Manufacturing method of magnetic substrate

Abstract

A manufacturing method for a magnetic substrate that is for manufacturing a magnetic substrate by using a resin sheet comprising a support and a resin composition layer formed on the support, the resin composition layer including a resin composition containing a magnetic powder, the manufacturing method comprising a step (I) for placing the resin sheet on a core substrate having a through hole formed therein and a step (II) for pressing the resin sheet with a rigid plate to fill the through hole with the resin composition, wherein the step (II) comprises pressing the resin sheet such that the rigid plate is in contact with the resin sheet under a heating condition of 80-160°C inclusive in an environment with a degree of vacuum of 1.3 kPa or less.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a magnetic substrate. [Background technology]

[0002] One type of circuit board used in electronic devices is obtained by filling through holes in a core substrate with a resin composition and then curing the resin composition (Patent Documents 1, 2, and 3). Resin compositions containing magnetic powder have also been used to fill through holes in circuit boards for inductor components (Patent Document 4). Circuit boards using resin compositions containing magnetic powder in this way include a core substrate with through holes formed therein and a cured product of the resin composition filled in the through holes. Since the cured product contains magnetic powder, it can be used as a magnetic material. Hereinafter, a board whose through holes are filled with a material containing magnetic powder in this way may be referred to as a "magnetic board." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-149758 [Patent Document 2] Patent No. 4992514 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-100546 [Patent Document 4] Patent Publication No. 2021-86856 Summary of the Invention [Problem to be solved by the invention]

[0004] When manufacturing inductor components with good characteristics using a magnetic material, the magnetic material is required to have high magnetic permeability. In order to obtain a magnetic material with high magnetic permeability by curing a resin composition, it is desirable to increase the content of magnetic powder in the resin composition.

[0005] Conventionally, printing methods such as screen printing have been used to fill through-holes with a resin composition containing magnetic powder. However, when the content of magnetic powder is high, the resin composition has low fluidity and therefore poor printability, making filling by printing difficult. Therefore, the present inventors have investigated a method that allows the resin composition to be successfully filled into through-holes even when the content of magnetic powder in the resin composition is high.

[0006] Specifically, the present inventors have investigated a method for filling a through-hole with a resin composition using a resin sheet including a support and a resin composition layer formed on the support, but when the resin composition is filled into the through-hole using the resin sheet, unfilled portions or voids are formed, making it difficult to achieve good filling.

[0007] For example, the present inventors have attempted to use a vacuum laminator to laminate a resin sheet and a core substrate and fill the through-holes with a resin composition. Generally, vacuum laminators use an elastic member to pressurize the resin sheet in a vacuum environment to laminate the resin sheet and the core substrate. For example, a rubber press method, in which pressure is applied using an elastic mold made of rubber, or a diaphragm method, in which pressure is applied using a film made of an elastic material, are commonly used. By applying pressure using an elastic member in this way, the resin sheet can adequately conform to the surface shape of the core substrate, and it was expected that vacuum laminators would be able to achieve gap-free lamination. However, when using a vacuum laminator, the resin composition could not be filled entirely within the through-holes, resulting in unfilled portions lacking the resin composition.

[0008] Therefore, the present inventors attempted to use a two-chamber vacuum laminator. In a two-chamber vacuum laminator, a resin sheet and a core substrate are laminated in a vacuum environment in the first chamber as described above, and then the resin sheet is pressurized in an atmospheric pressure environment in the second chamber. Generally, two-chamber vacuum laminators are designed for fully automated continuous production, and in the second chamber, the resin sheet is often pressed with a smooth plate to smooth the resin composition layer. It was expected that further pressurizing the resin composition in the second chamber would allow the resin composition to further penetrate into the through-holes and prevent the formation of unfilled portions. However, when a two-chamber vacuum laminator was used, voids (air bubbles) were formed in the resin composition.

[0009] For example, the present inventors have attempted to use a vacuum hot press to laminate a resin sheet and a core substrate and fill the through-holes with a resin composition. Generally, vacuum hot pressing involves heating the resin sheet and core substrate in a vacuum environment under high pressure for a long period of time (see Japanese Patent Publication No. 6812091). Because of the high temperature, high pressure, and long duration conditions, vacuum hot pressing generally does not require a high level of vacuum, and it was expected that lamination could be achieved while reducing the cost of decompression. However, when using vacuum hot pressing, voids were found when observing the cured resin composition formed in the through-holes.

[0010] Further investigation by the present inventors revealed that if the resin composition layer of the resin sheet is thickened, the resin composition can be filled into the through-holes using a vacuum laminator. However, when a resin sheet is used, the resin composition typically adheres not only to the through-holes but also to the main surface of the core substrate. If the resin composition layer is thick, a larger amount of resin composition adheres to the main surface of the core substrate. Generally, when a resin composition adheres to the main surface of the core substrate, the cured resin composition is removed by polishing after curing. However, cured resin compositions containing magnetic powder have low polishing properties, which increases the load of the polishing process. Therefore, if there is a large amount of cured material, more time and energy are required for polishing. Therefore, a method that can fill the through-holes with the resin composition even if the resin composition layer is thin is desirable.

[0011] The present invention was devised in consideration of the above-mentioned problems, and aims to provide a method for manufacturing a magnetic substrate that can fill a resin composition into a through hole of a core substrate using a resin sheet while suppressing the formation of voids and unfilled areas. [Means for solving the problem]

[0012] The present inventors have conducted extensive research to solve the above-mentioned problems, and as a result, have found that a method including pressurizing a resin sheet with a rigid plate under specific heating conditions at a specific vacuum level makes it possible to fill through-holes with a resin composition while suppressing the formation of voids and unfilled portions, thereby completing the present invention. That is, the present invention includes the following.

[0013] [1] A manufacturing method for manufacturing a magnetic substrate using a resin sheet including a support and a resin composition layer formed on the support; the resin composition layer comprises a resin composition containing magnetic powder; The manufacturing method comprises: A step (I) of placing a resin sheet on a core substrate having through holes formed therein; (II) pressing the resin sheet with a rigid plate to fill the through-holes with the resin composition; The method for producing a magnetic substrate, wherein the step (II) comprises applying pressure so that the rigid plate contacts the resin sheet under heating conditions of 80°C or higher and 160°C or lower at a vacuum degree of 1.3 kPa or lower. [2] Step (I) includes disposing resin sheets on both sides of a core substrate; The method for producing a magnetic substrate according to [1], wherein step (II) includes pressing resin sheets placed on both sides of the core substrate with rigid plates. [3] The pressure in step (II) is 5 kgf / cm 2 The method for producing a magnetic substrate according to [1] or [2], which is carried out under the above pressure conditions. [4] The method for producing a magnetic substrate according to any one of [1] to [3], comprising, after step (II), step (III) of curing the resin composition. [5] The method for producing a magnetic substrate according to [4], further comprising the step (IV) of polishing the cured resin composition after the step (III). [6] The step (III) includes forming a cured product layer containing a cured product of the resin composition in the through-hole; The method for producing a magnetic substrate according to [4] or [5], wherein the method comprises, after step (III), step (V) of forming a through-hole in the cured material layer in the through-hole. [7] The method for producing a magnetic substrate according to any one of [4] to [6], comprising, after step (III), step (VI) of forming a conductor layer. [8] The method for producing a magnetic substrate according to any one of [1] to [7], wherein the amount of the magnetic powder is 65% by volume or more relative to 100% by volume of the nonvolatile components of the resin composition. [9] The method for producing a magnetic substrate according to any one of [1] to [8], wherein the resin composition layer of the resin sheet has a thickness of 150 μm or less. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a method for manufacturing a magnetic substrate that can fill a through-hole in a core substrate with a resin composition using a resin sheet while suppressing the formation of voids and unfilled portions. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a laminator used in a manufacturing method according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view schematically showing a magnetic substrate obtained by the manufacturing method according to the first embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view schematically showing a magnetic substrate obtained by the manufacturing method according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view schematically showing a magnetic substrate obtained by the manufacturing method according to the first embodiment of the present invention. [Figure 5] FIG. 5 is a cross-sectional view schematically showing a magnetic substrate obtained by the manufacturing method according to the first embodiment of the present invention. [Figure 6] FIG. 6 is a cross-sectional view schematically showing a magnetic substrate obtained by the manufacturing method according to the first embodiment of the present invention. [Figure 7] FIG. 7 is a cross-sectional view schematically showing a laminator used in the production method according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described in detail below with reference to embodiments and examples. However, the present invention is not limited to the following embodiments and examples, and may be modified and implemented as desired within the scope of the claims and their equivalents.

[0017] <Outline of manufacturing method for magnetic substrate> A method for manufacturing a magnetic substrate according to one embodiment of the present invention is a method for manufacturing a magnetic substrate using a resin sheet including a support and a resin composition layer formed on the support. The resin composition layer contains a resin composition containing magnetic powder, and preferably contains only the resin composition. This manufacturing method includes: A step (I) of placing a resin sheet on a core substrate having through holes formed therein; Step (II) of pressing the resin sheet with a rigid plate to fill the through-holes with the resin composition; The through-holes formed in the core substrate may be referred to as "first through-holes" hereinafter. In step (I), a resin sheet is placed on the core substrate so that the core substrate and the resin composition layer are in contact with each other. Then, in step (II), the resin sheet is pressed with a rigid plate, thereby filling the first through-holes with the resin composition contained in the resin composition layer.

[0018] Step (II) of the method for manufacturing a magnetic substrate according to one embodiment of the present invention includes pressurizing the resin sheet with a rigid plate so that the rigid plate contacts the resin sheet in an environment having a specific range of vacuum degree. According to step (II), the resin composition can smoothly enter the first through-holes. Therefore, the resin composition can be filled into the first through-holes without gaps, thereby preventing the formation of unfilled portions in the first through-holes where no resin composition is present. Furthermore, according to step (II), the generation of voids (air bubbles) in the resin composition can be prevented. Therefore, the formation of both voids and unfilled portions can be prevented, achieving excellent filling properties. Therefore, a magnetic substrate can be obtained that includes a core substrate and a resin composition that has adequately filled the core substrate.

[0019] The method for manufacturing a magnetic substrate according to an embodiment of the present invention typically includes the steps of: After step (II), step (III) of curing the resin composition When the resin composition filled in the first through-holes is cured, a magnetic substrate can be obtained that includes a core substrate and a cured product of the resin composition that fills the first through-holes of the core substrate.

[0020] The inventors speculate as follows about the mechanism by which the manufacturing method according to the present embodiment provides the above-described effects, although the technical scope of the present invention is not limited to the mechanism below.

[0021] When a resin sheet is pressurized with an elastic member, as in the method using a vacuum laminator, some of the pressure is consumed by the deformation of the elastic member. Therefore, the pressure applied to the resin composition may be insufficient, preventing a sufficient amount of resin composition from entering the first through-hole. Furthermore, when pressurizing, the elastic member under pressure may deform to block the opening of the first through-hole. If the opening is blocked by the elastic member, no more resin composition can enter the first through-hole, and an unfilled portion may be formed in the first through-hole.

[0022] Furthermore, the vacuum hot press method involves heating for a long period of time under high pressure, which is expected to suppress the formation of unfilled areas. However, by its very nature, vacuum hot presses do not provide a high-level vacuum environment at the expense of cost. Therefore, gas tends to remain in the press, typically resulting in the formation of voids. Furthermore, the formation of voids due to gas in a pressurized environment is similar to the method of pressing a resin sheet with a flat plate using a two-chamber vacuum laminator. The second chamber of a two-chamber vacuum laminator is generally intended to press a resin sheet with a flat plate to achieve smoothness, and since the operator has no incentive to incur the expense of a vacuum environment, the formation of voids could not be suppressed.

[0023] In contrast, in the manufacturing method according to this embodiment, a resin sheet is pressurized with a rigid plate in a vacuum environment with a high level of vacuum. Because the rigid plate does not consume pressure due to elastic deformation, it can apply a sufficiently large pressure to the resin composition, thereby allowing a sufficient amount of resin composition to enter the first through-hole. Furthermore, the rigid plate does not block the opening of the first through-hole due to deformation. Furthermore, in a vacuum environment with a high level of vacuum, residual gas is negligibly small, so the gas can be prevented from remaining in the resin composition and its cured product. Therefore, the formation of voids and unfilled portions can be suppressed, achieving excellent filling properties.

[0024] <Process (I)> A method for producing a magnetic substrate according to one embodiment of the present invention includes the step (I) of placing a resin sheet on a core substrate. The resin sheet is usually placed so that the core substrate and the resin composition layer are in contact with each other.

[0025] The core substrate is a substrate having a first through hole formed therein, and typically includes a support substrate. Examples of the support substrate include insulating substrates such as glass epoxy substrates, metal substrates, polyester substrates, polyimide substrates, BT resin substrates, and thermosetting polyphenylene ether substrates. A conductor layer may be provided on the support substrate. The conductor layer may be provided on one side or both sides of the support substrate. Examples of the conductor layer include a layer formed of a metal such as copper. The conductor layer may be, for example, a copper foil such as a carrier-attached copper foil. The conductor layer may also be a layer made of the same material as the conductor layer described in step (V) below. Furthermore, the conductor layer may be formed on the inner circumferential surface of the first through hole.

[0026] Typically, the first through holes penetrate the core substrate in the thickness direction. Therefore, the first through holes open on both main surfaces (i.e., the front and back surfaces) of the core substrate. The shape of the opening of the first through holes is not particularly limited and may be any shape, such as rectangular, circular, approximately rectangular, or approximately circular. The dimensions of the opening depend on the design of the magnetic substrate. For example, if the opening is rectangular, it is preferably 5 mm × 5 mm or less, more preferably 3 mm × 3 mm or less, or 2 mm × 2 mm or less. If the opening is circular, it is preferably 5 mm or less in diameter, more preferably 3 mm or less, or 2 mm or less. The lower limit of the opening dimensions depends on the design of the magnetic substrate, but for rectangular openings, it may typically be 0.2 mm × 0.2 mm or more, and for circular openings, it may typically be 0.2 mm or more in diameter. When a circuit board is used as the core substrate, the opening is typically formed in an area of ​​the circuit board where no circuit wiring is formed.

[0027] The core substrate can be manufactured, for example, by forming the first through-holes in a core substrate before the first through-holes are formed therein by a processing method such as drilling, laser irradiation, or plasma irradiation, and further forming a conductor layer, if necessary, by a forming method such as plating. Alternatively, the core substrate may be purchased from the market.

[0028] The resin sheet includes a support and a resin composition layer. The support can usually be a film-like or sheet-like member. The resin composition layer is formed on the support. The resin composition layer includes a resin composition containing magnetic powder. In step (II), this resin composition is filled into the first through-holes of the core substrate. Details of the resin sheet will be described later.

[0029] In step (I), a resin sheet is typically placed so that the resin composition layer covers the opening of the first through hole opened in the main surface of the core substrate. The resin sheet may be placed on one side or both sides of the core substrate. From the viewpoint of suppressing warping of the manufactured magnetic substrate, it is preferable to place the resin sheet on both sides of the core substrate. Therefore, step (I) preferably includes placing the resin sheet on both sides of the core substrate. Placing the resin sheet on one side of the core substrate and placing the resin sheet on the other side of the core substrate may be performed simultaneously or sequentially. The thickness of the resin composition layer of the resin sheet placed on one side of the core substrate and the thickness of the resin composition layer of the resin sheet placed on the other side of the core substrate may be different, but from the viewpoint of easily polishing the cured product of the resin composition, it is preferable that they are the same.

[0030] When the resin sheet is placed on the core substrate, the resin sheet may be disposed so as to be in partial contact with the core substrate, or the resin composition layer may be adhered tightly onto the core substrate.

[0031] <Process (II)> A method for manufacturing a magnetic substrate according to one embodiment of the present invention includes, after step (I), step (II) of pressing the resin sheet with a rigid plate to fill the first through-holes with the resin composition. By pressing the resin sheet with the rigid plate, the resin composition contained in the resin composition layer flows and enters the first through-holes in the core substrate, filling the first through-holes.

[0032] The term "rigid plate" refers to a plate material formed from a rigid material. The rigid material may be a material that is rigid enough to fill the first through-holes of the core substrate with a resin composition. The rigid material is preferably a material that does not deform when pressurized, and therefore is preferably a material that does not deform under the pressurizing and heating conditions in step (II), with metal materials being particularly preferred. Examples of metal materials include iron, aluminum, and alloys thereof. Examples of alloys include stainless steel. Among these, stainless steel is preferred due to its excellent rust resistance.

[0033] The rigid plate has a pressure surface that can contact the resin sheet and apply pressure to the resin sheet. This pressure surface is usually a smooth plane. Furthermore, the pressure surface has high rigidity, and therefore usually does not deform even when pressure is applied. In one example, the HV hardness of the pressure surface of the rigid plate is preferably 150 or more, more preferably 200 or more, and even more preferably 300 or more, and preferably 1000 or less, more preferably 700 or less. HV hardness is also called Vickers hardness and can be measured in accordance with JIS Z 2244.

[0034] The thickness of the rigid plate is not limited as long as it can fill the first through-holes of the core substrate with the resin composition. In one example, the thickness of the rigid plate is preferably 0.1 mm or more, more preferably 1 mm or more, and preferably 10 mm or less, more preferably 5 mm or less.

[0035] In step (II), the resin sheet is pressed so that the rigid plate is in contact with the resin sheet. "The rigid plate is in contact with the resin sheet" means that there is no layer, such as a rubber film, between the rigid plate and the resin sheet. Typically, the pressing surface of the rigid plate is in contact with the resin sheet, and the pressing surface presses the resin sheet to achieve pressurization. The absence of any layer between the rigid plate and the resin sheet allows a large pressure to be applied to the entire resin sheet. Therefore, not only the resin composition on the opening of the first through-hole but also the resin composition around the opening can be forced into the first through-hole with a large pressure, allowing the first through-hole to be filled smoothly.

[0036] The resin sheet is pressurized in step (II) at a vacuum level within a specific range. Typically, in step (II), the resin sheet is pressurized in a closed space having a vacuum level within a specific range. Therefore, the resin sheet can be pressurized in an environment within the closed space having a vacuum level within a specific range. The vacuum level range is typically 1.3 kPa or less, preferably 1.0 kPa or less, more preferably 0.5 kPa or less, and particularly preferably 0.2 kPa or less. The lower limit is ideally 0 kPa or more, but is typically above 0.01 kPa. By pressurizing the resin sheet at such a high level of vacuum, the formation of voids can be suppressed.

[0037] The resin sheet is pressed under specific heating conditions in step (II). Typically, the temperature of the rigid plate is adjusted to a specific temperature, thereby controlling the temperature of the resin sheet in contact with the rigid plate to a specific temperature. The temperature range of the heating conditions is typically 80°C or higher, preferably 85°C or higher, more preferably 90°C or higher, and preferably 160°C or lower, more preferably 155°C or lower, and particularly preferably 150°C or lower. When pressurization is performed under such heating conditions, the fluidity of the resin composition contained in the resin composition layer is increased, allowing the resin composition to smoothly enter the first through-holes.

[0038] In step (II), the pressure conditions applied by the rigid plate to the resin sheet are not limited as long as the resin composition can be filled into the first through-holes. From the viewpoint of particularly smoothly filling the first through-holes with the resin composition, the pressure conditions are preferably 5 kgf / cm. 2 More than 7kgf / cm 2 More than 10 kgf / cm, particularly preferably 10 kgf / cm 2 Generally, resin compositions containing magnetic powder tend to have low fluidity, so it is preferable to apply pressure under high pressure conditions as described above. The upper limit of the pressure conditions is, for example, 100 kgf / cm. 2 Below 70kgf / cm 2 Below, 50kgf / cm 2 It could be the following, etc.

[0039] In step (II), the time for which the rigid plate presses the resin sheet is not limited as long as the resin composition can be filled into the first through-holes. The specific pressurization time varies depending on the composition of the resin composition and the size of the first through-holes, but is preferably 10 seconds or more, more preferably 20 seconds or more, and particularly preferably 30 seconds or more, and is preferably 30 minutes or less, more preferably 20 minutes or less, and particularly preferably 10 minutes or less.

[0040] When step (I) includes disposing resin sheets on both sides of the core substrate, step (II) includes pressurizing at least one of the resin sheets. From the viewpoint of more reliably suppressing the formation of unfilled portions, step (II) preferably includes pressurizing both resin sheets disposed on both sides of the core substrate with rigid plates.

[0041] Step (II) allows the first through-holes of the core substrate to be filled with the resin composition. At this time, the formation of unfilled portions, which are voids where no resin composition is present in the first through-holes, can be suppressed. Furthermore, the formation of voids within the resin composition in the first through-holes can be suppressed. Thus, step (II) allows the first through-holes to be filled with the resin composition with excellent filling properties.

[0042] Typically, a portion of the resin composition contained in the resin composition layer fills the first through-holes, and therefore another portion of the resin composition contained in the resin composition layer does not enter the first through-holes and can adhere to the main surface of the core substrate to form a layer.

[0043] Usually, the support of the resin sheet is peeled off after the step (II), which may be carried out before or after the step (III) described below.

[0044] <Process (III)> The method for producing a magnetic substrate according to one embodiment of the present invention may include, after step (II), step (III) of curing the resin composition. By curing the resin composition, a cured product of the resin composition can be formed. Thus, a magnetic substrate including the cured product of the resin composition can be obtained.

[0045] The resin composition is usually cured by thermal curing. The thermal curing conditions for the resin composition can be appropriately set within a range in which the curing of the resin composition layer proceeds. The curing temperature is preferably 60°C or higher, more preferably 70°C or higher, and even more preferably 80°C or higher, and preferably 245°C or lower, more preferably 220°C or lower, and even more preferably 200°C or lower. The curing time is preferably 5 minutes or longer, more preferably 10 minutes or longer, and even more preferably 15 minutes or longer, and preferably 120 minutes or shorter, more preferably 110 minutes or shorter, and even more preferably 100 minutes or shorter.

[0046] The degree of cure of the cured product obtained in step (III) is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The degree of cure can be measured, for example, using a differential scanning calorimeter.

[0047] Typically, the cured product of the resin composition forms a cured product layer in the first through-hole. Therefore, step (III) typically includes forming a cured product layer in the first through-hole. In the following description, the cured product layer formed in the first through-hole may be referred to as a "filled cured product layer." Furthermore, the cured product of the resin composition typically also forms a cured product layer on the main surface of the core substrate. Therefore, step (III) typically includes forming a cured product layer on the main surface of the core substrate. The cured product layer formed on the main surface of the core substrate may be referred to as an "adhered cured product layer." Cured product layers such as a filled cured product layer and an attached cured product layer are layers containing a cured product of the resin composition, and preferably contain only a cured product of the resin composition.

[0048] In the manufacturing method according to this embodiment, a resin sheet having a thin resin composition layer can be used, and therefore the deposited cured material layer can be thin. In one example, the thickness of the deposited cured material layer before step (IV) described below can be preferably 100 μm or less, more preferably 80 μm or less, and particularly preferably 60 μm or less.

[0049] <Process (IV)> A method for manufacturing a magnetic substrate according to one embodiment of the present invention may include, after step (III), step (IV) of polishing the cured product as the cured resin composition. Typically, the deposited cured product layer outside the first through-hole is an unnecessary excess portion of the product, and is therefore preferably removed. Therefore, in step (IV), it is preferable to remove the deposited cured product layer by polishing. Furthermore, in step (IV), a portion of the filled cured product layer in the first through-hole may be polished simultaneously with the deposited cured product layer on the main surface of the core substrate, and a portion of the core substrate may also be polished.

[0050] Examples of the polishing method include buff polishing, belt polishing, ceramic polishing, etc. Examples of commercially available buff polishing devices include "NT-700IM" manufactured by Ishii Hyoki Co., Ltd.

[0051] Typically, a flat polished surface can be formed on the surface of the filled cured layer by polishing. The arithmetic mean roughness (Ra) of this polished surface is preferably 100 nm or more, more preferably 150 nm or more, even more preferably 200 nm or more, from the viewpoint of forming a conductive layer with high adhesion on the polished surface, and is preferably 1000 nm or less, more preferably 900 nm or less, even more preferably 800 nm or less. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0052] Typically, the polished surface of the filled and cured material layer formed by polishing is flush with the main surface of the core substrate. Here, "flush" between one surface and another surface means that the surfaces form a single plane. Therefore, the main surface of the core substrate and the polished surface of the filled and cured material layer can form a smooth plane. A conductor layer may be formed on this smooth plane in step (VI).

[0053] <Process (V)> A method for manufacturing a magnetic substrate according to one embodiment of the present invention may include, after step (III), step (V) of forming a through-hole in the filled cured material layer within the first through-hole. When the method for manufacturing a magnetic substrate includes step (IV), step (V) is usually performed after step (IV). The through-hole formed in the filled cured material layer may be referred to as a "second through-hole" hereinafter. The second through-hole can be formed by a known method using, for example, a drill, a laser, plasma, an etching medium, or the like, taking into consideration the characteristics of the cured material and the dimensions of the first through-hole. The shape of the opening of the second through-hole may be the same as the shape of the opening of the first through-hole. The dimensions of the opening of the second through-hole are not particularly limited as long as they are smaller than the dimensions of the opening of the first through-hole.

[0054] <Process (VI)> A method for producing a magnetic substrate according to one embodiment of the present invention may include a step (VI) of forming a conductive layer after the step (III). When the method for producing a magnetic substrate includes the step (IV), the step (VI) is usually carried out after the step (IV). When the method for producing a magnetic substrate includes the step (V), the step (VI) may be carried out after the step (V) to form a conductive layer on the wall surface of the second through-hole.

[0055] The conductor layer is usually formed on the cured material layer. When the adhered cured material layer is removed in step (IV), the conductor layer is preferably formed on the filled cured material layer. The conductor layer may also be formed on the core substrate. In one example, the conductor layer is formed on the polished surface of the filled cured material layer and the main surface of the core substrate. The conductor layer may be formed on one side or both sides of the magnetic substrate. The conductor layer may also be formed on the wall surface of the second through-hole formed in step (V).

[0056] The conductor layer can be formed from a conductor. Examples of conductors include single metals such as gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium; and alloys of two or more metals selected from the group consisting of gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium. Among these, from the viewpoints of versatility, cost, ease of patterning, and the like, it is preferable to use chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or a nickel-chromium alloy, a copper-nickel alloy, or a copper-titanium alloy, and it is more preferable to use chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or a nickel-chromium alloy, and it is even more preferable to use copper.

[0057] The thickness of the conductor layer is preferably 1 μm or more, more preferably 3 μm or more, even more preferably 5 μm or more, and is preferably 70 μm or less, more preferably 50 μm or less, even more preferably 40 μm or less, particularly preferably 30 μm or less.

[0058] The conductor layer can be formed by a formation method such as plating, sputtering, or vapor deposition. Among these, plating is preferred. A patterned conductor layer having a desired planar shape may be obtained by removing a portion of the formed conductor layer by a removal process such as etching. The planar shape refers to the shape as viewed in the thickness direction, unless otherwise specified. In a preferred embodiment, a patterned conductor layer having a desired wiring pattern may be formed by plating using an appropriate method such as a semi-additive method or a full-additive method. When removing a portion of the conductor layer by a removal method such as etching, a portion of the conductor layer provided on the core substrate may also be removed. For example, a coil-shaped wiring may be formed by the conductor layer formed on the cured material layer and the core substrate, and the conductor layer provided inside the core substrate, to obtain an inductor element within the magnetic substrate.

[0059] Here, an example of a method for forming a patterned conductor layer will be described in detail. A plating seed layer is formed on a cured product layer by electroless plating. Next, a mask pattern is formed on the formed plating seed layer as needed, and then an electroplated layer is formed by electroplating. Thereafter, the mask pattern is removed as needed, and unnecessary plating seed layer is further removed by etching or other treatment, thereby forming a patterned conductor layer having a desired wiring pattern. After forming the patterned conductor layer, an annealing treatment may be performed as needed to improve the adhesion strength of the patterned conductor layer. The annealing treatment can be performed, for example, by heating at 150°C to 200°C for 20 to 90 minutes.

[0060] <Advantages of the manufacturing method for magnetic substrates> The above-described manufacturing method can provide a magnetic substrate having a cured material layer formed of a cured material of a resin composition containing magnetic powder. In the magnetic substrate obtained by the manufacturing method, the formation of unfilled portions as gaps without cured material and voids as air bubbles in the cured material can be suppressed in the first through-holes of the core substrate.

[0061] Furthermore, in the above-described manufacturing method, not only the resin composition on the opening of the first through-hole but also the resin composition around the opening can be filled into the first through-hole, so that even when a resin sheet including a thin resin composition layer is used, the first through-hole can be filled with the resin composition.

[0062] Furthermore, when the resin composition layer is thin as described above, the thickness of the adhered cured material layer formed on the main surface of the core substrate can be reduced, thereby shortening the time required to remove the adhered cured material layer by polishing, thereby shortening the manufacturing time of the magnetic substrate.

[0063] The magnetic substrate thus produced can be used to produce an inductor component including the magnetic substrate. For example, by forming a coil-shaped wiring using a conductor layer around at least a portion of the filled and cured material layer, an inductor component having an inductor pattern including the wiring can be obtained. For example, the inductor component described in JP 2016-197624 A can be used.

[0064] The magnetic substrate can be used as a wiring board for mounting electronic components such as semiconductor chips, and can also be used as a (multilayer) printed wiring board using such a wiring board as an inner layer substrate. Furthermore, such a wiring board can be used as an individual chip inductor component, or as a surface-mounted printed wiring board. Furthermore, various types of semiconductor devices can be manufactured using such a wiring board. Semiconductor devices including such wiring boards can be suitably used in electrical appliances (e.g., computers, mobile phones, digital cameras, televisions, etc.) and vehicles (e.g., motorcycles, automobiles, trains, ships, aircraft, etc.).

[0065] <Optional step (VII)> The method for producing a magnetic substrate according to one embodiment of the present invention may further include any step in combination with the steps described above. For example, the method for producing a magnetic substrate may include a step (VII) of pressing the resin sheet with an elastic member between steps (I) and (II).

[0066] For example, a two-chamber laminator may have a first chamber equipped with an elastic member capable of applying pressure to a resin sheet and a second chamber equipped with a rigid plate capable of applying pressure to the resin sheet. Examples of such two-chamber laminators include the rubber press type "CVP-700" manufactured by Nikko Materials Co., Ltd. and the diaphragm type laminator "MVLP-500 / 600IIB" manufactured by Meiki Seisakusho. When using such a two-chamber laminator, the pressurization in the above-mentioned step (II) may be carried out in the second chamber. In this case, step (VII) of applying pressure to the resin sheet with an elastic member in the first chamber may be carried out before step (II).

[0067] In step (VII), the resin sheet is pressed by an elastic member to fill the first through-holes of the core substrate with the resin composition contained in the resin composition layer. However, since further pressurization is performed in step (II) after step (VII), the resin composition does not necessarily have to fill the entire first through-holes depending on step (VII).

[0068] The elastic member is usually a rubber plate or sheet. Alternatively, an elastic member may be provided on a rigid plate and the resin sheet may be pressed by the elastic member. The resin sheet is pressed in step (VII) so that the elastic member is in contact with the resin sheet. "The elastic member is in contact with the resin sheet" means that there is no layer between the elastic member and the resin sheet.

[0069] The resin sheet is preferably pressed in step (VII) at a vacuum degree within the specific range described in step (II). When the resin sheet is pressed at such a high level of vacuum, the formation of voids can be effectively suppressed.

[0070] The resin sheet is preferably pressed in step (VII) under the specific heating conditions described in step (II). When the resin sheet is pressed under such heating conditions, the resin composition can be allowed to penetrate particularly smoothly into the first through-holes.

[0071] The resin sheet may be pressed in step (VII) under the pressure conditions described in step (II). The resin sheet may be pressed in step (VII) for the time period described in step (II). Furthermore, when step (I) includes disposing resin sheets on both sides of the core substrate, step (VII) may include pressing both resin sheets placed on both sides of the core substrate with an elastic member.

[0072] <Optional step (VIII)> The method for producing a magnetic substrate according to one embodiment of the present invention may optionally include, between steps (II) and (III), step (VIII) of heating the resin composition layer at a temperature lower than the curing temperature. The heating in step (VIII) may be referred to as "preheating" hereinafter. For example, prior to curing the resin composition layer in step (III), the resin composition layer may be preheated at a temperature of typically 50°C or higher but lower than 120°C (preferably 60°C or higher but 110°C or lower, more preferably 70°C or higher but 100°C or lower) for typically 5 minutes or longer (preferably 5 to 150 minutes, more preferably 15 to 120 minutes).

[0073] <Process (IX)> The method for producing a magnetic substrate according to one embodiment of the present invention may optionally include a step (IX) between steps (III) and (IV) in which the cured material layer is subjected to a heat treatment to further increase the degree of curing of the cured material layer. The temperature in the heat treatment may be the same as the curing temperature of the resin composition described above. Specific heat treatment temperatures are preferably 120°C or higher, more preferably 130°C or higher, and even more preferably 150°C or higher, and preferably 245°C or lower, more preferably 220°C or lower, and even more preferably 200°C or lower. The heat treatment time is preferably 5 minutes or longer, more preferably 10 minutes or longer, and even more preferably 15 minutes or longer, and preferably 150 minutes or shorter, more preferably 120 minutes or shorter, and even more preferably 100 minutes or shorter.

[0074] <Process (X)> The method for producing a magnetic substrate according to one embodiment of the present invention may optionally include step (X) of roughening the surface of the cured material layer after step (III). Step (X) is usually performed after step (IV). Step (X) is usually performed before step (VI). In step (X), roughening may be performed not only on the surface of the cured material layer but also on the main surface of the core substrate. The roughening treatment can increase the surface roughness of the treated surface, thereby increasing the adhesion strength of the conductor layer formed on the treated surface.

[0075] The procedure and conditions for the roughening treatment are not particularly limited, and may be, for example, the procedure and conditions used in the manufacturing method of a multilayer printed wiring board. As a specific example, the roughening treatment may be performed by a method including, in this order, a swelling treatment with a swelling liquid, a roughening treatment with an oxidizing agent, and a neutralization treatment with a neutralizing liquid.

[0076] Examples of swelling liquids used in the swell treatment include alkaline solutions and surfactant solutions, with alkaline solutions being preferred. Sodium hydroxide solution and potassium hydroxide solution are more preferred as alkaline solutions used as swelling liquids. Examples of commercially available swelling liquids include "Swelling Dip Securigans P" and "Swelling Dip Securigans SBU" manufactured by Atotech Japan. Swelling treatment using a swelling liquid can be performed, for example, by immersing the cured material layer in the swelling liquid at 30°C to 90°C for 1 to 20 minutes. From the viewpoint of suppressing swelling of the resin contained in the cured material layer to an appropriate level, it is preferable to immerse the cured material layer in the swelling liquid at 40°C to 80°C for 5 to 15 minutes.

[0077] Examples of oxidizing agents used in the roughening treatment include alkaline permanganate solutions prepared by dissolving potassium permanganate or sodium permanganate in an aqueous solution of sodium hydroxide. Roughening treatment using an oxidizing agent such as alkaline permanganate solution is preferably carried out by immersing the cured material layer in a solution of the oxidizing agent heated to 60°C to 80°C for 10 to 30 minutes. The concentration of permanganate in the alkaline permanganate solution is preferably 5% to 10% by mass. Commercially available oxidizing agents include alkaline permanganate solutions such as "Concentrate Compact P" and "Dosing Solution Securigance P" manufactured by Atotech Japan.

[0078] The neutralizing solution used in the neutralization treatment is preferably an acidic aqueous solution. An example of a commercially available neutralizing solution is "Reduction Solution Securigance P" manufactured by Atotech Japan. Neutralization treatment with a neutralizing solution can be performed by immersing the surface roughened with an oxidizing solution in the neutralizing solution at 30°C to 80°C for 5 to 30 minutes. From the standpoint of workability, etc., a preferred method is to immerse the cured material layer roughened with an oxidizing solution in the neutralizing solution at 40°C to 70°C for 5 to 20 minutes.

[0079] The arithmetic mean roughness (Ra) of the surface of the cured layer after the roughening treatment is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more, from the viewpoint of improving adhesion with the conductor layer. The upper limit is preferably 1500 nm or less, more preferably 1200 nm or less, and even more preferably 1000 nm or less. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0080] <First specific example of manufacturing method> A first specific example of the method for manufacturing the magnetic substrate described above will now be described with reference to the drawings. Fig. 1 is a cross-sectional view schematically showing a laminator 1 used in a manufacturing method according to a first embodiment of the present invention. As shown in Fig. 1, the first embodiment describes a manufacturing method using a core substrate 10 having a first through-hole 11 formed therein, a resin sheet 20 having a support 21 and a resin composition layer 22, and a resin sheet 30 having a support 31 and a resin composition layer 32. Core substrate 10 may include a conductor layer (not shown) on its surface and inside.

[0081] 1, a laminator 1 serving as a manufacturing apparatus used in a manufacturing method according to a first embodiment of the present invention includes a stage 100 for filling a resin composition into first through-holes 11 in a core substrate 10. The stage 100 includes a lower press member 110 serving as a first press member, an upper press member 120 serving as a second press member disposed opposite the lower press member 110, and a hydraulic cylinder 130 serving as a drive device. The hydraulic cylinder 130 includes a retractable piston rod 131 that can be extended and retracted by hydraulic pressure.

[0082] The lower press member 110 includes a lower support member 111 , a lower plate 112 as a rigid plate, and a lower frame member 113 .

[0083] The lower support member 111 is provided so as to be able to move back and forth relative to the upper press member 120. The lower support member 111 has a support surface 111U facing the upper press member 120. The lower support member 111 is also connected to a hydraulic cylinder 130 so that the lower plate 112 can apply pressure to the core substrate 10, resin sheet 20, and resin sheet 30 provided between the lower press member 110 and the upper press member 120. Here, an example will be described in which, when the piston rod 131 of the hydraulic cylinder 130 extends, the lower support member 111 rises to approach the upper press member 120, and when the piston rod 131 contracts, the lower support member 111 descends to move away from the upper press member 120.

[0084] The lower plate 112 is a flat plate provided on the support surface 111U of the lower support member 111. The lower plate 112 is formed from a rigid material. The lower plate 112 also has a pressure surface 112U as a flat surface facing the upper press member 120. A heater 114 is provided within the lower plate 112 so that the lower plate 112 can be heated. The lower plate 112 may be provided so as to be in contact with the support surface 111U of the lower support member 111, or may be provided via any member. Here, an example will be described in which the lower plate 112 is provided on the support surface 111U via a heat insulating material and a buffer material (not shown).

[0085] The lower frame member 113 is airtightly mounted on the support surface 111U of the lower support member 111 so as to surround the lower plate 112. This lower frame member 113 is arranged so that, when joined to an upper frame member 123 provided on the upper press member 120, it can form a vacuum frame together with the upper frame member 123. Here, an example will be described in which the lower frame member 113 includes a fixed frame portion 115 airtightly fixed to the support surface 111U, a movable frame portion 116 provided slidably relative to the fixed frame portion 115, and an elastic support portion 117 such as a spring that supports the movable frame portion 116 so as to push it up toward the upper press member 120. The space between the fixed frame portion 115 and the movable frame portion 116 is sealed with a sealing material (not shown), so the movable frame portion 116 is provided slidably while maintaining an airtight state.

[0086] The upper press member 120 includes an upper support member 121 , an upper plate 122 as a rigid plate, and an upper frame member 123 .

[0087] The upper support member 121 is provided so as to be movable back and forth relative to the lower press member 110. The upper support member 121 has a support surface 121D facing the lower press member 110. Here, an example will be described in which the lower press member 110 is provided so as to be movable by driving the hydraulic cylinder 130 as described above, and the upper press member 120 is provided so as to be fixed in position. In this example, the movement of the lower press member 110 causes the upper press member 120 to move relative to the lower press member 110, allowing the upper plate 122 to apply pressure to the core substrate 10, resin sheet 20, and resin sheet 30 provided between the lower press member 110 and the upper press member 120.

[0088] The upper plate 122 is a flat plate provided on the support surface 121D of the upper support member 121. The upper plate 122 is formed from a rigid material. The upper plate 122 also has a pressure surface 122D as a flat surface facing the lower press member 110. A heater 124 is provided within the upper plate 122 so that the upper plate 122 can be heated. The upper plate 122 may be provided so as to be in contact with the support surface 121D of the upper support member 121, or may be provided via any member. Here, an example will be described in which the upper plate 122 is provided on the support surface 121D via a heat insulating material and a buffer material (not shown).

[0089] The upper frame member 123 is airtightly provided on the support surface 121D of the upper support member 121 so as to surround the upper plate 122. This upper frame member 123 is provided so that when joined to the lower frame member 113 provided in the lower press member 110, it can form a vacuum frame together with the lower frame member 113. In addition, the upper frame member 123 is provided with a nozzle 125, and this nozzle 125 is connected to a pressure adjustment device (not shown) such as a vacuum pump.

[0090] When the manufacturing method according to the first specific example is carried out using the laminator 1, a magnetic substrate can be manufactured by the following method. Here, an example will be described in which a resin sheet 20 is placed on one side of a core substrate 10 and a resin sheet 30 is placed on the other side of the core substrate 10.

[0091] In the manufacturing method according to the first specific example, the core substrate 10, the resin sheet 20, and the resin sheet 30 are supplied between the lower pressed member 110 and the upper pressed member 120 of the stage 100. For example, the long resin sheets 20 and 30 are transported through a transport path between the lower pressed member 110 and the upper pressed member 120. At this time, the core substrate 10 may be placed on the lower resin sheet 20 and transported, thereby supplying the core substrate 10 between the lower pressed member 110 and the upper pressed member 120.

[0092] Thereafter, the hydraulic cylinder 130 is driven to extend the piston rod 131. As the piston rod 131 extends, the lower press member 110 rises and approaches the upper press member 120. As the lower press member 110 rises, the upper frame member 123 comes into contact with the movable frame portion 116 of the lower frame member 113 and pushes the movable frame portion 116. This closes the gap between the lower frame member 113 and the upper frame member 123, forming a closed space surrounded by the lower support member 111, the upper support member 121, the lower frame member 113, and the upper frame member 123. A pressure regulator (not shown) then depressurizes the closed space through a nozzle 125. As a result of the depressurization, the environment within the closed space becomes a vacuum state with a specific range of vacuum level.

[0093] Furthermore, as the lower press member 110 rises, the pressure surface 112U of the lower plate 112 eventually comes into contact with the resin sheet 20 and pushes up the resin sheet 20. Furthermore, the pressure surface 122D of the upper plate 122 comes into contact with the resin sheet 30 and pushes down the resin sheet 30. Thus, the resin composition layer 22 of the resin sheet 20 contacts one side of the core substrate 10, and the resin composition layer 32 of the resin sheet 30 contacts the other side of the core substrate 10, so that the resin sheets 20 and 30 are arranged on both sides of the core substrate 10 (step (I)).

[0094] After the resin sheets 20 and 30 are placed on both sides of the core substrate 10, the resin composition is filled into the first through-holes 11 (step (II)). Here, an example will be described in which the resin sheet 20 is pressed with the lower plate 112 to fill the first through-holes 11 with the resin composition contained in the resin composition layer 22, and the resin sheet 30 is pressed with the upper plate 122 to fill the first through-holes 11 with the resin composition contained in the resin composition layer 32.

[0095] Specifically, the process is as follows. After the closed space containing the core substrate 10, resin sheet 20, and resin sheet 30 is evacuated, the hydraulic cylinder 130 further elevates the lower press member 110. As the lower press member 110 elevates, the lower plate 112 in contact with the resin sheet 20 presses the resin sheet 20, filling the first through-holes 11 with the resin composition of the resin composition layer 22. Furthermore, the upper plate 122 in contact with the resin sheet 30 presses the resin sheet 30, filling the first through-holes 11 with the resin composition of the resin composition layer 32. At this time, the heaters 114 and 124 adjust the temperatures of the lower plate 112 and the upper plate 122 to control the temperature conditions of the pressurization within the specific range described above. This pressurization fills the first through-holes 11 with the resin composition. When the conditions described in the above-described embodiment are adopted, the formation of voids and unfilled portions can be suppressed, thereby achieving excellent fillability.

[0096] After the resin composition has been filled into the first through-holes 11, the vacuum state in the closed space is released through the nozzle 125, and the piston rod 131 is retracted to lower the lower press member 110. Thereafter, the core substrate 10 filled with the resin composition is subjected to the next process.

[0097] Usually, the resin composition is cured after filling the first through-holes 11 with the resin composition (step (III)). For example, the resin composition is thermally cured to obtain a cured product.

[0098] Furthermore, the method for manufacturing a magnetic substrate may include a step of peeling off supports 21 and 31 after filling first through-hole 11 with the resin composition. Supports 21 and 31 may be peeled off before or after the resin composition is cured.

[0099] Fig. 2 is a cross-sectional view schematically showing a magnetic substrate 40 obtained by a manufacturing method according to a first embodiment of the present invention. As shown in Fig. 2, by curing the resin composition, magnetic substrate 40 is obtained, which includes core substrate 10 and a cured product of the resin composition filled in first through-holes 11 of core substrate 10. Magnetic substrate 40 includes filled cured product layer 41 as a layer of the cured product formed in first through-holes 11. Furthermore, in the manufacturing method using resin sheets 20 and 30 as described above, the resin composition can be adhered to main surfaces 10D and 10U of core substrate 10, so that magnetic substrate 40 can include adhered cured product layers 42 and 43 on main surfaces 10D and 10U of core substrate 10.

[0100] In many cases, the adhered cured material layers 42 and 43 are unnecessary for the final product. Therefore, the method for producing a magnetic substrate may include polishing the cured product as the cured resin composition after the resin composition is cured (step (IV)). Preferably, the adhered cured material layers 42 and 43 are removed by polishing.

[0101] Fig. 3 is a cross-sectional view schematically illustrating a magnetic substrate 40 obtained by a manufacturing method according to a first embodiment of the present invention. As shown in Fig. 3, the adhered cured material layers 42 and 43 are removed by polishing to obtain a magnetic substrate 40 including a core substrate 10 and a filled cured material layer 41. After polishing, a surface 41D of the filled cured material layer 41 is usually flush with the main surface 10D of the core substrate 10. Furthermore, after polishing, a surface 41U of the filled cured material layer 41 is usually flush with the main surface 10U of the core substrate 10.

[0102] 4 is a cross-sectional view schematically showing a magnetic substrate 40 obtained by the manufacturing method according to the first embodiment of the present invention. In the manufacturing method of the magnetic substrate, after the resin composition has cured, second through-holes 44 may be formed in the filled cured material layer 41 in the first through-holes 11 as shown in FIG. 4 (step (V)).

[0103] 5 and 6 are cross-sectional views schematically illustrating a magnetic substrate 40 obtained by a manufacturing method according to a first embodiment of the present invention. The manufacturing method for a magnetic substrate may include forming conductor layers 51-53 after curing the resin composition, as shown in FIG. 5 (step (VI)). FIG. 5 illustrates an example in which conductor layer 51 is formed on surface 41D of filled and cured layer 41 and main surface 10D of core substrate 10, conductor layer 52 is formed on surface 41U of filled and cured layer 41 and main surface 10U of core substrate 10, and conductor layer 53 is formed in second through-hole 44. However, there are no limitations on the positions at which conductor layers 51-53 are formed. Therefore, conductor layers 51-53 may be formed on surfaces 41D and 41U of filled and cured layer 41, on main surfaces 10D and 10U of core substrate 10, in second through-hole 44, or in some or all of these. Furthermore, the manufacturing method of the magnetic substrate may involve patterning the conductor layers 51-53 by etching or other processing methods, as shown in Fig. 6. By forming and processing the conductor layers 51-53, it is possible to obtain a magnetic substrate 40 having conductor layers 51-53 with a desired pattern shape. When the conductor layers 51-53 form a coil-shaped inductor pattern, it is possible to obtain an inductor component in which the filled and cured layer 41 can function as a core portion of the magnetic substrate 40. Furthermore, the conductor layers 51-53 may be combined with a conductor layer (not shown) provided in the core substrate 10 to form an inductor pattern.

[0104] <Second specific example of the manufacturing method> The method for manufacturing the magnetic substrate described above may include a step (VII) of pressing the resin sheet with an elastic member before the step (II) of pressing the resin sheet with a rigid plate to fill the first through-holes with the resin composition. A second specific example of the manufacturing method including this step (VII) will be described below.

[0105] 7 is a cross-sectional view schematically illustrating a laminator 2 used in a manufacturing method according to a second embodiment of the present invention. As shown in FIG. 7, the laminator 2 used as a manufacturing apparatus in the manufacturing method according to the second embodiment of the present invention is configured similarly to the laminator 1 used in the manufacturing method according to the first embodiment, except that it includes a stage 200 combined with a stage 100. In the following description, for the sake of distinction, the stage 100 may be referred to as the "heat press stage" 100, and the stage 200 may be referred to as the "compression stage" 200. The heat press stage 100 is as described in the first embodiment.

[0106] In the compression stage 200, an elastic member 215 such as a rubber sheet is provided on a pressure surface 212U of the lower plate 212 so that the resin sheet 20 can be pressed by the elastic member 215. In addition, in the compression stage 200, an elastic member 225 is provided on a pressure surface 222D of the upper plate 222 so that the resin sheet 30 can be pressed by the elastic member 225. Except for the provision of the elastic members 215 and 225 in this manner, the compression stage 200 is provided in the same manner as the heat press stage 100.

[0107] Therefore, the crimping stage 200 includes a lower press member 210 as a third press member, an upper press member 220 as a fourth press member provided opposite the lower press member 210, and a hydraulic cylinder 230 as a drive device. The hydraulic cylinder 230 is provided in the same manner as the hydraulic cylinder 130 of the heat press stage 100, and includes a piston rod 231 similar to the piston rod 131.

[0108] The lower pressing member 210 includes a lower support member 211, a lower plate 212, a lower frame member 213, and an elastic member 215 provided on a pressing surface 212U of the lower plate 212. The lower support member 211, the lower plate 212, and the lower frame member 213 are provided in the same manner as the lower support member 111, the lower plate 112, and the lower frame member 113. Therefore, the lower support member 211 is provided so as to be able to move back and forth relative to the upper pressing member 220, and has a support surface 211U facing the upper pressing member 220. The lower plate 212 also has a pressing surface 212U facing the upper pressing member 220, and is further provided with a heater 214 so as to be able to adjust the pressing temperature. Furthermore, the lower frame member 213 is provided with a fixed frame portion 215, a movable frame portion 216, and an elastic support portion 217 that are provided similarly to the fixed frame portion 115, the movable frame portion 116, and the elastic support portion 117 so that when joined to the upper frame member 223 provided on the upper press member 220, the lower frame member 213 can form a vacuum frame together with the upper frame member 223. An elastic member 215 such as a rubber sheet is provided on the pressure surface 212U of the lower plate 212.

[0109] The upper press member 220 includes an upper support member 221, an upper plate 222, an upper frame member 223, and an elastic member 225 attached to the pressing surface 222D of the upper plate 222. The upper support member 221, the upper plate 222, and the upper frame member 223 are provided in the same manner as the upper support member 121, the upper plate 122, and the upper portion 123. The upper support member 221 is provided so as to be movable back and forth relative to the lower press member 210 and has a support surface 221D facing the lower press member 210. The upper plate 222 has a pressing surface 222D facing the lower press member 210 and is further provided with a heater 224 to adjust the pressing temperature. The upper frame member 223 is provided with a nozzle 225, which is connected to a pressure adjustment device (not shown) such as a vacuum pump. The pressing surface 222D of the upper plate 222 is provided with an elastic member 225 such as a rubber sheet.

[0110] When the manufacturing method according to the second specific example is carried out using the laminator 2, a magnetic substrate can be manufactured by the following method. Here, as in the first specific example, an example will be described in which a resin sheet 20 is placed on one side of a core substrate 10 and a resin sheet 30 is placed on the other side of the core substrate 10.

[0111] In the manufacturing method according to the second specific example, the core substrate 10, the resin sheet 20, and the resin sheet 30 are supplied between the lower press member 210 and the upper press member 220 of the compression bonding stage 200. Then, the hydraulic cylinder 230 is driven to extend the piston rod 231, thereby lifting the lower press member 210 and bringing it closer to the upper press member 220. When the lower press member 210 is lifted, the gap between the lower frame member 213 and the upper frame member 223 closes, similar to the gap between the lower frame member 113 and the upper frame member 123 in the first specific example. This closes a closed space surrounded by the lower support member 211, the upper support member 221, the lower frame member 213, and the upper frame member 223. A pressure regulator (not shown) then depressurizes the closed space through a nozzle 225. The reduced pressure creates a vacuum within the closed space.

[0112] Furthermore, as the lower press member 210 rises, the elastic member 215 on the lower plate 212 eventually comes into contact with the resin sheet 20 and pushes up the resin sheet 20. Furthermore, the elastic member 225 on the upper plate 222 comes into contact with the resin sheet 30 and pushes down the resin sheet 30. Thus, the resin composition layer 22 of the resin sheet 20 contacts one side of the core substrate 10, and the resin composition layer 32 of the resin sheet 30 contacts the other side of the core substrate 10, so that the resin sheets 20 and 30 are arranged on both sides of the core substrate 10 (step (I)).

[0113] In the method for manufacturing a magnetic substrate according to the second specific example, after placing resin sheets 20 and 30 on both sides of core substrate 10, resin sheets 20 and 30 are pressed with elastic members 215 and 225 (step (VII)). That is, resin sheet 20 is pressed with elastic member 215 on lower plate 212, and resin sheet 30 is pressed with elastic member 225 on upper plate 222.

[0114] Specifically, the process is as follows. After the closed space containing the core substrate 10, resin sheet 20, and resin sheet 30 is evacuated, the hydraulic cylinder 230 further elevates the lower press member 210. As the lower press member 210 elevates, the elastic member 215 in contact with the resin sheet 20 presses the resin sheet 20, filling the first through-holes 11 with the resin composition of the resin composition layer 22. Furthermore, the elastic member 225 in contact with the resin sheet 30 presses the resin sheet 30, filling the first through-holes 11 with the resin composition of the resin composition layer 32. At this time, the temperature conditions of the pressurization are controlled by the heaters 214 and 224. As a result of this pressurization, the first through-holes 11 are filled with the resin composition. However, at this point, the first through-holes 11 do not necessarily have to be entirely filled with the resin composition; an unfilled portion (not shown) may be formed in the first through-holes 11.

[0115] Thereafter, the vacuum state in the closed space is released through the nozzle 225, and the piston rod 231 is retracted to lower the lower press member 210. Then, the core substrate 10 is transported to the heat press stage 100.

[0116] In the heat press stage 100, as described in the first specific example, the resin sheets 20 and 30 are pressed by the lower plate 112 and the upper plate 122, which serve as rigid plates, to further fill the resin composition into the first through holes 11 (step (II)). Even if there are unfilled portions in the first through holes 11 when the sheets are supplied to the heat press stage 100, as described in the first specific example, by applying pressure in the heat press stage 100, the resin composition can be filled into the first through holes 11 while suppressing the formation of voids and unfilled portions.

[0117] Thereafter, the vacuum state in the closed space is released through nozzle 125, and piston rod 131 is retracted to lower lower press member 110. Then, as in the first specific example, any of the optional steps such as curing the resin composition (step (III)), polishing the cured resin composition (step (IV)), forming second through-holes in the filled cured material layer (step (V)), and forming a conductor layer (step (VI)) can be carried out as needed to obtain the desired magnetic substrate.

[0118] <Other specific examples> In the first and second specific examples described above, the nozzles 125 and 225 are provided on the upper frame members 123 and 223, but the position of the nozzles may be changed. For example, the nozzles may be provided on the lower frame members 113 and 213, on the lower support members 111 and 211, on the upper support members 121 and 221, or on more than one of these.

[0119] In the first and second specific examples described above, heaters 114, 124, 214, and 224 are provided in the lower plates 112 and 212 and upper plates 122 and 222, which serve as rigid plates, but the positions of the heaters may be changed. For example, when the rigid plates are made of a metal material such as stainless steel, an electric current device may be provided to pass electricity through the rigid plates so that the rigid plates themselves can function as heaters by generating heat due to electrical resistance.

[0120] In the first and second specific examples described above, hydraulic cylinders 130 and 230 are provided as the driving devices, but the driving devices are not limited to hydraulic cylinders 130 and 230. Examples of driving devices include air cylinders and diaphragms. When a diaphragm is used, a stage may be used that includes a diaphragm as a film that covers the airtight space and a rigid plate that is mounted on the diaphragm via an appropriate member such as a heat insulator. By injecting gas or liquid into the airtight space, pressure can be applied by the rigid plate supported by the diaphragm.

[0121] In the second specific example described above, a two-chamber laminator having two chambers was used as an example, but the method for manufacturing a magnetic substrate may also be carried out using a laminator having three or more chambers and stages installed in the chambers.

[0122] <Resin sheet> The resin sheet includes a support and a resin composition layer formed on the support.

[0123] Examples of the support include films made of plastic materials, metal foils, and release papers, with plastic films and metal foils being preferred.

[0124] When a film made of a plastic material is used as the support, examples of the plastic material include polyesters such as polyethylene terephthalate (hereinafter sometimes abbreviated as "PET") and polyethylene naphthalate (hereinafter sometimes abbreviated as "PEN"); polycarbonate (hereinafter sometimes abbreviated as "PC"); acrylic polymers such as polymethyl methacrylate (hereinafter sometimes abbreviated as "PMMA"); cyclic polyolefins; triacetyl cellulose (hereinafter sometimes abbreviated as "TAC"); polyether sulfide (hereinafter sometimes abbreviated as "PES"); polyether ketone; polyimide; etc. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, and inexpensive polyethylene terephthalate is particularly preferred.

[0125] When a metal foil is used as the support, examples of the metal foil include copper foil and aluminum foil. Of these, copper foil is preferred. The copper foil may be a foil made of a single metal, copper, or a foil made of an alloy of copper and another metal (e.g., tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.).

[0126] The surface of the support that is to be bonded to the resin composition layer may be subjected to a matte treatment, a corona treatment, an antistatic treatment or the like.

[0127] The support may be a support with a release layer, which has a release layer on the surface that bonds with the resin composition layer. Examples of the release agent used in the release layer of the support with a release layer include one or more release agents selected from the group consisting of alkyd resins, polyolefin resins, urethane resins, and silicone resins. Commercially available release agents include alkyd resin-based release agents such as "SK-1," "AL-5," and "AL-7" manufactured by Lintec Corporation. Examples of support with a release layer include "Lumirror T60" manufactured by Toray Industries, Inc.; "Purex" manufactured by Teijin Limited; and "Uni-Peel" manufactured by Unitika Limited.

[0128] The thickness of the support is not particularly limited, but is preferably 1 μm or more, more preferably 5 μm or more, even more preferably 10 μm or more, and is preferably 75 μm or less, more preferably 60 μm or less, even more preferably 50 μm or less, and particularly preferably 40 μm or less.

[0129] The resin composition layer is formed on a support. Usually, the support and the resin composition layer are directly bonded to each other without any other member therebetween. The resin composition layer contains a resin composition, and preferably contains only the resin composition.

[0130] The resin composition includes (A) magnetic powder. The (A) magnetic powder as the component (A) can be particles of a material having a relative magnetic permeability greater than 1. The material of the (A) magnetic powder is usually an inorganic material, and may be a soft magnetic material or a hard magnetic material. The material of the (A) magnetic powder may be used alone or in combination of two or more types. Therefore, the (A) magnetic powder may be a soft magnetic powder, a hard magnetic powder, or a combination of a soft magnetic powder and a hard magnetic powder. The (A) magnetic powder may be used alone or in combination of two or more types. In particular, the (A) magnetic powder preferably includes a soft magnetic powder, and more preferably includes only a soft magnetic powder.

[0131] (A) Examples of the magnetic powder include magnetic metal oxide powder and magnetic metal powder.

[0132] Examples of magnetic metal oxide powders include ferrite powders such as Fe-Mn ferrite powder, Fe-Mn-Mg ferrite powder, Fe-Mn-Mg-Sr ferrite powder, Fe-Mg-Zn ferrite powder, Fe-Mg-Sr ferrite powder, Fe-Zn-Mn ferrite powder, Fe-Cu-Zn ferrite powder, Fe-Ni-Zn ferrite powder, Fe-Ni-Zn-Cu ferrite powder, Fe-Ba-Zn ferrite powder, Fe-Ba-Mg ferrite powder, Fe-Ba-Ni ferrite powder, Fe-Ba-Co ferrite powder, Fe-Ba-Ni-Co ferrite powder, and Fe-Y ferrite powder; iron oxide powders such as iron(III) oxide powder and triiron tetroxide powder; and the like. Among these, ferrite powders are preferred. Ferrite powder is usually made of a composite oxide mainly composed of iron oxide and is chemically stable. Therefore, ferrite powder has advantages such as high corrosion resistance, low risk of fire, and resistance to demagnetization. Among them, ferrite powder containing at least one element selected from the group consisting of Mn and Zn is preferred, ferrite powder containing Mn is more preferred, and Fe-Mn ferrite powder is particularly preferred. Fe-Mn ferrite powder refers to ferrite powder containing Fe and Mn.

[0133] Examples of magnetic metal powders include pure iron powder; crystalline or amorphous alloy powders such as Fe-Si alloy powder, Fe-Si-Al alloy powder, Fe-Cr alloy powder, Fe-Cr-Si alloy powder, Fe-Ni-Cr alloy powder, Fe-Cr-Al alloy powder, Fe-Ni alloy powder, Fe-Ni-Si alloy powder, Fe-Ni-B alloy powder, Fe-Ni-Mo alloy powder, Fe-Ni-Mo-Cu alloy powder, Fe-Co alloy powder, Fe-Ni-Co alloy powder, and Co-based amorphous alloy powder. Among these, alloy powders are preferred, with iron alloy powders being more preferred. Iron alloy powders containing Fe and at least one element selected from the group consisting of Si, Cr, and Ni are preferred, with Fe-Ni alloy powders being particularly preferred. Fe-Ni alloy powder refers to alloy powders containing Fe and Ni.

[0134] The average particle size of the (A) magnetic powder is preferably 1 μm or more, more preferably 1.4 μm or more, particularly preferably 1.6 μm or more, and preferably 10 μm or less, more preferably 7.5 μm or less, particularly preferably 5.0 μm or less.

[0135] Unless otherwise specified, the average particle size refers to the median size on a volume basis. This average particle size can be measured using a laser diffraction / scattering method based on Mie scattering theory. Specifically, a particle size distribution on a volume basis is created using a laser diffraction / scattering particle size distribution analyzer, and the median size can be measured as the average particle size. A preferred measurement sample is powder dispersed in water using ultrasonic waves. Examples of laser diffraction / scattering particle size distribution analyzers that can be used include the LA-500 manufactured by Horiba, Ltd. and the SALD-2200 manufactured by Shimadzu Corporation.

[0136] Two or more types of magnetic powders having different average particle sizes may be used in combination as the (A) magnetic powder. It is particularly preferable to use a combination of (A-1) magnetic powder having an average particle size of less than 1 μm and (A-2) magnetic powder having an average particle size of 1 μm or more. Hereinafter, the "(A-1) magnetic powder having an average particle size of less than 1 μm" may be referred to as the "(A-1) small-diameter magnetic powder," and the "(A-2) magnetic powder having an average particle size of 1 μm or more" may be referred to as the "(A-2) large-diameter magnetic powder." When the (A-1) small-diameter magnetic powder and the (A-2) large-diameter magnetic powder are used in combination, the particles of the (A-1) small-diameter magnetic powder can be inserted between the particles of the (A-2) large-diameter magnetic powder, thereby increasing the packing density of the (A) magnetic powder.

[0137] The average particle size of the small-diameter magnetic powder (A-1) is, specifically, usually less than 1 μm, preferably 0.8 μm or less, and more preferably 0.6 μm or less. There is no particular lower limit, and the average particle size can be, for example, 0.1 μm or more, 0.2 μm or more, or 0.3 μm or more.

[0138] The amount (volume %) of the (A-1) small-diameter magnetic powder contained in the resin composition is preferably 1% by volume or more, more preferably 5% by volume or more, and particularly preferably 10% by volume or more, relative to 100% by volume of the nonvolatile components of the resin composition, and is preferably 50% by volume or less, more preferably 45% by volume or less, and particularly preferably 40% by volume or less. The volume content (volume %) of each component contained in the resin composition is calculated from the mass of the component contained in the resin composition. Specifically, the mass is divided by the specific gravity to determine the volume of each component, and the volume content (volume %) can be calculated from the volume of each component thus determined.

[0139] The average particle size of the (A-2) large-diameter magnetic powder is, specifically, usually 1 μm or more, preferably 2 μm or more, and more preferably 3 μm or more. There is no particular upper limit, and it can be, for example, 20 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less.

[0140] The amount (vol %) of the (A-2) large-diameter magnetic powder is preferably greater than the amount (vol %) of the (A-1) small-diameter magnetic powder. The specific amount (vol %) of the (A-2) large-diameter magnetic powder contained in the resin composition is preferably 10% by volume or more, more preferably 20% by volume or more, and particularly preferably 30% by volume or more, relative to 100% by volume of the nonvolatile components of the resin composition, and is preferably 80% by volume or less, more preferably 70% by volume or less, and particularly preferably 60% by volume or less.

[0141] (A) The specific surface area of ​​the magnetic powder is preferably 0.05 m from the viewpoint of improving the relative magnetic permeability. 2 / g or more, more preferably 0.1m 2 / g or more, more preferably 0.3m 2 / g or more, preferably 10m 2 / g or less, more preferably 8m 2 / g or less, more preferably 5m 2 / g or less. (A) The specific surface area of ​​the magnetic powder can be measured by the BET method. Specifically, the specific surface area can be measured according to the BET method using a specific surface area measuring device ("Macsorb HM Model 1210" manufactured by Mountech Co., Ltd.) by adsorbing nitrogen gas onto the surface of the sample and using the BET multipoint method.

[0142] The particles of the (A) magnetic powder are preferably spherical or ellipsoidal. The aspect ratio (ratio of the major axis length divided by the minor axis length) of the particles of the (A) magnetic powder is preferably 2 or less, more preferably 1.5 or less, even more preferably 1.2 or less, and is usually 1.0 or more. In general, when the shape of the magnetic powder particles is flat rather than spherical, it is easier to improve the relative magnetic permeability. On the other hand, when the shape of the magnetic powder particles is closer to spherical, it is easier to reduce magnetic loss.

[0143] (A) The true specific gravity of the magnetic powder is, for example, 4 g / cm 3 ~10g / cm 3 It is possible.

[0144] The amount (volume %) of the (A) magnetic powder contained in the resin composition is preferably 65 volume % or more, more preferably 67 volume % or more, and particularly preferably 70 volume % or more, relative to 100 volume % of the nonvolatile components of the resin composition, and is preferably 95 volume % or less, more preferably 90 volume % or less, and particularly preferably 85 volume % or less. When using a resin composition containing a large amount of (A) magnetic powder, it has been difficult to fill the first through-holes with the resin composition using conventional methods, but the method according to the above-mentioned embodiment allows the first through-holes to be filled with the resin composition with good filling properties.

[0145] The amount (% by mass) of the (A) magnetic powder contained in the resin composition is preferably 75% by mass or more, more preferably 80% by mass or more, and particularly preferably 85% by mass or more, relative to 100% by mass of the nonvolatile components of the resin composition, and is preferably 99% by mass or less, more preferably 98% by mass or less, and particularly preferably 96% by mass or less. When using a resin composition containing a large amount of (A) magnetic powder, it has been difficult to fill the first through-holes with the resin composition using conventional methods, but the method according to the above-mentioned embodiment allows the first through-holes to be filled with the resin composition with good filling properties.

[0146] The resin composition typically contains a (B) thermosetting resin in combination with a (A) magnetic powder. The (B) thermosetting resin as the (B) component can bind the (A) magnetic powder. The (B) thermosetting resin also reacts with heat to form bonds, thereby curing the resin composition. Thus, a resin composition containing a combination of the (A) magnetic powder and the (B) thermosetting resin can be cured to form a cured product.

[0147] Examples of the (B) thermosetting resin include epoxy resins, phenolic resins, active ester resins, amine resins, acid anhydride resins, benzoxazine resins, cyanate ester resins, carbodiimide resins, etc. One type of (B) thermosetting resin may be used alone, or two or more types may be used in combination.

[0148] The (B) thermosetting resin preferably contains a (B-1) epoxy resin. The (B-1) epoxy resin refers to a resin having one or more epoxy groups in the molecule. Examples of the (B-1) epoxy resin include bixylenol-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol S-type epoxy resins, bisphenol AF-type epoxy resins, dicyclopentadiene-type epoxy resins, trisphenol-type epoxy resins, phenol novolac-type epoxy resins, glycidyl amine-type epoxy resins, glycidyl ester-type epoxy resins, cresol novolac-type epoxy resins, biphenyl-type epoxy resins, linear aliphatic epoxy resins, epoxy resins having a butadiene structure, alicyclic epoxy resins, and alicyclic epoxy resins having an ester skeleton. Examples of the epoxy resin include heterocyclic epoxy resins, spiro ring-containing epoxy resins, cyclohexane epoxy resins, cyclohexanedimethanol epoxy resins, trimethylol epoxy resins, tetraphenylethane epoxy resins, epoxy resins containing a condensed ring skeleton such as naphthylene ether epoxy resins, tert-butyl-catechol epoxy resins, naphthalene epoxy resins, naphthol epoxy resins, anthracene epoxy resins, and naphthol novolac epoxy resins, isocyanurate epoxy resins, epoxy resins containing an alkyleneoxy skeleton and a butadiene skeleton, and epoxy resins containing a fluorene structure. The (B-1) epoxy resin may be used alone or in combination of two or more.

[0149] The (B-1) epoxy resin preferably contains an epoxy resin having two or more epoxy groups per molecule, and the proportion of the epoxy resin having two or more epoxy groups per molecule relative to the total amount of the (B-1) epoxy resin (100% by mass) is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more.

[0150] The (B-1) epoxy resin preferably has an aromatic structure. When two or more epoxy resins are used, it is preferable that at least one of the epoxy resins has an aromatic structure. The aromatic structure is a chemical structure generally defined as aromatic, and includes polycyclic aromatic rings and aromatic heterocycles.

[0151] (B-1) epoxy resins include epoxy resins that are liquid at a temperature of 20°C (hereinafter sometimes referred to as "liquid epoxy resins") and epoxy resins that are solid at a temperature of 20°C (hereinafter sometimes referred to as "solid epoxy resins"). (B-1) epoxy resin may be liquid epoxy resin alone, solid epoxy resin alone, or a combination of liquid epoxy resin and solid epoxy resin. In particular, (B-1) epoxy resin preferably contains liquid epoxy resin, and particularly preferably contains liquid epoxy resin alone.

[0152] The liquid epoxy resin is preferably a liquid epoxy resin having two or more epoxy groups per molecule. Examples of liquid epoxy resins include bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol AF epoxy resins, naphthalene epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, phenol novolac epoxy resins, alicyclic epoxy resins having an ester skeleton, cyclohexane epoxy resins, cyclohexanedimethanol epoxy resins, epoxy resins having a butadiene structure, epoxy resins containing an alkyleneoxy skeleton and a butadiene skeleton, epoxy resins containing a fluorene structure, and dicyclopentadiene epoxy resins. Among these, bisphenol A epoxy resins, bisphenol F epoxy resins, naphthalene epoxy resins, glycidyl amine epoxy resins, and alicyclic epoxy resins having an ester skeleton are particularly preferred.

[0153] Specific examples of liquid epoxy resins include "YX7400" manufactured by Mitsubishi Chemical Corporation; "HP4032", "HP4032D", and "HP4032SS" (naphthalene-type epoxy resins) manufactured by DIC Corporation; "828US", "828EL", "jER828EL", "825", and "Epikote 828EL" (bisphenol A-type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "jER807" and "1750" (bisphenol F-type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "jER152" (phenol novolac-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "630", "630LSD", and "604" (glycidylamine-type epoxy resins) manufactured by Mitsubishi Chemical Corporation; "ED-523T" (glycilol-type epoxy resin) manufactured by ADEKA Corporation; "EP-3950L" and "EP-3980S" (glycidylamine-type epoxy resins) manufactured by ADEKA Corporation; and "EP-4088S" (glycidylamine-type epoxy resins) manufactured by ADEKA Corporation. Examples include: "ZX-1059" manufactured by Nippon Steel Chemical & Material Co., Ltd. (a mixture of bisphenol A and bisphenol F epoxy resins); "EX-721" manufactured by Nagase ChemteX Corporation (glycidyl ester epoxy resin); "EX-991L" manufactured by Nagase ChemteX Corporation (an epoxy resin containing an alkyleneoxy skeleton); "Celloxide 2021P" and "Celloxide 2081" manufactured by Daicel Corporation (alicyclic epoxy resins with an ester skeleton); "PB-3600" manufactured by Daicel Corporation, and "JP-100" and "JP-200" manufactured by Nippon Soda Co., Ltd. (epoxy resins with a butadiene structure); "ZX1658" and "ZX1658GS" manufactured by Nippon Steel Chemical & Material Co., Ltd. (liquid 1,4-glycidylcyclohexane epoxy resin); and "EG-280" manufactured by Osaka Gas Chemicals Co., Ltd. (an epoxy resin containing a fluorene structure). The liquid epoxy resin may be used alone or in combination of two or more.

[0154] The solid epoxy resin is preferably a solid epoxy resin having three or more epoxy groups in one molecule, more preferably an aromatic solid epoxy resin having three or more epoxy groups in one molecule.The solid epoxy resin is preferably a bixylenol type epoxy resin, a naphthalene type epoxy resin, a naphthalene type tetrafunctional epoxy resin, a cresol novolac type epoxy resin, a dicyclopentadiene type epoxy resin, a trisphenol type epoxy resin, a naphthol type epoxy resin, a biphenyl type epoxy resin, a naphthylene ether type epoxy resin, an anthracene type epoxy resin, a bisphenol A type epoxy resin, a bisphenol AF type epoxy resin, or a tetraphenylethane type epoxy resin, and particularly preferably a dicyclopentadiene type epoxy resin.

[0155] Specific examples of solid epoxy resins include DIC Corporation's "HP4032H" (naphthalene-type epoxy resin); DIC Corporation's "HP-4700" and "HP-4710" (naphthalene-type tetrafunctional epoxy resins); DIC Corporation's "N-690" (cresol novolac-type epoxy resin); DIC Corporation's "N-695" (cresol novolac-type epoxy resin); and DIC Corporation's "HP-7200," "HP-7200HH," and "HP-7200H" (dicyclopentadiene-type epoxy resins). DIC's "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", and "HP6000" (naphthylene ether type epoxy resins); Nippon Kayaku's "EPPN-502H" (trisphenol type epoxy resin); Nippon Kayaku's "NC7000L" (naphthol novolac type epoxy resin); Nippon Kayaku's "NC3000H", "NC3000", "NC3000L", and "NC3100" (biphenyl type epoxy resins). resin); "ESN475V" (naphthol-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "ESN485" (naphthol novolac-type epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd.; "YX4000H", "YX4000", and "YL6121" (biphenyl-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YX4000HK" (bixylenol-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YX8800" (anthracene-type epoxy resin) manufactured by Mitsubishi Chemical Corporation; Examples of suitable solid epoxy resins include "YX7700" (xylene structure-containing novolac epoxy resin) manufactured by Mitsubishi Chemical Corporation; "PG-100" and "CG-500" manufactured by Osaka Gas Chemicals Co., Ltd.; "YL7760" (bisphenol AF epoxy resin) manufactured by Mitsubishi Chemical Corporation; "YL7800" (fluorene epoxy resin) manufactured by Mitsubishi Chemical Corporation; "jER1010" (solid bisphenol A epoxy resin) manufactured by Mitsubishi Chemical Corporation; and "jER1031S" (tetraphenylethane epoxy resin) manufactured by Mitsubishi Chemical Corporation. One type of solid epoxy resin may be used alone, or two or more types may be used in combination.

[0156] When a liquid epoxy resin and a solid epoxy resin are used in combination as the epoxy resin, the mass ratio of the liquid epoxy resin to the solid epoxy resin (liquid epoxy resin / solid epoxy resin) is preferably 0.5 or more, more preferably 1 or more, even more preferably 5 or more, and particularly preferably 10 or more.

[0157] The epoxy equivalent of the (B-1) epoxy resin is preferably 50 g / eq to 5000 g / eq, more preferably 50 g / eq to 3000 g / eq, even more preferably 80 g / eq to 2000 g / eq, and even more preferably 110 g / eq to 1000 g / eq. The epoxy equivalent is the mass of a resin containing one equivalent of epoxy groups. This epoxy equivalent can be measured according to JIS K7236.

[0158] The weight average molecular weight (Mw) of the epoxy resin (B-1) is preferably 100 to 5000, more preferably 250 to 3000, and even more preferably 400 to 1500. The weight average molecular weight of the resin can be measured by gel permeation chromatography (GPC) as a polystyrene-equivalent value.

[0159] The amount (% by mass) of the (B-1) epoxy resin contained in the resin composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and particularly preferably 1% by mass or more, relative to 100% by mass of the non-volatile components of the resin composition, and is preferably 15% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less.

[0160] The amount (% by mass) of the (B-1) epoxy resin contained in the resin composition is preferably 10% by mass or more, more preferably 20% by mass or more, particularly preferably 30% by mass or more, and is preferably 80% by mass or less, more preferably 70% by mass or less, particularly preferably 60% by mass or less, relative to 100% by mass of the resin components of the resin composition. Unless otherwise specified, the resin components of the resin composition refer to the non-volatile components of the resin composition excluding inorganic particles such as magnetic powder.

[0161] When the (B) thermosetting resin contains a (B-1) epoxy resin, the (B) thermosetting resin preferably contains a resin capable of reacting with and bonding to the (B-1) epoxy resin. Hereinafter, the resin capable of reacting with and bonding to the (B-1) epoxy resin may be referred to as the "(B-2) curing agent." Examples of the (B-2) curing agent include phenolic resins, active ester resins, amine resins, carbodiimide resins, acid anhydride resins, benzoxazine resins, cyanate ester resins, and thiol resins. One type of (B-2) curing agent may be used alone, or two or more types may be used in combination. Among these, phenolic resins are preferred.

[0162] As the phenolic resin, a resin having one or more, preferably two or more, hydroxyl groups bonded to an aromatic ring such as a benzene ring or a naphthalene ring per molecule can be used. From the viewpoint of heat resistance and water resistance, a phenolic resin having a novolac structure is preferred. From the viewpoint of adhesion, a nitrogen-containing phenolic resin is preferred, and a triazine skeleton-containing phenolic resin is more preferred. Among them, a triazine skeleton-containing phenolic novolac resin is preferred from the viewpoint of highly satisfying heat resistance, water resistance, and adhesion.

[0163] Specific examples of phenolic resins include "MEH-7700", "MEH-7810", "MEH-7851", and "MEH-8000H" manufactured by Meiwa Chemical Industry Co., Ltd.; "NHN", "CBN", and "GPH" manufactured by Nippon Kayaku Co., Ltd.; and "SN-170", "SN-180", "SN-190", "SN-475", "SN-485", "SN-495", "SN-495V", "SN-375", and "SN" manufactured by Nippon Steel Chemical & Material Co., Ltd. -395"; "TD-2090", "TD-2090-60M", "LA-7052", "LA-7054", "LA-1356", "LA-3018", "LA-3018-50P", "EXB-9500", "HPC-9500", "KA-1160", "KA-1163", and "KA-1165" manufactured by DIC Corporation; and "GDP-6115L", "GDP-6115H", and "ELPC75" manufactured by Gun-ei Chemical Co., Ltd.

[0164] The active ester resin may be a compound having one or more, preferably two or more, active ester groups per molecule. Among these, preferred active ester resins are compounds having two or more highly reactive ester groups per molecule, such as phenol esters, thiophenol esters, N-hydroxyamine esters, and esters of heterocyclic hydroxy compounds. The active ester resin is preferably one obtained by a condensation reaction between a carboxylic acid compound and / or a thiocarboxylic acid compound and a hydroxy compound and / or a thiol compound. In particular, from the viewpoint of improving heat resistance, active ester resins obtained from a carboxylic acid compound and a hydroxy compound are preferred, and active ester resins obtained from a carboxylic acid compound and a phenol compound and / or a naphthol compound are more preferred. Examples of carboxylic acid compounds include benzoic acid, acetic acid, succinic acid, maleic acid, itaconic acid, phthalic acid, isophthalic acid, terephthalic acid, and pyromellitic acid. Examples of phenol compounds or naphthol compounds include hydroquinone, resorcinol, bisphenol A, bisphenol F, bisphenol S, phenolphthalene, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucin, benzenetriol, dicyclopentadiene-type diphenol compounds, and phenol novolak. Here, "dicyclopentadiene-type diphenol compounds" refers to diphenol compounds obtained by condensing one dicyclopentadiene molecule with two phenol molecules.

[0165] Preferred examples of the active ester resin include active ester resins containing a dicyclopentadiene-type diphenol structure, active ester resins containing a naphthalene structure, active ester resins containing an acetylated product of phenol novolac, and active ester resins containing a benzoylated product of phenol novolac. Among these, active ester resins containing a naphthalene structure and active ester resins containing a dicyclopentadiene-type diphenol structure are more preferred. The "dicyclopentadiene-type diphenol structure" refers to a divalent structural unit consisting of phenylene-dicyclopentylene-phenylene.

[0166] Commercially available activated ester resins include activated ester resins containing a dicyclopentadiene-type diphenol structure, such as "EXB9451," "EXB9460," "EXB9460S," "HPC-8000-65T," "HPC-8000H-65TM," and "EXB-8000L-65TM" (manufactured by DIC Corporation); activated ester resins containing a naphthalene structure, such as "EXB-9416-70BK," "EXB-8150-65T," "EXB-8100L-65T," and "EXB-8150L-65T" (manufactured by DIC Corporation); and phenol novolac resins. Examples of active ester resins containing acetylated compounds include "DC808" (manufactured by Mitsubishi Chemical Corporation); active ester resins containing benzoylated phenol novolac include "YLH1026" (manufactured by Mitsubishi Chemical Corporation); active ester resins that are acetylated phenol novolac include "DC808" (manufactured by Mitsubishi Chemical Corporation); and active ester resins that are benzoylated phenol novolac include "YLH1026" (manufactured by Mitsubishi Chemical Corporation), "YLH1030" (manufactured by Mitsubishi Chemical Corporation), and "YLH1048" (manufactured by Mitsubishi Chemical Corporation).

[0167] As the amine-based resin, a resin having one or more, preferably two or more amino groups in one molecule can be used. Examples of the amine-based resin include aliphatic amines, polyether amines, alicyclic amines, and aromatic amines. Among these, aromatic amines are preferred. The amine-based resin is preferably a primary amine or a secondary amine, and more preferably a primary amine. Specific examples of the amine-based resin include 4,4'-methylenebis(2,6-dimethylaniline), diphenyldiaminosulfone, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, m-phenylenediamine, m-xylylenediamine, diethyltoluenediamine, 4,4'-diaminodiphenyl ether, 3,3'-dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxybenzidine, 2,2-bis(3-amino-4-hydroxybenzoyl) Examples of suitable amine resins include 4,4'-bis(4-aminophenyl)propane, 3,3-dimethyl-5,5-diethyl-4,4-diphenylmethanediamine, 2,2-bis(4-aminophenyl)propane, 2,2-bis(4-(4-aminophenoxy)phenyl)propane, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, bis(4-(4-aminophenoxy)phenyl)sulfone, and bis(4-(3-aminophenoxy)phenyl)sulfone. Commercially available amine resins may be used, such as "KAYABOND C-200S," "KAYABOND C-100," "KAYAHARD AA," "KAYAHARD AB," and "KAYAHARD AS" manufactured by Nippon Kayaku Co., Ltd., and "Epicure W" manufactured by Mitsubishi Chemical Corporation.

[0168] As the carbodiimide resin, a resin having one or more, preferably two or more, carbodiimide structures in one molecule can be used. Specific examples of the carbodiimide resin include aliphatic biscarbodiimides such as tetramethylene-bis(t-butylcarbodiimide) and cyclohexanebis(methylene-t-butylcarbodiimide); aromatic biscarbodiimides such as phenylene-bis(xylylcarbodiimide); aliphatic polycarbodiimides such as polyhexamethylenecarbodiimide, polytrimethylhexamethylenecarbodiimide, polycyclohexylenecarbodiimide, poly(methylenebiscyclohexylenecarbodiimide), and poly(isophoronecarbodiimide); poly(phenylenecarbodiimide), poly(naphthalenecarbodiimide); Examples of polycarbodiimides include aromatic polycarbodiimides such as poly(methylenediphenylenecarbodiimide), poly(tolylenecarbodiimide), poly(methyldiisopropylphenylenecarbodiimide), poly(triethylphenylenecarbodiimide), poly(diethylphenylenecarbodiimide), poly(triisopropylphenylenecarbodiimide), poly(diisopropylphenylenecarbodiimide), poly(xylylenecarbodiimide), poly(tetramethylxylylenecarbodiimide), poly(methylenediphenylenecarbodiimide), and poly[methylenebis(methylphenylene)carbodiimide]. Commercially available carbodiimide resins include, for example, "Carbodilite V-02B," "Carbodilite V-03," "Carbodilite V-04K," "Carbodilite V-07," and "Carbodilite V-09" manufactured by Nisshinbo Chemical Inc.; and "Stavaxol P," "Stavaxol P400," and "Hykasil 510" manufactured by Rhein Chemie.

[0169] As the acid anhydride resin, a resin having one or more acid anhydride groups in one molecule can be used, and a resin having two or more acid anhydride groups in one molecule is preferred. Specific examples of the acid anhydride resin include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, dodecenyl succinic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, trimellitic anhydride, pyromellitic anhydride, and benzophenonetetracarboxylic dianhydride. Examples of suitable anhydrides include anhydrides, biphenyltetracarboxylic dianhydride, naphthalenetetracarboxylic dianhydride, oxydiphthalic dianhydride, 3,3'-4,4'-diphenylsulfonetetracarboxylic dianhydride, 1,3,3a,4,5,9b-hexahydro-5-(tetrahydro-2,5-dioxo-3-furanyl)-naphtho[1,2-C]furan-1,3-dione, ethylene glycol bis(anhydrotrimellitate), and polymeric anhydrides such as styrene-maleic acid resins, which are copolymers of styrene and maleic acid. Commercially available acid anhydride resins include, for example, "HNA-100," "MH-700," "MTA-15," "DDSA," and "OSA" manufactured by New Japan Chemical Co., Ltd.; "YH-306" and "YH-307" manufactured by Mitsubishi Chemical Corporation; "HN-2200" and "HN-5500" manufactured by Hitachi Chemical Co., Ltd.; and "EF-30," "EF-40," "EF-60," and "EF-80" manufactured by Clay Valley.

[0170] Specific examples of benzoxazine resins include "JBZ-OD100," "JBZ-OP100D," and "ODA-BOZ" manufactured by JFE Chemical Corporation; "Pd" and "Fa" manufactured by Shikoku Chemical Industry Co., Ltd.; and "HFB2006M" manufactured by Showa Polymer Co., Ltd.

[0171] Examples of cyanate ester resins include bifunctional cyanate resins such as bisphenol A dicyanate, polyphenol cyanate, oligo(3-methylene-1,5-phenylene cyanate), 4,4'-methylenebis(2,6-dimethylphenyl cyanate), 4,4'-ethylidene diphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanatephenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanatephenyl-1-(methylethylidene))benzene, bis(4-cyanatephenyl)thioether, and bis(4-cyanatephenyl)ether; polyfunctional cyanate resins derived from phenol novolac, cresol novolac, etc.; and prepolymers in which these cyanate resins are partially triazine converted. Specific examples of cyanate ester resins include "PT30" and "PT60" (phenol novolac type multifunctional cyanate ester resins), "ULL-950S" (multifunctional cyanate ester resin), "BA230" and "BA230S75" (prepolymers in which part or all of bisphenol A dicyanate has been triazine converted to a trimer), all of which are manufactured by Lonza Japan.

[0172] Examples of thiol-based resins include trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate), and tris(3-mercaptopropyl)isocyanurate.

[0173] The active group equivalent of the (B-2) curing agent is preferably 50 g / eq. to 3000 g / eq., more preferably 100 g / eq. to 1000 g / eq., even more preferably 100 g / eq. to 500 g / eq., and particularly preferably 100 g / eq. to 300 g / eq. The active group equivalent represents the mass of the (B-2) curing agent per equivalent of the active group.

[0174] When the number of epoxy groups in the (B-1) epoxy resin is taken as 1, the number of active groups in the (B-2) curing agent is preferably 0.01 or more, more preferably 0.1 or more, particularly preferably 0.5 or more, and preferably 10 or less, more preferably 5 or less, particularly preferably 3 or less. The active groups in the (B-2) curing agent are active hydroxyl groups, etc., and vary depending on the type of curing agent. The number of epoxy groups in the (B-1) epoxy resin is the total value for all epoxy resins obtained by dividing the mass of the nonvolatile components of each epoxy resin by the epoxy equivalent. The number of active groups in the (B-2) curing agent is the total value for all curing agents obtained by dividing the mass of the nonvolatile components of each curing agent by the active group equivalent.

[0175] The amount (mass %) of the (B-2) curing agent contained in the resin composition is preferably 0.1 mass % or more, more preferably 0.5 mass % or more, and particularly preferably 1 mass % or more, relative to 100 mass % of the non-volatile components of the resin composition, and is preferably 15 mass % or less, more preferably 10 mass % or less, and particularly preferably 5 mass % or less.

[0176] The amount (mass %) of the (B-2) curing agent contained in the resin composition is preferably 10 mass % or more, more preferably 15 mass % or more, and particularly preferably 20 mass % or more, relative to 100 mass % of the resin components of the resin composition, and is preferably 70 mass % or less, more preferably 60 mass % or less, and particularly preferably 50 mass % or less.

[0177] The range of the weight average molecular weight (Mw) of the (B) thermosetting resin can usually be the same as the range of the weight average molecular weight of the (B-1) epoxy resin described above.

[0178] The amount (mass%) of the (B) thermosetting resin contained in the resin composition is preferably 0.1 mass% or more, more preferably 1 mass% or more, and particularly preferably 2 mass% or more, relative to 100 mass% of the non-volatile components of the resin composition, and is preferably 15 mass% or less, more preferably 13 mass% or less, and particularly preferably 10 mass% or less.

[0179] The amount (mass%) of the (B) thermosetting resin contained in the resin composition is preferably 40 mass% or more, more preferably 50 mass% or more, and particularly preferably 60 mass% or more, relative to 100 mass% of the resin components of the resin composition, and is preferably 95 mass% or less, more preferably 90 mass% or less, and particularly preferably 85 mass% or less.

[0180] The resin composition may further contain a curing accelerator (C) in combination with the above-described components (A) and (B). The curing accelerator (C) as component (C) does not include those corresponding to the above-described components (A) and (B). The curing accelerator (C) functions as a catalyst that accelerates the curing of the thermosetting resin (B), and therefore can accelerate the curing of the resin composition.

[0181] Examples of the (C) curing accelerator include phosphorus-based curing accelerators, amine-based curing accelerators, imidazole-based curing accelerators, guanidine-based curing accelerators, and metal-based curing accelerators. Among these, imidazole-based curing accelerators are preferred. One type of (C) curing accelerator may be used alone, or two or more types may be used in combination.

[0182] Examples of the imidazole curing accelerator include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2, 4-Diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, Examples of imidazole compounds include phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, and 2-phenylimidazoline, as well as adducts of imidazole compounds with epoxy resins, with 2-ethyl-4-methylimidazole and 1-benzyl-2-phenylimidazole being preferred. Commercially available imidazole curing accelerators include Mitsubishi Chemical Corporation's "P200-H50" and Shikoku Chemicals Corporation's "Curezol 2MZ," "2E4MZ," "Cl1Z," "Cl1Z-CN," "Cl1Z-CNS," "Cl1Z-A," "2MZ-OK," "2MA-OK," "2MA-OK-PW," and "2PHZ."

[0183] Examples of the amine curing accelerator include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, 1,8-diazabicyclo(5,4,0)-undecene, 1,8-diazabicyclo[5,4,0]undecene-7,4-dimethylaminopyridine, and 2,4,6-tris(dimethylaminomethyl)phenol, with 4-dimethylaminopyridine being preferred.

[0184] Examples of phosphorus-based curing accelerators include triphenylphosphine, phosphonium borate compounds, tetraphenylphosphonium tetraphenylborate, n-butylphosphonium tetraphenylborate, tetrabutylphosphonium decanoate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and butyltriphenylphosphonium thiocyanate, with triphenylphosphine and tetrabutylphosphonium decanoate being preferred.

[0185] Examples of guanidine-based curing accelerators include dicyandiamide, 1-methylguanidine, 1-ethylguanidine, 1-cyclohexylguanidine, 1-phenylguanidine, 1-(o-tolyl)guanidine, dimethylguanidine, diphenylguanidine, trimethylguanidine, tetramethylguanidine, pentamethylguanidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene. Examples of suitable biguanide include 1-methylbiguanide, 1-ethylbiguanide, 1-n-butylbiguanide, 1-n-octadecylbiguanide, 1,1-dimethylbiguanide, 1,1-diethylbiguanide, 1-cyclohexylbiguanide, 1-allylbiguanide, 1-phenylbiguanide, and 1-(o-tolyl)biguanide. Of these, dicyandiamide and 1,5,7-triazabicyclo[4.4.0]dec-5-ene are preferred.

[0186] Examples of metal-based curing accelerators include organometallic complexes or organometallic salts of metals such as cobalt, copper, zinc, iron, nickel, manganese, and tin. Specific examples of organometallic complexes include organic cobalt complexes such as cobalt(II) acetylacetonate and cobalt(III) acetylacetonate, organic copper complexes such as copper(II) acetylacetonate, organic zinc complexes such as zinc(II) acetylacetonate, organic iron complexes such as iron(III) acetylacetonate, organic nickel complexes such as nickel(II) acetylacetonate, and organic manganese complexes such as manganese(II) acetylacetonate. Examples of organometallic salts include zinc octoate, tin octoate, zinc naphthenate, cobalt naphthenate, tin stearate, and zinc stearate.

[0187] The amount (mass%) of the (C) curing accelerator contained in the resin composition is preferably 0.001 mass% or more, more preferably 0.005 mass% or more, and particularly preferably 0.01 mass% or more, relative to 100 mass% of the non-volatile components of the resin composition, and is preferably 1 mass% or less, more preferably 0.5 mass% or less, and particularly preferably 0.1 mass% or less.

[0188] The amount (mass%) of the (C) curing accelerator contained in the resin composition is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and particularly preferably 0.1 mass% or more, relative to 100 mass% of the resin components of the resin composition, and is preferably 2.0 mass% or less, more preferably 1.0 mass% or less, and particularly preferably 0.5 mass% or less.

[0189] The resin composition may further contain a thermoplastic resin (D) in addition to the above-described components (A) to (C). The thermoplastic resin (D) as component (D) does not include those corresponding to the above-described components (A) to (C). The thermoplastic resin (D) can effectively improve the mechanical properties of a cured product of the resin composition.

[0190] Examples of the (D) thermoplastic resin include phenoxy resin, polyimide resin, polyvinyl acetal resin, polyolefin resin, polybutadiene resin, polyamideimide resin, polyetherimide resin, polysulfone resin, polyethersulfone resin, polyphenylene ether resin, polycarbonate resin, polyetheretherketone resin, polyester resin, etc. The (D) thermoplastic resin may be used alone or in combination of two or more.

[0191] Examples of phenoxy resins include phenoxy resins having one or more skeletons selected from the group consisting of bisphenol A, bisphenol F, bisphenol S, bisphenolacetophenone, novolac, biphenyl, fluorene, dicyclopentadiene, norbornene, naphthalene, anthracene, adamantane, terpene, and trimethylcyclohexane. The terminal of the phenoxy resin may be any functional group such as a phenolic hydroxyl group or an epoxy group. Specific examples of phenoxy resins include "1256" and "4250" manufactured by Mitsubishi Chemical Corporation (both of which are phenoxy resins containing a bisphenol A skeleton); "YX8100" manufactured by Mitsubishi Chemical Corporation (phenoxy resin containing a bisphenol S skeleton); "YX6954" manufactured by Mitsubishi Chemical Corporation (phenoxy resin containing a bisphenol acetophenone skeleton); "FX280" and "FX293" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.; and "YL7500BH30," "YX6954BH30," "YX7553," "YX7553BH30," "YL7769BH30," "YL6794," "YL7213," "YL7290," "YL7482," and "YL7891BH30" manufactured by Mitsubishi Chemical Corporation.

[0192] Specific examples of polyimide resins include "SLK-6100" manufactured by Shin-Etsu Chemical Co., Ltd., and "Rikacoat SN20" and "Rikacoat PN20" manufactured by New Japan Chemical Co., Ltd. Specific examples of polyimide resins also include modified polyimides such as linear polyimides obtained by reacting bifunctional hydroxyl group-terminated polybutadiene, a diisocyanate compound, and a tetrabasic acid anhydride (polyimides described in JP-A No. 2006-37083), and polysiloxane skeleton-containing polyimides (polyimides described in JP-A Nos. 2002-12667 and 2000-319386).

[0193] Examples of polyvinyl acetal resins include polyvinyl formal resins and polyvinyl butyral resins, with polyvinyl butyral resins being preferred. Specific examples of polyvinyl acetal resins include Denka Butyral 4000-2, Denka Butyral 5000-A, Denka Butyral 6000-C, and Denka Butyral 6000-EP, manufactured by Denki Kagaku Kogyo Co., Ltd.; and S-LEC BH series, BX series (e.g., BX-5Z), KS series (e.g., KS-1), BL series, and BM series, manufactured by Sekisui Chemical Co., Ltd.

[0194] Examples of polyolefin resins include ethylene copolymer resins such as low-density polyethylene, very low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and ethylene-methyl acrylate copolymer; and polyolefin polymers such as polypropylene and ethylene-propylene block copolymer.

[0195] Examples of polybutadiene resins include hydrogenated polybutadiene skeleton-containing resins, hydroxy group-containing polybutadiene resins, phenolic hydroxy group-containing polybutadiene resins, carboxy group-containing polybutadiene resins, acid anhydride group-containing polybutadiene resins, epoxy group-containing polybutadiene resins, isocyanate group-containing polybutadiene resins, urethane group-containing polybutadiene resins, and polyphenylene ether-polybutadiene resins.

[0196] Specific examples of polyamide-imide resins include "Vylomax HR11NN" and "Vylomax HR16NN" manufactured by Toyobo Co., Ltd. Specific examples of polyamide-imide resins also include modified polyamide-imides such as "KS9100" and "KS9300" (polysiloxane skeleton-containing polyamide-imides) manufactured by Hitachi Chemical Co., Ltd.

[0197] A specific example of the polyethersulfone resin is "PES5003P" manufactured by Sumitomo Chemical Co., Ltd.

[0198] Specific examples of polysulfone resins include polysulfones "P1700" and "P3500" manufactured by Solvay Advanced Polymers.

[0199] A specific example of the polyphenylene ether resin is NORYL SA90 manufactured by SABIC, etc. A specific example of the polyetherimide resin is ULTEM manufactured by GE, etc.

[0200] Examples of polycarbonate resins include hydroxyl group-containing carbonate resins, phenolic hydroxyl group-containing carbonate resins, carboxyl group-containing carbonate resins, acid anhydride group-containing carbonate resins, isocyanate group-containing carbonate resins, and urethane group-containing carbonate resins. Specific examples of polycarbonate resins include "FPC0220" manufactured by Mitsubishi Gas Chemical Company, Inc., "T6002" and "T6001" (polycarbonate diols) manufactured by Asahi Kasei Chemicals Corporation, and "C-1090," "C-2090," and "C-3090" (polycarbonate diols) manufactured by Kuraray Co., Ltd. Specific examples of polyether ether ketone resins include "Sumiploy K" manufactured by Sumitomo Chemical Co., Ltd.

[0201] Examples of polyester resins include polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene terephthalate resin, polybutylene naphthalate resin, polytrimethylene terephthalate resin, polytrimethylene naphthalate resin, and polycyclohexane dimethyl terephthalate resin.

[0202] The weight average molecular weight (Mw) of the (D) thermoplastic resin is preferably greater than 5,000, more preferably at least 8,000, even more preferably at least 10,000, and particularly preferably at least 20,000. There is no particular upper limit, and it can be, for example, 1,000,000 or less, 500,000 or less, or 100,000 or less.

[0203] The amount (mass%) of the (D) thermoplastic resin contained in the resin composition is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and particularly preferably 0.1 mass% or more, relative to 100 mass% of the non-volatile components of the resin composition, and is preferably 5 mass% or less, more preferably 3 mass% or less, and particularly preferably 2 mass% or less.

[0204] The amount (mass%) of the (D) thermoplastic resin contained in the resin composition is preferably 1 mass% or more, more preferably 5 mass% or more, and particularly preferably 10 mass% or more, relative to 100 mass% of the resin components of the resin composition, and is preferably 40 mass% or less, more preferably 30 mass% or less, and particularly preferably 20 mass% or less.

[0205] The resin composition may further contain a dispersant (E) in combination with the above-described components (A) to (D). The dispersant (E) as component (E) does not include those corresponding to the above-described components (A) to (D). The dispersant (E) can effectively improve the dispersibility of the magnetic powder (A).

[0206] As the (E) dispersant, a compound capable of reducing the viscosity of the resin composition can be used. Examples of the (E) dispersant include phosphate ester-based dispersants, polyoxyalkylene-based dispersants, acetylene-based dispersants, silicone-based dispersants, anionic dispersants, and cationic dispersants. One type of (E) dispersant may be used alone, or two or more types may be used in combination. Among these, phosphate ester-based dispersants are preferred.

[0207] Among phosphate ester-based dispersants, polyether-type phosphate ester-based dispersants are preferred. Polyether-type phosphate ester-based dispersants are phosphate ester-based dispersants containing a poly(alkyleneoxy) structure in the molecule. Examples of polyether-type phosphate ester-based dispersants include polyoxyalkylene alkyl ether phosphate esters and polyoxyalkylene alkylphenyl ether phosphate esters. Among these, polyoxyalkylene alkyl ether phosphate esters are preferred.

[0208] The polyoxyalkylene alkyl ether phosphate ester may have a structure in which 1 to 3 alkyl-oxy-poly(alkyleneoxy) groups are bonded to the phosphorus atom of the phosphate. The number of alkyleneoxy units (repeating units) in the poly(alkyleneoxy) moiety in the alkyl-oxy-poly(alkyleneoxy) group is preferably 2 to 30, more preferably 3 to 20. The alkylene group in the poly(alkyleneoxy) moiety is preferably an alkylene group having 2 to 4 carbon atoms. Examples of such alkylene groups include an ethylene group, a propylene group, an isopropylene group, a butylene group, and an isobutyl group. Furthermore, the alkyl group in the alkyl-oxy-poly(alkyleneoxy) group is preferably an alkyl group having 6 to 30 carbon atoms, more preferably an alkyl group having 8 to 20 carbon atoms. Examples of such alkyl groups include decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups. When the polyoxyalkylene alkyl ether phosphate ester has multiple alkyl-oxy-poly(alkyleneoxy) groups, the multiple alkyl groups may be the same or different. Furthermore, the multiple alkylene groups may be the same or different.

[0209] The acid value of the polyether phosphate ester dispersant is preferably 10 mgKOH / g or more, more preferably 15 mgKOH / g or more, and is preferably 200 mgKOH / g or less, more preferably 150 mgKOH / g or less. The acid value can be measured by neutralization titration.

[0210] Commercially available examples of phosphate ester dispersants include polyether phosphate ester dispersants manufactured by Kusumoto Chemical Industries Co., Ltd. (e.g., the HIPLAAD series "ED152," "ED153," "ED154," "ED118," "ED174," and "ED251"); and the Phosphanol series "RS-410," "RS-610," and "RS-710" manufactured by Toho Chemical Industry Co., Ltd.

[0211] Examples of polyoxyalkylene dispersants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines, polyoxyethylene alkylamides, etc. Commercially available examples of polyoxyalkylene dispersants include "AKM-0531," "AFB-1521," "SC-0505K," "SC-1015F," and "SC-0708A," as well as "HKM-50A," from the "Marialim" series manufactured by NOF Corporation.

[0212] An example of an acetylene-based dispersant is acetylene glycol. Examples of commercially available acetylene-based dispersants include "82," "104," "440," "465," and "485" from the "Surfynol" series manufactured by Air Products and Chemicals Inc., as well as "Olefin Y."

[0213] Examples of silicone-based dispersants include polyether-modified polydimethylsiloxane, polyether-modified siloxane, polyester-modified polydimethylsiloxane, etc. Examples of commercially available silicone-based dispersants include "BYK347" and "BYK348" manufactured by BYK-Chemie.

[0214] Examples of anionic dispersants include sodium polyacrylate, sodium dodecyl benzyl sulfonate, sodium laurate, polyoxyethylene alkyl ether ammonium sulfate, carboxymethyl cellulose sodium salt, etc. Examples of commercially available anionic dispersants include "PN-411" and "PA-111" manufactured by Ajinomoto Fine-Techno Co., Ltd., and "A-550" and "PS-1900" manufactured by Lion Corporation.

[0215] Examples of cationic dispersants include amino group-containing polyacrylate resins and amino group-containing polystyrene resins. Commercially available cationic dispersants include "161," "162," "164," "182," "2000," and "2001" manufactured by BYK-Chemie; "PB-821," "PB-822," and "PB-824" manufactured by Ajinomoto Fine-Techno Co., Ltd.; "V-216" and "V-220" manufactured by ISP Japan; and "Solsperse 13940," "Solsperse 24000," and "Solsperse 32000" manufactured by Lubrizol Corporation.

[0216] The dispersant (E) may be used alone or in combination of two or more.

[0217] The amount (mass%) of the (E) dispersant contained in the resin composition is preferably 0.01 mass% or more, more preferably 0.1 mass% or more, and particularly preferably 0.2 mass% or more, relative to 100 mass% of the non-volatile components of the resin composition, and is preferably 5 mass% or less, more preferably 3 mass% or less, and particularly preferably 2 mass% or less.

[0218] The amount (mass%) of the (E) dispersant contained in the resin composition is preferably 1 mass% or more, more preferably 5 mass% or more, and particularly preferably 10 mass% or more, relative to 100 mass% of the resin components of the resin composition, and is preferably 40 mass% or less, more preferably 30 mass% or less, and particularly preferably 20 mass% or less.

[0219] The resin composition may further contain an optional additive (F) in combination with the above-described components (A) to (E). The optional additive (F) as component (F) does not include those corresponding to the above-described components (A) to (E). Examples of the optional additive (F) include radical polymerizable compounds such as maleimide-based radical polymerizable compounds, vinylphenyl-based radical polymerizable compounds, (meth)acrylic-based radical polymerizable compounds, allyl-based radical polymerizable compounds, and polybutadiene-based radical polymerizable compounds; radical polymerization initiators such as peroxide-based radical polymerization initiators and azo-based radical polymerization initiators; inorganic fillers such as silica particles; organic fillers such as rubber particles; organometallic compounds such as organocopper compounds and organozinc compounds; polymerization inhibitors such as hydroquinone, catechol, pyrogallol, and phenothiazine; leveling agents such as silicone-based leveling agents and acrylic polymer-based leveling agents; thickeners such as bentone and montmorillonite; silicone-based defoamers, acrylic defoamers, and fluorine-containing compounds. Examples of the additives include antifoaming agents such as fluorine-based antifoaming agents and vinyl resin-based antifoaming agents; ultraviolet absorbers such as benzotriazole-based ultraviolet absorbers; adhesion improvers such as urea silanes; adhesion promoters such as triazole-based adhesion promoters, tetrazole-based adhesion promoters, and triazine-based adhesion promoters; antioxidants such as hindered phenol-based antioxidants; flame retardants such as phosphorus-based flame retardants (e.g., phosphate ester compounds, phosphazene compounds, phosphinic acid compounds, and red phosphorus), nitrogen-based flame retardants (e.g., melamine sulfate), halogen-based flame retardants, and inorganic flame retardants (e.g., antimony trioxide); and stabilizers such as borate-based stabilizers, titanate-based stabilizers, aluminate-based stabilizers, zirconate-based stabilizers, isocyanate-based stabilizers, carboxylic acid-based stabilizers, and carboxylic anhydride-based stabilizers. (F) Optional additives may be used singly or in combination of two or more.

[0220] The resin composition may further contain a (G) solvent as a volatile component in addition to the nonvolatile components (A) to (F) described above. The (G) solvent is typically an organic solvent. Examples of organic solvents include ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone; ether-based solvents such as tetrahydropyran, tetrahydrofuran, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, and diphenyl ether; alcohol-based solvents such as methanol, ethanol, propanol, butanol, and ethylene glycol; 2-ethoxyethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl diglycol acetate, γ-butyrolactone, and methyl methoxypropionate. Examples of the solvent include ether ester solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate; ether alcohol solvents such as 2-methoxypropanol, 2-methoxyethanol, 2-ethoxyethanol, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether (butyl carbitol); amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; sulfoxide solvents such as dimethyl sulfoxide; nitrile solvents such as acetonitrile and propionitrile; aliphatic hydrocarbon solvents such as hexane, cyclopentane, cyclohexane, and methylcyclohexane; and aromatic hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, and trimethylbenzene. The (G) solvent may be used singly or in combination of two or more.

[0221] The amount of (G) solvent is preferably set so as to adjust the melt viscosity of the resin composition or the resin composition layer containing the resin composition within an appropriate range. From the viewpoint of effectively suppressing the formation of voids, it is preferable that the amount of solvent in the resin composition contained in the resin composition layer is small. The amount (mass %) of (G) solvent relative to 100 mass % of the resin composition is preferably 5% or less, more preferably 3% or less, particularly preferably 1% or less, and ideally 0%. In other words, the resin composition may not contain (G) solvent. The amount of solvent contained in the resin composition can be measured by the method described in <Test Example 1: Measurement of the amount of remaining solvent in a resin composition> in the Examples below.

[0222] The resin composition contained in the resin composition layer typically has a high minimum melt viscosity. The minimum melt viscosity of the resin composition can range, for example, from 5,000 poise or more, from 7,500 poise or more, to 10,000 poise or more. Resin compositions containing (A) magnetic powder typically have a high minimum melt viscosity, as described above, making smooth filling of the first through-holes generally difficult. However, according to the method of the above-described embodiment, even when using a resin composition with such a high minimum melt viscosity, filling of the first through-holes with the resin composition can be achieved. From the viewpoint of smooth filling, the upper limit of the minimum melt viscosity of the resin composition is preferably 50,000 poise or less, more preferably 45,000 poise or less, and particularly preferably 40,000 poise or less. The minimum melt viscosity of the resin composition can be measured in a temperature range from 60°C to 160°C. Specifically, the minimum melt viscosity of the resin composition can be measured by the method described in <Test Example 2: Measurement of Minimum Melt Viscosity of Resin Composition> in the Examples section below.

[0223] A cured product can be obtained by curing the resin composition. For example, a resin composition containing a thermosetting resin (B) can be thermally cured to form a cured product. Among the components contained in the resin composition, volatile components such as the solvent (G) can usually be volatilized by the heat during curing, but nonvolatile components such as components (A) to (F) do not volatilize by the heat during curing. Therefore, a cured product of the resin composition can contain the nonvolatile components of the resin composition or their reaction products.

[0224] A cured product of the resin composition can have excellent magnetic properties. Therefore, a cured layer containing the cured product can also have excellent magnetic properties. In a preferred embodiment, the cured product of the resin composition and the cured layer containing the cured product can have high relative magnetic permeability and low magnetic loss.

[0225] For example, the relative magnetic permeability (μ') of the cured product of the resin composition is preferably in the range of 5 or more, more preferably 7 or more, even more preferably 9 or more, and particularly preferably 11 or more. There is no particular upper limit, and it can be, for example, 30 or less. The relative magnetic permeability of the cured product can be measured using a three-turn coil method under conditions of a measurement frequency of 20 MHz and a room temperature of 23°C. Specifically, the relative magnetic permeability of the cured product of the resin composition can be measured by the method described in <Test Example 3: Measurement of relative magnetic permeability and loss factor of cured product of resin composition> in the Examples below.

[0226] For example, the magnetic loss (μ'') of the cured product of the resin composition is preferably in the range of 0.10 or less, more preferably 0.08 or less, even more preferably 0.06 or less, and particularly preferably 0.05 or less. The lower limit is ideally 0.00 or more, but is usually 0.01 or more. The magnetic loss of the cured product can be measured using a 3-turn coil method under conditions of a measurement frequency of 20 MHz and a room temperature of 23°C. Specifically, the magnetic loss of the cured product of the resin composition can be measured by the method described in <Test Example 3: Measurement of relative permeability and loss factor of cured product of resin composition> in the Examples below.

[0227] The thickness of the resin composition layer is preferably thin, although this depends on the thickness of the core substrate and the dimensions of the first through-holes. Even when a resin composition layer is used that is so thin that it would be impossible to fill the first through-holes using conventional methods, the method according to the above-described embodiment allows the first through-holes to be filled with the resin composition contained in the resin composition layer. For example, the thickness of the resin composition layer provided in the resin sheet can be smaller than the depth of the first through-holes, and may even be less than half the depth of the first through-holes. In a preferred embodiment, the thickness of the resin composition layer is preferably 5 μm or more, more preferably 10 μm or more, particularly preferably 50 μm or more, and preferably 600 μm or less, more preferably 300 μm or less, even more preferably 200 μm or less, and particularly preferably 150 μm or less.

[0228] The resin sheet may further include an optional member, if necessary. An example of the optional member is a protective film provided on the surface of the resin composition layer that is not bonded to the support (i.e., the surface opposite the support). The thickness of the protective film is not particularly limited, but is, for example, 1 μm to 40 μm. When a protective film is provided, adhesion of dust and scratches to the surface of the resin composition layer can be suppressed. When a resin sheet including a protective film is used, the protective film is usually peeled off before step (I).

[0229] The resin sheet may be a single sheet or a long sheet. Unless otherwise specified, a "long sheet" refers to a sheet having a length 10 times or more the width. The length is preferably 20 times or more the width, and specifically may be long enough to be wound into a roll for storage or transportation. There is no particular upper limit to the length, and it may be, for example, 100,000 times or less the width.

[0230] The resin sheet can be produced, for example, by a method including forming a resin composition layer on a support. The resin composition layer can be formed, for example, by a method including preparing a resin composition and applying the resin composition onto a support.

[0231] The resin composition can be produced, for example, by mixing the above-mentioned components. Some or all of the above-mentioned components may be mixed simultaneously, or they may be mixed sequentially. In the process of mixing each component, the temperature may be appropriately set, and thus heating and / or cooling may be performed temporarily or throughout. Furthermore, stirring or shaking may be performed in the process of mixing each component.

[0232] To improve application properties, the resin composition to be applied is preferably prepared as a liquid resin varnish. If the resin composition is not liquid, the non-volatile components of the resin composition may be mixed with a solvent to obtain the resin varnish as needed. For example, the resin composition may be formed by a method that includes, in this order, mixing the non-volatile components of the resin composition with a solvent to prepare a resin varnish, applying the resin varnish to a support surface, and drying the applied resin varnish. The solvent (G) described above may be used as the solvent.

[0233] Coating can be carried out using a coating device such as a die coater. Drying can be carried out by a drying method such as heating or hot air blowing. The drying conditions are not particularly limited, but drying is carried out until the amount of solvent in the resin composition layer falls within the above-mentioned range. Although this may vary depending on the boiling point of the solvent in the resin varnish, drying can be carried out, for example, at 50°C to 150°C for 3 to 10 minutes. [Example]

[0234] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following description, "parts" and "%" representing amounts mean "parts by mass" and "% by mass", respectively, unless otherwise specified. Furthermore, unless otherwise specified, the operations described below were carried out at room temperature and atmospheric pressure (23°C, 1 atmosphere). In the following description, "MEK" stands for methyl ethyl ketone, unless otherwise specified.

[0235] <Production Example 1: Production of Resin Sheet> Epoxy resin ("ZX-1059", a mixture of bisphenol A epoxy resin and bisphenol F epoxy resin, manufactured by Nippon Steel Chemical & Material Co., Ltd., epoxy equivalent 169 g / eq., specific gravity 1.18 g / cm 3 ) 1.6 parts by mass, triazine skeleton-containing phenolic resin (DIC Corporation "LA-7054", hydroxyl group equivalent weight approximately 125 g / eq., MEK solution of 60% solids, specific gravity of solids 1.31 g / cm 3 ) 1.9 parts by mass, phenoxy resin (Mitsubishi Chemical Corporation "YX7553BH30", a 1:1 solution of MEK and cyclohexanone with a solid content of 30%, specific gravity of the solid content 1.18 g / cm 3 ) 1.6 parts by mass, dispersant ("ED-152", polyether phosphate ester, manufactured by Kusumoto Chemicals Co., Ltd., specific gravity 1.00 g / cm 3 ) 0.7 parts by mass, solvent (cyclohexanone) 3.5 parts by mass, imidazole curing accelerator ("2E4MZ", 2-ethyl-4-methylimidazole, manufactured by Shikoku Chemicals Corporation, specific gravity 0.97 g / cm 3 ) 0.01 mass parts, magnetic powder ("M03S", Fe-Mn ferrite, average particle size 0.5 μm, specific gravity 5.1 m 2 / g, manufactured by Powder Tech Co., Ltd.) 20 parts by mass, and magnetic powder ("AKT-PB" manufactured by Mitsubishi Steel Corporation, Fe-Ni alloy, average particle size 5.0 μm, specific gravity 8.1 m 2 56 parts by mass of each of these components (1 / g) were mixed to prepare a magnetic varnish.

[0236] A PET film ("Lumirror R80" manufactured by Toray Industries, Inc., thickness 38 μm, softening point 130°C, hereinafter sometimes referred to as "release PET") that had been release-treated with an alkyd resin-based release agent ("AL-5" manufactured by Lintec Corporation) was prepared. The magnetic varnish was applied to this release PET using a die coater so that the thickness of the resin composition layer after drying would be 100 μm, and the film was dried at 65°C to 120°C (average 100°C) for 6 minutes to obtain a resin sheet.

[0237] <Test Example 1: Measurement of the amount of remaining solvent in a resin composition> The resin sheet was cut into a 10 cm square to obtain a sheet piece. The mass W of this sheet piece (before drying) A was measured. Next, the sheet pieces cut into 10 cm squares were dried at 130° C. for 15 minutes. The mass W of the sheet pieces after drying was B was measured. Finally, the release PET used as the support for the resin sheet was cut into 10 cm squares, and its mass W C was measured. The amount of residual solvent in the resin composition is determined by the measured mass W A , W B and W C was calculated by applying it to the following equation 1. Residual solvent amount (%) = (W A -W B ) / (W A -W C )×100 (Equation 1) As a result of measurement, the amount of remaining solvent was 0.5%.

[0238] <Test Example 2: Measurement of minimum melt viscosity of resin composition> The release PET film was peeled off from the resin sheet to obtain a resin composition layer. The resin composition layer was compressed in a mold to produce measurement pellets (18 mm diameter, 3.4 g to 3.6 g). The dynamic viscoelastic modulus was measured for 1 g of the measurement pellets, with the temperature rising from a starting temperature of 60°C to 160°C at a heating rate of 5°C / min, and the minimum melt viscosity (poise) was calculated. The dynamic viscoelastic modulus was measured using a dynamic viscoelasticity measuring device (Rheosol-G3000 manufactured by UBM) and 18 mm diameter parallel plates under the following measurement conditions: a temperature interval of 2.5°C, a frequency of 1 Hz, and a strain of 1 deg. The measurement results showed that the minimum melt viscosity of the resin composition was 12,000 poise.

[0239] <Test Example 3: Measurement of relative magnetic permeability and loss factor of cured resin composition> The resin sheet was cut into 200 mm square pieces. The cut resin sheet (200 mm square) was laminated onto one side of a polyimide film (Ube Industries, Ltd., Upilex 25S, 25 μm thick, 240 mm square) using a batch-type vacuum pressure laminator (Nikko Materials Co., Ltd., two-stage build-up laminator, CVP700). This lamination was performed so that the resin composition layer of the resin sheet was in contact with the center of one smooth side of the polyimide film. This lamination was also performed by reducing the pressure to 13 hPa or less for 30 seconds, followed by pressure bonding at 100°C and a pressure of 0.74 MPa for 30 seconds. This lamination resulted in an intermediate laminate comprising a resin composition layer and a polyimide film.

[0240] The obtained intermediate laminate was heated at 190°C for 90 minutes to thermally cure the resin composition layer, and the polyimide film was peeled off to obtain a sheet-like cured product. The obtained sheet-like cured product was cut into an evaluation sample with a width of 5 mm and a length of 18 mm. The evaluation sample was measured for relative permeability (μ') and magnetic loss (μ'') using a measuring device (Agilent Technologies, "HP8362B") by the 3-turn coil method at a measurement frequency of 20 MHz and a room temperature of 23°C. The loss factor (μ'') was calculated using the loss factor (tanδ) according to the formula "tanδ = μ'' / μ'". The measurement results showed that the relative permeability (μ') was 20 and the magnetic loss (μ'') was 0.016.

[0241] [Example 1] (1) Preparing the core board: A core substrate was prepared by drilling through holes in a glass cloth-based epoxy resin double-sided copper-clad laminate (copper foil thickness 18 μm, substrate thickness 0.8 mm, Panasonic R1515A). The through holes were cylindrical, with a diameter of 350 μm and a spacing of 100 μm between them.

[0242] (2) Filling holes in the resin sheet: A batch-type vacuum pressure laminator (Nikko Materials Co., Ltd., two-stage build-up laminator, CVP700) was prepared. This laminator had a first chamber for crimping and a second chamber for heat pressing. The first chamber had a first stage (rubber press stage) that could apply pressure to the sample using a flat plate with a rubber sheet on its surface as an elastic member. The second chamber had a second stage (SUS press stage) that could apply pressure to the sample using a stainless steel flat plate (rigid plate).

[0243] A 200 mm square resin sheet piece was cut from the resin sheet produced in Production Example 1. The obtained resin sheet piece was placed on both sides of a core substrate so that the resin composition layer of the resin sheet was in contact with the center of the core substrate, thereby obtaining a sample laminate having a layer structure of resin sheet piece / core substrate / resin sheet piece. Using the batch-type vacuum pressure laminator described above, the resin composition was filled into the through-holes of the core substrate in the following manner.

[0244] Specifically, the sample laminate was fed to the first stage of the laminator, and the closed space containing the sample laminate in the first stage was decompressed for 30 seconds to a pressure of 1.3 kPa or less, and then the sample laminate was heated at 100°C under a pressure of 15 kgf / cm. 2 The pressure (degree of vacuum) in the closed space during pressurization in the first stage was 0.1 kPa.

[0245] Next, the sample stack was moved to the second stage, and the closed space containing the sample stack on the second stage was depressurized for 30 seconds to a pressure of 1.3 kPa or less, and then the sample stack was heated at 100°C under a pressure of 15 kgf / cm. 2 The pressure (vacuum level) in the closed space during the second stage of pressurization was 0.1 kPa.

[0246] (3) Thermal curing of the resin composition: The sample laminate was removed from the laminator, and the release PET film on the resin sheet was peeled off.The resin composition was then cured at 130°C for 30 minutes, followed by 180°C for 30 minutes, to obtain a magnetic substrate.

[0247] [Example 2] The resin composition was filled into the through-holes of the core substrate using only the second stage of the batch-type vacuum pressure laminator, without using the first stage. A magnetic substrate was obtained by carrying out the same operations as in Example 1, except for the above.

[0248] [Example 3] The pressure application conditions using the second stage of the batch-type vacuum pressure laminator were changed to a temperature of 140° C. and a time of 60 seconds. A magnetic substrate was obtained by carrying out the same operations as in Example 2 except for the above.

[0249] [Comparative Example 1] When applying pressure using the second stage of the batch-type vacuum pressure laminator, the closed space of the second stage was not depressurized. Therefore, the pressure application using the second stage was performed in an atmospheric pressure environment. A magnetic substrate was obtained by performing the same operations as in Example 1, except for the above points.

[0250] Comparative Example 2 The resin composition was filled into the through-holes of the core substrate using only the first stage of the batch-type vacuum pressure laminator, without using the second stage. A magnetic substrate was obtained by carrying out the same operations as in Example 1, except for the above.

[0251] Comparative Example 3 A 200 mm square resin sheet piece was cut from the resin sheet produced in Production Example 1. The obtained resin sheet piece was placed on both sides of a core substrate so that the resin composition layer of the resin sheet was in contact with the center of the core substrate. Furthermore, a release film ("Aflex 50N NT" manufactured by AGC Corporation), cushion paper ("AACP-9N" manufactured by Awa Paper Co., Ltd.), and a SUS plate (1 mm thick) were placed on the resin sheet in this order so as to cover the entire resin sheet, thereby obtaining a sample laminate having a layer structure of SUS plate / cushion paper / release film / resin sheet / core substrate / resin sheet / release film / cushion paper / SUS plate.

[0252] The sample laminate was placed in a thermoforming press (Kitagawa Seiki Co., Ltd., KVHC). The pressure inside the press was reduced and the temperature was maintained at 100°C and a pressure of 15 kgf / cm. 2 The pressure inside the press during the heat pressing was 2 kPa.

[0253] The sample laminate was removed from the press, and the SUS plate, cushion paper, release film, and release PET resin sheet were peeled off. The resin composition was then cured at 130°C for 30 minutes, followed by 180°C for 30 minutes, to obtain a magnetic substrate.

[0254] <Test Example 4: Confirmation of filling ability> The cross section of the magnetic substrate was observed. Specifically, the magnetic substrate was cut out so that a cross section parallel to the thickness direction of the magnetic substrate and passing through the center of the through-hole was revealed. This cross section was observed using a digital microscope (Keyence Corporation, "VHX-7000"). From the observed image, the presence or absence of gaps (unfilled areas) and voids in the through-holes where no cured material was present was confirmed. The observation was carried out on 10 randomly selected through-holes. The observation results were evaluated according to the following criteria. ◯: There are no voids in the through-holes, and the through-holes are completely filled with the cured material. △: The through-holes are completely filled with the cured product, but voids are present. ×: A part of the through-hole is not filled with the cured material, and there is an unfilled part in the through-hole.

[0255] [result] The results of the above-mentioned Examples and Comparative Examples are shown in the table below.

[0256] [Table 1] [Explanation of symbols]

[0257] 1. Laminator 2. Laminator 10 Core Board 10D main surface 10U main surface 11 First through hole 20 Resin sheet 21 Support 22 Resin composition layer 30 Resin sheet 31 Support 32 Resin composition layer 40 Magnetic substrate 41 Filled cured material layer 41D side 41U side 42 Adhesive cured material layer 43 Adhesive cured material layer 44 Second through hole 51 Conductor layer 52 Conductor layer 53 Conductor layer 100 stage (heat press stage) 110 Lower press material 111 Lower support material 111U support surface 112 Lower Plate 112U Pressure surface 113 Lower frame material 114 Heater 115 Fixed frame 116 Working frame 117 Elastic support part 120 Upper press material 121 Upper support material 121D Support surface 122 Upper Plate 122D Pressure surface 123 Upper frame material 124 Heater 125 nozzles 130 Hydraulic Cylinder 131 Piston rod 200 stage (crimping stage) 210 Lower press material 211 Lower support material 211U support surface 212 Lower Plate 212U Pressure surface 213 Lower frame material 214 Heater 215 Fixed frame part 216 Working Frame 217 Elastic support part 220 Upper press material 221 Upper support material 221D Support surface 222 Upper Plate 222D Pressure surface 223 Upper frame material 224 Heater 225 nozzle 230 Hydraulic Cylinder 231 Piston rod

Claims

1. A manufacturing method for manufacturing a magnetic substrate using a resin sheet including a support and a resin composition layer formed on the support; the resin composition layer contains a resin composition containing magnetic powder; The manufacturing method comprises: Step (I) of placing a resin sheet on a core substrate having through holes formed therein; and (II) pressing the resin sheet with a rigid plate to fill the through-holes with the resin composition; The method for producing a magnetic substrate, wherein the step (II) comprises applying pressure so that the rigid plate contacts the resin sheet under heating conditions of 80°C or higher and 160°C or lower at a vacuum degree of 1.3 kPa or lower.

2. Step (I) includes disposing resin sheets on both sides of a core substrate; The method for producing a magnetic substrate according to claim 1 , wherein step (II) comprises pressing the resin sheets placed on both sides of the core substrate with rigid plates.

3. The pressure in step (II) is 5 kgf / cm ２ The method for producing a magnetic substrate according to claim 1, wherein the method is carried out under the above pressure conditions.

4. The method for producing a magnetic substrate according to claim 1 , further comprising, after step (II), step (III) of curing the resin composition.

5. The method for producing a magnetic substrate according to claim 4, further comprising, after step (III), a step (IV) of polishing the cured resin composition.

6. Step (III) includes forming a cured product layer containing a cured product of the resin composition in the through-hole; The method for producing a magnetic substrate according to claim 4 , further comprising, after step (III), a step (V) of forming a through-hole in the cured material layer in the through-hole.

7. The method for producing a magnetic substrate according to claim 4 , further comprising, after step (III), step (VI) of forming a conductor layer.

8. 2. The method for producing a magnetic substrate according to claim 1, wherein the amount of the magnetic powder is 65% by volume or more relative to 100% by volume of the nonvolatile components of the resin composition.

9. The method for manufacturing a magnetic substrate according to claim 1 , wherein the resin composition layer provided on the resin sheet has a thickness of 150 μm or less.

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