KR20090033378A - Layered inductor - Google Patents

Abstract

[PROBLEMS] To provide a layered inductor capable of exhibiting an excellent DC superposition characteristic and suppressing AC resistance during low flow of DC bias current as well as a high characteristic that an inductance change is comparatively gentle in the entire current region where the coil current is within a rating range. [MEANS FOR SOLVING PROBLEMS] A layered inductor (10) includes an electrically insulating magnetic layer (22) and a conductive pattern (20) which are layered so that the conductive patterns are successively connected to form a coil wound spirally while superimposing in the layering direction in the magnetic body. Each of the two ends of the coil is pulled out of the layered body chip external surface via a pull-out conductor (24) and connected to an electrode terminal (12). At least one layer (26) of the electrically insulating magnetic gap is arranged over the entire layered surface. An electrically insulating non-magnetic pattern (28) corresponding to the conductive pattern shape is arranged in the proximity of the conductive pattern between the conductive patterns superimposed with a gap.

Description

Multilayer Inductors {LAYERED INDUCTOR}

The present invention relates to a laminated inductor having a structure in which a coil is embedded in a magnetic body. More particularly, the present invention relates to a multilayer inductor having more than one layer of an electrically insulating nonmagnetic layer throughout the laminated surface, and between the conductive patterns polymerized at intervals. The present invention relates to a laminated inductor having a structure in which an electrically insulating nonmagnetic pattern corresponding to the shape of the conductor pattern is disposed in proximity to the conductor pattern. This multilayer inductor is particularly useful for inductors for DC-DC converters that require high bias.

In the case of transformers and choke coils used in power circuits such as DC-DC converters, the coils were wound around magnetic cores in the past, but in recent years, in accordance with demands for miniaturization and thinning of power circuit components, chips having a stacked structure Chip components have been developed and put into practical use.

In the multilayer inductor, an electrically insulating magnetic layer and a conductor pattern are alternately stacked so that the conductor patterns are sequentially connected, and coils are formed spirally circumferentially overlapping with each other in the stacking direction in the magnetic body, and both ends of the coils are formed. It is a structure which is drawn out to the outer surface of the laminated chip via the lead conductor and connected to the electrode terminal. That is, the coil is embedded in the tip magnetic material. The magnetic layer and the conductor pattern are formed and laminated using, for example, a screen printing technique.

Since the multilayer inductor is surrounded by a magnetic body around the coil, there is a characteristic that there is little magnetic leakage and the required inductance can be obtained with a relatively small number of turns, and is suitable for miniaturization and thinning. However, the AC resistance increases at low DC bias currents, and even a small coil current (excitation current) causes a sudden decrease in inductance due to magnetic saturation of the magnetic body (that is, DC overlap). Bad characteristics).

In particular, a high AC resistance at low DC bias currents means a large loss due to standby current, which is a big problem, for example, a short waiting time in a device such as a mobile terminal.

Thereby, substituting a part of the entire magnetic layer with the nonmagnetic layer interposes a magnetic gap in the multilayer inductor, thereby increasing the magnetic saturation level, thereby obtaining a sufficient rated current for the transformer, the choke coil, and the like. A multilayer inductor has been proposed (see Patent Document 1).

Certainly, such a structure has a certain effect on suppressing the increase in the AC resistance during the low DC bias current and reducing the deterioration of the DC superposition characteristic. However, such an effect is not necessarily sufficient, and as the number of coil turns increases, the problem decreases, and the problem is recognized.

[Patent Document 1]: Japanese Patent Laid-Open No. 2005-45108

The problem to be solved by the present invention is excellent DC overlapping characteristics, it is possible to suppress the AC resistance in the low DC bias current, the coil current is relatively inductance change in the entire current range within the rated range It is to achieve a gentle high characteristic.

According to the present invention, an electrically insulating magnetic layer and a conductor pattern are laminated, and the conductor patterns are sequentially connected. A coil is formed spirally circumferentially overlapping in the stacking direction in a magnetic body, and both ends of the coil are each formed through a lead conductor. In the multilayer inductor which is drawn out to the outer surface of the laminated chip and connected to the electrode terminal, one or more electrically insulating magnetic gap layers covering the entire laminated surface are disposed, and the conductive patterns are spaced between the conductive patterns polymerized at intervals. And an electrically insulating nonmagnetic pattern corresponding to the shape of the conductor pattern is arranged.

Here, the electrically insulating nonmagnetic pattern may have a shape that matches the conductor pattern, but it is preferable to have a shape larger or smaller than the conductor pattern. Especially, it is preferable to make it larger shape than a conductor pattern.

Further, the electrically insulating magnetic gap layer and the electrically insulating nonmagnetic pattern are preferably arranged symmetrically with respect to the center of the stacking direction. In the case where one electrically insulating magnetic gap layer is one layer, the magnetic gap layer is disposed almost at the center of the stacking direction, and the electrically insulating nonmagnetic pattern is disposed at two or more layers symmetrically with respect to the center of the stacking direction. It is also possible to set the thickness of the electrically insulating magnetic gap layer to be smaller than the interval between conductor patterns which are polymerized with each other. The electrically insulating nonmagnetic pattern is preferably arranged between all conductor patterns which are polymerized at intervals.

In the multilayer inductor according to the present invention, since one or more electrically insulating magnetic gap layers covering the entire laminated surface are disposed, the overall magnetic saturation level is increased, the DC superposition characteristic is increased, and the rated current (current upper limit value that can guarantee a predetermined inductance or higher). Can be increased. Further, in the multilayer inductor according to the present invention, an electrically insulating nonmagnetic pattern corresponding to the shape of the conductor pattern is disposed between the conductor patterns to be polymerized at intervals so as to provide a low DC bias current. It is possible to prevent the occurrence of minute magnetization loops in the vicinity of the coil, so that no rapid inflow of the magnetic flux between the conductor patterns occurs, and a sudden change in inductance can be prevented and the rise of the AC resistance can be suppressed.

1A is an explanatory diagram showing one embodiment of a multilayer inductor according to the present invention;

1B is an explanatory diagram showing one embodiment of a multilayer inductor according to the present invention;

1C is an explanatory diagram showing one embodiment of a multilayer inductor according to the present invention;

1D is an explanatory diagram showing one embodiment of a multilayer inductor according to the present invention.

Figure 2A is a longitudinal sectional view showing another embodiment of the present invention.

Figure 2B is a longitudinal sectional view showing another embodiment of the present invention.

3A is a graph showing the difference in DC overlapping characteristics between the present invention and a comparative example.

3B is a graph showing the difference in DC overlapping characteristics between the present invention and the comparative example.

Figure 4A is a graph showing the difference in frequency characteristics between the present invention and the comparative example.

4B is a graph showing the difference in frequency characteristics between the present invention and the comparative example.

4C is a graph showing the difference in frequency characteristics between the present invention and the comparative example.

* Explanation of Codes *

10 multilayer inductors

12 electrode terminal

20 Conductor Pattern

22 magnetic layer

24 lead conductor

26 magnetic gap layer

28 Nonmagnetic Pattern

Best Mode for Carrying Out the Invention

The decrease in inductance due to the increase in the DC overlapping current is caused by the increase in the magnetic flux generated from the coil due to the increase in the DC current, which saturates the magnetic material. In addition, the sudden decrease in inductance and the increase in AC resistance at the low DC bias current are caused by the micromagnetization loop around the conductor pattern. In order to suppress magnetic saturation of the magnetic body, minimize the decrease in inductance, increase the DC overlapping characteristic, and suppress the rise of the AC resistance, it is important to arrange the position and shape of the magnetic body and the nonmagnetic body with respect to the conductor pattern.

Therein, the multilayer inductor of the present invention is provided with an electrically insulating magnetic gap layer covering the entire laminated surface, and between the conductor patterns to be polymerized at intervals, the electrode pattern being close to the conductor pattern and substantially matching the shape of the conductor pattern. An insulating nonmagnetic pattern is disposed. Typically, the electrically insulating magnetic gap layer is disposed in the center of the stacking direction, and the electrically insulating nonmagnetic pattern is disposed between all conductor patterns that polymerize at intervals.

With such a structure, it is possible to control the overall magnetic saturation and to increase the DC overlapping characteristic. In addition, it is possible to prevent the rapid inflow of the magnetic flux between the conductor pattern and the conductor pattern at the time of the low direct current bias current, to prevent the sudden decrease of the inductance, and to suppress the rise of the AC resistance.

1A to 1D are explanatory views showing a temporary example of a laminated inductor according to the present invention.

Fig. 1A shows the appearance, Fig. 1B shows the perspective state seen from the top surface of the conductor pattern, Fig. 1C shows the longitudinal section, and Fig. 1D shows the structure of the conductor pattern and the nonmagnetic pattern, respectively.

The stacked pattern 10 is a chip component for surface mounting which has a substantially rectangular parallelepiped shape, and a coil is embedded in a material made mostly of a magnetic material (for example, a Ni-Zn-based ferrite material), and both ends of the coil are both ends of the chip. It is a structure electrically connected to the electrode terminal 12 formed in the inside (see Fig. 1A).

The internal coil structure is formed by printing and stacking a substantially annular (or semi-annular) conductor pattern 20 and an electrically insulating magnetic layer 22 or the like by screen printing or the like. The conductor pattern 20 is connected in a magnetic body by the magnetic layer 22 so as to circulate in a spiral while overlapping in the lamination direction to form a coil. In Fig. 1B, the conductor pattern 20 is wound in a rectangular shape while being bent at right angles, but of course, a circle or a rectangular shape may be used. Both ends of the coil are led out to opposite end surfaces of the laminated chip outer surface via the lead conductors 24, respectively, and are connected to the electrode terminals 12. FIG.

Here, in the present invention, as shown in Fig. 1C, between the conductive pattern 20 layer forming a part of the coil and the layer of the other conductive pattern 20 overlapping at intervals therebetween, all of the electrically insulating nonmagnetic materials (e.g., For example, Zn ferrite material). One part is the electrically insulating magnetic gap layer 26 over the whole lamination surface, and the other part is the nonmagnetic pattern 28 (refer FIG. 1D) substantially matching the shape of a conductor pattern. For example, a nonmagnetic pattern is printed, and a magnetic layer having a shape in which the portion is removed is printed (in reverse order). Or a conductor pattern is printed and the magnetic layer of the shape except that part is printed (in reverse order). By repeating these operations, printing can be laminated. In addition, the upper and lower conductor patterns may be electrically contacted using a via hole or the like. In this embodiment, four layers of conductor patterns 20 are provided, and between the second layer and the third layer from below, the magnetic gap layer 26 is formed over the entire lamination surface, and the first layer and the second layer from below. The nonmagnetic pattern 28 is used between the layers and between the third and fourth layers. When printing the conductor pattern 20, in order to prevent short circuit caused by the inflow of the conductor paste, the boundary between the nonmagnetic pattern 28 and the magnetic body is larger than the conductor pattern 20 as a whole, so that the conductor pattern 20 is non-magnetic. Although it is loaded with a margin in a sex pattern, it is desirable to set it so that it may be carried in a magnetic layer by making it smaller at times.

The multilayer inductor of the structure of the present invention can meet the specifications required with a relatively small number of coils for use in a DC-DC converter or the like. The position where the magnetic gap layer and the nonmagnetic pattern are inserted is appropriately determined depending on the coil shape, the number of turns, and the like.

Another embodiment of the multilayer inverter according to the present invention is shown in Figs. 2A and 2B. 2A is an example in which the thickness of the electrically insulating magnetic gap layer 26 is set smaller than the distance between the conductor patterns 20 overlapping each other. Since the basic configuration is the same as that shown in Figs. 1A to 1D, the same reference numerals are given to corresponding parts, and detailed description thereof will be omitted. The space | interval of the conductor pattern 20 which overlaps with space | interval up and down needs to be about 15 micrometers normally in order to ensure electrical insulation. On the other hand, in order to control the level of magnetic saturation, the thickness of the magnetic gap layer 26 over the entire lamination surface is set to a desired size (for example, about 7.5 µm), and the difference with the distance between the conductor patterns 20 (here 7.5 µm). The nonmagnetic pattern is additionally arranged thinly (in this example, although the upper layer of the magnetic gap layer is provided, the installation door may be provided on the lower side or may be provided evenly on both the upper and lower sides). In this way, it is possible to set the thickness of the magnetic gap layer 26 to the thickness of the conductive pattern 20 without setting a short circuit of the coil, while setting the angular spacing of the conductor patterns 20 to a size that can sufficiently secure electrical insulation.

2B is a modification of the multilayer inductor shown in FIG. 2A. Since this is basically the same configuration as that in FIG. 1, the same reference numerals are given to corresponding parts, and detailed description thereof will be omitted. In this example, the layers of the conductor pattern 20 forming a part of the coil are laminated so as to overlap each other at six layers. The regions between the conductor patterns 20 are all made of an electrically insulating nonmagnetic material, and a part (in this case, two places) of the electrically insulating magnetic gap layer 26 covering the entire laminated surface is provided. Specifically, between the second layer and the third layer from below, and between the fourth layer and the fifth layer, the magnetic gap layer 26 is formed over the entire lamination surface, and from below the first layer and the second layer Between the third layer and the fourth layer, and between the fifth layer and the sixth layer, the nonmagnetic pattern 28 is used. Also in this case, the thickness of the magnetic gap layer 26 is set thin (for example, about 7.5 mu m), and a nonmagnetic pattern having a thickness different from the conductor pattern spacing (here, 7.5 mu m) is additionally arranged.

As described above, according to the present invention, it is possible to increase or decrease the number of layers of the conductor pattern forming the coil in accordance with the requirements, and the number of magnetic gap layers, the thickness of the magnetic gap layers, the number of layers of the nonmagnetic pattern, etc. can be appropriately changed. . As described above, for example, Ni-Zn-based ferrite can be used as the magnetic material, and for example, Zn-based ferrite can be used as the nonmagnetic material for forming the magnetic gap layer or the nonmagnetic pattern.

An example of the measurement result is shown in FIG. 3A, FIG. 3B, and FIG. 4A-4C. In the two kinds of laminated patterns having the same material and the same dimension but different internal structures, their linear superposition characteristics were measured. The present invention has the same structure as the multilayer inductor shown in Figs. 1A to 1D, and has a single electrically insulating magnetic gap layer formed over the entire lamination surface at the center, and is electrically connected between all conductor patterns overlapping at intervals. It is a structure in which an insulating nonmagnetic pattern is arrange | positioned. In contrast, the comparative example has a structure in which only one electrically insulating magnetic gap layer is formed in the center (no electrically insulating nonmagnetic pattern). In all, the conductor pattern is four layers, and the coil of 4.5 turns is formed.

3A and 3B show DC bias current characteristics. 3A shows a change in inductance. Comparing the present invention with a comparative example, it can be seen that the present invention can maintain a relatively high inductance up to a high current, and the change in inductance is small even when the DC current changes. In addition, Fig. 3B shows a change in the AC resistance. Comparing the present invention with the comparative example, it can be seen that the present invention has a particularly low AC resistance at low current and a small change in AC resistance even when the DC current changes. From the above measurement results, as in the present invention, by forming an electrically insulating magnetic gap layer over the entire laminated surface and by arranging the electrically insulating nonmagnetic pattern between the conductor patterns overlapping at intervals, the DC overlapping characteristics are improved. It is understood that the AC resistance at the time of low DC bias current can be reduced.

4A to 4C show frequency characteristics. 4A shows the Q value, FIG. 4B shows the inductance, and FIG. 4C shows the AC characteristics. The present invention has a high Q value and a low AC resistance. Although the inductance is slightly low, it is possible to be nearly constant regardless of frequency. Currently, the operating frequency of the DC-DC converter is about 1 to 3 MHz, but is expected to be higher in the future (for example, close to 10 MHz). The present invention is considered to be more useful as the frequency increases because the high frequency characteristics are good.

Moreover, the coil turns can be appropriately increased or decreased in accordance with the requirements. However, if the number of coil turns excessively, the number of manufacturing steps increases and the cost increases, so it is desirable to minimize the number of coil turns necessary.

Claims (5)

The electrically insulating magnetic layer and the conductor pattern are laminated, and the conductor patterns are sequentially connected. A coil is formed spirally circumferentially overlapping in the stacking direction in the magnetic body, and both ends of the coil are connected to each other via a lead conductor. In a multilayer inductor which is drawn to the surface and connected to an electrode terminal, one or more electrically insulating magnetic gap layers covering the entire laminated surface are disposed, and adjacent to and between the conductor patterns polymerized at intervals. An electrically insulated nonmagnetic pattern corresponding to the shape of a conductor pattern is disposed. The method of claim 1, And the electrically insulating magnetic gap layer and the electrically insulating nonmagnetic pattern are symmetrically disposed with respect to the center of the stacking direction. The method of claim 1, And the electrically insulating magnetic gap layer is located at the center of the stacking direction, and the electrically insulating nonmagnetic pattern is symmetrically disposed at two or more layers with respect to the center of the stacking direction. The method of claim 1, The thickness of the electrically insulating magnetic gap layer is set smaller than the interval of the conductor pattern to be polymerized with each other. The method of claim 1, And said electrically insulating nonmagnetic pattern is disposed between all conductor patterns polymerized at intervals.

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