JPH0620843A - Manufacture of laminated chip inductor - Google Patents

Abstract

PURPOSE:To prevent the misalignment of coil conductor patterns from being generated when green sheets are stacked and are pressed and pressure-bonded. CONSTITUTION:When through holes (a diameter of 0.2mm) 3 for interlayer connection use are made in a ceramic green sheet 1 of a thickness of 30mum, cavities which are used as holes 5 for stress relaxation use are simultaneously provided in the peripheries of conductor patterns 2 which are printed on the sheet 1. Alternatively the green sheets 1 printed with the U-shaped conductor patterns 2 with two holes in their central parts are prepared, these sheets are stacked, pressure-bonded and are formed into a multilayered body, the body is cut by a normal method into chip elements and each element is burned, and external electrodes are provided. Thereby, a manolithic chip inductor is constituted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer chip inductor having no defect in the connection of through-hole conductors and a method for manufacturing the same.

[0002]

2. Description of the Related Art A method for manufacturing a laminated chip inductor is as follows. Prepare a sheet cut into corners. Since hundreds of chips are simultaneously formed on this ceramic green sheet, a sheet in which through holes for connecting conductor patterns are formed according to the number of chips,
A sheet having no through holes is prepared.

The conductor pattern for the coil is a substantially U-shaped pattern and is formed by an ordinary screen printing method. Therefore, a screen plate having a plurality of the patterns is prepared. When these are prepared, a substantially U-shaped pattern is printed on the green sheet having the through holes with a conductive paste such as silver paste.

FIG. 5 is an exploded perspective view of the laminated layers of the respective ceramic green sheets 1. In the laminating procedure, first, a desired number of green sheets having no through holes are stacked, and the through holes 3 are formed thereon. A predetermined number of the green sheets on which the conductor patterns 2 are formed are printed, and the sheets on which the through holes are not formed are further stacked and pressed to form a laminated body in which the sheets are connected and integrated ( No through hole is formed in the sheet having the conductor lead-out portion of the lowermost layer).

Next, this laminated body is cut along a predetermined cut line 4 according to the individual chip size and fired to obtain a fired body as shown in the perspective view of FIG. As shown in the perspective view of FIG. 7, external electrodes 6 are provided to form a laminated chip inductor.

[0006]

SUMMARY OF THE INVENTION In the above conventional method,
The conductor pattern on the ceramic green sheet is 20-30μ
When the sheet is printed with a thickness of m and the number of coil turns is large, when the sheets are stacked, the conductor pattern is in contact with the adjacent sheets, but the green sheet portion other than the conductor pattern has a gap between the adjacent sheets. Become.

When pressure is applied in that state, as shown in FIG. 8, that is, an enlarged cross-sectional view around the conductor pattern when the green sheets are laminated and pressed, the pressure is concentrated on the conductor pattern 2 and The nearby green sheet is pushed in the direction of the arrow in the figure and extends in the peripheral direction.

As shown in the sectional view of the laminated body after lamination and pressure bonding shown in FIG. 9, the influence is great in the peripheral portion of the sheet 1 and the conductor pattern 2 in the peripheral portion is displaced.

Therefore, if the chips obtained from the peripheral portion are cut at the cut lines 4 which are set at regular intervals according to a predetermined dimension, the conductor pattern 2 is formed in an unbalanced position, which impairs reliability. It was

SUMMARY OF THE INVENTION An object of the present invention is to provide a laminated chip inductor which does not cause a positional deviation of a coil conductor pattern when laminating and pressing green sheets and a method for manufacturing the same.

[0011]

Means for Solving the Problems The present inventor has carried out research to achieve the above object, and the positional deviation of the conductor pattern is caused by the pressure concentrated on the conductor pattern at the peripheral portion of the green sheet during lamination and pressure bonding of the green sheet. As a result of considering measures to absorb the concentrated pressure, a cavity for absorbing strain generated in the green sheet due to atmospheric pressure is dispersed in the periphery of the conductor pattern. If the number of cavities provided and arranged is calculated and provided so that the total volume of the cavities is equal to, or preferably more than, the volume of the conductor pattern to be printed, the above problems can be solved. That is, the present invention has been achieved.

Therefore, according to the present invention, a through hole is formed in a ceramic green sheet made of a ceramic magnetic material, and a coil conductor pattern is printed on the sheet and laminated to form a coil inside the ceramic laminate. In the method of manufacturing a multilayer chip inductor,
In addition to the usual through holes for connecting the conductor patterns on the adjacent sheets, a second hole as a stress relaxation hole for absorbing the strain at the time of crimping is provided on the periphery where the coil conductor patterns are printed or inside the patterns. The present invention provides a method for manufacturing a laminated chip inductor, characterized in that the coil conductor pattern is printed after forming the through hole.

[0013]

According to the present invention, a plurality of cavities, which are second through holes penetrating the coil conductor pattern formed on the ceramic green sheet, are formed at the periphery of the coil conductor pattern. The stress of the green sheet around the conductor pattern generated at the time of stretching extends the green sheet, and the second through hole acts so as to absorb the stress of the ceramic green sheet, and the influence of this stress affects the adjacent conductor pattern. In addition, there is an effect that the displacement of the conductor pattern is not generated.

FIGS. 3 (a) and 3 (b) are enlarged cross-sectional views before and after crimping for explaining the above-mentioned action. The stress relaxation hole 5 causes the green sheet 1 to extend in the direction of the arrow.
The pressure concentrated on the conductor pattern 2 is dispersed.

[0015]

1 and 2 show a green sheet used in this embodiment, in which the former is formed with a conductor pattern and the latter is formed with a cavity (stress relaxation hole) inside the pattern. FIG. 4 is a perspective view in the case of being pressed, and FIG. 4 is a cross-sectional view of the green sheet laminate after pressure bonding, which will be described below with reference to these drawings.

Ceramic green sheet 1 with a thickness of 30 μm
When opening a through hole (diameter 0.2 mm) 3 for interlayer connection,
At the same time, a cavity as the stress relaxation hole 5 is formed around the printed conductor pattern 2 as shown in FIG.

The conductor pattern has a length of 3 mm, a width of 0.1 mm, and a film thickness.
0.02mm, so the volume is 0.006mm ³ , so 0.
(Since shared with adjacent pattern 12) 24 mm ^phi hole (volume 0.0009mm ³⁾ 6 pieces of per pattern was placed.

On the other hand, a sheet in which two holes are arranged in the central portion of a U-shaped conductor pattern was also prepared (see FIG. 2).

Next, the sheet on which the conductor pattern 2 is printed by a conventional method is dried, and a plurality of ceramic green sheets are laminated and pressure-bonded so that the sheets of FIG. 1 and the sheet of FIG. When this is cut along a predetermined cut line 4 and cut into individual chip elements,
When the presence or absence of a defective product in which the internal conductor is exposed due to the positional deviation on the end face of the chip element is examined, 10% occurs in the case of the conventional method as shown in FIG. As shown in the cross-sectional view of Fig. 3, no chip was found in which the internal conductor was exposed at the cut line due to the displacement.

The cavity as the stress relaxation hole is the first
The arrangement shown in FIG. 2 or the arrangement shown in FIG. 2 can be used. If the hole diameter and the number of holes are substantially the same as or larger than the volume of the conductor pattern to be printed, the desired effect can be obtained. It has also been found that it is effective to obtain the holes and arrange the holes on the cut lines in the laminate.

[0021]

As described above, in the multilayer chip inductor manufactured by the method of the present invention, since the cavity for stress relaxation is arranged at the periphery of the conductor pattern or the central portion of the U-shape, the conductor pattern is formed. The stacking deviation and the distortion of the conductor are reduced, and the conductor does not laterally protrude as in the conventional case, so that the yield is improved and the product reliability is improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing a ceramic green sheet having a cavity formed along a coil conductor pattern used in an embodiment of the present invention.

FIG. 2 is a perspective view showing a ceramic green sheet used in an example of the present invention, in which a U-shaped conductor pattern has a cavity inside.

FIG. 3A is an enlarged cross-sectional view of a green sheet before lamination and FIG. 3B is an enlarged cross-sectional view of the inductor according to the present invention before pressure bonding during lamination.

FIG. 4 is a cross-sectional view of the inductor of the present invention after green sheet lamination pressure bonding.

FIG. 5 is an exploded perspective view of laminated layers in a conventional inductor.

6 is a perspective view of a fired body obtained by cutting the laminated body of FIG. 5 into chip elements and then firing.

FIG. 7 is a perspective view of a multilayer chip inductor completed by adding external electrodes to the fired body.

FIG. 8 is an enlarged cross-sectional view of a conventional inductor after laminated pressure bonding.

FIG. 9 is a cross-sectional view of a conventional inductor after green sheet lamination and pressure bonding.

[Explanation of symbols]

 1 ... Ceramic green sheet 2 ... Conductor pattern 3 ... Through hole 4 ... Cut line 5 ... Stress relaxation hole 6 ... External electrode

Claims (1)

[Claims] 1. A multilayer chip inductor comprising a ceramic green sheet made of a ceramic magnetic material having a through hole formed therein, a coil conductor pattern being printed on the sheet and laminated to form a coil inside the ceramic laminated body. In addition to the usual through-holes for connecting the conductor patterns on the adjacent sheets in the manufacturing method of 1), for the stress relaxation for absorbing the strain at the time of crimping on the periphery where the coil conductor pattern is printed or the inside of the pattern. A method of manufacturing a laminated chip inductor, comprising forming a second through hole as a hole and then printing a coil conductor pattern.