Copper-clad laminate and sputtering target for forming copper-clad laminate

Abstract

Provided is a copper-clad laminate (10) in which a base material (11) containing a fluororesin and a metal copper layer (12) are laminated, the copper-clad laminate (10) being characterized in that: an alloy layer (13) is formed between the base material (11) and the metal copper layer (12), the alloy layer (13) being composed of 25.0-75.0 at% Co, with the balance being Mo and unavoidable impurities; and the metal copper layer (12) has a copper plating layer.

Description

Copper-clad laminates and sputtering targets for forming copper-clad laminates

[0001] The present invention relates to a copper-clad laminate having a copper layer laminated on a substrate containing a fluororesin, and a sputtering target for forming the copper-clad laminate used in producing the copper-clad laminate. This application claims priority based on Japanese Patent Application No. 2023-196734 filed on November 20, 2023, and Japanese Patent Application No. 2024-201601 filed on November 19, 2024, the contents of which are incorporated herein by reference.

[0002] Generally, copper-clad laminates, in which a copper layer is laminated as a conductive layer or a heat-transfer layer on the surface of an insulating resin layer, are used as wiring substrates for electronic and electrical devices. Here, wiring substrates for high-frequency signal transmission devices, such as antennas and radars operating in the GHz band or higher, are required to have low transmission loss when used in the high-frequency range. Therefore, as shown in Patent Documents 1 and 2, for example, copper-clad laminates using fluororesin films have been provided. Because fluororesins have a low dielectric constant and low dielectric loss, they are particularly suitable as resin materials for constituting wiring substrates for high-frequency signal transmission.

[0003] However, since the surface of a fluororesin film is very chemically stable, its adhesive strength with other materials tends to be low. Therefore, in Patent Document 1, a metal thin film (nickel film or titanium film) is formed on the surface of the fluororesin by physical vapor deposition, and then a copper film is formed by copper plating on this metal thin film, thereby improving the adhesion between the copper film and the fluororesin. Furthermore, in Patent Document 2, protrusions are formed on the surface of the fluororesin, the metal foil is roughened, and the pressure lamination conditions are optimized, thereby improving the adhesion between the copper film and the fluororesin through the anchor effect.

[0004] International Publication No. 2018 / 179904 (A) Japanese Patent Application Laid-Open No. 2004-006668 (A)

[0005] However, in Patent Document 1, there is a problem that the bonding interface becomes smooth, so there is no anchor effect to improve adhesion, making it difficult to obtain sufficient adhesion strength. Furthermore, there is a risk of oxidation or the like progressing in the metal film in contact with the fluororesin, resulting in a problem of reduced durability, particularly in high-temperature and high-humidity environments. Furthermore, in Patent Document 2, there is a problem that the interface between the fluororesin and the metal foil becomes rough, resulting in an increase in transmission loss.

[0006] The present invention has been made in view of the above-mentioned circumstances, and aims to provide a copper-clad laminate that has low transmission loss in the high frequency range, is particularly excellent in adhesion between a substrate containing a fluororesin and a copper layer, and does not significantly decrease in adhesion even when used in a high-temperature environment or a high-humidity environment, and is particularly suitable for wiring boards for high-frequency signal transmission, and a sputtering target for forming the copper-clad laminate that is used in producing the copper-clad laminate.

[0007] In order to solve the above problems, a copper-clad laminate according to aspect 1 of the present invention is a copper-clad laminate in which a substrate containing a fluororesin and a metallic copper layer are laminated together, and an alloy layer having a composition containing Co in a range of 25.0 at% to 75.0 at% and the balance being Mo and unavoidable impurities is formed between the substrate and the metallic copper layer, and the metallic copper layer has a copper plating layer.

[0008] According to the copper-clad laminate of the first aspect of the present invention, an alloy layer is formed between the substrate containing a fluororesin and the metallic copper layer. The alloy layer contains Co in a range of 25.0 at% to 75.0 at% and the remainder is Mo and unavoidable impurities. This allows the Mo in the alloy layer to form a strong bond with the C in the main chain of the fluororesin contained in the substrate, improving adhesion strength. Furthermore, since the alloy layer contains Co in addition to Mo in the above-mentioned range, it has a dense nanocrystalline structure, which is highly resistant to oxidation caused by heat and moisture. This prevents a decrease in adhesion strength even when used in high-temperature and high-humidity environments. Furthermore, the alloy layer has high barrier properties, which prevents reaction between the metallic copper layer (copper plating layer) and the fluororesin of the substrate. Furthermore, since the metallic copper layer (copper plating layer) is formed on this alloy layer, the roughness of the interface is reduced, thereby reducing transmission loss.

[0009] The copper-clad laminate of Aspect 2 of the present invention is characterized in that, in the copper-clad laminate of Aspect 1, the thickness of the alloy layer is in the range of 5 nm to 50 nm. According to the copper-clad laminate of Aspect 2 of the present invention, since the thickness of the alloy layer is 5 nm or more, the oxidation resistance (resistance to oxidation due to heat or moisture) and barrier properties of the alloy layer can be sufficiently ensured, and even when used in high-temperature and high-humidity environments, a decrease in adhesion strength can be reliably suppressed. Meanwhile, since the thickness of the alloy layer is 50 nm or less, warping of the substrate due to membrane stress can be suppressed.

[0010] The copper-clad laminate of Aspect 3 of the present invention is characterized in that, in the copper-clad laminate of Aspect 1 or Aspect 2, the thickness of the metallic copper layer is in the range of 1 μm or more and 20 μm or less. According to the copper-clad laminate of Aspect 3 of the present invention, since the thickness of the metallic copper layer is 1 μm or more, the influence of radiation loss can be suppressed and transmission loss can be reliably kept low. Meanwhile, since the thickness of the metallic copper layer is 20 μm or less, pattern formation by etching can be performed efficiently and accurately.

[0011] A copper clad laminate of Aspect 4 of the present invention is characterized in that the electrical conductivity of the metallic copper layer is 80% IACS or more in the copper clad laminate of any one of Aspects 1 to 3. According to the copper clad laminate of Aspect 4 of the present invention, the electrical conductivity of the metallic copper layer is 80% IACS or more, and therefore the copper clad laminate has particularly excellent transmission characteristics.

[0012] A sputtering target for forming a copper-clad laminate according to aspect 5 of the present invention is a sputtering target for forming a copper-clad laminate used in forming the alloy layer of the copper-clad laminate according to any one of aspects 1 to 4 of the present invention, characterized in that it is made of an alloy having a composition containing Co in a range of 25.0 at% to 75.0 at% and the balance being Mo and unavoidable impurities.

[0013] According to the sputtering target of aspect 5 of the present invention, the target is composed of an alloy containing Co in a range of 25.0 at% or more and 75.0 at% or less, with the remainder being Mo and unavoidable impurities. Therefore, an alloy layer with a dense nanocrystalline structure can be formed by sputtering on a substrate containing a fluororesin, and the oxidation resistance and barrier properties of the alloy layer can be sufficiently ensured. This makes it possible to produce a copper-clad laminate that has particularly excellent adhesion between the substrate and the copper plating layer and does not suffer a significant decrease in adhesion even when used in high-temperature and high-humidity environments.

[0014] According to the present invention, it is possible to provide a copper-clad laminate that has low transmission loss in the high frequency range, is particularly excellent in adhesion between a substrate containing a fluororesin and a copper layer, and does not significantly decrease in adhesion even when used in a high-temperature environment or a high-humidity environment, and is particularly suitable for wiring boards for high-frequency signal transmission, as well as a sputtering target for forming the copper-clad laminate that is used in producing the copper-clad laminate.

[0015] 1 is a schematic explanatory diagram of a copper-clad laminate according to an embodiment of the present invention; FIG. 2 is a flow chart showing an example of a method for producing a copper-clad laminate according to an embodiment of the present invention; FIG. 3 is a schematic diagram of a peel test in an example; FIG. 4 is an upward arrow showing the peel direction (measurement of the load applied during peeling); the peel angle is 90°, and the peel speed in the direction shown by the arrow extending downward to the left is 50 mm / min; FIG. 5 is a cross-sectional SEM observation photograph of the interface of a copper-clad laminate according to Example 1 of the present invention; and FIG. 6 is a cross-sectional SEM observation photograph of the interface of a copper-clad laminate according to Comparative Example 3.

[0016] A copper clad laminate according to one embodiment of the present invention will be described below. The copper clad laminate according to one embodiment of the present invention is used as a wiring board for transmitting high frequency signals.

[0017] As shown in FIG. 1 , the copper-clad laminate 10 of this embodiment comprises a substrate 11 containing a fluororesin and a copper plating layer 12 laminated on the substrate 11, with an alloy layer 13 formed between the substrate 11 and the metallic copper layer 12.

[0018] The substrate 11 contains, as a fluororesin, for example, PFA (perfluoroalkoxyalkane), PTFE (polytetrafluoroethylene), ETFE (ethylene-tetrafluoroethylene copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), PCTFE (polychlorotrifluoroethylene), etc. Fluororesins have a low dielectric constant and low dielectric loss, making them particularly suitable as substrates for constituting wiring boards for high-frequency signal transmission. There are no particular restrictions on the thickness t1 of the substrate 11, but it is preferably within the range of 5 μm to 200 μm.

[0019] The metallic copper layer 12 is made of copper or a copper alloy, which has excellent electrical and thermal conductivity, and functions as a conductive layer or a heat transfer layer. The metallic copper layer 12 preferably has a conductivity of 80% IACS or higher, and more preferably 85% IACS or higher. In this embodiment, as described below, the metallic copper layer 12 is formed by a seed layer formed on the alloy layer 13 and a copper plating layer formed on this seed layer. This reduces the roughness of the interface between the substrate 11 and the metal layer (alloy layer 13 + metallic copper layer 12); specifically, the maximum interface height is 0.2 μm or less.

[0020] Furthermore, the thickness t2 of the metallic copper layer 12 is preferably in the range of 1 μm or more and 20 μm or less. If the thickness t2 of the metallic copper layer 12 is 1 μm or more, the effect of radiation loss can be ignored without being equivalent to the skin effect. On the other hand, if the thickness t2 of the metallic copper layer 12 is 20 μm or less, etching can be performed efficiently and accurately when forming a circuit pattern on the metallic copper layer 12 by etching. The lower limit of the thickness t2 of the metallic copper layer 12 is more preferably 3 μm or more, and even more preferably 5 μm or more. The upper limit of the thickness t2 of the metallic copper layer 12 is more preferably 18 μm or less, and even more preferably 15 μm or less.

[0021] An alloy layer 13 is formed between the substrate 11 and the metallic copper layer 12. The alloy layer 13 contains Co in a range of 25.0 at% to 75.0 at% and the remainder is Mo and unavoidable impurities. The Mo contained in this alloy layer 13 has a high bond energy with C. As a result, the C in the main chain of the fluororesin and the Mo in the alloy layer form a strong bond, increasing the adhesion strength between the substrate 11 and the alloy layer 13. Furthermore, because the Co and Mo have the above-mentioned composition, when this alloy layer 13 is formed by sputtering, it has an amorphous-like dense nanocrystalline structure, which is particularly excellent in oxidation resistance and barrier properties. Therefore, even when used in high-temperature and high-humidity environments, a decrease in adhesion can be suppressed. Here, the lower limit of the Co content in the alloy layer 13 is preferably 50 at% or more, and more preferably 60 at% or more. On the other hand, the upper limit of the Co content in the alloy layer 13 is preferably 73 at % or less, and more preferably 70 at % or less.

[0022] Furthermore, the thickness t3 of the alloy layer 13 is preferably in the range of 5 nm or more and 50 nm or less. If the thickness t3 of the alloy layer 13 is 5 nm or more, sufficient oxidation resistance and barrier properties can be ensured, and even when used in high-temperature and high-humidity environments, a decrease in adhesion can be reliably suppressed. On the other hand, if the thickness t3 of the alloy layer 13 is 50 nm or less, warping of the substrate 11 due to film stress can be suppressed. The lower limit of the thickness t3 of the alloy layer 13 is more preferably 8 nm or more, and even more preferably 10 nm or more. The upper limit of the thickness t3 of the alloy layer 13 is more preferably 30 nm or less, and even more preferably 20 nm or less.

[0023] Next, a method for manufacturing the copper clad laminate 10 according to this embodiment will be described with reference to the flow chart of FIG.

[0024] (Substrate Preparation Step S01) First, a substrate 11 containing a fluororesin is prepared. Note that, for the purpose of introducing functional groups into the surface of the substrate 11, a surface treatment such as a plasma treatment may be performed.

[0025] (Alloy layer forming step S02) Next, alloy layer 13 is formed to a predetermined thickness on the surface of substrate 11 by sputtering using the sputtering target for forming a copper-clad laminate of this embodiment. Here, the sputtering target of this embodiment is configured from an alloy having a composition containing Co in the range of 25 at% to 75.0 at% and the remainder being Mo and unavoidable impurities. Alloy layer 13 formed by this alloy layer forming step S02 has an amorphous-like dense nanocrystalline structure.

[0026] (Seed layer formation step S03) Next, a copper layer is formed by sputtering on the alloy layer 13 as a seed layer for plating. The thickness of the seed layer (sputtered copper layer) is preferably in the range of 10 nm to 1000 nm. The seed layer is preferably formed continuously after the formation of the above-mentioned alloy layer 13 without being exposed to the atmosphere.

[0027] (Copper plating layer forming step S04) Next, after forming a seed layer, a copper plating layer of a predetermined thickness is formed by electrolytic plating. The seed layer formed on the alloy layer 13 and the copper plating layer formed on this seed layer form a metal copper layer 12.

[0028] The copper-clad laminate 10 of this embodiment is manufactured through the above-mentioned steps. When forming copper plating layers 12 on both sides of the substrate 11, the alloy layer forming step S02 and the seed layer forming step S03 may be performed on one side of the substrate 11, and then the alloy layer forming step S02 and the seed layer forming step S03 may be performed on the opposite side, followed by the copper plating layer forming step S04.

[0029] According to the copper-clad laminate 10 of this embodiment configured as described above, an alloy layer 13 having a composition containing 25.0 at% to 75.0 at% Co, with the remainder being Mo and unavoidable impurities, is formed on a substrate 11 containing a fluororesin. This allows the Mo in the alloy layer 13 to form a strong bond with the C in the main chain of the fluororesin contained in the substrate 11, thereby improving the adhesion strength between the alloy layer 13 and the substrate 11. Furthermore, since the alloy layer 13 contains Mo and Co in the above-mentioned range, the alloy layer 13 has a dense nanocrystalline structure when formed by sputtering, providing high resistance to oxidation caused by heat and moisture. This prevents a decrease in adhesion strength even when used in high-temperature and high-humidity environments. Furthermore, the alloy layer 13 has high barrier properties, which prevents reaction between the metallic copper layer 12 and the fluororesin of the substrate 11. Furthermore, forming the metallic copper layer 12 on the alloy layer 13 by plating reduces the interface roughness of the metallic copper layer 12, thereby reducing transmission loss.

[0030] In the copper-clad laminate 10 of this embodiment, when the thickness t3 of the alloy layer 13 is within the range of 5 nm or more and 50 nm or less, the oxidation resistance and barrier properties of the alloy layer 13 can be sufficiently ensured, and even when used in a high-temperature environment and a high-humidity environment, a decrease in adhesion strength can be reliably suppressed, and warping of the substrate 11 due to film stress can be suppressed.

[0031] In the copper-clad laminate 10 of this embodiment, when the thickness t2 of the metal copper layer 12 is in the range of 1 μm to 20 μm, the influence of radiation loss can be suppressed, transmission loss can be reliably kept low, and pattern formation by etching can be performed efficiently and accurately. Furthermore, in the copper-clad laminate 10 of this embodiment, when the conductivity of the metal copper layer 12 is 80% IACS or more, the transmission characteristics are particularly excellent.

[0032] According to the sputtering target for forming a copper-clad laminate of this embodiment, the target is composed of an alloy containing Co in a range of 25.0 at% or more and 75.0 at% or less, with the remainder being Mo and unavoidable impurities.Therefore, an alloy layer 13 with a dense nanocrystalline structure can be formed by sputtering on a substrate 11 containing a fluororesin, and the oxidation resistance and barrier properties of the alloy layer 13 can be sufficiently ensured.A copper-clad laminate 10 can be produced which has particularly excellent adhesion between the substrate 11 and the copper plating layer 12 and which does not lose adhesion significantly even when used in high-temperature and high-humidity environments.

[0033] Although the embodiment of the present invention has been described above, the present invention is not limited to this and can be modified as appropriate within the scope of the technical idea of ​​the invention.

[0034] The results of confirmation experiments conducted to confirm the effectiveness of the present invention will be described below.

[0035] A PFA film (50 μm thick) manufactured by AGC was prepared as a substrate containing fluororesin. An alloy layer having the composition shown in Table 1 was formed on the surface of this substrate by sputtering. The film formation conditions are shown below. The at% of Mo / Co (Mo / Al in the case of Comparative Example 4) in the sputtering target for forming a copper-clad laminate was the same as the composition ratio in the formed alloy layer. Here, the sputtering target for forming a copper-clad laminate was manufactured as follows. Raw material powders containing the constituent elements were prepared, weighed and mixed to obtain a predetermined composition, and the resulting mixed raw material powder was hot-pressed to obtain a sintered body. This sintered body was cut and machined to obtain a disk target of a predetermined size.

[0036] Target material: Mo—Co alloy (Mo—Al alloy in the case of Comparative Example 4) Degree of vacuum at the start of film formation: 1.0×10 －４ Sputtering gas: high-purity argon Sputtering gas pressure in chamber: 0.2 Pa DC power density: 7.5 W / cm ２

[0037] Next, a copper layer of 100 nm was formed as a seed layer for plating by sputtering. The sputtering conditions were as follows. The seed layer was formed continuously after the alloy layer was formed without being exposed to the atmosphere. (Seed layer formation conditions) Target material: Cu (purity 99.99 mass% or more) Degree of vacuum at the start of film formation: 1.0 × 10 －４ Sputtering gas: high-purity argon Sputtering gas pressure in chamber: 0.2 Pa DC power density: 7.5 W / cm ２

[0038] <Inventive Examples 1 to 7, Comparative Examples 1, 2, and 4> Next, electrolytic plating was performed on the seed layer under the following conditions to form a copper plating layer with the thickness shown in Table 1. This resulted in the formation of copper-clad laminates of Inventive Examples 1 to 7 and Comparative Examples 1, 2, and 4. (Electrolytic plating conditions) Pretreatment: Sulfuric acid washing Solution temperature: 25°C Anode: Phosphorous copper Stirring conditions: Air 12.5 L / min Plating conditions: 4 A, 45 min Plating solution: CuSO ４ ・5H ２ O 200g / L H ２ SO ４ 54g / L 1 mol HCl 1.37mL / L Top Lucina α-M 4.5mL / L Top Lucina α-2 1.0mL / L Top Lucina α-3 3.0mL / L

[0039] Comparative Example 3 After forming the alloy layer as described above, an 18 μm thick electrolytic copper foil (V9 series manufactured by Fukuda Metal Foil & Powder Co., Ltd.) was laminated on the alloy layer and thermocompression bonded to form a copper-clad laminate of Comparative Example 3. The electrolytic copper foil had been roughened, and the roughened surface was laminated and thermocompression bonded facing the alloy layer. The thermocompression bonding conditions were a nitrogen atmosphere, a pressure of 0.1 MPa, a temperature of 350°C, and a holding time of 20 minutes.

[0040] The copper-clad laminates manufactured as described above were evaluated for the thickness of the alloy layer, the thickness of the metallic copper layer, the conductivity of the metallic copper layer, adhesion strength, heat resistance test, constant temperature and humidity test, transmission loss, and maximum interfacial height of the metallic copper layer as follows. The evaluation results are shown in Table 2.

[0041] (Thickness of alloy layer) The thickness of the alloy layer is a target value based on the film formation rate. The film formation rate was calculated by measuring the film thickness after film formation on a dummy substrate for a certain period of time using a step measurement meter (Dektak-XT by Bruker) and dividing the film thickness by the film formation time. The thickness of the alloy layer was confirmed by observing the cross section of the copper-clad laminate with a TEM (transmission electron microscope), and the result was a value equivalent to the target value based on the film formation rate.

[0042] (Thickness of Metallic Copper Layer) The thickness of the metallic copper layer was confirmed by an eddy current method.

[0043] (Conductivity of metal copper layer) Conductivity of metal copper layer σ Ａ The resistivity (S / m) was measured by a four-probe method using a low resistivity meter (Loresta GP manufactured by Mitsubishi Chemical Corporation), and was converted to % IACS using the following formula: σ (% IACS) = σ Ａ / (5.8 x 10 ７ )

[0044] (Adhesion Strength) As shown in FIG. 3, the alloy layer and the metallic copper layer formed on the substrate were cut into 5 mm widths and evaluated using a Tensilon universal testing machine (RTF-1310) manufactured by A&D Corporation under the conditions of a peel angle of 90 degrees and a peel speed of 50 mm / min.

[0045] (Heat Resistance Test) As a heat resistance test, the copper-clad laminate was stored in a clean oven under the conditions of 150°C x 240 hours. After storage, the adhesion strength of the copper-clad laminate was measured as described above. The rate of change in adhesion strength before and after the heat resistance test was then calculated. The rate of change in adhesion strength before and after the heat resistance test is preferably in the range of -30% or more and less than 0%. (Change rate) = (Adhesion strength after test - Adhesion strength before test) / Adhesion strength before test x 100 (%)

[0046] (Constant Temperature and Humidity Test) As a humidity resistance test, a sample piece was stored in a constant temperature and humidity chamber under conditions of a temperature of 85°C and a relative humidity of 85% for 240 hours, and after storage, the adhesion strength was measured in the same manner as above, and the rate of change before and after the test was calculated. Note that the rate of change in adhesion strength before and after the constant temperature and humidity test is preferably in the range of -50% or more and less than 0%.

[0047] (Transmission Loss) Using the prepared copper-clad laminate, a microstrip line was prepared by a wet etching process (the circuit width was adjusted so that the characteristic impedance was 50Ω), and the S (S21) parameter of the prepared circuit board at a frequency of 50 GHz was measured using a network analyzer.

[0048] (Maximum Interface Height) The cross section of the prepared copper-clad laminate was observed using a scanning electron microscope (JSM-7001FA manufactured by JEOL Ltd.). The observation magnification was 1000 times. An example of the observation results is shown in Figures 4A and 4B. The maximum height (height difference between the highest and lowest points of the interface outline) of the interface between the substrate and the copper plating layer was calculated (note that the lower limit in terms of magnification was approximately 0.2 µm).

[0049]

[0050]

[0051] In Comparative Examples 1 and 2, the Co content in the alloy layer formed between the substrate and the metallic copper layer was outside the range of the present invention, and adhesion significantly decreased after the heat resistance test and the constant temperature and humidity test. This is presumably because the alloy layer did not have a dense nanocrystalline structure. In Comparative Example 3, electrolytic copper foil was thermocompression bonded, but the maximum interface height between the substrate and the metallic copper layer was 4.2 μm, resulting in large transmission loss. In Comparative Example 4, the alloy layer formed between the substrate and the metallic copper layer contained Al (50.0 at%) instead of Co, and adhesion significantly decreased after the heat resistance test and the constant temperature and humidity test. This is presumably because the alloy layer did not have a dense nanocrystalline structure.

[0052] In contrast, in Examples 1 to 7 of the present invention, an alloy layer containing 25 at% to 75.0 at% Co and the remainder being Mo and unavoidable impurities was formed between the substrate and the metallic copper layer, and it was confirmed that the initial adhesion was excellent, and the adhesion strength did not decrease significantly even after heat resistance tests and constant temperature and humidity tests, so that the heat resistance was excellent and the material could be used stably even in high temperature and high humidity environments.In addition, the maximum interface height between the substrate and the metallic copper layer was 0.2 μm or less, and transmission loss was small.

[0053] From the above, it was confirmed that the present invention can provide a copper-clad laminate that has low transmission loss in the high frequency range, is particularly excellent in adhesion between the substrate containing a fluororesin and the copper layer, and does not significantly reduce adhesion even when used in high-temperature and high-humidity environments, and is particularly suitable for wiring boards for high-frequency signal transmission, as well as a sputtering target for forming the copper-clad laminate that is used in producing the copper-clad laminate.

[0054] The present invention provides a copper-clad laminate that has low transmission loss in the high frequency range, is particularly excellent in adhesion between a substrate containing a fluororesin and a copper layer, and does not significantly reduce adhesion even when used in high-temperature and high-humidity environments, making it particularly suitable for wiring boards for high-frequency signal transmission. It also provides a sputtering target for forming the copper-clad laminate that is used in producing the copper-clad laminate.

[0055] 10 Copper-clad laminate 11 Base material 12 Metal copper layer 13 Alloy layer t1 Thickness of base material 11 t2 Thickness of metal copper layer 12 t3 Thickness of alloy layer 13

Claims

1. A copper-clad laminate comprising a substrate containing a fluororesin and a metallic copper layer, wherein an alloy layer is formed between the substrate and the metallic copper layer, the alloy layer having a composition containing 25.0 at% or more and 75.0 at% or less of Co, with the balance being Mo and unavoidable impurities, and the metallic copper layer has a copper plating layer.

2. The copper clad laminate according to claim 1, wherein the thickness of the alloy layer is within the range of 5 nm to 50 nm.

3. The copper-clad laminate according to claim 1, wherein the thickness of the metallic copper layer is within the range of 1 μm or more and 20 μm or less.

4. The copper clad laminate according to claim 1, characterized in that the electrical conductivity of the metallic copper layer is 80% IACS or more.

5. A sputtering target for forming a copper-clad laminate used in forming the alloy layer of the copper-clad laminate described in any one of claims 1 to 4, characterized in that the sputtering target for forming a copper-clad laminate is made of an alloy having a composition containing Co in the range of 25.0 at% or more and 75.0 at% or less, with the balance being Mo and unavoidable impurities.

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