JP2604022Y2 - Multilayer ceramic inductor - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monolithic ceramic inductor having an inductance lower than that of one turn.

[0002]

2. Description of the Related Art In today's growing demand for smaller and thinner electronic components, multilayer ceramic inductors, in which conductor patterns provided in a magnetic material are laminated so as to form a coil, have attracted attention.

[0003] As a method of manufacturing this laminated ceramic inductor, a so-called printing method in which a conductor paste having a predetermined pattern and a magnetic paste are alternately screen-printed, and a through hole provided at a predetermined position in a magnetic green sheet, are used. A so-called sheet method for connecting the coil conductor patterns formed on the sheet may be used.

An advantage of these multilayer ceramic inductors is that a high inductance can be easily obtained by increasing the number of turns (turns) of the coil, and the number of turns can be easily increased by repeating a conductor pattern that goes around. is there.

In any of the above methods, since a large number of pieces are simultaneously printed in a certain area in the laminating step, after lamination is completed, cutting is performed according to a predetermined chip element size.

FIG. 3 shows an example of an exploded perspective view of a stack of chip bodies cut by the green sheet method, and shows a coil conductor pattern printed on a green sheet 2 obtained from a magnetic slurry. 3 are sequentially stacked so as to be connected by through holes 4 provided at predetermined positions on the sheets, and a plurality of cover sheets 1 having no through holes above and below these sheets are stacked and pressed. It is a laminate.

In any of the above methods, after the chip body obtained by cutting the laminate is fired, an external electrode is applied to the end face from which the conductor lead-out portion is led out.

[0008]

Generally, a multilayer ceramic inductor is generally determined by the magnetic permeability and the number of turns of a magnetic material, and the higher the number of turns, the higher the inductance can be obtained. It is also desired that the DC resistance of the conductor, which causes copper loss (resistance loss), be lower.

Therefore, in order to further expand the applications of the multilayer ceramic inductor, it is easier to increase the number of turns as described above for a high-inductance inductor, but it is easier to increase the number of turns for a low-inductance inductor. Since it shows the lowest value,
Lower inductances cannot be obtained by changing the number of turns.

Therefore, in order to obtain a material having a lower inductance than one turn, it is necessary to develop a new material having a low magnetic permeability. Needless to say, it is difficult to develop new materials, and even if they can be developed, it is necessary to review all processes, which is extremely difficult.

Accordingly, an object of the present invention is to provide a multilayer ceramic which does not require the development of a new material, and which uses a conventional material to obtain an inductance lower than one-turn inductance and at the same time reduces the DC resistance of the conductor. It is to provide an inductor.

[0012]

Means for Solving the Problems In order to achieve the above-mentioned object, the present inventor has first studied with a focus on a structure in which a plurality of coils are connected in parallel in a magnetic body.

That is, the mutual inductance generated between the two coils is determined by the direction in which the magnetic flux generated by one coil passes through the other coil, and its polarity is determined. For example, as shown in FIG. In addition, the magnetic flux φ generated in the coil 1 in which the direction of the current I _{1 is} the direction of the arrow is the current I 1
₂ passes through the coil 2 having the same direction in the direction in which the magnetic flux is added, and the mutual inductance is (+). On the other hand, as shown in FIG. 6B, the direction of the magnetic flux φ ₁ generated by the coil 1 whose current I _{1 is in} the direction of the arrow and the direction of the current I ₂ are I
_The magnetic flux φ ₂ generated in the coil 2 opposite to ₁ penetrates these coils in opposite directions, and the mutual inductance becomes (−). Therefore, the two coils are connected as shown in FIG.
As shown in (b), if the stacking order in the stacked body is devised so that the mutual inductance becomes negative, the above-described problem can be solved, and at the same time, the direct current resistance which is a cause of the resistance loss can be reduced. Reached.

Therefore, in the present invention, the coil provided inside the laminate obtained by laminating the magnetic green sheets spirals around the coil, and the start and end thereof are respectively connected to different external electrode terminals. A laminated ceramic inductor, wherein at least two of the above-mentioned internally provided coils are connected in parallel to an external electrode terminal, and a magnetic flux generated in one of the two coils forming the pair is the other coil. Are provided so as to penetrate each other in a direction opposite to a direction in which magnetic fluxes are added to each other, and have a coil arrangement in which mutual inductance is negative. In this case, the coils forming a pair may have the axes of the coils coincided with each other, and the directions of the currents may be opposite to each other, or the coils may be opposed to each other left and right, and the directions of the currents may be the same. In the former case, coils having the same diameter and having the same axis may be arranged vertically, or coils having a small diameter may be arranged inside a coil having a large diameter in the same plane.

[0015]

When two coils are electrically connected in parallel, as described above, the mutual inductance is determined by the direction in which the magnetic flux generated by one coil passes through the other coil. As shown in (1), when the coils have different directions of current indicated by currents, negative magnetic coupling, that is, mutual inductance becomes negative, can reduce the inductance.

Therefore, an inductance lower than one-turn inductance can be obtained only by changing the coil conductor pattern.

Further, the DC resistance of the conductor can also be made smaller than the DC resistance of each coil since the combined DC resistance is connected in parallel.

[0018]

Embodiment 1 FIG. 1 is an exploded perspective view showing a stacking order of a stacked body in which coils having the same diameter and the same diameter are connected in parallel in this embodiment. This will be described below.

(1) A slurry prepared from Ni-Cu-Zn ferrite powder was formed into a magnetic green sheet by a doctor blade method.

(2) A through hole was formed at a predetermined position on the obtained magnetic green sheet having a thickness of 50 μm, and a conductor pattern for a coil was printed with a conductor paste containing Ag as a main component.

(3) Next, the first coils are laminated in the order shown in the right side of FIG. That is, a cover sheet 1 composed of three magnetic green sheets
And a group of sheets sandwiching a plurality of superimposed green sheets on top of each other by a pair of upper and lower green sheets each having a conductor lead-out portion so that predetermined conductor patterns 3 are connected by through holes 4 therebetween. .

(4) Next, in the same order as the second coil shown on the left side of the figure is formed, the direction in which the coil is wound and the direction of the current are opposite to those in the case of the sheet group. The sheets on which the conductor patterns are arranged are stacked so as to be oriented.

(5) Finally, the cover sheet 1 composed of four magnetic green sheets is stacked to obtain a laminate.

In the actual laminating step, a large number of conductor patterns are simultaneously printed on the green sheet.

(6) After the obtained laminate is thermocompressed, the chip is cut into chip bodies and fired, and an electrode paste is applied to the end face of the fired body having the conductor lead-out portion and baked to provide external electrodes. .

By the above steps, the mutual inductance becomes negative by negatively magnetically coupling the right coil and the left coil in FIG. 1 to obtain an inductance lower than one turn.

[0027]

Embodiment 2 FIG. 2 is an exploded perspective view showing a stacking order of a stacked body in which coils having different diameters are connected in parallel in the present embodiment. This will be described below.

When an outer first coil and an inner second coil are formed between the upper cover sheet 1 and the lower cover sheet 1 as shown in FIG. The green sheets 2 connected by the respective through holes 4 were stacked in the opposite directions.

The obtained laminate was obtained according to the procedure of Example 1.
After cutting to obtain a chip inductor body, which was fired, an external electrode was applied to the end face.

Through the above steps, a multilayer ceramic inductor having an inductance lower than one turn was obtained.

In each of the first and second embodiments, an example is shown in which the winding cores are the same. However, when the coils are arranged on the left and right, the magnetic flux generated in the first coil is obtained even if the current directions of the respective coils are the same. Is reversed when passing through the second coil, so that the same effect as in the above embodiment can be obtained.

Therefore, the material of the ferrite magnetic material, the sheet thickness, the number of cover sheets arranged above and below, the shape of the coil conductor pattern, the size of the through hole, and the like can be arbitrarily set so as to obtain a desired inductance. Needless to say, the laminating step is easy not only by the sheet method but also by the printing method.

[0033]

As described above, according to the present invention, it is possible to obtain a lower inductance than the case of the minimum number of coil turns of 1 by only changing the conductor pattern for the coil using only the conventional material. There is. Specifically, according to the present invention, the magnetic green sheet
One conductive pattern is formed on each
Coil with the same number of spiral turns
Or two magnetic cores in the vertical direction.
Two conductive patterns are formed on each of the
When multiple spiral sheets have the same number of spiral turns
Coil can be easily formed by forming two parallel coils
Obtains a lower inductance than the one with the minimum number of turns
The effect is that Note that these two coils are
Set the coil inductor so that the mutual inductance of the coils becomes negative.
Of course, the direction of the The present invention
According to these two coils are connected in parallel
Of course, the advantage that the resistance value is reduced is obtained.
is there.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a stacking order of a stacked body used in one embodiment of the present invention, in which coils having the same winding core and the same diameter are connected in parallel.

FIG. 2 is an exploded perspective view showing a stacking order of a stacked body used in another embodiment of the present invention, in which coils having the same winding core and different coil diameters are connected in parallel.

FIG. 3 is an exploded perspective view showing a lamination process by a sheet method in a conventional multilayer ceramic inductor.

4A and 4B are diagrams for explaining the mutual inductance of two coils, wherein FIG. 4A is a schematic diagram when the mutual inductance is (+) and FIG. 4B is a schematic diagram when the mutual inductance is (−). is there.

[Explanation of symbols]

Magnetic flux generated by the magnetic flux phi ₂ current of the coil 2 caused by the first cover sheet 2 green sheet 3 conductive pattern 4 through holes 5 coil 1 6 coil 2 I ₁ current of the coil 1 of the current I ₂ current phi flux phi ₁ coil 1 of the coil 2

Claims (1)

(57) [Scope of request for utility model registration] 1. A conductive pattern formed on a magnetic green sheet.
And stacking a plurality of the green sheets to form a laminate
In a multilayer ceramic inductor having a spiral coil formed therein and connecting the start end and the end of the coil to different external electrode terminals, the number of spiral turns is the same.
Form two coils, connect each start end and each end
To each other and connect them to the other external electrode terminals.
So that the mutual inductance of the two coils is negative
A multilayer ceramic inductor , characterized in that: