Laminate

Abstract

An object of the present invention is to provide a novel laminate of a composite copper material and a resin substrate. By using the present invention, there is provided a laminate in which a resin substrate having a dielectric constant of 3.8 or less is laminated on the above-described surface of a copper material having a plurality of fine convex portions on at least a part of the surface, and the fractal dimension of the laminated surface of the above-described copper material and the above-described resin substrate is 1.25 or more.

Description

Technical Field

[0001] The present invention relates to a laminate. Background Art

[0002] The copper foil used for printed circuit wiring boards has requirements for the adhesion to resin. In order to improve this adhesion, a method of roughening the surface of the copper foil by etching or the like and improving the mechanical adhesion force by the so-called anchoring effect has been applied. However, from the viewpoints of high density of printed circuit boards and transmission loss in high-frequency bands, flattening of the copper foil surface is required. In order to meet such contrary requirements, a copper surface treatment method such as an oxidation process and a reduction process has been developed (International Publication No. 2014 / 126193). According to its description, the copper foil is pretreated, the surface of the copper foil is oxidized by dipping it in a chemical agent containing an oxidant to form irregularities of copper oxide, and then it is dipped in a chemical agent containing a reducing agent to reduce the copper oxide, thereby adjusting the irregularities on the surface and trimming the surface roughness. In addition, as a method for improving the adhesion in the treatment of copper foil by oxidation and reduction, a method of adding a surface active molecule in the oxidation process (Japanese Patent Application Laid-Open No. 2013-534054) or a method of forming a protective film on the surface of the copper foil using an aminothiazole-based compound or the like after the reduction process (Japanese Patent Application Laid-Open No. 8-97559) has been developed. A method of roughening the surface of a copper conductor pattern on an insulating substrate and forming a plating film having discretely distributed metal particles by electroless plating on the surface formed with a copper oxide layer has also been developed (Japanese Patent Application Laid-Open No. 2000-151096).

[0003] On the other hand, in addition to the mechanical adhesion force, 1) the physical bonding force generated by the intermolecular force between the resin and the metal and 2) the chemical bonding force generated by the covalent bond between the functional group of the resin and the metal also participate in the bonding between the resin and the metal. In order to achieve low dielectric constant and low dielectric loss tangent, the proportion of OH groups (hydroxyl groups) in the insulating resin for high-frequency circuits is reduced, but since the OH groups of the resin participate in the bonding with the metal, the chemical bonding force with the copper foil becomes weak (International Publication No. 2017 / 150043). Therefore, for the bonding between the insulating resin for high-frequency circuits and the copper foil, a stronger mechanical adhesion force is required. Summary of the Invention

[0004] Technical Problem to be Solved by the Invention

[0005] An object of the present invention is to provide a novel laminate of a composite copper material and a resin substrate.

[0006] Technical Solution for Solving the Technical Problem

[0007] The inventors of the present invention conducted elaborate research and as a result, successfully produced a novel laminate of a composite copper material and a resin substrate with excellent peel strength and heat resistance. The present invention includes the following embodiments:

[0008] [1] A laminate in which a resin substrate having a dielectric constant of 3.8 or less is laminated on the surface of a copper material having a plurality of fine convex portions on at least a part of the surface,

[0009] The fractal dimension of the laminated surface of the copper material and the resin substrate is 1.25 or more.

[0010] [2] The laminate according to [1], wherein the fractal dimension of the laminated surface is greater than 1.4.

[0011] [3] The laminate according to [1] or [2], wherein at least a part of the surface of the copper material includes a copper oxide layer.

[0012] [4] The laminate according to [1] or [2], wherein a metal layer other than copper is formed on at least a part of the surface of the copper material, and the metal other than copper is at least one metal selected from Sn, Ag, Zn, Al, Ti, Bi, Cr, Fe, Co, Ni, Pd, Au, and Pt.

[0013] [5] The laminate according to [4], wherein the average thickness in the vertical direction of the metal layer other than copper is 10 nm or more and 150 nm or less.

[0014] [6] The laminate according to any one of [1] to [5], wherein in the vertical cross-section of the laminate, the height of the convex portion is on average 50 nm or more and 500 nm or less.

[0015] [7] The laminate according to [6], wherein in the vertical cross-section of the laminate, there are 30 or more of the convex portions per 3.78 μm cross-sectional width on average.

[0016] [8] The laminate according to any one of [1] to [7], wherein the resin substrate contains polyphenylene ether, polytetrafluoroethylene, or a liquid crystal polymer containing p-hydroxybenzoic acid.

[0017] [9] The laminate according to [8], wherein

[0018] When the resin substrate and the composite copper material are peeled, the peeling mode is cohesive failure.

[0019]

[10] The laminate according to [9], wherein in the heat resistance test, the deterioration rate is 50% or less.

[0020]

[11] The laminate according to any one of [1] to

[10] is used for high-frequency circuits of 1 GHz or higher.

[0021]

[12] An electronic component manufactured using the laminate according to any one of [1] to

[11] .

[0022] == Cross-reference to related documents ==

[0023] This invention claims priority based on Japanese Patent Application No. 2019-089122 filed on May 9, 2019, and incorporates the content of this basic application into this specification by reference. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a diagram showing an SEM cross-sectional analysis image (fractal dimension) of an embodiment of the present invention.

[0025] Figure 2A It is a schematic diagram for explaining the shape of the convex portion in the present invention.

[0026] Figure 2B It is a diagram showing the shape of the convex portion of the laminated layer in the SEM cross-sectional analysis image of an embodiment of the present invention.

[0027] Figure 3 It is a diagram showing the appearance of the test piece after the peel test of an embodiment of the present invention.

[0028] Figure 4 It is a diagram showing the transmission loss measurement result of an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not necessarily limited thereto. Among them, through the description of this specification, the purpose, features, advantages, and concept of the present invention are clear to those skilled in the art, and those skilled in the art can easily reproduce the present invention based on the description of this specification. The following-described embodiments and specific examples of the invention represent the preferred embodiments of the present invention, and are intended to illustrate or explain, and do not limit the present invention to these. Those skilled in the art can clearly understand that various changes and modifications can be made based on the description of this specification within the intention and scope of the present invention disclosed in this specification.

[0030] == Laminate ==

[0031] One aspect of the present invention is a laminate in which a resin substrate having a dielectric constant of 3.8 or less is laminated on a copper material having a plurality of fine convex portions on its surface.

[0032] The copper material and the resin substrate are preferably closely bonded. For example, when observing the cross-section of a laminate made by focused ion beam (FIB), in the obtained scanning electron microscope (SEM) cross-sectional image (magnification 30,000 times, resolution 1024x768), it is preferably at a level where no voids can be detected between the copper material and the resin substrate layer.

[0033] The copper material includes copper foils such as electrolytic copper foil or rolled copper foil, copper wire, copper plate, and copper lead frame, but is not limited thereto. The copper material is a material containing 50% by mass or more of Cu, that is, a material forming part of the structure, and may include materials covered with copper alloy (i.e., cupronickel, brass, aluminum bronze, etc.) or copper (such as copper-plated iron). Preferably, it is a material formed of pure copper with a Cu purity of 99.9% by mass or more, more preferably formed of tough pitch copper, deoxidized copper, or oxygen-free copper, and further preferably formed of oxygen-free copper with an oxygen content of 0.001% to 0.0005% by mass.

[0034] As the resin substrate, there is no particular limitation. It may contain thermoplastic resin or may contain thermosetting resin. Specifically, it may include polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyvinyl acetate (PVAc), polyamide (PA), polyoxymethylene (POM), polycarbonate (PC), modified polyphenylene ether (m-PPE), polyphenylene ether containing polystyrene-based polymer, polymer or copolymer of triallyl cyanurate, phenolic adduct butadiene polymer, diallyl phthalate, divinylbenzene, polyfunctional methacrylate, unsaturated polyester, polybutadiene, styrene-butadiene, cross-linked polymer of styrene-butadiene / styrene-butadiene, bismaleimide triazine (BT), polyethylene terephthalate (PET), glass fiber-reinforced polyethylene terephthalate (GF-PET), polybutylene terephthalate (PBT), cyclic olefin polymer (COP), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE), polysulfone (PSF), polyethersulfone (PES), amorphous polyarylate (PAR), liquid crystal polymer (LCP) (such as condensate of p-hydroxybenzoic acid and ethylene glycol terephthalate; condensate of p-hydroxybenzoic acid, phenol and phthalic acid; condensate of p-hydroxybenzoic acid and 2,6-hydroxynaphthoic acid, etc.), polyetheretherketone (PEEK), thermoplastic polyimide (PI), polyamideimide (PAI), and substrates of their mixtures.

[0035] The resin substrate may also contain inorganic fillers and glass fibers.

[0036] The dielectric constant of such a resin substrate can be measured by known methods. For example, it can be measured according to standards such as IPC TM (Test Method of the Institute for Interconnecting and Packaging Electronic Circuits) - 650 2.5.5.5 and IPC TM - 650 2.5.5.9. As an example of the resin substrate, MEGTRON6 (manufactured by Panasonic Corporation; dielectric constant 3.71 (1 GHz)) composed of 20 to 70% by weight of polyphenylene ether (PPE), 0 to 20% by weight of silica, and 30 to 70% of glass fiber can be cited.

[0037] The laminated surface of the resin substrate and the metal layer preferably has a plurality of fine convex portions. The shape of the convex portion can be defined as the fractal dimension or the inradius of the front end portion of the convex portion. Regarding the fractal dimension, a scanning electron microscope (SEM) can be used, and in a cross-sectional image formed by a focused ion beam (FIB), it can be calculated as the fractal dimension of the curve appearing on the laminated surface. For example, the fractal dimension can be calculated by the box counting method, but the calculation method is not limited thereto. Using a scanning electron microscope (SEM), the convex portions are measured in a cross-sectional image formed by a focused ion beam (FIB), and thus the inradius of the front end portion of the convex portion can be calculated.

[0038] The fractal dimension is an index indicating the complexity of a figure, the degree of unevenness of a surface, etc. The larger the value of the fractal dimension, the more complex the unevenness. For example, the fractal dimension using the box counting method is defined as follows:

[0039] For a certain figure F, when the number of boxes required to cover it with boxes of side length δ is set as Nδ(F), the fractal dimension is defined by the following formula.

[0040]

[0041] In the present invention, the cross-section of the laminate is divided by a lattice with an equal interval δ, and for a plurality of δ, the number of boxes (i.e., squares that can be divided by the lattice) including the curve appearing on the laminated surface is counted. Then, with the size of δ as the horizontal axis and the number of boxes counted for each δ as the vertical axis, a double logarithmic curve graph is drawn, and the fractal dimension can be obtained from the slope of this curve graph.

[0042] More specifically, according to the SEM cross-sectional image (magnification 30000 times, resolution 1024x768), the contour of the obtained fine convex portions is pasted with a sheet having a resolution of 256, 128, 64, 32, 16, or 8 pixels, and the number of pixels including the contour is counted. Taking the logarithm of the pixel size as the vertical axis and the logarithm of the number of pixels as the horizontal axis, the number of pixels counted for each pixel size is plotted to form an approximate straight line, and the value of the fractal dimension is calculated based on its slope.

[0043] The value of the fractal dimension of the curve exhibited by the laminated layer is 1.250 or more, or a value greater than 1.250, preferably 1.300 or more, or a value greater than 1.300, more preferably 1.350 or more, or a value greater than 1.350, and further preferably 1.400 or more, or a value greater than 1.400.

[0044] In one aspect of the present invention, a copper oxide layer containing copper(I) oxide and / or copper(II) oxide may also be included on the surface of the copper material. Such a copper oxide layer can be formed by an oxidation treatment, an oxidation dissolution treatment, a redox treatment, or an oxidation dissolution redox treatment.

[0045] The oxidation treatment includes a step of converting pure copper into copper(II) oxide using an oxidizing agent.

[0046] The dissolution treatment includes a step of dissolving the copper(II) oxide oxidized by the oxidation treatment using a solvent.

[0047] The reduction treatment includes a step of reducing the copper(II) oxide oxidized by the oxidation treatment to copper(I) oxide or pure copper using a reducing agent.

[0048] The oxidation treatment, the dissolution treatment, and the reduction treatment may also include a step of forming fine convex portions (i.e., fine hairs) on the surface of the copper material and a step of adjusting the shape or number of the fine convex portions. The multiple fine convex portions of the laminated layer of the resin substrate and the metal layer may also be generated from the fine convex portions formed by these treatments.

[0049] A metal layer other than copper may be formed on at least a part of the surface of the copper material. When forming the above copper oxide layer, the metal layer is preferably formed on at least a part of the surface of the copper oxide layer, and a resin substrate having a dielectric constant of 3.8 or less is laminated on at least a part of the surface of the metal layer. The type of metal constituting the metal layer is not particularly limited, and is preferably at least one metal selected from Sn, Ag, Zn, Al, Ti, Bi, Cr, Fe, Co, Ni, Pd, Au, and Pt. In particular, in order to have heat resistance, a metal having higher heat resistance than copper, such as Ni, Pd, Au, and Pt, is preferred.

[0050] The average thickness of the metal layer in the vertical direction is not particularly limited, preferably 6 nm or more, more preferably 10 nm or more, 14 nm or more, 18 nm or more, or 20 nm or more. However, when it is too thick, the fine protrusions on the surface of the composite copper material are smoothed by leveling, the value of the fractal dimension becomes smaller, and the adhesion decreases. Therefore, it is preferably 150 nm or less, more preferably 100 nm or less, or 75 nm or less.

[0051] As a method for measuring the thickness, for example, the copper material is dissolved in 12% nitric acid, and for the obtained solution, the concentration of the metal component is measured using an ICP emission analyzer 5100SVDV ICP - OES (manufactured by Agilent Technologies). Considering the density of the metal and the surface area of the metal layer, the thickness of the layered metal layer can be calculated.

[0052] The metal layer can also be formed on the surface of the copper material by plating. The plating method is not particularly limited, and examples thereof include electroplating, electroless plating, vacuum evaporation, chemical surface treatment, etc., and electroplating is preferred.

[0053] In one aspect of the present invention, in the SEM cross-sectional image of the laminate, the average height of the protrusions of the curve appearing on the laminate surface is preferably 10 nm or more, more preferably 50 nm or more, further preferably 100 nm or more, still preferably 1000 nm or less, more preferably 500 nm or less, and further preferably 200 nm or less. The height of the protrusion can be, for example, the distance between the midpoint of the line segment connecting the minimum points of the adjacent concave portions sandwiching the protrusion and the maximum point of the protrusion located between the concave portions in the SEM cross-sectional image.

[0054] In one aspect of the present invention, in the SEM cross-sectional image of the laminate, the number of protrusions with a height of 50 nm or more on the laminate surface can have an average of 25, 30, or 35 or more per 3.78 μm cross-sectional width. Or, the number of protrusions with a height of 100 nm or more has an average of 6, 10, or 12 or more per 3.78 μm cross-sectional width. Or, the number of protrusions with a height of 150 nm or more has 2 or 3 or more per 3.78 μm cross-sectional width.

[0055] The greater the height of the convex portion, the greater the mechanical adhesion force generated by the anchoring effect. Therefore, from the perspective of peel strength, it is preferred. However, the influence of the skin effect phenomenon becomes greater. The skin effect is a phenomenon in which the current flowing in a conductor concentrates on the surface of the conductor as the frequency increases, resulting in a decrease in the current density inside. The thickness (skin depth) of the skin portion where the current flows is inversely proportional to the square root of the frequency. Utilizing this skin effect phenomenon, when transmitting high-frequency signals in the GHz band in a conductor circuit, the skin depth is about 2 μm or less than 2 μm, and the current only flows on the outermost surface of the conductor. Therefore, in a high-frequency circuit, when the convex portion on the surface of the copper material is large, the transmission path of the conductor formed by this copper material becomes longer due to the influence of the skin effect phenomenon, and the transmission loss increases. Therefore, it is desirable that the convex portion on the surface of the copper material used for a high-frequency circuit is small. However, when it is too small, sufficient peel strength cannot be obtained, and a convex portion of the above-mentioned degree is preferred.

[0056] In this specification, the in-circle radius of the front end portion of the convex portion can be used as an index of the thickness of the convex portion. The in-circle radius of the front end portion of the fine convex portion here is defined as: in the SEM cross-sectional image, a circle with a radius ([ Figure 2A ) using three points, namely, the maximum point a of the convex portion with a height of 10 nm or more, the intersection points b and c of the straight line parallel to the tangent line of the maximum point a of the convex portion and at a distance of 10 nm from it with the outer peripheral portion of the convex portion, as the outer periphery. The larger the in-circle radius, the thicker the front end portion of the convex portion; the smaller the in-circle radius, the thinner the front end portion of the convex portion.

[0057] In one aspect of the present invention, when peeling the resin substrate from the composite copper material, it is preferred that at least a part of the failure mode of the peeling surface on the composite copper material side is cohesive failure. Among them, cohesive failure is a state in which resin adheres to more than about half of the area when observing the copper side of the peeling surface.

[0058] In one aspect of the present invention, the deterioration rate in the heat resistance test of the laminate can be 50% or less, preferably 40% or less, 30% or less, or 20% or less. The deterioration rate in the heat resistance test can be measured by a known method. For example, it can be expressed as: measuring the peel strength before and after the heat resistance test, and obtaining the ratio by dividing the difference in the peel strength by the peel strength before the heat resistance test. As the heat resistance test, for example, it can be measured according to standards such as IPC TM-650 2.4.8.

[0059] ==Manufacturing method of laminate==

[0060] One embodiment of the present invention is a manufacturing method of a laminate. The manufacturing method of the laminate includes: a first step of forming a convex portion on the surface of the copper material; and a third step of heat-sealing the resin substrate to the surface of the copper on which the convex portion is formed or the surface after plating treatment. This manufacturing method may include a second step of performing plating treatment on the surface of the copper on which the convex portion is formed after the first step.

[0061] First, in the first step, the copper surface is oxidized using an oxidizing agent to form a copper oxide layer, and convex portions are formed on the surface. Before this oxidation step, a roughening treatment step such as etching is not required, but it can be performed. An alkali treatment can be performed to prevent the mixing of acid into the degreasing cleaning or oxidation step. The method of the alkali treatment is not particularly limited, and it is sufficient to treat with an aqueous alkali solution preferably at 0.1 to 10 g / L, more preferably at 1 to 2 g / L, such as an aqueous sodium hydroxide solution, at 30 to 50 °C for about 0.5 to 2 minutes.

[0062] The oxidizing agent is not particularly limited. For example, an aqueous solution of sodium chlorite, sodium hypochlorite, potassium chlorate, potassium perchlorate, etc. can be used. Various additives (such as phosphates like trisodium phosphate dodecahydrate) and surface-active molecules can also be added to the oxidizing agent. Examples of the surface-active molecules include porphyrin, porphyrin macrocycle, expanded porphyrin, contracted porphyrin, linear porphyrin polymer, porphyrin sandwich coordination compound, porphyrin array, silane, tetra-organic-silane, aminoethyl-aminopropyl-trimethoxysilane, (3-aminopropyl)trimethoxysilane, 1-[3-(trimethoxysilyl)propyl]urea, (3-aminopropyl)triethoxysilane, ((3-glycidoxypropyl)trimethoxysilane), (3-chloropropyl)trimethoxysilane, (3-glycidoxypropyl)trimethoxysilane, dimethyldichlorosilane, 3-(trimethoxysilyl)propyl methacrylate, ethyltriacetoxysilane, triethoxy(isobutyl)silane, triethoxy(octyl)silane, tris(2-methoxyethoxy)(vinyl)silane, chlorotrimethylsilane, methyltrichlorosilane, silicon tetrachloride, tetraethoxysilane, phenyltrimethoxysilane, chlorotriethoxysilane, vinyl-trimethoxysilane, amine, sugar, etc.

[0063] The oxidation reaction conditions are not particularly limited. The liquid temperature of the oxidizing agent is preferably 40 to 95 °C, more preferably 45 to 80 °C. The reaction time is preferably 0.5 to 30 minutes, more preferably 1 to 10 minutes.

[0064] In the first step, the surface of the oxidized copper material can be dissolved using a solvent to adjust the uneven portions on the surface of the oxidized copper material.

[0065] The solvent used in this step is not particularly limited, and preferably a chelating agent, especially a biodegradable chelating agent. Examples thereof may include ethylenediaminetetraacetic acid, diethanolglycine, tetrasodium L-glutamate diacetate, ethylenediamine-N,N'-disuccinic acid, 3-hydroxy-2,2'-iminodisuccinic acid sodium salt, trisodium methylglycine diacetate, tetrasodium aspartate diacetate, disodium N-(2-hydroxyethyl)iminodiacetate, sodium gluconate, etc.

[0066] The pH of the solvent is not particularly limited, preferably alkaline, more preferably pH 8 to 10.5, further preferably pH 9.0 to 10.5, and still further preferably pH 9.8 to 10.2.

[0067] In addition, in the first step, a liquid medicine containing a reducing agent (reducing liquid medicine) may also be used to reduce the copper oxide layer formed on the copper material and adjust the number and height of the convex portions.

[0068] As the reducing agent, DMAB (dimethylamine borane), diborane, sodium borohydride, hydrazine, etc. can be used. In addition, the reducing liquid medicine is a liquid containing a reducing agent, a basic compound (such as sodium hydroxide, potassium hydroxide, etc.) and a solvent (such as pure water, etc.).

[0069] In the second step, for the copper oxide layer having convex portions, plating treatment is performed using a metal other than copper to manufacture a composite copper material. The plating treatment method can use known techniques. For example, as the metal other than copper, Sn, Ag, Zn, Al, Ti, Bi, Cr, Fe, Co, Ni, Pd, Au, Pt or various alloys can be used. The plating step is not particularly limited, and plating can be performed by electroplating, electroless plating, vacuum evaporation plating, chemical surface treatment, etc.

[0070] When performing electroless nickel plating, it is preferable to perform treatment using a catalyst. As the catalyst, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and their salts are preferably used. By performing treatment using a catalyst, a uniform metal layer in which particles do not exist in a dot shape can be obtained. Thus, the heat resistance of the composite copper foil is improved. When performing electroless nickel plating, as the reducing agent, a reducing agent that does not have catalytic activity for copper and copper oxide is preferably used. As the reducing agent that does not have catalytic activity for copper and copper oxide, hypophosphites such as sodium hypophosphite can be cited.

[0071] For the composite copper material manufactured in these steps, coupling treatment using a silane coupling agent, etc. and rust prevention treatment using benzotriazoles, etc. can be arbitrarily performed.

[0072] As a third process, a resin substrate is laminated on the copper oxide layer having convex portions formed in the first process or the plating layer of the copper material after plating in the second process to manufacture a laminate. The manufacturing method of the laminate is not particularly limited, and for example, a known method such as vacuum hot press bonding using a vacuum press can be used. The pressing pressure, temperature, and pressing time are appropriately changed according to the resin substrate used. For example, it is recommended that: when the resin substrate contains PPE resin MEGTRON6 (Panasonic Corporation), while heating, hot press bonding is performed at 0.49 MPa up to 110 °C, and then hot press bonding is performed at 210 °C and 2.94 MPa for 120 minutes; when it contains NX9255 (Park Electrochemical Corporation) of PTFE resin, while heating, hot press bonding is performed at 0.69 MPa up to 260 °C, and then while heating to 385 °C, press bonding is performed at 1.03 MPa to 1.72 MPa, and hot press bonding treatment is performed at 385 °C for 10 minutes, but it is not limited thereto.

[0073] Compared with a resin substrate for high-frequency circuits having a dielectric constant of 3.8 or less and a resin substrate for circuit boards having a dielectric constant greater than 3.8 (for example, FR-4), the pressing temperature tends to be high, and it becomes a state where fine irregularities are more likely to be changed. Copper is affected by heat, and the smaller the irregularities, the greater the influence. This is because when changing due to the same degree of heat, the smaller the object affected, the greater the degree of influence. For example, in the case of fine irregularities, after pressing, the shape of the irregularities may be damaged and sufficient peel strength may not be exhibited. Therefore, for the convex portions, an irregularity shape that can withstand the temperature during pressing and can also exhibit sufficient peel strength after lamination is required.

[0074] In this way, by performing the first to third processes on the copper material, a new type of laminate of the copper material and the resin substrate can be produced. In addition, the copper material used for the laminate can also be formed into a pattern by wiring using a known method (for example, etching).

[0075] The laminate according to the present invention can be used for the manufacture of printed circuit wiring boards, or can also be used for the manufacture of electronic components including printed circuit wiring boards and electronic component classes.

[0076] The printed circuit wiring board manufactured using this laminate is particularly suitable as a substrate for a high-frequency band of 1 GHz or more of signal frequency.

[0077] In addition, since the laminate has an irregularity shape on the laminated surface, the adhesion is excellent, and it is also suitable for flexible substrates.

[0078] Examples

[0079] <1. Manufacture of laminate>

[0080] In Examples 1 and 2 and Comparative Examples 1 and 2, DR-WS (manufactured by Furukawa Electric Co., Ltd., thickness: 18 μm) was used as the copper foil.

[0081] (1) Pretreatment

[0082] [Alkaline degreasing treatment]

[0083] The copper foil was immersed in an aqueous sodium hydroxide solution at a liquid temperature of 50 °C and a concentration of 40 g / L for 1 minute, and then washed with water.

[0084] [Acid cleaning treatment]

[0085] The copper foil after the alkaline degreasing treatment was immersed in a 10 wt% aqueous sulfuric acid solution at a liquid temperature of 25 °C for 2 minutes, and then washed with water.

[0086] [Pre-impregnation treatment]

[0087] Pretreatment was carried out in a 1.2 g / L aqueous sodium hydroxide solution at 40 °C for 1 minute. This is for degreasing and cleaning to reduce non-uniformity of the oxidation treatment.

[0088] (2) Oxidation treatment

[0089] The copper foil after the alkaline treatment was subjected to an oxidation treatment in an oxidation treatment aqueous solution (NaClO2 130 g / L; NaOH 12 g / L) at 45 °C for 1 minute. After these treatments, the copper foil was washed with water. In Comparative Examples 1 and 2, after the oxidation treatment, it was immersed in a reducing agent (dimethylamine borane 5 g / L; sodium hydroxide 5 g / L) at room temperature for 1 minute for reduction treatment.

[0090] (3) Plating treatment

[0091] Regarding Examples 1 and 2, electroplating was performed on the smooth surface (glossy surface. When compared with the reverse side, it is the flat surface.) of the copper foil after the oxidation treatment using an electrolytic solution for nickel plating (nickel sulfamate 470 g / L - boric acid 40 g / L). The conditions were 50 degrees and a current density of 0.5 A / dm 2 ×30 seconds (= 15 C / dm 2 per unit copper foil area).

[0092] (4) Thermal press bonding of the resin substrate

[0093] Regarding Example 1 and Comparative Example 1, for each copper foil, MEGTRON6 (prepreg R5670KJ, manufactured by Panasonic Corporation, dielectric constant 3.71 (1 GHz), thickness 100 μm) was laminated, and using a vacuum high-pressure press, thermal press bonding was carried out under the conditions of a pressing pressure of 2.9 MPa, a temperature of 210 °C, and a pressing time of 120 minutes to obtain a laminate.

[0094] Regarding Example 2 and Comparative Example 2, for each copper foil, a PTFE substrate (NX9255, manufactured by Park Electrochemical Corporation, dielectric constant 2.55 (10 GHz), thickness 0.762 mm) was laminated, and hot pressing was performed using a vacuum high-pressure press under the conditions of a pressing pressure of 1.5 MPa, a temperature of 385 °C, and a pressing time of 10 minutes to obtain a laminate.

[0095] Regarding the examples and comparative examples, a plurality of test pieces were fabricated under the same conditions, respectively.

[0096] <2. SEM Cross-Section Image Analysis>

[0097] 1. Method

[0098] The cross-sections of the obtained laminates (Examples 1 and 2; Comparative Examples 1 and 2) were obtained by FIB (focused ion beam) processing under the conditions of an acceleration voltage of 30 kV and a probe current of 4 nA. Using a focused ion beam scanning electron microscope (Auriga, manufactured by Carl Zeiss), the obtained cross-sections were observed under the conditions of a magnification of 30,000 times and a resolution of 1024x768 to obtain SEM cross-section images. The obtained SEM cross-section images are shown in Figure 1 Based on the images of the cross-sections, the values of the fractal dimension, the measurement of the height of the convex portions, and the measurement of the inscribed circle radius of the front ends of the convex portions were performed. Regarding the measurement of the height of the convex portions and the measurement of the inscribed circle radius of the front ends of the convex portions, image analysis software WinROOF2018 (manufactured by Mitani Corporation, Ver4.5.5) was used. An example of the measurement of the inscribed circle radius of the front ends of the convex portions is illustrated in Figure 2B .

[0099] 2. Results

[0100] The results are shown in Tables 1 to 3 below.

[0101] [Table 1]

[0102]

[0103] [Table 2]

[0104]

[0105] [Table 3]

[0106]

[0107] <The Measurement of Peel Strength>

[0108] 1. Method

[0109] Regarding the laminates of Example 1 and 2 and Comparative Example 1 and 2, the peel strength was measured based on the 90° peel test (Japanese Industrial Standard (JIS) C5016).

[0110] 2. Results

[0111] The results are shown in Table 4.

[0112] In the comparative examples, the peel strength was lower than that in the examples, and the failure mode was also interfacial peeling or partial interfacial peeling. In contrast, in the examples, it was resin agglomeration failure. Thus, the laminate according to the present invention has excellent peel strength compared to the comparative examples.

[0113] [Table 4]

[0114]

[0115] <4. Measurement of heat resistance>

[0116] 1. Method

[0117] Regarding the laminates of Example 1 and Comparative Example 1, the peel strength before and after the heat resistance test was measured. After baking at 125 °C for 4 hours, it was floated in a solder bath at 288 °C for 10 seconds, thereby performing the heat resistance test (in accordance with IPC TM-650 2.4.8). The difference in peel strength before and after the heat resistance test was divided by the peel strength before the heat resistance test to calculate the ratio.

[0118] 2. Results

[0119] The results are shown in Table 5 and Figure 3 .

[0120] When comparing the peel strength in the normal state and after the heat resistance test, a 53% deterioration occurred in Comparative Example 1, but only 19% deterioration occurred in Example 1 (Table 5). In addition, after the heat resistance test, discoloration of the copper material was confirmed in the comparative example ( Figure 3 with a red frame emphasized). This is because the unevenness on the surface of the copper material was dissolved due to the heat resistance test. Thus, the laminate according to the present invention has excellent peel strength and heat resistance compared to the comparative examples.

[0121] [Table 5]

[0122]

[0123] <4. High-frequency characteristics>

[0124] 1. Method

[0125] As Example 1 and Comparative Example 3, after laminating MEGTRON6 (prepreg R5670KJ, manufactured by Panasonic Corporation, thickness: 100 μm) as a resin substrate on a copper foil FV-WS (manufactured by Furukawa Electric Co., Ltd., thickness: 18 μm, Rz: 1.2 μm) by thermocompression molding, a sample for measuring transmission characteristics was fabricated, and the transmission loss in the high-frequency band was measured. The evaluation of the transmission characteristics was performed by measuring using a known stripline resonator method suitable for the measurement in the 0 to 50 GHz band. Specifically, the S21 parameter was measured in a non-coated state under the following conditions.

[0126] Measurement conditions: microwave transmission line structure; substrate MEGTRON6; circuit length 150 mm; conductor width 250 μm; conductor thickness 18 μm; substrate thickness 100 μm; characteristic impedance 50 Ω.

[0127] 2. Results

[0128] The results are shown in Figure 4 .

[0129] The copper foil FV-WS used in Comparative Example 3 has low roughness and is a copper foil for high-frequency substrates with low transmission loss required for information and communication machines such as high-end routers / servers and antennas for communication base stations. The transmission loss of Example 1 is less than that of Comparative Example 3. Thus, the high-frequency characteristics of the laminate according to the present invention are excellent.

[0130] Industrial Applicability

[0131] By using the present invention, a novel laminate of a copper material and a resin substrate can be provided.

Claims

1. A laminate, characterized in that: A resin substrate having a dielectric constant of 3.8 or less is laminated on the surface of a copper material having a plurality of fine convex portions on at least a part of the surface. At least a part of the surface of the copper material is formed of a metal layer other than copper. The average thickness in the vertical direction of the metal layer other than copper is 150 nm or less. In the vertical cross-section of the laminate, the height of the convex portion is on average 10 nm or more and 1000 nm or less. By laminating the copper material and the resin substrate, the fractal dimension obtained by the box-counting method of the laminated surface of the copper material and the resin substrate becomes 1.25 or more.

2. The laminate according to claim 1, characterized in that: The fractal dimension of the laminated surface is greater than 1.

4.

3. The laminate according to claim 1 or 2, characterized in that: At least a part of the surface of the copper material contains a copper oxide layer.

4. The laminate according to claim 1 or 2, characterized in that: The metal other than copper is at least one metal selected from Sn, Ag, Zn, Al, Ti, Bi, Cr, Fe, Co, Ni, Pd, Au, and Pt.

5. The laminate according to claim 1 or 2, characterized in that: The average thickness in the vertical direction of the metal layer other than copper is 10 nm or more.

6. The laminate according to claim 1 or 2, characterized in that: In the vertical cross-section of the laminate, the height of the convex portion is on average 50 nm or more and 500 nm or less.

7. The laminate according to claim 6, characterized in that: In the vertical cross-section of the laminate, there are 30 or more of the convex portions per 3.78 μm cross-sectional width on average.

8. The laminate according to claim 1 or 2, characterized in that: The resin substrate contains polyphenylene ether, polytetrafluoroethylene, or a liquid crystal polymer containing p-hydroxybenzoic acid.

9. The laminate according to claim 8, characterized in that: When the resin substrate is peeled from the copper material, the peeling mode is cohesive failure.

10. The laminate according to claim 9, characterized in that: In the heat resistance test, the deterioration rate is 50% or less. The deterioration rate is a ratio obtained by measuring the peel strength of the laminate before and after the heat resistance test and dividing the difference in peel strength before and after the test by the peel strength before the heat resistance test.

11. The laminate according to claim 1 or 2, characterized in that: It is used for high-frequency circuits of 1 GHz or more.

12. An electronic component manufactured using the laminate according to any one of claims 1 to 11.

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