Method of pretreating electrolyte film

Abstract

To provide a method of pretreating an electrolyte film suitable for forming a metallic film.SOLUTION: There is provided a method of pretreating an electrolyte film 13 to be used in a film forming device 1 for forming a metallic film F on a base material B. The electrolyte film 13 is attached to a device body 1A of the film forming device 1, and is used upon forming the metallic film F on the base material B by electrolytic plating in a state of contacting with the base material B. The pretreatment method includes a swelling step S2 of swelling the electrolyte film 13 by heating the electrolyte film 13 under a humidified atmosphere, and a storage step S4 of immersing the swollen electrolyte film 13 in pure water W to store the electrolyte film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for pretreating an electrolyte membrane used in a membrane forming apparatus that forms a metal film on a substrate. [Background technology]

[0002] As an example of this type of technology, Patent Document 1 proposes a film formation device for forming a metal film on a substrate. The film formation device is equipped with an electrolyte membrane, and forms a metal film on the substrate by electroplating with the electrolyte membrane in contact with the substrate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-122377 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the electrolyte membrane used in the film forming apparatus may be boiled in a boiling liquid such as pure water before being attached to the main body of the film forming apparatus, which causes the electrolyte membrane to swell in the boiling liquid and allows metal ions in the plating solution to pass through during electroplating.

[0005] However, when an electrolyte membrane is boiled in a boiling solution with air dissolved therein adhering to the membrane, the swelling state of the adhering air portion may differ from that of other portions due to temperature variations. As a result, the permeability of the metal ions forming the electrolyte membrane varies, making it difficult to consistently produce a metal coating with a uniform thickness. In particular, it is difficult to determine the swelling state of the electrolyte membrane from its appearance, and it is difficult to determine from the appearance of the electrolyte membrane whether the electrolyte membrane was boiled under appropriate boiling conditions.

[0006] The present invention has been made in view of the above points, and has as its object to provide a method for pretreating an electrolyte membrane suitable for forming a metal film. [Means for solving the problem]

[0007] In view of the above-described problems, the pretreatment method for an electrolyte membrane according to the present invention is a pretreatment method for an electrolyte membrane used in a film-forming apparatus that forms a metal film on a substrate, wherein the electrolyte membrane is attached to the main body of the film-forming apparatus and is used when forming the metal film on the substrate by electrolytic plating while in contact with the substrate, and the pretreatment method is characterized by including a swelling step of heating the electrolyte membrane in a humidified atmosphere to cause the electrolyte membrane to swell, and a storage step of immersing the swollen electrolyte membrane in pure water and storing the electrolyte membrane.

[0008] In a preferred embodiment, the method further comprises a step of immersing the electrolyte membrane in pure water before the swelling step. In another preferred embodiment, the method further comprises a step of cooling the swollen electrolyte membrane in the humidified atmosphere after the swelling step and before the storage step. [Effects of the Invention]

[0009] According to the present invention, in the swelling step, the electrolyte membrane is heated in a humidified atmosphere, whereby moisture in the air is uniformly adsorbed onto the electrolyte membrane, and the adsorbed moisture causes the electrolyte membrane to swell uniformly. In this way, in the storage step, the electrolyte membrane is immersed in pure water, whereby the electrolyte membrane can be maintained in a swollen state. The stored electrolyte membrane is attached to the main body of the membrane-forming apparatus. During membrane formation, with the uniformly swollen electrolyte membrane in contact with the substrate, electroplating allows metal ions in the plating solution to uniformly permeate the electrolyte membrane, thereby forming a uniform metal coating. [Brief explanation of the drawings]

[0010] [Figure 1]1 is a flow diagram including a method for pretreating an electrolyte membrane according to an embodiment of the present invention. [Figure 2] 1. (a) is a perspective view showing the state in which the electrolyte membrane is attached to the frame, and (b) is a schematic view for explaining the immersion step and the storage step shown in FIG. [Figure 3] FIG. 2 is a schematic diagram for explaining the swelling step shown in FIG. [Figure 4] 2(a) is a diagram for explaining the attachment step shown in FIG. 1, and FIG. 2(b) is a diagram for explaining the film formation step shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] A method for pretreating an electrolyte membrane and a method for forming a metal coating using the pretreated electrolyte membrane will be described below with reference to FIGS. 1 to 4. The pretreatment method according to this embodiment is a method for pretreating an electrolyte membrane 13 used in a film formation apparatus 1 that forms a metal coating F on a substrate B. The electrolyte membrane 13 is attached to the apparatus body 1A of the film formation apparatus 1 and is used when forming the metal coating F on the substrate B by electrolytic plating while being in contact with the surface Ba of the substrate B (see FIGS. 4(a) and (b)).

[0012] In this embodiment, the pretreatment method for the electrolyte membrane 13 corresponds to the immersion step S1 to the storage step S4 shown in Fig. 1, and this pretreatment method is performed in a state where the electrolyte membrane 13 is attached to a frame 40, as shown in Fig. 2(a). The frame 40 is rectangular parallelepiped-shaped and has four support columns 41. The support columns 41 are connected to each other by an upper long frame 42, an upper short frame 43, a lower long frame 44, and a lower short frame 45.

[0013] In this embodiment, the electrolyte membranes 13 are attached inside the frame 40 at intervals in the longitudinal direction of the frame 40. Specifically, each electrolyte membrane 13 is attached to a pair of upper long frames 42, 42 and a pair of lower long frames 44, 44 with clips or the like. In this case, it is desirable that the electrolyte membrane 13 be attached to the frame 40 so that no tension other than its own weight is generated in the electrolyte membrane 13 (so that creep strain is not generated in the electrolyte membrane 13).

[0014] In this embodiment, the electrolyte membrane 13 is in a dry state (not swollen). The electrolyte membrane 13 is an electrolyte membrane (ion exchange membrane) that allows metal ions to pass through, and examples of the electrolyte membrane 13 include, but are not limited to, fluorine-based resins such as Nafion (registered trademark) manufactured by DuPont, hydrocarbon-based resins, polyamic acid resins, and polymer resins with ion exchange function such as Selemion (CMV, CMD, CMF series) manufactured by Asahi Glass Co., Ltd. The membrane thickness of the electrolyte membrane 13 is preferably 5 μm or more and 200 μm or less, and more preferably 20 μm or more and 160 μm or less.

[0015] In this embodiment, first, as shown in FIG. 1, in an immersion step S1, the electrolyte membrane 13 is immersed in pure water W. Specifically, as shown in FIG. 2(b), a plurality of electrolyte membranes 13 attached to a frame 40 are immersed in pure water W contained in a glass water tank 20. The pure water W is preferably water controlled to have a conductivity of 3 μS / cm or less. This makes it possible to prevent impurity ions contained in the pure water W from adhering to the electrolyte membrane 13. The immersion time of the electrolyte membrane 13 is preferably, for example, 1 hour to 24 hours, and the electrolyte membrane 13 is preferably immersed in the pure water W until the pure water W penetrates into the fine pores formed in the electrolyte membrane 13. The temperature of the pure water W is, for example, room temperature, and the pure water W is in an unheated state.

[0016] Next, as shown in Fig. 1, in a swelling step S2, the electrolyte membrane 13 is heated in a humidified atmosphere to swell the electrolyte membrane 13. Specifically, as shown in Fig. 3, a plurality of electrolyte membranes 13 attached to a frame 40 are placed in a chamber 60A of a humidifier 60. A hygrometer 63 and a thermometer 66 are attached to the chamber 60A to measure the humidity and temperature within the chamber 60A.

[0017] The humidity signal measured by the hygrometer 63 is sent to the humidifier 61 and the fan 62. Based on the humidity signal, the humidifier 61 vaporizes or mists the pure water W so that the atmosphere in the chamber 60A reaches a predetermined humidity level, and the fan 62 supplies the vaporized or misted pure water W together with air as humid air A into the chamber 60A. This allows the humid air A to be supplied into the chamber 60A, and the humidity in the chamber 60A can be maintained at a predetermined humidity level. The humidifier 61 may be a heating or ultrasonic humidifier, and is not particularly limited as long as it can vaporize or mist the pure water and humidify the interior of the chamber 60A.

[0018] Meanwhile, a temperature signal measured by the thermometer 66 is sent to the control unit 65a of the heating device 65. Based on the temperature signal, the control unit 65a controls the heater 65b to generate heat so that the atmosphere in the chamber 60A reaches a predetermined temperature. This heats the humid air A in the chamber 60A to the predetermined temperature. In this embodiment, an electric heater is disposed in the chamber 60A as the heater 65b, but the heating method of the chamber 60A and the position where the heater is disposed are not particularly limited as long as the atmosphere in the chamber 60A can be heated to the predetermined temperature.

[0019] On the premise that electrolyte membrane 13 will swell with moisture and the like from humid air A, the humidity and temperature within chamber 60A and the time for which electrolyte membrane 13 is placed (treatment time) are set depending on the material and thickness of electrolyte membrane 13. For example, the relative humidity within chamber 60A is preferably 90% Rh or higher, the temperature within chamber 60A is preferably 70°C to 95°C, and the time for which electrolyte membrane 13 is placed (treatment time) is preferably in the range of 30 minutes to 8 hours.

[0020] In this way, in the swelling step S2, by heating the electrolyte membrane 13 in a humidified atmosphere, moisture in the air is uniformly adsorbed onto the electrolyte membrane 13, and the adsorbed moisture and heat cause the electrolyte membrane 13 to absorb moisture, thereby uniformly swelling the electrolyte membrane 13. In particular, in this embodiment, by performing the immersion step S1, the pure water W can be uniformly adhered to the electrolyte membrane 13, thereby further enhancing this effect.

[0021] 1, after the swelling step S2 and before the storage step S4, which will be described later, in a cooling step S3, the swollen electrolyte membranes 13 are cooled in a humidified atmosphere. Specifically, as shown in FIG. 3, with a plurality of swollen electrolyte membranes 13 placed in a chamber 60A of a humidifier 60, heating by the heater 65 is stopped, a valve 67 is opened, and the operation of the humidifier 61 and the fan 62 is continued. As a result, the heated moist air A in the chamber 60A is discharged through the valve 67, and the electrolyte membranes 13 are cooled by the moist air A sent from the humidifier 61 and the fan 62 into the chamber 60A. In this way, the swollen state of the electrolyte membranes 13 can be maintained, thereby reducing shrinkage of the electrolyte membranes 13 due to drying.

[0022] 1, in a storage step S4, the swollen electrolyte membrane 13 is immersed in pure water W to store the electrolyte membrane 13. Specifically, as shown in FIG. 2(b), the plurality of electrolyte membranes 13 are quickly removed from the chamber 60A together with the frame 40, and are immersed in pure water W contained in the water tank 20. By immersing the swollen electrolyte membrane 13 in pure water, shrinkage of the electrolyte membrane 13 due to drying can be suppressed, and the swollen state of the electrolyte membrane 13 can be maintained in the water tank 20.

[0023] 1, in an attachment step S5, the electrolyte membrane 13 is attached to the apparatus body 1A of the film formation apparatus 1. Specifically, as shown in FIG. 4, the film formation apparatus 1 includes the apparatus body 1A including the anode 11 and a container 15 that contains the anode 11 and the plating solution L. The film formation apparatus 1 further includes a power source 14 that applies a voltage between the anode 11 and the substrate B, a mounting table 80 on which the substrate B is placed, and a linear actuator 70 that raises and lowers the container 15.

[0024] The linear actuator 70 moves the rod 72 linearly to raise and lower the housing 15 so that the electrolyte membrane 13 and the substrate B can be moved toward and away from each other. The linear actuator 70 has a rod 72 that moves linearly relative to a main body 71, and the housing 15 is fixed to the tip of the rod 72.

[0025] The container 15 has a storage space 15a formed therein for storing the plating solution L. The anode 11 is disposed in the storage space 15a of the container 15. An opening 15d is formed on the substrate B side of the storage space 15a. With the opening 15d of the container 15 covered with the electrolyte membrane 13, the frame 17 is fitted into the container 15, thereby attaching the electrolyte membrane 13 to the device main body 1A. As a result, with the plating solution L stored in the storage space 15a, the plating solution L is sealed by the electrolyte membrane 13.

[0026] The container 15 has a supply port 15b for supplying the plating solution L to the container space 15a and a discharge port 15c for discharging the plating solution L from the container space 15a. The supply port 15b and the discharge port 15c are formed on either side of the container space 15a. The supply port 15b is fluidly connected to a supply pipe 51. The discharge port 15c is fluidly connected to a discharge pipe 52.

[0027] The film forming apparatus 1 further includes a tank 58, a supply pipe 51, a discharge pipe 52, and a circulation pump 59. The tank 58 contains a plating solution L. The supply pipe 51 connects the tank 58 to the accommodation body 15, and the supply pipe 51 is provided with the circulation pump 59. The discharge pipe 52 connects the tank 58 to the accommodation body 15, and the discharge pipe 52 is provided with a pressure adjustment valve 54. The pressure adjustment valve 54 adjusts the pressure (liquid pressure) of the plating solution L in the accommodation space 15a to a predetermined pressure.

[0028] In this embodiment, by driving the circulation pump 59, the plating solution L is sucked from the tank 58 into the supply pipe 51 and then pumped from the supply port 15b to the accommodation space 15a. The plating solution L in the accommodation space 15a is returned to the tank 58 through the discharge port 15c. This completes the circulation path 50.

[0029] Here, the substrate B functions as a cathode. The material of the substrate B is not particularly limited as long as it functions as a cathode (i.e., a surface having electrical conductivity). The substrate B may be made of a metal material such as aluminum or copper.

[0030] The plating solution L is a solution containing the metal of the metal coating to be formed in an ionic state. Examples of such metals include copper, nickel, gold, silver, and iron. The plating solution L is a solution in which these metals are dissolved (ionized) with an acid such as nitric acid, phosphoric acid, succinic acid, sulfuric acid, or pyrophosphoric acid. Examples of the solvent for the solution include water and alcohol. For example, when the metal is copper, the plating solution L can be an aqueous solution containing copper sulfate, copper pyrophosphate, or the like.

[0031] Next, as shown in FIG. 1 , in a film-forming step S6, a metal film F is formed on the substrate B. Specifically, as shown in FIG. 4( b), the substrate B is placed on a mounting table 80, and the linear actuator 70 brings the electrolyte membrane 13 attached to the housing 15 into contact with the substrate B. At the same time, the circulation pump 59 is driven, and the electrolyte membrane 13 presses the substrate B with the hydraulic pressure of the plating solution L in the housing space 15 a. As a result, the electrolyte membrane 13 conforms to the substrate B, and the pressure of the plating solution L in the housing 15 is set to a constant pressure by the pressure regulating valve 54. As a result, the electrolyte membrane 13 can be uniformly pressed against the surface of the substrate B with the hydraulic pressure regulated by the plating solution L in the housing 15.

[0032] In this pressed state, a voltage is applied between the anode 11 and the substrate B by the power supply 14. Metal ions in the plating solution are caused to permeate the electrolyte membrane 13 by electroplating, and a metal coating F can be formed on the surface of the substrate B by electroplating. In this embodiment, during film formation, the uniformly swollen electrolyte membrane 13 is in contact with the substrate B, and the metal ions in the plating solution L are caused to uniformly permeate the electrolyte membrane 13 by electroplating, so that a homogeneous metal coating F with a uniform thickness can be formed.

[0033] <Example> A 1 cm × 2 cm × oxygen-free copper substrate was prepared as the substrate on which the film was to be formed. Next, a copper film was formed using the film-forming apparatus shown in Figure 4(a). A copper sulfate solution (1 M CuSO4 + 0.2 M H2SO4) was used as the plating solution, and an 8 μm-thick Nafion N212 (manufactured by DuPont) was used as the electrolyte membrane. The electrolyte membrane had undergone a series of pretreatments, from the immersion step S1 to the storage step S4 shown in Figure 1. The immersion time in the immersion step S1 was 1 hour, and the relative humidity in the swelling step S2 was 90% Rh, the heating temperature was 70°C, and the treatment time was 30 minutes. The film-forming conditions were: the temperature of the plating solution was room temperature and 40°C; the voltage applied between the anode and the substrate was increased from 0 to 1000 mmV at a rate of 2 mV / s; and the current density during the voltage increase was measured. The maximum value of the current density (maximum current density) was confirmed from the waveforms of the applied voltage and current density obtained, and the results are shown in Table 1 below.

[0034] <Comparative Example 1> A copper film was formed in the same manner as in the example. The maximum current value (maximum current density) during film formation was confirmed. The results are shown in Table 1 below. The difference from the example is that instead of performing the pretreatment of the example, the electrolyte membrane was immersed in pure water.

[0035] <Comparative Example 2> A copper film was formed in the same manner as in Example 1. The difference from Example 1 was that, as a pretreatment, instead of heating under humidified conditions, the electrolyte membrane was immersed in pure water and boiled in the pure water to swell it.

[0036] [Table 1]

[0037] The results in Table 1 show that the maximum current density was increased by forming an electrolyte membrane pretreated as in the Example compared to Comparative Example 1. This is because swelling the electrolyte membrane increased the permeability of copper ions in the electrolyte membrane. Specifically, at room temperature, the Example showed a 33% increase in maximum current density compared to Comparative Example 1, and at 40°C, the Example showed an 83% increase in maximum current density compared to Comparative Example 1. These results suggest that heating the electrolyte membrane in a humidified environment to swell it can increase the efficiency of metal film formation.

[0038] Furthermore, the metal coating formed in the Example had no plating unevenness, whereas the metal coating formed in Comparative Example 2 had plating unevenness. This is thought to be because, in the pretreatment of the Example, the electrolyte membrane was uniformly heated in a humidified environment, resulting in uniform swelling of the electrolyte membrane. However, in the pretreatment of Comparative Example 2, air adhered to the surface of the electrolyte membrane when boiled in pure water, preventing the electrolyte membrane from swelling uniformly. Therefore, in the case of Comparative Example 2, if dissolved oxygen and the like contained in the pure water are degassed and the electrolyte membrane is then boiled in this pure water, air is less likely to adhere to the surface of the electrolyte membrane, allowing the electrolyte membrane to swell uniformly. However, even in such a case, the pure water used for boiling cannot be reused and must be discharged and new pure water must be used. Therefore, the pretreatment of Comparative Example 2 tends to be more expensive than that of the Examples.

[0039] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various design modifications can be made without departing from the spirit of the present invention as set forth in the claims. [Explanation of symbols]

[0040] 1: Film forming equipment, 13: Electrolyte membrane, 1A: Equipment body, B: Base material, F: Metal coating, S1: Immersion process, S2: Swelling process, S3: Cooling process, S4: Storage process, W: Pure water

Claims

1. A method for pretreating an electrolyte membrane used in a membrane forming apparatus that forms a metal coating on a substrate, comprising: the electrolyte membrane is attached to a main body of the film-forming apparatus and is used when forming the metal coating on the substrate by electrolytic plating in a state of contact with the substrate, The pretreatment method includes: a swelling step of heating the electrolyte membrane in a humidified atmosphere to cause the electrolyte membrane to swell; a storage step of immersing the swollen electrolyte membrane in pure water and storing the electrolyte membrane; A method for pretreating an electrolyte membrane, comprising:

2. 2. The method for pretreating an electrolyte membrane according to claim 1, further comprising a step of immersing the electrolyte membrane in pure water before the swelling step.

3. 2. The method for pretreating an electrolyte membrane according to claim 1, further comprising a cooling step of cooling the swollen electrolyte membrane in the humidified atmosphere after the swelling step and before the storage step.

Images