Electronic component

An electronic component includes overlapping coils in a rectangular laminate to form a substantially annular orbit. The orbit passes about an intersection of diagonal lines of an insulator layer of the laminate and is divided into a first orbit portion and a second orbit portion by a straight line parallel to a short side of the insulator layer. When an orbit obtained by the axisymmetric movement of the first orbit portion relative to the straight line is defined as a third orbit portion, a part of the second orbit portion overlaps with a part of the third orbit portion, and the non overlapped portion of the second orbit portion is positioned closer to the intersection than the non overlapped portion of the third orbit portion. A via hole conductor is provided in a region outboard an outer side of the non overlapping portion of the second orbit portion and inboard an outer side of the non overlapping portion of the third orbit portion.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Japanese Patent Application No. JP 2009-150418, filed Jun. 25, 2009, the entire contents of which are incorporated herein by reference in their entirety.

BACKGROUND

1. Field of the Invention

The present invention relates to an electronic component, and more particularly, relates to an electronic component containing a coil.

2. Description of the Related Art Japanese Unexamined Patent Application Publication No. 2002-260925 (the '925 application) describes a known multilayer chip inductor.FIG. 9is a perspective view of a multilayer chip inductor500described in the '925 application.

The multilayer chip inductor500has a laminate502, external electrodes504aand504b, via hole conductors506aand506b, and a coil L as shown inFIG. 9. The laminate502is obtained by laminating insulator layers and contains the coil L. The coil L is a spiral coil having a coil axis extending in the lamination direction (vertical direction ofFIG. 9). The external electrodes504aand504bare provided on the bottom surface of the laminate502. The via hole conductors506aand506beach are provided in such a manner as to extend in the lamination direction while being exposed to the side surfaces of the laminate502, and connect the ends of the coil L and the external electrodes504aand504b.

Here, the via hole conductors506aand506bwill be described in detail. The via hole conductors506aand506bform a semi-circular shape when viewed in plan view in the lamination direction. This is because the via hole conductors506aand506bare formed by dividing a substantially cylindrical via hole conductor extending in the lamination direction into two parts. More specifically, when a mother laminate is cut into separate laminates502, a via hole conductor formed extending over two laminates502is divided into two via hole conductors.

In the multilayer chip inductor500, the diameter of the coil L can be enlarged, and thus a high inductance value can be achieved. In more detail, the via hole conductors506aand506bare provided in such a manner as to be exposed to the side surfaces of the laminate502. Thus, in the multilayer chip inductor500, an area where the coil L can be formed becomes large compared with the case where the via hole conductors506aand506bare formed in the laminate502. Thus, in the multilayer chip inductor500, the diameter of the coil L can be enlarged, and thus a high inductance value can be obtained.

However, the multilayer chip inductor500has a problem in that the resistance value between the external electrodes504aand504bvaries as described later. In more detail, the coil L is connected to the external electrodes504aand504bthrough the via hole conductors506aand506b, respectively. The via hole conductors506aand506bare formed by dividing a substantially cylindrical via hole conductor into two parts as described above. Thus, the shape of the via hole conductors506aand506bvaries due to variation in the cut position when the mother laminate is cut. As a result, the resistance value of the via hole conductors506aand506bvaries, and thus the resistance value between the external electrode504aand504balso varies.

SUMMARY

Embodiments consistent with the claimed invention provide an electronic component that allows for obtaining a high inductance value and can reduce variation in a resistance value.

According to an embodiment consistent with the claimed invention, an electronic component includes a plurality of substantially rectangular insulator layers formed as a laminate in a lamination direction. A coil is provided in the laminate in such a manner that a first end of the coil is positioned at an upper side in the lamination direction relative to a second end of the coil. External electrodes are provided at an undersurface of the laminate, and a via hole conductor is provided in the laminate and connects the first end of the coil to one of the external electrodes.

The coil is formed by connecting a plurality of coil conductors that are overlapped with each other to form a substantially annular orbit when viewed in plan view in the lamination direction. The substantially annular orbit is arranged about an intersection of diagonal lines of the insulator layers and is divided into a first orbit portion and a second orbit portion by a straight line parallel to a short side of the rectangular insulator layers.

When an orbit obtained by an axisymmetric movement of the first orbit portion relative to the straight line is defined as a third orbit portion, a part of the second orbit portion is overlapped with a part of the third orbit portion, and a portion of the second orbit portion non overlapped with the third orbit portion is positioned closer to the intersection than a non overlapped portion of the third orbit portion.

The via hole conductor is provided in a region outboard the non overlapped portion of the second orbit portion and inboard an outer side of the non overlapped portion of the third orbit portion.

DETAILED DESCRIPTION

Hereinafter, an electronic component according to exemplary embodiments will be described with reference to the drawings.FIG. 1is a perspective view of the electronic component10according to embodiments.FIG. 2is an exploded perspective view of a laminate12of an electronic component10according to one embodiment. Hereinafter, the lamination direction of the electronic component10is defined as the z axis direction or the direction in which insulator layers, described in detail later, are laminated to form the laminate12. The direction along the short side of the electronic component10is defined as the x axis direction, and the direction along the long side of the electronic component10is defined as the y axis direction. The x axis, the y axis, and the z axis are orthogonal to each other.

The electronic component10has the laminate12, external electrodes14aand14b, a coil L, and via hole conductors V1and V2(not shown inFIG. 1) as shown inFIG. 1andFIG. 2. The laminate12has a substantially rectangular parallelepiped shape and contains the coil L and the via hole conductors V1and V2.

The external electrodes14aand14bare electrically connected to the coil L through the via hole conductors V1and V2, respectively and are provided on the bottom surface (undersurface) located on the negative direction side in the z axis direction of the laminate12. In this embodiment, the external electrode14ais provided along the side located on the positive direction side in the y axis direction on the bottom surface of the laminate12and the external electrode14bis provided along the side located on the negative direction side in the y axis direction relative to the external electrode14aon the bottom surface of the laminate12.

As shown inFIG. 2, the laminate12is constituted by laminating insulator layers16a,17ato17j, and16bin this order in the z axis direction. The insulator layers16a,17ato17j, and16beach form a substantially rectangular shape and are formed of magnetic materials containing, for example a Ni—Cu—Zn ferrite.

The coil L is constituted by coil conductors18ato18jand via hole conductors v12to v20as shown inFIG. 2. More specifically, the coil L is constituted by connection of the coil conductors18ato18jby the via hole conductors v12to v20. The coil L has a coil axis extending in the z axis direction and has a spiral shape in which the coil is directed to the positive direction side in the z axis direction while turning in the clockwise direction (the direction of arrow A shown with coil conductor18j). The end t1of the coil L is positioned on the positive direction side in the z axis direction relative to the end t2of the coil L.

The coil conductors18ato18jare provided on the insulator layers17ato17j, respectively, as shown inFIG. 2. Each of the coil conductors18ato18jcan contain Ag-containing conductive materials, have a number of turns of about ⅞ turn, and can be formed by bending a line conductor. The coil conductor18ahas a number of turns of about ¾ turn. More specifically, the coil conductors18ato18jhave a shape such that a part of a substantially annular orbit, or ring (¼ in the coil conductor18aand ⅛ in the coil conductors18bto18j) is cut or not present. The coil conductors18ato18jare overlapped with each other to constitute a substantially annular orbit R when viewed in plan view in the z axis, as shown in dashed lines on insulator layer16a. The end t1of the coil L is the end on the downstream side in the direction of the arrow A of the coil conductor18aand the end t2of the coil L is the end on the upstream side in the direction of the arrow A of the coil conductor18j.

The via hole conductors v12to v20connect the coil conductors18ato18j. More specifically, the via hole conductor v12connects the position apart from the end t1of the coil conductor18aby only about ⅝ turn in the direction of the arrow A and the end on the downstream side in the direction of the arrow A of the coil conductor18b. The via hole conductor v13connects the end on the upstream side in the direction of the arrow A of the coil conductor18band the end on the downstream side in the direction of the arrow A of the coil conductor18c. The via hole conductor v14connects the end on the upstream side in the direction of the arrow A of the coil conductor18cand the end on the downstream side in the direction of the arrow A of the coil conductor18d. The via hole conductor v15connects the end on the upstream side in the direction of the arrow A of the coil conductor18dand the end on the downstream side in the direction of the arrow A of the coil conductor18e. The via hole conductor v16connects the end on the upstream side in the direction of the arrow A of the coil conductor18eand the end on the downstream side in the direction of the arrow A of the coil conductor18f. The via hole conductor v17connects the end on the upstream side in the direction of the arrow A of the coil conductor18fand the end on the downstream side in the direction of the arrow A of the coil conductor18g. The via hole conductor v18connects the end on the upstream side in the direction of the arrow A of the coil conductor18gand the end on the downstream side in the direction of the arrow A of the coil conductor18h. The via hole conductor v19connects the end on the upstream side in the direction of the arrow A of the coil conductor18hand the end on the downstream side in the direction of the arrow A of the coil conductor18i. The via hole conductor v20connects the end on the upstream side in the direction of the arrow A of the coil conductor18iand the end on the downstream side in the direction of the arrow A of the coil conductor18j.

As shown inFIG. 2, the via hole conductors v1to vii penetrate the insulator layers17ato17jand16bin the z axis direction and are connected in a straight line to constitute one via hole conductor V1. The via hole conductor V1is provided in the laminate12and connects the end t1of the coil L and the external electrode14a. More specifically, the end positioned on the positive direction side in the z axis direction of the via hole conductor V1is connected to the end on the downstream side in the direction of the arrow A of the coil conductor18aand the end positioned on the negative direction side in the z axis direction of the via hole conductor V1is connected to the external electrode14a.

Via hole conductors v21and v22(V2) penetrate the insulator layers17jand16bin the z axis direction as shown inFIG. 2. The via hole conductors v21and v22(V2) are provided in the laminate12and connect the end t2of the coil L and the external electrode14b. More specifically, the end positioned on the positive direction side in the z axis direction of the via hole conductor V2is connected to the end on the upstream side in the direction of the arrow A of the coil conductor18jand the end positioned on the negative direction side in the z axis direction of the via hole conductor V2is connected to the external electrode14b.

Next, the positional relationship between the via hole conductor V1and the orbit R will be described with reference to the drawings.FIG. 3is a perspective view of the laminate12as viewed from the z axis.

The via hole conductor V1is provided at the outside of the orbit R containing the coil conductors18ato18jas shown inFIG. 3A. Thus, the via hole conductor V1does not pass through the inside of the coil L, and thus does not block the magnetic flux generated by the coil L.

As shown inFIG. 3A, the orbit R passes the intersection of the diagonal lines C1and C2of the insulator layer16aand is classified into an orbit portion R1and an orbit portion R2by a straight line L1parallel to the short side of the insulator layer16a. Specifically, in the orbit R, a portion positioned on the negative direction side in the y axis direction relative to the straight line L1is an orbit portion R1and a portion positioned on the positive direction side in the y axis direction relative to the straight line L1is an orbit portion R2. As shown inFIG. 3B, when an orbit obtained by the axisymmetric movement of the orbit portion R1relative to the straight line L1is defined as an orbit R3, a part of the orbit portion R2(hereinafter referred to as an orbit portion r2) is overlapped with a part of the orbit portion R3(hereinafter referred to as an orbit portion r3). The remaining non overlapped portion (hereinafter referred to as an orbit portion r4) of the orbit portion R2is positioned closer to the intersection P than the remaining non overlapped portion (hereinafter referred to as an orbit portion r5) of the orbit portion R3. The remaining portions of the orbit portions R2and R3(orbit portions r4and r5) refer to portions other than the orbit portions r2and r3in the orbit portions R2and R3.

The orbit portions R1and R3are combined to form a substantially rectangular orbit as shown inFIG. 3B. The orbit portion r5constitutes the corner of the substantially rectangular orbit defined by the orbit portions R1and R3.

As shown inFIG. 3B, the via hole conductor V1is provided in a region E outboard an outer side of the orbit portion r4and inboard an outer side of the orbit portion r5when viewed in plan view from the z axis direction. The via hole conductor V1is provided at the position overlapping with the orbit portion R2when viewed from the long side direction (i.e., y axis direction) and the short side direction (i.e., x axis direction) of the insulator layer16a. In this embodiment, the via hole conductor V1is positioned at the corner constituted by the orbit portion r5when viewed in plan view from the z axis. The orbit portion r4forms a substantially arc shape projecting toward the intersection P and forms a substantially arc shape centering on the via hole conductor V1. Thus, as shown inFIG. 2, the maximum proximity distance of the coil conductors18bto18fand18hto18jand the via hole conductor V1is fixed.

According to the electronic component10, a high inductance value can be obtained. In more detail, in the electronic component10, the via hole conductor V1extends in the z axis direction in the outside of the coil L and does not pass through the inside of the coil L. Therefore, the via hole conductor V1does not block the magnetic flux passing through the inside of the coil L. Thus, a high inductance value can be obtained in the electronic component10.

Furthermore, in the electronic component10, the via hole conductor V1is provided in a region E surrounded by the orbit portions r4and r5when viewed in plan view from the z axis direction as shown inFIG. 3and is provided at a position overlapping with the orbit portion R2when viewed in plan view from the long side direction and the short side direction of the insulator layer16a. More specifically, the coil conductors18ato18jdraw a substantially rectangular orbit and form a substantially arc shape projecting toward the intersection P of the diagonal lines C1and C2only in the vicinity of the via hole conductor V1, thereby avoiding the via hole conductor V1. Thus, each side of the coil conductors18ato18jcan be brought close to each side of the insulator layers17ato17jas much as possible and the contact of the via hole conductor V1and the coil conductors18ato18jcan be avoided. Therefore, in the electronic component10, the coil L can be enlarged, and a high inductance value can be obtained.

Furthermore, in the electronic component10, variation in the resistance value between the external electrodes14aand14bcan be reduced. More specifically, in the multilayer chip inductor500described in Japanese Unexamined Patent Application Publication No. 2002-260925, the via hole conductors506aand506bare formed by dividing a substantially cylindrical via hole conductor into two parts as described above. Therefore, the shape of the via hole conductors506aand506bvaries due to variation in the cut position when a mother laminate is cut. As a result, the resistance values of the via hole conductors506aand506bvary, and thus the resistance value between the external electrodes504aand504balso varies.

In contrast, in the electronic component10, the via hole conductor V1and V2are not divided. Therefore, in the electronic component10, the resistance values of the via hole conductors V1and V2are hard to vary, and thus the variation in the resistance value between the external electrodes14aand14bcan be reduced.

As shown inFIG. 3B, in the electronic component10, the orbit portion r4forms a substantially arc shape projecting toward the intersection P and forms a substantially arc shape centering on the via hole conductor V1. Thus, as shown inFIG. 2, the maximum proximity distance of the coil conductors18bto18fand18hto18jand the via hole conductor V1is fixed. More specifically, in the electronic component10, the distance between the coil conductors18bto18fand18hto18jand the via hole conductor V1can be made small while maintaining the insulation state of the coil conductors18bto18fand18hto18jand the via hole conductor V1. As a result, in the electronic component10, the coil L can be enlarged as much as possible, and a high inductance value can be obtained.

In the electronic component10, as shown inFIG. 3B, the via hole conductor V1is positioned at the corner constituted by the orbit portion r5when viewed in plan view from the z axis. Thus, due to the presence of the via hole conductor V1, the reduction amount of the area of the coil L when viewed in plan view from the z axis can be suppressed to be equal to the area of a substantially sector shape having a central angle of about 90°. Therefore, in the electronic component10, a high inductance value can be obtained.

The inventors performed computer simulation described below in order to further clarify the effects demonstrated by the electronic component10.FIG. 4is a perspective view from the z axis direction of a laminate112of an electronic component according to a comparative example.

The inventors produced a model of the electronic component10having the structure shown inFIG. 1andFIG. 2as a first model. Moreover, the inventors produced a model of an electronic component having the laminate112shown inFIG. 4as a second model which is a comparative example. As is understood from the comparison betweenFIGS. 3A and 3BandFIG. 4, the area of the coil L of the first model is larger than that of the second model. Other simulation conditions are as follows: chip size: about 2.5 mm×about 2.0 mm×about 1.1 mm; diameter of via-hole conductor: about 100 μm to about 150 μm; line width of coil conductor: about 250 μm to about 250 μm; thickness of coil conductor: about 20 μm to about 60 μm; number of turns of coil L: about 8.5 turns; maximum proximity distance of via hole conductor V1and coil L: about 200 μm; area of coil L when viewed in plan view from the z axis: about 1.0 mm2to About 1.5 mm2; number of insulator layers16a:10 to 30 layers. For the insulator layers17a,17d, and17h, non-magnetic material layers were used.

Using the first model and the second model, the relationship between the current value flowing into the coil L and the inductance value was analyzed.FIG. 5andFIG. 6are graphs showing the simulation results. InFIG. 5, the vertical axis represents the inductance value and the horizontal axis represents the current value. InFIG. 6, the vertical axis represents the inductance value change rate and the horizontal axis represents the current value. The inductance value change rate is a value obtained by (Inductance value at each current value−Inductance value at a current value of 0)/Inductance value at a current value of 0×100.

According to the simulation results shown inFIG. 5, a higher inductance value is obtained by the first model rather than by the second model. Therefore, it is found that, in the electronic component10, a high inductance value can be obtained.

Moreover, the simulation results shown inFIG. 6show that a reduction in the inductance value change rate when the current value increases is smaller in the first model than in the second model. Therefore, it is found that the direct current superposition characteristics of the first model are superior to those of the second model. This is because it is considered that since the area of the coil L of the first model is larger than the area of the coil L of the second model, it is more difficult for magnetic saturation to occur. Hereinafter, a method for manufacturing the electronic component10will be described with reference to the drawings. Hereinafter, a method for manufacturing the electronic component10for simultaneously manufacturing a plurality of the electronic components10will be described.

First, ceramic green sheets are prepared to serve as the insulator layers16a,16b, and17ato17jofFIG. 2. Specifically, ferric oxide (Fe2O3), zinc oxide (ZnO), copper oxide (CuO), and nickel oxide (NiO) are weighed in a given ratio, the respective materials are supplied in a ball mill as raw materials, and wet mixing is performed. The obtained mixture is dried and ground, and the obtained powder is calcined at about 800° C. for about 1 hour. The obtained calcined powder is subjected to wet-grinding in a ball mill, dried, and then disintegrated, thereby obtaining ferrite ceramic powder.

To the ferrite ceramic powder, a binding agent (vinyl acetate, water-soluble acryl, and the like), a plasticizer, a wetting material, and a dispersing agent are added, mixed in a ball mill, and degassed by reducing a pressure. The obtained ceramic slurry is formed in a sheet shape on a career sheet by a doctor blade method, and is dried, thereby producing ceramic green sheets to serve as the insulator layers16a,16b, and17ato17j.

Next, as shown inFIG. 2, the via hole conductor v1to v22are formed in each of the ceramic green sheets to serve as the insulator layers17ato17jand16b. Specifically, the ceramic green sheets to serve as the insulator layers17ato17jand16bare irradiated with a laser beam to form via holes. Next, the via holes are charged with a conductive paste of Ag, Pd, Cu, Au, alloys thereof, or the like by a printing and coating method or the like.

Next, as shown inFIG. 2, the coil conductors18ato18jare formed on the principal surface (hereinafter referred to as a front surface) on the positive direction side in the z axis direction of the ceramic green sheets to serve as the insulator layers17ato17j. Specifically, on the front surface of the ceramic green sheets to serve as the insulator layers17ato17j, a conductive paste containing Ag, Pd, Cu, Au, alloys thereof, or the like as the main ingredients is applied by a screen-printing method, a photolithographic method, or the like, thereby forming the coil conductors18ato18j. The process for forming the coil conductors18ato18jand the process for charging the via holes with a conductive paste may be performed in the same process.

As shown inFIG. 2, the external electrodes14aand14bare formed on the principal surface (hereinafter referred to as a rear surface) on the negative direction side in the z axis direction of the ceramic green sheet to serve as the insulator layer16b. Specifically, the external electrodes14aand14bare formed by applying a conductive paste containing Ag, Pd, Cu, Au, alloys thereof, or the like as the main ingredients to the rear surface of the ceramic green sheet to serve as the insulator layer16bby a screen-printing method, a photolithographic method, or the like.

Next, as shown inFIG. 2, the ceramic green sheets to serve as the insulator layers16a,17ato17j, and16bare laminated and bonded under a pressure in this order, thereby obtaining a non-calcined mother laminate. In the lamination and bonding under a pressure of the ceramic green sheets to serve as the insulator layers16a,17ato17j, and16b, the ceramic green sheets are laminated one by one and pre-bonded under a pressure to obtain a mother laminate, and then a non-calcined mother laminate is pressurized by isostatic pressing or the like for bonding under a pressure.

Next, the mother laminate is cut into a laminate12having a given dimension (e.g., about 2.5 mm×about 2.0 mm×about 1.1 mm) with a cutting edge. Thus, a non-calcined laminate12is obtained. The non-calcined laminate12is subjected to binder removal treatment and calcination. The binder removal treatment is performed at about 500° C. in a low oxygen environment for about 2 hours, for example. The calcination is performed at about 800° C. to about 900° C. for about 2.5 hours, for example. By the above-described processes, the electronic component10as shown inFIG. 1is completed. Hereinafter, electronic components10aand10baccording to modifications will be described.FIG. 7is a perspective view from the z axis of a laminate12aof an electronic component10aaccording to a first exemplary modification.

In the laminate12ashown inFIG. 7, the coil L has a spiral shape in which the coil is directed to the positive direction side in the z axis direction while turning in the clockwise direction (the direction of the arrow A) in the same manner as in the coil L of the electronic component10. Then, as shown inFIG. 7, the end t1of the coil L is positioned at the corner on the positive direction side in the x axis direction and on the positive direction side in the y axis direction. In contrast, as shown inFIG. 7, the end t2of the coil L is positioned at the corner on the positive direction side in the x axis direction and on the negative direction side in the y axis direction. More specifically, the end t1is provided at the corner at the farthest position in the direction of the arrow A as viewed from the end t2. Thus, the distance between the end t1and the end t2can be enlarged, and thus the number of turns of the coil L can be increased.

FIG. 8is a perspective view from the z axis direction of a laminate12bof an electronic component10baccording to a second modification. As shown inFIG. 8, the orbit portion r4may be provided not at the corner but on the short side on a substantially rectangular orbit constituted by the orbit portions R1and R3. In this case, the orbit portion r4draws a semi-circular orbit portion centering on the via hole conductor V1. Although not shown, the orbit portion r4may be provided on the long side on a substantially rectangular orbit constituted by the orbit portions R1and R3. In this case, the external electrode14ais provided on the bottom surface of the laminate12aalong the side positioned on the negative direction side in the x axis direction and the external electrode14bis provided on the bottom surface of the laminate12aalong the side positioned on the positive direction side in the x axis direction.

In the electronic components10,10a, and10b, the orbit constituted by the orbit portions R1and R3have a substantially rectangular shape. However, the shape of the orbit constituted by the orbit portions R1and R3is not limited to a substantially rectangular shape.

The orbit portion r4forms a substantially arc shape. However, the orbit portion r4may not be a substantially arc shape and may be constituted by combination of straight lines.

Embodiments consistent with the claimed invention are useful for electronic components, and are particularly excellent in the respect that a high inductance value can be obtained and that variation in a resistance value can be reduced.

Although a limited number of embodiments are described herein, one of ordinary skill in the art will readily recognize that there could be variations to any of these embodiments and those variations would be within the scope of the appended claims. Thus, it will be apparent to those skilled in the art that various changes and modifications can be made to the electronic component described herein without departing from the scope of the appended claims and their equivalents.