Laminate, method for manufacturing the same, and circuit board

Abstract

To provide a laminate demonstrating low transmission loss and excellent properties when used as a circuit board.SOLUTION: A laminate unconditionally comprises a metal layer and a fluororesin-containing layer adjacent to the metal layer, wherein the arithmetic average surface roughness Sa on the metal side of the adhesion surface between the metal layer and the fluororesin-containing layer is 0.05 μm or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a laminate, a method for manufacturing the same, and a circuit board.

Background Art

[0002] In the field of circuit boards, laminates having a fluororesin-containing layer and a metal layer are widely known (for example, Patent Documents 1 and 2). Such laminates are manufactured by heating and bonding a fluororesin film and a metal foil.

[0003] In such laminates, in order to improve the adhesion between the fluororesin film and the metal, it has been common to use a metal foil with a roughened surface as the metal foil layer. In recent years, in order to reduce transmission loss, consideration has also been given to using a metal foil with high surface smoothness.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present disclosure is to provide a laminate having low transmission loss and excellent properties when used as a circuit board.

Means for Solving the Problems

[0006] The present disclosure is a laminate including a metal layer and a fluororesin-containing layer adjacent to the metal layer, wherein the arithmetic mean surface roughness Sa on the metal side of the adhesion surface between the metal layer and the fluororesin-containing layer is 0.05 μm or less.

[0007] The above laminate preferably has an adhesive strength between the metal layer and the fluororesin-containing layer of 0.1 N / mm or more. The above laminate is preferably a long laminate having a width of 200 mm or more. The above laminate preferably has an oxygen element ratio of 1.35 atomic% or more when measured by a scanning X-ray photoelectron spectrometer (XPS / ESCA) on the surface of the fluororesin-containing layer. The above oxygen element ratio is preferably 1.5 atomic% or more.

[0008] In the laminate of the present disclosure, the difference between the oxygen element ratio when measured by a scanning X-ray photoelectron spectrometer (XPS / ESCA) on the surface of the fluororesin-containing layer on the side not facing the metal layer of the fluororesin-containing layer and the oxygen element ratio when measured by a scanning X-ray photoelectron spectrometer (XPS / ESCA) after etching the fluororesin-containing layer in the depth direction at an incident angle of 45° for 15 minutes with an argon gas cluster ion beam is preferably 1.0 atomic% or more.

[0009] The above laminate preferably has a coefficient of kinetic friction between the surface of the metal layer and the surface of the fluororesin-containing layer of 0.70 or less. In the above laminate, when the surfaces of the fluororesin-containing layers in two laminates are bonded together at 200 °C, the adhesive strength is preferably greater than 30 N / m.

[0010] The above fluororesin-containing layer is preferably a tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer or a tetrafluoroethylene / hexafluoropropylene copolymer. The above fluororesin-containing layer preferably consists of a fluororesin having less than 10 unstable end groups per carbon atom number of 1×10 6 per carbon atom. The above fluororesin-containing layer preferably has a melt flow rate of the fluororesin of 1 to 50 g / 10 minutes at 372 °C and a load of 49 N.

[0011] The laminate of the present disclosure further has a layer (A) other than the metal layer and the fluororesin-containing layer, and the layer (A) may contain at least one selected from the group consisting of polyimide, liquid crystal polymer, polyphenylene sulfide, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, divinylbenzene, and polybutadiene.

[0012] It is preferable that the metal layer is formed using a metal foil having a surface roughness Rz of 1.5 μm or less.

[0013] The present disclosure is also a method for manufacturing the laminate described above, which is characterized by having a step of laminating a fluororesin film and a metal foil by roll-to-roll at a temperature of 280°C or less.

[0014] In the method for manufacturing the laminate, it is preferable that the oxygen element ratio when the surface state of at least one surface of the fluororesin film is measured by a scanning X-ray photoelectron spectrometer (XPS / ESCA) is 1.35 atomic% or more. It is preferable that the fluororesin film has an oxygen element ratio of 1.5 atomic% or more.

[0015] In the method for manufacturing the laminate, the difference between the oxygen element ratio when the surface state of one or both surfaces of the fluororesin film is measured by a scanning X-ray photoelectron spectrometer (XPS / ESCA) and the oxygen element ratio when the film is etched in the depth direction for 15 minutes at an incident angle of 45° by an argon gas cluster ion beam and then measured by a scanning X-ray photoelectron spectrometer (XPS / ESCA) is preferably 1.0 atomic% or more. The present disclosure is also a circuit board having the fluororesin laminate.

Advantages of the Invention

[0016] The laminate of the present disclosure has a high smoothness of the adhesive surface between the fluororesin-containing layer and the metal layer, and thus has low transmission loss. Therefore, it can be suitably used as a circuit board.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0018] Hereinafter, the present disclosure will be described in detail. As described above, the adhesiveness between the fluororesin-containing layer and the metal layer is better when the surface roughness is higher. However, in order to reduce the transmission loss, it is desirable that the adhesive surface has high smoothness. In the present disclosure, such problems have been studied.

[0019] As a method for obtaining a laminate in which a fluororesin-containing layer and a metal layer are adhered, a method of adhering a metal foil and a fluororesin film, a method of performing metal vapor deposition on a fluororesin film, etc. are known. Among these, when adhering a metal foil and a fluororesin film, a metal foil with high smoothness is used as the material, and at the same time, by examining the adhesion conditions, a laminate with excellent surface smoothness of the adhesive surface can be obtained.

[0020] Furthermore, when obtaining a laminate by metal vapor deposition, a laminate with excellent surface smoothness of the adhesive surface can be obtained by sufficiently bringing the cooling roll and the film into close contact during vapor deposition.

[0021] In the case of a laminate obtained by a method of bonding a metal foil and a fluororesin film, the bonding conditions are important. If the bonding conditions are not appropriate, it is impossible to achieve both the surface smoothness and the adhesiveness of the bonding surface. That is, even if a metal foil with high smoothness is used as the material, if the bonding conditions are inappropriate, either the bonding strength or the surface smoothness of the bonding surface will deteriorate. In the present disclosure, by using a metal foil with excellent smoothness and examining the bonding conditions with a fluororesin film (which is the raw material for the fluororesin-containing layer in the laminate), the above-described object has been achieved.

[0022] When metal vapor deposition is performed on a fluororesin film, the surface smoothness of the bonding surface is achieved by obtaining the adhesion with the cooling roll during vapor deposition.

[0023] (Arithmetic mean surface roughness Sa) The laminate of the present disclosure is characterized in that the arithmetic mean surface roughness Sa on the metal side of the bonding surface between the metal layer and the fluororesin interlayer is 0.05 μm or less. Regarding the above Sa, refer to FIG. 2. FIG. 2 is a drawing showing an example of the laminate of the present disclosure, which is a laminate having a structure in which a fluororesin-containing layer (3-A) and a metal layer (3-B) are bonded. The surface on the metal side of the bonding surface (3-C) between the metal layer (3-B) and the fluororesin-containing layer (3-A) in such a laminate is the surface to be measured for Sa of the present disclosure. The arithmetic mean surface roughness Sa is a parameter defined in ISO25178 and is a measurement of three-dimensional surface properties. A laminate that satisfies such a parameter has extremely high surface smoothness of the metal layer and reduced transmission loss.

[0024] More specifically, the above Sa is a parameter obtained by expanding the line roughness parameter Ra (arithmetic mean height of the line) to three dimensions (surface). It represents the average of the absolute values of the differences (z(x,y)) in height from the average surface of each measurement point in the reference area A, and the calculation formula is expressed as follows.

[0025]

Equation

[0026] The arithmetic mean surface roughness Sa on the metal side at the adhesion surface between the above metal layer and the fluororesin-containing layer is obtained by observing the adhesion surface between the metal layer and the fluororesin-containing layer with a laser microscope VK-X1000 (manufactured by Keyence Corporation) and calculating the arithmetic mean roughness (Sa) in accordance with ISO25178. The measurement area has a two-dimensional surface area of 60091 μm 2 and is set as such. In particular, the measurement of the adhesion surface between the metal layer and the fluororesin-containing layer is performed as follows. The laminate is set in the apparatus with the fluororesin side facing up and the metal side facing down. Since the laser microscope is an apparatus that performs surface analysis from the reflected light by applying laser light, when the irradiation position of the laser is lowered, there are two reflection points on the laminate. The reflection from the outermost surface is derived from the resin surface, and the second reflection is the reflection from the adhesion surface between the metal layer and the fluororesin-containing layer. The arithmetic mean surface roughness Sa on the metal side of the adhesion surface between the metal layer and the fluororesin-containing layer is the analysis of the second reflection data at this time.

[0027] The laminate obtained by adhering the metal layer and the fluororesin-containing layer is a known one. However, a laminate that maintains high surface smoothness of the adhesion surface after adhesion in this way has not been known in the past. According to the present disclosure, a laminate with a small reduction in transmission loss when comparing the transmission loss before and after adhesion can be obtained, and thus it can have excellent performance as a circuit board.

[0028] It is more preferable that the above Sa is 0.10 μm or less, and even more preferable that it is 0.05 μm or less. The lower limit of the above Sa is not particularly limited, but for example, it can be 0.01 μm or more.

[0029] (Surface roughness Rz) In the surface shape of the metal side of the adhesion surface between the above metal layer and the fluororesin-containing layer, it is preferable that the surface roughness Rz of the metal before lamination is 1.5 μm or less. Rz is a parameter in the height direction called "maximum height". A part of the roughness curve measured by a laser microscope is extracted with a reference length (282 μm), and the value is obtained as the sum of the highest part (maximum peak height: Rp) and the deepest part (maximum valley depth: Rv).

[0030] The specific measurement method is as follows. Rz was obtained by analyzing the reflection data of the surface of the metal layer of the bonding surface before bonding to the resin side.

[0031] (Adhesive strength between the metal layer and the fluororesin-containing layer) In the laminate of the present disclosure, the adhesive strength between the metal layer and the fluororesin-containing layer is preferably 0.1 N / mm or more. That is, it preferably has the smoothness of the bonding surface as described above and sufficient adhesive strength. The adhesive strength in the present disclosure is the value measured by the method described in the examples.

[0032] The adhesive strength is more preferably 0.1 N / mm or more, still more preferably 0.2 N / mm or more, and even more preferably 0.4 N / mm or more.

[0033] (Increase rate of transmission loss with respect to the unroughened copper foil) In the laminate of the present disclosure, the increase rate of transmission loss with respect to the unroughened copper foil is preferably 2% or less at 28 GHz. It is preferably 1.5% or less, and more preferably 1% or less. It is preferably 4% or less at 80 GHz. It is preferably 3% or less, and more preferably 2% or less.

[0034] The increase rate of transmission loss with respect to the unroughened copper foil is measured by the following measurement methods (1) to (3). (1) A printed circuit board is fabricated by forming a transmission line on one copper foil surface of a laminate in which copper foils are bonded to both sides of a fluororesin-containing layer. The transmission line constitutes a microstrip line, and a pattern with a characteristic impedance of 50 Ω is selected, and the transmission losses (S21: dB / cm) at 28 GHz and 80 GHz are measured. (2) Next, the transmission losses of laminates with the same configuration in the ideal pasted state (unroughened copper foil: Sa 0.02 μm) were calculated (at 28 GHz and 80 GHz) using an electromagnetic field simulator (ideal values). (3) The value obtained by dividing the difference between the measured value and the ideal value by the ideal value was defined as the increase rate of the transmission loss.

[0035] (Long film) The laminate of the present disclosure is preferably a long film. A long film is particularly preferable in terms of production cost when it is a continuously produced long film. The long film preferably has a width of 200 mm or more. Further, the length is preferably 1 m or more, more preferably 3 m or more, still more preferably 5 m or more, and even more preferably 10 m or more.

[0036] (Oxygen element ratio) In the laminate of the present disclosure, the oxygen element ratio when measured by a scanning X-ray photoelectron spectrometer (XPS / ESCA: PHI5000 VersaProbe II (manufactured by ULVAC-PHI, Inc.)) on the surface of the fluororesin-containing layer is preferably 1.35 atomic% or more.

[0037] Here, the oxygen element ratio was measured using a scanning X-ray photoelectron spectrometer (XPS / ESCA) PHI5000 VersaProbe II (manufactured by ULVAC-PHI, Inc.). Carbon, oxygen, fluorine, nitrogen, and silicon were the detection targets, and the oxygen element ratio was determined from the composition ratios of C1s, O1s, F1s, N1s, and Si2p. Details of the method for performing the surface treatment will be described later.

[0038] Furthermore, in the laminate of the present disclosure, the difference between the oxygen element ratio measured by a scanning X-ray photoelectron spectrometer (XPS / ESCA) on the surface of the fluororesin-containing layer and the oxygen element ratio measured by a scanning X-ray photoelectron spectrometer (XPS / ESCA) after etching the fluororesin-containing layer in the depth direction at an incident angle of 45° for 15 minutes with an argon gas cluster ion beam is preferably 1.0 atomic% or more. The greater the difference in the oxygen element ratio in the depth direction from the surface, the more preferable it is in terms of being able to obtain a predetermined transmission loss while maintaining adhesiveness.

[0039] The oxygen element ratio after the above etching is the oxygen element ratio on the surface before surface treatment in the fluororesin film that is the raw material of the fluororesin-containing layer. Therefore, the difference in the oxygen element ratio represents the increased oxygen element ratio due to surface treatment.

[0040] (Coefficient of kinetic friction between the surface of the metal layer and the surface of the fluororesin-containing layer) In the above laminate, the coefficient of kinetic friction between the surface of the metal layer and the surface of the fluororesin-containing layer is preferably 0.70 or less. In particular, in the case of a long film, it is more preferably 0.70 or less, even more preferably 0.50 or less, and still more preferably 0.40 or less.

[0041] Therefore, by setting the coefficient of kinetic friction between the surface of the metal layer and the surface of the fluororesin-containing layer to 0.70 or less, the above-mentioned problems are improved, and a long film can be wound up well. The coefficient of kinetic friction was measured using a surface property tester Heidon Type: 38 (manufactured by Shin-Tech Co., Ltd.). The indenter uses a roller type with a width of 60 mm and a diameter of 30 mm. The metal side of the laminate was fixed to the base with the metal side on the upper surface, and the laminate was fixed so that the fluororesin-containing layer was on the surface of the roller for a friction test. A 750 g weight was used for the balance, and the load applied to the sample was 100 g.

[0042] (Adhesion strength when the surfaces of the fluororesin-containing layers in two laminates are bonded together at 200 °C) When two laminates of the present disclosure are prepared and the surfaces of the fluororesin-containing layers thereof are bonded together at 200 °C, the adhesion strength is preferably greater than 30 N / m. The laminate of the present disclosure is often used after being laminated with other materials in many cases. In such cases, it is preferably excellent in adhesiveness. Using the adhesion strength described above as such an index, it is preferable that the adhesion strength is within the above-described range.

[0043] More specifically, the above adhesion strength is obtained by overlapping the surface-treated surfaces of the fluororesin films that are the raw materials of the fluororesin-containing layers, cutting the sample prepared by heat pressing (200 °C, 0.1 MPa, 60 s) into strips 10 mm wide, and using a precision universal testing machine Autograph AGS-X 100N (manufactured by Shimadzu Corporation). While gripping the unbonded part of the strip-shaped sample with the upper and lower chucks of the autograph, the peel strength is measured by pulling at a speed of 100 mm per minute, and the obtained value is taken as the adhesion strength.

[0044] (Fluororesin-containing layer) In the laminate of the present disclosure, the resin constituting the fluororesin-containing layer is not particularly limited as long as it is a resin containing fluorine, and known fluororesins can be used. Among them, it is preferably composed of a tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer (PFA) or a tetrafluoroethylene / hexfluoropropylene copolymer (FEP).

[0045] (Per)fluoro(alkyl vinyl ether) (PAVE) may be a fluoroalkyl vinyl ether or a perfluoro(alkyl vinyl ether). In the present disclosure, "perfluoro(alkyl vinyl ether)" means an alkyl vinyl ether that does not contain a C-H bond. As the PAVE constituting the above PAVE unit, the general formula (1): CF2=CFO(CF2CFY 1 O)p -(CF2CF2CF2O) q -R f (1) (In the formula, Y 1 represents F or CF3, and R f represents a perfluoroalkyl group having 1 to 5 carbon atoms. p represents an integer from 0 to 5, and q represents an integer from 0 to 5.) The monomer represented by the formula, and the general formula (2): CFX=CXOCF2OR 1 (2) (In the formula, X is the same or different and represents H, F or CF3, and R 1 represents a linear or branched fluoroalkyl group having 1 to 6 carbon atoms which may contain 1 to 2 atoms selected from the group consisting of H, Cl, Br and I, or a cyclic fluoroalkyl group having 5 or 6 carbon atoms which may contain 1 to 2 atoms selected from the group consisting of H, Cl, Br and I.) At least one selected from the group consisting of monomers represented by the formula can be mentioned.

[0046] Among them, as the above PAVE, the monomer represented by the general formula (1) is preferable, at least one selected from the group consisting of perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether) and perfluoro(propyl vinyl ether) (PPVE) is more preferable, and PPVE is even more preferable.

[0047] The content of the PAVE unit in the above TFE / PAVE copolymer is preferably 1.0 to 10% by mass, more preferably 2.0% by mass or more, still more preferably 3.5% by mass or more, particularly preferably 4.0% by mass or more, most preferably 5.0% by mass or more, more preferably 8.0% by mass or less, still more preferably 7.0% by mass or less, particularly preferably 6.5% by mass or less, and most preferably 6.0% by mass or less, based on all monomer units. Incidentally, the amount of the above PAVE unit is 19 measured by the F-NMR method. The above TFE / PAVE copolymer may be a copolymer consisting only of TFE units and PAVE units.

[0048] When the fluororesin-containing layer is made of a TFE / PAVE copolymer, the melting point is preferably 280 to 322 °C, more preferably 290 °C or higher, and more preferably 315 °C or lower.

[0049] When the fluororesin-containing layer is made of a TFE / PAVE copolymer, the glass transition temperature (Tg) is preferably 70 to 110 °C, more preferably 80 °C or higher, and more preferably 100 °C or lower. The above glass transition temperature is a value obtained by measuring with dynamic viscoelasticity measurement.

[0050] The above TFE / HFP copolymer contains TFE units and HFP units. The content of TFE units in the above TFE / HFP copolymer is preferably 70% by mass or more, more preferably 85% by mass or more, preferably 99.8% by mass or less, more preferably 99% by mass or less, and still more preferably 98% by mass or less with respect to all monomer units.

[0051] The above TFE / HFP copolymer preferably has a mass ratio of TFE units to HFP units (TFE / HFP) of 70 to 99 / 1 to 30 (mass%). The above mass ratio (TFE / HFP) is more preferably 85 to 95 / 5 to 15 (mass%).

[0052] The above TFE / HFP copolymer may further contain (per)fluoro(alkyl vinyl ether) (PAVE) units. Examples of the PAVE units contained in the above TFE / HFP copolymer may be the same as the above-described PAVE units. Since the above-described TFE / PAVE copolymer does not contain HFP units, it is different from the TFE / HFP / PAVE copolymer in that respect.

[0053] When the above-mentioned TFE / HFP copolymer is a copolymer containing TFE units, HFP units, and PAVE units (hereinafter, also referred to as "TFE / HFP / PAVE copolymer"), the mass ratio (TFE / HFP / PAVE) is preferably 70 to 99.8 / 0.1 to 25 / 0.1 to 25 (mass%). The above mass ratio (TFE / HFP / PAVE) is more preferably 75 to 98 / 1.0 to 15 / 1.0 to 10 (mass%). The above TFE / HFP / PAVE copolymer preferably contains a total of 1 mass% or more of HFP units and PAVE units based on all monomer units.

[0054] It is preferable that the HFP units in the above TFE / HFP / PAVE copolymer are 25 mass% or less of all monomer units. The content of HFP units is more preferably 20 mass% or less, still more preferably 18 mass% or less, and particularly preferably 15 mass% or less. Also, the content of HFP units is preferably 0.1 mass% or more, more preferably 1 mass% or more, and particularly preferably 2 mass% or more. The content of HFP units can be measured by the F-NMR method. 19 It can be measured by the F-NMR method.

[0055] The content of PAVE units is more preferably 20 mass% or less, still more preferably 10 mass% or less, and particularly preferably 3 mass% or less. Also, the content of PAVE units is preferably 0.1 mass% or more, more preferably 1 mass% or more. The content of PAVE units can be measured by the F-NMR method. 19 It can be measured by the F-NMR method.

[0056] The above-mentioned TFE / PAVE copolymer and the above-mentioned TFE / HFP copolymer may further contain units of other ethylenically unsaturated monomer (α). The units of other ethylenically unsaturated monomer (α) are not particularly limited as long as they are monomer units copolymerizable with TFE, HFP, and PAVE. For example, fluorinated ethylenically unsaturated monomers such as vinyl fluoride (VF), vinylidene fluoride (VdF), trifluoroethylene (TrFE), chlorotrifluoroethylene (CTFE), etc., non-fluorinated ethylenically unsaturated monomers such as ethylene, propylene, alkyl vinyl ether, etc., ethylenically unsaturated monomers having a hydroxyl group-containing group or a carbonyl group-containing group such as itaconic anhydride, citraconic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, etc. may be mentioned. The content of the units of other ethylenically unsaturated monomer (α) is preferably 0 to 25% by mass, more preferably 0.1 to 25% by mass.

[0057] When the above-mentioned copolymer is a TFE / HFP / PAVE / other ethylenically unsaturated monomer (α) copolymer, the mass ratio (TFE / HFP / PAVE / other ethylenically unsaturated monomer (α)) is preferably 70 to 98 / 0.1 to 25 / 0.1 to 25 / 0.1 to 25 (mass%). The above-mentioned TFE / HFP / PAVE / other ethylenically unsaturated monomer (α) copolymer preferably contains a total of 1% by mass or more of monomer units other than TFE units.

[0058] The melting point of the above-mentioned TFE / HFP copolymer is preferably 200 to 322 °C, more preferably above 200 °C, still more preferably 220 °C or higher, more preferably 300 °C or lower, still more preferably 280 °C or lower.

[0059] The glass transition temperature (Tg) of the above-mentioned TFE / HFP copolymer is preferably 60 to 110 °C, more preferably 65 °C or higher, more preferably 100 °C or lower. The above-mentioned glass transition temperature is a value obtained by measurement by dynamic viscoelasticity measurement.

[0060] The above fluororesin can be produced by a conventionally known method such as appropriately mixing monomers that are its constituent units and additives such as a polymerization initiator, and performing emulsion polymerization, suspension polymerization, etc. Among them, those obtained by emulsion polymerization are more preferable.

[0061] The fluororesin contained in the fluororesin-containing layer preferably has a melt flow rate of 1 to 50 g / 10 min at 372 °C and a load of 49 N.

[0062] The fluororesin-containing layer is preferably composed of a fluororesin having less than 10 unstable end groups per 1 × 10 6 carbon atoms.

[0063] For the above fluororesin, it is better that it has fewer functional groups, and particularly better that it has fewer unstable end groups. Such fluororesins can be produced by adjusting the conditions during production (polymerization reaction), or by performing fluorine gas treatment, heat treatment, supercritical gas extraction treatment, etc. on the fluororesin after polymerization to reduce the number of unstable end groups. Fluorine gas treatment is preferable in terms of excellent treatment efficiency and the fact that some or all of the unstable end groups are converted to -CF3 to become stable end groups. Using a fluororesin with a reduced number of unstable end groups in this way is preferable in that the dielectric tangent decreases and the loss of electrical signals decreases.

[0064] The number of the above unstable end groups is not particularly limited, but it is preferably 450 or less, more preferably 250 or less, still more preferably 100 or less, and most preferably 50 or less per 10 6 main chain carbon atoms of the fluororesin. Considering the effect of reducing the dielectric tangent, less than 10 is preferable, and more preferably 5 or less.

[0065] Examples of the unstable end groups include functional groups such as -COF, -COOH free (free COOH), -COOH bonded (associated -COOH), hydroxyl group (-CH2OH, etc.), -CONH2, -COOR (R = CH3, etc.), -CF2H, -OCOO-R (normal propyl carbonate, etc.).

[0066] The number of unstable end groups is specifically measured by the following method. First, the fluororesin is melted and compression molded to produce a film with a thickness of 0.25 to 0.3 mm. This film is analyzed by Fourier transform infrared spectroscopy to obtain the infrared absorption spectrum of the fluororesin, and a difference spectrum from the base spectrum that is completely fluorinated and has no functional groups is obtained. From the absorption peak of the specific functional group appearing in this difference spectrum, the number of unstable end groups per 1 × 10 6 carbon atoms in the above fluororesin is calculated according to the following formula (A). N = I × K / t (A) I: Absorbance K: Correction coefficient t: Thickness of the film (mm)

[0067] For reference, Table 1 shows the absorption frequency, molar extinction coefficient, and correction coefficient for the unstable end groups in this specification. The molar extinction coefficient was determined from the FT-IR measurement data of low molecular weight model compounds.

[0068]

Table 1

[0069] The fluororesin-containing layer in the laminate of the present disclosure may contain components other than the fluororesin. The components that can be contained are not particularly limited, and examples include fillers such as silica particles and short glass fibers, and fluorine-free thermosetting resins and thermoplastic resins. The content of components other than the fluororesin is not particularly limited, but is more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0070] In the laminate of the present disclosure, the fluororesin-containing layer preferably has a thickness of 1 to 100 μm. The above upper limit is more preferably 50 μm or less, and even more preferably 30 μm or less. The above lower limit is more preferably 3 μm or more, and even more preferably 5 μm or more.

[0071] Note that the thickness of the fluororesin-containing layer is a value measured by the reflection spectroscopy of a film thickness measurement system F20 (manufactured by Filmetrics).

[0072] (Metal layer) In the present disclosure, examples of the metal species constituting the metal foil layer include copper, aluminum, SUS, nickel, gold, etc. These alloys can be used. From the viewpoints of conductivity and circuit processability, it is preferable to use copper. A heat-resistant layer (such as nickel plating, titanium plating, etc.) and a rust-proof layer (such as a chromate treatment layer, etc.) may be formed on the surface of the copper foil. Further, the surface may be treated with a chemical solution using a silane coupling agent. Among them, it is preferable to use copper foil. The above metal foil layer preferably has a thickness of 1 to 100 μm.

[0073] The above metal layer may be a metal foil layer, or a metal layer or metal foil vacuum-deposited on the fluororesin-containing layer can be used.

[0074] (Layer structure of the laminate) The laminate of the present disclosure may have a two-layer structure composed of the above-mentioned fluororesin-containing layer and metal layer, or may have a three-layer or more structure having two or more layers of any one or both of these. Further, it may have a three-layer or more structure having a layer (A) other than the metal layer and the fluororesin-containing layer.

[0075] Examples of the layer (A) other than the metal layer and the fluororesin-containing layer include polyimide, liquid crystal polymer, polyphenylene sulfide, cycloolefin polymer, polystyrene, etc. Examples of the thermosetting resin include those containing epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, divinylbenzene, polybutadiene, etc.

[0076] When the laminate of the present disclosure has the above layer (A), the layer structure can be metal / fluororesin-containing layer / layer (A). There may be a laminate of fluororesin-containing layer / metal on one side or both sides of layer (A).

[0077] (Manufacturing method) The manufacturing method of the laminate of the present disclosure will be described in detail below. In order to obtain the laminate of the present disclosure, it is necessary that the metal foil used as a material has high smoothness, and further adjust the conditions in the step of bonding with the fluororesin film.

[0078] The metal foil used as a raw material for manufacturing the laminate of the present disclosure preferably has an arithmetic mean surface roughness Sa of 0.3 μm or less, more preferably 0.15 μm or less. Further, it is preferably 0.04 μm or less. Thus, using a metal foil with high surface smoothness before bonding is important for achieving the object of the present invention. As the metal foil having an arithmetic mean surface roughness Sa of 0.04 μm or less, commercially available ones can be used. For example, electrolytic copper foil CF-T9DA-SV-18 (thickness 18 μm, Rz 0.85 μm, Sa 0.02 μm (manufactured by Fukuda Metal Foil & Powder Co., Ltd.)) etc. can be mentioned.

[0079] The fluororesin film used as a raw material for manufacturing the laminate of the present disclosure is not particularly limited, and known general ones made of the fluororesin as described above can be used.

[0080] When bonding the above-mentioned metal foil and fluororesin film, heating is required. However, in the production of the laminate of the present disclosure, it is preferable that the heating temperature be -20°C or lower than the melting point of the fluororesin. For example, when the fluororesin is PFA, it is preferably 280°C or lower, and preferably 120 - 280°C. More preferably, it is 200 - 280°C, and even more preferably 220 - 280°C. Regarding the heat treatment process, a roll-to-roll lamination method or a method of heat-treating the fluororesin coated on the metal foil may be used.

[0081] That is, by setting the heating temperature to a low temperature of -20°C or lower than the melting point, it is preferable in that the smoothness of the bonding surface is less likely to be impaired in the step of bonding the metal foil layer and the fluororesin-containing layer. Although the mechanism is not clear, it is presumed as follows. Since the resin expands when heated and melted and contracts when cooled and solidified, when heated at -20°C or higher than the melting point and bonded to the metal foil, the metal foil will be deformed under the shrinkage of the resin. Therefore, if the bonding is performed at -20°C or lower than the melting point, the deformation of the metal foil due to the shrinkage can be suppressed, and the smoothness of the bonding surface is less likely to be impaired.

[0082] In the present disclosure, the melting point of the fluororesin is determined by using a differential scanning calorimeter, in accordance with ASTM D-4591, performing heat measurement at a heating rate of 10°C / min, and taking the temperature corresponding to the peak of the obtained endothermic curve as the melting point.

[0083] In the production of the laminate of the present disclosure, the method of bonding the metal foil and the fluororesin film is not particularly limited. However, from the viewpoint of excellent production efficiency, the roll-to-roll lamination method is particularly preferable.

[0084] By manufacturing by roll-to-roll, it is possible to reduce costs, and it is also preferable in that a long laminate can be obtained. When manufacturing a laminate by such a method, the width of the laminate is not particularly limited, but it is preferably 200 mm or more.

[0085] The fluororesin film is preferably capable of being adhered at a melting point of the fluororesin of -20°C or lower, for example, 120°C to 280°C, by performing surface modification on one or both sides to improve the adhesiveness. By laminating a metal foil on the fluororesin film obtained in such a manner under appropriate conditions, the laminate of the present disclosure can be preferably obtained.

[0086] The specific method of the surface modification is not particularly limited, and specific examples thereof will be described in detail below. As the surface modification of the fluororesin film, discharge treatments such as corona discharge treatment, glow discharge treatment, plasma discharge treatment, and sputtering treatment, which have been conventionally performed, can be employed. For example, the surface free energy can be controlled by introducing oxygen gas, nitrogen gas, hydrogen gas, carbon dioxide gas, methane gas, ethylene gas, etc. into the discharge atmosphere. In addition, the surface to be modified is exposed to an atmosphere of an inert gas containing an organic compound, i.e., an organic compound-containing inert gas, and a high-frequency voltage is applied between the electrodes to cause discharge, thereby generating active species on the surface. Subsequently, surface modification can be performed by introducing a functional group of the organic compound or graft-polymerizing a polymerizable organic compound. Examples of the inert gas include nitrogen gas, helium gas, argon gas, etc.

[0087] Examples of the organic compound in the inert gas containing the organic compound include polymerizable or non-polymerizable organic compounds containing an oxygen atom, such as vinyl esters such as vinyl acetate and vinyl formate; acrylic esters such as glycidyl methacrylate; ethers such as vinyl ethyl ether, vinyl methyl ether, and glycidyl methyl ether; carboxylic acids such as acetic acid and formic acid; alcohols such as methyl alcohol, ethyl alcohol, phenol, and ethylene glycol; ketones such as acetone and methyl ethyl ketone; carboxylic acid esters such as ethyl acetate and ethyl formate; acrylic acids such as acrylic acid and methacrylic acid, etc. Among these, vinyl esters, acrylic esters, and ketones are preferred from the viewpoint that the modified surface is less likely to be deactivated, that is, the lifespan is long, and vinyl acetate and glycidyl methacrylate are particularly preferred.

[0088] The concentration of the organic compound in the inert gas containing the organic compound varies depending on its type, the type of fluororesin to be surface-modified, etc., but is usually 0.1 to 3.0% by volume, preferably 0.1 to 1.0% by volume, more preferably 0.15 to 1.0% by volume, and still more preferably 0.30 to 1.0% by volume. The discharge conditions may be appropriately selected according to the desired degree of surface modification, the type of fluororesin, the type and concentration of the organic compound, etc. Usually, the discharge amount is 50 to 1500 W·min / m 2 , preferably 70 W·min / m 2 or more and 1400 W·min / m 2The discharge treatment is carried out within the following range. The treatment temperature can be any temperature within the range of 0°C or higher and 100°C or lower. From concerns such as film elongation and wrinkles, it is preferably 80°C or lower. Considering that during lamination with a metal foil, the oxygen element on the surface is deactivated due to heat and the like, resulting in a decrease in adhesion ability, the abundance ratio of the oxygen element observed by ESCA is 1.5% or more, preferably 1.75% or more, more preferably 2.0% or more, and still more preferably 2.5% or more. Although there is no particular regulation regarding the upper limit, considering the influence on productivity and other physical properties, it is preferably 25.0% or lower. The abundance ratio of the nitrogen element is not particularly specified, but it is preferably 0.1% or more. Also, the thickness of one fluororesin film is preferably 1.0 to 1000 μm, more preferably 12.5 to 100 μm, and still more preferably 5 to 30 μm.

[0089] In the above method, it is preferable to perform a surface treatment such that the oxygen element ratio is 1.5 atomic% or more when measuring the surface states of both sides of the fluororesin film by a scanning X-ray photoelectron spectrometer (XPS / ESCA). The above oxygen element ratio is more preferably 1.75 atomic% or more.

[0090] In the above method, when performing surface treatment with a gas containing an organic compound, it is also preferable in that the coefficient of kinetic friction between the surface of the metal foil layer and the surface of the fluororesin-containing layer can be made 0.4 or less by imparting local irregularities to the resin surface. That is, in addition to good adhesion strength, the coefficient of kinetic friction can be made small. Thus, it is preferable in that when forming a long laminated body, no winding defects occur.

[0091] The fluororesin film plasma-treated by the above method may be annealed to remove residual stress in advance. By doing so, in the process of laminating with a metal foil to manufacture a laminate, the dimensional change of the fluororesin film due to heat from the pressure roll can be reduced, and it can be laminated without wrinkles, so that the appearance defects of the laminate can be suppressed. By undergoing these heat treatments, the amount of oxygen on the surface of the fluororesin film will decrease. Therefore, it is preferable to perform surface modification under conditions that can obtain a sufficient surface oxygen amount when the fluororesin film and the metal foil are laminated together.

[0092] The annealing treatment can be carried out by heat treatment. The heat treatment can be carried out, for example, by passing through a heating furnace in a roll-to-roll manner. It may also be heat-treated by putting it into a batch drying furnace.

[0093] The annealing treatment temperature is preferably not less than the glass transition temperature of the fluororesin - 20°C and less than the melting point, more preferably not less than the glass transition temperature of the fluororesin and not more than the melting point - 20°C, and even more preferably not less than the glass transition temperature of the fluororesin and not more than the melting point - 60°C. The annealing treatment time is not particularly limited, but can be appropriately adjusted within, for example, 0.5 to 60 minutes.

[0094] When heating in the above roll-to-roll manner, the tension can be appropriately adjusted according to the film thickness, set temperature, etc., but it is preferably 20 N / m or less. Heating under such conditions is preferable in that the internal stress can be sufficiently relaxed and no dimensional change or the like occurs.

[0095] The order of the above surface treatment and annealing treatment is not particularly limited, and the number of times each process is performed is not limited to once, and may be performed two or more times.

[0096] The laminate of the present disclosure has a small surface unevenness on the adhesion surface between the metal layer and the fluororesin-containing layer, and thus has the advantage of low transmission loss. Therefore, it can be suitably used for circuit boards and the like. In particular, it can be particularly suitably used for circuit boards of high-frequency circuits.

[0097] In the present disclosure, the high-frequency circuit includes not only a circuit that simply transmits only high-frequency signals, but also a transmission path that converts a high-frequency signal into a low-frequency signal and outputs the generated low-frequency signal to the outside, and a transmission path for supplying a power source supplied for driving high-frequency compatible components. A circuit in which transmission paths for transmitting signals that are not high-frequency signals, such as a transmission path, are also provided side by side on the same plane is also included. In addition, it can also be used as a circuit board such as an antenna or a filter.

Example

[0098] Hereinafter, the present disclosure will be specifically described based on examples. In the following examples, unless otherwise specified, "parts" and "%" represent "parts by mass" and "mass%", respectively.

[0099] [Manufacturing method of film] (Manufacturing method of long roll film 1) #A nickel filter obtained by ultrasonic cleaning a plurality of meshes of 300 or more was inserted between a screw and a die, and a TFE / PPVE copolymer (composition: TFE / PPVE = 96.1 / 3.9 (mass%), MFR: 16.0 g / 10 min, melting point: 305 °C, unstable end group number: undetectable (less than 1 per 10 main chain carbon atoms)) (hereinafter: F-PFA) was used as the fluororesin in an extruder at 360 °C, extruded from a T-die with a width of 1700 mm, taken up by a metal cooling roll, and further wound around a winding core to form a long roll film 1 with a width of 1300 mm and a thickness of 12.5 μm. 6 per unit)) was used, extruded from a T-die with a width of 1700 mm, taken up by a metal cooling roll, and further wound around a winding core to form a long roll film 1 with a width of 1300 mm and a thickness of 12.5 μm.

[0100] (Manufacturing method of long roll film 2) In the same process, a TFE / PPVE copolymer (composition: TFE / PPVE = 95.4 / 4.6 (mass%), MFR: 15.8 g / 10 min, melting point: 305 °C, number of unstable end groups: 297 per 10 main chain carbon atoms 6 )(hereinafter referred to as PFA), which is not end-fluorinated as a fluororesin, is used as the long roll film 2.

[0101] (Manufacturing method of long films 3 and 4) Next, surface treatment is performed on both sides of the obtained long roll film 1 (while flowing nitrogen gas containing 0.50% by volume of vinyl acetate near the discharge electrode of the plasma discharge device and the roll-shaped ground electrode, the film is continuously passed along the roll-shaped ground electrode, and the discharge amount is 265 W·min / m 2 The long film 3 with surface treatment in a roll shape is wound up by performing plasma discharge treatment on both sides of the film. The film slit to a width of 500 mm is used as the long film 4.

[0102] (Manufacturing method of long films 5 and 6) Next, surface treatment is performed on both sides of the obtained long roll film 2 (while flowing nitrogen gas containing 0.50% by volume of vinyl acetate near the discharge electrode of the plasma discharge device and the roll-shaped ground electrode, the film is continuously passed along the roll-shaped ground electrode, and the discharge amount is 265 W·min / m 2 The long film 5 with surface treatment in a roll shape is wound up by performing plasma discharge treatment on both sides of the film. The film slit to a width of 500 mm is used as the long film 6.

[0103] (Manufacturing method of long film 7) The long film 4 is passed through an annealing furnace at 180 °C (in an air atmosphere) in a roll-to-roll manner, the film is cooled in the cooling zone, and the long film is wound up in a roll shape. The film slit to a width of 500 mm is used as the long film 7.

[0104] (Manufacturing method of long film 8) Both sides of the obtained long roll film 1 were surface-treated (while flowing He gas containing 0.5% by volume of CO2 and 0.5% by volume of O2 near the discharge electrode of the plasma discharge device and the roll-shaped ground electrode, the film was continuously passed along the roll-shaped ground electrode, and the discharge amount was 1200 W·min / m 2 to perform plasma discharge treatment on both sides of the film), and the long film surface-treated in a roll shape was wound up. The film slit to a width of 500 mm was designated as the long film 8.

[0105] [Lamination with copper foil] (Example 1) Using the thermal laminating device shown in Fig. 1, the long film 4 was laminated with a long copper foil 2 having a width of 520 mm (electrolytic copper foil CF-T9DA-SV-18 (thickness 18 μm / Rz0.85 μm, Sa0.020 μm) (manufactured by Fukuda Metal Foil & Powder Co., Ltd.) to obtain a laminate 21. During lamination, the surface temperature (press temperature) of a pair of laminating rolls 100 (metal rolls) was 280°C, the pressure applied by the laminating rolls was 20 kN / m, and the conveyance speeds of the film and the copper foil were 3 m / min.

[0106] (Examples 2 to 9) Laminates 22 to 29 were obtained in the same manner as the above laminate 21, except that the press temperature was changed as described in Table 2.

[0107] (Example 10) A laminate 30 was obtained in the same manner as the above laminate 21, except that the long film 7 was used instead of the long film 2 and the press temperature was 280°C.

[0108] (Example 11) A laminate 31 was obtained in the same manner as the above laminate 21, except that the long film 6 was used instead of the long film 2 and the press temperature was 280°C.

[0109] (Example 12) A laminate 32 was obtained in the same manner as the above laminate 21, except that the long film 8 was used instead of the long film 2 and the press temperature was 260°C.

[0110] (Reference Examples 1 to 3) (Except that the press temperature was changed as described in Table 3, laminates 33 to 35 were obtained in the same manner as the above laminate 21.)

[0111] (Reference Example 4) (Except that the long film 7 was used and the press temperature was set to 300°C, laminate 36 was obtained in the same manner as the above laminate 21.)

[0112] (Comparative Examples 1 to 3) (Except that the press temperature was changed as described in Table 3, laminates 37 to 3940 were obtained in the same manner as the above laminate 32.)

[0113] (Measurement method and evaluation method of oxygen element ratio) (Using a scanning X-ray photoelectron spectrometer (XPS / ESCA) PHI5000 VersaProbe II (manufactured by ULVAC-PHI, Inc.), the oxygen element ratio of the resin surface after surface treatment was measured under the conditions of a monochromatic AlKα light source and an incident angle of 45°. Carbon, oxygen, fluorine, nitrogen, and silicon are the detection targets. The oxygen element ratio is determined from the composition ratios of C1s, O1s, F1s, N1s, and Si2p.)

[0114] (Sa on the copper foil side at the adhesion surface between the metal foil and the fluororesin-containing layer after bonding) The adhesion surface between the metal layer and the fluororesin-containing layer was observed with a laser microscope VK-X1000 (manufactured by Keyence Corporation), and the arithmetic mean roughness (Sa) was calculated in accordance with ISO25178. The measurement area had a two-dimensional surface area of 60091 μm2. In particular, the measurement of the adhesion surface between the metal layer and the fluororesin was performed as follows. The laminate was set in the apparatus with the side of the fluororesin facing up and the metal side facing down. The laser microscope is an apparatus that performs surface analysis from the reflected light by applying a laser beam. As the irradiation position of the laser is lowered, there are two reflection points on the laminate. The reflection from the outermost surface is derived from the resin surface, and the second reflection is from the adhesion surface between the metal layer and the fluororesin-containing layer. The data obtained by analyzing the second reflection data at this time is defined as the arithmetic mean surface roughness Sa on the metal side of the adhesion surface between the metal layer and the fluororesin-containing layer. The measurement conditions are as follows: Gaussian filter type, S filter: 2.5 μm, L filter: 0.08 mm are applied. Also, the correction during the analysis of Sa is carried out as follows. Surface shape correction: quadratic curve, waviness removal (strength: 5) Smoothing: median, size 3×3

[0115] (Increase rate of transmission loss for unroughened copper foil) First, a printed circuit board was fabricated by forming a transmission line on one copper foil surface of a laminate in which copper foils were laminated on both sides of a fluororesin-containing layer (thickness 50 μm), and the high-frequency transmission characteristics were evaluated using a vector network analyzer (N5290A manufactured by Keysight Technologies). The transmission line constituted a microstrip line, and a pattern with a characteristic impedance of 50 Ω was selected, and the transmission losses (S21: dB / cm) at 28 GHz and 80 GHz were measured (actual measured values). Next, the transmission losses for a laminate of the same configuration in an ideal bonding state (unroughened copper foil: Sa 0.02 μm) were calculated (28 GHz and 80 GHz) with an electromagnetic field simulator (manufactured by Ansys) (ideal values). In each example and comparative example, the difference between the actual measured value and the ideal value was obtained and used as the increase rate of the transmission loss.

[0116] (Adhesion strength between copper foil and fluororesin-containing layer) Prepare prepreg R-5680(J) (thickness: 132 μm, manufactured by Panasonic Corporation). Cut two 200 mm square laminates 21 made in Example 1, and stack a copper foil layer / fluororesin-containing layer / prepreg / fluororesin-containing layer / copper foil layer on both sides of the prepreg so that the fluororesin surface is in contact with the prepreg to obtain a laminate. Then, after setting the pressing conditions to a temperature of 200 °C, a time of 75 minutes, and a pressure of 3.0 MPa to create a measurement sample, cut it into 10 mm widths. Attach an adhesive tape to one side of the cut sample, stick it to an aluminum plate, and then use a precision universal testing machine Autograph AGS-X 100N (manufactured by Shimadzu Corporation) to grasp and pull a 10 mm wide copper foil in a direction 90° to the plane of the laminate at a speed of 50 mm per minute to measure the peel strength between the copper foil and the fluororesin-containing layer, and use the obtained value as the adhesive strength.

[0117] (Coefficient of kinetic friction between the copper foil surface and the fluororesin-containing layer surface) Measure using a surface property tester Heidon Type: 38 (manufactured by Shinto Kagaku Co., Ltd.). The indenter uses a roller type with a width of 60 mm and a diameter of 30 mm. Fix the laminate with the metal side on the upper surface to the base, and fix the laminate so that the fluororesin-containing layer comes to the surface of the roller to conduct a friction test. Use a 750 g weight for the balance and a 100 g load on the sample. The average value of the values obtained by dividing the test force obtained by the load cell of this tester by the load for 500 ms in the stable range of the test force is defined as the coefficient of kinetic friction.

[0118] (Appearance of the wound shape) For the appearance of the 500 mm wide laminate wound shape, the quality is visually judged and defined as follows: ○: No wrinkles △: 1 - 2 wrinkles inside the roll ×: 3 or more wrinkles inside the roll

[0119]

Table 2

[0120]

Table 3

[0121] From the results of Tables 2 and 3, it is clear that the laminate of the present disclosure has low transmission loss. Furthermore, it is clear that the laminates of Examples 1 to 12 have low friction and do not cause problems due to poor winding.

Industrial Applicability

[0122] The laminate of the present disclosure can be suitably used as a circuit board.

Explanation of Signs

[0123] 1: Fluorine film 2: Metal foil 21: Laminate 100, 101: Pressing roll 102: Fluorine film supply roll 103: Metal foil supply roll 104a~c: Conveyor roll 105: Laminate winding roll 3-A: Fluororesin-containing layer 3-B: Metal foil layer 3-C: Adhesive surface of fluororesin-containing layer / metal foil layer

Claims

1. A laminate comprising a metal layer and a fluororesin-containing layer adjacent to the metal layer, wherein the arithmetic mean surface roughness Sa on the metal side of the adhesion surface between the metal layer and the fluororesin-containing layer is 0.05 μm or less.

2. The laminate according to Claim 1, wherein the adhesive strength between the metal layer and the fluororesin-containing layer is 0.1 N / mm or more.

3. The laminate according to any one of Claims 1 to 2, wherein the laminate is a long laminate having a width of 200 mm or more.

4. The laminate according to Claim 1 or 2, wherein the oxygen element ratio when the surface of the fluororesin-containing layer is measured by a scanning X-ray photoelectron spectrometer (XPS / ESCA) is 1.35 atomic% or more.

5. The laminate according to Claim 4, wherein the oxygen element ratio is 1.5 atomic% or more.

6. The difference between the oxygen element ratio when the surface of the fluororesin-containing layer is measured by a scanning X-ray photoelectron spectrometer (XPS / ESCA) and the oxygen element ratio when the fluororesin-containing layer is etched in the depth direction at an incident angle of 45° for 15 minutes by an argon gas cluster ion beam and then measured by a scanning X-ray photoelectron spectrometer (XPS / ESCA) is 1.0 atomic% or more. The laminate according to Claim 1 or 2.

7. The laminate according to Claim 1 or 2, wherein the coefficient of kinetic friction between the surface of the metal layer and the surface of the fluororesin-containing layer is 0.70 or less.

8. The laminate according to Claim 1 or 2, wherein the adhesive strength is greater than 30 N / m when the surfaces of the fluororesin-containing layers in two laminates are bonded together at 200°C.

9. The laminate according to Claim 1 or 2, wherein the fluororesin-containing layer is a tetrafluoroethylene / perfluoro(alkyl vinyl ether) copolymer or a tetrafluoroethylene / hexafluoropropylene copolymer.

10. The fluororesin-containing layer is the laminate according to claim 1 or 2, which is composed of a fluororesin having an amount of unstable end groups of less than 10 per 1 × 10 ６ carbons.

11. The laminate according to Claim 1 or 2, wherein the fluororesin-containing layer has a melt flow rate of 1 to 50 g / 10 minutes for the fluororesin at 372°C and a load of 49 N.

12. The fluororesin-containing layer uses a film surface-treated by plasma discharge with nitrogen gas containing vinyl acetate on both sides, the metal layer uses a copper foil with a surface roughness Rz of 1.5 μm or less, and the laminate is obtained by laminating these. The laminate according to Claim 1 or 2.

13. Furthermore, it has a layer (A) other than the metal layer and the fluororesin film layer, The laminate according to claim 1 or 2, wherein the layer (A) contains at least one selected from the group consisting of polyimide, liquid crystal polymer, polyphenylene sulfide, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, divinylbenzene, and polybutadiene.

14. The laminate according to claim 1 or 2, wherein the metal layer is formed using a metal foil having a surface roughness Rz of 1.5 µm or less.

15. A method for manufacturing the laminate according to claim 1 or 2, characterized by having a step of heat-treating a fluororesin film and a metal foil by roll-to-roll at a temperature of the melting point of the fluororesin - 20°C or lower.

16. A method for manufacturing the laminate according to claim 1 or 2, characterized by having a step of heat-treating a fluororesin film and a metal foil by roll-to-roll at a temperature of 280°C or lower.

17. The method for manufacturing the laminate according to claim 15, wherein the oxygen element ratio when the surface states of both surfaces of the fluororesin film are measured by a scanning X-ray photoelectron spectrometer (XPS / ESCA) is 1.5 atomic% or more.

18. The method for manufacturing the laminate according to claim 15, wherein the difference in the oxygen element ratio when the surface states of one or both surfaces of the fluororesin film are measured by a scanning X-ray photoelectron spectrometer (XPS / ESCA) and the oxygen element ratio when the film is etched in the depth direction at an incident angle of 45° for 15 minutes by an argon gas cluster ion beam and then measured by a scanning X-ray photoelectron spectrometer (XPS / ESCA) is 1.0 atomic% or more.

19. A circuit board characterized by having the laminate according to claim 1 or 2.

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