JP2975275B2 - Copper foil surface treatment method for printed circuit by submerged current collection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface of a copper foil for a printed circuit by a submerged current collecting method in which a current is collected without using a current collecting roll in a case where the copper foil is subjected to an electrochemical surface treatment. The present invention relates to a treatment method, and eliminates metal electrodeposition on the surface of a current collecting roll, thereby eliminating a decrease in copper foil quality (press, dent, transfer, etc.) due to the metal deposition. It relates to a surface treatment method.

[0002]

2. Description of the Related Art Copper and copper alloy foils (hereinafter referred to as copper foils)
Has contributed greatly to the development of the electrical and electronics related industries,
In particular, it is indispensable as a printed circuit material. Copper foils include electrolytic copper foils and rolled copper foils. Copper foils used for printed circuits have a roughened surface (adhesive surface) and a glossy surface that adhere to the resin base according to quality requirements. (Non-adhesive surface) and many surface treatments are performed on each. In general, for example, on a roughened surface, a roughening process of performing copper-like bumpy electrodeposition,
In order to prevent the electrodeposited particles from falling off, a thin copper plating process for forming a cover layer, a treat process for forming a metal or alloy layer as needed, and a rust prevention process are performed.

In a conventional copper foil surface treatment process for a printed circuit, a current collecting roll (contact roll or conductor roll) is required to collect current. That is, in the step of performing surface cleaning, electrodeposition, etc. in the copper foil production surface treatment line, a number of rolls are used to make the copper foil run at a high speed along a predetermined path, but several rolls are used in the middle of the line. Current collector rolls are used. FIG. 8 is a conceptual view of the use of a current collecting roll, and shows a copper foil 1.
Is wrapped around the current collecting roll 12 into the electrolytic solution, goes vertically downward, turns upward by the immersion rolls 13 and 13 ′, rises vertically upward, is pulled out through the guide roll 14, and is sent to the next step. Can be The current collecting roll 12 is a DC power source 1
It is directly connected to 5. An anode plate 16 directly connected to the DC power supply 15 is immersed in the electrolyte facing the copper foil, and the current applied from the positive electrode of the DC power supply flows from the anode to the current collector roll through the copper foil to the negative electrode of the DC power supply. To complete the circuit. For example, a large current of 1 to 30,000 A may be applied to the current collecting roll.

In a conventional collector roll, a stainless steel material is formed into a flat plate by rolling, and a clad flat plate having a copper plate bonded thereto is bent into a cylindrical shape, and the joint is welded to form a roll cylinder. Was. However, in the current collector roll having such a welded seam, the quality of the copper foil product deteriorated due to the welded seam. For example, the current tends to be non-uniform at the weld seam, and in addition to damaging the copper foil that comes into contact with the weld seam, metal holes that are locally deposited on the weld defect may cause defects such as pinholes and press damage on the copper foil. In addition, there was a problem that the metal particles were generated and the electrodeposited metal particles fell off and adhered to the copper foil surface. Therefore, a seamless current collector roll having a structure in which a stainless steel material is forged and formed into a seamless pipe by extrusion processing, and a copper pipe is shrink-fitted therein has been proposed (Japanese Patent Laid-Open No. 4-66696).

The current collecting roll generally needs to be placed in a place where the copper foil is sufficiently dry. It is customary that some electrolytic solution adheres to the copper foil along with the washing solution, and when the electrolytic solution or the like adheres, electrolysis of metal or the like occurs at the contact point between the current collector roll and the copper foil. This is because a discharge reaction, a spark, or the like occurs, which adversely affects the copper foil quality. In an actual copper foil surface treatment line, it is necessary to perform several times of surface treatment at high speed, and several current collecting rolls are arranged in the middle of the line to collect current respectively. In the middle of the line, since the copper foil cannot be sufficiently dried in a hot air oven or the like, problems such as metal deposition on the metal surface and sparks are likely to occur, and even when a seamless current collector roll is used, Deposited metal particles cause defects such as pinholes and dents in the copper foil, and also cause problems such as the deposited metal particles falling off and adhering to the copper foil surface.

[0006]

In order to avoid this problem, at present, a squeezing roll is installed for the purpose of draining the liquid on the current collecting roll, or an appropriate control of the copper foil tension is performed. Alternatively, the material and the surface roughness of the current collecting roll are optimized, but none of them has essentially solved the problem. Another problem is that the cost of the current collecting roll itself is extremely high. An object of the present invention is to fundamentally eliminate the inconvenience occurring in the above-mentioned current collecting roll.

[0007]

In order to eliminate the problem caused by the current collecting roll, a technique of eliminating the current collecting roll itself and establishing a technique for collecting current from a copper foil without using the current collecting roll is established. It was concluded that it was necessary, and as a result of repeated studies, we succeeded in establishing a submerged current collection method. With the submerged current collection method, both the anode plate applied to the copper foil and the cathode plate collecting current from the copper foil are directly connected to the DC power supply and placed in the electrolytic solution, and it is necessary to use the current collector roll without using This method applies a current to the copper foil and collects the current, and it has been found that the method can be suitably applied to a surface treatment process of the copper foil. Based on this finding, the present invention provides both an anode plate directly connected to a power supply for applying a current to a copper foil and a cathode plate directly connected to a power supply for collecting a current from the copper foil. Apply the required current to the copper foil without using a current collector roll, facing the copper foil inside, an electrochemical reaction where the copper foil becomes an anode and an electrochemical reaction where the copper foil becomes a cathode The present invention also provides a method for treating the surface of a copper foil for a printed circuit by a submerged current collection method, wherein the surface of the copper foil is electrochemically treated while using the same.
As an application example, a cathode plate is arranged in a first electrolytic cell to perform electrolytic treatment on a copper foil roughened surface, and then an anode plate is arranged in a second electrolytic bath to roughen the copper foil roughened surface. Or a combination in which the surface of the copper foil roughened surface is roughened using an anode plate in a single electrolytic cell, and the electrolytic treatment of the copper foil glossy surface is performed using a cathode plate. .
In the latter case, it is advantageous to separate the cathode plate by an anion exchange membrane.

[0008]

FIG. 1 is a conceptual view in which the submerged current collection method is applied to an electrolytic cell 2 for performing a process A on a copper foil 1 and an electrolytic cell 3 for performing a process B. An anode plate 5 directly connected to the positive electrode of the DC power supply 4 and a cathode plate 6 directly connected to the negative electrode of the DC power supply 4 are arranged facing the copper foil. Arrows indicate current flow. In FIG. 1, an electrochemical reaction is established in which the copper foil becomes an anode in the treatment A and the copper foil becomes the cathode in the treatment B. Therefore,
Treatment A can result in an electrolytic treatment, such as electrolytic polishing or electrolytic degreasing, that removes copper or deposits from the copper foil, and treatment B can result in an electrodeposition reaction, such as surface roughening or plating. On the other hand, by arranging the anode plate 5 and the cathode plate 6 in a single tank as shown in FIG. 3 or 5, the treatment A and the treatment B can be performed simultaneously on both surfaces of the copper foil in FIG. In the above, treatment A on one side of copper foil
And the process B can be performed continuously. Since the surface treatment of the copper foil involves a number of steps, the electrochemical reaction treatment A in which the copper foil becomes the anode and the electrochemical reaction treatment B in which the copper foil becomes the cathode are appropriately combined as described above. This makes it possible to perform various copper foil surface treatments by a submerged current collection method.

[0009]

(Copper roughening treatment conditions)

_{Cu: 5~50g / l H 2 SO} 4: 10~100g / l As: 0.01~5g / l liquid temperature: room temperature _{~50 ℃ D k: 5~80A / dm} 2 Time: 1-30 seconds

After the roughening treatment, thin copper plating (normal plating) is performed as a covering layer for preventing the particles from falling off. For example, the following conditions can be adopted. [Cover thin copper layer plating conditions] _{Cu: 30~100g / l H 2 SO} 4: 10~200g / l liquid temperature: room temperature _{~75 ℃ D k: 5~60A / dm} 2 Time: 1-30 seconds

It is preferable to perform a treatment for forming a metal layer composed of a metal selected from Cu, Cr, Ni, Fe, Co and Zn or an alloy layer composed of an alloy of two or more of these metals on the roughened surface. . Examples of alloy plating include Cu-Ni, Cu-Co, Cu-Ni-Co, C
Examples thereof include u-Zn and the like (for details, see JP-B-56-9028, JP-A-54-13971, JP-A-2-292895, JP-A-2-292894, JP-B-51-35711, See Japanese Patent Publication No. 54-6701). Such a treated layer serves as a final property of the copper foil and also functions as a barrier layer.

On the other hand, the glossy surface has a corrosion resistance and a heat oxidation resistance (160 ° C. or more × 30 minutes in air, preferably 200 ° C.
(For preventing discoloration such as oxidation under the conditions of at least 30 minutes, particularly preferably at least 240 ° C. for 30 minutes). For such a treatment, any of known methods can be used. For example, Zn plating is a typical example. The electrolysis conditions are given. [Zn plating conditions] _{ZnSO 4 · 7H 2 O: 50~35g} / l pH ( sulfate): 2.5 to 4.5 Liquid _{temperature: 40~60 ℃ D k: 0.05~0.4A /} dm 2 hours : 10 to 30 seconds The amount of deposited Zn is generally 30 to 250 µg / dm ² .

Then, in order to enhance the thermal oxidation resistance, Zn and Ni, Co, V,
A Zn alloy plating treatment made of one or more metals selected from W, Mo, Sn, Cr and the like can be performed. For example, taking a Zn-Ni alloy treatment as an example, this is preferably performed using a Zn-Ni electroplating bath, and preferably using a Zn-Ni electroplating bath.
Z having a composition of 0 to 97 wt% Zn and 3 to 50 wt% Ni
The n-Ni alloy layer is formed so as to be extremely thin with an adhesion amount of 100 to 500 μg / dm ² . If the Ni content is less than 3% by weight, the required improvement in thermal oxidation resistance cannot be obtained. On the other hand, if the Ni content exceeds 50% by weight, the solder wettability deteriorates, and the thermal oxidation resistance also deteriorates. If the amount of the Zn—Ni alloy layer is less than 100 μg / dm ² , the improvement in thermal oxidation resistance cannot be obtained. On the other hand, when it exceeds 500 μg / dm ² ,
The conductivity deteriorates due to the diffusion of Zn or the like. The Zn-Ni alloy layer enhances the thermal oxidation resistance of the glossy surface of the copper foil, and does not impair other properties such as solder wettability and resist adhesion. The amount of adhesion is made thin as described above so that the appearance is not so different from the copper color. The same applies to the Zn—Co alloy treatment. Examples of the composition and conditions of the Zn—Ni plating bath and the Zn—Co plating bath are as follows: [Zn—Ni (or Zn—Co) plating bath conditions] Zn: 5 to 50 g / l Ni (or Co): 1 to 50 g / l pH: 2.5 to 4 Temperature: 30 to 60 ° C. Current density: 0.5 to 5 A / dm ² Plating time: 0.1 to 10 seconds

Thereafter, the roughened surface and the glossy surface are subjected to a Cr-based antirust treatment. The Cr-based rust-preventive layer is formed by (1) a single coating treatment of chromium oxide, (2) a mixed coating treatment of chromium oxide and zinc and / or zinc oxide, or (3) a combination thereof. Rust prevention layer mainly composed of chromium oxide.

Regarding the single coating treatment of chromium oxide,
Immersion chromate may be used, but electrolytic chromate is often used. When weather resistance is required, electrolytic chromate is preferred. For example, conditions Examples of the electrolytic chromate treatment is as follows: (electrolytic chromate _{treatment): K 2 Cr 2 O 7} : 0.2~20g / l (Na 2 Cr 2 O 7, CrO 3) acid: phosphoric acid Sulfuric acid, organic acid pH: 1.0 to 3.5 Liquid temperature: 20 to 40 ° C. D _k : 0.1 to 0.5 A / dm ² hours: 10 to 60 seconds Cr adhesion amount is 50 μg / dm ² or less, Preferably 15 to 3
0 μg / dm ² .

[0016] The coating treatment of a mixture of chromium oxide and zinc / zinc oxide means that zinc or zinc oxide and chromium oxide are formed by electroplating using a plating bath containing zinc salt or zinc oxide and chromate. This is a process for coating the anticorrosive layer of the zinc-chromium group mixture thus formed, and is called electrolytic zinc-chromium treatment. As a plating bath, typically, K ₂ Cr ₂ O ₇ ,
At least one of dichromate such as Na ₂ Cr ₂ O ₇ or CrO ₃ and a water-soluble zinc salt such as ZnO, ZnSO
₄ - at least one 7H ₂ O, etc., a mixed aqueous solution of alkali hydroxide is used. Typical plating bath compositions and examples of electrolysis conditions are as follows: (electrolytic zinc / chromium treatment): K ₂ Cr ₂ O ₇ (Na ₂ Cr ₂ O ₇ or CrO ₃ ): 2 to 10 g / l NaOH or KOH: 10 to 50 g / l ZnO or _{ZnSO 4 · 7H 2 O: 0.05~10g} / l pH: 7~13 bath temperature: 20 to 80 ° C. current density: 0.05~5A / dm ² Time: 5 Anode: Pt-Ti plate, stainless steel plate, etc. Chromium oxide is required to have a coating amount of 15 μg / dm ² or more, and zinc is required to have a coating amount of 30 μg / dm ² or more. The thickness may be different between the roughened side and the glossy side. Such a rust prevention method is disclosed in JP-B-58-7077, 61-339.
08, 62-14040 and the like. It is also effective to combine chromium oxide alone and a mixture of chromium oxide and zinc / zinc oxide.

As described above, the roughened surface of the copper foil passes through the steps of electrolytic degreasing (only in the case of rolled copper foil), surface roughening, covering copper thin-layer plating, treating, and rustproofing. The glossy surface of copper foil is also alkaline degreasing (only for rolled copper foil)
Through processes such as corrosion resistance / heat oxidation treatment-rust prevention treatment.
Hereinafter, a submerged current collecting method will be described for some examples of processing of a copper foil.

(Example 1): Combination example of electrolytic treatment and roughening treatment This example shows an example in which the electrolytic treatment and the roughening treatment of a rolled copper foil are performed in two separate electrolytic tanks. Here, the processing A in FIG.
Corresponds to electrolytic treatment (specifically, electrolytic degreasing), and treatment B corresponds to roughening treatment. As shown in FIG. 2, the electrolytic cell 2 contains an alkaline solution for electrolytic treatment, for example, NaOH at 30 to 50 ° C .: an aqueous sodium hydroxide solution of 5 to 50 g / l. In the electrolytic cell 3, a general copper sulfate solution (for example, Cu: 10 to 50 g /
1, H ₂ SO ₄ : 50-100 g / l).
Further, in the electrolytic cell 2, a cathode for electrolytic treatment such as a stainless steel plate directly connected to a negative electrode of the DC power supply 4 is provided as a cathode plate 6. In the electrolytic cell 3, a roughening anode, which is a soluble anode or an insoluble anode directly connected to the positive electrode of the DC power supply 4, is provided as an anode plate 5. A current is supplied from the DC power supply 4 in the electrolytic cell 3 so as to have a current density of 5 to 50 A / dm ² . The copper foil 1 is subjected to an electrolytic treatment (specifically, electrolytic degreasing) in the electrolytic cell 2 on the roughened surface, and then subjected to a roughening treatment for performing copper-like electrodeposition in the electrolytic cell 3. . Under the above conditions, when the copper foil for a printed circuit was subjected to a roughening treatment, it was possible to obtain a uniform surface treatment and good peel properties over the entire surface.

(Example 2): Example of double-sided copper foil treatment using a surface treatment tank alone (No. 1) As shown in FIG. 3, the positive electrode of the DC power supply 4 is connected to the anode plate 5, and the negative electrode is connected to the cathode plate 6, respectively. Connecting. The anode plate 5 and the cathode plate 6 are arranged in the electrolytic cell 7 so as to face the path of the copper foil 1, and the cathode plate 6 forms a counter cathode. A general copper sulfate solution (for example, Cu: 10 to 50 g / l, H ₂ SO ₄ : 50) used for roughening a copper foil is provided in the electrolytic cell 7.
１００100 g / l). Thereby, on the roughened surface, a copper roughening treatment reaction is performed by the anode plate 5, while on the glossy surface, an electrolytic treatment (specifically, electrolytic polishing) by the cathode plate 6 is performed.
Each reaction was formed, and a copper foil having a good and uniform treated surface and peeling properties could be produced without using a current collecting roll.

When a conventional current collecting roll is used, the defect occurrence rate of several to several tens of km / km due to the transfer of metal objects deposited on the current collecting roll, the pressing damage, etc. is reduced. It has become possible to completely maintain 0 pcs / km. In this case, there were concerns about changes in surface characteristics and appearance due to the electropolishing reaction of the glossy surface, but this problem could be completely solved by optimizing the current density of the cathode plate 6 and the like. . That is, it was also found that by partially masking the cathode plate 6 to increase the current density, the electropolishing was not surprisingly performed so much. It is presumed that the reason is that the current is concentrated on a relatively sharp portion of the glossy surface or the like, and the glossy surface is entirely smoothed.

(Example 3): Example of double-sided copper foil treatment using a surface treatment tank alone (No. 2) As a disadvantage of Example 2, a copper deposition reaction is formed on the cathode plate 6, so that it is periodically replaced. Need work. Therefore, in order to solve this problem, as shown in FIG. 4, an example in which an anion exchange membrane 8 is arranged between the cathode plate 6 and the copper foil 1 is shown. Practically, it is preferable that the entire cathode plate 6 is covered with the anion exchange membrane 8, and the inside thereof is made only of sulfuric acid. The working conditions are the same as in the second embodiment.

(Example 4): Example of single-sided continuous processing of copper foil using only a surface treatment tank As shown in FIG. 5, the anode plate 5 and the cathode plate 6 from the DC power supply 4 are only applied to the roughened surface of the copper foil. The cathode plate 6 was subjected to an electrolytic treatment (specifically, electrolytic polishing), and the anode plate 5 was subjected to a copper roughening treatment reaction. An anion exchange membrane 8 was arranged between the cathode plate 6 and the copper foil 1. It was possible to obtain a copper foil for a printed circuit having very good peel characteristics without giving any change in characteristics or appearance on the glossy surface.

(Example 5): Example of double-sided copper foil treatment using a surface treatment tank alone (part 3) This example is an example of continuous double-sided copper foil treatment. As shown in FIG.
The anode plate 5 and the cathode plate 6 from the DC power supply 4 and the anode plate 5 'and the cathode plate 6' from the DC power supply 4 'are arranged with respect to the copper foil 1, and the electrolytic treatment of the roughened surface of the copper foil in the cathode plate 6 The treatment (specifically, electrolytic polishing) and the electrodeposition reaction of copper on the glossy surface of the copper foil on the anode plate 5, and the electrolytic treatment (specifically, electrolytic polishing) of the glossy surface of the copper foil on the cathode plate 6 ′ Then, a roughening treatment reaction was performed on the roughened surface of the copper foil on the anode plate 5 '. The anion exchange membrane 8 was arranged between the cathode plate 6 and the copper foil 1 and around the cathode plate 6 '.

Specifically, 10 A / dm ² ×
28 A and 80 A / dm ² × 3.5 seconds on the cathode plate 6 and 70 A / dm ² × 4 seconds on the anode plate 5 ′ and the cathode plate 6 ′
After applying a current of 320 A / dm ² × 0.88 seconds to the roughened surface, the roughened surface was subjected to normal plating at 30 A / dm ² × 7.2 seconds, showing a normal peel strength of 2.25 kg / cm and a glossy surface. Had no change in appearance due to any characteristics.

On the other hand, as shown in FIG. 7, the roughened surface of the copper foil was subjected to a two-step roughening treatment by a conventional method using a current collecting roll. After applying a current of 70 A / dm ² × 2 seconds to the anode plate 16 and a current of 70 A / dm ² × 2 seconds to the cathode plate 16 ′, the roughened surface was subjected to normal plating at 30 A / dm ² × 7.2 seconds. The normal peel strength was 0.11 kg / cm.

As can be seen from this example, when the current collecting method in a liquid according to the present invention is used, the electropolishing before the roughening treatment has at least no adverse effect on the normal peel strength, but is caused by the current collecting roll. This is very effective because it can completely prevent the occurrence of defects due to the transfer of metal objects and the damage caused by pressing.

[0027]

【The invention's effect】

1. It enables the production of defect-free copper foil without any indentation or dents. 2. It enables low-cost surface treatment that does not require a current collecting roll.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram in a case where a submerged current collection method is applied to an electrolytic cell for performing a process A on a copper foil and an electrolytic cell for performing a process B.

FIG. 2 shows an example in which the electrolytic treatment and the roughening treatment are performed in two separate electrolytic cells according to the present invention.

FIG. 3 shows an example of a double-sided copper foil treatment using the surface treatment tank alone according to the present invention.

FIG. 4 shows an example of a copper foil double-sided treatment in a surface treatment tank alone using an anion exchange membrane according to the present invention.

FIG. 5 shows an example of single-sided continuous processing of copper foil in a surface treatment tank using the anion exchange membrane according to the present invention alone.

FIG. 6 shows a specific example of another continuous treatment of a copper foil double-side treatment example using only a surface treatment tank using an anion exchange membrane according to the present invention.

FIG. 7 shows an example of single-sided continuous processing of copper foil by a conventional method.

FIG. 8 is a conceptual view showing the use of a conventional current collecting roll in a part of a copper foil production surface treatment line.

[Explanation of symbols]

 Reference Signs List 1 Copper foil 2, 3, 7 Electrolyzer 4, 4 'DC power supply 5, 5' Anode plate 6, 6 'Cathode plate 8 Anion exchange membrane 9, 9', 9 ", 9 '" Guide roll 10, 10' Immersion roll 12, 12 'Current collecting roll 13, 13' Immersion roll 14 Guide roll 15, 15 'DC power supply 16, 16' Anode plate

Claims (4)

(57) [Claims] 1. An anode plate directly connected to a power supply for applying a current to a copper foil and a cathode plate directly connected to a power supply for collecting a current from the copper foil are both connected to the copper foil in an electrolytic bath. Apply the required current to the copper foil without using a current collector roll, and collect the copper while using the electrochemical reaction in which the copper foil becomes the anode and the electrochemical reaction in which the copper foil becomes the cathode. A surface treatment method for a copper foil for a printed circuit by a submerged current collection method, wherein the foil is subjected to an electrochemical surface treatment. 2. A roughened surface of a copper foil is subjected to electrolytic treatment by disposing a cathode plate in a first electrolytic cell, and thereafter, a roughened surface of the copper foil is disposed by disposing an anode plate in a second electrolytic bath. 2. The method for treating a copper foil surface for a printed circuit according to claim 1, wherein: 3. The printed circuit according to claim 1, wherein the surface of the copper foil roughened surface is roughened using an anode plate in a single electrolytic cell, and the copper foil glossy surface is electrolytically processed using a cathode plate. Copper foil surface treatment method. 4. The method according to claim 3, wherein the cathode plate is separated by an anion exchange membrane.