JP7069949B2 - Composite magnetic material - Google Patents

Description

The present invention relates to a composite magnetic material.

In recent years, the frequency of use of electric signals of wireless communication devices such as mobile phones and personal digital assistants has been increasing, and the demand for multi-band is increasing in order to support a plurality of communication methods. Along with this, it is desired that the electronic components mounted on these devices also support higher frequencies and wider bandwidths.

Examples of electronic components used in the high frequency band (GHz band and the like) include inductors, low-pass filters, diplexers, EMI filters, antennas and the like. The EMI filter is used as a countermeasure against high frequency noise in electronic devices, and the antenna is used in wireless communication devices. In the field of these electronic components, the development of materials having high magnetic permeability and low magnetic loss is active for the purpose of improving the characteristics required in the high frequency band and reducing the size.

Fe and FeCo-based magnetic particles have high magnetic permeability, but because of their low resistivity, magnetic loss due to eddy currents increases in the high-frequency band, making it difficult to achieve both magnetic permeability and magnetic loss requirements. .. Therefore, in order to reduce the magnetic loss when Fe and FeCo-based magnetic particles are used as the magnetic material, (1) insulation between the particles suppresses the occurrence of eddy current loss, and (2) particle size. By making it nano-order, it is made into a single magnetic domain to eliminate the loss of domain wall resonance and at the same time suppress the eddy current loss. (3) By increasing the aspect ratio of the particles and increasing the difference between the frequency used and the resonance frequency. It has been studied to reduce magnetic loss (see Patent Document 1).

Japanese Unexamined Patent Publication No. 2013-207234

However, considering the case where the electronic component is used for a long period of time or in a harsh environment, it is desired that a stable magnetic permeability can be obtained even in such an environment. Although high magnetic permeability and low magnetic loss are obtained in Patent Document 1, reliability in such a harsh environment has not been investigated.

The present invention has been made in view of the above circumstances, and is a composite magnetic material having high magnetic permeability and low magnetic loss, and capable of suppressing a decrease in magnetic permeability even when exposed to a high temperature and high humidity environment. The purpose is to provide.

The present invention is a composite magnetic material including a metal core portion and a metal oxide film covering the metal core portion and an insulator, and the metal particles have an average aspect ratio of 1.5 to 10. The metal particles have an average major axis diameter of 30 to 500 nm, the metal particles contain Fe or Fe and Co as main components, and the metal particles contain Mn of 0.05 to 3. Provided is a composite magnetic material containing 0% by mass in a mass ratio and having a mass ratio of Mn in the metal oxide film larger than the mass ratio of Mn in the metal particles.

According to the composite magnetic material, high magnetic permeability and low magnetic loss can be obtained, and a decrease in magnetic permeability can be suppressed even when exposed to a high temperature and high humidity environment. The composite magnetic material can have a high magnetic permeability by containing Fe having a high saturation magnetization or metal particles containing Fe and Co as main components. Further, by setting the average aspect ratio of the metal particles within the above range, the natural resonance frequency can be controlled and the magnetic loss can be reduced. Further, by reducing the size of the metal particles to the above range, the eddy current loss in one particle can be suppressed. Further, the metal particles are provided with a metal oxide film on the surface, and the metal oxide film contains a predetermined amount of Mn in a larger amount than the entire metal particles, whereby the insulating property between the metal particles can be improved. The magnetic loss caused by the eddy current between particles can be reduced, and the reliability of the magnetic properties when exposed to a high temperature and high humidity environment can be improved. At that time, by keeping the mass ratio of Mn inside the metal particles below a certain level and making it higher in the metal oxide film than in the whole metal particles, the saturation magnetization of the metal particles and the insulating property between the particles are improved. Therefore, the composite magnetic material having high magnetic permeability and low magnetic loss can be obtained.

In the composite magnetic material, the mass ratio of Mn in the metal oxide film is preferably 5 times or more the mass ratio of Mn in the metal particles. As a result, it becomes easier to obtain the effect of the metal particles having the metal oxide film containing Mn and the effect of suppressing the decrease in saturation magnetization, and it becomes easier to obtain a higher magnetic permeability and a lower magnetic loss.

In the composite magnetic material, it is preferable that the metal particles further contain Al and R. The above R indicates a rare earth element or Y. Further, it is preferable that the mass ratio of Al in the metal particles is 0.1 to 5.0% by mass, and the mass ratio of R in the metal particles is 0.5 to 10.0% by mass. As a result, the metal oxide film of the metal particles is further strengthened, magnetic loss can be further reduced, and the reliability of magnetic characteristics is also improved.

In the composite magnetic material, it is preferable that the metal particles further contain at least one non-magnetic metal element selected from the group consisting of Ti, Zr, Hf, Mg, Ca, Sr, Ba and Si. Further, it is preferable that the mass ratio of the non-magnetic metal element in the metal particles is 0.1 to 1.0 mass%, respectively.

According to the present invention, it is possible to provide a composite magnetic material which can obtain high magnetic permeability and low magnetic loss and can suppress a decrease in magnetic permeability even when exposed to a high temperature and high humidity environment.

It is a schematic cross-sectional view which shows the metal particle contained in the composite magnetic material which concerns on one Embodiment of this invention. It is a schematic cross-sectional view which shows the manufacturing process of the metal particle contained in the composite magnetic material which concerns on one Embodiment of this invention, (a) shows the metal particle before the heat treatment step, (b) is the metal particle in the heat treatment step. (C) shows the metal particles after the slow oxidation step. It is a side view which shows an example of the apparatus for producing the steam-containing hydrogen gas used in the heat treatment process in the production of the metal particles contained in the composite magnetic material which concerns on one Embodiment of this invention.

Hereinafter, preferred embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments.

[Composite magnetic material]
The composite magnetic material according to the present embodiment includes metal particles and an insulator. FIG. 1 is a schematic cross-sectional view showing the metal particles contained in the composite magnetic material according to the present embodiment. In FIG. 1, the metal particles 10 include a metal core portion 2 and a metal oxide film 4 that covers the metal core portion 2.

(Metal particles)
The metal particles 10 preferably contain Fe or Fe and Co as main components, and preferably contain Fe and Co as main components. When the metal particles 10 contain Fe having a high saturation magnetization or Fe and Co as main components, the composite magnetic material can have a high magnetic permeability. Further, the metal particles 10 further contain Mn. The metal particles 10 preferably further contain at least one non-magnetic metal element selected from the group consisting of Al, R, Ti, Zr, Hf, Mg, Ca, Sr, Ba and Si, and Al or R. It is more preferable to contain Al and R, and it is further preferable to contain Al and R. R represents a rare earth element or Y, and is preferably Y. Examples of rare earth elements include La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y. The metal particles 10 further contain, as the non-magnetic metal element, at least one selected from the group consisting of Ti, Zr, Hf, Mg, Ca, Sr, Ba and Si, in addition to Al and / or R. May be. The metal particles 10 can also be said to be metal magnetic particles.

The total mass ratio of Fe and Co in the metal particles 10 (when the metal particles 10 do not contain Co, the mass ratio of Fe) is preferably 80% by mass or more, and preferably 85% by mass or more. It is more preferably 90% by mass or more, and further preferably 90% by mass or more. When the mass ratio of Fe and Co is 80% by mass or more, high magnetic permeability can be easily obtained. Further, the mass ratio of Fe and Co in the metal particles 10 can be 99% by mass or less, and may be 95% by mass or less. When the mass ratio of Fe and Co is 99% by mass or less, a low magnetic loss can be easily obtained. When the metal particles 10 contain Co, the mass ratio of Co in the metal particles 10 is preferably 1.0 to 30% by mass. When the mass ratio of Co is 1.0% by mass or more, the metal particles are suppressed from being easily oxidized, and stable magnetic properties can be easily obtained. When the mass ratio of Co is 30% by mass or less, stable control of the size or shape of the metal particles at the time of producing the metal particles becomes easy. From the same viewpoint, the mass ratio of Co is more preferably 3.0 to 25% by mass, further preferably 5.0 to 20% by mass. In the present specification, the mass ratio is the mass ratio based on the total mass of the element having an atomic number of 11 (Na) or more. Therefore, for example, oxygen contained in the metal oxide film 4 is not considered in the measurement and calculation of the mass ratio.

In the present embodiment, the mass ratio of Mn in the metal particles 10 is 0.05 to 3.0% by mass, and the mass ratio of Mn in the metal oxide film 4 is larger than the mass ratio of Mn in the metal particles 10. .. The mass ratio of Mn in the entire metal particles is 0.05% by mass or more, and more Mn is present in the metal oxide film, thereby improving the insulating property between the metal particles and the eddy current between the particles. The magnetic loss caused by the above can be reduced, and the reliability of the magnetic properties when exposed to a high temperature and high humidity environment can be improved. Further, since the mass ratio of Mn in the metal particles is 3.0% by mass or less and more Mn is present in the metal oxide film, the saturation magnetization of the metal particles 10 and the insulating property between the particles are improved. Therefore, a composite magnetic material having a high magnetic permeability and a low magnetic loss can be obtained. From the same viewpoint, the mass ratio of Mn in the metal particles 10 is preferably 0.1 to 1.0% by mass.

Further, it is preferable that the mass ratio of Mn in the metal oxide film 4 is 5 times or more the mass ratio of Mn in the metal particles 10. As a result, the effect of further reducing the magnetic loss due to the improvement of the insulating property between the metal particles and the effect of further suppressing the increase of the magnetic loss due to the decrease of the saturation magnetization can be obtained, and a higher magnetic permeability and a lower magnetic loss can be obtained. It will be easier. From the same viewpoint, the mass ratio of Mn in the metal oxide film 4 is more preferably 7 times or more, and further preferably 10 times or more, the mass ratio of Mn in the metal core portion 2.

The mass ratio of Al in the metal particles 10 is preferably 0.1 to 5.0% by mass. Further, the mass ratio of R in the metal particles 10 is preferably 0.5 to 10.0 mass%. When the mass ratio of Al and / or R is at least the above lower limit value, the metal oxide film of the metal particles is further strengthened, the magnetic loss can be further reduced, and the reliability of the magnetic characteristics is also improved. When the mass ratio of Al and / or R is not more than the above upper limit value, it is possible to suppress the decrease in saturation magnetization and the accompanying decrease in magnetic permeability. From the same viewpoint, the mass ratio of Al is more preferably 1.0 to 3.0% by mass. Further, the mass ratio of R is more preferably 2.0 to 6.0 mass%.

The mass ratio of at least one non-magnetic metal element selected from the group consisting of Ti, Zr, Hf, Mg, Ca, Sr, Ba and Si in the metal particles 10 is 0.1 to 1.0 mass%, respectively. There can be.

In this embodiment, the metal particles 10 have an average aspect ratio of 1.5 to 10. The average aspect ratio is the average value of the ratio (aspect ratio) of the major axis diameter of the particles to the minor axis diameter. When the average aspect ratio of the metal particles is within the above range, the natural resonance frequency can be controlled and the magnetic loss can be reduced. That is, when the average aspect ratio is 1.5 or more, the difference between the used frequency and the resonance frequency can be increased, and thereby the magnetic loss of the composite magnetic material can be reduced. Further, since the average aspect ratio is 10 or less, it is possible to suppress an increase in magnetic loss even in the GHz band while suppressing a decrease in the magnetic permeability of the composite magnetic material, and the composite magnetism applicable to a wider wavelength band. You can get a body. From the same viewpoint, the average aspect ratio of the metal particles 10 is preferably 1.8 to 8, and more preferably 2 to 7. The shape of the metal particles 10 is preferably needle-shaped.

In this embodiment, the metal particles 10 have an average major axis diameter of 30 to 500 nm. When the average major axis diameter of the metal particles is 30 nm or more, the filling property of the metal particles in the composite magnetic material is improved, and a high magnetic permeability can be obtained. Further, since the average major axis diameter of the metal particles is 500 nm or less, it is possible to eliminate the loss of domain wall resonance by making a single magnetic domain and at the same time suppress the eddy current loss in one particle. From the same viewpoint, the average major axis diameter of the metal particles 10 is preferably 40 to 350 nm, more preferably 45 to 200 nm. The average minor axis diameter of the metal particles 10 is, for example, about 5 to 50 nm, and can be 7 to 30 nm. When the metal particles 10 have an average major axis diameter and an average minor axis diameter in the above range, a desired average aspect ratio can be easily obtained.

In the metal particles 10, the metal core portion 2 contains the above-mentioned element contained in the metal particles 10 as a metal (zero valence), and has Fe or a magnetic portion containing Fe and Co as main components. Since the metal core portion 2 is covered with the metal oxide film 4, it can exist in the atmosphere without being oxidized. The magnetic part is preferably a Fe—Co alloy. By forming an Fe—Co alloy in which Co is solid-solved in Fe, saturation magnetization is improved and high magnetic permeability can be easily obtained.

In the metal particles 10, the metal oxide film 4 contains the above-mentioned elements contained in the metal particles 10 as an oxide. In the present embodiment, it is preferable that elements other than Fe and Co are contained in the metal oxide film 4. Since the metal oxide film 4 contains elements other than Fe and Co, the insulating property between the metal particles 10 is further improved without deteriorating the magnetic characteristics, and the magnetic loss due to the generation of eddy current is further reduced. be able to.

The mass ratio of Mn in the metal oxide film 4 is preferably 0.5 to 70% by mass, more preferably 1.0 to 10% by mass, and further preferably 2.0 to 10% by mass. preferable. It is preferable that the mass ratio of the non-magnetic metal element containing Al and R in the metal oxide film 4 is larger than the mass ratio of these in the metal core portion 2.

The thickness of the metal oxide film 4 can be, for example, 1 to 20 nm. When the thickness of the metal oxide film 4 is 1 nm or more, the insulating property between the metal particles can be easily obtained, and the effect of reducing the magnetic loss can be easily obtained. When the thickness of the metal oxide film 4 is 20 nm or less, it becomes easy to suppress the deterioration of the magnetic properties. From the same viewpoint, the thickness of the metal oxide film 4 may be 1.5 to 15 nm or 2.0 to 10 nm.

(Insulator)
The insulator is a material having an electrical insulating property, and is a material that is present between the metal particles 10 in the composite magnetic material and can bond them to further improve the insulating property between the metal particles 10. Examples of the insulator include an insulating resin and rubber, and a cured product thereof. Examples of the insulating resin include silicone resin, phenol resin, acrylic resin, epoxy resin and the like. These may be used individually by 1 type, or may be used in combination of 2 or more type.

The mass ratio of the insulator in the composite magnetic material can be, for example, 1.0 to 30% by mass. When the mass ratio of the insulator is 1.0 mass% or more, the insulating property and the bonding force between the metal particles 10 can be easily obtained. When the mass ratio of the insulator is 30% by mass or less, the characteristics of the metal particles can be easily exhibited even in the composite magnetic material.

[Manufacturing method of composite magnetic material]
The method for producing a composite magnetic material according to the present embodiment includes a mixing step of mixing metal particles and an insulating material to obtain a composite magnetic material, and a molding step of molding the composite magnetic material. When the insulator is a cured product of an insulating resin or rubber, the method for producing the composite magnetic material further comprises a curing step. Further, the method for producing metal particles includes a neutralization step, an oxidation step, a dehydration / annealing step, a heat treatment step, and a slow oxidation step. It is preferable that the method for producing metal particles further includes a coating step after the oxidation step and before the dehydration / annealing step. First, as an example, a method for producing metal particles containing Fe and Co as main components will be described.

(Neutralization process)
In the neutralization step, particles containing ferrous hydroxide (Fe (OH) ₂ ) are obtained by neutralization. The particles further contain Co in the form of substituting a part of Fe of ferrous hydroxide, or in the form of a hydroxide of Co independent of ferrous hydroxide. First, raw materials for Fe, Co and Mn are prepared. Examples of the raw material for Fe include iron sulfate. Examples of the raw material of Co include cobalt sulfate. Examples of the raw material for Mn include manganese sulfate. In the neutralization step, the above raw materials are dissolved in water to prepare an acidic aqueous solution, which is mixed with an alkaline aqueous solution. By neutralizing the (acidic) aqueous solution of the raw material with an alkaline aqueous solution to make the aqueous solution weakly acidic, ferrous hydroxide-containing particles can be obtained. By variously changing the conditions of the neutralization step and the oxidation step described later, it is possible to control the growth of particles in the oxidation step and the size and shape of the obtained goethite particles, and further, the size and shape of the obtained metal particles. Can be controlled. For example, the size of goethite particles can be controlled by adjusting the metal ion concentration in the aqueous solution of the raw material. Further, the aspect ratio of the goethite particles can be controlled by adjusting the neutralization rate with the alkaline aqueous solution (for example, the aspect ratio can be increased by increasing the neutralization rate). By controlling the size and shape of the goethite particles, it becomes easy to control the size and shape of the metal particles.

(Oxidation process)
In the oxidation step, the particles containing ferrous hydroxide after the neutralization step are oxidized. That is, bubbling is performed in the aqueous solution after the neutralization step, and oxygen is given to the aqueous solution. Goethite (α-FeO (OH)) particles containing Co and Mn can be obtained by oxidizing the particles containing ferrous hydroxide and growing the particles during the oxidation reaction. Further, compounds of elements such as Al, R, Ti, Zr and Hf can be further added to the aqueous solution for bubbling. R represents a rare earth element or Y. As a result, these elements are incorporated into the particles during the growth of the particles, and goethite particles containing the above elements in addition to Co and Mn are obtained. The compound added to the aqueous solution can be, for example, a sulfate of the above element. The obtained goethite particles are filtered, washed with ion-exchanged water, and then dried to isolate them.

(Coating process)
In the coating step, the surface of the goethite particles containing Co and Mn obtained after the oxidation step is coated with a non-magnetic metal element. In the coating step, the gateite particles after the oxidation step are put into an alcohol solution of an alkoxide of a non-magnetic metal element such as Al, R, Ti, Zr, Hf, Mg, Ca, Sr, Ba and Si. R represents a rare earth element or Y. The surface of the goethite particles can be coated with the non-magnetic metal element by stirring while gradually hydrolyzing the alkoxide. In the coating step, a single element may be coated, or a plurality of kinds of elements may be coated. When a plurality of kinds of elements are coated, a plurality of kinds of elements may be coated separately by repeating two or more steps, or a plurality of kinds of elements may be coated at the same time in one step. good. The goethite particles after coating are filtered, washed with alcohol or the like, and then dried to be isolated. In the coating step, it is preferable that Al or R is coated. The thickness of the coating is controlled by the concentration of alkoxide in the alcohol solution, and is appropriately set so as to obtain a desired thickness of the metal oxide film. The coating causes the goethite particles to contain the non-magnetic metal element on their surface. Further, in the coating step, the coated element is mainly contained in the metal oxide film of the metal particles.

(Dehydration / annealing process)
In the dehydration / annealing step, the goethite particles containing Co and Mn obtained above are heated in an oxidizing atmosphere. Upon heating, the goethite particles are dehydrated and oxidized to become hematite (α-Fe ₂ O ₃ ) particles containing Co and Mn. The heating temperature is, for example, 300 to 600 ° C. When the goethite particles contain a non-magnetic metal element, hematite particles containing Co, Mn and the non-magnetic metal element can be obtained.

(Heat treatment process)
In the heat treatment step, the hematite particles containing Co and Mn obtained in the dehydration / annealing step are heated in a redox atmosphere. The heating temperature is, for example, 300 to 600 ° C. Here, the redox atmosphere refers to an atmosphere in which both an oxidation reaction and a reduction reaction can occur in hematite particles containing Co and Mn, which are the targets of heat treatment. The redox atmosphere is obtained, for example, by sending a redox gas into the furnace to be heat-treated. Examples of the redox gas include a mixed gas of oxygen monoxide and carbon dioxide, a mixed gas of hydrogen and water vapor, and the like. When a mixed gas of carbon monoxide and carbon dioxide is used, the ratio of the partial pressure P _CO of carbon monoxide to the partial pressure P _CO 2 of carbon dioxide (P _CO / P _{CO 2} ) is preferably 1 to ¹⁰⁷ , preferably 100. It is more preferably to 10 ⁷ . When a mixed gas of hydrogen and water vapor is used, the ratio of the partial pressure _PH2 of hydrogen to the partial pressure _PH2O of water vapor ( _PH2 / _PH2O ) is preferably 10 to ¹⁰⁸ , preferably 100 to ¹⁰⁸ . It is more preferable to have. By heat treatment in a redox atmosphere with a mixed gas having a partial pressure ratio of P _CO / P _CO2 or _PH2 / _PH2O within the above range, only Fe and Co in the hematite particles containing Co and Mn are reduced. Elements other than these are discharged and concentrated on the surface of the particles as oxides. By setting the partial pressure ratio P _CO / P _CO2 or _PH2 / _PH2O to a more preferable range, the reduction reaction of Fe and Co is rapidly carried out. As a result, the discharge of the oxide to the surface is promoted, and the production efficiency of the magnetic particles can be improved. This utilizes the fact that the standard enthalpy of formation of oxides differs depending on each element. That is, an environment in which the oxygen partial pressure in the redox atmosphere is controlled by controlling the partial pressure ratio of the mixed gas at a temperature of 300 to 600 ° C., Fe and Co are not oxidized, and Mn and the like are oxidized. Is making.

2A and 2B are schematic cross-sectional views showing a manufacturing process of metal particles, where FIG. 2A shows particles before the heat treatment step and FIG. 2B shows particles after the heat treatment step. In FIG. 2A, the hematite particle 1 after the dehydration / annealing step is composed of a Mn atom 3 and a component 2'other than Mn. In FIG. 2A, Mn atoms 3 are distributed almost uniformly throughout the hematite particles 1. Subsequently, as shown in FIG. 2B, when the heat treatment step is started, the Mn atoms 3 distributed throughout move to the particle surface and are concentrated on the particle surface.

After the heat treatment, the inside of the furnace is switched from the redox gas to the inert gas and cooled to around 200 ° C.

(Slow oxidation process)
In the slow oxidation step, the oxygen partial pressure in the furnace cooled to around 200 ° C. after the heat treatment step is gradually increased, and the mixture is slowly cooled to room temperature. As a result, the surface of the particles is gradually oxidized, and a metal oxide film containing the elements existing on the surface of the particles before the heat treatment step and the elements concentrated on the surface in the heat treatment step is formed. Fe, Co, Mn and other elements that were added to the surface of the particles before the heat treatment step and were present on the surface of the gateite particles after the oxidation step, as well as the coating. Examples thereof include non-magnetic metal elements coated on the surface of particles in the process. FIG. 2 (c) shows the particles after the slow oxidation step. In FIG. 2C, the metal oxide film 4 is formed on the surface of the particles, and the metal oxide film 4 contains concentrated elements such as Mn. Then, the inside of the particles that have not been oxidized in the slow oxidation step becomes the metal core portion 2. Due to the concentration of elements such as Mn on the particle surface in the heat treatment step, the mass ratio of the elements such as Mn in the metal oxide film 4 becomes larger than that of the entire particles, and the mass of the elements such as Mn in the metal core portion 2 The proportion is smaller than the whole particle.

As described above, the metal particles 10 having the metal core portion 2 and the metal oxide film 4 covering the metal core portion 2 can be obtained.

Next, a composite magnetic material is produced using the obtained metal particles.

(Mixing process)
In the mixing step, the metal particles 10 obtained as described above and the insulating material are mixed to obtain a composite magnetic material. The mixing method may be appropriately selected depending on the insulator. That is, when the insulator is, for example, an insulating resin, a stirrer / mixer such as a pressurized kneader and a ball mill is selected. Further, even when the insulator is rubber, it is mixed by a pressurized kneader or the like. At this time, other components such as a dispersant and a coupling agent may be added. When the insulator is a cured product of a resin, for example, a thermosetting resin and a curing agent, and if necessary, a curing accelerator may be added. The mixing conditions are not particularly limited, but the metal particles 10 are mixed, for example, at room temperature to 100 ° C. for 20 to 60 minutes so that the metal particles 10 can be dispersed in the insulator. As described above, a composite magnetic material containing metal particles, a thermosetting resin, and a curing agent can be obtained. A thermoplastic resin can be used instead of the thermosetting resin and the curing agent. It is also possible to improve the dispersibility of the metal particles by using an organic solvent.

(Molding process)
In the molding step, a molded product is obtained by heating and pressurizing the composite magnetic material for molding. The molding temperature is equal to or higher than the softening point of the resin, and is lower than the heating temperature in the next curing step when the composite magnetic material contains a thermosetting resin and a curing agent. The molding temperature is, for example, 60 to 80 ° C. When the insulator is not a cured product of resin, the molded product is a composite magnetic material.

(Curing process)
When the insulator is a cured product of an insulating resin, the method for producing a composite magnetic material further comprises a curing step. A composite magnetic material can be obtained by heating and curing the molded product. The heating temperature is appropriately selected depending on the type of the resin and the curing agent, but is higher than the molding temperature in the molding step and can be 120 to 200 ° C. The heating time can be 0.5 to 3 hours. When the insulator is a cured product of rubber, for example, it is molded in a mold having a temperature suitable for the cross-linking reaction of rubber, and the pressure is maintained until the cross-linking reaction is completed to obtain a composite magnetic material. Can be done.

Temporary curing may be performed before the above curing. When performing temporary curing, the above-mentioned curing after temporary curing may be referred to as main curing. The heating temperature for temporary curing can be 80 to 120 ° C. The heating time can be 0.5 to 3 hours. By performing the temporary curing, it is possible to suppress the extremely low viscosity of the resin during the main curing.

The temporary curing and the main curing may be carried out in an atmospheric atmosphere, an inert gas atmosphere, or in a vacuum, but in order to suppress the oxidation of the metal particles, the temporary curing and the main curing are carried out in an inert gas atmosphere or in a vacuum. Is preferable.

The composite magnetic material according to the present embodiment has a high magnetic permeability, and even when used for an electronic component used in a wide high frequency band, the eddy current loss is suppressed while having a high magnetic permeability. Therefore, it has a low magnetic loss. Further, even when the electronic component using the composite magnetic material is used for a long period of time or in a harsh environment, it is possible to suppress a decrease in magnetic permeability. Therefore, the composite magnetic material according to the present embodiment is useful as a constituent material for high-frequency electronic components.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.

[Manufacturing of composite magnetic material]
(Example 1)
An aqueous solution of ferrous sulfate, cobalt sulfate and manganese sulfate was mixed so that Fe, Co and Mn in the metal particles had the mass ratios shown in Table 1 below, and these were partially neutralized with an alkaline aqueous solution (neutralization). Process). “Bal.” In Table 1 indicates the balance. The neutralized aqueous solution was bubbling and aerated, and the aqueous solution was stirred to obtain goethite particles containing Co and Mn (oxidation step). Goethite particles containing Co and Mn obtained by filtering an aqueous solution were washed with ion-exchanged water, dried, and then heated in air to obtain hematite particles containing Co and Mn (dehydration).・ Annealing process).

The obtained hematite particles containing Co and Mn were heated at 550 ° C. in a redox atmosphere furnace (heat treatment step). After that, the atmosphere in the furnace was switched to argon gas and cooled to about 200 ° C. Further, by cooling to room temperature while increasing the oxygen partial pressure to 21% over 24 hours, metal particles having a metal core portion and a metal oxide film were obtained (slow oxidation step).

In the heat treatment step, the redox atmosphere was created by sending a mixed gas of steam and hydrogen (hydrogen gas containing steam) into the furnace. FIG. 3 is a side view of an instrument for producing water vapor-containing hydrogen gas. First, the flask 12 shown in FIG. 3 was prepared. Water 14 was put in the flask 12, and the mouth was closed with a rubber stopper. The flask 12 was immersed in a water bath equipped with a cooler 16, and the water 14 in the flask 12 was cooled to 5 ° C. Then, hydrogen gas was injected from the glass tube 18a at 1 mL / min through the glass stoppers 18a and 18b, the hydrogen gas was submerged in the water 14 in the flask 12, and the gas was recovered from the glass tube 18b. The gas recovered from the glass tube 18b was mixed with water vapor volatilized from water 14, and the partial pressure ratio ( _PH2 / _PH2O ) of the gas was 111. This is due to the fact that the vapor pressure of water at 5 ° C. is about 9 hPa. By further injecting hydrogen gas into this and controlling the water vapor concentration, a water vapor-containing hydrogen gas having a partial pressure ratio ( _PH2 / _PH2O ) of 10,000 was obtained. The water vapor-containing hydrogen gas thus obtained was sent into the furnace in the heat treatment step to create a redox atmosphere.

Epoxy resin (trade name: JER806, manufactured by Mitsubishi Chemical Corporation) and a curing agent are added to the obtained metal particles, and the mixture is kneaded at 95 ° C. using a mixing roll, and the kneading is continued while slowly cooling to 70 ° C. The kneading was stopped when the temperature became 70 ° C. or lower, and the mixture was rapidly cooled to room temperature to obtain a slurry-like composite magnetic material (mixing step). Table 3 shows the mass ratio (mass%) of the metal particles in the obtained composite magnetic material. Next, the obtained composite magnetic material was put into a mold heated to 100 ° C., and molding was performed at a molding pressure of 980 MPa. The obtained molded product was heat-cured at 180 ° C., cut out, and processed to obtain the composite magnetic material of Example 1. The shape of the composite magnetic material was a rectangular parallelepiped of 1 mm × 1 mm × 100 mm.

(Examples 2 to 3 and Comparative Examples 1 to 2)
In the neutralization step, an aqueous solution of iron sulfate, cobalt sulfate, and manganese sulfate was blended in the same manner as in Example 1 except that Fe, Co, and Mn had the mass ratios shown in Table 1 below. The composite magnetic materials of No. 3 and Comparative Examples 1 and 2 were obtained.

(Example 4)
In the neutralization step, the same as in Example 1 except that an aqueous solution of iron sulfate, cobalt sulfate and manganese sulfate was blended so that Fe, Co and Mn in the alloy particles had the mass ratios shown in Table 1 below. , Co and Mn-containing gateite particles were obtained. Next, alcohol solutions of aluminum alkoxide and yttrium alkoxide were prepared. The obtained gateite particles were put into the alcohol solution so that Al and Y in the alloy particles had the mass ratios shown in Table 1 below, and (water) aluminum oxide and (water) yttrium oxide were placed on the surface of the gateite particles. Was coated (coating process).

The coated particles were subjected to a dehydration / annealing step, a heat treatment step and a slow oxidation step in the same manner as in Example 1 to obtain metal particles. From the obtained metal particles, the composite magnetic material of Example 4 was obtained in the same manner as in Example 1.

(Examples 5 to 6)
In the neutralization step, the same as in Example 4 except that an aqueous solution of iron sulfate, cobalt sulfate and manganese sulfate was blended so that Fe, Co and Mn in the alloy particles had the mass ratios shown in Table 1 below. , Getite particles were obtained. Next, in the coating step, an alcohol solution was prepared so that Al and Y in the alloy particles had the mass ratios shown in Table 1 below, and the goethite particles were charged in the same manner as in Example 4. The composite magnetic materials of Examples 5 to 6 were obtained.

(Comparative Example 3)
In the neutralization step, the same as in Example 4 except that an aqueous solution of iron sulfate, cobalt sulfate and manganese sulfate was blended so that Fe, Co and Mn in the alloy particles had the mass ratios shown in Table 1 below. , A composite magnetic material of Comparative Example 3 was obtained.

(Comparative Example 4)
In the neutralization step, the same as in Example 6 except that an aqueous solution of iron sulfate, cobalt sulfate and manganese sulfate was blended so that Fe, Co and Mn in the alloy particles had the mass ratios shown in Table 1 below. , The composite magnetic material of Comparative Example 4 was obtained.

(Examples 7 to 8)
In the heat treatment step, the same as in Example 5 except that the partial pressure ratio ( _PH2 / _PH2O ) of the steam-containing hydrogen gas sent into the furnace was changed to 1000 and 100, respectively, of Examples 7 to 8 A composite magnetic material was obtained.

(Comparative Example 5)
A composite magnetic material of Comparative Example 5 was obtained in the same manner as in Example 5 except that the steam-containing hydrogen gas sent into the furnace was changed to pure hydrogen gas in the heat treatment step.

(Examples 9 to 25)
In the neutralization step, the same as in Example 5 except that an aqueous solution of iron sulfate, cobalt sulfate and manganese sulfate was blended so that Fe, Co and Mn in the alloy particles had the mass ratios shown in Table 1 below. , Co and Mn-containing gateite particles were obtained. Next, alcohol solutions of titanium tetraalkoxide, zirconium tetraalkoxide, hafnium tetraalkoxide, magnesium dialkoxide, calcium dialkoxide, strontium dialkoxide, barium dialkoxide, and silane tetraalkoxide were further prepared. In the coating step, each alcohol solution is mixed so that Al and Y and Ti, Zr, Hf, Mg, Ca, Sr, Ba and Si in the alloy particles have the mass ratios shown in Table 1 below. The obtained Co and Mn-containing gateite particles were added to the surface of the Co and Mn-containing gateite particles, and together with (water) aluminum oxide and (water) yttrium oxide, (water) titanium oxide and (water) oxidation. Coated with zirconium hydride, (water) hafnium oxide, (water) magnesium oxide, (water) calcium oxide, (water) strontium oxide, (water) barium oxide, or (water) silicon oxide (coating step).

The coated particles were subjected to a dehydration / annealing step, a heat treatment step and a slow oxidation step in the same manner as in Example 5 to obtain metal particles. From the obtained metal particles, the composite magnetic materials of Examples 9 to 25 were obtained in the same manner as in Example 5.

(Examples 26 to 29 and Comparative Examples 6 to 7)
In the neutralization step, an aqueous solution of iron sulfate, cobalt sulfate and manganese sulfate was blended so that Fe, Co and Mn in the alloy particles had the mass ratios shown in Table 1 below, the concentration of each metal ion in the aqueous solution and the concentration of each metal ion. Examples 26 to 29 and Comparative Examples 6 to 6 are the same as in Example 5 except that the neutralization rate with the alkaline aqueous solution is changed to adjust the metal particle size and the aspect ratio so as to be as shown in Table 2 below. 7 composite magnetic materials were obtained.

[Evaluation methods]
(Mass ratio of elements with atomic numbers higher than Na in the composite magnetic material)
The surface of the composite magnetic material obtained in Examples and Comparative Examples was analyzed by a fluorescent X-ray apparatus, and the mass ratio (mass%) of the element having an atomic number of Na or more was measured. As a result, the mass ratio of the element to the entire metal particle is measured. The measurement results are shown in Table 1.

(Size and aspect ratio of metal particles and thickness of metal oxide film)
The metal particles obtained in Examples and Comparative Examples were observed with a transmission electron microscope (TEM) at a magnification of 500,000 times, and the dimensions (major axis diameter and short axis) of the metal particles in the major axis and minor axis directions were observed. The shaft diameter) (nm) was measured to determine the aspect ratio. Similarly, 200 to 500 metal particles were observed, and the average values of the major axis diameter, the minor axis diameter and the aspect ratio were calculated. Table 2 shows the average value of the aspect ratio and the average value of the major axis diameter.

In the TEM image, the portion of the metal oxide film of the metal particles looks brighter (whiter) than the other portions. That is, the metal particles are composed of a central dark portion located in the metal core portion and a bright portion surrounding the metal particles in a layered manner. In the TEM image, the thickness of the metal oxide film (6 places) on the three lines in the short axis direction which divides the metal particle into four equal parts in the long axis direction was measured, and the average value of the thickness was calculated. The same measurement was performed on a total of 5 metal particles, and the average value of the thickness of the metal oxide film in the 5 metal particles was calculated. Table 2 shows the average value of the thickness of the metal oxide film.

(Mn mass ratio)
The metal particles obtained in Examples and Comparative Examples are divided into four equal parts in the major axis direction by energy dispersive X-ray analysis (STEM-EDS) using a scanning transmission electron microscope, and the metal particles are divided into three equal parts in the minor axis direction. The Mn mass ratio (mass%) of the metal oxide film on the line of the book was measured by line analysis. The measurement point spacing for line analysis was 0.3 nm. The measurement result of the Mn mass ratio at the measurement point within the range of 70% in the center of the analysis line crossing the metal oxide film was extracted, and the average value was obtained. Such measurements were made on a total of 10 metal particles. The obtained values are shown in Table 2 as the Mn mass ratio in the metal oxide film.

(Resistivity)
The electrical resistivity ρ (Ωm) of the composite magnetic materials obtained in Examples and Comparative Examples was measured using an ultrahigh resistance tester (R8340 manufactured by Advantest). The measurement results of ρ are shown in Table 3.

(Complex magnetic permeability and magnetic loss)
The real part μ', imaginary part μ'', and magnetic loss tan δ _μ of the complex magnetic permeability of the composite magnetic material obtained in Examples and Comparative Examples are subjected to cavity resonance with a network analyzer (manufactured by Agilent Technologies, Inc., HP8753D). Measurements were made at frequencies of 1 GHz, 2 GHz and 3 GHz by a perturbation method using a device (manufactured by Kanto Electronics Applied Development Co., Ltd.). The measurement results of μ'and tan δ _μ are shown in Table 3.

The composite magnetic material after the measurement was placed in a high-temperature and high-humidity tank, and exposed to air at a temperature of 85 ° C. and a relative humidity of 85% for 1000 hours. The real part μa'of complex magnetic permeability after exposure was measured at a frequency of 1 GHz. The difference between the real part μ'and μa' of the complex magnetic permeability at a frequency of 1 GHz before and after exposure was divided by μ'(μa'-μ') / μ'(%) and evaluated as reliability. The reliability evaluation results are shown in Table 3. In Table 3, (μa'-μ') / μ'is shown as Δμ'.

It was confirmed that the composite magnetic material obtained in the examples had a high magnetic permeability and a low magnetic loss, and the decrease in the magnetic permeability was suppressed even when exposed to a high temperature and high humidity environment.

2 ... Metal core part, 4 ... Metal oxide film, 10 ... Metal particles.

Claims (3)

A composite magnetic material including metal particles having a metal core portion and a metal oxide film covering the metal core portion and an insulator.
The metal particles have an average aspect ratio of 1.5-10 and have an average aspect ratio of 1.5-10.
The metal particles have an average major axis diameter of 30-500 nm.
The metal particles contain Fe or Fe and Co as main components.
The metal particles contain Mn in a mass ratio of 0.05 to 3.0% by mass, and contain Mn in a mass ratio of 0.05 to 3.0% by mass.
A composite magnetic material in which the mass ratio of Mn in the metal oxide film is 5 times or more the mass ratio of Mn in the metal particles. The metal particles further contain Al in a mass ratio of 0.1 to 5.0% by mass and R in a mass ratio of 0.5 to 10.0% by mass, wherein R represents a rare earth element or Y. Item 1. The composite magnetic material according to Item 1. The metal particles further contain at least one non-magnetic metal element selected from the group consisting of Ti, Zr, Hf, Mg, Ca, Sr, Ba and Si in a mass ratio of 0.1 to 1.0% by mass, respectively. The composite magnetic material according to claim 1 or 2 , which is contained.

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