JP2000323320A - Manufacture of soft magnetic ferrite powder and manufacture of laminated chip inductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of manufacturing Ni-Cu-Zn ferrite powder excellent in sintering property at a low temperature, and a method for manufacturing a laminated chip inductor by using the ferrite powder. SOLUTION: In a method manufacturing soft magnetic ferrite powder whose main component is Fe, Ni, Cu and Zn, a process wherein organic additive is made to exist in slurry containing a calcinated object of material powder and water is installed. As the organic additive, organic compound having hydroxyl group and carboxyl group, or neutralization salt of the organic compound, or lactone of the organic compound is used. As another way, organic compound having hydroxymethyl carbonyl group, or organic compound having enol type hydroxyl group which can be dissocitated as acid, or neutralization salt of the organic compound is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a soft magnetic ferrite powder capable of being sintered at a low temperature, and a method for producing a multilayer chip inductor using the soft magnetic ferrite powder produced by the method.

[0002]

2. Description of the Related Art In recent years, there has been remarkable progress in technology for reducing the size and weight of various electronic devices, and accordingly, surface mounting of components has been rapidly promoted. In particular, as the inductor element, a so-called chip inductor in which a magnetic material and a coil are integrated is often used, and improvement in performance thereof is desired.

In a chip inductor, Ni--Cu--Zn ferrite, which is an oxide magnetic material, is used as a magnetic material.
It is common to use Ag or an Ag-Pd alloy as the conductor for the coil.

In manufacturing a chip inductor, first, raw materials containing Fe, Ni, Cu, and Zn are mixed in a ball mill or the like, and then calcined. The calcined product is pulverized to obtain a soft magnetic ferrite powder. obtain. This soft magnetic ferrite powder is kneaded with a binder and a solvent to prepare a magnetic paste. In addition, the conductor powder is kneaded with a binder and a solvent to prepare a conductor paste. And
After the printing of these pastes is repeated to laminate the magnetic layer and the conductor layer, firing is performed, and further, external electrodes are formed to obtain a chip inductor.

In order to improve the performance of the chip inductor, it is essential that the ferrite be sufficiently dense and not react with the conductor at this time, so that the conductor does not suffer from problems such as disconnection. As the conductor, it is preferable to use Ag alone because of its low electric resistance, but Ag has a low melting point of 960 ° C. Therefore, in order to achieve high performance without causing a reaction between the conductor and the ferrite, disconnection or separation of the conductor, etc., it is preferable to fire at a temperature lower than the melting point of Ag and at the lowest possible temperature, for example, 920 ° C. or lower. .

However, when Ni-Cu-Zn ferrite powder is fired at 920 ° C. or lower, it is pointed out that ferrite densification does not proceed and it is difficult to obtain a ferrite sintered body having excellent electric properties such as magnetic permeability. Have been.

A method for producing a Ni—Cu—Zn ferrite sintered body is disclosed, for example, in Japanese Patent Application Laid-Open No. 5-175032 by the present applicant.
No., published in Japanese Unexamined Patent Publication No. This publication describes that firing in an atmosphere having an oxygen concentration lower than that of air improves the density of the ferrite sintered body. In the example, firing is performed at 870 ° C. Japanese Patent Publication No. 6-30297 filed by the present applicant discloses iron oxide and an oxide of a divalent metal (M ² ) (where M ² is nickel and / or nickel).
Or ferrite containing copper or zinc added thereto) and Li ₂ O and a tetravalent metal (M ⁴ ).
(The proviso M ⁴ titanium, one or more of tin and germanium) oxide by adding and, it has been described that has become possible to low-temperature firing at 950 ° C. or less.

[0008] However, no means has been proposed for enabling firing at a low temperature without controlling the atmosphere or the composition.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a Ni-Cu-Zn ferrite powder having excellent sinterability at a low temperature, and to use this ferrite powder. Accordingly, it is possible to perform firing at a low temperature when manufacturing a multilayer chip inductor.

[0010]

This and other objects are achieved by the present invention which is defined below as (1) to (7). (1) A method for producing a soft magnetic ferrite powder containing Fe, Ni, Cu and Zn as main components, comprising a step of allowing an organic additive to be present in a slurry containing a calcined raw material powder and water. As the organic additive, an organic compound having a hydroxyl group and a carboxyl group or a neutralized salt thereof or a lactone thereof, or an organic compound having a hydroxymethylcarbonyl group, an organic compound having an enol type hydroxyl group which can be dissociated as an acid or A method for producing a soft magnetic ferrite powder using a neutralized salt. (2) The amount of the organic additive to be added is 0.1 to the calcined product.
The method for producing a soft magnetic ferrite powder according to the above (1), wherein the content is from 0.05 to 3.0% by weight. (3) In the slurry, Fe derived from the calcined material
The method for producing a soft magnetic ferrite powder according to the above (1) or (2), wherein ions and / or Cu ions are contained in a total of 0.005 to 2% by weight of the calcined product. (4) The above (1) to (1) to wherein the organic compound having a hydroxyl group and a carboxyl group is gluconic acid or citric acid.
(3) The method for producing a soft magnetic ferrite powder according to any of (3). (5) The above-mentioned (1) to (1), wherein the organic compound having an enol-type hydroxyl group which can be dissociated as the acid is ascorbic acid.
(3) The method for producing a soft magnetic ferrite powder according to any of (3). (6) The method for producing a soft magnetic ferrite powder according to any one of the above (1) to (5), wherein ammonia is added to the slurry. (7) A method for manufacturing a multilayer chip inductor, comprising a step of forming a magnetic layer using the soft magnetic ferrite powder manufactured by any one of the methods (1) to (6).

[0011]

When the calcined product is wet-pulverized to produce a Ni-Cu-Zn ferrite powder, the present inventors make the sintering temperature of the ferrite powder by allowing the above-mentioned organic additive to be present in the slurry. Was found to be lower. Specifically, it was found that a sintered body having a sufficient density and an initial magnetic permeability could be obtained even when the firing temperature was 920 ° C. or lower, at which simultaneous firing with the Ag electrode was possible.

When a calcined ferrite and the above-mentioned organic additive are allowed to coexist in a slurry, it is not clear what mechanism enables sintering at a low temperature. However, when the present inventors examined the amount of metal ions in the slurry, the amount of Cu ions and the amount of Fe ions were:
It was found that the presence or absence of the organic additive was strongly affected. Specifically, when the total amount of Cu ions and Fe ions derived from the calcined ferrite in the slurry finally becomes 0.005 to 2% by weight of the calcined ferrite, Cu ions and Fe It was found that the effect of sintering at a low temperature was clearly exhibited when both the amount of the ion and the amount of the ion were 0.01 to 1.0% by weight. This suggests that these metal ions eluted from the calcined ferrite re-attached to the finely pulverized calcined material, and by acting as a sintering aid, sintering at low temperatures became possible. . If the total of Cu ions and Fe ions is too small, sintering at a low temperature becomes difficult. On the other hand, in order to elute ions exceeding the above range, the amount of the organic additive must be significantly increased, which is not preferable. When the total amount of both ions is 2% by weight or less, the low-temperature sintering effect is sufficiently realized.

In the present invention, if ammonia is added to the slurry in addition to the organic additive, the effect of the present invention is further improved.

Incidentally, among the organic additives used in the present invention,
For example, tartaric acid, 1-ascorbic acid, and citric acid are known as dispersing agents for improving moldability in a slurry casting method ("Fine Ceramics Molding and Organic Materials", pp. 187-188, Saito). Katsuyoshi,
Published by CMC Corporation). In addition, sodium gluconate is known as a dispersant in the concrete industry (“Chemistry of Dispersion and Aggregation”, pages 92 to 95, written by Noboru Moriyama, published by Sangyo Tosho). However, in these fields, all of the above organic additives are used as dispersants.

[0015] WO 98/25278 discloses that
It has been proposed to add an organic additive used in the present invention to a water slurry at the time of pulverization when producing an oxide magnetic material. However, in the publication, the organic additive is used as a dispersant for improving the degree of orientation when performing magnetic field orientation. In addition, the same publication describes a dispersion effect in a hexagonal ferrite magnet, but does not describe an example relating to a soft magnetic ferrite powder, and is effective for magnetic field orientation of acicular soft magnetic ferrite particles. There is only a description. Further, the publication does not disclose or suggest that soft magnetic ferrite powder can be sintered at a low temperature when manufactured using the above-mentioned organic additive.

On the other hand, in the present invention, a completely new effect which has not been known hitherto is realized by adding the above organic additive to the aqueous slurry of soft magnetic ferrite.
According to the experiments of the present inventor, even when the organic additive is added, the time required for pulverizing the calcined soft magnetic ferrite (the pulverization time until a specific surface area is obtained) is not substantially reduced. Therefore, it is considered that the organic additive does not show a dispersing effect on the soft magnetic ferrite powder.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The soft magnetic ferrite powder produced according to the present invention is composed of Ni-Cu-Zn ferrite. In the present invention, dense sintering at a low temperature is possible regardless of the ferrite composition. Therefore, the main component composition of the Ni-Cu-Zn ferrite to which the present invention is applied is:
There is no particular limitation, and it may be appropriately selected from a general composition range according to required characteristics and the like. When the main component oxides are respectively represented by Fe ₂ O ₃ , NiO, CuO and ZnO, the general composition ranges are, for example, Fe ₂ O ₃ : 35 to 50 mol%, NiO: 4 to 50 mol%, CuO: 4 １６16 mol%, ZnO: 5-40 mol%. That is, the present invention, Fe ₂ O ₃ in many high-permeability material having the content, it can be applied to Fe ₂ O ₃ less content low permeability material. The reasons for limiting the content of the main component oxide are as follows. If the amount of Fe ₂ O ₃ is too small, the amount of the non-magnetic phase generated increases, causing an increase in the loss. If the amount of Fe ₂ O ₃ is too large, the sinterability deteriorates remarkably. If the amount of NiO is too small, the loss becomes large, and if the amount of NiO is too large, it becomes expensive. If the amount of CuO is too small, the sinterability deteriorates, and if the amount of CuO is too large, the amount of NiO becomes relatively small, resulting in a large loss. If the ZnO content is too small, the magnetic permeability will be low, and if the ZnO content is too large, the Curie temperature will be too low.

In the ferrite powder, in addition to the main component oxide, other metal oxides such as Co, W, Bi, Si, B, Mn, and Z as subcomponents or inevitable impurities.
Oxides such as r, Ca, Ta, Mo, P, Y, and Mg may be included as necessary.

In the present invention, a soft magnetic ferrite powder is produced by the method described below.

First, a calcined product of a raw material powder is produced. As the raw material powder, various raw materials usually used for the production of Ni-Cu-Zn ferrite, that is, various compounds that become oxides or oxides by firing may be used. The calcination may be performed in an oxidizing atmosphere, usually in the air. Preferably, it is 10 hours.

The calcined product thus obtained is mixed with water to prepare a slurry for grinding. Then, wet crushing is performed on the crushing slurry, and the calcined product is crushed to a predetermined particle size or specific surface area, and then dried to obtain a soft magnetic ferrite powder.

In the present invention, the pulverizing slurry contains an organic additive. The organic additive may be added at any time before, during and after the pulverization. If the organic additive is present in the slurry and metal ions are eluted in the slurry, the effect of the present invention is realized.

The time for wet grinding is not particularly limited, and the average particle size of the calcined product is about 0.4 to 2.0 μm, or the specific surface area of the calcined product is about 3 to 11 m ² / g, preferably 3 to 8 m ^2. / g
The degree may be appropriately determined according to various conditions such as a pulverizing means. The crushing means is not particularly limited,
Usually, it is preferable to use a ball mill, an attritor, a vibration mill or the like. By the way, in order to sinter at low temperature,
It is known that the calcined product should be ground to a fine diameter.However, if strong grinding is performed for a long time to obtain a fine particle, the grinding media composed of zirconia balls, iron balls, etc., wears out and the resulting temporary Contamination of pottery becomes a problem. On the other hand, in the present invention, even if relatively coarse pulverization is performed such that the average particle size and the specific surface area of the calcined material fall within the above range,
Since low-temperature sintering is possible, contamination of the calcined product due to abrasion of the pulverization medium is less likely to occur, and ferrite having stable characteristics can be obtained.

The content of the calcined product in the slurry for pulverization, that is, the concentration of the solid component is preferably 15 to 50% by weight,
More preferably, it is 20 to 35% by weight. If the solid content is too low or too high, the grinding efficiency and the uniformity of the grinding will be low.

Next, the organic additive will be described. The organic additive used in the present invention is an organic compound having a hydroxyl group and a carboxyl group, a neutralized salt thereof, a lactone thereof, an organic compound having a hydroxymethylcarbonyl group, or dissociated as an acid. It is an organic compound having an enol type hydroxyl group which can be used or a neutralized salt thereof, and among these, a compound which functions as an acid is preferable.

Each of the above organic compounds has preferably 3 to 20, more preferably 4 to 12, carbon atoms, and preferably 50% or more of carbon atoms other than carbon atoms double-bonded to oxygen atoms. It has a hydroxyl group bonded. In addition, the bonding ratio of the hydroxyl group is limited for the above organic compound, and is not limited for the organic additive itself. For example, when a lactone of an organic compound (hydroxycarboxylic acid) having a hydroxyl group and a carboxyl group is used as the organic additive, the limitation of the bonding ratio of the hydroxyl group is applied not to the lactone but to the hydroxycarboxylic acid itself.

The basic skeleton of the organic compound may be linear or cyclic, and may be saturated or contain an unsaturated bond.

As the organic additive, specifically, a hydroxycarboxylic acid or a neutralized salt thereof or a lactone thereof is preferable. Particularly, gluconic acid (C = 6; OH = 5; CO
OH = 1) or its neutralized salt or its lactone, lactobionic acid (C = 12; OH = 8; COOH = 1);
Tartaric acid (C = 4; OH = 2; COOH = 2) or a neutralized salt thereof, glucoheptonic acid γ-lactone (C = 7;
OH = 5) is preferred. Among these, gluconic acid or its neutralized salt or its lactone is preferable because it has a high effect of improving the characteristics in low-temperature sintering and is inexpensive.

As the organic compound having a hydroxymethylcarbonyl group, sorbose is preferred.

As the organic compound having an enol type hydroxyl group which can be dissociated as an acid, ascorbic acid is preferable.

In the present invention, citric acid or a neutralized salt thereof can also be used as an organic additive. Although citric acid has a hydroxyl group and a carboxyl group, the condition that a hydroxyl group is bonded to 50% or more of carbon atoms other than a carbon atom double-bonded to an oxygen atom is not satisfied, but the effect of the present invention is realized.

The structures of some of the preferred organic additives described above are shown below.

[0033]

Embedded image

Incidentally, two or more organic additives may be used in combination.

The amount of the organic additive is preferably 0.05 to 3.0% by weight, more preferably 0.1% by weight, based on the calcined product.
10 to 2.0% by weight. If the amount of the organic additive is too small, the effect of the present invention becomes insufficient. On the other hand, if the amount of the organic additive is too large, cracks are likely to occur in the molded body and the sintered body.

When the organic additive is one that can be ionized in an aqueous solution, for example, an acid or a metal salt, the amount of the organic additive is an ion equivalent. That is, the amount of addition is determined in terms of organic components excluding hydrogen ions and metal ions. When the organic additive is a hydrate, the amount of addition is determined excluding water of crystallization.

When the organic additive comprises lactone or contains lactone, the amount of addition is determined in terms of hydroxycarboxylic acid ions, assuming that all of the lactone is opened to form hydroxycarboxylic acid.

In the present invention, it is preferable that ammonia is present in the slurry in addition to the organic additive. By adding ammonia, sintering at a lower temperature becomes possible, or a denser sintered body can be obtained at the same temperature.
Ammonia may be added as aqueous ammonia. When ammonia is added, the amount of ions in the slurry,
In particular, the amount of Fe ions tends to increase. However, if the amount of added ammonia is too large, ion elution may be suppressed instead, so the amount of added ammonia is preferably 5% by weight or less based on the calcined product. Further, in order to sufficiently exert the effect of adding ammonia, it is preferable that the amount of added ammonia is 0.1% by weight or more based on the calcined product. Ammonia may be added at any time before, during, or after the pulverization, but usually, it may be added simultaneously with the organic additive.

The soft magnetic ferrite powder produced by the above-described procedure can be applied to various uses, but is particularly suitable for producing magnetic cores of various inductors. The magnetic core of the inductor is manufactured by molding and baking soft magnetic ferrite powder. The soft magnetic ferrite powder produced according to the present invention may be fired in an oxidizing atmosphere, usually in the air. The firing temperature (holding temperature) is usually
The firing time (holding time) is usually from 800 to 1100 ° C.
It may be 1 to 6 hours. However, the soft magnetic ferrite powder produced according to the present invention has sufficient properties as a magnetic core even when calcined at 920 ° C. or lower. Therefore, the soft magnetic ferrite powder manufactured according to the present invention is particularly suitable for manufacturing a multilayer chip inductor that needs to be co-fired with an Ag electrode. In the production of a multilayer chip inductor having an Ag electrode, the firing temperature is preferably 910 ° C. or lower, particularly 900 ° C. or lower, in order to sufficiently suppress the deterioration of ferrite characteristics due to reaction with Ag. Even when fired at an extremely low temperature, sufficient characteristics as a magnetic core can be obtained.

Next, a multilayer chip inductor and a method of manufacturing the same will be described.

The multilayer chip inductor shown in FIG.
It has an inductor chip body 10 formed by laminating a magnetic layer 6 and an internal conductor 5, and external electrodes 41 and 45 provided on the surface of the inductor chip body 10.

The configuration of each part of the multilayer chip inductor may be selected from various types of conventionally known configurations. For example, the external shape is substantially a rectangular parallelepiped. Usually, as shown in FIG. 3, the internal conductor 5 is spirally arranged in the magnetic layer 6 to form an internal winding, and both ends of the internal conductor 5 are external electrodes 41, 4.
5 is connected. The external electrodes 41 and 45 may be a single electrode layer, or may further include a coating layer formed of Cu, Ni, Sn, solder, or the like. Such a coating layer improves solder wettability and solder heat resistance during soldering. The winding pattern of the internal conductor 5 is not particularly limited. The number of turns may be appropriately selected according to the application, but is usually about 1.5 to 15.5 turns.

The dimensions of each part of the multilayer chip inductor are not particularly limited, and may be appropriately determined according to the application. For example, the thickness of the magnetic layer may be about 20 to 100 μm. Usually, the thickness of the external electrode may be about 10 to 100 μm, and the total thickness including the coating layer may be about 15 to 130 μm. The width of the external electrode may be selected according to the purpose, but is usually about 0.2 to 0.4 mm. Usually, the thickness of the internal conductor 5 may be about 5 to 30 μm. The dimensions of the inductor chip body 10 may be appropriately determined according to the intended use, but are usually (1.0 to 4.5 mm) ×
(0.5-3.2 mm) × (0.6-2.0 mm).

The conductive material contained in the internal conductor 5 is preferably mainly composed of Ag having a small specific resistance.
As the conductive material mainly composed of Ag, Ag or Ag
Ag alloys such as -Pd, Ag-Pt and Ag-Pd-Pt are preferable, and Ag is particularly preferable. The Ag content in the Ag alloy is preferably at least 75% by mass.

It is preferable to use a conductive material mainly composed of Ag for the external electrodes 41 and 45. The conductive material mainly composed of Ag is preferably Ag or an Ag alloy.
g is preferred. Further, as the Ag alloy, an Ag-Pd alloy and an Ag-Cu alloy are preferable.
-Pd alloy is preferred. The Ag content in the Ag alloy is:
It is preferably at least 75% by mass. Various glasses such as lead borosilicate glass may be contained in the external electrode.

In manufacturing a multilayer chip inductor,
First, a magnetic paste, an internal conductor paste, and an external electrode paste are prepared.

The magnetic paste can be prepared by kneading the soft magnetic ferrite powder produced according to the present invention with an organic vehicle. The organic vehicle is obtained by dissolving a binder in an organic solvent. The binder used for the organic vehicle is not particularly limited, and may be appropriately selected from various ordinary binders such as ethyl cellulose and polyvinyl butyral. In addition, the organic solvent to be used is not particularly limited, and may be appropriately selected from various organic solvents such as terpineol, butyl carbitol, acetone, and toluene according to a method to be used such as a printing method and a sheet method. When the magnetic paste is used as an aqueous paint, an aqueous vehicle in which a water-soluble binder or dispersant or the like is dissolved in water may be kneaded with a soft magnetic ferrite powder. The water-soluble binder used for the aqueous vehicle is not particularly limited, and for example, polyvinyl alcohol, cellulose, a water-soluble acrylic resin, or the like may be used.

The internal conductor paste can be prepared by kneading the above-mentioned conductive material or various oxides, organometallic compounds, resinates and the like which become the above-mentioned conductive material by firing and the above-mentioned organic vehicle.

The external electrode paste may be prepared in the same manner as the above-mentioned internal conductor paste.

When manufacturing a multilayer chip inductor by a printing method, first, a magnetic material paste and an internal conductor paste are mixed so that the internal conductor paste forms a coil pattern.
A laminate is formed by alternately printing on a substrate made of a PET film or the like. Next, it is cut into a predetermined shape and size to obtain a green chip, and then separated from the substrate. On the other hand, when manufacturing by a sheet method, first, a green sheet is formed using a magnetic paste, and a through hole for conduction is formed in the green sheet. Then
The internal conductor paste is printed on a green sheet, these are laminated, and the obtained laminate is cut into a green chip. Next, in either case, the green chip is fired to obtain an inductor chip body, and an external electrode paste is printed or transferred to the inductor chip body and fired to obtain a multilayer chip inductor. The firing conditions for the external electrode paste are preferably, for example, at 600 to 800 ° C. for about 10 minutes to 1 hour.

The multilayer chip inductor manufactured as described above is mounted on a printed circuit board or the like by soldering or the like, and is used for various electronic devices and the like.

The soft magnetic ferrite powder produced according to the present invention can be applied not only to a multilayer chip inductor but also to various chip components having a multilayer inductor portion, for example, an LC composite component.

[0053]

Examples 1 to 5 These oxides were weighed so as to have a ratio of 49 mol% of Fe ₂ O ₃ , 18 mol% of NiO, 12 mol% of CuO, and 21 mol% of ZnO, and were wet-processed. The mixture was wet-mixed for 4 hours using a media stirring type pulverizer. In this wet mixing, pure water was used as a dispersion medium.

Next, the mixture was dried with a spray drier and calcined at 700 ° C. for 2 hours to obtain a Ni—Cu—Z
A calcined product of n ferrite was obtained.

The calcined product was mixed with pure water to prepare a slurry for grinding. The solid content (calcined material) concentration in the slurry for grinding was 25% by weight. In addition, as shown in Table 1, an organic additive or ammonia and this were added to the slurry. The ammonia was added as 50% by weight ammonia water. The amounts of the organic additives and ammonia shown in Table 1 are the amounts added to the calcined product.

This slurry for pulverization was pulverized for 7 hours by a wet media stirring type pulverizer and then dried by a spray drier to obtain a Ni—Cu—Zn ferrite powder. By this pulverization, the specific surface area of the ferrite powder became 4.4 m ² / g (average particle size: 1.4 μm). After grinding,
The metal ions in the slurry were measured by ICP emission spectrometry, and the weight ratios of Cu ions and Fe ions to the calcined product were determined. Table 1 shows the results.

[0057]

[Table 1]

To 100 g of this ferrite powder, 1.0 g of polyvinyl alcohol as a binder was added and mixed to obtain granules. The granules are subjected to 98 MPa (1000 kgf / c
Press molding was performed at a pressure of m ² ) to obtain a ring-shaped molded body having a diameter of 21 mm. This molded body was fired by maintaining the temperature at the temperature shown in FIGS. 1 and 2 for 2 hours to obtain a Ni—Cu—Zn ferrite sintered body.

The density of the sintered body was measured according to the Archimedes method. The initial permeability at 100 kHz of this sintered body was measured using LCR METER 4274A (manufactured by HEWLETT PACKARD).
Was measured. FIG. 1 shows the relationship between the firing temperature and the density, and FIG. 2 shows the relationship between the firing temperature and the initial magnetic permeability.

Comparative Example 1 A sintered body was prepared in the same manner as in the above example except that neither the organic additive nor ammonia was added to the slurry for grinding, and the same measurement as in the above example was performed. The results are shown in FIG. 1 and FIG. As a result of measuring the amount of ions in the slurry in the same manner as in the above example, no Cu ion or Fe ion was detected.

Evaluation FIG. 1 and FIG. 2 clearly show the effect of the present invention. That is, in Examples 1 to 5 in which a predetermined organic additive was added to the slurry in the wet pulverization step when producing the soft magnetic ferrite powder, even when the firing temperature was lowered to about 900 ° C., 4.8 g / g. A sufficient density of cm ³ or more is obtained,
In addition, a sufficient initial magnetic permeability exceeding 150 is obtained.
On the other hand, in Comparative Example 1 in which the organic additive was not added, both the sintered body density and the initial magnetic permeability at the time of low-temperature firing were significantly inferior to Examples 1 to 5.

When the soft magnetic ferrite powder produced in the above example was used as the material for the magnetic layer and Ag was used as the internal conductor material, and the firing temperature was 910 ° C., a laminated chip inductor was produced. Excellent inductor characteristics according to the characteristics shown in FIG. 2 were obtained.

[Brief description of the drawings]

FIG. 1 shows a Ni—Cu—Zn ferrite sintered body.
4 is a graph showing a relationship between a firing temperature and a density of a sintered body.

FIG. 2 shows a Ni—Cu—Zn ferrite sintered body.
4 is a graph showing a relationship between a firing temperature and an initial magnetic permeability of a sintered body.

FIG. 3 is a plan view with a part of a configuration example of a multilayer chip inductor cut away.

[Explanation of symbols]

 Reference Signs List 5 internal conductor 6 magnetic layer 10 inductor chip body 41, 45 external electrode

Claims (7)

[Claims] 1. A method for producing a soft magnetic ferrite powder containing Fe, Ni, Cu and Zn as main components, wherein an organic additive is present in a slurry containing a calcined raw material powder and water. As the organic additive, an organic compound having a hydroxyl group and a carboxyl group or a neutralized salt thereof or a lactone thereof, or an organic compound having a hydroxymethylcarbonyl group, an organic compound having an enol-type hydroxyl group that can be dissociated as an acid. Alternatively, a method for producing a soft magnetic ferrite powder using a neutralized salt thereof. 2. The method for producing a soft magnetic ferrite powder according to claim 1, wherein the amount of the organic additive is 0.05 to 3.0% by weight based on the calcined product. 3. The soft magnetic ferrite powder according to claim 1, wherein the slurry contains Fe ions and / or Cu ions derived from the calcined material in a total amount of 0.005 to 2% by weight of the calcined material. Manufacturing method. 4. The method for producing a soft magnetic ferrite powder according to claim 1, wherein the organic compound having a hydroxyl group and a carboxyl group is gluconic acid or citric acid. 5. The organic compound having an enol-type hydroxyl group that can be dissociated as an acid is ascorbic acid.
3. The method for producing a soft magnetic ferrite powder according to any one of items 1 to 3. 6. The method for producing a soft magnetic ferrite powder according to claim 1, wherein ammonia is added to the slurry. 7. A method for manufacturing a multilayer chip inductor, comprising the step of forming a magnetic layer using the soft magnetic ferrite powder manufactured by the method according to claim 1.