Copper-clad laminates and printed wiring boards

Abstract

Provided is a copper-clad laminate plate for which a copper foil and a resin are joined together with high heat-resistant adhesion strength while using a fluororesin which is a thermoplastic resin having a low dielectric constant. This copper-clad laminate plate includes: a surface-treated copper foil comprising a copper foil and a zinc-containing layer disposed on at least one surface of the copper foil; and a sheet-like fluororesin disposed on the zinc-containing layer side of the surface-treated copper foil. The zinc-containing layer is constituted by Zn and a transition element M having a melting point of 1,200˚C or higher. When an elemental analysis of the interface between the copper foil and the zinc-containing layer is performed by means of a glow discharge optical emission spectrometry (GD-OES) method, emission intensity ratio IZn / ICu, that is, the ratio of emission intensity IZn of the Zn to emission intensity ICu of the Cu, is 3.0 x 10-3 or lower, and emission intensity ratio IZn / IM , that is, the ratio of emission intensity IZn of the Zn to emission intensity IMof the transition element M, is 0.30 to 0.50.

Description

[Technical Field]

[0001] The present invention relates to 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 at high temperatures still decreases significantly. Therefore, further improvement in heat-resistant adhesion is required to improve reliability in applications that also require heat resistance. 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 this regard, in the past, the only way to ensure adhesion strength and reliability was to increase the roughness of the copper foil's adhesive surface with the resin, which inevitably resulted in increased transmission loss in high-frequency applications. Therefore, a new method for achieving both adhesion and heat resistance between the copper foil and the fluororesin substrate is needed.

[0006] The present inventors have now discovered that by interposing a zinc-containing layer having a predetermined interfacial composition between the copper foil and the fluororesin, it is possible to provide 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., in which the copper foil and the fluororesin are bonded with high heat-resistant adhesion.

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

[0008] According to one aspect of the present invention, 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 sheet-shaped fluororesin provided on the zinc-containing layer side of the surface-treated copper foil; A copper clad laminate comprising: 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 was analyzed by glow discharge optical emission spectroscopy (GD-OES), the emission intensity of Cu I Cu Zn emission intensity I Zn The emission intensity ratio I is the ratio Zn / I Cu is 3.0×10 -3 and the emission intensity I of the transition element M is M Zn emission intensity I Zn The emission intensity ratio I is the ratio Zn / I M is 0.30 or more and 0.50 or less.

[0009] According to another aspect of the present invention, there is provided a printed wiring board manufactured using the copper-clad laminate. [Brief explanation of the drawings]

[0010] [Figure 1] This is an example of a depth profile of the emission intensity of various elements measured by glow discharge optical emission spectroscopy (GD-OES). The horizontal axis represents the sputtering time in the depth direction from the copper foil to the resin in the copper clad laminate, and the vertical axis represents the emission intensity of each of the elements Si, Cu, Zn, Ni, and Cr. DETAILED DESCRIPTION OF THE INVENTION

[0011] Copper-clad laminate The copper-clad laminate of the present invention includes a surface-treated copper foil and a sheet-like fluororesin provided on the zinc-containing layer side of the surface-treated copper foil. The surface-treated copper foil comprises a copper foil and a zinc-containing layer provided on at least one side of the copper foil. 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 analyzed by glow discharge optical emission spectroscopy (GD-OES), the emission intensity I of Cu is Cu Zn emission intensity I Zn The emission intensity ratio I is the ratio Zn / I Cu is 3.0×10 -3 and the emission intensity I of the transition element M is MZn emission intensity I Zn The emission intensity ratio I is the ratio Zn / I M In this way, by interposing a zinc-containing layer having a predetermined interfacial composition between the copper foil and the fluororesin, it is possible to provide a copper-clad laminate that not only has high adhesion but also has excellent heat resistance such that the adhesion is not easily deteriorated even at high temperatures, i.e., in which the copper foil and the fluororesin are bonded with high heat-resistant adhesion.

[0012] 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 adhesion between the copper foil and the substrate still decreases significantly at high temperatures. In this regard, in the past, the only way to ensure adhesion strength and reliability was to increase the roughness of the copper foil's adhesive surface with the resin, which inevitably resulted in increased transmission loss in high-frequency applications. In contrast, the copper-clad laminate of the present invention achieves both adhesion strength and heat resistance between the copper foil and the fluororesin by interposing a zinc-containing layer with a predetermined interfacial composition at the interface.

[0013] The surface-treated copper foil used in 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.

[0014] 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.

[0015] As mentioned above, when the interface between the copper foil and the zinc-containing layer of the copper clad laminate was analyzed by GD-OES, the emission intensity of Cu I Cu Zn emission intensity I Zn The emission intensity ratio I is the ratio Zn / I Cu is 3.0×10 -3 or less, preferably 1.5 × 10 -3 Over 3.0 x 10 -3 Less than 2.0 × 10, more preferably -3 Over 3.0 x 10 -3 In addition, when the interface between the copper foil and the zinc-containing layer was subjected to elemental analysis by GD-OES, the emission intensity I of the transition element M was M Zn emission intensity I Zn The emission intensity ratio I is the ratio Zn / I M is 0.30 or more and 0.50 or less, preferably 0.30 or more and 0.45 or less, more preferably 0.33 or more and 0.45 or less, and further preferably 0.35 or more and 0.45 or less. Cu and I Znis determined at the interface between the copper foil and the zinc-containing layer, and this interface refers to the part of the zinc-containing layer directly above the copper foil. This part is less susceptible to surface oxidation and is considered to be an important area for imparting adhesion and heat resistance.

[0016] Elemental analysis by GD-OES can be performed by sputtering from the copper foil side of a copper-clad laminate toward the resin, thereby obtaining a depth profile of the emission intensity of various elements, as shown in Figure 1. In the depth profile shown in Figure 1, the horizontal axis corresponds to the sputtering time in the depth direction from the copper foil toward the resin of the copper clad laminate, and the vertical axis corresponds to the emission intensity of each element, such as Cu, Zn, Ni, and Cr. As shown in Figure 1, in the depth profile of the copper-clad laminate of the present invention, broad peaks of anti-corrosion elements, such as Zn, Ni, and Cr, resulting from anti-corrosion layers such as zinc-containing layers and chromate layers (hereinafter referred to as anti-corrosion element peaks) are inevitably observed. Therefore, in the depth direction from the copper foil side toward the resin (the direction in which sputtering time increases), it is inferred that the interface between the copper foil and the zinc-containing layer exists in the rising part slightly before the anti-corrosion element peak (where the sputtering time is slightly shorter). In fact, the Cu depth profile maintains a generally constant emission intensity (although there may be some fluctuations or steps) in the depth direction from the copper foil side toward the resin until just before the anti-rust element peak, and then linearly descends at a constant gradient in the region corresponding to the anti-rust element peak. By utilizing these characteristics of the Cu depth profile, the interface between the copper foil and the zinc-containing layer can be uniquely identified. Specifically, the interface between the copper foil and the zinc-containing layer is defined as the intersection X of two tangent lines L1 and L2 drawn in the Cu depth profile so that the correlation coefficient is maximized just before the anti-rust element peak (slightly shorter sputtering time), and then a second tangent line L2 is drawn so that the correlation coefficient is maximized in the descending portion just past the anti-rust element peak (slightly longer sputtering time). The Cu emission intensity I at the sputtering time (depth) thus identified as intersection X is Cu , Zn emission intensity I Zn , and the emission intensity of transition element M, I Mcan be read from the depth profile of the emission intensity of each element.

[0017] The sheet-like fluororesin used in the copper-clad laminate of the present invention 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.

[0018] 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.

[0019] Manufacturing method of copper clad laminate The copper-clad laminate of the present invention can be produced by (1) preparing a surface-treated copper foil, and (2) attaching a sheet-shaped fluororesin to the zinc-containing layer side of the surface-treated copper foil.

[0020] (1) Preparation of surface-treated copper foil The surface-treated copper foil used to manufacture the copper-clad laminate of the present invention may be any foil provided with a zinc-containing layer that provides the above-described interface composition.

[0021] The surface-treated copper foil used in the manufacture of copper-clad laminates preferably has a Zn content of 10 wt% or less, more preferably 1.0 wt% to 10.0 wt%, even more preferably 2.0 wt% to 8.0 wt%, particularly preferably 2.1 wt% to 7.5 wt%, and most preferably 2.1 wt% to 7.0 wt% when the interface between the copper foil and the zinc-containing layer is analyzed by X-ray photoelectron spectroscopy (XPS). 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 transition element M, is preferably 0.2 to 0.6, more preferably 0.22 to 0.58, and even more preferably 0.25 to 0.55.

[0022] The Zn content and Zn / M weight ratio are determined at the interface between the copper foil and the zinc-containing layer, which 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 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 measured 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.

[0023] 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.

[0024] (2) Fluorine resin attachment The fluororesin can be attached to the surface-treated copper foil 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, known techniques such as the so-called build-up method can be used. In any case, according to a preferred method for manufacturing the copper-clad laminate of the present invention, a surface-treated copper foil having a zinc-containing layer and an interface with an emission intensity ratio within the above range is selectively used 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 fluororesin is preferably attached to the surface-treated copper foil 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.

[0025] 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.

[0026] (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.

[0027] (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.

[0028] (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.

[0029] (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.

[0030] printed wiring board The copper-clad laminate of the present invention is preferably used for producing printed wiring boards. That is, according to a preferred embodiment of the present invention, a printed wiring board is provided which is manufactured using the copper-clad laminate. 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 in which these are multilayered. The multilayer printed wiring board may be a multilayer copper-clad laminate in which a copper foil is attached to an inner layer substrate via a thermoplastic resin (e.g., a fluororesin) and a circuit is formed on the multilayer copper-clad laminate, or a multilayer printed wiring board 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. The printed wiring board produced using the copper-clad laminate of the present invention is suitable for use as a high-frequency substrate 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]

[0031] The present invention is further illustrated by the following examples.

[0032] Examples 1 to 7 (1) Preparation of surface-treated copper foil Various surface-treated copper foils with a zinc-containing layer on the surface were prepared using known techniques. 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 agent treatment to the electrode surface of electrolytic copper foil (35 μm thick) using known techniques. Each surface-treated copper foil was subjected to elemental analysis using XPS while drilling 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 Corporation) 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

[0033] 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 1A.

[0034] (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.

[0035] (3) Evaluation of copper clad laminates The copper-clad laminates thus produced were subjected to the following various evaluations.

[0036] <Elemental analysis of the interface between copper foil and zinc-containing layer> Elemental analysis was performed by GD-OES while drilling the depth direction from the copper foil side of the copper-clad laminate toward the PTFE substrate by sputtering. This elemental analysis was performed using a glow discharge optical emission spectrometer (JY-5000RF, manufactured by JOBIN YVON) under the following measurement conditions. (Measurement conditions) - Output: 30W - Gas pressure: 665 Pa (Gas type: Ar) - Sputtering rate: 7 μm / min (Cu equivalent) - DS (duty cycle) = 0.0625 (the ratio of the time when sputtering is ON to the total time when sputtering is ON and the total time when sputtering is OFF) - Frequency: 100Hz - step (sec) / point: 0.1 (measurement point interval; 1 point measured per 0.1 seconds) - Measurement mode: After measuring for 140 seconds in normal mode, the measurement was switched to pulse mode (to shorten the measurement time). - Measurement elements: C, O, N, Si, Cr, Ni, Cu, Zn, Mo (Examples 6 and 7 only)

[0037] Based on the obtained depth profile of Cu emission intensity, two tangent lines L1 and L2 were drawn according to the above-mentioned definitions and procedures, and their intersection point X was determined to identify the interface between the copper foil and the zinc-containing layer. The Cu emission intensity I at the sputtering time (depth) corresponding to the interface thus identified as intersection point X was Cu , Zn emission intensity I Zn , and the emission intensity of transition element M, I M (In this example, this corresponds to the total emission intensity of Ni and Mo) was read from the depth profile of the emission intensity of each element. From these emission intensities, the emission intensity ratio I Zn / I Cu and I Zn / I M was calculated. The results are shown in Table 1A. The depth profile of the luminescence intensity shown in FIG. 1 was obtained in Example 2.

[0038] <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 1B.

[0039] <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 1B.

[0040] <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, and the results are shown in Table 1B.

[0041] <Overall rating> Each example was comprehensively evaluated according to the following criteria. Pass: Normal peel strength of 1.2 kgf / cm or more and heat deterioration rate of 10% or less Fail: Normal peel strength is less than 1.2 kgf / cm or heat resistance degradation rate is more than 10%.

[0042] [Table 1A]

[0043] [Table 1B]

[0044] From the results shown in Tables 1A and 1B, the luminescence intensity ratio I Zn / I Cu is 3.0×10 -3 and the emission intensity ratio I Zn / I M It can be seen that Examples 1, 2, 6 and 7, which satisfy the condition of the present invention that the value is 0.30 or more and 0.50 or less, generally have higher peel strength (i.e., higher adhesion) and significantly lower heat resistance degradation rate (i.e., excellent heat resistance) than the comparative examples of Examples 3 to 5, which do not satisfy this condition.

Claims

1. 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 sheet-shaped fluororesin provided on the zinc-containing layer side of the surface-treated copper foil; A copper clad laminate comprising: the surface-treated copper foil has only a chromate layer and a silane coupling agent layer on the surface of the zinc-containing layer side, and the surface of the surface-treated copper foil on the zinc-containing layer side is in contact with the fluororesin; 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 was subjected to elemental analysis by glow discharge optical emission spectroscopy (GD-OES), the emission intensity I Ｃｕ Zn emission intensity I Ｚｎ The emission intensity ratio I Ｚｎ / I Ｃｕ is 3.0 x 10 －３ and the emission intensity I of the transition element M is Ｍ Zn emission intensity I Ｚｎ The emission intensity ratio I Ｚｎ / I Ｍ A copper clad laminate having a coefficient of elasticity of 0.30 or more and 0.50 or less.

2. 2. The 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 copper clad laminate according to claim 1, wherein the transition element M is Ni and / or Mo.

4. The emission intensity ratio I Ｚｎ / I Ｃｕ is 1.5 x 10 －３ Above 3.0 x 10 －３ The copper clad laminate according to any one of claims 1 to 3, wherein:

5. The emission intensity ratio I Ｚｎ / I Ｍ The copper clad laminate according to any one of claims 1 to 4, wherein is 0.30 or more and 0.45 or less.

6. The emission intensity ratio I Ｚｎ / I Ｍ The copper clad laminate according to any one of claims 1 to 5, wherein the coefficient of friction coefficient is 0.35 or more and 0.45 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 copper-clad laminate according to any one of claims 1 to 6.

8. The 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 printed wiring board manufactured using the copper-clad laminate according to any one of claims 1 to 8.

Images