JPH11345731A - Manufacture for inductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture an inductor which holds a metal coil wire at a predetermined position with high accuracy, reduces restrictions in manufacturing and is superior in electric characteristics. SOLUTION: After a metal coil wire 22 is inserted into a through-hole 23a provided at the center of a ceramic body 23, a slurry-like ferrite ceramic raw material is made to flow into the through-hole 23a. At this time, as the metal coil wire 22 is held on an inner wall face of the through-hole 23a, even if the slurry-like ferrite ceramic raw material is made to flow in, the metal coil wire 22 win not be moved from the position. Next, the ceramic body 23 is put in an oven to have the ferrite ceramic raw material solidify in the through-hole 23a. Then, after the ceramic body is burnt, an external electrode is formed at both the upper and lower end parts of the ceramic body 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an inductor, particularly an inductor for a large current used for removing noise radiated from electronic equipment and the like and noise entering electronic equipment and the like.

[0002]

2. Description of the Related Art An inductor using a metal coil wire has an electric resistance value of about 1/10 or less as compared with a laminated inductor and the like when the same coil diameter and the same number of turns are used. Can do it. As a method of manufacturing an inductor using such a metal coil wire, there is known a method described in Japanese Patent Application Laid-Open No. Hei 8-181221. According to this method of manufacturing an inductor, a metal coil wire is wound around an extruded ceramic to form a coil shape, and then the outer casing is continuously formed, so that the metal coil wire is accurately held at a predetermined position. .

[0003] However, it is difficult to reduce the coil pitch and to wind a thick metal coil wire having a wire diameter of 100 µm or more. Also, due to the characteristic of the manufacturing method, since the metal coil wire is wound around the entire length of the inductor in a rough winding state, the impedance generation efficiency is higher than that of a metal coil wire having a tightly wound coil portion and a linear lead portion. Becomes lower. Therefore, in order to obtain a desired impedance, there is a problem that the length of the metal coil wire becomes long, and the resistance value of the metal coil wire itself as an internal electrode unnecessarily increases.

As a countermeasure, the applicant has set an inductor by a method of setting a metal coil wire processed into a predetermined shape in a mold, and then pouring a slurry-like ceramic material into the mold (gel casting method). is suggesting.

[0005]

However, this method can solve the problem of the inductor manufacturing method described in Japanese Patent Application Laid-Open No. HEI 8-181221, but when the slurry-like ceramic raw material is poured into the mold, it is difficult to remove the metal. There is a new problem that the position of the coil wire is easily displaced, and thus the variation in the electrical characteristics is large.

Accordingly, an object of the present invention is to provide a method of manufacturing an inductor capable of manufacturing an inductor having excellent electrical characteristics, while maintaining a metal coil wire at a predetermined position with high accuracy, with less restrictions on manufacturing. To provide.

[0007]

To achieve the above object, a method of manufacturing an inductor according to the present invention comprises the steps of: forming a ceramic body having a cavity for accommodating a metal coil wire; Inserting a metal coil wire into the hollow portion, filling the hollow portion with a ceramic material, and molding the ceramic material. As a method of filling and molding the ceramic material in the cavity of the ceramic body, for example, a gel casting method is employed.

[0008]

According to the above method, the metal coil wire is inserted into and held in the cavity of the ceramic body, so that when the ceramic material is filled in the cavity, no displacement of the metal coil wire occurs, and the metal coil wire is not displaced. Are accurately positioned. Further, a metal coil wire having a structure having a close-wound coil portion and a linear lead portion can also be adopted, and this method has less restrictions on manufacturing such as the structure of the metal coil wire.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing an inductor according to the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the metal coil wire 22 is
A coil portion 22a wound spirally, and linear extraction portions 22b provided at both ends of the coil portion 22a,
22b. As a material of the metal coil wire 22,
For example, a metal or alloy containing one or more of Ag, Ag-Pd, Pt, Au, and Cu is used. In the case of the present embodiment, an Ag wire having a wire diameter of 200 μm is used as a material of the metal coil wire 22, and the Ag wire is spirally wound to have a coil diameter of 1.5 mm, a length of about 2.4 mm, and the number of turns. Formed a coil part 22a having six turns, and formed lead parts 22b, 22b each having a length of about 0.8 mm.

The ceramic body 23 is a rectangular parallelepiped having a rectangular cross section, and a through hole 23a having a circular cross section having an axis parallel to the longitudinal direction is provided at the center. The ceramic body 23 is formed by a gel casting method described in detail below.

First, the raw material powder has an average particle size of 2.2 μm.
m, a CuCu ferrite ceramic powder, a water-soluble epoxy resin (polyethylene glycol diglycidyl ether) as a curable resin, water and ethanol as compatible liquids, a polyoxyalkylene glycol as a dispersant, and a polyalkylene as a defoamer. Glycol was charged into a pot mill at the ratio shown in Table 1, and then wet-mixed for 20 hours to form a slurry.

[0013]

[Table 1]

Next, a modified diamine adduct as a curing agent is mixed into the slurry-like ceramic raw material at a ratio of 0.3% by weight, and the mixture is stirred for 5 minutes. Next, the slurry-like ceramic raw material was defoamed for 30 minutes, and poured into a polyethylene mold under a reduced pressure of 60 cmHg. Next, the mold is placed in an oven maintained at 90 ° C. for about 30 minutes to solidify the slurry-like ceramic raw material. Next, the solidified ceramic raw material was taken out of the mold and dried for another 30 minutes.
A rectangular parallelepiped ceramic body 23 having a width of 3.0 mm and a height of 3.84 mm was obtained. The volume shrinkage at the time of solidification at this time was about 1%.

Next, the rectangular parallelepiped ceramic body 23
A through hole 23a having a circular cross section (1.5 mm in diameter) having an axis parallel to the longitudinal direction is formed by a cutting method using a drill. However, this through-hole 23a may be formed by a method such as using a die frame during molding. The through hole 23a becomes a cavity for accommodating the metal coil wire 22.

Next, the through hole 23a of the ceramic body 23
After inserting the metal coil wire 22, a slurry-like ceramic raw material was poured into the through-hole 23a under a reduced pressure condition of 60 cmHg. At this time, since the metal coil wire 22 is held on the inner wall surface of the through hole 23a, the position of the metal coil wire 22 does not move even when the slurry-like ceramic material is poured. Therefore, the positioning accuracy of the metal coil wire 22 is high, and variations in the electrical characteristics of the obtained inductor can be suppressed. The poured slurry-like ceramic raw material has an average particle size of 2.2 μm as raw material powder.
m, a water-soluble epoxy resin (polyethylene glycol diglycidyl ether) as a curable resin, water and ethanol as compatible liquids, a polyalkylene glycol as a dispersant, and a polyalkylene glycol as a defoamer. And Table 1
, And wet-mixed for 20 hours. Then, 0.3% by weight of a modified diamine adduct as a curing agent was mixed in the mixture, and the mixture was stirred for 5 minutes and stirred for 30 minutes.
For a minute.

Next, the ceramic body 23 is placed in an oven maintained at 90 ° C. for about 30 minutes, so that
The slurry-like ceramic raw material in a is solidified. In this way, as shown in FIG. 2, a cylindrical ceramic body 24 filled in the through hole 23a and having the metal coil wire 22 embedded therein was formed by a gel casting method. Next, the ceramic body 23 was placed in a firing furnace, and the temperature was raised for 9 hours.
After degreasing by holding at a temperature of 50 ° C. for 3 hours, baking was performed at a temperature rising time of 9 hours and a temperature of 900 ° C. for 2 hours. The ceramic bodies 23 and 24 thus obtained were sufficiently densified and had a sintered density of 5.25. And
The ceramic body 23 after firing has a length of 2.5 mm and a width of 2.
The rectangular parallelepiped was 5 mm in height and 3.2 mm in height, and the firing shrinkage was 1.20%.

Next, as shown in FIG.
External electrodes 26, 26 are formed on both upper and lower ends of the third electrode. The external electrodes 26, 26 are respectively connected to the lead portions 22 of the metal coil wires 22 exposed on both upper and lower end surfaces of the ceramic body 23.
b, 22b. As a material of the external electrode 26, for example, a metal or an alloy containing at least one of Cu, Ni, Ag, Ag-Pd and the like is used.

Table 2 shows the measurement results of the electric resistance value and the inductance value of the inductor 30 thus obtained (see Examples). For comparison, see JP-A-8-181021.
The electrical resistance value and the inductance value of the inductor manufactured by the method described in Japanese Patent Application Laid-Open Publication No. H10 (1995) (see Comparative Example 1) and the electrical resistance value and the inductance value of the inductor manufactured by the conventional gel casting method (see Comparative Example 2) are combined. It is listed in Table 2. The design value of the inductance value was 4.0 μH in each case. From Table 2, it can be seen that the electrical resistance value of the inductor 30 manufactured by the method of the present embodiment is low, and that the variation of the inductance value is small.

[0020]

[Table 2]

The method of manufacturing the inductor according to the present invention is not limited to the above embodiment, but can be variously modified within the scope of the invention. For example, the ceramic body may be not only rectangular in cross section but also circular in cross section, and the cross sectional shape of the through hole provided in the ceramic body is variously changed in accordance with the shape of the entire coil wire. .

[0022]

As is apparent from the above description, according to the present invention, since the metal coil wire is inserted and held in the hollow portion provided in the ceramic body, no displacement of the metal coil wire occurs. The metal coil wire can be accurately positioned. Further, the manufacturing restrictions can be reduced without being restricted by the structure of the metal coil wire. As a result, the metal coil wire can be accurately held at a predetermined position, and there can be manufactured an inductor excellent in electric characteristics with few restrictions on manufacturing.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a method for manufacturing an inductor according to the present invention.

FIG. 2 is a perspective view showing a manufacturing process following FIG. 1;

FIG. 3 is a perspective view showing a manufacturing step following FIG. 2;

[Explanation of symbols]

 22: Metal coil wire 23: Ceramic body 23a: Through hole (hollow part) 24: Ceramic body 30: Inductor

Claims (2)

[Claims] 1. A step of forming a ceramic body having a cavity for accommodating a metal coil wire, and after inserting a metal coil wire into the cavity of the ceramic body, filling the cavity with a ceramic material and molding. A method for manufacturing an inductor, comprising: 2. The method for manufacturing an inductor according to claim 1, wherein the cavity of the ceramic body is filled with a ceramic material by a gel casting method and molded.