Copper-clad laminate and method for manufacturing copper-clad laminate

Abstract

To provide a copper-clad laminate with excellent fracture resistance and a method for producing the copper-clad laminate.SOLUTION: A copper-clad laminate 1 comprises a base material 10, and a copper plating film 20 formed on a surface of the base material 10. The copper plating film 20 includes: a lower layer 21 formed on the surface of the base material 10; an intermediate layer 22 formed on a surface of the lower layer 21 by electroplating at a low current density; and a surface layer 23 formed on the surface of the intermediate layer 22. Since the intermediate layer 22 formed at a low current density is inserted into the copper plating film 20, the fracture resistance of the copper-clad laminate 1 can be improved.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to copper-clad laminates and methods for manufacturing copper-clad laminates. More specifically, this invention relates to copper-clad laminates used in the manufacture of flexible printed circuit boards (FPCs) and the like, and methods for manufacturing the copper-clad laminates. [Background technology]

[0002] Flexible printed circuit boards (PCBs), which have wiring patterns formed on the surface of a resin film, are used in electronic devices such as LCD panels, laptop computers, digital cameras, and mobile phones. Flexible printed circuit boards are manufactured from copper-clad laminates, which are made by laminating copper foil onto a resin film.

[0003] A known method for manufacturing copper-clad laminates is the metallizing method (for example, Patent Document 1). The manufacturing of copper-clad laminates by the metallizing method is carried out, for example, in the following steps: First, a base metal layer made of nickel-chromium alloy is formed on the surface of a resin film. Next, a thin copper film layer is formed on the base metal layer. Next, a copper plating film is formed on the thin copper film layer. The copper plating thickens the conductor layer to a thickness suitable for forming wiring patterns. By the metallizing method, a copper-clad laminate of a type known as a two-layer substrate is obtained, in which the conductor layer is formed directly on the resin film. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2010-205799 [Overview of the project] [Problems that the invention aims to solve]

[0005] With the recent miniaturization and thinning of electronic devices, flexible printed circuit boards (PCBs) are increasingly being used in applications that involve bending with small radii of curvature. Repeated bending and straightening of flexible PCBs with small radii of curvature can cause cracks to form on the surface of the wiring, and these cracks can grow and lead to disconnection. Therefore, copper-clad laminates with superior bending resistance are in demand.

[0006] In view of the above circumstances, the present invention aims to provide a copper-clad laminate with excellent bending resistance, and a method for manufacturing the copper-clad laminate. [Means for solving the problem]

[0007] The copper-clad laminate of the present invention comprises a substrate and a copper plating film formed on the surface of the substrate. The copper plating film comprises a lower layer formed on the surface of the substrate, an intermediate layer formed on the surface of the lower layer by electroplating at a low current density, and a surface layer formed on the surface of the intermediate layer. [Effects of the Invention]

[0008] According to the present invention, since an intermediate layer formed at a low current density is inserted into the copper plating film, the folding resistance of the copper-clad laminate can be improved. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view of a copper-clad laminate according to one embodiment of the present invention. [Figure 2] This is a plan view of the plating tank. [Figure 3] This graph shows the relationship between the thickness of the intermediate layer and its folding resistance. [Figure 4] This graph shows the relationship between the position of the intermediate layer and its folding resistance. [Modes for carrying out the invention]

[0010] Next, embodiments of the present invention will be described based on the drawings. As shown in FIG. 1, a copper-clad laminate 1 according to an embodiment of the present invention includes a base material 10 and a copper plating film 20 formed on the surface of the base material 10. The copper plating film 20 may be formed only on one side of the base material 10 as shown in FIG. 1, or may be formed on both sides of the base material 10.

[0011] The base material 10 is obtained by forming a metal layer 12 on the surface of an insulating base film 11. As the base film 11, a resin film such as a polyimide film or a liquid crystal polymer (LCP) film can be used. The metal layer 12 is formed by a dry film-forming method such as a sputtering method. The metal layer 12 includes an underlayer metal layer 13 and a copper thin film layer 14. The underlayer metal layer 13 and the copper thin film layer 14 are laminated in this order on the surface of the base film 11. Generally, the underlayer metal layer 13 is made of nickel, chromium, or a nickel-chromium alloy. Although not particularly limited, the thickness of the base film 11 is generally 10 to 100 μm, the thickness of the underlayer metal layer 13 is generally 5 to 50 nm, and the thickness of the copper thin film layer 14 is generally 50 to 400 nm.

[0012] Note that the underlayer metal layer 13 may not be provided. The copper thin film layer 14 may be formed on the surface of the base film 11 via the underlayer metal layer 13, or may be directly formed on the surface of the base film 11 without passing through the underlayer metal layer 13.

[0013] The copper plating film 20 is formed on the surface of the copper thin film layer 14. Although not particularly limited, the thickness of the copper plating film 20 is generally 8 to 12 μm in the case of the copper-clad laminate 1 processed by the subtractive method. The metal layer 12 and the copper plating film 20 are collectively referred to as a "conductor layer".

[0014] The copper plating film 20 has a three-layer structure composed of a lower layer 21, an intermediate layer 22, and a surface layer 23. The lower layer 21, the intermediate layer 22, and the surface layer 23 are laminated in this order on the surface of the base material 10 (copper thin film layer 14). More specifically, the lower layer 21 is directly formed on the surface of the base material 10 (copper thin film layer 14). The intermediate layer 22 is directly formed on the surface of the lower layer 21. The surface layer 23 is directly formed on the surface of the intermediate layer 22. The surface layer 23 is located on the outermost side of the copper plating film 20. In other words, the intermediate layer 22 is inserted in the middle in the thickness direction of the copper plating film 20, and the copper plating film 20 is divided into the lower layer 21 on the base material 10 side and the surface layer 23 on the surface side from the intermediate layer 22.

[0015] The lower layer 21 and the surface layer 23 mainly contribute to the thickness of the copper plating film 20. The intermediate layer 22 is thinner than each of the lower layer 21 and the surface layer 23. Specifically, it is preferable that the thicknesses of the lower layer 21 and the surface layer 23 are each 40 to 90 times the thickness of the intermediate layer 22.

[0016] Such a three-layer-structured copper plating film 20 can be obtained by providing a period during electrolytic plating for forming the copper plating film 20 in which the current density is lower than normal. The layer formed by electrolytic plating at a low current density becomes the intermediate layer 22. Hereinafter, the method for forming the copper plating film 20 will be specifically described.

[0017] The copper plating film 20 can be formed, for example, by a roll-to-roll plating apparatus. This type of plating apparatus is an apparatus that performs electrolytic plating on the long-strip-shaped base material 10 while transporting it by roll-to-roll. The plating apparatus has a supply apparatus that pays out the base material 10 wound in a roll shape and a winding apparatus that winds up the base material 10 (copper-clad laminate 1) after plating in a roll shape.

[0018] The plating apparatus is equipped with multiple clamps for transporting the substrate 10. The multiple clamps grip both edges of the substrate 10 and transport the substrate 10. A pre-treatment tank, a plating tank 30, and a post-treatment tank are arranged along the transport path of the substrate 10. As the substrate 10 is transported through the plating tank 30, a copper plating film 20 is formed on its surface by electroplating. This results in a long, strip-shaped copper-clad laminate 1.

[0019] As shown in Figure 2, the plating tank 30 is a single, horizontally elongated tank aligned with the transport direction of the substrate 10. The substrate 10 is transported along the center of the plating tank 30. The plating tank 30 contains a copper plating solution. As the substrate 10 is transported within the plating tank 30, its entire body is immersed in the copper plating solution.

[0020] The copper plating solution contains a water-soluble copper salt. Any water-soluble copper salt commonly used in copper plating solutions is acceptable. The copper plating solution may also contain sulfuric acid. The pH and sulfate ion concentration of the copper plating solution can be adjusted by adjusting the amount of sulfuric acid added. The copper plating solution may also contain additives commonly added to plating solutions. As additives, one type selected from brightener components, leveler components, polymer components, chlorine components, etc., may be used alone, or two or more types may be used in combination.

[0021] The content of each component in the copper plating solution can be arbitrarily selected. However, it is preferable that the copper plating solution contains 15 to 70 g / L of copper and 20 to 250 g / L of sulfuric acid. This allows the copper plating film 20 to be formed at a sufficient rate. It is preferable that the copper plating solution contains 1 to 50 mg / L of brightener components. This refines the precipitated crystals and makes the surface of the copper plating film 20 smooth. It is preferable that the copper plating solution contains 1 to 300 mg / L of leveler components. This suppresses protrusions and allows the formation of a flat copper plating film 20. It is preferable that the copper plating solution contains 10 to 1,500 mg / L of polymer components. This mitigates current concentration at the edges of the substrate 10 and allows the formation of a uniform copper plating film 20. It is preferable that the copper plating solution contains 20 to 80 mg / L of chlorine components. This suppresses abnormal deposition.

[0022] The temperature of the copper plating solution is preferably 20 to 35°C. It is also preferable to stir the copper plating solution in the plating tank 30. For example, the copper plating solution can be stirred by spraying it onto the substrate 10 from a nozzle.

[0023] Inside the plating tank 30, multiple anodes 31 are arranged along the transport direction of the substrate 10. The clamps that hold the substrate 10 also function as cathodes. By passing an electric current between the anodes 31 and the clamps (cathodes), a copper plating film 20 can be formed on the surface of the substrate 10.

[0024] In addition, the plating tank 30 shown in Figure 2 has anodes 31 on both the front and back sides of the substrate 10. Therefore, if a substrate 10 is used in which a metal layer 12 is formed on both sides of the base film 11, a copper plating film 20 can be formed on both sides of the substrate 10.

[0025] Multiple anodes 31 arranged inside the plating tank 30 are each connected to a rectifier. Therefore, a different current density can be set for each anode 31. In this embodiment, the inside of the plating tank 30 is divided into multiple areas along the transport direction of the substrate 10. Specifically, from upstream to downstream, a current density increase area RZ, a first area FZ, a second area SZ, and a third area TZ are set. Each area corresponds to a region where one or more consecutive anodes 31 are arranged.

[0026] Since the metal layer 12 formed on the base film 11 is relatively thin, if the current density is high in the initial stages of electroplating, there is a risk that the portion of the metal layer 12 in contact with the power supply unit (clamp) may dissolve. On the other hand, it is preferable to increase the current density as much as possible to increase productivity. Therefore, in the initial stages of electroplating, the current density is gradually increased. In the current density increase zone RZ, electroplating is performed while gradually increasing the current density. Hereinafter, the period in which the current density is gradually increased in the initial stages of electroplating, that is, the period in which the substrate 10 passes through the current density increase zone RZ, will be referred to as the "current density increase period". The current density in the current density increase period is 1 to 5 A / dm 2 It is preferable to gradually increase it within the range.

[0027] After a period of increasing current density, once the copper plating film 20 has thickened to a thickness that does not pose a risk of dissolution (for example, 1.0 μm), electroplating is performed at a relatively high, constant current density. The areas where this electroplating is performed are the first area FZ and the third area TZ. Hereinafter, the current density in the first area FZ will be referred to as "first current density D1," and the current density in the third area TZ will be referred to as "third current density D3."

[0028] In the second zone SZ, located between the first zone FZ and the third zone TZ, electroplating is performed at a relatively low current density. Hereafter, the current density in the second zone SZ will be referred to as "second current density D2".

[0029] The substrate 10 passes through the current density increasing region RZ, the first region FZ, the second region SZ, and the third region TZ in that order. As a result, a copper plating film 20 is formed on the surface of the substrate 10. More specifically, the lower layer 21 is formed by electroplating in the current density increasing region RZ and the first region FZ (lower layer formation process). Next, the intermediate layer 22 is formed by electroplating in the second region SZ (intermediate layer formation process). Finally, the surface layer 23 is formed by electroplating in the third region TZ (surface layer formation process).

[0030] In other words, the layer formed by electroplating at a first current density D1 after a period of increasing current density is the lower layer 21. The layer formed by electroplating at a second current density D2 is the intermediate layer 22. The layer formed by electroplating at a third current density D3 is the surface layer 23. In this way, a copper plating film 20 having a three-layer structure can be formed.

[0031] Furthermore, if there is no risk of the metal layer 12 dissolving, it is not necessary to provide a current density increase zone RZ in the plating tank 30. In this case, the first zone FZ, the second zone SZ, and the third zone TZ are set up inside the plating tank 30 from upstream to downstream. The lower layer 21 is formed by electroplating at the first current density D1 without going through a current density increase period.

[0032] The copper plating film 20 can also be formed using a single-wafer plating apparatus. A single-wafer substrate 10 is immersed in a copper plating solution in a plating tank and electroplated to form a copper plating film 20 on the surface of the substrate 10. During this process, the current density is changed over time. Specifically, electroplating is performed at a first current density D1 with or without a period of increasing current density to form the lower layer 21 (lower layer formation process). Next, electroplating is performed at a second current density D2 to form the intermediate layer 22 (intermediate layer formation process). Finally, electroplating is performed at a third current density D3 to form the surface layer 23 (surface layer formation process).

[0033] The copper-clad laminate 1 of this embodiment has excellent folding resistance because an intermediate layer 22, which is formed at a low current density, is inserted into the copper plating film 20. Here, folding resistance refers to the strength against repeated bending and stretching, and is evaluated by MIT testing.

[0034] While the exact reasons for the improved folding resistance are unclear, it is generally believed to be as follows: When the copper-clad laminate 1 is bent with a small radius of curvature, strong tensile stress is applied to the outermost surface of the copper plating film 20. Therefore, repeated bending and straightening can cause cracks to form on the surface of the copper plating film 20, often triggered by grain boundaries. When an intermediate layer 22 is inserted into the copper plating film 20, recrystallization proceeds separately in the lower layer 21 and the surface layer 23, resulting in the crystal grains being separated above and below the copper plating film 20. Therefore, when the copper-clad laminate 1 is bent, the tensile stress applied to the outermost surface of the copper plating film 20 is reduced, making it less likely for cracks to form. This is thought to improve folding resistance.

[0035] The folding resistance of the copper-clad laminate 1 is affected by the current density (second current density D2) during the deposition of the intermediate layer 22 and the thickness of the intermediate layer 22. From the perspective of improving folding resistance, the second current density D2 should be 0.25 to 1.0 A / dm 2 Furthermore, it is preferable that the thickness of the intermediate layer 22 is 0.05 to 0.1 μm.

[0036] Here, the layer thickness is determined from the current density and plating time in electroplating. Specifically, as shown in equation (1), the current density J[A / dm 2 The thickness d [μm] is determined by multiplying the plating time T [minutes] by a predetermined coefficient k. Note that the coefficient k is a value that depends on conditions such as the plating solution and is determined by testing.

number

[0037] The first current density D1 and the third current density D3 should be higher than the second current density D2. However, the first current density D1 and the third current density D3 should be between 4 and 10 A / dm². 2 This is preferable. The first current density D1 and the third current density D3 may be the same or different.

[0038] The folding resistance of the copper-clad laminate 1 is also affected by the position of the intermediate layer 22 in the thickness direction of the copper plating film 20. From the viewpoint of improving folding resistance, it is preferable that the intermediate layer 22 be located within the range of 40-60% in the thickness direction of the copper plating film 20. Here, 0% means the surface of the substrate 10, and 100% means the surface of the copper plating film 20. [Examples]

[0039] (Common conditions) A 35 μm thick polyimide film (Ube Industries, Ltd., Upilex-35SGAV1) was prepared as the base film. The base film was set in a magnetron sputtering apparatus. A nickel-chromium alloy target and a copper target were installed inside the magnetron sputtering apparatus. The nickel-chromium alloy target was composed of 20 mass% Cr and 80 mass% Ni. Under a vacuum atmosphere, a 25 nm thick underlying metal layer made of nickel-chromium alloy was formed on one side of the base film, and a 150 nm thick copper thin film layer was formed on top of it.

[0040] Next, a copper plating solution was prepared. The copper plating solution contained 120 g / L of copper sulfate, 70 g / L of sulfuric acid, 16 mg / L of a brightener component, 20 mg / L of a leveler component, 1,100 mg / L of a polymer component, and 50 mg / L of a chlorine component. Bis(3-sulfopropyl) disulfide (reagent manufactured by RASCHIG GmbH) was used as the brightener component. Diallyldimethylammonium chloride-sulfur dioxide copolymer (PAS-A-5 manufactured by Nitto Boseki Medical Co., Ltd.) was used as the leveler component. Polyethylene glycol-polypropylene glycol copolymer (Unilube 50MB-11 manufactured by NOF Corporation) was used as the polymer component. Hydrochloric acid (35% hydrochloric acid manufactured by Wako Pure Chemical Industries, Ltd.) was used as the chlorine component.

[0041] A substrate was supplied to a plating bath in which the copper plating solution was stored. A copper plating film with a thickness of 8.5 μm was formed on one side of the substrate by electrolytic plating. Here, the temperature of the copper plating solution was set at 31°C. Also, during the electrolytic plating, the copper plating solution ejected from the nozzle was sprayed onto the surface of the substrate substantially perpendicularly to stir the copper plating solution.

[0042] (Reference sample) The current density and plating time in electrolytic plating were set as shown in Table 1. The layer numbers in Table 1 are numbered in order from the layer contacting the surface of the substrate. That is, at the initial stage of electrolytic plating, the current density was increased step by step to 1.38 A / dm 2 and 3.02 A / dm 2 and then the current density was set at 5.03 A / dm 2 to form a copper plating film until the thickness reached 8.5 μm. Therefore, the copper plating film has no intermediate layer. The obtained copper-clad laminate was used as a reference sample.

[0043]

Table 1

[0044] The flexural resistance of the reference sample was evaluated by the MIT test. The MIT test was conducted in accordance with JIS C6471 (1995). As a testing machine, a type D MIT flexural fatigue tester manufactured by Toyo Seiki Seisakusho was used. A wiring pattern with a width of 1 mm was formed on the sample. The sample was bent at a curvature radius of 0.36 mm by 135° and then bent by 135° in the opposite direction, and the number of times (number of breakage-resistant times) when the conduction of the wiring was interrupted was measured. Hereinafter, taking the number of breakage-resistant times of the reference sample as 100%, the number of breakage-resistant times of other samples was evaluated.

[0045] (Evaluation of current density and thickness) Next, the relationship between the current density and thickness of the intermediate layer of the copper plating film and the flexural resistance was evaluated. The current density and plating time in electrolytic plating were set as shown in Table 2. That is, at the initial stage of electrolytic plating, the current density was 1.38 A / dm 2 and 3.02 A / dm 2The current density is gradually increased, and then the current density (first current density) is set to 5.03 A / dm 2 A lower layer with a thickness of 4.17 μm was then deposited. Next, the current density (second current density) was set to 0.25 A / dm 2 An intermediate layer was then deposited. Finally, the current density (third current density) was set to 5.03 A / dm². 2 The surface layer was then formed. The plating time for the intermediate layer was varied to form three types of copper plating films with intermediate layer thicknesses of 0.05, 0.07, and 0.10 μm. The resulting copper-clad laminates were designated as Samples 1-3.

[0046] [Table 2]

[0047] The current density and plating time for electroplating were set as shown in Table 3. Specifically, the current density (second current density) when forming the intermediate layer was set to 0.50 A / dm². 2 The process was carried out as described above. In addition, the plating time for the intermediate layer was varied to deposit three types of copper plating films with intermediate layer thicknesses of 0.05, 0.07, and 0.10 μm. The resulting copper-clad laminates were designated as samples 4 to 6.

[0048] [Table 3]

[0049] The current density and plating time for electroplating were set as shown in Table 4. Specifically, the current density (second current density) when forming the intermediate layer was set to 0.75 A / dm². 2 Furthermore, the plating time for the intermediate layer was varied to deposit three types of copper plating films with intermediate layer thicknesses of 0.05, 0.07, and 0.10 μm. The resulting copper-clad laminates were designated as samples 7-9.

[0050] [Table 4]

[0051] The current density and plating time for electroplating were set as shown in Table 5. Specifically, the current density (second current density) when forming the intermediate layer was set to 1.00 A / dm². 2 The process was carried out as described above. In addition, the plating time for the intermediate layer was varied to deposit three types of copper plating films with intermediate layer thicknesses of 0.05, 0.07, and 0.10 μm. The resulting copper-clad laminates were designated as samples 10 to 12.

[0052] [Table 5]

[0053] The folding resistance of samples 1 to 12 was evaluated by MIT testing. The results are shown in Figure 3. From the graph in Figure 3, to obtain a copper-clad laminate with superior folding resistance compared to the reference sample, the current density (second current density) during film formation of the intermediate layer should be 0.25 to 1.0 A / dm 2 It can be seen that the thickness of the intermediate layer should be 0.05 to 0.1 μm. Note that the thickness of the intermediate layer may be less than 0.1 μm, or even less than 0.1 μm.

[0054] Furthermore, from the perspective of improving bending resistance, the second current density should be 0.25~0.5A / dm 2 Furthermore, the thickness of the intermediate layer is set to 0.05~0.07 μm, or the second current density is set to 0.75~1.0 A / dm 2 Furthermore, it is more preferable to set the thickness of the intermediate layer to 0.07 to 0.1 μm. In this case, the number of breakage cycles will be 107% or more of that of the reference sample.

[0055] (Evaluation of position in the thickness direction) Next, we evaluated the relationship between the position of the intermediate layer in the thickness direction of the copper plating film and its folding resistance. The current density and plating time for electroplating were set as shown in Table 6. Specifically, the current density was set to 1.38 A / dm² at the beginning of the electroplating process. 2 , 3.02 A / dm 2 The current density is gradually increased, and then the current density (first current density) is set to 5.03 A / dm 2 The lower layer was then deposited. Next, the current density (second current density) was set to 0.25 A / dm2 An intermediate layer with a thickness of 0.07 μm was deposited. Finally, the current density (third current density) was set to 5.03 A / dm 2 A surface layer was formed. Here, the electroplating time was varied using the first and third current densities to form five types of copper plating films with different intermediate layer positions in the thickness direction of the copper plating film. The resulting copper-clad laminates were designated as samples 13 to 17.

[0056] [Table 6]

[0057] The folding resistance of samples 13-17 was evaluated by MIT testing. The results are shown in Figure 4. From the graph in Figure 4, it can be seen that in order to obtain a copper-clad laminate with better folding resistance than the reference sample, it is preferable to position the intermediate layer within the range of 40-60% of the thickness of the copper plating film, and more preferably within the range of 45-55%. [Explanation of Symbols]

[0058] 1 Copper-clad laminate 10 Base material 11 Base film 12 metal layer 13. Underlayment metal layer 14 Copper thin film layer 20 Copper plating film 21 Lower layer 22 Middle Class 23 Surface layer

Claims

1. base film and A metal layer formed on the surface of the base film by a dry film formation method, The metal layer comprises a copper plating film formed on the surface of the metal layer, The aforementioned copper plating film is A lower layer is formed directly above the surface of the metal layer by electroplating at a first current density (excluding the current density during the current density increase period) with or without a current density increase period, and An intermediate layer is formed directly above the surface of the lower layer by electroplating at a second current density so as to be in contact with the surface of the lower layer, It comprises a surface layer which is the outermost layer of the copper plating film, formed directly above the surface of the intermediate layer by electroplating at a third current density so as to be in contact with the surface of the intermediate layer, The second current density is 0.25 to 1.0 A / dm ２ The current density is fixed to a constant value selected from the range, and the thickness of the intermediate layer is 0.05 to 0.1 μm. The first current density is a current density fixed at a constant value higher than the second current density. The third current density is a current density fixed at a constant value higher than the second current density. The intermediate layer has a total thickness that is within the range of 40-60% in the thickness direction of the copper plating film. A copper-clad laminate characterized by the following features.

2. The first current density is 4 to 10 A / dm ２ This is a current density fixed to a constant value selected from a range. The third current density is a current density fixed to a constant value selected from the range of 4 to 10 A / dm². The copper-clad laminate according to feature 1.

3. The thickness of the lower layer and the surface layer are, respectively, 40 to 90 times the thickness of the intermediate layer. A copper-clad laminate according to claim 1 or 2.

4. A method for obtaining a copper-clad laminate having a copper-plated film consisting of one lower layer, one intermediate layer, and one surface layer, wherein a copper-plated film is formed on the surface of a base film by a dry film formation method, and a copper-plated film is formed on the surface of the base film, A lower layer deposition step is performed by electroplating at a first current density (excluding the current density during the current density increase period) with or without a current density increase period, so as to deposit the lower layer directly above the surface of the metal layer so as to be in contact with it. An intermediate layer deposition step is performed by electroplating at a second current density to deposit the intermediate layer directly above the surface of the lower layer so as to be in contact with it, The process includes a surface layer deposition step in which the surface layer, which is the outermost layer of the copper plating film, is deposited directly above the surface of the intermediate layer by electroplating at a third current density, so as to be in contact with the surface of the intermediate layer, The second current density is 0.25 to 1.0 A / dm ２ The current density is fixed to a constant value selected from the range, and the thickness of the intermediate layer is 0.05 to 0.1 μm. The first current density is a current density fixed at a constant value higher than the second current density. The third current density is a current density fixed at a constant value higher than the second current density. The overall thickness of the intermediate layer is within the range of 40 to 60% of the thickness of the copper plating film. A method for manufacturing copper-clad laminates, characterized by the following:

5. The second current density is 0.75 to 1.0 A / dm ２ The current density is fixed to a constant value selected from the range, and the thickness of the intermediate layer is 0.07 to 0.1 μm. The method for manufacturing a copper-clad laminate according to claim 4.

6. The first current density is 4 to 10 A / dm ２ This is a current density fixed to a constant value selected from a range. The third current density is a current density fixed to a constant value selected from the range of 4 to 10 A / dm². A method for manufacturing a copper-clad laminate according to claim 4 or 5, characterized by the above.

7. The thickness of the lower layer and the surface layer are, respectively, 40 to 90 times the thickness of the intermediate layer. A method for manufacturing a copper-clad laminate according to any one of 4 to 6.

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