Plating tank, plating apparatus, and electrolytic plating method

Abstract

A plating tank according to an embodiment of the present disclosure for electroplating a substrate for a flexible printed wiring board comprises a container configured so that the substrate is inserted as a cathode along the vertical direction, an anode positioned in the container so as to face the inserted substrate, a supply part capable of supplying a plating solution into the container from beside or above the container, and a discharge part which is positioned lower than the substrate in the container and which is capable of discharging the plating solution, the distance between outer surfaces of two opposing side surface parts of the container in the direction perpendicular to the substrate being 100 mm or less.

Description

Technical Field

[0001] The present disclosure relates to a plating bath, a plating apparatus, and an electrolytic plating method. This application claims priority based on Japanese Application No. 2020-091691 filed on May 26, 2020, and incorporates all the descriptions described in the above Japanese application.

Background Art

[0002] Patent Document 1 describes a plating bath configured to electrolytically plate a substrate while supplying and storing a plating solution into a container from below or laterally of the container and overflowing the supplied plating solution from the upper end of the container (hereinafter sometimes referred to as the "overflow method") (see Japanese Patent Application Laid-Open No. 2004-143478).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] A plating bath according to an aspect of the present disclosure is a plating bath for electrolytically plating a substrate for a flexible printed wiring board, and includes a container configured such that the substrate is inserted along the vertical direction as a cathode, an anode disposed in the container so as to face the inserted substrate, a supply unit capable of supplying a plating solution into the container from the side or above of the container, and a discharge unit disposed below the substrate in the container and capable of discharging the plating solution, wherein the distance between the outer surfaces of two opposing side portions of the container in a direction perpendicular to the substrate is 100 mm or less.

[0005] The plating apparatus according to another aspect of the present disclosure includes a plating bath for electrolytically plating a substrate for a flexible printed wiring board, a storage section capable of storing a plating solution supplied to the plating bath, and a liquid feeding section capable of feeding the plating solution from the storage section to the plating bath. The plating bath includes a container configured such that the substrate is inserted along the vertical direction as a cathode, an anode disposed in the container so as to face the inserted substrate, a supply section capable of supplying the plating solution into the container from a side or above the container, and a discharge section disposed below the substrate in the container and capable of discharging the plating solution. The distance between the outer surfaces of two opposing side portions of the container in a direction perpendicular to the substrate is 100 mm or less. The storage section is capable of storing the plating solution discharged from the discharge section, and the liquid feeding section is capable of feeding the plating solution from the storage section to the supply section.

[0006] The electrolytic plating method according to another aspect of the present disclosure is an electrolytic plating method for a substrate for a flexible printed wiring board, and includes an electrolytic plating step of electrolytically plating the substrate using a plating bath. The plating bath includes a container configured such that the substrate is inserted along the vertical direction as a cathode, an anode disposed in the container so as to face the inserted substrate, a supply section capable of supplying the plating solution into the container from a side or above the container, and a discharge section disposed below the substrate in the container and capable of discharging the plating solution. The distance between the outer surfaces of two opposing side portions of the container in a direction perpendicular to the substrate is 100 mm or less. In the electrolytic plating step, electrolytic plating is performed by supplying the plating solution into the container from the supply section and applying an electric current to the substrate and the anode while discharging the supplied plating solution from the discharge section.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0008] In the field of electronic devices, flexible printed wiring boards are widely used. A flexible printed wiring board is obtained, for example, by forming a plating layer (plating body) on the outer surface of a conductive base layer of a substrate for a printed wiring board having a base film and a conductive base layer (a thin conductive layer with a thickness of about several nm) laminated on the surface of the base film, and further patterning the conductive base layer and the plating body.

[0009] Generally, a plating apparatus for forming the plating body includes a plating bath having a container for storing a plating solution, an anode disposed opposite to the substrate immersed in the plating solution, and a mechanism for applying a voltage to the substrate and the anode.

[0010] As this type of plating bath, for example, the plating bath described in Patent Document 1 is proposed.

[0011] [Problems to be Solved by the Present Disclosure] Here, in the electrolytic plating as described above, it is desired to reduce the amount of plating used, and in addition, space saving is also desired.

[0012] However, in the plating bath as described in Patent Document 1 above, as the dimension of the container in the direction perpendicular to the substrate becomes smaller, there is a possibility that the thickness of the formed plating layer varies.

[0013] Therefore, an object of the present invention is to provide a plating bath, a plating apparatus, and an electrolytic plating method capable of forming a plating layer with a relatively small amount of plating used, in a space-saving manner, and with suppressed thickness variation on a substrate for a flexible printed wiring board.

[0014] [Effects of the Present Disclosure] The plating bath, the plating apparatus, and the electrolytic plating method according to one aspect of the present disclosure can form a plating layer with a relatively small amount of plating used, in a space-saving manner, and with suppressed thickness variation on a substrate for a flexible printed wiring board.

[0015] [Description of Embodiments of the Present Disclosure] First, the embodiments of the present disclosure will be listed and described.

[0016] A plating bath for a printed wiring board according to one aspect of the present disclosure is a plating bath for electrolytically plating a substrate for a flexible printed wiring board, and includes a container configured such that the substrate is inserted along the vertical direction as a cathode, an anode disposed in the container so as to face the inserted substrate, a supply unit capable of supplying a plating solution into the container from a side or above the container, and a discharge unit disposed below the substrate in the container and capable of discharging the plating solution, wherein the distance between the outer surfaces of two opposing side portions of the container in the direction perpendicular to the substrate is 100 mm or less.

[0017] Here, as a result of intensive research by the present inventors, the following findings were obtained. That is, as a measure for reducing the amount of plating used in electrolytic plating and saving space, it is conceivable to reduce the dimensions of the container of the plating bath. More specifically, it is conceivable to reduce the distance between the outer surfaces of the two opposing side portions of the container in the direction perpendicular to the substrate. However, as shown in the examples described later, when the plating solution is supplied to the container of the plating bath by the overflow method as described in Patent Document 1, the present inventors have found that if the above distance is reduced, the thickness of the plating formed on the substrate may vary. The reason for such variation is not clear, but for example, in the overflow method, irregular flows such as convection of the plating solution are likely to occur in the container, and due to this irregular flow, a flexible substrate that is inherently relatively easy to bend bends, and due to this bending, it is speculated that the thickness of the plating formed on the substrate varies. In addition, the smaller the above distance, the smaller the space in which the plating solution can flow, so it becomes more difficult to eliminate the irregularity of the above flow, and as a result, it is speculated that the above variation becomes larger.

[0018] On the other hand, the plating bath includes the supply section and the discharge section, and by setting the distance of the container within the above range, the plating solution can be sequentially supplied into the container, stored in the container, and discharged from the discharge section without overflowing from the upper end of the container while performing electrolytic plating on the substrate. Thus, by sequentially discharging the plating solution from within the container, compared with the overflow method, the plating solution can be made to exist in the container in a state where the irregularity (degree of irregularity) of the flow of the plating solution is smaller. Therefore, even if the above distance is a small distance of 100 mm or less, variations in the thickness of the plating can be suppressed. In addition, by reducing the above distance, the capacity of the container is reduced, so the amount of plating used can be reduced, and space can be saved. Therefore, the plating bath can form a plating on a substrate for a flexible printed wiring board with a relatively small amount of plating used and in a space-saving manner, and can suppress variations in the thickness of the formed plating.

[0019] It is preferable that the supply unit can supply the plating solution into the container from above the container.

[0020] By supplying the plating solution from above the container to the container by the supply unit, the irregularity of the flow of the plating solution in the container can be made smaller. Thereby, it becomes easier to suppress the variation in the thickness of the plating formed on the substrate.

[0021] A plating apparatus according to another aspect of the present disclosure includes a plating tank for electrolytic plating on a substrate for a flexible printed wiring board, a storage unit capable of storing a plating solution supplied to the plating tank, and a liquid feeding unit capable of feeding the plating solution from the storage unit to the plating tank. The plating tank includes a container configured such that the substrate is inserted vertically along the cathode, an anode disposed in the container so as to face the inserted substrate, a supply unit capable of supplying the plating solution into the container from the side or above the container, and a discharge unit disposed below the substrate in the container and capable of discharging the plating solution. The distance between the outer surfaces of the two opposing side portions of the container in the direction perpendicular to the substrate is 100 mm or less. The storage unit can store the plating solution discharged from the discharge unit, and the liquid feeding unit can feed the plating solution from the storage unit to the supply unit.

[0022] Since the plating apparatus includes the above-described plating tank, as described above, a plating can be formed on the substrate with a relatively small amount of plating and in a space-saving manner, and the variation in the thickness of the formed plating can be suppressed.

[0023] An electrolytic plating method according to another aspect of the present disclosure is an electrolytic plating method for a substrate for a flexible printed wiring board, and includes an electrolytic plating step of electrolytically plating the substrate using a plating bath. The plating bath includes a container configured such that the substrate is inserted vertically as a cathode, an anode disposed in the container so as to face the inserted substrate, a supply unit capable of supplying a plating solution into the container from a side or above the container, and a discharge unit disposed below the substrate in the container and capable of discharging the plating solution. The distance between the outer surfaces of two opposing side portions of the container in a direction perpendicular to the substrate is 100 mm or less. In the electrolytic plating step, electrolytic plating is performed by supplying a plating solution into the container from the supply unit and energizing the substrate and the anode while discharging the supplied plating solution from the discharge unit.

[0024] Since the electrolytic plating method uses the above-described plating bath, as described above, it is possible to form a plating layer with a relatively small amount of plating used, in a space-saving manner, and with suppressed thickness variation on the substrate for a flexible printed wiring board.

[0025] [Details of Embodiments of the Present Disclosure] Hereinafter, a plating bath, a plating apparatus, and an electrolytic plating method according to embodiments of the present disclosure will be described with reference to the drawings as appropriate.

[0026] [First Embodiment] <Plating Bath> The plating bath 1 in FIG. 1 is for electrolytic plating on a substrate X for a flexible printed circuit board. The plating bath 1 includes a container 3 (see FIG. 2) configured such that the substrate X is inserted along the vertical direction as a cathode, two anodes 5 disposed in the container 3 so as to face the inserted substrate X, a supply unit 7 capable of supplying a plating solution Y2 into the container 3 from the side or above (above in FIG. 1) of the container 3, and a discharge unit 9 disposed below the substrate X in the container 3 and capable of discharging the plating solution Y2. The plating bath 1 further includes a shielding film 11 that contacts the surface of each anode 5 on the side of the substrate X and is disposed facing the substrate X. The plating bath 1 further includes a mechanism (also referred to as a "voltage application mechanism", not shown) for applying a voltage to the inserted substrate X and the two anodes 5 respectively.

[0027] The plating bath 1 is used with a printed circuit board X having, for example, a base film and two conductive base layers (also called seed layers) laminated on both surfaces of this base film, with the outer surfaces of the respective conductive base layers facing one anode 5 each. The plating bath 1 supplies current from the voltage application mechanism to the substrate X and each anode 5, and reduces metal ions dissolved in the plating solution Y2 on the outer surfaces of the respective conductive base layers constituting the cathode, thereby forming a plating layer on the outer surface of each seed layer.

[0028] (Container) The container 3 is configured such that the substrate X is inserted therein, the plating solution Y2 for electrolytic plating on the inserted substrate X is supplied and discharged without overflowing, and the plating solution Y2 can be stored so that the substrate X is immersed in the plating solution Y2 for the time required for electrolytic plating on the substrate X.

[0029] In FIG. 1, the container 3 is formed such that the cross-sectional shape (longitudinal section, see FIG. 1) cut in the vertical direction is rectangular, the cross-sectional shape (transverse section) cut in the horizontal direction (the direction perpendicular to the substrate X, the left-right direction in FIG. 1) is rectangular, and the upper part is open.

[0030] A substrate X is inserted into the container 3. A plating solution Y2 is supplied from the supply unit 7 into the container 3. A discharge unit 9 for discharging the plating solution Y2 in the container 3 is provided on the bottom surface portion 3b of the container 3. Two anodes 5 are respectively arranged in the container 3 so as to face the surfaces on both sides of the inserted substrate X.

[0031] The container 3 is formed such that the distance (first distance) L between the outer surfaces of the two opposing side surface portions 3a of the container 3 in the direction perpendicular to the substrate X is 100 mm or less.

[0032] Here, as described above and as will be described later, in a conventional plating bath that supplies a plating solution by an overflow method, the smaller the distance L, the more likely there is a variation in the thickness of the plating formed on the substrate X.

[0033] However, in the present embodiment, by supplying the plating solution Y2 into the container 3 from above or the side (above in FIG. 1) of the container 3 and performing electrolytic plating while discharging the plating solution Y2 in the container 3 from the discharge unit 9 so as not to overflow, even when the distance L is as small as 100 mm or less, the variation in the thickness of the plating can be suppressed. In addition, electrolytic plating can be performed with less plating consumption and less space than before. Also, the smaller the distance L is than 100 mm, the higher the superiority of the plating bath 1 becomes.

[0034] The upper limit of the distance L is 100 mm as described above, more preferably 80 mm, and even more preferably 60 mm. The lower limit of the distance L is not particularly limited and can be appropriately set so that, for example, electrolytic plating can be performed without short - circuiting. For example, as the lower limit of the distance L, 30 mm is preferable and 40 mm is more preferable. If the distance L exceeds the upper limit, an excessive amount of the plating solution Y2 may be wasted and supplied into the container 3 compared to the amount of the plating solution Y2 required for electrolytic plating. On the other hand, if the distance L is less than the lower limit, there is a risk of short - circuiting, and there is also a risk that the amount of the plating solution Y2 required for electrolytic plating may not be present in the container 3.

[0035] The thickness (wall thickness) of the container 3 is not particularly limited and is set as appropriate. The thickness of the container 3 can be set, for example, to about 10 mm.

[0036] The distance between the substrate X and each anode 5, that is, the shortest distance connecting the substrate X and each anode 5 (second distance, hereinafter also referred to as "inter-electrode distance") is not particularly limited and can be appropriately set according to the distance L of the container, the thickness of the substrate X, the thickness of the anode 5, the thickness of the shielding film 11, etc. For example, usually, the smaller the distance L, the smaller the inter-electrode distance can be. Considering this, the smaller the inter-electrode distance, the higher the superiority of the plating bath 1. For example, as the upper limit of the inter-electrode distance, 50 mm is preferable, and 45 mm is more preferable. As the lower limit of the inter-electrode distance, 30 mm is preferable, and 35 mm is more preferable. If the inter-electrode distance exceeds the upper limit, an excessive amount of the plating solution Y2 may be wasted and supplied into the container 3 compared to the amount of the plating solution Y2 required for electroplating. On the other hand, if the inter-electrode distance is less than the lower limit, there is a risk of short circuit, and there is also a risk that the amount of the plating solution Y2 required for electroplating does not exist in the container 3.

[0037] (Anode) Each anode 5 has a constant thickness and is formed in a plate shape. Also, each anode 5 is formed in a rectangular shape in a plan view, that is, when viewed in a direction perpendicular to the substrate X. Each anode 5 may be a soluble anode mainly composed of a metal such as copper, nickel, silver, etc., or may be an insoluble anode using platinum, iridium-coated titanium, etc. However, an insoluble anode that can easily prevent changes in the shape of the anode itself and achieve uniform thickness of the plating formed on the substrate X is preferable. Here, in the present disclosure, the "main component" means the component with the highest content, for example, a component occupying 50% by mass or more in the forming material.

[0038] The thickness of the anode 5 is not particularly limited and is set as appropriate. The thickness of the anode 5 can be set, for example, to about 5 mm.

[0039] (Supply section) In FIG. 1, the supply unit 7 is disposed above the container 3. The supply unit 7 is configured to discharge the plating solution Y2 downward and supply it into the container 3. Examples of such a supply unit 7 include ejection devices such as a known spray having a plurality of ejection ports capable of ejecting the plating solution Y2 into the container 3 along the extending direction of the substrate X. The supply rate of the plating solution Y2 from the supply unit 7 can be appropriately set so that the substrate X is completely immersed in the plating solution Y2 in the container 3 while the plating solution Y2 does not overflow from the upper end portion of the container 3. By supplying the plating solution Y2 from the supply unit 7 above the container 3 into the container 3, the irregularity of the flow of the plating solution Y2 in the container 3 can be made smaller. Thereby, it becomes easier to suppress the variation in the thickness of the plating layer formed on the substrate X.

[0040] (Discharge unit) As described above, the discharge unit 9 is provided on the bottom surface portion 3b of the container 3. Examples of the discharge unit 9 include a discharge port capable of discharging the plating solution Y2 from inside the container 3, and a known discharge mechanism capable of adjusting the discharge amount. The discharge rate of the plating solution Y2 from the discharge unit 9 can be appropriately set so that the substrate X is completely immersed in the plating solution Y2 in the container 3 while the plating solution Y2 does not overflow from the upper end portion of the container 3.

[0041] (Masking film) Each masking film 11 is for equalizing the current density and thereby equalizing the film thickness of the plating layer. As the masking film 11, a known masking film can be used. The thickness of the masking film 11 is not particularly limited and is appropriately set. The thickness of the masking film 11 can be set to about 1 mm, for example.

[0042] (Plating solution) The plating solution Y2 is not particularly limited, and for example, a known plating solution containing copper sulfate, copper pyrophosphate, etc. can be used.

[0043] <Advantages> The plating tank 1 includes the supply section 7 and the discharge section 9. When the distance L in the container 3 is within the above range, the plating solution Y2 can be sequentially supplied into the container 3 from the supply section 7 without overflowing from the upper end of the container 3, and the plating solution is stored in the container 3 so that the substrate X is immersed in the plating solution Y2. Then, it is moved by gravity from the supply section 7 to the discharge section 9 and electrolytic plating can be performed on the substrate X while discharging from the discharge section 9. By performing electrolytic plating without overflowing in this way, even when the distance L is as small as 100 mm or less, variations in the thickness of the plated body can be suppressed. Also, since the distance L is 100 mm or less, the amount of plating used in electrolytic plating can be reduced, and space can be saved.

[0044] Therefore, the plating tank 1 can form a plated body on the substrate X for a flexible printed wiring board with a relatively small amount of plating used and in a space-saving manner, and can suppress variations in the thickness of the formed plated body.

[0045] [Second Embodiment] <Electrolytic Plating Method> Next, an electrolytic plating method using the plating tank 1 will be described. The electrolytic plating method is an electrolytic plating method for the substrate X for a flexible printed wiring board, and includes an electrolytic plating step of performing electrolytic plating on the substrate X using the above-described plating tank 1.

[0046] (Electrolytic Plating Step) In the electrolytic plating step, the plating solution Y2 is supplied from the supply section 7 of the plating tank 1 into the container 3, and electrolytic plating is performed by energizing the substrate X and each anode 5 while discharging the supplied plating solution Y2 from the discharge section 9.

[0047] Specifically, in the above electrolytic plating process, the substrate X is inserted into the container 3, the plating solution Y2 is supplied from the supply unit 7 into the container 3, and the supplied plating solution Y2 is discharged from the discharge unit 9. As a result, the plating solution Y2 is stored in the container 3 so that it does not overflow and the entire substrate X is immersed in the plating solution Y2. In this state, the substrate X and the anode 5 are energized by the voltage application device. When performing this electrolytic plating method in the manufacture of a flexible printed wiring board using the subtractive method, in the above electrolytic plating process, a substrate X on which a resist pattern is not formed on the conductive base layer is used. On the other hand, when performing this electrolytic plating method in the manufacture of a flexible printed wiring board using the semi-additive method, in the above electrolytic plating process, a substrate X on which a resist pattern is formed on the conductive base layer is used.

[0048] Examples of the main component of the plating layer formed in the above electrolytic plating process include copper, nickel, silver, etc. Among them, copper is preferred because it has excellent conductivity, is relatively inexpensive, and is easy to form a plating layer with a uniform thickness.

[0049] In the above electrolytic plating process, as described above, the upper limit of the distance between the substrate X and each anode 5 is preferably 50 mm, more preferably 45 mm. The lower limit of the above interval is preferably 30 mm, more preferably 35 mm.

[0050] <Advantages> Since the above electrolytic plating method uses the above-described plating tank 1, as described above, it is possible to form a plating layer with a relatively small amount of plating used, in a space-saving manner, and with suppressed thickness variation on the substrate X for a flexible printed wiring board.

[0051] [Third Embodiment] <Plating Apparatus> Next, a plating apparatus including the above-described plating tank 1 of the first embodiment will be described. The plating apparatus is configured to be able to perform a plurality of processes (steps) including an electrolytic plating process (step) on the substrate X in one plating tank 1.

[0052] In FIG. 2, the plating apparatus 20 includes the plating bath 1, a first storage section 21, a second storage section 23, and a third storage section 25 that can store the liquid discharged from the discharge section 9 of the container 3 of the plating bath 1, and a first valve 27 configured to be able to switch the storage destination of the liquid discharged from the discharge section 9 of the container 3 to the first storage section 21, the second storage section 23, and the third storage section 25, and a second valve 29 for sending any one of the liquids Y sent from the first storage section 21, the second storage section 23, and the third storage section 25 to the supply section 7.

[0053] The plating apparatus 20 further includes a first pipe 31 that constitutes a liquid supply path for sending liquid from the discharge section 9 of the container 3 to the first valve 27, a second pipe 33 that constitutes a liquid supply path for sending liquid from the first valve 27 to the first storage section 21, a third pipe 35 that constitutes a liquid supply path for sending liquid from the first valve 27 to the second storage section 23, and a fourth pipe 37 that constitutes a liquid supply path for sending liquid from the first valve 27 to the third storage section 25.

[0054] The plating apparatus 20 further includes a fifth pipe 41 that constitutes a liquid supply path for sending liquid from the first storage section 21 to the second valve 29, a sixth pipe 43 that constitutes a liquid supply path for sending liquid from the second storage section 23 to the second valve 29, and a seventh pipe 45 that constitutes a liquid supply path for sending liquid from the third storage section 25 to the second valve 29.

[0055] The plating apparatus 20 further includes a first liquid supply section 51 disposed in the fifth pipe 41 and capable of sending the liquid from the first storage section 21 to the second valve 29 by a driving force, a second liquid supply section 53 disposed in the sixth pipe 43 and capable of sending the liquid from the second storage section 23 to the second valve 29 by a driving force, and a third liquid supply section 55 disposed in the seventh pipe 45 and capable of sending the liquid from the third storage section 25 to the second valve 29 by a driving force.

[0056] The plating apparatus 20 further includes an eighth pipe 47 that constitutes a liquid supply path for sending liquid from the second valve 29 to the supply section 7.

[0057] (Plating bath) Since the configuration of the plating tank 1 is as detailed in the above-described first embodiment, a detailed description thereof will be omitted. In the present embodiment, the plating tank 1 is used not only for electrolytic plating treatment but also for other treatments. That is, not only the plating solution Y2 but also other liquids (here, the degreasing solution Y1 and the cleaning solution Y3) are supplied from the supply unit 7 into the container 3 of the plating tank 1. More specifically, any one of the degreasing solution Y1, the plating solution Y2, and the cleaning solution Y3, i.e., the liquid Y, is sequentially switched and sent from the supply unit 7 to the container 3.

[0058] (First storage part) For example, the above-described degreasing solution Y1 is stored in the first storage part 21. The first storage part 21 is arranged at a position where the degreasing solution Y1 can be sent from the discharge part 9 in the container 3. The first storage part 21 is arranged, for example, below the container 3. The degreasing solution Y1 stored in the first storage part 21 is sent to the second valve 29 through the fifth pipe 41 by the driving force of the first liquid sending part 51, further sent from the second valve 29 to the supply unit 7, and supplied from the supply unit 7 into the container 3. The degreasing solution Y1 supplied into the container 3 is sent from the discharge part 9 of the container 3 to the first valve 27 through the first pipe 31, and further sent (returned) from the first valve 27 to the first storage part 21 through the second pipe 33. In this way, the degreasing solution Y1 is circulated between the first storage part 21 and the container 3.

[0059] (Second storage part) For example, the above-described plating solution Y2 is stored in the second storage part 23. The second storage part 23 is arranged at a position where the plating solution Y2 can be sent from the discharge part 9 in the container 3. The second storage part 23 is arranged, for example, below the container 3. The plating solution Y2 stored in the second storage part 23 is sent to the second valve 29 through the sixth pipe 43 by the driving force of the second liquid sending part 53, further sent from the second valve 29 to the supply unit 7, and supplied from the supply unit 7 into the container 3. The plating solution Y2 supplied into the container 3 is sent from the discharge part 9 of the container 3 to the first valve 27 through the first pipe 31, and further sent (returned) from the first valve 27 to the second storage part 23 through the third pipe 35. In this way, the plating solution is circulated between the second storage part 23 and the container 3.

[0060] (Third storage section) In the third storage section 25, for example, the above-described cleaning liquid Y3 is stored. The third storage section 25 is disposed at a position where the cleaning liquid Y3 can be sent from the discharge section 9 in the container 3. The third storage section 25 is disposed, for example, below the container 3. The cleaning liquid Y3 stored in the third storage section 25 is sent to the second valve 29 through the seventh pipe 45 by the driving force of the third liquid sending section 55, further sent from the second valve 29 to the supply section 7, and supplied into the container 3 from the supply section 7. The cleaning liquid Y3 supplied into the container 3 is sent from the discharge section 9 of the container 3 to the first valve 27 through the first pipe 31, and further sent from the first valve 27 to the third storage section 23 through the fourth pipe 37 (returned). In this way, the cleaning liquid Y3 is circulated between the third storage section 23 and the container 3.

[0061] (First valve) The first valve 27 is a switching valve capable of switching the liquid sending path so that the liquid discharged from the container 3 can be sent to any one of the above three storage sections. Specifically, when sending the degreasing liquid Y1 discharged from the container 3 to the first storage section 21, the first valve 27 is switched so as to send the degreasing liquid Y1 only to the first storage section 21 and not to the second storage section 23 and the third storage section 25. When sending the plating liquid Y2 discharged from the container 3 to the second storage section 23, the first valve 27 is switched so as to send the plating liquid Y2 only to the second storage section 23 and not to the first storage section 21 and the third storage section 25. When sending the cleaning liquid Y3 discharged from the container 3 to the third storage section 25, the first valve 27 is switched so as to send the cleaning liquid Y3 only to the third storage section 25 and not to the first storage section 21 and the second storage section 23. Examples of such a first valve 27 include a known four-way switching valve and the like.

[0062] (Second valve) The second valve 29 is a switching valve capable of switching the liquid delivery path so that the liquid from any one of the storage sections of the above-mentioned three storage sections can be sent to the supply section 7. Specifically, when sending the degreasing liquid Y1 from the first storage section 21 to the supply section 7, the second valve 29 is switched so that the plating liquid Y2 and the cleaning liquid Y3 from the second storage section 23 and the third storage section 25 are not sent to the supply section 7, and only the degreasing liquid Y1 from the first storage section 21 is sent to the supply section 7. When sending the plating liquid Y2 from the second storage section 23 to the supply section 7, the second valve 29 is switched so that the degreasing liquid Y1 and the cleaning liquid Y3 from the first storage section 21 and the third storage section 25 are not sent to the supply section 7, and only the plating liquid Y2 from the second storage section 23 is sent to the supply section 7. When sending the cleaning liquid Y3 from the third storage section 25 to the supply section 7, the second valve 29 is switched so that the degreasing liquid Y1 and the plating liquid Y2 from the first storage section 21 and the second storage section 23 are not sent to the supply section 7, and only the cleaning liquid Y3 from the third storage section 25 is sent to the supply section 7. Examples of such a second valve 29 include a known four-way switching valve and the like.

[0063] (First to Eighth Pipes) For each of the above-mentioned first to eighth pipes, for example, known pipes can be used.

[0064] (First to Third Liquid Delivery Sections) As each of the above-mentioned first to third liquid delivery sections, a known pump capable of delivering liquid can be used.

[0065] (Degreasing Liquid) The above-mentioned degreasing liquid Y1 is a liquid for removing fat and the like adhering to the surface of the substrate X. As such a degreasing liquid Y1, a known degreasing liquid can be used.

[0066] (Plating Liquid) As the above-mentioned plating liquid Y2, the plating liquid Y2 described above can be used.

[0067] (Cleaning Liquid) The above-mentioned cleaning liquid Y3 is for cleaning the substrate X on which the plating layer is formed. As such a cleaning liquid Y3, a known cleaning liquid can be used.

[0068] (Processing of a substrate using a plating apparatus) The processing of the substrate X using the plating apparatus 20 (operation of the plating apparatus 20) will be described. In the present embodiment, for example, degreasing treatment of the substrate X, electrolytic plating treatment on the substrate X, and cleaning treatment of the substrate X on which a plating layer is formed are performed in this order using the plating apparatus 20.

[0069] In the above degreasing treatment, first, the substrate X is inserted into the container 3. Next, the degreasing liquid Y1 is sent from the first storage unit 21 to the supply unit 7 through the fifth pipe 41, the second valve 29, and the eighth pipe 47 by the first liquid supply unit 51, and the degreasing liquid Y1 is supplied from the supply unit 7 into the container 3. The supplied degreasing liquid Y1 is stored in the container 3 so that the substrate X is completely immersed in the degreasing liquid Y1, and is discharged from the discharge unit 9 so as not to overflow from the upper end of the container 3. The degreasing liquid Y1 discharged from the discharge unit 9 is sent to the first storage unit 21 through the first pipe 31, the first valve 27, and the second pipe 33 by gravity or the like. In this way, the degreasing liquid Y1 is circulated between the first storage unit 21 and the container 3. During this circulation, the surface of the substrate X is degreased by the contact between the degreasing liquid Y1 and the substrate X in the container 3.

[0070] After the above degreasing treatment, all of the degreasing liquid Y1 in the container 3 is discharged into the first storage unit 21. The substrate X in the container 3 is placed in the container 3 as it is. Thereafter, if necessary, the inside of the container 3, the first pipe 31, the first valve 27, the second valve 29, and the eighth pipe 47 are appropriately cleaned by a known method.

[0071] In the above electrolytic plating process, the substrate X has already been inserted into the container 3. Next, the plating solution Y2 is sent from the second storage unit 23 to the supply unit 7 through the sixth pipe 43, the second valve 29, and the eighth pipe 47 by the second liquid supply unit 53, and this plating solution Y2 is supplied from the supply unit 7 into the container 3. The supplied plating solution Y2 is stored in the container 3 so that the substrate X is completely immersed in the plating solution Y2, and is discharged from the discharge unit 9 so as not to overflow from the upper end of the container 3. The plating solution Y2 discharged from the discharge unit 9 is sent to the second storage unit 23 through the first pipe 31, the first valve 27, and the third pipe 35 by gravity or the like. In this way, the plating solution Y2 is circulated between the second storage unit 23 and the container 3. During this circulation, as shown in the above-described first embodiment and second embodiment, by energizing the substrate X and each anode 5 with the above voltage applying device, electrolytic plating is performed on both surfaces of the substrate X in the container 3, and plating layers are formed on the respective surfaces.

[0072] After the above electrolytic plating process, all of the plating solution Y2 in the container 3 is discharged into the second storage unit 23. The substrate X (laminated body) on which the plating layer is formed in the container 3 is placed as it is in the container 3. Thereafter, if necessary, the inside of the container 3, the inside of the first pipe 31, the inside of the first valve 27, the inside of the second valve 29, and the inside of the eighth pipe 47 are appropriately cleaned by a known method.

[0073] In the above cleaning process, the laminated body has already been inserted into the container 3. Next, the cleaning solution Y3 is sent from the third storage unit 25 to the supply unit 7 through the seventh pipe 45 and the second valve 29 by the third liquid supply unit 55, and this cleaning solution Y3 is supplied from the supply unit 7 into the container 3. The supplied cleaning solution Y3 is stored in the container 3 so that the substrate X is completely immersed in the cleaning solution Y3, and is discharged from the discharge unit 9 so as not to overflow from the upper end of the container 3. The cleaning solution Y3 discharged from the discharge unit 9 is sent to the third storage unit 25 through the first pipe 31, the first valve 27, and the fourth pipe 37 by gravity or the like. In this way, the cleaning solution Y3 is circulated between the third storage unit 25 and the container 3. During this circulation, the surface of the laminated body is cleaned by the contact between the cleaning solution Y3 and the laminated body in the container 3.

[0074] In this way, by using the plating apparatus 20, a plurality of processes can be performed on the substrate X in the container 3 without taking out the substrate X from the container 3. Therefore, the size of the apparatus can be reduced. Further, in the above electrolytic plating process, since the plating bath 1 described above is used, variations in the thickness of the plating layer formed on the substrate X can be suppressed.

[0075] <Advantages> Since the plating apparatus 20 includes the plating bath 1, as described above, it is possible to form a plating layer with relatively little plating amount, in a space-saving manner, and with suppressed thickness variations, on the substrate X for a flexible printed wiring board.

[0076] In addition, the plating apparatus 20 can perform a plurality of processes on the substrate X while the substrate X is disposed in the container 3 by switching the liquid supplied to the plating bath 1. Therefore, the plating apparatus 20 can be reduced in size compared to a plating apparatus having a plurality of tanks for performing a plurality of processes, and moreover, the processing time can be shortened.

[0077] Furthermore, the plating apparatus 20 can perform a plurality of processes on the substrate X without taking it out while the substrate X is disposed in the container 3 of the plating bath 1. Therefore, it is possible to further suppress the substrate X, which is relatively easy to bend, from bending between each process.

[0078] The plating bath, plating apparatus, and electrolytic plating method according to the embodiment of the present disclosure are suitable for manufacturing a high-quality flexible printed wiring board because it is possible to form a plating layer with relatively little plating amount, in a space-saving manner, and with suppressed thickness variations, on a substrate for a flexible printed wiring board.

[0079] [Other Embodiments] The embodiments disclosed this time should be considered illustrative in all respects and not restrictive. The scope of the present invention is not limited to the configuration of the above embodiments, but is indicated by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0080] For example, in the above first embodiment, the case where the plating tank includes a supply unit 7 for supplying the plating solution Y2 into the container 3 from above the container 3 has been described. However, alternatively, an aspect in which the plating tank includes a supply unit for supplying the plating solution Y2 from the side of the container 3 may be adopted.

[0081] For example, in the above first embodiment, the case where the plating tank includes a discharge unit 9 at the bottom surface portion 3b of the container 3 has been described. However, alternatively, an aspect in which the plating tank includes a discharge unit below the substrate X on the side surface portion 3a of the container 3 may be adopted.

[0082] For example, in the above first embodiment, the case where the plating tank includes two anodes 5 in the container 3 has been described. However, alternatively, an aspect in which the plating tank includes one anode in the above container may be adopted. Accordingly, an aspect in which the plating tank includes one shielding film in the above container may also be adopted. Further, an aspect in which the plating tank does not include a shielding film may be adopted.

[0083] For example, in the above third embodiment, the case where the plating apparatus includes three storage units 21, 23, 25 has been described. However, an aspect in which the plating apparatus includes only one storage unit (i.e., the second storage unit 23) may be adopted, and an aspect in which the plating apparatus includes four or more storage units may also be adopted. Further, as the liquid stored in the storage unit other than the storage unit for the plating solution, not only the degreasing solution and the cleaning solution but also a known liquid for processing the substrate X can be used. Further, the order of supplying a plurality of liquids to the plating tank (the order of performing a plurality of processes) is not particularly limited and can be appropriately set as necessary.

Examples

[0084] Hereinafter, the present disclosure will be described in more detail by way of examples. However, the present invention is not limited to the following examples.

[0085] As a model experiment, by changing the degree of bending of the substrate (when the substrate bends and when it does not bend), the influence on the distance between the substrate and the anode 1 (inter-electrode distance) and the thickness of the plating layer formed on the substrate was examined by simulation using the following methods, conditions, and analysis software. Note that the above inter-electrode distance depends on the distance L between the outer surfaces of the two side portions of the container in the direction perpendicular to the substrate. Therefore, in this experiment, a small inter-electrode distance corresponds to a small distance L.

[0086] <Method and Conditions> · Model used: 2D simple model As this 2D simple model, in order to examine only the influence of the inter-electrode distance, a model in which plating concentration does not occur at both horizontal ends of the substrate was designed. · Substrate length: 250 mm · Substrate bending: 0 mm (no bending), 3 mm (with bending) · Inter-electrode distance: The following 7 levels 200 mm, 150 mm, 100 mm, 50 mm, 30 mm, 20 mm, 10 mm · Analysis software: Film Thickness Guide · Current condition: 2.0 A / dm 2 · Thickness of plating layer (target value): 40 μm

[0087] <Results> The results are shown in FIGS. 3, 4, and 5. In FIGS. 3 and 4, the center of the substrate is set as x = 0 (origin), the x-axis represents the distance from the origin in the above horizontal direction on the substrate, and the y-axis represents the thickness of the plating layer. In FIG. 5, the x-axis represents the inter-electrode distance, and the y-axis represents the standard deviation of the thickness of the plating layer and the magnification of deterioration (increase rate) of the standard deviation at each inter-electrode distance when the standard deviation at an inter-electrode distance of 200 mm is set to 1.

[0088] As shown in Fig. 3, it was found that even when it is assumed that the substrate does not bend (the bending is 0 mm), the smaller the interelectrode distance, the smaller the thickness of the plating body. As shown in Fig. 4, when it is assumed that a relatively large bending occurs in the substrate (the bending is 3 mm), it was found that the greater the difference in position on the substrate, the greater the variation in thickness due to the smaller interelectrode distance. That is, when the interelectrode distance is 200 mm or less, it was found that the smaller the interelectrode distance, the greater the variation in the thickness itself and the greater the variation in thickness due to the difference in position on the substrate (variation in thickness distribution). As is clear from Fig. 5, the variation in this thickness distribution becomes more prominent as the distance L is smaller.

[0089] Thus, when the plating solution is supplied by an overflow method from the bottom surface portion of the container of the plating tank, it is presumed that a large variation in the thickness of the plating body formed on the substrate may occur. On the other hand, the plating tank shown in the above embodiment can supply the plating solution from above or the side of the container and discharge it from the discharge portion of the bottom surface portion of the container so as not to overflow. Thereby, when performing electrolytic plating on a substrate for a flexible printed wiring board that is relatively easy to bend, even if the interelectrode distance is reduced, that is, even if the distance L of the container is reduced (100 mm or less), it is presumed that the variation in the thickness of the plating body formed on the substrate is suppressed.

Explanation of Signs

[0090] 1 Plating tank 3 Container 3a Side surface portion 3b Bottom surface portion 5 Anode 7 Supply portion 9 Discharge portion 11 Masking film 20 Plating apparatus 21 First storage portion 23 Second storage portion 25 Third storage portion 27 First valve 29 Second valve 31 First pipe 33 Second pipe 35th pipe 37th pipe 41st pipe 43rd pipe 45th pipe 47th pipe 1st liquid delivery section 2nd liquid delivery section 3rd liquid delivery section X substrate Y liquid Y1 degreasing liquid Y2 plating liquid Y3 cleaning liquid

Claims

1. A plating bath for electrolytically plating a substrate for a flexible printed wiring board, comprising: a container configured such that the substrate is inserted vertically as a cathode; an anode disposed in the container so as to face the inserted substrate; a supply unit capable of supplying a plating solution into the container from above the container; a discharge unit disposed below the substrate in the container and capable of discharging the plating solution; and a distance between outer surfaces of two opposing side portions of the container in a direction perpendicular to the substrate is 100 mm or less; a plating bath in which the plating solution is supplied and discharged without overflowing.

2. A plating apparatus comprising a plating bath for electrolytically plating a substrate for a flexible printed wiring board, and a plating solution storage unit capable of storing the plating solution supplied to the plating bath, and a liquid feeding unit capable of feeding the plating solution from the plating solution storage unit to the plating bath, wherein the plating bath includes a container configured such that the substrate is inserted vertically as a cathode; an anode disposed in the container so as to face the inserted substrate; a supply unit capable of supplying a plating solution into the container from a side or above the container; a discharge unit disposed below the substrate in the container and capable of discharging the plating solution; and a distance between outer surfaces of two opposing side portions of the container in a direction perpendicular to the substrate is 100 mm or less; the plating solution storage unit is capable of storing the plating solution discharged from the discharge unit; the liquid feeding unit is capable of feeding the plating solution from the plating solution storage unit to the supply unit; two or more other storage units capable of storing the liquid discharged from the discharge unit; a first valve capable of switching a storage destination of the liquid discharged from the discharge unit to either the plating solution storage unit or the other storage unit; and a second valve capable of switching to feed any one of the liquids from the plating solution storage unit and the other storage units to the supply unit. The plating apparatus further comprising.

3. The plating apparatus according to claim 2, wherein the supply unit is capable of supplying the plating solution into the container from above the container.

4. An electrolytic plating method for a substrate for a flexible printed wiring board, comprising an electrolytic plating step of electrolytically plating the substrate using a plating bath, wherein the plating bath includes a container configured such that the substrate is inserted vertically as a cathode; An anode disposed in the container so as to face the inserted substrate; A supply unit capable of supplying a plating solution into the container from above the container; A discharge unit disposed below the substrate in the container and capable of discharging the plating solution; Comprising; The distance between the outer surfaces of the two opposing side portions of the container in the direction perpendicular to the substrate is 100 mm or less; In the electrolytic plating step, electrolytic plating is performed by supplying a plating solution from the supply unit into the container, energizing the substrate and the anode while discharging the supplied plating solution from the discharge unit without overflowing. An electrolytic plating method.

5. An electrolytic plating method for a substrate for a flexible printed wiring board, A plating solution storage unit capable of storing a plating solution supplied to the plating tank; Two or more other storage units capable of storing the liquid supplied to the plating tank; Using a plating apparatus comprising; The plating tank is, A container configured such that the substrate is inserted along the vertical direction as a cathode; An anode disposed in the container so as to face the inserted substrate; A supply unit capable of supplying a plating solution into the container from the side or above the container; A discharge unit disposed below the substrate in the container and capable of discharging the plating solution; Including; The distance between the outer surfaces of the two opposing side portions of the container in the direction perpendicular to the substrate is 100 mm or less; The plating apparatus is, A first valve capable of switching the storage destination of the liquid discharged from the discharge unit to either the plating solution storage unit or the other storage unit; A second valve capable of switching to send any one of the liquids from the plating solution storage unit and the other storage unit to the supply unit; Further comprising; An electrolytic plating step of performing electrolytic plating on the substrate using the plating tank; In the electrolytic plating step, the plating solution stored in the plating solution storage unit is supplied from the supply unit into the container via the second valve, and the supplied plating solution is discharged from the discharge unit via the first valve. Electrolytic plating is performed by energizing the substrate and the anode while sending the plating solution to the plating solution storage unit. An electrolytic plating method.

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