Resin composition, resin-coated copper foil, dielectric layer, copper-clad laminate, capacitor element, and printed circuit board with built-in capacitor

Abstract

The present invention relates to a resin composition, a resin-coated copper foil, a dielectric layer, a copper-clad laminate, a capacitor element, and a printed circuit board with a built-in capacitor. The present invention provides a resin composition which, when used as a dielectric layer of a capacitor element or a printed circuit board with a built-in capacitor, is capable of ensuring excellent circuit adhesion and improving the capacity stability and insulation of the capacitor element under high temperature and high humidity. The resin composition contains a resin component and a dielectric filler, the resin component containing an epoxy resin, an active ester resin, and an aromatic polyamide resin.

Description

[0001] This application is a divisional application of the application filed on March 9, 2018, with application number 201880005716.7, entitled "Resin Composition, Resin Copper Foil, Dielectric Layer, Copper-Clad Laminate, Capacitor Element, and Printed Circuit Board with Built-in Capacitor". Technical Field

[0002] This invention relates to resin compositions, resin-coated copper foil, dielectric layers, copper-clad laminates, capacitor elements, and printed circuit boards with built-in capacitors. Background Technology

[0003] As a resin composition used in the manufacture of copper-clad laminates and printed circuit boards, a resin composition for printed circuit boards with built-in capacitors is known. This resin composition is used as a dielectric layer in the capacitor by curing. For example, Patent Document 1 (Japanese Patent No. 4148501) discloses a resin composition for printed circuit boards with built-in capacitors, which (based on 100 parts by weight of resin content) contains 20 to 80 parts by weight of epoxy resin and 20 to 80 parts by weight of aromatic polyamide resin, and (based on 100 wt% of resin composition) contains 75 to 85 wt% of dielectric filler. In addition, Patent Document 2 (International Publication No. 2009 / 008471) discloses a resin composition for manufacturing a printed circuit board with an embedded capacitor, which (based on 100 parts by weight of resin composition) contains 25 to 60 parts by weight of epoxy resin, 28 to 60 parts by weight of reactive ester resin, 1 to 20 parts by weight of polyvinyl acetal resin, and (based on 100 wt% of resin composition) contains 65 to 85 wt% of dielectric filler.

[0004] On the other hand, a resin composition is known that can achieve a low dielectric loss tangent in the cured resin composition and can suppress smear in the through-holes after the cured composition has been processed by opening and roughening. For example, Patent Document 3 (Japanese Patent Application Publication No. 2016-156019) discloses a resin composition containing (A) epoxy resin, (B) active ester compound, (C) smear suppressing component and (D) inorganic filler, wherein when the non-volatile component of the resin composition is 100% by mass, the content of (B) active ester compound is 5% by mass or more, when the non-volatile component of the resin composition is 100% by mass, the content of (C) smear suppressing component is 0.001 to 10% by mass, when the non-volatile component of the resin composition is 100% by mass, the content of (D) inorganic filler is 70% by mass or more, and (C) smear suppressing component is rubber particles.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 4148501

[0008] Patent Document 2: International Publication No. 2009 / 008471

[0009] Patent Document 3: Japanese Patent Application Publication No. 2016-156019

[0010] Patent Document 4: Japanese Patent Application Publication No. 2004-277460 Summary of the Invention

[0011] However, printed circuit boards (PCBs) are widely used in portable electronic devices and other electronic communication equipment. Especially with the recent development of miniaturization, thinness, and high functionality in portable electronic communication devices, reducing interference in PCBs has become a technical challenge. Capacitors are crucial for reducing interference, but to achieve high performance, it is desirable for these capacitors to be miniaturized and thinned to the point where they can be assembled into the inner layers of the PCB. Simultaneously, it is desirable for them to maintain the required capacitance stability even in harsher environments with high temperature and humidity.

[0012] Therefore, in order to achieve high performance in portable electronic devices and other electronic communication devices, it is desirable to suppress the decrease in capacitance or dielectric constant of capacitors built into printed circuit boards under high temperature and humidity conditions. To this end, it is desirable to further improve the resin layer constituting the dielectric layer of the capacitor. On the other hand, it is also desirable to have high adhesion between the resin layer and the circuit (i.e., circuit adhesion).

[0013] The inventors have discovered that by using a resin composition containing a dielectric filler along with epoxy resin, reactive ester resin and aromatic polyamide resin as the dielectric layer of a capacitor, excellent circuit tightness can be ensured and capacitance reduction or dielectric constant reduction under high temperature and high humidity conditions can be suppressed.

[0014] Therefore, the object of the present invention is to provide a resin composition that, when used as a dielectric layer of a capacitor, can ensure excellent circuit tightness and suppress capacitance reduction or dielectric constant reduction under high temperature and high humidity conditions.

[0015] According to one embodiment of the present invention, a resin composition containing a resin component and a dielectric filler is provided, wherein,

[0016] The resin composition includes epoxy resin, reactive ester resin and aromatic polyamide resin.

[0017] According to another embodiment of the present invention, a resin-coated copper foil is provided, comprising a copper foil and a resin composition of any one of claims 1 to 5 disposed on at least one side of the copper foil.

[0018] According to another embodiment of the present invention, a dielectric layer is provided, which is a layer obtained by curing the resin composition.

[0019] According to another embodiment of the present invention, a copper-clad laminate is provided, which sequentially comprises a first copper foil, the dielectric layer and a second copper foil.

[0020] According to another embodiment of the present invention, a capacitor element is provided having the dielectric layer.

[0021] According to another embodiment of the present invention, a printed circuit board with a built-in capacitor is provided, having the dielectric layer described above. Attached Figure Description

[0022] Figure 1 The diagram illustrates the fabrication process of the resin-coated copper foil, copper-clad laminate, and evaluation circuit in Examples 1 to 8. Detailed Implementation

[0023] The embodiments of the present invention will be described below. It should be noted that the numerical range expressed in the form of "X to Y" in this specification means "X or more and Y or less".

[0024] Resin Composition

[0025] The resin composition of the present invention contains a resin component and a dielectric filler. Furthermore, the resin component contains an epoxy resin, an active ester resin, and an aromatic polyamide resin. Thus, by using a resin composition containing a dielectric filler along with epoxy resin, an active ester resin, and an aromatic polyamide resin as the dielectric layer of a capacitor, excellent circuit tightness can be ensured, and capacitance or dielectric constant reduction under high temperature and high humidity can be suppressed. That is, the dielectric layer containing the resin composition of the present invention has a high original capacitance, and its high capacitance is not easily reduced even under high temperature and high humidity. In addition, the dielectric layer containing the resin composition of the present invention is not prone to migration of circuit components (usually metals such as Cu) even under high temperature and high humidity, and therefore can maintain interlayer insulation for a long time. Therefore, the dielectric constant of the dielectric layer is not easily reduced under high temperature and high humidity, and thus the capacitance is not easily reduced under high temperature and high humidity. Because of this, the dielectric layer containing the resin composition of the present invention also has excellent circuit tightness, and circuit stripping in the capacitor is not easily caused.

[0026] The resin composition of the present invention preferably contains 9 to 85 parts by weight of aromatic polyamide resin and 5 to 50 parts by weight of active ester resin relative to 100 parts by weight of resin component; more preferably, it contains 10 to 80 parts by weight of aromatic polyamide resin and 10 to 40 parts by weight of active ester resin; more preferably, it contains 15 to 70 parts by weight of aromatic polyamide resin and 12 to 38 parts by weight of active ester resin; even more preferably, it contains 25 to 60 parts by weight of aromatic polyamide resin and 15 to 35 parts by weight of active ester resin; and particularly preferably, it contains 30 to 50 parts by weight of aromatic polyamide resin and 20 to 30 parts by weight of active ester resin. With these contents, the effects of the present invention can be exerted more effectively.

[0027] Epoxy resins are suitable for electrical and electronic applications as long as they have two or more epoxy groups within their molecules. Examples of epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, phenolic varnish type epoxy resins, biphenyl phenolic varnish type epoxy resins, cresol phenolic varnish type epoxy resins, alicyclic epoxy resins, glycidylamine type epoxy resins, naphthalene type epoxy resins, anthracene type epoxy resins, dicyclopentadiene type epoxy resins, and any combination thereof. From the perspective of maintaining the heat resistance of the cured product, aromatic epoxy resins or multifunctional epoxy resins are preferred, and phenolic varnish type epoxy resins, naphthalene type epoxy resins, cresol phenolic varnish type epoxy resins, or biphenyl phenolic varnish type epoxy resins are more preferred. These epoxy resins are effective in maintaining the heat resistance of the cured product.

[0028] The reactive ester resin functions as an epoxy resin curing agent that reacts with and cures the epoxy resin. There are no particular limitations on the reactive ester resin; known reactive ester resins can be used. For example, the reactive ester compound disclosed in Patent Document 4 (Japanese Patent Application Publication No. 2004-277460) can also be used. Alternatively, commercially available reactive ester compounds can be used. Examples of commercially available reactive ester compounds include reactive ester curing agents containing a dicyclopentadiene structure, reactive ester curing agents containing a naphthalene structure, reactive ester curing agents containing an acetylated form of phenolic varnish, and reactive ester curing agents containing a benzoyl form of phenolic varnish. Preferably, reactive ester curing agents containing a naphthalene structure and reactive ester curing agents containing a dicyclopentadiene diol structure are also included. Examples of reactive ester curing agents containing a dicyclopentadiene diol structure include EXB9451, EXB9460, EXB9460S, and HPC-8000-65T (manufactured by DIC Corporation). Examples of reactive ester-based curing agents containing naphthalene structures include EXB9416-70BK (manufactured by DIC Corporation). Examples of reactive ester-based curing agents containing acetylated phenolic varnishes include DC808 (manufactured by Mitsubishi Chemical Corporation). Examples of reactive ester-based curing agents containing benzoylated phenolic varnishes include YLH1026 (manufactured by Mitsubishi Chemical Corporation). Using the above-mentioned reactive ester resins ensures the heat resistance of the cured epoxy resin and reduces water absorption.

[0029] When the resin composition contains 25 to 60 parts by weight of aromatic polyamide resin and 15 to 35 parts by weight of reactive ester resin per 100 parts by weight of resin component, the content of reactive ester resin is preferably 0.75 to 1.25 equivalents of hydroxyl groups relative to 1 equivalent of epoxy resin. When the content of reactive ester resin is 0.75 equivalents or more relative to epoxy resin, the epoxy resin is less prone to self-polymerization, preventing the curing reaction from terminating due to insufficient epoxy resin molecules. This results in a dielectric layer with a large dielectric loss tangent and no residual hydroxyl groups from the reactive ester resin. Furthermore, when the amount of reactive ester resin is 1.25 equivalents or less relative to epoxy resin, the reactive ester resin is less likely to remain in the cured dielectric layer due to unreacted reaction, preventing deterioration of the thermal resistance of the dielectric layer.

[0030] Aromatic polyamide resins contribute to improving the heat resistance of resin layers. Aromatic polyamide resins are resins synthesized through the condensation polymerization of aromatic diamines and dicarboxylic acids. Examples of aromatic diamines used in the aforementioned condensation polymerization include 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenyl sulfone, m-phenylenediamine, 3,3'-diaminodiphenyl ether, and any combination thereof. Examples of dicarboxylic acids used in the aforementioned condensation polymerization include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, fumaric acid, and any combination thereof. To impart heat resistance to aromatic polyamide resins, the dicarboxylic acid is preferably an aromatic dicarboxylic acid. Examples of aromatic dicarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, fumaric acid, and any combination thereof. Aromatic polyamide resins containing phenolic hydroxyl groups within the molecule are particularly preferred. Furthermore, without compromising heat resistance, the aromatic polyamide resin may also contain appropriate chemical bonds within the molecule to impart flexibility as a flexible chain, or it may be a substance that forms a crosslinked polymer alloy with the polyamide resin and exists in a locally aggregated state. Examples of compounds that can impart flexibility to aromatic polyamide resins as flexible chains include butadiene, ethylene-propylene copolymers, styrene-butadiene copolymers, carboxylic acid-butadiene copolymers, acrylonitrile-butadiene copolymers, polyurethane, polychloroprene, and siloxanes. By using the aforementioned aromatic polyamides, the flexibility of the cured epoxy resin can be ensured, thereby improving peel strength reliability and heat resistance.

[0031] To promote the reaction of the resin, it is preferable to add a curing accelerator to the resin composition. Preferred examples of curing accelerators include imidazole-based and amine-based curing accelerators. From the perspective of the storage stability of the resin composition and the efficiency of curing, the content of the curing accelerator is preferably 0.01 to 3% by mass, more preferably 0.1 to 2% by mass, relative to the non-volatile components in 100% by mass of the resin composition.

[0032] Because imidazole-based curing accelerators, after undergoing a curing reaction with epoxy resin, are incorporated into the molecular structure of the epoxy resin as part of the resin rather than becoming free ions, they result in excellent dielectric properties and insulation reliability of the resin layer. The content of imidazole-based curing accelerators can be appropriately determined to achieve the desired curing amount, taking into account various conditions such as the composition of the resin layer; there are no particular limitations. Examples of imidazole curing accelerators include 2-undecylimazole, 2-heptadecylimazole, 2-ethyl-4-methylimazole, 2-phenyl-4-methylimazole, 1-cyanoethyl-2-undecylimazole, 1-cyanoethyl-2-ethyl-4-methylimazole, 2-ethyl-4-methylimazole, 1-cyanoethyl-2-phenylimazole, 2-phenyl-4,5-dihydroxymethylimazole, 2-phenyl-4-methyl-5-hydroxymethylimazole, 2-methylimazole, 1,2-dimethylimazole, 2-phenylimazole, 1-benzyl-2-methylimazole, 1-benzyl-2-methylimazole, 1-benzyl-2-phenylimazole, 1-cyanoethyl-2-methylimazole, 1-cyanoethyl-2-undecylimazole trimellitate, 1-cyanoethyl-2-methylimazole, 1-cyanoethyl-2-undecylimazole trimellitate, 1-cyanoethyl-2-undecyl ... Ethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-triazine isocyanuric acid adduct, 2-phenylimidazolium isocyanuric acid adduct, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline, and any combination thereof. Preferred examples of imidazole-based curing accelerators include 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, and 2-phenyl-4-methyl-5-hydroxymethylimidazole. From the perspective of chemical stability of the resin layer in its semi-cured (B-stage) state, phenyl-containing imidazole-based curing accelerators 2-phenyl-4-methylimidazole and 2-phenyl-4-methyl-5-hydroxymethylimidazole are preferred examples. 2-phenyl-4-methyl-5-hydroxymethylimidazole is particularly preferred.

[0033] Examples of amine-based curing accelerators include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, 1,8-diazabicyclo(5,4,0)-undecene, and any combination thereof.

[0034] Dielectric filler is a component that imparts the desired high electrostatic capacitance to the resin composition serving as the dielectric layer, and known substances can be used. Preferred dielectric fillers contain at least one selected from the group consisting of BaTiO3, SrTiO3, Pb(Zr,Ti)O3, PbLaTiO3, PbLaZrO, and SrBi2Ta2O9. From the perspective of improving the electrostatic capacitance of the capacitor formed by the dielectric layer, BaTiO3 is particularly preferred as the dielectric filler. The preferred content of dielectric filler in the resin composition is 60 to 95 parts by weight, more preferably 70 to 90 parts by weight, and even more preferably 70 to 80 parts by weight, relative to 100 parts by weight of the solids content of the resin composition.

[0035] As needed, 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 mixing the resin varnish and the dielectric filler. As a filler dispersant, any known and applicable substance can be used appropriately, without particular limitation. Examples of preferred filler dispersants include phosphonic acid type, cationic type, carboxylic acid type, and anionic dispersants as ionic dispersants, and ether type, ester type, sorbitol ester type, diester type, monoglyceride type, ethylene oxide addition type, ethylene diamine base type, and phenol type dispersants as anionic dispersants. In addition, coupling agents such as silane coupling agents, titanate coupling agents, and aluminate coupling agents can also be listed.

[0036] Resin-copper foil

[0037] The resin composition of the present invention is preferably used as a resin for resin-coated copper foil. From the perspective of forming a dielectric layer by laminating two resin-coated copper foils with the resin composition facing each other, it is preferable that the resin composition in the resin-coated copper foil is in a semi-cured state. By pre-forming it into the form of resin-coated copper foil, it is possible to efficiently manufacture capacitor elements and printed circuit boards with built-in capacitors without having to form a separate resin layer or dielectric layer. That is, according to a preferred embodiment of the present invention, a resin-coated copper foil is provided, which contains a copper foil and a resin composition disposed on at least one side of the copper foil. Typically, the resin composition is in the form of a resin layer, and the resin composition is coated onto the copper foil by gravure coating and dried so that the thickness of the dried resin layer reaches a predetermined thickness to obtain the resin-coated copper foil. The coating method can be any method, including gravure coating, die coating, blade coating, etc. In addition, a blade or doctor blade coater can also be used for coating.

[0038] There is no particular limitation on the thickness of the resin layer, as long as it can ensure the required capacitance when bonded to the capacitor as a dielectric layer. However, it is preferably 0.1 to 15 μm, more preferably 0.2 to 10 μm, and even more preferably 0.5 to 5.0 μm. Thicknesses within these ranges have advantages such as easy achievement of high capacitance, easy formation of the resin layer through coating of the resin composition, and easy assurance of sufficient adhesion to the copper foil.

[0039] Copper foil can be either a metal foil produced by electrolysis or rolling (so-called raw foil), or a surface-treated foil with surface treatment applied to at least one surface. Surface treatment can be any of the following to improve or impart any property to the surface of the metal foil (e.g., rust resistance, moisture resistance, chemical resistance, acid resistance, heat resistance, and adhesion to the substrate). Surface treatment can be performed on at least one side of the metal foil, or on both sides. Examples of surface treatments for copper foil include rust prevention treatment, silane treatment, roughening treatment, and barrier layer formation treatment.

[0040] The ten-point average roughness Rzjis of the resin layer side surface of the copper foil, as measured according to JIS B0601-2001, is preferably 2.0 μm or less, more preferably 1.5 μm or less, even more preferably 1.0 μm or less, and particularly preferably 0.5 μm or less. Within this range, the resin layer thickness can be thinner. There is no particular limitation on the lower limit of the ten-point average roughness Rzjis of the resin layer side surface of the copper foil; however, from the perspective of improving adhesion to the resin layer, Rzjis is preferably 0.005 μm or more, more preferably 0.01 μm or more, and even more preferably 0.05 μm or more.

[0041] The thickness of the copper foil is not particularly limited, but is preferably 0.1 to 100 μm, more preferably 0.5 to 70 μm or less, further preferably 2 to 70 μm or less, particularly preferably 10 to 70 μm or less, and most preferably 10 μm to 35 μm or less. For thicknesses within these ranges, conventional patterning methods for forming wiring on printed circuit boards, such as MSAP (modified semi-additive process), SAP (semi-additive process), and subtractive process, can be used. However, when the copper foil thickness is, for example, 10 μm or less, the resin-coated copper foil of the present invention may also be a copper foil on which a resin layer is formed on the surface of a carrier copper foil having a release layer and a carrier in order to improve operability.

[0042] dielectric layer

[0043] Preferably, the resin composition of the present invention is cured to form a dielectric layer. That is, according to a preferred embodiment of the present invention, a dielectric layer is provided, which is a layer obtained by curing the resin composition of the present invention. The curing of the resin composition can be carried out based on known methods, but is preferably carried out by vacuum hot pressing. The thickness of the dielectric layer is not particularly limited as long as it can ensure the required electrostatic capacitance, but is preferably 0.2 to 30 μm, more preferably 0.5 to 20 μm, further preferably 1 to 8 μm, and most preferably 2 to 6 μm. Thicknesses within these ranges have advantages such as easy achievement of high electrostatic capacitance, easy formation of a resin layer by coating the resin composition, and easy assurance of sufficient adhesion to the copper foil.

[0044] Copper-clad laminate

[0045] The resin composition of the present invention, or the dielectric layer comprising it, is preferably suitable for copper-clad laminates. Specifically, according to a preferred embodiment of the present invention, a copper-clad laminate is provided, which sequentially comprises a first copper foil, the aforementioned dielectric layer, and a second copper foil. By adopting the form of a copper-clad laminate, capacitor elements containing the resin composition of the present invention as the dielectric layer and printed circuit boards with built-in capacitors can be preferably manufactured. There are no particular limitations on the method of manufacturing the copper-clad laminate, but for example, it can be manufactured by laminating two of the aforementioned resin-coated copper foils opposite each other with resin layers and performing vacuum pressing at high temperature.

[0046] Capacitor components and printed circuit boards with built-in capacitors

[0047] Preferably, the resin composition of the present invention or a dielectric layer containing therein is incorporated into the capacitor element. That is, according to a preferred embodiment of the present invention, a capacitor element having the aforementioned dielectric layer is provided. There are no particular limitations on the construction of the capacitor element; known constructions can be employed. A particularly preferred form is a printed circuit board with a built-in capacitor, incorporating a capacitor or its dielectric layer as an inner layer portion of a printed circuit board. That is, according to a particularly preferred embodiment of the present invention, a printed circuit board with a built-in capacitor having the aforementioned dielectric layer is provided. In particular, by using the resin-coated copper foil of the present invention, capacitor elements and printed circuit boards with built-in capacitors can be manufactured efficiently using known methods.

[0048] Example

[0049] The invention will be described in more detail by way of the following examples.

[0050] Examples 1 to 7

[0051] (1) Preparation of resin varnish

[0052] First, prepare the following resin components, imidazole-based curing accelerator, and dielectric filler as raw material components for resin varnish.

[0053] - Epoxy resin: Biphenyl phenolic varnish type epoxy resin, manufactured by Nippon Kayaku Co., Ltd., NC-3000

[0054] - Reactive ester resin: Manufactured by DIC Corporation, HPC-8000-65T

[0055] - Aromatic polyamide resin: Manufactured by Nippon Kayaku Co., Ltd., BPAM-155

[0056] - Imidazole curing accelerator: Manufactured by Shikoku Chemical Industry Co., Ltd., 2P4MHZ, addition amount 1.0wt% (relative to 100wt% resin composition).

[0057] - Dielectric filler: BaTiO3, manufactured by Nippon Chemical Industries, Ltd., AKBT-M

[0058] - Filler dispersant: Titanate coupling agent, manufactured by Ajinomoto Fine-Techno Co., Inc., KR-44

[0059] Weigh the raw materials for the resin varnish according to the mixing ratio (by weight) shown in Table 1. Further, add cyclopentanone as a solvent and stir at 60°C. After confirming the transparency of the resin varnish, recover the resin varnish.

[0060] (2) Mixing with fillers

[0061] Cyclopentanone, dielectric filler, and filler dispersant were weighed separately. The weighed solvent, dielectric filler, and filler dispersant were slurried using a disperser. After confirming slurry formation, the resin varnish was weighed and mixed with the slurry containing the dielectric filler using a disperser to obtain resin composition 4.

[0062] (3) Resin coating

[0063] like Figure 1 As shown, the obtained resin composition 4 was coated onto copper foil 2 (manufactured by Mitsui Metals & Mining Co., Ltd., thickness 35 μm, surface roughness Rz = 0.5 μm) using a doctor blade coater to achieve a thickness of 1.5 μm. Then, it was dried in an oven heated to 130°C for 3 minutes to allow the resin to reach a semi-cured state. This yielded a resin-coated copper foil 6.

[0064] (4) Suppression

[0065] like Figure 1 As shown, two resin-coated copper foils 6 are laminated together with the resin composition 4 against each other at a pressure of 40 kgf / cm². 2The resin composition 4 is cured by vacuum pressing at 200°C for 90 minutes. This yields a copper-clad laminate 8 containing the cured resin composition 4 as the dielectric layer.

[0066] (5) Circuit formation and evaluation

[0067] Etching is performed on one or both sides of the obtained copper-clad laminate 8 to form circuits 10 for various evaluations, and the following evaluations are performed.

[0068] <Evaluation 1: Peel Strength>

[0069] After etching a 10mm wide linear circuit on one side of a copper-clad laminate, the circuit was peeled off using an automated drawing process at a peeling speed of 50mm / min, and its peel strength was measured. This measurement was performed according to IPC-TM-650 2.4.8. The measured peel strength was evaluated according to the following criteria. The results are shown in Table 1.

[0070] - Rating A: Above 0.8 kgf / cm² (Good)

[0071] - Rating B: Above 0.4 kgf / cm² and less than 0.8 kgf / cm² (acceptable)

[0072] - Rating C: Less than 0.4 kgf / cm² (Not acceptable)

[0073] <Evaluation 2: Rate of decrease in electrostatic capacitance after heat treatment>

[0074] First, a circular circuit with a diameter of 0.5 inches (12.6 mm) was etched onto one side of the copper-clad laminate. The capacitance at a frequency of 1 kHz was then measured using an LCR meter (manufactured by Hioki Electric Co., Ltd., LCR HiTESTER 3532-50). This measurement was performed according to IPC-TM-650 2.5.2. The results are shown in Table 1.

[0075] Then, the samples that had undergone the above measurements were placed in an oven at 230°C for 110 minutes, and the capacitance was measured again to calculate the rate of decrease in capacitance before and after heat treatment. The calculated rate of decrease in capacitance was evaluated according to the following criteria. The results are shown in Table 1.

[0076] - Rating AA: Less than 2% (best)

[0077] - Rating A: 2% or higher but less than 3% (Good)

[0078] - Rating B: 3% or higher but less than 6% (acceptable)

[0079] - Rating C: 6% or higher (not acceptable)

[0080] <Evaluation 3: Interlayer insulation retention time>

[0081] After etching 0.5-inch (12.6 mm) diameter circular circuits on both sides of the copper-clad laminate, wiring was soldered to the upper and lower electrodes, and then connected to a migration measurement instrument. The evaluation circuit was placed in a constant temperature and humidity bath at 85°C and 85%RH, a 3V load was applied, and measurements were taken at 1×10⁻⁶. 5 The duration of insulation resistance above Ω was measured. The interlayer insulation retention time was evaluated according to the following criteria. The results are shown in Table 1.

[0082] - Rating AA: 1000+ hours (Best)

[0083] - Rating A: 500+ hours but less than 1000 hours (Good)

[0084] - Rating B: 200+ hours but less than 500 hours (acceptable)

[0085] - Rating C: Less than 200 hours (not allowed)

[0086] <Overall Evaluation>

[0087] The evaluation results from evaluations 1 to 3 were applied to the following criteria for comprehensive evaluation. The results are shown in Table 1.

[0088] - Rating AA: All ratings are rated A or higher (best).

[0089] - Rating A: No one was rated C, and 1 was rated B (Good).

[0090] - Evaluation B: No one was rated C, and there are 2 rated B (acceptable).

[0091] - Rating C: At least one item must be rated C (not acceptable)

[0092] Example 8 (Compare)

[0093] Except that 20.0 parts by weight of phenolic resin (manufactured by Meiwa Kasei Corporation, MEH-7500) was used instead of the reactive ester resin, and the mixing ratio of epoxy resin was increased to 40.0 parts by weight, the resin varnish was prepared and various evaluations were performed in the same manner as in Example 3. The results are shown in Table 1.

[0094] Example 9 (Compare)

[0095] Except that polyvinyl butyral resin (manufactured by Sekisui Chemicals, KS-5Z) was used instead of aromatic polyamide resin, the preparation and various evaluations of the resin varnish were carried out in the same manner as in Example 2. The results are shown in Table 1.

[0096] Example 10 (Compare)

[0097] Except that aromatic polyamide resin was not used, the epoxy resin mixing ratio was increased to 56.0 parts by weight, and the reactive ester resin mixing ratio was increased to 44.0 parts by weight, the resin varnish was prepared and various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[0098] [Table 1]

[0099]

Claims

1. A resin composition comprising a resin component and a dielectric filler, The resin composition includes epoxy resin, reactive ester resin, and aromatic polyamide resin containing phenolic hydroxyl groups, wherein the epoxy resin is a biphenyl phenolic varnish-type epoxy resin. Relative to 100 parts by weight of the resin component, it contains 25 to 50 parts by weight of the aromatic polyamide resin and 15 to 35 parts by weight of the active ester resin. The resin composition contains 60 to 95 parts by weight of the dielectric filler relative to 100 parts by weight of its solids content.

2. The resin composition according to claim 1, wherein, The dielectric filler contains at least one selected from the group consisting of BaTiO3, SrTiO3, Pb(Zr,Ti)O3, PbLaTiO3, PbLaZrO and SrBi2Ta2O9.

3. The resin composition according to claim 1 or 2, wherein, The dielectric filler is BaTiO3.

4. The resin composition according to claim 1 or 2, wherein, The resin composition contains 70 to 90 parts by weight of the dielectric filler relative to 100 parts by weight of its solids content.

5. A resin-coated copper foil comprising a copper foil and a resin composition as described in any one of claims 1 to 4 disposed on at least one side of the copper foil.

6. A dielectric layer, which is a layer obtained by curing the resin composition according to any one of claims 1 to 4.

7. The dielectric layer according to claim 6, wherein, The thickness of the dielectric layer is 0.2–30 μm.

8. A copper-clad laminate comprising, in sequence, a first copper foil, a dielectric layer as described in claim 6 or 7, and a second copper foil.

9. A capacitor element having the dielectric layer as described in claim 6 or 7.

10. A printed circuit board with an integrated capacitor having a dielectric layer as described in claim 6 or 7.

Images