JP3401298B2 - Low loss Mn-Zn soft ferrite - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for applications such as transformers for switching power supplies, and is suitable for use with Mn-
It relates to Zn-based soft ferrite.

[0002]

2. Description of the Related Art Mn-Zn soft ferrite is widely used as a coil material for various communication equipments, power supplies, etc., and a transformer material. However, with the recent spread of OA equipments, it operates in a high frequency region of about 100kHz. It is also used as a transformer material for switching power supplies.

Used as such a transformer material
The characteristics required for the Mn-Zn ferrite include various characteristics such as high saturation magnetic flux density, high permeability and low loss, but especially as a switching power supply transformer targeted by the present invention, under a high magnetic field. Low loss is particularly important in. For this reason, in the Mn-Zn soft ferrite, it has been attempted to improve the loss by adding various trace additives, and as the iron loss characteristics particularly in the high frequency band, the loss at 100 kHz and 200 mT is 300. It has been realized up to the level of ~ 400 mW / cm ³ .

Among them, JP-A-61-42104 and JP-A-61-42104
In Japanese Patent Publication No. 61-42105, loss is further improved by adding calcium oxide, silicon oxide, niobium oxide and potassium oxide, and as a result, a switching frequency of 25k
The loss at Hz is reduced to a level of about 60 mW / cm ³ at a magnetic flux density of 200 mT. Further, Japanese Patent Application Laid-Open No. 4-325493 proposes a method for further improving the characteristics by applying a solution of an alcoholate compound of K, Rb, and Cs to a sintered product and then heat-treating it. Further, Japanese Patent Laid-Open No. 5-36516 proposes a method of removing the adverse effect of the impurity P by adding K ₂ O.

[0005]

DISCLOSURE OF THE INVENTION The present invention effectively improves the iron loss characteristics in the high frequency band of 100 kHz or more, which is currently used as a switching power supply frequency, and reduces the loss when used as a switching power supply transformer. The purpose is to propose a Mn-Zn soft ferrite that can be significantly reduced.

[0006]

[Means for Solving the Problems] That is, the present invention provides a basic component consisting of Fe ₂ O ₃ : 52 to 54.5 mol% MnO: 33 to 40 mol% ZnO: 6 to 14 mol% and SiO ₂ : 0.005 to 0.040 wt% CaO: 0.02~0.20wt% niobium oxide: 0.01～0.08Wt% titanium oxide: containing 0.05~0.40wt%, 1 kind or 2 kinds chosen further potassium, among the oxides of rubidium and cesium The above is a low-loss Mn-Zn-based soft ferrite (first invention) characterized by containing 100 to 2000 ppm in terms of metal.

Further, the present invention _{is, Fe 2 O 3: 52~54.5 mol} % MnO: 33~40 mol% ZnO: SiO 2 to the basic component consisting 6~14 mol%: 0.005 ~0.040 wt% CaO: 0.02 ~ 0.20wt% Niobium oxide: 0.01 ~ 0.08wt% Antimony oxide: 0.005 ~ 0.08wt% is included , and one or more selected from each oxide of potassium, rubidium and cesium is 100 in terms of metal. It is a low-loss Mn-Zn-based soft ferrite (second invention) characterized by containing ˜2000 ppm.

Furthermore, the present _{invention, Fe 2 O 3: 52~54.5 mol} % MnO: 33~40 mol% ZnO: SiO 2 to the basic component consisting 6~14 mol%: 0.005 ~0.040 wt% CaO: 0.02 ～0.20Wt% niobium oxide: 0.01～0.08Wt% titanium oxide: 0.05～0.40Wt% antimony oxide: 0.005 contained ～0.08Wt%, further potassium, one selected from among the oxides of rubidium and cesium or It is a low-loss Mn-Zn soft ferrite (third invention) characterized by containing 100 to 2000 ppm of two or more metal equivalents.

[0009]

In the present invention, the reason why the composition of the soft ferrite is limited to the above range will be described below. First, the reason why the ratio of the basic components is limited to the above range is as follows. Fe ₂ O ₃ : 52-54.5 mol%, MnO: 33-40 mol%, ZnO:
6 to 14 mol% Switching power supply transformer operating temperature is usually 60 to 70 ℃
Therefore, it is desirable that the power loss is low in this temperature range, and that the iron loss from room temperature to a temperature range of about 80 to 120 ° C. above the operating temperature has a negative temperature dependence. From this viewpoint, as a result of examining the proportions of Fe ₂ O ₃ , MnO, and ZnO, the above range was obtained.

In the present invention, one or two of SiO ₂ , CaO, niobium oxide, titanium oxide and antimony oxide are added to the above-mentioned basic components.
Furthermore, it is characterized by containing one or more selected from the oxides of potassium, rubidium and cesium. In this case, the contents of these components are as follows.

SiO ₂ : 0.005 to 0.40 wt% SiO ₂ enhances the specific resistance of the grain boundary by coexistence with CaO and effectively contributes to the reduction of eddy current loss. On the other hand, if it exceeds 0.040wt%, on the other hand, the loss becomes large, so the SiO ₂ content is 0.005 to 0.04.
It was limited to the range of 0 wt%.

CaO: 0.02 to 0.20 wt% CaO is a useful component that effectively increases the grain boundary resistance in the presence of SiO ₂ and brings about a low loss, but if the content is less than 0.02 wt%, Poor improvement in field resistance, while 0.20 wt%
On the contrary, if it exceeds, the loss will increase, so 0.02 to 0.20wt%
Was added in the range.

Niobium oxide: 0.01 to 0.08 wt% The reason why the loss is improved by the addition of niobium oxide (mainly Nb ₂ O ₅ ), is that, like SiO ₂ and CaO, it precipitates at the grain boundaries and has a high resistance. It is considered that the magnetic adverse effect is mitigated by the formation of different phases at grain boundaries. However, if the content is less than 0.01 wt%, the effect is poor, while 0.08
If it is contained in excess of wt%, abnormal grain growth is likely to occur during sintering, so it was added in the range of 0.01 to 0.08 wt%.

Titanium oxide: 0.05 to 0.40 wt% Titanium oxide (mainly TiO ₂ ) enhances the specific resistance of the core by promoting reoxidation of grain boundaries in the cooling process during firing of the ferrite core, and Although it has an effect of reducing loss, if it is less than 0.05 wt%, its effect is poor, while if it is contained in excess of 0.40 wt%, it causes an increase in loss, so it is added in the range of 0.05 to 0.40 wt%. I decided to do it.

Antimony oxide: 0.005 to 0.08 wt% Antimony oxide (mainly Sb ₂ O ₃ ) is added to SiO ₂ , CaO and Nb ₂ O.
_{By including} it in combination with ₅ , the loss is improved. Although the reason has not been clarified yet at this point, it is considered that the reason is that it precipitates at the grain boundaries and gives the same effect as that of niobium oxide described above. This effect
Large in the presence of SiO ₂ , CaO and Nb ₂ O ₅ . However, if it is less than 0.005 wt%, its effect is poor, while 0.
On the contrary, if the content exceeds 08 wt%, it causes an increase in loss. Therefore, it was added in the range of 0.005 to 0.08 wt%.

Further, in the present invention, in addition to the above-mentioned respective components, K, Rb and / or Cs is added to an oxide, especially K ₂ O, Rb.
₂ O, Cs ₂ O, etc. are contained. It is considered that these oxides also have a loss reducing effect and exist at grain boundaries to suppress abnormal grain growth. Here, the content of the above-mentioned oxide is in the range of 100 to 2000 ppm in terms of metal. This is because if the content is less than 100 ppm, the effect of addition is poor, while if it exceeds 2000 ppm, on the contrary, it causes an increase in loss.

These oxides are added as potassium compounds, rubidium compounds and cesium compounds, and examples of such compounds include K ₂ CO ₃ , KCl, K ₂ SO ₄ ,
Rb ₂ CO ₃ , RbCl, Rb ₂ SO ₄ , Cs ₂ CO ₃ , CsCl, Cs ₂ SO _{4 and the} like are preferable.

As described above, increasing the specific resistance is particularly effective for reducing the loss in the high frequency range up to 100 kHz. In the present invention, however, niobium oxide and niobium oxide coexist in the presence of SiO ₂ and CaO. , Titanium oxide and / or antimony oxide, and one or more kinds selected from the oxides of potassium, rubidium and cesium oxide are added and uniformly dispersed in the grain boundaries. It achieves the purpose.

Here, in order to produce the ferrite according to the present invention, the treatment may be performed according to a conventional method. That is,
As the final composition of ferrite, iron oxide is 52% in terms of Fe ₂ O _3.
~ 54.5 mol%, manganese oxide 33-40 mol in terms of MnO
%, Zinc oxide was mixed so as to be 6 to 14 mol% in terms of ZnO, and then SiO ₂ as a minor component: 0.005 to 0.040 wt
%, CaO: 0.02 to 0.20 wt%, niobium oxide (Nb ₂ O ₅ conversion): 0.01 to 0.08 wt%, titanium oxide (TiO ₂ conversion): 0.
05-0.40wt% and antimony oxide (Sb ₂ O ₃ conversion): 0.
One or two kinds of 005 to 0.08 wt% and one or more kinds of potassium oxide, rubidium oxide and cesium oxide are contained as a raw material in an amount of 100 to 2000 ppm in terms of metal. However, the trace components may be added after the calcination described below. This raw material powder is calcined at a temperature of 800 ° C or higher, then pulverized and then
Baking is performed in nitrogen gas whose oxygen concentration is controlled at a temperature of 50 ° C or higher.

[0020]

Examples Example 1 Fe ₂ O ₃ : 53.5 mol% and MnO: 34.5 mol% as final composition
After mixing the raw materials of the basic composition of ZnO and ZnO: 12 mol%, calcination was performed in the air at 900 ° C. for 3 hours. With respect to the calcined powder, the Si content was adjusted so that the final composition was as shown in Table 1.
O ₂ , CaO (added as CaCO ₃ ), Nb ₂ O ₅ , TiO ₂ and K ₂ CO ₃ ,
Rb ₂ CO ₃ and Cs ₂ CO ₃ were added and mixed, and at the same time pulverized and mixed by a wet ball mill. Then, add P as a binder to the crushed powder.
After adding VA and granulating, outer diameter: 36 mm, inner diameter: 24 mm,
After being formed into a ring shape having a height of 12 mm, firing was performed at 1320 ° C. for 3 hours in a nitrogen atmosphere with controlled oxygen partial pressure. Table 1 also shows the results of measuring the iron loss value of the thus obtained sintered core at a frequency of 100 kHz, a maximum magnetic flux density of 0.2 T and a temperature of 80 ° C. with an AC BH loop tracer.

[0021]

[Table 1]

As is clear from Table 1, according to the present invention, SiO ₂ , CaO, Nb ₂ O ₅ , TiO ₂ and K, R as auxiliary components are used.
b, Cs oxides that contain a complex content are both 300 mW /
Low power losses below cm ³ have been achieved. On the other hand, in all cases that deviate from the proper range of the present invention, the effect of improving loss is small, and in extreme cases, the loss characteristics are conversely deteriorated due to abnormal grain growth.

Example 2 Fe ₂ O ₃ : 52.7 mol%, MnO: 34.6 mol% as the final composition
After mixing raw materials having a basic composition of ZnO: 12.7 mol% and calcination in the atmosphere at 900 ° C. for 3 hours. SiO ₂ , CaO (added as CaCO ₃ ) Nb ₂ O ₅ , S so that the final composition is in the ratios shown in Tables 2 and 3 with respect to this calcined powder.
b ₂ O ₃ and K ₂ CO ₃ , Rb ₂ CO ₃ and Cs ₂ CO ₃ were added and blended, and at the same time pulverized and mixed by a wet ball mill. Next, PVA was added as a binder to the pulverized powder, and after granulating, the outer diameter: 36
After being formed into a ring shape having a size of mm, an inner diameter of 24 mm, and a height of 12 mm, firing was performed at 1320 ° C. for 3 hours in a nitrogen atmosphere with controlled oxygen partial pressure. The frequency of the sintered core thus obtained:
Tables 2 and 3 show the results of measuring the iron loss value at 100 kHz, maximum magnetic flux density: 0.2 T, temperature: 80 ° C. with an AC BH loop tracer.

[0024]

[Table 2]

[0025]

[Table 3]

As is clear from Tables 2 and 3, all of the components of the present invention adjusted in the proper component composition range have a low power loss of less than 300 mW / cm ³ .

[0027]

As described above, according to the present invention, as a core of a transformer for a high frequency power supply having a switching power supply frequency of about 100 kHz, a low loss Mn-Zn system software having a significantly smaller loss under a high magnetic field than conventional materials. Ferrite can be obtained.

Claims (3)

(57) [Claims] 1. A basic component composed of Fe ₂ O ₃ : 52 to 54.5 mol% MnO: 33 to 40 mol% ZnO: 6 to 14 mol%, SiO ₂ : 0.005 to 0.040 wt% CaO: 0.02 to 0.20 wt. % Niobium oxide: 0.01 to 0.08wt% Titanium oxide: 0.05 to 0.40wt%, and one or more selected from the oxides of potassium, rubidium and cesium 100 to 2000ppm in terms of metal A low-loss Mn-Zn-based soft ferrite characterized by containing. 2. A basic component consisting of Fe ₂ O ₃ : 52 to 54.5 mol% MnO: 33 to 40 mol% ZnO: 6 to 14 mol% SiO ₂ : 0.005 to 0.040 wt% CaO: 0.02 to 0.20 wt% Niobium oxide: 0.01 to 0.08wt% Antimony oxide: 0.005 to 0.08wt%, and 100 to 2000ppm in terms of metal of one or more selected from the oxides of potassium, rubidium and cesium. A low-loss Mn-Zn-based soft ferrite characterized by containing. 3. Fe ₂ O ₃ : 52 to 54.5 mol% MnO: 33 to 40 mol% ZnO: 6 to 14 mol% in a basic component SiO ₂ : 0.005 to 0.040 wt% CaO: 0.02 to 0.20 wt% niobium oxide: 0.01～0.08Wt% titanium oxide: 0.05～0.40Wt% antimony oxide: 0.005 contained ～0.08Wt%, further potassium, select one or more I from among the oxides of rubidium and cesium Low loss Mn-Zn soft ferrite characterized by containing 100 to 2000 ppm in terms of metal.