JPH03223119A - Low loss mn-zn-based ferrite - Google Patents

Abstract

PURPOSE:To obtain a ferrite capable of remarkably reducing loss in using a transformer for a switching power source by blending SiO2, CaO, V2O5, Ta2O5 and TiO2 with Fe2O3, MnO and ZnO as basic components. CONSTITUTION:A low loss Mn-Zn-based ferrite obtained by adding and blending 0.008-0.025wt.% SiO2, 0.02-0.15wt.% CaO, 0.001-0.05wt.% V2O5, 0.01-0.1wt.% Ta2O5 and 0.05-0.4wt.% TiO2 with 52-54.5mol% Fe2O3, 33-40mol% MnO and 6-13mol% ZnO as basic components. The operating temperature of a transformer for a switching power source is normally 60-70 deg.C. Accordingly, it is desirable that power loss within the aforementioned temperature range is low and the iron loss has negative temperature dependence from ambient temperature to a temperature range of about 80-120 deg.C exceeding the operating temperature. The blending ratio of the Fe2O3, MnO and ZnO is preferably within the above- mentioned range from the aforementioned viewpoint.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a low-loss Mn-Zn ferrite suitable for use in transformers for switching power supplies and the like.

(Prior Art) Mn-Zn ferrite is used as a transformer material for various communication devices, consumer devices, and the like. This Mn-Zn
The properties required of the ferrite-based ferrite include various properties such as high saturation magnetic flux density, high magnetic permeability, high resistance, and low iron loss.In particular, for transformers for switching power supplies as the subject of this invention, Low loss under high magnetic fields is particularly important.

For this reason, attempts have been made to improve Mn-Zn ferrite by adding various trace components.

For example, in JP-A-58-15037, Nb2O2 is added, and in JP-A-60-132301, Nb2O is added.

Cab, 5io2. V2O5+ Zr0z+ Al
zO,,5n02. By adding CuO, CaO, etc., we aim to improve the loss at 100 kHz, which is currently becoming the standard switching frequency.
The iron loss value at 0 kHz and 200 mT is 30
Levels from 0 to 350 mW/cm'' have been achieved.

By the way, recently, in order to further downsize power supplies, the frequency used has tended to become higher (500 kHz to I MHz), and Mn-Zn ferrites that meet this purpose are being developed. Showa 63-62
In Publication No. 206, TiO2, Taxes, Si
Attempts have been made to improve iron loss at frequencies above 500 kHz by adding O2tCaO.

(Problem B to be Solved by the Invention) As mentioned above, this invention deals with the power supply frequency of 100 kHz, which is currently becoming the standard frequency for power notching.

Iron loss value at 200 mT 300-3501/Cl1
The purpose of the present invention is to further improve 1'' and to propose a low-loss Mn-Zn-based ferrite that can significantly reduce loss when used as a transformer for a switching power supply.

Note that the technology for reducing core loss at frequencies of 500 k)lz or higher is
Looking at the iron loss in high magnetic fields reaching mT, it is not possible to provide a lower iron loss that exceeds that of conventional materials, and there is no example in which the above characteristic values have been obtained.

For example, in the above-mentioned Japanese Patent Application Publication No. 63-62206,
The curve GI disclosed in FIG. 4 showing the characteristics of Example 1
Regarding O, the iron loss value at 100 kl (z, 1000 Gauss (100 mT) is approximately 50 m at 70°C.
W/cm3, but based on this value and evaluating the iron loss value at 100 k) Iz and 200 mT from the maximum magnetic flux density dependence, it is approximately 340 to 380 mW/cm.
becomes.

(Means for solving problems) That is, the gist of the present invention is as follows.

(1) FezO:+: 52-54.5 mol%, M
n0=33~4011IO1% and ZnO: 6~
13 mol% as a basic component, and this basic component contains SiO□: 0.008 to 0.025 wt%, CaO
: 0.02-0.15 wt%, V2O5: 0.0
01-0.05 wt%, Ta2es: 0.01
"0.1 wt% and TiO□: 0.05-0.
A low-loss Mn-Znn-based adhesive (first invention) obtained by adding and blending 4 wt% of Mn-Znn.

Fe2r3: 52-54.5 mol%, MnO=
33-40 mol% and ZnO: 6-13 mo
1% (2) is the basic component, and this basic component contains Sing: 0.008 to 0.025wt%, Ca
O: 0.02-0.15 wt%, vanadium oxide:
0.001-0.05 wt%, tantalum oxide: 0
．． 01~0.1 wt% and titanium oxide: O, OS~
Low-loss Mn-Zn ferrite containing 0.4 ivt% (2 invention).

Fe2O:+: 52-54.5 mol%, MnO
: 33-40 mol% and ZnO: 6-13
mol% is the basic component, and this basic component includes SiO□: 0.008 to 0.025wt%, CaO
: 0.02-0.15 iyt%, V2O5: 0.
001-0.05 wt%, Ta2O5: 0.01
~0.1 wt% and Ti (h: 0.05~0
．． 4 wt% (3) (Phosphorus oxide and/or boron oxide: 0.003 wt%
Low-loss Mn-Zn ferrite made by adding and blending the following (
Third invention).

Fezes: 52-54.5 mol%, MnO:
33-40 mol% and ZnO: 6-13
mol% is the basic component, and this basic component contains 5in2: 0.008-0.025wt%, CaO:
0.02-0.15 wt%, vanadium oxide: o
, ooi~0.05 imt%, tantalum oxide: 0.
01~0.1 wt% and titanium oxide: 0.05~
(4) Phosphorus oxide and/or boron oxide: 0.003 wt%
A low-loss Mn-Zn-based ferrite (fourth invention) comprising:

(Function) First, in this invention, the reason why the blending ratio of the basic components is limited to the above range will be explained.

FezO:+: 52-54.5 mol%, Mn0
=33~4011I01%, ZnO: 6~13 m
ol%; The operating temperature of a switching power supply transformer is usually 60~
70'C, therefore, it is desirable that the power loss is low in this temperature range, and that the iron loss has a negative temperature dependence from room temperature to a temperature range of about 80 to 120 degrees Celsius, which exceeds the operating temperature. From this point of view, as a result of examining the blending ratios of Fe, O, MnO, and ZnO, the above range was obtained.

Note that FezO3 raw materials include not only FezO1 but also
FeO and Fe50. , and further by firing 3. Fe2O
Compounds that can be substituted with 3, such as iron hydroxide, iron oxalate, etc., can be used. In addition, MnO raw materials include not only MnO but also Mn0z, Mn30. Furthermore, it is possible to use compounds that can be converted into Mn(l) by calcination, such as manganese carbonate and manganese oxalate.Furthermore, the ZnO raw material is not limited to only ZnO, but also compounds that can be converted to ZnQ by calcination. For example, zinc carbonate, zinc oxalate, etc. can be used.

Sing: 0.008~0.025wt%Si
O□ increases the specific resistance of grain boundaries by coexisting with CaO,
It effectively contributes to reducing eddy current loss, but the content is 0.0
If the amount is less than 0.08 wt%, the addition effect will be poor;
．． If it exceeds 0.025 wt%, abnormal grain growth tends to occur during firing and the properties become unstable, so 0.008 to 0.025
The range was limited to wt%.

CaO: 0.02 to 0.15 wt% CaO is a useful component that effectively increases grain boundary resistance in coexistence with Sing and thereby brings about low core loss, but the content is less than 0.02 wt%. Without it, the effect of improving grain boundary resistance will be poor, and on the other hand, if it exceeds 0.15 wt%, the loss will increase, so the content was determined to be in the range of 0.02 to 0.15 wt%.

Vanadium oxide 70.001 to 0.05 wt% In this invention, vanadium oxide mainly refers to v20. However, it is not necessarily limited to this oxide form,
It also includes cases where oxides other than V2O5 are contained. Even if it contains oxides other than Naori 205, its composition range is ■20. It shall be expressed in terms of conversion.

Now, vanadium oxide has the effect of increasing grain boundary resistance, and this effect becomes even greater when it coexists with 5t(h), CaO, and tantalum oxide, which will be described later.

However, if the content is less than 0.001 wt%, the effect is small, while if the content exceeds 0.05 wt%, abnormal growth of crystal grains will occur, leading to a significant increase in loss.

Tantalum oxide: 0.01 to 0.1 wt% In this invention, tantalum oxide mainly refers to Ta205, but it is not necessarily limited to this oxide form, and Taz
This also includes cases where oxides other than 05 are contained. Please note that Tax
Even when oxides other than es are contained, the composition range shall be expressed in terms of Ta2O5.

Now, like vanadium oxide, tantalum oxide is SiO□
, CaO effectively contributes to increasing resistivity in the coexistence with vanadium oxide, but if the content is less than 0.01 wt%, the effect is poor, while if it exceeds 0.1 wt%, the loss increases. Invite (.

Titanium oxide: 0.05-0.1wt% In this invention, titanium oxide mainly refers to Tie.

However, it is not necessarily limited to this oxide form (it also includes cases in which oxides other than Tie are contained. Even if oxides other than Tie are contained, the composition range is Ti(h It shall be expressed in terms of conversion.

Now, titanium oxide has the effect of promoting grain boundary reoxidation during the cooling process during ferrite core firing and increasing grain boundary resistance, but if it is less than 0.05 wt%, the effect is small; If it exceeds .4 wt%, the loss will increase.

Phosphorus oxide and/or boron oxide: 0.003 wt% or less In this invention, phosphorus oxide and boron oxide are:
Mainly P2O and B20. Although it refers to
It is not necessarily limited to this oxide form, but P2O,
It also includes cases where oxides other than B2O3 are contained.

In addition, P2O5 and B20. Even when containing oxides other than oxides, the composition range shall be expressed in terms of P2O, Bz (h).

Both phosphorus oxide and boron oxide are useful components that reduce iron loss when added in trace amounts. However, if the content exceeds 0.003wt%, it will actually cause deterioration of iron loss, so whether these components are used alone or in combination, 0.003wt%
% (preferably 0.0001% 1t% or more).

When adding phosphorous oxide, phosphoric acid ()lsPO4
), phosphoric anhydride (P2O5), and metal phosphates constituting the oxide magnetic material are advantageously suitable. Further, when adding boron oxide, boric acid (13BO3), anhydrous boric acid (BzO, ), and borates of metals constituting the oxide magnetic material are advantageously suitable.

As mentioned above, increasing the resistivity is very effective in reducing loss in the high frequency range of 100 kHz, but in this invention, vanadium oxide (mainly vzos ), tantalum oxide (mainly Tag's) and titanium oxide (mainly Ti1t), as well as phosphorus oxide (mainly P2O
5) and/or boron oxide (mainly Bz(h 2 )), and by uniformly dispersing it in the grain boundaries, the above object is achieved.

In order to produce the ferrite according to the present invention, the powdered raw materials of each component are mixed to a predetermined composition, and then compression molded and sintered according to a conventional method.

(Example) Example I Fezes: 52.9 mol%, MnO: 35
．． 4 n+o1% and ZnO: 11.7 a+o1
After mixing the raw materials with a basic composition of 10%, they were calcined in the air at 900°C for 13 hours.

To this calcined powder, 5iO
t+ CaO (using CaCO*) + V2O3, Ta
g's and Ti (h) were added and blended, and simultaneously ground and mixed in a wet ball mill. Next, PVA was added as a binder to the ground powder, and after granulation, the outer diameter was 36 m and the inner diameter was 24 m.
After molding into a ring shape with a height of 12 am+ and a height of 12 am+, firing was performed at 1320° C. for 13 hours in a nitrogen atmosphere with controlled oxygen concentration.

The sintered core thus obtained was 5t02. Cab, V
tOs+Ta2O5 and TiO□ content (subscript b)
Table 1 also shows the results of measuring the iron loss value using an AC BH loop tracer at a frequency of 100 kHz, a maximum magnetic flux density of 200+aT, and a temperature of 80°C.

Example 2 As in Example 1, Fe! 0@, MnO and ZnO
are 52.9 mol% and 35.4 so1, respectively.
%, 11.7 mol% of the basic composition of the raw materials were mixed,
After calcining, add 5jOz+ Cab, v to this calcined powder.
,o,, Taxes and Tie, and even B20
．． and B20. were added in the proportions shown in Table 2 (subscript a), and simultaneously ground and mixed using a wet ball mill. Then, after granulation and press molding, firing was performed at 1320'C for 3 hours.

5jCh+ Cab, V of the sintered core thus obtained
Content of 2O5Tat03 and TiO□ (subscript b),
Table 2 also shows the measurement results of iron loss values at 100 kHz, 200 mT, and 80°C.

Example 3 Same as Example 1.2. Fe2O3: 52.9 m
ol%, MnO: 35.4 mol% and ZnO:
After mixing and calcining raw materials with a basic composition of 11.7 mol%, 5IOz+ Cab,
V! 051 Taxes and Tie, and further p.
o, and B20. was added (subscript a) L, and simultaneously ground and mixed in a wet ball mill. Then, after granulation and press molding, firing was performed at 1320°C for 3 hours.

Sin, Cab, ν2 of the sintered core thus obtained
The content of 0°Ta, Ol, and TiO□ (subscript b) and the measurement results of iron loss values at 100 kHz, 200 mT, and 80°C are also listed in Table 3.

(Effects of the Invention) Thus, according to the present invention, the Mn-Zn soft material, which has much lower loss under high magnetic fields than conventional materials, can be used as the core of a transformer for a high-frequency power supply with a switching power supply frequency of about 100 kHz. Ferrite can be obtained.

Claims (4)

[Claims] 1. Fe_2O_3: 52-54.5 mol%, MnO
:33-40 mol% and ZnO: 6-13 mol% as basic components, SiO_2: 0.008-0.025 wt%, CaO:
0.02-0.15 wt%, V_2O_5:0.001-0.05 wt%, Ta_
2O_5: 0.01-0.1wt% and TiO_2:
A low-loss Mn-Zn ferrite containing 0.05 to 0.4 wt%. 2. Fe_2O_3: 52-54.5 mol%, MnO
:33-40 mol% and ZnO: 6-13 mol% as basic components, SiO_2: 0.008-0.025 wt%, CaO:
0.02 to 0.15 wt%, vanadium oxide: 0.001 to 0.05 wt%, tantalum oxide: 0.01 to 0.1 wt%, and titanium oxide: 0
．． A low-loss Mn-Zn ferrite containing 05 to 0.4 wt%. 3. Fe_2O_3: 52-54.5 mol%, MnO
:33-40 mol% and ZnO: 6-13 mol% as basic components, SiO_2: 0.008-0.025 wt%, CaO:
0.02-0.15wt%, V_2O_5:0.001-0.05wt%, Ta_2
O_5:0.01-0.1wt% and TiO_2:0
．． 05 to 0.4 wt% and 0.003 wt% or less of phosphorus oxide and/or boron oxide. 4. Fe_2O_3: 52-54.5 mol%, MnO
:33-40 mol% and ZnO: 6-13 mol% as basic components, SiO_2: 0.008-0.025 wt%, CaO:
0.02 to 0.15 wt%, vanadium oxide: 0.001 to 0.05 wt%, tantalum oxide: 0.01 to 0.1 wt%, and titanium oxide: 0
．． 05 to 0.4 wt%, and 0.003 wt% or less of phosphorus oxide and/or boron oxide.