Double-sided copper-clad laminate

Abstract

To provide a double-sided copper-clad laminate for forming a capacitor which can exhibit excellent characteristics in voltage resistance and peel strength while securing a high capacitor capacitance when used as a capacitor.SOLUTION: A double-sided copper-clad laminate has an adhesive layer and a copper foil in this order on both surfaces of a resin film, in which the resin film is in a cured state at 25°C, and the copper foil has a maximum ridge height Sp measured according to ISO 25178 on a surface on a side contacting the adhesive layer of 0.05 μm or more and 3.3 μm or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a double-sided copper-clad laminate.

Background Art

[0002] Printed wiring boards are widely used in electronic communication devices such as portable electronic devices. In particular, with the recent trend towards thinner, lighter, shorter, and higher-function portable electronic communication devices, reducing noise in printed wiring boards has become an issue. Capacitors are important for reducing noise, but in order to achieve higher performance, capacitors are desired to be miniaturized and thinned to the extent that they can be incorporated into the inner layer of a printed wiring board. And, in order to form such capacitors, double-sided copper-clad laminates are used. Double-sided copper-clad laminates generally have a structure in which both sides of a resin layer that functions as a dielectric layer are sandwiched between copper foils, and the selection of these constituent elements that are more appropriate is important for the high functionality of capacitors.

[0003] For example, Patent Document 1 (Japanese Patent No. 5048181) discloses a passive electrical article capable of forming a pattern for creating an electric circuit. This passive electrical article includes (a) a first self-supporting substrate having two opposing main surfaces, (b) a second self-supporting substrate having two opposing main surfaces, and (c) a polymer, and an electrically insulating layer or a conductive layer having a thickness in the range of about 0.5 to about 10 μm between the first and second substrates. And, the RMS average surface roughness of the main surface of the first substrate in contact with these layers and the main surface of the second substrate in contact with the layers is in the range of about 10 to about 300 nm, and all of z, which is the distance above or below from the substrate surface used to measure the RMS average, does not exceed half of the thickness of the electrically insulating layer or the conductive layer, and a passive electrical article is disclosed, characterized in that the force required to separate the first and second substrates of the passive electrical article at a peeling angle of 90° exceeds about 3 pounds per inch (about 0.5 kN / m).

[0004] Patent Document 2 (Japanese Patent No. 4148501) discloses a dielectric filler-containing resin composition comprising a binder resin and a dielectric filler. The binder resin consists of 20 to 80 parts by weight of an epoxy resin (including a curing agent), 20 to 80 parts by weight of an aromatic polyamide resin polymer soluble in an organic solvent, and a curing accelerator added in an appropriate amount as required. The dielectric filler is composed of any one or more of BaTiO3, SrTiO3, Pb(Zr-Ti)O3, PbLaTiO3·PbLaZrO, SrBi2Ta2O9, has an average particle diameter DIA of 0.1 to 1.0 μm, a weight cumulative particle diameter D50 of 0.2 to 2.0 μm by a laser diffraction scattering type particle size distribution measurement method, and a value of the degree of aggregation represented by D50 / DIA using the weight cumulative particle diameter D50 and the average particle diameter DIA obtained by image analysis is 4.5 or less, and is a dielectric powder having a perovskite structure with a substantially spherical shape.

[0005] Patent Document 3 (Japanese Patent No. 3770537) discloses a capacitor housed in an inner layer portion of a multilayer printed wiring board, which is formed by a double-sided copper-clad laminate having a layer structure in which copper foil layers as conductors are disposed on outer layers on both sides, and a resin layer serving as a dielectric is sandwiched between the copper foil layer on one side and the copper foil layer on the other side. The resin layer has a three-layer structure in which the layer structure is a thermosetting resin layer / a heat-resistant film layer / a thermosetting resin layer, and the total thickness is 25 μm or less. The thermosetting resin layer is composed of an epoxy-based resin material, and the heat-resistant film layer has a Young's modulus of 300 kg / mm 2 or more, a tensile strength of 20 kg / mm 2 or more, a normal state property with an elongation at break of 5% or more, has a softening temperature higher than the molding temperature of the thermosetting resin constituting the thermosetting resin layers located on both sides, and a relative dielectric constant of 2.5 or more under the measurement conditions of 1 MHz in accordance with Paragraph 2.5.5.9 of IPC-TM-650, and is formed from a double-sided copper-clad laminate composed of a resin material which is a heat-resistant film having a thickness of 0.5 to 12.5 μm.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

[0007] However, as described above, although the resin layer and copper foil constituting the double-sided copper-clad laminate have been studied, further improvement is desired. For example, as described in Patent Document 3, in the case of a configuration having a heat-resistant film (resin film) in the middle of the dielectric layer, due to large bumps or the like on the surface of the copper foil, the bumps or the like may penetrate through the resin layers in contact with the resin film from above and below. When such bumps or the like on the copper foil surface exist on the resin-side surfaces of both copper foils constituting the capacitor, it is necessary to satisfy the withstand voltage characteristics only by the insulation of the resin film in the middle of the double-sided copper-clad laminate. Depending on the required withstand voltage level, the resin film has to be made thicker. However, since the resin film portion does not contain a composite oxide such as a filler and has dielectric properties inferior to those of the resin layer, increasing the thickness of the resin film causes a problem of a decrease in capacitor capacitance. That is, there is a trade-off relationship between the thickness of the resin film and the capacitor capacitance (i.e., capacitance). Furthermore, it is also desired to ensure not only capacitance but also withstand voltage and peel strength (i.e., circuit adhesion). From the viewpoint of ensuring circuit adhesion, generally a copper foil with high roughness (with large bumps or the like on the surface) is desired, but as described above, it is not desirable from the viewpoint of withstand voltage. In addition, since it is also necessary to realize a good bonding state between the copper foil, the resin layer, and the resin film, it has not been easy to control the surface shape of the copper foil that satisfies each requirement.

[0008] The inventors have now found that by controlling the surface properties of the copper foil of a double-sided copper-clad laminate, when used as a capacitor, it is possible to exhibit excellent characteristics in terms of withstand voltage and peel strength while ensuring a high capacitance.

[0009] Accordingly, an object of the present invention is to provide a double-sided copper-clad laminate that can exhibit excellent characteristics in terms of withstand voltage and peel strength while ensuring a high capacitance when used as a capacitor.

[0010] According to one aspect of the present invention, there is provided a double-sided copper-clad laminate having an adhesive layer and a copper foil on each side of a resin film in this order, wherein the resin film is in a cured state at 25°C, and each of the copper foils has a maximum peak height Sp measured in accordance with ISO25178 on the surface in contact with the adhesive layer of 0.05 μm or more and 3.3 μm or less, and a double-sided copper-clad laminate is provided.

[0011] According to another aspect of the present invention, there is provided a double-sided copper-clad laminate having an adhesive layer and a copper foil on each side of a resin film in this order, wherein the resin film is in a cured state at 25°C, and each of the copper foils has a root mean square gradient Sdq measured in accordance with ISO25178 on the surface in contact with the adhesive layer of 0.01 or more and 2.3 or less, and a double-sided copper-clad laminate is provided.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0013] Definition The definitions of the parameters used to specify the present invention are shown below.

[0014] In this specification, the "maximum peak height Sp" is a three-dimensional parameter representing the maximum value of the height from the average surface plane, measured in accordance with ISO25178.

[0015] In this specification, the "root mean square slope Sq" is a parameter calculated by the root mean square of the slopes at all points in the defined area, measured in accordance with ISO25178. That is, since it is a three-dimensional parameter for evaluating the magnitude of the local inclination angle, the ruggedness of the surface unevenness can be quantified. For example, the Sq of a completely flat surface is 0, and the Sq increases when there is an inclination on the surface. The Sq of a plane composed of a 45-degree inclination component is 1.

[0016] In this specification, the "kurtosis Sku" is a parameter representing the sharpness of the height distribution, measured in accordance with ISO25178, and is also referred to as the peakedness. Sku = 3 means that the height distribution is a normal distribution. When Sku>3, there are many sharp peaks and valleys on the surface, and when Sku<3, it means that the surface is flat.

[0017] Double-sided copper-clad laminate The double-sided copper-clad laminate of the present invention includes an adhesive layer and a copper foil on each side of a resin film in this order. The resin film is in a cured state at 25°C. For both copper foils, on the surface in contact with the adhesive layer, the maximum peak height Sp measured in accordance with ISO25178 is 0.05 μm or more and 3.3 μm or less, or the root mean square slope Sq measured in accordance with ISO25178 is 0.01 or more and 2.3 or less. Thus, by controlling Sp or Sq on the surface of the copper foil in contact with the adhesive layer, that is, by controlling the surface properties of the copper foil, when used as a capacitor, it is possible to exhibit excellent characteristics in terms of withstand voltage and peel strength while ensuring a high capacitance.

[0018] As described above, in the case of a double-sided copper-clad laminate having a resin film in the middle of the dielectric layer, due to large bumps or the like on the surface of the copper foil, the bumps or the like may penetrate the resin layers that contact the resin film from above and below. In that case, depending on the required withstand voltage level, the resin film has to be made thicker, but increasing the thickness of the resin film causes a problem that the capacitor capacitance decreases. Moreover, it is also desired to ensure the withstand voltage property and the peel strength. In this regard, according to the double-sided copper-clad laminate of the present invention, these problems are favorably solved.

[0019] In the double-sided copper-clad laminate, the peel strength between the copper foil and the resin film, which is measured in accordance with IPC-TM650-2.4.6.C, is preferably 0.5 kgf / cm or more and 4.0 kgf / cm or less, more preferably 0.6 kgf / cm or more and 3.5 kgf / cm or less, and even more preferably 0.6 kgf / cm or more and 3.0 kgf / cm or less.

[0020] All of the copper foils provided in the double-sided copper-clad laminate of the present invention have a maximum peak height Sp measured in accordance with ISO25178 on the surface of the side in contact with the adhesive layer of 0.05 μm or more and 3.3 μm or less. This maximum peak height Sp is preferably 0.06 μm or more and 3.1 μm or less, more preferably 0.06 μm or more and 3.0 μm or less, and even more preferably 0.07 μm or more and 2.9 μm or less. From the viewpoint of obtaining a particularly thin double-sided laminate, the maximum peak height Sp is more preferably 2.5 μm or less, even more preferably 1.7 μm or less, and most preferably 1.1 μm or less. By controlling the surface properties of the copper foil in this way, when used as a capacitor, a double-sided copper-clad laminate capable of exhibiting excellent characteristics in terms of withstand voltage property and peel strength while ensuring a high capacitor capacitance can be obtained more effectively. In particular, with respect to the peel strength, it is possible to obtain a performance that can withstand practical use even in a smooth region where sufficient adhesion has conventionally been considered not to be obtained.

[0021] In another aspect of the present invention, all of the copper foils provided in the double-sided copper-clad laminate have a root mean square gradient Sq measured in accordance with ISO25178 on the surface in contact with the adhesive layer of 0.01 or more and 2.3 or less. This root mean square gradient Sq is preferably 0.02 or more and 2.2 or less, more preferably 0.03 or more and 2.0 or less, and even more preferably 0.04 or more and 1.8 or less. From the perspective of obtaining a particularly thin double-sided laminate, the root mean square gradient Sq is more preferably 1.6 or less, even more preferably 1.3 or less, and most preferably 0.4 or less. By controlling the surface properties of the copper foil in this way, when used as a capacitor, a double-sided copper-clad laminate capable of exhibiting excellent characteristics in terms of withstand voltage and peel strength while ensuring a high capacitance can be obtained more effectively. In particular, with respect to the peel strength, practical performance can be obtained even in a smooth region where sufficient adhesion has conventionally been considered not to be obtained.

[0022] All of the copper foils preferably have a kurtosis Sku measured in accordance with ISO25178 on the surface in contact with the adhesive layer of 2.6 or more and 4.0 or less, more preferably 2.7 or more and 3.8 or less, and even more preferably 2.7 or more and 3.7 or less. By controlling the kurtosis Sku in addition to controlling the maximum peak height Sp and the root mean square gradient Sq as the surface properties of the copper foil in this way, a desired double-sided copper-clad laminate can be obtained more effectively.

[0023] The thickness of the copper foil is not particularly limited, but is preferably 0.1 μm or more and 200 μm or less, more preferably 0.5 μm or more and 105 μm or less, and even more preferably 1.0 μm or more and 70 μm or less. By doing so, manufacturing methods such as the subtractive method, SAP (semi-additive) method, and MSAP (modified semi-additive) method, which are common pattern formation methods for forming wiring on a printed wiring board, can be adopted.

[0024] The combination of the adhesive layer and the resin film provided in the double-sided copper-clad laminate of the present invention preferably has a relative permittivity at a frequency of 1 MHz after curing of 2.5 or more and 30 or less, more preferably 3.0 or more and 27 or less, and even more preferably 3.5 or more and 25 or less. By having the relative permittivity within such a range, a good capacitor capacitance can be more effectively ensured.

[0025] The resin film preferably has a relative permittivity at a frequency of 1 MHz after curing of 2 or more and 30 or less, more preferably 2.5 or more and 27 or less, and even more preferably 3.0 or more and 25 or less.

[0026] The thickness of the resin film is preferably 0.5 μm or more and 30 μm or less, more preferably 1.0 μm or more and 25 μm or less, and even more preferably 1.5 μm or more and 18 μm or less. As described above, when there are large bumps or the like on the surface of the copper foil, the resin film may have to be made thicker. However, since the surface properties of the copper foil provided in the double-sided copper-clad laminate of the present invention are controlled, the resin film can be made to have a thickness within the above range. That is, it is possible to balance the thickness of the resin film and the capacitor capacitance.

[0027] The resin film preferably contains at least one selected from the group consisting of epoxy resin, polyethylene terephthalate, polyethylene naphthalate, polyvinyl carbazole, polyphenylene sulfide, polyimide, polyamide, aromatic polyamide (for example, wholly aromatic polyamide), polyamideimide, polyethersulfone, polyether nitrile, polyether ether ketone, and polytetrafluoroethylene, more preferably contains at least one selected from the group consisting of epoxy resin, polyphenylene sulfide, polyimide, polyamide, polyamideimide, and wholly aromatic polyamide (aramid), and even more preferably contains at least one selected from the group consisting of epoxy resin, polyimide, polyamide, and wholly aromatic polyamide (aramid). Examples of commercially available products of such resin films include para-aramid films, polyimide films, and the like.

[0028] The resin film is preferably subjected to a surface roughening treatment. Examples of the method of the surface roughening treatment include plasma treatment, corona discharge treatment, sandblasting treatment, etc. By performing such a surface roughening treatment, the area of the contact interface between the resin film and the adhesive layer can be increased, the adhesion (peel strength) can be improved, and delamination can be avoided. More preferable surface roughening treatments for the resin film include plasma treatment and corona discharge treatment.

[0029] The adhesive layer provided in the double-sided copper-clad laminate of the present invention preferably has a relative permittivity at a frequency of 1 MHz after curing of 2.5 or more and 30 or less, more preferably 3.0 or more and 28.0 or less, and even more preferably 4.0 or more and 26 or less.

[0030] The adhesive layer is preferably composed of a resin composition containing a resin component and a dielectric filler. This resin component is composed of a thermoplastic component and / or a thermosetting component. Specifically, it preferably contains at least one selected from the group consisting of epoxy resin, polyethylene terephthalate resin, polyethylene naphthalate resin, polyvinyl carbazole resin, polyphenylene sulfide resin, polyamide resin, aromatic polyamide resin, polyamideimide resin, polyimide resin, polyethersulfone resin, polyether nitrile resin, polyether ether ketone resin, polytetrafluoroethylene resin, urethane resin, isocyanate resin, active ester resin, phenol resin, and diamine compound, and more preferably contains at least one selected from the group consisting of epoxy resin, polyimide resin, aromatic polyamide resin, active ester resin, phenol resin, and diamine compound.

[0031] The next layer preferably further contains a dielectric filler which is a composite metal oxide containing at least two selected from the group consisting of Ba, Ti, Sr, Pb, Zr, La, Ta, Ca, and Bi. This composite metal oxide more preferably contains at least two selected from the group consisting of Ba, Ti, and Sr. By doing so, a double-sided copper-clad laminate having a good capacitor capacitance can be obtained more effectively.

[0032] The composite metal oxide preferably contains at least one selected from the group consisting of BaTiO3, SrTiO3, Pb(Zr,Ti)O3, PbLaTiO3, PbLaZrO, and SrBi2Ta2O9, and more preferably contains at least one selected from the group consisting of BaTiO3 and SrTiO3. Note that Pb(Zr,Ti)O3 means Pb(Zr x Ti 1-x )O3 (where 0 ≦ x ≦ 1, typically 0 < x < 1). By doing so, a double-sided copper-clad laminate having a good capacitor capacitance can be obtained more effectively.

[0033] It is preferable to use a dielectric filler which is a composite metal oxide. When using a dielectric filler, the dielectric filler is preferably contained in an amount of 0 parts by weight or more and 90 parts by weight or less, more preferably 15 parts by weight or more and 85 parts by weight or less, and still more preferably 25 parts by weight or more and 80 parts by weight or less based on 100 parts by weight of the solid content of the resin composition.

[0034] The particle size of the dielectric filler which is a composite metal oxide is not particularly limited, but from the viewpoint of maintaining the adhesion between the adhesive layer and the copper foil, the average particle size D 50 measured by laser diffraction scattering particle size distribution measurement is preferably 0.001 μm or more and 2.0 μm or less, more preferably 0.01 μm or more and 1.8 μm or less, and still more preferably 0.03 μm or more and 1.6 μm or less.

[0035] The resin composition may further contain a filler dispersant. By further containing a filler dispersant, the dispersibility of the dielectric filler can be improved when kneading the resin varnish and the dielectric filler. As the filler dispersant, known ones that can be used can be appropriately used and are not particularly limited. Examples of preferable filler dispersants include phosphonic acid type, cationic type, carboxylic acid type, and anionic type dispersants which are ionic dispersants, and ether type, ester type, sorbitan ester type, diester type, monoglyceride type, ethylene oxide addition type, ethylenediamine base type, phenol type dispersants, etc. which are nonionic dispersants. In addition, coupling agents such as silane coupling agents, titanate coupling agents, and aluminate coupling agents can be mentioned.

[0036] A curing accelerator may be added to the resin composition in order to accelerate the curing of the resin component. Preferable examples of the curing accelerator include imidazole-based curing accelerators and amine-based curing accelerators. From the viewpoints of the storage stability of the resin component contained in the resin composition and the efficiency of curing, the content of the curing accelerator is preferably 0.01 parts by weight or more and 3.0 parts by weight or less, more preferably 0.1 parts by weight or more and 2.0 parts by weight or less, based on 100 parts by weight of the non-volatile components in the resin composition.

[0037] Typically, the double-sided copper-clad laminate of the present invention is obtained by applying a resin composition constituting an adhesive layer to a copper foil using a gravure coating method so that the thickness of the adhesive layer after drying becomes a predetermined value and then drying it. Although the coating method is arbitrary, other than the gravure coating method, a die coating method, a knife coating method, etc. can be adopted. In addition, it is also possible to apply using a doctor blade, a bar coater, etc.

Examples

[0038] The present invention will be described more specifically by the following examples.

[0039] Examples 1 to 9 (1) Preparation of resin varnish First, as raw material components for the resin varnish, the resin components and imidazole-based curing accelerators shown below were prepared. - Biphenyl-aralkyl type epoxy resin: manufactured by Nippon Kayaku Co., Ltd., NC-3000 - Polyfunctional phenol resin (curing agent): manufactured by Meiwafosis Co., Ltd., MEH-7500 - Phenolic hydroxyl group-containing polybutadiene-modified aromatic polyamide resin: manufactured by Nippon Kayaku Co., Ltd., BPAM-155 - Imidazole-based epoxy resin curing accelerator: manufactured by Shikoku Kasei Kogyo Co., Ltd., 2P4MHZ

[0040] The raw material components for the resin varnish were weighed at the compounding ratios (weight ratios) shown in Tables 1A and 1B. Then, cyclopentanone solvent was weighed, and the raw material components for the resin varnish and the cyclopentanone solvent were charged into a flask and stirred at 60°C. After confirming that there was no undissolved raw material in the resin varnish and that the resin varnish was transparent, the resin varnish was recovered.

[0041] (2) Kneading with filler Subsequently, the dielectric fillers and dispersants shown below were prepared. - Barium titanate: manufactured by Nippon Chemical Industry Co., Ltd. - Titanate-based coupling agent: manufactured by Ajinomoto Fine-Techno Co., Inc., KR-44 (addition amount: 1.5 parts by weight with respect to 100 parts by weight of the dielectric filler)

[0042] Cyclopentanone solvent, dielectric filler, and dispersant were each weighed. The weighed solvent, dielectric filler, and dispersant were slurried with a disperser. After this slurrying was confirmed, the resin varnish was weighed so that the final dielectric filler would be at the compounding ratios (weight ratios) shown in Tables 1A and 1B, and kneaded with the dielectric filler-containing slurry using a disperser. After kneading, it was confirmed that the dielectric filler was not aggregated. Thus, a coating liquid containing the resin composition constituting the adhesive layer was obtained.

[0043] (3) Preparation of copper foil As a copper foil for applying the above coating liquid, a roughened copper foil was prepared. The production of this copper foil was carried out by a known method as disclosed in Patent Document 4, Patent Document 5, etc.

[0044] (4) Resin coating The coating liquid obtained in the above (2) was applied to the copper foil described in the above (3) using a bar coater so that the thickness of the adhesive layer after drying was as shown in Tables 1A and 1B, and then dried in an oven heated to 130 °C for 3 minutes to make the resin in a semi-cured state. Thus, a copper foil with an adhesive layer was obtained.

[0045] (5) Preparation of resin film The following resin films were prepared. - Aramid film: Aramil, manufactured by Teijin Advanced Films Ltd. - Polyimide film: Apical, manufactured by Kaneka Corporation

[0046] These resin films were subjected to surface roughening treatment. Specifically, corona discharge treatment was performed on Aramil, and plasma treatment was performed on Apical.

[0047] (6) Pressing In Examples 1 to 5, the coated resin surface of the copper foil with an adhesive layer was placed upward, and a resin film was stacked on the coated resin surface. Further, a copper foil with an adhesive layer having the coated resin surface facing down was stacked on the surface of the resin film that was not in contact with the coated resin surface. At this time, vacuum pressing was performed at 180 °C for 120 minutes to harden the adhesive layer. Thus, a double-sided copper-clad laminate was obtained.

[0048] In Examples 6 to 9, without using a resin film, two copper foils with adhesive layers were stacked with their coated resin surfaces facing each other, and vacuum pressing was performed at 180 °C for 120 minutes to harden the adhesive layer, obtaining a double-sided copper-clad laminate.

[0049] (7) Evaluation The following various evaluations were performed on the copper foil and the obtained double-sided copper-clad laminate.

[0050] <Evaluation 1: Surface Property Parameters of Copper Foil> By performing surface roughness analysis using a laser microscope (OLS5000, manufactured by Olympus Corporation), the roughened surface of the roughened copper foil in (3) above was measured in accordance with ISO25178. Specifically, the surface profile of a region with an area of 16384 μm 2 on the roughened surface of the roughened copper foil was measured with a 100x lens with a numerical aperture (N.A.) of 0.95 using the above laser microscope. After performing noise removal and primary linear surface inclination correction on the obtained surface profile of the roughened surface, various parameters of Sp, Sq, and Sk were measured by surface property analysis. All of these Sp, Sq, and Sk were measured with a cut-off wavelength of 0.55 μm by an S filter and a cut-off wavelength of 10 μm by an L filter. The results were as shown in Tables 1A and 1B.

[0051] <Evaluation 2: Capacitance (Cp)> After etching one side of a double-sided copper-clad laminate to form a circular circuit with a diameter of 0.5 inches (12.6 mm), the capacitance at a frequency of 1 MHz was measured using an LCR meter (LCR Hi-Tester 3532-50, manufactured by Hioki Electric Co., Ltd.). This measurement was performed in accordance with IPC-TM-650 2.5.2. The measured capacitance was evaluated according to the following criteria. The results were as shown in Table 2. - Evaluation A: 10.0 nF / in 2 Above (best) - Evaluation B: 5.0 nF / in 2 Above and less than 10.0 nF / in 2 Less than (good) - Evaluation C: 1.0 nF / in 2 Above and less than 5.0 nF / in 2 Less than (acceptable) - Evaluation D: Less than 1.0 nF / in 2 Less than (unacceptable)

[0052] <Evaluation 3: Breakdown Voltage (BDV)> After etching one side of a double-sided copper-clad laminate to produce a circular circuit with a diameter of 0.5 inches (12.6 mm), the dielectric breakdown voltage under the condition of a voltage rise rate of 167 V / sec was measured using an insulation resistance meter (manufactured by Hioki E.E. Corporation, super insulation meter SM7110). This measurement was carried out in accordance with IPC-TM-650 2.5.6.2a. The measured dielectric breakdown voltage was evaluated according to the following criteria. The results were as shown in Table 2. - Evaluation A: Greater than 5000 V (best) - Evaluation B: Greater than 3500 V and less than or equal to 5000 V (good) - Evaluation C: Greater than 2000 V and less than or equal to 3500 V (acceptable) - Evaluation D: Less than or equal to 2000 V (unacceptable)

[0053] <Evaluation 4: Dielectric breakdown strength> The dielectric breakdown voltage (BDV) measured in Evaluation 3 was divided by the dielectric layer thickness (the thickness of the resin film with the adhesive layer) to calculate the value. The calculated dielectric breakdown strength was evaluated according to the following criteria. The results were as shown in Table 2. - Evaluation A: Greater than 220 kV / mm (best) - Evaluation B: Greater than 200 kV / mm and less than or equal to 220 kV / mm (good) - Evaluation C: Greater than 100 kV / mm and less than or equal to 200 kV / mm (acceptable) - Evaluation D: Less than or equal to 100 kV / mm (unacceptable)

[0054] <Evaluation 5: Normal state peel strength (circuit adhesion)> After etching one side of a double-sided copper-clad laminate to produce a 3-mm-wide linear circuit, the circuit was peeled off at a peeling speed of 50 mm / min using an autograph, and the peel strength was measured at room temperature (for example, 25°C). This measurement was carried out in accordance with IPC-TM-650 2.4.8. The measured normal state peel strength was evaluated according to the following criteria. The results were as shown in Table 2. - Evaluation A: 1.5 kgf / cm or more (best) - Evaluation B: 1.0 kgf / cm or more and less than 1.5 kgf / cm (good) - Evaluation C: 0.6 kgf / cm or more and less than 1.0 kgf / cm (acceptable) - Evaluation D: less than 0.6 kgf / cm (unacceptable)

[0055] <Evaluation 6: Dielectric constant (Dk)>[[]]END]] All of the copper on both sides of the double-sided copper-clad laminate was removed by etching to obtain a resin film having an adhesive layer (a combination of an adhesive layer and a resin film). For this resin film having an adhesive layer, the capacitance (Cp) measured in Evaluation 2 and the formula Cp = ε0 × Dk × (S / d) (where ε0 is the permittivity of vacuum, S is the area of the circular circuit, and d is the thickness of the dielectric layer) were used to measure the dielectric constant at 1 MHz. The calculated dielectric constant was evaluated according to the following criteria. The results were as shown in Table 2. - Evaluation A: The dielectric constant at 1 MHz is 6.5 or more - Evaluation B: The dielectric constant at 1 MHz is 5.0 or more and less than 6.5 - Evaluation C: The dielectric constant at 1 MHz is 2.5 or more and less than 5.0 - Evaluation D: The dielectric constant at 1 MHz is less than 2.5

[0056] <Evaluation 7: Laminated state>[[]]END]] After cutting out the double-sided copper-clad laminate into a size of about 8 mm in width and 5 mm in length, it was cut in the thickness direction of the double-sided copper-clad laminate using a microtome (Leica Biosystems, RM2265, fully automatic universal rotary microtome) to expose the cross-section. The cross-section was observed with an optical microscope (Leica Microsystems, Leica DM LM) to confirm whether the copper foil and the film were properly laminated by the adhesive layer. The quality of the confirmed laminated state was evaluated according to the following criteria. The results were as shown in Table 2. Figure 1 shows a dark-field cross-sectional observation image of the cross-section of the double-sided copper-clad laminate obtained in Example 4, and Figure 2 shows a dark-field cross-sectional observation image of the cross-section of the double-sided copper-clad laminate obtained in the same manner as in Example 5 except that the thickness of the copper foil was changed to 12 μm. - Good: The adhesive layer is uniformly present between the copper foil surface and the resin film. - Defect: The adhesive layer is non-uniform between the copper foil surface and the resin film (there are voids in the adhesive layer, or the copper foil surface is directly bonded to the resin film).

[0057] In the above evaluations 2 to 6, if the evaluation is C or higher, it has performance that can withstand practical use, and if the evaluation is B or higher, it is judged that excellent characteristics as a capacitor can be exhibited. Also, in evaluation 7, if the evaluation is defective, voids or the like will occur inside, so that the original capacitor performance cannot be exhibited. Based on such criteria, it is preferable that there is no evaluation D in the results of the above evaluations 2 to 6, the total number of evaluations C is three or less, and the result of evaluation 7 is good.

[0058]

Table 1A

[0059]

Table 1B

[0060]

Table 2

[0061] The present invention includes the following aspects. [Item 1] A double-sided copper-clad laminate having an adhesive layer and a copper foil on each side of a resin film in this order, wherein the resin film is in a cured state at 25°C, and each of the copper foils has a maximum peak height Sp measured in accordance with ISO25178 on the surface in contact with the adhesive layer of 0.05 μm or more and 3.3 μm or less, the double-sided copper-clad laminate. [Item 2] A double-sided copper-clad laminate having an adhesive layer and a copper foil on each side of a resin film in this order, wherein the resin film is in a cured state at 25°C, All of the copper foils are double-sided copper-clad laminates in which the root mean square gradient Sdq measured in accordance with ISO25178 on the surface in contact with the adhesive layer is 0.01 or more and 2.3 or less. [Item 3] The combination of the adhesive layer and the resin film is the double-sided copper-clad laminate according to Item 1 or 2, in which the relative permittivity at a frequency of 1 MHz after curing is 2.5 or more and 30 or less. [Item 4] The resin film is the double-sided copper-clad laminate according to any one of Items 1 to 3, in which the relative permittivity at a frequency of 1 MHz after curing is 2 or more and 30 or less. [Item 5] The adhesive layer is the double-sided copper-clad laminate according to any one of Items 1 to 4, in which the relative permittivity at a frequency of 1 MHz after curing is 2.5 or more and 30 or less. [Item 6] The resin film has a thickness of 0.5 μm or more and 30 μm or less, and is the double-sided copper-clad laminate according to any one of Items 1 to 5. [Item 7] The resin film contains at least one selected from the group consisting of epoxy resin, polyethylene terephthalate, polyethylene naphthalate, polyvinyl carbazole, polyphenylene sulfide, polyimide, polyamide, aromatic polyamide, polyamideimide, polyethersulfone, polyether nitrile, polyether ether ketone, and polytetrafluoroethylene, and is the double-sided copper-clad laminate according to any one of Items 1 to 6. [Item 8] The adhesive layer contains a resin component composed of a thermoplastic component and / or a thermosetting component, and the resin component contains at least one selected from the group consisting of an epoxy resin, a polyethylene terephthalate resin, a polyethylene naphthalate resin, a polyvinyl carbazole resin, a polyphenylene sulfide resin, a polyamide resin, an aromatic polyamide resin, a polyamideimide resin, a polyimide resin, a polyethersulfone resin, a polyether nitrile resin, a polyether ether ketone resin, a polytetrafluoroethylene resin, a urethane resin, an isocyanate resin, an active ester resin, a phenol resin, and a diamine compound. The double-sided copper-clad laminate according to any one of items 1 to 7. [Item 9] The adhesive layer further includes a dielectric filler that is a composite metal oxide containing at least two selected from the group consisting of Ba, Ti, Sr, Pb, Zr, La, Ta, Ca, and Bi. The double-sided copper-clad laminate according to any one of items 1 to 8. [Item 10] The composite metal oxide contains at least one selected from the group consisting of BaTiO3, SrTiO3, Pb(Zr,Ti)O3, PbLaTiO3, PbLaZrO, and SrBi2Ta2O9. The double-sided copper-clad laminate according to item 9. [Item 11] All of the copper foils have a kurtosis Sku measured in accordance with ISO25178 on the surface in contact with the adhesive layer of 2.6 or more and 4.0 or less. The double-sided copper-clad laminate according to any one of items 1 to 10. [Item 12] The peel strength between the copper foil and the resin film measured in accordance with IPC-TM650-2.4.6.C is 0.5 kgf / cm or more and 4.0 kgf / cm or less. The double-sided copper-clad laminate according to any one of items 1 to 11.

Claims

1. A double-sided copper-clad laminate having an adhesive layer and a copper foil on each side of a resin film, The resin film is in a cured state at 25° C. In each of the copper foils, the maximum peak height Sp measured in accordance with ISO 25178 on the surface in contact with the adhesive layer is 0.05 μm or more and 3.3 μm or less, and the kurtosis Sku measured in accordance with ISO 25178 is 2.6 or more and 4.0 or less, A double-sided copper-clad laminate, wherein the combination of the adhesive layer and the resin film has a relative dielectric constant of 3.5 or more and 30 or less at a frequency of 1 MHz after curing.

2. 2. The double-sided copper-clad laminate according to claim 1, wherein the combination of the adhesive layer and the resin film has a relative dielectric constant of 3.5 or more and 27 or less at a frequency of 1 MHz after curing.

3. 3. The double-sided copper-clad laminate according to claim 1, wherein the resin film has a relative dielectric constant of 2 or more and 30 or less at a frequency of 1 MHz after curing.

4. The double-sided copper-clad laminate according to any one of claims 1 to 3, wherein the adhesive layer has a relative dielectric constant of 2.5 or more and 30 or less at a frequency of 1 MHz after curing.

5. The double-sided copper-clad laminate according to any one of claims 1 to 4, wherein the resin film has a thickness of 0.5 μm or more and 30 μm or less.

6. The double-sided copper-clad laminate according to any one of claims 1 to 5, wherein the resin film comprises at least one selected from the group consisting of epoxy resin, polyethylene terephthalate, polyethylene naphthalate, polyvinyl carbazole, polyphenylene sulfide, polyimide, polyamide, aromatic polyamide, polyamideimide, polyethersulfone, polyether nitrile, polyether ether ketone, and polytetrafluoroethylene.

7. The adhesive layer comprises a resin component composed of a thermoplastic component and / or a thermosetting component, and the resin component is selected from the group consisting of epoxy resin, polyethylene terephthalate resin, polyethylene naphthalate resin, polyvinyl carbazole resin, polyphenylene sulfide resin, polyamide resin, aromatic polyamide resin, polyamideimide resin, polyimide resin, polyethersulfone resin, polyethernitrile resin, polyetheretherketone resin, polytetrafluoroethylene resin, urethane resin, isocyanate resin, active ester resin, phenolic resin, and diamine compound. The double-sided copper-clad laminate according to any one of claims 1 to 6, comprising at least one selected from the group consisting of:

8. The double-sided copper-clad laminate according to any one of claims 1 to 7, wherein the adhesive layer further comprises a dielectric filler which is a composite metal oxide containing at least two selected from the group consisting of Ba, Ti, Sr, Pb, Zr, La, Ta, Ca and Bi.

9. The composite metal oxide is BaTiO ３ , SrTiO ３ , Pb(Zr,Ti)O ３ , PbLaTiO ３ , PbLaZrO, and SrBi ２ T ２ O ９ The double-sided copper-clad laminate according to claim 8, comprising at least one selected from the group consisting of:

10. The double-sided copper-clad laminate according to any one of claims 1 to 9, wherein the peel strength between the copper foil and the resin film measured in accordance with IPC-TM650-2.4.6.C is 0.5 kgf / cm or more and 4.0 kgf / cm or less.

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