JP2005314177A - Spherical ferrite particle for radio wave absorbing material and its manufacturing method, and resin composition for semiconductor sealing containing ferrite particles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spherical ferrite particle for radio wave absorbing materials which has high volume resistivity and very few micropores, of which the particle size is 1 to 45 μm, and which is superior in electro-magnetic wave absorptivity in high frequency region, and its manufacturing method, and a resin composition for semiconductor sealing containing the ferrite particles. <P>SOLUTION: The ferrite particle contains 60 mol or less of one kind or two or more kinds of metal elements selected from the group consisting of Li, Mg, Ni, Cu, Zn, Mn, Ca, Co, Zr, Sn, Ba, and Ti, to 100 mol of Fe element, and has a spinel structure, and has one kind or two or more kinds of metal oxides selected from among SiO<SB>2</SB>, Al<SB>2</SB>O<SB>3</SB>and TiO<SB>2</SB>, in its surface layer part, and the content of the metal oxide is 1 to 30 pts.wt. to 100 pts.wt. of the ferrite, the mean particle diameter is 1 to 45 μm, the volume resistivity is 1×10<SP>11</SP>Ωcm or higher, the BET specific surface area is 0.2 m<SP>2</SP>/g or smaller, and the micropore volume by mercury porosimetry is 0.05 mL/g or smaller. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to spherical ferrite particles for radio wave absorbers, a method for producing the same, and a resin composition for semiconductor encapsulation containing the spherical ferrite particles. Specifically, the volume resistivity is high, the pores are extremely small, and the particle size. Can be freely controlled in the range of 1 to 45 μm, and has a high magnetic permeability and is particularly effective in a resin dispersion for a radio wave absorber, a method for producing the same, and a resin composition for semiconductor encapsulation containing the spherical ferrite particles Related to things.

  Ferrite particles, for example, Mn—Zn based ferrite mainly exhibits high magnetic permeability at a frequency of 10 kHz to 30 MHz, and Ni—Zn based ferrite mainly exhibits high magnetic permeability at a frequency of 30 MHz to 300 MHz. Used as a radio wave absorber in each frequency range. With the recent miniaturization of electronic devices, improvement of ferrite magnetic loss in a high frequency region, that is, improvement of eddy current loss due to low resistance has been attempted.

For example, the formula: (MO) _100-X (Fe ₂ O ₃ ) _X (where M is at least one metal selected from Li, Mg, Ni, Cu, Zn, Mn, Ca and Fe; The average particle size is 1 to 45 μm, the BET specific surface area is 0.2 m ² / g or less, and the pore volume by the mercury intrusion method is 0. There are known spherical ferrite particles for radio wave absorbers of .05 ml / g or less.
JP 2003-318015 A

However, the spherical ferrite particles have a volume resistivity of about 10 ⁸ to 10 ¹⁰ Ωcm and cannot be said to be sufficiently high. Improvement of magnetic loss in a high frequency region, that is, eddy current due to low resistance Loss cannot be improved sufficiently, and when used as an additive for a sealant, it is easily affected by the environment and has a problem in reliability.

  The present invention has been made in view of the above circumstances, and its purpose is that the volume resistivity value is high, the number of pores is extremely small, and the particle size can be freely controlled in the range of 1 to 45 μm. An object of the present invention is to provide a spherical ferrite particle for a radio wave absorber excellent in electromagnetic wave absorption performance in the frequency domain, a method for producing the same, and a resin composition for semiconductor encapsulation containing the spherical ferrite particle for a radio wave absorber.

As a result of various studies, the present inventors have obtained the following knowledge. That is, according to the spherical ferrite particles in which the metal oxide surface layer containing Al and / or Si is formed on the surface of the ferrite particles, the average particle size can be freely controlled in the range of 1 to 45 μm, and the BET specific surface area is 0. .2 m ² / g or less, the pore volume by mercury intrusion method is 0.05 ml / g or less, and in addition to extremely few pores, the volume resistivity is 1 × 10 ¹¹ Ωcm or more. The problem of eddy current loss due to magnetic loss in the frequency domain, that is, low resistance is solved.

The present invention has been completed based on the above findings, and the first gist thereof is selected from Li, Mg, Ni, Cu, Zn, Mn, Ca, Co, Zr, Sn, Ba and Ti. Ferrite particles containing 60 mol or less of seed or two or more metal elements with respect to 100 mol of Fe element, and having a spinel structure, the surface layer portion being selected from SiO ₂ , Al ₂ O ₃ and TiO ₂ The metal oxide content is 1 to 30 parts by weight with respect to 100 parts by weight of ferrite, the average particle size is 1 to 45 μm, and the volume resistivity is 1 to 45 parts by weight. is a but 1 × ^{10 11} Ωcm or more, BET specific surface area of not more than 0.2 m ² / g, resides in the spherical ferrite particles for radio wave absorption materials the pore volume by mercury porosimetry is less than 0.05 ml / g .

The second gist of the present invention is that a metal of Al ₂ O ₃ and / or SiO ₂ is formed during a phenol resin formation reaction in which phenols and aldehydes are reacted and cured in an aqueous medium in which a ferrite precursor is dispersed. Oxides are added to form composite particles composed of a core portion composed of a ferrite precursor and a phenol resin and a surface layer portion composed of a metal oxide and a phenol resin, and the resulting composite particles are 400 to 400 It exists in the manufacturing method of the spherical ferrite particle which heat-processes at 700 degreeC, removes a phenol resin, and then heat-processes at 800-1400 degreeC, and ferritizes a ferrite precursor.

  According to a third aspect of the present invention, there is provided a resin composition for encapsulating a semiconductor comprising the spherical ferrite particles and a binder resin.

According to the present invention, it is spherical and has a high volume resistivity of 1 × 10 ¹¹ Ωcm or more, a BET specific surface area of 0.2 m ² / g or less, and a pore volume of 0.05 ml / g or less. Since it has a structure with few pores, it can improve magnetic loss in the high frequency range, that is, eddy current loss due to low resistance, and when used as an additive for sealant, And is useful as a radio wave absorber.

Hereinafter, the present invention will be described in detail. The spherical ferrite particles of the present invention contain one or more metal elements selected from Li, Mg, Ni, Cu, Zn, Mn, Ca, Co, Zr, Sn, Ba and Ti with respect to 100 mol of Fe element. Ferrite particles having a spinel structure and having a metal oxide of Al ₂ O ₃ and / or SiO _{2 in} the surface layer.

    Examples of metal elements other than the Fe element constituting the ferrite particles having the spinel structure include Li, Mg, Ni, Cu, Zn, Mn, Ca, Co, Zr, Sn, Ba, and Ti. Among these, Mg, Ni, Cu, Zn and Mn are preferred.

  The amount of one or more metal elements selected from Li, Mg, Ni, Cu, Zn, Mn, Ca, Co, Zr, Sn, Ba and Ti in the ferrite particles having a spinel structure is 100 mol of Fe element. The amount is 60 mol or less, preferably 2 to 55 mol. When the amount exceeds 60 mol, the magnetization value of the obtained spherical ferrite particles becomes insufficient, and there is a problem that carriers are scattered or attached to the photoreceptor.

Surface portion constituting the spherical ferrite particles containing _Al 2 _{O 3} and / or SiO ₂ metal oxide. The amount of the metal oxide in the spherical ferrite particles is usually 1 to 30 parts by weight, preferably 2 to 20 parts by weight with respect to 100 parts by weight of ferrite. When the amount of the metal oxide is 1 part by weight, the volume resistivity may be less than 1 × 10 ¹¹ Ωcm. On the other hand, when the amount exceeds 30 parts by weight, there is a problem that the magnetization value of the spherical ferrite particles becomes insufficient, and carriers are scattered or attached to the photoreceptor. In addition, the composition and content of the spherical ferrite particles can be measured by a usual analysis method for inorganic particles, for example, an X-ray diffraction analysis method and an X-ray photoelectron analysis method.

  The average particle diameter of the spherical ferrite particles is usually 1 to 45 μm, preferably 10 to 45 μm. When the average particle diameter is less than 1 μm, scattering to the photoreceptor occurs, and when it exceeds 45 μm, it is difficult to achieve high image quality.

The volume resistivity of the spherical ferrite particles is usually 1 × 10 ¹¹ Ωcm or more, preferably 1 × 10 ¹¹ to 1 × 10 ¹⁵ Ωcm, and more preferably 1 × 10 ¹² to 1 × 10 ¹⁵ Ωcm. If it is less than 1 × 10 ¹¹ Ωcm, there are problems such as the carrier adhering to the image area of the photoconductor or the latent image charge escaping through the carrier, resulting in disturbance of the latent image or image loss. is there. However, if it exceeds 1 × 10 ¹⁵ Ωcm, problems such as white spots in solid printing may occur.

The BET specific surface area of the spherical ferrite particles is 0.2 m ² / g or less, preferably 0.15 m ² / g or less. When the BET specific surface area exceeds 0.2 m ² / g, the environmental stability of charging is deteriorated. Moreover, the pore volume by the mercury intrusion method to be described later is 0.05 ml / g or less, preferably 0.01 ml / g or less. When the pore volume exceeds 0.05 ml / g, the environmental stability of charging is deteriorated. The lower limits of the BET specific surface area and pore volume are not particularly limited, but from the viewpoint of measurement accuracy of the measuring instrument, the BET specific surface area is usually about 0.01 m ² / g and the pore volume is about 0.001 ml / g. .

  The sphericity (l / w) of the spherical ferrite particles is usually 1.0 to 1.5, preferably 1.0 to 1.3, and the true specific gravity is usually 4.0 to 6.0, preferably 4 The bulk density is usually 2.0 to 3.0 g / ml, preferably 2.1 to 2.7 g / ml.

  Since the spherical ferrite particles of the present invention have a high volume resistivity as described above, magnetic loss in a high frequency region can be suppressed. Furthermore, when non-magnetic particles are mixed with ferrite particles, the relative permeability usually decreases, but surprisingly, the spherical ferrite particles of the present invention have a relative permeability equal to or higher than that of conventional spherical ferrite particles. As a result, the radio wave absorption ability is also excellent.

  The surface layer portion of the spherical ferrite particles of the present invention may be coated with at least one resin selected from an epoxy resin, a phenol resin, and a silicone resin. By covering the surface layer of spherical ferrite particles with resin, the volume resistivity is increased, and when filled in a sealing material, the viscosity is lowered and the fluidity is improved. The filling amount of particles can be increased.

  Examples of the epoxy resin include epoxy resins having two or more epoxy groups in one molecule and having an epoxy equivalent of 200 or more. Specifically, bisphenol A type epoxy resins, novolac type epoxy resins, Examples thereof include halogenated epoxy resins and glycidyl ester type epoxy resins.

  The epoxy equivalent is usually 200 to 600 g / equivalent, preferably 200 to 500 g / equivalent. When the number of epoxy groups in one molecule is less than 2, the adhesion with the ferrite particles is insufficient. When used as a semiconductor encapsulant, the upper limit of epoxy groups in one molecule is 3 in view of lowering the viscosity of the epoxy resin composition. When the epoxy equivalent is less than 200 g / equivalent, the fluidity during molding of the epoxy resin composition is not good. When it exceeds 600 g / equivalent, the packing property of the obtained molded article becomes insufficient.

  Examples of the phenolic resin include resole phenolic resins usually having a molar ratio of phenol to formalin in the range of 1/1 to 1/3, and the OH equivalent thereof is usually 150 g / equivalent or more, preferably 180 g / equivalent. Equivalent to 300 g / equivalent. When the OH equivalent is less than 150 g / equivalent, the water absorption of the obtained molded product is high and the packing property is also deteriorated.

  Examples of the silicone resin include silicone resins in which the molar ratio of trifunctional units to bifunctional units is usually 100: 0 to 60:40, preferably 100: 0 to 70:30. When the molar ratio is outside the above range, the fluidity of the resin composition is poor and the packing property is also poor. Epoxy-modified or acrylic-modified silicone resins can also be used.

  The resin coating amount is usually 0.1 to 10% by weight, preferably 0.2 to 5% by weight, based on the ferrite particles. When the resin coating amount is less than 0.1% by weight, the improvement of the compatibility with the epoxy resin is insufficient, and the improvement of the fluidity of the resin composition is also insufficient. When it exceeds 10% by weight, it is difficult to increase the filling amount of the ferrite particles, and it becomes difficult to sufficiently exhibit the function of the ferrite particles.

Next, a method for producing spherical ferrite particles will be described. Spherical ferrite particles are added with Al ₂ O ₃ and / or SiO ₂ metal oxides during the phenol resin formation reaction in which phenols and aldehydes are reacted and cured in an aqueous medium in which ferrite precursors are dispersed. Then, composite particles composed of a surface layer portion made of a metal oxide and a phenol resin and a core portion of a ferrite precursor are formed, and the obtained composite particles are heated at 400 to 700 ° C. to obtain a phenol resin. It is then removed and then heat treated at 800 to 1400 ° C. to obtain a ferrite precursor that is made into a ferrite.

The ferrite precursor to be used is a supply source of elements constituting the core particles, for example, oxides such as Li, Mg, Ni, Cu, Zn, Mn, Ca, Fe, hydroxide, oxalate, Examples of the particles include carbonates. Further, Fe ₂ O ₃ particles may be mentioned as a source of Fe element. The supply source of each element may be any element as long as it does not dissolve in water and is not altered or modified by water, and oxide particles of each element are preferable. For example, Li ₂ O, Li ₂ CO ₃ , MgO, NiO, CuO, ZnO, MnO, Mn ₃ O ₄ , CaO, CoO, and ZrO ₂ are used so that the ferrite precursor has the desired composition ratio of ferrite particles. , SnO ₂ , BaO, TiO _{2 and the} like and Fe ₂ O ₃ particles are mixed and used.

  The particle form of the ferrite precursor may be any form such as a cube, polyhedron, sphere, needle, or plate. The average particle diameter may be a particle smaller than the average particle diameter of the composite particles, and is usually 0.01 to 5.0 μm, preferably 0.1 to 2.0 μm. When the average particle diameter of the ferrite precursor is less than 0.01 μm, the content of the ferrite precursor in the composite particles becomes low, and the magnetization value of the spherical ferrite particles becomes insufficient. On the other hand, when it exceeds 5.0 μm, the sphericity of the composite particles and the ferrite particles deteriorates.

  The ferrite precursor is temporarily fired as necessary in order to improve the uniformity of the composition. Temporary baking is normally performed at 700-1000 degreeC for about 1-4 hours.

As metal oxide particles to be added, SiO ₂ , Al ₂ O ₃ and a mixture thereof are used. The average particle size is usually 0.01 to 5.0 μm, preferably 0.1 to 2.0 μm. When the average particle diameter of the metal oxide particles is less than 0.01 μm, it is insufficient to increase the volume resistivity, and when it exceeds 5.0 μm, the surfaces of the composite particles and the ferrite particles are uneven. Or sphericity deteriorates.

  The ferrite precursor and metal oxide particles are preferably lipophilic particles. When a non-lipophilic ferrite precursor is used, it may be difficult to obtain composite particles having excellent sphericity. When metal oxide particles that have not been oleophilicized are used, the metal oxide particles may not be firmly embedded in the surface of the composite particle and may be separated from the composite particle.

  As the oleophilic treatment, a method of treating a ferrite precursor and metal oxide particles with a coupling agent such as a silane coupling agent or a titanate coupling agent, a ferrite precursor in an aqueous medium containing a surfactant, and Examples include a method of dispersing metal oxide particles and adsorbing a surfactant on the particle surface.

  Examples of the silane coupling agent include those having a hydrophobic group, an epoxy group, and an amino group, and these may be used alone or in combination of two or more as required.

  Examples of the silane coupling agent having a hydrophobic group include vinyltrichlorosilane, vinyltriethoxysilane, and vinyltris (β-methoxy) silane. Examples of the silane coupling agent having an epoxy group include γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) trimethoxysilane, and the like. Examples of the silane coupling agent having an amino group include γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, and N-β- (aminoethyl) -γ-aminopropyl. Examples include methyldimethoxysilane and N-phenyl-γ-aminopropyltrimethoxysilane.

  Examples of titanate coupling agents include isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris (dioctyl pyrophosphate) titanate, and the like.

  There is no restriction | limiting in particular as surfactant, A well-known surfactant can be used. Examples thereof include ferrite precursors and metal oxide particles and those having a functional group capable of binding to a hydroxyl group on the particle surface. In terms of ionicity, cationic or anionic ones are preferable. These may be used alone or in combination of two or more as required.

  In view of the adhesion with the phenol resin during the lipophilic treatment of the ferrite precursor and the metal oxide particles, the lipophilic treatment with a silane coupling agent having an amino group or an epoxy group is preferable.

  The amount of the oleophilic treatment agent is preferably 0.1 to 5.0% by weight with respect to the ferrite precursor or metal oxide particles. If it is less than 0.1% by weight, it is difficult to obtain composite particles having the desired ferrite particle content due to insufficient lipophilic treatment, and the metal oxide particles become composite particles. It may not be firmly embedded. On the other hand, when it exceeds 5.0% by weight, the produced composite particles are aggregated, and it becomes difficult to control the particle size of the composite particles.

  In the production of spherical ferrite particles, first, a spherical core composed of a ferrite precursor and a phenol resin is prepared by reacting a phenol and an aldehyde in an aqueous medium in the presence of a ferrite precursor and a basic catalyst. Then, by adding metal oxide particles during the reaction, a surface layer portion composed of the metal oxide particles and the phenol resin is prepared, and composite particles having a core portion and a surface layer portion are formed.

  The content of the ferrite precursor and the metal oxide particles in the composite particles is usually 80 to 98% by weight. When the content is less than 80% by weight, since there is a large amount of phenol resin, a large amount of energy for removing the ferrite resin is required during the heat treatment, which is not preferable. On the other hand, if it exceeds 98% by weight, the strength of the composite particles before the heat treatment becomes weak, and the particles may be destroyed during the heat treatment.

  As a basic catalyst used by this invention, the basic catalyst used for normal phenol resin manufacture is mentioned. Examples thereof include aqueous ammonia, hexamethylenetetramine, and alkylamines such as dimethylamine, diethyltriamine, and polyethyleneimine. The amount (molar ratio) of the basic catalyst to the phenol is usually 0.02 to 0.7. When the molar ratio is less than 0.02, the reaction does not proceed sufficiently, and when it exceeds 0.7, a large amount of excess basic catalyst remains in the reaction solution, which increases the wastewater treatment load. Absent.

  As phenols used in the present invention, in addition to phenol, alkylphenols such as m-cresol, p-tert-butylphenol, o-propylphenol, resorcinol, bisphenol A, benzene nucleus, and a part or all of alkyl groups are included. Examples thereof include compounds having a phenolic hydroxyl group such as halogenated phenols substituted with a chlorine atom or a bromine atom, and these are used alone or in combination of two or more as required. Of these, phenol is preferred.

  Examples of the aldehydes used in the present invention include formaldehyde and furfural in any form of formalin or paraformaldehyde, and these are used alone or in combination of two or more as required. Of these, formaldehyde is preferable. The amount (molar ratio) of aldehydes to phenols is usually 1 to 4, preferably 1.2 to 3. When the molar ratio is less than 1, the particles are difficult to form, and even if they are formed, the curing of the resin is difficult to proceed, and the strength of the generated particles is weak. On the other hand, when the molar ratio exceeds 4, the amount of unreacted aldehydes remaining in the aqueous medium after the reaction increases, which is not preferable.

  The temperature of the phenol resin formation reaction in which the above phenols and aldehydes are reacted / cured is usually 70 to 90 ° C. And after reaction and hardening, it cools to 40 degrees C or less, and obtains the water dispersion liquid containing a spherical composite particle.

  Next, the obtained aqueous dispersion is separated into solid and liquid according to conventional methods such as filtration and centrifugation, and then dried to obtain spherical composite particles composed of a ferrite precursor, metal oxide particles, and a phenol resin.

  In the phenol resin formation reaction, a suspension stabilizer may be present if necessary. Examples of the suspension stabilizer include hydrophilic organic compounds such as carboxymethyl cellulose and polyvinyl alcohol, fluorine compounds such as calcium fluoride, and water-insoluble inorganic salts such as calcium sulfate. These may be used alone or as necessary. Two or more types are used in combination depending on the condition.

  Next, the obtained spherical composite particles are heat-treated to remove the phenol resin. The temperature of heat processing is the temperature which a phenol resin decomposes | disassembles, ie, 400-700 degreeC, Preferably it is 500-600 degreeC. When the temperature of the heat treatment exceeds 700 ° C., aggregation between particles occurs and the particle size distribution becomes wide. Moreover, when it is less than 400 degreeC, a phenol resin is not fully decomposed and removed. The heat treatment time varies depending on the heating temperature, but is usually about 2 to 8 hours. In the case of less than 2 hours, the phenol resin is not sufficiently decomposed and the resin is not sufficiently removed. On the other hand, if it exceeds 8 hours, the processing time itself becomes too long, which is not efficient.

  The heat treatment furnace may be any processing machine such as a fixed type or a rotary type. From the viewpoint of preventing aggregation of particles, a rotary type is preferable. The atmosphere of the heat treatment is preferably an oxidizing atmosphere in consideration of not decomposing the phenol resin and leaving it as carbon. As the oxidizing atmosphere, air may be flowed into the heat treatment furnace, and the flow rate is usually 1 L / min or more. If it is less than 1 L / min, the heat treatment furnace may be filled with resin decomposition gas, and as a result, carbon may remain.

  After removing the phenol resin, it is ferritized by heat treatment (firing). Although the temperature of heat processing changes also with ferrite compositions, it is 800-1400 degreeC normally, Preferably it is 900-1300 degreeC. When the temperature of the heat treatment exceeds 1400 ° C., the particles are sintered with each other, and there is a disadvantage that the particle size distribution becomes wide. On the other hand, when the temperature is less than 800 ° C., there is a disadvantage that the ferrite formation is insufficient and the magnetic flux density is insufficient. The heat treatment time varies depending on the heating temperature, but is usually about 1 to 10 hours. If it is less than 1 hour, ferritization is insufficient, and if it exceeds 10 hours, productivity is lowered.

  The atmosphere of the heat treatment (firing) may be changed depending on the composition in order to make the saturation magnetization and the electric resistance value a desired value. When performing in an oxidizing atmosphere in which air is passed, an inert gas such as nitrogen gas is allowed to flow. When the treatment is performed in a non-oxidizing atmosphere, a case where the treatment is performed while flowing a mixed gas of air and nitrogen may be appropriately selected. The gas flow rate is usually 1 L / min or more. If it is less than 1 L / min, it is difficult to obtain desired saturation magnetization and electrical resistance.

  The spherical ferrite particles may be coated with at least one resin selected from an epoxy resin, a phenol resin, and a silicone resin. This resin coating is performed by mixing and stirring the spherical ferrite particles, the resin, and some solvent with a processing machine having a stirring function. High-speed mixer (Fukae Powtech Co., Ltd.), Henschel Mixer (Mitsui San Co., Ltd.), CF Granulator (Freund Sangyo Co., Ltd.), Vertical Granulator (Powrec Co., Ltd.) ), Flow jet granulator (manufactured by Okawara Manufacturing Co., Ltd.), universal stirrer (manufactured by Dalton Co., Ltd.), Nauta mixer (manufactured by Hosokawa Micron Co., Ltd.), and the like.

  When coating the spherical ferrite particles with a resin, various curing agents can be used as necessary. Examples of the curing agent include amines, acid anhydrides, metal alkoxides, and phenol novolac resins. The addition amount of the curing agent is usually 0.01 to 5% by weight with respect to the resin. When the amount is less than 0.01% by weight, the spherical ferrite particles may aggregate. Moreover, when it exceeds 5 weight%, when it uses as a sealing material, the problem of a hygroscopic property may be produced.

  Next, the resin composition for semiconductor encapsulation will be described. The resin composition for encapsulating a semiconductor comprises spherical ferrite particles or resin-coated spherical ferrite particles and a binder resin, and may contain a phenol resin curing agent, a curing accelerator, and silica powder as necessary. .

  Examples of the binder resin include epoxy resins. Specifically, bisphenol A type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, brominated bisphenol A type epoxy resins, brominated phenol novolac type epoxy resins, and the like. Is mentioned.

  Examples of the curing agent include amines, acid anhydrides, phenol novolac resins, and the like, and phenol novolac resins are preferable.

  The content of the spherical ferrite particles in the resin composition is usually 10 to 50% by weight, preferably 20 to 50% by weight. The content of silica particles in the resin composition is usually 30% by weight or less, preferably 20% by weight or less. Considering the radio wave absorptivity, the larger the content of the spherical ferrite particles, the better.

The spherical ferrite particles according to the present invention have a sphericity close to a true sphere, have a specific particle size distribution, and have a high volume resistivity of 1 × 10 ¹¹ to 1 × 10 ¹⁵ Ωcm and a BET ratio. Since the surface area is 0.2 m ² / g or less, the pore volume is 0.04 ml / g or less, and the structure has few pores, it has a high magnetic permeability. As useful.

  Furthermore, the spherical ferrite particles coated with a specific resin and the resin composition for semiconductor encapsulation containing the ferrite particles have a low melt viscosity, can contain a high amount of ferrite particles, and have high reliability and high magnetic permeability. Therefore, it is useful as a radio wave absorber.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to a following example, unless the summary is exceeded. The characteristics were measured by the following method.

  The average particle size was measured with a laser diffraction particle size distribution meter (RODOS, manufactured by SYMPATEC).

  The bulk density was measured according to the method described in JISK5101.

  For the measurement of sphericity, 250 or more spherical composite particles are randomly extracted with a scanning electron microscope (S-800, manufactured by Hitachi, Ltd.), and an average major axis diameter l and an average minor axis diameter w are obtained. Degree = l / w (where l represents the average major axis diameter of the spherical composite particles and w represents the average minor axis diameter of the spherical composite particles).

  The BET specific surface area was measured by a nitrogen adsorption method.

  The pore volume was indicated by a value measured with a mercury intrusion autopore 9220 (manufactured by Shimadzu Corporation).

  As the volume resistivity value, a value measured with a high resistance meter 4329A (trade name, manufactured by Yokogawa Hewlett-Packard Company) was used.

  The specific permeability is such that spherical ferrite particles are filled into 60 vol% thermoplastic elastomer (Shell Kraton G1657) by roll kneading. The obtained kneaded material was formed into a hollow cylinder (outer diameter 7 mm, inner diameter 3 mm, thickness 1.0 ± 0.1 mm) and measured by a coaxial tube S-parameter method using a network analyzer 8720D (manufactured by Hewlett-Packard Company). When the relative permeability (μr ′) value at 500 MHz is 2.5 or more, the radio wave absorption performance is excellent.

  Reliability was measured as follows. A molded body having a width of 10 mm, a length of 10 mm, and a thickness of 0.5 mm was made by struggling with the resin composition for semiconductor encapsulation, and two aluminum wires with a thickness of 25 μm were arranged on the surface at intervals of 100 μm. In a pressure vessel having a relative humidity of 85% and a temperature of 120 ° C., a bias voltage of DC 30V was loaded on two aluminum wires, and the test was performed for 30 hours. Appearance abnormalities such as a sudden drop in electrical resistance and corrosion of aluminum wires were observed. The evaluation is shown in the three stages of Table 1.

  The fluidity was evaluated by the melt viscosity at 175 ° C. of the resin composition measured using a Koka flow tester.

Example 1:
A silane-based cup having an epoxy group, charged with a precursor of a total amount of 1 kg at a ratio of 48.5 mol% Fe ₂ O _3, 20.6 mol% NiO, 10.4 mol% CuO and 20.5 mol% ZnO in a Henschel mixer 10 g of a ring agent KBM-403 (trade name: manufactured by Shin-Etsu Chemical Co., Ltd.) was added and mixed, and the surface of the precursor particles was oleophilicized with a silane coupling agent having an epoxy group.

Separately, 7.5 g of a silane coupling agent KBM-403 having an epoxy group was added to 1 kg of silica (SiO ₂ ) particles (Excelica SE-1; average particle size 1.8 μm) and mixed to form a metal oxide. The particle surface of the product was oleophilicized with a silane coupling agent having an epoxy group.

  Next, 105 g of phenol, 120 g of 37% formalin, 1 kg of oleophilic precursor, 37 g of 25% aqueous ammonia and 140 g of water were charged into a 1 L flask, and the temperature was raised to 70 ° C. over 60 minutes with stirring. Then, 70 g of silica particles treated with a silane coupling agent having an epoxy group on the particle surface was added, reacted at the same temperature for 60 minutes, and then heated to 85 ° C. over 30 minutes. By reacting and curing at the same temperature for 120 minutes, composite particles having a surface layer portion composed of a phenol resin and silica particles and a core portion composed of a phenol resin and a ferrite precursor were obtained.

  Next, after the contents in the flask were cooled to 30 ° C. and the supernatant was removed, the precipitate was filtered and dried at 80 ° C. for 7 hours with an air dryer to obtain composite particles.

  The obtained composite particles had an average particle size of 30 μm, a content of the precursor and silica particles of 88.8% by weight, and a pore volume of 0.001 ml / g.

  The obtained composite particles are put into a rotary heat treatment furnace having an internal volume of 10 L, and the temperature in the heat treatment furnace is raised to 600 ° C. in 2 hours while flowing air at a flow rate of 3 L / min, and heated at the same temperature for 4 hours. The phenol resin was removed by treatment (heat treatment). Subsequently, the temperature was raised to 1000 ° C. in 2 hours, and heat treatment (heat treatment II) was performed at the same temperature for 4 hours to perform ferrite formation. Then, after cooling to room temperature, it took out and obtained spherical ferrite particles.

The obtained spherical ferrite particles had an average particle size of 26 μm, a BET specific surface area of 0.02 m ² / g, a pore volume of 0.007 ml / g, and a volume resistivity of 3.8 × 10 ¹⁴ Ωcm. there were.

Examples 2-5, Comparative Example 1:
In Example 1, composite particles were obtained in the same manner as in Example 1 except that the type of ferrite precursor, the type and amount of the lipophilic agent, and other reaction conditions were changed. The production conditions and various characteristics at this time are shown in Table 1.

  Next, spherical ferrite particles were obtained in the same manner as in Example 1 except that the type of composite particles, the conditions of the heat treatment I and the heat treatment II were changed in Example 1. The production conditions and various characteristics at this time are shown in Table 2, and the various characteristics of the obtained spherical ferrite particles are shown in Table 3.

Example 6:
_{Fe 2 O 3 55.5mol%, MnO30.5mol} %, the precursor of the proportion of ZnO14.0Mol% were mixed for 3 hours in a ball mill. The obtained mixture was dried, calcined at 900 ° C. for 1 hour, and pulverized again with a ball mill. 10 g of the silane coupling agent KBM-403 (trade name: manufactured by Shin-Etsu Chemical Co., Ltd.) having an epoxy group was added to 1 kg of the obtained calcined particles, and the mixture was oleophilicized with a silane coupling agent having an epoxy group. . Next, a phenol resin production reaction was performed in the same manner as in Example 1 to obtain composite particles, and heat treatment I and heat treatment II were performed in the same manner as in Example 1 except that the composite particles were changed as shown in Table 2. Spherical ferrite particles were obtained. The production conditions and characteristics at this time are shown in Tables 1, 2 and 3, and the characteristics of the obtained spherical ferrite particles are shown in Table 4.

Comparative Example 2:
Each precursor was mixed for 3 hours in a ball mill at the same ratio as in Example 1. The mixture was dried, calcined at 800 ° C. for 1 hour, and pulverized again with a ball mill. 20 kg of polyvinyl alcohol and 200 g of water were added to 1 kg of the obtained calcined particles to form a slurry. The resulting slurry was granulated and dried with a splat liner to prepare composite particles having an average particle size of 35 μm. Next, the obtained composite particles are put into a rotary heat treatment furnace, and the temperature in the heat treatment furnace is raised to 600 ° C. in 2 hours while flowing air at 3 L / min. The polyvinyl alcohol was removed. Subsequently, the temperature in the heat treatment furnace was raised to 1000 ° C. in 3 hours, and heat treatment II was performed at the same temperature for 4 hours to obtain ferrite particles. The characteristics are shown in Table 4.

Example 7:
<Resin coating>
1 kg of the spherical ferrite particles obtained in Example 1 was put into a universal stirrer, and subsequently, 14 g of an epoxy resin having an epoxy equivalent of 300 g / equivalent (Epiclon 5300-70: Dainippon Ink and Chemicals) and 20 g of MEK (methyl ethyl ketone). Was added to coat the surface of the spherical ferrite particles with an epoxy resin.
The obtained epoxy resin-coated spherical ferrite particles had an average particle size of 27 μm and a volume resistivity of 4.2 × 10 ¹⁴ Ωcm.

<Manufacture of resin composition for semiconductor encapsulation>
The obtained epoxy resin-coated spherical ferrite particles were mixed by a Henschel mixer at a ratio of 40 vol%, spherical silica powder (fused silica: average particle size 10 μm) 21 vol%, and polyethylene wax 0.8 vol%. Next, the mixture was cooled by melting and mixing for 3 minutes with a hot roll heated to a temperature of 95 to 110 ° C., and then passed through a 10-mesh sieve to obtain a powdery resin composition for encapsulating a semiconductor.

(Resin composition)
Biphenyl type epoxy resin (softening point 105 ° C., epoxy equivalent 192) 100 parts Phenol aralkyl resin (softening point 60 ° C., hydroxyl group equivalent 169) 70 parts Brominated bisphenol A type epoxy resin (softening point 77 ° C., hydroxyl group equivalent 465) 8 parts Antimony trioxide 3 parts Carbon black 0.5 parts

Examples 8-9, Comparative Example 3:
Resin-coated spherical ferrite particles were obtained in the same manner as in Example 7, except that the type of spherical ferrite particles and the type and amount of the coating resin were changed. Table 5 shows the manufacturing conditions and characteristics at this time.

Claims (6)

Containing one or more metal elements selected from Li, Mg, Ni, Cu, Zn, Mn, Ca, Co, Zr, Sn, Ba and Ti, in an amount of 60 mol or less with respect to 100 mol of Fe element; and , A ferrite particle having a spinel structure, and having one or more metal oxides selected from SiO ₂ , Al ₂ O ₃ and TiO ₂ in the surface layer portion, and the content of the metal oxide is ferrite 1 to 30 parts by weight with respect to 100 parts by weight, an average particle diameter of 1 to 45 μm, a volume resistivity of 1 × 10 ¹¹ Ωcm or more, and a BET specific surface area of 0.2 m ² / g or less. A spherical ferrite particle for a radio wave absorber, wherein the pore volume by mercury porosimetry is 0.05 ml / g or less.   Furthermore, the spherical ferrite particle of Claim 1 by which the surface layer part is coat | covered with at least 1 sort (s) of resin chosen from the epoxy resin, the phenol resin, and the silicone resin. During the phenol resin formation reaction in which phenols and aldehydes are reacted and cured in an aqueous medium in which the ferrite precursor is dispersed, a metal oxide of Al ₂ O ₃ and / or SiO ₂ is added to the ferrite precursor. Forming composite particles composed of a core composed of a body and a phenol resin and a surface layer composed of a metal oxide and a phenol resin, and subjecting the resulting composite particles to a heat treatment at 400 to 700 ° C. And then heat-treating at 800-1400 ° C. to ferritize the ferrite precursor. Ferrite _{precursor, Li 2 O, Li 2 CO} 3, MgO, NiO, CuO, ZnO, MnO, Mn 3 O 4, CaO, CoO, ZrO 2, SnO 2, 1 kind selected from BaO, and TiO ₂ or 2 the method according to claim 3 comprising a seed or more particles and Fe ₂ O ₃ particles.   The production method according to claim 1, wherein the ferrite precursor and the metal oxide are lipophilic particles.   A resin composition for encapsulating a semiconductor comprising the ferrite particles according to claim 1 or 2 and a binder resin.