JPH0669057A - Manufacture of laminated chip inductor - Google Patents

Abstract

PURPOSE:To obtain a desired inductance even when the inductor is made small by preventing the short circuit of coils which have been buried and installed inside a magnetic ferrite blank body. CONSTITUTION:First, a bout 3400 pieces of through holes 2 0.3mm in diameter are made in an N-Zn-Cu-based magnetic ferrite green sheet 1 at intervals of 1.92mm lengthwise and 0.96mm breadth-wise. Then, a nearly C-shaped coil conductor pattern 3 whose line width is 0.16mm and whose end parts on both sides are bent perpendicularly by 180 deg. is printed, by using an Ag paste, on the green sheet 1 in which the through holes 2 have been made. Then, the sheets 1 in which the through holes 2 and the coil conductor patterns 3 have been formed are laminated in a prescribed constitution, three sheets each of dummy sheets are laminated and compression-bonded respectively to the upper part and the lower part, and this laminated body is then cut to chip sizes. Then, each chip blank body is baked at 900 deg.C, and external terminal electrodes are formed on one pair of opposite edges from which coil terminals have been extracted at the chip blank body.

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 a laminated chip inductor.

[0002]

2. Description of the Related Art A laminated chip inductor has a spiral coil embedded in a magnetic ferrite body, and external terminal electrodes are formed on a pair of opposing end faces from which the coil ends of the magnetic ferrite body are led out. Such a multilayer chip inductor has been generally manufactured by the following method.

First, a slurry obtained by kneading a ferrite magnetic powder raw material and an organic binder and a long base film made of, for example, a polyethylene terephthalate film are set on a coating machine, and a doctor blade method is applied to the base film. After continuously applying the slurry to a thickness of several tens to several hundreds of μm, the slurry on the base film is dried. Next, the dried slurry is peeled from the base film and cut into, for example, 100 mm square to obtain a magnetic ferrite green sheet 1.

Next, through holes 2 are formed at predetermined positions in the ferrite green sheet 1 obtained as described above, and a coil conductor pattern 3 as shown in FIG. 2 is formed on the surface of the through holes 2 by printing. . The coil conductor pattern printed on the green sheet has a width wider than the diameter of the through hole, and the spiral coil is formed by stacking and connecting the through holes. It has a substantially U-shape facing two different directions, and the through hole is located at one end thereof.

Next, a predetermined number of sheets having the above-mentioned through holes and coil conductor patterns and a dummy sheet having no through holes and coil conductor patterns formed above and below are laminated and pressure-bonded, A magnetic ferrite element body in which a spiral coil having a predetermined number of turns is embedded is obtained.

Next, by cutting this element body into a chip size, the coil ends are led out to a pair of opposed end faces of the chip element body, and this is fired. After firing, a conductive paste is applied to the end surface of the element body from which the coil end is led out, and this is fired to form an external terminal electrode, thereby obtaining a multilayer chip inductor.

[0007]

However, according to the above-mentioned conventional method for manufacturing a laminated chip inductor, when the magnetic ferrite green sheets 1 having through holes and coil conductor patterns are laminated, as shown in FIG. The holes 2 were arranged in a straight line in the stacking direction. Therefore, when such a laminated body is pressure-bonded, the pressure becomes coarse in the through-hole portion, and the stress of the green sheet is concentrated in the through-hole, and depending on the case, it is overlapped under the sheet having the through-hole. In some cases, the green sheet was destroyed and brought into contact with another conductor, short-circuiting the coil, and the desired inductance could not be obtained. This tendency was particularly noticeable when the chip was miniaturized.

Therefore, the present invention solves the above-mentioned problems of the prior art, prevents short-circuiting of the coil embedded in the magnetic ferrite element body, and provides a multilayer chip inductor capable of obtaining a desired inductance even when miniaturized. It is intended to provide a manufacturing method.

[0009]

Means for Solving the Problems As a result of intensive studies for achieving the above-mentioned object, the inventors of the present invention have found that through-holes in a laminated body are dispersed in a direction perpendicular to the laminating direction. The inventors have found that the above problems can be solved, and have reached the present invention.

That is, according to the present invention, through holes and coil conductor patterns are formed at predetermined positions in a plurality of magnetic ceramic green sheets, and adjacent coil conductor patterns are connected through holes by stacking and crimping these sheets. Then, after manufacturing the obtained magnetic ferrite element body in which the spiral coil is embedded, the external terminal electrodes are formed on the pair of opposed end faces from which the coil ends of the magnetic ferrite element element are led out. In the method, the coil conductor pattern in the sheets is printed in the through holes such that the arrangement of the through holes in the sheet stacking direction when the sheets are stacked is shifted in a direction orthogonal to the sheet stacking direction instead of in a straight line. Multilayer chip characterized by being formed by being dispersed within the part There is provided a method of manufacturing the inductor.

[0011]

According to the method of the present invention, when the sheets are laminated, the through holes are not aligned in the sheet laminating direction but are shifted in the direction orthogonal to the laminating direction so that the coil conductor patterns on the sheets are printed. It is dispersed within the part.

For example, one sheet has a through hole formed at a position where one end of the coil conductor pattern is printed in a portion of the sheet where the coil conductor pattern is printed, and another sheet has a sheet hole. In the portion where one end of the coil conductor pattern is printed in, a through hole is formed at a position shifted by one through hole from one end of the coil conductor pattern. The through hole is formed by repeatedly forming a through hole at a position where one end of the coil conductor pattern is printed and a position shifted by two through holes from one end of the coil conductor pattern. When these sheets are laminated by forming the coil conductor patterns in the The arrangement in the stacking direction of the definitive through holes, can be dispersed in the direction perpendicular to the stacking direction.

As described above, by arranging the arrangement of the through holes in the sheet stacking direction in the direction orthogonal to the sheet stacking direction, the stress applied to the through hole positions when the stacked body is pressure-bonded is dispersed. for that reason,
It is possible to prevent the coil conductor pattern from extending or breaking, which has occurred in the conventional method of manufacturing a laminated chip inductor in which the arrangement of through holes in the laminated body is aligned in the sheet laminating direction. The fluctuation disappears.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited by the following examples.

[0015]

EXAMPLE An example of a method of manufacturing the multilayer chip inductor of the present invention will be described below.

First, a Ni-Zn-Cu system magnetic ferrite green sheet 1 (100 mm ^W x 100 mm ^L x 0.1 mm ^T )
Further, about 3400 through holes 2 having a diameter of 0.3 mm were formed at intervals of 1.92 mm in length and 0.96 mm in width. In this way, six types of sheets having different positions for forming the through holes 2 were prepared. Next, the green sheet 1 having the through holes 2 formed therein
1 was printed using Ag paste with a line width of 0.16 mm, as shown in FIG. 1, that is, a substantially C-shaped coil conductor pattern 3 in which both ends were bent at 180 degrees at a right angle. Note that FIG.
FIG. 4 is a diagram showing one chip.

Next, the sheets 1 on which the through holes 2 and the coil conductor patterns 3 are formed are laminated in a structure as shown in FIG. 1, and three dummy sheets are laminated on each of the upper and lower portions of the sheet 1 and pressure-bonded thereto. It was cut into a chip size of mm × 0.96 mm to obtain a chip element body in which coil ends were led out to a pair of opposing end faces. Note that FIG. 3 shows a cross-sectional view of the obtained chip element body cut in the stacking direction.

Next, these chip bodies were fired at 900 ° C. (chip size 1.6 mm × 0.8 mm), and external terminal electrodes were formed on a pair of opposing end faces from which the coil ends of the chip bodies were led out, A multilayer chip inductor was obtained.

From the multilayer chip inductor obtained as described above, 100 pieces were randomly sampled and the inductance (L) was measured. The average value of L was 0.068 ± 0.007.
It was μH, and none of the L values fluctuated due to the short circuit of the coil.

[0020]

Comparative Example As shown in FIGS. 2 and 4, when laminated,
A plurality of layered chip inductors were produced in the same manner as in the example except that the through holes 2 were formed in the sheet 1 so that the through holes were aligned in a straight line in the stacking direction. , Inductance (L)
The average value of L was 0.062 ± 0.022 μH, and a part of the coil was short-circuited and the L value was varied.

[0021]

As a result of the development of the present invention, the stress concentrated in the through holes can be dispersed. for that reason,
The green sheet is prevented from being broken due to the partial concentration of stress, and the coil conductor pattern is prevented from being extended or cut, so that not only the L value does not fluctuate due to the short circuit of the coil, but also the characteristic change in the acceleration test is reduced and the reliability is maintained It became possible to miniaturize it as it was.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a stacking mode of sheets constituting a multilayer chip inductor of the present invention.

FIG. 2 is an exploded perspective view showing a stacking mode of sheets forming a conventional multilayer chip inductor.

FIG. 3 is a side sectional view of a laminated body including the sheet shown in FIG.

FIG. 4 is a side sectional view of a laminate including the sheet shown in FIG.

[Explanation of symbols]

 1 Magnetic Ferrite Green Sheet 2 Through Hole 3 Coil Conductor Pattern

Claims (1)

[Claims] 1. A through-hole and a coil conductor pattern are formed at a predetermined position in a plurality of magnetic ceramic green sheets, and the adjacent coil conductor patterns are through-hole connected by laminating and crimping these sheets, which is obtained. A method for manufacturing a multilayer chip inductor, comprising forming an external terminal electrode on a pair of opposing end faces from which a coil end of a magnetic ferrite element body is led out after firing a magnetic ferrite element body in which a spiral coil is embedded. , When the sheets are stacked, the through holes are dispersed and formed in the portion of the sheet where the coil conductor pattern is printed so that the arrangement of the through holes in the sheet stacking direction is displaced from each other in the direction orthogonal to the sheet stacking direction. And a method of manufacturing a multilayer chip inductor.