JP2004343036A - Mutlilayer inductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain excellent DC superposition characteristics in a multilayer inductor in which magnetic layers are stacked. <P>SOLUTION: The multilayer inductor having a part body in which a plurality of magnetic layers and coil conductor layers are laminated, and a pair of external electrodes provided on the surface of the part body. In this inductor, the coil conductor layers are connected with each other via through holes provided on the magnetic layers to form a spiral coil to be embedded into the part body, and both the ends of the coil are pulled out to the surface of the part body and are each connected to the pair of external electrodes. The inductor is 0.5≤T'/T≤0.85 and T'/n≥27 μm, where the thickness in a laminating direction of the part body is T, the length in a laminating direction of the coil is T', and the number of turns of the coil is n. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laminated inductor, and more particularly to a laminated inductor for a choke coil.

  A chip-type laminated inductor used for applications such as a choke coil has a configuration in which a plurality of magnetic layers and a coil conductor layer are laminated, and a coil formed by connecting the coil conductor layers to each other is embedded in the component body. Are generally known.

  For example, in FIG. 11, the laminated inductor 21 includes a component body 22 and a pair of external electrodes 23a and 23b provided on the surface of the component body 22.

  As shown in FIG. 10, the component body 22 is formed by laminating magnetic layers 24a to 24l. The coil conductor layers 25a to 25g are provided on the magnetic layers 24d to 24j, respectively. In the magnetic layers 24d to 24i, through holes 26a to 26f are provided at positions where one ends of the coil conductor layers 25a to 25f are provided above. The coil conductor layers 25a to 25g are connected to each other through the through holes 26a to 26f to form a spiral coil inside the component element body 22.

  Further, one ends of the coil conductor layers 25a and 25g are respectively drawn out to the surface of the component body 22, and are connected to the external electrodes 23b and 23a, respectively.

  A multilayer inductor having such a configuration is described in numerous documents such as Japanese Patent No. 2518757 and Japanese Patent No. 2921594.

  When the above-described laminated inductor is used for a choke coil, the inductance is generally used in the range of 1 μH to 22 μH, although it depends on the circuit used. In this range, for example, in order to obtain an inductance of 1, 2.2, 4.7, 10, and 22 μH, the number of turns of the coil is changed according to the inductance value. That is, by changing the number of coil conductor layers, the number of turns of the coil is changed to obtain a desired inductance.

At this time, the thickness of the magnetic layer between the coil conductors is often designed to be constant regardless of the inductance value, and the thickness of the coil portion is varied depending on the number of turns. The advantage of this design is that only one type of ceramic green sheet is used, and it can be manufactured easily and at low cost.
Japanese Patent No. 2518757 Japanese Patent No. 2921594

  In recent years, as electronic devices have become smaller, smaller choke coils have been required. At the same time, the demand for improving the rated current in small laminated inductors is increasing.

However, since the laminated inductor having the magnetic layers laminated as described above has a closed magnetic circuit structure, when a direct current is applied, magnetic saturation is likely to occur, and thus the inductance is easily reduced. For this reason, the above-described laminated inductor generally has a problem that the direct current superposition characteristic is poor and it is difficult to secure a sufficient rated current.
SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problem and to obtain a good DC superimposition characteristic in a laminated inductor having magnetic layers laminated.

  In order to solve the above-mentioned problems, the inventor has conducted intensive studies on the relationship between the coil structure of the multilayer inductor and the DC bias characteristics. As a result, they have found a certain correlation between the coil structure and the DC bias characteristics, and have obtained a multilayer inductor having good DC bias characteristics.

  That is, the laminated inductor of the present invention is a laminated inductor having a component element body in which a plurality of magnetic layers and coil conductor layers are laminated, and a pair of external electrodes provided on the surface of the component element element, The coil conductor layers are connected to each other through through holes provided in the magnetic layer to form a spiral coil embedded in the component body, and both ends of the coil are drawn out to the surface of the component body. When the thickness of the component body in the stacking direction is T, the length of the coil in the stacking direction is T ′, and the number of turns of the coil is n, 0.50 ≦ 0.50 ≦ T ′ / T ≦ 0.85 (more preferably 0.60 ≦ T ′ / T ≦ 0.77) and T ′ / n ≧ 27 μm.

  With such a configuration, it is possible to reduce the occurrence of magnetic saturation around the coil when a DC current is applied to the laminated inductor. For this reason, a laminated inductor having good direct-current superposition characteristics can be obtained.

  In the laminated inductor, at least one conductor layer connected to the through hole is provided in each of the magnetic layers adjacent to each of the coil conductor layers.

  With such a configuration, it is possible to prevent the coil conductor layer from being deformed during press molding and the shape of the coil from being lost.

Also, when the area inside the coil is M1 and the area outside the coil is M2 when the component body of the laminated inductor is viewed from the laminating direction,
0.24 ≦ M1 / M2 ≦ 0.36
It is characterized by being.

  With such a configuration, it is possible to reduce the occurrence of magnetic saturation around the coil when a DC current is applied to the laminated inductor. For this reason, a multilayer inductor having high inductance and good DC superimposition characteristics can be obtained.

  The laminated inductor of the present invention includes a component element body in which a plurality of magnetic layers and a coil conductor layer are stacked, and a pair of external electrodes provided on a surface of the component element body, and the coil conductor layer is A spiral coil connected to each other through a through hole provided in the magnetic layer and buried in the component body constitutes a spiral coil, and both ends of the coil are drawn out to the surface of the component body and the pair of the external A laminated inductor connected to each of the electrodes, wherein the relationship between the thickness of the component body in the laminating direction, the length of the coil in the laminating direction, and the number of turns of the coil is optimized, so that a good direct current is achieved. This has an effect that superimposition characteristics can be obtained.

  In addition, at least one conductor layer connected to the through hole is provided in each of the magnetic layers adjacent to each of the coil conductor layers, so that the coil conductor layer is deformed at the time of press molding and the shape of the coil is reduced. Has the effect that it can be prevented from collapsing.

  Further, by optimizing the shape of the coil pattern, there is an effect that a high inductance and a good DC superimposition characteristic can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an exploded perspective view of a multilayer inductor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the multilayer inductor taken along the line AA 'shown in FIG.

  As shown in FIG. 2, the laminated inductor 1 is composed of a component body 2 and a pair of external electrodes 3a and 3b provided on the surface of the component body 2.

  As shown in FIG. 1, the component element body 2 has connection magnetic layers 8a to 8g inserted between the magnetic layers 4a to 4h, respectively, and the component element body 2 has an upper part of the magnetic layers and the connection magnetic layers. The protective magnetic layer 7a is formed by laminating a protective magnetic layer 7b below. The coil conductor layers 5a to 5f are provided on the magnetic layers 4b to 4g, respectively, and the lead conductor layers 9a and 9b are provided on the magnetic layers 4a and 4h, respectively. In the magnetic layers 4a to 4g and the connection magnetic layers 8a to 8g, through holes 6a to 6n are provided at positions where one ends of the coil conductor layers 5a to 5f or the lead-out conductor layer 4a are provided. . The coil conductor layers 5a to 5f and the lead conductor layers 9a and 9b are connected to each other via the through holes 6a to 6n to form a spiral coil inside the component body 2.

  Next, a method for manufacturing the multilayer inductor 1 will be described.

  First, a through hole is formed at a predetermined position of a ceramic green sheet containing ferrite as a main component. Thereafter, a coil conductor pattern or a lead conductor pattern is formed on the green sheet by a method such as screen printing, and a coil conductor formation sheet and a lead conductor formation sheet are obtained.

  After a through hole is formed at a predetermined position of the ceramic green sheet, the through hole is filled with a conductive paste to obtain a connection sheet.

  Next, a predetermined number of coil conductor forming sheets and one lead conductor forming sheet are provided above and below the coil conductor forming sheet, and a predetermined number of the connection sheets are inserted between the respective sheets, A predetermined number of ceramic green sheets are laminated on the uppermost and lowermost portions for the protective magnetic layer, respectively, to obtain a laminate of green sheets.

  The sheet laminate is fired after being pressed. External electrodes are formed on the side surfaces of the obtained sintered body where the lead conductor layer is exposed, and the multilayer inductor 1 is obtained.

  As shown in FIG. 2, the thickness in the stacking direction of the component element body 2 in the multilayer inductor 1 is T, the length of the coil including the lead conductor layers 9a and 9b in the stacking direction is T ′, and the number of turns of the coil is n. Then, T ′ / T and T ′ / n can be changed by changing the number of ceramic green sheets forming the connecting magnetic layer and the number of ceramic green sheets forming the protective magnetic layer. it can.

  Hereinafter, the T ′ / T and the DC bias characteristics of the multilayer inductor 1 with n = 4.5 (hereinafter referred to as a 4.5-turn product) and the inductor with n = 16.5 (the same 16.5-turn product) The result of examining the relationship will be described.

  Here, the external dimensions of the component element body were 2.0 mm × 1.25 mm × 1.25 mm (T = 1.25 mm). The green sheet used had a thickness of 20 μm after firing. The width of the coil pattern was 200 μm, and the diameter of the through hole was 150 μm.

  The shape of the coil pattern was as shown in FIG. Further, in the same drawing, the coil pattern was designed so that M1 / M2 = 0.30 when the area of the inner region of the coil composed of the coil conductor layers 5a to 5f was M1 and the area of the outer region was M2.

  FIG. 4 shows the relationship between T '/ T and the allowable current in the 4.5-turn product and the 16.5-turn product. FIG. 5 shows the relationship between T '/ T and the inductance in both products. As shown in FIG. 3, the allowable current is defined as a current value at which the inductance is reduced by 10% from the initial value when a direct current is applied to the laminated inductor.

  As shown in FIG. 5, in both the 4.5-turn product and the 16.5-turn product, the inductance gradually decreases as T '/ T increases. This is because the magnetic resistance increases as T '/ T increases. In addition, as shown in FIG. 4, in a region where T '/ T is relatively small, the allowable current sharply increases as T' / T increases. This is because the increase in T '/ T makes it difficult for magnetic saturation to occur between the coil conductor layers. Note that the allowable current is saturated as T '/ T approaches 1, because the thickness T' '(FIG. 2) of the protective magnetic layer becomes small, and magnetic saturation occurs in this portion.

  From the above results, it is clear that there is a region where the inductance when a direct current is applied increases as T ′ / T increases, and the design for increasing the T ′ / T of the multilayer inductor in this region is a direct current superposition. It is effective for improving characteristics.

  In general, it is known that the allowable current also increases by reducing the number of turns n of the coil while keeping T '/ n constant. Hereinafter, a description will be given of the result of comparing which of the method of increasing T '/ T and the method of reducing the number of turns n is superior in improving the DC superimposition characteristics.

  FIG. 6 shows the relationship between the inductance and the allowable current when T '/ T is varied between the 4.5-turn product and the 16.5-turn product of the present embodiment. Further, as a comparative example, the relationship between the inductance and the allowable current when the number of turns n is varied with T ′ / n = 27 μm is also shown.

As shown in the figure, it can be said that the present embodiment (solid line) has a larger allowable current with the same inductance and better DC superposition characteristics than the comparative example (dotted line). Here, the range of T ′ / T is
0.50 ≦ T ′ / T ≦ 0.85
In this case, the allowable current is improved by 20% or more in both the 4.5-turn product and the 16-turn product as compared with the comparative example. Furthermore, the range of T '/ T is
0.60 ≦ T ′ / T ≦ 0.77
In this case, the allowable current of both the 4.5-turn product and the 16-turn product is improved by 40% or more compared to the comparative example. That is, by designing T '/ T in the above-described range, a multilayer inductor having good direct-current superposition characteristics can be obtained.

  In the above-described laminated inductor, generally, the higher the number of turns n of the coil, the higher the inductance can be obtained. However, as the number of turns n increases, the thickness T '/ n per turn decreases, so that magnetic saturation easily occurs between the coil conductors, and the DC superimposition characteristics deteriorate. That is, when the number of turns of the coil exceeds a certain limit, the deterioration of the DC superimposition characteristic becomes remarkable, and it is not possible to obtain an inductance corresponding to the increase in the number of turns of the coil. In general, T '/ n is preferably about 27 [mu] m or more regardless of the size of the component body. If T ′ / n is smaller than 27 μm, the above-described problem is likely to occur.

  FIG. 8 shows the relationship between M1 / M2, the inductance value, and the DC bias characteristic when the area of the inner region of the coil formed of the coil conductor layers 5a to 5f is M1 and the area of the outer region is M2. Show. Here, the number of turns n = 16.5 and T '/ T = 0.68.

As shown in FIG. 8, M1 / M2 is approximately 24 ≦ M1 / M2 ≦ 0.36
It is evident that when the value falls within the range, it has a high inductance, a high allowable current and good DC bias characteristics. That is, M1 / M2 is preferably designed to be within the above range.

  On the other hand, when M1 / M2 is smaller than the above range, the inductance value decreases. This is because the area M1 inside the coil decreases and the magnetic flux in the coil decreases. At the same time, magnetic saturation is likely to occur in the region inside the coil, so that the allowable current decreases. Also, when M1 / M2 is larger than the above range, the inductance value decreases. This is because the magnetic resistance increases due to leakage of magnetic flux. At the same time, magnetic saturation is likely to occur in a region outside the coil, thereby reducing the allowable current.

  Note that, even when the size of the component body changes in the above-described multilayer inductor, the relationship between T '/ T and the DC superimposition characteristic is almost the same. This is because even if only the size of the component body changes while the coil structure remains the same, the shape of the magnetic flux generated by the coil does not change, and the likelihood of magnetic saturation does not change. Therefore, the present invention does not limit the size of the component body at all.

  Next, FIG. 9 shows an exploded perspective view of a multilayer inductor according to another embodiment described above.

  The component element body of the laminated inductor has connection magnetic layers 18a to 18g inserted between the magnetic layers 14a to 14h, respectively, similarly to the above-described laminated inductor 1, and includes the magnetic layer and the connection magnetic substance. The protective magnetic layer 17a is laminated on the upper part of the layer, and the protective magnetic layer 17b is laminated on the lower part. The coil conductor layers 15a to 15f are provided on the magnetic layers 14b to 14g, respectively, and the lead conductor layers 19a and 19b are provided on the magnetic layers 14a and 14h, respectively.

  Further, in this embodiment, linear dummy conductor layers 20a to 20f are provided on the connection magnetic material layers 18b to 18g at positions corresponding to the open portions of the coil conductor layers 15a to 15f, respectively. That is, for example, when the coil conductor layer 15a and the dummy coil conductor 20a are viewed from above, a rectangle is formed by both coil conductors.

  In the magnetic layers 14a to 14g and the connection magnetic layers 18a to 18g, through holes 16a to 16n are provided at positions where one ends of the coil conductor layers 15a to 15f or the lead conductor layer 14a are provided. . The coil conductor layers 15a to 15f and the lead conductor layers 19a and 19b are connected to each other via the through holes 16a to 16n, and form a spiral coil inside the component body.

  Also in the present embodiment, by setting T '/ T and T' / n in the above ranges, a laminated inductor having good DC superimposition characteristics can be obtained.

  As described above, since the dummy conductor layer having a shape corresponding to the open portion of each coil conductor layer is provided in the magnetic layer adjacent to the coil conductor layer, the coil conductor layer is deformed during press molding. Thus, the shape of the coil can be prevented from collapsing.

  In the above-described embodiment, only one dummy conductor layer is provided for each coil conductor layer. However, two or more dummy conductor layers may be provided.

  Further, in the above-described embodiment, one end of the dummy conductor layer is connected to a through hole, but both ends may be connected to a through hole.

1 is an exploded perspective view of a multilayer inductor according to an embodiment of the present invention. Sectional drawing which cut | disconnected the laminated inductor of FIG. 1 in the AA 'direction. FIG. 4 is a diagram for explaining the definition of allowable current in the present invention. FIG. 2 is a diagram showing a relationship between a coil structure of the multilayer inductor of FIG. 1 and an allowable current. The figure which shows the relationship between the coil structure and inductance of the laminated inductor of FIG. FIG. 2 is a diagram showing a relationship between allowable current and inductance in the multilayer inductor of FIG. 1 and a comparative example. 1. Top view of the multilayer inductor of FIG. The figure which shows the coil structure of the laminated inductor of FIG. 1, and the relationship of an inductance and an allowable current. FIG. 10 is an exploded perspective view of a multilayer inductor according to another embodiment. FIG. 5 is an exploded perspective view of a conventional multilayer inductor. The external appearance perspective view of the laminated inductor of FIG.

Explanation of reference numerals

1,21 laminated inductor 2,22 component element body 3a, 3b, 23a, 23b external electrode 4a-4h, 14a-14h, 24a-24l magnetic material layer 5a-5f, 15a-15f, 25a-25g coil conductor layer 6a- 6n, 16a to 16n, 26a to 26f Through hole 7a, 7b, 17a, 17b Protective magnetic layer 8a to 8g, 18a to 18g Connection magnetic layer 9a, 9b, 19a, 19b Leader conductor layer 20a to 20f Dummy conductor layer T Thickness of component body T 'Thickness of conductor forming portion T''Thickness of protective magnetic layer M1 Area of inner area of coil M2 Area of outer area of coil

Claims (4)

A component element formed by laminating a plurality of magnetic layers and a coil conductor layer; and a pair of external electrodes provided on a surface of the component element, wherein the coil conductor layer is provided on the magnetic layer. Forming a spiral coil connected to each other through a through-hole and embedded in the component element body, both ends of the coil are drawn out to the surface of the component element body and connected to the pair of external electrodes, respectively; When the thickness of the element body in the stacking direction is T, the length of the coil in the stacking direction is T ′, and the number of turns of the coil is n,
0.50 ≦ T ′ / T ≦ 0.85
T '/ n ≧ 27 μm
A multilayer inductor, characterized in that:   2. The multilayer inductor according to claim 1, wherein at least one conductor layer connected to the through hole is provided in each of the magnetic layers adjacent to each of the coil conductor layers. 3. 0.60 ≦ T ′ / T ≦ 0.77
T '/ n ≧ 27 μm
The multilayer inductor according to claim 1 or 2, wherein When the area inside the coil is M1 and the area outside the coil is M2 when the component element body is viewed from the laminating direction,
0.24 ≦ M1 / M2 ≦ 0.36
The multilayer inductor according to any one of claims 1 to 3, wherein

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