Carrier-layer-included metal laminate base material and method for manufacturing the same, metal laminate base material and method for manufacturing the same, and printed wiring board

Abstract

To provide a carrier-layer-included metal laminate base material, in which high adhesiveness between an ultra-thin metal layer and a low-dielectric film is secured while maintaining low adhesiveness between a carrier layer and the ultra-thin metal layer.SOLUTION: A carrier-layer-included metal laminate base material 1A is provided, which comprises a three-layered carrier-layer-included metal foil 10 comprising a carrier layer 11, a release layer 12 and an ultra-thin metal layer 13, laminated on one surface of a low-dielectric film 20. The bonding strength between the ultra-thin metal layer 13 and the low-dielectric film 20 is larger than the peel strength between the carrier layer 11 and the ultra-thin metal layer 13.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a metal laminated substrate with a carrier layer and a method for producing the same, a metal laminated substrate and a method for producing the same, and a printed wiring board. [Background technology]

[0002] Conventionally, metal foils with carrier layers have been known as members for forming fine wiring (fine pitch). The metal foils with carrier layers are laminates of a peelable carrier layer and an extremely thin metal layer, and are laminated with a rigid substrate made of glass epoxy resin or the like to obtain a metal laminated substrate (metal-clad laminate) with a carrier layer. Also known is a substrate in which a flexible polymer film is laminated instead of the rigid substrate, and is used as a metal laminated substrate for forming a flexible circuit board. In particular, a substrate using a low dielectric constant polymer film such as low dielectric constant polyimide as the polymer film is useful for high frequency circuits in the fifth generation mobile communication system (5G).

[0003] Patent Document 1 discloses a carrier-attached copper foil having an intermediate layer and an ultrathin copper layer in this order on one or both sides of the carrier, the ultrathin copper layer being a copper foil obtained by forming a primary particle layer containing copper on the surface of the copper foil, and then forming a secondary particle layer containing a ternary alloy of copper, cobalt and nickel on the primary particle layer, and the carrier-attached copper foil is a copper foil for high-frequency circuits having a color difference Δa* value of 4.0 or less and a color difference Δb* value of 3.5 or less from a white color when the color difference of the roughened surface is measured in the color difference system described in JIS Z 8730. Patent Document 1 also discloses a carrier-attached copper-clad laminate in which a rigid substrate such as a paper-based phenolic resin or a polymer film such as a liquid crystal polymer (LCP) is laminated with the carrier-attached copper foil. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-224318 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the above (Patent Document 1), when bonding a carrier-attached copper foil to a rigid substrate, a prepreg is prepared by impregnating a substrate such as glass cloth with resin and curing the resin to a semi-cured state, and the copper foil is placed on the prepreg and heated and pressurized. Also, when a polymer film is used instead of a rigid substrate, the copper foil is laminated and bonded (thermocompression bonded) to a substrate such as a liquid crystal polymer under high temperature and high pressure.

[0006] However, when a metal foil with a carrier is thermocompression bonded to a low dielectric film such as a liquid crystal polymer, polyethylene fluoride, or low dielectric constant polyimide, which is particularly suitable for high frequency circuit applications, the thermocompression temperature must be 280°C or higher, or 300°C or higher, taking into consideration the melting point and other characteristics of the low dielectric film. At such a temperature range, the peel layer between the carrier layer and the ultra-thin metal layer is altered, and the peelability of the carrier is impaired. On the other hand, if the thermocompression temperature is lowered to maintain the peelability, the adhesion between the ultra-thin metal layer and the low dielectric film is reduced. Therefore, it has been difficult to maintain the peelability (low adhesion) between the carrier and the ultra-thin metal layer while ensuring high adhesion between the ultra-thin metal layer and the low dielectric film at the same time.

[0007] Therefore, the present invention aims to provide a metal laminated substrate with a carrier layer, which maintains low adhesion between the carrier layer and the ultrathin metal layer while ensuring high adhesion between the ultrathin metal layer and a low dielectric film, and a method for producing the same. Another object of the present invention is to provide a metal laminated substrate in which a low dielectric film and an ultrathin metal layer are laminated, and a method for producing the same. Another object of the present invention is to provide a printed wiring board obtained from the above metal laminated substrate, which is suitable for use in high-frequency circuits. [Means for solving the problem]

[0008] As a result of intensive research, the present inventors have found that the above-mentioned problems can be solved by adopting a specific bonding method when laminating a low dielectric film and a metal foil with a carrier layer, which includes a carrier layer, a release layer, and an extremely thin metal layer, and by controlling the bonding strength between the extremely thin metal layer and the low dielectric film and the peel strength between the carrier layer and the extremely thin metal layer, respectively, and have completed the invention. That is, the gist of the present invention is as follows.

[0009] (1) A metal laminated substrate with a carrier layer, in which a metal foil with a carrier layer, which comprises at least three layers including a carrier layer, a release layer, and an extremely thin metal layer, is laminated on at least one surface of a low dielectric film, The metal laminate substrate with a carrier layer, wherein the bonding strength between the extremely thin metal layer and the low dielectric film is greater than the peel strength between the carrier layer and the extremely thin metal layer. (2) The metal laminated substrate with a carrier layer according to the above (1), which has one or more intermediate layers containing a metal between the low dielectric film and the extremely thin metal layer. (3) The metal laminated substrate according to (2) above, wherein the intermediate layer contains any one metal or alloy thereof selected from the group consisting of copper, iron, nickel, zinc, chromium, cobalt, titanium, tin, platinum, silver and gold. (4) The metal laminate substrate with a carrier layer according to any one of the above (1) to (3), wherein the low dielectric film is a film of a low dielectric polymer selected from the group consisting of liquid crystal polymers, polyethylene fluoride, polyamides and low dielectric constant polyimides. (5) The metal laminated substrate with a carrier layer according to any one of the above (1) to (4), wherein the peel strength between the carrier layer and the ultrathin metal layer is 0.15 N / cm or more and 0.5 N / cm or less. (6) The metal laminated substrate with a carrier layer according to any one of the above (1) to (5), wherein the bonding strength between the ultrathin metal layer and the low dielectric film is 2.0 N / cm or more. (7) The metal laminated substrate with a carrier layer according to any one of the above (1) to (6), wherein the release layer is an organic release layer or an inorganic release layer. (8) The metal laminated substrate with a carrier layer according to any one of the above (1) to (7), wherein the thickness of the ultrathin metal layer is from 0.5 μm to 10 μm. (9) A method for producing a metal laminate substrate with a carrier layer according to the above (2), comprising the steps of: A step of preparing a low dielectric film and a metal foil with a carrier layer, the metal foil having at least three layers including a carrier layer, a release layer, and an extremely thin metal layer; a step of activating at least one surface of the low dielectric film by sputter etching, and then sputter-forming an intermediate layer containing a metal on the surface; activating the surface of the intermediate layer by sputter etching; activating the surface of the ultrathin metal layer by sputter etching; A step of rolling-bonding the activated surfaces together at a rolling reduction of 0 to 30%; A method for producing the metal laminate substrate with a carrier layer comprising the steps of: (10) The method for producing a metal laminated substrate with a carrier layer according to the above (9), wherein the low dielectric film is a film of a low dielectric polymer selected from the group consisting of liquid crystal polymers, polyethylene fluoride, polyamides and low dielectric constant polyimides. (11) The method for producing a metal laminated substrate with a carrier layer according to the above (9) or (10), further comprising carrying out a heat treatment at 160° C. or more and 300° C. or less after the roll bonding. (12) A metal laminated substrate in which an extremely thin metal layer is laminated on at least one surface of a low dielectric constant film via an intermediate layer containing a metal, and the bonding strength between the low dielectric constant film and the extremely thin metal layer is 2.0 N / cm or more. (13) The metal laminated substrate according to (12) above, wherein the intermediate layer contains any one metal selected from the group consisting of copper, iron, nickel, zinc, chromium, cobalt, titanium, tin, platinum, silver and gold, or an alloy thereof. (14) The metal laminated substrate according to (12) or (13) above, in which a roughening particle layer containing any one metal selected from the group consisting of Cu, Co, and Ni or an alloy thereof, and / or a rust-preventive layer containing any one metal selected from the group consisting of Cr, Ni, and Zn or an alloy thereof is laminated on the surface of the intermediate layer side of the ultrathin metal layer. (15) The metal laminated substrate according to any one of the above (12) to (14), wherein the thickness of the ultrathin metal layer is from 0.5 μm to 10 μm. (16) A method for producing a metal laminated substrate in which an extremely thin metal layer is laminated on at least one surface of a low dielectric film via an intermediate layer containing a metal, comprising: A method for producing a metal laminated substrate, comprising the step of peeling off the carrier layer in the metal laminated substrate with a carrier layer described in (2) above. (17) A printed wiring board comprising a circuit formed in the intermediate layer and the ultrathin metal layer of the metal laminated base material according to any one of (12) to (15) above. Effect of the Invention

[0010] According to the present invention, in a metal laminated substrate with a carrier layer, it is possible to maintain low adhesion between the carrier layer and the ultrathin metal layer while ensuring high adhesion between the ultrathin metal layer and the low dielectric film. In addition, a metal laminated substrate in which a low dielectric film and an ultrathin metal layer are laminated can be obtained. This metal laminated substrate is suitable for use in high frequency circuits. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view of a carrier layer-attached metal laminate substrate according to a first embodiment of the present invention. [Diagram 2] FIG. 4 is a cross-sectional view of a carrier layer-attached metal laminate substrate according to a second embodiment of the present invention. [Figure 3A] 5A to 5C are diagrams illustrating a process for producing a carrier layer-attached metal laminate base material according to a second embodiment of the present invention. [Figure 3B] 5A to 5C are diagrams illustrating a process for producing a carrier layer-attached metal laminate base material according to a second embodiment of the present invention. [Figure 4] 1A to 1C are diagrams illustrating a manufacturing process of a metal laminated substrate according to one embodiment of the present invention. [Diagram 5] 1 is a scanning electron microscope (SEM) image of the peeled surfaces when the ultrathin copper layer and the low dielectric film are peeled off from the carrier layer-attached metal laminate substrate of Example 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will be described in detail below. A cross section of a carrier layer-attached metal laminated substrate according to a first embodiment of the present invention is shown in Fig. 1. The carrier layer-attached metal laminated substrate 1A shown in Fig. 1 is roughly composed of a carrier layer-attached metal foil 10 composed of a carrier layer 11, a release layer 12, and an extremely thin metal layer 13, and a low dielectric film 20 laminated in this order.

[0013] Although not shown in FIG. 1, a roughened particle layer, an anti-rust layer, a layer treated with a silane coupling agent, or the like may be laminated on the surface of the ultrathin metal layer 13 on the side of the low dielectric film 20. Any one of these layers may be laminated, or multiple types of layers may be laminated. The roughened particle layer may contain, for example, any one metal selected from the group consisting of Cu, Co, and Ni, or an alloy thereof. Specific examples include a cobalt-nickel alloy plating layer, a copper-cobalt-nickel alloy plating layer, and the like. The anti-rust layer may contain, for example, any one metal selected from the group consisting of Cr, Ni, and Zn, or an alloy thereof. Specific examples include a chromium oxide coating, a mixture coating of chromium oxide and zinc / zinc oxide, and a Ni plating layer. Furthermore, examples of the silane coupling agent include, but are not limited to, olefin-based silanes, epoxy-based silanes, acrylic-based silanes, amino-based silanes, and mercapto-based silanes. The silane coupling agent can be applied by appropriately using a method such as spraying, coating with a coater, or immersion.

[0014] The carrier layer 11 has a sheet shape and functions as a support material or protective layer for preventing wrinkles or folds in the carrier layer-attached metal laminate substrate 1A and scratches in the ultrathin metal layer 13. Examples of the carrier layer 11 include foils or plates made of copper, aluminum, nickel, and alloys thereof (stainless steel, brass, etc.), resins with metal coatings on the surface, etc. Copper foil is preferred.

[0015] The thickness of the carrier layer 11 is not particularly limited, and is appropriately set according to the desired characteristics such as flexibility. Specifically, it is preferably about 10 μm or more and 100 μm or less. If the thickness is too thin, the handleability of the metal foil 10 with the carrier layer may be impaired, which is not preferable. That is, the carrier layer 11 may deform during handling, causing wrinkles or cracks in the ultrathin metal layer 13. In addition, if the carrier layer 11 is too thick, it is not preferable because it has excessive rigidity as a support material and may be difficult to peel off from the ultrathin metal layer 13. Furthermore, the cost of producing the metal foil 10 with the carrier layer also increases.

[0016] The release layer 12 reduces the peel strength of the carrier layer 11, and also has the function of suppressing mutual diffusion that may occur between the carrier layer 11 and the ultrathin metal layer 13 when the carrier layer-attached metal foil 10 is heated when bonding to the low dielectric film 20. The release layer 12 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. Examples of components used in the inorganic release layer include Ni, Mo, Co, Cr, Fe, Ti, W, P, Zn, and chromate-treated films. The release layer 12 can be formed by contacting the surface of the carrier layer 11 with a solution containing the components of the release layer 12 and fixing the release layer components to the surface of the carrier layer 11. When contacting the carrier layer 11 with the solution containing the components of the release layer 12, this contact can be performed by immersing the carrier layer 11 in the solution containing the components of the release layer 12, spraying the solution containing the components of the release layer 12, or flowing the solution containing the components of the release layer 12 down, and then drying or the like can be performed to fix the components. In addition, a method of forming a film of the components of the release layer 12 by a gas phase method such as deposition or sputtering can also be adopted.

[0017] The thickness of the release layer 12 is typically 1 nm to 1 μm, and preferably 5 nm to 500 nm, but is not limited thereto. If the thickness of the release layer 12 is too thin, there is a problem that separation from the ultrathin metal layer 13 cannot be performed sufficiently, resulting in poor peeling. If the thickness is too large, peeling is possible, but the manufacturing cost will be high, so the thickness is appropriately set in consideration of the balance between these factors.

[0018] The metal constituting the ultrathin metal layer 13 can be appropriately selected depending on the application and the desired properties of the metal laminated substrate 1A with a carrier layer. Specific examples include copper, iron, nickel, zinc, tin, chromium, gold, silver, platinum, cobalt, titanium, and alloys based on any of these. In particular, a layer of copper or a copper alloy is preferable. By rolling-bonding these metals to the low dielectric film 20, a flexible substrate for forming fine wiring, for example, can be obtained.

[0019] The thickness of the ultrathin metal layer 13 is 0.5 μm or more and 10 μm or less, and preferably 1 μm or more and 7 μm or less. Here, the thickness of the ultrathin metal layer 13 refers to an average value of values ​​obtained by taking an optical microscope photograph of a cross section of the metal laminated substrate 1A with a carrier layer, measuring the thickness of the ultrathin metal layer 13 at any 10 points in the optical microscope photograph.

[0020] The manufacturing method of such an ultra-thin metal layer 13 is not particularly limited, but it can be formed on the release layer 12 by wet film formation methods such as electroless plating and electrolytic plating, dry film formation methods such as sputtering and chemical vapor deposition, or a combination of these.

[0021] In this embodiment, when comparing the bonding strength between the ultrathin metal layer 13 and the low dielectric film 20 with the peel strength between the carrier layer 11 and the ultrathin metal layer 13, the bonding strength between the ultrathin metal layer 13 and the low dielectric film 20 is greater. This allows the carrier layer 11 to be peeled off from the ultrathin metal layer 13 without causing wrinkles or tears in the ultrathin metal layer 13. However, if the bonding strength between the ultrathin metal layer 13 and the low dielectric film 20 and the peel strength between the carrier layer 11 and the ultrathin metal layer 13 are too close, it may be difficult to peel off the carrier layer 11 without affecting the interface between the ultrathin metal layer 13 and the low dielectric film 20. Therefore, it is preferable that the difference between the bonding strength between the ultrathin metal layer 13 and the low dielectric film 20 and the peel strength between the carrier layer 11 and the ultrathin metal layer 13 is 0.25 N / cm or more. More preferably, it is 0.5 N / cm or more, and most preferably, it is 1.5 N / cm or more. As specific values ​​of the bonding strength between the ultrathin metal layer 13 and the low dielectric film 20, and the peel strength between the carrier layer 11 and the ultrathin metal layer 13, the bonding strength between the ultrathin metal layer 13 and the low dielectric film 20 is preferably 2.0 N / cm or more. The peel strength between the carrier layer 11 and the ultrathin metal layer 13 may be greater than 0, and is preferably 0.5 N / cm or less. However, in the range below about 0.05 N / cm, the peel strength may not be accurately measured due to the influence of the rigidity of the material to be peeled (the carrier layer 11, the ultrathin metal layer 13, the low dielectric film 20, other anti-rust layers, etc.). The peel strength between the carrier layer 11 and the ultrathin metal layer 13 is preferably in the range of 0.15 N / cm or more and 0.5 N / cm or less. In order to measure the above bonding strength value, first, a test piece having a width of 1 cm is prepared from the metal laminated base material 1A with a carrier layer. Thereafter, after removing the carrier layer 11, electrolytic plating (e.g., copper plating when the ultrathin metal layer 13 is copper) is performed on the surface of the ultrathin metal layer 13 to form a metal layer (including the ultrathin metal layer 13) having a thickness of about 10 to 20 μm on the surface of the low dielectric film 20. Then, after the metal layer having a thickness of about 10 to 20 μm and the low dielectric film 20 are partially peeled off, the low dielectric film 20 is fixed to a support, and the metal layer having a thickness of about 10 to 20 μm is pulled in a direction at an angle of 90° to the low dielectric film 20. The force required for peeling off at this time is taken as the bonding strength (unit: N / cm).To measure the peel strength, a test piece with a width of 1 cm is first prepared from the metal laminated substrate 1A with a carrier layer. After partially peeling off the carrier layer 11, the low dielectric film 20 including the ultrathin metal layer 13 is fixed to a support, and the carrier layer 11 is pulled in a direction at an angle of 90° to the low dielectric film 20 including the ultrathin metal layer 13. The force required to peel off the carrier layer 11 at this time is taken as the peel strength (unit: N / cm).

[0022] In this specification, the term "bonding strength between an extremely thin metal layer and a low dielectric film" refers not only to the bonding strength when peeling occurs at the interface between the extremely thin metal layer and the low dielectric film, but also to the bonding strength when peeling occurs due to internal destruction of the extremely thin metal layer, and the bonding strength when peeling occurs due to internal destruction of the low dielectric film. Furthermore, as described above, when a roughening particle layer, an anti-rust layer, a treatment layer using a silane coupling agent, etc. (collectively referred to as a "treatment layer") are laminated on the surface of the extremely thin metal layer facing the low dielectric film, it also means the bonding strength when peeling occurs at the interface between the extremely thin metal layer and the treatment layer, the bonding strength when peeling occurs at the interface between the treatment layer and the low dielectric film, and the bonding strength when peeling occurs due to internal destruction of the treatment layer. Furthermore, in the case of a metal laminate substrate with a carrier layer according to the second embodiment described later (FIG. 2), in which a metal-containing intermediate layer 30 is present between the low dielectric film 20 and the extremely thin metal layer 13, the "bonding strength between the extremely thin metal layer and the low dielectric film" means any of the bonding strength when peeling occurs due to internal destruction of the extremely thin metal layer, the bonding strength when peeling occurs at the interface between the extremely thin metal layer (or the treatment layer, if a treatment layer is present) and the intermediate layer, the bonding strength when peeling occurs at the interface between the intermediate layer and the low dielectric film, the bonding strength when peeling occurs due to internal destruction of the intermediate layer, and the bonding strength when peeling occurs due to internal destruction of the low dielectric film.

[0023] The low dielectric film 20 is laminated on the extremely thin metal layer 13. The low dielectric film 20 can be made of any low dielectric polymer material that can be used as a flexible substrate. For example, the low dielectric film 20 can be made of any low dielectric polymer material having a relative dielectric constant ε rThe dielectric constant of the low dielectric film 20 is 3.3 or less and the dielectric loss tangent tanδ is 0.006 or less, but is not limited thereto. Specifically, the material may be appropriately selected from liquid crystal polymers, polyethylene fluoride (fluorine-based resins such as polytetrafluoroethylene), polyamide, isocyanate compounds, polyamideimide, polyimide, low dielectric constant polyimide, polyethylene terephthalate, polyetherimide, and the like. Preferably, the low dielectric film 20 is a liquid crystal polymer, polyethylene fluoride, polyamide, or low dielectric constant polyimide. The low dielectric film 20 is a single-layer film or a laminate consisting of multiple layers. In the case of multiple layers, 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 composed 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.

[0024] The thickness of the low dielectric film 20 can be appropriately set depending on the application of the metal laminated substrate. For example, when used as a flexible printed wiring board, the thickness is preferably 10 μm or more and 150 μm or less, more preferably 10 μm or more and 120 μm or less. The thickness of the low dielectric film 20 before bonding can be measured with a micrometer or the like, and refers to the average value of thicknesses measured at 10 points randomly selected from the surface of the target low dielectric film. In addition, it is preferable that the deviation of all measured values ​​from the average value of the 10 measured values ​​is within 10% for the low dielectric film used.

[0025] Next, a second embodiment of the present invention will be described. Fig. 2 shows a cross section of a metal laminated substrate with a carrier layer according to the second embodiment of the present invention. In this embodiment, as shown in Fig. 2, an intermediate layer 30 containing a metal is provided between an extremely thin metal layer 13 and a low dielectric film 20. This intermediate layer 30 may be a single layer, or two or more layers may be laminated. Examples of the intermediate layer 30 containing a metal include a metal layer formed on the low dielectric film 20 by vapor deposition, electroless plating, or sputtering.

[0026] Although not shown in FIG. 2, a roughened particle layer, an anti-rust layer, a silane coupling agent layer, or the like may be laminated on the surface of the intermediate layer 30 side of the ultrathin metal layer 13, as in the case of the metal laminated substrate with a carrier layer according to the first embodiment. Any one of these layers may be laminated, or a plurality of layers may be laminated. The roughened particle layer may contain, for example, any one of metals selected from the group consisting of Cu, Co, and Ni, or an alloy thereof, but is not limited thereto. The anti-rust layer may contain, for example, any one of metals selected from the group consisting of Cr, Ni, and Zn, or an alloy thereof, but is not limited thereto.

[0027] The intermediate layer 30 preferably contains any one of metals selected from the group consisting of copper, iron, nickel, zinc, chromium, cobalt, titanium, tin, platinum, silver, and gold, or an alloy thereof. In particular, when the ultra-thin metal layer 13 is copper or an alloy thereof, the metal constituting the intermediate layer 30 is preferably copper or an alloy containing copper, such as a copper-nickel alloy. When the intermediate layer 30 is, for example, a Cu-Ni alloy, the ratio of Ni to Cu is preferably 10 to 90% in at%. However, it is not limited thereto. By providing such an intermediate layer 30, it is possible to protect the surface of the ultra-thin metal layer 13 or the low dielectric film 20, improve the adhesion between the ultra-thin metal layer 13 and the low dielectric film 20, and also to impart a function specific to the intermediate layer 30 (for example, a function as an etching stopper layer during etching). The thickness of the intermediate layer 30 may be any thickness that can exhibit a function such as improving adhesion, and is not particularly limited. Specifically, it is preferable to set the thickness to 5 nm or more and 200 nm or less, and more preferably 10 nm or more and 100 nm or less.

[0028] Next, the manufacturing method of the carrier layer-attached metal laminated substrate according to the present invention will be described by taking as an example the case of manufacturing a carrier layer-attached metal laminated substrate 1B having a metal-containing intermediate layer 30 between a low dielectric film 20 and an extremely thin metal layer 13 as shown in FIG. 2. The carrier layer-attached metal laminated substrate 1B shown in FIG. 2 is obtained by preparing a carrier layer-attached metal foil 10 consisting of a carrier layer 11, a peeling layer 12, and an extremely thin metal layer 13, and a low dielectric film 20, providing a metal-containing intermediate layer 30 on the surface of the low dielectric film 20, and then bonding these to each other by various methods such as cold rolling bonding and surface activation bonding to bring the layers into close contact with each other. Note that bonding and / or heat treatment under high pressure when manufacturing the carrier layer-attached metal laminated substrate 1B may significantly change the structure of each layer of the carrier layer-attached metal laminated substrate 1B before and after bonding and / or heat treatment, which may impair the properties of the carrier layer-attached metal laminated substrate 1B, and therefore it is preferable to select bonding and heat treatment conditions that can avoid such structure changes.

[0029] A preferred embodiment of a method for producing a carrier layer-attached metal laminated substrate 1B will be described with reference to Figures 3A and 3B. First, as shown in Figure 3A, the surface 20a of the low dielectric film 20 is activated by sputter etching (Figure 3A (a)), and then the intermediate layer 30 containing a metal is sputter-deposited on the surface 20a of the low dielectric film 20. The conditions for sputter-deposition can be appropriately set depending on the type of metal constituting the intermediate layer 30 and the thickness of the intermediate layer 30.

[0030] Next, as shown in FIG. 3B, the surface 30a of the intermediate layer 30 is activated by sputter etching, the surface 13a of the ultrathin metal layer 13 in the metal foil 10 with the carrier layer is activated by sputter etching, and the activated surfaces are roll-bonded together ((c) of FIG. 3B), thereby producing a metal laminated substrate 1B with a carrier layer ((d) of FIG. 3B). If the surface 13a of the ultrathin metal layer 13 contains a roughened particle layer or an anti-rust layer, the surface of the roughened particle layer or the anti-rust layer is activated by sputter etching. At that time, the roughened particle layer or the anti-rust layer may be completely removed by sputter etching, or may remain without being removed. The rolling reduction rate in the rolling bonding is 0 to 30%, preferably 0 to 15%. The above-mentioned method using surface activation bonding can reduce the rolling reduction rate, so that it is possible to bond while maintaining the function (low adhesion) of the peel layer 12, and it is also possible to form an ultrathin metal layer 13 with excellent thickness accuracy without causing wrinkles, cracks, etc. Furthermore, since the waviness at the interfaces between the ultra-thin metal layer 13 and the intermediate layer 30 and the low dielectric film 20 can be reduced, when a circuit is formed by pattern etching the ultra-thin metal layer 13 and the intermediate layer 30, a precise circuit can be obtained due to excellent thickness accuracy.

[0031] Surface 30a of intermediate layer 30 or surface 13a of ultrathin metal layer 13 before activation by sputter etching may be subjected to Ni plating, chromate treatment, silane coupling agent treatment, etc., to prevent oxidation or improve adhesion, as necessary. Surface 13a of ultrathin metal layer 13 may be subjected to roughening treatment, as necessary, to improve adhesion to intermediate layer 30.

[0032] The sputter etching process can be performed, for example, by preparing the metal foil 10 with a carrier layer or the low dielectric film 20 with an intermediate layer 30 to be joined as a long coil with a width of 100 mm to 600 mm, using the joining surface of the metal foil 10 with a carrier layer or the low dielectric film 20 as one electrode grounded to earth, applying an AC current of 1 MHz to 50 MHz between the joining surface and another electrode supported insulated to generate a glow discharge, and setting the area of ​​the electrode exposed to the plasma generated by the glow discharge to 1 / 3 or less of the area of ​​the other electrode. During the sputter etching process, the earthed electrode is in the form of a cooling roll to prevent the temperature of the transported material from increasing.

[0033] In the sputter etching process, the bonding surface of the metal foil 10 with the carrier layer or the low dielectric film 20 is sputtered with an inert gas under vacuum to completely remove the adsorbed matter on the surface and to remove a part or all of the oxide layer on the surface. It is preferable to completely remove the copper oxide layer. As the inert gas, argon, neon, xenon, krypton, etc., or a mixed gas containing at least one of these can be applied. Although it depends on the type of metal, the adsorbed matter on the surface of the ultrathin metal layer 13 or the intermediate layer 30 can be completely removed with an etching amount of about 1 nm, and in particular, the copper oxide layer can be usually removed with an etching amount of about 5 nm to 12 nm (SiO2 equivalent).

[0034] The processing conditions for sputter etching can be appropriately set depending on the type of ultrathin metal layer 13 or intermediate layer 30. For example, the processing 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 of substances onto the surface, and may be, for example, 1×10 -5 Pa~10Pa is fine.

[0035] The surfaces of the ultrathin metal layer 13 and the intermediate layer 30 that have been subjected to sputter etching can be pressed together by roll pressing. The rolling line load of the roll pressing 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 10 with the carrier layer or the low dielectric film 20 with the intermediate layer 30 before bonding is large, it may be necessary to increase the rolling line load to ensure pressure during bonding, and the rolling line load is not limited to this numerical range. On the other hand, if the rolling line load is too high, not only the surface layer of the ultrathin metal layer 13 or the intermediate layer 30 but also the bonding interface is easily deformed, so that the thickness accuracy of each layer in the metal laminated base material 1B with the carrier layer may decrease. In addition, if the rolling line load is high, the processing strain applied during bonding may be large.

[0036] The reduction ratio during pressure welding is 30% or less, preferably 8% or less, and more preferably 6% or less. Note that since the thickness does not need to change before and after pressure welding, the lower limit of the reduction ratio is 0%.

[0037] The bonding by roll pressure is preferably carried out in a non-oxidizing atmosphere, such as a vacuum or an inert gas atmosphere such as Ar, in order to prevent a decrease in the bonding strength between the two due to re-adsorption of oxygen onto the surface of the ultrathin metal layer 13 or the intermediate layer 30.

[0038] In addition, the metal laminated substrate 1B with the carrier layer obtained by pressure bonding can be further subjected to heat treatment as necessary. The heat treatment removes the distortion of the ultrathin metal layer 13 or the intermediate layer 30, and can improve the adhesion between the layers. If this heat treatment is performed at a high temperature for a long time, there is a risk that a blister will occur in the carrier layer 11 starting from the peeling layer 12, and the carrier layer 11 will peel off from the blister, or conversely, there is a risk that the adhesion between the carrier layer 11 and the ultrathin metal layer 13 will increase due to mutual diffusion, etc., making it difficult to peel off the carrier layer 11. In addition, depending on the combination of the ultrathin metal layer 13 and the intermediate layer 30, an intermetallic compound will be generated at the interface, and the adhesion (bonding strength) will tend to decrease. Therefore, the above heat treatment is performed at a temperature of 160°C or more and 300°C or less. More preferably, it is 180°C or more and 290°C or less. Alternatively, it is preferable not to perform heat treatment after rolling bonding. After the carrier layer 11 has been peeled off and removed from the bonded metal laminated substrate 1B, a heat treatment may be performed within a temperature range that does not generate an intermetallic compound at the interface between the ultrathin metal layer 13 and the intermediate layer 30.

[0039] Next, the metal laminated substrate and its manufacturing method according to the present invention will be described. FIG. 4 is a diagram showing the manufacturing process of the metal laminated substrate according to one embodiment of the present invention. The metal laminated substrate 2 shown in FIG. 4 is roughly configured by laminating an extremely thin metal layer 13 on one side of a low dielectric film 20 via an intermediate layer 30 containing a metal. The metal laminated substrate 2 is the same as the carrier layer-attached metal laminated substrate 1B shown in FIG. 2 except that it does not have the carrier layer 11 and the release layer 12, and the configuration of each layer is the same as the configuration of each layer in the carrier layer-attached metal laminated substrate 1B. This metal laminated substrate 2 can be obtained from the carrier layer-attached metal laminated substrate 1B. That is, as shown in FIG. 4, the carrier layer-attached metal laminated substrate 1B is prepared ((a) of FIG. 4), and the carrier layer 11 in the carrier layer-attached metal laminated substrate 1B is peeled off together with the release layer 12 ((b) of FIG. 4), thereby obtaining a three-layer structure metal laminated substrate 2 ((c) of FIG. 4).

[0040] The produced metal laminated substrate 2 has an extremely thin metal layer 13 having a thickness of, for example, 0.5 μm to 10 μm, and can be used as a metal laminated substrate (metal-clad laminate) for producing a flexible circuit board. The metal laminated substrate of the present invention includes a form in which an additional metal layer is laminated by electroless plating, electrolytic plating (e.g., copper plating) or the like on the surface of the extremely thin metal layer 13 opposite to the low dielectric film.

[0041] A printed wiring board having a fine circuit formed thereon can be obtained using the metal laminated substrate 2. In the process of forming the circuit, the additional metal layer can be formed only on the circuit portion. Specifically, a printed wiring board can be obtained by appropriately using a conventionally known method such as a modified semi-additive process (MSAP method) or a semi-additive process (SAP method). For example, a printed wiring board can be manufactured by masking the non-circuit portion on the ultra-thin metal layer 13 in the metal laminated substrate 2, plating the unmasked portion with copper to form an additional metal layer, removing the mask, and removing the ultra-thin metal layer 13 hidden by the mask by etching. Note that the "printed wiring board" in the present invention includes not only a laminate having a circuit formed thereon, but also a board on which electronic components such as ICs are mounted after the circuit is formed.

[0042] In the embodiments of the metal laminated substrate 1A with a carrier layer in FIG. 1, the metal laminated substrate 1B with a carrier layer in FIG. 2, and the metal laminated substrate 2 in FIG. 4, the case where the metal foil 10 with a carrier layer or the very thin metal layer 13 is laminated on one side of the low dielectric film 20 has been described, but the present invention is not limited to this. That is, an intermediate layer 30, a very thin metal layer 13, a release layer 12, and a carrier layer 11 may be provided on both sides of the low dielectric film 20 as necessary. By using a metal laminated substrate with a carrier layer in which these layers are provided on both sides of the low dielectric film 20, a flexible printed wiring board in which a circuit is formed on both sides of the low dielectric film 20 can be obtained. EXAMPLES

[0043] 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.

[0044] Example 1 First, as a metal foil with a carrier layer, a copper foil with a carrier layer (MITSUI MINING & SMELTING CO., LTD. MT18FL) was prepared, which was a copper carrier layer with a thickness of 18 μm, on which a 1.5 μm ultrathin copper layer and a roughening particle layer and an anti-rust layer were provided on its surface via a release layer (organic release layer), and a liquid crystal polymer (LCP) film with a thickness of 25 μm was prepared as a low dielectric film. After the surface of the LCP film was activated by sputter etching, an intermediate layer (thickness 40 nm) made of copper was formed by sputter deposition. Then, the surfaces of the ultrathin copper layer and the intermediate layer were roll-bonded together to produce the intended metal laminated substrate with a carrier layer. The line load during pressure bonding was 1.5 t / cm, and the rolling reduction rate by surface activation bonding was 2.2%. After roll bonding, heat treatment was performed at 240°C.

[0045] Example 2 As the metal foil with a carrier layer, a copper foil with a carrier layer (MITSUI MINING & SMELTING CO., LTD. MT18FL) was used, which was a copper carrier layer with a thickness of 18 μm, a 1.5 μm ultrathin copper layer with a roughening particle layer and an anti-rust layer on its surface, via a release layer (organic release layer). As the low dielectric film, a 100 μm thick LCP film was used, the surface of which was activated by sputter etching, and then an intermediate layer (40 nm thick) made of copper was formed by sputter deposition. Then, the surfaces of the ultrathin copper layer and the intermediate layer were roll-bonded together, and then heat-treated to produce a metal laminated base material with a carrier layer. The bonding conditions are as shown in Table 1. The rolling reduction rate by surface activation bonding was 2.5%.

[0046] (Examples 3 and 4) A metal laminated substrate with a carrier layer was produced in the same manner as in Example 2, except that the joining conditions were changed as shown in Table 1. The rolling reductions in Examples 3 and 4 were 2.5% and 3.5%, respectively.

[0047] Example 5 As the low dielectric film and intermediate layer, a copper intermediate layer (40 nm thick) formed by sputtering on the surface of a 25 μm thick LCP film was used as in Example 1, and a metal laminated substrate with a carrier layer was produced in the same manner as in Example 2, except that the bonding conditions were changed as shown in Table 1. The rolling reduction was 2.2%.

[0048] Example 6 A carrier layer-attached metal foil (JXUT-III manufactured by JX Metals Corporation) was used as the carrier layer-attached metal foil, which was a copper foil having a thickness of 18 μm, a 3.0 μm-thick ultrathin copper layer having a roughened particle layer and an anti-rust layer on its surface, provided on a release layer (inorganic release layer) on a copper carrier layer having a thickness of 18 μm, and was manufactured in the same manner as in Example 5, except that the bonding conditions were changed as shown in Table 1. The rolling reduction was 4.3%.

[0049] Example 7 A metal laminated substrate with a carrier layer was produced in the same manner as in Example 4, except that a low dielectric film and intermediate layer were used in which an intermediate layer (40 nm thick) made of copper was formed on the surface of a 25 μm thick low dielectric polyimide (modified polyimide, MPI) film by sputtering deposition. The rolling reduction was 2.2%.

[0050] Example 8 A carrier layer-attached metal foil (prototype material 1) was used, which was a copper foil having a carrier layer of 18 μm thickness, on which an ultrathin copper layer of 2.0 μm thickness and only an anticorrosive layer (without a roughening particle layer) were provided on its surface, via a release layer (inorganic release layer), and a carrier layer-attached metal laminated base material was produced in the same manner as in Example 6, except that the bonding conditions were changed as shown in Table 1. The rolling reduction was 2.2%.

[0051] Example 9 A carrier layer-attached metal foil (prototype material 2) was used as the carrier layer-attached metal foil, which was a copper carrier layer having a thickness of 18 μm, on which an ultrathin copper layer having a thickness of 5.0 μm and only an anticorrosive layer (without a roughening particle layer) were provided on the surface of the carrier layer (prototype material 2) was used, and the bonding conditions were changed as shown in Table 1. A carrier layer-attached metal laminated base material was produced in the same manner as in Example 8. The rolling reduction was 6.3%.

[0052] Comparative Example 1 A metal laminated substrate with a carrier layer was produced in the same manner as in Example 5, except that the joining conditions were changed as shown in Table 1. The rolling reduction was 2.2%.

[0053] Comparative Example 2 A metal laminated substrate with a carrier layer was produced in the same manner as in Example 6, except that the joining conditions were changed as shown in Table 1. The rolling reduction was 4.3%.

[0054] Comparative Example 3 A metal laminated substrate with a carrier layer was produced in the same manner as in Example 5, except that the joining conditions were changed as shown in Table 1. The rolling reduction was 2.2%.

[0055] Comparative Example 4 A metal laminated substrate with a carrier layer was produced in the same manner as in Example 6, except that the joining conditions were changed as shown in Table 1. The rolling reduction was 4.3%.

[0056] Comparative Example 5 First, as a metal foil with a carrier layer, a copper foil with a carrier layer (MITSUI MINING & SMELTING CO., LTD. MT18FL) was prepared, which was a 18 μm-thick copper carrier layer, on which an ultra-thin copper layer with a thickness of 2.0 μm and a roughening particle layer and an anti-rust layer were provided on its surface via a release layer (organic release layer), and a liquid crystal polymer (LCP) film with a thickness of 25 μm was prepared as a low dielectric film. Next, the copper foil with the carrier layer and the LCP film were bonded by thermocompression bonding to produce a metal laminated substrate with a carrier layer. The thermocompression bonding conditions are as shown in Table 2.

[0057] (Comparative Examples 6 and 7) A metal laminated substrate with a carrier layer was produced in the same manner as in Comparative Example 5, except that the conditions for thermocompression bonding were changed as shown in Table 2.

[0058] Comparative Example 8 First, as the metal foil with a carrier layer, a copper foil with a carrier layer (JXUT-III manufactured by JX Metals Corporation) was prepared, which had a 18 μm-thick copper carrier layer, a 3.0 μm-thick ultra-thin copper layer with a roughening particle layer and an anti-rust layer on its surface, via a release layer (inorganic release layer), and a 25 μm-thick liquid crystal polymer (LCP) film as a low dielectric film. Next, the copper foil with the carrier layer and the LCP film were bonded by thermocompression bonding to produce a metal laminated substrate with a carrier layer. The thermocompression bonding conditions are as shown in Table 2.

[0059] (Comparative Examples 9 and 10) Except for changing the thermocompression bonding conditions as shown in Table 2, a metal laminate substrate with a carrier layer was produced in the same manner as in Comparative Example 8.

[0060] The bonding strength between the ultra-thin copper layer and the low dielectric film, the peel strength between the carrier layer and the ultra-thin copper layer, and the total thickness were measured for the metal laminated base materials with a carrier layer obtained in Examples 1 to 9 and Comparative Examples 1 to 10. The measurement results are shown in Table 3.

[0061] [Table 1]

[0062] [Table 2]

[0063] [Table 3]

[0064] As shown in Tables 1 and 3, when the heat treatment temperature was high (Comparative Examples 1 and 2) and when the heat treatment temperature was low (Comparative Examples 3 and 4), it was not possible to achieve both low adhesion between the carrier layer and the ultra-thin copper layer and high adhesion between the ultra-thin copper layer and the low dielectric film.

[0065] In addition, as shown in Tables 2 and 3, when the copper foil with the carrier layer and the low dielectric film were bonded by thermocompression bonding, it was not possible to achieve both low adhesion between the carrier layer and the ultrathin copper layer and high adhesion between the ultrathin copper layer and the low dielectric film. In particular, in Comparative Examples 6, 7, 9, and 10, the low dielectric film became brittle and deteriorated, making it unsuitable as a metal laminated substrate for forming a circuit. In Comparative Example 10, the carrier layer and the ultrathin copper layer could not be peeled off.

[0066] Furthermore, after measuring the bonding strength in Example 5, each peeled surface was observed using a scanning electron microscope (SEM) and subjected to surface elemental analysis using EDX. Scanning electron microscope images are shown in FIG. 5. As a result of the analysis, it was confirmed that no copper was attached to the peeled surface on the LCP side of Example 5. In addition, since some LCP that had undergone cohesive failure was attached to the ultrathin copper layer side (the peeled surface was the intermediate layer), it became clear that the peeling was caused by both internal failure of the LCP and interfacial peeling between the intermediate layer and the LCP.

[0067] (Examples 10 to 16) By removing the carrier layer from the metal laminated substrate with a carrier layer obtained in Examples 1 to 7, a metal laminated substrate having an extremely thin copper layer with a thickness of 1.5 μm to 3.0 μm including a roughening particle layer and an anticorrosive layer was produced.

[0068] (Examples 17 and 18) By removing the carrier layer from the metal laminated substrate with a carrier layer obtained in Examples 8 and 9, a metal laminated substrate having an extremely thin copper layer with a thickness of 2.0 μm to 5.0 μm including only an anti-rust layer (not including a roughening particle layer) was produced.

[0069] The bonding strength between the ultra-thin copper layer and the low dielectric film, the total thickness, and the thickness of the ultra-thin copper layer were measured for the obtained metal laminated base materials of Examples 10 to 18. The measurement results are shown in Table 4.

[0070] [Table 4]

[0071] The metal laminated substrates of Examples 10 to 16 are configured to include an ultra-thin copper layer, a roughened particle layer, an anti-rust layer, an intermediate layer (copper), and an LCP or MPI film, and the metal laminated substrates of Examples 17 and 18 are configured to include an ultra-thin copper layer, an anti-rust layer, an intermediate layer (copper), and an LCP. For these metal laminated substrates, the lamination state of each layer can be identified by measuring the distribution state of elements in the depth direction (depth profile) using glow discharge optical emission spectroscopy (GDS) or Auger electron spectroscopy (AES) or by observing the cross section using a transmission electron microscope (TEM).

[0072] In addition, it is possible to form a circuit pattern using a resist or the like on the extremely thin copper layer of a metal laminated substrate, and then form fine circuits on a low dielectric film using the modified semi-additive method (MSAP method) or semi-additive method (SAP method), etc. [Explanation of symbols]

[0073] 1A Metal laminate substrate with carrier layer 1B Metal laminate substrate with carrier layer 2. Metal laminated substrate 10 Metal foil with carrier layer 11 Carrier Layer 12 Release layer 13 Ultra-thin metal layer 13a Surface of ultra-thin metal layer 20 Low dielectric film 20a Low dielectric film surface 30 Middle Class 30a Surface of the middle layer

Claims

1. A metal laminated substrate with a carrier layer, comprising a metal foil with a carrier layer, the metal foil comprising at least three layers including a carrier layer, a release layer, and an extremely thin metal layer, laminated on at least one surface of a low dielectric film, The bonding strength between the ultra-thin metal layer and the low dielectric film is greater than the peel strength between the carrier layer and the ultra-thin metal layer, and the bonding strength between the ultra-thin metal layer and the low dielectric film is 2.0 N / cm or more; The low dielectric film has a thickness of 10 μm or more and 150 μm or less, In the low dielectric film, the deviation of all of the thickness measurements at 10 points from the average value is within 10%; The above-mentioned metal laminate substrate with a carrier layer, wherein the release layer is a single layer consisting of an organic release layer or an inorganic release layer.

2. 2. The metal laminate substrate with a carrier layer according to claim 1, wherein the low dielectric film is a film of a low dielectric polymer selected from the group consisting of liquid crystal polymers, polyethylene fluoride, polyamides and low dielectric constant polyimides.

3. 3. The metal laminate substrate with a carrier layer according to claim 1, wherein a peel strength between the carrier layer and the ultrathin metal layer is 0.15 N / cm or more and 0.5 N / cm or less.

4. The metal laminate substrate with a carrier layer according to any one of claims 1 to 3, wherein the thickness of the ultrathin metal layer is 0.5 µm or more and 10 µm or less.

5. A metal laminated substrate, comprising: an extremely thin metal layer laminated on at least one surface of a low dielectric film; a bonding strength between the low dielectric film and the extremely thin metal layer being 2.0 N / cm or more; a thickness of the low dielectric film being 10 μm or more and 150 μm or less; and a deviation from the average value of 10 thickness measurement points in the low dielectric film being within 10% for all measurement values.

6. 6. The metal laminated substrate according to claim 5, wherein the thickness of the ultrathin metal layer is 0.5 μm or more and 10 μm or less.

7. A printed wiring board comprising a circuit formed on the ultrathin metal layer of the metal laminated substrate according to claim 5 or 6.

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