Metal laminated material and method for manufacturing the same, printed wiring board

Abstract

The present invention provides a metal laminate that has both high-frequency characteristics and close adhesion of a laminate interface. The present invention relates to a metal laminate, a method for manufacturing the same, and a printed wiring board. The metal laminate is a metal laminate in which a metal layer composed of at least one layer containing a metal foil is laminated on at least one surface of a low-dielectric film, wherein a plurality of protrusions of the metal foil are formed on the surface of the metal foil on the low-dielectric film side, the width of the protrusions is set as a, the height of the protrusions is set as b, the average value of b / a + 3σ (where σ is the standard deviation of b / a) is 2.5 or less, and the peeling strength of the low-dielectric film and the metal layer is 3 N / cm or more.

Description

Technical Field

[0001] This invention relates to metal laminated materials and their manufacturing methods, and printed circuit boards. Background Technology

[0002] Currently, metal laminates, which are made by laminating copper foil and other metal foils on a low-dielectric film, are known as substrates for printed circuit board manufacturing. In recent years, the service of fifth-generation mobile communication systems (5G) has begun in various countries, requiring metal laminates with excellent 5G frequency band, i.e., high-frequency characteristics.

[0003] As a metal laminate, from the perspective of ensuring tight adhesion of the low-dielectric film, it is known to use a thermal lamination method that involves heating and pressing a metal foil with a roughened bonding surface. Generally, the thermal lamination method uses a metal foil with a roughened surface, and heats the low-dielectric film to near its melting point to soften it. This causes the roughened particles on the surface of the metal foil to be deeply embedded inside the low-dielectric film, ensuring tight adhesion through a so-called anchoring effect.

[0004] Patent Document 1 discloses a surface-treated copper foil with a roughened surface, a copper-clad laminate formed by laminating the copper foil on an insulating substrate, and a printed circuit board using the copper-clad laminate. It also discloses that the copper-clad laminate can be manufactured by thermal lamination.

[0005] As is well known, metal laminates with smooth metal foil surfaces exhibit excellent transmission characteristics in high-frequency applications. While existing metal laminates fabricated using thermal lamination can roughen the metal foil surface and ensure adhesion through anchoring effects, the skin effect at roughened lamination interfaces leads to degraded transmission characteristics at high frequencies, rendering them unsuitable for high-frequency applications.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2018-90906. Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] As described above, in existing metal laminates manufactured using thermal lamination, roughening the surface of the metal foil ensures tight adhesion at the lamination interface, but sometimes high-frequency characteristics are insufficient. Therefore, the object of the present invention is to provide a metal laminate that balances high-frequency characteristics and tight adhesion at the lamination interface.

[0011] Technical solutions for solving technical problems

[0012] To address the aforementioned problems, the inventors conducted in-depth research and discovered that by utilizing a surface activation bonding method to fabricate metal laminates, it is possible to laminate metal foils onto a low-dielectric film while maintaining the smoothness of the metal foil surface. This achieves a balance between high-frequency characteristics and the tightness of the laminated interface, thus completing the invention. In essence, the key points of this invention are as follows.

[0013] (1) A metal laminate material having a metal layer consisting of at least one layer comprising a metal foil laminated on at least one surface of a low dielectric film, wherein a plurality of protrusions of the metal foil are formed on the surface of the low dielectric film side of the metal foil, wherein the width of the protrusion is a and the height of the protrusion is b, and 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.

[0014] (2) The metal laminate material according to (1) 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.

[0015] (3) The metal laminate material according to (1) or (2) above, wherein the metal foil is rolled copper foil, copper foil with carrier or electrolytic copper foil.

[0016] (4) A method for manufacturing a metal laminate, wherein the metal laminate is a metal laminate on at least one surface of a low dielectric film having a metal layer consisting of at least one layer comprising a metal foil.

[0017] A plurality of protrusions are formed on the surface of the metal foil on the side of the low-dielectric film. Let the width of each protrusion be 'a' and the height of each protrusion be 'b'. Then, the average value of b / a + 3σ (where σ is the standard deviation of b / a) is less than 2.5, and the peel strength between the low-dielectric film and the metal layer is greater than 3 N / cm.

[0018] The method includes:

[0019] Steps for preparing low-dielectric films and metal foils;

[0020] The step of activating at least one surface of the low-dielectric film by sputter etching;

[0021] The step of activating the surface of the metal foil by sputter etching; and

[0022] The step of rolling the activated surface of the low dielectric film and the activated surface of the metal foil together with a reduction rate of 0% to 30%.

[0023] (5) A method for manufacturing a metal laminate, wherein the metal laminate is a metal laminate on at least one surface of a low dielectric film having a metal layer consisting of at least one layer comprising a metal foil.

[0024] The metal layer has an intermediate layer containing metal between the low-dielectric film and the metal foil.

[0025] A plurality of protrusions are formed on the surface of the metal foil on the side of the low-dielectric film. Let the width of each protrusion be 'a' and the height of each protrusion be 'b'. Then, the average value of b / a + 3σ (where σ is the standard deviation of b / a) is less than 2.5, and the peel strength between the low-dielectric film and the metal layer is greater than 3 N / cm.

[0026] The method includes:

[0027] Steps for preparing low-dielectric films and metal foils;

[0028] The step of activating at least one surface of the low-dielectric film by sputter etching;

[0029] The step of forming a metal-containing intermediate layer on the activated surface of the low-dielectric film;

[0030] The step of activating the surface of the intermediate layer by sputter etching;

[0031] The step of activating the surface of the metal foil by sputter etching; and

[0032] The step of rolling the activated surface of the intermediate layer and the activated surface of the metal foil together with a reduction rate of 0% to 30%.

[0033] (6) The method for manufacturing a metal laminate 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.

[0034] (7) The method for manufacturing a metal laminate material according to any one 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.

[0035] (8) A method for manufacturing a metal laminate according to any one of (4) to (6) above, wherein at least one surface of the low dielectric film is activated by oxygen sputtering etching.

[0036] (9) The method for manufacturing a metal laminate according to any one of (4) to (6) above, wherein the temperature of the rolling and joining step is 15°C or more and 100°C or less.

[0037] (10) The method for manufacturing a metal laminate material according to any one of (4) to (6) above, wherein the temperature of the rolling and joining step is 15°C or more and 100°C or less.

[0038] (11) A printed circuit board, wherein the printed circuit board is formed on a metal laminate material as described in any one of (1) to (3) above.

[0039] This specification contains the disclosure of Japanese Patent Application No. 2021-174667, which forms the basis of the priority claim of this application.

[0040] Invention Effects

[0041] According to the present invention, a metal laminate material that combines high-frequency characteristics and tight adhesion of the laminate interface can be provided. Attached Figure Description

[0042] Figure 1 This is a schematic cross-sectional view of a metal laminate material representing one aspect of the first embodiment of the present invention;

[0043] Figure 2 This is a schematic cross-sectional view of a metal laminate material representing another aspect of the first embodiment of the present invention;

[0044] Figure 3 This is a schematic cross-sectional view of a metal laminate material representing one aspect of the second embodiment of the present invention;

[0045] Figure 4 This is a schematic cross-sectional view of a metal laminate material representing another aspect of the second embodiment of the present invention;

[0046] Figure 5 A represents an enlarged schematic diagram of the cross-section of the metal laminate 1A; Figure 5 B represents an enlarged schematic diagram of the cross-section of the convex portion of the metal foil;

[0047] Figure 6 A cross-sectional photograph of the metal laminate material of Example 1;

[0048] Figure 7 A cross-sectional photograph of the metal laminate material of Example 2;

[0049] Figure 8 A cross-sectional photograph of the metal laminate material of Example 3;

[0050] Figure 9 A cross-sectional photograph of the metal laminate material of Example 4;

[0051] Figure 10 A cross-sectional photograph of the metal laminate material of Example 6;

[0052] Figure 11 A cross-sectional photograph of the metal laminate material of Example 7;

[0053] Figure 12 A cross-sectional photograph of the metal laminate material of Example 8;

[0054] Figure 13 A cross-sectional photograph of the metal laminate material of Example 14;

[0055] Figure 14 A cross-sectional photograph of the metallic laminate material in Comparative Example 1;

[0056] Figure 15 This is a cross-sectional photograph of the metal laminate material in Comparative Example 2. Detailed Implementation

[0057] The present invention will now be described in detail. The present invention relates to a metal laminate material having a metal layer comprising at least one layer including a metal foil laminated on at least one surface of a low-dielectric film. The metal laminate material of the present invention includes a metal laminate material having a metal layer laminated on one surface of a low-dielectric film, and a metal laminate material having metal layers laminated on both surfaces of a low-dielectric film. Because the surface of the low-dielectric film side of the metal foil is smooth, the metal laminate material of the present invention exhibits excellent high-frequency characteristics, and the low-dielectric film and the metal layer have sufficient adhesion.

[0058] A. Metal laminates

[0059] The metal laminate material of the first embodiment of the present invention will be described below.

[0060] Figure 1 This is a schematic cross-sectional view of a metal laminate material representing one aspect of the first embodiment of the present invention. (See diagram below.) Figure 1 As shown, in the first embodiment, a metal layer 10 composed of metal foil is stacked on one surface of a low dielectric film 20.

[0061] Figure 2 This is a schematic cross-sectional view showing a metal laminate material according to another aspect of the first embodiment of the present invention. In this embodiment, a carrier-supported metal foil having an extremely thin metal layer, a release layer, and a carrier layer is used as the metal foil. Figure 2 As shown, the metal laminate material 1B of the present invention has a metal layer 10 composed of a metal foil with a carrier laminated on one surface of a low dielectric film 20. In the metal layer 10, the layers are laminated in the following order, starting from the low dielectric film 20 side: an extremely thin metal layer 14, a release layer 13, and a carrier layer 12.

[0062] The composition of the metal laminate material according to the first embodiment of the present invention will be described in detail below.

[0063] 1. Low dielectric film

[0064] As a material for low-dielectric films, any low-dielectric polymer material that can be used as a flexible substrate can be applied, such as one with a relative permittivity ε. r Materials with a dielectric constant of 3.3 or less and a dielectric loss tangent (tanδ) of 0.006 or less are preferred, but not limited to these. Specifically, materials such as liquid crystal polymers, fluorinated polyethylene (fluorinated resins such as polytetrafluoroethylene), polyamides, isocyanate compounds, polyamide-imides, polyimides, low-dielectric-constant polyimides, polyethylene terephthalate, polyether-imides, and cyclic olefin polymers can be appropriately selected. Liquid crystal polymers, fluorinated polyethylene, polyamides, or low-dielectric-constant polyimides are preferred, and liquid crystal polymers are more preferred. The low-dielectric film is a single-layer film or a multilayer laminate. If it is a multilayer film, any one or more layers can be made of a low-dielectric polymer material. Layers other than those made of low-dielectric polymer materials can be made of various currently known materials such as epoxy resins. It should be noted that liquid crystal polymers refer to aromatic polyester resins with a basic structure such as p-hydroxybenzoic acid that exhibit liquid crystal properties in the molten state.

[0065] The thickness of the low-dielectric film can be appropriately set according to the intended use of the metal laminate. For example, when used as a flexible printed circuit board, the thickness is typically 10 μm to 150 μm, preferably 10 μm to 100 μm, more preferably 10 μm to 75 μm, and particularly preferably 10 μm to 50 μm. The thickness of the low-dielectric film refers to the average value obtained by measuring the thickness of the low-dielectric film at any 10 points in an optical microscope photograph of a cross-section of the metal laminate. It should be noted that the thickness of the low-dielectric film before bonding refers to the average value of the thickness measured at 10 randomly selected points on the surface of the low-dielectric film to be bonded, which can be measured using a micrometer or similar measuring device. Furthermore, for the low-dielectric film used, the deviation of the measured values ​​at the 10 points from the average value is preferably within 20% of all measured values, more preferably within 10%.

[0066] 2. Metal layer

[0067] There are no particular restrictions on the metal layer as long as it includes a metal foil; it can be composed of the metal foil or may have other layers besides the metal foil. When the metal layer has other layers, it is preferable that the other layers are located between the low-dielectric film and the metal foil.

[0068] The type of metal constituting the metal foil varies depending on the intended use of the metal laminate and is not particularly limited. Examples include copper, iron, nickel, zinc, tin, chromium, gold, silver, platinum, cobalt, titanium, and their alloys. Copper foil or copper alloy foil is preferred as the metal foil. This is because by rolling them together with a low-dielectric film, a flexible substrate for forming fine wiring can be obtained, for example.

[0069] The thickness of the metal foil varies depending on the application of the metal laminate and is not particularly limited. For example, if used for flexible printed circuit boards, a thickness of 3 μm to 100 μm is preferred, with 10 μm to 50 μm being more preferred. Here, the thickness of the metal foil refers to the average value obtained by measuring the thickness of the metal foil at any 10 points in an optical microscope photograph of the cross-section of the metal laminate.

[0070] The metal foil is preferably rolled metal foil, metal foil with a carrier, or electrolytic metal foil, and more preferably rolled copper foil, copper foil with a carrier, or electrolytic copper foil. Furthermore, the metal foil can be a single layer foil or a laminate of both.

[0071] When using rolled copper foil as the metal foil, there are no particular restrictions on the type of rolled copper foil; examples include HA-V2 manufactured by JX Metals Co., Ltd. and C1020R-H manufactured by Mitsui Sumitomo Metal Mining Shindoh Co., Ltd. Similarly, when using electrolytic copper foil as the metal foil, there are no particular restrictions on the type of electrolytic copper foil; examples include CF-T9DA-SV, CF-V9S-SV, and CF-PLFA manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.

[0072] When fabricating a flexible substrate for forming fine wiring, it is preferable to use a carrier-supported metal foil having an extremely thin metal layer, a release layer, and a carrier layer. When using a carrier-supported metal foil, such as... Figure 2 As shown, starting from the low-dielectric film side, a carrier-bearing metal foil is laminated in the order of an extremely thin metal layer, a release layer, and a carrier layer. When using a carrier-bearing metal foil, the "metal foil" in the resulting metal laminate material refers to the portion composed of the extremely thin metal layer, the release layer, and the carrier layer. It should be noted that the metal foil prepared in the manufacturing method of the metal laminate material can be a metal foil with a roughened particle layer and a rust-preventive layer on the surface of the extremely thin metal layer of the carrier-bearing metal foil.

[0073] The carrier layer of a metal foil with a carrier is a sheet-like carrier layer that functions as a support material or protective layer to prevent wrinkles or breakage of the laminated metal material and to prevent scratches on the extremely thin metal layer. Examples of carrier layers include foils or plates made of copper, aluminum, nickel, and their alloys (stainless steel, brass, etc.), or resins with a metal coating. Copper foil is preferred as the carrier layer. The thickness of the carrier layer is not particularly limited, for example, it can be 10 μm to 100 μm.

[0074] The release layer of the carrier-supported metal foil functions to reduce the peel strength of the carrier layer and suppress interdiffusion that may occur between the carrier layer and the extremely thin metal layer due to heat treatment. The release layer can be either an organic or inorganic release layer. Components used in organic release layers include, for example, nitrogen-containing organic compounds, sulfur-containing organic compounds, and carboxylic acids. Examples of 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-benzimidazole thiol. Examples of carboxylic acids include monocarboxylic acids and dicarboxylic acids. In addition, examples of components used for the inorganic release layer include Ni, Mo, Co, Cr, Fe, Ti, W, P, Zn, and chromate-treated films. The thickness of the release layer is typically 1 nm to 1 μm, preferably 5 nm to 500 nm.

[0075] The metal constituting the extremely thin metal layer of the carrier-supported metal foil varies depending on the intended use of the metal laminate and is not particularly limited. Examples include copper, iron, nickel, zinc, tin, chromium, gold, silver, platinum, cobalt, titanium, and their alloys. The extremely thin metal layer is preferably a layer of copper or a copper alloy. The thickness of the extremely thin metal layer is typically 0.5 μm to 10 μm, preferably 1 μm to 7 μm.

[0076] The preferred carrier-bearing metal foil is one in which the carrier layer and the ultrathin metal layer are copper or copper alloys, and more preferably, it is a copper-bearing foil in which the carrier layer and the ultrathin metal layer are copper. There are no particular limitations on the type of copper-bearing foil; examples include MT18FL, MT18GN, MT18EX, and MT18SD-H manufactured by Mitsui Metals & Minerals Co., Ltd.

[0077] It should be noted that, although in Figures 1-2Not described in the text, but the metal layer may also have at least one of the following (hereinafter sometimes referred to as "treatment layer") on the surface of the low-dielectric film side of the metal foil: a roughening particle layer, a rust-preventive layer, a heat-resistant layer, and a treatment layer utilizing a silane coupling agent. The treatment layer may be any one layer or multiple layers. The roughening particle layer may, for example, contain any metal or alloy thereof selected from the group consisting of Cu, Co, and Ni, but is not limited to these. Examples include cobalt-nickel alloy plating and copper-cobalt-nickel alloy plating. The rust-preventive layer may, for example, contain any metal or alloy thereof selected from the group consisting of Cr, Ni, and Zn, but is not limited to these. Examples include chromium oxide film treatment, a mixture film treatment of chromium oxide and zinc / zinc oxide, and nickel plating. The heat-resistant layer may, for example, contain any metal or alloy thereof selected from the group consisting of Co, Ni, and Mo, but is not limited to these. Furthermore, as a silane coupling agent, examples include olefinic silanes, epoxy silanes, acrylic silanes, amino silanes, and mercapto silanes, but are not limited to these. The silane coupling agent can be applied using methods such as spraying, coating machine application, or impregnation. It should be noted that the roughened particle layer, rust-preventive layer, and heat-resistant layer are different from the intermediate layer described below for the metal laminate material in the second embodiment.

[0078] Preferably, the metal laminate material of the first embodiment does not have the intermediate layer described below for the metal laminate material of the second embodiment. The absence of an intermediate layer in the metal laminate material improves productivity and reduces manufacturing costs. In a preferred embodiment, the metal laminate material of the present invention does not have an intermediate layer containing metal between the low-dielectric film and the metal foil, and preferably does not have a sputtered layer composed of copper, nickel, chromium, or alloys thereof. In one embodiment of the metal laminate material without an intermediate layer, the low-dielectric film and the metal foil (preferably rolled metal foil) are directly laminated. Furthermore, in another embodiment of the metal laminate material without an intermediate layer, the aforementioned coarsening particle layer and / or the aforementioned anti-rust layer are laminated on the low-dielectric film, and the metal foil (preferably a carrier-supported metal foil) is laminated thereon. In this type of metal laminate material, specifically, a coarsened granular layer comprising any metal or alloy thereof selected from the group consisting of Cu, Co and Ni is laminated on a low dielectric film, and / or a film, i.e. a rust-preventive layer, comprising any metal or alloy thereof selected from the group consisting of Cr, Ni and Zn, is laminated on the film, and a metal foil with a carrier is laminated on the film.

[0079] The metal laminate material of the second embodiment of the present invention will now be described. Figure 3 This is a schematic cross-sectional view of a metal laminate material representing one aspect of a second embodiment of the present invention. (See diagram below.) Figure 3As shown, 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 a metal-containing intermediate layer 15 between the low-dielectric film 20 and the metal foil 11. Therefore, the metal layer 10 has a metal-containing intermediate layer 15 laminated on one surface of the low-dielectric film 20, and a metal foil 11 laminated on the surface of the intermediate layer 15 opposite to one side of the low-dielectric film 20.

[0080] Figure 4 This is a schematic cross-sectional view showing a metal laminate material according to another aspect of the second embodiment of the present invention. In this embodiment, a carrier-supported metal foil having an extremely thin metal layer, a release layer, and a carrier layer is used as the metal foil. Figure 4 As shown, 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 extremely thin metal layer 14, a release layer 13, and a carrier layer 12. Therefore, the metal layers 10 are laminated in the following order, starting from the low-dielectric film 20 side: intermediate layer 15, extremely thin metal layer 14, release layer 13, and carrier layer 12.

[0081] In the metal laminate material of the second embodiment, by providing an intermediate layer, the surface of the metal foil or the low-dielectric film can be protected, and the adhesion between the metal foil and the low-dielectric film can be improved. There are no particular limitations on the intermediate layer, as long as it contains metal; it can be a layer containing one metal layer or a layer composed of two or more metal-containing layers stacked together. Examples of intermediate layers include layers formed on the low-dielectric film by sputtering, vapor deposition, or chemical plating, with layers formed by sputtering (sputtered layers) being preferred. The presence 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 20,000x or higher).

[0082] There are no particular restrictions on the intermediate layer as long as it contains metal. Preferably, it contains any metal or alloy thereof selected from the group consisting of copper, iron, nickel, zinc, chromium, cobalt, titanium, tin, platinum, silver, gold, aluminum, palladium, and zirconium. More preferably, it contains copper, nickel, chromium, or alloy thereof. Particularly preferred is copper, an alloy of copper and nickel, or an alloy of nickel or chromium. Alternatively, the intermediate layer may be a layer composed of multiple layers containing metal.

[0083] The intermediate layer is preferably a sputtered layer made of copper, nickel, chromium or their alloys, formed by sputtering between a low-dielectric film and a metal foil.

[0084] The thickness of the intermediate layer is not particularly limited, as long as it can improve adhesion. For example, it is preferably 5nm to 200nm, and more preferably 10nm to 100nm.

[0085] Regarding the metal laminate material of the second embodiment, the metal laminate material of the first embodiment is as described above for other configurations.

[0086] Because the surface of the low-dielectric film side, which corresponds to the lamination interface of the metal foil, is smooth, the high-frequency characteristics of the metal laminate of the present invention are superior compared to existing metal laminates produced by thermal lamination. Metal foil surfaces typically exhibit uneven shapes due to roughness, curling, etc. In this invention, the smoothness of the metal foil surface is evaluated using the ratio of the width to the height of the protrusions of the metal foil (hereinafter sometimes referred to as the aspect ratio), calculated by observing the cross-section of the metal laminate. Surface roughness is commonly used as an indicator of surface smoothness. Surface roughness generally measures the degree of deviation in the vertical direction of an object's surface shape compared to an ideal surface. Here, in existing metal laminates produced by thermal lamination, the coarsened 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 these intricate concave shapes. In this invention, the aspect ratio of the protrusions calculated by observing the cross-section of the metal laminate is used as an indicator of smoothness, allowing for appropriate comparison with existing metal laminates. It should be noted that the protrusions on the surface of the metal foil come from the metal foil used as the material, rather than being formed by adding other elements to the metal foil.

[0087] As described above, in this invention, the ratio of the width to the height of the protrusion, calculated by cross-sectional observation, is used as an indicator of surface smoothness. Specifically, in the metal laminate material of this invention, when the width of the protrusion of the metal foil is set as 'a' and the height of the protrusion is set as '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 value of the average value of b / a + 3σ indicates that the smaller the value, 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 high-frequency characteristics of the metal laminate material are excellent. When using rolled copper foil with an unroughened surface as the metal foil, the average value of b / a + 3σ can be set very small, typically 0.5 or less, preferably 0.3 or less, and more preferably 0.2 or less. It should be noted that in this invention, the minimum value of b / a is 0. In this invention, when the protrusion is so small that its width or height cannot be measured, b / a is set to 0. In this case, the average value of b / a +3σ is also 0. Therefore, in the metal laminate material of this invention, the average value of b / a +3σ is 0 or more and 2.5 or less. Furthermore, in this invention, even when no protrusion is observed on the surface of the metal foil through cross-section, b / a is set to 0.

[0088] The aspect ratio b / a of the protrusions of the metal foil is measured on the surface (bonding surface) of the low-dielectric film side of the metal foil. For example, in the case where the metal laminate has an intermediate layer between the low-dielectric film and the metal foil, the measurement is also performed on the surface of the low-dielectric film side of the metal foil.

[0089] The width 'a' and height 'b' of the protrusions on the metal foil can be measured as follows: First, a cross-sectional photograph of the metal laminate is obtained using a scanning electron microscope. In this cross-sectional photograph, the width 'a' and height 'b' of the protrusions are measured on the surface of the low-dielectric film side of the metal foil. Figure 5 A represents Figure 1 This is an enlarged schematic diagram of the cross-section of the metal laminate 1A shown. In the metal laminate 1A, a metal layer 10 made of metal foil is laminated on one surface of the low-dielectric film 20. Furthermore, Figure 5 B represents an enlarged schematic diagram of the cross-section of the convex portion of the metal foil. For example... Figure 5 As shown in Figure B, the protrusions of the metal foil are composed of metal particles that make up the foil. Each metal particle can be a single particle or... Figure 5 As shown in B, these are particles formed by the stacking of metal particles, such as secondary and even tertiary particles, which are formed from primary particles. For example... Figure 5 A and Figure 5 As shown in Figure B, the length of the straight line connecting the two starting points of the protrusion (the length of the bottom section of the first-stage particle) is defined as the width 'a' of the protrusion, and the length from this straight line to the apex of the protrusion (the apex of the final particle) is defined as the height 'b' of the protrusion. In this invention, the average value of b / a is used as an indicator of surface smoothness, and considering the deviation of 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.

[0090] In the metal laminate material of the present invention, the peel strength between the low-dielectric film and the metal layer is 3 N / cm or more, preferably 5 N / cm or more. When the peel strength is 3 N / cm or more, the reliability of fine wiring in the printed circuit board can be improved.

[0091] To measure the peel strength value, a test piece is first prepared using a metal laminate material. A 1 cm wide incision is made in the metal layer using a knife or similar tool. Then, after peeling off a portion of the metal layer and the low-dielectric film, the low-dielectric film is fixed to a support, and the metal layer is stretched at a speed of 50 mm / min in a 90° direction relative to the low-dielectric film. The force required for peeling at this point is defined as the peel strength (unit: N / cm). Furthermore, if the metal layer is thin and brittle, there is a risk of breakage when measuring the peel strength. In such cases, electroplating (e.g., copper plating if the metal layer is copper) can be performed on the surface of the metal layer to increase its thickness to approximately 5 μm to approximately 50 μm before measuring the peel strength. The method for measuring the peel strength value is the method specified in JJIS C6471.

[0092] In this specification, "peel strength between the low-dielectric film and the metal layer" refers to the peel strength when peeling at the interface between the low-dielectric film and the metal layer. It also refers to the peel strength when peeling occurs due to damage to the interior of the metal layer, and the peel strength when peeling occurs due to damage to the interior of the low-dielectric film. Furthermore, as mentioned above, when a coarsening particle layer, a rust-preventive layer, a heat-resistant layer, or a treatment layer using a silane coupling agent is laminated on the surface of the low-dielectric film side of the metal foil, the term also refers to the peel strength when peeling at the interface between the metal foil and the treatment layer, and the peel strength when peeling occurs due to damage to the interior of the treatment layer. Additionally, as mentioned above, when the metal laminate material has an intermediate layer, the term also refers to the peel strength when peeling at the interface between the metal foil and the intermediate layer, and the peel strength when peeling occurs due to damage to the interior of the intermediate layer.

[0093] B. Manufacturing methods for metallic laminated materials

[0094] The present invention also relates to a method for manufacturing the aforementioned metal laminate. The metal laminate of the present invention can be manufactured by a surface activation bonding method. By using the surface activation bonding method, metal foils can be laminated onto a low-dielectric film while maintaining their surface smoothness. Therefore, the metal laminate exhibits excellent high-frequency characteristics. Furthermore, through surface activation treatment, a strong bond is formed at the bonding interface, thus ensuring the tightness of the laminate interface without relying on the physical anchoring effect of coarsened particles, as is the case with metal laminates manufactured by thermal lamination.

[0095] 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 rolling the activated surface of the low-dielectric film and the activated surface of the metal foil together with a reduction rate of 0% to 30% (step 3-1). It should be noted that steps 1, 2 (steps 2-1 and 2-2), and 3-1 are performed sequentially, while steps 2-1 and 2-2 can be performed simultaneously or sequentially.

[0096] The metal laminate material of the second embodiment of the present invention has an intermediate layer containing metal between a low-dielectric film and a metal foil. The manufacturing method of the metal laminate material of the second embodiment, after step 2-1 of the manufacturing method of the metal laminate material of the first embodiment, includes: a step of forming an intermediate layer containing metal on an 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); and, as an alternative to step 3-1, a step of rolling the activated surface of the intermediate layer and the activated surface of the metal foil together with a reduction rate of 0% to 30% (step 3-2). In this case, steps 2-2 and 2-4 can be performed simultaneously or sequentially.

[0097] That is, the method for manufacturing the metal laminate material according to 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 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 rolling the activated surface of the intermediate layer and the activated surface of the metal foil together with a reduction rate of 0% to 30% (step 3-2).

[0098] In the method for manufacturing the metal laminate of the present invention, the steps of activating at least one surface of the low-dielectric film by sputter etching (step 2-1), activating the surface of the metal foil by sputter etching (step 2-2), forming an intermediate layer containing metal on the activated surface of the low-dielectric film as needed (step 2-3), activating the surface of the intermediate layer by sputter etching (step 2-4), rolling the activated surface of the low-dielectric film and the activated surface of the metal foil together with a reduction rate of 0% to 30% (step 3-1), and rolling the activated surface of the intermediate layer and the activated surface of the metal foil together with a reduction rate of 0% to 30% (step 3-2) can be performed at a temperature of 15°C to 100°C, preferably at a temperature of 15°C to 60°C, and more preferably at room temperature (15°C to 25°C). By performing these steps at room temperature, the low-dielectric film can be laminated while maintaining the smoothness of the metal foil surface.

[0099] Next, each step of the method for manufacturing the metal laminate material of the present invention will be described in detail.

[0100] 1. Preparation steps

[0101] In step 1, a low-dielectric film and a metal foil are prepared. The metal laminate material described above can be used as the low-dielectric film and the metal foil.

[0102] 2. Surface activation step and intermediate layer formation step

[0103] 2-A. Surface activation steps for low dielectric films

[0104] 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, as follows: the low-dielectric film is prepared as a long coil 100 mm to 600 mm wide; the bonding surface of the low-dielectric film is used as a grounded electrode; an alternating current of 1 MHz to 50 MHz is applied between the low-dielectric film and other electrodes with insulating support to generate a glow discharge; and the area of ​​the electrode exposed in the plasma generated by the glow discharge is set to less than 1 / 3 of the area of ​​the other electrodes. In the sputter etching process, the grounded electrode is shaped like a cooling roller to prevent the temperature of the transported material from rising.

[0105] In the sputtering etching process of the surface activation step, adsorbates on the bonding surface of the low-dielectric film are completely removed by sputtering the surface with an active gas or an inert gas under vacuum. As the active gas, oxygen or a mixture containing oxygen can be used. As the inert gas, argon, neon, xenon, krypton, nitrogen, etc., and mixtures containing at least one of these can be used. Oxygen is preferred as the gas for the sputtering etching process of the low-dielectric film. Compared with the use of inert gases such as argon and nitrogen, the peel strength between the low-dielectric film and the metal layer is higher when oxygen is used, especially when the metal laminate does not have an interlayer, the increase in peel strength is greater.

[0106] The sputtering etching process conditions can be appropriately set; for example, under vacuum, it can be performed with a plasma power of 100W to 10kW and a linear velocity of 0.5m / min to 30m / min. Even when using oxygen, the sputtering etching process conditions are, for example, under vacuum with a plasma power of 100W to 10kW and a linear velocity of 0.5m / min to 30m / min. To prevent adsorbates from re-adsorbing onto the surface, a high vacuum level is preferred, for example, 1×10⁻⁶. -5 Pa to 10 Pa is sufficient.

[0107] 2-B. Intermediate Layer Formation Steps

[0108] As needed, in step 2-3, a metal-containing intermediate layer is formed on the surface of the low-dielectric film activated in step 2-1. There are no particular limitations on the method for forming the intermediate layer; for example, a method of forming a sputtered layer by sputtering an intermediate layer containing metal onto the activated surface of the low-dielectric film is preferred. The conditions for sputtering film formation using this method can be appropriately set according to the type of metal constituting the intermediate layer and the thickness of the intermediate layer. Regarding the type of metal constituting the intermediate layer and the thickness of the intermediate layer, the metal laminate material is as described above.

[0109] 2-C. Surface activation steps for metal foil and intermediate layer

[0110] In step 2-2, the surface of the metal foil is activated by sputter etching. Additionally, if necessary, in step 2-4, the surface of the intermediate layer is activated by sputter etching.

[0111] Regarding the sputtering process in the surface activation step, it can be performed as follows: The metal foil to be bonded or the low-dielectric film with an interlayer is prepared as a long coil 100mm to 600mm wide. The bonding surface of the metal foil or interlayer is used as a grounded electrode. An alternating current of 1MHz to 50MHz is applied between the metal foil and the other electrodes with insulating support to generate a glow discharge. The area of ​​the electrode exposed in the plasma generated by the glow discharge is set to be less than 1 / 3 of the area of ​​the other electrodes. In the sputtering etching process, the grounded electrode is shaped like a cooling roller to prevent the temperature of the transported material from rising.

[0112] In the sputtering etching process of the surface activation step, the adsorbates on the surface are completely removed and part or all of the oxide layer is removed by sputtering the metal foil or the bonding surface of the low-dielectric film with the intermediate layer under vacuum using an inert gas. Complete removal of the oxide layer is preferred. Argon, neon, xenon, krypton, and mixtures containing at least one of these gases can be used as the inert gas. Depending on the type of metal, the adsorbates on the surface of the metal foil and the intermediate layer can be completely removed with an etching depth of about 1 nm, especially the oxide layer of copper, which can typically be removed with a depth of about 5 nm to 12 nm (SiO2 conversion).

[0113] The sputtering etching conditions can be appropriately set according to the type of metal foil and intermediate layer. For example, under vacuum, it can be performed with a plasma power of 100W to 10kW and a linear velocity of 0.5m / min to 30m / min. To prevent adsorbates from re-adsorbing onto the surface, a high vacuum level is preferred, for example, 1×10⁻⁶. -5 Pa to 10 Pa is sufficient.

[0114] It should be noted that when a coarsening particle layer and a rust-preventive layer are formed on the surface of the metal foil, the surface of these layers is activated by sputter etching. In this case, the coarsening particle layer and the rust-preventive layer can either be completely removed by sputter etching, or they can remain as is.

[0115] Additionally, nickel plating, chromate treatment, or silane coupling agent treatment can be applied to the surface of the metal foil or intermediate layer before activation by sputtering etching, as needed, to prevent oxidation and improve adhesion. Furthermore, the surface of the metal foil can be roughened as needed to improve adhesion to the low-dielectric film or intermediate layer.

[0116] 3. Rolling Joining Step

[0117] In steps 3-1 and 3-2, the pressing (roll bonding) of the surfaces activated by sputter etching can be performed by roll bonding. There are no particular limitations on the rolling line load for roll bonding; for example, it can be set in the range of 0.1 tf / cm to 10 tf / cm. However, in cases where the thickness of the metal foil or low-dielectric film before bonding is large, it is sometimes necessary to increase the rolling line load to ensure the pressure during bonding, and it is not limited to this value range. On the other hand, when the rolling line load is too high, not only the surface of the low-dielectric film, metal foil, or intermediate layer is prone to deformation, but the bonding interface is also prone to deformation, thus potentially reducing the thickness accuracy of each layer in the metal laminate. Furthermore, when the rolling line load is high, the processing deformation applied during bonding may increase.

[0118] The reduction rate during rolling bonding is set to 0% to 30%, preferably 0% to 15%. The surface activation bonding method described above reduces the reduction rate, thus preventing wrinkles and cracks and enabling the formation of a metal layer with excellent thickness accuracy. Furthermore, since the interface undulation between the metal foil and the low-dielectric film or interlayer is reduced, excellent thickness accuracy is achieved when sputtering etching is performed on the metal foil and the metal layer with the interlayer to form wiring, resulting in precise wiring. Additionally, the rolling bonding temperature is, for example, 15°C to 100°C, preferably 15°C to 60°C, and more preferably room temperature.

[0119] The bonding by roll forming is preferably carried out in a non-oxidizing atmosphere, such as a vacuum atmosphere or an inert gas atmosphere like Ar, to prevent the metal foil from re-absorbing oxygen, which would reduce the adhesion of the laminated interface.

[0120] The metal laminate obtained by pressing can be further heat-treated as needed, preferably. Heat treatment can remove deformation of the metal layers and improve the adhesion between the layers. The heat treatment temperature can be set within a range of -150°C to the melting point of the low-dielectric film and +10°C to the melting point of the low-dielectric film. For example, in the case of a liquid crystal polymer film, the temperature is 160°C to 350°C, preferably 160°C to 320°C, and more preferably 260°C to 320°C.

[0121] There are no particular restrictions on the atmosphere for heat treatment, but a vacuum atmosphere or an inert gas atmosphere such as N2 or Ar is preferred. This is because it can prevent the metal layer from oxidizing due to heat treatment, which would reduce the adhesion between the metal layer and the low-dielectric film.

[0122] If the adhesion between the metal layer and the low-dielectric film can be sufficiently improved, there is no particular limitation on the heat treatment time. For example, the soaking time is preferably 0 seconds to 25,200 seconds, more preferably 0 seconds to 18,000 seconds, and particularly preferably 180 seconds to 15,000 seconds. This is because setting the time above the lower limit of these ranges ensures sufficient adhesion between the metal layer and the low-dielectric film; setting the time below the upper limit of these ranges enables high production efficiency and low cost of the metal laminate material. It should be noted that even if the soaking time is 0 seconds (i.e., cooling immediately after reaching the target temperature without soaking time), the adhesion between the metal layer and the low-dielectric film can still be sufficiently improved.

[0123] Examples of methods for performing heat treatment include: using an intermittent heat treatment furnace, maintaining the metal laminate at a desired heat treatment temperature for a desired time only in a desired atmosphere (e.g., a vacuum atmosphere or an inert gas atmosphere such as N2 or Ar). Alternatively, depending on the heat treatment temperature and atmosphere, a continuous heat treatment furnace can be used to perform heat treatment in a roll-to-roll manner. In this case, examples include: using a desired atmosphere (e.g., a vacuum atmosphere or an inert gas atmosphere such as N2 or Ar), maintaining at least the heating and cooling sections within the continuous heat treatment furnace at a desired temperature, and then passing the metal laminate through the heating and cooling sections at a desired speed, thereby maintaining the metal laminate at the desired heat treatment temperature for a desired time only.

[0124] C. Use of metallic laminated materials

[0125] The metal laminate material of the present invention can be used as a metal-clad laminate for fabricating flexible printed circuit boards.

[0126] Using the metal laminate material of the present invention, a printed circuit board with fine wiring can be obtained. Therefore, the present invention also relates to a printed circuit board formed by forming circuits on a metal laminate material. In the wiring formation step, an additional metal layer may be formed only in the wiring portion. Specifically, existing known methods such as modified semi-additive process (MSAP), semi-additive process (SAP), and subtractive process can be appropriately used to obtain the printed circuit board. For example, when using the modified semi-additive process (MSAP), the non-wiring portion of the metal layer in the metal laminate material is masked, copper plating is performed on the uncovered portion to form an additional metal layer, and then the mask is removed, and the metal layer hidden by the mask is removed by etching, thereby manufacturing a printed circuit board. It should be noted that the "printed circuit board" in the present invention includes not only a laminate with wiring formed, but also a laminate on which electronic components such as ICs are mounted after wiring is formed.

[0127] Figures 1-4The text describes a case where a metal layer is stacked on one surface of a low-dielectric film in a metal laminate material, but the metal laminate material is not limited to this. That is, metal layers can be disposed on both surfaces of the low-dielectric film as needed. By using a metal laminate material with metal layers disposed on both surfaces of the low-dielectric film, a flexible printed circuit board with wiring formed on both surfaces of the low-dielectric film can be obtained.

[0128] Example

[0129] The present invention will be further described in detail below based on embodiments and comparative examples, but the present invention is not limited to these embodiments.

[0130] (Example 1)

[0131] First, a 25 μm thick liquid crystal polymer film (Vexter CTQ manufactured by Kuraray Co., Ltd.) and an 18 μm thick rolled copper foil (HA-V2 manufactured by JX Metals Co., Ltd.) were prepared as the metal foil. Then, one surface of the liquid crystal polymer film was activated by oxygen-based sputtering etching. A 5 nm NiCr alloy sputtered layer was then sputtered onto this activated surface as the base layer, and a 10 nm Cu sputtered layer was sputtered as the top layer, forming an intermediate layer (hereinafter also referred to as the Cu / NiCr alloy intermediate layer). Next, the surfaces of the intermediate layer and the rolled copper foil were activated by Ar gas-based sputtering etching. The activated surfaces of the intermediate layer and the rolled copper foil were rolled together with a line load of 1.5 tf / cm to form a metal laminate. The reduction rate was 2.3%. Then, the metal laminate was heat-treated at 300°C to obtain the metal laminate of Example 1 (layer composition: rolled copper foil / intermediate layer / liquid crystal polymer film).

[0132] (Example 2)

[0133] Except for using rolled copper foil (C1020R-H manufactured by Mitsui Sumitomo Metal Mining Shindoh Co., Ltd.) with a thickness of 16μm as the rolled copper foil, the same as in Example 1, the metal laminate material of Example 2 (layer composition: rolled copper foil / intermediate layer / liquid crystal polymer film) was made.

[0134] (Example 3)

[0135] First, a 25 μm thick liquid crystal polymer film (Vexter CTQ manufactured by Kuraray Co., Ltd.) was prepared, and the rolled copper foil (HA-V2 manufactured by JX Metals Co., Ltd.) used in Example 1 was prepared as the metal foil. Then, one surface of the liquid crystal polymer film was activated by oxygen-based sputtering etching, and the surface of the rolled copper foil was activated by Ar gas-based sputtering etching. The activated surfaces of the liquid crystal polymer film and the rolled copper foil were rolled together with a line load of 1.5 tf / cm to form a metal laminate. The reduction rate was 2.3%. Then, the metal laminate was heat-treated at 320°C to obtain the metal laminate of Example 3 (layer composition: rolled copper foil / liquid crystal polymer film).

[0136] (Example 4)

[0137] Except for using the rolled copper foil (C1020R-H manufactured by Mitsui Sumitomo Metal Mining Shindoh Co., Ltd.) as the rolled copper foil used in Example 2, the same as in Example 3, the metal laminate material of Example 4 (layer composition: rolled copper foil / liquid crystal polymer film) was obtained.

[0138] (Example 5)

[0139] Except for using a liquid crystal polymer film with a thickness of 50 μm (Vexter CTQ manufactured by Kuraray Co., Ltd.), the same as in Example 4, the metal laminate material of Example 5 (layer composition: rolled copper foil / liquid crystal polymer film) was obtained.

[0140] (Example 6)

[0141] First, a 25 μm thick liquid crystal polymer film (Vexter CTQ manufactured by Kuraray Co., Ltd.) was prepared. A copper foil (MT18FL manufactured by Mitsui Metals & Mining Co., Ltd.) with a carrier layer, consisting of an 18 μm thick copper carrier layer, an extremely thin copper layer of 1.5 μm thickness, and a coarsening particle layer and an anti-rust layer on its surface, was prepared as the metal foil. Then, after activating one surface of the liquid crystal polymer film by oxygen-based sputtering etching, a Cu / NiCr alloy interlayer was sputtered onto this activated surface in the same manner as in Example 1. Next, the surfaces of the interlayer and the extremely thin copper layer were activated by Ar gas-based sputtering etching. The activated surfaces of the interlayer and the extremely thin copper layer were then rolled together with a line load of 1.5 tf / cm to form a metal laminate. The reduction rate was 3.4%. Then, the metal laminate was subjected to a heat treatment at 300°C to obtain the metal laminate of Example 6 (layer composition: copper foil with carrier / intermediate layer / liquid crystal polymer film).

[0142] (Example 7)

[0143] Except for using a copper foil with a carrier (prototype A) on a carrier layer with a thickness of 18 μm made of copper, with an extremely thin copper layer of 2 μm separated by a release layer (inorganic release layer) and an anti-rust layer on its surface, the same as in Example 6, the metal laminate material of Example 7 (layer composition: copper foil with carrier / intermediate layer / liquid crystal polymer film) was obtained.

[0144] (Example 8)

[0145] First, a 25 μm thick liquid crystal polymer film (Vexter CTQ manufactured by Kuraray Co., Ltd.) was prepared, and a carrier-supported copper foil (MT18FL manufactured by Mitsui Metal Mining Co., Ltd.) used in Example 6 was prepared as the metal foil. Then, one surface of the liquid crystal polymer film was activated by oxygen-based sputtering etching, and the surface of the extremely thin copper layer of the carrier-supported copper foil was activated by Ar gas sputtering etching. The activated surface of the liquid crystal polymer film and the activated surface of the extremely thin copper layer were rolled together with each other at a line load of 1.5 tf / cm to form a metal laminate. The reduction rate was 3.4%. Then, the metal laminate was heat-treated at 300°C to obtain the metal laminate of Example 8 (layer composition: carrier-supported copper foil / liquid crystal polymer film).

[0146] (Example 9)

[0147] Except for the use of a copper foil (MT18EX manufactured by Mitsui Metals & Mining Co., Ltd.) as the carrier copper foil, which has an extremely thin copper layer of 2 μm thickness on a carrier layer of 18 μm thickness with an interlayer of release layer (organic release layer) and a coarsening particle layer and an anti-rust layer on its surface, the same as in Example 8, the metal laminate material of Example 9 (layer composition: carrier copper foil / liquid crystal polymer film) was obtained.

[0148] (Example 10)

[0149] Except for the use of a copper foil (MT18SD-H manufactured by Mitsui Metals & Mining Co., Ltd.) as the carrier copper foil, which has an extremely thin copper layer of 5 μm thickness provided between a carrier layer (organic release layer) and a coarsening particle layer and an anti-rust layer provided on its surface, the same as in Example 8, the metal laminate material of Example 10 (layer composition: carrier copper foil / liquid crystal polymer film) was obtained.

[0150] (Example 11)

[0151] Except for using the carrier-bearing copper foil (prototype material A) used in Example 7 as the carrier-bearing copper foil, the same as in Example 8, the metal laminate material of Example 11 (layer composition: carrier-bearing copper foil / liquid crystal polymer film) was obtained.

[0152] (Example 12)

[0153] Except for the use of a copper foil (MT18GN manufactured by Mitsui Metals & Mining Co., Ltd.) as the carrier copper foil, which has an extremely thin copper layer of 1.5 μm thickness on a carrier layer with an interval of a release layer (organic release layer) and a coarsening particle layer and an anti-rust layer on its surface, the same as in Example 8, the metal laminate material of Example 12 (layer composition: carrier copper foil / liquid crystal polymer film) was obtained.

[0154] (Example 13)

[0155] Except for using a copper foil (FUTF-7DAF-5 manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.) as the carrier copper foil, which has an extremely thin copper layer of 2 μm thickness on a carrier layer of 18 μm thickness with an interval between a release layer (inorganic release layer) and a coarsening particle layer and an anti-rust layer on its surface, the same as in Example 8, the metal laminate material of Example 13 (layer composition: carrier copper foil / liquid crystal polymer film) was obtained.

[0156] (Example 14)

[0157] A 50 μm thick liquid crystal polymer film (Vexter CTQ manufactured by Kuraray Co., Ltd.) and a 12 μm thick electrolytic copper foil (CF-T9DA-SV manufactured by Fukuda Metal Foil Powder Co., Ltd.) were prepared as the metal foil. One surface of the liquid crystal polymer film was activated by oxygen-based sputtering etching, and the surface of the electrolytic copper foil was activated by Ar gas-based sputtering etching. The activated surfaces of the liquid crystal polymer film and the electrolytic copper foil were rolled together with a line load of 1.5 tf / cm to form a metal laminate. The reduction rate was 2.3%. The metal laminate was then heat-treated at 320°C to obtain the metal laminate of Example 14 (layer composition: electrolytic copper foil / liquid crystal polymer film).

[0158] (Example 15)

[0159] Except for using an electrolytic copper foil (CF-PLFA manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.) with a thickness of 12 μm, which is made of copper, as in Example 14, the metal laminate material of Example 15 (layer composition: electrolytic copper foil / liquid crystal polymer film) was obtained.

[0160] (Example 16)

[0161] Except for using a 25 μm thick liquid crystal polymer film (Vexter CTQ manufactured by Kuraray Co., Ltd.) and an 18 μm thick electrolytic copper foil (CF-V9S-SV manufactured by Fukuda Metal Foil Powder Co., Ltd.) as the electrolytic copper foil, the same as in Example 14 was used to obtain the metal laminate material of Example 16 (layer composition: electrolytic copper foil / liquid crystal polymer film).

[0162] (Comparative Example 1)

[0163] By hot lamination, a rolled copper foil with a thickness of 18 μm having a treatment layer consisting of a roughened particle layer, etc., is hot-pressed at a temperature of 310°C or higher onto the two surfaces of a liquid crystal polymer film (Vexter CTQ manufactured by Kuraray Co., Ltd.) with a thickness of 50 μm, thereby producing a metal laminate material of Comparative Example 1 [Layer composition: rolled copper foil (with roughening treatment) / liquid crystal polymer film / rolled copper foil (with roughening treatment)].

[0164] (Comparative Example 2)

[0165] Except for using an electrolytic copper foil with a thickness of 18 μm having a treatment layer consisting of a coarsened particle layer on one side as the rolled copper foil, the same as in Comparative Example 1, a metal laminate material (layer composition: electrolytic copper foil / liquid crystal polymer film / electrolytic copper foil) was made as in Comparative Example 2.

[0166] For the metal laminates of Examples 1-16 and Comparative Examples 1-2, cross-sectional photographs of the metal laminates were obtained using a scanning electron microscope (20,000x magnification). In the obtained cross-sectional photographs of the metal laminates, Figures 6 to 13 These are cross-sectional photographs of the metal laminates in Examples 1-4, 6-8, and 14, respectively. Figure 14 and Figure 15 The images show cross-sectional photographs of the metal laminates of Comparative Example 1 and Comparative Example 2, respectively. Furthermore, the following properties were evaluated for the metal laminates of Examples 1-16 and Comparative Examples 1-2.

[0167] [Aspect ratio of the raised portion of the metal foil]

[0168] As described in the project “A. Metallic Laminated Materials”, in the obtained cross-sectional photographs of the metallic laminated materials, the width a and height b of the copper foil protrusions were measured on the surface of the copper foil on the side of the liquid crystal polymer film.

[0169] As an example of using rolled copper foil, a cross-sectional photograph of the metal laminate material used in Example 3 is shown. Figure 8 Please provide an explanation. For example... Figure 8 As shown, in copper foil ( Figure 8Liquid crystal polymer film of HA-V2 ( Figure 8 On the surface of the LCP side, the width 'a' of the protrusion, which is the length of the straight line connecting the two points where the protrusion begins to the copper foil, and the height 'b' of the protrusion, which is the length from the straight line to the apex of the protrusion, are measured for each protrusion. Based on the measured width 'a' and height 'b', the average value of b / a is calculated. Then, considering the deviation of the value, the average value of b / a + 3σ is calculated (where σ is the standard deviation of b / a).

[0170] Additionally, as an example of using copper foil with a carrier, a cross-sectional photograph of the metal laminate material from Example 8 is shown below. Figure 12 Please provide an explanation. For example... Figure 12 As shown, in the copper foil with carrier ( Figure 12 The liquid crystal polymer film with an ultra-thin copper layer (MT18FL) Figure 12 On the surface of the LCP side, measure the width a of the protrusion, which is the length of the straight line connecting the two points where the protrusion begins, and the height b of the protrusion, which is the length from the straight line to the apex of the protrusion. Calculate the average value of b / a + 3σ as described above.

[0171] [Transmission Loss (S21)]

[0172] To evaluate the high-frequency transmission characteristics of the metal laminate materials of Example 5 and Comparative Example 2, transmission loss was measured (S21). Since Example 5 is a single-sided material, a copper layer was formed on the exposed surface of the liquid crystal polymer film opposite to the side with the laminated rolled copper foil using electroless copper plating. Electrolytic copper plating was performed after creating through-holes, thereby obtaining a measurement sample with copper layers (25 μm) on both sides. For the metal laminate material of Comparative Example 2, electrolytic copper plating was performed after creating through-holes, thereby obtaining a measurement sample with copper layers (25 μm) on both sides.

[0173] The transmission line uses a single-ended microstrip transmission line with a height of 25 μm, a width of 110 μm, and a length of 100 mm. Measurements were performed using a network analyzer E8363B (manufactured by Keysight Technologies) at a frequency of 40 GHz. It should be noted that in Example 5, the microstrip line was fabricated on the side of a laminated rolled copper foil for measurement.

[0174] [Peel strength]

[0175] Test specimens were prepared using a metal laminate material, and 1 cm wide incisions were made in the metal layer using a knife or similar tool. Then, a portion of the metal layer was peeled off from the liquid crystal polymer film. The liquid crystal polymer film was then fixed to a support, and the metal layer was stretched at a speed of 50 mm / min in a 90° direction relative to the liquid crystal polymer film. The force required for peeling at this point was defined as the peel strength (unit: N / cm). Additionally, for the metal laminate materials of Examples 6-13, after removing the carrier layer and release layer containing the copper foil to expose an extremely thin copper layer, an 18 μm thick electrolytic copper plating was performed on the surface of the extremely thin copper layer to increase its thickness. The peel strength between the metal layer and the liquid crystal polymer film was then measured.

[0176] The composition and evaluation results of the metal laminates of Examples 1-16 and Comparative Examples 1-2 are shown in Table 1. It should be noted that in Table 1, LCP represents a liquid crystal polymer film.

[0177] Table 1

[0178]

[0179] like Figures 6-15 As shown, it can be seen that the metal laminates of Comparative Example 1 and Comparative Example 2, which were fabricated by thermal lamination (respectively...), are... Figure 14 and Figure 15 The coarsened copper foil particles in the liquid crystal polymer film are deeply embedded, resulting in increased unevenness at the bonding interface. In contrast, the metal laminates of Examples 1-4 and 14, which are made using surface-activated bonding with smooth rolled or electrolytic copper foil, respectively... Figures 6-9 and Figure 13 The interface between the copper foil and the liquid crystal polymer film in the composite becomes very smooth. Furthermore, it can be seen that, compared to the metal laminates of Comparative Examples 1-2, the metal laminates of Examples 6-8 (which are respectively) prepared using a carrier-supported copper foil with a surface-activated bonding method having a coarsened particle layer and a rust-preventive layer on the surface, exhibit significantly smoother surfaces. Figures 10-12 In the case of copper foil, the convex portion of the copper foil surface is buried at a relatively shallow depth. This indicates that by using surface activation bonding, metal foil can be laminated onto a low-dielectric film while maintaining its surface smoothness.

[0180] This can also be confirmed by the aspect ratio (average 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, this value is very small for the metal laminate materials of Examples 1-5 using rolled copper foil with a smooth surface. In addition, this value is also significantly smaller for the metal laminate materials of Examples 6-13 using copper foil with a carrier and for the metal laminate materials of Examples 14-16 using electrolytic copper foil. Therefore, it shows that in the metal laminate materials of Examples 1-16 produced by surface activation bonding, the surface unevenness of the rolled copper foil, the copper foil with a carrier, or the electrolytic copper foil is small, and the surface is smoother.

[0181] Regarding the high-frequency transmission characteristics of the metal laminate, as shown in Table 1, the average value of b / a +3σ of the protrusion is smaller. Compared with the metal laminate of Comparative Example 2, the metal laminate of Example 5, with its smooth copper foil surface, exhibits lower transmission loss (S21) at high frequencies, demonstrating excellent high-frequency characteristics. Generally speaking, if the metal foil surface of the metal laminate is smooth, transmission loss can be suppressed. Therefore, it can be inferred that the high-frequency transmission characteristics of the metal laminates of Examples 1-4 and Examples 6-16 are also as excellent as those of the metal laminate of Example 5.

[0182] Regarding the peel strength between the liquid crystal polymer film and the metal layer of the metal laminate, as shown in Table 1, compared with the metal laminates of Comparative Examples 1 and 2, the copper foil surface of the metal laminates of Examples 1 to 16 is smooth, while the peel strength is equal or higher. This is because, in the metal laminates of Examples 1 to 16, a strong bond is formed at the interface between the liquid crystal polymer film and the copper foil through surface activation treatment, thus ensuring the tightness of the laminate interface without relying on the physical anchoring effect of coarsened particles.

[0183] These results indicate that, compared to the metal laminates of Comparative Examples 1 and 2 prepared by thermal lamination, the metal laminates of Examples 1-16 prepared by surface activation bonding have equal or greater peel strength between the metal layer and the liquid crystal polymer film, and exhibit superior high-frequency characteristics due to the smoother surface of the metal foil.

[0184] The influence of gases used in sputter etching of liquid crystal polymer films

[0185] By changing the type of gas used to activate the liquid crystal polymer film via sputter etching, the effect on the peel strength of the metal laminate was confirmed.

[0186] Metal laminates with intermediate layers

[0187] Oxygen, Ar, and nitrogen were used as the gases for sputtering etching of the liquid crystal polymer film. The metal laminate material from Example 2 was used as the sample when oxygen was used.

[0188] (Example 17)

[0189] Except for using Ar gas as the sputtering etching gas for the liquid crystal polymer film, the same as in Example 2, the metal laminate material of Example 17 was obtained.

[0190] (Example 18)

[0191] Except for using nitrogen as the gas for sputtering and etching the liquid crystal polymer film, the same as in Example 2, the metal laminate material of Example 18 was obtained.

[0192] Metal laminates without an intermediate layer

[0193] Oxygen, Ar, and nitrogen were used as the gases for sputtering etching of the liquid crystal polymer film. The metal laminate material of Example 4 was used as the sample when oxygen was used.

[0194] (Comparative Example 3)

[0195] Except for using Ar gas as the sputtering etching gas for the liquid crystal polymer film, the same metal laminate material as in Example 4 was obtained in Comparative Example 3.

[0196] (Comparative Example 4)

[0197] Except for using nitrogen as the gas for sputtering and etching the liquid crystal polymer film, the metal laminate material of Comparative Example 4 was obtained in the same manner as in Example 4.

[0198] Regarding the fabricated metal laminate, the peel strength between the liquid crystal polymer film and the metal layer was measured as described above. The results showed that for the metal laminate with an intermediate layer, the peel strength was 8.2 N / cm in Example 2 (oxygen), 5.4 N / cm in Example 17 (Ar gas), and 7.9 N / cm in Example 18 (nitrogen gas). Furthermore, for the metal laminate without an intermediate layer, the peel strength was 7.6 N / cm in Example 4 (oxygen), 1.0 N / cm in Comparative Example 3 (Ar gas), and 2.2 N / cm in Comparative Example 4 (nitrogen gas). Therefore, when oxygen is used for sputtering etching of the liquid crystal polymer film, the peel strength tends to be higher compared to the cases using Ar gas and nitrogen gas; the increase in peel strength is greater for the metal laminate without an intermediate layer than for the metal laminate with an intermediate layer.

[0199] Symbol Explanation

[0200] 1A Metal laminate material

[0201] 1B Metallic laminated materials

[0202] 1C Metallic laminates

[0203] 1D Metallic Laminates

[0204] 10 Metal Layers

[0205] 11 metal foil

[0206] 12. Carrier layer

[0207] 13. Peel-off layer

[0208] 14. Extremely thin metal layer

[0209] 15. Intermediate Layer

[0210] 20 Low Dielectric Film

[0211] All publications, patents, and patent applications referenced in this specification are incorporated herein by direct reference.

Claims

1. A metal laminate which is a metal laminate in which a metal layer composed of at least one layer containing a metal foil is laminated on at least one surface of a low dielectric film, wherein the metal laminate does not have an intermediate layer containing a metal between the low dielectric film and the metal foil, a plurality of projections of the metal foil are formed on a surface of the metal foil on the low dielectric film side, a width of the projections is set as a, a height of the projections is set as b, σ is set as a standard deviation of b / a, an average value of b / a + 3σ is 2.5 or less, and a peeling strength of the low dielectric film and the metal layer is 3 N / cm or more, the metal foil is a rolled metal foil or an electrolytic metal foil. The metal laminate does not have a sputtering layer composed of copper, nickel, chromium, or an alloy thereof between the low dielectric film and the metal foil. The metal foil is a rolled copper foil or an electrolytic copper foil.

4. A method of manufacturing a metal laminate which is a metal laminate in which a metal layer composed of at least one layer containing a metal foil is laminated on at least one surface of a low dielectric film, wherein the metal laminate does not have an intermediate layer containing a metal between the low dielectric film and the metal foil, a plurality of projections of the metal foil are formed on a surface of the metal foil on the low dielectric film side, a width of the projections is set as a, a height of the projections is set as b, σ is set as a standard deviation of b / a, an average value of b / a + 3σ is 2.5 or less, and a peeling strength of the low dielectric film and the metal layer is 3 N / cm or more, the metal foil is a rolled metal foil or an electrolytic metal foil, the method comprising: a step of preparing the low dielectric film and the metal foil; a step of activating at least one surface of the low dielectric film by sputter etching using oxygen; a step of activating a surface of the metal foil by sputter etching; and a step of roll-bonding the activated surface of the low dielectric film and the activated surface of the metal foil to each other at a reduction ratio of 0% to 30%.

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

3. The metal laminate material according to claim 1 or 2, wherein The metal foil is a rolled copper foil or an electrolytic copper foil. The temperature of the step of roll-bonding is 15°C or higher and 100°C or lower. wherein After the roll-bonding, heat treatment is performed at a temperature of the melting point of the low dielectric film or higher and the melting point + 10°C or lower.

9. A printed wiring board which is produced by forming a circuit on the metal laminate described in any one of claims 1 to 3. ​ ​ ​ ​ ​ ​ 5. The method of manufacturing a metal laminate material according to claim 4, wherein ​ 6. The method of manufacturing a metal laminate according to claim 4 or 5, wherein ​ 7. The method of producing a metal laminate according to claim 4 or 5, wherein ​ 8. The method of manufacturing a metal laminate according to claim 4 or 5, wherein ​ ​

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