Double-sided copper-clad laminate

Abstract

Provided is a double-sided copper-clad laminate for forming a capacitor, which, when used as a capacitor, can exhibit excellent characteristics in terms of voltage resistance and peel strength while ensuring high capacitor capacitance. [Solution] A double-sided copper-clad laminate comprising an adhesive layer and copper foil, in that order, on each side of a resin film, the resin film being in a cured state at 25°C, and the copper foil on the side in contact with the adhesive layer has a maximum peak height Sp of 0.05 μm or more and 3.3 μm or less, measured in accordance with ISO 25178.

Description

[Technical field]

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

[0002] Printed wiring boards are widely used in electronic communication devices such as portable electronic devices. In particular, with the recent trend toward lighter, thinner, shorter, smaller, and more highly functional portable electronic communication devices, reducing noise in printed wiring boards has become an issue. Capacitors are important for noise reduction, but in order to achieve high performance, it is desirable for capacitors to be small and thin enough to be incorporated into the inner layers of printed wiring boards. To form such capacitors, double-sided copper-clad laminates are used. Double-sided copper-clad laminates are generally configured such that both sides of a resin layer functioning as a dielectric layer are sandwiched between copper foils, and it is important to select more appropriate components to improve the performance of the capacitor.

[0003] For example, Patent Document 1 (JP Patent No. 5048181) discloses a passive electrical article that can be patterned to create an electrical circuit. The passive electrical article includes (a) a first free-standing substrate having two opposing main surfaces, (b) a second free-standing substrate having two opposing main surfaces, and (c) an electrically insulating or conductive layer comprising a polymer and having a thickness in the range of about 0.5 to about 10 μm between the first and second substrates. The passive electrical article is characterized in that 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 layer ranges from about 10 to about 300 nm, all of the distances z above or below the substrate surface used to measure the RMS average do not exceed half the thickness of the electrically insulating or conductive layer, and the force required to separate the first and second substrates of the passive electrical article at a peel angle of 90° exceeds about 3 pounds / inch (about 0.5 kN / m).

[0004] Patent Document 2 (Japanese Patent No. 4148501) discloses a dielectric filler-containing resin composition consisting of 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 BaTiO 3 , SrTiO 3 , Pb(Zr-Ti)O 3 , PbLaTiO 3 PbLaZrO, SrBi 2 Ta 2 O 9 The dielectric powder has a perovskite structure and an approximately spherical shape, and is composed of one or more of the following: an average particle size DIA of 0.1 to 1.0 μm; a weight cumulative particle size D50 of 0.2 to 2.0 μm as measured by a laser diffraction / scattering particle size distribution measurement method; and a degree of aggregation expressed as D50 / DIA, using the weight cumulative particle size D50 and the average particle size DIA obtained by image analysis, of 4.5 or less.

[0005] Patent Document 3 (Japanese Patent No. 3770537) discloses a capacitor to be placed in the inner layer of a multilayer printed wiring board, which is formed from a double-sided copper-clad laminate having a layer structure in which copper foil layers as a conductor are arranged on the outer layers of both sides, and a resin layer 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 with a layer structure of a thermosetting resin layer / heat-resistant film layer / thermosetting resin layer, and has a total thickness of 25 μm or less. The thermosetting resin layer is made of an epoxy resin material, and the heat-resistant film layer has a Young's modulus of 300 kg / mm 2 Above, tensile strength 20kg / mm 2 The laminate is characterized in that it is formed from a double-sided copper-clad laminate made of a resin material that is a heat-resistant film having a thickness of 0.5 to 12.5 μm and a dielectric constant of 2.5 or more when measured at 1 MHz in accordance with paragraph 2.5.5.9 of IPC-TM-650, and that has normal state properties of a tensile elongation of 5% or more and a softening temperature higher than the molding temperature of the thermosetting resin that constitutes the thermosetting resin layers located on both sides. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5048181 [Patent Document 2] Patent No. 4148501 [Patent Document 3] Patent No. 3770537 [Patent Document 4] WO2015 / 033917A1 [Patent Document 5] WO2003 / 096776A1 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, if there are large bumps on the surface of the copper foil, these bumps may penetrate the resin layer that contacts the resin film from above and below. If such bumps on the copper foil surface are present on the resin side surfaces of both copper foils constituting the capacitor, it is necessary to satisfy the voltage resistance characteristics only with the insulation properties of the resin film in the middle of the double-sided copper-clad laminate, and depending on the level of voltage resistance required, the resin film must be made thicker. However, since the resin film portion does not contain a complex oxide such as a filler and has inferior dielectric properties to the resin layer, there is a problem that the capacitor capacitance decreases when the resin film is made thicker. In other words, there is a trade-off relationship between the thickness of the resin film and the capacitor capacitance (i.e., electrostatic capacitance). Furthermore, it is desired to ensure not only electrostatic capacitance but also voltage resistance and peel strength (i.e., circuit adhesion). From the viewpoint of ensuring circuit adhesion, generally a highly rough copper foil (with large bumps on the surface) is desired, but as mentioned above, this is undesirable from the viewpoint of voltage resistance. In addition, it is also necessary to achieve a good bonding state between the copper foil, resin layer, and resin film, so it was not easy to control the surface shape of the copper foil to meet each of these requirements.

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

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

[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 both sides of a resin film, in that order, The resin film is in a cured state at 25°C, The double-sided copper-clad laminate is provided, in which the copper foil has a maximum peak height Sp of 0.05 μm or more and 3.3 μm or less on the surface in contact with the adhesive layer, as measured in accordance with ISO25178.

[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 both sides of a resin film, in that order, The resin film is in a cured state at 25°C, The copper foil has a root mean square gradient Sdq of 0.01 or more and 2.3 or less on the surface in contact with the adhesive layer, as measured in accordance with ISO25178. [Brief description of the drawings]

[0012] [Figure 1] 1 is a dark-field cross-sectional observation image showing a cross section cut in the thickness direction of the double-sided copper-clad laminate obtained in Example 4. [Diagram 2] 1 is a dark-field cross-sectional observation image showing a cross section cut in the thickness direction of a 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. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] definition The following are definitions of the parameters used to define the present invention.

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

[0015] In this specification, the "root mean square gradient Sdq" is a parameter calculated by the root mean square of the slope at all points in a defined area measured in accordance with ISO25178. In other words, since it is a three-dimensional parameter that evaluates the magnitude of the local slope angle, it can quantify the steepness of the surface unevenness. For example, the Sdq of a completely flat surface is 0, and if the surface is inclined, the Sdq becomes larger. The Sdq of a plane consisting of a 45-degree slope component is 1.

[0016] In this specification, "kurtosis (Sku)" is a parameter that indicates the sharpness of the height distribution, and is also called kurtosis, measured in accordance with ISO 25178. Sku=3 means that the height distribution is normal, Sku>3 means that the surface has many sharp peaks and valleys, and Sku<3 means that the surface is flat.

[0017] Double-sided copper-clad laminate The double-sided copper-clad laminate of the present invention comprises an adhesive layer and a copper foil on both sides of a resin film in that order. The resin film is in a cured state at 25°C. The copper foil has a maximum peak height Sp of 0.05 μm or more and 3.3 μm or less on the side in contact with the adhesive layer, as measured in accordance with ISO25178, or a root-mean-square gradient Sdq of 0.01 or more and 2.3 or less on the side in contact with the adhesive layer, as measured in accordance with ISO25178. In this way, by controlling the Sp or Sdq of the side 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 ensure high capacitance and exhibit excellent characteristics in terms of voltage resistance and peel strength.

[0018] As mentioned above, in the case of a double-sided copper-clad laminate having a resin film between dielectric layers, if there is a large bump on the surface of the copper foil, the bump may penetrate the resin layer that contacts the resin film from above and below. In that case, depending on the required level of withstand voltage, the resin film must be made thicker, but making the resin film thicker causes a problem of reduced capacitor capacitance. In addition, it is also desirable to ensure withstand voltage and peel strength. In this regard, the double-sided copper-clad laminate of the present invention conveniently solves these problems.

[0019] The double-sided copper-clad laminate preferably has a peel strength between the copper foil and the resin film, measured in accordance with IPC-TM650-2.4.6.C, of ​​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] The copper foil of the double-sided copper-clad laminate of the present invention has a maximum peak height Sp of 0.05 μm or more and 3.3 μm or less on the surface in contact with the adhesive layer, measured according to ISO25178. 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 that can exhibit excellent characteristics in terms of voltage resistance and peel strength while ensuring a high capacitor capacitance can be more effectively obtained. In particular, with regard to peel strength, it is possible to obtain performance that can withstand practical use even in a smooth area where sufficient adhesion was previously thought to be impossible to obtain.

[0021] In another embodiment of the present invention, the copper foil of the double-sided copper-clad laminate has a root-mean-square gradient Sdq of 0.01 or more and 2.3 or less on the side in contact with the adhesive layer, as measured in accordance with ISO25178. This root-mean-square gradient Sdq 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 viewpoint of obtaining a particularly thin double-sided laminate, the root-mean-square gradient Sdq 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 that can exhibit excellent characteristics in terms of voltage resistance and peel strength while ensuring a high capacitor capacitance can be more effectively obtained. In particular, with regard to peel strength, it is possible to obtain practical performance even in a smooth area where sufficient adhesion was previously thought to be impossible to obtain.

[0022] For each copper foil, the surface in contact with the adhesive layer preferably has a kurtosis Sku 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, as measured in accordance with ISO 25178. In this way, by controlling the kurtosis Sku in addition to controlling the maximum peak height Sp and the root-mean-square gradient Sdq as the surface properties of the copper foil, a desired double-sided copper-clad laminate can be more effectively obtained.

[0023] The thickness of the copper foil is not particularly limited, but is preferably 0.1 μm to 200 μm, more preferably 0.5 μm to 105 μm, and even more preferably 1.0 μm to 70 μm. This allows the use of processes such as the subtractive process, the SAP (semi-additive) process, and the MSAP (modified semi-additive) process, which are general pattern formation processes for wiring on printed wiring boards.

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

[0025] The resin film preferably has a relative dielectric constant 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 further 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 mentioned above, if there are large bumps 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 of 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. In other words, the thickness of the resin film and the capacitor capacity can be compatible.

[0027] The resin film preferably contains at least one selected from the group consisting of epoxy resin, polyethylene terephthalate, polyethylene naphthalate, polyvinylcarbazole, polyphenylene sulfide, polyimide, polyamide, aromatic polyamide (e.g., fully aromatic polyamide), polyamideimide, polyethersulfone, polyethernitrile, polyetheretherketone, and polytetrafluoroethylene, more preferably contains at least one selected from the group consisting of epoxy resin, polyphenylene sulfide, polyimide, polyamide, polyamideimide, and fully aromatic polyamide (aramid), and further preferably contains at least one selected from the group consisting of epoxy resin, polyimide, polyamide, and fully aromatic polyamide (aramid). Examples of such resin films that are commercially available include para-aramid films and polyimide films.

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

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

[0030] The adhesive layer is preferably made of a resin composition containing a resin component and a dielectric filler. The resin component is made of a thermoplastic component and / or a thermosetting component. Specifically, the adhesive layer 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, polyethernitrile resin, polyetheretherketone 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 BaTiO 3 , SrTiO 3 , Pb(Zr,Ti)O 3 , PbLaTiO 3 , PbLaZrO, and SrBi 2 Ta 2 O 9 and more preferably contains at least one selected from the group consisting of BaTiO 3 and SrTiO 3 . Note that Pb(Zr,Ti)O 3 means Pb(Zr x Ti 1-x )O 3 (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 measured by laser diffraction scattering particle size distribution measurement 50is 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 further 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 the resin varnish and the dielectric filler are kneaded. The filler dispersant may be any known dispersant that can be used as appropriate, and is not particularly limited. Examples of preferred filler dispersants include ionic dispersants such as phosphonic acid type, cationic type, carboxylic acid type, and anionic type dispersants, as well as nonionic dispersants such as ether type, ester type, sorbitan ester type, diester type, monoglyceride type, ethylene oxide addition type, ethylenediamine base type, and phenol type dispersants. Other examples include coupling agents such as silane coupling agents, titanate coupling agents, and aluminate coupling agents.

[0036] A curing accelerator may be added to the resin composition to accelerate the curing of the resin component. Preferred examples of the curing accelerator include imidazole curing accelerators and amine curing accelerators. 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, from the viewpoint of storage stability and curing efficiency of the resin components contained in the resin composition.

[0037] The double-sided copper-clad laminate of the present invention is typically obtained by applying the resin composition constituting the adhesive layer to a copper foil using a gravure coating method so that the adhesive layer has a predetermined thickness after drying, and then drying the resin composition. The coating method is arbitrary, but in addition to the gravure coating method, a die coating method, a knife coating method, etc. can be used. In addition, it is also possible to apply the resin composition using a doctor blade, a bar coater, etc. EXAMPLES

[0038] The present invention will now be further illustrated by the following examples.

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

[0040] The raw material components for the resin varnish were weighed out in the mixing ratios (weight ratios) shown in Tables 1A and 1B. Then, the cyclopentanone solvent was weighed out, 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 residual raw material in the resin varnish and that the resin varnish was transparent, the resin varnish was collected.

[0041] (2) Mixing with filler Next, the following dielectric fillers and dispersants were prepared. - Barium titanate: manufactured by Nippon Chemical Industry Co., Ltd. - Titanate coupling agent: KR-44 manufactured by Ajinomoto Fine-Techno Co., Ltd. (1.5 parts by weight added per 100 parts by weight of dielectric filler)

[0042] Cyclopentanone solvent, dielectric filler, and dispersant were each weighed. The weighed solvent, dielectric filler, and dispersant were slurried in a disperser. After the slurry was confirmed, a resin varnish was weighed so that the final dielectric filler had the compounding ratio (weight ratio) shown in Tables 1A and 1B, and was kneaded with the dielectric filler-containing slurry in a disperser. It was confirmed that the dielectric filler had not aggregated after kneading. In this way, a coating liquid containing a resin composition constituting the adhesive layer was obtained.

[0043] (3) Preparing copper foil A roughened copper foil was prepared as the copper foil for coating with the coating liquid. The copper foil was produced by a known method such as those disclosed in Patent Documents 4 and 5.

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

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

[0046] These resin films were subjected to surface roughening treatment. Specifically, the aramica film was subjected to corona discharge treatment, and the apical film was subjected to plasma treatment.

[0047] (6) Press In Examples 1 to 5, the copper foil with adhesive layer was placed with the coated resin surface facing upward, and a resin film was laminated on the coated resin surface. Furthermore, the copper foil with adhesive layer was laminated with the coated resin surface facing downward on the surface of the resin film that was not in contact with the coated resin surface. At this time, a vacuum press was performed at 180°C for 120 minutes to harden the adhesive layer. In this way, a double-sided copper-clad laminate was obtained.

[0048] In Examples 6 to 9, no resin film was used, and two sheets of copper foil with adhesive layer were stacked with their resin-coated surfaces facing each other and vacuum pressed at 180° C. for 120 minutes to cure the adhesive layer, thereby obtaining a double-sided copper-clad laminate.

[0049] (7) Evaluation The copper foil and the resulting double-sided copper-clad laminate were subjected to the following various evaluations.

[0050] <Evaluation 1: Surface quality parameters of copper foil> The surface roughness of the roughened copper foil of (3) above was measured in accordance with ISO 25178 using a laser microscope (OLS5000, manufactured by Olympus Corporation). 2 The surface profile of the region was measured with the above-mentioned laser microscope using a 100x lens with a numerical aperture (NA) of 0.95. After noise removal and linear surface inclination correction were performed on the obtained surface profile of the roughened surface, various parameters Sp, Sdq, and Sku were measured by surface property analysis. Sp, Sdq, and Sku were all measured with an S filter cutoff wavelength of 0.55 μm and an L filter cutoff wavelength of 10 μm. The results are shown in Tables 1A and 1B.

[0051] <Evaluation 2: Capacitance (Cp)> One side of the double-sided copper-clad laminate was etched to create a circular circuit with a diameter of 0.5 inches (12.6 mm), and the capacitance was measured at a frequency of 1 MHz using an LCR meter (HIOKI EE Corporation, LCR HiTester 3532-50). 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 are shown in Table 2. - Rating A: 10.0nF / in 2 Above (best) - Rating B: 5.0nF / in 2 or more and 10.0 nF / in 2 Less than (good) - Rating C: 1.0nF / in 2 or more and 5.0nF / in 2 Less than (OK) - Rating D: 1.0nF / in 2 Less than (not acceptable)

[0052] <Evaluation 3: Dielectric breakdown voltage (BDV)> One side of the double-sided copper-clad laminate was etched to create a circular circuit with a diameter of 0.5 inches (12.6 mm), and the dielectric breakdown voltage was measured at a voltage rise rate of 167 V / sec using an insulation resistance tester (Super Meter SM7110, manufactured by Hioki E.E. Corporation). This measurement was performed in accordance with IPC-TM-650 2.5.6.2a. The measured dielectric breakdown voltage was evaluated according to the following criteria. The results are shown in Table 2. - Rating A: Greater than 5000V (best) - Rating B: greater than 3500V and less than 5000V (good) - Rating C: More than 2000V and less than 3500V (acceptable) - Rating D: 2000V or less (not acceptable)

[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 having the adhesive layer) to calculate the value. The calculated dielectric breakdown strength was evaluated according to the following criteria. The results are shown in Table 2. - Rating A: Greater than 220kV / mm (best) - Rating B: greater than 200kV / mm and less than 220kV / mm (good) - Rating C: greater than 100kV / mm and less than or equal to 200kV / mm (acceptable) - Rating D: 100kV / mm or less (unacceptable)

[0054] <Evaluation 5: Normal peel strength (circuit adhesion)> After etching one side of a double-sided copper-clad laminate to create a linear circuit 3 mm wide, 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 (e.g., 25°C). This measurement was performed in accordance with IPC-TM-650 2.4.8. The measured normal peel strength was evaluated according to the following criteria. The results are shown in Table 2. - Rating A: 1.5kgf / cm or more (best) - Rating B: 1.0kgf / cm or more and less than 1.5kgf / cm (good) - Rating C: 0.6kgf / cm or more and less than 1.0kgf / cm (acceptable) - Rating D: Less than 0.6kgf / cm (unacceptable)

[0055] <Evaluation 6: Dielectric constant (Dk)> The copper on both sides of the double-sided copper-clad laminate was all removed by etching to obtain a resin film with an adhesive layer (a combination of an adhesive layer and a resin film). The electrostatic capacitance (Cp) of this resin film with an adhesive layer measured in Evaluation 2 and the relationship between Cp=ε 0 ×Dk×(S / d) (where ε 0 The relative dielectric constant at 1 MHz was measured using the formula (where is the dielectric constant of a vacuum, S is the area of ​​the circular circuit, and d is the thickness of the dielectric layer). The calculated relative dielectric constant was evaluated according to the following criteria. The results are shown in Table 2. - Rating A: Dielectric constant at 1MHz is 6.5 or more - Rating B: Dielectric constant at 1 MHz is 5.0 or more and less than 6.5 - Rating C: Dielectric constant at 1 MHz is 2.5 or more and less than 5.0 - Rating D: Dielectric constant at 1 MHz is less than 2.5

[0056] <Evaluation 7: Bonding condition> The double-sided copper-clad laminate was cut into a size of about 8 mm wide and 5 mm long, and then 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 bonded together by the adhesive layer. The quality of the bonded state was evaluated according to the following criteria. The results are 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. - Poor: The adhesive layer is not 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 was C or higher, it was determined that the performance was sufficient for practical use, and if the evaluation was B or higher, it was determined that the capacitor exhibited excellent characteristics. In addition, if the evaluation was poor in evaluation 7, voids or the like would be generated inside, and the capacitor would not be able to exhibit its original performance. Based on these criteria, it is preferable that there is no evaluation D in the results of evaluations 2 to 6, the total number of evaluations C is 3 or less, and the result of evaluation 7 is good.

[0058] [Table 1A]

[0059] [Table 1B]

[0060] [Table 2]

[0061] The present invention encompasses the following aspects. [Section 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, The double-sided copper-clad laminate has a maximum peak height Sp of 0.05 μm or more and 3.3 μm or less on the surface of the copper foil that contacts the adhesive layer, as measured in accordance with ISO 25178. [Section 2] 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, A double-sided copper-clad laminate, wherein the copper foil has a root-mean-square gradient Sdq of 0.01 or more and 2.3 or less on the side in contact with the adhesive layer, as measured in accordance with ISO 25178. [Section 3] Item 3. The double-sided copper-clad laminate according to item 1 or 2, wherein the combination of the adhesive layer and the resin film has a relative dielectric constant of 2.5 or more and 30 or less at a frequency of 1 MHz after curing. [Section 4] 4. The double-sided copper-clad laminate according to any one of items 1 to 3, 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. [Section 5] 5. The double-sided copper-clad laminate according to any one of items 1 to 4, 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. [Section 6] 6. The double-sided copper-clad laminate according to any one of items 1 to 5, wherein the resin film has a thickness of 0.5 μm or more and 30 μm or less. [Section 7] The double-sided copper-clad laminate according to any one of items 1 to 6, 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, polyethernitrile, polyetheretherketone, and polytetrafluoroethylene. [Section 8] The adhesive layer contains a resin component composed of a thermoplastic component and / or a thermosetting component, and the resin component is 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 items 1 to 7, comprising at least one selected from the group consisting of. [Section 9] The adhesive layer 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. The double-sided copper-clad laminate according to any one of items 1 to 8. [Section 10] The composite metal oxide is BaTiO 3 , SrTiO 3 , Pb(Zr,Ti)O 3 , PbLaTiO 3 , PbLaZrO, and SrBi 2 Ta 2 O 9 Item 10. The double-sided copper-clad laminate according to item 9, comprising at least one selected from the group consisting of: [Section 11] Item 11. The double-sided copper-clad laminate according to any one of items 1 to 10, wherein the copper foil has a kurtosis (Sku) of 2.6 or more and 4.0 or less on the side in contact with the adhesive layer, as measured in accordance with ISO25178. [Section 12] Item 12. The double-sided copper-clad laminate according to any one of items 1 to 11, 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.

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, The adhesive layer 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.

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 2.5 or more and 30 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 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 any one of claims 1 to 7, comprising at least one selected from the group consisting of:

9. The double-sided copper-clad laminate according to any one of claims 1 to 8, 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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