KR102149296B1 - Soft magnetic core having excellent dc bias characteristics and method for manufacturing the same - Google Patents

Abstract

Disclosed are a soft magnetic core having excellent direct current superposition characteristics and a method of manufacturing the same. One aspect of the present invention, a soft magnetic core having excellent direct current superposition characteristics, includes an inner core made of a molded body of one or more powders selected from the group consisting of Mega Flux powder and High Flux powder; And an outer core made of a molded body of sendust powder and surrounding the inner core.

Description

Soft magnetic core with excellent DC superposition characteristics and its manufacturing method {SOFT MAGNETIC CORE HAVING EXCELLENT DC BIAS CHARACTERISTICS AND METHOD FOR MANUFACTURING THE SAME}

This technology relates to a soft magnetic core with excellent DC superposition characteristics and a manufacturing method thereof, and more specifically, as an inductor of a secondary DC circuit of a switching mode power supply (SMPS), for suppressing electronic noise or smoothing. It relates to a soft magnetic core for a choke coil and a method of manufacturing the same.

In recent years, with the trend of miniaturization, compactness, and high reliability of switching power supplies, characteristics required for soft magnetic core materials for electronic noise suppression of switching power supplies (SMPS) or smooth choke coils are becoming more difficult. , In particular, it is required to be inexpensive, have a low core loss value, and have excellent DC superposition characteristics.

Here, the DC superimposed characteristic is the characteristic of the magnetic core against claudication in which DC current is superimposed on weak AC current generated in the process of converting AC input into DC in the power supply device. The permeability of the core decreases in proportion to the direct current, and the direct current superposition characteristic is evaluated by the ratio of the permeability of the direct current superposition to the permeability of the non-superimposed state.

As a material that satisfies these characteristics, there is a soft magnetic core made from powder, and the most widely used powders for producing soft magnetic cores are Fe-Si-Al-based Sendust powder and Fe-Ni-based high There are high flux powder and Fe-Si-based mega flux powder.

Among the materials, Sendust alloy has excellent stability of permeability, low core loss, and low price, but it is difficult to obtain high permeability and has low DC superposition characteristics. In addition, high flux alloys have low core loss and excellent direct current superposition characteristics, but have disadvantages of high price because they contain more than 50% nickel (Ni).Mega Flux alloys have direct current Although it has excellent overlapping properties and is inexpensive, it has a disadvantage that the core loss is about three times higher than that of Sendust alloy.

On the other hand, Patent Document 1 discloses a technology for producing a soft magnetic core by mixing high flux powder or Molly Permalloy Powder (MPP) with sendust powder, followed by molding and heat treatment.

Korean Patent Application Publication No. 2000-0046247

An aspect of the present invention is to provide a soft magnetic core that is inexpensive, has a low core loss value, and has excellent DC superposition characteristics, and a method of manufacturing the same.

One aspect of the present invention, the inner core made of a molded body of at least one type of powder selected from the group consisting of a mega flux (Mega Flux) powder and a high flux (High Flux) powder; And it is made of a molded body of sendust (sendust) powder, and provides a soft magnetic core having excellent direct current superposition characteristics including an outer core surrounding the inner core.

In addition, another aspect of the present invention is an insulating coating by adding 0.1 to 4 parts by weight of mixed ceramic to 100 parts by weight of at least one powder selected from the group consisting of Mega Flux powder and High Flux powder. , Pressing and heat treatment to prepare an inner core; Insulating coating by adding 0.1 to 4 parts by weight of mixed ceramic to 100 parts by weight of sendust powder, followed by pressing and heat treatment to prepare an outer core; And it provides a method of manufacturing a soft magnetic core excellent in direct current superposition characteristics comprising the step of pressing the inner core into the inside of the outer core.

In addition, not all of the features of the present invention are listed in the means for solving the above-described problems. Various features of the present invention and advantages and effects thereof may be understood in more detail with reference to the following specific embodiments.

The soft magnetic core provided by the present invention has excellent DC superposition characteristics when it has a low core loss value, and can be preferably applied to a soft magnetic core material for suppressing electromagnetic noise of a switching power supply (SMPS) or a smooth choke coil.

Furthermore, there is an advantage of excellent price competitiveness by simplifying the manufacturing process.

The inventors of the present invention have been studying to secure low core loss and excellent DC superposition characteristics among the characteristics required for the soft magnetic core material for suppressing electromagnetic noise or smoothing choke coil of a switching power supply (SMPS). It was found that (flux) was concentrated, and when a high flux core or a mega flux core with excellent direct current superposition characteristics is inserted in the sendust core with low core loss, the saturation magnetic flux density is increased and direct current superposition It was found that the properties could be further improved, and the present invention was completed.

Furthermore, as one means for manufacturing the soft magnetic core material as described above, one or more powders selected from the group consisting of an outer core, a mega flux powder, and a high flux powder, which are molded Sendust powders It was further discovered that the inner core of the molded body was separately manufactured, and the manufacturing process was simplified by simply assembling them, and economic efficiency could be secured through this.

Hereinafter, a method of manufacturing a soft magnetic core having excellent direct current superposition characteristics, which is an aspect of the present invention, will be described in detail.

Steps of manufacturing the inner core

First, 0.1 to 4 parts by weight of mixed ceramic is added to 100 parts by weight of one or more powders selected from the group consisting of Mega Flux powder and High Flux powder, and the powder is insulating coated.

Here, the Mega Flux powder is in wt%, Si: 5-8%, the balance Fe and means an alloy powder included as inevitable impurities, and High Flux powder is in wt%, Ni: 45 It means an alloy powder containing ~55%, the balance Fe and inevitable impurities.

The mixed ceramic means a ceramic mixture based on sodium silicate or potassium silicate, and the ceramic coating reduces eddy current loss (Pev) of the soft magnetic core material by separating individual powders from each other. For. In the present invention, it is preferable to add 0.1 parts by weight or more of the mixed ceramic to 100 parts by weight of the powder in order to obtain the above effects. However, when it exceeds 4 parts by weight, not only the effect is saturated, but also economically disadvantageous, the content of the mixed ceramic is preferably 0.1 to 4 parts by weight based on 100 parts by weight of the powder.

Thereafter, the powder formed with the insulating coating is press-molded and heat treated by a press in a molding die to manufacture an inner core.

According to an embodiment of the present invention, in order to improve the moldability of the core by reducing the friction between the powder particles during the pressure molding, and to protect the mold of the press, a lubricant may be further added to the powder having the insulating coating. . The type and content of the lubricant is not particularly limited, but zinc (Zn), Acrowax, zinc-stearate or aluminum-stearate may be used, and powder 2 parts by weight or less may be added based on 100 parts by weight.

The heat treatment is to remove residual stress and stress of the pressurized powder, and the conditions during the heat treatment are not particularly limited, but according to an embodiment of the present invention, hydrogen, nitrogen or a mixture of hydrogen and nitrogen Heat treatment can be performed for 20 to 180 minutes at a temperature of 500 to 900°C in an atmosphere.

When the heat treatment temperature is less than 500°C, hysteresis loss is large, and when it exceeds 900°C, there is a concern that the mixed ceramic may be damaged. In addition, when the heat treatment time is less than 20 minutes, the effect of removing residual stress and stress of the powder is not sufficient, and when it exceeds 180 minutes, the effect is saturated and economically disadvantageous.

Meanwhile, according to an embodiment of the present invention, the surface of the inner core may be coated with polyester or epoxy resin. This is to protect the characteristics of the inner core from moisture or external atmosphere.

Steps of manufacturing the outer core

First, 0.1 to 4 parts by weight of mixed ceramics are added to 100 parts by weight of Sendust powder to insulate the powder.

Here, the Sendust (Sendust) powder refers to an alloy powder including in weight %, Si: 8-10%, Al: 4-6%, the balance Fe and inevitable impurities.

The mixed ceramic means a ceramic mixture based on sodium silicate or potassium silicate, and the ceramic coating reduces eddy current loss (Pev) of the soft magnetic core material by separating individual powders from each other. For. In the present invention, it is preferable to add 0.1 parts by weight or more of the mixed ceramic to 100 parts by weight of the powder in order to obtain the above effects. However, when it exceeds 4 parts by weight, not only the effect is saturated, but also economically disadvantageous, the content of the mixed ceramic is preferably 0.1 to 4 parts by weight based on 100 parts by weight of the powder.

Thereafter, the Sendust powder having an insulating coating is formed by pressing in a molding die and heat-treated to produce an outer core.

In this case, the mold of the press for the Sendust powder is preferably manufactured such that there is no gap between the inner core and the outer core. This is to secure adhesion between the inner core and the outer core.

On the other hand, according to one embodiment of the present invention, in order to improve the moldability of the core by reducing friction between the particles of the Sendust powder during the pressure molding, and to protect the mold of the press, the insulating coating is formed. (Sendust) More lubricants can be added to the powder. The type and content of the lubricant is not particularly limited, but zinc (Zn), Acrowax, zinc-stearate or aluminum-stearate may be used. 2 parts by weight or less may be added based on 100 parts by weight of the dust powder.

The heat treatment is to remove the residual stress and stress of the press-molded Sendust powder, and the conditions during the heat treatment are not particularly limited, but according to an embodiment of the present invention, hydrogen, nitrogen or hydrogen It can be heat-treated for 20 to 180 minutes at a temperature of 500 to 900 ℃ in a mixed gas atmosphere of and nitrogen.

When the heat treatment temperature is less than 500°C, hysteresis loss is large, and when it exceeds 900°C, there is a concern that the mixed ceramic may be damaged. In addition, when the heat treatment time is less than 20 minutes, the effect of removing residual stress and stress of the powder is not sufficient, and when it exceeds 180 minutes, the effect is saturated and economically disadvantageous.

Meanwhile, according to one embodiment of the present invention, the surface of the outer core may be coated with polyester or epoxy resin. This is to protect the characteristics of the outer core from moisture or external atmosphere.

Inner core to the inside of outer core Press-in step

The inner core manufactured by the above-described method is press-fit into the outer core to manufacture a soft magnetic core. According to one embodiment of the present invention, the press fitting may be performed by a press, and after press fitting to improve adhesion between the inner core and the outer core, additional heat treatment may be performed.

Hereinafter, another aspect of the present invention, a soft magnetic core having excellent direct current superposition characteristics, will be described in detail.

Another aspect of the present invention, a soft magnetic core having excellent direct current superposition characteristics, includes an inner core made of a molded body of one or more powders selected from the group consisting of a mega flux powder and a high flux powder; And an outer core made of a molded body of sendust powder and surrounding the inner core.

In the operating environment of the soft magnetic core for suppressing electromagnetic noise or smoothing choke coil of a switching power supply (SMPS), since the flux is concentrated inside the core, the DC superposition characteristic is excellent inside the core as described above. When a high flux core or a mega flux core is located, the saturation magnetic flux density is increased to show improved DC superposition characteristics.

Hereinafter, the present invention will be described in more detail through examples. However, it should be noted that the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by matters described in the claims and matters reasonably inferred therefrom.

( Example One)

Prepare a powder for an inner core coated with 0.1 parts by weight of mixed ceramic for 100 parts by weight of High Flux powder, and prepare a powder for an inner core coated with 0.1 parts by weight of mixed ceramic for 100 parts by weight of Sendust powder The powder was prepared.

Before molding the powder for the inner core and the powder for the outer core, a mold for press molding was produced, and the mold for the outer core was made in a cylindrical shape with an outer diameter of 46.74mm, an inner diameter of 32.8mm, and a height of 18mm, and a mold for the inner core. Was manufactured in a cylindrical shape with an outer diameter of 32.8 mm, an inner diameter of 24.13 mm, and a height of 18 mm.

Subsequently, the inner core powder and the outer core powder were molded and heat-treated for 1 hour in a nitrogen atmosphere. The heat treatment temperature was kept constant at 770°C for the Sendust core and 660°C for the High-Flux core. Thereafter, the inner core was press-fit into the outer core to prepare a soft magnetic core (invention material 1).

On the other hand, as a comparative material (Comparative Material 1) in weight%, 70% of Sendust powder and 30% of High Flux powder are mixed, and an insulation coating of 0.1 parts by weight of mixed ceramics is applied to 100 parts by weight of the mixed powder. Prepared mixed powder. The mold for press molding was manufactured in a cylindrical shape with an outer diameter of 46.74 mm, an inner diameter of 24.13 mm, and a height of 18 mm.

The insulating-coated mixed powder was charged into the mold, molded, and heat-treated in a nitrogen atmosphere for 1 hour. The heat treatment temperature was kept constant at 730°C.

The permeability, core loss value, and DC superposition characteristics of the soft magnetic core (inventive material 1 and comparative material 1) were measured, and the results are shown in Table 1.

In the evaluation of the magnetic properties of the soft magnetic core, after winding 36 times of enameled copper wire of 0.55mm on the surface of the manufactured core, measuring the inductance (L:uH) using a precision LCR meter, the following Equation 1 The permeability (μ) was obtained by the relational expression of the toroidal core represented by. Measurement conditions are frequency 100kHz, AC voltage 1V, and DC is not superimposed (I _DC = 0A).

[Equation 1]

(However, L is the inductance (uH), μ is the permeability, N is the number of windings, A is the longitudinal area of the core (cm ² ), and l is the length of the average furnace (cm))

In addition, by changing the DC current and measuring the change in the permeability, the DC superposition characteristic is checked. In this case, the measurement conditions are frequency 100 kHz, AC voltage 1 V, and measured magnetization strength (HDC) = 50 Oe (HDC = 0.4πI/l Current calculation).

In addition, the core loss value was measured by a BH analyzer, and the primary and secondary windings were measured 22 times at a frequency of 50 kHz and a magnetic flux density of 500 G.

division Permeability Core loss value
(mW/cm ³ ) DC superposition characteristic
(%) Invention 1 58 48 86 Conventional material 1 61 46 80

As shown in Table 1, it can be seen that Inventive Material 1 has improved DC superposition characteristics by about 6% compared to Comparative Material 1 of the same weight.

( Example 2)

Prepare a powder for an inner core coated with 0.1 parts by weight of mixed ceramic for 100 parts by weight of Mega Flux powder, and for an outer core coated with 0.1 parts by weight of mixed ceramic with respect to 100 parts by weight of Sendust powder The powder was prepared.

Before molding the powder for the inner core and the powder for the outer core, a mold for press molding was produced, and the mold for the outer core was made in a cylindrical shape with an outer diameter of 46.74mm, an inner diameter of 32.8mm, and a height of 18mm, and a mold for the inner core. Was manufactured in a cylindrical shape with an outer diameter of 32.8 mm, an inner diameter of 24.13 mm, and a height of 18 mm.

Subsequently, the inner core powder and the outer core powder were molded and heat-treated for 1 hour in a nitrogen atmosphere. The heat treatment temperature was kept constant at 770°C for both the Sendust powder and the Mega Flux powder. Thereafter, the inner core was pressed into the outer core to prepare a soft magnetic core (invention material 2).

On the other hand, as a comparative material (Comparative Material 2), as a weight%, 70% of Sendust powder and 30% of Mega Flux powder are mixed, and insulating coating with 0.1 parts by weight of mixed ceramic based on 100 parts by weight of the mixed powder Prepared mixed powder. The mold for press molding was manufactured in a cylindrical shape with an outer diameter of 46.76 mm, an inner diameter of 24.13 mm, and a height of 18 mm.

The insulating-coated mixed powder was charged into the mold, molded, and heat-treated in a nitrogen atmosphere for 1 hour. The heat treatment temperature was kept constant at 770°C.

The permeability, core loss value, and DC superposition characteristics of the soft magnetic core (inventive material 2 and comparative material 2) were measured, and the results are shown in Table 2, and the measurement conditions were the same as in Example 1.

division Permeability Core loss value
(mW/cm ³ ) DC superposition characteristic
(%) Invention 2 61 75 85 Conventional material 2 61 71 77

As shown in Table 2, it can be seen that Inventive Material 2 has improved DC superposition characteristics by about 8% compared to Comparative Material 2 of the same weight.

Claims (3)

An outer core made of a molded body of sendust powder; And
The soft magnetic property is excellent in direct current superposition characteristics including an inner core made of a molded body of one or more powders selected from the group consisting of Mega Flux powder and High Flux powder, but located by press-fitting inside the outer core. core.
0.1 to 4 parts by weight of mixed ceramic is added to 100 parts by weight of one or more powders selected from the group consisting of Mega Flux powder and High Flux powder, and the powder is insulating coated, pressed and heat treated to Manufacturing a core;
Adding 0.1 to 4 parts by weight of mixed ceramics to 100 parts by weight of sendust powder to insulate the powder, press-molding and heat treatment to prepare an outer core; And
A method of manufacturing a soft magnetic core having excellent direct current superposition characteristics, comprising the step of press-fitting the inner core into the outer core.
The method of claim 2,
The heat treatment is performed for 20 to 180 minutes at a temperature of 500 to 900 °C in an atmosphere of hydrogen, nitrogen or a mixture of hydrogen and nitrogen.