JPH0774024A - Ferrite magnetic material chip inductor and its preparation - Google Patents

Abstract

PURPOSE: To manufacture a ferrite chip inductor having high reliability, at a low manufacturing cost, by preventing short-circuit between an inner conductor and an outer electrode, at the time of surface mounting of a ferrite magnetic material chip inductor. CONSTITUTION: This manufacturing method comprises; a primary molding step of extrusion-molding and drying ferrite slurry 1, a step of winding a lead wire 3 around a first molded object, a second molding step of extrusion-molding ferrite so as to cover the outer surface of the wound molded object, and a step where, after a secondary molded object is cut out and baked, outer electrodes 4 are fixed on both ends.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-mounting chip inductor, and more specifically, a lead wire is provided inside a ferrite magnetic material and is joined to an external electrode to form an internal conductor for surface mounting. The present invention relates to a ferrite chip inductor having a low production cost and high reliability by preventing a short circuit between external electrodes and simplifying the manufacturing process, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Ferrite chip inductors are L inductors on an electric circuit that have various inductance values depending on the permeability characteristics of the ferrite magnetic material and the number of windings of the inner conductor.
It is used as an (inductance) element and manufactured so as to be surface-mounted. The conventional method of manufacturing a chip inductor is to form a coil-shaped conductive wire inside by alternately stacking a conductive paste and a ferrite paste on a sheet of a ferrite magnetic material by printing or spraying and firing. After that, the external electrodes are attached.

[0003]

However, in the conventional technique as described above, since the conductive paste and the ferrite paste are repeatedly laminated as described above, the process is complicated and the internal conductor is short-circuited due to the difference in shrinkage ratio during firing. There is a danger of. Therefore, there is a limit to the use as an L ((inductance) element on an electronic circuit that requires high reliability. Therefore, the present invention has been made in view of the above conventional problems,
By configuring the inner conductor in the form of a conductor, especially a coil-shaped conductor, there is no problem of short-circuiting of the inner conductor during firing or during use, and the end area of the inner conductor is constant and the rate of change of the inductance value of the element is The object is to provide a small ferrite chip inductor. Another object of the present invention is to solve the problem of short circuit between the inner conductor and the outer electrode by joining the outer conductor with the end portion of the inner conductor slightly protruding.

[0004]

In order to achieve the above object, a ferrite chip inductor of the present invention has a coil-shaped conductor wire having a projecting end portion inside a ferrite magnetic body and is in contact with the projecting end portion. At the same time, the external electrode is formed so as to be in contact with the ferrite magnetic body.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in more detail with reference to the accompanying drawings illustrated as embodiments. FIG. 5 shows the structure of the ferrite magnetic chip inductor of the present invention. As shown in FIG. 5, the ferrite magnetic chip inductor of the present invention has a structure in which the ferrite magnetic body 1 is internally provided with a coil-shaped conductor 3 having a projecting end portion 2 in contact with an external electrode. Then, external electrodes that are in contact with the protruding end portion 2 and are in contact with the ferrite magnetic body 1 are attached to both ends of the ferrite magnetic body 1.
In the configuration of the present invention, the conductive wire 3 having a coil shape has low resistance and excellent thermal characteristics that it does not melt at the firing temperature at the time of firing, and it should be selected from Ag, Pd or Ag-Pd and used. Is desirable.

FIG. 1 is an overall process diagram for manufacturing the ferrite magnetic chip inductor shown in FIG. 5, and FIGS.
FIG. 2 is a working state diagram showing extrusion molding during the step shown in FIG. 1. The present invention is based on MO · Fe ₂ O ₃ (M: Mn, Ni, Z
n, Cu, Mg, Co, Be, which is one metal), and a ferrite powder composed of 85 to 96% by weight, a binder made of rubber or an organic polymer compound, a plasticizer, a defoaming agent, a wetting agent, An organic binder such as a lubricant is mixed in an amount of 4 to 5% by weight, and then water is added so as to have a water content of 15 to 25% by weight and sufficiently kneaded to prepare a ferrite slurry.

The ferrite slurry thus prepared is used for primary extrusion molding (FIG. 2) and secondary extrusion molding (FIG. 4). As shown in FIG. 2, the ferrite slurry 1 is
A molded product 8 is obtained by primary extrusion molding into a uniform cylindrical shape through the inner nozzle 5 and the outer nozzle 6 of the extruder and drying.
At this time, in order to prevent the molded product from being broken in the next step, extrusion molding is performed while inserting the fibrous reinforcing material 7 of about 0.1 mm or less in the center of the nozzle of the extruder. Then, as shown in FIG. 3, Ag, Pd, or Ag-
The Pd conducting wire 3 is continuously wound at regular intervals.

Then, as shown in FIG. 4, the ferrite slurry 1 is extrusion-molded while inserting the molded product 9 in which the conducting wire is wound into the internal nozzle of the rectangular cross section of the secondary extrusion molding machine. The extruded product 10 extruded in this manner has a cross section of 1.2 × 1.6 to 1.6 × 3.6 mm depending on the size of the nozzle hole.

The extruded product 10 is dried, cut into a predetermined length, and fired at a temperature of 950 to 1150 ° C.
During such firing, both ends of the conductor wire are projected to the outside due to shrinkage of the ferrite, so that the protruding end portion 2 as shown in FIG. 5 is formed. After depositing Ag, Pd or Ag-Pd paste on both ends of the chip inductor thus fired to form an external electrode, it is fired, and then nickel and tin are sequentially plated to provide solderability and durability. And improve heat resistance. In this way, the manufacture of the chip inductor is completed.

As described above, according to the present invention, after the conductive wire is wound on the outside of the first extruded molded product 8, the outer surface of the rolled molded product 9 is extruded so that the ferrite magnetic material is covered. And bake. By firing in this way, the conductor wire projects outward due to shrinkage of the ferrite during firing, so that the projecting end portion 2 is formed. Then, external electrodes are attached to both ends of the ferrite chip inductor having the projecting end portions.

[0011]

As described above, the present invention can prevent the occurrence of a short circuit between the inner conductor and the outer electrode during surface mounting,
A ferrite chip inductor with a low manufacturing cost can be obtained by simplifying the manufacturing process.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram of the present invention.

FIG. 2 is a working state diagram of primary extrusion molding.

FIG. 3 is a working state diagram of winding a conductor wire on a ferrite extruded and molded.

FIG. 4 is a working state diagram of secondary extrusion molding.

FIG. 5 is a sectional view of a ferrite chip inductor of the present invention.

[Explanation of symbols]

 1 Ferrite magnetic substance 2 Projection end 3 Conductive wire 4 External electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H01F 41/04 B 8019-5E

Claims (3)

[Claims] 1. A ferrite magnetic body (1), and a conductor (3) which is internally provided in the ferrite magnetic body (1) and has a projecting end portion (2) projecting from the ferrite magnetic body,
The magnetic body (1) is in contact with the protruding end (2) and
A surface-mountable ferrite magnetic chip inductor comprising: an external electrode (4) in contact with both ends of the. 2. The lead wire (3) is made of Ag, Pd and Ag-.
The surface-mountable ferrite magnetic chip inductor according to claim 1, which is a composition selected from Pd. 3. A primary molding step of extruding and drying a ferrite slurry (1); a step of winding a conducting wire (3) outside the primary molded article (8); A secondary molding step of extruding the molded product (9) so that the outer surface of the molded product (9) is covered with the ferrite, and cutting and firing the secondary molded product (10), and then fixing external electrodes to both ends thereof. A method of manufacturing a surface-mountable ferrite magnetic chip inductor, comprising: