JP2654205B2 - High frequency low loss Mn-Zn ferrite with a frequency of 100KHz or more - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high-frequency low-loss Mn-Zn ferrite suitable for use as a transformer material for a high-frequency power supply.

(Prior Art) Mn-Zn ferrite is used as a transformer material for various communication devices and consumer devices. The characteristics required of this Mn-Zn ferrite include high saturation magnetic flux density, high magnetic permeability, high resistance and low loss, etc. It is said.

For this reason, in the case of Mn-Zn ferrite, improvement has been attempted by adding various trace components. For example, Japanese Patent Publication No. 36-2283 discloses CaCO ₃ and SiO ₂
The combination of the above is intended to improve the loss of the magnetic core. This is presumably because a high-resistance phase was formed at the grain boundaries of the ferrite crystal grains and the eddy current loss was controlled, so that the characteristics were improved.

JP-B-36-2281 reports that the addition of P ₂ O ₅ improves the quality factor Q and the initial magnetic permeability. According to this method, it is necessary to add 0.01 to 0.1 wt% of P ₂ O ₅ , but since the amount of addition is very large, 1250 to 1400
At a high temperature of about ℃, abnormal grain growth is liable to occur, and it is extremely difficult to control the firing.

By the way, conventionally, the switching frequency is 50 to 10
Although a frequency of about 0 kHz is used, recently, there is a tendency to use a higher frequency in order to reduce the size of the power supply, and a further reduction in high-frequency iron loss has been demanded as a transformer material meeting the purpose. ing.

(Problems to be Solved by the Invention) However, in the conventional low-loss oxide magnetic material as described above, when used as a transformer for a high-frequency switching power supply having a switching frequency of 100 kHz or more,
The problem remains where satisfactory low losses cannot be obtained.

The present invention advantageously solves the above-mentioned problems.
An object of the present invention is to propose a low-loss Mn-Zn ferrite capable of suppressing a loss sufficiently low even when used as a transformer for a high-frequency switching power supply of 0 kHz or more.

(Means for Solving the Problems) That is, the present invention comprises Fe ₂ O ₃ : 50 to 55 mol%, MnO: 30 to 40 mol% and ZnO: 8 to 14 mol% as basic components, and SiO ₂ : 0.005 0.04 wt% CaO: 0.02 to 0.2 wt%, phosphorus oxide and / or boron oxide: less than 0.01 wt%, niobium oxide: 0.01 to 0.05 wt% It is a low loss Mn-Zn ferrite.

(Operation) First, the reason why the blending ratio of the basic component is limited to the above range in the present invention will be described.

Fe ₂ O ₃ : 50 to 55 mol%, MnO: 30 to 40 mol%, ZnO: 8 to 14 mol% The operating temperature of the power transformer is usually 60 to 100 ° C.
Therefore, it is desirable that the loss be low within this temperature range.
Here, in Mn-Zn ferrite, Fe ₂ O ₃ , MnO, ZnO
Is within the above range, the loss is extremely small in the temperature range of 60 to 100 ° C., whereas the loss is increased in other compositions, which is not preferable. Therefore, the composition is limited to the above range.

The Fe ₂ O ₃ raw material includes not only Fe ₂ O ₃ but also FeO and Fe ₃
O ₄ , or a compound that can be converted to Fe ₂ O ₃ by firing, such as iron hydroxide and oxalate, can be used. In addition, MnO raw materials include not only MnO but also MnO.
O ₂ , Mn ₃ O _4, and compounds that can be converted to MnO by firing, such as manganese carbonate and manganese oxalate, can be used. Further, as the ZnO raw material, not only ZnO but also a compound that can be converted to ZnO by firing, for example, zinc carbonate, zinc oxalate and the like can be used.

SiO ₂ : 0.005 to 0.04 wt% SiO ₂ increases the specific resistance of the grain boundary by coexistence with CaO,
Effectively reduces eddy current loss, but content is 0.005wt
%, The effect of the addition is poor. On the other hand, if it exceeds 0.04 wt%, abnormal grain growth tends to occur during firing and the characteristics become unstable. Therefore, the content is limited to the range of 0.005 to 0.04 wt%.

CaO: 0.02 to 0.2 wt% CaO is a useful component that enhances grain boundary resistance and refines crystal grains to cause low iron loss.
%, The effect of improving grain boundary resistance is poor, while 0.2w
Above t%, abnormal grain growth is likely to occur when sintering at high temperature to increase the density.
%.

Phosphorous oxide and / or boron oxide: less than 0.01 wt% Phosphorus oxide (mainly P ₂ O ₅ ) and boron oxide (mainly B ₂ O ₃ )
Are all useful components that reduce iron loss by adding a small amount. However, when the content is 0.01 wt% or more, iron loss is rather deteriorated. Therefore, these components may be used individually or in combination with 0.01 wt%.
% (Preferably 0.00005% or more).

For the addition of phosphorus oxide, phosphoric acid (H ₃ PO ₄ ), phosphoric anhydride (P ₂ O ₅ ), and metal phosphates constituting the oxide magnetic material are advantageously adapted. When boron oxide is added, boric acid (H ₃ BO ₃ ) or boric anhydride (B ₂ O
₃ ) and furthermore, a borate of a metal constituting the oxide magnetic material and the like are advantageously suitable.

Niobium oxide: 0.01 to 0.05 wt% Niobium oxide (mainly Nb ₂ O ₅ ) is a useful component that causes low iron loss by relaxing grain boundary stress, but its content is 0.01 wt%
If less than 0.05 wt.%, The effect of the addition is poor, while if it exceeds 0.05 wt%, the magnetic properties will be degraded.
It was added in the range of 05 wt%.

For use in a high frequency range, if the resistance of the grain boundary is not increased, the dielectric breakdown of the grain boundary will occur, but in the present invention, in the presence of P ₂ O ₅ and / or B ₂ O ₃ , SiO ₂ , CaO, Nb ₂ O ₅
Is uniformly dispersed at the grain boundaries to cope with this.

That is, during firing, P ₂ O ₅ and / or B ₂ O ₃ are dissolved to form a liquid phase, and the generated liquid phase causes a small amount of contained SiO ₂ , CaO, and Nb ₂ O ₅ to reach a grain boundary. , And as a result, the resistance of the grain boundary is improved, and the loss due to the eddy current is reduced. According to the observation of the fracture surface of the sintered body, it is considered that the deterioration of the magnetic properties is caused by the generation of coarse grains.

Example 1 Example 1 Fe ₂ O ₃ , MnO and ZnO were weighed to 53 mol%, 35 mol% and 12 mol%, respectively, and pure water was added to obtain a 50% slurry concentration. Mixing was performed for 12 hours. After mixing and drying, 850 ° C in air,
It was calcined for 3 hours. SiO ₂ , CaO, P ₂ O ₅ and Nb ₂ O ₅
Was added and blended in the proportions shown in Table 1. P ₂ O ₅ was added in the form of phosphoric acid (H ₃ PO ₄ ).

Pure water was added to the mixture to adjust the slurry concentration to 50%, and the mixture was again pulverized by a rotary ball mill for 8 hours. Then, PVA was added as a binder to the pulverized powder, and after granulation, molded into a toroidal mold having an outer diameter of 36 mm, an inner diameter of 24 mm, and a height of 8 mm, and baked at 1340 ° C. for 3 hours in a nitrogen atmosphere containing 5% oxygen. After sintering, the atmosphere was switched to a nitrogen atmosphere and cooled to room temperature while cooling in a furnace.

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. using an AC BH loop tracer.

Example 2 Fe ₂ O ₃ , MnO and ZnO were weighed to 53 mol%, 35 mol% and 12 mol%, respectively, and pure water was added to make a 50% slurry concentration, followed by mixing for 12 hours by a rotary ball mill. Was done. After mixing and drying, 850 ° C in air,
It was calcined for 3 hours. SiO ₂ , CaO, B ₂ O ₃ and Nb ₂ O ₅
Was added and blended in the proportions shown in Table 2. B ₂ O ₃ was added in the form of boric acid (H ₃ BO ₃ ).

Pure water was added to the mixture to adjust the slurry concentration to 50%, and the mixture was again pulverized by a rotary ball mill for 8 hours. Then, PVA was added as a binder to the pulverized powder, and after granulation, molded into a toroidal mold having an outer diameter of 36 mm, an inner diameter of 24 mm, and a height of 8 mm, and baked at 1340 ° C. for 3 hours in a nitrogen atmosphere containing 5% oxygen. After sintering, the atmosphere was switched to a nitrogen atmosphere and cooled to room temperature while cooling in a furnace.

Table 2 also shows the results of measuring the iron loss values of the sintered core thus obtained at 100 kHz, 0.2 T and 80 ° C. using an AC BH loop tracer.

Example 3 Fe ₂ O ₃ , MnO and ZnO were weighed to 53 mol%, 35 mol% and 12 mol%, respectively, and pure water was added thereto to obtain a slurry concentration of 50%, followed by mixing in a rotary ball mill for 12 hours. Was done. After mixing and drying, 850 ° C in air,
It was calcined for 3 hours. SiO ₂ , CaO, P ₂ O ₅ , B ₂ O ₃ and
Nb ₂ O ₅ was added and blended in the ratio shown in Table 3. CaO is in the form of calcium carbonate (CaCO ₃ ), and P ₂ O ₅ is phosphoric acid (H
₃ PO ₄ ) and B ₂ O _{3 in} the form of boric acid (H ₃ BO ₃ ).

Pure water was added to the mixture to adjust the slurry concentration to 50%, and the mixture was again pulverized by a rotary ball mill for 8 hours. Then, PVA was added as a binder to the pulverized powder, and after granulation, formed into a toroidal shape having an outer diameter of 36 mm, an inner diameter of 24 mm, and a height of 8 mm, and baked at 1340 ° C. for 3 hours in a nitrogen atmosphere containing 5% oxygen. After sintering, the atmosphere was changed to a nitrogen atmosphere and cooled to room temperature while being furnace-cooled.

Table 3 also shows the results of measuring the iron loss value of the thus obtained sintered core at 100 kHz, 0.2 T, and 80 ° C. using an AC BH loop tracer.

Example 4 Fe ₂ O ₃ , MnO and ZnO were respectively 52.5 mol% and 35.5 mol
% And 11.0 mol%, and add pure water to
After the slurry concentration was 0%, the mixture was mixed for 12 hours by a rotating ball mill. Dry after mixing, then in air
Calcination was performed at 0 ° C. for 3 hours. SiO ₂ , CaO, P ₂ O ₅ , B ₂ O
₃ and Nb ₂ O ₅ were added and blended in the proportions shown in Table 4. Note that CaO
Was added in the form of calcium carbonate (CaCO ₃ ), P ₂ O ₅ was added in the form of phosphoric acid (H ₃ PO ₄ ), and B ₂ O ₃ was added in the form of boric acid (H ₃ BO ₃ ).

Pure water was added to the mixture to adjust the slurry concentration to 50%, and the mixture was again pulverized by a rotary ball mill for 8 hours. Then, PVA was added as a binder to the pulverized powder, and after granulation, formed into a toroidal shape having an outer diameter of 36 mm, an inner diameter of 24 mm, and a height of 8 mm, and baked at 1340 ° C. for 3 hours in a nitrogen atmosphere containing 2% oxygen. After sintering, the atmosphere was changed to a nitrogen atmosphere and cooled to room temperature while being furnace-cooled.

Table 4 also shows the results of measuring the iron loss values of the sintered cores thus obtained at 200 kHz, 0.1 T, and 90 ° C. using an AC BH loop tracer.

Example 5 Fe ₂ O ₃ , MnO and ZnO were respectively 52.5 mol% and 36.0 mol.
% And 11.5 mol%, and add pure water to
After the slurry concentration was 0%, the mixture was mixed for 12 hours by a rotating ball mill. Dry after mixing, then in air
Calcination was performed at 0 ° C. for 3 hours. SiO ₂ , CaO, P ₂ O ₅ , B ₂ O
₃ and Nb ₂ O ₅ were added and blended in the proportions shown in Table 5. Note that CaO
Was added in the form of calcium carbonate (CaCO ₃ ), P ₂ O ₅ was added in the form of phosphoric acid (H ₃ PO ₄ ), and B ₂ O ₃ was added in the form of boric acid (H ₃ BO ₃ ).

Pure water was added to the mixture to adjust the slurry concentration to 50%, and the mixture was again pulverized by a rotary ball mill for 8 hours. Then, PVA was added as a binder to the pulverized powder, and after granulation, formed into a toroidal shape having an outer diameter of 36 mm, an inner diameter of 24 mm, and a height of 8 mm, and baked at 1340 ° C. for 3 hours in a nitrogen atmosphere containing 2% oxygen. After sintering, the atmosphere was changed to a nitrogen atmosphere and cooled to room temperature while being furnace-cooled.

Table 5 also shows the results of measuring the iron loss value of the thus obtained sintered core at 400 kHz, 0.05 T, and 60 ° C. using an AC BH loop tracer.

(Effect of the Invention) Thus, according to the present invention, the switching frequency is 10
Even when used as a transformer for a high-frequency power supply of 0 kHz or more, it is possible to obtain an Mn-Zn soft ferrite with extremely small loss.

 ────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-58-114401 (JP, A) JP-B-36-2281 (JP, B1) JP-B-30-8781 (JP, B1)

Claims (1)

(57) [Claims] 1. A _{Fe 2 O 3: 50~55mol%,} MnO: 30~40mol% and ZnO: a 8～14Mol% as basic components, SiO ₂ in the basic components: 0.005~0.04wt%, CaO: 0.02~ A high-frequency low-loss Mn-Zn ferrite having a frequency of 100 kHz or more, comprising 0.2 wt%, phosphorus oxide and / or boron oxide: less than 0.01 wt%, and niobium oxide: 0.01 to 0.05 wt%.