Metal laminated substrate with carrier layer and method for manufacturing same, metal laminated substrate and method for manufacturing 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 laminate substrate with a carrier layer and a method for producing the same, a metal laminate substrate and a method for producing the same, and a printed wiring board. [Background technology]

[0002] Metal foils with carrier layers have been known as components for forming fine wiring (fine pitch). These metal foils are laminates of a peelable carrier layer and an ultrathin metal layer, and can be laminated with a rigid substrate made of glass epoxy resin or the like to obtain a metal laminate substrate with a carrier layer (metal-clad laminate). Laminating a flexible polymer film instead of the rigid substrate is also known and is used as a metal laminate substrate for forming flexible circuit boards. In particular, those using a low-dielectric polymer film, such as low-dielectric-constant polyimide, as the polymer film is useful for high-frequency circuits in fifth-generation mobile communication systems (5G).

[0003] Patent Document 1 discloses a carrier-attached copper foil having an intermediate layer and an ultrathin copper layer, in that order, on one or both sides of the carrier, wherein the ultrathin copper layer is a copper foil formed 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 wherein 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 surface when the color difference of the roughened surface is measured using the color difference system specified 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] Japanese Patent Application Laid-Open No. 2014-224318 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 base material such as glass cloth with a resin and curing the resin to a semi-cured state, and the copper foil is then 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 base material such as a liquid crystal polymer under high temperature and high pressure.

[0006] However, when thermocompression bonding a carrier-attached metal foil to a low-dielectric film, such as a liquid crystal polymer, polyethylene fluoride, or low-dielectric polyimide, which is particularly suitable for high-frequency circuits, the thermocompression temperature must be 280°C or higher, or even 300°C or higher, taking into account the melting point and other properties of the low-dielectric film. At these temperatures, the peel layer between the carrier layer and the ultra-thin metal layer deteriorates, impairing the carrier's releasability. On the other hand, lowering the thermocompression temperature to maintain releasability reduces the adhesion between the ultra-thin metal layer and the low-dielectric film. Therefore, it has traditionally been difficult to maintain both the releasability (low adhesion) between the carrier and the ultra-thin metal layer and the high adhesion between the ultra-thin metal layer and the low-dielectric film.

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

[0008] As a result of intensive research, the inventors of the present invention 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 ultrathin metal layer, and by controlling the bonding strength between the ultrathin metal layer and the low dielectric film and the peel strength between the carrier layer and the ultrathin 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 is composed of at least three layers including a carrier layer, a release layer, and an ultrathin 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 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. (2) The metal laminated substrate with a carrier layer according to (1) above, which has one or more intermediate layers containing a metal between the low dielectric film and the ultrathin metal layer. (3) The metal laminated substrate according to (2) 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. (4) A metal laminate substrate with a carrier layer according to any one of (1) to (3) above, 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 (1) to (4) above, 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 (1) to (5) above, 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 0.5 μm or more and 10 μm or less. (9) A method for producing the carrier layer-attached metal laminate substrate according to (2) above, comprising: 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 ultrathin 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 and 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: (10) The method for producing a metal laminated substrate with a carrier layer according to (9) above, 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 (9) or (10) above, wherein after the roll-bonding, a heat treatment is carried out at 160° C. or more and 300° C. or less. (12) A metal laminated substrate in which an ultrathin 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 ultrathin 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) A 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 (12) to (14) above, wherein the thickness of the ultrathin metal layer is 0.5 μm or more and 10 μm or less. (16) A method for producing a metal laminated substrate in which an ultrathin metal layer is laminated on at least one surface of a low dielectric film via an intermediate layer containing a metal, the method comprising: A method for producing a metal laminated substrate, comprising the step of peeling off the carrier layer from the carrier layer-attached metal laminated substrate described in (2) above. (17) A printed wiring board comprising a metal laminated substrate according to any one of (12) to (15) above, in which a circuit is formed on the intermediate layer and the ultrathin metal layer. [Effects of the Invention]

[0010] According to the present invention, in a metal laminate 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. Furthermore, a metal laminate substrate in which a low dielectric film and an ultrathin metal layer are laminated can be obtained. This metal laminate substrate is suitable for use in high-frequency circuits. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view of a carrier layer-attached metal laminate substrate according to a first embodiment of the present invention. [Figure 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 manufacturing process of a carrier layer-attached metal laminate substrate according to a second embodiment of the present invention. [Figure 3B] 5A to 5C are diagrams illustrating a manufacturing process of a carrier layer-attached metal laminate substrate 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. [Figure 5] 10 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 metal laminate substrate with a carrier layer of Example 5. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below. A cross section of a carrier layer-attached metal laminate substrate according to a first embodiment of the present invention is shown in Fig. 1. The carrier layer-attached metal laminate 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 ultrathin metal layer 13, and a low dielectric film 20 laminated in this order.

[0013] Although not shown in FIG. 1 , the surface of the ultrathin metal layer 13 facing the low-dielectric film 20 may be laminated with a roughened particle layer, an anti-corrosion layer, a layer treated with a silane coupling agent, or the like. These layers may be laminated alone or in combination. The roughened particle layer may contain, for example, a metal selected from the group consisting of Cu, Co, and Ni, or an alloy thereof. Specific examples include a cobalt-nickel alloy plating layer and a copper-cobalt-nickel alloy plating layer. The anti-corrosion layer may contain, for example, a metal selected from the group consisting of Cr, Ni, and Zn, or an alloy thereof. Specific examples include a chromium oxide coating, a chromium oxide and zinc / zinc oxide mixture coating, and a Ni plating layer. Furthermore, examples of silane coupling agents include, but are not limited to, olefin-based silanes, epoxy-based silanes, acrylic-based silanes, amino-based silanes, and mercapto-based silanes. The silane coupling agent can be applied by suitable methods 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 on 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 set appropriately depending on the desired properties, 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 carrier layer-attached metal foil 10 may be impaired, which is undesirable. That is, the carrier layer 11 may deform during handling, causing wrinkles or cracks in the ultrathin metal layer 13. Furthermore, if the carrier layer 11 is too thick, it may have excessive rigidity as a support material, making it difficult to peel from the ultrathin metal layer 13, which is undesirable. Furthermore, the cost of producing the carrier layer-attached metal foil 10 increases.

[0016] The release layer 12 reduces the peel strength of the carrier layer 11 and also suppresses interdiffusion between the carrier layer 11 and the ultrathin metal layer 13 when heating is applied during bonding of the carrier layer-attached metal foil 10 to the low-dielectric film 20. The release layer 12 may be either an organic or inorganic release layer. Examples of components used in organic release layers 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 inorganic release layers 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 achieved by immersion in the solution containing the release layer components, spraying the solution containing the release layer components, or allowing the solution to flow down, followed by drying or other methods to fix the components. Alternatively, a method can be used in which the components of the release layer 12 are coated by a gas-phase method such as vapor deposition or sputtering.

[0017] The thickness of the release layer 12 is typically 1 nm or more and 1 μm or less, and preferably 5 nm or more and 500 nm or less, but is not limited thereto. If the thickness of the release layer 12 is too thin, there is a problem that it cannot be sufficiently separated from the ultrathin metal layer 13, resulting in poor release. On the other hand, if the thickness is too large, release is possible but the manufacturing cost increases, so the thickness is set appropriately taking these factors into consideration.

[0018] The metal constituting the ultrathin metal layer 13 can be appropriately selected depending on the application and desired properties of the carrier layer-attached metal laminate substrate 1A. Specific examples include copper, iron, nickel, zinc, tin, chromium, gold, silver, platinum, cobalt, titanium, and alloys based on any of these. A layer of copper or a copper alloy is particularly preferred. By roll-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 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 ultrathin metal layer 13 refers to the average value of the thicknesses of ultrathin metal layer 13 measured at any 10 points on an optical microscope photograph of the cross section of carrier layer-attached metal laminate substrate 1A.

[0020] The method for manufacturing such an ultrathin 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 thereof.

[0021] In this embodiment, when the bond strength between the ultrathin metal layer 13 and the low dielectric film 20 is compared with the peel strength between the carrier layer 11 and the ultrathin metal layer 13, the bond strength between the ultrathin metal layer 13 and the low dielectric film 20 is greater. This allows the carrier layer 11 to be peeled from the ultrathin metal layer 13 without wrinkling or tearing the ultrathin metal layer 13. However, if the bond strength between the ultrathin metal layer 13 and the low dielectric film 20 and the peel strength between the carrier layer 11 and the low dielectric film 20 are too close, it may be difficult to peel the carrier layer 11 without affecting the interface between the ultrathin metal layer 13 and the low dielectric film 20. Therefore, the difference between the bond 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 preferably 0.25 N / cm or more, more preferably 0.5 N / cm or more, and most preferably 1.5 N / cm or more. Specific values ​​for the bond 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 preferably 2.0 N / cm or greater. The peel strength between the carrier layer 11 and the ultrathin metal layer 13 should be greater than 0, preferably 0.5 N / cm or less. However, in the range below approximately 0.05 N / cm, accurate measurement of the peel strength may be hindered due to the influence of the rigidity of the materials being peeled (carrier layer 11, ultrathin metal layer 13, low dielectric film 20, other anticorrosive 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 greater and 0.5 N / cm or less. To measure the bond strength, a 1 cm wide test piece is first prepared from the metal laminate substrate 1A with a carrier layer. Thereafter, carrier layer 11 is removed, and then electrolytic plating (for example, copper plating when ultrathin metal layer 13 is copper) is performed on the surface of ultrathin metal layer 13, forming a metal layer (including ultrathin metal layer 13) approximately 10 to 20 μm thick on the surface of low dielectric film 20. Then, after the approximately 10 to 20 μm thick metal layer and low dielectric film 20 are partially peeled off, low dielectric film 20 is fixed to a support, and the approximately 10 to 20 μm thick metal layer is pulled in a direction at an angle of 90° to low dielectric film 20. The force required for peeling at this time is taken as the bonding strength (unit: N / cm).To measure the peel strength, a 1 cm wide test piece is first prepared from the carrier layer-attached metal laminate substrate 1A. 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 is taken as the peel strength (unit: N / cm).

[0022] In this specification, the term "bonding strength between an ultra-thin metal layer and a low dielectric film" refers not only to the bond strength when peeling occurs at the interface between the ultra-thin metal layer and the low dielectric film, but also to the bond strength when peeling occurs due to internal destruction of the ultra-thin metal layer, and the bond strength when peeling occurs due to internal destruction of the low dielectric film.Furthermore, when a roughening particle layer, anti-rust layer, silane coupling agent treated layer, etc. (collectively referred to as a "treated layer") are laminated on the surface of the ultra-thin metal layer facing the low dielectric film as described above, it also refers to the bond strength when peeling occurs at the interface between the ultra-thin metal layer and the treated layer, the bond strength when peeling occurs at the interface between the treated layer and the low dielectric film, and the bond strength when peeling occurs due to internal destruction of the treated layer. Furthermore, when there is a metal-containing intermediate layer 30 between the low dielectric film 20 and the ultra-thin metal layer 13, as in the metal laminate substrate with a carrier layer according to the second embodiment described below (Figure 2), the "bonding strength between the ultra-thin metal layer and the low dielectric film" means any of the bonding strength when peeling occurs due to internal destruction of the ultra-thin metal layer, the bonding strength when peeling occurs at the interface between the ultra-thin metal layer (or the treatment layer, if 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 ultrathin 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 a low dielectric polymer material having a relative dielectric constant ε rThe dielectric constant of the low-dielectric film 20 is preferably a material having a dielectric constant of 3.3 or less and a dielectric loss tangent tanδ of 0.006 or less, but is not limited to these. Specifically, materials such as liquid crystal polymers, polyethylene fluoride (fluorine-based resins such as polytetrafluoroethylene), polyamides, isocyanate compounds, polyamideimides, polyimides, low-dielectric-constant polyimides, polyethylene terephthalate, and polyetherimides can be appropriately selected and used. Liquid crystal polymers, polyethylene fluoride, polyamides, or low-dielectric-constant polyimides are preferred. The low-dielectric film 20 may be a single-layer film or a laminate consisting of multiple layers. If it is a multilayer film, at least one of the multiple layers may be made of the low-dielectric polymer material described above. Layers other than the layer made of the low-dielectric polymer material may be made of various conventional materials, such as epoxy resins. Liquid crystal polymers refer to aromatic polyester resins whose basic structure is, for example, parahydroxybenzoic acid, that exhibit liquid crystal properties in the molten state.

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

[0025] Next, a second embodiment of the present invention will be described. Fig. 2 shows a cross section of a carrier layer-attached metal laminate substrate according to the second embodiment of the present invention. In this embodiment, as shown in Fig. 2, an intermediate layer 30 containing metal is provided between an ultrathin 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 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 , similar to the carrier layer-attached metal laminate substrate according to the first embodiment, a roughened particle layer, an anticorrosion layer, a silane coupling agent layer, or the like may be laminated on the surface of the ultrathin metal layer 13 facing the intermediate layer 30. Any one of these layers may be laminated, or multiple layers may be laminated. The roughened particle layer may contain, for example, a metal or alloy thereof selected from the group consisting of Cu, Co, and Ni, but is not limited thereto. The anticorrosion layer may contain, for example, a metal or alloy thereof selected from the group consisting of Cr, Ni, and Zn, but is not limited thereto.

[0027] The intermediate layer 30 preferably 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. In particular, when the ultrathin 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 at%. However, this is not limited thereto. The provision of such an intermediate layer 30 not only protects the surface of the ultrathin metal layer 13 or the low-dielectric film 20 and improves adhesion between the ultrathin metal layer 13 and the low-dielectric film 20, but also imparts functions unique to the intermediate layer 30 (e.g., functioning as an etching stopper layer during etching). The thickness of the intermediate layer 30 may be any thickness that can exhibit its function of improving adhesion, and is not particularly limited. Specifically, the thickness is preferably 5 nm to 200 nm, more preferably 10 nm to 100 nm.

[0028] Next, the manufacturing method of the carrier layer-attached metal laminate substrate according to the present invention will be described, particularly with reference to the case of manufacturing a carrier layer-attached metal laminate substrate 1B having a metal-containing intermediate layer 30 between a low dielectric film 20 and an ultrathin metal layer 13, as shown in FIG. 2 . The carrier layer-attached metal laminate substrate 1B shown in FIG. 2 can be obtained by preparing a carrier layer-attached metal foil 10 consisting of a carrier layer 11, a release layer 12, and an ultrathin 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 together by various methods such as cold roll bonding or surface activated bonding to achieve interlayer adhesion. Note that bonding and / or heat treatment under high pressure during the production of the carrier layer-attached metal laminate substrate 1B can significantly change the structure of each layer of the carrier layer-attached metal laminate substrate 1B before and after bonding and / or heat treatment, potentially impairing the properties of the carrier layer-attached metal laminate substrate 1B. Therefore, it is preferable to select bonding and heat treatment conditions that can avoid such structural changes.

[0029] A preferred embodiment of a method for producing a carrier layer-attached metal laminate 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 ((a) in Figure 3A), and then a metal-containing intermediate layer 30 is sputter-deposited on the surface 20a of the low dielectric film 20. The conditions for sputter-deposition can be set appropriately 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 30 a of the intermediate layer 30 is activated by sputter etching, and the surface 13 a of the ultrathin metal layer 13 in the carrier-layer-attached metal foil 10 is activated by sputter etching. These activated surfaces are then roll-bonded together ((c) of FIG. 3B ), thereby producing a carrier-layer-attached metal laminate substrate 1B ((d) of FIG. 3B ). If the surface 13 a of the ultrathin metal layer 13 includes a roughened particle layer or an anticorrosive layer, the roughened particle layer or the anticorrosive layer surface is activated by sputter etching. The roughened particle layer or the anticorrosive layer may be completely removed by sputter etching, or may remain. The rolling reduction during roll-bonding is 0 to 30%, preferably 0 to 15%. The surface-activated bonding method described above allows for a low rolling reduction, thereby maintaining the functionality (low adhesion) of the release layer 12 while bonding. Furthermore, the ultrathin metal layer 13 can be formed with excellent thickness precision without wrinkles or cracks. Furthermore, since the waviness at the interface 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] Before activation by sputter etching, surface 30a of intermediate layer 30 or surface 13a of ultrathin metal layer 13 may be subjected to Ni plating, chromate treatment, silane coupling agent treatment, or the like to prevent oxidation or improve adhesion, as needed. Furthermore, surface 13a of ultrathin metal layer 13 may be subjected to roughening treatment as needed 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, and applying an AC current of 1 MHz to 50 MHz between the other electrode supported by insulation 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 grounded electrode is in the form of a cooling roll to prevent the temperature of the transported material from rising.

[0033] In sputter etching, the bonding surface of the carrier layer-attached metal foil 10 or the low dielectric film 20 is sputtered with an inert gas under vacuum to completely remove any adsorbed material on the surface and partially or entirely remove any oxide layer on the surface. It is preferable to completely remove the copper oxide layer. Examples of inert gases that can be used include argon, neon, xenon, krypton, and mixtures containing at least one of these. Depending on the type of metal, adsorbed material on the surface of the ultrathin metal layer 13 or intermediate layer 30 can be completely removed with an etching depth of approximately 1 nm. In particular, the copper oxide layer can usually be removed with an etching depth of approximately 5 nm to 12 nm (SiO2 equivalent).

[0034] The conditions for sputter etching can be set appropriately depending on the type of ultrathin metal layer 13 or intermediate layer 30. For example, the 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. The degree of vacuum is preferably high to prevent re-adsorption of substances onto the surface. -5 Pa to 10Pa is fine.

[0035] The surfaces of the sputter-etched ultrathin metal layer 13 and intermediate layer 30 can be pressure-welded together by roll pressure welding. The rolling wire load for roll pressure welding is not particularly limited and can be set, for example, in the range of 0.1 tf / cm to 10 tf / cm. However, if the thickness of the carrier-layer-attached metal foil 10 or the low-dielectric film 20 provided with the intermediate layer 30 before bonding is large, it may be necessary to increase the rolling wire load to ensure sufficient 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 ultrathin metal layer 13 or the intermediate layer 30 but also the bonding interface will be easily deformed, which may reduce the thickness accuracy of each layer in the carrier-layer-attached metal laminated substrate 1B. Furthermore, if the rolling wire load is too high, there is a risk of increased processing strain being applied during bonding.

[0036] The reduction rate 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 rate 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, 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] Furthermore, the carrier layer-attached metal laminate substrate 1B obtained by pressure welding can be further subjected to heat treatment as needed. Heat treatment removes strain in the ultrathin metal layer 13 or intermediate layer 30, improving interlayer adhesion. If this heat treatment is performed at high temperatures for a long period of time, blistering may occur in the carrier layer 11 starting from the release layer 12, which may cause the carrier layer 11 to peel from the blister. Conversely, the adhesion between the carrier layer 11 and the ultrathin metal layer 13 may increase due to interdiffusion or other factors, making peeling of the carrier layer 11 difficult. Furthermore, depending on the combination of the ultrathin metal layer 13 and the intermediate layer 30, intermetallic compounds may form at the interface, reducing adhesion (bonding strength). Therefore, the heat treatment is performed at a temperature of 160°C or higher and 300°C or lower, more preferably 180°C or higher and 290°C or lower. Alternatively, it is preferable not to perform heat treatment after roll bonding. After the carrier layer 11 is peeled off and removed from the metal laminated substrate 1B with a carrier layer after bonding, 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, a metal laminated substrate and a method for manufacturing the same according to the present invention will be described. FIG. 4 is a diagram showing the manufacturing process of a metal laminated substrate according to one embodiment of the present invention. The metal laminated substrate 2 shown in FIG. 4 is generally configured by laminating an ultrathin metal layer 13 on one side of a low dielectric film 20 via a metal-containing intermediate layer 30. 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 (FIG. 4(a)), and the carrier layer 11 of this carrier layer-attached metal laminated substrate 1B is peeled off together with the release layer 12 (FIG. 4(b)), thereby obtaining a three-layered metal laminated substrate 2 (FIG. 4(c)).

[0040] The produced metal laminated substrate 2 has an ultrathin metal layer 13 with 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 also 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 ultrathin metal layer 13 opposite the low dielectric film.

[0041] A printed wiring board having a fine circuit formed thereon can be obtained using the metal laminate substrate 2. In the process of forming the circuit, the additional metal layer can also be formed only in the circuit portion. Specifically, a printed wiring board can be obtained by appropriately using conventionally known techniques such as the modified semi-additive process (MSAP process) or the semi-additive process (SAP process). For example, a printed wiring board can be manufactured by masking the non-circuit portion on the ultra-thin metal layer 13 of the metal laminate substrate 2, copper plating the unmasked portion to form an additional metal layer, removing the mask, and removing the ultra-thin metal layer 13 hidden by the mask by etching. The term "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 has been formed.

[0042] In the embodiments of the carrier layer-attached metal laminate substrate 1A in FIG. 1, the carrier layer-attached metal laminate substrate 1B in FIG. 2, and the metal laminate substrate 2 in FIG. 4, cases have been described in which the carrier layer-attached metal foil 10 or the ultrathin metal layer 13 is laminated on one side of the low dielectric film 20, but the present invention is not limited to this. That is, if necessary, an intermediate layer 30, an ultrathin metal layer 13, a release layer 12, and a carrier layer 11 may be provided on both sides of the low dielectric film 20. By using a carrier layer-attached metal laminate substrate in which these layers are provided on both sides of the low dielectric film 20, a flexible printed wiring board in which circuits are formed on both sides of the low dielectric film 20 can be obtained. [Example]

[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, a carrier-layered metal foil (MT18FL manufactured by Mitsui Mining & Smelting Co., Ltd.) was prepared. The carrier-layered metal foil consisted of an 18 μm-thick copper carrier layer, a 1.5 μm-thick ultrathin copper layer, and a roughened particle layer and anti-corrosion layer on its surface, separated by a release layer (organic release layer). A 25 μm-thick liquid crystal polymer (LCP) film was also prepared as a low-dielectric film. The surface of the LCP film was activated by sputter etching, and then a 40 nm-thick copper intermediate layer was formed by sputter deposition. The surfaces of the ultrathin copper layer and the intermediate layer were then roll-bonded together to produce the desired carrier-layered metal laminate substrate. The line load during pressure bonding was 1.5 t / cm, and the rolling reduction rate for surface activation bonding was 2.2%. After roll-bonding, the substrate was heat-treated at 240°C.

[0045] Example 2 The carrier-layered metal foil used was a copper foil (MT18FL manufactured by Mitsui Mining & Smelting Co., Ltd.) with a carrier layer of 18 μm thick made of copper, a 1.5 μm thick ultrathin copper layer with a roughened particle layer and an anti-corrosion layer provided on its surface via a release layer (organic release layer). A 100 μm thick LCP film was used as the low-dielectric film, and its surface was activated by sputter etching. A copper intermediate layer (40 nm thick) was then formed by sputter deposition. The surfaces of the ultrathin copper layer and the intermediate layer were then roll-bonded together, followed by heat treatment to produce a carrier-layered metal laminate substrate. The bonding conditions are shown in Table 1. The rolling reduction rate for surface activated bonding was 2.5%.

[0046] Examples 3 and 4 A metal laminate 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 in Example 1, a low dielectric film and intermediate layer were prepared by forming an intermediate layer (40 nm thick) made of copper on the surface of a 25 μm thick LCP film by sputtering, 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 laminated substrate was produced in the same manner as in Example 5, except that the metal foil with a carrier layer was a copper foil (JXUT-III manufactured by JX Nippon Mining & Metals Corporation) having an 18 μm-thick copper carrier layer, an ultrathin copper layer with a thickness of 3.0 μm provided on its surface via a release layer (inorganic release layer), and a roughened particle layer and an anti-corrosion layer, and 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 the low dielectric film and intermediate layer were formed by sputtering an intermediate layer (40 nm thick) made of copper on the surface of a 25 μm thick low dielectric polyimide (modified polyimide, MPI) film. The rolling reduction was 2.2%.

[0050] Example 8 A carrier layer-attached metal foil (prototype material 1) was used as the carrier layer-attached metal foil, which had a carrier layer made of copper and having a thickness of 18 μm, a 2.0 μm ultrathin copper layer with only an anticorrosion layer (without a roughening particle layer) provided on its surface via a release layer (inorganic release layer), and a carrier layer-attached metal laminated substrate 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 laminated substrate was produced in the same manner as in Example 8, except that a carrier layer-attached copper foil (prototype material 2) was used, which had a carrier layer made of copper and having a thickness of 18 μm, a 5.0 μm ultrathin copper layer with only an anti-rust layer (without a roughening particle layer) provided on its surface via a release layer (organic release layer), and the bonding conditions were changed as shown in Table 1. 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 laminate 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 laminate 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, a carrier-layered metal foil was prepared using a carrier-layered copper foil (MITSUI MINING & SMELTING CO., LTD., MT18FL) consisting of an 18 μm-thick copper carrier layer, a 2.0 μm-thick ultrathin copper layer, and a roughened particle layer and anti-corrosion layer on its surface, via a release layer (organic release layer). A 25 μm-thick liquid crystal polymer (LCP) film was also prepared as a low-dielectric film. The carrier-layered copper foil and the LCP film were then bonded by thermocompression bonding to produce a carrier-layered metal laminate substrate. The thermocompression bonding conditions are 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 thermocompression bonding conditions were changed as shown in Table 2.

[0058] (Comparative Example 8) First, a carrier-layered metal foil was prepared using a carrier-layered copper foil (JXUT-III manufactured by JX Nippon Mining Corporation) consisting of an 18 μm-thick copper carrier layer, a 3.0 μm-thick ultrathin copper layer with a roughened particle layer and an anti-corrosion layer on its surface, and a 25 μm-thick liquid crystal polymer (LCP) film as a low-dielectric film. The carrier-layered copper foil and the LCP film were then bonded by thermocompression bonding to produce a carrier-layered metal laminate substrate. The thermocompression bonding conditions are shown in Table 2.

[0059] (Comparative Examples 9 and 10) A metal laminated substrate with a carrier layer was produced in the same manner as in Comparative Example 8, except that the thermocompression bonding conditions were changed as shown in Table 2.

[0060] The bonding strength between the ultrathin copper layer and the low dielectric film, the peel strength between the carrier layer and the ultrathin copper layer, and the total thickness were measured for the metal laminate substrates with carrier layers 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] Furthermore, as shown in Tables 2 and 3, when the copper foil with a 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 laminate substrate for forming a circuit. Furthermore, 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, the peeled surfaces of each sample were observed using a scanning electron microscope (SEM) and subjected to surface elemental analysis using EDX. Scanning electron microscope images are shown in Figure 5. The analysis results confirmed that no copper was attached to the peeled surface on the LCP side of Example 5. Furthermore, 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 peeling was caused by both internal fracture 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 ultrathin 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 carrier layer obtained in Examples 8 and 9, a metal laminated substrate was produced having an ultrathin 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).

[0069] The resulting metal laminated substrates of Examples 10 to 18 were measured for the bonding strength between the ultrathin copper layer and the low dielectric film, the total thickness, and the thickness of the ultrathin copper layer. The measurement results are shown in Table 4.

[0070] [Table 4]

[0071] The metal laminated substrates of Examples 10 to 16 were configured to include an ultrathin copper layer, a roughened particle layer, an anticorrosive layer, an intermediate layer (copper), and an LCP or MPI film, while the metal laminated substrates of Examples 17 and 18 were configured to include an ultrathin copper layer, an anticorrosive layer, an intermediate layer (copper), and an LCP. The lamination state of each layer of these metal laminated substrates can be identified by measuring the element distribution state 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, a circuit pattern can be formed using a resist or the like on an ultra-thin copper layer in a metal laminated substrate, and fine circuits can be formed on a low-dielectric film using a modified semi-additive method (MSAP method) or semi-additive method (SAP method). [Explanation of symbols]

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

Claims

1. A metal laminated substrate with a carrier layer, in which a metal foil with a carrier layer, which is composed of at least three layers including a carrier layer, a release layer, and an ultrathin metal layer, is laminated on at least one surface of a low dielectric film, the bonding strength between the ultrathin metal layer and the low dielectric film is greater than the peel strength between the carrier layer and the ultrathin metal layer, and the bonding strength between the ultrathin metal layer and the low dielectric film is 2.0 N / cm or more; The thickness of the low dielectric film is 10 μm or more and 150 μm or less, In the low dielectric film, the deviation of all the measured thicknesses at 10 points from the average value is within 10%; The 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 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.

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.

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