Copper-clad laminate

Abstract

To provide a copper-clad laminate that can produce flexible circuit boards with low transmission loss of a high-frequency electrical signal.SOLUTION: A copper-clad laminate 10 and 11 includes a copper foil 17 laminated on one or both sides of a base film 15 via an adhesive layer 16, where the base film is mainly composed of syndiotactic polystyrene, is biaxially oriented, and has a relative dielectric constant of 2.6 or less and a dielectric loss tangent of 0.002 or less at a frequency of 10 GHz, the adhesive layer has a relative dielectric constant of 2.6 or less and a dielectric loss tangent of 0.005 or less at a frequency of 10 GHz.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a copper clad laminate. [Background technology]

[0002] Copper-clad laminates, which are formed by laminating a synthetic resin film with copper foil bonded to one or both sides of the film, are used to manufacture flexible circuit boards and the like. Electrical signal transmission loss consists of conductor loss and dielectric loss, with the dielectric loss becoming more important as the signal frequency increases. In recent years, as the frequency of electrical signals has rapidly increased, reducing dielectric loss due to materials adjacent to the copper foil has become an issue. Patent documents 1 to 5 describe copper-clad laminates aimed at reducing dielectric loss, such as three- or five-layer copper-clad laminates composed of a synthetic resin film, an adhesive layer, and copper foil. Patent document 6 describes a laminate for electronic circuit boards in which a metal layer is formed by plating on the surface of a syndiotactic polystyrene-based resin film. Patent document 7 describes a film containing a syndiotactic polystyrene-based resin as a base film for flat cables for efficiently transmitting high-frequency signals. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-038281 [Patent Document 2] International Publication No. 2018 / 030026 [Patent Document 3] Japanese Patent Application Publication No. 2017-121807 [Patent Document 4] Patent No. 6539404 [Patent Document 5] International Publication No. 2016 / 017473 [Patent Document 6] Japanese Patent Application Laid-Open No. 2015-002334 [Patent Document 7] International Publication No. 2019 / 049922 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made in consideration of the above circumstances, and has as its object to provide a copper-clad laminate that can be used to manufacture flexible circuit boards with low transmission loss of high-frequency electrical signals. [Means for solving the problem]

[0005] The copper-clad laminate of the present invention is a copper-clad laminate in which copper foil is laminated on one or both sides of a base film via an adhesive layer, the base film being primarily composed of syndiotactic polystyrene and being biaxially oriented, and having a relative dielectric constant of 2.6 or less and a dielectric dissipation factor of 0.002 or less at a frequency of 10 GHz, and the adhesive layer having a relative dielectric constant of 2.6 or less and a dielectric dissipation factor of 0.005 or less at a frequency of 10 GHz.

[0006] This configuration provides a copper clad laminate that can be used to manufacture flexible circuit boards with low transmission loss for high frequency electrical signals.

[0007] The copper clad laminate preferably has an S21 parameter of -5 dB / 100 mm or more and less than 0 at 40 GHz when a microstrip line is fabricated by pattern etching the copper foil and the impedance is adjusted to 50 Ω.

[0008] Preferably, the base film is made substantially of syndiotactic polystyrene, which can further reduce the transmission loss of the copper-clad laminate.

[0009] Alternatively, preferably, the base film is made substantially of syndiotactic polystyrene and a styrene-based thermoplastic elastomer, which can increase the peel strength of the copper-clad laminate.

[0010] Preferably, the base film has a glass transition temperature of 180° C. or higher. Here, the glass transition temperature is a value measured by thermomechanical analysis (TMA). This can increase the strength and heat resistance of the copper-clad laminate.

[0011] Preferably, the maximum height roughness Rz of the interface between the copper foil and the adhesive layer is 2.0 μm or less, where Rz is the maximum height roughness defined in JIS B0601:2013, thereby further reducing the transmission loss of the copper-clad laminate. [Effects of the Invention]

[0012] The copper-clad laminate of the present invention uses a substrate film mainly composed of syndiotactic polystyrene as the substrate, which allows flexible circuit boards to be produced at lower cost and with lower transmission loss for high-frequency electrical signals than when liquid crystal polymers or polyimides are used. Furthermore, the low water absorption of syndiotactic polystyrene means that the transmission characteristics of the copper-clad laminate are less likely to deteriorate even when used in a humid environment. [Brief explanation of the drawings]

[0013] [Figure 1] 1A and 1B are diagrams showing the layer structure of a copper-clad laminate according to one embodiment of the present invention, where A is a five-layer structure and B is a three-layer structure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Referring to FIG. 1A, a copper-clad laminate 10 of this embodiment has a five-layer structure in which copper foil 17 is laminated on both sides of a substrate film 15 via an adhesive layer 16. Referring to FIG. 1B, another copper-clad laminate 11 of this embodiment has a three-layer structure in which copper foil 17 is laminated on one side of a substrate film 15 via an adhesive layer 16. A flexible circuit board is manufactured by etching the copper foil 17 of the copper-clad laminates 10 and 11 into a circuit pattern. Furthermore, the copper-clad laminates 10 and 11 can also be combined with other resin films, glass cloth, and the like to manufacture build-up boards. Note that the following description of the properties and materials of each layer will be given with reference to the five-layer copper-clad laminate 10, but the same description also applies to the three-layer copper-clad laminate 11.

[0015] The base film 15 is made mainly of syndiotactic polystyrene (SPS) and is biaxially oriented.

[0016] Biaxial orientation means that the polymer is oriented in two different directions in the plane, for example, the extrusion direction (MD) of the film and the direction perpendicular to it (TD). Biaxial orientation can be achieved by biaxially stretching an unstretched precursor film.

[0017] SPS is a styrene-based polymer with a syndiotactic structure. A syndiotactic structure refers to a three-dimensional structure in which side chains of phenyl or substituted phenyl groups are alternately positioned in opposite directions relative to the main chain formed by carbon-carbon bonds. The degree of stereoregularity (tacticity) of SPS can be quantified by nuclear magnetic resonance spectroscopy using a carbon isotope (C-NMR). The tacticity of an SPS-based resin measured by C-NMR can be expressed as the proportion of chains consisting of several monomer units, e.g., two units forming a diad, three units forming a triad, or five units forming a pentad, in which the structural unit configuration is reversed (e.g., racemic diads). The SPS of this embodiment is typically a styrene-based polymer with a syndiotacticity of 75% or more, preferably 85% or more, racemic diads, 60% or more, preferably 75% or more, racemic triads, or 30% or more, preferably 50% or more, racemic pentads. The base film 15 may be made of a mixture of two or more different types of SPS.

[0018] Examples of styrene-based polymers usable as SPS include polystyrene, poly(alkylstyrene), poly(halogenated styrene), poly(halogenated alkylstyrene), poly(alkoxystyrene), poly(vinyl benzoate ester), hydrogenated polymers thereof, and mixtures or copolymers containing these as main components. Examples of poly(alkylstyrene)s include poly(methylstyrene), poly(ethylstyrene), poly(isopropylstyrene), poly(tertiary butylstyrene), poly(phenylstyrene), poly(vinylnaphthalene), and poly(vinylstyrene). Examples of poly(halogenated styrene)s include poly(chlorostyrene), poly(bromostyrene), and poly(fluorostyrene). Examples of poly(halogenated alkylstyrene)s include poly(chloromethylstyrene). Examples of poly(alkoxystyrenes) include poly(methoxystyrene) and poly(ethoxystyrene). Polystyrene is preferred as the styrene-based polymer usable as SPS.

[0019] The weight average molecular weight of SPS is 10,000 to 3,000,000, preferably 30,000 to 1,500,000, and particularly preferably 50,000 to 500,000.

[0020] In one preferred embodiment, the base film 15 consists essentially of SPS. "Consisting essentially of SPS" means that the base film 15 may contain resins other than SPS as long as the required transmission loss is obtained for the copper-clad laminate 10. Specifically, the proportion of SPS in the total resin of the base film 15 is set to 90% by mass or more, more preferably 95% by mass or more. This allows the transmission loss of the copper-clad laminate to be kept even lower.

[0021] In another preferred embodiment, the base film 15 is made essentially of SPS and a styrene-based thermoplastic elastomer (TPS). TPS is a thermoplastic elastomer (TPE) whose hard segment is made of polystyrene. "Made essentially of SPS and TPS" means that the base film 15 may contain resins other than SPS and TPS as long as the required transmission loss is achieved for the copper-clad laminate 10. Specifically, the combined proportion of SPS and TPS in the total resin content of the base film 15 is 90% by mass or more, more preferably 95% by mass or more. This allows the peel strength of the copper-clad laminate 10 to be increased while suppressing deterioration of the dielectric properties of the base film 15.

[0022] Various commercially available TPSs can be used. It is preferable to use a hydrogenated TPS. This improves the heat resistance of the TPS and prevents unexpected reactions during the high-temperature melting and extrusion process of the base film raw material.

[0023] The hydrogenated TPS may be a variety of TPSs with different soft segments, such as polystyrene-poly(ethylene / butylene)-polystyrene (TPS-SEBS), polystyrene-poly(ethylene / propylene)-polystyrene (TPS-SEPS), polystyrene-poly(ethylene-ethylene / propylene)-polystyrene (TPS-SEEPS), or polystyrene-poly(ethylene / propylene)-polystyrene (TPS-SEP). It is particularly preferred to use TPS-SEEPS, in which the soft segment is a random copolymer of poly(ethylene-ethylene / propylene), in all or part of the TPS. The TPS contained in the base film 15 may be a mixture of two or more different resins.

[0024] The amount of TPS blended is preferably such that the weight ratio of SPS (a) to TPS (b) is (a) / (b) = 97 / 3 to 51 / 49, more preferably 97 / 3 to 60 / 40, 97 / 3 to 70 / 30, or 97 / 3 to 80 / 20. This preferred blending ratio also applies when the soft segment of the TPS is composed of a poly(ethylene / propylene) block or a poly(ethylene-ethylene / propylene) random copolymer block, such as TPS-SEEPS, as all or part of the TPS. If the amount of TPS blended is too low, the effect of improving the peel strength of the copper-clad laminate 10 is small. On the other hand, if the amount of TPS blended is too high, the deterioration of the dielectric properties of the base film 15 becomes significant.

[0025] In addition to the polymer, the base film 15 may contain additives such as plasticizers, antioxidants, UV absorbers, light stabilizers, lubricants, antistatic agents, inorganic fillers, colorants, crystal nucleating agents, and flame retardants.

[0026] The glass transition temperature Tg of the substrate film 15 is preferably 180°C or higher, more preferably 190°C or higher. If the glass transition temperature Tg is too low, the quality of the copper-clad laminate 10 may be reduced during the heating process during production, and the strength and heat resistance of the copper-clad laminate may not be sufficiently high. Although a high glass transition temperature Tg does not pose any particular problems, substrate films primarily composed of SPS typically do not exceed 250°C. Note that, in this specification, the glass transition temperature Tg refers to the temperature measured by thermomechanical analysis (TMA). While the glass transition temperature Tg can be measured by several methods, TMA is the most suitable indicator of practical heat resistance. The glass transition temperature Tg measured by TMA can be determined from a TMA curve obtained using the test method specified in JIS K7197:1991. While the SPS material itself has a low glass transition temperature Tg and poor heat resistance, biaxial orientation can increase the glass transition temperature Tg and improve heat resistance.

[0027] The thermal expansion coefficient of the base film 15 is preferably 80 ppm / °C or less, more preferably 70 ppm / °C or less, in both MD and TD. The smaller the thermal expansion coefficient, the better, but for base films containing SPS as the main component, it usually does not fall below 10 ppm / °C. The absolute value of the difference between the thermal expansion coefficients in MD and TD is preferably 50 ppm / °C or less, more preferably 20 ppm / °C or less.

[0028] The thickness of the base film 15 is preferably 10 to 110 μm, more preferably 35 to 80 μm, which allows the copper-clad laminate to have a good balance between strength and flexibility.

[0029] The dielectric constant Dk of the base film 15 is 2.6 or less, preferably 2.5 or less, at a frequency of 10 GHz. The dielectric dissipation factor Df of the base film 15 is 0.002 or less, preferably 0.001 or less, at a frequency of 10 GHz. The transmission loss of the copper-clad laminate 10 is affected by all layers: the base film 15, the adhesive layer 16, and the copper foil 17. However, the low dielectric constant Dk and dielectric dissipation factor Df of the base film 15 make it possible to keep the transmission loss of high-frequency electrical signals low, even when using commercially available adhesives and copper foils. Note that base films primarily composed of SPS typically have a dielectric constant of 2.0 or more and a dielectric dissipation factor of 0.00001 or more.

[0030] The relative dielectric constant Dk of the adhesive layer 16 is 2.6 or less, preferably 2.5 or less, at a frequency of 10 GHz. The dielectric loss tangent Df of the adhesive layer is 0.005 or less, preferably 0.003 or less, at a frequency of 10 GHz. Such an adhesive layer can be formed using a commercially available adhesive such as AF-700 manufactured by Toagosei Co., Ltd. or SAFY manufactured by Nikkan Kogyo Co., Ltd.

[0031] The components of the adhesive layer 16 are not particularly limited as long as they have the required adhesive strength to the base film 15 and copper foil 17, and various known adhesives can be used, for example, the adhesives described in Patent Documents 2, 3, or 5. The adhesive layer may be formed by applying a liquid adhesive to the surface of the base film 15 or copper foil 17, or may be formed using an adhesive formed into a film (hereinafter referred to as an "adhesive film"). The adhesive layer is preferably formed using an adhesive film.

[0032] The thickness of the adhesive layer 16 is preferably 3 to 40 μm, more preferably 5 to 25 μm. If the adhesive layer is too thin, sufficient adhesive performance may not be obtained. On the other hand, if the adhesive layer is too thick, the solvent is likely to remain, which may cause foaming during the manufacturing process of the flexible circuit board.

[0033] Various commercially available copper foils can be used as the copper foil 17. The smoother the interface between the copper foil 17 and the adhesive layer 16 of the copper-clad laminate 10, the lower the transmission loss of the copper-clad laminate 10. For this reason, it is preferable that the surface of the copper foil that faces the adhesive layer 16 is smooth, and the maximum height roughness Rz of that surface of the copper foil is preferably 2.0 μm or less, more preferably 1.0 μm or less. Here, the maximum height roughness Rz is the maximum height roughness specified in JIS B0601:2013. Meanwhile, the maximum height roughness Rz of the surface of the copper foil that faces the adhesive layer is preferably 0.2 μm or more. This ensures sufficient adhesive strength with the adhesive layer. The maximum height roughness Rz of the surface of the copper foil that faces the adhesive layer is the maximum height roughness Rz of the interface between the copper foil 17 and the adhesive layer 16 in the copper-clad laminate 10.

[0034] The thickness of the copper foil 17 is not particularly limited, but is preferably 5 to 100 μm, and more preferably 10 to 40 μm. A thickness within these ranges can achieve both sufficient conductivity and the high level of flexibility required for a flexible circuit board.

[0035] Next, a method for manufacturing the copper-clad laminate 10 of this embodiment will be described.

[0036] The resin composition that is the raw material for the base film 15 is melted and kneaded to form a precursor film. The precursor film can be formed by, for example, extrusion molding, calendar molding, or casting, and is preferably formed by extrusion molding.

[0037] The formed unstretched precursor film is biaxially oriented, for example, by simultaneous biaxial stretching or sequential biaxial stretching, preferably by simultaneous biaxial stretching. The stretching ratio, stretching temperature, and stretching speed for biaxial stretching can be appropriately selected depending on the thermal properties of the resin, the desired thermal expansion coefficient, and the nominal tensile strain at break. In this embodiment, the stretching ratios in both MD and TD are preferably 2.0 to 5.0, more preferably 2.2 to 4.0. It is preferable that the stretching ratios in MD and TD are similar. Specifically, the difference between the stretching ratio in MD and the stretching ratio in TD is preferably 0.6 or less, more preferably 0.3 or less.

[0038] It is preferable to further perform a relaxation heat treatment on the biaxially stretched film. This is to reduce the absolute value of the heat shrinkage rate and improve the heat-resistant dimensional stability. The relaxation ratio in both MD and TD is preferably 0.80 to 1.00, more preferably 0.85 to 1.00, and most preferably 0.90 to 0.98. It is preferable that the relaxation ratios in MD and TD are similar. Specifically, the difference between the relaxation ratio in MD and the relaxation ratio in TD is preferably 0.1 or less, more preferably 0.05 or less, and most preferably 0.02 or less.

[0039] Next, an adhesive layer 16 and copper foil 17 are laminated onto the base film 15 manufactured as described above. In a copper-clad laminate 10 having a five-layer structure, the adhesive layer 16 and copper foil 17 are laminated onto both sides of the base film 15. In a copper-clad laminate 11 having a three-layer structure, the adhesive layer 16 and copper foil 17 are laminated onto one side of the base film 15.

[0040] Since the SPS constituting the base film 15 has poor adhesiveness, the surface of the base film is first subjected to an activation treatment, which can be performed using methods such as corona discharge treatment, ozone oxidation treatment, UV / ozone treatment, plasma discharge treatment, and electron beam irradiation.

[0041] When a liquid adhesive is used to form the adhesive layer 16, the adhesive is applied to both sides of the base film 15, copper foil 17 is placed on the applied surface, and the whole is sandwiched between a press or the like and the adhesive is cured by heating. When an adhesive film is used to form the adhesive layer 16, the adhesive film and copper foil are placed between both sides of the base film 15, and the whole is sandwiched between a press or the like and the adhesive is cured by heating. In this way, all layers are integrated to produce the copper-clad laminate 10.

[0042] According to the manufacturing method of this embodiment, the base film and copper foil are bonded together with an adhesive, which makes manufacturing easier than forming a conductive layer by plating. [Example]

[0043] The copper clad laminates of the above embodiment and the comparative example were fabricated, and the transmission loss of electrical signals was evaluated.

[0044] Example 1 SPS (Idemitsu Kosan Co., Ltd., Xarek, glass transition temperature 95°C, melting point 247°C) was melt-extruded at 320°C using an extruder equipped with a T-die and cooled to obtain a precursor film (approximately 500 μm). This precursor film was simultaneously biaxially stretched at 110°C with a stretching rate of 500% / min and a stretch ratio of 3.3 × 3.4 (MD × TD), followed by a relaxation heat treatment at 230°C with a relaxation ratio of 0.94 × 0.96 (MD × TD) to produce a 50 μm thick substrate film (CN). The glass transition temperature (Tg) of the substrate film (CN) was 200°C. After plasma treatment on both sides of the base film (CN), an adhesive film (AF-700, Toa Gosei Co., Ltd., 15 μm thick) was placed on top of the base film (CN) from which the separate film on one side had been peeled off, and the film was attached using a vacuum press at 120°C x 0.4 MPa x 30 seconds. Next, the separate film on the opposite side of the adhesive film was peeled off, and copper foil (maximum height roughness Rz of the adhesive film side surface = 0.85 μm, thickness 18 μm) was placed on top and attached using a vacuum press at 120°C x 0.4 MPa x 30 seconds. Furthermore, the laminate was pressed in a hot press at 180°C x 3 MPa x 30 minutes, and after the press was opened, it was placed in a heating oven and heated at 180°C x 30 minutes to produce the copper-clad laminate (5-layer structure) of Example 1.

[0045] Example 2 A copper-clad laminate (five-layer structure) of Example 2 was produced using the same materials and method as in Example 1, except that an adhesive film with a thickness of 5 μm was used.

[0046] Example 3 A full compound consisting of 80% by weight of SPS (Idemitsu Kosan Co., Ltd., Xarek, glass transition point 95°C, melting point 247°C) and 20% by weight of TPS-SEEPS (Kuraray Co., Ltd., Septon 4055) was melt-extruded at 280°C using an extruder equipped with a T-die at the tip and cooled to obtain a precursor film. This precursor film was simultaneously biaxially stretched at 110°C with a stretching rate of approximately 500% / min and a stretch ratio of 3.4 × 3.4 (MD × TD), followed by a relaxation heat treatment at 210°C with a relaxation ratio of 0.95 × 0.95 (MD × TD) to produce a 50 μm-thick substrate film (CE). The glass transition temperature (Tg) of the substrate film (CE) was 200°C. Next, using the same materials and method as in Example 1, an adhesive film and copper foil were laminated on both sides of the base film (CE) to produce a copper-clad laminate (five-layer structure) of Example 3.

[0047] Example 4 A copper-clad laminate (five-layer structure) of Example 4 was produced using the same materials and method as in Example 3, except that an adhesive film with a thickness of 5 μm was used.

[0048] Example 5 The copper-clad laminate (five-layer structure) of Example 5 was produced using the same materials and method as in Example 3, except that the adhesive film was 5 μm thick and the copper foil had a maximum height roughness Rz of 1.3 μm on the adhesive film side surface.

[0049] (Comparative Example 1) A copper-clad laminate (five-layer structure) of Comparative Example 1 was produced using the same materials and method as in Example 5, except that a commercially available liquid crystal polymer (LCP) film (thickness: 50 μm) was used as the substrate film.

[0050] (Comparative Example 2) A copper-clad laminate (five-layer structure) of Comparative Example 2 was produced using the same materials and method as in Example 5, except that a commercially available polyimide (PI) film (thickness: 50 μm) was used as the substrate film.

[0051] (Comparative Example 3) The base film (CN) used in Example 1 was sandwiched between copper foils (maximum height roughness Rz of the base film side surface = 0.3 μm, thickness 18 μm) on both sides, and pressed in a heat press at 280°C x 2 MPa x 5 minutes to soften the base film (CN) and integrate the entire structure, thereby producing a copper-clad laminate for Comparative Example 3.

[0052] Comparative Example 4 A copper clad laminate of Comparative Example 4 was produced using the same materials and method as in Comparative Example 3, except that the copper foil had a maximum height roughness Rz of 2 μm on the surface on the base film side.

[0053] Table 1 shows the relative permittivity Dk and dielectric loss tangent Df of the base films (CN, CE) and adhesive layer. The dielectric properties of the base films were measured using the cavity resonance method specified in ASTM D2520. The dielectric properties of the adhesive layer are the values ​​provided in the manufacturer's catalog.

[0054] [Table 1]

[0055] The layer configurations of the examples and comparative examples, together with the evaluation results, are shown in Table 2. In Table 2, the maximum height roughness Rz of the copper foil is the value of the surface on the adhesive layer or base film side.

[0056] The transmission loss of each sample was evaluated by creating a 100 mm long microstrip line by pattern etching copper foil and measuring the S21 parameter at frequencies up to 40 GHz when the impedance was adjusted to 50 Ω using a network analyzer (Keysight Technologies, E8363B) and a probe (FormFactor, ACP40-GSG250). A negative S21 parameter indicates transmission loss, and the smaller the absolute value, the smaller the transmission loss.

[0057] The peel test was conducted in accordance with JIS C 5016 by peeling the copper foil in a direction 90° to the copper foil removal surface. The symbols for the peel test results have the following meanings: ○: Material destruction of the base film △: Material destruction of the base film. However, peel strength is slightly inferior to "○". ×: Interfacial failure between base film and copper foil

[0058] [Table 2]

[0059] From the S21 parameters shown in Table 2, it was confirmed that the transmission losses of Examples 1 to 5 were all equal to or less than that of the comparative example.

[0060] Regarding the peel test results, in Comparative Examples 3 and 4, in which a base film mainly composed of SPS (hereinafter referred to as "SPS film") was softened and directly bonded to copper foil, the samples underwent interfacial failure. In contrast, in Examples 1 to 5, in which the SPS film and copper foil were bonded via an adhesive layer, the SPS film underwent material failure in all samples. This demonstrates that when manufacturing a copper-clad laminate using an SPS film and copper foil, it is preferable to activate the surface of the SPS film and then bond it to the copper foil using an adhesive.

[0061] The present invention is not limited to the above-described embodiments and examples, and various modifications are possible within the scope of the technical concept thereof. [Explanation of symbols]

[0062] 10 Copper-clad laminate (5-layer structure) 11 Copper-clad laminate (3-layer structure) 15 Base film 16 Adhesive layer 17 Copper foil

Claims

1. A copper clad laminate in which copper foil is laminated on one or both sides of a base film via an adhesive layer, the base film is composed primarily of syndiotactic polystyrene, is substantially composed of syndiotactic polystyrene and a styrene-based thermoplastic elastomer, is biaxially oriented, and has a relative dielectric constant of 2.6 or less and a dielectric loss tangent of 0.002 or less at a frequency of 10 GHz; The adhesive layer has a relative dielectric constant of 2.6 or less and a dielectric loss tangent of 0.005 or less at a frequency of 10 GHz. Copper clad laminate.

2. The base film It consists of a single layer The sum of the proportion of syndiotactic polystyrene and the proportion of styrene-based thermoplastic elastomer in all resins is 90% by mass or more, The weight ratio of the syndiotactic polystyrene to the styrene-based thermoplastic elastomer is 97 / 3 to 51 / 49. The copper clad laminate of claim 1.

3. The copper foil is pattern-etched to produce a microstrip line, and the S21 parameter when the impedance is adjusted to 50 Ω is −5 dB / 100 mm or more and less than 0 at 40 GHz. The copper clad laminate according to claim 1 or 2.

4. The glass transition temperature of the substrate film is 180°C or higher. The copper clad laminate according to any one of claims 1 to 3.

5. The maximum height roughness Rz of the interface between the copper foil and the adhesive layer is 2.0 μm or less. The copper clad laminate according to any one of claims 1 to 4.

Images