Method for manufacturing copper-clad laminate and printed wiring board

Abstract

Provided is a manufacturing method for a copper-clad laminate in which a copper foil and a resin are bonded with high heat-resistant adhesive strength while using a fluororesin, which is a thermoplastic resin having a low dielectric constant. This manufacturing method comprises: a step for preparing a surface-treated copper foil, which includes a copper foil and a zinc-containing layer provided on at least one surface of the copper foil; and a step for obtaining a copper-clad laminate by attaching a sheet-like fluororesin to the zinc-containing layer side of the surface-treated copper foil. The zinc-containing layer is composed of Zn and a transition element M having a melting point of at least 1,200ºC. When the boundary surface between the copper foil and the zinc-containing layer is subjected to elemental analysis by X-ray photoelectron spectroscopy (XPS), the content of Zn is at most 10 wt%, and the Zn / M weight ratio, which is the ratio of the content of Zn to the content of the transition element M, is 0.2-0.6.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a copper-clad laminate and a printed wiring board. [Background technology]

[0002] In recent years, the increasing sophistication of portable electronic devices has led to an increase in signal frequencies to enable high-speed processing of large amounts of information. This has created a demand for printed wiring boards suitable for high-frequency applications, such as base station antennas. Such high-frequency printed wiring boards are required to reduce transmission loss in order to transmit high-frequency signals without degrading their quality. Printed wiring boards comprise copper foil processed into a wiring pattern and an insulating resin substrate. Transmission loss is primarily due to conductor loss caused by the copper foil and dielectric loss caused by the insulating resin substrate. Therefore, it would be advantageous to use a thermoplastic resin with a low dielectric constant to reduce the dielectric loss caused by the insulating resin substrate. However, unlike thermosetting resins, low-dielectric-constant thermoplastic resins, such as fluororesins such as polytetrafluoroethylene (PTFE), have low chemical activity and therefore poor adhesion to copper foil. Therefore, techniques for improving adhesion between copper foil and thermoplastic resins have been proposed.

[0003] For example, Patent Document 1 (WO 2017 / 150043) discloses that adhesion to fluororesin is ensured by using copper foil with fine irregularities formed by oxidation and reduction treatments. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 150043 Summary of the Invention

[0005] However, in the copper-clad laminate disclosed in Patent Document 1, in which a copper foil and a fluororesin substrate are bonded together, the adhesion between the copper foil and the substrate still decreases significantly at high temperatures, and further improvement in heat-resistant adhesion is required. In particular, printed wiring boards using fluororesins are sometimes exposed to harsh environments such as high temperatures, and high adhesion between the copper foil and the resin substrate is desired even after exposure to such harsh environments. In fact, printed wiring boards using fluororesins such as PTFE are sometimes used in aviation, space, and other applications, and from this perspective, further improvement in adhesion at high temperatures is also desired. In other words, there is a need to achieve both adhesion and heat resistance between the copper foil and the fluororesin substrate.

[0006] The present inventors have now discovered that by bonding a surface-treated copper foil having a zinc-containing layer of a predetermined interfacial composition to a fluororesin, it is possible to produce a copper-clad laminate that not only has high adhesion but also has excellent heat resistance such that the adhesion is resistant to deterioration even at high temperatures, i.e., the copper foil and the fluororesin are bonded with high heat-resistant adhesion.

[0007] Therefore, an object of the present invention is to produce a copper-clad laminate in which copper foil and resin are bonded with high heat-resistant adhesion, even when using a fluororesin, which is a thermoplastic resin with a low dielectric constant.

[0008] According to one aspect of the present invention, there is provided a method for producing a copper clad laminate, comprising the steps of: A step of preparing a surface-treated copper foil comprising a copper foil and a zinc-containing layer provided on at least one surface of the copper foil; a step of attaching a sheet-shaped fluororesin to the zinc-containing layer side of the surface-treated copper foil to obtain a copper-clad laminate; Including, the zinc-containing layer is composed of Zn and a transition element M having a melting point of 1200°C or higher, The method for producing a copper-clad laminate is provided, in which, when elemental analysis of the interface between the copper foil and the zinc-containing layer is performed by X-ray photoelectron spectroscopy (XPS), the Zn content is 10% by weight or less, and the weight ratio of Zn / M, which is the content ratio of Zn to the content of the transition element M, is 0.2 or more and 0.6 or less.

[0009] According to another aspect of the present invention, producing the copper clad laminate by the method; forming a circuit on the copper-clad laminate to form a printed wiring board; A method for manufacturing a printed wiring board is provided, comprising: DETAILED DESCRIPTION OF THE INVENTION

[0010] Manufacturing method of copper clad laminate The present invention relates to a method for producing a copper-clad laminate. The method of the present invention includes the steps of (1) preparing a surface-treated copper foil having a copper foil and a zinc-containing layer provided on at least one side of the copper foil, and (2) laminating a sheet-like fluororesin to the zinc-containing layer side of the surface-treated copper foil to obtain a copper-clad laminate. The zinc-containing layer is composed of Zn and a transition element M having a melting point of 1200°C or higher. When the interface between the copper foil and the zinc-containing layer is subjected to elemental analysis by X-ray photoelectron spectroscopy (XPS), the Zn content is 10 wt% or less, and the weight ratio of Zn to the transition element M, Zn / M, is 0.2 to 0.6. By laminating a surface-treated copper foil having a zinc-containing layer of a predetermined interfacial composition to a fluororesin, a copper-clad laminate can be produced that not only has high adhesion but also excellent heat resistance, such that the adhesion is resistant to deterioration even at high temperatures. In other words, a copper-clad laminate in which the copper foil and the fluororesin are bonded with high heat-resistant adhesion can be produced.

[0011] That is, as mentioned above, low-dielectric-constant thermoplastic resins, such as fluororesins such as polytetrafluoroethylene (PTFE), have low chemical activity, unlike thermosetting resins, and therefore inherently have low adhesion to copper foil. Even in the copper-clad laminate disclosed in Patent Document 1, which addresses this problem, the decrease in adhesion between the copper foil and the substrate at high temperatures remains significant. In this regard, the method of the present invention selectively employs a surface-treated copper foil having a zinc-containing layer and an interface with a Zn content and Zn / M ratio within the above-mentioned ranges, and then attaches it to a fluororesin. This makes it possible to produce a copper-clad laminate that not only has high adhesion between the copper foil and the fluororesin, but also has excellent heat resistance, meaning that the adhesion is resistant to deterioration even at high temperatures.

[0012] (1) Preparation of surface-treated copper foil The surface-treated copper foil used in the method of the present invention comprises a copper foil and a zinc-containing layer provided on at least one surface of the copper foil. The copper foil is preferably a roughened copper foil having roughening particles on at least one surface, and more preferably the surface of the copper foil facing the zinc-containing layer is the roughened surface. Known roughened copper foils can be used. The thickness of the copper foil is not particularly limited, but is preferably 0.1 μm to 70 μm, more preferably 0.5 μm to 18 μm.

[0013] The zinc-containing layer may be formed of any suitable alloy of Zn and M, i.e., a zinc alloy, as long as it is made of Zn and a transition element M having a melting point of 1200°C or higher. Preferred examples of the transition element M having a melting point of 1200°C or higher include Co, Fe, Ni, Mo, W, and combinations thereof, more preferably Co, Ni, Mo, and combinations thereof, even more preferably Ni and / or Mo, and particularly preferably Ni. Therefore, the zinc-containing layer is preferably formed of a Zn-Co alloy, a Zn-Fe alloy, a Zn-Ni alloy, a Zn-Mo alloy, a Zn-W alloy, a Zn-Ni-Mo alloy, or a combination thereof, more preferably a Zn-Co alloy, a Zn-Ni alloy, a Zn-Mo alloy, a Zn-Ni-Mo alloy, or a combination thereof, more preferably a Zn-Ni alloy, a Zn-Mo alloy, a Zn-Ni-Mo alloy, or a Zn-Ni-Mo alloy, even more preferably a Zn-Ni alloy, a Zn-Mo alloy, or a Zn-Ni-Mo alloy, and particularly preferably a Zn-Ni alloy.

[0014] As described above, when the interface between the copper foil and the zinc-containing layer is analyzed by XPS, the Zn content is 10 wt% or less, preferably 1.0 wt% to 10.0 wt%, more preferably 2.0 wt% to 8.0 wt%, even more preferably 2.1 wt% to 7.5 wt%, and particularly preferably 2.1 wt% to 7.0 wt%. A Zn content within this range contributes particularly to improving the adhesion between the copper foil and the substrate (particularly, normal peel strength). Furthermore, when the interface between the copper foil and the zinc-containing layer is analyzed by XPS, the Zn / M weight ratio, which is the ratio of Zn to the content of the transition element M, is 0.2 to 0.6, preferably 0.22 to 0.58, and more preferably 0.25 to 0.55. A Zn / M weight ratio within this range contributes particularly to improving heat resistance (particularly, the property of preventing the adhesion between the copper foil and the substrate from deteriorating at high temperatures).

[0015] In the present invention, the Zn content and Zn / M weight ratio are determined at the interface between the copper foil and the zinc-containing layer, and this interface refers to the portion of the zinc-containing layer directly above the copper foil. This portion is less susceptible to surface oxidation and is considered to be an important region for imparting adhesion and heat resistance. The position (depth) of the interface between the copper foil and the zinc-containing layer is defined as the inflection point on the curve between the measurement depth (horizontal axis) and the Cu content (vertical axis) in elemental analysis by XPS performed in the depth direction from the zinc-containing layer toward the copper foil. Specifically, it is determined by the following steps i) to vi). i) The surface of the zinc-containing layer opposite the copper foil is set to a measurement depth D1 = 0 nm, and elemental analysis is performed by XPS while digging from there in the depth direction toward the copper foil by sputtering. Elemental analysis is performed at the measurement depth D1 = 0 nm at the same time as the start of XPS measurement, and thereafter, elemental analysis is performed at the measurement depth D1 = 0 nm every predetermined sputtering time (for example, 20 seconds) from the start of measurement. n Elemental analysis is performed at points (n represents the measurement point). For example, measurements are performed at equal time intervals, such as D2 at 20 seconds after the start of measurement, D3 at 40 seconds, and so on. An example of a preferred XPS measurement condition is shown below (more specific measurement conditions will be shown in the Examples below). (Measurement conditions) - Ion gun settings: Ar gas, 1kV, 2mm x 2mm - Sputtering rate: 3.43nm / min ii) According to i) above, the Cu content C at measurement point n n (% by weight) is measured. iii) Measurement depth D n is the horizontal axis, and Cu content C n Create a graph with the vertical axis as the ordinate, and calculate the slope S of the tangent at measurement point n for the obtained curve. n =(C n+1 -C n ) / (D n+1 -D n ) is calculated. iv) The slope of the obtained tangent line, S n From this, the rate of change of the slope of the tangent line ΔS n =S n+1 -S n Calculate. v) The rate of change of the slope of the obtained tangent line, ΔS n from curvature c n =ΔS n / (D n+1 -D n ) is calculated. vi) curvature c n The measurement point where = 0 is identified as the Cu inflection point, and the measurement depth D n The point is determined as the interface between the copper foil and the zinc-containing layer. n Accidental curvature c due to plus / minus fluctuations of n To avoid =0, we stably n The curvature c in the region where begins to converge towards 0 n The measurement point where σ is the thickness of the copper foil and the zinc-containing layer is used. By adopting such a method, the interface between the copper foil and the zinc-containing layer can be uniquely identified.

[0016] The surface-treated copper foil preferably further comprises a chromate layer and / or a silane coupling agent layer on the zinc-containing layer side, more preferably both a chromate layer and a silane coupling agent layer. The chromate layer and / or the silane coupling agent layer improves rust prevention, moisture resistance, and chemical resistance, and in combination with the zinc-containing layer, the adhesion to the fluororesin substrate can also be improved.

[0017] (2) Fluorine resin attachment A copper-clad laminate is obtained by attaching a sheet-shaped fluororesin to the zinc-containing layer side of the surface-treated copper foil. The attachment of this fluororesin to the surface-treated copper foil can be performed according to known copper-clad laminate manufacturing procedures and is not particularly limited. Alternatively, a method of attaching copper foil to an inner layer substrate via a fluororesin can also be employed. In this case, it can be performed according to known techniques such as the so-called build-up method. In either case, according to the method of the present invention, a surface-treated copper foil having a zinc-containing layer and an interface with a Zn content and Zn / M ratio within the above range is selectively selected and attached to the fluororesin. This allows for the production of a copper-clad laminate that not only has high adhesion between the copper foil and the fluororesin but also has excellent heat resistance, such that the adhesion is not easily deteriorated even at high temperatures. The attachment of the fluororesin to the surface-treated copper foil is preferably performed by pressing while heating. The pressing temperature can be determined appropriately depending on the properties of the fluororesin used and is not particularly limited, but is preferably 150 to 500°C, more preferably 180 to 400°C. The pressing pressure is also not particularly limited, but is preferably 1 to 10 MPa, more preferably 2 to 5 MPa.

[0018] The sheet-like fluororesin may be in the form of a cut piece of sheet or a long sheet drawn from a roll, and its form is not particularly limited. Preferred examples of the fluororesin include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), and any combination thereof.

[0019] The surface-treated copper foil may be provided on one or both sides of a sheet-shaped fluororesin. The sheet-shaped fluororesin may contain a fluororesin and may further contain other materials. Therefore, the sheet-shaped fluororesin may be a prepreg. Prepreg is a general term for a composite material in which a substrate such as a synthetic resin plate, a glass plate, a woven glass fabric, a nonwoven glass fabric, or paper is impregnated with a synthetic resin. Furthermore, the fluororesin may further contain filler particles made of various inorganic particles such as silica and alumina to improve insulation properties. The thickness of the sheet-shaped fluororesin is not particularly limited, but is preferably 1 to 1000 μm, more preferably 2 to 400 μm, and even more preferably 3 to 200 μm. The fluororesin layer may be composed of multiple layers.

[0020] Manufacturing method of surface-treated copper foil The surface-treated copper foil of the present invention may be produced by any method as long as a zinc-containing layer can be formed on the copper foil, but is preferably produced via zinc alloy plating. An example of a preferred method for producing the surface-treated copper foil of the present invention will be described below. This preferred method comprises the steps of preparing copper foil and plating the surface with a zinc alloy.

[0021] (1) Preparing the copper foil The copper foil used to manufacture the surface-treated copper foil can be either an electrolytic copper foil or a rolled copper foil, with electrolytic copper foil being more preferred. The copper foil is preferably subjected to a roughening treatment, for example, by electroplating using an aqueous solution containing sulfuric acid and copper sulfate to form a roughened surface with roughening particles attached to the copper foil surface. The roughened surface preferably has a maximum height Sz measured in accordance with ISO 25178 of 3.0 μm to 15.0 μm, more preferably 4.0 μm to 12.0 μm. When the copper foil is prepared in the form of a carrier-attached copper foil, the copper foil may be formed by a wet film-forming method such as electroless copper plating or electrolytic copper plating, a dry film-forming method such as sputtering or chemical vapor deposition, or a combination thereof.

[0022] (2) Formation of a zinc-containing layer by zinc alloy plating The zinc-containing layer is preferably formed by plating the surface (e.g., the roughened surface) of the copper foil with a zinc alloy. Examples of zinc alloy plating include Zn-Co alloy plating, Zn-Fe alloy plating, Zn-Ni alloy plating, Zn-Mo alloy plating, Zn-W alloy plating, Zn-Ni-Mo alloy plating, and combinations thereof. Zinc alloy plating can be performed by preparing a plating solution to obtain the desired zinc alloy composition and using a known electroplating method. For example, when performing Zn-Ni alloy plating, electroplating is preferably performed using an aqueous solution containing zinc oxide, nickel sulfate, and potassium diphosphate.

[0023] (3) Chromate treatment It is preferable to form a chromate layer by subjecting the copper foil on which the zinc-containing layer has been formed to a chromate treatment. The chromate treatment is carried out using a chromate treatment solution having a chromic acid concentration of 0.5 to 8 g / L and a pH of 1 to 13, at a current density of 0.1 to 10 A / dm 2 It is preferable to carry out the electrolysis at 1 to 30 seconds.

[0024] (4) Silane coupling agent treatment The copper foil is preferably treated with a silane coupling agent to form a silane coupling agent layer, which can be formed by applying an appropriately diluted silane coupling agent to the copper foil and drying the applied agent. Examples of the silane coupling agent include (i) epoxy-functional silane coupling agents such as 4-glycidylbutyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane; (ii) amino-functional silane coupling agents such as 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-3-(4-(3-aminopropoxy)butoxy)propyl-3-aminopropyltrimethoxysilane and N-phenyl-3-aminopropyltrimethoxysilane; (iii) mercapto-functional silane coupling agents such as 3-mercaptopropyltrimethoxysilane; (iv) olefin-functional silane coupling agents such as vinyltrimethoxysilane and vinylphenyltrimethoxysilane; (v) acrylic-functional silane coupling agents such as 3-methacryloxypropyltrimethoxysilane; (vi) imidazole-functional silane coupling agents such as imidazole silane; and (vii) triazine-functional silane coupling agents such as triazine silane. When both the chromate layer and the silane coupling agent layer are formed on the surface of the zinc-containing layer, the order in which they are formed is not particularly limited.

[0025] Printed wiring board manufacturing method The copper-clad laminate of the present invention is preferably used for producing a printed wiring board. That is, according to a preferred embodiment of the present invention, there is provided a method for producing a printed wiring board, comprising the steps of producing the copper-clad laminate and forming a circuit on the copper-clad laminate to produce a printed wiring board. Specific examples of printed wiring boards include single-sided or double-sided printed wiring boards in which a circuit is formed on the copper-clad laminate of the present invention, and multilayer printed wiring boards obtained by multilayering these. Multilayer printed wiring boards may be those in which a circuit is formed on a multilayer copper-clad laminate in which copper foil is attached to an inner layer substrate via a thermoplastic resin (e.g., a fluororesin), or those in which a build-up layer is further formed. The circuit formation method may be a subtractive method or a modified semi-additive (MSAP) method. Printed wiring boards produced using the copper-clad laminate of the present invention are suitable for use as high-frequency substrates for applications such as automobile antennas, mobile phone base station antennas, high-performance servers, and collision prevention radars, which are used in high-frequency bands with signal frequencies of 10 GHz or higher. [Example]

[0026] The present invention is further illustrated by the following examples.

[0027] Examples 1-7 (1) Preparation of surface-treated copper foil Various surface-treated copper foils were prepared by known methods, each having a zinc-containing layer on the surface. These surface-treated copper foils were prepared by sequentially applying a roughening treatment, Zn-Ni alloy plating (Examples 1 to 5) or Zn-Ni-Mo alloy plating (Examples 6 and 7), chromate treatment, and silane coupling treatment to the electrode surface of an electrolytic copper foil (35 μm thick) using known methods. Each surface-treated copper foil was subjected to elemental analysis by XPS while being drilled in the depth direction from the zinc-containing layer toward the copper foil by sputtering. This elemental analysis was performed using a scanning dual X-ray photoelectron spectrometer (XPS) (PHI Quantes, manufactured by ULVAC-PHI) under the following measurement conditions: (Measurement conditions) - Output: 200μmφ, 50W - X-ray type: Monochromated Al Kα rays - Ion gun settings: Ar gas, 1 kV (examples 1 to 5) or 2 kV (examples 6 and 7), 2 mm x 2 mm - Sputtering rate (SiO2 equivalent): 3.43 nm / min (Examples 1 to 5) or 12.3 nm / min (Examples 6 and 7) - Measurement elements and orbitals: C 1s, O 1s, Si 2p, Cr 3p, Ni 2p3, Cu 2p3, Zn 2p3, Mo 3d (Examples 6 and 7 only) - Measurement surface: Measured from the zinc-containing layer toward the interface

[0028] Based on the obtained elemental analysis results, the Cu inflection point was identified according to the definitions and procedures described above, and the position (depth) of the interface between the copper foil and the zinc-containing layer was determined. Although the copper foil had been roughened, the roughened layer (roughening particles) was also considered to be included in the copper foil when identifying the interface position. The Zn content (wt%) was calculated as the percentage of Zn element content relative to the total weight of the measured elements at the interface, and the M content (wt%) was calculated as the percentage of transition element M (here, Ni and Mo) content relative to the total weight of the measured elements. The Zn / M weight ratio was calculated using the obtained Zn and M contents. The results are shown in Table 1.

[0029] (2) Preparation of copper-clad laminate A PTFE substrate (RO3003 Bondply, manufactured by ROGERS Corporation, thickness 125 μm, 1 ply) was prepared as the fluororesin substrate. The surface-treated copper foil described above was laminated onto this PTFE substrate so that the zinc-containing layer side of the copper foil was in contact with the substrate, and pressed using a vacuum press under conditions of a pressure of 2.4 MPa, a temperature of 370°C, and a pressing time of 30 minutes to produce a copper-clad laminate.

[0030] (3) Evaluation of copper clad laminates The copper-clad laminates thus produced were subjected to the following various evaluations.

[0031] <Normal peel strength against fluororesin (PTFE)> A 0.4 mm wide linear circuit was formed on a copper-clad laminate by subtractive etching using cupric chloride etching solution to obtain a test substrate equipped with a linear circuit for peel strength measurement. This linear circuit was peeled from the PTFE substrate in accordance with JIS C 5016-1994, Method A (90° peel), and the normal peel strength (kgf / cm) was measured. This measurement was performed using a desktop precision universal testing machine (AGS-50NX, manufactured by Shimadzu Corporation). The results are shown in Table 1.

[0032] <Heat-resistant peel strength against fluororesin (PTFE)> The heat-resistant peel strength (kgf / cm) to PTFE was measured in the same manner as for the normal peel strength to PTFE described above, except that a test board equipped with a 0.4 mm wide linear circuit for measuring peel strength was placed in an oven, heated at 150°C for 4 hours, and then floated in a solder bath at 288°C for 10 seconds. The results are shown in Table 1.

[0033] <Heat resistance deterioration rate> The rate of decrease (%) in the heat-resistant peel strength relative to the normal peel strength was calculated as the heat deterioration rate. The results are shown in Table 1.

[0034] [Table 1]

[0035] From the results shown in Table 1, it can be seen that Examples 1, 2, 6 and 7, which satisfy the conditions of the present invention that the Zn content is 10 wt % or less and the weight ratio of Zn / M (here, Zn / (Ni+Mo)) is 0.2 or more and 0.6 or less at the interface between the copper foil and the zinc-containing layer, generally have higher peel strength (i.e., higher adhesion) and significantly lower heat resistance degradation rate (i.e., excellent heat resistance) compared to the comparative examples of Examples 3 to 5, which do not satisfy these conditions.

Claims

1. A method for manufacturing a copper clad laminate, A step of preparing a surface-treated copper foil comprising a copper foil and a zinc-containing layer provided on at least one surface of the copper foil; a step of attaching a sheet-shaped fluororesin to the zinc-containing layer side of the surface-treated copper foil to obtain a copper-clad laminate; Including, the zinc-containing layer is composed of Zn and a transition element M having a melting point of 1200°C or higher, When an interface between the copper foil and the zinc-containing layer is subjected to elemental analysis by X-ray photoelectron spectroscopy (XPS), the Zn content is 10% by weight or less, and the weight ratio of Zn / M, which is the content ratio of Zn to the content of the transition element M, is 0.2 or more and 0.6 or less, The position of the interface between the copper foil and the zinc-containing layer is defined as an inflection point on a curve formed by measurement depth (horizontal axis) and Cu amount (vertical axis) in elemental analysis by XPS performed in the depth direction from the zinc-containing layer toward the copper foil.

2. 2. The method for producing a copper clad laminate according to claim 1, wherein the transition element M is at least one selected from the group consisting of Co, Fe, Ni, Mo and W.

3. 3. The method for producing a copper clad laminate according to claim 1, wherein the transition element M is Ni and / or Mo.

4. The method for producing a copper-clad laminate according to any one of claims 1 to 3, wherein the Zn content at the interface is 1.0 wt% or more and 10.0 wt% or less.

5. The method for producing a copper-clad laminate according to any one of claims 1 to 4, wherein the Zn content at the interface is 2.0 wt% or more and 8.0 wt% or less.

6. The method for producing a copper-clad laminate according to any one of claims 1 to 5, wherein the weight ratio of Zn / M at the interface is 0.25 or more and 0.55 or less.

7. The fluororesin is at least one selected from the group consisting of polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and tetrafluoroethylene-ethylene copolymer. The method for producing a copper-clad laminate according to any one of claims 1 to 6.

8. The method for producing a copper-clad laminate according to any one of claims 1 to 7, wherein the surface of the copper foil on the zinc-containing layer side is a roughened surface.

9. A step of producing the copper clad laminate by the method according to any one of claims 1 to 8; forming a circuit on the copper-clad laminate to form a printed wiring board; A method for manufacturing a printed wiring board, comprising:

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