JPH08107009A - Ferrite sintered body and its manufacture - Google Patents

Abstract

PURPOSE: To enable improvement of heat shock resistance without damaging electromagnetic characteristic by carrying out sintering by adding vitrenous material in a raw material step. CONSTITUTION: Vitrenous material is added to ferrite material containing Fe2 O3 , Nip, ZnO and CuO and sintered. In a raw material step, vitrenous material added to ferrite material is mixed at the rate of PbO<=20wt%, 40wt.%<=H3 BO3 <=90wt.% and 10wt.%<=SiO2 <=40wt.%. An addition amount of vitrenous material is within a range of 0.1 to 2.0wt.% to ferrite material of 100wt%. Even if the ferrite sintered body 1 is inersed in a solder bath 6 without using a base part in a finish process, thermal striction is relaxed by vitrenous material of crystal grain boundary and crazing and crack can be prevented. Since the ferrite sintered body is excellent in electromagnetic characteristic and in heat shock resistance, useful ferrite magnetic core can be produced from the sintered body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferrite sintered body used as various magnetic materials and a method for producing the same, and more particularly to a magnetic material excellent in heat shock resistance and a method for producing the same.

[0002]

2. Description of the Related Art A drum-shaped product made of ferrite is usually manufactured through a manufacturing process from compounding to finishing as shown in FIG. In this finishing step, as shown in FIG. 4, normally, the winding 2 is applied to the magnetic core 1 after firing,
A lead pin 5 is bonded to the magnetic core 1 through a portion called a base portion 3 made of a resin, and then a winding end portion 4 wound on the lead pin 5 is soldered. Since the winding wire 2 is covered with an epoxy-based insulating layer and it is necessary to solder while peeling off the covering layer, the finishing process is 4
The winding end 4 is immersed in a solder bath 6 at a temperature of 00 ° C. or higher. If the base portion 3 is not used, conventionally,
It was necessary to preheat the magnetic core at 200 ° C. before dipping it in the solder bath 6. As another method, there is also a method of reducing the molding density at the time of molding during the above-mentioned manufacturing process to produce a sintered body having pores for relaxing thermal strain.

[0003]

With the miniaturization of ferrite products, it is no longer possible to use the base portion of the ferrite core that has been conventionally used. However, if the winding of the ferrite core and the lead pin are soldered only with the base portion removed, the ferrite core will crack, so that as described above, it was always necessary to preheat at about 200 ° C. For this reason, there are problems in that the number of steps increases and the process time also becomes extra. Further, there is a problem in that the sintered body having pores for alleviating the thermal strain as described above is inferior in electromagnetic characteristics. Conventionally, a ferrite core has poor heat shock resistance, and this tendency is particularly remarkable in a ferrite core having a good DC superposition characteristic (one having a constant inductance when a DC bias current is applied). A material having a good DC superposition characteristic was inferior in heat shock resistance because no material other than the main component of ferrite was added. Since the electromagnetic characteristics are sacrificed when trying to improve the heat shock resistance, and the heat shock resistance is sacrificed when trying to improve the electromagnetic characteristics.So far, both the electromagnetic characteristics and the heat shock resistance have been improved. There was nothing satisfying at the same time.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sintered ferrite material having improved heat shock resistance without deteriorating electromagnetic characteristics. Therefore, the present inventors have examined the addition of vitreous substances, and examined the type and amount of addition in detail. As a result, PbO-H ₃ B
The inventors have found that the heat shock resistance can be improved without impairing the electromagnetic characteristics by adding an appropriate amount of O ₃ —SiO ₂ (or Cr ₂ O ₃ ) glass, and have completed the present invention. The sintered ferrite of the present invention is Fe ₂ O ₃ ,
Glass material is added to a ferrite material containing NiO, ZnO, and CuO and sintered at the raw material stage. Further, in the sintered ferrite body of the present invention, the glass material added to the ferrite material in the raw material stage is Pb.
O, H ₃ BO ₃ and SiO ₂ in PbO ≦ 20 wt%, 4
0 wt% ≦ H ₃ BO ₃ ≦ 90 wt% and 10 wt% ≦ Si
O ₂ ≦ 40 wt% (total 100 wt%), and the addition amount of the glassy material is 0. It is preferably in the range of 1 to 2.0 wt%. Also, 10 wt% ≦ SiO
10 wt% ≤ Cr ₂ O ₃ ≤ 40 instead of ₂ ≤ 40 wt%
A glassy material containing wt% may be added. The sintered ferrite of the present invention is made of Fe ₂ O ₃ , NiO, ZnO and C.
It is manufactured by adding the glassy material to a ferrite material containing uO and sintering it. Generally, glass-containing ferrite has improved heat resistance, but
The electromagnetic characteristics such as ac and Bs deteriorate as compared with the case where no glassy material is added. The lower limit of the amount of vitreous addition is limited to maintain heat resistance, and the upper limit is to prevent the electromagnetic characteristics from remarkably decreasing. That is, as is clear from the results of the following Examples and Comparative Examples, if it is lower than 0.1 wt%, the heat resistance is not improved, and if it exceeds 0.1 wt%, the heat resistance is improved and exceeds 2 wt%. And the electromagnetic characteristics are significantly deteriorated (Examples 9 to 11 and Comparative Example 1).
4-15). Therefore, the range is limited to 0.1 to 2.0 wt%. Next, regarding the individual glassy components,
In the case of PbO, if it exceeds 20 wt%, the heat resistance becomes poor (Comparative Examples 2 to 4), but even if it is 0 wt%, there is no problem in heat resistance and electromagnetic characteristics (Examples 5 to 7), so PbO ≦
It was limited to the range of 20 wt%. 40 W for H ₃ BO ₃
If it is less than t% or 100 wt%, the heat resistance is deteriorated (Comparative Examples 5 to 7 and 11), but if it is 90 wt% or less, the heat resistance and electromagnetic characteristics are good (Examples 5 to 7), so 40 wt% ≦ It was limited to the range of H ₃ BO ₃ ≦ 90 wt%. In the case of SiO ₂ (or Cr ₂ O ₃ ), 40w
If it exceeds t%, the heat resistance is good, but the electromagnetic characteristics are poor, and if it is less than 10 wt%, the heat resistance is poor (Comparative Example 2).
~ 12), so 10 wt% ≤ SiO ₂ (or Cr
₂ O ₃ ) ≤ 40 wt%.

[0005]

[Function] In the case of a sintered ferrite material having excellent electromagnetic characteristics,
Since no vitreous substances are added, crystals with uniform grain size are in direct contact with each other, so if a sudden thermal stress is applied by immersion in the solder bath, the generated thermal strain cannot be alleviated. , Cracks and cracks will occur. However,
According to the present invention, PbO- is added to the ferrite material at the raw material stage.
Since an appropriate amount of H ₃ BO ₃ —SiO ₂ (or Cr ₂ O ₃ ) glass is added, as shown in FIG. 1, the ferrite sintered body 1 is soldered without using the base portion in the finishing process. Even when immersed in the bath 6, the glass strain at the crystal grain boundaries alleviates the thermal strain, and as a result, cracks and cracks can be prevented. Furthermore, by adjusting the addition amount of the above glassy material within a predetermined range, a crystal grain size of the sintered body can be obtained, for example, in which the crystal grain size is randomly distributed within a range of approximately 3 to 30 μm. It is considered that the small space existing between them helps to alleviate the thermal strain. However, since the density of the sintered body is 5.1 g / cm ³ (theoretical density is 5.2), the electromagnetic characteristics are not impaired.

[0006]

EXAMPLES The present invention will be described below based on Examples and Comparative Examples. (Example 1~11) Fe ₂ O _3: 48.5 mol%, Ni
O: 21.5 mol%, ZnO: 25.0 mol% and Cu
100 g of a powder obtained by adding a glassy component to a ferrite material prepared by mixing O: 5.0 mol% at a ratio (amount added to 100 wt% of ferrite material) as shown in Table 1 below. Were mixed in a 0.5 liter ball mill for 2 hours. After drying, what was calcined at 900 to 1000 ° C. was crushed for 2 hours by a ball mill. After drying, granulation, toroidal (outer diameter 28φ, inner diameter 20φ) and drum core (outer diameter 3.8φ, central axis 1.9φ, brim thickness l.Om
m) was molded. The molded body thus obtained is made to be 1040-
It was fired at 1100 ° C. to produce a sintered ferrite body.

(Comparative Example 1) Fe ₂ O ₃ : 48.5 mol%,
Powder 100 obtained by blending NiO: 21.5 mol%, ZnO: 25.0 mol% and CuO: 5.0 mol%
g was mixed in a 0.5 liter ball mill for 2 hours.
After being dried, it was calcined at 900 to 1000 ° C., pulverized with a ball mill for 2 hours, and further pulverized with an attritor for 20 minutes. After drying, the ferrite sintered body was produced by granulating, molding and firing under the same conditions and methods as those in Examples 1 to 11 above. (Comparative Examples 2 to 15) The amounts described in Table 1 were added as glassy components, and the methods described in Examples 1 to 11 were repeated to produce sintered ferrite bodies. Examples 1 to 11 above
The heat resistance and electromagnetic characteristics of the sintered samples obtained in Comparative Examples 1 to 15 were measured as follows. The heat shock resistance was measured by immersing the drum core-shaped sample with the brim down and immersing the lower half in a solder bath kept at a predetermined temperature for 3 seconds to examine the occurrence of cracks and cracks in the sample. The temperature of the solder bath was raised stepwise by 20 ° C., and the above operation was repeated using another sample. The maximum temperature at which cracking did not occur was taken as the heat resistance temperature of the sample. The electromagnetic characteristics are
The winding of 60 turns is applied to the toroidal sample, and the initial permeability μ
Iac and saturation magnetic flux density Bs were measured and evaluated. Table 1 below shows the measurement results of the above glassy composition and the heat shock resistance and electromagnetic characteristics of the obtained sample.

[0008]

[Table 1]

As is clear from Table 1, the ferrite sintered bodies of the comparative examples have a large electromagnetic characteristic (Bs), but the heat resistance is remarkably inferior. It can be seen that the sintered ferrite products of (8) and (8) are excellent in both electromagnetic properties (Bs, μ iac) and heat resistance. From Examples 2 and 4, it can be seen that the electromagnetic characteristics tend to deteriorate as the amount of glassy component added increases. Further, Comparative Examples 2 to 15 show examples of the composition of the glassy component when the heat resistance is poor. Further, FIG. 2 shows the DC superposition characteristics when the samples of Comparative Example 1 and Example 1 in Table 1 were formed into a drum-shaped product. In the case of Example 1, the characteristics shown in FIG. 2 are also equal to or higher than those of the comparative example. In Example 8 in Table 1, Cr ₂ O ₃ was used instead of SiO ₂ . It can be seen that the same result as in the case of SiO ₂ is obtained.

[0010]

Since the ferrite sintered body of the present invention has excellent electromagnetic characteristics and good heat shock resistance, a useful ferrite magnetic core can be produced from the sintered body. Further, when the ferrite sintered body of the present invention is manufactured, the preheating step when soldering the lead pins can be omitted, so that the productivity can be improved and the equipment and the place can be omitted.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a finishing process of a sintered ferrite body of the present invention.

FIG. 2 is a diagram showing DC superimposition characteristics of a sample of Example 1 of the present invention and a sample of Comparative Example 1.

FIG. 3 is a process drawing showing a process for manufacturing a ferrite drum-shaped product.

FIG. 4 is a diagram for explaining a finishing process of a conventional sintered ferrite body.

[Explanation of symbols]

 1 Ferrite magnetic core 2 Winding 3 Base 4 Winding end 5 Lead pin 6 Solder tank

Claims (6)

[Claims] 1. A ferrite sintered body obtained by adding glassy material to a ferrite material containing Fe ₂ O ₃ , NiO, ZnO and CuO and sintering it at the raw material stage. 2. The glassy material is PbO, H ₃ BO ₃ and S.
iO ₂ is added to PbO ≦ 20 wt%, 40 wt% ≦ H ₃ BO ₃
≦ 90 wt% and 10 wt% ≦ SiO ₂ ≦ 40 wt% (100 wt% in total), and the addition amount of the glassy material is 100 wt% of the ferrite material.
% To 0. The ferrite sintered body according to claim 1, which is 1 to 2.0 wt%. 3. The glassy material is PbO, H ₃ BO ₃ and C.
r ₂ O ₃ is added to PbO ≦ 20 wt%, 40 wt% ≦ H ₃ BO ₃
≦ 90 wt% and 10 wt% ≦ Cr ₂ O ₃ ≦ 40 wt% (100 wt% in total), and the addition amount of the glassy material is 100 wt% of the ferrite material.
% To 0. The ferrite sintered body according to claim 1, which is 1 to 2.0 wt%. 4. A method for producing a ferrite sintered body, which comprises adding a glass material to a ferrite material containing Fe ₂ O ₃ , NiO, ZnO and CuO and sintering the resultant. 5. The glassy material is PbO, H ₃ BO ₃ and S.
iO ₂ is added to PbO ≦ 20 wt%, 40 wt% ≦ H ₃ BO ₃
≦ 90 wt% and 10 wt% ≦ SiO ₂ ≦ 40 wt% (100 wt% in total), and the addition amount of the glassy material is 100 wt% of the ferrite material.
% To 0. The method for producing a ferrite sintered body according to claim 4, wherein the content is 1 to 2.0 wt%. 6. The glassy material is PbO, H ₃ BO ₃ and C.
r ₂ O ₃ is added to PbO ≦ 20 wt%, 40 wt% ≦ H ₃ BO ₃
≦ 90 wt% and 10 wt% ≦ Cr ₂ O ₃ ≦ 40 wt% (total 100 wt%), and the addition amount of the glassy material is 100 wt% of the ferrite material.
% To 0. The method for producing a ferrite sintered body according to claim 4, wherein the content is 1 to 2.0 wt%.