JP2014183182A - Non-magnetic material, and method for manufacturing non-magnetic ceramic composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-magnetic material which allows a low temperature baking to be conducted while preventing the worsening of a direct current superposition property owing to the diffusion of a magnetic substance from a magnetic layer in a multilayer inductor.SOLUTION: A non-magnetic material is used to form a non-magnetic layer functioning as a magnetic gap in a multilayer inductor. The non-magnetic material comprises: a mixture including a mol% of FeO, b mol% of ZnO and c mol% of CuO; and d wt% of BiOadded to the mixture. In the non-magnetic material, "a", "b", "c" and "d" satisfy the conditions: a+b+c=100, 30≤a≤40, 0≤c≤10 and 0<d≤3.0. Preferably, "c" and "d" meet the conditions: 5≤c≤10 and 0<d≤1.5.

Description

  The present invention relates to a nonmagnetic material used for a multilayer inductor and a method for producing a nonmagnetic ceramic composition obtained by sintering the nonmagnetic material.

  As is well known, in a multilayer inductor, an electrically insulating magnetic layer and a conductor pattern are alternately stacked, and the conductor pattern of each layer is connected between the layers in sequence, thereby spiraling while overlapping in the stacking direction in the magnetic material. A coil that circulates in a shape is formed. Such a multilayer inductor is characterized by the fact that the coil is surrounded by a magnetic material, so there is little magnetic leakage to the outside, and the required inductance can be obtained with a relatively small number of turns, making it suitable for downsizing and thinning. ing. However, since magnetic saturation of the magnetic material occurs even with a small coil current (excitation current), the inductance fluctuates greatly even if the DC superimposed current is in a low current region. That is, there is a problem that the direct current superimposition characteristic is bad.

  Therefore, in the multilayer inductor described in the following Patent Document 1, a magnetic gap is interposed in the multilayer inductor by replacing a part of the entire magnetic layer with an electrically insulating nonmagnetic layer, thereby magnetically. The saturation level is increased so that a large rated current can be obtained as a transformer or choke coil. Such a multilayer inductor is obtained by firing a laminated body obtained by firing a paste sheet corresponding to each of the magnetic and nonmagnetic layers through an electrode layer forming an electrode pattern by thick film technology. It is manufactured by forming an external electrode paste on the surface of the bonded body. Since the electrode layer generally uses silver having a melting point of 962 ° C. as a conductor, the magnetic layer and the non-magnetic layer are made of a material mainly composed of Fe and capable of being sintered at a low temperature of 900 ° C. or lower. It is done. For example, Ni—Cu—Zn-based ferrite and Ni—Zn-based ferrite are used as the magnetic material constituting the magnetic layer, and Zn-based ferrite is used as the nonmagnetic material constituting the nonmagnetic layer. The following Patent Documents 2 and 3 describe the composition of the nonmagnetic material used for the multilayer inductor.

JP-A-2005-45108 JP 2007-91538 A Japanese Patent Laid-Open No. 06-77022

  The magnetic layer and the nonmagnetic layer constituting the multilayer inductor are a sheet-like ceramic (a porcelain composition) made of a magnetic material and a sheet-like porcelain composition made of a nonmagnetic material, respectively. For this reason, if the heat shrinkage characteristics of the magnetic material and the nonmagnetic material are deviated, a deviation occurs at the interface between the magnetic layer and the nonmagnetic layer during firing, and the sintered density is lowered. Of course, the dimensional accuracy as an electronic component also deteriorates, and the quality uniformity as a product cannot be secured.

Therefore, since the magnetic material constituting the magnetic layer is basically a spinel type ferrite, the spinel type ferrite in which the proportion of Fe ₂ O _{3 in} the composition of the nonmagnetic material constituting the nonmagnetic layer is about 50 mol%. Ferrite is used so as not to greatly deviate from the heat shrinkage characteristics of the magnetic material. In addition, in the multilayer inductor, an electrode pattern is formed between the magnetic layer and the nonmagnetic layer. Therefore, the nonmagnetic material is required to have sufficiently high insulation characteristics so that a short circuit does not occur in the electrode pattern. . In Patent Documents 2 and 3, the composition of the nonmagnetic material suitable for the use of the multilayer inductor is described.

However, the multilayer inductor is an electronic component manufactured by sintering a multilayer body including a magnetic layer and a nonmagnetic layer as a porcelain composition, and includes conventional nonmagnetic materials described in Patent Documents 2 and 3. It has been found that the non-magnetic material has a problem that the direct current superposition characteristics of the multilayer inductor deteriorate due to the firing. Specifically, a substance containing a magnetic material such as Ni or Cu contained in the magnetic layer at the time of sintering diffuses into the Fe ₂ O _{3 of the} nonmagnetic layer, and the magnetic layer has the same physical thickness. There is a problem that the thickness of the nonmagnetic layer functioning as the gap is substantially reduced, and the DC superimposition characteristics as expected cannot be obtained. Further, since the diffusion of the magnetic material is not uniform, the thickness functioning as the magnetic gap is also non-uniform. As a result, the direct current superimposition characteristics of the multilayer inductor deteriorate, and the characteristics of the multilayer inductor become non-uniform between solids.

Therefore, in the composition of ferrite, which is a nonmagnetic material, it is conceivable to increase the proportion of Zn, which is a major component other than Fe ₂ O ₃ , but increasing the proportion of Zn increases the sintering temperature, and as a sintered body If a sufficient density is to be ensured, the sintering temperature will exceed the melting point of Ag forming the electrode pattern. When firing at a low temperature below the melting point of Ag, a sufficient density cannot be maintained, and a “displacement” due to a mismatch in heat shrinkage characteristics occurs at the interface between the magnetic layer and the nonmagnetic layer, and the dimensional accuracy as an electronic component deteriorates. .

  The present invention has been made in view of the above problems, and a main object of the present invention is to enable low-temperature firing in a multilayer inductor while preventing deterioration of direct current superposition characteristics due to diffusion of a magnetic substance from a magnetic layer. It is to provide a non-magnetic material.

The present invention for achieving the above object is a nonmagnetic material constituting a nonmagnetic layer functioning as a magnetic gap in a multilayer inductor,
it is added dwt% of _Bi 2 _{O 3} to the mixture containing amol% of _Fe 2 _{O 3} and Bmol% of ZnO and cmol% of CuO,
a + b + c = 100, 30 ≦ a ≦ 40, 0 ≦ c ≦ 10, 0 <d ≦ 3.0
It is a non-magnetic material characterized by Further, it is more preferable to use a nonmagnetic material satisfying 5 ≦ c ≦ 10 and 0 <d ≦ 1.5.

The present invention also extends to a method for producing a non-magnetic porcelain composition.
Assuming that a + b + c = 100, 35 ≦ a ≦ 40, and 0 ≦ c ≦ 10, a mixture obtained by mixing amol% Fe ₂ O ₃ , bmol% ZnO and cmol% CuO was temporarily prepared at a temperature lower than 900 ° C. Firing, and
Further crushing to a powder of a predetermined particle size or less obtained by the preliminary firing,
Adding 0 wt% Bi ₂ O ₃ to the powder having a predetermined particle size or less and adding a binder to obtain a granulated product, with 0 <d ≦ 3.0;
Molding the granulated product into a molded body having a predetermined shape;
Firing the molded body at a temperature below the melting point of silver to obtain a sintered body;
It is characterized by including.

  According to the nonmagnetic material of the present invention, when applied to a nonmagnetic layer of a multilayer inductor, it is possible to perform low-temperature firing, and to prevent deterioration of DC superimposition characteristics due to diffusion of a magnetic material from the magnetic layer. it can.

It is a figure which shows an example of the manufacturing method of the sintered compact using a nonmagnetic material. It is a figure which shows an example of the manufacturing method of the sintered compact containing a nonmagnetic material and a magnetic material. It is a figure which shows an example of the manufacturing method of the sintered compact formed by laminating | stacking a sheet-like nonmagnetic material and a sheet-like magnetic material.

=== Technical thought of the present invention ===
As described above, the non-magnetic material used in the non-magnetic layer of the conventional multilayer inductor achieves the expected DC superposition characteristics due to the phenomenon that a magnetic material such as Ni or Cu diffuses from the magnetic layer. In addition, there is a problem that the characteristics become non-uniform. However, this phenomenon cannot be suppressed in principle because the laminated inductor is a sintered body composed of a magnetic layer and a nonmagnetic layer. Therefore, the present inventor tried to change the idea of suppressing the deterioration of the DC superposition characteristics to a minimum by limiting the amount of the magnetic material that can be diffused, rather than suppressing the diffusion of the magnetic material itself.

In general, both magnetic and non-magnetic materials contain Fe ₂ O ₃ as a main composition, and it is an inevitable phenomenon that a magnetic material from a magnetic layer diffuses into Fe ₂ O ₃ of the non-magnetic layer. Instead, the inventors came up with the technical idea of limiting the amount of magnetic material that can be diffused by reducing the proportion of Fe ₂ O ₃ in the nonmagnetic material. Of course, there is a possibility that a sufficient density cannot be obtained by simply reducing the proportion of Fe ₂ O ₃ . If the composition of the nonmagnetic material is easily changed to ensure sinterability, the insulation resistance may be increased. The firing temperature for sintering may exceed the melting point of Ag. The present invention has been made as a result of intensive studies in order to solve various problems that may occur, with the above technical idea as a starting point.

  In the nonmagnetic material according to the embodiment of the present invention, the kind and amount of the sintering aid for ensuring the sinterability are optimized, and the conventional low temperature firing at 900 ° C. which is not higher than the melting point of Ag. Is equal to or higher than that of the non-magnetic layer in the multilayer inductor and has a sufficiently high insulation performance. Hereinafter, the composition of the nonmagnetic material according to the embodiment of the present invention will be described.

=== Optimization of composition of non-magnetic material ===
In order to define the composition of the nonmagnetic material according to the embodiment of the present invention, a sintered body made of various nonmagnetic materials having different compositions, a sintered body of a mixed material of magnetic materials and various magnetic materials having different compositions, or Similar to the multilayer inductor, a sintered body obtained by firing a laminate of nonmagnetic layers made of various magnetic materials having different compositions from the magnetic layer was prepared as a sample, and various characteristics of each sample were evaluated.

<Sample manufacturing method>
In defining the composition of the nonmagnetic material according to the embodiment of the present invention, a sufficiently high density as a sintered body and a sufficiently high resistance value as an insulator can be obtained while reducing the proportion of Fe ₂ O _3. The conditions were sought. FIG. 1 shows a sample manufacturing procedure for obtaining the conditions. First, Fe ₂ O ₃ and ZnO as raw materials for Zn-based ferrite and CuO as a sintering aid according to the sample are weighed and mixed (s1 → s2 → s4 or s1 → s3 → s4), and the mixture (Hereinafter, non-magnetic ferrite material) is temporarily fired at 700 to 850 ° C. (s5). The powder obtained by the preliminary calcination is pulverized for 20 hours or more by a ball mill, and finally made into a powder of 1 μm or less (s6). Here, Bi ₂ O ₃ which is a sintering aid is mixed in the pulverized powder according to the sample (s7 → s8). Since Bi ₂ O ₃ has a higher effect of enhancing the sinterability than CuO, when added together with the non-magnetic ferrite material and temporarily fired, there is a possibility of sintering at the temperature at the time of the temporary firing. Therefore, Bi ₂ O ₃ is added after the pre-baking step (s5).

Then, a PVA aqueous solution is added as a binder to the pulverized powder or a mixture of the powder and Bi ₂ O ₃ added as necessary, and mixed, and granulated to obtain an appropriate particle size. (S8 → s9 or s6 → s7 → s9). Further, the granulated product is formed into a desired shape (s10). Here, it was molded into a ring shape. And the molded object was baked at 900 degreeC which is below melting | fusing point of Ag, and the sintered compact used as a sample was obtained (s11).

<Insulation resistance and density>
Table 1 below shows the composition, insulation resistance, and density of each sample.

As shown in Table 1, in the prepared sample, either or both of CuO and Bi ₂ O ₃ were added as sintering aids to Fe ₂ O ₃ and ZnO, which are the main compositions of Zn-based ferrite. Is. Here, nine types of samples (samples 1 to 9) having different compositions were produced.

In the various samples shown in Table 1, sample 9 corresponds to a conventional nonmagnetic material, the proportion of Fe ₂ O ₃ is 49 mol%, and the remaining 51 mol% is the main component of Zn-based ferrite together with the Fe ₂ O _3. Some ZnO and CuO which is a sintering aid. The CuO content is 11 mol so that 5.0 g / cm ² which is sufficiently soft as a sintered body and an insulation resistance of 1.0 × 10 ¹⁰ Ω (1.0 × 10 ⁴ MΩ) or more can be obtained. % Has been adjusted.

On the other hand, the nonmagnetic material according to the embodiment of the present invention is based on the technical idea that the deterioration of the DC superimposition characteristic is suppressed by limiting the amount of the magnetic material diffusing from the magnetic layer to the nonmagnetic layer in the multilayer inductor. Since the composition is a condition, Samples 1 to 8 other than Sample 9 (hereinafter also referred to as Comparative Example 1) corresponding to the conventional non-magnetic material have a proportion (49 mol%) of Fe ₂ O ₃ in Comparative Example 1. Is also set to 40 mol% or less, which is about 20% lower. Regarding the proportion of ZnO, in view of the fact that ZnO is a factor that raises the firing temperature, that is, the density decreases at low temperature firing, it is intentionally increased relative to Comparative Example 1 and is uniformly set to 60 mol%. ing. That is, the object here is to find a composition that can obtain a sufficiently high density by low-temperature firing even under disadvantageous conditions. For CuO, it changed its percentage in proportion to the _Fe 2 _{O 3.} Therefore, regarding the Fe ₂ O ₃ , ZnO, and CuO that are raw materials to be mixed before pre-baking, the sum of the proportions of the respective raw materials is 100 mol%.

From the results shown in Table 1, on the basis of the insulation resistance and density of Comparative Example 1, conditions that are equal to or higher than the standard were examined. As a result, in 4 and 5 where the ratio of the sample CuO was relatively high, the insulation resistance decreased by about 2 to 3 digits compared to Comparative Example 1. In Sample 2, the CuO ratio was 10 mol%, which was lower than 11 mol% of Sample 9, but the insulation resistance was the same as Sample 9. From the above results, the insulation resistance decreases as the proportion of CuO increases. When Fe ₂ O _{3 is set} to 40 mol% or less, sufficient insulation equivalent to or higher than that of Comparative Example 1 can be obtained if the proportion of CuO is set to 10 mol% or less. It turns out that resistance is obtained.

On the other hand, regarding the density, only the sample 4 to which Bi ₂ O ₃ was not added was lower than the density of the sample 9. Samples 6 to 8 did not contain CuO in the composition, but the density exceeded the characteristics of sample 9. Therefore, when the composition composed of Fe ₂ O ₃ , ZnO and CuO is 100 mol%, the condition is that CuO is 10 mol% or less in the composition. Even if Bi ₂ O ₃ needs to be added, CuO Not a necessary condition but a nonmagnetic ferrite material composed of Fe ₂ O ₃ , ZnO and CuO is not less than 0 mol% and not more than 10 mol%.

<Permeability>
Next, in order to obtain the conditions for suppressing the deterioration of the DC superposition characteristics due to the diffusion of a magnetic material such as Ni from the magnetic layer to the nonmagnetic layer in the multilayer inductor, the raw material of the nonmagnetic material and the raw material of the magnetic material An integrated sintered body containing the sample was prepared as a sample, and the magnetic permeability of each sample was measured. FIG. 2 is a diagram showing a sample production procedure. Based on the sample production procedure shown in FIG. 1, the step (s1) of weighing the nonmagnetic ferrite material in FIG. 1 and the raw material of the nonmagnetic ferrite material are shown. The step of mixing (s4) includes a step of weighing raw materials of the Ni—Zn ferrite magnetic material (hereinafter referred to as magnetic material) together with the nonmagnetic ferrite material (s21), and a step of mixing the respective raw materials of the nonmagnetic ferrite material and the magnetic material. (S22) is substituted. Here, in all samples, CuO is included in the nonmagnetic ferrite material. And from the temporary baking process (s5) in FIG. 1 to a baking process (s11), it is the same procedure (s23-s29). A commercially available product called “ferrite magnetic powder” can be used as a raw material for the magnetic material.

Table 2 shows the relationship between the composition and permeability of each sample.

In Table 2, a sample 16 (hereinafter also referred to as Comparative Example 2) is obtained by adding a raw material of a magnetic material to the composition of Comparative Example 1 and firing. The magnetic permeability of Comparative Example 2 is shown in Table 2 below. This is a standard for evaluating the magnetic permeability of samples 10 to 15. Since it is considered that the deterioration of the DC superimposition characteristic due to the diffusion of the magnetic material from the magnetic layer to the nonmagnetic layer depends on the amount of Fe ₂ O ₃ in the nonmagnetic layer, in samples 10 to 15 Fe ₂ in Zn ferrite The ratio of O ₃ is changed. Further, CuO in Zn ferrite in Samples 10 to 15 is set to 10 mol% or less from the results shown in Table 1. Here, it is 5 mol% or 10 mol%. As for the addition amount of _Bi 2 _{O 3} in the samples 10 to 15 was adjusted to an equivalent density and Comparative Example 2. About the mixing amount of the raw material of a magnetic material, it adjusted so that the magnetic permeability in the comparative example 2 might be set to 65, and the other samples 10-15 are also mixing the same quantity as this comparative example 2.

And from the magnetic permeability of each sample shown in Table 2, in samples 10, 13, and 14 in which the proportion of Fe ₂ O ₃ in Zn ferrite is more than 40 mol%, the magnetic permeability was equal to or higher than that of the comparative example. Therefore, the condition is that the proportion of Fe ₂ O ₃ in Zn ferrite is 40 mol% or less. Then, since the upper limit of the proportion of CuO was 10 mol% from the results shown in Table 1, it was defined 30 mol% is the percentage of _Fe 2 _{O 3} in this case as the upper limit of the proportion of _Fe 2 _{O 3.} That is, the proportion of Fe ₂ O ₃ in the nonmagnetic ferrite material before calcination is 30 mol% or more and 40 mol% or less, the proportion of CuO is 0 mol% or more and 10 mol% or less, the remainder is ZnO, and Bi ₂ O ₃ after calcination. If added and fired, an insulation resistance and density equivalent to or higher than those of Comparative Example 1 can be secured. In the sintered body obtained by further mixing a nonmagnetic ferrite material with a magnetic material and firing, the magnetic permeability is lower than that of Comparative Example 2. Therefore, the nonmagnetic material having the above composition is not used in the multilayer inductor. When employed as a magnetic layer, it is possible to prevent the deterioration of the DC superposition characteristics.

<Amount of Bi ₂ O ₃ added>
From the results in Table 1, it was an essential condition to add Bi ₂ O ₃ . That is, it was necessary to add an amount larger than 0 wt% with respect to Zn ferrite. However, since Bi ₂ O ₃ has an extremely high effect of improving the sinterability, if the addition amount is too large, the crystallinity of the magnetic layer in the multilayer inductor may be hindered. Specifically, since a multilayer inductor is manufactured by sintering a laminate in which a sheet-like magnetic material and a nonmagnetic material are laminated via an electrode layer serving as an electrode pattern, a large amount of Bi is added to the nonmagnetic material. _{When 2} O ₃ is added, abnormal grain growth occurs in the magnetic layer and the electrode layer, and the strength and sinterability of the magnetic layer and the electrode layer may change. If the sinterability of Ag is impaired, a short circuit may occur in the wiring of the electrode layer. Therefore, in order to determine the optimum amount of Bi ₂ O _3, prepare a sintered body added amount of the sheet-like magnetic material and Bi ₂ O ₃ is sintered after having stacked the different sheet of various non-magnetic material as a sample did. FIG. 3 shows a method for manufacturing the sintered body. The manufacturing procedure is basically the same as that shown in FIG. 1, but here, a non-magnetic material and a magnetic material are individually formed into sheets (s31 to s38, s39 to s41), and these sheets are laminated. To sinter (s42, s43). And the sintered compact was observed using SEM etc., and the sinterability (state of crystal growth) in a magnetic layer was evaluated.

Table 3 shows the relationship between the composition of each sample and the sinterability of the magnetic layer.

As shown in Table 3, sample prepared is in all compositions except Bi ₂ O ₃ in order to express only the effect of the addition amount of Bi ₂ O ₃ same. Further, CuO which is the same sintering aid as Bi ₂ O ₃ is not included. As shown in Table 3, in Samples 17 and 18 to which Bi ₂ O ₃ was added at 2.0 wt% and 3.0 wt%, no abnormality was observed in the sinterability of the magnetic layer, but 4.0 wt% was added. Sample 19 was observed to be abnormal. Therefore, the upper limit of the addition amount of Bi ₂ O ₃ can be defined as 3.0 mol% or less. That is, the optimum addition amount of Bi ₂ O ₃ in the nonmagnetic material according to the embodiment of the present invention is more than 0 wt% and not more than 3.0 wt% with respect to the nonmagnetic ferrite material.

<CuO and Bi ₂ O ₃ >
From the above, the non-magnetic material according to an embodiment of the present invention, in which Bi ₂ O ₃ is added to the non-magnetic ferrite material including CuO as necessary while the main component Fe ₂ O ₃ and ZnO. The composition of the nonmagnetic ferrite material is that the total ratio of Fe ₂ O ₃ , ZnO and CuO is 100 mol%, Fe ₂ O ₃ is 30 mol% to 40 mol%, CuO is 0 mol% to 10 mol%, and the rest It is ZnO, and the addition amount of Bi ₂ O ₃ is more than 0 wt% and not more than 3.0 wt% with respect to the nonmagnetic ferrite material.

By the way, since Bi is an expensive rare metal, it is more preferable that the amount of Bi ₂ O ₃ in the nonmagnetic material is small. Therefore, it is conceivable to reduce the amount of Bi ₂ O ₃ that is a sintering aid and to increase as much as possible CuO that is the same sintering aid in the composition of the nonmagnetic ferrite material. From the compositions of Samples 11, 23, and 15 in Table 2, it can be seen that when the CuO ratio is 5 mol% or more and 10 mol% or less, the upper limit of Bi ₂ O ₃ addition can be reduced to 1.5 wt%.

s4 raw material mixing step, s5 temporary firing step, s6 crushing step, s9 granulation step, s10 molding step, s11 firing step

Claims (3)

A nonmagnetic material constituting a nonmagnetic layer that functions as a magnetic gap in a multilayer inductor,
it is added dwt% of _Bi 2 _{O 3} to the mixture containing amol% of _Fe 2 _{O 3} and Bmol% of ZnO and cmol% of CuO,
a + b + c = 100, 30 ≦ a ≦ 40, 0 ≦ c ≦ 10, 0 <d ≦ 3.0
A non-magnetic material characterized by   The nonmagnetic material according to claim 1, wherein 5 ≦ c ≦ 10 and 0 <d ≦ 1.5. A method for producing a nonmagnetic porcelain composition, comprising:
Assuming that a + b + c = 100, 35 ≦ a ≦ 40, and 0 ≦ c ≦ 10, a mixture obtained by mixing amol% Fe ₂ O ₃ , bmol% ZnO and cmol% CuO was temporarily prepared at a temperature lower than 900 ° C. Firing, and
Further crushing to a powder of a predetermined particle size or less obtained by the preliminary firing,
Adding 0 wt% Bi ₂ O ₃ to a powder having a predetermined particle size or less as 0 <d ≦ 3.0 and adding a binder to obtain a granulated product;
Molding the granulated product into a molded body having a predetermined shape;
Firing the molded body at a temperature below the melting point of silver to obtain a sintered body;
The manufacturing method of the nonmagnetic porcelain composition characterized by including.

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