Laminate and method for manufacturing a laminate

Abstract

To provide a laminate having, in this order, a support layer including a resin, an adhesive layer, and a copper layer having a pattern shape capable of obtaining a good cross-sectional shape in a pattern of the copper layer, and enabling highly precise patterning.SOLUTION: A laminate 1 has, in this order, a support layer 2 including a resin, an adhesive layer 3 and a copper layer 4 having a pattern shape and including copper or a copper alloy. The thickness of the copper layer is 2 μm or more and 5 μm or less, and maximum height roughness Rz of a surface opposite to the adhesive layer of the copper layer is 1.3 μm or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0007]

[0001] The present disclosure relates to a laminate having a support layer, an adhesive layer, and a copper layer in this order, and a method for manufacturing the same.

Background Art

[0002] Copper foil is used in various fields such as printed wiring boards and lithium ion batteries. In recent years, miniaturization, weight reduction, and thinning of devices have been required, and thinning of the copper foil used has also been demanded.

[0003] However, thin copper foil is difficult to handle, and it is difficult to process the copper foil alone. Therefore, it has been practiced to support the copper foil with a support. For example, Patent Document 1 discloses an ultra-thin copper foil including a support copper foil, a release layer laminated on the support copper foil, and an ultra-thin copper layer laminated on the release layer. Further, for example, Patent Document 2 discloses a film carrier tape for electronic component mounting obtained using a flexible copper-clad laminate composed of a copper foil and a base film (resin film).

[0004] In recent years, in printed wiring boards and the like, miniaturization of patterns has been required, and high-definition patterning has been demanded.

[0005] When forming a copper foil in a pattern, the photolithography method is the mainstream as a method for patterning the copper foil. When patterning a copper foil by the photolithography method, side etching during etching of the copper foil using a resist pattern as a mask becomes a problem.

[0006] In the case of a copper foil with a carrier foil having a carrier copper foil, a release layer, and an ultra-thin copper foil in this order as in Patent Document 1, when etching the ultra-thin copper foil using a resist pattern as a mask, the carrier copper foil as a support is also etched. Therefore, side etching of the ultra-thin copper foil can be suppressed, and the cross-sectional shape of the pattern of the ultra-thin copper foil can be made good.

[0007] In contrast, in the case of copper foil with a carrier film having a resin film and copper foil, as described in Patent Document 2, when etching the copper foil using a resist pattern as a mask, the etching speed differs between the copper foil and the resin film, and the resin film acts as an etching stopper. As a result, side etching of the copper foil is likely to occur, and there is a problem in that it is difficult to control the cross-sectional shape of the copper foil pattern.

[0008] On the other hand, the copper foil with carrier foil mentioned above has the problem of being expensive. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] International Publication No. 2014 / 006781 [Patent Document 2] Japanese Patent Publication No. 2008-66416 [Overview of the project] [Problems that the invention aims to solve]

[0010] This disclosure has been made in view of the above circumstances, and its main purpose is to provide a laminate having a support layer containing resin, an adhesive layer, and a copper layer having a patterned shape in that order, in which a good cross-sectional shape can be obtained with the pattern of the copper layer and a laminate that enables high-precision patterning. [Means for solving the problem]

[0011] The inventors of this disclosure conducted diligent research to solve the above problems and found that by reducing the thickness of the copper foil, side etching during etching of the copper foil using a resist pattern as a mask can be suppressed when patterning the copper foil by photolithography. However, there are limits to how thin the copper foil can be. The inventors of this disclosure then conducted further research and found that in a laminate having a support layer, an adhesive layer, and a copper layer in that order, the thickness of the copper layer can be reduced and the surface roughness of the copper layer can be reduced by performing half etching on the entire surface of the copper layer. Furthermore, they found that by reducing the thickness of the copper layer and reducing the surface roughness of the copper layer, the patterning accuracy can be improved. This disclosure is based on these findings.

[0012] One embodiment of the present disclosure provides a laminate having, in this order, a support layer containing a resin, an adhesive layer, and a copper layer having a pattern shape and containing copper or a copper alloy, wherein the thickness of the copper layer is 2 μm or more and 5 μm or less, and the maximum height roughness Rz of the surface of the copper layer opposite to the adhesive layer is 1.3 μm or less.

[0013] Other embodiments of the present disclosure provide a method for manufacturing a laminate, comprising: a bonding step of bonding a copper layer containing copper or a copper alloy to one side of a support layer containing a resin via an adhesive layer; a half-etching step of performing half-etching on the entire surface of the copper layer so that the thickness of the copper layer is 2 μm or more and 5 μm or less, and the maximum height roughness Rz on the side of the copper layer opposite to the adhesive layer is 1.3 μm or less; a resist pattern forming step of forming a resist pattern on the side of the copper layer opposite to the adhesive layer after half-etching; an etching step of etching the copper layer using the resist pattern as a mask; and a resist pattern removal step of removing the resist pattern. [Effects of the Invention]

[0014] In this disclosure, a laminate having a support layer, an adhesive layer, and a copper layer having a patterned shape in that order provides the advantage of being able to obtain a good cross-sectional shape with the pattern of the copper layer and to provide a laminate that enables high-definition patterning. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic cross-sectional view illustrating an example of a laminate in this disclosure. [Figure 2] This is a process diagram illustrating a method for manufacturing the laminate of the present disclosure. [Figure 3] This is a cross-sectional SEM image of the laminate in Example 1. [Figure 4] This is a cross-sectional SEM image of the laminate in Example 2. [Figure 5] This is a cross-sectional SEM image of the laminate in Comparative Example 1. [Figure 6] This is a cross-sectional SEM image of the laminate in Comparative Example 2. [Figure 7] This is a cross-sectional SEM image of the laminate in Comparative Example 3. [Modes for carrying out the invention]

[0016] Embodiments of this disclosure will be described below with reference to drawings and other figures. However, this disclosure can be implemented in many different ways and should not be interpreted as being limited to the embodiments described below. In addition, in order to make the explanation clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual form, but these are merely examples and should not limit the interpretation of this disclosure. Furthermore, in this specification and each figure, elements similar to those described above with respect to previously shown figures will be denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

[0017] In this specification, when expressing the manner of arranging one member on another member, if simply denoted as "above" or "below" without particular notice, it shall include both the case where another member is arranged directly above or below so as to be in contact with a certain member, and the case where another member is arranged above or below a certain member with yet another member interposed therebetween. Further, in this specification, when expressing the manner of arranging one member on the surface of another member, if simply denoted as "on the surface", without particular notice, it shall include both the case where another member is arranged directly above or below so as to be in contact with a certain member, and the case where another member is arranged above or below a certain member with yet another member interposed therebetween.

[0018] Hereinafter, the laminate and the method for manufacturing the laminate according to the present disclosure will be described in detail.

[0019] A. Laminate The laminate according to the present disclosure is a laminate having, in this order, a support layer containing a resin, an adhesive layer, and a copper layer having a pattern shape and containing copper or a copper alloy, wherein the thickness of the copper layer is 2 μm or more and 5 μm or less, and the maximum height roughness Rz of the surface of the copper layer on the side opposite to the adhesive layer is 1.3 μm or less.

[0020] The laminate according to the present disclosure will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example of the laminate according to the present disclosure. As illustrated in FIG. 1, the laminate 1 has, in this order, a support layer 2 containing a resin, an adhesive layer 3, and a copper layer 4 having a pattern shape and containing copper or a copper alloy. The thickness of the copper layer 4 is within a predetermined range, and the maximum height roughness Rz of the surface of the copper layer 4 on the side opposite to the adhesive layer 3 is within a predetermined range.

[0021] Figures 2(a) to 2(f) are process diagrams showing an example of a method for manufacturing a laminate according to this disclosure. First, as shown in Figure 2(a), a copper layer 4 is bonded to one side of a support layer 2 via an adhesive layer 3. Next, as shown in Figure 2(b), half-etching is performed on the entire surface of the copper layer 4. This reduces the thickness of the copper layer 4 and the surface roughness of the copper layer 4. Next, as shown in Figure 2(c), a resist layer 11a is formed on the side of the copper layer 4 opposite to the adhesive layer 3. Subsequently, although not shown, the resist layer 11a is exposed and developed to form a resist pattern 11b as shown in Figure 2(d). Then, as shown in Figure 2(e), etching is performed on the copper layer 4 using the resist pattern 11b as a mask. After that, as shown in Figure 2(f), the resist pattern 11b is removed. This makes it possible to obtain a laminate 1 having a copper layer 4 with a pattern shape.

[0022] In this specification, half-etching refers to etching a copper layer partway through its thickness.

[0023] In the laminate according to this disclosure, the thickness of the copper layer is thin, within the above range. Therefore, when patterning the copper foil using photolithography during the manufacturing process of the laminate, side etching when etching the copper foil using the resist pattern as a mask can be suppressed, resulting in a good cross-sectional shape of the copper layer pattern. Furthermore, in the laminate according to this disclosure, the maximum height roughness Rz of the side of the copper layer opposite the adhesive layer is small, within the above range. This results in a copper layer with excellent smoothness and minimal thickness distribution. Therefore, when patterning the copper foil using photolithography during the manufacturing process of the laminate, the surface smoothness of the resist layer formed on the copper layer can also be improved, increasing patterning accuracy. This allows for good control of the dimensions and cross-sectional shape of the copper layer pattern. Consequently, it is possible to create a laminate with a copper layer having a highly detailed pattern shape.

[0024] Here, copper foil can be broadly divided into rolled copper foil and electrolytic copper foil.

[0025] In the case of rolled copper foil, the surface roughness can be reduced by stretching the copper foil with metal rollers to make a thin film. However, there are limits to how thin the copper foil can be, and even the thinnest copper foil is about 6 μm thick. Generally, copper foil with a thickness of 10 or more μm is used. Therefore, simply using general rolled copper foil and bonding the copper foil to one side of a support layer via an adhesive layer does not make it possible to obtain a laminate with a copper layer of the desired thickness.

[0026] Furthermore, in the case of electrolytic copper foil, it is not possible to form a thin film as a single layer. In this case, a thick support film called a carrier copper foil is generally prepared, a release layer is formed on the carrier copper foil, and then a thin copper foil is formed on the release layer. Electrolytic copper foil is laminated from an electrolytic drum, but the more layers are added, the more uneven the surface becomes and the worse the surface roughness becomes. Therefore, it is very difficult to reduce the surface roughness of electrolytic copper foil. Consequently, it is not possible to obtain a copper layer with the desired surface roughness using general electrolytic copper foil.

[0027] In contrast, as described above, in the present disclosure, the thickness of the copper layer can be reduced and the maximum height roughness Rz of the copper layer surface can be reduced by half-etching the copper layer during the manufacturing process of the laminate. Therefore, in the present disclosure, it is possible to obtain a laminate comprising a copper layer having a predetermined thickness and a predetermined maximum height roughness Rz.

[0028] The following describes each component of the laminate in this disclosure.

[0029] 1. Copper layer The copper layer in this disclosure is a layer located on the side opposite to the support layer of the adhesive layer, has a patterned shape, contains copper or a copper alloy, has a predetermined thickness, and has a predetermined maximum height roughness Rz.

[0030] As the copper layer is attached to the support layer via an adhesive layer, copper foil can be used. For example, either electrolytic copper foil or rolled copper foil can be used as the copper foil. Electrolytic copper foil has the advantage of being able to produce wide copper foils.

[0031] The copper layer contains copper or a copper alloy.

[0032] Copper alloys have copper as their main component. Preferably, the copper content of the copper alloy is, for example, 99.80% by mass or more, more preferably 99.85% by mass or more, and even more preferably 99.90% by mass or more.

[0033] Elements other than copper that make up copper alloys include, for example, tin, nickel, zinc, titanium, silicon, magnesium, beryllium, cobalt, iron, manganese, lead, and phosphorus. Specific examples of copper alloys include nickel silver, phosphor bronze, brass, titanium copper, Corson alloy, and beryllium copper.

[0034] The thickness of the copper layer is 2 μm or more and 5 μm or less, preferably 4 μm or less, and particularly preferably 3 μm or less. By making the copper layer thin enough to be within the above range, side etching can be suppressed when patterning the copper layer by photolithography in the manufacturing process of the laminate according to this disclosure, enabling high-resolution patterning. On the other hand, when thinning the thickness of the copper layer by half etching in the manufacturing process of the laminate according to this disclosure, it is difficult to manufacture if the copper layer is too thin.

[0035] The maximum height roughness Rz of the copper layer on the side opposite the adhesive layer is 1.3 μm or less, preferably 1.25 μm or less, and particularly preferably 1.2 μm or less. Because the maximum height roughness Rz of the copper layer on the side opposite the adhesive layer is small enough to be within the above range, and the copper layer has excellent surface smoothness, the surface smoothness of the resist layer formed on the copper layer can also be improved when patterning the copper layer by photolithography during the manufacturing process of the laminate in this disclosure. This allows for a good cross-sectional shape of the copper layer pattern and enables high-resolution patterning.

[0036] Here, the maximum height roughness Rz of the copper layer surface can be measured in accordance with JIS B0601:2001. A stylus-type surface roughness measuring instrument can be used to measure the maximum height roughness Rz of the copper layer surface. Specifically, the Mitutoyo Surftest SJ-210 compact surface roughness measuring instrument (measuring force: 0.75 mN, stylus shape: tip radius 2 μm, tip angle 60°) can be used. Details of the measurement method for the maximum height roughness Rz will be described in the Examples section below.

[0037] Furthermore, the copper layer has a pattern shape. The pattern shape is designed appropriately according to the application of the laminate in this disclosure. Specific examples of pattern shapes include line-shaped, stripe-shaped, mesh-shaped, dot-shaped patterns, or patterns with dot-shaped holes.

[0038] The method for forming the copper layer will be described later in the section on the manufacturing method of the laminate.

[0039] 2.Support layer The support layer in this disclosure is a layer that supports the copper layer and includes resin.

[0040] As a support layer, for example, a resin substrate can be used. The resin constituting the resin substrate is not particularly limited, and examples include polyethylene terephthalate (PET), polyethylene (PE), polyimide (PI), polypropylene (PP, OPP), polyethylene naphthalate (PEN), polyvinyl chloride resin (PVC), and polystyrene (PS). Among these, polyethylene terephthalate (PET), polyimide (PI), and polyethylene naphthalate (PEN) are preferred. PET has the advantages of being inexpensive, readily available, having relatively high heat resistance, and having a low thermal shrinkage rate. PI and PEN are also preferred in terms of physical properties. Furthermore, the resin substrate may be a stretched film or an unstretched film.

[0041] The support layer may or may not be transparent. As will be described later, if the adhesive layer is an energy-responsive adhesive layer whose adhesive strength decreases or disappears upon irradiation with energy rays, it is preferable that the support layer be transparent in order to irradiate the adhesive layer with sufficient energy rays from the support layer side to reduce its adhesive strength. In this case, the transmittance of the support layer only needs to be permeable to energy rays and can be set as appropriate.

[0042] Furthermore, the support layer may be subjected to surface treatments such as corona treatment or primer treatment on the surface where the adhesive layer is formed, in order to improve adhesion with the adhesive layer.

[0043] The thickness of the support layer is not particularly limited; for example, it can be 12 μm or more and 350 μm or less, preferably 38 μm or more and 188 μm or less, and more preferably 50 μm or more and 100 μm or less. If the thickness of the support layer is too thin, it may not be able to adequately support the copper layer, which may make handling difficult or increase costs.

[0044] Furthermore, as a support layer, an adhesive support layer having a support layer and an adhesive layer as described later can also be used.

[0045] 3. Adhesive layer The adhesive layer in this disclosure is a layer for attaching the copper layer to the support layer.

[0046] The adhesive layer preferably exhibits re-peelability. Here, re-peelability refers to the property of being able to peel off the support layer and adhesive layer from the laminate without damaging the copper layer and support layer, and without leaving any adhesive residue on the surface of the copper layer.

[0047] Examples of such adhesive layers include an adhesive layer exhibiting slight tackiness (first embodiment) and an adhesive layer whose tackiness decreases or disappears when exposed to external stimuli (second embodiment). Among these, the adhesive layer exhibiting slight tackiness is preferred from a cost standpoint. The adhesive layers will be described below in detail according to their respective embodiments.

[0048] (1) First aspect of the adhesive layer The first embodiment of the adhesive layer is an adhesive layer exhibiting slight tackiness. The adhesive layer of this embodiment can fix the copper layer to one side of the support layer due to its initial tackiness, and can be easily peeled off from the copper layer due to its low initial tackiness.

[0049] The adhesive used in the adhesive layer is not particularly limited as long as it can produce an adhesive layer having the above-mentioned adhesive strength. Examples include acrylic adhesives, urethane adhesives, silicone adhesives, etc. Among these, acrylic adhesives are preferred. With acrylic adhesives, an adhesive layer exhibiting re-peelability and slight tackiness can be easily obtained.

[0050] As the acrylic adhesive, it can be appropriately selected from known acrylic adhesives. One preferred acrylic adhesive is, for example, an acrylic adhesive containing a copolymer that includes an alkyl acrylate monomer such as 2-ethylhexyl acrylate as a copolymer component.

[0051] The thickness of the adhesive layer is not particularly limited as long as it is a thickness that can obtain an adhesive layer having the above-mentioned adhesive strength. For example, it is preferably 2 μm or more and 50 μm or less, more preferably 4 μm or more and 30 μm or less, and even more preferably 5 μm or more and 15 μm or less. If the thickness of the adhesive layer is too thin, the desired adhesive strength cannot be obtained, which may make it difficult to fix the copper layer to one side of the support layer, or it may become difficult to form the adhesive layer. On the other hand, if the thickness of the adhesive layer is too thick, the adhesive strength tends to be high, which may make the copper layer more prone to curling when the support layer and adhesive layer are peeled off from the laminate, and may also increase costs.

[0052] (2) Second aspect of the adhesive layer A second embodiment of the adhesive layer is an adhesive layer whose adhesive strength decreases or disappears in response to external stimuli. The adhesive layer of this embodiment can fix the copper layer to one surface of the support layer with its initial adhesive strength, and can be easily peeled off from the copper layer as the adhesive strength decreases or disappears in response to external stimuli.

[0053] In this embodiment, external stimuli include, for example, energy rays and heat. Hereinafter, among the adhesive layers of this embodiment, an adhesive layer whose adhesive strength decreases or disappears due to irradiation with energy rays will be referred to as an energy ray-responsive adhesive layer, and an adhesive layer whose adhesive strength decreases or disappears due to heat will be referred to as a heat-responsive adhesive layer.

[0054] (a) Energy ray responsive adhesive layer An energy-response adhesive layer is an adhesive layer whose adhesive strength decreases or disappears upon irradiation with energy rays. By hardening upon irradiation with energy rays, the energy-response adhesive layer can reduce its adhesive strength and exhibit easy peelability.

[0055] Examples of energy rays include far-ultraviolet, ultraviolet, near-ultraviolet, and infrared rays, as well as electromagnetic waves such as X-rays and gamma rays, and electron beams, proton beams, and neutron beams. Among these, ultraviolet rays are preferred from the viewpoint of versatility.

[0056] The adhesive composition included in the energy-ray responsive adhesive layer can be any material that can be cured by irradiation with energy rays, and for example, it can contain at least a resin (main adhesive component) and an energy-ray polymerizable monomer or oligomer. With such a composition, the energy-ray polymerizable oligomer or monomer hardens upon irradiation with energy rays, thereby reducing the adhesive strength. Furthermore, since the cohesive force increases at this time, transfer to the copper layer surface becomes less likely, and peeling becomes easier.

[0057] Examples of the above-mentioned resins include acrylic resins, polyester resins, polyimide resins, and silicone resins, which are generally used as the main component of adhesives. Among these, acrylic resins are preferred.

[0058] For adhesive compositions used in energy-ray responsive adhesive layers, for example, those described in Japanese Patent Publication No. 2016-203536 and Japanese Patent Publication No. 2018-98260 can be referenced.

[0059] (b) Thermally responsive adhesive layer A heat-responsive adhesive layer is an adhesive layer whose adhesive strength decreases or disappears due to heat.

[0060] The adhesive composition included in the heat-responsive adhesive layer is not particularly limited as long as its adhesive strength decreases or disappears with heat. Examples include a composition containing a resin that serves as the main adhesive component, such as an acrylic resin, and a thermal expansion agent such as microcapsules or a foaming agent, or a composition containing a heat-meltable resin such as a heat-meltable acrylic resin or a heat-meltable epoxy resin as the main adhesive component.

[0061] (c) Others The thickness of the adhesive layer in this embodiment should be such that sufficient initial adhesion can be obtained and that it can withstand external stimuli. That is, if the adhesive layer in this embodiment is an energy-ray responsive adhesive layer, the thickness should be such that energy rays can penetrate to the interior. If the adhesive layer in this embodiment is a heat-responsive adhesive layer, the thickness should be such that heat can be transferred to the interior. Specifically, in the case of an energy-ray responsive adhesive layer, the thickness of the adhesive layer can be 3 μm or more and 50 μm or less, and is preferably 5 μm or more and 30 μm or less.

[0062] One method for forming the adhesive layer is to apply an adhesive composition onto a support layer.

[0063] Furthermore, the method for reducing the adhesive strength of the adhesive layer is appropriately selected in response to external stimuli. The conditions for applying external stimuli should be such that the adhesive strength of the adhesive layer is reduced and peelability is achieved, and these conditions can be appropriately set according to the type and thickness of the adhesive layer. For example, in the case of an energy ray-responsive adhesive layer, the irradiation conditions described in Japanese Patent Application Publication No. 2012-031316 can be applied.

[0064] 4. Other configurations The laminate in this disclosure may have other components in addition to the support layer, adhesive layer, and copper layer as needed. Examples of other components include an insulating layer and a conductive adhesive layer.

[0065] 5. Laminate The laminate in this disclosure may be in the form of a roll or a single sheet, for example.

[0066] When using the laminate described in this disclosure, the support layer and adhesive layer can be peeled off from the laminate before use.

[0067] Applications of the laminate in this disclosure include, for example, electrodes, wiring, terminals, conductive layers, springs, and heat dissipation layers. Specifically, the laminate in this disclosure can be used as a current collector for lithium-ion batteries, wiring and terminals for printed circuit boards, conductive layers for electronic components, springs for foldable displays, conductive copper foil adhesive tapes, and heat dissipation sheets for electronic components.

[0068] B. Method for manufacturing laminates The method for manufacturing a laminate in this disclosure comprises: a bonding step of bonding a copper layer containing copper or a copper alloy to one side of a support layer containing a resin via an adhesive layer; a half-etching step of performing half-etching on the entire surface of the copper layer so that the thickness of the copper layer is 2 μm or more and 5 μm or less, and the maximum height roughness Rz on the side of the copper layer opposite to the adhesive layer is 1.3 μm or less; a resist pattern formation step of forming a resist pattern on the side of the copper layer opposite to the adhesive layer after half-etching; an etching step of etching the copper layer using the resist pattern as a mask; and a resist pattern removal step of removing the resist pattern.

[0069] Figures 2(a) to 2(f) are process diagrams illustrating the manufacturing method of the laminate in this disclosure. Since Figures 2(a) to 2(f) are described in section "A. Laminate" above, their explanation is omitted here.

[0070] In the method for manufacturing the laminate described herein, the thickness of the copper layer can be reduced and the maximum height roughness Rz of the copper layer surface can be decreased by half-etching the copper layer. Therefore, as described in section "A. Laminate" above, high-resolution patterning is possible.

[0071] The following describes each step in the method for manufacturing the laminate according to this disclosure.

[0072] 1.Lamination process The bonding step in this disclosure is a step of bonding a copper layer containing copper or a copper alloy to one surface of a support layer containing resin via an adhesive layer.

[0073] The method for bonding the copper layer to one side of the support layer via an adhesive layer is not particularly limited, as long as it allows for good adhesion between the support layer and the copper layer.

[0074] The support layer, adhesive layer, and copper layer are the same as those described in section "A. Laminate" above, so their explanation is omitted here.

[0075] The thickness of the copper layer can be, for example, 6 μm or more, and preferably 8 μm to 12 μm. A relatively thin copper layer reduces the amount of half-etching, thereby suppressing unevenness in the copper layer thickness after half-etching.

[0076] Furthermore, the maximum height roughness Rz on the side of the copper layer opposite the adhesive layer can be, for example, 1.4 μm or more and 3.0 μm or less. If the above maximum height roughness Rz before the half-etching process is too large, it may be difficult to reduce the above maximum height roughness Rz to a predetermined value or less even after half-etching.

[0077] 2. Half-etching process The half-etching step in this disclosure is a step of performing half-etching on the entire surface of the copper layer such that the thickness of the copper layer becomes 2 μm or more and 5 μm or less, and the maximum height roughness Rz on the side of the copper layer opposite to the adhesive layer is 1.3 μm or less.

[0078] Both wet etching and dry etching can be applied as half-etching methods. Of these, wet etching is preferred from a cost standpoint. Known methods can be used for both wet etching and dry etching. In the case of wet etching, examples of etching solutions include alkaline etching solutions such as amines and ammonia water, or ferric chloride aqueous solution, cupric chloride aqueous solution, persulfate aqueous solution, and acidic etching solutions made by mixing sulfuric acid and hydrogen peroxide. Of these, ferric chloride aqueous solution is preferred because it can reduce surface roughness. Furthermore, from the viewpoint of thickness uniformity, in a laminate having a support layer, an adhesive layer, and a copper layer in this order, it is preferable to have the copper layer side (treated surface) facing downwards and spray the etching solution from the bottom surface.

[0079] The amount of half-etching is adjusted appropriately according to the desired thickness of the copper layer, but a smaller amount is preferable. Specifically, the amount of half-etching is preferably such that the thickness of the copper layer after half-etching is 1 / 3 to 5 / 6 of the thickness of the copper layer before half-etching, more preferably 1 / 2 to 4 / 5, and even more preferably 5 / 8 to 3 / 4. By reducing the amount of half-etching, thickness unevenness of the copper layer after half-etching can be suppressed.

[0080] The thickness of the copper layer after half-etching and the maximum height roughness Rz of the side of the copper layer opposite the adhesive layer are the same as those described in section "A. Laminate 1. Copper Layer" above, so the explanation is omitted here.

[0081] 3. Resist pattern formation process The resist pattern formation step in this disclosure is a step of forming a resist pattern on the side of the copper layer opposite to the adhesive layer after half-etching. In the resist pattern formation step, a resist layer can be formed on the side of the copper layer opposite to the adhesive layer, and the resist layer can be exposed and developed to form a resist pattern.

[0082] The resist can be the same as that used in general photolithography, and both positive and negative types can be used. Furthermore, either a liquid resist or a dry film resist may be used.

[0083] The method for forming the resist layer can be appropriately selected depending on the type of resist, and known methods such as coating or lamination can be applied. The thickness of the resist layer is not particularly limited.

[0084] Known methods can also be applied to the exposure and development of the resist layer.

[0085] 4. Etching process The etching step in this disclosure is a step of etching the copper layer using the resist pattern as a mask.

[0086] Both wet etching and dry etching can be applied as etching methods. Of these, wet etching is preferred from a cost standpoint. Known methods can be used for both wet etching and dry etching. In the case of wet etching, examples of etching solutions include alkaline etching solutions such as amines and ammonia water, aqueous solutions of ferric chloride, aqueous solutions of cupric chloride, aqueous solutions of persulfate, and acidic etching solutions made by mixing sulfuric acid and hydrogen peroxide. In particular, from the viewpoint of high-resolution patterning, in a laminate having a support layer, an adhesive layer, and a copper layer in this order, it is preferable to have the copper layer side (processing surface) facing upwards and to spray the etching solution from the upper surface. Furthermore, it is even more preferable to oscillate the spray nozzle in order to spray the etching solution uniformly over the entire surface.

[0087] 5. Resist pattern removal process The resist pattern removal step in this disclosure is a step of removing the resist pattern.

[0088] The method for removing the resist pattern can be appropriately selected depending on the type of resist, and known methods can be applied. For example, methods such as stripping using an alkaline solution such as an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution can be used.

[0089] This disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of this disclosure and achieves similar effects is included within the technical scope of this disclosure. [Examples]

[0090] The present disclosure will be further explained below with reference to examples.

[0091] [Example 1] For the copper layer, copper foil (NC-WS, 8 μm thick) manufactured by Furukawa Electric Industries, Ltd. was used. Furthermore, for the adhesive support layer, a carrier film was used, comprising a PET substrate (GP3500(50), 50 μm thick) manufactured by Fujimori Industries, Ltd., an adhesive layer (10 μm thick, acrylic adhesive), and a release film, in that order.

[0092] The release film was peeled off the carrier film, and the copper foil was bonded to the exposed adhesive layer. Next, using ferric chloride solution as the etching solution, the copper layer side (treated surface) was placed facing downwards, and the etching solution was sprayed from the bottom surface to perform half-etching until the thickness of the copper foil was 3 μm. Then, a dry film resist was laminated onto the copper foil, exposed and developed to form a resist pattern, and using ferric chloride solution as the etching solution, the copper layer side (treated surface) was placed facing upwards, and the etching solution was sprayed from the top surface, using the resist pattern as a mask to etch the copper foil and remove the resist pattern. This resulted in obtaining a laminate.

[0093] [Example 2] In Example 1, a laminate was formed in the same manner as in Example 1, except that a carrier film was used which, as the support layer with an adhesive layer, consisted of a Somar Somatack PS-1080WA PET substrate (thickness 50 μm), an adhesive layer (thickness 5 μm, acrylic adhesive), and a release film in that order.

[0094] [Comparative Example 1] For the copper layer, copper foil (NC-WS, 8 μm thick) manufactured by Furukawa Electric Industries, Ltd. was used. Furthermore, as the adhesive support layer, a carrier film was used, comprising a Somar PS-1093WA PET substrate (50 μm thick), an adhesive layer (5 μm thick, acrylic adhesive), and a release film in that order.

[0095] The release film was peeled off the carrier film, and copper foil was bonded to the exposed adhesive layer. Next, in the same manner as in Example 1, a dry film resist was laminated onto the copper foil, exposed and developed to form a resist pattern, and the copper foil was etched using the resist pattern as a mask to remove the resist pattern. This obtained a laminate.

[0096] [Comparative Example 2] In Comparative Example 1, the laminate was formed in the same manner as in Comparative Example 1, except that a copper foil (NC-WS, 15 μm thick) manufactured by Furukawa Electric Industries, Ltd. was used as the copper layer.

[0097] [Comparative Example 3] A copper foil with a carrier foil (IUT3, manufactured by Iljin) was used, having an 18 μm thick carrier copper foil, a release layer, and a 3 μm thick ultrathin copper foil in that order. In the same manner as in Example 1, a dry film resist was laminated onto the ultrathin copper foil, exposed and developed to form a resist pattern, and the ultrathin copper foil was etched using the resist pattern as a mask to remove the resist pattern.

[0098] [evaluation] 1. Maximum height roughness Rz The Rz of the copper layer surface was measured in accordance with JIS B0601:2001. Specifically, a small surface roughness measuring instrument, Surftest SJ-210 (measuring force: 0.75 mN, stylus shape: tip radius 2 μm, tip angle 60°) manufactured by Mitutoyo Corporation was used, and the measurement was performed at a length of 4 mm. Five measurements were taken, and the average value was taken as the Rz of the copper layer surface.

[0099] 2. Cross-sectional shape of the copper layer pattern Cross-sectional SEM images of the laminates of the examples and comparative examples are shown in Figures 3 to 7. Note that Figure 3(b) is an enlarged view of Figure 3(a), and Figure 7(b) is an enlarged view of Figure 7(a). The cross-sectional shape of the copper layer pattern was evaluated. A: The edge shape of the pattern is almost perpendicular. B: The pattern's edge shape is tapered, and the taper is small. C: The pattern's edge shape is tapered, and the taper is large.

[0100] [Table 1]

[0101] Table 1 confirms that when the thickness of the copper layer is within a predetermined range and the Rz of the copper layer surface is within a predetermined range, the cross-sectional shape of the copper layer pattern is good. Furthermore, Examples 1 and 2 confirm that half-etching reduces the Rz of the copper layer surface and improves its smoothness. [Explanation of symbols]

[0102] 1… Laminate 2 … Support layer 3 … Adhesive layer 4… Copper layer

Claims

1. A laminate comprising, in this order, a support layer containing resin, an adhesive layer, and a copper layer having a pattern shape and containing copper or a copper alloy, The thickness of the copper layer is 2 μm or more and 5 μm or less. The maximum height roughness Rz of the copper layer on the side opposite to the adhesive layer is 1.3 μm or less. A laminate in which the adhesive layer is an adhesive containing an acrylic adhesive.

2. The laminate according to claim 1, wherein the adhesive layer is an adhesive layer having slight tackiness.

3. A bonding process in which a copper layer containing copper or a copper alloy is bonded to one side of a support layer containing resin via an adhesive layer, A half-etching step is performed on the entire surface of the copper layer such that the thickness of the copper layer is 2 μm or more and 5 μm or less, and the maximum height roughness Rz on the side of the copper layer opposite to the adhesive layer is 1.3 μm or less. A method for manufacturing a laminate, having the following characteristics: A method for manufacturing a laminate, wherein the copper layer of the laminate has a patterned shape.

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