Ultrathin electrolytic copper foil and method of producing the same

Abstract

To provide a carrier-less ultrathin copper electrolytic foil of high tensile strength and low roughness not requiring a carrier foil, and a method of producing the same.SOLUTION: In order to achieve the objective, an ultrathin electrolytic copper foil or the like is employed which has a gauge thickness of 5 μm or less, is composed of a first copper layer formed by electrolytic copper strike plating and a second copper layer formed using a sulfuric acid acidic copper electrolytic solution, exhibits tensile strength of 300 N / mm2 or more and 620 n / mm2 or less, and reduces generation of pinholes to the extent practicable.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ultra-thin electrolytic copper foil and a manufacturing method thereof, and in particular to an ultra-thin electrolytic copper foil with no carrier and a gauge thickness of 5 μm or less and a manufacturing method thereof. [Background technology]

[0002] Copper foil with a gauge thickness of 5 μm or less is used to form fine-pitch circuits. Such copper foils are mainly classified into electrolytic copper foil and rolled copper foil.

[0003] As an example of an ultra-thin electrolytic copper foil, a carrier-attached ultra-thin copper foil and a manufacturing method thereof are disclosed in Patent Document 1. More specifically, Patent Document 1 discloses an electrolytic copper foil with a carrier foil in which "a carrier foil having a surface in which the average distance between valleys of the surface irregularities is 15 μm or less and the maximum waviness height difference is 0.8 μm or less," an "organic release layer," and an "ultra-thin copper foil" are laminated in this order.

[0004] Next, Patent Document 2 discloses a method for producing an ultra-thin electrolytic copper foil with a carrier foil, in which the surface of a carrier foil is plated with Cr, Ni, Fe, or an alloy thereof to form a release layer with an inorganic component, a P-containing Cu layer or a P-containing Cu alloy layer is strike-plated on the release layer in a P-containing Cu or P-containing Cu alloy plating bath, an ultra-thin layer is formed on the strike-plated layer by Cu or Cu alloy plating, and an ultra-thin copper foil is formed on the ultra-thin layer by Cu or Cu alloy plating.

[0005] As can be understood from the above, in the case of ultra-thin electrodeposited copper foils, as in Patent Document 1, in order to ensure handleability and prevent defects such as wrinkles and folds from occurring in the ultra-thin copper foil when the ultra-thin electrodeposited copper foil is supplied to the market, it is common to laminate a "carrier foil" as a support layer and an "ultra-thin copper foil." [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2016 / 117587 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-207032 Summary of the Invention [Problem to be solved by the invention]

[0007] However, conventional ultra-thin copper foils have the following problems. In the case of ultra-thin electrolytic copper foils, the use of a carrier foil improves the handling of the foil during handling. However, after lamination with a substrate, base material, etc., the carrier foil is peeled from the copper foil, and the carrier foil is either disposed of as waste or requires recycling, which requires post-processing costs. Furthermore, the additional process required to peel the carrier foil increases manufacturing costs. Furthermore, because "ultra-thin electrolytic copper foil" is sold integrated with a "carrier foil" via a "bonding interface," product costs rise dramatically compared to when a carrier foil is not required.

[0008] On the other hand, in the case of rolled ultra-thin copper foil, the thinner the copper foil thickness to be obtained, the more severe the damage to the rolling rolls used in the rolling process, which increases the maintenance costs of the rolling rolls and shortens the life of the rolling rolls, resulting in an increase in the manufacturing equipment costs. As a result, the product cost of rolled ultra-thin copper foil becomes very expensive.

[0009] For the reasons mentioned above, there has been a demand in the market for cheaper, higher quality ultra-thin electrodeposited copper foils. [Means for solving the problem]

[0010] Therefore, in order to solve the above-mentioned problems, it was thought that it would be preferable to develop an ultra-thin electrodeposited copper foil that does not require a carrier foil, and as a result of extensive research, the following invention was conceived.

[0011] A. Ultra-thin electrodeposited copper foil according to the present application The electrodeposited copper foil according to the present application is an electrodeposited copper foil with a gauge thickness of 5 μm or less, which comprises a first copper layer formed by electrolytic copper strike plating and a second copper layer formed in a sulfuric acid copper electrolyte, and has a strength of 300 N / mm 2 More than 620N / mm 2 It has the following tensile strength and minimizes pinhole formation. Its greatest feature is that it can be supplied to the market without using a carrier foil.

[0012] The outer surface (deposit surface) of the second copper layer of the electrodeposited copper foil according to the present application preferably has Rzjis of less than 1 μm.

[0013] The electrodeposited copper foil according to the present application preferably contains sulfur in an amount of 90 ppm to 108 ppm, chlorine in an amount of 280 ppm to 350 ppm, and carbon in an amount of 300 ppm to 350 ppm.

[0014] The first copper layer of the electrodeposited copper foil according to the present application is preferably a copper layer formed by electrolytic copper strike plating to a gauge thickness of 0.3 μm or more and 0.5 μm or less, and the second copper layer is preferably a copper layer formed in a sulfuric acid copper electrolyte to a gauge thickness of 2.5 μm or more and 4.7 μm or less.

[0015] The first copper layer formed by the electrolytic copper strike plating of the electrolytic copper foil according to the present application is preferably a layer containing P and K as components.

[0016] B. Surface-treated ultra-thin electrodeposited copper foil according to the present application The surface-treated ultra-thin electrodeposited copper foil according to the present application is the one in which the surface of the above-mentioned ultra-thin electrodeposited copper foil has been subjected to at least one of rust prevention treatment, roughening treatment, silane coupling agent treatment, etc. Here, the "surface of the ultra-thin electrodeposited copper foil" refers to the outer surfaces of the first copper layer and the second copper layer constituting the ultra-thin electrodeposited copper foil, and both sides or only one of the sides may be surface-treated.

[0017] C. Manufacturing method of ultra-thin electrodeposited copper foil according to the present application The method for producing an ultrathin electrodeposited copper foil according to the present application is characterized in that the ultrathin electrodeposited copper foil is produced by electrolysis using a stainless steel cathode as a cathode and an insoluble anode as an anode in the following steps:

[0018] Step 1: The electrodeposition surface of the stainless steel cathode is cleaned. Step 2: A strike plating layer having a gauge thickness of 0.3 μm or more and 0.5 μm or less is deposited on the cleaned electrodeposited surface of the stainless steel cathode using an electrolytic copper strike plating solution to form a first copper layer. Step 3: The surface of the first copper layer is subjected to an electrolytic treatment using a sulfuric acidic copper electrolyte to form a second copper layer having a gauge thickness of 2.5 μm or more and 4.7 μm or less, thereby forming an ultra-thin electrolytic copper foil layer consisting of the first copper layer and the second copper layer and having a gauge thickness of 5.0 μm or less on the surface of the stainless steel cathode. Step 4: The ultra-thin electrolytic copper foil layer on the surface of the stainless steel cathode is peeled off and collected to obtain an ultra-thin electrolytic copper foil having a gauge thickness of 5.0 μm or less.

[0019] The electrolytic copper strike plating solution used in the method for producing an ultra-thin electrodeposited copper foil according to the present application preferably has the following basic composition: Copper sulfate pentahydrate concentration: 18~25g / L Potassium pyrophosphate concentration: 30-40g / L Surfactant: 10-100mg / L

[0020] The sulfuric acid copper electrolyte used in the method for producing an ultra-thin electrodeposited copper foil according to the present application preferably has the following basic composition: Copper sulfate pentahydrate concentration: 180~300g / L Free sulfuric acid concentration: 80-140g / L Chlorine concentration: 15-70mg / L Additives (brighteners, smoothing agents, suppressors, etc.): appropriate amount [Effects of the Invention]

[0021] The ultra-thin electrodeposited copper foil according to the present application, which has a gauge thickness of 5 μm or less, has good tensile strength due to the "first copper layer formed by electrolytic copper strike plating" and the "second copper layer formed with a sulfuric acid copper electrolyte," and minimizes the occurrence of pinholes despite its thinness. Furthermore, ultra-thin electrodeposited copper foils with excellent handleability can now be supplied to the market even without the carrier foil according to the present application. This makes it possible to provide high-quality copper-clad laminates, printed wiring boards, and other laminate materials using inexpensive ultra-thin electrodeposited copper foils. Furthermore, as will be described later, the method for producing the ultra-thin electrodeposited copper foil according to the present application does not require the use of an electrolytic drum conventionally used in the production of electrodeposited copper foil, and can be produced using a general surface treatment machine or a more easily introduced, compact treatment machine, making it possible to adopt an economical production method. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic cross-sectional view of an ultra-thin electrodeposited copper foil according to the present application. [Figure 2] This shows the detected peaks of P and K in a line analysis by GD-OES from the first copper layer to the second copper layer in a cross section of an ultra-thin electrodeposited copper foil. [Figure 3] FIG. 2 is a diagram showing the physical properties of an electrolytic copper foil and the results of SEM image observation of the surface of the electrolytic copper foil. DETAILED DESCRIPTION OF THE INVENTION

[0023] The configuration and manufacturing method of the ultrathin electrodeposited copper foil according to the present application will be described below.

[0024] A. Form of the ultra-thin electrodeposited copper foil according to the present application The ultra-thin electrodeposited copper foil according to the present application is an electrodeposited copper foil with a gauge thickness of 5 μm or less, and is shown in the schematic cross section of FIG. 1. This ultra-thin electrodeposited copper foil 1 is composed of a "first copper layer 2 formed by electrolytic copper strike plating" and a "second copper layer 3 formed in a sulfuric acid copper electrolyte." This two-layer structure allows for a "strength of 300 N / mm 2 More than 620N / mm 2As a result, it will be possible to supply the product to the market without using a carrier foil, which was not possible with conventional ultra-thin electrodeposited copper foil.

[0025] Moreover, the ultra-thin electrodeposited copper foil according to the present application, even though thin, can minimize pinholes that tend to occur in ultra-thin electrodeposited copper foils. In the case of an ultra-thin electrodeposited copper foil manufactured using only a sulfuric acid copper electrolyte, many pinholes occur in the ultra-thin electrodeposited copper foil, allowing penetration of resist solutions, etching solutions, etc., and causing defects in the formed conductor. In contrast, by providing a "second copper layer 3 formed with a sulfuric acid copper electrolyte" on the surface of a "first copper layer 2 formed by electrolytic copper strike plating" as a base, pinholes occurring in the second copper layer can be minimized.

[0026] The reason why the gauge thickness of the ultra-thin electrodeposited copper foil in the present application is set to 5.0 μm or less is as follows: It is generally accepted that electrodeposited copper foils with a thickness exceeding 5.0 μm do not pose a handling problem, are generally marketed without a carrier foil, and the concept of ultra-thin copper foil no longer applies. Just to be clear, the "gauge thickness of the ultra-thin electrodeposited copper foil" referred to here refers to the total thickness of the "first copper layer 2 formed by electrolytic copper strike plating" and the "second copper layer 3 formed in a sulfuric acid copper electrolyte." The "gauge thickness" refers to a value measured with a micrometer or an eddy current film thickness meter.

[0027] In the ultra-thin electrodeposited copper foil according to the present application, the first copper layer 2 is preferably a copper layer formed by electrolytic copper strike plating to a gauge thickness of 0.3 μm to 0.5 μm, and the second copper layer 3 is preferably a copper layer formed using a sulfuric acid copper electrolyte to a gauge thickness of 2.5 μm to 4.7 μm. If the gauge thickness of the first copper layer 2 is less than 0.3 μm, the ultra-thin electrodeposited copper foil cannot obtain sufficient tensile strength, and the pinhole generation suppression effect of the second copper layer is also difficult to obtain. On the other hand, if the gauge thickness of the first copper layer 2 exceeds 0.5 μm, there is no particular problem, but the pinhole generation suppression effect also saturates, so it is preferable to switch to forming the second copper layer 3 using a sulfuric acid copper electrolyte.

[0028] In the ultrathin electrodeposited copper foil 1 according to the present application, the outer surface 4 (deposit surface) of the second copper layer 3 preferably has a surface roughness Rzjis of less than 1 μm, providing a sufficiently low-profile surface. This is because such a low-profile surface can provide an adhesive surface that facilitates the formation of fine-pitch circuits even after subsequent roughening treatment, rust prevention treatment, etc. Here, the term "outer surface 4 (deposit surface) of the second copper layer 3" is used to clarify that it is not the surface of the second copper layer 3 that comes into contact with the first copper layer 2, but rather the final copper deposit surface.

[0029] Furthermore, when analyzed by total dissolution, the ultra-thin electrodeposited copper foil 1 according to the present application contains sulfur of 90 ppm to 108 ppm, chlorine of 280 ppm to 350 ppm, and carbon of 300 ppm to 350 ppm. When the sulfur content of the ultra-thin electrodeposited copper foil 1 is less than 90 ppm, the mechanical strength of the ultra-thin electrodeposited copper foil 1 is not improved, which is undesirable. On the other hand, when the sulfur content exceeds 108 ppm, the ultra-thin electrodeposited copper foil 1 tends to become embrittled, which is undesirable. When the chlorine concentration of the ultra-thin electrodeposited copper foil 1 is less than 280 ppm, the electrolysis operation becomes unstable, and a good product cannot be obtained. On the other hand, when the chlorine concentration of the ultra-thin electrodeposited copper foil 1 is more than 350 ppm, the roughness of the copper deposit surface tends to increase, which is undesirable. When the carbon concentration of the ultra-thin electrodeposited copper foil 1 is less than 300 ppm, the mechanical strength decreases, which is undesirable. On the other hand, when the carbon concentration of the ultra-thin electrodeposited copper foil 1 is more than 350 ppm, the electrical resistance increases, which is undesirable.

[0030] The first copper layer 2 formed by the electrolytic copper strike plating of the ultra-thin electrodeposited copper foil 1 according to the present application preferably contains P and K as components. FIG. 2 shows the results of a component analysis performed by GD-OES depth profile analysis from the first copper layer side 2 to the second copper layer 3 in a cross section of the ultra-thin electrodeposited copper foil 1. As can be seen from FIG. 2, the peaks of P and K are clearly observed. The inclusion of P and K in the first copper layer 2 allows for a dense copper precipitate structure. Then, when the second copper layer 3 is formed on the surface of this first copper layer 2 using a sulfuric acid acid copper electrolyte, a thin copper layer free from defects such as pinholes can be provided.

[0031] B. Surface-treated ultra-thin electrodeposited copper foil according to the present application The surface-treated ultra-thin electrodeposited copper foil according to the present application is obtained by subjecting the surface of the above-mentioned ultra-thin electrodeposited copper foil to at least one of rust prevention treatment, roughening treatment, silane coupling agent treatment, etc. These surface treatments are intended not only for rust prevention but also to generate an anchor effect between the ultra-thin electrodeposited copper foil and the resin material when the foil is laminated with a resin layer, a resin substrate, etc. to form a copper-clad laminate and processed into a printed wiring board, thereby improving adhesion and heat resistance.

[0032] The roughening treatment referred to here generally involves depositing fine metal particles made of copper or a copper alloy on the surface of an ultra-thin electrolytic copper foil. For example, a method is employed in which fine particles are deposited and deposited on the ultra-thin electrolytic copper foil under burnt plating conditions, and then, if necessary, a coating plating is applied to prevent the fine particles from falling off.

[0033] For the rust prevention treatment of the ultra-thin electrodeposited copper foil 1, it is preferable to selectively use either inorganic or organic rust prevention depending on the application. For inorganic rust prevention, zinc, brass, zinc-nickel alloy, zinc-cobalt alloy, chromate treatment, etc. are preferred. For organic rust prevention, imidazoles, triazoles, etc. are preferred. Next, silane coupling agent treatment is used as an auxiliary agent to improve adhesion between the surface of the surface-treated ultra-thin electrodeposited copper foil and the resin layer, improving the wettability between the surface of the surface-treated ultra-thin electrodeposited copper foil and the resin layer. For this silane coupling agent treatment, various agents can be used depending on the application, including general epoxy-functional silane coupling agents, olefin-functional silane coupling agents, and acrylic-functional silane coupling agents.

[0034] The "surface of the ultra-thin electrodeposited copper foil" mentioned above refers to the outer surfaces of the first copper layer and the second copper layer constituting the ultra-thin electrodeposited copper foil, and both sides or only one of the sides may be surface-treated.

[0035] C. Manufacturing Method of Ultra-thin Electrodeposited Copper Foil Related to the Present Application The method for producing an ultra-thin electrodeposited copper foil according to the present application involves electrolysis of the ultra-thin electrodeposited copper foil using a stainless steel cathode as the cathode and an insoluble anode as the anode. Each step will be described below.

[0036] Step 1: Cleaning the electrodeposited surface of the stainless steel cathode. There are no particular limitations on the cleaning method used, and any of the following procedures can be selected as the cleaning treatment: degreasing, pickling, water washing, hot water washing, etc.

[0037] Step 2: A first copper layer is formed on the cleaned electrodeposited surface of the stainless steel cathode using an electrolytic copper strike plating solution. The following pyrophosphate strike copper plating solution is preferably used as this electrolytic copper strike plating solution. The "P ratio" shown below is a value defined as the weight ratio of Cu to P2O7 in the plating solution [total P2O7 / Cu]. Polyethylene glycol or the like is preferably used as the surfactant.

[0038] [Composition and operating conditions of copper pyrophosphate plating solution] Copper sulfate pentahydrate concentration: 18~25g / L Potassium pyrophosphate concentration: 30-40g / L Surfactant: 10-100mg / L Potassium hydroxide 200g / L: 1-3mg / L P ratio: 3.3~4.6 pH: 8.5~9 Cathode current density: 0.3~1A / dm 2 Bath temperature: 20~40℃

[0039] In this manner, a strike-plated layer with a gauge thickness of 0.3 μm to 0.5 μm, which will become the first copper layer, is deposited on the electrodeposited surface of the stainless steel cathode. By using a copper pyrophosphate plating solution in this way, a copper deposit coating with excellent throwing power and a smooth surface can be obtained. In the following step 3, a second copper layer is formed on the surface of the first copper layer. However, since the solution composition used is different, it is preferable to carry the solution from step 2 into step 3 and clean it with water, hot water, pickling, etc. to prevent compositional changes.

[0040] Step 3: The surface of the first copper layer is electrolytically treated using a sulfuric acid acid copper electrolyte to form a second copper layer on the surface of the first copper layer. The sulfuric acid acid copper electrolyte used here can be any solution that can be used in conventional electrolytic copper foil manufacturing, and there are no particular limitations. Furthermore, it is preferable to use a brightener such as disodium 3,3'-dithiobis(1-propanesulfonate), a smoothing agent such as polyethylene glycol or polyethyleneimine, and an inhibitor such as a cationic organic dye or a thiol-based organic substance. Examples are shown below.

[0041] [Composition of sulfuric acid copper electrolyte and operating conditions] Copper sulfate pentahydrate concentration: 180~300g / l Free sulfuric acid concentration: 80~140g / l Chlorine concentration: 15-70 ppm Brightener: 10-100mg / L Smoothing agent: 20-60mg / L Inhibitor: 20-40mg / L Current density: 20~80A / dm 2 Bath temperature: 40~60℃

[0042] In this way, a "second copper layer having a gauge thickness of 2.5 μm to 4.7 μm" is formed on the smooth surface of the first copper layer having a gauge thickness of 0.3 μm to 0.5 μm. At this stage, an "ultra-thin electrolytic copper foil layer consisting of the first copper layer and the second copper layer and having a gauge thickness of 5.0 μm or less" is obtained on the surface of the stainless steel cathode. In the following step 4, ultra-thin electrolytic copper foil is obtained, so it is preferable to perform cleaning by washing with water, washing with hot water, etc.

[0043] Step 4: The ultra-thin electrolytic copper foil layer on the surface of the stainless steel cathode is peeled off and harvested. There are no particular limitations on the harvesting method at this time, and it is common to peel off the ultra-thin electrolytic copper foil layer on the surface of the stainless steel cathode, dry the obtained ultra-thin electrolytic copper foil with a gauge thickness of 5.0 μm or less, and wind it up on a roll.

[0044] Surface treatment step: The surface treatment of the ultra-thin electrolytic copper foil is an optional step depending on the application. The following methods are preferably employed as the surface treatment method. For example, various surface treatments are performed on the outer surface of the second copper layer of the ultra-thin electrolytic copper foil, while leaving the ultra-thin electrolytic copper foil layer on the surface of the stainless steel cathode. When this method is employed, it is preferable to provide a surface treatment step between the above steps 3 and 4. It is also preferable to employ a method in which the ultra-thin electrolytic copper foil layer on the surface of the stainless steel cathode is peeled off, and the obtained roll-shaped ultra-thin electrolytic copper foil is surface-treated on both sides or one side using a surface treatment machine. [Example]

[0045] The ultra-thin electrolytic copper foils according to the examples were produced as follows, using a stainless steel cathode as the negative electrode and an insoluble anode as the positive electrode.

[0046] Step 1: The electrodeposited surface of the stainless steel cathode was degreased with a sodium hydroxide solution and washed with hot water for cleaning.

[0047] Step 2: A first copper layer was formed on the electrodeposited surface of the stainless steel cathode that had been subjected to the cleaning treatment using an electrolytic copper strike plating solution.

[0048] [Composition and operating conditions of copper pyrophosphate plating solution] Copper sulfate pentahydrate concentration: 5g / L Potassium pyrophosphate concentration: 35g / L Surfactant: 50mg / L Potassium hydroxide 200g / L: 1mL / L P ratio:3.7 pH: 8.5 Cathode current density: 0.5A / dm 2 Bath temperature: 25℃

[0049] In this manner, a strike plating layer with a smooth surface and a gauge thickness of 0.5 μm, which would become the first copper layer, was deposited on the electrodeposited surface of the stainless steel cathode, and the layer was then cleaned by rinsing with water to prevent any change in the composition of the solution used to form the second copper layer.

[0050] Step 3: The surface of the first copper layer was electrolytically treated using a sulfuric acid acidic copper electrolyte to form a second copper layer on the surface of the first copper layer. The following sulfuric acid acidic copper electrolyte was used at this time.

[0051] [Composition of sulfuric acid copper electrolyte and operating conditions] Copper sulfate pentahydrate concentration: 50g / L Free sulfuric acid concentration: 120g / L Chlorine concentration: 50 ppm Brightener: 100mg / L Smoothing agent: 50mg / L Inhibitor: 30mg / L Current density: 30A / dm 2 Bath temperature: 50℃

[0052] In this way, a "second copper layer with a gauge thickness of 2.6 μm" was formed on the surface of the "smooth first copper layer with a gauge thickness of 0.5 μm." At this stage, an "ultra-thin electrolytic copper foil layer with a gauge thickness of 3.1 μm consisting of the first copper layer and the second copper layer" was obtained on the surface of the stainless steel cathode, and was then cleaned by rinsing with water.

[0053] Step 4: The ultra-thin electrolytic copper foil on the surface of the stainless steel cathode was peeled off, and the resulting ultra-thin electrolytic copper foil with a gauge thickness of 3.1 μm was dried and taken up in a roll.

[0054] The evaluation results of the physical properties of the ultra-thin electrodeposited copper foil obtained in Example 1 are shown in a list in FIG. 3 so as to enable comparison with other Examples and Comparative Examples. [Example]

[0055] In Example 2, steps 1 to 3 were carried out in the same manner as in Example 1, and a "second copper layer with a gauge thickness of 4.3 μm" was formed on the surface of a "smooth first copper layer with a gauge thickness of 0.5 μm." At this stage, an "ultra-thin electrolytic copper foil layer with a gauge thickness of 4.8 μm consisting of the first copper layer and the second copper layer" was obtained on the surface of the stainless steel cathode, and cleaning was carried out by rinsing with water.

[0056] Step 4: The ultra-thin electrolytic copper foil on the surface of the stainless steel cathode was peeled off, and the resulting ultra-thin electrolytic copper foil with a gauge thickness of 4.8 μm was dried and taken up in a roll.

[0057] The evaluation results of the physical properties of the ultra-thin electrodeposited copper foil obtained in Example 2 are shown in a list in FIG. 3 so that they can be compared with other Examples and Comparative Examples.

[0058] In the comparative example, step 2 described in Example 1 was not performed, and only a "second copper layer having a gauge thickness of 3.2 μm" was formed, and an "ultra-thin electrolytic copper foil layer having a gauge thickness of 3.2 μm" was obtained on the surface of the stainless steel cathode, and cleaning was performed by rinsing with water. The subsequent steps were performed in the same manner as in Example 1.

[0059] The evaluation results of the physical properties of the ultra-thin electrodeposited copper foil obtained in this comparative example are shown in a list in FIG. 3 so that they can be compared with other examples.

[0060] 〔evaluation〕 The ultrathin electrodeposited copper foils produced in Examples 1 and 2 and Comparative Example were evaluated for physical properties such as tensile strength, elongation, and surface roughness, and the results of observation of the presence or absence of pinholes on the copper foil surface by SEM are shown in FIG. 3 below.

[0061] 3, it can be seen that pinholes do not occur on the surface of the ultra-thin electrodeposited copper foil in Examples 1 and 2 because they have a strike-plated layer with a gauge thickness of 0.5 μm and a smooth surface that serves as the first copper layer. In contrast, the Comparative Example does not have a strike-plated layer with a gauge thickness of 0.5 μm and a smooth surface that serves as the first copper layer, so the occurrence of pinholes can be clearly seen.

[0062] Next, with regard to the tensile strength, Example 1 was 474.4 N / mm 2 , and Example 2 is 604.0 N / mm 2 This gives 300N / mm 2 More than 620N / mm 2 On the other hand, the ultra-thin electrodeposited copper foil according to the comparative example was difficult to handle and had pinholes on the surface of the copper foil, making it difficult to measure the tensile strength accurately, and therefore measurement was not performed.

[0063] With regard to Rzjis, Example 1 achieved a result of 0.43 μm, and Example 2 achieved a result of 0.43 μm, which indicates that Examples 1 and 2 have a surface roughness Rzjis of less than 1 μm, making it possible to produce ultra-thin electrodeposited copper foils with a sufficiently low-profile surface. On the other hand, the comparative example achieved an Rzjis of 4.67 μm, which is significantly higher than the target of 1 μm. [Industrial Applicability]

[0064] By using the present invention, it becomes possible to produce an ultra-thin electrodeposited copper foil without using a carrier foil. As a result, it becomes possible to provide a higher-quality ultra-thin electrodeposited copper foil at a lower cost. Furthermore, since it can be produced without using large manufacturing equipment such as an electrolytic drum or a surface treatment machine used in the production of electrodeposited copper foil, there is also the advantage that excessive capital investment is not required. [Explanation of symbols]

[0065] 1 Ultra-thin electrolytic copper foil 2 First copper layer 3 Second copper layer 4. Outer surface of second copper layer

Claims

1. An electrolytic copper foil with a gauge thickness of 5 μm or less, which is composed of a first copper layer formed by electrolytic copper strike plating and a second copper layer formed in a sulfuric acid copper electrolyte, and has a strength of 300 N / mm ２ More than 620N / mm ２ An ultra-thin electrodeposited copper foil characterized by having the following tensile strength and minimizing the occurrence of pinholes.

2. The ultra-thin electrodeposited copper foil according to claim 1, wherein the outer surface (deposition surface) of the second copper layer of the electrodeposited copper foil has an Rzjis of less than 1 μm.

3. 2. The ultra-thin electrolytic copper foil according to claim 1, wherein the electrolytic copper foil contains 90 ppm to 108 ppm of sulfur, 280 ppm to 350 ppm of chlorine, and 300 ppm to 350 ppm of carbon.

4. 2. The ultra-thin electrodeposited copper foil according to claim 1, wherein the first copper layer of the electrodeposited copper foil is a copper layer formed by electrolytic copper strike plating having a gauge thickness of 0.3 μm or more and 0.5 μm or less, and the second copper layer is a copper layer formed in a sulfuric acid copper electrolytic solution having a gauge thickness of 2.5 μm or more and 4.7 μm or less.

5. 2. The ultra-thin electrolytic copper foil according to claim 1, wherein the first copper layer formed by electrolytic copper strike plating is a layer containing P and K as components.

6. The ultrathin surface-treated electrodeposited copper foil is characterized in that the surface of the ultrathin electrodeposited copper foil according to claim 1 is subjected to at least one of rust prevention treatment, roughening treatment, silane coupling agent treatment, etc.

7. 6. A method for producing an ultrathin electrodeposited copper foil according to claim 1, wherein the ultrathin electrodeposited copper foil is produced by electrolysis using a stainless steel cathode as a cathode and an insoluble anode as an anode in the following steps: Step 1: The electrodeposition surface of the stainless steel cathode is cleaned. Step 2: A strike plating layer having a gauge thickness of 0.3 μm to 0.5 μm is deposited on the cleaned electrodeposited surface of the stainless steel cathode using an electrolytic copper strike plating solution to form a first copper layer. Step 3: The surface of the first copper layer is subjected to an electrolytic treatment using a sulfuric acidic copper electrolyte to form a second copper layer having a gauge thickness of 2.5 μm or more and 4.7 μm or less, thereby forming an ultra-thin electrolytic copper foil layer consisting of the first copper layer and the second copper layer and having a gauge thickness of 5.0 μm or less on the surface of the stainless steel cathode. Step 4: The ultra-thin electrolytic copper foil layer on the surface of the stainless steel cathode is peeled off and collected to obtain an ultra-thin electrolytic copper foil having a gauge thickness of 5.0 μm or less.

8. 8. The method for producing an ultra-thin electrodeposited copper foil according to claim 7, wherein the electrolytic copper strike plating solution used in the method for producing an ultra-thin electrodeposited copper foil according to the present application has the following composition: Copper sulfate pentahydrate concentration: 18 to 25 g / L, Potassium pyrophosphate concentration: 30 to 40 g / L, Surfactant: 10 to 100 mg / L

9. The method for producing an ultrathin electrodeposited copper foil according to claim 7, wherein the sulfuric acidic copper electrolytic solution used in the method for producing an ultrathin electrodeposited copper foil according to the present application has the following composition: Copper sulfate pentahydrate concentration: 180-300g / L Free sulfuric acid concentration: 80 to 140 g / L Chlorine concentration: 15 to 70 mg / L Additives (brighteners, smoothing agents, suppressors, etc.): appropriate amount

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