JP2018206834A - Dust core - Google Patents

Abstract

To provide a dust core high in initial permeability μi, and also high in corrosion resistance even after being placed under a high temperature environment.SOLUTION: There is provided a dust core including a metal magnetic particle and a resin. An insulating film covering the metal magnetic particle is in contact with the surface of the metal magnetic particle. The insulating film contains an Si-O-based oxide and a metal element. The content by weight of the metal element with respect to the total amount of the metal magnetic particles is 30 ppm or more and 1,000 ppm or less.SELECTED DRAWING: Figure 1

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 magnetic cores used in coil parts such as inductors, reactors, choke coils, transformers, and motors. In particular, there is a need for a magnetic core that maintains high corrosion resistance even after being placed in a high temperature environment. Here, the metal magnetic particles are generally coated with a film.

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

  Patent Document 2 includes 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 covering with an insulating film is described.

  However, the phosphate coating as described in Patent Document 1 is not sufficient in improving the corrosion resistance. In addition, the heat resistance of the insulating film described in Patent Document 2 refers to the heat resistance when the molded body is heat-treated at 550 ° C. or higher to obtain a magnetic core. Corrosion resistance after putting the obtained magnetic core in a high temperature environment is not sufficient.

JP 2009-120915 A International Publication No. 2009/028486

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

In order to achieve the above object, the powder magnetic core according to the present invention comprises:
A dust core comprising metal magnetic particles and a resin,
The surface of the metal magnetic particle is in contact with an insulating film covering the metal magnetic particle,
The insulating film includes a Si-O-based oxide and a metal element,
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-described configuration, the initial permeability μi is high, and the corrosion resistance is enhanced even after being placed in a high temperature environment.

  In the dust core according to the present invention, the insulating film may include a metal complex having the metal element as a central metal.

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

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

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

  In the dust core according to the present invention, the insulating film may have a thickness of 5 nm to 500 nm.

It is a schematic diagram of the cross section of the powder magnetic 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. Furthermore, an insulating film 13 that contacts the surface 11 a of the metal magnetic particle 11 and covers the metal magnetic particle 11 is included.

  Although there is no restriction | limiting in particular in the component of the metal magnetic particle 11, It is preferable that the metal magnetic particle 11 contains Fe as a main component because 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 increased. In the present embodiment, “including as a main component” means that the total content 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. Further, the ratio of Fe and Si is not particularly limited, but it is preferable that Si / Fe = 0/100 to 10/90 by weight ratio because saturation magnetization becomes high. In addition, there is no restriction | limiting in particular in the kind of components other than the main component in the metal magnetic particle of this embodiment. Examples of the types of components other than the main component include Ni and Co.

  There is no restriction | limiting in particular in the kind of resin 12, You may use an epoxy resin and / or an imide resin. Examples of the epoxy resin include cresol novolac. Examples of the imide resin include bismaleimide.

  There is no restriction | limiting in particular in content of the metal magnetic particle 11 and the resin 12. FIG. The content of the metal magnetic particles 11 in the entire powder magnetic 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 in contact with the surface 11 a of the metal magnetic particle 11 and is characterized by covering the metal magnetic particle 11.

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

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

The Si—O-based oxide contained in the insulating film 13 is an oxide called silicon oxide. Moreover, there is no restriction | limiting in particular in the kind of Si-O type oxide. For example, it may be a complex oxide containing Si and other elements in addition to a Si oxide such as SiO ₂ .

  In this 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 be lowered. When the weight content of the metal element is more than 1000 ppm, the density of the dust core 1 is lowered and the initial permeability μi is lowered. 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, etc., whose oxides are insulative are mentioned. Among these, it is preferable that it is 1 or more types selected from Zr, Al, and Ba, and it is especially preferable that it is Zr. Further, it is preferable that the total metal element contained in the insulating film 13 is 100 mol%, and 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 It is preferable that it is 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, the metal element is preferably contained in the insulating film 13 in the form of a metal complex. Moreover, there is no restriction | limiting in particular in the kind of ligand of a metal complex. For example, acetylacetonate, trifluoroacetylacetonate, ethyl acetoacetate and the like can be mentioned.

  In this 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 with respect to all metal complexes contained in the insulating film 13 is 50 mol% or more. There is no restriction | limiting in particular in the kind of chelate ligand. Examples thereof include acetylacetonate and trifluoroacetylacetonate.

  Here, in the metal complex contained in the insulating film 13, one or more ligands are preferably acetylacetonate. Specifically, the proportion of the metal complex in which one or more ligands are acetylacetonate with respect to the total metal complex contained in the insulating film 13 is preferably 50 mol% or more.

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

  The thickness of the insulating film 13 is not particularly limited, but is preferably 5 nm or more and 500 nm or less. By being 5 nm or more, the corrosion resistance of the dust core 1 can be improved. Moreover, the density of the dust core 1 can be improved by being 500 nm or less, and the initial permeability μi can be improved.

  The reason why the corrosion resistance of the dust core 1 according to this 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. It is done.

  When the metal element is not added or when the amount of the metal element added is too small, the metal (particularly Fe) diffuses from the metal magnetic particles 11 to the insulating film 13 by placing the dust core 1 in a high temperature environment. End 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 is lowered, and the initial permeability μi is lowered.

  In addition, when the metal element contained in the insulating film 13 is Zr, Al, or Ba, the effect of preventing the diffusion is increased. Further, when the insulating film 13 is included in the form of a metal complex having the above metal element as a 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 thought to improve. Furthermore, when the metal complex is a metal chelate compound, it is considered that the density of the insulating film 13 can be improved by the metal chelate compound reacting with the Si—O-based oxide in the insulating film. And it is thought that the insulation of the insulating film 13 can be improved and the corrosion resistance can be further improved. Furthermore, when the ligand is acetylacetonate, the above effect is considered to be further increased.

  Although the manufacturing method of the powder magnetic core 1 which concerns on this embodiment is shown below, the manufacturing method of the powder magnetic core 1 is not limited to the following method.

  First, the metal magnetic particle 11 is produced. Although there is no restriction | limiting in particular in the preparation methods of the metal magnetic particle 11, For example, the gas atomizing method, the water atomizing method, etc. are mentioned. Although there is no restriction | limiting in particular in the particle diameter and circularity of a metal particle, since the magnetic permeability becomes high, it is preferable that the median value (D50) of a particle diameter becomes 1-100 micrometers.

  Next, coating for forming an insulating film 13 containing a Si—O-based oxide and a metal element on the metal magnetic particles 11 was performed. Although there is no restriction | limiting in particular in the coating method, For example, the method of apply | coating the alkoxysilane solution to the metal magnetic particle 11 is illustrated. There is no restriction | limiting in particular in the method of apply | coating an alkoxysilane solution to the metal magnetic particle 11, For example, the method by spray diffusion is mentioned. There is no restriction | limiting in particular in the kind of alkoxysilane, Trimethoxysilane etc. are used. There is no restriction | limiting in particular in the aspect which adds a metal element, For example, what is necessary is just to chelate and add a metal element previously.

  There are no particular restrictions on the concentration of alkoxysilane, the concentration of metal element, and the solvent in the coating solution. The concentration of alkoxysilane is preferably 50 to 99% by weight. The concentration of the metal element is preferably 1 to 30% by weight. Moreover, there is no restriction | limiting in particular also in the solvent of an alkoxysilane solution. Examples include water and ethanol.

  Moreover, it is preferable that the ratio of the alkoxysilane with respect to the metal magnetic particle 11 whole quantity is 0.1 to 2.0 weight% at the time of spray diffusion. The proportion of the metal element is preferably 0.001 to 0.03% by weight. In addition, as the amount of alkoxysilane increases, the thickness of the insulating film 13 tends to increase.

  Although there is no particular limitation on the conditions for spray diffusion, 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 the metal magnetic particles 11 after spray diffusion of the coating solution are dried and the solvent is removed, the sol-gel reaction proceeds by heating at 40 to 60 ° C. for 3 to 20 hours, and the Si—O-based oxide and An insulating film 13 containing a metal element is formed. At this time, the density of the insulating film 13 tends to be higher as the heating temperature is higher and the heating time is longer. In addition, before the metal magnetic particles 11 are heated, the metal magnetic particles may be sized by passing through a mesh screen.

  Next, a resin solution is prepared. In addition to the above-described epoxy resin and / or imide resin, a curing agent may be added to the resin solution. There is no restriction | limiting in particular in the kind of hardening | curing agent, For example, epichlorohydrin etc. are mentioned. The solvent for the resin solution is not particularly limited, but is preferably a volatile solvent. For example, acetone, ethanol or the like can be used. The total concentration of the resin and the curing agent when the total resin solution is 100% by weight is preferably 0.01 to 0.1% by weight.

  Next, the metal magnetic particles 11 on which the insulating film 13 is formed and the resin solution are mixed. And the solvent of a resin solution is volatilized and a granule is obtained. The obtained granule may be filled in the mold as it is, or may be filled in the mold after sizing. There is no restriction | limiting in particular in the sizing method in the case of sizing, For example, you may use a mesh with an opening of 45-500 micrometers.

  Next, the obtained granule is filled in a mold having a predetermined shape and pressed to obtain a green compact. There is no restriction | limiting in particular in the pressure at the time of pressurization, For example, it can be set as 600-1500 Mpa.

  A powder magnetic core can be obtained by subjecting the produced powder compact to a thermosetting treatment. There is no restriction | limiting in particular in the conditions of a thermosetting process, For example, heat processing is performed at 150-220 degreeC for 1 to 10 hours. Moreover, there is no restriction | limiting in particular in the atmosphere at the time of heat processing, You may heat-process in air | atmosphere.

  As mentioned above, although the dust core and its manufacturing method which concern on this embodiment were demonstrated, the dust core and its manufacturing method of this invention are not limited to said embodiment. The dust core of the present invention may be a soft magnetic dust core.

  Moreover, there is no restriction | limiting in particular also in the use of the powder magnetic core of this invention. For example, coil parts, such as an inductor, a reactor, a choke coil, and a transformer, are mentioned.

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

Example 1
As metal magnetic particles, Fe—Si-based 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 prepared by a gas atomization method. In addition, the median value (D50) of the particle diameter of the Fe—Si based 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 is 4.0% by weight ethanol, 1.22% by weight trimethoxysilane, 0.03% by weight zirconium acetylacetonate, and 1.0% by weight with respect to 100% by weight of the total amount of the metal magnetic particles. It was prepared by mixing pure water.

  The metal magnetic particles and the coating solution were mixed and heat-treated while spraying and stirring. The heat treatment temperature was 75 ° C. and the heat treatment time was 5 hours. Furthermore, the metal magnetic particle which has an insulating film on the surface was obtained by drying after heat processing.

  The obtained metal 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, a resin solution was prepared by mixing an epoxy resin, a curing agent, an imide resin, and acetone. Cresol novolak was used as the epoxy resin. Epichlorohydrin was used as a curing agent. Bismaleimide was used as the imide resin. The weight ratio of the epoxy resin, the curing agent and the imide resin is 96: 3: 1, and each component is mixed so that the total amount of the epoxy resin, the curing agent and the imide resin is 4% by weight with the entire resin solution being 100% by weight. did.

  4 wt% of the resin solution was added to and mixed with the total amount of the metal magnetic particles of 100 wt%. Next, it was dried and the acetone was volatilized to obtain granules. The granules were then sized through a 42 mesh screen. The obtained granules were dried on a hot plate at 50 ° C. for 0.5 hours to produce granulated powder.

  Molding was performed by adding 0.1% by weight of zinc stearate to 100% by weight of the granulated powder. 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 at a molding pressure of 589 MPa. Similarly, a rectangular parallelepiped core of 10 mm × 10 mm × 3 mm was produced.

  The obtained toroidal core and rectangular parallelepiped core were heat-cured by performing heat treatment at 180 ° C. for 3 hours to obtain a toroidal dust core and a cuboid dust core. The final powder magnetic core obtained as a whole was 100% by weight, and the metal magnetic particles were about 98% by weight. Hereinafter, a rectangular solid magnetic core was used in the high temperature test and the rust test. In tests other than the high temperature test and the rust test, a toroidal dust core was used.

  It was confirmed by TEM-EDS observation that an insulating film covering the metal magnetic particles was present. Further, 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. Measurement points were set on the surface of the metal magnetic particles. Then, a perpendicular line was drawn from the measurement point toward 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. And the average thickness of the measured insulating film was made into the thickness of the insulating film in the said metal magnetic particle.

  The high temperature test was performed by leaving the above-mentioned cuboid powder magnetic core in a thermostatic bath at 150 ° C. for 1000 hours.

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

  In the table below, samples with good rust test results after the high-temperature test were marked with ◯, and samples with poor rust test results were marked with x.

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

(Example 2)
Example 2 is 4.0 wt% ethanol, 1.22 wt% trimethoxysilane, 0.05 wt% zirconium acetylacetonate, and 1.0 wt% with respect to 100 wt% of the total amount of metal magnetic particles. % Pure water was mixed under the same conditions as in Example 1 except that a coating solution was prepared.

Example 3
Example 3 is 4.0 wt% ethanol, 1.22 wt% trimethoxysilane, 0.50 wt% zirconium acetylacetonate, and 1.0 wt% with respect to 100 wt% of the total amount of metal magnetic particles. % Pure water was mixed under the same conditions as in Example 1 except that a coating solution was prepared.

(Example 4)
Example 4 is 4.0 wt% ethanol, 1.22 wt% trimethoxysilane, 0.07 wt% aluminum acetylacetonate, and 1.0 wt% with respect to 100 wt% of the total amount of metal magnetic particles. % Pure water was mixed under the same conditions as in Example 1 except that a coating solution was prepared.

(Example 5)
Example 5 shows 4.0 wt% ethanol, 1.22 wt% trimethoxysilane, 0.03 wt% barium acetylacetonate, and 1.0 wt% with respect to 100 wt% of the total amount of metal magnetic particles. % Pure water was mixed under the same conditions as in Example 1 except that a coating solution was prepared.

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

(Comparative Example 2)
In Comparative Example 2, 4.0 wt% ethanol, 1.22 wt% trimethoxysilane, 0.01 wt% zirconium acetylacetonate, and 1.0 wt% with respect to 100 wt% of the total amount of metal magnetic particles % Pure water was mixed under the same conditions as in Example 1 except that a coating solution was prepared.

(Comparative Example 3)
In Comparative Example 3, 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 metal magnetic particles % Pure water was mixed under the same conditions as in Example 1 except that a coating solution was prepared.

(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. The process was performed under the same conditions as in Example 1 except that was manufactured.

(Comparative Example 5)
In Comparative Example 5, a coating solution was prepared by mixing 4.0 wt% ethanol, 1.22 wt% trimethoxysilane, and 1.0 wt% pure water with respect to 100 wt% of the total amount of metal magnetic particles. The test was performed under the same conditions as in Example 1 except for the points produced.

(Example 6)
In Example 6, 4.0% by weight of ethanol, 1.22% by weight of trimethoxysilane, 0.03% by weight of zirconium acetylacetonate, 0.07% by weight of the total amount of metal magnetic particles of 100% by weight It was carried out under the same conditions as in Example 1 except that aluminum acetylacetonate and 1.0 wt% pure water were mixed to prepare a coating solution.

(Example 7)
In Example 7, 4.0% by weight of ethanol, 1.22% by weight of trimethoxysilane, 0.07% by weight of aluminum monoacetylacetonate bis (ethylacetoacetate) with respect to 100% by weight of the total amount of metal magnetic particles , And 1.0 wt% pure water was mixed under the same conditions as in Example 1 except that a coating solution was prepared.

(Example 8)
Example 8 includes 4.0 wt% ethanol, 1.22 wt% trimethoxysilane, 0.07 wt% zirconium trifluoroacetylacetonate and 100 wt% total metal magnetic particles. The test 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 ammonium zirconium carbonate, and 1.0% by weight with respect to 100% by weight of the total amount of metal magnetic particles This was carried out under the same conditions as in Example 1 except that a coating solution was prepared by mixing pure water.
(Example 10)
Example 10 includes 4.0 wt% ethanol, 1.22 wt% trimethoxysilane, 0.05 wt% tetra n-butoxide zirconium, and 1.0 wt% with respect to 100 wt% of the total amount of metal magnetic particles. The test was carried out under the same conditions as in Example 1 except that a coating solution was prepared by mixing pure water of wt%.

  The test results of the above examples and comparative examples are shown in Table 1 below.

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

DESCRIPTION OF SYMBOLS 1 ... Powder magnetic core 11 ... Metal magnetic particle 11a ... Surface 12 of metal magnetic particle ... Resin 13 ... Insulating film

Claims (6)

A dust core comprising metal magnetic particles and a resin,
The surface of the metal magnetic particle is in contact with an insulating film covering the metal magnetic particle,
The insulating film includes a Si-O-based oxide and a metal element,
A dust core having a weight content of the metal element with respect to the total amount of the metal magnetic particles of 30 ppm to 1000 ppm.   The dust core according to claim 1, wherein the insulating film includes a metal complex having the metal element as a central metal.   The dust core according to claim 2, wherein the metal complex is a metal chelate compound.   The dust core according to claim 3, wherein at least one of the ligands of the metal chelate compound is acetylacetonate.   The dust core according to any one of claims 1 to 4, wherein the metal element is one or more selected from Zr, Al, and Ba.   The dust core according to claim 1, wherein the insulating film has a thickness of 5 nm to 500 nm.

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