JP2013026324A - Composite magnetic body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite magnetic body having sufficient flexibility which can be produced with high manufacturing efficiency without causing poor form during reflow soldering.SOLUTION: Soft magnetic metal powder is dispersed into a resin composition containing (A)component: bisphenol epoxy resin, (B)component: synthetic rubber, (C)component: phenol resin-based hardener for epoxy resin, and a mass ratio represented by (B)component/[(A)component+(C)component] is 0.5-1.5.

Description

 The present invention is used for the purpose of absorbing electromagnetic wave noise generated from an electronic device, etc., suppressing emission to the outside and entry from the outside, or preventing malfunction due to interference between components inside the electronic device. The composite magnetic material has the flexibility to follow irregularities such as circuit boards, electronic components, flexible printed wiring boards, etc., and is a basic process for surface mounting technology of electronic components such as chip components to the substrate. The present invention relates to a composite magnetic material that can be used for reflow soldering.

In recent years, due to higher functionality of electronic devices, the operating frequency of electronic components has been increased, the intensity of emitted noise electromagnetic waves has increased, and a wider range of frequency components has been included. There is an increasing demand for further downsizing and weight reduction in these electronic devices. With this demand, electronic components used tend to be downsized, thinned, and mounted with high density. There is a problem that noise electromagnetic waves radiated from electronic components, printed wiring, or wiring between modules are likely to be generated as electronic devices are increased in frequency and mounted in high density.
In general, a composite magnetic material is used as a measure for suppressing noise electromagnetic waves in various electronic devices.
Examples of the composite magnetic material include binder resin such as chlorinated polyethylene rubber, acrylic rubber, and ethylene acrylic rubber, and powder of soft magnetic metal such as Sendust (Fe-Si-Al alloy), Permalloy (Fe-Ni alloy), Fe An electromagnetic wave suppression sheet in which atomized powder such as a Cr alloy is dispersed and formed into a sheet shape is known (for example, Patent Document 1).

 The ability of the composite magnetic body to suppress noise electromagnetic waves depends on its thickness, and various thicknesses of composite magnetic bodies are supplied depending on the application. For this reason, in the supply of the composite magnetic material, a composite magnetic material having an arbitrary thickness is manufactured and laminated according to the user's request in order to improve manufacturing efficiency. For example, as in the electromagnetic wave suppression sheet of the invention of Patent Document 1, a composite magnetic body using a thermoplastic resin has a solution state (A stage) magnetism in which a soft magnetic metal powder is dispersed in a liquid resin composition. A body paint, this magnetic paint is applied to a substrate and dried to form a semi-cured sheet material in a semi-cured state (B stage), and the semi-cured sheet material is cured and cured (C stage) It is said. And the electromagnetic wave suppression sheet | seat is made into the electromagnetic wave suppression sheet | seat of desired thickness by overlapping as needed and heat-pressing.

 By the way, reflow soldering is a basic process for surface mounting technology of electronic parts such as chip parts to a substrate. Since general composite magnetic materials have poor heat resistance, they are softened by heating in a reflow furnace during reflow soldering and cannot retain their shape, or are in the form of local powdering, cracking, cracking, foaming, etc. Defects tend to occur and cannot be used in high-temperature atmospheres such as reflow soldering. Therefore, the composite magnetic body has to be pasted after reflow soldering, which has been a process problem.

Conventionally, inventions that improve heat resistance and flexibility have been proposed.
For example, an electromagnetic wave suppression sheet in which flat soft magnetic powder is dispersed in a polyurethane resin is mounted on the upper surface of a semiconductor component, and heat such as a phenol resin, an epoxy resin, or an unsaturated polyester resin is covered so as to cover the electromagnetic wave suppression sheet. An invention has been proposed in which a curable resin is applied and fixed, and then passed through a solder reflow oven at 240 ° C. to cure the thermosetting resin, and the electromagnetic wave suppression sheet is sealed and fixed with the thermosetting resin (for example, Patent Document 2). According to the invention of Patent Document 2, it is described that the electromagnetic wave suppression sheet was not altered or malfunctioned even after the reflow process.
In addition, an electromagnetic wave suppression sheet in which soft magnetic metal powder is embedded in a thermosetting resin sheet of any one of an epoxy resin, an unsaturated polyester resin, a phenol resin, a melamine resin, and a urea resin has been proposed (for example, Patent Document 3). ).
Alternatively, an electromagnetic wave absorbing material composition comprising a compound having two or more carboxyl groups and / or acid anhydride groups in one molecule, a compound having two or more epoxy groups in one molecule, and soft magnetic powder Has been proposed (for example, Patent Document 4).
Further, for example, flat soft magnetic material powder, epoxy resin, epoxy resin curing agent, curing accelerator, epoxy group-containing acrylic copolymer containing glycidyl (meth) acrylate, dispersant, organic phosphinate compound, A flame retardant noise suppression sheet containing a metal hydroxide has been proposed (for example, Patent Document 5).

JP 2002-299112 A JP 11-307983 A JP 2002-111276 A JP 2005-252221 A JP 2009-59752 A

However, the inventions of Patent Documents 2 to 3 are not satisfactory in flexibility, although prevention of form defects (reflow resistance) is achieved in reflow soldering. Although the inventions of Patent Documents 4 to 5 are improved in flexibility, they are not satisfactory reflow resistance. In addition, the composite magnetic body using the thermosetting resin is hard to adhere even if it is cured and stacked. For this reason, there is a problem in that it is necessary to produce a semi-cured sheet according to the thickness of the final product, which cannot be produced efficiently.
Accordingly, the present invention is directed to a composite magnetic body that can be efficiently manufactured and that can achieve both sufficient flexibility and reflow resistance.

In general, when engineering plastics with high heat resistance increase the amount of soft magnetic metal powder in order to obtain an electromagnetic wave suppression function, the molded body becomes brittle or the flexibility is impaired, so that a satisfactory composite magnetic body can be obtained. Is difficult. On the other hand, some thermoplastic resins having low heat resistance can increase the filling amount of the soft magnetic metal powder, but the heat resistance of the resulting composite magnetic material is insufficient.
As a result of intensive studies, the present inventors have blended a specific epoxy resin and a synthetic rubber at a specific ratio, and by using a specific curing agent for an epoxy resin, the electromagnetic wave suppression function is not impaired and sufficient. It has been found that a composite magnetic body having an arbitrary thickness can be efficiently produced by stacking semi-cured sheet materials and laminating them by heat treatment so that both flexibility and reflow resistance can be achieved. It was.

That is, the composite magnetic body of the present invention has a resin composition containing (A) component: bisphenol type epoxy resin, (B) component: synthetic rubber, and (C) component: phenol resin-based curing agent for epoxy resin. The soft magnetic metal powder is dispersed in the product, and the mass ratio represented by (B) component / [(A) component + (C) component] is 0.5 to 1.5. .
The component (A) preferably has an average epoxy equivalent of 100 to 700 g / eq, and the component (B) is at least one selected from polyisobutene, butadiene rubber, styrene-butadiene rubber and nitrile rubber. Preferably, the nitrile rubber is preferably 5 to 50% by mass of acrylonitrile, more preferably a nitrile rubber having a carboxyl group, and the nitrile rubber having a carboxyl group has a Mooney viscosity of 50 to 90 M _{1 + 4} (100 ° C.). It is particularly preferable that the component (C) is an amount such that the active hydrogen equivalent is 0.1 to 1.0 equivalent relative to 1 equivalent of the epoxy group of the component (A).

 According to the composite magnetic body of the present invention, it can be efficiently produced, and both sufficient flexibility and reflow resistance can be achieved.

(Composite magnetic material)
The composite magnetic body of the present invention is one in which soft magnetic metal powder is dispersed in a resin composition, for example, formed into a sheet shape.

<Resin composition>
The resin composition of the present invention contains (A) component: bisphenol type epoxy resin, (B) component: synthetic rubber, and (C) component: phenol resin-based curing agent for epoxy resin.
2-50 mass% is preferable, as for content of the resin composition in a composite magnetic body, 5-40 mass% is more preferable, and 5-20 mass% is further more preferable. If it is less than the lower limit, the function of the soft magnetic metal powder as a binder may be impaired, and the moldability of the composite magnetic body may be impaired. If the upper limit is exceeded, the electromagnetic wave control performance of the composite magnetic body may be impaired. May be insufficient.

≪ (A) component: bisphenol type epoxy resin≫
The component (A) is a bisphenol type epoxy resin. (A) As a component, it is obtained by reaction of bisphenols and haloepoxides, such as epichlorohydrin or (beta) -methyl epichlorohydrin. Bisphenols include reaction products of phenol or 2,6-dihalophenol with aldehydes or ketones such as formaldehyde, acetaldehyde, acetone, acetophenone, cyclohexanone, benzophenone, oxides of perhydroxy acids of dihydroxyphenyl sulfide, hydroquinone What is obtained by mutual etherification reaction etc. is mentioned.
As the component (A), a bisphenol A type epoxy resin is preferable because it is the most versatile and inexpensive.

 Although the average epoxy equivalent of (A) component can be determined according to a use, 100-700 g / eq is preferable. If it is less than 100 g / eq, the shape-retaining property of the obtained composite magnetic body tends to decrease at high temperatures, and if it exceeds 700 g / eq, the storage stability of the composite magnetic body tends to decrease.

 The content of the component (A) in the resin composition is determined in consideration of the average epoxy equivalent, the content of the component (C) described later and the active hydrogen equivalent, and the component (A) in the resin composition ( The total amount of the component (C) is preferably 20 to 67% by mass, more preferably 40 to 67% by mass. If it is less than the lower limit, the reflow resistance of the composite magnetic body may be reduced, and if it exceeds the upper limit, the flexibility of the composite magnetic body may be reduced.

≪ (B) component: Synthetic rubber≫
The component (B) is a synthetic rubber. As the component (B), any compound that can impart appropriate flexibility to the obtained composite magnetic material may be used. For example, nitrile rubber (NBR), polyisobutene (PIB), butadiene rubber (BR), styrene-butadiene rubber (SBR) and the like. Among them, nitrile rubber is preferable in consideration of the electrical characteristics of the composite magnetic material.
The nitrile rubber is an acrylonitrile-butadiene copolymer, and more preferably has a carboxyl group. Since the nitrile rubber having a carboxyl group has a high melt viscosity when heated, the thermal stability of the composite magnetic body can be further increased, and the tensile strength of the composite magnetic body can be increased. In addition, since the nitrile rubber having a carboxyl group is highly compatible with other resins, it is easy to increase the production efficiency or obtain a composite magnetic body having a stable quality.

 5-50 mass% is preferable, as for the content rate (acrylonitrile (AN) content rate) of the acrylonitrile origin monomer unit in a nitrile rubber, 10-40 mass% is more preferable, and 10-30 mass% is further more preferable. When the AN content is less than the lower limit, it is difficult to improve the reflow resistance. When the AN content exceeds the upper limit, the solubility in a solvent is reduced or it is difficult to stack semi-cured sheets. The manufacturing workability of the composite magnetic body may be reduced.

The Mooney viscosity of the nitrile rubber having a carboxyl _{group, 50~90M 1 + 4 (100 ℃} ) are _{preferred, 55~90M 1 + 4 (100 ℃} ) is more _{preferable, 60~70M 1 + 4 (100 ℃} ) it is more preferred. When the Mooney viscosity is within the above range, the thermal stability of the composite magnetic material is improved, and the reflow resistance is further improved. In addition, when the Mooney viscosity is within the above range, the workability and adhesiveness of the magnetic coating material are improved due to the improvement in solvent solubility and the decrease in melt viscosity.
When the Mooney viscosity is less than the above lower limit, the heat resistance of the resin composition is lowered, and the reflow resistance may be lowered. In addition, the melt viscosity of the semi-cured sheet decreases, and the flow of the magnetic coating material increases in the film forming process described later, which may reduce the workability. If the Mooney viscosity exceeds the above upper limit, the solubility in a solvent is reduced in the coating preparation process described later, or the fluidity of the magnetic coating material is decreased in the film forming process described later, making film formation difficult. Or it may become difficult to laminate semi-cured sheets, and the production efficiency of the composite magnetic body may be reduced.
The Mooney viscosity is a value measured using a Mooney viscometer (manufactured by Shimadzu Corporation) in accordance with JIS K6300-1.

 The content of (B) in the resin composition can be determined in consideration of the content of component (A) and component (C), and is (B) component / [(A) component + (C) component]. The expressed mass ratio (hereinafter sometimes referred to as (B) / [(A) + (C)] ratio) is 0.5 to 1.5, preferably 0.5 to 1.25, More preferably, it is 0.6-1.0. If it is less than the above lower limit value, the flexibility may be insufficient or the adhesion of the soft magnetic metal powder may be insufficient, and if it exceeds the above upper limit value, the reflow resistance becomes insufficient.

≪ (C) component: Phenolic resin type epoxy resin curing agent≫
Component (C) is a phenol resin-based curing agent for epoxy resins. (C) It does not specifically limit as a component, For example, a phenol novolak resin, a cresol novolak resin, a bisphenol novolak resin, poly p-vinylphenol etc. are mentioned. Since the component (C) is a latent curing agent, the curing reaction with the epoxy group of the component (A) hardly proceeds in a semi-cured state. For this reason, the semi-cured sheet material is overlaid and subjected to heat treatment, whereby unreacted epoxy groups develop surface tack and are easily adhered.

 The content of the component (C) in the resin composition is preferably determined in consideration of the type and content of the component (A), the type of the component (C), etc., and an epoxy group derived from the component (A) The amount that the active hydrogen equivalent of the component (C) (equivalent of the functional group having an active hydrogen group) is preferably 0.1 to 1 equivalent, more preferably 0.5 to 1 equivalent, relative to 1 equivalent, More preferably, the amount is 0.8 to 1 equivalent. When the content of the component (C) is less than the lower limit, the curing of the component (A) may be insufficient and the reflow resistance may be lowered. When the content exceeds the upper limit, the resin is in a semi-cured state. In the composition, the residual amount of the unreacted component (C) increases, and the reflow resistance may decrease.

 The greater the total amount of components (A) to (C) that are essential components in the resin composition, the higher the effect of the present invention is, and 90 mass% or more is preferable, 95 mass% or more is preferable, and 100 More preferred is mass%.

≪Optional component in resin composition≫
The resin composition is a resin (arbitrary resin) other than the components (A) to (C), an epoxy resin curing agent (arbitrary curing agent) other than the component (C), and curing acceleration, as long as the effects of the present invention are not hindered. You may contain arbitrary components, such as an agent (henceforth the arbitrary components of a resin composition generally).

Examples of the optional resin include epoxy resins other than the component (A), natural rubber, and the like. (C) Polyamideamine etc. are mentioned as resin other than a component.
These optional resins can be used alone or in combination of two or more.
The content of the optional resin in the resin composition is preferably 10% by mass or less, more preferably 5% by mass or less, and still more preferably not contained (1% by mass or less).

Optional curing agents include polyamine curing agents such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dicyandiamide, ketimine compounds, isophorone diamine, m-xylene diamine, m-phenylene diamine, 1,3-bis (aminomethyl) Cyclohexane, N-aminoethylpiperazine, 4,4′-diaminodiphenylmethane, 4,4′-diamino-3,3′-diethyldiphenylmethane, diaminodiphenylsulfone and the like. Examples of polycarboxylic acid curing agents include phthalic anhydride Acid, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, 3,6-endomethylenetetrahydrophthalic anhydride, hexachloroendomethylenetetrahydrophthalic anhydride, methyl-3,6-endomethylenetetrahydrophthalic anhydride An example is taric acid. By using these optional curing agents, the melting temperature of the semi-cured sheet can be increased.
The content of the optional curing agent in the resin composition can be appropriately determined in consideration of the melting point and the like required for the semi-cured sheet.

Any curing accelerator may be used as long as it can accelerate the curing reaction between the component (A) and the component (C). For example, 1,8-diaza-bicyclo [5.4.0] undecene-7, triethylenediamine , Tertiary amines such as benzyldimethylamine, triethanolamine, dimethylaminoethanol, tris (dimethylaminomethyl) phenol; 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-heptadecyl Imidazoles such as imidazole; Organic phosphines such as tributylphosphine, methyldiphenylphosphine, triphenylphosphine, diphenylphosphine, and phenylphosphine; tetraphenylphosphonium tetraphenylborate, 2-ethyl-4-methylimidazole tetraf Niruboreto, tetraphenyl boron salts such as N- methylmorpholine tetraphenylborate and the like. These curing accelerators can be used alone or in combination of two or more.
As for content of the hardening accelerator in a resin composition, 0.1-5 mass parts is preferable with respect to 100 mass parts of epoxy resins.

<Soft magnetic metal powder>
Examples of soft magnetic metal powders include those conventionally used in composite magnetic materials, such as pure iron powder, Fe-Si alloy powder, Fe-Si-Al alloy powder, Fe-Ni alloy powder. Fe-Ni-Mo alloy powder, Fe-Ni-Mo-Cu alloy powder, Fe-Co alloy powder, Fe-Ni-Co alloy powder, Fe-Cr alloy powder, Fe-Cr-Si alloy Alloy powder, Fe—Ni—Cr alloy powder, Fe—Cr—Al alloy powder, etc. Among them, Fe—Cr alloy powder such as PC permalloy powder, Fe—Cr alloy powder, Fe—Cr alloy powder, Fe— Si-based alloy powder, Fe-Si-Al-based alloy powder, Fe-Co-based alloy powder, and Fe-Ni-based alloy powder are preferable. The soft magnetic metal powder is obtained by a wet method using a water atomization method, a gas atomization method, a pulverization method, or a chemical treatment.
As the soft magnetic metal powder, a powder obtained by treating the atomized powder with an attritor or a bead mill is preferable. By performing such treatment, the desired average particle diameter or flatness of the soft magnetic metal powder can be obtained.
The average particle size of the soft magnetic metal powder is preferably 30 to 200 μm. When the average particle size is less than the lower limit, the magnetic properties tend to be low, and when the average particle size exceeds the upper limit, it is difficult to maintain a desired shape.
The average particle diameter is a value determined by a laser diffraction / scattering particle diameter / particle size distribution measuring apparatus.

The flatness of the soft magnetic metal powder is preferably 30 to 200. When the flatness is less than the above lower limit value, the magnetic characteristics tend to be low, and when the flatness exceeds the upper limit value, it is difficult to maintain a desired shape.
Here, the value of “flatness” is represented by L _a / d _a . L _a is the average size of the soft magnetic metal powder, the soft magnetic metal powder and SEM observation from the surface direction to measure the major axis L and the short axis S, but sought the average value (L + S) / 2 is there. d _a is the thickness of the soft magnetic metal powder. The soft magnetic metal powder is embedded in the resin and polished, and the thickness direction of the powder is observed with an optical microscope, and the maximum thickness d _max and the minimum thickness d _min are , And the average value (d _max + d _min ) / 2 is obtained.

 The content of the soft magnetic metal powder in the composite magnetic material can be determined in consideration of the content of the resin composition. The mass ratio represented by the soft magnetic metal powder / resin composition (hereinafter referred to as the metal / resin ratio). However, it is preferably 2-12. If the metal / resin ratio is less than the above lower limit, the electromagnetic wave suppression characteristics may be reduced, and if the metal / resin ratio exceeds the above upper limit, the adhesion of the soft magnetic metal powder by the resin composition is insufficient. There is a risk of becoming.

<Arbitrary component in composite magnetic material>
The soft magnetic metal powder is a flame retardant, a flame retardant aid, a filler, a mold release agent, a surface treatment agent, a viscosity modifier, a plasticizer, an antibacterial agent, as long as the effect of the present invention is not impaired. You may contain arbitrary components, such as an antifungal agent, a leveling agent, an antifoamer, a coloring agent, a stabilizer, a coupling agent (henceforth, it is generally called the arbitrary component of a composite magnetic body).

Examples of the flame retardant include conventionally known flame retardants, and include aluminum hydroxide and / or magnesium hydroxide from the viewpoint of halogen-free and further improvement in reflow resistance.
The content of the flame retardant in the composite magnetic body is preferably 40 to 150 parts by mass with respect to 100 parts by mass of the resin composition. If it is less than the lower limit, sufficient flame retardancy may not be obtained, and if it exceeds the upper limit, the adhesion of the soft magnetic metal powder may be insufficient.

Examples of the flame retardant aid include conventionally known flame retardant aids. From the viewpoint of halogen-free, for example, at least one selected from red phosphorus, ammonium polyphosphate, melamine polyphosphate, and phosphate ester is preferable.
The content of the flame retardant aid in the composite magnetic material is preferably 1 to 10 parts by mass with respect to 100 parts by mass of the resin composition. If it is less than the lower limit, sufficient flame retardancy may not be obtained, and if it exceeds the upper limit, heat resistance may be reduced.

(Production method)
The method for producing a composite magnetic body of the present invention includes, for example, a step of obtaining a magnetic coating material in which components (A) to (C) and a soft magnetic metal powder are dispersed in a solvent (paint preparation step), and a magnetic coating material. Is applied to a desired thickness and dried to obtain a semi-cured sheet material (film forming process), and a process of curing the semi-cured sheet material by heating (curing process).

 As a method for preparing the magnetic coating material, a conventionally known method can be used. For example, the components (A) to (C) and optional components of the resin composition are added to a solvent, and stirred. A method of adding a soft magnetic metal powder and, if necessary, an optional component of the composite magnetic material to the resin solution and stirring the resin solution may be mentioned. In addition, for example, the components (A) to (C) and the optional component of the resin composition or the optional component of the composite magnetic material are added to the solvent, if necessary, and then the soft magnetic metal powder is added. And stirring.

Solvents used in the coating preparation process include, for example, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and isophorone, ester solvents such as ethyl acetate and butyl acetate, aromatic solvents such as toluene and xylene, cellosolve acetate, methyl cellosolve acetate And an aprotic polar solvent such as dimethylformamide, an ether solvent such as tetrahydrofuran and diethylene glycol dimethyl ether, an alcohol such as isopropyl alcohol and n-butyl alcohol, and the like.
The content of the solvent in the magnetic coating material is appropriately determined in consideration of the viscosity required for the magnetic coating material.

In the film forming step, a conventionally known film forming method can be used, and examples thereof include a method in which a magnetic coating material is applied to a peelable film at an arbitrary thickness and dried.
Examples of the coating method include a method using a bar coater, a comma coater, a die coater, or the like.
Although the thickness of a semi-hardened sheet material is not specifically limited, For example, 50-500 micrometers is preferable and 50-100 micrometers is more preferable.

Examples of the peelable film include a polypropylene film, a fluororesin film, a polyethylene film, a polyethylene terephthalate (PET) film, paper, and those obtained by subjecting these to a release treatment with a silicone resin (release treatment film).
Although the thickness of a peelable film is not specifically limited, 1-200 micrometers is preferable and 10-50 micrometers is more preferable.
The peelable film preferably has a peel strength of 0.01 to 7.0 g / cm. If the above lower limit is exceeded, the composite magnetic body and the peelable film are not easily peeled off, and the composite magnetic body is easy to handle. If less than the above upper limit, the composite magnetic body is peeled from the peelable film. When this is done, defects and the like do not occur, and manufacturing efficiency increases.

The drying method is not particularly limited as long as it evaporates the solvent in the magnetic coating material applied to the peelable film and brings the resin composition into a semi-cured state. For example, the magnetic material applied to the peelable film The method of heating a coating material at arbitrary temperatures is mentioned.
The heating temperature in the film forming step can be determined in consideration of the component (A), the component (C), the type of solvent, and the like.
The heating time in the film forming process can be determined in consideration of the types of the component (A), the component (C) and the solvent.
The semi-cured sheet material may be immediately subjected to a curing process after drying, or may be stored as a work in progress.

The curing step is a step of heating the semi-cured sheet material to cure the resin composition to obtain a composite magnetic body.
A conventionally known curing method can be used as the curing method, and examples thereof include a method of heating at an arbitrary temperature and a method of heating at an arbitrary temperature while pressing at an arbitrary pressure.
The heating temperature in the curing step can be determined in consideration of the types of the component (A) and the component (C).
When pressing in the curing step, the pressure is not particularly limited, but is, for example, 5 to 30 MPa.
The composite magnetic body in which the resin composition is in a cured state is cut into a desired dimension and commercialized.
In the curing step, the semi-cured sheet material may be stacked according to the thickness of the final product and cured by, for example, hot pressing to form a composite magnetic body. An unreacted epoxy group (derived from the component (A)) remains in the semi-cured sheet. For this reason, when the semi-cured sheet material is stacked and subjected to heat treatment, the unreacted epoxy groups are brought into close contact with each other on the contact surface.

  As needed, you may laminate | stack a new peelable film on the exposed surface of the semi-hardened sheet material or composite magnetic body on a peelable film before or after a hardening process. Thus, by providing the peelable film on both surfaces of the composite magnetic body, it is possible to prevent adhesion of foreign matters.

The composite magnetic body may be provided with a heat resistant adhesive layer on one side or both sides. By providing the heat-resistant adhesive layer, the composite magnetic body can be easily fixed to the object to be pasted.
Examples of the pressure-sensitive adhesive constituting the heat-resistant pressure-sensitive adhesive layer include conventionally known pressure-sensitive adhesives such as a methylphenyl silicone pressure-sensitive adhesive, an addition reaction type silicone pressure-sensitive adhesive, and a peroxide sulfide type silicone pressure-sensitive adhesive.

As described above, according to the present invention, since the component (A) and the component (B) are contained at a specific ratio, both flexibility and reflow resistance can be achieved.
In addition, since the component (C) is used as a curing agent, it is possible to efficiently produce a composite magnetic body product having a desired thickness by stacking semi-cured sheets as necessary and performing hot pressing or the like. .

 EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited by these Examples.

Example 1
The molten Fe—Si—Al alloy was gas atomized to obtain a spherical powder having an average particle size of 100 μm. This was put into an attritor and stirred to obtain a soft magnetic metal powder having an average particle diameter of 50 μm, a thickness of 1 μm, and a flatness of 50.
(A) component: Bisphenol A type epoxy resin (average epoxy equivalent 190 g / eq, Epicoat 828, manufactured by Mitsubishi Chemical Corporation) 8 g, (B) component: NBR having a carboxyl group (Mooney viscosity 60M _{1 + 4} (100 ° C.), acrylonitrile) Content (AN content 27 mass%) 8 g, (C) component: phenol novolak resin (active hydrogen equivalent 106 g / eq, Tamano 759, Arakawa Chemical Industries, Ltd.) 4 g, epoxy resin curing accelerator: 2- Add 0.02 g of ethyl-4-methylimidazole, flame retardant: 21 g of aluminum hydroxide, flame retardant aid: 1.2 g of red phosphorus to 200 g of toluene, stir, and further add 170 g of soft magnetic metal powder, stir, A magnetic coating was obtained.
The obtained magnetic coating material was applied to the release-treated surface of the release-treated film (PET) so that the thickness after drying was 150 μm, and heated at 120 ° C. for 3 minutes in a hot-air circulating dryer, A semi-cured sheet was obtained. The resulting semi-cured sheet was evaluated for laminate properties. Further, in order to enhance the orientation of the soft magnetic metal powder, the semi-cured sheet was pressed at 150 ° C. for 30 minutes at 20 MPa by a hot press machine to obtain a composite magnetic body having a thickness of 99 μm. The obtained composite magnetic body was evaluated for magnetic permeability, reflow resistance, flexibility, and internal stress relaxation.
In the table, the component (C) was described as “P system”, and the active hydrogen equivalent of the component (C) was described as an equivalent to 1 equivalent of the epoxy group of the component (A) (the same applies hereinafter).

(Example 2)
A semi-cured sheet and a composite magnetic body having a thickness of 102 μm were obtained in the same manner as in Example 1 except that a soft magnetic metal powder having an average particle size of 30 μm, a thickness of 1 μm, and a flatness of 30 was used. The magnetic permeability, reflow resistance, flexibility, and internal stress relaxation were evaluated.

(Example 3)
A semi-cured sheet and a composite magnetic body having a thickness of 100 μm were obtained in the same manner as in Example 1 except that a soft magnetic metal powder having an average particle size of 50 μm, a thickness of 2 μm, and a flatness of 25 was used. The magnetic permeability, reflow resistance, flexibility, and internal stress relaxation were evaluated.

Example 4
A semi-cured sheet material and a composite magnetic material having a thickness of 98 μm were used in the same manner as in Example 1 except that an Fe—Si alloy soft magnetic metal powder having an average particle size of 49 μm, a thickness of 1 μm, and a flatness of 30 was used. A body was obtained and evaluated for laminateability, magnetic permeability, reflow resistance, flexibility, and internal stress relaxation.

(Example 5)
A semi-cured sheet material and a composite magnetic material with a thickness of 98 μm were used in the same manner as in Example 1 except that an Fe—Ni alloy soft magnetic metal powder having an average particle size of 52 μm, a thickness of 1 μm, and a flatness of 52 was used. A body was obtained and evaluated for laminateability, magnetic permeability, reflow resistance, flexibility, and internal stress relaxation.

(Example 6)
Example 1 except that component (A) is 12 g, component (B) is 12 g, component (C) is 6 g, aluminum hydroxide is 32 g, red phosphorus is 1.8 g, and soft magnetic metal powder is 150 g. Similarly, a semi-cured sheet and a composite magnetic body having a thickness of 100 μm were obtained, and the lamination property, magnetic permeability, reflow resistance, flexibility, and internal stress relaxation were evaluated.

(Example 7)
The component (A) is a bisphenol type epoxy resin (Epicoat 1001, manufactured by Mitsubishi Chemical Corporation) having an average epoxy equivalent of 480 g / eq, the component (A) is 8 g, the component (B) is 8 g, the component (C) is 1 g, water Except for 20 g of aluminum oxide, 1 g of red phosphorus, and 160 g of soft magnetic metal powder, a semi-cured sheet and a composite magnetic body having a thickness of 99 μm were obtained in the same manner as in Example 1 to obtain laminate properties, transparent properties. The magnetic susceptibility, reflow resistance, flexibility, and internal stress relaxation were evaluated.

(Example 8)
The semi-cured sheet and the thickness of 103 μm were the same as in Example 1 except that the component (B) was a Mooney viscosity of 60M _{1 + 4} (100 ° C.), an _N content of 27% by mass, and NBR having no carboxyl group. The composite magnetic body was obtained and evaluated for laminateability, magnetic permeability, reflow resistance, flexibility, and internal stress relaxation.

Example 9
(B) A semi-cured sheet and a thickness in the same manner as in Example 1 except that the component is NBR having a carboxyl group with a Mooney viscosity of 75M _{1 + 4} (100 ° C.) and an AN content of 40.5% by mass. A composite magnetic body having a thickness of 100 μm was obtained and evaluated for lamination properties, magnetic permeability, reflow resistance, flexibility, and internal stress relaxation properties.

(Example 10)
The component (A) is a bisphenol type epoxy resin having an average epoxy equivalent of 90 g / eq, the component (A) is 8 g, the component (B) is 8 g, the component (C) is 8 g, the aluminum hydroxide is 25.5 g, red phosphorus A semi-cured sheet and a composite magnetic body having a thickness of 100 μm were obtained in the same manner as in Example 1 except that 1.5 g and the soft magnetic metal powder were 204 g, and the lamination property, magnetic permeability, reflow resistance, Flexibility and internal stress relaxation were evaluated.

(Example 11)
(A) A semi-cured sheet and a composite magnetic body having a thickness of 100 μm were obtained in the same manner as in Example 10 except that the component was a bisphenol type epoxy resin having an average epoxy equivalent of 100 g / eq, and a laminate property and magnetic permeability were obtained. Evaluation was made on reflow resistance, flexibility, and internal stress relaxation.

(Example 12)
The component (A) is a bisphenol type epoxy resin having an average epoxy equivalent of 700 g / eq, the component (A) is 8 g, the component (B) is 8 g, the component (C) is 1 g, the aluminum hydroxide is 20 g, the red phosphorus is 1 g, A semi-cured sheet and a composite magnetic body having a thickness of 100 μm were obtained in the same manner as in Example 1 except that the amount of the soft magnetic metal powder was 160 g, and the lamination property, magnetic permeability, reflow resistance, flexibility, internal The stress relaxation property was evaluated.

(Example 13)
(A) A semi-cured sheet and a composite magnetic body having a thickness of 100 μm were obtained in the same manner as in Example 12 except that the component was a bisphenol type epoxy resin having an average epoxy equivalent of 750 g / eq, and the laminate property and magnetic permeability were obtained. Evaluation was made on reflow resistance, flexibility, and internal stress relaxation.

(Example 14)
The component (B) was a semi-cured sheet and a thickness of 100 μm in the same manner as in Example 1 except that the component was a Mooney viscosity 45M _{1 + 4} (100 ° C.), an _N content of 27 mass%, and NBR having a carboxyl group. A composite magnetic body was obtained and evaluated for laminateability, magnetic permeability, reflow resistance, flexibility, and internal stress relaxation.

(Example 15)
The component (B) was a semi-cured sheet and a thickness of 100 μm in the same manner as in Example 1 except that the component was Mooney viscosity 95M _{1 + 4} (100 ° C.), AN content 27% by mass, and NBR having a carboxyl group. A composite magnetic body was obtained and evaluated for laminateability, magnetic permeability, reflow resistance, flexibility, and internal stress relaxation.

(Example 16)
The component (B) was a semi-cured sheet and a thickness of 100 μm in the same manner as in Example 1 except that the component was Mooney viscosity 60M _{1 + 4} (100 ° C.), AN content 3% by mass, and NBR having a carboxyl group. A composite magnetic body was obtained and evaluated for laminateability, magnetic permeability, reflow resistance, flexibility, and internal stress relaxation.

(Example 17)
The component (B) was a semi-cured sheet and a thickness of 100 μm in the same manner as in Example 1 except that the component was a Mooney viscosity 60M _{1 + 4} (100 ° C.), an _N content of 55% by mass, and an NBR having a carboxyl group. A composite magnetic body was obtained and evaluated for laminateability, magnetic permeability, reflow resistance, flexibility, and internal stress relaxation.

(Example 18)
(B) A semi-cured sheet and a composite magnetic body having a thickness of 100 μm are obtained in the same manner as in Example 1 except that the component is polyisobutene (PIB), and laminateability, magnetic permeability, reflow resistance, and flexibility are obtained. The internal stress relaxation property was evaluated.

(Example 19)
(B) A semi-cured sheet and a composite magnetic body having a thickness of 100 μm were obtained in the same manner as in Example 1 except that the component was butadiene rubber (BR), and the lamination property, magnetic permeability, reflow resistance, and flexibility were obtained. And internal stress relaxation properties were evaluated.

(Example 20)
(B) A semi-cured sheet and a composite magnetic body having a thickness of 100 μm were obtained in the same manner as in Example 1 except that the component was styrene-butadiene rubber (SBR), and the lamination property, magnetic permeability, and reflow resistance were obtained. , Flexibility and internal stress relaxation were evaluated.

(Comparative Example 1)
(A) Component 8g, (B) Component 0g, (C) Component 4g, Epoxy Resin Curing Accelerator 0.02g, Flame Retardant 13g, Flame Retardant Aid 0.7g, Soft Magnetic Metal Powder The composite magnetic body having a semi-cured sheet and a thickness of 99 μm was obtained in the same manner as in Example 1 except that the thickness was changed to 104 g, and the lamination property, magnetic permeability, reflow resistance, flexibility, and internal stress relaxation were evaluated. .

(Comparative Example 2)
A semi-cured sheet and a thickness of 100 μm were obtained in the same manner as in Example 1 except that chlorinated polyethylene (chlorinated PE) was used instead of the components (A) to (C) and the epoxy resin curing accelerator. The composite magnetic body was obtained and evaluated for laminateability, magnetic permeability, reflow resistance, flexibility, and internal stress relaxation.

(Comparative Example 3)
(A) component 8g, (B) component 1.2g, (C) component 4g, epoxy resin curing accelerator 0.01g, flame retardant 13g, flame retardant aid 0.72g, soft magnetic A semi-cured sheet and a composite magnetic body having a thickness of 100 μm were obtained in the same manner as in Example 1 except that the metal powder was changed to 104 g, and the lamination property, magnetic permeability, reflow resistance, flexibility, and internal stress relaxation properties were obtained. evaluated.

(Comparative Example 4)
(A) component 8g, (B) component 24g, (C) component 4g, epoxy resin curing accelerator 0.02g, flame retardant 19g, flame retardant auxiliary 1.2g, soft magnetic metal powder The composite magnetic body having a semi-cured sheet and a thickness of 100 μm was obtained in the same manner as in Example 1 except that the weight was changed to 152 g, and the lamination property, magnetic permeability, reflow resistance, flexibility, and internal stress relaxation were evaluated. .

(Comparative Example 5)
(C) A semi-cured sheet material and a composite magnetic material having a thickness of 100 μm were used in the same manner as in Example 1 except that diethylenetriamine, which is a polyamine-based curing agent (described as PA-based in the table), was used in place of the component. Were evaluated for laminateability, magnetic permeability, reflow resistance, flexibility, and internal stress relaxation.

(Comparative Example 6)
(C) In the same manner as in Example 1, except that 1,2,3,4-butanetetracarboxylic acid, which is a polycarboxylic acid curing agent (in the table, described as PC-based), was used instead of component (C). A semi-cured sheet and a composite magnetic body having a thickness of 100 μm were obtained and evaluated for laminateability, magnetic permeability, reflow resistance, flexibility, and internal stress relaxation.

(Evaluation method)
<Permeability>
For the composite magnetic body of each example, a real term and an imaginary term are obtained, and those having a real term of 80 or more and an imaginary term of 20 or more are regarded as “good”, and those having a real number less than 80 or less than the imaginary term 20 are rejected. ".

≪Real term of permeability≫
The composite magnetic material of each example was punched into a ring shape having an outer diameter of 7 mm and an inner diameter of 3 mm, and this was wound with 12 turns to obtain a test piece. About this test piece, it calculated with the impedance in 1 MHz using the impedance measuring instrument "Precision Impedance Analyzer HP4294A" by Agilent Technologies.

≪Imaginary term of permeability≫
For the test piece prepared in “<< Real number term of magnetic permeability >>”, the loss term is measured in the range of 1 MHz to 10 GHz using an S-parameter measuring device “Network Analyzer E5071C” manufactured by Agilent Technologies, and the maximum value is an imaginary number. Term.

≪Reflow resistance≫
The composite magnetic material of each example was used as a 50 mm long × 50 mm wide test piece. The test piece was subjected to a solder reflow test (twice at 260 ° C. for 10 seconds × 2 times) in accordance with JIS C-5012 “Test method for printed wiring board” 10.4.1 “Solder float method”. The test piece after the solder reflow test was observed with the naked eye and evaluated according to the following evaluation criteria.

[Evaluation criteria]
A: No change in appearance is observed before and after the reflow test.
○: Almost no change in appearance was observed before and after the reflow test.
Δ: Strain is observed after the reflow test, but swelling, powdering, cracking and cracking are not observed.
X: Swelling, powdering, cracking or cracking is observed before and after the reflow test.

≪Flexibility≫
The composite magnetic material of each example was used as a 50 mm long × 50 mm wide test piece. The test piece was subjected to a solder reflow test (twice at 260 ° C. for 10 seconds × 2 times) in accordance with JIS C-5012 “Test method for printed wiring board” 10.4.1 “Solder float method”. The test pieces before and after the solder reflow test were bent with a MIT anti-fatigue testing machine, model number: DA, manufactured by Toyo Seiki Seisakusho Co., Ltd., with a bending speed of 175 times / minute, a bending angle of 135 °, and a load of 4.9 N. It was. The test piece after bending was observed with the naked eye and evaluated according to the following evaluation criteria.

[Evaluation criteria]
A: No whitening, cracks or cracks are observed at the bent part.
○: Cracks and cracks are not observed in the bent part, but whitening is observed.
Δ: Cracks or cracks are observed in the bent portion.
X: It cut | disconnected by the bending part.

≪Internal stress relaxation≫
The composite magnetic material of each example was bonded to a commercially available glass epoxy-printed wiring board at 150 ° C., and then pressed at 150 ° C. and 20 MPa with a hot press machine to obtain a test piece. About this test piece, 150 degreeC * 2 hours and -40 degreeC * 2 hours were made into 1 cycle, and the heat cycle test of 10 cycles was done. The test piece after the heat cycle test was observed with the naked eye and evaluated according to the following evaluation criteria.

[Evaluation criteria]
A: No change in appearance was observed before and after the thermal cycle test.
○: Almost no change in appearance was observed before and after the thermal cycle test.
(Triangle | delta): Although distortion is recognized after a heat cycle test, a swelling, powdering, a crack, and a crack are not recognized.
X: Swelling, cracking or cracking is observed before and after the reflow test.

≪Laminating properties≫
Three semi-cured sheets of each example were stacked and subjected to hot pressing at 150 ° C. and 20 MPa for 10 seconds. After the hot pressing, the composite magnetic body was visually observed, and the adhesion state was evaluated according to the following evaluation criteria.

[Evaluation criteria]
(Double-circle): The boundary of each layer is not recognized but it has become one composite magnetic body as a whole.
○: The boundary of each layer is recognized, but each layer is in close contact and does not peel off.
(Triangle | delta): The boundary of each layer is recognized and each layer can be peeled with fingers.
X: Each layer is separated and separated (efficient production is impossible).

Tables 1 to 4 show the composition of the composite magnetic body of each example and the evaluation results.
As shown in Tables 1 to 3, all of Examples 1 to 20 to which the present invention was applied had a permeability of “◯”, and could sufficiently absorb electromagnetic wave noise generated from an electronic device or the like. In addition, in Examples 1 to 20, the internal stress relaxation property was “◯” or “◎”, and quality deterioration hardly occurred even in long-term use. Further, in Examples 1 to 20, the reflow resistance, the flexibility, and the laminate property were “◯” or “◎”.
As shown in Table 4, in Comparative Example 1 not containing the component (B), the internal stress relaxation property and flexibility were “x”.
In Comparative Example 2 in which the resin composition was made of chlorinated polyethylene, the reflow resistance was “x”, and after solder reflow, deformation was significant and the flexibility could not be evaluated. In Comparative Example 3 in which the (B) / [(A) + (C)] ratio is 0.1, the flexibility is “x”, and the (B) / [(A) + (C)] ratio is 2. In Comparative Example 4, the reflow resistance was “x”.
Comparative Examples 5 to 6 using a resin curing agent other than the P-based resin could not be efficiently manufactured because the lamination property was “x”.
From these results, it was found that by applying the present invention, it is possible to obtain a composite magnetic body that has sufficient flexibility and does not cause a defective shape in reflow soldering and can be manufactured with high manufacturing efficiency.

Claims (7)

Soft magnetic metal powder is dispersed in a resin composition containing (A) component: bisphenol type epoxy resin, (B) component: synthetic rubber, and (C) component: phenol resin-based curing agent for epoxy resin. And
A mass ratio represented by (B) component / [(A) component + (C) component] is 0.5 to 1.5.   The composite magnetic body according to claim 1, wherein the component (A) has an average epoxy equivalent of 100 to 700 g / eq.   The composite magnetic body according to claim 1, wherein the component (B) is at least one selected from polyisobutene, butadiene rubber, styrene-butadiene rubber, and nitrile rubber.   The composite magnetic body according to claim 1, wherein the component (B) is a nitrile rubber having an acrylonitrile content of 5 to 50% by mass.   The composite magnetic body according to claim 1, wherein the component (B) is a nitrile rubber having a carboxyl group. 6. The composite magnetic body according to claim 5, wherein the nitrile rubber having a carboxyl group has a Mooney viscosity of 50 to 90 M _{1 + 4} (100 ° C.).   The component (C) is an amount such that an active hydrogen equivalent is 0.1 to 1.0 equivalent relative to 1 equivalent of the epoxy group of the component (A). 2. The composite magnetic material according to claim 1.