Metal laminate, method for manufacturing same, and printed wiring board

Abstract

The purpose of the present invention is to provide a metal laminate that exhibits both high cycle characteristics and high adhesiveness at a lamination interface.　The present invention relates to: a metal laminate in which a metal layer formed from at least one metal-foil-including layer is laminated on at least one surface of a low-dielectric film, a plurality of protrusions of the metal foil being formed on the low-dielectric-film-side surface of the metal foil, and the sum of the average value of b / a and 3σ (in this expression, σ is the standard deviation of b / a) being 2.5 or less, where a is the width of the protrusions and b is the height of the protrusions, and the peel strength of the metal layer with respect to the low-dielectric film is 3N / cm or greater; a method for manufacturing the metal laminate; and a printed wiring board.

Description

Metal laminate material, its manufacturing method, and printed wiring board

[0001] The present invention relates to a metal laminate material, a method for manufacturing the same, and a printed wiring board.

[0002] Conventionally, metal laminate materials in which a metal foil such as copper foil is laminated onto a low dielectric film have been known as substrates for producing printed wiring boards. In recent years, fifth-generation mobile communication system (5G) services have been launched in various countries, and metal laminate materials with excellent 5G frequency band, i.e., high-frequency characteristics, are required.

[0003] Metal laminates are generally known to be produced using a thermal lamination method in which a metal foil with a roughened surface is heated and pressed to a low dielectric film from the viewpoint of adhesion to the low dielectric film. Generally, the thermal lamination method uses a metal foil with a roughened surface, and the low dielectric film is softened by heating it to near its melting point, so that the roughening particles on the metal foil surface are deeply embedded in the low dielectric film, thereby ensuring adhesion by a so-called anchor effect.

[0004] Patent Document 1 discloses a surface-treated copper foil whose surface has been subjected to a roughening treatment, a copper-clad laminate in which the copper foil is laminated on an insulating substrate, and a printed wiring board using the copper-clad laminate, and it also discloses that the copper-clad laminate can be produced by a thermal lamination method.

[0005] It is known that when used in high frequency bands, the smoother the surface of the metal foil in the metal laminate material, the better the transmission characteristics. In conventional metal laminate materials produced by thermal lamination, the metal foil surface is roughened to ensure adhesion through the anchor effect, but the roughened laminate interface deteriorates the transmission characteristics in the high frequency band due to the skin effect, making it insufficient for use in the high frequency band.

[0006] JP 2018-90906 A

[0007] As described above, in conventional metal laminate materials produced by thermal lamination, roughening the metal foil surface ensures adhesion at the lamination interface, but the high-frequency characteristics may be insufficient. Therefore, an object of the present invention is to provide a metal laminate material that achieves both high-frequency characteristics and adhesion at the lamination interface.

[0008] The present inventors conducted extensive research to solve the above-mentioned problems, and discovered that by preparing a metal laminate material using a surface activated bonding method, it is possible to laminate a metal foil to a low dielectric film while maintaining the smoothness of its surface, thereby achieving both high-frequency characteristics and adhesion at the lamination interface, and thus completed the present invention. Specifically, the gist of the present invention is as follows: (1) A metal laminate material in which a metal layer consisting of at least one layer including a metal foil is laminated on at least one surface of a low dielectric film, the metal foil having a plurality of convex portions formed on the surface of the metal foil facing the low dielectric film, the width of the convex portions being a and the height of the convex portions being b, where the average value of b / a + 3σ (where σ is the standard deviation of b / a) is 2.5 or less, and the peel strength between the low dielectric film and the metal layer is 3 N / cm or more. (2) The metal laminate material according to (1), in which the metal layer does not have a sputtered layer made of copper, nickel, chromium, or an alloy thereof between the low dielectric film and the metal foil. (3) The metal laminate material according to (1) or (2), wherein the metal foil is a rolled copper foil, a copper foil with a carrier, or an electrolytic copper foil. (4) A method for producing a metal laminate material in which a metal layer consisting of at least one layer including a metal foil is laminated on at least one surface of a low dielectric film, wherein a plurality of convex portions of the metal foil are formed on the surface of the metal foil facing the low dielectric film, and when the width of the convex portions is a and the height of the convex portions is b, the average value of b / a + 3σ (where σ is the standard deviation of b / a) is 2.5 or less, and the peel strength of the low dielectric film and the metal layer is 3 N / cm or more, the method comprising the steps of: preparing a low dielectric film and a metal foil; activating at least one surface of the low dielectric film by sputter etching; activating the surface of the metal foil by sputter etching; and roll-bonding the activated surfaces of the low dielectric film and the metal foil together at a reduction ratio of 0 to 30%.(5) A method for producing a metal laminate material in which a metal layer consisting of at least one layer containing a metal foil is laminated on at least one surface of a low dielectric film, wherein the metal layer has an intermediate layer containing a metal between the low dielectric film and the metal foil, and a plurality of convex portions of the metal foil are formed on the surface of the metal foil facing the low dielectric film, and when the width of the convex portion is a and the height of the convex portion is b, the average value of b / a + 3σ (where σ is the standard deviation of b / a) is 2.5 or less, and the peel strength of the low dielectric film and the metal layer is 3 N / cm or more, the method includes the steps of: preparing a low dielectric film and a metal foil; activating at least one surface of the low dielectric film by sputter etching; forming an intermediate layer containing a metal on the activated surface of the low dielectric film; activating the surface of the intermediate layer by sputter etching; and activating the surface of the metal foil by sputter etching. and a step of roll-bonding the activated surfaces of the intermediate layer and the metal foil together at a rolling reduction of 0 to 30%. (6) The method for producing a metal laminate material according to (4) above, wherein the metal layer does not have a sputtered layer made of copper, nickel, chromium, or an alloy thereof between the low dielectric film and the metal foil. (7) The method for producing a metal laminate material according to any of (4) to (6) above, wherein the metal foil is a rolled copper foil, a copper foil with a carrier, or an electrolytic copper foil. (8) The method for producing a metal laminate material according to any of (4) to (6) above, wherein at least one surface of the low dielectric film is activated by sputter etching with oxygen. (9) The method for producing a metal laminate material according to any of (4) to (6) above, wherein the temperature in the roll-bonding step is 15°C or higher and 100°C or lower. (10) A method for producing a metal laminate material according to any one of (4) to (6), wherein after roll bonding, heat treatment is performed at a temperature of not less than the melting point of the low dielectric film -150°C and not more than the melting point +10°C. (11) A printed wiring board having a circuit formed on the metal laminate material according to any one of (1) to (3). This specification includes the disclosure of Japanese Patent Application No. 2021-174667, which is the basis for the priority of the present application.

[0009] According to the present invention, it is possible to provide a metal laminate material that achieves both high frequency characteristics and adhesion at the laminate interface.

[0010] FIG. 5A is a schematic cross-sectional view showing a metal laminate material of one aspect of the first embodiment of the present invention. FIG. 5B is a schematic cross-sectional view showing a metal laminate material of one aspect of the second embodiment of the present invention. FIG. 5B is a schematic cross-sectional view showing a metal laminate material of another aspect of the second embodiment of the present invention. FIG. 5A shows an enlarged schematic view of a cross-section of a metal laminate material 1A. FIG. 5B shows an enlarged schematic view of a cross-section of a convex portion of a metal foil. FIG. 5B shows a cross-sectional photograph of a metal laminate material of Example 1. FIG. 5B shows a cross-sectional photograph of a metal laminate material of Example 2. FIG. 5B shows a cross-sectional photograph of a metal laminate material of Example 3. FIG. 5C shows a cross-sectional photograph of a metal laminate material of Example 4. FIG. 5D shows a cross-sectional photograph of a metal laminate material of Example 6. FIG. 5E shows a cross-sectional photograph of a metal laminate material of Example 7. FIG. 5F shows a cross-sectional photograph of a metal laminate material of Example 8. FIG. 5G shows a cross-sectional photograph of a metal laminate material of Example 14. FIG. 5G shows a cross-sectional photograph of a metal laminate material of Comparative Example 1. FIG. 5H shows a cross-sectional photograph of a metal laminate material of Comparative Example 2.

[0011] The present invention is described in detail below. The present invention relates to a metal laminate material in which a metal layer consisting of at least one layer including a metal foil is laminated on at least one surface of a low dielectric film. The metal laminate material of the present invention includes one in which a metal layer is laminated on one surface of a low dielectric film, and one in which a metal layer is laminated on both surfaces of a low dielectric film. In the metal laminate material of the present invention, since the surface of the metal foil on the side of the low dielectric film is smooth, the metal laminate material has excellent high-frequency characteristics and sufficient adhesion between the low dielectric film and the metal layer.

[0012] A. Metal Laminate Material First, a metal laminate material according to a first embodiment of the present invention will be described below.

[0013] 1 is a schematic cross-sectional view showing a metal laminate material according to one aspect of the first embodiment of the present invention. As shown in FIG. 1, the metal laminate material 1A of the first embodiment has a metal layer 10 made of metal foil laminated on one surface of a low dielectric film 20.

[0014] Figure 2 is a schematic cross-sectional view showing another aspect of the metal laminate material of the first embodiment of the present invention. In this aspect, a carrier-attached metal foil having an ultrathin metal layer, a release layer, and a carrier layer is used as the metal foil. As shown in Figure 2, the metal laminate material 1B of the present invention has a metal layer 10 made of a carrier-attached metal foil laminated on one surface of a low dielectric film 20. The metal layer 10 is laminated in the order of ultrathin metal layer 14, release layer 13, and carrier layer 12 from the low dielectric film 20 side.

[0015] Hereinafter, each component of the metal laminate material according to the first embodiment of the present invention will be described in detail.

[0016] 1. Low-dielectric film The low-dielectric film can be made of any low-dielectric polymer material that can be used as a flexible substrate. For example, a low-dielectric film having a relative dielectric constant ε ｒ The dielectric constant of the low-dielectric film is preferably a material having a dielectric constant of 3.3 or less and a dielectric loss tangent tanδ of 0.006 or less, but is not limited thereto. Specifically, the material may be appropriately selected from materials such as liquid crystal polymers, polyethylene fluoride (fluorine-based resins such as polytetrafluoroethylene), polyamides, isocyanate compounds, polyamideimides, polyimides, low-dielectric-constant polyimides, polyethylene terephthalate, polyetherimides, and cycloolefin polymers. Liquid crystal polymers, polyethylene fluoride, polyamides, or low-dielectric-constant polyimides are preferred, and liquid crystal polymers are more preferred. The low-dielectric film may be a single-layer film or a laminate consisting of multiple layers. In the case of a multiple-layer film, at least one of the multiple layers may be made of the low-dielectric polymer material. Layers other than the layer made of the low-dielectric polymer material may be made of various conventional materials, such as epoxy resins. Liquid crystal polymers refer to aromatic polyester resins having a basic structure such as parahydroxybenzoic acid, which exhibit liquid crystal properties in the molten state.

[0017] The thickness of the low dielectric film can be appropriately set depending on the application of the metal laminate material. For example, when used as a flexible printed wiring board, the thickness is usually 10 μm or more and 150 μm or less, preferably 10 μm or more and 100 μm or less, more preferably 10 μm or more and 75 μm or less, and particularly preferably 10 μm or more and 50 μm or less. The thickness of the low dielectric film refers to the average value obtained by taking an optical microscope photograph of the cross section of the metal laminate material, measuring the thickness of the low dielectric film at any 10 points on the optical microscope photograph, and measuring the obtained values. The thickness of the low dielectric film before bonding can be measured using a micrometer or the like, and refers to the average value of the thickness measured at 10 points randomly selected from the surface of the target low dielectric film. Furthermore, for the low dielectric film used, the deviation from the average value of the measured values ​​at 10 points is preferably within 20%, more preferably within 10% for all measured values.

[0018] 2. Metal Layer The metal layer is not particularly limited as long as it contains a metal foil, and may consist of the metal foil or may further contain another layer in addition to the metal foil. When the metal layer contains another layer, it is preferable that the other layer be present between the low dielectric film and the metal foil.

[0019] The type of metal constituting the metal foil varies depending on the application of the metal laminate and is not particularly limited, but examples include copper, iron, nickel, zinc, tin, chromium, gold, silver, platinum, cobalt, titanium, and alloys thereof. Copper foil or copper alloy foil is particularly preferred as the metal foil. This is because, by roll-bonding these with a low dielectric film, a flexible substrate for forming fine wiring can be obtained.

[0020] The thickness of the metal foil varies depending on the application of the metal laminate material and is not particularly limited, but for example, for flexible printed wiring board applications, it is preferably 3 μm to 100 μm, and more preferably 10 μm to 50 μm. Here, the thickness of the metal foil refers to the average value of the values ​​obtained by taking an optical microscope photograph of the cross section of the metal laminate material and measuring the thickness of the metal foil at any 10 points on the optical microscope photograph.

[0021] The metal foil is preferably a rolled metal foil, a carrier-attached metal foil, or an electrolytic metal foil, more preferably a rolled copper foil, a carrier-attached copper foil, or an electrolytic copper foil. The metal foil may be a single-layer foil or a laminate foil thereof.

[0022] When a rolled copper foil is used as the metal foil, the rolled copper foil is not particularly limited, but examples thereof include HA-V2 manufactured by JX Nippon Mining Corporation and C1020R-H manufactured by Sumitomo Mitsui Metal Mining Copper Brazing Co., Ltd. When an electrolytic copper foil is used as the metal foil, the electrolytic copper foil is not particularly limited, but examples thereof include CF-T9DA-SV, CF-V9S-SV, and CF-PLFA manufactured by Fukuda Metal Foil & Powder Co., Ltd.

[0023] When producing a flexible substrate for forming fine wiring, it is preferable to use a carrier-attached metal foil having an ultrathin metal layer, a release layer, and a carrier layer as the metal foil. When using a carrier-attached metal foil, as shown in Figure 2, the carrier-attached metal foil is laminated in the order of ultrathin metal layer, release layer, and carrier layer from the low dielectric film side. When a carrier-attached metal foil is used, the "metal foil" in the obtained metal laminate material refers to the portion consisting of the ultrathin metal layer, release layer, and carrier layer. Note that the metal foil prepared in the manufacturing method of the metal laminate material may have a roughened particle layer or an anti-rust layer on the surface of the ultrathin metal layer of the carrier-attached metal foil.

[0024] The carrier layer of the carrier-attached metal foil has a sheet shape and functions as a support material or protective layer to prevent wrinkles and folds in the metal laminate and scratches on the ultrathin metal layer. Examples of the carrier layer include foils or plates made of copper, aluminum, nickel, and their alloys (stainless steel, brass, etc.), or resins coated with metal. The carrier layer is preferably copper foil. The thickness of the carrier layer is not particularly limited, but is, for example, 10 μm or more and 100 μm or less.

[0025] The release layer of the carrier-attached metal foil reduces the peel strength of the carrier layer and also functions to suppress interdiffusion that may occur between the carrier layer and the ultrathin metal layer due to heat treatment. The release layer may be either an organic or inorganic release layer, and components used in organic release layers include, for example, nitrogen-containing organic compounds, sulfur-containing organic compounds, and carboxylic acids. Nitrogen-containing organic compounds include triazole compounds and imidazole compounds. Examples of triazole compounds include 1,2,3-benzotriazole, carboxybenzotriazole, N',N'-bis(benzotriazolylmethyl)urea, 1H-1,2,4-triazole, and 3-amino-1H-1,2,4-triazole. Examples of sulfur-containing organic compounds include mercaptobenzothiazole, thiocyanuric acid, and 2-benzimidazolethiol. Examples of carboxylic acids include monocarboxylic acids and dicarboxylic acids. Examples of components used in the inorganic release layer include Ni, Mo, Co, Cr, Fe, Ti, W, P, Zn, chromate-treated films, etc. The thickness of the release layer is usually 1 nm or more and 1 μm or less, and preferably 5 nm or more and 500 nm or less.

[0026] The metal constituting the ultrathin metal layer of the carrier-attached metal foil varies depending on the application of the metal laminate material and is not particularly limited, but examples include copper, iron, nickel, zinc, tin, chromium, gold, silver, platinum, cobalt, titanium, and alloys thereof. The ultrathin metal layer is preferably a layer of copper or a copper alloy. The thickness of the ultrathin metal layer is usually 0.5 μm or more and 10 μm or less, preferably 1 μm or more and 7 μm or less.

[0027] The carrier-attached metal foil is preferably one in which the carrier layer and the ultrathin metal layer are made of copper or a copper alloy, and more preferably a carrier-attached copper foil in which both are made of copper. The carrier-attached copper foil is not particularly limited, but examples thereof include MT18FL, MT18GN, MT18EX, and MT18SD-H manufactured by Mitsui Mining & Smelting Co., Ltd.

[0028] Although not shown in FIGS. 1 and 2 , the metal layer may further include at least one layer (hereinafter sometimes referred to as a “treated layer”) selected from the group consisting of a roughened particle layer, an anticorrosive layer, a heat-resistant layer, and a silane coupling agent treatment layer on the surface of the metal foil facing the low dielectric film. The treatment layer may be a laminate of any one layer, or a laminate of multiple layers. The roughened particle layer may include, for example, any metal selected from the group consisting of Cu, Co, and Ni, or an alloy thereof, but is not limited thereto. Specific examples include a cobalt-nickel alloy plating layer and a copper-cobalt-nickel alloy plating layer. The anticorrosive layer may include, for example, any metal selected from the group consisting of Cr, Ni, and Zn, or an alloy thereof, but is not limited thereto. Specific examples include a chromium oxide coating, a mixture coating of chromium oxide and zinc / zinc oxide, and a Ni plating layer. The heat-resistant layer may contain, for example, any one metal or alloy thereof selected from the group consisting of Co, Ni, and Mo, but is not limited thereto. Furthermore, examples of silane coupling agents include, but are not limited to, olefin-based silanes, epoxy-based silanes, acrylic-based silanes, amino-based silanes, and mercapto-based silanes. The silane coupling agent can be applied by spraying, applying with a coater, immersion, or other suitable methods. The roughening particle layer, the rust-preventive layer, and the heat-resistant layer are different from the intermediate layer described in the metal laminate of the second embodiment below.

[0029] The metal laminate material of the first embodiment preferably does not have an intermediate layer, which will be described below in connection with the metal laminate material of the second embodiment. The absence of an intermediate layer in the metal laminate material improves the productivity of the metal laminate material and reduces manufacturing costs. In a preferred embodiment, the metal laminate material of the present invention does not have a metal-containing intermediate layer between the low dielectric film and the metal foil, and preferably does not have a sputtered layer made of copper, nickel, chromium, or an alloy thereof. In one embodiment of the metal laminate material without an intermediate layer, the low dielectric film and the metal foil (preferably a rolled metal foil) are directly laminated together. In another embodiment of the metal laminate material without an intermediate layer, the roughening particle layer and / or the rust-preventive layer are laminated on the low dielectric film, and a metal foil (preferably a metal foil with a carrier) is laminated thereon. Specifically, in this embodiment of the metal laminate material, a roughened particle layer containing any one metal selected from the group consisting of Cu, Co, and Ni or an alloy thereof, and / or an anti-rust layer which is a coating containing any one metal selected from the group consisting of Cr, Ni, and Zn or an alloy thereof is laminated on a low dielectric film, and a metal foil with a carrier is laminated on top of that.

[0030] Next, a metal laminate material according to a second embodiment of the present invention will be described below. Fig. 3 is a schematic cross-sectional view showing a metal laminate material according to one aspect of the second embodiment of the present invention. As shown in Fig. 3, the metal laminate material 1C of the present invention has a metal layer 10 laminated on one surface of a low dielectric film 20. The metal laminate material 1C has an intermediate layer 15 containing a metal between the low dielectric film 20 and the metal foil 11. Thus, the metal layer 10 has the intermediate layer 15 containing a metal laminated on one surface of the low dielectric film 20, and the metal foil 11 laminated on the surface of the intermediate layer 15 opposite the low dielectric film 20 side.

[0031] Figure 4 is a schematic cross-sectional view showing another aspect of the metal laminate material of the second embodiment of the present invention. In this aspect, a carrier-attached metal foil having an ultrathin metal layer, a release layer, and a carrier layer is used as the metal foil. As shown in Figure 4, the metal laminate material 1D of the present invention has a metal layer 10 laminated on one surface of a low dielectric film 20. The metal laminate material 1D has an intermediate layer 15 containing metal between the low dielectric film 20 and a metal foil 11 having an ultrathin metal layer 14, a release layer 13, and a carrier layer 12. Therefore, the metal layer 10 is laminated in the following order from the low dielectric film 20 side: intermediate layer 15, ultrathin metal layer 14, release layer 13, and carrier layer 12.

[0032] In the metal laminate material of the second embodiment, the provision of an intermediate layer protects the surface of the metal foil or low dielectric film and improves adhesion between the metal foil and the low dielectric film. The intermediate layer is not particularly limited as long as it is a layer containing metal, and may be a single metal-containing layer or a laminate of two or more metal-containing layers. Examples of the intermediate layer include a layer formed by sputtering, vapor deposition, or electroless plating on the low dielectric film, but preferably a layer formed by sputtering (sputtered layer). The presence or absence of an intermediate layer can be determined by analyzing the interface between the metal foil and the low dielectric film of the metal laminate material using a scanning electron microscope or a transmission electron microscope (magnification of 20,000 times or more).

[0033] The intermediate layer is not particularly limited as long as it contains a metal, but is preferably one containing any one metal selected from the group consisting of copper, iron, nickel, zinc, chromium, cobalt, titanium, tin, platinum, silver, gold, aluminum, palladium, and zirconium or an alloy thereof, more preferably one containing copper, nickel, chromium, or an alloy thereof, and particularly preferably one containing copper, an alloy of copper and nickel, nickel, or an alloy of nickel and chromium. The intermediate layer may also be one in which a plurality of layers containing a metal are laminated.

[0034] The intermediate layer is preferably a sputtered layer made of copper, nickel, chromium or an alloy thereof, formed by sputtering between the low dielectric film and the metal foil.

[0035] The thickness of the intermediate layer is not particularly limited as long as it can exhibit the function of improving adhesion, but is preferably, for example, 5 nm or more and 200 nm or less, and more preferably 10 nm or more and 100 nm or less.

[0036] Other configurations of the metal laminate material of the second embodiment are the same as those of the metal laminate material of the first embodiment.

[0037] The metal laminate of the present invention has a smooth surface on the low-dielectric film side, which corresponds to the lamination interface of the metal foil, and therefore has superior high-frequency characteristics compared to conventional metal laminates produced by thermal lamination. The surface of the metal foil typically has an uneven shape due to roughness, waviness, etc. In the present invention, the smoothness of the metal foil surface was evaluated using the ratio of the width to the height of the convex portions of the metal foil (hereinafter sometimes referred to as the aspect ratio) calculated from cross-sectional observation of the metal laminate. Surface roughness is widely used as an index of surface smoothness. Surface roughness generally measures the degree of vertical deviation when comparing the surface shape of an object with an ideal surface. Here, in conventional metal laminates produced by thermal lamination, the roughening particles on the metal foil surface are deeply embedded within the low-dielectric film, forming intricate concave shapes within the low-dielectric film. Surface roughness measurements cannot accurately capture such intricate concave shapes. In the present invention, the aspect ratio of the convex portions calculated from cross-sectional observation of the metal laminate material is used as an index of smoothness, thereby enabling appropriate comparison with conventional metal laminate materials. Note that the convex portions on the metal foil surface originate from the metal foil used as the material, and are not formed by adding other elements to the metal foil.

[0038] As described above, in the present invention, the ratio of the width to the height of the convex portion calculated from cross-sectional observation is used as an index of surface smoothness. Specifically, in the metal laminate material of the present invention, when the width of the convex portion of the metal foil is a and the height of the convex portion is b, the average value of b / a + 3σ (where σ is the standard deviation of b / a) is 2.5 or less, preferably 2.0 or less, more preferably 1.5 or less, and particularly preferably 1.0 or less. The smaller the value of the average value of b / a + 3σ, the smoother the surface. By setting this value to 2.5 or less, the surface of the low dielectric film side of the metal foil becomes smooth, and the metal laminate material has excellent high-frequency characteristics. When a rolled copper foil whose surface has not been roughened is used as the metal foil, the average value of b / a + 3σ can be made very small, and this value is usually 0.5 or less, preferably 0.3 or less, and more preferably 0.2 or less. In the present invention, the minimum value of b / a is 0. In the present invention, when the convex portions are so small that the width or height of the convex portions cannot be measured, b / a is considered to be 0, and in this case, the average value of b / a + 3σ is also 0. Therefore, in the metal laminate material of the present invention, the average value of b / a + 3σ is 0 or more and 2.5 or less. Also, in the present invention, b / a is considered to be 0 even when no convex portions are present on the metal foil surface upon cross-sectional observation.

[0039] The aspect ratio b / a of the protrusions of the metal foil is measured on the surface (bonding surface) of the metal foil on the low dielectric film side. For example, even when the metal laminate has an intermediate layer between the low dielectric film and the metal foil, the measurement is performed on the surface of the metal foil on the low dielectric film side.

[0040] The width a and height b of the protrusions of the metal foil can be measured as follows. First, a cross-sectional photograph of the metal laminate is obtained using a scanning electron microscope, and the width a and height b of the protrusions are measured on the surface of the metal foil facing the low dielectric film in this cross-sectional photograph. FIG. 5A shows an enlarged schematic cross-section of the metal laminate 1A shown in FIG. 1. The metal laminate 1A has a metal layer 10 made of metal foil laminated on one surface of a low dielectric film 20. FIG. 5B also shows an enlarged schematic cross-section of the protrusions of the metal foil. As shown in FIG. 5B, the protrusions of the metal foil are made of metal particles that constitute the metal foil. Each metal particle may be a single particle, or may be a stack of metal particles such as secondary particles formed from primary particles and tertiary particles, as shown in FIG. 5B. 5A and 5B, the length of the line connecting the two points where the protrusion starts (the length of the bottom intercept of the primary particle) is defined as the width a of the protrusion, and the length from this line to the apex of the protrusion (the apex of the final particle) is defined as the height b of the protrusion. In the present invention, the average value of b / a is used as an index of surface smoothness, and further, taking into account the variation in the value, the average value of b / a + 3σ (where σ is the standard deviation of b / a) is used. It is preferable to measure any 10 or more protrusions.

[0041] The metal laminate of the present invention has a peel strength between the low dielectric film and the metal layer of 3 N / cm or more, preferably 5 N / cm or more. A peel strength of 3 N / cm or more can improve the reliability of fine wiring in printed wiring boards.

[0042] To measure the peel strength, a test piece is first prepared from the metal laminate and a 1 cm-wide cut is made in the metal layer using a knife or the like. After partially peeling the metal layer from the low-dielectric film, the low-dielectric film is fixed to a support, and the metal layer is pulled at a 90° angle relative to the low-dielectric film at a rate of 50 mm / min. The peel strength is determined by the force required to peel the film (unit: N / cm). Furthermore, if the metal layer is thin and brittle, it may break during peel strength measurement. In this case, the metal layer surface may be electroplated (e.g., copper plating if the metal layer is copper) to increase the thickness of the metal layer to approximately 5 μm to approximately 50 μm, and then the peel strength may be measured. The peel strength value is measured according to the method specified in JIS C6471.

[0043] In this specification, the term "peel strength between a low dielectric film and a metal layer" refers not only to the peel strength when the low dielectric film and the metal layer peel at their interface, but also to the peel strength when the metal layer is internally destroyed and the low dielectric film is internally destroyed. Furthermore, when a roughening particle layer, anti-rust layer, heat-resistant layer, silane coupling agent-treated layer, etc. are laminated on the surface of the metal foil on the low dielectric film side as described above, the term also refers to the peel strength when the metal foil peels at its interface with the treated layer and the peel strength when the treated layer is internally destroyed. Furthermore, when the metal laminate has an intermediate layer as described above, the term also refers to the peel strength when the metal foil peels at its interface with the intermediate layer and the peel strength when the intermediate layer is internally destroyed and the peel strength when the intermediate layer is internally destroyed.

[0044] B. Manufacturing Method of Metal Laminate Material The present invention also relates to a manufacturing method of the above-mentioned metal laminate material. The metal laminate material of the present invention can be manufactured by a surface activated bonding method. By manufacturing using the surface activated bonding method, it is possible to laminate a metal foil to a low dielectric film while maintaining the smoothness of its surface, so that the metal laminate material has excellent high-frequency characteristics. Furthermore, since a strong bond is formed at the bonding interface by the surface activation treatment, it is possible to ensure adhesion at the lamination interface without relying on the physical anchor effect of roughening particles, as is the case with metal laminate materials manufactured by thermal lamination methods.

[0045] The metal laminate material of the first embodiment of the present invention preferably does not have an intermediate layer containing metal. The manufacturing method of the metal laminate material of this first embodiment includes a step of preparing a low dielectric film and a metal foil (step 1), a step of activating at least one surface of the low dielectric film by sputter etching (step 2-1), a step of activating the surface of the metal foil by sputter etching (step 2-2), and a step of roll-bonding the activated surfaces of the low dielectric film and the metal foil together at a rolling reduction of 0 to 30% (step 3-1). Note that steps 1, 2 (steps 2-1 and 2-2), and 3-1 are performed sequentially, but steps 2-1 and 2-2 can be performed simultaneously or sequentially.

[0046] A metal laminate material according to a second embodiment of the present invention has an intermediate layer containing metal between a low dielectric film and a metal foil. The method for producing the metal laminate material of this second embodiment includes, after step 2-1 of the method for producing the metal laminate material of the first embodiment, a step of forming an intermediate layer containing metal on the activated surface of the low dielectric film (step 2-3), and a step of activating the surface of the intermediate layer by sputter etching (step 2-4). Furthermore, instead of step 3-1, the method further includes a step of roll-bonding the activated surfaces of the intermediate layer and the metal foil together at a rolling reduction of 0 to 30% (step 3-2). In this case, steps 2-2 and 2-4 can be performed simultaneously or sequentially.

[0047] That is, the manufacturing method of the metal laminate material of the second embodiment includes a step of preparing a low dielectric film and a metal foil (step 1), a step of activating at least one surface of the low dielectric film by sputter etching (step 2-1), a step of forming an intermediate layer containing a metal on the activated surface of the low dielectric film (step 2-3), a step of activating the surface of the intermediate layer by sputter etching (step 2-4), a step of activating the surface of the metal foil by sputter etching (step 2-2), and a step of roll-bonding the activated surfaces of the intermediate layer and the metal foil together at a reduction ratio of 0 to 30% (step 3-2).

[0048] In the method for producing a metal laminate of the present invention, a step of activating at least one surface of a low dielectric film by sputter etching (step 2-1), a step of activating the surface of a metal foil by sputter etching (step 2-2), a step of forming an intermediate layer containing a metal on the activated surface of the low dielectric film as needed (step 2-3), and a step of activating the surface of the intermediate layer by sputter etching (step 2-4), a step of roll-bonding the activated surfaces of the low dielectric film and the metal foil together at a rolling reduction of 0 to 30% (step 3-1), and a step of roll-bonding the activated surfaces of the intermediate layer and the metal foil together at a rolling reduction of 0 to 30% (step 3-2) can be performed at a temperature of 15 ° C. or higher and 100 ° C. or lower, preferably at a temperature of 15 ° C. or higher and 60 ° C. or lower, and more preferably at room temperature (15 ° C. or higher and 25 ° C. or lower). By performing these steps at room temperature, the low dielectric film can be laminated while maintaining the smoothness of the surface of the metal foil.

[0049] Next, each step of the method for producing the metal laminate material of the present invention will be described in detail.

[0050] 1. Preparation Step In step 1, a low dielectric film and a metal foil are prepared. As the low dielectric film and the metal foil, those described above for the metal laminate material can be used.

[0051] 2. Surface Activation Step and Intermediate Layer Formation Step 2-A. Low Dielectric Film Surface Activation Step In step 2-1, at least one surface of the low dielectric film is activated by sputter etching. The sputter etching process can be performed, for example, by preparing the low dielectric film as a long coil with a width of 100 mm to 600 mm, using the bonding surface of the low dielectric film as one electrode grounded to earth, and applying an alternating current of 1 MHz to 50 MHz between the low dielectric film and another electrode supported by insulation to generate a glow discharge, with the area of ​​the electrode exposed to the plasma generated by the glow discharge set to 1 / 3 or less of the area of ​​the other electrode. During the sputter etching process, the grounded electrode takes the form of a cooling roll to prevent the temperature of the transported material from rising.

[0052] In the sputter etching process in the surface activation step, the surface to be bonded of the low dielectric film is sputtered under vacuum with an active gas or an inert gas to completely remove any adsorbed material on the surface. The active gas can be oxygen or a mixed gas containing oxygen. The inert gas can be argon, neon, xenon, krypton, nitrogen, or a mixed gas containing at least one of these. Oxygen is preferred as the gas used in the sputter etching process of the low dielectric film. When oxygen is used, the peel strength between the low dielectric film and the metal layer is higher than when an inert gas such as argon or nitrogen is used. This improvement in peel strength is particularly significant when the metal laminate does not have an intermediate layer.

[0053] The sputter etching conditions can be set appropriately, for example, under vacuum with a plasma output of 100 W to 10 kW and a line speed of 0.5 m / min to 30 m / min. Even when oxygen gas is used, the sputter etching conditions are, for example, under vacuum with a plasma output of 100 W to 10 kW and a line speed of 0.5 m / min to 30 m / min. The degree of vacuum is preferably high to prevent re-adsorption of substances onto the surface, but it is also preferable to use a vacuum of 1×10 －５ Pa to 10 Pa is sufficient.

[0054] 2-B. Intermediate Layer Formation Step In step 2-3, if necessary, an intermediate layer containing a metal is formed on the surface of the low dielectric film activated in step 2-1. The method for forming the intermediate layer is not particularly limited, but for example, a method of forming a sputtered layer by sputtering an intermediate layer containing a metal on the activated surface of a low dielectric film is preferred. The conditions for sputtering deposition using this method can be appropriately set depending on the type of metal constituting the intermediate layer and the thickness of the intermediate layer. The type of metal constituting the intermediate layer and the thickness of the intermediate layer are as described above for the metal laminate material.

[0055] 2-C. Surface Activation Step of Metal Foil and Intermediate Layer In step 2-2, the surface of the metal foil is activated by sputter etching. If necessary, in step 2-4, the surface of the intermediate layer is activated by sputter etching.

[0056] The sputter etching treatment in the surface activation step can be carried out, for example, by preparing a low-dielectric film provided with a metal foil or intermediate layer to be bonded as a long coil 100 mm to 600 mm wide, using the bonding surface of the metal foil or intermediate layer as one electrode grounded to earth, and applying an alternating current of 1 MHz to 50 MHz between the electrode and another electrode supported insulated to generate a glow discharge, and setting the area of ​​the electrode exposed to the plasma generated by the glow discharge to 1 / 3 or less of the area of ​​the other electrode. During the sputter etching treatment, the grounded electrode is in the form of a cooling roll to prevent the temperature of the transported material from rising.

[0057] In the sputter etching treatment in the surface activation step, the surface to be joined of the metal foil or the low dielectric film provided with the intermediate layer is sputtered with an inert gas under vacuum to completely remove any adsorbed matter on the surface and to remove part or all of the oxide layer on the surface. It is preferable to completely remove the oxide layer. As the inert gas, argon, neon, xenon, krypton, etc., or a mixed gas containing at least one of these can be used. Depending on the type of metal, adsorbed matter on the surface of the metal foil and the intermediate layer can be completely removed with an etching amount of about 1 nm, and in particular, the oxide layer of copper is usually 5 nm to 12 nm (SiO ２ It is possible to remove it by about 100% (equivalent).

[0058] The sputter etching conditions can be appropriately set depending on the type of metal foil and intermediate layer. For example, the process can be performed under vacuum with a plasma output of 100 W to 10 kW and a line speed of 0.5 m / min to 30 m / min. The degree of vacuum is preferably high to prevent re-adsorption of substances onto the surface. －５ Pa to 10 Pa is sufficient.

[0059] When a roughened particle layer or an anticorrosive layer is provided on the surface of the metal foil, the surface of the roughened particle layer or the anticorrosive layer is activated by sputter etching. At this time, the roughened particle layer or the anticorrosive layer may be completely removed by sputter etching, or may remain.

[0060] Furthermore, the surface of the metal foil or the surface of the intermediate layer before activation by sputter etching may be subjected to Ni plating, chromate treatment, silane coupling agent treatment, etc., as needed, to prevent oxidation or improve adhesion. Furthermore, the surface of the metal foil may be subjected to a roughening treatment as needed to improve adhesion with the low dielectric film or intermediate layer.

[0061] 3. Rolling Bonding Step In steps 3-1 and 3-2, the pressure bonding (rolling bonding) of the surfaces activated by sputter etching can be performed by roll bonding. The rolling wire load for roll bonding is not particularly limited and can be set, for example, in the range of 0.1 tf / cm to 10 tf / cm. However, when the thickness of the metal foil or low dielectric film before bonding is large, it may be necessary to increase the rolling wire load to ensure pressure during bonding, and this numerical range is not limited to this. On the other hand, if the rolling wire load is too high, not only the surface layer of the low dielectric film, metal foil, or intermediate layer but also the bonding interface will be easily deformed, which may reduce the thickness accuracy of each layer in the metal laminate. Furthermore, a high rolling wire load may increase the processing strain applied during bonding.

[0062] The reduction ratio during roll bonding is 0 to 30%, preferably 0 to 15%. The surface activated bonding method described above allows for a low reduction ratio, so a metal layer with excellent thickness precision can be formed without wrinkles, cracks, or the like. Furthermore, since waviness at the interface between the metal foil and the low-dielectric film or intermediate layer can be reduced, when pattern etching is performed on the metal foil or a metal layer having an intermediate layer to form wiring, precision wiring can be obtained due to excellent thickness precision. Furthermore, the temperature during roll bonding is, for example, 15°C or higher and 100°C or lower, preferably 15°C or higher and 60°C or lower, and more preferably room temperature.

[0063] The joining by roll pressure is preferably carried out in a non-oxidizing atmosphere, for example, a vacuum atmosphere or an inert gas atmosphere such as Ar, in order to prevent a decrease in adhesion at the lamination interface due to re-adsorption of oxygen onto the metal foil.

[0064] The metal laminate obtained by pressure welding can be further heat-treated as needed, and preferably is. Heat treatment removes distortion in the metal layer and improves adhesion between the layers. The heat treatment temperature can be in the range of from the melting point of the low dielectric film -150°C to the melting point of the low dielectric film +10°C. For example, in the case of a liquid crystal polymer film, the heat treatment temperature is 160°C to 350°C, preferably 160°C to 320°C, and more preferably 260°C to 320°C.

[0065] The atmosphere in which the heat treatment is performed is not particularly limited, but may be a vacuum atmosphere or a N ２ An inert gas atmosphere such as Ar is preferred because it is possible to avoid oxidation of the metal layer due to heat treatment and a decrease in the adhesion between the metal layer and the low dielectric film.

[0066] The duration of the heat treatment is not particularly limited as long as it can sufficiently enhance the adhesion between the metal layer and the low dielectric film. For example, the soaking time is preferably 0 to 25,200 seconds, more preferably 0 to 18,000 seconds, and particularly preferably 180 to 15,000 seconds. By setting the time at or above the lower limit of these ranges, sufficient adhesion between the metal layer and the low dielectric film can be ensured. By setting the time at or below the upper limit of these ranges, high production efficiency and low cost of the metal laminate material can be achieved. Note that even if the soaking time is 0 seconds (i.e., cooling is performed immediately after reaching the target temperature without a soaking time), it is possible to sufficiently enhance the adhesion between the metal layer and the low dielectric film.

[0067] The heat treatment is carried out, for example, in a batch-type heat treatment furnace in a desired atmosphere (for example, a vacuum atmosphere or N ２ In this case, the metal laminate material is maintained at a desired heat treatment temperature for a desired time in an inert gas atmosphere such as Ar. Alternatively, depending on the heat treatment temperature and atmosphere, a continuous heat treatment furnace may be used to perform the heat treatment by a roll-to-roll method. In this case, at least the heating section and the cooling section in the continuous heat treatment furnace are maintained in a desired atmosphere (for example, a vacuum atmosphere or N ２ and a method in which the metal laminate material is maintained at a desired heat treatment temperature for a desired period of time by passing the metal laminate material through a heating section or a cooling section at a desired speed after the metal laminate material is heated in an atmosphere of an inert gas such as Ar or the like and maintained at a desired temperature.

[0068] C. Use of Metal Laminate The metal laminate of the present invention can be used as a metal-clad laminate for producing a flexible printed circuit board.

[0069] A printed wiring board having fine wiring formed thereon can be obtained using the metal laminate material of the present invention. Therefore, the present invention also relates to a printed wiring board having a circuit formed on the metal laminate material. In the process of forming wiring, an additional metal layer can be formed only in the wiring portion. Specifically, a printed wiring board can be obtained by appropriately using conventionally known methods such as the modified semi-additive process (MSAP process), the semi-additive process (SAP process), or the subtractive process. For example, when the modified semi-additive process (MSAP process) is used, a printed wiring board can be produced by masking the non-wiring portion on the metal layer of the metal laminate material, copper plating the unmasked portion to form an additional metal layer, removing the mask, and removing the metal layer hidden by the mask by etching. Note that the "printed wiring board" in the present invention includes not only a laminate having wiring formed thereon, but also a board on which electronic components such as ICs are mounted after wiring has been formed.

[0070] 1 to 4 illustrate a metal laminate material in which a metal layer is laminated on one surface of a low dielectric film, but the metal laminate material is not limited to this. That is, if necessary, a metal layer may be provided on both surfaces of a low dielectric film. By using a metal laminate material in which a metal layer is provided on both surfaces of a low dielectric film, a flexible printed circuit board in which wiring is formed on both surfaces of a low dielectric film can be obtained.

[0071] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to these examples.

[0072] Example 1 First, a liquid crystal polymer film (Vexstar CTQ manufactured by Kuraray Co., Ltd.) having a thickness of 25 μm was prepared, and a rolled copper foil (HA-V2 manufactured by JX Nippon Mining & Metals Corporation) having a thickness of 18 μm was prepared as the metal foil. Next, one surface of the liquid crystal polymer film was covered with O ２After activation by sputter etching with gas, a 5 nm NiCr alloy sputter layer was sputter-deposited on the activated surface as a base layer, and a 10 nm Cu sputter layer was sputter-deposited as an upper layer to form an intermediate layer (hereinafter also referred to as a Cu / NiCr alloy intermediate layer). Next, the surface of the intermediate layer and the surface of the rolled copper foil were activated by sputter etching with Ar gas, and the activated surfaces of the intermediate layer and the rolled copper foil were roll-bonded together at a linear load of 1.5 tf / cm to produce a metal laminate material. The rolling reduction was 2.3%. Next, the metal laminate material was subjected to heat treatment at 300 ° C. to obtain the metal laminate material of Example 1 (layer structure: rolled copper foil / intermediate layer / liquid crystal polymer film).

[0073] (Example 2) A metal laminate material of Example 2 (layer structure: rolled copper foil / intermediate layer / liquid crystal polymer film) was produced in the same manner as in Example 1, except that a rolled copper foil having a thickness of 16 μm (C1020R-H manufactured by Mitsui Sumitomo Metal Mining Copper Brazing Co., Ltd.) was used as the rolled copper foil.

[0074] Example 3 First, a liquid crystal polymer film (Vexstar CTQ manufactured by Kuraray Co., Ltd.) having a thickness of 25 μm was prepared, and the rolled copper foil (HA-V2 manufactured by JX Nippon Mining & Metals Corporation) used in Example 1 was prepared as the metal foil. Next, one surface of the liquid crystal polymer film was coated with O ２ The surface of the rolled copper foil was activated by sputter etching with Ar gas, and the activated surfaces of the liquid crystal polymer film and the rolled copper foil were rolled and bonded together at a linear load of 1.5 tf / cm to produce a metal laminate. The reduction ratio was 2.3%. Next, the metal laminate was subjected to a heat treatment at 320 ° C. to obtain the metal laminate of Example 3 (layer structure: rolled copper foil / liquid crystal polymer film).

[0075] (Example 4) A metal laminate material (layer structure: rolled copper foil / liquid crystal polymer film) of Example 4 was obtained in the same manner as in Example 3, except that the rolled copper foil (C1020R-H manufactured by Mitsui Sumitomo Metal Mining Co., Ltd.) used in Example 2 was used as the rolled copper foil.

[0076] Example 5 A metal laminate material (layer structure: rolled copper foil / liquid crystal polymer film) of Example 5 was obtained in the same manner as in Example 4, except that a liquid crystal polymer film having a thickness of 50 μm (Vexstar CTQ manufactured by Kuraray Co., Ltd.) was used.

[0077] (Example 6) First, a liquid crystal polymer film having a thickness of 25 μm (Vexstar CTQ manufactured by Kuraray Co., Ltd.) was prepared, and as a metal foil, a carrier-attached copper foil (MT18FL manufactured by Mitsui Mining & Smelting Co., Ltd.) was prepared, which had a copper carrier layer having a thickness of 18 μm, a release layer (organic release layer) interposed therebetween, an ultrathin copper layer having a thickness of 1.5 μm, and a roughened particle layer and an anti-corrosion layer provided on the surface of the copper carrier layer. Next, one surface of the liquid crystal polymer film was O ２ After activation by sputter etching with Ar gas, a Cu / NiCr alloy intermediate layer was sputter-formed on the activated surface in the same manner as in Example 1. Next, the surfaces of the intermediate layer and the ultrathin copper layer were activated by sputter etching with Ar gas, and the activated surfaces of the intermediate layer and the ultrathin copper layer were roll-bonded together at a linear load of 1.5 tf / cm to produce a metal laminate. The rolling reduction was 3.4%. Next, the metal laminate was subjected to a heat treatment at 300 ° C. to obtain the metal laminate of Example 6 (layer structure: carrier-attached copper foil / intermediate layer / liquid crystal polymer film).

[0078] (Example 7) A metal laminate material of Example 7 (layer structure: carrier-attached copper foil / intermediate layer / liquid crystal polymer film) was obtained in the same manner as in Example 6, except that a carrier-attached copper foil (prototype material A) was used, which had a carrier layer made of copper and having a thickness of 18 μm, an ultrathin copper layer having a thickness of 2 μm and a rust-preventive layer provided on its surface via a release layer (inorganic release layer).

[0079] (Example 8) First, a liquid crystal polymer film (Vexstar CTQ manufactured by Kuraray Co., Ltd.) having a thickness of 25 μm was prepared, and the carrier-attached copper foil (MT18FL manufactured by Mitsui Mining & Smelting Co., Ltd.) used in Example 6 was prepared as the metal foil. Next, one surface of the liquid crystal polymer film was coated with O ２The surface of the ultrathin copper layer of the carrier-attached copper foil was activated by sputter etching with Ar gas, and the activated surfaces of the liquid crystal polymer film and the ultrathin copper layer were roll-bonded together at a line load of 1.5 tf / cm to produce a metal laminate. The rolling reduction was 3.4%. Next, the metal laminate was subjected to a heat treatment at 300 ° C. to obtain the metal laminate of Example 8 (layer structure: carrier-attached copper foil / liquid crystal polymer film).

[0080] (Example 9) A metal laminate material of Example 9 (layer structure: carrier-attached copper foil / liquid crystal polymer film) was obtained in the same manner as in Example 8, except that a carrier-attached copper foil (MT18EX manufactured by Mitsui Mining & Smelting Co., Ltd.) was used as the carrier-attached copper foil, which had a carrier layer made of copper and having a thickness of 18 μm, an ultrathin copper layer having a thickness of 2 μm, and a roughened particle layer and an anti-corrosion layer provided on the surface of the carrier layer, via a release layer (organic release layer).

[0081] (Example 10) A metal laminate material of Example 10 (layer structure: carrier-attached copper foil / liquid crystal polymer film) was obtained in the same manner as in Example 8, except that a carrier-attached copper foil (MT18SD-H manufactured by Mitsui Mining & Smelting Co., Ltd.) was used as the carrier-attached copper foil, which had a carrier layer made of copper and having a thickness of 18 μm, an ultrathin copper layer having a thickness of 5 μm, and a roughened particle layer and an anti-corrosion layer provided on the surface of the copper foil, via a release layer (organic release layer).

[0082] (Example 11) As the carrier-attached copper foil, the carrier-attached copper foil (prototype material A) used in Example 7 was used, and the same procedure as in Example 8 was carried out to obtain a metal laminate material (layer structure: carrier-attached copper foil / liquid crystal polymer film) of Example 11.

[0083] (Example 12) A metal laminate material of Example 12 (layer structure: carrier-attached copper foil / liquid crystal polymer film) was obtained in the same manner as in Example 8, except that a carrier-attached copper foil (MT18GN manufactured by Mitsui Mining & Smelting Co., Ltd.) was used as the carrier-attached copper foil, which had a carrier layer made of copper and having a thickness of 18 μm, an ultrathin copper layer having a thickness of 1.5 μm, and a roughened particle layer and an anti-corrosion layer provided on the surface of the carrier layer (MT18GN manufactured by Mitsui Mining & Smelting Co., Ltd.) via a release layer (organic release layer).

[0084] (Example 13) A metal laminate material of Example 13 (layer structure: carrier-attached copper foil / liquid crystal polymer film) was obtained in the same manner as in Example 8, except that a carrier-attached copper foil (FUTF-7DAF-5 manufactured by Fukuda Metal Foil and Powder Co., Ltd.) was used as the carrier-attached copper foil, which had a carrier layer made of copper and having a thickness of 18 μm, an ultrathin copper layer having a thickness of 2 μm provided thereon via a release layer (inorganic release layer), and a roughened particle layer and an anti-rust layer provided on the surface of the copper foil.

[0085] Example 14 A liquid crystal polymer film having a thickness of 50 μm (Vexstar CTQ manufactured by Kuraray Co., Ltd.) was prepared, and an electrolytic copper foil having a thickness of 12 μm (CF-T9DA-SV manufactured by Fukuda Metal Foil and Powder Co., Ltd.) was prepared as the metal foil. Next, one surface of the liquid crystal polymer film was O ２ The electrodeposited copper foil was activated by sputter etching with Ar gas, and the surface of the electrodeposited copper foil was activated by sputter etching with Ar gas. The activated surfaces of the liquid crystal polymer film and the electrodeposited copper foil were roll-bonded together at a linear load of 1.5 tf / cm to produce a metal laminate. The rolling reduction was 2.3%. Next, the metal laminate was subjected to a heat treatment at 320°C to obtain the metal laminate of Example 14 (layer structure: electrodeposited copper foil / liquid crystal polymer film).

[0086] (Example 15) A metal laminate material of Example 15 (layer structure: electrolytic copper foil / liquid crystal polymer film) was obtained in the same manner as in Example 14, except that an electrolytic copper foil having a thickness of 12 μm made of copper (CF-PLFA manufactured by Fukuda Metal Foil and Powder Co., Ltd.) was used as the electrolytic copper foil.

[0087] (Example 16) A metal laminate material (layer structure: electrolytic copper foil / liquid crystal polymer film) of Example 16 was obtained in the same manner as in Example 14, except that a 25 μm thick liquid crystal polymer film (Vexstar CTQ manufactured by Kuraray Co., Ltd.) was used and an 18 μm thick electrolytic copper foil made of copper (CF-V9S-SV manufactured by Fukuda Metal Foil and Powder Co., Ltd.) was used as the electrolytic copper foil.

[0088] (Comparative Example 1) A metal laminate material of Comparative Example 1 (layer structure: rolled copper foil (roughened) / liquid crystal polymer film / rolled copper foil (roughened)) was produced by thermocompression bonding, at a temperature of 310°C or higher, a rolled copper foil having a thickness of 18 μm, one side of which had a treatment layer consisting of a roughened particle layer or the like, to both surfaces of a liquid crystal polymer film having a thickness of 50 μm (Vexstar CTQ manufactured by Kuraray Co., Ltd.) by a thermal lamination method.

[0089] (Comparative Example 2) A metal laminate material of Comparative Example 2 (layer structure: electrolytic copper foil / liquid crystal polymer film / electrolytic copper foil) was produced in the same manner as in Comparative Example 1, except that an electrolytic copper foil having a thickness of 18 μm and having a treatment layer made of a roughening particle layer or the like on one side was used as the rolled copper foil.

[0090] Cross-sectional photographs of the metal laminate materials of Examples 1 to 16 and Comparative Examples 1 and 2 were obtained using a scanning electron microscope (magnification 20,000 times). Of the cross-sectional photographs of the obtained metal laminate materials, Figures 6 to 13 show cross-sectional photographs of the metal laminate materials of Examples 1 to 4, 6 to 8, and 14, respectively, and Figures 14 and 15 show cross-sectional photographs of the metal laminate materials of Comparative Examples 1 and 2, respectively. In addition, the following properties were evaluated for the metal laminate materials of Examples 1 to 16 and Comparative Examples 1 and 2.

[0091] [Aspect ratio of the convex portion of the metal foil] As described in the section "A. Metal laminate material", in the cross-sectional photograph of the obtained metal laminate material, the width a and height b of the convex portion of the copper foil were measured on the surface of the copper foil on the liquid crystal polymer film side.

[0092] As an example using rolled copper foil, a cross-sectional photograph (FIG. 8) of the metal laminate of Example 3 will be used for explanation. As shown in FIG. 8, on the surface of the copper foil (HA-V2 in FIG. 8) facing the liquid crystal polymer film (LCP in FIG. 8), the width a of the convex portion, which is the length of the line connecting the two points where the convex portion of the copper foil starts, and the height b of the convex portion, which is the length from this line to the apex of the convex portion, were measured for each convex portion. From the measured width a and height b of the convex portion, the average value of b / a was calculated, and further, taking into account the variation in the value, the average value of b / a + 3σ (where σ is the standard deviation of b / a) was calculated.

[0093] An example using a carrier-attached copper foil will be described below with reference to a cross-sectional photograph (Fig. 12) of the metal laminate material of Example 8. As shown in Fig. 12, on the surface of the liquid crystal polymer film (LCP in Fig. 12) side of the ultrathin copper layer of the carrier-attached copper foil (MT18FL in Fig. 12), the width a of the convex portion, which is the length of the line connecting the two points where the convex portion of the copper foil (ultrathin copper layer) starts, and the height b of the convex portion, which is the length from this line to the apex of the convex portion, were measured, and the average value of b / a + 3σ was calculated as described above.

[0094] [Transmission loss (S21)] Transmission loss (S21) was measured to evaluate the high-frequency transmission characteristics of the metal laminate materials of Example 5 and Comparative Example 2. Since Example 5 is a single-sided material, a copper layer was provided by electroless copper plating on the exposed surface of the liquid crystal polymer film opposite to the surface on which the rolled copper foil was laminated, and after through-holes were made, electrolytic copper plating was performed to obtain a measurement sample having a copper layer (25 μm) on both sides. For the metal laminate material of Comparative Example 2, after through-holes were made, electrolytic copper plating was performed to obtain a measurement sample having a copper layer (25 μm) on both sides.

[0095] The transmission line was a single-ended microstrip transmission line with a wiring height of 25 μm, a wiring width of 110 μm, and a wiring length of 100 mm. Measurements were performed at a frequency of 40 GHz using a network analyzer E8363B (manufactured by Keysight Technologies, Inc.). In Example 5, a microstrip line was created on the laminated rolled copper foil side and the measurements were performed.

[0096] [Peel Strength] Test pieces were prepared from the metal laminate material, and a 1 cm wide cut was made in the metal layer using a knife or the like. Then, after the metal layer and the liquid crystal polymer film were partially peeled off, the liquid crystal polymer film was fixed to a support, and the metal layer was pulled in a 90° direction relative to the liquid crystal polymer film at a speed of 50 mm / min. The force required for peeling at this time was taken as the peel strength (unit: N / cm). In addition, for the metal laminate materials of Examples 6 to 13, the carrier layer and the release layer of the carrier-attached copper foil were removed to expose the ultrathin copper layer, and then an 18 μm thick electrolytic copper plating was applied to the surface of the ultrathin copper layer to increase the thickness of the ultrathin copper layer, and the peel strength between the metal layer and the liquid crystal polymer film was measured.

[0097] The configurations and evaluation results of the metal laminate materials of Examples 1 to 16 and Comparative Examples 1 and 2 are shown in Table 1. In Table 1, LCP means liquid crystal polymer film.

[0098]

[0099] As shown in Figures 6 to 15, in the metal laminates of Comparative Examples 1 and 2 (Figures 14 and 15, respectively) prepared by thermal lamination, the roughening particles of the copper foil are deeply embedded in the liquid crystal polymer film, resulting in large irregularities at the bonding interface. In contrast, in the metal laminates of Examples 1 to 4 and 14 (Figures 6 to 9 and 13, respectively) prepared by surface-activated bonding using smooth rolled copper foil or electrolytic copper foil, the interface between the copper foil and the liquid crystal polymer film is very smooth. Furthermore, in the metal laminates of Examples 6 to 8 (Figures 10 to 12, respectively) prepared by surface-activated bonding using carrier-attached copper foil having a roughening particle layer or anticorrosion layer on its surface, the embedding depth of the protrusions on the copper foil surface is smaller than in the metal laminates of Comparative Examples 1 and 2. Therefore, it can be seen that by using surface-activated bonding, metal foil can be laminated to a low-dielectric film while maintaining its surface smoothness.

[0100] This can also be confirmed from the value of the aspect ratio (average value of b / a + 3σ) of the copper foil protrusions shown in Table 1. Compared with the metal laminate materials of Comparative Examples 1 and 2, the metal laminate materials of Examples 1 to 5 using rolled copper foil with a smooth surface had a very small value, and the metal laminate materials of Examples 6 to 13 using carrier-attached copper foil and the metal laminate materials of Examples 14 to 16 using electrolytic copper foil also had a significantly small value. Thus, it was shown that the metal laminate materials of Examples 1 to 16 produced by the surface activated bonding method had a smaller degree of surface irregularity on the rolled copper foil, carrier-attached copper foil, or electrolytic copper foil, and had a smoother surface.

[0101] Regarding the high-frequency transmission characteristics of the metal laminate material, as shown in Table 1, the metal laminate material of Example 5, which has a smaller value of the average value of b / a of the convex portions + 3σ and a smooth copper foil surface, had a smaller transmission loss (S21) at high frequencies and was shown to have excellent high-frequency characteristics compared to the metal laminate material of Comparative Example 2. Generally, if the surface of the metal foil of a metal laminate material is smooth, transmission loss can be suppressed, so it is presumed that the metal laminate materials of Examples 1 to 4 and 6 to 16 will also have excellent high-frequency transmission characteristics like the metal laminate material of Example 5.

[0102] Regarding the peel strength of the liquid crystal polymer film and the metal layer of the metal laminate material, as shown in Table 1, the metal laminate materials of Examples 1 to 16 had smoother copper foil surfaces but had equal or greater peel strength than the metal laminate materials of Comparative Examples 1 and 2. This is thought to be because, in the metal laminate materials of Examples 1 to 16, a strong bond is formed at the interface between the liquid crystal polymer film and the copper foil by the surface activation treatment, ensuring adhesion at the laminate interface without relying on the physical anchor effect of the roughening particles.

[0103] These results show that the metal laminates of Examples 1 to 16 prepared by the surface activated bonding method have the same or higher peel strength between the metal layer and the liquid crystal polymer film as the metal laminates of Comparative Examples 1 and 2 prepared by the thermal lamination method, and the surface of the metal foil is smoother. Therefore, it was shown that they have excellent high-frequency characteristics.

[0104] Effect of gas used in sputter etching of liquid crystal polymer film The type of gas used when activating the liquid crystal polymer film by sputter etching was changed to check the effect on the peel strength of the metal laminate material.

[0105] Metal laminate material with intermediate layer O is used as a gas for sputter etching of liquid crystal polymer film ２ Gas, Ar gas and N ２ Gas was used. ２ As a sample for gas, the metal laminate material of Example 2 was used.

[0106] Example 17 A metal laminate material of Example 17 was obtained in the same manner as in Example 2, except that Ar gas was used as the gas used for sputter etching of the liquid crystal polymer film.

[0107] Example 18: N gas used in sputter etching of a liquid crystal polymer film ２ A metal laminate material of Example 18 was obtained in the same manner as in Example 2 except that gas was used.

[0108] Metal laminate material without intermediate layer O is used as a gas for sputter etching of liquid crystal polymer film. ２ Gas, Ar gas and N ２ Gas was used. ２ As a sample for gas, the metal laminate material of Example 4 was used.

[0109] Comparative Example 3 A metal laminate material of Comparative Example 3 was obtained in the same manner as in Example 4, except that Ar gas was used as the gas used for sputter etching of the liquid crystal polymer film.

[0110] Comparative Example 4: N gas was used for sputter etching of the liquid crystal polymer film. ２ A metal laminate material of Comparative Example 4 was obtained in the same manner as in Example 4 except that gas was used.

[0111] The peel strength of the liquid crystal polymer film and the metal layer of the prepared metal laminate material was measured as described above. As a result, the peel strength of the metal laminate material having an intermediate layer was ２ gas), 8.2 N / cm, Example 17 (Ar gas), 5.4 N / cm, Example 18 (N ２ In the case of the metal laminate material without an intermediate layer, the peel strength was 7.9 N / cm. ２ gas), 7.6 N / cm, Comparative Example 3 (Ar gas), 1.0 N / cm, Comparative Example 4 (N ２ Therefore, the gas used for sputter etching of the liquid crystal polymer film was O ２ In the case of gas, Ar gas and N ２The peel strength tended to be higher compared to when gas was used, and the improvement in peel strength for the metal laminate material without an intermediate layer was greater than that for the metal laminate material with an intermediate layer.

[0112] 1A Metal Laminate 1B Metal Laminate 1C Metal Laminate 1D Metal Laminate 10 Metal Layer 11 Metal Foil 12 Carrier Layer 13 Release Layer 14 Ultra-Thin Metal Layer 15 Intermediate Layer 20 Low Dielectric Film All publications, patents and patent applications cited herein are hereby incorporated by reference in their entirety.

Claims

1. A metal laminate material in which a metal layer including at least one layer including a metal foil is laminated on at least one surface of a low dielectric film, the metal layer does not have an intermediate layer containing a metal between the low dielectric film and the metal foil, A metal laminate material in which a plurality of convex portions of the metal foil are formed on the surface of the metal foil facing the low dielectric film, and when the width of the convex portions is a and the height of the convex portions is b, the average value of b / a + 3σ (where σ is the standard deviation of b / a) is 2.5 or less, and the peel strength of the low dielectric film and the metal layer is 3 N / cm or more.

2. 2. The metal laminate material according to claim 1, wherein the metal layer does not have a sputtered layer made of copper, nickel, chromium, or an alloy thereof between the low dielectric film and the metal foil.

3. 3. The metal laminate material according to claim 1, wherein the metal foil is a rolled copper foil, a copper foil with a carrier, or an electrolytic copper foil.

4. A method for producing a metal laminate material in which a metal layer including at least one layer including a metal foil is laminated on at least one surface of a low dielectric film, the metal layer does not have an intermediate layer containing a metal between the low dielectric film and the metal foil, a plurality of convex portions of the metal foil are formed on the surface of the metal foil facing the low dielectric film, and when the width of the convex portions is a and the height of the convex portions is b, the average value of b / a + 3σ (where σ is the standard deviation of b / a) is 2.5 or less, and the peel strength between the low dielectric film and the metal layer is 3 N / cm or more; The method comprises: providing a low dielectric film and a metal foil; activating at least one surface of the low dielectric film by sputter etching; activating the surface of the metal foil by sputter etching; a step of rolling-bonding the activated surfaces of the low dielectric film and the metal foil together at a rolling reduction of 0 to 30%; A method for manufacturing a metal laminate, comprising:

5. The method for producing a metal laminate material according to claim 4, wherein the metal layer does not have a sputtered layer made of copper, nickel, chromium or an alloy thereof between the low dielectric film and the metal foil.

6. The method for producing a metal laminate material according to claim 4 or 5, wherein the metal foil is a rolled copper foil, a copper foil with a carrier, or an electrolytic copper foil.

7. The method for producing a metal laminate material according to claim 4 or 5, wherein at least one surface of the low dielectric film is activated by sputter etching with oxygen.

8. The method for producing a metal laminate material according to claim 4 or 5, wherein the temperature in the roll-bonding step is 15°C or higher and 100°C or lower.

9. 6. The method for producing a metal laminate material according to claim 4, wherein after the roll bonding, a heat treatment is performed at a temperature of not less than the melting point of the low dielectric film -150°C and not more than the melting point +10°C.

10. A printed wiring board comprising a circuit formed on the metal laminate material according to claim 1 or 2.