JP6891638B2 - Powder magnetic core - Google Patents

Description

The present invention relates to a dust core.

In recent years, it has been required to improve corrosion resistance while maintaining various characteristics of a magnetic core used in coil parts such as inductors, reactors, choke coils, transformers, and motors. In particular, there is a demand for a magnetic core that maintains high corrosion resistance even after being placed in a high temperature environment. Here, it is common to coat the metal magnetic particles with a film.

Patent Document 1 describes an example in which metal magnetic particles are coated with an inorganic coat (phosphate) in order to improve heat resistance and electrical insulation.

Patent Document 2 contains an organic group derived from an organic acid having one or more elements selected from Ti, Al, Si, Ca, Mg, V, Cr, Sr and Zr in order to improve the heat resistance of the insulating film. An example of coating with an insulating film is described.

However, the phosphate coating as described in Patent Document 1 does not have a sufficient effect of improving corrosion resistance. The heat resistance of the insulating film described in Patent Document 2 is the heat resistance when a molded product is heat-treated at 550 ° C. or higher to obtain a magnetic core. The corrosion resistance of the obtained magnetic core after being placed in a high temperature environment is not sufficient.

Japanese Unexamined Patent Publication No. 2009-120915 International Publication No. 2009/028486

The present invention has been made in view of such an actual situation, and an object of the present invention is to provide a dust core having a high initial magnetic permeability μi and high corrosion resistance even after being placed in a high temperature environment.

In order to achieve the above object, the dust core according to the present invention is
A dust core containing metallic magnetic particles and resin.
The insulating film covering the metal magnetic particles comes into contact with the surface of the metal magnetic particles.
The insulating film contains Si—O oxides and metal elements, and contains
The weight content of the metal element with respect to the total amount of the metal magnetic particles is 30 ppm or more and 1000 ppm or less.

Since the dust core according to the present invention has the above structure, the initial magnetic permeability μi is high, and the corrosion resistance is high even after being placed in a high temperature environment.

The dust core according to the present invention may contain a metal complex in which the insulating film has the metal element as a central metal.

In the powder magnetic core according to the present invention, the metal complex may be a metal chelate compound.

In the powder magnetic core according to the present invention, at least one of the ligands of the metal chelate compound may be acetylacetonate.

The dust core according to the present invention may be one or more of the metal elements selected from Zr, Al and Ba.

In the dust core according to the present invention, the film thickness of the insulating film may be 5 nm or more and 500 nm or less.

It is a schematic diagram of the cross section of the dust core which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the dust core 1 according to the present embodiment includes metal magnetic particles 11 and a resin 12. Further, the insulating film 13 that is in contact with the surface 11a of the metal magnetic particles 11 and is coated with the metal magnetic particles 11 is included.

The components of the metal magnetic particles 11 are not particularly limited, but it is preferable that the metal magnetic particles 11 contain Fe as a main component because the saturation magnetization becomes high. Further, it is preferable that the metal magnetic particles 11 contain Fe and Si as main components because the magnetic permeability is high. The term "included as the main component" in the present embodiment means that the total content of the metal magnetic particles 11 is 80% by weight or more when the total amount of the metal magnetic particles 11 is 100% by weight. That is, when Fe is contained as a main component, the Fe content is 80% by weight or more. When Fe and Si are contained as main components, the total content of Fe and Si is 80% by weight or more. The ratio of Fe to Si is not particularly limited, but it is preferable that Si / Fe = 0/100 to 10/90 in terms of weight ratio because the saturation magnetization becomes high. The type of component other than the main component in the metallic magnetic particles of the present embodiment is not particularly limited. Examples of the types of components other than the main component include Ni and Co.

The type of the resin 12 is not particularly limited, and an epoxy resin and / or an imide resin may be used. Examples of the epoxy resin include cresol novolac and the like. Examples of the imide resin include bismaleimide and the like.

The contents of the metal magnetic particles 11 and the resin 12 are not particularly limited. The content of the metal magnetic particles 11 in the entire dust core 1 is preferably 90% by weight to 98% by weight, and the content of the resin 12 is preferably 2% by weight to 10% by weight.

As shown in FIG. 1, the insulating film 13 is characterized in that it is in contact with the surface 11a of the metal magnetic particles 11 and covers the metal magnetic particles 11.

The insulating film 13 does not have to cover the entire surface 11a of the metal magnetic particles 11, and may cover 90% or more of the entire surface 11a of the metal magnetic particles 11. With this configuration, the rust preventive effect can be enhanced.

Here, the insulating film 13 contains a Si—O oxide and a metal element.

The Si—O oxide contained in the insulating film 13 is an oxide also called a silicon oxide. Further, the type of Si—O oxide is not particularly limited. For example, _{in addition to an oxide of Si such as SiO 2} , a composite oxide containing Si and other elements may be used.

In the present embodiment, the weight content of the metal element with respect to the total amount of the metal magnetic particles 11 is 30 ppm or more and 1000 ppm or less. When the weight content of the metal element is less than 30 ppm, the corrosion resistance of the dust core 1 after being placed in a high temperature environment tends to decrease. When the weight content of the metal element exceeds 1000 ppm, the density of the dust core 1 decreases, and the initial magnetic permeability μi decreases. The weight content of the metal element may be 51 ppm or more and 959 ppm or less.

There are no particular restrictions on the type of metal element. For example, Ba, Ca, Mg, Al, Si, Ti, Zr, Ni, Mn, Zn and the like having insulating oxides can be mentioned. Among them, one or more selected from Zr, Al and Ba is preferable, and Zr is particularly preferable. Further, assuming that the total amount of metal elements contained in the insulating film 13 is 100 mol%, the content ratio of one or more selected from Zr, Al and Ba is preferably 0.8 mol% or more, and the content ratio of Zr is preferably 0.8 mol% or more. It is preferably 0.4 mol% or more.

The insulating film 13 preferably contains a metal complex having the above metal element as a central metal. In other words, it is preferable that the above metal element is contained in the insulating film 13 in the form of a metal complex. Further, the type of ligand of the metal complex is not particularly limited. For example, acetylacetonate, trifluoroacetylacetonate, ethylacetacetate and the like can be mentioned.

In the present embodiment, the ligand of the metal complex is preferably a chelate ligand, and the metal complex is preferably a metal chelate compound. Specifically, it is preferable that the ratio of the metal complex in which one or more ligands are chelate ligands to the total metal complex contained in the insulating film 13 is 50 mol% or more. The type of chelate ligand is not particularly limited. For example, acetylacetonate, trifluoroacetylacetonate and the like can be mentioned.

Here, in the metal complex contained in the insulating film 13, it is preferable that one or more ligands are acetylacetonate. Specifically, it is preferable that the ratio of the metal complex in which one or more ligands are acetylacetonate to the total metal complex contained in the insulating film 13 is 50 mol% or more.

Further, it is preferable that all the ligands of the metal complex contained in the insulating film 13 are acetylacetonate. Specifically, it is preferable that the ratio of the metal complex in which all the ligands are acetylacetonate to the total metal complex contained in the insulating layer 13 is 50 mol% or more.

The film thickness of the insulating film 13 is not particularly limited, but is preferably 5 nm or more and 500 nm or less. When it is 5 nm or more, the corrosion resistance of the dust core 1 can be improved. Further, when it is 500 nm or less, the density of the dust core 1 can be improved and the initial magnetic permeability μi can be improved.

It is considered that the reason why the corrosion resistance of the dust core 1 according to the present embodiment is improved after being placed in a high temperature environment is that the stability of the insulating film 13 is improved by adding a metal element to the insulating film 13. Be done.

When the metal element is not added, or when the amount of the metal element added is too small, the metal (particularly Fe) is diffused from the metal magnetic particles 11 to the insulating film 13 by placing the dust core 1 in a high temperature environment. It ends up. As a result, the stability of the insulating film 13 is lowered, and the corrosion resistance of the dust core 1 is lowered.

On the other hand, when a metal element is added, the metal element prevents the metal from diffusing from the metal magnetic particles 11 to the insulating film 13. As a result, the stability of the insulating film 13 is improved, and the corrosion resistance of the dust core 1 after being placed in a high temperature environment is improved. However, when the content of the metal element is excessive, the density of the dust core 1 decreases, and the initial magnetic permeability μi decreases.

Further, when the metal element contained in the insulating film 13 is Zr, Al or Ba, the effect of preventing the above diffusion becomes large. Further, when the insulating film 13 is contained in the form of the metal complex having the above metal element as the central metal, the adhesion between the metal magnetic particles 11 and the insulating film 13 is improved, and the corrosion resistance of the dust core 1 is improved. Is expected to improve. Further, when the metal complex is a metal chelate compound, it is considered that the density of the insulating film 13 can be improved by reacting the metal chelate compound with the Si—O oxide in the insulating film. Then, it is considered that the insulating property of the insulating film 13 can be improved and the corrosion resistance can be further improved. Further, when the ligand is acetylacetonate, the above effect is considered to be further enhanced.

The manufacturing method of the dust core 1 according to the present embodiment is shown below, but the manufacturing method of the dust core 1 is not limited to the following method.

First, the metal magnetic particles 11 are produced. The method for producing the metal magnetic particles 11 is not particularly limited, and examples thereof include a gas atomizing method and a water atomizing method. The particle size and circularity of the metal particles are not particularly limited, but it is preferable that the median particle size (D50) is 1 μm to 100 μm because the magnetic permeability is high.

Next, the metal magnetic particles 11 were coated to form an insulating film 13 containing a Si—O oxide and a metal element. The coating method is not particularly limited, and examples thereof include a method of applying an alkoxysilane solution to the metal magnetic particles 11. The method of applying the alkoxysilane solution to the metal magnetic particles 11 is not particularly limited, and examples thereof include a method of spray diffusion. The type of alkoxysilane is not particularly limited, and trimethoxysilane or the like is used. The mode in which the metal element is added is not particularly limited, and for example, the metal element may be chelated in advance and added.

Further, the concentration of alkoxysilane in the coating solution, the concentration of the metal element, and the solvent are not particularly limited. The concentration of alkoxysilane is preferably 50 to 99% by weight. The concentration of the metal element is preferably 1 to 30% by weight. Further, the solvent of the alkoxysilane solution is not particularly limited. For example, water, ethanol and the like can be mentioned.

Further, at the time of spray diffusion, the ratio of alkoxysilane to the total amount of the metal magnetic particles 11 is preferably 0.1 to 2.0% by weight. The proportion of metal elements is preferably 0.001 to 0.03% by weight. Further, the larger the amount of alkoxysilane, the thicker the thickness of the insulating film 13 tends to be.

The conditions for spray diffusion are not particularly limited, but it is preferable to perform spray diffusion while performing heat treatment at 50 to 80 ° C. because the sol-gel reaction for forming the insulating film 13 is promoted.

After spraying and diffusing the coating solution, the metal magnetic particles 11 are dried to remove the solvent, and then heated at 40 to 60 ° C. for 3 to 20 hours to promote the sol-gel reaction to promote the Si—O oxide and the Si—O oxide. The insulating film 13 containing a metal element is formed. At this time, the higher the heating temperature and the longer the heating time, the higher the density of the insulating film 13 tends to be. Further, before heating the metal magnetic particles 11, the metal magnetic particles may be sized by passing them through a mesh sieve.

Next, a resin solution is prepared. In addition to the above-mentioned epoxy resin and / or imide resin, a curing agent may be added to the resin solution. The type of curing agent is not particularly limited, and examples thereof include epichlorohydrin. The solvent of the resin solution is also not particularly limited, but is preferably a volatile solvent. For example, acetone, ethanol and the like can be used. Further, when the total concentration of the resin solution is 100% by weight, the total concentration of the resin and the curing agent is preferably 0.01 to 0.1% by weight.

Next, the metal magnetic particles 11 forming the insulating film 13 and the resin solution are mixed. Then, the solvent of the resin solution is volatilized to obtain granules. The obtained granules may be filled in the mold as they are, or may be sized and then filled in the mold. The sizing method for sizing is not particularly limited, and for example, a mesh having an opening of 45 to 500 μm may be used.

Next, the obtained granules are filled in a mold having a predetermined shape and pressed to obtain a green compact. The pressure at the time of pressurization is not particularly limited and may be, for example, 600 to 1500 MPa.

A powder magnetic core can be obtained by subjecting the produced green compact to a thermosetting treatment. The conditions of the thermosetting treatment are not particularly limited, and heat treatment is performed at 150 to 220 ° C. for 1 to 10 hours, for example. Further, the atmosphere at the time of heat treatment is not particularly limited, and the heat treatment may be performed in the atmosphere.

Although the dust core and the method for producing the powder magnetic core according to the present embodiment have been described above, the powder magnetic core of the present invention and the method for producing the same are not limited to the above-described embodiment. The dust core of the present invention may be a soft magnetic dust core.

Further, there is no particular limitation on the use of the dust core of the present invention. For example, coil components such as inductors, reactors, choke coils, and transformers can be mentioned.

Hereinafter, the present invention will be described based on more detailed examples, but the present invention is not limited to these examples.

(Example 1)
As the metallic magnetic particles, Fe—Si alloy particles having a weight ratio of Si / Fe = 4.5 / 95.5 and a total amount of Fe and Si of 99% by weight were produced by a gas atomization method. The median particle size (D50) of the Fe—Si alloy particles was 30 μm.

Next, a coating solution for forming an insulating film on the surface of the metal magnetic particles was prepared. The coating solution was 4.0% by weight of ethanol, 1.22% by weight of trimethoxysilane, 0.03% by weight of zirconium acetylacetonate, and 1.0% by weight based on 100% by weight of the total amount of the metal magnetic particles. It was prepared by mixing pure water of.

The metal magnetic particles and the coating solution were mixed and heat-treated while stirring with a spray. The heat treatment temperature was 75 ° C. and the heat treatment time was 5 hours. Further, the metal magnetic particles having an insulating film on the surface were obtained by drying after the heat treatment.

The obtained metallic magnetic particles were passed through a 140-mesh sieve and then heat-treated. The heat treatment temperature was 180 ° C. and the heat treatment time was 1 hour.

Next, an epoxy resin, a curing agent, an imide resin and acetone were mixed to prepare a resin solution. Cresol novolac was used as the epoxy resin. Epichlorohydrin was used as the curing agent. Bismaleimide was used as the imide resin. Each component is mixed so that the weight ratio of the epoxy resin, the curing agent and the imide resin is 96: 3: 1 and the total of the epoxy resin, the curing agent and the imide resin is 4% by weight with the entire resin solution as 100% by weight. did.

4% by weight of the above resin solution was added to 100% by weight of the total amount of the above metal magnetic particles and mixed. It was then dried to volatilize acetone to give granules. Next, the granules were passed through a 42-mesh sieve and sized. The obtained granules were dried on a hot plate at 50 ° C. for 0.5 hours to prepare a granulated powder.

Zinc stearate was added in an amount of 0.1% by weight based on 100% by weight of the granulated powder, and mold molding was performed. A toroidal core having an outer diameter of 17.5 mm, an inner diameter of 10.0 mm, and a thickness of 4.0 mm was produced with a molding pressure of 589 MPa. In the same manner, a rectangular parallelepiped core having a size of 10 mm × 10 mm × 3 mm was produced.

The obtained toroidal core and rectangular parallelepiped core were heat-treated at 180 ° C. for 3 hours to perform a thermosetting treatment to obtain toroidal dust cores and rectangular parallelepiped dust cores. The total amount of the powder magnetic core finally obtained was 100% by weight, and the amount of metal magnetic particles was about 98% by weight. Hereinafter, a rectangular parallelepiped powder magnetic core was used in the high temperature test and the rust test. A toroidal dust core was used in tests other than the high temperature test and the rust test.

By TEM-EDS observation, it was confirmed that an insulating film covering the metal magnetic particles was present. Furthermore, the weight content of the metal element contained in the insulating film was quantified by ICP.

The film thickness of the insulating film was measured by TEM observation. A measurement point was set on the surface of the metal magnetic particles. Then, a perpendicular line was drawn from the measurement point in the direction of the insulating film, and the length of the portion of the perpendicular line in the insulating film was defined as the thickness of the insulating film at the measurement point. Ten measurement points were set, and the thickness of the insulating film was measured at each measurement point. Then, the average of the measured thicknesses of the insulating films was taken as the thickness of the insulating film in the metal magnetic particles.

The high temperature test was carried out by leaving the rectangular parallelepiped powder magnetic core in a constant temperature bath at 150 ° C. for 1000 hours.

In the rust test, first, 100 mL of 5% saline solution was placed in a plastic container, and the rectangular parallelepiped powder magnetic core after the high temperature test was immersed in the saline solution. Next, the plastic container was placed in a constant temperature bath at 50 ° C. and left for 5 hours. Next, the rectangular parallelepiped powder magnetic core was taken out from the saline solution and dried at room temperature. Then, the surface of the rectangular parallelepiped powder magnetic core was observed with a microscope (magnification 150 times, measurement range 4 mm × 10 mm), and the area of rust was visually measured. The case where the area of rust was 10% or less of the entire measurement range was regarded as good.

In the table below, the sample with a good rust test result after the high temperature test was marked with ◯, and the sample with a poor rust test result was marked with x.

The initial magnetic permeability μi was measured by winding a wire around a toroidal dust core with a number of turns of 50 turns and using an LCR meter (HP LCR428A). The density of the dust core was calculated from the dimensions and weight of the obtained powder core. The initial magnetic permeability μi was set to 15 or more. The density of the dust core was set to 5.500 g / cm ³ or more.

(Example 2)
In Example 2, 4.0% by weight of ethanol, 1.22% by weight of trimethoxysilane, 0.05% by weight of zirconium acetylacetonate, and 1.0% by weight of total amount of metal magnetic particles were obtained. It was carried out under the same conditions as in Example 1 except that a coating solution was prepared by mixing% pure water.

(Example 3)
In Example 3, 4.0% by weight of ethanol, 1.22% by weight of trimethoxysilane, 0.50% by weight of zirconium acetylacetonate, and 1.0% by weight based on 100% by weight of the total amount of magnetic metal particles. It was carried out under the same conditions as in Example 1 except that a coating solution was prepared by mixing% pure water.

(Example 4)
Example 4 shows 4.0% by weight of ethanol, 1.22% by weight of trimethoxysilane, 0.07% by weight of aluminum acetylacetonate, and 1.0% by weight based on 100% by weight of the total amount of magnetic metal particles. It was carried out under the same conditions as in Example 1 except that a coating solution was prepared by mixing% pure water.

(Example 5)
Example 5 shows 4.0% by weight of ethanol, 1.22% by weight of trimethoxysilane, 0.03% by weight of barium acetylacetonate, and 1.0% by weight based on 100% by weight of the total amount of metal magnetic particles. It was carried out under the same conditions as in Example 1 except that a coating solution was prepared by mixing% pure water.

(Comparative Example 1)
Comparative Example 1 is the same as that of Example 1 except that a coating solution was prepared by mixing 1.0% by weight of ethanol and 0.1% by weight of phosphoric acid with respect to 100% by weight of the total amount of metal magnetic particles. It was carried out under the conditions of.

(Comparative Example 2)
Comparative Example 2 shows 4.0% by weight of ethanol, 1.22% by weight of trimethoxysilane, 0.01% by weight of zirconium acetylacetonate, and 1.0% by weight based on 100% by weight of the total amount of magnetic metal particles. It was carried out under the same conditions as in Example 1 except that a coating solution was prepared by mixing% pure water.

(Comparative Example 3)
Comparative Example 3 shows 4.0% by weight of ethanol, 1.22% by weight of trimethoxysilane, 1.00% by weight of zirconium acetylacetonate, and 1.0% by weight based on 100% by weight of the total amount of magnetic metal particles. It was carried out under the same conditions as in Example 1 except that a coating solution was prepared by mixing% pure water.

(Comparative Example 4)
Comparative Example 4 is a coating solution in which 4.0% by weight of ethanol, 0.03% by weight of zirconium acetylacetonate, and 1.0% by weight of pure water are mixed with respect to 100% by weight of the total amount of metal magnetic particles. It was carried out under the same conditions as in Example 1 except that the above was prepared.

(Comparative Example 5)
In Comparative Example 5, 4.0% by weight of ethanol, 1.22% by weight of trimethoxysilane, and 1.0% by weight of pure water were mixed with respect to 100% by weight of the total amount of the magnetic magnetic particles to prepare a coating solution. It was carried out under the same conditions as in Example 1 except that it was prepared.

(Example 6)
In Example 6, 4.0% by weight of ethanol, 1.22% by weight of trimethoxysilane, 0.03% by weight of zirconium acetylacetonate, and 0.07% by weight based on 100% by weight of the total amount of metal magnetic particles. The procedure was carried out under the same conditions as in Example 1 except that a coating solution was prepared by mixing aluminum acetylacetonate and 1.0% by weight of pure water.

(Example 7)
In Example 7, 4.0% by weight of ethanol, 1.22% by weight of trimethoxysilane, and 0.07% by weight of aluminum monoacetylacetonate bis (ethylacetoacetate) based on 100% by weight of the total amount of metal magnetic particles. And, except that a coating solution was prepared by mixing 1.0% by weight of pure water, the procedure was carried out under the same conditions as in Example 1.

(Example 8)
In Example 8, 4.0% by weight of ethanol, 1.22% by weight of trimethoxysilane, 0.07% by weight of zirconium trifluoroacetylacetonate, and 1. The procedure was carried out under the same conditions as in Example 1 except that a coating solution was prepared by mixing 0% by weight of pure water.
(Example 9)
In Example 9, 4.0% by weight of ethanol, 1.22% by weight of trimethoxysilane, 1.06% by weight of zirconium ammonium carbonate, and 1.0% by weight based on 100% by weight of the total amount of metal magnetic particles. It was carried out under the same conditions as in Example 1 except that a coating solution was prepared by mixing pure water of.
(Example 10)
In Example 10, 4.0% by weight of ethanol, 1.22% by weight of trimethoxysilane, 0.05% by weight of tetran-butoxide zirconium, and 1.0% by weight based on 100% by weight of the total amount of magnetic metal particles. The procedure was carried out under the same conditions as in Example 1 except that a coating solution was prepared by mixing wt% pure water.

The test results of each of the above Examples and Comparative Examples are shown in Table 1 below.

From Table 1, the examples in which the insulating film contained a Si—O oxide and a metal element and the content of the metal element was within a predetermined range were excellent in corrosion resistance and initial magnetic permeability μi after the high temperature test. On the other hand, the corrosion resistance of Comparative Examples 1 and 4 in which the insulating film contained neither Si—O oxide nor metal element was remarkably low. Further, Comparative Example 2 containing Si—O oxide and metal element but containing too little metal element and Comparative Example 5 containing Si—O oxide but not containing metal element have corrosion resistance by high temperature test. Has decreased significantly. Further, in Comparative Example 3 containing Si—O oxide and metal element but having too much metal element content, the density of the dust core decreased and the initial magnetic permeability μi decreased.

1 ... Powder magnetic core 11 ... Metal magnetic particles 11a ... Surface of metal magnetic particles 12 ... Resin 13 ... Insulating film

Claims (5)

A dust core containing metallic magnetic particles and resin.
The insulating film covering the metal magnetic particles comes into contact with the surface of the metal magnetic particles.
The insulating film contains Si—O oxides and metal elements, and contains
The insulating film contains a metal complex having the metal element as a central metal.
The metal complex is a metal chelate compound.
A dust core characterized in that the weight content of the metal element with respect to the total amount of the metal magnetic particles is 30 ppm or more and 1000 ppm or less. The dust core according to claim 1 , wherein at least one of the ligands of the metal chelate compound is acetylacetonate. The dust core according to claim 1 or 2 , wherein the metal element is at least one selected from Zr, Al and Ba. The dust core according to any one of claims 1 to 3, wherein the content ratio of Zr to the entire metal element is 0.4 mol% or more. The dust core according to any one of claims 1 to 4 , wherein the thickness of the insulating film is 5 nm or more and 500 nm or less.

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