closing the opening of the housing. Further, when the housing is made of a metal serving as a sacrificial anode, the lid is preferably made of the same material as the housing. This is because the lid functions as a sacrificial anode together with the housing, so that a more uniform and thick gold-plated film can be formed.

The shape of the housing space is not particularly limited, and examples thereof include a prism having a rectangular bottom surface and a cylinder having a circular bottom surface. The size of the bottom surface of the accommodation space is not particularly limited, but for example, when the bottom surface is rectangular, it is preferably 1 cm or more and 100 cm or less in length and 1 cm or more and 100 cm or less in width. When the bottom surface is circular, the diameter is preferably 1 cm or more and 100 cm or less. This is because the size of the bottom surface of the accommodation space is within this range, so that when the film forming apparatus has a float material, it is easy to form a uniform metal plating film. The depth of the accommodating space can be set to the depth required for accommodating the electroless plating solution having a depth required for forming a desired metal plating film.

Here, FIG. 3 is a schematic cross-sectional view showing the film forming apparatus according to the third embodiment. As the film forming apparatus, as shown in FIG. 3, it is preferable that the film forming apparatus further includes a seal 12 provided inside the housing 2. As shown in FIG. 3, the seal 12 is preferably inscribed in the inner side surface 2ss of the housing 2 and circumscribed in the outer peripheral surface 4p or the like of the metal base material 4. The constituent material of the housing 2 (a metal serving as a sacrificial anode such as aluminum) to the electroless gold plating solution L (replacement type electroless gold plating bath) interposed between the side surface 2ss of the housing 2 and the outer peripheral surface 4p of the metal base material 4. ) Is larger than the amount of metal ions eluted from the constituent material of the housing 2 into the electroless gold plating solution L on the upper side of the surface 8s of the float material 8. Therefore, the deterioration rate of the electroless gold plating solution L interposed between the side surface 2ss of the housing 2 and the outer peripheral surface 4p of the metal base material 4 is higher than that of the electroless gold plating solution L on the upper side of the surface 8s of the float material 8. fast. Further, ion-exchanged water (non-replacement type non-electrolytic gold) is filled in the region surrounded by the inner side surface 2ss of the housing 2, the seal 12, and the outer peripheral surface 4p of the metal base material 4 instead of the electroless gold plating solution L. If the metal ions of the constituent material of the housing 2 are eluted in the liquid L2 such as the plating bath), the gold plating film M can be formed on the metal substrate 4. Therefore, as shown in FIG. 3, the film forming apparatus further includes a seal 12, and ion-exchanged water is provided in a region surrounded by the inner side surface 2ss of the housing 2, the seal 12, and the outer peripheral surface 4p of the metal substrate 4. It is preferable to fill with liquid L2 such as. As a result, the amount of the electroless gold plating solution L used can be reduced.
The constituent material of the seal 12 is not particularly limited, but for example, an elastomer, a flexible polymer, a polymer foam, or the like is preferable.

b. Electroless plating solution The electroless plating solution is a plating solution used in the substitution type electroless plating method. The electroless plating solution contains, for example, a metal compound and a complexing agent, and may contain an additive if necessary. Examples of the additive include a pH buffer and a stabilizer. A commercially available plating solution may be used. The electroless plating solution is, for example, an electroless gold plating solution. Hereinafter, the electroless gold plating solution will be described in detail.

The electroless gold plating solution contains at least a gold compound and a complexing agent, and may contain an additive if necessary.

The gold compound is not particularly limited, and examples thereof include cyanide-based gold salts and non-cyanide-based gold salts. Examples of the cyanated gold salt include gold cyanide, potassium gold cyanide, sodium gold cyanide, and ammonium gold cyanide. Examples of the non-cyan gold salt include gold sulfite, gold thiosulfate, gold chloride, and gold thioapple acid. One kind of gold salt may be used alone, or two or more kinds may be used in combination. As the gold salt, it is preferable to use a non-cyan gold salt from the viewpoint of handling, environment and toxicity, and it is preferable to use a sulfite gold salt among the non-cyan gold salts. Examples of the gold sulfite salt include gold ammonium sulfite, potassium gold sulfite, sodium gold sulfite, and gold methanesulfonic acid.

The content of the gold compound in the electroless gold plating solution is preferably 0.5 g / L or more and 2.5 g / L or less, and 1.0 g / L or more and 2.0 g / L or less. More preferred. The upper limit value and the lower limit value of these numerical values can be arbitrarily combined to define a preferable range. When the gold content is 0.5 g / L or more, the gold precipitation reaction can be improved. Further, when the gold content is 2.5 g / L or less, the stability of the plating solution can be improved.

The complexing agent stably complexes gold ions (Au ⁺ ), reduces the occurrence of Au ⁺ disproportionation reaction (3Au ⁺ → Au ³⁺ + 2Au), and as a result, improves the stability of the liquid. It works. One type of complexing agent may be used alone, or two or more types may be used in combination.

Examples of the complexing agent include cyanide-based complexing agents and non-cyanide-based complexing agents. Examples of the cyanide complexing agent include sodium cyanide, potassium cyanide and the like. Examples of the non-cyan complexing agent include sulfite, thiosulfate, thiophosphate, thiocyanate, mercaptosuccinic acid, mercaptoacetic acid, 2-mercaptopropionic acid, 2-aminoethanethiol, 2-mercaptoethanol, and the like. Glucose cysteine, 1-thioglycerol, sodium mercaptopropanesulfonate, N-acetylmethionine, thiosalicylic acid, ethylenediamine tetraacetic acid (EDTA), pyrophosphate and the like can be mentioned. As the complexing agent, it is preferable to use a non-cyanide complexing agent from the viewpoint of handling, environment and toxicity, and among the non-cyanide complexing agents, sulfites are preferably used.

The content of the complexing agent in the electroless gold plating solution is preferably 1 g / L or more and 200 g / L or less, and more preferably 20 g / L or more and 50 g / L or less. The upper limit value and the lower limit value of these numerical values can be arbitrarily combined to define a preferable range. When the content of the complexing agent is 1 g / L or more, the gold complexing force is increased and the stability of the plating solution can be improved. When the content of the complexing agent is 200 g / L or less, the formation of recrystallization in the plating solution can be suppressed.

The electroless gold plating solution may contain additives as required. Examples of the additive include a pH buffering agent, a stabilizer and the like.

The pH buffer can adjust the precipitation rate to a desired value and can keep the pH of the plating solution constant. One type of pH buffer may be used alone, or two or more types may be used in combination. Examples of the pH buffer include phosphates, acetates, carbonates, boron salts, citrates, sulfates and the like.

The pH of the electroless gold plating solution is preferably 5.0 or more and 8.0 or less, more preferably 6.0 or more and 7.8 or less, and preferably 6.8 or more and 7.5 or less. Especially preferable. The upper limit value and the lower limit value of these numerical values can be arbitrarily combined to define a preferable range. When the pH is 5.0 or more, the stability of the plating solution tends to be improved. When the pH is 8.0 or less, corrosion of the metal base material as the base metal can be suppressed. The pH can be adjusted by adding, for example, potassium hydroxide, sodium hydroxide, ammonium hydroxide and the like.

Stabilizers can improve the stability of the plating solution. Examples of the stabilizer include a thiazole compound, a bipyridyl compound, a phenanthroline compound and the like.

As the electroless gold plating solution, a commercially available one may be used. Examples of commercially available products include Epitaph TDS-25 (manufactured by C. Uyemura & Co., Ltd.), Epitaph TDS-20 (manufactured by C. Uyemura & Co., Ltd.), Flash Gold (manufactured by Okuno Pharmaceutical Industry Co., Ltd.) and the like.

The depth of the electroless plating solution contained in the housing space is not particularly limited, but is preferably 0.5 cm or more and 100 cm or less, for example. This is because when the depth of the electroless plating solution is within this range, it is easy to form a uniform metal plating film when the film forming apparatus has a float material.

c. Metal base material The metal base material is composed of a metal having a greater tendency to ionize than the metal constituting the metal plating film so that a metal plating film can be formed on the surface of the metal base material by the solid phase displacement type electroless plating method. It is a thing. The metal constituting the metal base material is not particularly limited as long as it is a metal as described above, but for example, when the metal constituting the metal plating film is gold, copper, nickel, cobalt, palladium, these are used. Examples include alloys containing at least two types. Of these, nickel, nickel alloys and the like are preferable. This is because the gold plating film can be easily formed. The metal base material is not particularly limited as long as it is as described above, but for example, when the metal constituting the metal plating film is gold, a nickel plating film is provided on the surface of the copper substrate. Can be mentioned.

The metal substrate can have any shape. Examples of the shape of the metal base material include plate-like objects such as flat plates or curved plates, rod-like objects, and spherical objects. Further, the metal base material may be one that has been finely processed such as grooves and holes, and is, for example, wiring for electronic industrial parts such as a printed wiring board, an ITO board, and a ceramic IC package board. May be good. The metal base material may be a plating film formed on a product such as a resin product, a glass product, or a ceramic component.

d. Porous film The porous film can contain an electroless plating solution inside, and can be deposited on the surface of a metal substrate by reducing metal ions derived from the electroless plating solution contained inside the porous film. Anything is not particularly limited as long as it is, but one having an anionic group is preferable. When the porous membrane has an anionic group, the anionic group can capture the metal ion eluted from the metal substrate. Therefore, it is possible to prevent the electroless plating solution from being deteriorated by metal ions (for example, nickel ions) derived from the metal substrate. Further, since the porous membrane having an anionic group has hydrophilicity, the wettability of the porous membrane is improved. Therefore, the porous film having an anionic group is easy to get wet with the electroless plating solution, and the electroless plating solution can be uniformly spread on the surface of the metal substrate. As a result, the porous film having an anionic group also has the effect of being able to form a uniform metal-plated film.

The anionic group is not particularly limited, but is, for example, a sulfonic acid group, a thiosulfonic acid group (-S ₂ O ₃ H), a carboxy group, a phosphoric acid group, a phosphonic acid group, a hydroxy group, a cyano group and a thiocyano. At least one selected from the groups. These anionic groups are capable of capturing positively charged metal ions. In addition, these anionic groups can impart hydrophilicity to the porous membrane. The anionic group is preferably a sulfonic acid group or a carboxy group. In particular, a sulfonic acid group (sulfo group) is preferable because it can effectively capture nickel ions.

An anionic polymer can be used as a material for the porous membrane having an anionic group. That is, the porous membrane having an anionic group contains an anionic polymer. The anionic polymer has an anionic group (for example, the above-mentioned sulfonic acid group, thiosulfonic acid group, carboxy group, phosphoric acid group, phosphonic acid group, hydroxy group, cyano group or thiocyano group). The anionic polymer may have one kind of anionic group alone, or may have two or more kinds of anionic groups in combination. A preferred anionic group is a sulfonic acid group.

The anionic polymer is not particularly limited, but may be composed of, for example, a polymer containing a monomer having an anionic group.

Typical anionic polymers include, for example, polymers having a carboxyl group [eg, (meth) acrylic acid polymers (eg, poly (meth) acrylic acid and other (meth) acrylic acids and other copolymerizable monomers. Copolymer with), fluororesin having a carboxyl group (eg, perfluorocarboxylic acid resin, etc.)], styrene resin having a sulfonic acid group [eg, polystyrene sulfonic acid, etc.], sulfonated polyarene ether Examples thereof include based resins [for example, sulfonated polyether ketone-based resins, sulfonated polyether sulfone-based resins, etc.].

As the porous membrane, a solid electrolyte membrane having ionic conductivity is preferable among those having an anionic group. The solid electrolyte membrane has an ion cluster structure inside, and the plating solution impregnates the ion cluster structure. Since the metal ions such as gold ions in the plating solution are coordinated with the anionic groups in the solid electrolyte membrane, the metal ions are effectively diffused in the solid electrolyte membrane. Therefore, a uniform plating film can be formed by using the solid electrolyte membrane.

The solid electrolyte membrane has a porous structure (that is, an ion cluster structure), and the pores of this porous structure are very small, and the average pore diameter is, for example, 0.1 μm or more and 100 μm or less. By applying pressure, the solid electrolyte membrane can be impregnated with the electroless plating solution. Examples of the solid electrolyte membrane include ion exchange functions such as fluororesins such as Nafion (registered trademark) manufactured by DuPont, hydrocarbon resins, polyamic acid resins, and Celemion (CMV, CMD, CMF series) manufactured by Asahi Glass Co., Ltd. However, the resin is not particularly limited thereto. The solid electrolyte membrane is preferably a fluororesin having a sulfonic acid group. The fluorinated resin having a sulfonic acid group has a hydrophobic part of a fluorinated carbon skeleton and a hydrophilic part of a side chain part having a sulfonic acid group, and these parts form an ion cluster. .. The metal ions in the plating solution impregnated in the ion cluster coordinate with the sulfonic acid groups of the solid electrolyte membrane and are uniformly diffused in the solid electrolyte membrane. Further, since the solid electrolyte membrane having a sulfonic acid group has high hydrophilicity and excellent wettability, the plating solution can be easily wetted and the plating solution can be uniformly spread on the surface of the metal substrate. Therefore, a uniform plating film can be formed by using a fluororesin having a sulfonic acid group. Further, when a fluororesin having a sulfonic acid group is used, the Maxwell-Wagner effect increases the dielectric polarization generated in the diffusion layer existing between the solid electrolyte membrane and the metal substrate, and as a result, the metal ions of the metal ion are increased. High-speed transportation becomes possible. Such a fluororesin is available from DuPont under the trade name "Nafion" series and the like.

The equivalent weight (EW) of the solid electrolyte membrane is preferably 850 g / mol or more and 950 g / mol or less, and more preferably 874 g / mol or more and 909 g / mol or less. The upper limit value and the lower limit value of these numerical values can be arbitrarily combined to define a preferable range. Here, the equivalent weight is the dry mass of the solid electrolyte membrane per one equivalent of the ion exchange group. When the equivalent weight of the solid electrolyte membrane is in this range, the uniformity of the metal-plated membrane can be improved.

The method for adjusting the equivalent weight of the solid electrolyte membrane is not particularly limited, but for example, in the case of a perfluorocarbon sulfonic acid polymer, it is adjusted by changing the polymerization ratio of the vinyl fluoride ether compound and the fluoroolefin monomer. be able to. Specifically, for example, by increasing the polymerization ratio of the vinyl fluoride ether compound, the equivalent weight of the obtained solid electrolyte membrane can be reduced. Equivalent weight can be measured using the titration method.

The density of the porous film is not particularly limited, but is preferably 0.005 times or more and 0.9 times or less the density of the electroless plating solution, particularly 0.01 of the density of the electroless plating solution. It is preferably fold or more and 0.8 times or less. This is because the float material effectively realizes that the porous film is brought close to the surface of the metal base material without being brought into close contact with the surface.

The thickness of the porous membrane is preferably 10 μm or more and 200 μm or less, and more preferably 20 μm or more and 160 μm or less. The upper limit value and the lower limit value of these numerical values can be arbitrarily combined to define a preferable range. When the thickness of the porous membrane is 10 μm or more, the porous membrane is not easily torn and the durability is excellent. When the thickness of the porous film is 200 μm or less, the pressure required for the electroless plating solution to pass through the porous film can be reduced.

The shape and size of the porous film in a plan view are not particularly limited, but for example, when the shape of the accommodation space of the housing is a prism having a rectangular bottom surface, the shape of the porous film in a plan view is rectangular. The size of the porous film in a plan view is -10 mm or more in length and -10 mm or more in length of the bottom surface of the accommodation space, and -10 mm or more in width and -10 mm or more in width or less than the width of the bottom surface of the accommodation space. Is preferable. This is because it is easy to form a uniform metal plating film by operating the float material in the vertical direction while contacting the inner side surface of the housing. Examples of the size of such a porous membrane include a size of 190 mm in length × 280 mm in width × 51 μm in thickness. As for the shape and size of the porous film in a plan view, for example, when the shape of the accommodation space of the housing is a cylinder having a circular bottom surface, the shape of the porous film in a plan view is circular and porous. The size of the ply film in a plan view is preferably such that the diameter is -10 mm or more of the diameter of the bottom surface of the accommodation space and not more than the diameter of the bottom surface of the accommodation space. This is because it is easy to form a uniform metal plating film by operating the float material in the vertical direction while contacting the inner side surface of the housing.

The water contact angle of the porous membrane is preferably 15 ° or less, more preferably 13 ° or less, and even more preferably 10 ° C or less. When the range of the porous membrane is within this range, the wettability of the porous membrane can be improved.

e. The float material film forming apparatus further includes a float material arranged on the surface of the porous film, and the density of the float material is 1.09 times or more and 1.65 times the density of the electroless plating solution. It is preferable that the weight of the float material is larger than the weight of the porous membrane. When such a float material is further provided, the float material is electroless plated when the metal ions derived from the electroless plating solution contained inside the porous film are reduced to precipitate on the surface of the metal substrate. As the liquid moves due to thermal convection, the porous film becomes close to the surface of the metal substrate without being in close contact with it. As a result, by forming a sufficient diffusion layer between the metal base material and the porous membrane, gas such as hydrogen generated by the precipitation of metal ions can escape from between the metal base material and the porous membrane. A uniform metal plating film can be formed. Here, "the porous film adheres to the surface of the metal substrate" means that the total interaction energy (electric double layer repulsion and van der) between the surfaces of the porous film and the nickel plating film in the electroless gold plating solution is used. When Waals attraction sum) is a function with the surface-to-surface distance as an argument, the surface-to-surface distance is less than or equal to the distance at which the total interaction energy reaches the maximum value (energy barrier) (usually a distance of 1 nm or more and 4 nm or less). (Derjaguin, BV and Landau, L. (1941). Acta Physicochim. URSS14, 633-662). The electrostatic double layer repulsion between two charged surfaces separated by a solvent containing counterion, such as an electrolytic gold plating bath, is given by the contact value theorem, and the two surfaces are in close proximity to the electroless gold on the surface. When the plating solution density changes, solvation pressure occurs (Evans, R. and Parry, AO (1990). J. Phys.: Condens. Matter. 2, SA15-SA32.). Solvation pressure is an electroless gold plating solution density on the surface that is a vibration function over a distance between surfaces that is a multiple of the molecular diameter. When the distance between the surfaces is very small, the solvation pressure becomes a negative finite value and becomes an adhesive force. Therefore, if the distance between the surface of the porous membrane and the surface of the metal substrate is reduced, the solvation pressure becomes oscillating. Since the float material vibrates in a circle due to heat convection, if the solvation pressure and the natural period of the float material are synchronized, the adhesive force on the contact surface can be made constant.

When the density of the float material is less than the lower limit of the above range, the metal ions derived from the electroless plating solution contained inside the porous film are reduced to precipitate on the surface of the metal substrate. When the float material floats from the surface of the porous film due to the thermal convection of the electroless plating solution, there is a possibility that a portion where the metal plating film is not formed may occur. When the density of the float material exceeds the upper limit of the above range, the float is formed on the surface of the metal substrate by reducing the metal ions derived from the electroless plating solution contained inside the porous membrane. The material adheres to the porous film despite the thermal convection of the electroless plating solution, so that the porous film adheres to the surface of the metal substrate, so that sufficient diffusion is sufficient between the metal substrate and the porous film. The layer may not be formed and a uniform metal plating film may not be formed. When the weight of the float material is less than or equal to the weight of the porous membrane, the float material is used to precipitate metal ions derived from the electroless plating solution contained inside the porous membrane on the surface of the metal substrate. It becomes difficult to bring the porous film close to the surface of the metal substrate, and there is a risk that a uniform metal plating film cannot be formed.

The constituent material of the float material is not particularly limited as long as it has chemical resistance to the electroless plating solution, and may be an organic material or an inorganic material, but an organic material such as a resin is preferable. This is because it has high chemical resistance. The organic material of the float material is not particularly limited and varies depending on the type of electroless plating solution. For example, when the electroless plating solution is Epitus TDS-25 manufactured by Uemura Kogyo Co., Ltd., PA66 (Nylon 66), phenol resin, PET (polyethylene terephthalate), PVDC (polyvinylidene chloride) and the like can be mentioned.

The shape of the float material is not particularly limited as long as it can form a uniform metal plating film, and is, for example, a plate shape such as a flat plate shape or a curved plate shape. Further, the float material has holes such as through holes that make the float material irregular when it moves due to heat convection of the electroless plating solution and hinder the formation of a desired uniform metal plating film. No one is preferable. Such a hole is, for example, a hole having a hole diameter of 1 μm or more.

The thickness of the float material is preferably 0.5 mm or more and 10 mm or less, and more preferably 1.0 mm or more and 5.0 mm or less. The upper limit value and the lower limit value of these numerical values can be arbitrarily combined to define a preferable range. If the thickness of the float material is equal to or greater than the lower limit of these numerical values, it is possible to prevent the float material from being too light and making it difficult for the float material to bring the porous film close to the surface of the metal substrate. be. This is because when the thickness of the float material is not more than the upper limit of these numerical values, it is possible to prevent the float material from being too heavy and the porous film and the metal base material from adhering to each other. Therefore, if the thickness of the float material is within the numerical range, the float can sink in the liquid and vibrate without the porous membrane and the metal substrate coming into close contact with each other. Further, the shape of the float material is preferably a flat plate shape rather than a curved plate shape. In the plating liquid, the force acting on the surface of the flat plate-shaped float material is equal to the product of the pressure at the center of gravity of the surface of the float material and the area of the surface of the float material, and acts at right angles to the surface of the float material. This is because it is easy to form a uniform metal plating film.

The shape and size of the float material in a plan view are not particularly limited, but a shape and size in which the region of the porous film fits in the region of the float material when the float material and the porous film are viewed in a plan view are preferable. As for the shape and size of such a float material in a plan view, for example, when the shape of the accommodation space of the housing is a prism having a rectangular bottom surface, the shape of the float material in a plan view is rectangular and the float material. The size in a plan view is preferably -10 mm or more in length and -10 mm or more in length of the bottom surface of the accommodation space, and -10 mm or more in width and -10 mm or more in width or less than the width of the bottom surface of the accommodation space. This is because it is easy to form a uniform metal plating film by operating the float material in the vertical direction while contacting the inner side surface of the housing. Examples of the size of such a float material include a size of 195 mm in length × 282 mm in width × 2 mm in thickness. As for the shape and size of the float material in a plan view, for example, when the shape of the accommodation space of the housing is a cylinder having a circular bottom surface, the shape of the float material in a plan view is circular, and the float material is used. It is preferable that the size in a plan view is -10 mm or more in length and equal to or less than the diameter of the bottom surface of the accommodation space. This is because it is easy to form a uniform metal plating film by operating the float material in the vertical direction while contacting the inner side surface of the housing.

f. As another film forming apparatus, the electroless gold plating solution contains a gold sulfite as a gold compound and / or a sulfite as a complexing agent, and the porous film has a sulfonic acid group as an anionic group. A film is preferable. Gold sulfite and sulfite are easily impregnated in the solid electrolyte membrane having a sulfonic acid group, and gold ions are coordinated with the sulfonic acid group and effectively diffused in the solid electrolyte membrane. Therefore, gold ions are sufficiently supplied to the film-forming portion, and the plating film can be uniformly formed.

Further, as the film forming apparatus, it is preferable that the electroless gold plating solution contains a carboxyl group-containing compound as a complexing agent and the porous film is a solid electrolyte film having a carboxy group as an anionic group. Examples of the carboxyl group-containing compound include the compounds listed above, and examples thereof include mercaptosuccinic acid, acetylcysteine, and cysteine. The carboxyl group-containing compound can form a stable complex with gold ions. Further, by combining a solid electrolyte film having a carboxyl group and a gold plating solution containing a carboxyl group-containing compound, the plating solution can be stably maintained at a weak acidity, and as a result, a uniform plating film can be formed. .. Further, the carboxyl group-containing compound is easily impregnated in the solid electrolyte membrane having a carboxyl group, and the gold ion is coordinated with the carboxy group and effectively diffused in the solid electrolyte membrane. Therefore, gold ions are sufficiently supplied to the film-forming portion, and the plating film can be uniformly formed.

(2) Film formation step In the film formation step, the film forming apparatus is used to reduce the metal ions derived from the electrolytically-free plating solution contained inside the porous film to the surface of the metal substrate. By precipitating, a metal plating film is formed on the surface of the metal base material.

The plating temperature (temperature of electroless plating when forming a metal plating film) is, for example, 50 ° C. or higher and 95 ° C. or lower, preferably 60 ° C. or higher and 90 ° C. or lower. The upper limit value and the lower limit value of these numerical values can be arbitrarily combined to define a preferable range. When the plating temperature is 50 ° C. or higher, the precipitation rate of the metal plating film can be improved. Further, when the plating temperature is 95 ° C. or lower, decomposition of components in the plating solution can be suppressed. The plating time depends on the plating temperature, but is, for example, 1 to 60 minutes.

In the film forming process, by charging the film forming apparatus inside the constant temperature bath, metal ions derived from the electroless plating solution contained inside the porous film are generated while generating heat convection in the electroless plating solution. It is preferable to deposit it on the surface of the metal substrate by reducing it. This is because it is possible to suppress the intense heat convection when the electroless plating solution is heated, and to realize a uniform formation of a metal plating film. As the constant temperature bath, for example, one having an atmospheric atmosphere in which the inside is maintained at the above-mentioned plating temperature is preferable.

2. 2. The film forming apparatus according to the embodiment further includes a float material arranged on the surface of the porous film, and the density of the float material is 1.09 times or more the density of the electroless plating solution. It is 1.65 times or less, and the weight of the float material is preferably larger than the weight of the porous membrane. Further, as the film forming apparatus, it is preferable that the housing is made of a metal serving as a sacrificial anode. Among such film forming devices, it is preferable that a lid for closing the opening of the housing is further provided, and the lid is made of the same material as the housing. Further, the lid of the housing is connected to the center of gravity of the float material by a spring, and the natural circular frequency when the float material is hung in the electrolytic gold plating solution is smaller than the natural circular frequency in pure water. Then, the float material may be vibrated in a natural circle in a non-electrolytic gold plating bath.

Hereinafter, embodiments will be described with reference to examples, but the present disclosure is not limited to these examples.

[Example 1]
A film forming method for forming a gold plating film (metal plating film) on the surface of 60 metal substrates was carried out by a solid phase substitution type electroless plating method. 4 (a) to 4 (c) are schematic process sectional views showing a method for forming a metal plating film according to Example 1.

In this method of forming a gold-plated film, first, as shown in FIG. 4A, the film forming apparatus 1 was prepared (preparation step). The film forming apparatus 1 has a bottom wall 2bw and a side wall 2s that surrounds the bottom wall 2bw, is provided with an opening 2h facing the bottom wall 2bw, and is provided with a prism-shaped accommodation space 2S having a rectangular bottom surface 2bs inside. The housing 2 is provided. The film forming apparatus 1 has 60 flat metal substrates 4 arranged on the bottom surface 2bs inside the housing 2 and a planar shape arranged on the surface 4s of the 60 metal substrates 4. Is a rectangular porous film 6, a flat and planar float material 8 arranged on the surface 6s of the porous film 6, and an electroless metal housed in the accommodation space 2S of the housing 2. It includes a plating solution (electroless plating solution) L. The film forming apparatus 1 further includes a lid 10 that closes the opening 2h. The metal base material 4, the porous film 6, and the float material 8 are arranged in order in the vertical direction on the bottom surface 2bs inside the housing 2, are housed in the storage space 2S of the housing 2, and are electroless gold plating solutions. Immersed in L. The metal base material 4 has a nickel plating film 4n provided on the surface of a copper block substrate 4c by electroless plating. The porous film 6 is not fixed anywhere and is arranged on the surface 4ns (the surface 4s of the metal substrate 4) of the nickel-plated film 4n of the 60 metal substrates 4. The electroless gold plating solution contains at least a gold compound and a complexing agent. The 60 metal base materials 4 are arranged in 4 rows × 15 columns on the bottom surface 2bs inside the housing 2 when viewed in a plan view, and are arranged in one row in FIGS. 4 (a) to 4 (c). Fifteen metal substrates 4 arranged are shown. The configurations of each member and the electroless gold plating solution used in the film forming apparatus 1 are shown below.

(housing)
Constituent material: PTFE (polytetrafluoroethylene)
Storage space size: length 200 mm x width 284 mm x depth 9.2 mm

(Metal base material)
Configuration: Nickel-plated copper block copper block substrate with nickel plating film provided on the surface of the copper block substrate by electroless plating Size: Length 18 mm x Width 34.5 mm x Thickness 3 mm
Nickel plating film thickness: 80 nm
Nickel plating film formation conditions:
-Nickel plating solution: Top Nicolon TOM-LF (manufactured by Okuno Pharmaceutical Industry Co., Ltd.)
-Plating temperature: 90 ° C
・ Film formation time: 15 minutes

(Porous membrane)
Constituent material: Nafion (registered trademark) NRE-212 (manufactured by DuPont)
Size: length 190 mm x width 280 mm x thickness 51 μm [size smaller than the size of the accommodation space]
Density: 0.01 g / cm ³ [Density smaller than float material]
Weight: 5.3g [Weight smaller than float material]

(Float material)
Constituent material: PA66 (nylon 66)
Size: length 195 mm x width 282 mm x thickness 2 mm [size smaller than the size of the accommodation space]
Density: 1.13 g / cm ³ [Density higher than porous membrane]
Weight: 124 g [Weight larger than porous membrane]
Through hole: None

(Electroless gold plating solution)
Type: Epitaph TDS-25 (manufactured by C. Uyemura & Co., Ltd.)
Density: 1.04 g / cm ³
Depth: 9.2 mm [The inside of the housing was filled with an electroless gold plating bath. ]
* Epitus TDS-25 is TDS-25-M (mixture of oxalate, alkylaminophosphonic acid, alkylaminophosphonate, and water), TDS-25-A (mixture of sulfite and water), and gold sulfite. Contains sodium solution.

In this method of forming a gold-plated film, next, as shown in FIG. 4 (b), the film-forming apparatus 1 was charged into the inner 20N of the atmospheric atmosphere held at 80 ° C. in the constant temperature bath 20. As a result, the housing 2 of the film forming apparatus 1 was uniformly heated to heat the electroless gold plating solution L, and heat convection was generated in the electroless gold plating solution L.

Next, as shown in FIG. 4C, the electroless gold plating solution L contained inside the porous film 6 is generated by using the film forming apparatus 1 to generate heat convection in the electroless gold plating solution L. By reducing the gold ions (metal ions) derived from the above, the gold ions (metal ions) were deposited on the surface 4ns (the surface 4s of the metal base material 4) of the nickel plating film 4n of the 60 metal base materials 4. As a result, a gold plating film M (metal plating film) was formed on the surface 4ns of the nickel plating film 4n of the 60 metal base materials 4 (deposition step). At this time, the film forming time was set to 15 minutes, and the film forming area of each metal substrate 4 was set to 18 mm in length × 34.5 mm in width. As a result, the gold plating film M could be formed without causing damage to the porous film 6.

[Example 2]
A film forming method for forming a gold-plated film on the surface of 60 metal substrates was carried out in the same manner as in Example 1, except that a housing in which the constituent materials were changed as described below was used as the housing. As a result, a gold-plated film could be formed without causing damage to the porous film.

(housing)
Constituent material: Aluminum (A1050)

[Example 3]
A gold plating film is formed on the surface of 60 metal substrates in the same manner as in Example 2, except that the float material whose constituent material, density, and weight are changed as described below is used as the float material. The membrane method was carried out. As a result, a gold-plated film could be formed without causing damage to the porous film.

(Float material)
Constituent material: PTFE (polytetrafluoroethylene)
Density: 2.14 g / cm ³ [Density higher than porous membrane]
Weight: 235 g [Weight larger than porous membrane]

[Example 4]
A gold plating film is formed on the surface of 60 metal substrates in the same manner as in Example 2, except that the float material whose constituent material, density, and weight are changed as described below is used as the float material. The membrane method was carried out. As a result, a gold-plated film could be formed without causing damage to the porous film.

(Float material)
Constituent material: PP (polypropylene)
Density: 0.90 g / cm ³ [Density higher than porous membrane]
Weight: 99.0 g [Weight larger than porous membrane]

[Example 5]
A gold plating film is formed on the surface of 60 metal substrates in the same manner as in Example 2, except that the float material whose constituent material, density, and weight are changed as described below is used as the float material. The membrane method was carried out. As a result, a gold-plated film could be formed without causing damage to the porous film.

(Float material)
Constituent material: Phenol resin Density: 1.21 g / cm ³ [Density higher than porous membrane]
Weight: 133 g [Weight larger than porous membrane]

[Example 6]
A gold plating film is formed on the surface of 60 metal substrates in the same manner as in Example 2, except that the float material whose constituent material, density, and weight are changed as described below is used as the float material. The membrane method was carried out. As a result, a gold-plated film could be formed without causing damage to the porous film.

(Float material)
Constituent material: PET (polyethylene terephthalate)
Density: 1.34 g / cm ³ [Density higher than porous membrane]
Weight: 147g [Weight larger than porous membrane]

[Example 7]
A gold plating film is formed on the surface of 60 metal substrates in the same manner as in Example 2, except that the float material whose constituent material, density, and weight are changed as described below is used as the float material. The membrane method was carried out. As a result, a gold-plated film could be formed without causing damage to the porous film.

(Float material)
Constituent material: PVDC (polyvinylidene chloride)
Density: 1.72 g / cm ³ [Density higher than porous membrane]
Weight: 189 g [Weight larger than porous membrane]

[Comparative Example 1]
First, the porous film 6 is not provided, and the float material 8 is arranged on the surface 4s of the 60 metal base materials 4 without interposing the porous film 6, and the metal base material 4 and the float material 8 are arranged. Example 1 except that they are arranged in order in the vertical direction on the bottom surface 2bs inside the housing 2, are housed in the storage space 2S of the housing 2, and are immersed in the electroless gold plating solution L. The same film forming apparatus 1 as above was prepared (preparation step).

Next, the film forming apparatus 1 was charged into the inner 20N of the atmospheric atmosphere held at 80 ° C. in the constant temperature bath 20. As a result, the housing 2 of the film forming apparatus 1 was uniformly heated to heat the electroless gold plating solution L, and heat convection was generated in the electroless gold plating solution L.

Next, using the film forming apparatus 1, gold ions (metal ions) derived from the electroless gold plating solution L, which is supplied without passing through the porous film while generating heat convection in the electroless gold plating solution L, are used. Was reduced to cause precipitation on the surface 4ns (surface 4s of the metal substrate 4) of the nickel plating film 4n of the 60 metal substrate 4. As a result, a gold plating film M (metal plating film) was formed on the surface 4ns of the nickel plating film 4n of the 60 metal base materials 4 (deposition step). At this time, the film forming time and the film forming area of each metal base material were the same as in Example 1. As a result, the gold plating film M could be formed.

[Comparative Example 2]
A film forming method for forming a gold-plated film on the surface of 60 metal substrates was carried out in the same manner as in Comparative Example 1, except that a housing in which the constituent materials were changed as described below was used as the housing. As a result, a gold plating film could be formed.

(housing)
Constituent material: Aluminum (A1050)

<< Evaluation of the effect on film formation of the housing constituent materials and the presence or absence of the arrangement of the porous film >>
In the substitutional electroless plating method, when a metal plating film is formed on the surface of a metal substrate in a state where the metal substrate is in contact with a dissimilar material, it is formed between the metal substrate and the dissimilar material. The current density changes according to the electroplating power of the local battery, and the film formation is affected. The current density depends on the type, contact area, and weight of the dissimilar materials that the metal substrate is in contact with. Therefore, in the method for forming a gold-plated film according to the examples and comparative examples, the current density changes depending on the type of the constituent material of the housing with which the metal base material is brought into contact during the film formation, and the film formation has an influence. receive. Hereinafter, in the method for forming a gold-plated film according to Examples and Comparative Examples, the influence on the film formation of the constituent material of the housing in which the metal base material is brought into contact during the film formation, together with the influence of the presence or absence of the arrangement of the porous film. The evaluation result will be described.

[Evaluation of the morphology of the gold-plated film]
Regarding the form of the gold-plated film formed on the surface of the nickel-plated film of 60 metal substrates in Example 1 and Comparative Example 1 and Example 2 and Comparative Example 2, a digital microscope (VH- manufactured by Keyence Co., Ltd.) 8000) was used for evaluation. As a result, it was found that in Example 1 and Comparative Example 1 using the PTFE housing, there were many portions where the gold plating film was not formed on the 60 metal substrates. On the other hand, in Example 2 and Comparative Example 2 using the aluminum housing, there were few parts where the gold plating film was not formed on the 60 metal substrates. Further, when these Examples 2 and Comparative Examples 2 are compared, in Example 2 in which the porous film is arranged on the surface of the metal base material and the float material is arranged on the surface of the porous film, each metal is arranged. It was found that a uniform metal plating film could be formed on the substrate. If a uniform metal plating film can be formed by one treatment, the yield can be improved and the cost can be reduced.

[Evaluation of the weight of the gold plating film]
In Example 1 and Comparative Example 1, and in Example 2 and Comparative Example 2, the weights of 60 metal substrates before and after film formation were measured, and the weight of the gold plating film was evaluated from the weight change before and after film formation. Further, the average of the weight changes before and after the film formation of 60 metal substrates was calculated, and the average weight of the gold plating film was evaluated from the average of the weight changes before and after the film formation. FIG. 5 shows Example 1 (using a PTFE housing × with a porous membrane), Comparative Example 1 (using a PTFE housing × without a porous membrane), and Example 2 (using an aluminum housing × with a porous membrane) and comparison. It is a graph which shows the average of the weight change before and after film formation of 60 metal substrates in Example 2 (using an aluminum housing × without a porous film).

As shown in FIG. 5, the average of the weight changes before and after film formation in Example 2 and Comparative Example 2 using the aluminum housing is the weight before and after film formation in Example 1 and Comparative Example 1 using the PTFE housing. It was larger than the average of the changes. Further, comparing Example 1 and Comparative Example 1 using the PTFE housing, the average weight change in Example 1 in which the porous film was arranged was the film formation in Comparative Example 1 in which the porous film was not arranged. The average weight change before and after was smaller than that. Further, when comparing Example 2 and Comparative Example 2 using the aluminum housing, the average weight change in Example 2 in which the porous film was arranged was the film formation of Comparative Example 2 in which the porous film was not arranged. The average weight change before and after was smaller than that.

From the above results, in Example 2 and Comparative Example 2 using the aluminum housing, the aluminum constituting the housing functions as a sacrificial anode to increase the current density, thereby promoting the substitution reaction of gold and nickel. It is considered that the weight of the gold plating film has increased. Further, in Comparative Example 1 and Comparative Example 2 in which the porous film was not arranged, a large amount of electroless gold plating solution was supplied to the surface of the nickel plating film of the metal substrate by thermal convection, so that gold and nickel were used. It is considered that the substitution reaction occurred remarkably and the weight of the gold plating film increased. When the weight of the metal plating film such as the gold plating film increases, the film formation speed of the metal plating film is improved, so that mass production of the product using the metal plating film in a short time can be realized.

[Evaluation of surface roughness of gold-plated film]
In Example 1 and Comparative Example 1 and Example 2 and Comparative Example 2, the surface roughness measuring machine (surface roughness Ra) of the gold plating film formed on the surface of the nickel plating film of 60 metal substrates was used. It was measured from the cross-sectional curve of the surface of the gold plating film using SURFCOM 1400G25) manufactured by Tokyo Precision Co., Ltd. Further, the average surface roughness Ra of the gold-plated coatings of 60 metal substrates was calculated. FIG. 6 shows Example 1 (using a PTFE housing × with a porous membrane), Comparative Example 1 (using a PTFE housing × without a porous membrane), and Example 2 (using an aluminum housing × with a porous membrane) and comparison. It is a graph which shows the average of the surface roughness Ra of the gold plating film of 60 metal base materials in Example 2 (using an aluminum housing × without a porous film).

As shown in FIG. 6, the surface roughness Ra of the gold-plated film in Example 2 and Comparative Example 2 using the aluminum housing is the surface roughness Ra of the gold-plated film in Example 1 and Comparative Example 1 using the PTFE housing. It tended to be lower than the roughness Ra. Comparing Example 1 and Comparative Example 1 using the PTFE housing, the surface roughness Ra of the gold-plated film in Example 1 in which the porous film was arranged was Comparative Example in which the porous film was not arranged. The surface roughness Ra of the gold plating film in No. 1 was lower than that of Ra. Further, comparing Example 2 and Comparative Example 2 using the aluminum housing, the surface roughness Ra of the gold-plated film in Example 2 in which the porous film was arranged was Comparative Example in which the porous film was not arranged. The surface roughness Ra of the gold plating film in No. 2 was lower than that of Ra.

From the above results, in Example 2 and Comparative Example 2 using the aluminum housing, the aluminum constituting the housing functions as a sacrificial anode to increase the current density, so that the gold and nickel substitution reaction becomes uniform. It is considered that the gold plating film was uniformly formed. Further, in Comparative Example 1 and Comparative Example 2 in which the porous film was not arranged, a large amount of electroless gold plating solution was supplied to the surface of the nickel plating film of the metal substrate by thermal convection, so that gold and nickel were used. It is probable that the substitution reaction did not occur uniformly and the gold plating film was not uniformly formed. When the surface roughness of a metal plating film such as a gold plating film is reduced, the wettability of solder to the surface of the metal plating film is improved, so that the number of initial failures of electronic parts using the metal plating film is increased. Reduction can be realized.

<< Evaluation of the effect of the composition of the float material on the film formation >>
The influence of the structure of the float material on the film formation in the gold plating film film forming method according to Examples 2 to 7 was evaluated. Specifically, in the method for forming a gold-plated film according to Examples 2 to 7, the movement and action of the float material in the film-forming process are evaluated, and the nickel-plated film of 60 metal substrates is used. The morphology of the gold-plated film formed on the surface was evaluated using a digital microscope (VH-8000 manufactured by Keyence Co., Ltd.). Then, from those evaluation results, the influence of the composition of the float material on the film formation was evaluated.

In the film forming step in the film forming method according to Example 2, the float material (constituent material: PA66, density: 1.13 g / cm ³ ) comes into contact with the inner side surface of the housing by the thermal convection of the electrolytic gold plating solution. However, the surface of the porous membrane is subjected to simple vibration with an amplitude of 0.2 mm in the vertical direction, with the position separated from the surface of the porous membrane by a distance of 0.2 mm in the vertical direction as the center of vibration. The contact and separation of the float material were repeated. Along with this, the porous film was in a state of being close to the surface of the nickel-plated film of 60 metal substrates without being in close contact with the surface. As a result, a diffusion layer sufficient to allow gas such as hydrogen generated by the precipitation of metal ions to escape was formed between the metal substrate and the porous film. Then, a uniform gold plating film was formed on the surface of the nickel plating film of 60 metal substrates.

On the other hand, in the film forming step in the film forming method according to Example 3, the float material (constituent material: PTFE, density: 2.14 g / cm ³ ) is porous despite the thermal convection of the electroless gold plating solution. It adhered to the membrane. Along with this, the porous film adhered to the surface of the nickel-plated film of the 60 metal substrates, so that a sufficient diffusion layer was not formed between the metal substrate and the porous film. Then, bubble marks were generated in a part of the gold plating film formed on the surface of the nickel plating film of 60 metal substrates. On the other hand, in the film forming step in the film forming method according to Example 4, the float material (constituent material: PP, density: 0.90 g / cm ³ ) floats from the surface of the porous film by the thermal convection of the electroless gold plating solution. bottom. Then, a portion where the gold plating film was not formed was formed on the surface of the nickel plating film of the 60 metal substrates.

Further, in the film forming step in the film forming method according to Examples 5 to 7, the float material of Example 5 (constituent material: phenol resin, density: 1.21 g / cm ³ ) and the float material of Example 6 (constituent material). : PET, density: 1.34 g / cm ³ ), and the float material of Example 7 (constituent material: PVDC, density: 1.72 g / cm ³ ) are all of the housing due to the thermal convection of the electroless gold plating solution. By making a simple vibration with an amplitude of 0.2 mm or less in the vertical direction, with the position separated by a distance of 0.2 mm or less in the vertical direction from the surface of the porous film as the center of vibration while contacting the inner side surface. , The contact and separation of the float material to the surface of the porous film was repeated. Along with this, the porous film is in a state of being close to the surface of the nickel-plated film of 60 metal substrates without being in close contact with the surface. As a result, a sufficient diffusion layer was formed between the metal substrate and the porous film. Then, a uniform gold plating film was formed on the surface of the nickel plating film of 60 metal substrates.

From the above results, it is preferable to use a float material having a density of 1.13 g / cm ³ or more and 1.72 g / cm ³ or less, a weight larger than that of the porous membrane, and no through holes. found. Since the float material does not have through holes, the resistance due to the electroless gold plating solution is uniformly applied to the float material, so that it is considered that the float material can undergo simple vibration.

Although the embodiments according to the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various aspects are described within the scope of the claims as long as the spirit of the present invention is not deviated. It is possible to make design changes.

1 Film forming device 2 Housing 2S Accommodation space 2h Opening 4 Metal substrate 4c Copper substrate (copper block substrate)
4n Nickel plating film 6 Porous film 8 Float material 10 Lid 12 Seal 20 Constant temperature bath L Electroless gold plating solution (electroless plating solution)
L2 Liquid M Gold plating film (metal plating film)

Claims (8)

It is a method of forming a metal plating film on the surface of a metal substrate by a solid phase substitution type electroless plating method.
A housing having at least a bottom wall and a side wall surrounding the bottom wall and having a storage space inside, a metal base material arranged on the bottom surface inside the housing, and an arrangement on the surface of the metal base material. A preparatory step for preparing a film forming apparatus having the formed porous film and the electroless plating solution accommodated in the accommodation space.
Using the film forming apparatus, the metal ions derived from the electrolytic plating solution contained inside the porous film are reduced to precipitate on the surface of the metal substrate, whereby the surface of the metal substrate is formed. A method for forming a metal plating film, which comprises a film forming process for forming a metal plating film. The film forming apparatus further includes a float material disposed on the surface of the porous film.
The density of the float material is 1.09 times or more and 1.65 times or less the density of the electroless plating solution.
The method for forming a metal plating film according to claim 1, wherein the weight of the float material is larger than the weight of the porous film. The method for forming a metal plating film according to claim 1 or 2, wherein the housing is made of a metal serving as a sacrificial anode. The film forming apparatus further has a lid that closes the opening of the housing.
The method for forming a metal plating film according to claim 3, wherein the lid is made of the same material as the housing. It is a film forming apparatus for forming a metal plating film on the surface of a metal substrate by a solid phase substitution type electroless plating method.
A housing having at least a bottom wall and a side wall surrounding the bottom wall and having a storage space inside, a metal base material arranged on the bottom surface inside the housing, and an arrangement on the surface of the metal base material. A film forming apparatus comprising the porous film formed and the electroless plating solution accommodated in the accommodation space. Further provided with a float material disposed on the surface of the porous membrane,
The density of the float material is 1.09 times or more and 1.65 times or less the density of the electroless plating solution.
The film forming apparatus according to claim 5, wherein the weight of the float material is larger than the weight of the porous film. The film forming apparatus according to claim 5 or 6, wherein the housing is made of a metal serving as a sacrificial anode. Further provided with a lid to close the opening of the housing
The film forming apparatus according to claim 7, wherein the lid is made of the same material as the housing.

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