Magnetic paste

Abstract

The present invention provides a magnetic paste and the like, which has low viscosity even when containing a magnetic powder, and which can provide a cured product having excellent mechanical strength. The present invention provides a magnetic paste, which contains (A) a magnetic powder, (B) an epoxy resin, (C) a dispersant, and (D) a curing agent, wherein the (C) component has a polyester skeleton represented by General Formula (1) below. In General Formula (1), R each independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer of 2 to 1000.

Description

Technical Field

[0001] This invention relates to magnetic pastes, resin compositions, cured products using the magnetic pastes or resin compositions, circuit boards, and sensor components. Background Technology

[0002] With the increasing demand for miniaturization and thinning of electronic devices in recent years, there is also a need for miniaturization and high-density wiring in circuit boards used in electronic devices. As such circuit boards, circuit boards formed by filling through-holes with a paste-like material are known.

[0003] For example, in Patent Document 1, a filling resin containing magnetic particles such as iron oxide (III) and cobalt iron oxide is described as being used as a resin for filling through holes in a circuit board for filling sensor components.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent document 1: Japanese Patent Application Publication No. 2016-197624. Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] To improve the relative magnetic permeability of cured magnetic pastes such as the filled resin described in Patent Document 1, a method of containing magnetic powder in the filled resin has been considered. However, if the magnetic paste contains magnetic powder, the viscosity of the magnetic paste sometimes increases, and the printability of the magnetic paste deteriorates. In particular, as with the filled resin described in Patent Document 1, when using a paste containing a large amount of magnetic powder, the viscosity of the paste increases significantly, resulting in even worse printability.

[0009] The present invention was made in view of the above circumstances, and its object is to provide a magnetic paste, a resin composition that can produce a cured product with relatively high magnetic permeability and excellent printability, as well as a cured product, circuit board, and sensor component using the magnetic paste or resin composition.

[0010] Means for solving technical problems

[0011] In order to achieve the above objectives, the inventors conducted in-depth research and found that by using a magnetic paste containing a dispersant with a polyester backbone, the viscosity of the paste can be reduced and the printability improved, while the relative magnetic permeability of the cured product can also be increased, thus completing the present invention.

[0012] That is, the present invention includes the following:

[0013] [1] A magnetic paste comprising (A) magnetic powder, (B) epoxy resin, (C) dispersant and (D) curing agent, wherein component (C) has a polyester backbone as shown in the following general formula (1).

[0014] [Chemical Formula 1]

[0015]

[0016] In general formula (1), R independently represents a divalent hydrocarbon group with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000;

[0017] [2] According to the magnetic paste described in [1], when the non-volatile component in the magnetic paste is set to 100% by mass, the content of component (C) is 0.1% by mass or more and 5% by mass or less;

[0018] [3] The magnetic paste according to [1] or [2], wherein component (A) comprises:

[0019] (A-1) Magnetic powder with an average particle size of 1 μm or more, and (A-2) Magnetic powder with an average particle size of less than 1 μm;

[0020] [4] The magnetic paste according to any one of [1] to [3], wherein component (A) comprises:

[0021] (A-1) Magnetic powder with an average particle size of 1 μm or more and 10 μm or less, and (A-2) Magnetic powder with an average particle size of 0.005 μm or more and less than 1 μm;

[0022] [5] The magnetic paste according to any one of [1] to [4], wherein (A) component is at least one selected from iron oxide powder and ferroalloy metal powder;

[0023] [6] The magnetic paste according to any one of [1] to [5], wherein (A) component comprises iron oxide powder, which comprises: ferrite containing at least one element selected from Ni, Cu, Mn and Zn;

[0024] [7] The magnetic paste according to any one of [1] to [6], wherein when the non-volatile component in the magnetic paste is set to 100% by mass, the content of component (A) is 70% by mass or more and 98% by mass or less;

[0025] [8] The magnetic paste according to any one of [1] to [7] is used to fill through holes;

[0026] [9] A cured product, which is a cured product of any one of [1] to [8] magnetic paste;

[0027]

[10] A circuit board having:

[0028] Substrate with through holes, and

[0029] A cured product of any one of the magnetic pastes [1] to [8] filled in the through-hole;

[0030]

[11] A resin composition comprising (A) magnetic powder, (B) epoxy resin, (C) dispersant and (D) curing agent.

[0031] Component (C) has a polyester skeleton as shown in the following general formula (1).

[0032] [Chemical Formula 2]

[0033]

[0034] In general formula (1), R independently represents a divalent hydrocarbon group with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000;

[0035]

[12] A cured product, which is a cured product of the resin composition described in

[11] ;

[0036]

[13] A circuit board having:

[0037] Substrate with through holes, and

[0038] The cured resin composition of

[12] filled in the through-hole;

[0039]

[14] A sensor component comprising the circuit board described in

[10] or

[13] .

[0040] Invention Effects

[0041] According to the present invention, it is possible to provide magnetic pastes and resin compositions that yield cured products with relatively high magnetic permeability and excellent printability, as well as cured products, circuit boards, and sensor components using the magnetic pastes or resin compositions. Attached Figure Description

[0042] Figure 1 This is a schematic cross-sectional view of a core substrate as an example of a method for manufacturing a circuit board according to the first embodiment.

[0043] Figure 2 This is a schematic cross-sectional view of a core substrate with through holes, which is an example of a method for manufacturing a circuit board according to the first embodiment.

[0044] Figure 3This is a schematic cross-sectional view showing a core substrate with a plating layer formed in the through-holes, as an example of a method for manufacturing a circuit board according to the first embodiment.

[0045] Figure 4 This is a schematic cross-sectional view showing the appearance of a core substrate with magnetic paste filled in the through holes, as an example of a method for manufacturing a circuit board according to the first embodiment.

[0046] Figure 5 This is a schematic cross-sectional view showing the appearance of a core substrate after thermal curing of the filled magnetic paste, as an example of a method for manufacturing a circuit board according to the first embodiment.

[0047] Figure 6 This is a schematic cross-sectional view showing the appearance of the core substrate after polishing and curing, as an example of the circuit board manufacturing method of the first embodiment.

[0048] Figure 7 This is a schematic cross-sectional view showing a core substrate with a conductor layer formed on a polished surface, as an example of a method for manufacturing a circuit board according to the first embodiment.

[0049] Figure 8 This is a schematic cross-sectional view showing the appearance of a core substrate with a patterned conductor layer as an example of a method for manufacturing a circuit board according to the first embodiment.

[0050] Figure 9 This is a schematic cross-sectional view used to explain step (A) included in an example of a method for manufacturing a circuit board as a second embodiment.

[0051] Figure 10 This is a schematic cross-sectional view used to explain step (A) included in an example of a method for manufacturing a circuit board as a second embodiment.

[0052] Figure 11 This is a schematic cross-sectional view used to explain step (B) included in an example of a method for manufacturing a circuit board as a second embodiment.

[0053] Figure 12 This is a schematic cross-sectional view used to explain step (D) included in an example of a method for manufacturing a circuit board as a second embodiment.

[0054] Figure 13 This is a schematic top view of a sensor component including a circuit board obtained by the manufacturing method of the circuit board of the second embodiment, as an example, viewed from one side in the thickness direction of the sensor component.

[0055] Figure 14This is a schematic diagram showing, as an example, the cut end face of the sensor component of the circuit board obtained by the circuit board manufacturing method of the second embodiment, which is cut at the position shown by the dotted line II-II.

[0056] Figure 15 This is a schematic top view used to illustrate the configuration of the first conductor layer in a sensor component comprising a circuit board obtained by the manufacturing method of the circuit board of the second embodiment, as an example. Detailed Implementation

[0057] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the drawings only schematically illustrate the shape, size, and arrangement of the constituent elements to the extent that the invention can be understood. The present invention is not limited to the following description, and the constituent elements may be suitably modified. In the drawings used in the following description, the same reference numerals are sometimes used to denote the same constituent elements, and repeated descriptions are omitted. Furthermore, the configurations involved in the embodiments of the present invention are not necessarily manufactured or used according to the configurations shown in the drawings.

[0058] [Magnetic paste]

[0059] The magnetic paste of the present invention comprises (A) magnetic powder, (B) epoxy resin, (C) dispersant and (D) curing agent, wherein component (C) has a polyester backbone as shown in the following general formula (1).

[0060] [Chemical Formula 3]

[0061]

[0062] In general formula (1), R independently represents a hydrocarbon group with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.

[0063] In this invention, by including a (C) dispersant, the viscosity of the magnetic paste is reduced, resulting in excellent printability. Furthermore, the mechanical strength of the cured paste is generally improved. Additionally, the cured magnetic paste typically exhibits increased relative permeability and reduced magnetic loss in the frequency range of 10–200 MHz.

[0064] The magnetic paste may further contain (E) other additives as needed. The components contained in the magnetic paste of the present invention will be described in detail below.

[0065] <(A) Magnetic Powder>

[0066] The magnetic paste contains (A) magnetic powder as component (A). Magnetic powder (A) can be used alone or in combination with two or more types. Examples of magnetic powder (A) include: pure iron powder; Mg-Zn ferrite, Fe-Mn ferrite, Mn-Zn ferrite, Mn-Mg ferrite, Cu-Zn ferrite, Mg-Mn-Sr ferrite, Ni-Zn ferrite, Ba-Zn ferrite, Ba-Mg ferrite, Ba-Ni ferrite, Ba-Co ferrite, Ba-Ni-Co ferrite, Y-based ferrite, iron oxide powder (III), and iron(III) oxide, etc. Iron-containing powders; Fe-Si alloy powders, Fe-Si-Al alloy powders, Fe-Cr alloy powders, Fe-Cr-Si alloy powders, Fe-Ni-Cr alloy powders, Fe-Cr-Al alloy powders, Fe-Ni alloy powders, Fe-Ni-Mo alloy powders, Fe-Ni-Mo-Cu alloy powders, Fe-Co alloy powders, or Fe-Ni-Co alloy powders, etc., are all ferroalloy metal powders; Co-based amorphous alloys and other amorphous alloys.

[0067] Of which, (A) the magnetic powder is preferably selected from at least one of iron oxide powder and ferroalloy metal powder. As the iron oxide powder, it is preferably a ferrite containing at least one element selected from Ni, Cu, Mn, and Zn, and more preferably a ferrite containing Mn. Furthermore, as the ferroalloy metal powder, it is preferably a ferroalloy metal powder containing at least one element selected from Si, Cr, Al, Ni, and Co.

[0068] As for (A) the magnetic powder, commercially available magnetic powders can be used. Specific examples of commercially available magnetic powders that can be used include: Powder-Tech's "M05S" and "M001"; Sanyo Special Steel's "PST-S"; EPSONATMIX's "AW2-08", "AW2-08PF20F", "AW2-08PF10F", "AW2-08PF3F", "Fe-3.5Si-4.5CrPF20F", "Fe-50NiPF20F", and "Fe-80Ni-4MoPF20F"; and JFE Chemical's "LD-M", "LD-MH", "KNI-106", "KNI-106GSM", "KNI-106GS", and "KNI-109". The following are examples of magnetic powders: "KNI-109GSM", "KNI-109GS"; "KNS-415", "BSF-547", "BSF-029", "BSN-125", "BSN-125", "BSN-714", "BSN-828", "S-1281", "S-1641", "S-1651", "S-1470", "S-1511", "S-2430" manufactured by Toda Kogyo Co., Ltd.; "JR09P2" manufactured by Nippon Heavy Chemical Industry Co., Ltd.; "Nanotek" manufactured by CIK NanoTEK Co., Ltd.; "JEMK-S" and "JEMK-H" manufactured by KinseiMatec Co., Ltd.; and "Yttrium iron oxide" manufactured by ALDRICH Co., Ltd. As for (A) magnetic powders, one type can be used alone, but from the viewpoint of significantly obtaining the effects of the present invention, it is preferable to use two or more types together.

[0069] (A) The magnetic powder is preferably spherical. The aspect ratio (length-to-width ratio) obtained by dividing the length of the major axis of the magnetic powder by the length of the minor axis is preferably 2 or less, more preferably 1.5 or less, and even more preferably 1.2 or less. Generally speaking, it is easier to improve the relative permeability if the magnetic powder is flat rather than spherical. However, from the viewpoint of reducing magnetic loss and obtaining a paste with a preferred viscosity, spherical magnetic powder is particularly preferred.

[0070] From the viewpoint of improving relative permeability, the average particle size of the magnetic powder (A) is preferably 0.01 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more. Furthermore, it is preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 8 μm or less. It should be noted that when using two or more types of magnetic powder (A), the overall average particle size of component (A) only needs to be within the above-mentioned range.

[0071] The average particle size of magnetic powder can be determined using laser diffraction-scattering based on the Mie scattering theory. Specifically, the particle size distribution of the magnetic powder can be prepared on a volume-based basis using a laser diffraction-scattering particle size distribution measuring device, and the median diameter can be set as the average particle size. The sample used for measurement is preferably a sample prepared by ultrasonically dispersing the magnetic powder in water. Suitable laser diffraction-scattering particle size distribution measuring devices include the "LA-500" manufactured by Horiba Corporation and the "SALD-2200" manufactured by Shimadzu Corporation.

[0072] From the perspective of improving relative permeability, (A) the specific surface area of ​​the magnetic powder is preferably 0.05 m². 2 / g or more, more preferably 0.1m 2 / g or more, more preferably 0.3m 2 / g or more. Furthermore, 10m is preferred. 2 / g or less, more preferably 8m 2 / g or less, more preferably 5m 2 / g or less. The specific surface area of ​​(A) magnetic powder can be determined by the BET method. It should be noted that, in the case of using two or more (A) magnetic powders, the overall specific surface area of ​​(A) component only needs to be within the above range.

[0073] From the viewpoint of improving relative permeability, (A) the magnetic powder preferably includes: (A-1) magnetic powder with an average particle size of 1 μm or more, and (A-2) magnetic powder with an average particle size of less than 1 μm.

[0074] (A-1) The magnetic powder with an average particle size of 1 μm or more has an average particle size of 1 μm or more, preferably 1.2 μm or more, and more preferably 1.5 μm or more. (A-1) The upper limit of the average particle size of the component is preferably 10 μm or less, more preferably 9 μm or less, and even more preferably 8 μm or less. The average particle size of the component (A-1) can be determined by the above method.

[0075] The specific surface area of ​​component (A-1) is preferably 0.01 m². 2 / g or more, more preferably 0.05m 2 / g or more, more preferably 0.1m 2 / g or more. Furthermore, 2m is preferred. 2 / g or less, more preferably 1.5m 2 / g or less, more preferably 1m 2 / g or less. The specific surface area of ​​component (A-1) can be determined by the above method.

[0076] (A-2) The magnetic powder with an average particle size of less than 1 μm has an average particle size of less than 1 μm, preferably less than 0.8 μm, and more preferably less than 0.5 μm. (A-2) The lower limit of the average particle size of the component is preferably 0.005 μm or more, more preferably 0.01 μm or more, and even more preferably 0.02 μm or more. (A-2) The average particle size of the component can be determined by the above method.

[0077] The preferred specific surface area of ​​component (A-2) is 1 m². 2 / g or more, preferably 2m 2 / g or more, preferably 3m 2 / g or more. Furthermore, 500m is preferred. 2 / g or less, more preferably 400m 2 / g or less, more preferably 300m 2 / g or less. The specific surface area of ​​component (A-2) can be determined by the above method.

[0078] As a suitable embodiment of component (A), it is preferable to include magnetic powder with an average particle size of 1 μm or more and 10 μm or less (A-1) and magnetic powder with an average particle size of 0.005 μm or more and less than 1 μm (A-2); more preferably, it includes magnetic powder with an average particle size of 1.2 μm or more and 9 μm or less (A-1) and magnetic powder with an average particle size of 0.01 μm or more and less than 0.8 μm (A-2); and even more preferably, it includes magnetic powder with an average particle size of 1.5 μm or more and 8 μm or less (A-1) and magnetic powder with an average particle size of 0.02 μm or more and less than 0.5 μm (A-2).

[0079] From the viewpoint of improving relative permeability and reducing loss coefficient, when the non-volatile component in the magnetic paste is set to 100% by volume, the content (by volume) of magnetic powder (A) is preferably 40% by volume or more, more preferably 50% by volume or more, and even more preferably 60% by volume or more. Furthermore, it is preferably 85% by volume or less, more preferably 80% by volume or less, and even more preferably 70% by volume or less.

[0080] From the viewpoint of improving relative permeability and reducing loss coefficient, when the non-volatile component in the magnetic paste is set to 100% by mass, the content (by mass%) of magnetic powder (A) is preferably 70% by mass or more, more preferably 75% by mass or more, and even more preferably 80% by mass or more. Furthermore, it is preferably 98% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less. It should be noted that, unless otherwise specified, the content of each component in the magnetic paste in this invention refers to the value when the non-volatile component in the magnetic paste is set to 100% by mass.

[0081] When component (A) includes components (A-1) and (A-2), from the viewpoint of improving relative permeability and reducing loss coefficient, when the non-volatile component in the magnetic paste is set to 100% by mass, the content (by mass%) of component (A-1) is preferably 65% ​​by mass or more, more preferably 70% by mass or more. Furthermore, it is preferably 98% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less.

[0082] When component (A) includes components (A-1) and (A-2), from the viewpoint of improving relative permeability and reducing loss coefficient, when the non-volatile component in the magnetic paste is set to 100% by mass, the content (by mass%) of component (A-2) is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. Furthermore, it is preferably 98% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less.

[0083] When the content of component (A-1) is set to 100% by mass in the magnetic paste, denoted as a1, and the content of component (A-2) is set to 100% by mass in the magnetic paste, denoted as a2, the ratio of a1 / a2 is preferably 10 or less, more preferably 8 or less, further preferably 5 or less, preferably 1 or more, more preferably 2 or more, and further preferably 3 or more. By adjusting the content of component (A) within the above-mentioned ranges for a1 / a2, the desired effect of the present invention can be obtained more significantly.

[0084] <(B) Epoxy Resin>

[0085] The magnetic paste contains epoxy resin as component (B). Examples of epoxy resins that can be classified as component (B) include: bisphenol A type epoxy resin; bisphenol F type epoxy resin; bisphenol S type epoxy resin; bisphenol AF type epoxy resin; dicyclopentadiene type epoxy resin; triphenol type epoxy resin; phenolnovolac type epoxy resin; tert-butylcatechol type epoxy resin; naphtholnovolac type epoxy resin; naphthalene type epoxy resin; naphthol type epoxy resin; anthracene type epoxy resin, etc. Epoxy resins with fused ring structures; glycidylamine type epoxy resins; glycidyl ester type epoxy resins; cresolnovolac type epoxy resins; biphenyl type epoxy resins; linear aliphatic epoxy resins; epoxy resins with butadiene structures; alicyclic epoxy resins; heterocyclic epoxy resins; epoxy resins containing spirocyclic rings; cyclohexanediol type epoxy resins; tris(hydroxymethyl) type epoxy resins; tetraphenylethane type epoxy resins; cyclic aliphatic diglycidyl ether type epoxy resins, etc. Epoxy resins can be used alone or in combination of two or more. (B) Preferably, the epoxy resin is selected from one or more of the following: cyclic aliphatic diglycidyl ether type epoxy resins, bisphenol A type epoxy resins, and bisphenol F type epoxy resins.

[0086] (B) The epoxy resin preferably comprises an epoxy resin having two or more epoxy groups in one molecule. Furthermore, (B) the epoxy resin preferably has an aromatic structure; when using two or more epoxy resins, at least one has an aromatic structure more preferably. An aromatic structure refers to a chemical structure generally defined as aromatic, and also includes polycyclic aromatics and aromatic heterocycles. The proportion of epoxy resin having two or more epoxy groups in one molecule is preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more, relative to 100% by mass of the non-volatile components of the epoxy resin.

[0087] Epoxy resins include liquid epoxy resins at 25°C (hereinafter sometimes referred to as "liquid epoxy resins") and solid epoxy resins at 25°C (hereinafter sometimes referred to as "solid epoxy resins"). In magnetic pastes, the epoxy resin (B) may consist only of liquid epoxy resin, only of solid epoxy resin, or a combination of both. From the viewpoint of reducing the viscosity of the magnetic paste, the presence of liquid epoxy resin is preferred.

[0088] As liquid epoxy resins, the preferred types are GLYCIROL type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AF type epoxy resin, naphthalene type epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, phenolic varnish type epoxy resin, alicyclic epoxy resin with an ester skeleton, cyclohexanediethanol type epoxy resin, cyclic aliphatic diglycidyl ether type epoxy resin, cyclic aliphatic glycidyl ether type epoxy resin, cyclic aliphatic glycidyl ether type epoxy resin, and epoxy resin with a butadiene structure. More preferably, the preferred types are bisphenol A type epoxy resin, bisphenol F type epoxy resin, cyclic aliphatic diglycidyl ether type epoxy resin, and cyclic aliphatic glycidyl ether type epoxy resin. Specific examples of liquid epoxy resins include: DIC's "HP4032", "HP4032D", and "HP4032SS" (naphthalene-type epoxy resin); Mitsubishi Chemical's "828US", "jER828EL" (bisphenol A type epoxy resin), "jER807" (bisphenol F type epoxy resin), and "jER152" (phenolic varnish type epoxy resin); Mitsubishi Chemical's "630" and "630LSD"; and ADEKA's "ED-523T" (GLYCIROL type epoxy resin (ADEKAGLYCIROL)) and "EP-3980S" (glycidylamine type epoxy resin). Epoxy resins such as "EP-4088S" (dicyclopentadiene type); "ZX1059" (a mixture of bisphenol A and bisphenol F type epoxy resins), "EX-201" (cyclic aliphatic glycidyl ether type epoxy resin), "ZX1658" and "ZX1658GS" (cyclic aliphatic diglycidyl ether type epoxy resins) manufactured by Nippon Steel Chemical & Materials Co., Ltd.; "EX-721" (glycidyl ester type epoxy resin) manufactured by Nagase ChemteX Co., Ltd.; and "Celloxide2021P" (alicyclic epoxy resin with an ester skeleton) and "PB-3600" (an epoxy resin with a butadiene structure) manufactured by Daicel Co., Ltd., etc., can be used individually or in combination of two or more.

[0089] As a solid epoxy resin, the preferred types are naphthalene-type tetrafunctional epoxy resin, cresol-phenolic varnish-type epoxy resin, dicyclopentadiene-type epoxy resin, triphenol-type epoxy resin, naphthol-type epoxy resin, biphenyl-type epoxy resin, naphthalene ether-type epoxy resin, anthracene-type epoxy resin, bisphenol A-type epoxy resin, and tetraphenylethane-type epoxy resin, and more preferably naphthalene-type tetrafunctional epoxy resin, naphthol-type epoxy resin, and biphenyl-type epoxy resin. Specific examples of solid epoxy resins include: DIC's "HP4032H" (naphthalene-type epoxy resin), "HP-4700", "HP-4710" (naphthalene-type tetrafunctional epoxy resin), "N-690" (cresol phenolic varnish type epoxy resin), "N-695" (cresol phenolic varnish type epoxy resin), "HP-7200", "HP-7200HH", "HP-7200H" (dicyclopentadiene type epoxy resin), "EXA-7311", "EXA-7311-G3", "EXA-7311-G4", "EXA-7311-G4S", and "HP6000" (naphthalene ether type epoxy resin); and Nippon Kayaku Co., Ltd.'s "EPPN-502H" (triphenol type epoxy resin), "NC7000L" (naphthalene phenolic varnish type epoxy resin), and "NC3" (naphthalene etheric varnish type epoxy resin). 000H, NC3000, NC3000L, NC3100 (biphenyl type epoxy resin); Nippon Steel Chemical & Materials Co., Ltd.'s "ESN475V" (naphthalene type epoxy resin) and "ESN485" (naphthalene phenolic varnish type epoxy resin); Mitsubishi Chemical Co., Ltd.'s "YX4000H", "YL6121" (biphenyl type epoxy resin), "YX4000HK" (bixylenol type epoxy resin), and "YX8800" (anthracite type epoxy resin); Osaka Gas Chemical Co., Ltd.'s "PG-100" and "CG-500"; Mitsubishi Chemical Co., Ltd.'s "YL7760" (bisphenol AF type epoxy resin), "YL7800" (fluorene type epoxy resin), "jER1010" (solid bisphenol A type epoxy resin), and "jER1031S" (tetraphenylethane type epoxy resin), etc. They can be used individually or in combination of two or more.

[0090] As for epoxy resin (B), when liquid epoxy resin and solid epoxy resin are used together, their mass ratio (liquid epoxy resin: solid epoxy resin) is preferably in the range of 1:0.1 to 1:4. By setting the mass ratio of liquid epoxy resin to solid epoxy resin within the above range, it is possible to obtain a cured product with sufficient tensile strength. From the viewpoint of the above effects, the mass ratio of liquid epoxy resin to solid epoxy resin (liquid epoxy resin: solid epoxy resin) is preferably in the range of 1:0.3 to 1:3.5, more preferably in the range of 1:0.6 to 1:3, and particularly preferably in the range of 1:0.8 to 1:2.5.

[0091] From the viewpoint of obtaining a magnetic layer exhibiting good mechanical strength, when the non-volatile component in the magnetic paste is set to 100% by mass, the content of epoxy resin (B) is preferably 1% by mass or more, more preferably 3% by mass or more, further preferably 5% by mass or more, and 10% by mass or more. The upper limit of the epoxy resin content is not particularly limited as long as the effects of the present invention can be achieved, but it is preferably 30% by mass or less, more preferably 25% by mass or less, and further preferably 20% by mass or less.

[0092] When the non-volatile component in the magnetic paste is set to 100% by volume, the content (B) of epoxy resin (by volume) is preferably 1% by volume or more, more preferably 3% by volume or more, and even more preferably 5% by volume or more. The upper limit is not particularly limited as long as the effect of the present invention can be achieved, but is preferably 25% by volume or less, more preferably 20% by volume or less, and even more preferably 15% by volume or less.

[0093] (B) The epoxy equivalent of the 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. Within this range, the crosslinking density of the cured product becomes sufficient, providing a magnetic layer with low surface roughness. It should be noted that the epoxy equivalent can be determined according to JIS K7236 and is the mass of resin containing 1 equivalent of epoxy groups.

[0094] (B) The weight-average molecular weight of the epoxy resin is preferably 100 to 5000, more preferably 250 to 3000, and even more preferably 400 to 1500. Here, the weight-average molecular weight of the epoxy resin is the weight-average molecular weight converted from polystyrene as determined by gel permeation chromatography (GPC).

[0095] <(C) Dispersant>

[0096] The magnetic paste contains (C) a dispersant having a polyester backbone as shown in the following general formula (1) as component (C);

[0097] [Chemical Formula 4]

[0098]

[0099] In general formula (1), R independently represents a divalent hydrocarbon group with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.

[0100] As mentioned above, the higher the content of (A) magnetic powder, the higher the viscosity of the magnetic paste, and consequently, the worse the mechanical strength of the cured magnetic paste. In this invention, the magnetic paste contains component (C) as a dispersant, thus reducing viscosity compared to a paste without component (C) (i.e., a paste with the same composition as the magnetic paste except for the absence of component (C)). Therefore, even with a high content of (A) magnetic powder, the increase in viscosity of the magnetic paste can be suppressed, further improving the mechanical strength of the cured magnetic paste.

[0101] (C) The component has the polyester backbone shown in general formula (1):

[0102] [Chemical Formula 5]

[0103]

[0104] In general formula (1), R independently represents a divalent hydrocarbon group with 2 to 10 carbon atoms, and n represents an integer from 2 to 1000.

[0105] In general formula (1), R represents a divalent hydrocarbon group having 2 to 10 carbon atoms. The hydrocarbon group has 2 or more carbon atoms, preferably 3 or more, and more preferably 4 or more. The upper limit for the number of carbon atoms is 10 or less, preferably 8 or less, and more preferably 6 or less. The hydrocarbon group can be any of the following: linear, branched, or cyclic, preferably linear or branched. Examples of hydrocarbon groups include aliphatic hydrocarbon groups and aromatic hydrocarbon groups, preferably aliphatic hydrocarbon groups. Specific examples of hydrocarbon groups include alkylene, alkenylene, ynylene, and arylene. From the viewpoint of significantly obtaining the effects of the present invention, the hydrocarbon group is preferably alkylene.

[0106] Examples of alkylene groups include: ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, and decylene. Examples of alkenylene groups include: vinylene, propenylene, butenylene, pentenylene, hexenylene, heptenylene, octylene, nonenylene, and decenylene. Examples of ynynylene groups include: ethynylene, propynylene, butynylene, pentyynylene, hexynylene, heptynylene, octyynylene, nonynylene, and decynylene. Examples of arylene groups include: phenylene and naphthylene. Preferably, R is butylene or pentylene.

[0107] In general formula (1), the divalent hydrocarbon group represented by R may or may not have substituents. There are no particular restrictions on substituents; examples include halogen atoms, -OH, and -OC. 1-6 Alkyl, -N(C) 1-10 Alkyl)2, C 1-10 Alkyl, C 6-10 Aryl, -NH2, -CN, -C(O)OC1-10 Alkyl groups, -COOH, -C(O)H, -NO2, etc. Here, the term "C" is used... p-q "(p and q are positive integers, satisfying p < q) indicates that the number of carbon atoms in the organic group immediately following the term is p to q. For example, "C 1-10 The term "alkyl" refers to alkyl groups with 1 to 10 carbon atoms. These substituents can bond with each other to form rings, and the ring structures include spirocyclic and fused rings.

[0108] The above-mentioned substituents may further have substituents (hereinafter, sometimes referred to as "secondary substituents"). Unless otherwise specified, the same substituents as the above-mentioned substituents may be used as secondary substituents.

[0109] In general formula (1), n ​​represents an integer from 2 to 1000. n is 2 or more, preferably 5 or more, more preferably 10 or more. The upper limit is 1000 or less, preferably 500 or less, more preferably 100 or less, or 50 or less.

[0110] Provided it does not impair the effects of the present invention, component (C) may contain any skeleton in addition to the polyester skeleton shown in general formula (1). Examples of arbitrary skeletons include polyester skeletons in general formula (1) where R is a divalent hydrocarbon group with 1 or more carbon atoms (n is the same as in formula (1)) and polyallylamine skeletons. For example, the ends of the polyester skeleton are not particularly limited.

[0111] Examples of the ends of component (C) include, for example, carboxylic acid residues, hydroxyl groups, hydrogen atoms, etc., as described later.

[0112] The (C) component having the polyester backbone shown in general formula (1) can be manufactured, for example, by reacting the lactone and carboxylic acid shown in general formula (2);

[0113] [Chemical Formula 6]

[0114]

[0115] In general formula (2), R 2 It is the same as R in general formula (1).

[0116] Examples of lactones represented by general formula (2) include ε-caprolactone, β-proprolactone, γ-butrolactone, δ-valerolactone, β-methyl-δ-valerolactone, 4-methylcaprolactone, 2-methylcaprolactone, etc.

[0117] Carboxylic acids can be used as initiators for the ring-opening polymerization of lactones represented by general formula (2). Examples of such carboxylic acids include ricinoleic acid, ricinoleic acid, 9- and 10-hydroxystearic acid, castor oil fatty acids, hydrogenated castor oil fatty acids, lactic acid, 12-hydroxystearic acid, glycolic acid, and other hydroxycarboxylic acids; dodecanoic acid, stearic acid, etc. Among these, hydroxycarboxylic acids are preferred from the viewpoint of significantly obtaining the effects of the present invention.

[0118] The reaction temperature is preferably 120–220°C, more preferably 160–210°C. Furthermore, the reaction time is preferably 0.5–72 hours. If the reaction is carried out under a nitrogen flow, a polyester with a high degree of polymerization can be obtained.

[0119] Furthermore, in the aforementioned reactions, polymerization catalysts or polymerization initiators may be used as needed, from the perspective of controlling the reaction.

[0120] Examples of polymerization catalysts include quaternary ammonium salts such as tetramethylammonium chloride, tetrabutylammonium chloride, tetramethylammonium bromide, tetrabutylammonium bromide, tetramethylammonium iodide, tetrabutylammonium iodide, benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, and benzyltrimethylammonium iodide; and tetramethylphosphonium chloride, tetrabutylphosphonium chloride, tetramethylphosphonium bromide, tetrabutylphosphonium bromide, tetramethylphosphonium iodide, tetrabutylphosphonium iodide, and benzyltrimethylammonium chloride. Quaternary phosphonium salts such as phosphonium chloride, benzyltrimethylphosphonium bromide, benzyltrimethylphosphonium iodide, tetraphenylphosphonium chloride, tetraphenylphosphonium bromide, and tetraphenylphosphonium iodide; phosphorus compounds such as triphenylphosphine; organic carboxylic acids such as potassium acetate, sodium acetate, potassium benzoate, and sodium benzoate; alkali metal alkoxides such as sodium alkoxide and potassium alkoxide; tertiary amines; organotin compounds; organoaluminum compounds; organotitanate compounds such as tetrabutyl titanate; zinc compounds such as zinc chloride; etc.

[0121] Examples of polymerization initiators include: aliphatic monocarboxylic acids such as acetic acid, propionic acid, caprylic acid, nonanoic acid, capric acid, octylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, isononanoic acid, and arachidic acid; aromatic monocarboxylic acids such as benzoic acid and p-butylbenzoic acid; and other monocarboxylic acids.

[0122] In the manufacture of component (C), any monomer other than the lactone and carboxylic acid shown in general formula (2) may be used, provided it does not impair the effects of the present invention. Examples of such monomers include polyallylamine. For instance, when polyallylamine is used as an arbitrary monomer, component (C) containing a polyallylamine backbone in addition to having a polyester backbone shown in general formula (1) can be manufactured. The reaction temperature and reaction time are the same as those used in the manufacture of component (C) having a polyester backbone shown in general formula (1).

[0123] Polyallylamine is obtained by polymerizing allylamine in the presence of a polymerization initiator and / or a chain transfer catalyst.

[0124] The polymerization initiator is not particularly limited, and examples include: ketone peroxides such as methyl ethyl ketone, diacyl peroxides such as benzoyl peroxide, diisopropyl peroxide such as diisopropyl peroxide, peroxide ketals such as 1,1-bis(tert-butylperoxy)cyclohexane, hydrogen peroxide such as tert-butyl hydroperoxide, peroxide esters such as tert-butyl peroxypentanoate, other azobisisobutyronitrile, hydrogen peroxide, ferrous salts, etc. Furthermore, polymerization initiators described in Japanese Patent Publication No. 2-14364 can also be used. One or more of these initiators can be used alone.

[0125] There are no particular limitations on chain transfer catalysts, and examples include: alkyl thiols such as lauryl thiols, thiocarboxylic acids such as mercaptoacetic acid, 2-mercaptopropionic acid, and 3-mercaptopropionic acid, thiocarboxylic acid esters such as butyl thioglycolate and 2-ethylhexyl thioglycolate, etc. One or more of them can be used alone.

[0126] The weight-average molecular weight of polyallylamine is preferably 150 to 100,000, more preferably 600 to 20,000. If the weight-average molecular weight is 150 or higher, the adsorption force on particles such as component (A) is increased, and the particle dispersibility is improved. If the weight-average molecular weight is 100,000 or lower, the aggregation of particles can be suppressed, and the particle dispersibility is improved. It should be noted that polyallylamine with any weight-average molecular weight can also be manufactured using the method described in Japanese Patent Publication No. 2-14364.

[0127] Commercially available polyallylamines are available. Examples of commercially available polyallylamines include "PAA-01", "PAA-03", "PAA-05", "PAA-08", "PAA-15", "PAA-15C", and "PAA-25" manufactured by Nittobo Medical.

[0128] The pH of component (C) in this invention is typically 4 or higher and less than 7. pH can be determined using an indicator method. Specifically, it can be determined by immersing a sample (22°C) prepared by dissolving a dispersant in acetone at a dispersant concentration of 0.1 g / mL in pH test paper. As pH test paper, pH test paper capable of measuring pH in the acidic range can be used (e.g., test paper with a measurement range of pH 0.0–14.0, pH 1.0–14.0, pH 0.5–5.0, etc.), such as the pH test paper "pH 1–14" (pH measurement range pH 1.0–14.0) manufactured by ASONE Corporation.

[0129] From the viewpoint of significantly obtaining the effects of the present invention, the acid value of component (C) is preferably 1 mg KOH / g or more, more preferably 3 mg KOH / g or more, even more preferably 5 mg KOH / g or more, preferably 30 mg KOH / g or less, more preferably 25 mg KOH / g or less, and even more preferably 20 mg KOH / g or less. The acid value can be determined by neutralization titration.

[0130] When component (C) is a dispersant obtained by reacting with polyallylamine, from the viewpoint of significantly obtaining the effects of the present invention, the amine value is preferably 1 mg KOH / g or more, more preferably 5 mg KOH / g or more, even more preferably 10 mg KOH / g or more, preferably 45 mg KOH / g or less, more preferably 40 mg KOH / g or less, and even more preferably 35 mg KOH / g or less. The amine value can be determined by neutralization titration.

[0131] From the viewpoint of significantly obtaining the effects of the present invention, the weight-average molecular weight of component (C) is preferably 2000 or more, more preferably 3000 or more, further preferably 5000 or more, preferably 50000 or less, more preferably 40000 or less, and further preferably 30000 or less. The weight-average molecular weight is the weight molecular weight converted from polystyrene as determined by gel permeation chromatography (GPC).

[0132] From the viewpoint of significantly maximizing the effects of the present invention, when the non-volatile component in the magnetic paste is set to 100% by mass, the content of component (C) is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, with an upper limit preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less.

[0133] When the mass of component (C) in the magnetic paste is set to 100% by mass, denoted as C1, and the mass of magnetic powder (A) in the magnetic paste is set to 100% by mass, denoted as A1, (C1 / A1)×100 is preferably 0.1 or more, more preferably 0.3 or more, further preferably 0.5 or more, preferably 10 or less, more preferably 5 or less, and further preferably 1 or less. By adjusting the mass of component (A) and component (C) within the above-mentioned ranges for (C1 / A1)×100, the desired effect of the present invention can be obtained more significantly.

[0134] <(D) Curing Agent>

[0135] The magnetic paste contains a (D) curing agent. The (D) curing agent includes: an epoxy resin curing agent that functions to cure the (B) epoxy resin, and a curing accelerator that functions to accelerate the curing speed of the (B) epoxy resin. The magnetic paste preferably contains an epoxy resin curing agent as the (D) curing agent. As the (D) curing agent, a curing accelerator may also be contained together with the epoxy resin curing agent. The curing accelerator is usually used in conjunction with the epoxy resin curing agent.

[0136] -Epoxy resin curing agent-

[0137] Epoxy resin curing agents typically react with epoxy resins to cure magnetic pastes. Examples of epoxy resin curing agents include phenol-based, naphthol-based, reactive ester-based, anhydride-based, benzoxazine-based, cyanate ester-based, and imidazole-based epoxy resin curing agents. From the viewpoint of reducing the viscosity of the magnetic paste, anhydride-based and imidazole-based epoxy resin curing agents are preferred, and from the viewpoint of the mechanical strength of the cured product, imidazole-based epoxy resin curing agents are more preferred. One epoxy resin curing agent can be used alone, or two or more can be used in combination.

[0138] From the viewpoint of heat resistance and water resistance, phenolic epoxy resin curing agents and naphthol-based epoxy resin curing agents with phenolic structures are preferred. As phenolic epoxy resin curing agents, nitrogen-containing phenolic epoxy resin curing agents are preferred, more preferably phenolic epoxy resin curing agents containing a triazine skeleton, and even more preferably phenolic phenolic varnish epoxy resin curing agents containing a triazine skeleton.

[0139] Specific examples of phenolic epoxy resin curing agents and naphthol-based epoxy resin curing agents include "MEH-7700", "MEH-7810", and "MEH-7851" manufactured by Meiwa Chemical Co., Ltd.; "NHN", "CBN", and "GPH" manufactured by Nippon Chemical Co., Ltd.; "SN170", "SN180", "SN190", "SN475", "SN485", "SN495V", "SN375", and "SN395" manufactured by Nippon Steel & Sumitomo Metal Chemical Co., Ltd.; "TD-2090", "LA-7052", "LA-7054", "LA-1356", "LA-3018-50P", "EXB-9500", "HPC-9500", "KA-1160", "KA-1163", and "KA-1165" manufactured by DIC Co., Ltd.; and "GDP-6115L" and "GDP-6115H" manufactured by Gunei Chemical Co., Ltd.

[0140] There are no particular limitations on reactive ester-based epoxy resin curing agents, but compounds with two or more highly reactive ester groups in one molecule, such as phenolic esters, thiophenolic esters, N-hydroxyamine esters, and heterocyclic hydroxyl compounds, are generally preferred. This reactive ester-based epoxy resin curing agent is preferably obtained through the condensation reaction of carboxylic acid compounds and / or thiocarboxylic acid compounds with hydroxyl compounds and / or thiols. Particularly from the viewpoint of improving heat resistance, reactive ester-based epoxy resin curing agents obtained from carboxylic acid compounds and hydroxyl compounds are preferred, and those obtained from carboxylic acid compounds and phenolic compounds and / or naphthol compounds 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 phenolic or naphthol compounds include: hydroquinone, resorcinol, bisphenol A, bisphenol F, bisphenol S, phenolphthalein, methylated bisphenol A, methylated bisphenol F, methylated bisphenol S, phenol, o-cresol, m-cresol, p-cresol, catechol, α-naphthol, β-naphthol, 1,5-dihydroxynaphthol, 1,6-dihydroxynaphthol, 2,6-dihydroxynaphthol, dihydroxybenzophenone, trihydroxybenzophenone, tetrahydroxybenzophenone, phloroglucinol, trihydroxybenzene, dicyclopentadiene-type diphenol compounds, and linear phenolic resins (phenolnovolac). Here, "dicyclopentadiene-type diphenol compounds" refers to diphenol compounds obtained by the condensation of two phenol molecules with one dicyclopentadiene molecule.

[0141] Specifically, the preferred curing agents are active ester-based epoxy resins containing a dicyclopentadiene-type diphenol structure, active ester-based epoxy resins containing a naphthalene structure, active ester-based epoxy resins containing an acetylated form of linear phenolic resin, and active ester-based epoxy resins containing a benzoyl form of linear phenolic resin. "Dicyclopentadiene-type diphenol structure" indicates a divalent structure containing a phenylene-dicyclopentene-phenylene group.

[0142] Commercially available reactive ester-based epoxy resin curing agents include, for example, those 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; and reactive ester compounds containing a naphthalene structure such as "EXB9416" manufactured by DIC Corporation. -70BK”; Examples of active ester epoxy resin curing agents containing acetylated linear phenolic resins include “DC808” manufactured by Mitsubishi Chemical Corporation; Examples of active ester epoxy resin curing agents containing benzoylated linear phenolic resins include “YLH1026”, “YLH1030”, and “YLH1048” manufactured by Mitsubishi Chemical Corporation; Examples of active ester epoxy resin curing agents containing acetylated linear phenolic resins include “DC808” manufactured by Mitsubishi Chemical Corporation; etc.

[0143] Anhydride-based epoxy resin curing agents include epoxy resin curing agents having one or more anhydride groups per molecule. Specific examples of anhydride-based epoxy resin curing agents include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, dodecenylsuccinic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, trimellitic anhydride, and pyromellitic anhydride. Polymer anhydrides such as benzophenone tetracarboxylic dianhydride, biphenyl tetracarboxylic dianhydride, naphthalene tetracarboxylic dianhydride, oxydiphthalic dianhydride, 3,3'-4,4'-diphenylsulfone tetracarboxylic 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(dehydrated trimellitate), and styrene-maleic acid resin copolymerized from styrene and maleic acid.

[0144] Commercially available anhydride-based epoxy resin curing agents include "HNA-100" and "MH-700" manufactured by Shin Nippon Rikka Co., Ltd.

[0145] Specific examples of benzoxazine-based epoxy resin curing agents include "HFB2006M" manufactured by Showa Polymer Co., Ltd., and "Pd" and "Fa" manufactured by Shikoku Chemical Co., Ltd.

[0146] Examples of cyanate ester-based epoxy resin curing agents include: bisphenol A dicyanate, polyphenol cyanate, oligomeric (3-methylene-1,5-phenylene cyanate), 4,4'-methylene bis(2,6-dimethylphenyl cyanate), 4,4'-ethylene diphenyl dicyanate, hexafluorobisphenol A dicyanate, 2,2-bis(4-cyanate)phenylpropane, 1,1-bis(4-cyanate phenylmethane), bis(4-cyanate-3,5-dimethylphenyl)methane, 1,3-bis(4-cyanate phenyl-1-(methylethylene))benzene, bis(4-cyanate phenyl) sulfide, and bis(4-cyanate phenyl) ether, etc., which are difunctional cyanate ester resins; multifunctional cyanate ester resins derived from phenolic varnish resins and cresol varnish resins; and some triazine-modified prepolymers of these cyanate ester resins. Specific examples of cyanate ester-based epoxy resin curing agents include Lonza Japan's "PT30" and "PT60" (both phenolic varnish-type multifunctional cyanate ester resins), "BA230", and "BA230S75" (prepolymers of bisphenol A dicyanate that have been partially or completely triazinized to become trimers).

[0147] Examples of imidazole-based epoxy resin curing agents include: 2-methylimidazolium, 2-undecylimidazolium, 2-heptadecylimidazolium, 1,2-dimethylimidazolium, 2-ethyl-4-methylimidazolium, 1,2-dimethylimidazolium, 2-ethyl-4-methylimidazolium, 2-phenylimidazolium, 2-phenyl-4-methylimidazolium, 1-benzyl-2-methylimidazolium, 1-benzyl-2-phenylimidazolium, 1-cyanoethyl-2-methylimidazolium, 1-cyanoethyl-2-undecylimidazolium, 1-cyanoethyl-2-ethyl-4-methylimidazolium, 1-cyanoethyl-2-phenylimidazolium, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-triazine, 2,4 -Diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-triazine isocyanuric acid adduct, 2-phenylimidazolyl isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazolium, 2-phenyl-4-methyl-5-hydroxymethylimidazolium, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline and other imidazole compounds and adducts of imidazole compounds with epoxy resins, preferably 2-ethyl-4-methylimidazolium and 1-benzyl-2-phenylimidazolium.

[0148] As an imidazole-based epoxy resin curing agent, commercially available products can be used, such as "2MZA-PW" and "2PHZ-PW" manufactured by Shikoku Chemical Industry Co., Ltd., and "P200-H50" manufactured by Mitsubishi Chemical Co., Ltd.

[0149] The ratio of epoxy resin to epoxy resin curing agent is preferably in the range of 1:0.2 to 1:2, more preferably in the range of 1:0.3 to 1:1.5, and even more preferably in the range of 1:0.4 to 1:1. Here, the reactive groups of epoxy resin curing agent refer to active hydroxyl groups, active ester groups, etc., which vary depending on the type of epoxy resin curing agent. Furthermore, the total number of epoxy groups in the epoxy resin is the value obtained by dividing the mass of the non-volatile component of each epoxy resin by the epoxy equivalent, and the total number of reactive groups in the epoxy resin curing agent is the value obtained by dividing the mass of the non-volatile component of each epoxy resin curing agent by the reactive group equivalent, and the total number of reactive groups in the epoxy resin curing agent is the value obtained by dividing the mass of the non-volatile component of each epoxy resin curing agent by the reactive group equivalent, and the total number of reactive groups in the epoxy resin curing agent is the value obtained by dividing the mass of the non-volatile component of each epoxy resin curing agent by the reactive group equivalent, and the total number of reactive groups in the epoxy resin curing agent is the value obtained by dividing the mass of the non-volatile component of each epoxy resin curing agent by the reactive group equivalent, and the heat resistance of the cured product is further improved by maintaining the epoxy resin to epoxy resin curing agent ratio within the above range.

[0150] -Curing Accelerator-

[0151] Curing accelerators typically act as catalysts in the curing reaction of epoxy resins, promoting the curing process. Examples of curing accelerators include amine-based, imidazole-based, phosphorus-based, guanidine-based, and metal-based accelerators. From the viewpoint of reducing the viscosity of magnetic pastes, amine-based, imidazole-based, and guanidine-based curing accelerators are preferred; further from the viewpoint of improving the mechanical strength of the cured product, imidazole-based curing accelerators are more preferred. Curing accelerators can be used alone or in combination of two or more. Curing accelerators are often used in conjunction with epoxy resin curing agents.

[0152] Examples of amine-based curing accelerators include trialkylamines such as triethylamine and tributylamine, 4-dimethylaminopyridine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, and 1,8-diazabicyclo(5,4,0)-undecene, with 4-dimethylaminopyridine and 1,8-diazabicyclo(5,4,0)-undecene being preferred.

[0153] As amine-based curing accelerators, commercially available products can be used, such as "PN-50", "PN-23", and "MY-25" manufactured by Ajinomoto Fine-Techno.

[0154] As an imidazole-based curing accelerator, it functions similarly to the aforementioned imidazole-based epoxy resin curing agents. When used in combination with other epoxy resin curing agents, the aforementioned imidazole-based epoxy resin curing agents sometimes function as curing accelerators.

[0155] Examples of phosphorus-based curing accelerators include triphenylphosphine, phosphonium borate compounds, tetraphenylphosphonium tetraphenylborate, n-butylphosphonium tetraphenylborate, tetrabutylphosphonium decanoate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, butyltriphenylphosphonium thiocyanate, etc., with triphenylphosphine and tetrabutylphosphonium decanoate being preferred.

[0156] 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, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, 1-methylbiguanidine, 1-ethylbiguanidine, 1-n-butylbiguanidine, 1-n-octadecylbiguanidine, 1,1-dimethylbiguanidine, 1,1-diethylbiguanidine, 1-cyclohexylbiguanidine, 1-allylbiguanidine, 1-phenylbiguanidine, 1-(o-tolyl)biguanidine, etc., with dicyandiamide and 1,5,7-triazabicyclo[4.4.0]dec-5-ene being preferred.

[0157] 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 organocobalt complexes such as cobalt(II) and cobalt(III) acetylacetone, organocopper complexes such as copper(II) acetylacetone, organozinc complexes such as zinc(II) acetylacetone, organoiron complexes such as iron(III) acetylacetone, organonickel complexes such as nickel(II) acetylacetone, and organomanganese complexes such as manganese(II) acetylacetone. Examples of organometallic salts include zinc octoate, tin octoate, zinc naphthenate, cobalt naphthenate, tin stearate, and zinc stearate.

[0158] (D) When the content of the curing agent is set to 100% by mass of the non-volatile component in the magnetic paste, from the viewpoint of reducing the viscosity of the magnetic paste and increasing the pot life of the viscosity, it is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more. The upper limit is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less.

[0159] When the mass of curing agent (D) is set to 100% by mass in the magnetic paste, denoted as D1, and the mass of dispersant (C) is set to 100% by mass in the magnetic paste, denoted as C1, the ratio of C1 to D1 is preferably 0.1 or more, more preferably 0.15 or more, further preferably 0.2 or more, preferably 5 or less, more preferably 3 or less, and further preferably 2.5 or less. By adjusting the mass of components (C) and (D) within the above-mentioned ranges for C1 / D1, the desired effect of the present invention can be obtained more significantly.

[0160] When the mass of (A) magnetic powder is set to 100% by mass in the magnetic paste, denoted as A1; the mass of (B) epoxy resin is set to 100% by mass in the magnetic paste, denoted as B1; the mass of (C) dispersant is set to 100% by mass in the magnetic paste, denoted as C1; and the mass of (D) curing agent is set to 100% by mass in the magnetic paste, denoted as D1, the ratio of (B1+C1+D1) / A1 is preferably 0.01 or more, more preferably 0.05 or more, further preferably 0.1 or more, preferably 1 or less, more preferably 0.5 or less, and further preferably 0.3 or less. By adjusting the mass of components (A) to (D) within the above-mentioned range for (B1+C1+D1) / A1, the desired effect of the present invention can be obtained more significantly.

[0161] When the mass of (A) magnetic powder (where the non-volatile component in the magnetic paste is set to 100% by mass) is denoted as A1, the mass of (C) dispersant (where the non-volatile component in the magnetic paste is set to 100% by mass) is denoted as C1, and the mass of (D) curing agent (where the non-volatile component in the magnetic paste is set to 100% by mass) is denoted as D1, the mass of ((C1+D1) / A1)×100 is preferably 0.1 or more, more preferably 0.5 or more, further preferably 1 or more, preferably 10 or less, more preferably 5 or less, and further preferably 3 or less. By adjusting the mass of components (A), (C), and (D) within the above-mentioned ranges for ((C1+D1) / A1)×100, the desired effect of the present invention can be obtained more significantly.

[0162] <(E) Other Additives>

[0163] The magnetic paste may further include (E) other additives as needed. Examples of such other additives include: curing delay agents such as triethyl borate; inorganic fillers (excluding those corresponding to magnetic powders); thermoplastic resins; flame retardants; organic fillers; organometallic compounds such as organocopper compounds, organozinc compounds, and organocobalt compounds; and resin additives such as thickeners; defoamers; leveling agents; adhesion promoters; and colorants.

[0164] Relative to the total mass of the magnetic paste, the content of organic solvent in the magnetic paste is preferably less than 1.0% by mass, more preferably 0.8% by mass or less, even more preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less. There is no particular limitation on the lower limit, which is 0.001% by mass or more, or none at all. Even without organic solvent, the viscosity of the magnetic paste can be reduced. Because the amount of organic solvent in the magnetic paste is small, the formation of voids caused by the evaporation of the organic solvent can be suppressed.

[0165] <Method for Manufacturing Magnetic Paste>

[0166] Magnetic pastes can be manufactured, for example, by mixing the compounding components using a stirring device such as a three-roll mill or a rotary mixer.

[0167] <Physical properties of magnetic paste, etc.>

[0168] Magnetic paste exhibits low viscosity. Therefore, it has excellent printability. The viscosity at 25°C is preferably less than 300 Pa·s, more preferably less than 250 Pa·s, even more preferably less than 200 Pa·s, preferably more than 10 Pa·s, more preferably more than 20 Pa·s, and even more preferably more than 30 Pa·s. Viscosity can be measured, for example, using an E-type viscometer (RE-80U manufactured by Toki Sangyo Co., Ltd.), and details can be obtained through the methods described in the examples below.

[0169] Cured products obtained by heating magnetic paste at 180°C for 90 minutes typically exhibit excellent mechanical strength (tensile strength at break). Therefore, the aforementioned cured product provides a magnetic layer with excellent tensile strength at break. The tensile strength at break is preferably 50 MPa or more, more preferably 60 MPa or more, and even more preferably 70 MPa or more. There is no particular upper limit, and it can be set to 100 MPa or less, etc. The tensile strength at break can be measured using the method described in the examples described later.

[0170] The cured product obtained by heating the magnetic paste at 180°C for 90 minutes exhibits a high relative permeability at a frequency of 100 MHz. Therefore, the aforementioned cured product provides a magnetic layer with high relative permeability. The relative permeability of this cured product at a frequency of 100 MHz is preferably 1 or higher, more preferably 3 or higher, and even more preferably 7 or higher. Furthermore, there is no particular upper limit, and it can be set to 20 or lower, etc. The relative permeability can be measured using the method described in the examples described later.

[0171] Cured products obtained by heating magnetic paste at 180°C for 90 minutes typically exhibit low magnetic loss at a frequency of 100MHz. Therefore, the aforementioned cured product provides a magnetic layer with low magnetic loss. The magnetic loss of this cured product at a frequency of 100MHz is preferably 1 or less, more preferably 0.5 or less, and even more preferably 0.3 or less. The lower limit is not particularly limited and can be set to 0.001 or more, etc. Magnetic loss can be measured using the method described in the examples described later.

[0172] [Resin Composition]

[0173] The magnetic paste described above may also have states other than a paste, depending on the need. For example, the magnetic paste may have a state other than a paste during storage or transportation. Therefore, the resin composition of the present invention can be obtained without specifying a state. Generally, the resin composition has the same composition, effects, and uses as the magnetic paste described above. Specifically, the resin composition may contain (A) magnetic powder, (B) epoxy resin, (C) dispersant, and (D) curing agent. The resin composition may be the same composition as the magnetic paste described above, except that it has a state other than a paste.

[0174] [cured material]

[0175] The cured product of the present invention is obtained by curing the magnetic paste of the present invention. Furthermore, the cured product of the present invention is obtained by curing the resin composition of the present invention. The curing conditions for the magnetic paste and resin composition can use the conditions of step (2) described later. Furthermore, preheating can be performed before heat curing the magnetic paste and resin composition, and the heating can also include multiple preheating cycles.

[0176] [Magnetic Sheets]

[0177] The magnetic sheet includes a support and a resin composition layer formed of a magnetic paste disposed on the support. Furthermore, the magnetic sheet includes a support and a resin composition layer formed of a resin composition disposed on the support.

[0178] From the viewpoint of achieving a thinner profile, the thickness of the resin composition layer is preferably 250 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, and 100 μm or less. The lower limit of the resin composition layer thickness is not particularly limited, and is typically set to 5 μm or more.

[0179] Examples of supports include films made of plastic materials, metal foils, and release paper, with films and metal foils made of plastic materials being more preferred.

[0180] When a film formed of a plastic material is used as a support, examples of plastic materials include: polyesters such as polyethylene terephthalate (hereinafter sometimes abbreviated as "PET") and polyethylene naphthalate (hereinafter sometimes abbreviated as "PEN"), acrylic polymers such as polycarbonate (hereinafter sometimes abbreviated as "PC") and polymethyl methacrylate (PMMA), cyclic polyolefins, triacetyl cellulose (TAC), polyether sulfide (PES), polyether ketone, and polyimide. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, and inexpensive polyethylene terephthalate is particularly preferred.

[0181] When using metal foil as a support, examples of metal foil include copper foil and aluminum foil, with copper foil being preferred. Copper foil can be used as the support, either as a single metal such as copper or as an alloy of copper with other metals (e.g., tin, chromium, silver, magnesium, nickel, zirconium, silicon, titanium, etc.).

[0182] The surface of the support that is bonded to the resin composition layer can be treated with matte finish or corona treatment.

[0183] Furthermore, as a support, a support with a release layer can be used on the surface bonded to the resin composition layer. Examples of release agents used in the release layer of the support with a release layer include, for example, one or more release agents selected from alkyd resins, polyolefin resins, polyurethane resins, and silicone resins. Commercially available products can be used as the support with a release layer, such as PET films having a release layer with an alkyd resin-based release agent as the main component, namely, Lintec's "SK-1", "AL-5", and "AL-7", Toray's "Lumirror T60", Teijin's "Purex", and UNITIKA's "Unipeel".

[0184] The thickness of the support is not particularly limited, but is preferably in the range of 5μm to 75μm, more preferably in the range of 10μm to 60μm. It should be noted that when using a support with a release layer, the overall thickness of the support with the release layer is preferably within the above range.

[0185] Magnetic sheets can be manufactured, for example, by preparing a resin varnish by dissolving a magnetic paste in an organic solvent, applying the resin varnish to a support using a diecoater or similar machine, and then drying it to form a resin composition layer. It should be noted that the resin composition layer can also be formed by directly coating the magnetic paste onto the support using a diecoater or similar machine.

[0186] Examples of organic solvents include: ketones such as acetone, methyl ethyl ketone (MEK), and cyclohexanone; acetates such as ethyl acetate, butyl acetate, acetic acid solvents, propylene glycol monomethyl ether acetate, and carbitol acetate; carbitols such as solvents and butyl carbitol; aromatic hydrocarbons such as toluene and xylene; and amide solvents such as dimethylformamide, dimethylacetamide (DMAc), and N-methylpyrrolidone. Organic solvents can be used alone or in combination of two or more.

[0187] Drying can be carried out using known methods such as heating or blowing hot air. Drying conditions are not particularly limited, but drying is generally carried out when the content of organic solvent in the resin composition layer is 10% by mass or less, preferably 5% by mass or less. The drying method also varies depending on the boiling point of the organic solvent in the resin varnish. For example, when using a resin varnish containing 30% to 60% by mass of organic solvent, the resin composition layer can be formed by drying at 50°C to 150°C for 3 to 10 minutes.

[0188] In magnetic sheets, a protective film, selected based on the support, can be further laminated on the side of the resin composition layer that is not bonded to the support (i.e., the side opposite to the support). The thickness of the protective film is not particularly limited, and is, for example, 1 μm to 40 μm. By laminating the protective film, the adhesion of dust and other contaminants or the formation of scratches on the surface of the resin composition layer can be suppressed. Magnetic sheets can be stored in rolls. When a magnetic sheet has a protective film, it can be used by peeling off the protective film.

[0189] [Circuit substrate and its manufacturing method]

[0190] The circuit board of the first embodiment includes a substrate having through holes and a cured product of the magnetic paste of the present invention filling the aforementioned through holes. Furthermore, the circuit board of the second embodiment includes a magnetic layer formed from a cured product of a resin composition layer of magnetic sheets. Hereinafter, the first and second embodiments of the circuit board manufacturing method will be described. However, the circuit board manufacturing method according to the present invention is not limited to the first and second embodiments illustrated below.

[0191] <First Embodiment>

[0192] The circuit board of the first embodiment is manufactured, for example, by a manufacturing method including steps (1) to (2) described below. Furthermore, this manufacturing method preferably further includes steps (3) and (4). In the first embodiment, a magnetic layer is preferably formed using a magnetic paste.

[0193] (1) The step of filling magnetic paste into the through holes of a substrate with through holes;

[0194] (2) The step of thermally curing the magnetic paste to obtain a cured product;

[0195] (3) The step of grinding the surface of the cured material or magnetic paste;

[0196] (4) The step of forming a conductor layer on the polished surface of the cured material. The method of manufacturing the circuit board of the present invention can be carried out in the order of steps (1) to (4), or step (2) can be carried out after step (3).

[0197] The steps (1) to (4) described above during the manufacturing of the circuit board will be explained in detail below.

[0198] <Step (1)>

[0199] Step (1) may also include the step of preparing a magnetic paste. The magnetic paste is the same as described above.

[0200] In addition, when performing step (1), such as Figure 1 As shown in the example, the process may also include preparing a core substrate 10, which includes a support substrate 11 and a first metal layer 12 and a second metal layer 13 formed of a metal such as copper foil disposed on two surfaces of the support substrate 11. Examples of materials for the support substrate 11 include insulating substrates such as glass epoxy boards, metal substrates, polyester substrates, polyimide substrates, BT resin substrates, and thermosetting polyphenylene ether substrates. Examples of materials for the first and second metal layers include copper foil with a carrier and materials for the conductor layers described later.

[0201] In addition, such as Figure 2 As shown in the example, the step of forming a through hole 14 on the core substrate 10 may also be included. The through hole 14 can be formed, for example, by drilling, laser irradiation, plasma irradiation, etc. Specifically, the through hole 14 can be formed by forming a through hole on the core substrate 10 using a drilling machine or the like.

[0202] The through hole 14 can be formed using a commercially available drilling rig. Examples of commercially available drilling rigs include the "ND-1S211" manufactured by Hitachi ViaMechanics.

[0203] After forming through holes 14 on the core substrate 10, as Figure 3 As shown in one example, it may also include the steps of roughening the core substrate 10 and forming a plating layer 20 in the through hole 14, on the surface of the first metal layer 12, and on the surface of the second metal layer 13.

[0204] As described above, roughening treatment can be performed using either dry or wet methods. Examples of dry roughening treatment include plasma treatment. Furthermore, examples of wet roughening treatment include methods that sequentially perform swelling treatment using a swelling solution, roughening treatment using an oxidizing agent, and neutralization treatment using a neutralizing solution.

[0205] The plating layer 20 is formed by plating, and the procedure for forming the plating layer 20 by plating is the same as that for forming the conductor layer in step (4) described later.

[0206] After preparing the core substrate 10 with the plating layer 20 formed in the through hole 14, as follows Figure 4 As shown in one example, magnetic paste 30a is filled into the through hole 14. Examples of filling methods include: filling magnetic paste 30a into the through hole 14 via a squeegee, filling magnetic paste 30a via a cartridge, filling magnetic paste 30a by mask printing, roller coating, inkjet printing, etc.

[0207] <Step (2)>

[0208] In step (2), after filling the through hole 14 with magnetic paste 30a, the magnetic paste 30a is heat-cured, such as... Figure 5 As shown in one example, a cured layer (magnetic layer) 30 is formed within the through-hole 14. The thermal curing conditions of the magnetic paste 30a vary depending on the composition and type of the magnetic paste 30a. The curing temperature is preferably 120°C or higher, more preferably 130°C or higher, even more preferably 150°C or higher, preferably 240°C or lower, more preferably 220°C or lower, and even more preferably 200°C or lower. The curing time of the magnetic paste 30a is preferably 5 minutes or more, more preferably 10 minutes or more, even more preferably 15 minutes or more, preferably 120 minutes or less, more preferably 100 minutes or less, and even more preferably 90 minutes or less.

[0209] The degree of curing of the magnetic layer 30 in step (2) is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The degree of curing can be measured using, for example, a differential scanning calorimeter.

[0210] Before heat curing the magnetic paste 30a, the magnetic paste 30a can be preheated at a temperature lower than the curing temperature. For example, before heat curing the magnetic paste 30a, it can be preheated at a temperature of 50°C or higher and lower than 120°C (preferably 60°C or higher and lower than 110°C, more preferably 70°C or higher and lower than 100°C) for a period of 5 minutes or more (preferably 5 minutes to 150 minutes, more preferably 15 minutes to 120 minutes).

[0211] <Step (3)>

[0212] In step (3), as Figure 6 As shown in one example, excess magnetic layer 30 protruding from or attached to the core substrate 10 is removed by grinding, thereby planarizing the substrate. As a grinding method, a method capable of grinding excess magnetic layer 30 protruding from or attached to the core substrate 10 can be used. Examples of such grinding methods include polishing and belt grinding. Commercially available polishing apparatuses include the "NT-700IM" manufactured by Ishii Optoelectronics Co., Ltd.

[0213] From the viewpoint of improving coating adhesion, the arithmetic mean roughness (Ra) of the polished surface of the magnetic layer is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more. The upper limit is preferably 1000 nm or less, more preferably 900 nm or less, and even more preferably 800 nm or less. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0214] When performing step (3) after step (2), heat treatment may be performed as needed after step (2) and before step (3) to further improve the curing degree of the magnetic layer. The temperature in the aforementioned heat treatment may be in accordance with the curing temperature described above, preferably 120°C or higher, more preferably 130°C or higher, even more preferably 150°C or higher, preferably 240°C or lower, more preferably 220°C or lower, even more preferably 200°C or lower. The heat treatment time is preferably 5 minutes or more, more preferably 10 minutes or more, even more preferably 15 minutes or more, preferably 90 minutes or less, more preferably 70 minutes or less, even more preferably 60 minutes or less.

[0215] Furthermore, when performing step (3) before step (2), a preheating treatment can be performed before step (3) at a temperature lower than the curing temperature of the magnetic paste. The temperature in the aforementioned preheating treatment is preferably 100°C or higher, more preferably 110°C or higher, even more preferably 120°C or higher, preferably 240°C or lower, more preferably 220°C or lower, even more preferably 200°C or lower. The heat treatment time is preferably 5 minutes or more, more preferably 10 minutes or more, even more preferably 15 minutes or more, preferably 90 minutes or less, more preferably 70 minutes or less, even more preferably 60 minutes or less.

[0216] <Step (4)>

[0217] In step (4), as Figure 7As shown in one example, a conductor layer 40 is formed on the polished surface of the magnetic layer 30 and on the plating layer 20. Furthermore, after forming the conductor layer 40, as... Figure 8 As shown in one example, a patterned conductor layer 41 can be formed by removing the conductor layer 40, the first metal layer 12, the second metal layer 13, and a portion of the plating layer 20 through processes such as etching. In this invention, since the cured material is polished in step (3), the step of roughening the magnetic layer is not included. Figure 7 In this process, the conductor layer 40 is formed on both sides of the core substrate 10, but the conductor layer 40 may also be formed on only one side of the core substrate 10.

[0218] Methods for forming the conductor layer include, for example, plating, sputtering, and vapor deposition, with plating being preferred. In suitable embodiments, a patterned conductor layer having the desired wiring pattern is formed by plating the surface of a cured material using appropriate methods such as semi-additive or fully additive methods. Materials for the conductor layer include, for example, 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 gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium. From the viewpoints of versatility, cost, and ease of patterning, chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or nickel-chromium alloys, copper-nickel alloys, or copper-titanium alloys, are preferred; chromium, nickel, titanium, aluminum, zinc, gold, palladium, silver, or copper, or nickel-chromium alloys, are more preferred; and copper is even more preferred.

[0219] Here, an example of an embodiment in which a patterned conductor layer is formed on a polished surface of a cured material will be described in detail. A plating seed layer is formed on the polished surface of the cured material by electroless plating. Next, an electrolytic plating layer is formed on the formed plating seed layer by electrolytic plating. Unwanted plating seed layers are removed as needed by etching or other processes, thereby forming a conductor layer with the desired wiring pattern. After forming the conductor layer, annealing may be performed as needed to improve the peel strength of the conductor layer. Annealing can be performed, for example, by heating the circuit board at 150–200°C for 20–90 minutes.

[0220] From the viewpoint of thinning, the thickness of the patterned conductor layer is preferably 70 μm or less, more preferably 60 μm or less, even more preferably 50 μm or less, even more preferably 40 μm or less, particularly preferably 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less. The lower limit is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more.

[0221] <Second Implementation>

[0222] The circuit board of the second embodiment includes a magnetic layer formed using a cured magnetic paste. In the second embodiment, it is preferable to use a magnetic sheet to form the magnetic layer. Hereinafter, a second embodiment of the method for manufacturing the substrate will be described. Descriptions that are repeated in the first embodiment will be omitted as appropriate.

[0223] The circuit board of the second embodiment is manufactured, for example, by a manufacturing method including step (A) below. Furthermore, this manufacturing method preferably further includes steps (B) to (D), including: (A) a step of laminating a magnetic sheet onto an inner layer substrate in such a manner that a resin composition layer is bonded to the inner layer substrate to form a magnetic layer;

[0224] (B) The step of creating an opening in the magnetic layer;

[0225] (C) The step of grinding the surface of the magnetic layer; and

[0226] (D) The step of forming a conductor layer on the polished surface of the magnetic layer.

[0227] The following is a detailed explanation of steps (A) to (D) in the manufacture of the circuit board.

[0228] <(A) Steps>

[0229] Step (A) is a step of laminating a magnetic sheet onto an inner substrate in such a way that a resin composition layer is bonded to the inner substrate to form a magnetic layer. As one embodiment of step (A), the magnetic sheet is laminated onto the inner substrate in such a way that a resin composition layer is bonded to the inner substrate, and the resin composition layer is thermocured to form a magnetic layer.

[0230] In step (A), as Figure 9 As shown in one example, a magnetic sheet 310, which includes a support 330 and a resin composition layer 320a disposed on the support 330, is laminated on the inner layer substrate 200 in such a way that the resin composition layer 320a is bonded to the inner layer substrate 200.

[0231] The inner layer substrate 200 is an insulating substrate. Examples of materials for the inner layer substrate 200 include insulating substrates such as glass epoxy boards, metal substrates, polyester substrates, polyimide substrates, BT resin substrates, and thermosetting polyphenylene ether substrates. The inner layer substrate 200 can also be an inner circuit substrate with wiring or the like embedded within its thickness.

[0232] like Figure 9As shown in one example, the inner substrate 200 has a first conductor layer 420 disposed on a first main surface 200a and an external terminal 240 disposed on a second main surface 200b. The first conductor layer 420 may include multiple wirings. In the example shown, only the wirings of the coil-shaped conductive structure 400 constituting the sensor element are shown. The external terminal 240 is a terminal for electrical connection to an external device, etc., not shown. The external terminal 240 may be configured as part of the conductor layer disposed on the second main surface 200b.

[0233] The conductor material that can form the first conductor layer 420 and the external terminal 240 is the same as the material of the conductor layer described in the “<Step (4)>” column of the first embodiment.

[0234] The first conductor layer 420 and the external terminal 240 can be a single-layer structure or a multi-layer structure obtained by stacking two or more single metal layers or alloy layers formed of different kinds of metals or alloys. In addition, the thickness of the first conductor layer 420 and the external terminal 240 is the same as that of the second conductor layer 440 described later.

[0235] The linewidth (L) / spacing (S) ratio of the first conductor layer 420 and the external terminal 240 is not particularly limited. From the viewpoint of reducing surface unevenness and obtaining a magnetic layer with excellent smoothness, it is generally 900 / 900 μm or less, preferably 700 / 700 μm or less, more preferably 500 / 500 μm or less, further preferably 300 / 300 μm or less, and even more preferably 200 / 200 μm or less. The lower limit of the linewidth / spacing ratio is not particularly limited. From the viewpoint of ensuring good filling of the resin composition layer into the wiring space, it is preferably 1 / 1 μm or more.

[0236] The inner layer substrate 200 may also have a plurality of through holes 220 that extend through the inner layer substrate 200 from the first main surface 200a to the second main surface 200b. Through-hole wiring 220a is provided in the through holes 220. The through-hole wiring 220a electrically connects the first conductor layer 420 to the external terminal 240.

[0237] The bonding between the resin composition layer 320a and the inner substrate 200 can be achieved, for example, by heating and pressing the magnetic sheet 310 to the inner substrate 200 from the support 330 side. Examples of components for heating and pressing the magnetic sheet 310 onto the inner substrate 200 (hereinafter also referred to as "heat-pressing component") include, for example, heated metal plates (stainless steel (SUS) end plates, etc.) or metal rollers (SUS rollers). It should be noted that, preferably, the heating and pressing component is not pressed directly into contact with the magnetic sheet 310, but rather pressed through a sheet made of an elastic material such as heat-resistant rubber, so that the magnetic sheet 310 fully follows the surface irregularities of the inner substrate 200.

[0238] The temperature during heat pressing is preferably in the range of 80℃ to 160℃, more preferably 90℃ to 140℃, and even more preferably 100℃ to 120℃. The pressure during heat pressing is preferably in the range of 0.098MPa to 1.77MPa, more preferably 0.29MPa to 1.47MPa. The time during heat pressing is preferably in the range of 20 seconds to 400 seconds, more preferably 30 seconds to 300 seconds. The bonding of the magnetic sheet to the inner substrate is preferably carried out under reduced pressure conditions of 26.7 hPa or less.

[0239] The bonding of the resin composition layer 320a of the magnetic sheet 310 to the inner substrate 200 can be performed using a commercially available vacuum laminator. Examples of commercially available vacuum laminators include, for example, the vacuum pressure laminator manufactured by Meiki Manufacturing Co., Ltd., and the vacuum dressing device manufactured by Nikko-Materials Co., Ltd.

[0240] After the magnetic sheet 310 is bonded to the inner substrate 200, the laminated magnetic sheet 310 can be smoothed by pressing the heated pressing member under normal pressure (atmospheric pressure), for example, from the support side. The pressing conditions for the smoothing process can be set to the same conditions as the heating pressing conditions for the lamination described above. The smoothing process can be performed using a commercially available laminating machine. It should be noted that lamination and smoothing processes can be performed continuously using the aforementioned commercially available vacuum laminating machine.

[0241] After the magnetic sheet is laminated onto the inner substrate, the resin composition layer is thermosetting to form the magnetic layer. For example... Figure 10 As shown in one example, the resin composition layer 320a bonded to the inner substrate 200 is thermocured to form the first magnetic layer 320.

[0242] The thermosetting conditions of the resin composition layer 320a vary depending on the composition and type of the resin composition. The curing temperature is preferably 120°C or higher, more preferably 130°C or higher, even more preferably 150°C or higher, preferably 240°C or lower, more preferably 220°C or lower, and even more preferably 200°C or lower. The curing time of the resin composition layer 320a is preferably 5 minutes or higher, more preferably 10 minutes or higher, even more preferably 15 minutes or higher, preferably 120 minutes or lower, more preferably 100 minutes or lower, and even more preferably 90 minutes or lower.

[0243] The support 330 can be removed between step (A) and step (B), or it can be peeled off after step (B).

[0244] <(B) Steps>

[0245] In step (B), as Figure 11 As shown in one example, an opening is formed in the first magnetic layer 320 to create a via 360. The via 360 serves as a pathway for electrically connecting the first conductor layer 420 to the second conductor layer 440, which will be described later. The formation of the via 360 can correspond to the composition of the resin composition used in the formation of the magnetic layer, and can be carried out using, for example, a drilling machine, laser, plasma, etc. The size and shape of the hole can be appropriately determined according to the design of the printed circuit board.

[0246] <(C) Steps>

[0247] In step (C), the surface of the magnetic layer in which the via is formed is polished. As for the polishing method in step (C), it can be performed by the same polishing method described in the “<Step (3)>” column of the first embodiment.

[0248] From the viewpoint of improving coating adhesion, the arithmetic mean roughness (Ra) of the polished surface of the magnetic layer is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more. The upper limit is preferably 1000 nm or less, more preferably 900 nm or less, and even more preferably 800 nm or less. The surface roughness (Ra) can be measured, for example, using a non-contact surface roughness meter.

[0249] <(D) Step>

[0250] In step (D), as Figure 12 As shown in one example, a second conductor layer 440 is formed on the first magnetic layer 320.

[0251] The conductor material that can form the second conductor layer 440 is the same as the material of the conductor layer described in the “<Step (4)>” column of the first embodiment.

[0252] From the viewpoint of thinning, the thickness of the second conductor layer 440 is preferably 70 μm or less, more preferably 60 μm or less, even more preferably 50 μm or less, even more preferably 40 μm or less, particularly preferably 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less. The lower limit is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more.

[0253] The second conductor layer 440 can be formed by plating. The second conductor layer 440 is preferably formed, for example, by a wet plating method including a semi-additive method, a fully additive method, a semi-additive method, an electroless plating step, a mask patterning step, an electrolytic plating step, and a rapid etching step. By forming the second conductor layer 440 using a wet plating method, a second conductor layer 440 containing the desired wiring pattern can be formed. It should be noted that, through this step, the in-via wiring 360a is also formed within the via 360.

[0254] The first conductor layer 420 and the second conductor layer 440 are, for example, described later. Figures 13-15 As shown in one example, it can be configured as a spiral. In one example, one end of the central side of the spiral wiring portion of the second conductor layer 440 is electrically connected to one end of the central side of the spiral wiring portion of the first conductor layer 420 through the via wiring 360a. The other end of the outer peripheral side of the spiral wiring portion of the second conductor layer 440 is electrically connected to the pad 420a of the first conductor layer 420 through the via wiring 360a. Therefore, the other end of the outer peripheral side of the spiral wiring portion of the second conductor layer 440 is electrically connected to the external terminal 240 via the via wiring 360a, the pad 420a, and the via wiring 220a.

[0255] The coil-shaped conductive structure 400 is composed of a spiral wiring portion that is part of the first conductor layer 420, a spiral wiring portion that is part of the second conductor layer 440, and a via wiring 360a that electrically connects the spiral wiring portion of the first conductor layer 420 and the spiral wiring portion of the second conductor layer 440.

[0256] Following step (D), a further step of forming a magnetic layer on the conductor layer can be performed. Details are as follows... Figure 14 As shown in one example, the second magnetic layer 340 is formed on the second conductor layer 440 and the first magnetic layer 320 on which the through-hole wiring 360a is formed. The second magnetic layer can be formed by the same steps as those already described.

[0257] [Sensor Components]

[0258] The sensor component includes the circuit board of the present invention. In the case of such a sensor component, which includes a circuit board obtained by the manufacturing method of the circuit board of the first embodiment, at least a portion of the area surrounding the cured magnetic paste has a sensor pattern formed of a conductor. Such a sensor component can be, for example, the sensor component described in Japanese Patent Application Publication No. 2016-197624.

[0259] Furthermore, in the case of a circuit board manufactured by the method of the second embodiment, the sensor board has a magnetic layer and a conductive structure at least a portion of which is embedded in the magnetic layer, and includes a sensor element composed of the conductive structure and a portion of the magnetic layer extending along the thickness direction of the magnetic layer and surrounded by the conductive structure. Here, Figure 13 This is a schematic top view of a sensor substrate containing sensor elements, viewed from one side in the thickness direction. Figure 14 It means that by Figure 13 The diagram shows a cut end face of the sensor substrate, indicated by the dotted line II-II. Figure 15 This is a schematic top view used to illustrate the structure of the first conductor layer in the sensor substrate.

[0260] like Figure 13 and Figure 14 As shown as an example, the circuit board 100 is a stacked wiring board having multiple magnetic layers (first magnetic layer 320, second magnetic layer 340) and multiple conductor layers (first conductor layer 420, second conductor layer 440), that is, having stacked magnetic layers and stacked conductor layers. In addition, the sensor board 100 includes an inner layer board 200.

[0261] according to Figure 14 The first magnetic layer 320 and the second magnetic layer 340 constitute a magnetic portion 300 that can be considered as an integral magnetic layer. Therefore, the coil-shaped conductive structure 400 is provided such that at least a portion of it is embedded in the magnetic portion 300. That is, in the sensor substrate 100 of this embodiment, the sensor element is composed of the coil-shaped conductive structure 400 and a core portion of the magnetic portion 300 that extends along the thickness direction of the magnetic portion 300 and is surrounded by the coil-shaped conductive structure 400.

[0262] like Figure 15As illustrated in the example, the first conductor layer 420 includes a spiral wiring portion for forming a coil-shaped conductive structure 400, and a rectangular pad 420a electrically connected to the wiring 220a within the via. In the example, the spiral wiring portion includes a straight portion, a curved portion bent at a right angle, and a detour portion that meanders at the pad 420a. In the example, the spiral wiring portion of the first conductor layer 420 has a generally rectangular overall outline and is wound counterclockwise from the center outwards.

[0263] Similarly, a second conductor layer 440 is provided on the first magnetic layer 320. The second conductor layer 440 includes helical wiring portions for forming a coil-shaped conductive structure 400. Figure 13 or Figure 14 In this design, the spiral wiring section includes straight sections and curved sections bent at right angles. Figure 13 or Figure 14 In the middle, the spiral wiring portion of the second conductor layer 440 has an overall outline that is roughly rectangular and is wound clockwise from the center side to the outside.

[0264] Such a sensor component can be used as a wiring board for mounting electronic components such as semiconductor chips, or as a (multilayer) printed wiring board in which the aforementioned wiring board is used as an inner substrate. Furthermore, it can be used as a chip sensor component formed by monolithically mounting the aforementioned wiring board, or as a printed wiring board on which the chip sensor component is surface-mounted.

[0265] In addition, the aforementioned wiring board can be used to manufacture various types of semiconductor devices. Semiconductor devices incorporating the aforementioned wiring board can be suitably used in electrical products (e.g., computers, mobile phones, digital cameras, and televisions) and vehicles (e.g., motorcycles, automobiles, trams, ships, and airplanes).

[0266] Example

[0267] The present invention will now be specifically described by way of examples, but the present invention is not limited to these examples. It should be noted that, in the following description, "parts" and "%" to indicate quantity mean "parts by mass" and "% by mass," respectively, unless otherwise specified.

[0268] <Determination of pH of Dispersant (Indicator Method)>

[0269] Dissolve the dispersant in acetone to prepare a test sample (22℃) with a dispersant concentration of 0.1 g / mL. Gently soak the pH test paper, lift it out, and dry off excess water. Compare the color of the wetted portion of the test paper with the color sample (color chart), and take the pH of the closest color as the pH of each sample.

[0270] <Synthesis Example 1: Synthesis of Dispersant 1>

[0271] 10.0 parts of 12-hydroxystearic acid (manufactured by Pure Chemical Industries, Inc.) and 190 parts of ε-caprolactone (manufactured by Pure Chemical Industries, Inc.) were added to a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux pipe. The mixture was heated to 160°C over a nitrogen flow for 4 hours, and then heated at 160°C for 2 hours until the remaining ε-caprolactone content was less than 1%. The mixture was then cooled to room temperature. Hereinafter, this reaction solution will be referred to as dispersant 1. Dispersant 1 has a polyester backbone of alkylene group with 5 carbon atoms in general formula (1), and has a weight-average molecular weight of 23,000 and an acid value of 9.0 mg KOH / g. The pH value was measured to be 5 by the indicator method.

[0272] <Synthesis Example 2: Synthesis of Dispersant 2>

[0273] 10.0 parts of 12-hydroxystearic acid (manufactured by Pure Chemical Industries, Inc.) and 180 parts of δ-valerolactone (manufactured by Tokyo Chemical Industry Co., Ltd.) were added to a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux pipe. The mixture was heated to 160°C over a nitrogen flow for 4 hours, and then heated at 160°C for 2 hours until the remaining δ-valerolactone content was less than 1%. The mixture was then cooled to room temperature. Hereinafter, this reaction solution will be referred to as dispersant 2. Dispersant 2 has a polyester backbone of alkylene group with 4 carbon atoms in general formula (1), and has a weight-average molecular weight of 22,000 and an acid value of 8.9 mg KOH / g. The pH value was measured to be 5 by the indicator method.

[0274] <Synthesis Example 3: Synthesis of Dispersant 3>

[0275] In a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, and reflux tube, a mixture consisting of 25.0 parts xylene and 70 parts of a 10% aqueous solution of polyallylamine ("PAA-1LV" manufactured by Nitto Boshoku Co., Ltd., with a number average molecular weight of approximately 3,000) was stirred at 160°C. The water was removed by distillation using a separation device. Simultaneously, while refluxing the xylene into the reaction solution, 114.21 parts of the polyester dispersant obtained in Synthesis Example 1 were added, heated to 160°C, and the reaction was carried out at 160°C for 2 hours. The mixture was further heated at 160°C for 4 hours, and the xylene was removed by distillation at 160°C to obtain dispersant 3. Dispersant 3 has a polyester backbone of alkylene with 5 carbon atoms (R) in general formula (1), and has an amine value of 31.0 mg KOH / g and an acid value of 19.5 mg KOH / g. The amine value immediately after mixing is 312.6 mg KOH / g. The pH value was 6, as determined by the indicator method.

[0276] <Synthesis Example 4: Synthesis of Dispersant 4>

[0277] 30.0 parts of xylene (manufactured by Pure Chemical Industries, Inc.), 300.0 parts of 12-hydroxystearic acid (manufactured by Pure Chemical Industries, Inc.), and 0.1 parts of tetrabutyl titanate (manufactured by Tokyo Chemical Industry Co., Ltd.) were added to a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, reflux pipe, and water separator. The mixture was heated to 160°C over a nitrogen flow for 4 hours. The mixture was further heated at 160°C for 4 hours, and the xylene was removed by distillation at 160°C. Dispersant 4 has a polyester backbone of general formula (1), where R is an alkylene group with 11 carbon atoms, and a weight-average molecular weight of 6000. The acid value of dispersant 4 is 23.0 mg KOH / g. The pH of dispersant 4, as determined by the indicator method, is 5.

[0278] <Synthesis Example 5: Synthesis of Dispersant 5>

[0279] In a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, reflux tube, and water separator, 30.0 parts of xylene (manufactured by Pure Chemical Industries, Inc.), 300.0 parts of 12-hydroxystearic acid (manufactured by Pure Chemical Industries, Inc.), and 0.1 parts of tetrabutyl titanate (manufactured by Tokyo Chemical Industry Co., Ltd.) were added. The mixture was heated to 160°C over a nitrogen stream for 4 hours. It was then heated further at 160°C for 4 hours (at which point the acid value was approximately 20 mg KOH / g). The xylene was removed by distillation at 160°C. The mixture was then cooled to room temperature, and the water produced during the heating reaction was separated from the xylene in the distillate. The xylene was then refluxed back into the reaction solution. This reaction solution was named polyester PE-1.

[0280] In a reaction flask equipped with a thermometer, stirrer, nitrogen inlet, reflux pipe, and water separator, a mixture consisting of 25.0 parts xylene and 70 parts of a 10% aqueous solution of polyallylamine ("PAA-1LV" manufactured by Nitto Boshoku Co., Ltd., with a number average molecular weight of approximately 3,000) was stirred at 160°C. The water was removed by distillation using a separation device, while xylene was refluxed back into the reaction solution, and 12.5 parts of polyester PE-1 were added. The reaction was carried out at 160°C for 2 hours. The mixture was further heated at 160°C for 4 hours, and xylene was removed by distillation at 160°C. Dispersant 5 has a polyester backbone of alkylene with 11 carbon atoms in general formula (1), and has an amine value of 38.5 mgKOH / g and an acid value of 23.5 mgKOH / g. The amine value of dispersant 5 after mixing is 317 mgKOH / g. The pH of dispersant 5, measured by the indicator method, is 6.

[0281] <Example 1: Preparation of Magnetic Paste 1>

[0282] 3 parts by weight of epoxy resin (“ZX-1059”, a mixture of bisphenol A type epoxy resin and bisphenol F type epoxy resin, manufactured by Nippon Steel Chemical & Materials Co., Ltd.), 5 parts by weight of epoxy resin (“ZX-1658GS”, cyclic aliphatic diglycidyl ether, manufactured by Nippon Steel Chemical & Materials Co., Ltd.), 10 parts by weight of epoxy resin (“EX-201”, cyclic aliphatic diglycidyl ether type epoxy resin, manufactured by Nagase ChemteX Co., Ltd.), and “dispersant 1” 1 part by weight of curing agent ("2MZA-PW", imidazole epoxy resin curing agent, manufactured by Shikoku Kasei Corporation), 1 part by weight of magnetic powder ("M05S", Fe-Mn ferrite, average particle size 3μm, manufactured by Powder-Tech Corporation), and 30 parts by weight of magnetic powder ("M001", Fe-Mn ferrite, average particle size 0.2μm, manufactured by Powder-Tech Corporation) are mixed to prepare magnetic paste 1.

[0283] <Example 2: Preparation of Magnetic Paste 2>

[0284] In Example 1, 1 part by mass of dispersant 1 was replaced with 1 part by mass of dispersant 2. Except as described above, the magnetic paste 2 was prepared in the same manner as in Example 1.

[0285] <Example 3: Preparation of Magnetic Paste 3>

[0286] In Example 1, 1 part by mass of dispersant 1 was replaced with 1 part by mass of dispersant 3. Except as described above, the magnetic paste 3 was prepared in the same manner as in Example 1.

[0287] <Comparative Example 1: Preparation of Magnetic Paste 4>

[0288] In Example 1, 1 part by mass of dispersant 1 was replaced with 1 part by mass of dispersant 4. Except as described above, the magnetic paste 4 was prepared in the same manner as in Example 1.

[0289] <Comparative Example 2: Preparation of Magnetic Paste 5>

[0290] In Example 1, 1 part by mass of dispersant 1 was replaced with 1 part by mass of dispersant 5. Except as described above, the magnetic paste 5 was prepared in the same manner as in Example 1.

[0291] <Comparative Example 3: Preparation of Magnetic Paste 6>

[0292] In Example 1, the amount of magnetic powder (“M05S”, Fe-Mn ferrite, average particle size 3 μm, manufactured by Powder-Tech) was changed from 120 parts by weight to 50 parts by weight, the amount of magnetic powder (“M001”, Fe-Mn ferrite, average particle size 0.2 μm, manufactured by Powder-Tech) was changed from 30 parts by weight to 11 parts by weight, and 1 part by weight of dispersant 1 was changed to 0.5 parts by weight of dispersant 4. Except for the above, the magnetic paste 6 was prepared in the same manner as in Example 1.

[0293] <Comparative Example 4: Preparation of Magnetic Paste 7>

[0294] In Example 1, 1 part by mass of dispersant 1 was replaced with 1 part by mass of dispersant ("SC-1015F", a dispersant without a polyester backbone, manufactured by Nippon Oil Company, with pH = 3 as measured by the indicator method). Except as described above, magnetic paste 7 was prepared in the same manner as in Example 1.

[0295] <Determination of Viscosity of Magnetic Paste>

[0296] The temperature of magnetic pastes 1 to 7 was maintained at 25±2℃, and the viscosity at 25℃ was measured using an E-type viscometer (Toki Sangyo Co., Ltd. "RE-80U", 3°×R9.7 conical rotor, rotation speed 5 rpm). Furthermore, from a processability perspective, the measured viscosity was evaluated according to the following criteria:

[0297] ○: Less than 300 Pa·s

[0298] ×: Above 300 Pa·s.

[0299] <Evaluation of print quality>

[0300] (1) Preparation of the support substrate

[0301] Prepare a support substrate with multiple through holes uniformly formed (the substrate is obtained by impregnating epoxy resin in glass cloth and curing it, with a thickness of 700 μm). The through holes are cylindrical holes with a diameter of 350 μm and a spacing of 100 μm between them.

[0302] (2) Mask preparation

[0303] As a mask, a metal mask with a hollow aperture is prepared to be formed on a metal plate with a thickness of 100 μm. The planar shape of the aperture is a square with a diameter of 20 mm.

[0304] (3) Printing of magnetic paste

[0305] Using the aforementioned mask, magnetic paste is printed on the support substrate according to the points outlined in (3-1) to (3-3) below. It should be noted that the printing is performed using a vacuum high-precision screen printing machine (NEWLONG Precision Industry Co., Ltd. "LS-100VC").

[0306] (3-1) Setup steps

[0307] A mask is disposed on one side of the support substrate. In this case, the mask is disposed in such a way that one opening of the mask communicates with multiple through holes in the support substrate.

[0308] (3-2) Supply Steps

[0309] Then, magnetic paste is supplied to the side of the mask opposite to the supporting substrate.

[0310] (3-3) First printing step

[0311] Then, a rubber applicator (NEWLONG Precision Industry "SVFSQ", 9mm thick, 90-degree rubber hardness) is moved along the surface of the mask to print the magnetic paste. Printing is performed under the conditions of an attack angle of 10°, a printing pressure of 4.4MPa, and a printing speed of 5mm / sec.

[0312] (4) Curing of magnetic paste

[0313] Through the aforementioned printing process, a filled substrate comprising a support substrate and a resin composition layer is obtained. This filled substrate is then heated at 130°C for 30 minutes. This heating causes the resin composition layer to thermally cure, forming a filled layer, thereby obtaining a hole-filled substrate.

[0314] (5) Evaluation of printability

[0315] The shape of the obtained via-filled substrate was measured using a laser microscope. Based on the measurement results, the printability of the magnetic paste was evaluated according to the following criteria:

[0316] ○: On the back side of the via-filling substrate, there are no through holes that are recessed compared to the supporting substrate.

[0317] ×: On the back side of the hole-filling substrate, there is one or more through holes that are recessed compared to the support substrate;

[0318] Here, "back side of the via-filling substrate" refers to the side of the support substrate opposite to the side where the mask is disposed. "A through-hole that is recessed compared to the support substrate on the back side of the via-filling substrate" means that the filler layer filling the through-hole is recessed compared to the back side of the support substrate. In other words, "a through-hole that is recessed compared to the support substrate on the back side of the via-filling substrate" means that the position of the filler layer filling the through-hole on the side opposite to the mask is closer to the through-hole of the mask in the thickness direction compared to the back side of the support substrate.

[0319] <Determination of Mechanical Strength (Tensive Breaking Strength)>

[0320] As a support, a polyethylene terephthalate (PET) film (Lintec Corporation "PET501010", 50 μm thick) treated with a silicone-based release agent was prepared. Magnetic pastes 1-7 were uniformly applied to the release surface of the PET film using a scraper, resulting in a dried paste layer thickness of 100 μm, thus obtaining a magnetic sheet. The obtained magnetic sheet was heated at 180°C for 90 minutes to thermally cure the paste layer. By peeling off the support, a sheet-like cured product was obtained. The tensile breaking strength of the obtained sample was determined according to JIS K 7127. The test results were evaluated according to the following criteria:

[0321] ○: Mechanical strength above 50MPa

[0322] ×: Mechanical strength is less than 50MPa.

[0323] <Determination of relative permeability and magnetic loss>

[0324] As a support, a polyethylene terephthalate (PET) film (Lintec Corporation "PET501010", 50 μm thick) treated with a silicone-based release agent was prepared. Magnetic pastes 1-7 were uniformly applied to the release surface of the PET film using a scraper, resulting in a dried paste layer thickness of 100 μm, thus obtaining a magnetic sheet. The obtained magnetic sheet was heated at 180°C for 90 minutes to thermally cure the paste layer. By peeling off the support, a sheet-like cured product was obtained. The cured product was cut into test pieces with a width of 5 mm and a length of 18 mm as evaluation samples. Using an Agilent Technologies (Agilent Technologies "HP8362B") oscilloscope, with a 3-turn coil method and a measurement frequency set to 100 MHz, the relative permeability (μ') and magnetic loss (μ") of the evaluation sample were measured at room temperature (23°C).

[0325] [Table 1]

[0326] (Table 1)

[0327]

[0328] Symbol Explanation

[0329] 10-core substrate

[0330] 11 Support base plate

[0331] 12 First metal layer

[0332] 13 Second metal layer

[0333] 14 Through holes

[0334] 20 coatings

[0335] 30a Magnetic Paste

[0336] 30 magnetic layers

[0337] 40 Conductor Layer

[0338] 41 Patterned Conductor Layer

[0339] 100 Circuit Board

[0340] 200 Inner Layer Substrate

[0341] 200a First Main Surface

[0342] 200b Second Main Surface

[0343] 220 through hole

[0344] 220a Through-hole Wiring

[0345] 240 external terminals

[0346] 300 Magnetic Section

[0347] 310 Magnetic Sheet

[0348] 320a resin composition layer

[0349] 320 First Insulation Layer

[0350] 330 Support

[0351] 340 Second Insulation Layer

[0352] 360° via

[0353] 360a Wiring within Vias

[0354] 400 coil-shaped conductive structure

[0355] 420 First conductor layer

[0356] 420a pad

[0357] 440 Second conductor layer.

Claims

1. A magnetic paste, which is a magnetic paste comprising (A) a magnetic powder, (B) an epoxy resin, (C) a dispersant, and (D) a curing agent, wherein The component (C) has a polyester skeleton represented by General Formula (1) below, and has a polyallylamine skeleton, In General Formula (1), each R independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer of 2 to 1000.

2. The magnetic paste of claim 1, wherein, The component (C) has a pH of 4 or more and less than 7.

3. The magnetic paste of claim 1, wherein, When the mass of the component (C) is C1 and the mass of the magnetic powder (A) is A1, each based on 100 mass% of the nonvolatile components in the magnetic paste, (C1 / A1) x 100 is 0.1 or more and 5 or less.

4. The magnetic paste of claim 1, wherein, When the mass of the component (C) is C1 and the mass of the magnetic powder (A) is A1, each based on 100 mass% of the nonvolatile components in the magnetic paste, (C1 / A1) x 100 is 0.1 or more and 1 or less.

5. The magnetic paste of claim 1, wherein, In General Formula (1), each R independently represents a divalent hydrocarbon group having 4 or more carbon atoms.

6. The magnetic paste of claim 1, wherein, In General Formula (1), each R independently represents a divalent hydrocarbon group having 6 or less carbon atoms.

7. The magnetic paste of claim 1, wherein, In General Formula (1), n represents an integer of 10 or more.

8. The magnetic paste of claim 1, wherein, In General Formula (1), n represents an integer of 50 or less.

9. The magnetic paste of claim 1, wherein, The content of the component (C) is 0.1 mass% or more and 5 mass% or less, based on 100 mass% of the nonvolatile components in the magnetic paste.

10. The magnetic paste of claim 1, wherein, The content of the component (C) is 0.5 mass% or more, based on 100 mass% of the nonvolatile components in the magnetic paste.

11. The magnetic paste of claim 1, wherein, The content of the component (C) is 3 mass% or less, based on 100 mass% of the nonvolatile components in the magnetic paste.

12. The magnetic paste of claim 1, wherein, The component (A) comprises: (A-1) a magnetic powder having an average particle diameter of 1 μm or more, and (A-2) a magnetic powder having an average particle diameter of less than 1 μm.

13. The magnetic paste of claim 1, wherein, The component (A) comprises: (A-1) a magnetic powder having an average particle diameter of 1 μm or more and 10 μm or less, and (A-2) a magnetic powder having an average particle diameter of 0.005 μm or more and less than 1 μm.

14. The magnetic paste of claim 12, wherein, The average particle diameter of the component (A-1) is 1.5 μm or more.

15. The magnetic paste of claim 12, wherein, The average particle diameter of the component (A-1) is 8 μm or less.

16. The magnetic paste of claim 12, wherein, The average particle diameter of the component (A-2) is 0.02 μm or more.

17. The magnetic paste of claim 12, wherein, The average particle diameter of the component (A-2) is 0.5 μm or less.

18. The magnetic paste of claim 1, wherein, The component (A) is at least one selected from the group consisting of an iron oxide powder and an iron alloy-based metal powder.

19. The magnetic paste of claim 1, wherein, The component (A) comprises an iron oxide powder, The iron oxide powder comprises a ferrite containing at least one element selected from the group consisting of Ni, Cu, Mn, and Zn.

20. The magnetic paste of claim 1, wherein, The content of the component (A) is 70 mass% or more and 98 mass% or less, based on 100 mass% of the nonvolatile components in the magnetic paste.

21. The magnetic paste of claim 1, wherein, The content of the component (A) is 80 mass% or more, based on 100 mass% of the nonvolatile components in the magnetic paste.

22. The magnetic paste of claim 1, wherein, The content of the component (A) is 90 mass% or less, based on 100 mass% of the nonvolatile components in the magnetic paste.

23. The magnetic paste of claim 1, wherein, The content of the component (B) is 1 mass% or more, based on 100 mass% of the nonvolatile components in the magnetic paste.

24. The magnetic paste of claim 1, wherein, The content of the (B) component is 10% by mass or more, based on 100% by mass of nonvolatile components in the magnetic paste.

25. The magnetic paste of claim 1, wherein, The content of the (B) component is 30% by mass or less, based on 100% by mass of nonvolatile components in the magnetic paste.

26. The magnetic paste of claim 1, wherein, The content of the (B) component is 20% by mass or less, based on 100% by mass of nonvolatile components in the magnetic paste.

27. The magnetic paste of claim 1, wherein, The content of the (D) component is 0.1% by mass or more, based on 100% by mass of nonvolatile components in the magnetic paste.

28. The magnetic paste of claim 1, wherein, The content of the (D) component is 0.5% by mass or more, based on 100% by mass of nonvolatile components in the magnetic paste.

29. The magnetic paste of claim 1, wherein, The content of the (D) component is 5% by mass or less, based on 100% by mass of nonvolatile components in the magnetic paste.

30. The magnetic paste of claim 1, wherein, The content of the (D) component is 1% by mass or less, based on 100% by mass of nonvolatile components in the magnetic paste.

31. The magnetic paste according to claim 1, which is used for filling a via.

32. A cured product, which is a cured product of the magnetic paste according to any one of claims 1 to 31.

33. A circuit substrate, which has: a substrate having a via, and a cured product of the magnetic paste according to any one of claims 1 to 31 filled in the via.

34. A resin composition, which is a resin composition comprising (A) a magnetic powder, (B) an epoxy resin, (C) a dispersant, and (D) a curing agent, wherein the (C) component has a polyester skeleton represented by the following general formula (1), and has a polyallylamine skeleton, in the general formula (1), R each independently represents a divalent hydrocarbon group having 2 to 10 carbon atoms, and n represents an integer of 2 to 1000.

35. The resin composition of claim 34, wherein, The (C) component has a pH of 4 or more and less than 7.

36. The resin composition of claim 34, wherein, When the mass of the (C) component based on 100% by mass of nonvolatile components in the magnetic paste is denoted as Cl, and the mass of the (A) magnetic powder based on 100% by mass of nonvolatile components in the magnetic paste is denoted as Al, (Cl / Al) x 100 is 0.1 or more and 5 or less.

37. The resin composition of claim 34, wherein, When the mass of the (C) component based on 100% by mass of nonvolatile components in the magnetic paste is denoted as Cl, and the mass of the (A) magnetic powder based on 100% by mass of nonvolatile components in the magnetic paste is denoted as Al, (Cl / Al) x 100 is 0.1 or more and 1 or less.

38. A cured product, which is a cured product of the resin composition according to any one of claims 34 to 37.

39. A circuit substrate, which has: a substrate having a via, and the cured product according to claim 38 filled in the via.

40. An inductor component, which comprises the circuit substrate according to claim 33 or 39.

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