WO2024219326A1

WO2024219326A1 - Metal laminate, method for manufacturing same, and printed wiring board

Info

Publication number: WO2024219326A1
Application number: PCT/JP2024/014800
Authority: WO
Inventors: 貴文畠田; 光司南部; 由和丸橋
Original assignee: 東洋鋼鈑株式会社
Priority date: 2023-04-19
Filing date: 2024-04-12
Publication date: 2024-10-24

Abstract

The purpose of the present invention is to provide a metal laminate that exhibits both high frequency characteristics and high adhesiveness at a lamination interface.　The present invention relates to a metal laminate comprising a metal layer that includes at least one layer including a metal foil, the metal layer being laminated on at least one surface of a low dielectric film. In an interface between the low dielectric film and the metal layer of the metal laminate, a metal included in a range of less than or equal to 1.3 μm from the surface of the metal layer on the low dielectric film side toward the metal layer side is a non-magnetic metal, and the peel strength of the low dielectric film and the metal layer is greater than or equal to 1.0 N/cm. The present invention also relates to a method for manufacturing the metal laminate and a printed wiring board.

Description

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

The present invention relates to a metal laminate material, a manufacturing method thereof, and a printed wiring board.

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

A metal laminate material is generally known that is produced using a thermal lamination method in which a metal foil with a roughened surface is thermally compressed from the viewpoint of adhesion to a low dielectric film. For example, Patent Document 1 discloses such a metal laminate material as a treated copper foil for copper-clad laminates having a roughened layer on at least one surface of untreated copper foil and an oxidation-resistant layer on the roughened layer, the oxidation-resistant layer containing molybdenum and cobalt, and a copper-clad laminate in which the treated copper foil for copper-clad laminates is laminated to an insulating resin substrate.

In addition, in the thermal lamination method, in order to ensure adhesion between the low dielectric film and the metal layer during the thermocompression bonding process, a layer containing a metal such as nickel (Ni) or cobalt (Co) is formed on the surface of the low dielectric film and then bonded to a metal foil. However, if ferromagnetic metals (also called high magnetic permeability metals) such as Ni and Co are present at the lamination interface between the low dielectric film and the metal layer, the transmission characteristics of the metal laminate material in the high frequency band deteriorate.

JP 2016-149438 A

As mentioned above, in conventional metal laminate materials produced by thermal lamination, the presence of ferromagnetic metals such as Ni and Co at the lamination interface between the low dielectric film and the metal layer can result in insufficient high-frequency characteristics. Therefore, the object of the present invention is to provide a metal laminate material that combines high-frequency characteristics with adhesion at the lamination interface.

As a result of intensive research to solve the above problems, the present inventors have found that by using a material that does not have a ferromagnetic metal on its surface to produce a metal laminate by a surface activated bonding method, it is possible to achieve both high frequency characteristics and adhesion at the laminate interface, and have completed the invention. That is, 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, wherein at the interface between the low dielectric film and the metal layer, the metal contained within a range of 1.3 μm or less from the surface of the metal layer on the low dielectric film side toward the metal layer side is made of a non-magnetic metal, and the peel strength of the low dielectric film and the metal layer is 1.0 N/cm or more.
(2) The metal laminate material according to (1) above, wherein the arithmetic mean height Sa of the surface on the metal layer side of the low dielectric film is 60 nm or less.
(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) The metal laminate material according to any one of (1) to (3), wherein the metal layer has a chromate treatment layer between the low dielectric film and the metal foil.
(5) The metal laminate material according to any one of (1) to (4), wherein the metal layer does not have an organic layer on the surface on the low dielectric film side.
(6) 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,
At the interface between the low dielectric film and the metal layer, a metal included in a range of 1.3 μm or less from the surface of the metal layer on the low dielectric film side toward the metal layer side is made of a nonmagnetic metal, and the peel strength between the low dielectric film and the metal layer is 1.0 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;
and rolling-bonding the activated surfaces of the low dielectric film and the metal foil together at a rolling reduction of 0 to 30%.
(7) The method for producing a metal laminate material according to (6) above, wherein the arithmetic mean height Sa of the surface of the low dielectric film on the metal layer side in the metal laminate material is 60 nm or less.
(8) The method for producing a metal laminate material according to (6) or (7), wherein the metal foil is a rolled copper foil, a copper foil with a carrier, or an electrolytic copper foil.
(9) The method for producing a metal laminate material according to any one of (6) to (8), wherein the metal foil has a chromate treatment layer on a surface thereof.
(10) The method for producing a metal laminate material according to any one of (6) to (9), wherein at least one surface of the low dielectric film is activated by sputter etching with oxygen.
(11) The method for producing a metal laminate material according to any one of (6) to (10), wherein the step of activating the surface of the metal foil by sputter etching includes removing an organic layer from the surface of the metal foil.
(12) A printed wiring board having a circuit formed on the metal laminate material according to any one of (1) to (5) above.
This specification includes the disclosure of Japanese Patent Application No. 2023-068300, which is the priority basis of this application.

The present invention makes it possible to provide a metal laminate material that combines high-frequency characteristics with adhesion at the laminate interface.

1 is a schematic cross-sectional view showing a metal laminate material according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a metal laminate according to another embodiment of the present invention. 1 is a schematic cross-sectional view showing a metal laminate material having a chromate treatment layer according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a metal laminate having a chromate treatment layer according to another embodiment of the present invention. The cross-sectional views of the metal laminate materials of Example 1 and Comparative Examples 2 and 3 showing the presence or absence of voids at the bonding interface are shown.

The present invention will be 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 a low dielectric film having a metal layer laminated on one surface thereof, and a low dielectric film having a metal layer laminated on both surfaces thereof. In the metal laminate material of the present invention, the metal contained at the interface between the low dielectric film and the metal layer is made of a non-magnetic metal, and no ferromagnetic metal is present at the interface. Therefore, the metal laminate material has excellent high frequency characteristics, and the low dielectric film and the metal layer have sufficient adhesion.

A. Metal Laminated Material Fig. 1 is a schematic cross-sectional view showing a metal laminated material according to one embodiment of the present invention. As shown in Fig. 1, the metal laminated material 1A has a metal layer 10 made of a metal foil laminated on one surface of a low dielectric film 20.

Figure 2 is a schematic cross-sectional view showing another embodiment of a metal laminate of the present invention. In this embodiment, a carrier-attached metal foil having an extremely thin metal layer, a release layer, and a carrier layer is used as the metal foil. As shown in Figure 2, the metal laminate 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 extremely thin metal layer 14, release layer 13, and carrier layer 12 from the low dielectric film 20 side.

The components of the metal laminate material of the present invention are described in detail below.

1. Low-dielectric film The low-dielectric film may be made of any low-dielectric polymer material that can be used as a flexible substrate, such as a material with a relative dielectric constant _εr of 3.3 or less and a dielectric loss tangent tanδ of 0.006 or less, but is not limited thereto. Specifically, the low-dielectric film may be appropriately selected from materials such as liquid crystal polymer, polyethylene fluoride (fluorine-based resin such as polytetrafluoroethylene), polyamide, isocyanate compound, polyamideimide, polyimide, low-dielectric constant polyimide, polyethylene terephthalate, polyetherimide, and cycloolefin polymer. Preferably, the low-dielectric film is a liquid crystal polymer, polyethylene fluoride, polyamide, or low-dielectric constant polyimide, and more preferably, a liquid crystal polymer. The low-dielectric film is a single-layer film or a laminate consisting of multiple layers, and in the case of a multiple-layer film, at least one of the multiple layers may be a layer consisting of the low-dielectric polymer material. Layers other than the layer consisting of the low-dielectric polymer material may be made of various conventionally known materials such as epoxy resin. The liquid crystal polymer refers to an aromatic polyester resin having a basic structure such as parahydroxybenzoic acid, which exhibits liquid crystal properties in a molten state.

The thickness of the low dielectric film can be appropriately set according to the application of the metal laminate. For example, when used as a flexible printed wiring board, the thickness is usually 10 μm to 150 μm, preferably 25 μm to 150 μm, more preferably 25 μm to 120 μm, and particularly preferably 25 μm to 100 μm. The thickness of the low dielectric film refers to the average value of the values obtained by taking an optical microscope photograph of the cross section of the metal laminate and measuring the thickness of the low dielectric film at any 10 points on the optical microscope photograph. The thickness of the low dielectric film before bonding can be measured with 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. In addition, for the low dielectric film used, the deviation from the average value of the measured values at 10 points is preferably within 20% for all measured values, more preferably within 10%.

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

The metal foil is preferably a rolled metal foil, a metal foil with a carrier, or an electrolytic metal foil, and more preferably a rolled copper foil, a copper foil with a carrier, or an electrolytic copper foil. The metal foil may be a single-layer foil or a laminated foil of these.

When a rolled metal foil or an electrolytic metal foil is used as the metal foil, the type of metal constituting the 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. Metal foils made of non-magnetic metals such as copper, zinc, tin, chromium, gold, silver, platinum, and titanium are preferred as the metal foil, and copper foil or copper alloy foil is particularly preferred. The copper alloy foil referred to here is one made of copper and a non-magnetic metal. This is because, for example, a flexible substrate for forming fine wiring can be obtained by rolling and joining these with a low dielectric film. When the metals constituting the metal foil include ferromagnetic metals such as iron, nickel, cobalt, and alloys thereof, it is desirable to use a laminate foil having a layer made of a non-magnetic metal on the upper layer of the surface of the low dielectric film side of the metal foil. By laminating such a laminate foil and a low dielectric film, it is possible to prevent the presence of ferromagnetic metals at the lamination interface of the metal laminate material. Examples of non-magnetic metals include copper, zinc, tin, chromium, gold, silver, platinum, and titanium.

When a rolled metal foil or an electrolytic metal foil is used as the metal foil, the thickness of the metal foil is not particularly limited because it varies depending on the application of the metal laminate material. For example, for flexible printed wiring board applications, the thickness is preferably 3 μm to 100 μm, more preferably 10 μm to 50 μm, and particularly preferably 10 μm to 35 μm. In addition, in the case of a laminated foil having a layer composed of a nonmagnetic metal on the upper layer of the surface on the low dielectric film side of the metal foil, the thickness of the nonmagnetic metal layer composed on the upper layer of the surface on the low dielectric film side of the metal foil is preferably 1.3 μm to 50 μm, more preferably 1.3 μm to 15 μm, and particularly preferably 1.5 μm to 10 μm. Here, the thickness of the metal foil or nonmagnetic metal layer 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 metal foil or nonmagnetic metal layer at any 10 points on the optical microscope photograph.

When 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 Co., Ltd. and C1020R-H manufactured by Mitsui Sumitomo Metal Mining Co., Ltd. When electrolytic copper foil is used as the metal foil, the electrolytic copper foil is not particularly limited, but examples thereof include CF-PLFA manufactured by Fukuda Metal Foil and Powder Co., Ltd.

When producing a flexible substrate for forming fine wiring, it is preferable to use a metal foil with a carrier having an extremely thin metal layer, a release layer, and a carrier layer as the metal foil. When using metal foil with a carrier, the metal foil with a carrier is laminated in the order of extremely thin metal layer, release layer, and carrier layer from the low dielectric film side, as shown in Figure 2. When using metal foil with a carrier, the "metal foil" in the resulting metal laminate material refers to the portion consisting of the extremely thin metal layer, release layer, and carrier layer.

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 or folds in the metal laminate and scratches on the ultra-thin metal layer. Examples of the carrier layer include foils or plates made of copper, aluminum, nickel, and their alloys (stainless steel, brass, etc.), resins with a metal coating on the surface, etc. 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.

The release layer of the carrier-attached metal foil reduces the peel strength of the carrier layer and also has the function of suppressing mutual diffusion that may occur between the carrier layer and the ultrathin metal layer due to heat treatment. The release layer may be either an organic release layer or an inorganic release layer, and examples of components used in the organic release layer include 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-benzimidazolethiol. Examples of carboxylic acids include monocarboxylic acids and dicarboxylic acids. In addition, 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.

The metal constituting the ultra-thin 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, zinc, tin, chromium, gold, silver, platinum, titanium, and alloys thereof. The ultra-thin metal layer is preferably a layer of copper or a copper alloy. The thickness of the ultra-thin metal layer is usually 1.5 μm or more and 10 μm or less, and preferably 1.5 μm or more and 7 μm or less.

The carrier-attached metal foil is preferably one in which the carrier layer and the ultra-thin metal layer are made of copper or a copper alloy, and more preferably a carrier-attached copper foil in which both are copper.

The metal layer may have a chromate treatment layer between the low dielectric film and the metal foil. When the metal foil is an electrolytic metal foil or a metal foil with a carrier, the metal layer preferably has a chromate treatment layer between the low dielectric film and the metal foil. The chromate treatment layer can function as an anti-rust layer. The chromate treatment layer is preferably formed on the surface of the metal foil. In particular, when the metal layer is a metal foil surface having a chromate treatment layer and a low dielectric film is laminated, this is preferable because it can further increase the adhesion between the metal layer and the low dielectric film.

The chromate treatment layer is preferably in contact with the surfaces of both the low dielectric film and the metal foil. The thickness of the chromate treatment layer is usually more than 0 nm and not more than 20 nm, and preferably 1 nm or more and not more than 10 nm. Here, methods for measuring the thickness of the chromate treatment layer include, but are not limited to, thickness measurements using X-ray photoelectron spectroscopy (XPS) or Auger electron spectroscopy (AES).

In the present invention, the chromate treatment layer refers to a layer formed using a solution containing chromic anhydride, chromic acid, dichromate, or dichromate (also called a chromate treatment solution). The chromate treatment layer is preferably made of chromate.

Figure 3 is a schematic cross-sectional view showing a metal laminate material having a chromate treatment layer according to one embodiment of the present invention. As shown in Figure 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 a chromate treatment layer 15 between the low dielectric film 20 and the metal foil 11. In the metal laminate material 1C, the chromate treatment layer 15 is in contact with the surfaces of both the low dielectric film 20 and the metal foil 11. The metal laminate material 1C is laminated in the order of the low dielectric film 20, the chromate treatment layer 15, and the metal foil 11.

FIG. 4 is a schematic cross-sectional view showing a metal laminate having a chromate treatment layer according to another embodiment of the present invention. In this embodiment, a carrier-attached metal foil having an extremely thin metal layer, a peeling layer, and a carrier layer is used as the metal foil. As shown in FIG. 4, the metal laminate 1D of the present invention has a metal layer 10 laminated on one surface of a low dielectric film 20. The metal laminate 1D has a chromate treatment layer 15 between the low dielectric film 20 and a metal foil 11 having an extremely thin metal layer 14, a peeling layer 13, and a carrier layer 12. In the metal laminate 1D, the chromate treatment layer 15 is in contact with both the surfaces of the low dielectric film 20 and the metal foil 11. The metal laminate 1D is laminated in the order of the low dielectric film 20, the chromate treatment layer 15, the extremely thin metal layer 14, the peeling layer 13, and the carrier layer 12.

The metal laminate material may have an organic layer, such as a treatment layer with a silane coupling agent, on the surface of the metal layer on the low dielectric film side. 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 may be applied by spraying, applying with a coater, immersing, or other suitable method. The metal laminate material may also have a treatment layer with a benzotriazole (BTA) compound on the surface of the metal layer on the low dielectric film side.

The metal laminate preferably does not have an organic layer such as a treatment layer with a silane coupling agent or a benzotriazole compound on the surface of the metal layer on the low dielectric film side. When the metal laminate does not have a treatment layer with a silane coupling agent, the silicon (Si) content on the surface of the metal layer on the low dielectric film side (for example, in a range of 100 nm or less from the outermost surface in the thickness direction) is preferably 0.03 μg/cm ² or less, more preferably 0.025 μg/cm ² or less. The Si content can be measured, for example, by fluorescent X-ray analysis.

The metal laminate preferably does not have a roughened particle layer or a heat-resistant layer on the surface of the metal foil. These layers usually contain ferromagnetic metals such as Ni and Co, and the presence of ferromagnetic metals at the lamination interface of the metal laminate would degrade the high-frequency characteristics of the metal laminate. The roughened particle layer contains, for example, any one metal selected from the group consisting of Cu, Co, and Ni, or an alloy thereof, and specific examples thereof include a cobalt-nickel alloy plating layer, a copper-cobalt-nickel alloy plating layer, etc. The heat-resistant layer contains, for example, any one metal selected from the group consisting of Co, Ni, and Mo, or an alloy thereof, and specific examples thereof include a Ni plating layer, etc.

The metal laminate of the present invention has excellent high frequency characteristics because no ferromagnetic metal (also called high magnetic permeability metal) is present at the interface between the low dielectric film and the metal layer, i.e., the metal contained at the interface between the low dielectric film and the metal layer is a non-magnetic metal.

In the present invention, the analysis of the components contained in the interface between the low dielectric film and the metal layer can be performed, for example, by glow discharge optical emission surface analysis (GDS). Specifically, the components contained in the range of 1.3 μm or less from the surface of the metal layer on the low dielectric film side toward the metal layer side can be measured, for example, by GDS. Therefore, in the metal laminate material of the present invention, at the interface between the low dielectric film and the metal layer, the metal contained in the range of 1.3 μm or less from the surface of the metal layer on the low dielectric film side toward the metal layer side (in the thickness direction) is made of a non-magnetic metal.

GDS is an analytical technique that performs elemental analysis in the depth direction of a sample, and is a destructive analysis using sputtering. In addition, analysis of components contained in the interface can also be performed using X-ray photoelectron spectroscopy (XPS).

In the present invention, non-magnetic metal refers to metals other than ferromagnetic metals (e.g., iron, nickel, cobalt, etc.). In the present invention, ferromagnetic metals are also called high magnetic permeability metals, and refer to, for example, metals with a relative magnetic permeability of 10.0 or more. The relative magnetic permeability of non-magnetic metals is, for example, 1.5 or less. Examples of non-magnetic metals include copper, zinc, tin, chromium, gold, silver, platinum, and titanium, and among these, copper or chromium is preferred. In particular, when chromium is contained as a component contained in the interface between the low dielectric film and the metal layer, it is preferable because the adhesion between the low dielectric film and the metal layer can be further improved. In one embodiment, the non-magnetic metals present at the lamination interface of the metal laminate material are copper and chromium. In one embodiment, iron, nickel, and cobalt are not present at the lamination interface of the metal laminate material.

In the present invention, the non-magnetic metal contained within a range of 1.3 μm or less from the surface of the low dielectric film side of the metal layer toward the metal layer side is preferably a single layer (one layer). In other words, it is preferable that the metal layer composed of a non-magnetic metal is a single layer composed of metal foil (excluding the chromate treatment layer). It is considered that a single layer configuration provides better high-frequency characteristics and suppresses voids at the bonding interface between the metal layer and the low dielectric film. On the other hand, if the metal layer has two or more layers composed of a non-magnetic metal (for example, a metal layer/metal foil composition composed of a non-magnetic metal) within a range of 1.3 μm or less from the surface of the low dielectric film side toward the metal layer side, voids may occur at the lamination interface between each metal layer during bonding, which is undesirable because it is possible that swelling may occur during the solder reflow process when applied to a printed wiring board.

The metal laminate of the present invention has a peel strength between the low dielectric film and the metal layer of 1.0 N/cm or more, preferably 3.0 N/cm or more, and more preferably 5.0 N/cm or more. A peel strength of 1.0 N/cm or more can improve the reliability of the fine wiring of the printed wiring board.

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 the metal layer and the low dielectric film are partially peeled off, the low dielectric film is fixed to a support, and the metal layer is pulled in a 90° direction to the low dielectric film at a speed of 50 mm/min. The force required to peel it off at this time is taken as the peel strength (unit: N/cm). If the metal layer is thin and brittle, it may break when measuring the peel strength. In that case, the surface of the metal layer may be electrolytically plated (for example, copper plating when the metal layer is copper) to increase the thickness of the metal layer to about 5 μm to about 50 μm, and then the peel strength may be measured. The method for measuring the peel strength is specified in JIS C6471.

In this specification, the term "peel strength between a low dielectric film and a metal layer" refers to the peel strength when peeling occurs at the interface between the low dielectric film and the metal layer, as well as the peel strength when peeling occurs due to internal destruction of the metal layer and the peel strength when peeling occurs due to internal destruction of the low dielectric film. Furthermore, as described above, when a chromate treatment layer or a treatment layer using a silane coupling agent or a benzotriazole compound is laminated between the low dielectric film and the metal foil, in addition to the peel strength when peeling occurs at the interface between the low dielectric film and the treatment layer, it also refers to the peel strength when peeling occurs at the interface between the metal foil and the treatment layer and the peel strength when peeling occurs due to internal destruction of the treatment layer.

The metal laminate of the present invention has a smooth lamination interface and therefore has superior high frequency characteristics compared to conventional metal laminates produced by thermal lamination. In the present invention, the smoothness of the lamination interface of the metal laminate can be confirmed by measuring the surface roughness of the surface on the metal layer side of the low dielectric film. For example, after removing the metal layer from the metal laminate by etching or the like, the surface (bonding surface) of the low dielectric film can be measured in accordance with ISO25178 using an atomic force microscope (AFM).

The metal laminate of the present invention has an arithmetic mean height Sa of the surface on the metal layer side of the low dielectric film, measured in accordance with ISO 25178, of preferably 60 nm or less, more preferably 50 nm or less, and particularly preferably 20 nm or less.

The metal laminate of the present invention has a maximum height Sz of the surface on the metal layer side of the low dielectric film, measured in accordance with ISO 25178, of preferably 700 nm or less, more preferably 600 nm or less, even more preferably 450 nm or less, and particularly preferably 300 nm or less.

The metal laminate of the present invention has a developed surface area ratio Sdr of the surface on the metal layer side of the low dielectric film, measured in accordance with ISO25178, of preferably 35% or less, more preferably 10% or less, even more preferably 5% or less, and particularly preferably 1.5% or less.

B. Manufacturing method of metal laminate The present invention also relates to a manufacturing method of the metal laminate. The metal laminate of the present invention can be manufactured by a surface activation bonding method. Since a strong bond is formed at the bonding interface by the surface activation treatment, the adhesion of the interface can be ensured even if a ferromagnetic metal such as Ni or Co is not present at the interface. In addition, the adhesion of the lamination interface can be ensured without relying on the physical anchor effect of roughening particles as in the case of a metal laminate manufactured by a thermal lamination method. Furthermore, by manufacturing by the surface activation bonding method, the metal foil can be laminated on the low dielectric film while maintaining the smoothness of its surface. From these points, the metal laminate has excellent high frequency characteristics and adhesion of the lamination interface.

The method for manufacturing a metal laminate of the present invention includes the steps of preparing a low dielectric film and a metal foil (step 1), 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), and rolling-bonding the activated surfaces of the low dielectric film and the metal foil together at a rolling reduction of 0 to 30% (step 3). Note that steps 1, 2 (steps 2-1 and 2-2), and 3 are performed sequentially, but steps 2-1 and 2-2 can be performed simultaneously or sequentially.

Next, we will explain in detail each step of the manufacturing method for the metal laminate material of the present invention.

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 can be used. In the present invention, by using a metal foil having no ferromagnetic metal on the surface, preferably having no roughening treatment layer on the surface, when the metal foil and the low dielectric film are laminated, a metal laminate having no ferromagnetic metal at the lamination interface can be obtained.

2. Surface activation step 2-1. Surface activation step of low dielectric film 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 a low dielectric film as a long coil with a width of 100 mm to 600 mm, using the joint surface of the low dielectric film as one electrode grounded to earth, applying an AC current of 1 MHz to 50 MHz between the low dielectric film and the other 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 process, the earthed electrode takes the form of a cooling roll to prevent the temperature of the transported material from increasing.

In the sputter etching process in the surface activation step, the surface to be joined of the low dielectric film is sputtered under vacuum with an active gas or an inert gas to completely remove any adsorbed matter on the surface. As the active gas, oxygen or a mixed gas containing oxygen can be used. As the inert gas, argon, neon, xenon, krypton, nitrogen, etc., or a mixed gas containing at least one of these can be used. Oxygen is preferred as the gas used in the sputter etching process of the low dielectric film. By using oxygen, functional groups such as carboxyl groups and hydroxyl groups can be added to the surface of the low dielectric film, and the adhesion between the low dielectric film and the metal layer can be improved compared to when an inert gas such as argon or nitrogen is used.

The treatment conditions for sputter etching can be appropriately set, and for example, sputter etching 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. Even when oxygen gas is used, the treatment conditions for sputter etching 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 in order to prevent re-adsorption onto the surface, and may be, for example, 1×10 ⁻⁵ Pa to 10 Pa.

2-2. Metal Foil Surface Activation Step In step 2-2, the surface of the metal foil is activated by sputter etching.

The sputter etching process in the surface activation process can be carried out, for example, by preparing the metal foil to be joined as a long coil with a width of 100 mm to 600 mm, using the joining surface of the metal foil as one electrode grounded to earth, and applying an alternating current of 1 MHz to 50 MHz between it and the other electrode that is insulated and supported to generate a glow discharge, with the area of the electrode exposed to the plasma generated by the glow discharge being 1/3 or less of the area of the other electrode. During the sputter etching process, the earthed electrode takes the form of a cooling roll to prevent the temperature of the transported material from rising.

In the sputter etching process in the surface activation step, the surface to be joined of the metal foil is sputtered with an inert gas under vacuum to completely remove the 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 applied, but argon is preferable. Depending on the type of metal, the adsorbed matter on the surface of the metal foil can be completely removed with an etching amount of about 1 nm, and in particular, the oxide layer of copper can usually be removed with an etching amount of about 5 nm to 12 nm ( _SiO2 equivalent).

The treatment conditions for sputter etching can be appropriately set depending on the type of metal foil, etc. For example, it 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 at this time is preferably high in order to prevent re-adsorption onto the surface, but a value of 1×10 ⁻⁵ Pa to 10 Pa will suffice.

Note that, if necessary, the surface of the metal foil before activation by sputter etching may be subjected to a chromate treatment, a silane coupling agent treatment, a treatment with a benzotriazole compound, or the like. That is, a metal foil having a chromate treatment layer, a silane coupling agent treatment layer, or a benzotriazole compound treatment layer on the surface can be used. When such a treatment layer is provided on the surface of the metal foil, the surface of the treatment layer is activated by sputter etching. At that time, the treatment layer may be completely removed by sputter etching, or may remain without being removed. Preferably, an organic layer such as a silane coupling agent treatment layer or a benzotriazole compound treatment layer is removed from the surface of the metal foil by sputter etching. In this case, the amount of etching is usually 1 nm to 100 nm. On the other hand, when a chromate treatment layer is provided on the surface of the metal foil before activation by sputter etching, it is preferable to activate the surface by sputter etching so that the treatment layer remains, since this can increase the adhesion when bonding with the above-mentioned low dielectric film. In particular, when bonding a surface of a low dielectric film having functional groups such as carboxyl groups or hydroxyl groups to a surface of a metal foil having a chromate treatment layer, the low dielectric film and the metal foil are firmly bonded, which is preferable because it can significantly increase adhesion.

3. Rolling bonding process In step 3, the pressure bonding (rolling bonding) between the surfaces activated by sputter etching can be performed by roll bonding. The rolling wire load of the roll bonding is not particularly limited, and can be set to, for example, a 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 the pressure during bonding, and the rolling wire load is not limited to this numerical range. On the other hand, if the rolling wire load is too high, not only the surface layer of the low dielectric film or metal foil but also the bonding interface is likely to deform, so that the thickness accuracy of each layer in the metal laminate material may decrease. In addition, if the rolling wire load is high, the processing strain applied during bonding may be large.

The reduction ratio during roll bonding is 0 to 30%, preferably 0 to 15%. The above-mentioned surface activated bonding method allows the reduction ratio to be low, so a metal layer with excellent thickness precision can be formed without wrinkles or cracks. Furthermore, since the waviness at the interface between the metal foil and the low dielectric film can be reduced, when wiring is formed by pattern etching of the metal foil, precise wiring can be obtained due to excellent thickness precision. The temperature during roll bonding is, for example, 15°C to 100°C, preferably 15°C to 60°C, and more preferably room temperature.

Joining by roll pressure is preferably performed in a non-oxidizing atmosphere, such as a vacuum atmosphere or an inert gas atmosphere such as Ar, to prevent a decrease in adhesion at the laminate interface due to re-adsorption of oxygen to the metal foil.

The metal laminate obtained by pressure welding can be further heat-treated as necessary, 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 -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 temperature is 150°C to 350°C, preferably 160°C to 340°C, and more preferably 260°C to 340°C.

The atmosphere in which the heat treatment is performed is not particularly limited, but a vacuum atmosphere or an inert gas atmosphere such as _N2 or Ar is preferable, because this can prevent the metal layer from being oxidized by the heat treatment and the adhesion between the metal layer and the low dielectric film from decreasing.

The time for the heat treatment is not particularly limited as long as it can sufficiently increase 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, and 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 mentioned above is 0 seconds (i.e., cooling is performed immediately after reaching the target temperature without a soaking time), it is possible to sufficiently increase the adhesion between the metal layer and the low dielectric film.

The method of performing the heat treatment includes, for example, a method of maintaining the metal laminate material at a desired heat treatment temperature for a desired time in a desired atmosphere (for example, a vacuum atmosphere or an inert gas atmosphere such as N ₂ or Ar) using a batch heat treatment furnace. Depending on the heat treatment temperature and atmosphere, the heat treatment may be performed by a roll-to-roll method using a continuous heat treatment furnace. In that case, at least the heating part and the cooling part in the continuous heat treatment furnace are set to a desired atmosphere (for example, a vacuum atmosphere or an inert gas atmosphere such as N ₂ or Ar) and maintained at a desired temperature, and the metal laminate material is passed through the heating part and the cooling part at a desired speed to maintain the metal laminate material at the desired heat treatment temperature for a desired time.

C. Uses of the Metal Laminate The metal laminate of the present invention can be utilized as a metal-clad laminate for producing a flexible printed circuit board.

The metal laminate of the present invention can be used to obtain a printed wiring board with fine wiring formed thereon. Thus, the present invention also relates to a printed wiring board in which a circuit is formed on a metal laminate. In the process of forming wiring, an additional metal layer can be formed only on the wiring portion. Specifically, a printed wiring board can be obtained by appropriately using a conventionally known method such as the modified semi-additive method (MSAP method), the semi-additive method (SAP method), or the subtractive method. For example, when the modified semi-additive method (MSAP method) is used, a printed wiring board can be manufactured by masking the non-wiring portion on the metal layer of the metal laminate, forming an additional metal layer by copper plating or the like on the unmasked portion, 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 with wiring formed thereon, but also a board on which electronic components such as ICs are mounted after wiring is formed.

In Figures 1 to 4, a metal laminate material is described 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. In other words, if necessary, metal layers may be provided on both surfaces of the low dielectric film. By using a metal laminate material in which metal layers are provided on both surfaces of a low dielectric film, a flexible printed circuit board in which wiring is formed on both surfaces of the low dielectric film can be obtained.

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.

Example 1
A liquid crystal polymer film having a thickness of 50 μm (Vexstar CTQ manufactured by Kuraray Co., Ltd.) was prepared, and a 12 μm thick electrolytic copper foil (CF-PLFA manufactured by Fukuda Metal Foil and Powder Co., Ltd.) having a chromate treatment layer on the surface and made of copper was prepared as the metal foil. Next, one surface of the liquid crystal polymer film was activated by sputter etching with O ₂ gas (etching amount 300 nm), and the surface of the electrolytic copper foil was activated by sputter etching with Ar gas (etching amount 2 nm), and the activated surfaces of the liquid crystal polymer film and the electrolytic copper foil were roll-bonded with a line load of 1.5 tf/cm to produce a metal laminate. The rolling reduction rate was 2.0%. Next, the metal laminate was subjected to a heat treatment at 310 ° C. to obtain the metal laminate of Example 1 (layer structure: electrolytic copper foil / liquid crystal polymer film).

Example 2
A liquid crystal polymer film having a thickness of 50 μm (Vexstar CTQ manufactured by Kuraray Co., Ltd.) was prepared, and a rolled copper foil having a thickness of 12 μm and made of copper having a benzotriazole compound treatment layer (organic layer) on the surface was prepared as the metal foil (HA-V2 manufactured by JX Metals Co., Ltd.). Next, one surface of the liquid crystal polymer film was activated by sputter etching with O ₂ gas (etching amount 300 nm), and the surface of the rolled copper foil was activated by completely removing the treatment layer by sputter etching with Ar gas (etching amount 2 nm), and the activated surfaces of the liquid crystal polymer film and the rolled copper foil were rolled and bonded with a line load of 1.5 tf / cm to produce a metal laminate material. The rolling reduction rate was 2.0%. Next, the metal laminate material was subjected to a heat treatment at 310 ° C. to obtain a metal laminate material of Example 2 (layer structure: rolled copper foil / liquid crystal polymer film).

Example 3
A 25 μm thick liquid crystal polymer film (Vexstar CTQ manufactured by Kuraray Co., Ltd.) was prepared, and a 18 μm thick rolled copper foil (C1020R-H manufactured by Mitsui Sumitomo Metal Mining Co., Ltd.) was prepared. One surface of the liquid crystal polymer film was activated by sputter etching with Ar gas (etching amount 10 nm). The same procedure as in Example 2 was followed to obtain a metal laminate material (layer structure: rolled copper foil/liquid crystal polymer film) of Example 3.

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 one surface of the liquid crystal polymer film was activated by _sputter etching (etching amount 140 nm) with N2 gas.

(Comparative Example 1)
A metal laminate material (layer structure: electrolytic copper foil/liquid crystal polymer film) of Comparative Example 1 was obtained in the same manner as in Example 1, except that an electrolytic copper foil having a thickness of 12 μm and having a surface with an anticorrosive layer containing Co or the like (CF-T9DA-SV manufactured by Fukuda Metal Foil and Powder Co., Ltd.) was used as the electrolytic copper foil.

(Comparative Example 2)
A liquid crystal polymer film having a thickness of 25 μm (Vexstar CTQ manufactured by Kuraray Co., Ltd.) was prepared, and a rolled copper foil having a thickness of 18 μm (HA-V2 manufactured by JX Metals Co., Ltd.) was prepared as the metal foil. Next, one surface of the liquid crystal polymer film was activated by sputter etching with O ₂ gas (etching amount 300 nm), and then a 5 nm NiCr alloy sputter layer was sputter-formed as a base layer on the activated surface, and a 10 nm Cu sputter layer was sputter-formed as an upper layer to form a metal layer. Next, the surface of the metal layer and the surface of the rolled copper foil were activated by sputter etching with Ar gas (etching amount: metal layer 2 nm, rolled copper foil 2 nm), and the activated surfaces of the metal layer and the rolled copper foil were roll-bonded with a line 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 300° C. to obtain a metal laminate of Comparative Example 2 (layer structure: rolled copper foil/metal layer/liquid crystal polymer film).

(Comparative Example 3)
A liquid crystal polymer film having a thickness of 25 μm (Vexstar CTQ manufactured by Kuraray Co., Ltd.) was prepared, and a rolled copper foil having a thickness of 18 μm (HA-V2 manufactured by JX Metals Co., Ltd.) was prepared as the metal foil. Next, one surface of the liquid crystal polymer film was activated by sputter etching with O ₂ gas (etching amount 300 nm), and then a 28 nm NiCr alloy sputter layer was sputter-deposited on the activated surface to form a metal layer. Next, the surface of the metal layer and the surface of the rolled copper foil were activated by sputter etching with Ar gas (etching amount: metal layer 2 nm, rolled copper foil 2 nm), and the activated surfaces of the metal layer and the rolled copper foil were roll-bonded with a line load of 1.5 tf/cm to produce a metal laminate. The rolling reduction rate was 2.3%. Next, the metal laminate was subjected to a heat treatment at 300 ° C. to obtain a metal laminate of Comparative Example 3 (layer structure: rolled copper foil / metal layer / liquid crystal polymer film).

(Comparative Example 4)
By a thermal lamination method, an 18 μm-thick electrolytic copper foil having a treatment layer made of a roughening particle layer or the like on one side was thermocompressed to both surfaces of a 50 μm-thick liquid crystal polymer film (Vexstar CTQ manufactured by Kuraray Co., Ltd.) at a temperature of 310° C. or higher to produce a metal laminate material of Comparative Example 4 (layer structure: electrolytic copper foil (roughened)/liquid crystal polymer film/electrolytic copper foil (roughened)).

The following characteristics were evaluated for the metal laminate materials of Examples 1 to 4 and Comparative Examples 1 to 4.

[Metallic components at the interface]
In order to analyze the metal components contained in the interface between the liquid crystal polymer film and the metal layer of the metal laminate, a glow discharge optical emission surface analysis (GDS) measurement was performed on the range of 1.3 μm or less from the surface of the metal layer on the liquid crystal polymer film side toward the metal layer side (thickness direction). The GDS measurement was performed under the following conditions.
GDS measurement device: High-frequency glow discharge optical emission spectrometer (Horiba, GD-Profiler 2)
Excitation mode: Normal Light source pressure: 600 Pa
Light source output: 30W
Anode diameter: 4 mm

[Interface surface morphology]
In order to evaluate the surface morphology of the lamination interface of the metal laminate, the surface roughness of the interface was measured. Specifically, after the copper foil (copper foil and metal layer in Comparative Example 2) was removed from the metal laminate by etching, the surface roughness of the liquid crystal polymer film surface after the copper foil removal was measured by atomic force microscope (AFM) in accordance with ISO25178.

[Transmission loss (S21)]
In order to evaluate the high-frequency transmission characteristics of the metal laminate material, the transmission loss (S21) of the metal laminate material of Examples 1-2 and Comparative Examples 1-2 and 4 was measured. Since Examples 1-2 and Comparative Examples 1-2 are single-sided materials, a copper layer was provided by electroless copper plating on the exposed surface of the liquid crystal polymer film opposite to the copper foil laminate, 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 4, after through-holes were made, electrolytic copper plating was performed to obtain a measurement sample having a copper layer (25 μm) on both sides.

The transmission line was a single-ended microstrip transmission line with a wiring height of 25 μm, width of 110 μm, and length of 100 mm. Measurements were performed at a frequency of 40 GHz using a network analyzer N5227B (Keysight Technologies, Inc.). Note that in Examples 1-2 and Comparative Examples 1-2, a microstrip line was created on the laminated copper foil side and measurements were performed.

[Peel strength]
A test piece was prepared from the metal laminate, 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 direction at 90° to the liquid crystal polymer film at a speed of 50 mm/min. The force required to peel off at that time was taken as the peel strength (unit: N/cm).

[Existence of voids at the interface]
In order to evaluate the presence or absence of voids at the lamination interface of the metal laminate, the cross sections of the laminates of Examples 1 to 4 and Comparative Examples 1 to 4 were observed at 20,000 times magnification using a scanning electron microscope (SEM).

Table 1 shows the configurations and evaluation results of the metal laminate materials of Examples 1 to 4 and Comparative Examples 1 to 4. In Table 1, LCP stands for liquid crystal polymer film.

As shown in Table 1, the metal laminates of Examples 1 and 2, which do not have a ferromagnetic metal at the lamination interface of the metal laminate, had smaller transmission loss (S21) at high frequencies and superior high frequency transmission characteristics compared to the metal laminates of Comparative Examples 1 to 2 and 4, which have a ferromagnetic metal (Ni, Co) at the lamination interface of the metal laminate. In particular, when compared to Comparative Example 4, which has a roughened particle layer, the metal laminates of Examples 1 and 2 have a smoother interface and no ferromagnetic metal at the lamination interface, so it was confirmed that the metal laminates of Examples 1 and 2 have smaller transmission loss (S21) at high frequencies and superior high frequency transmission characteristics. In addition, since no ferromagnetic metal is present at the lamination interface and the lamination interface is smooth in the metal laminates of Examples 3 and 4, it is presumed that the metal laminates of Examples 3 and 4 also have superior high frequency transmission characteristics like the metal laminates of Examples 1 and 2.

Regarding the peel strength of the metal laminate, as shown in Table 1, the metal laminate of Examples 1 to 4 had sufficient peel strength, although the ferromagnetic metal that contributes to the adhesion of the laminate interface was not present at the interface and the interface was smooth. This is thought to be because in the metal laminate of Examples 1 to 4, a strong bond is formed at the interface between the liquid crystal polymer film and the copper foil by the surface activation treatment, so that the adhesion of the laminate interface can be ensured without relying on the physical anchor effect of the roughening particles. In particular, it was confirmed that the metal laminate of Examples 1 and ₂ , in which the surface of the liquid crystal polymer film was activated by sputter etching with O ₂ gas, had a stronger bond between the interface of the liquid crystal polymer film and the copper foil and had excellent peel strength, compared to the metal laminate of Examples 3 and 4, in which the surface of the liquid crystal polymer film was activated by sputter etching with Ar gas or N 2 gas. In addition, it was confirmed that Example 1, which has a chromate treatment layer on the surface (liquid crystal polymer film side) of the metal foil of the metal laminate, has a stronger bond at the interface between the liquid crystal polymer film and the copper foil and has better peel strength than Example 2, which does not have a chromate treatment layer on the surface of the metal foil of the metal laminate.

Regarding the presence or absence of voids at the bonding interface of the metal laminate material, Table 1 shows the evaluation results of the metal laminate materials of Examples 1 to 4 and Comparative Examples 1 to 4, and Figure 5 shows cross-sectional views of the metal laminate materials of Example 1 and Comparative Examples 2 to 3 showing the presence or absence of voids at the bonding interface. As shown in Table 1 and Figure 5, the metal laminate materials of Examples 1 to 4, in which the metal contained within a range of 1.3 μm or less from the surface of the low dielectric film side of the metal layer toward the metal layer side is a single layer (one layer), have no voids at the bonding interface, and it was confirmed that they can be suitably used in the solder reflow process when applied as a printed wiring board. On the other hand, the metal laminate materials of Comparative Examples 2 to 3, in which the metal contained within a range of 1.3 μm or less from the surface of the low dielectric film side of the metal layer toward the metal layer side is composed of two or more layers (metal layer/copper foil), have voids at the bonding interface, and it was confirmed that there is a risk of swelling due to these voids during the solder reflow process when applied as a printed wiring board. In particular, it was confirmed that in Comparative Example 3, the thickness of the sputtered layer (metal layer) was greater than in Comparative Example 2, resulting in more voids at the bonding interface.

Reference Signs List 1A Metal laminate material 1B Metal laminate material 1C Metal laminate material 1D Metal laminate material 10 Metal layer 11 Metal foil 12 Carrier layer 13 Release layer 14 Ultra-thin metal layer 15 Chromate-treated layer 20 Low dielectric film

All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety.

Claims

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, and at the interface between the low dielectric film and the metal layer, the metal contained within a range of 1.3 μm or less from the surface of the metal layer on the low dielectric film side toward the metal layer side is made of a non-magnetic metal, and the peel strength of the low dielectric film and the metal layer is 1.0 N/cm or more.
The metal laminate material according to claim 1, wherein the arithmetic mean height Sa of the surface of the metal layer side of the low dielectric film is 60 nm or less.
The metal laminate material according to claim 1 or 2, wherein the metal foil is a rolled copper foil, a copper foil with a carrier, or an electrolytic copper foil.
The metal laminate material according to claim 1 or 2, wherein the metal layer has a chromate-treated layer between the low dielectric film and the metal foil.
The metal laminate material according to claim 1 or 2, which does not have an organic layer on the surface of the metal layer on the low dielectric film side.
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, comprising:
At the interface between the low dielectric film and the metal layer, a metal included in a range of 1.3 μm or less from the surface of the metal layer on the low dielectric film side toward the metal layer side is made of a nonmagnetic metal, and the peel strength between the low dielectric film and the metal layer is 1.0 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;
and rolling-bonding the activated surfaces of the low dielectric film and the metal foil together at a rolling reduction of 0 to 30%.
The method for manufacturing a metal laminate according to claim 6, wherein the arithmetic mean height Sa of the surface of the metal layer side of the low dielectric film in the metal laminate is 60 nm or less.
The method for producing a metal laminate according to claim 6 or 7, wherein the metal foil is a rolled copper foil, a copper foil with a carrier, or an electrolytic copper foil.
The method for manufacturing a metal laminate material according to claim 6 or 7, wherein the metal foil has a chromate-treated layer on its surface.
The method for manufacturing a metal laminate according to claim 6 or 7, wherein at least one surface of the low dielectric film is activated by sputter etching with oxygen.
The method for producing a metal laminate material according to claim 6 or 7, wherein the step of activating the surface of the metal foil by sputter etching includes removing an organic layer from the surface of the metal foil.
A printed wiring board having a circuit formed on the metal laminate material described in claim 1.