Laminated inductor component

Abstract

A laminated inductor component includes a multilayer body which includes a first side surface, a second side surface and a bottom surface, and in which a plurality of insulator layers is laminated in a lamination direction; a coil conductor in helical form including a plurality of coil conductor layers wound on the insulator layers, and having a coil length parallel to the lamination direction; a first outer conductor electrically connected to a first end of the coil conductor and exposed from the first side surface and the bottom surface in the multilayer body; and a second outer conductor electrically connected to a second end of the coil conductor and exposed from the second side surface and the bottom surface in the multilayer body. A width along the lamination direction of each of the first outer conductor and the second outer conductor is shorter than the coil length.

Claims

1. A laminated inductor component comprising: a multilayer body which includes a first side surface and a second side surface opposing each other, and a bottom surface connecting the first side surface and the second side surface, and in which a plurality of insulator layers is laminated in a lamination direction along the first side surface, the second side surface, and the bottom surface; a coil conductor in helical form including a plurality of coil conductor layers wound on the insulator layers, and having a coil length parallel to the lamination direction; a first outer conductor electrically connected to a first end of the coil conductor and exposed from the first side surface and the bottom surface in the multilayer body; and a second outer conductor electrically connected to a second end of the coil conductor and exposed from the second side surface and the bottom surface in the multilayer body, wherein a width along the lamination direction of each of the first outer conductor and the second outer conductor is shorter than the coil length, and an outermost layer of the plurality of insulator layers has a greater thickness in the lamination direction at the first side surface than at a midpoint of the outermost layer of the plurality of insulator layers between the first side surface and the second side surface.

2. The laminated inductor component according to claim 1, wherein when viewed from a direction orthogonal to the first side surface, an end portion of the first outer conductor on a first end side in the lamination direction overlaps with part of the coil conductor layer to be an outermost layer on the first end side.

3. The laminated inductor component according to claim 2, wherein when viewed from the direction orthogonal to the first side surface, an end portion of the first outer conductor on a second end side in the lamination direction overlaps with part of the coil conductor layer to be an outermost layer on the second end side.

4. The laminated inductor component according to claim 2, further comprising: an extended electrode connecting the first end and the first outer conductor, wherein a thickness on the first end side of the extended electrode is greater than a thickness on the first outer conductor side of the extended electrode.

5. The laminated inductor component according to claim 4, wherein a step having a different thickness is formed on the extended electrode.

6. The laminated inductor component according to claim 4, wherein a line width of the extended electrode is wider than a line width of the coil conductor layer.

7. The laminated inductor component according to claim 1, further comprising: a metal layer covering the first outer conductor, wherein both ends in the lamination direction of the metal layer are positioned in the bottom surface.

8. The laminated inductor component according to claim 2, further comprising: a metal layer covering the first outer conductor, wherein both ends in the lamination direction of the metal layer are positioned in the bottom surface.

9. The laminated inductor component according to claim 3, further comprising: a metal layer covering the first outer conductor, wherein both ends in the lamination direction of the metal layer are positioned in the bottom surface.

10. The laminated inductor component according to claim 4, further comprising: a metal layer covering the first outer conductor, wherein both ends in the lamination direction of the metal layer are positioned in the bottom surface.

11. The laminated inductor component according to claim 5, further comprising: a metal layer covering the first outer conductor, wherein both ends in the lamination direction of the metal layer are positioned in the bottom surface.

12. The laminated inductor component according to claim 6, further comprising: a metal layer covering the first outer conductor, wherein both ends in the lamination direction of the metal layer are positioned in the bottom surface.

13. A laminated inductor component comprising: a multilayer body which includes a first side surface and a second side surface opposing each other, and a bottom surface connecting the first side surface and the second side surface, and in which a plurality of insulator layers is laminated in a lamination direction along the first side surface, the second side surface, and the bottom surface; a coil conductor in helical form including a plurality of coil conductor layers wound on the insulator layers, and having a coil length parallel to the lamination direction; a first outer conductor electrically connected to a first end of the coil conductor and exposed from the first side surface and the bottom surface in the multilayer body; and a second outer conductor electrically connected to a second end of the coil conductor and exposed from the second side surface and the bottom surface in the multilayer body, wherein both ends in the lamination direction of the first outer conductor and the second outer conductor are positioned on an inner side relative to both ends in the lamination direction of the coil conductor, and an outermost layer of the plurality of insulator layers has a greater thickness in the lamination direction at the first side surface than at a midpoint of the outermost layer of the plurality of insulator layers between the first side surface and the second side surface.

14. The laminated inductor component according to claim 13, further comprising: a metal layer covering the first outer conductor, wherein both ends in the lamination direction of the metal layer are positioned in the bottom surface.

15. A laminated inductor component comprising: a multilayer body which includes a first side surface and a second side surface opposing each other, and a bottom surface connecting the first side surface and the second side surface, and in which a plurality of insulator layers is laminated in a lamination direction along the first side surface, the second side surface, and the bottom surface; a coil conductor in helical form including a plurality of coil conductor layers wound on the insulator layers, and having a coil length parallel to the lamination direction; a first outer conductor electrically connected to a first end of the coil conductor and exposed from the bottom surface in the multilayer body; and a second outer conductor electrically connected to a second end of the coil conductor and exposed from the bottom surface in the multilayer body, wherein a width along the lamination direction of each of the first outer conductor and the second outer conductor is shorter than the coil length, and an outermost layer of the plurality of insulator layers has a greater thickness in the lamination direction at the first side surface than at a midpoint of the outermost layer of the plurality of insulator layers between the first side surface and the second side surface.

16. The laminated inductor component according to claim 15, further comprising: a metal layer covering the first outer conductor, wherein both ends in the lamination direction of the metal layer are positioned in the bottom surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross-sectional view illustrating a laminated inductor component;

(2) FIGS. 2A to 2Q are explanatory diagrams illustrating a lamination process of a laminated inductor component;

(3) FIG. 3 is an explanatory diagram showing a transition of a Q factor based on changes in an outer layer thickness and a line width of a coil conductor;

(4) FIGS. 4A to 4C are cross-sectional views illustrating variations;

(5) FIG. 5 is a front view illustrating a laminated inductor component;

(6) FIGS. 6A and 6B are explanatory diagrams illustrating a production method for a step;

(7) FIG. 7 is a cross-sectional view illustrating an existing laminated inductor component;

(8) FIG. 8 is a cross-sectional view illustrating an existing laminated inductor component; and

(9) FIG. 9 is a cross-sectional view illustrating an existing laminated inductor component.

DETAILED DESCRIPTION

(10) Hereinafter, an embodiment as an aspect of the present disclosure will be described with reference to the accompanying drawings.

(11) In a laminated inductor component of the present embodiment illustrated in FIGS. 1 and 5, a plurality of coil conductor layers 23 and a plurality of insulator layers 24 are laminated by repeating, for example, a screen printing process and a photolithography process, thereby constituting a substantially rectangular parallelepiped multilayer body 11 including a first side surface 25a and a second side surface 25b opposing each other, and a bottom surface 25c connecting the first side surface 25a and the second side surface 25b. Further, there are provided a third side surface 25d and a fourth side surface 25e opposing each other in a direction orthogonal to a direction in which the first side surface 25a and the second side surface 25b oppose each other.

(12) Each coil conductor layer 23 is electrically connected through a via 14 passing through the insulator layer 24 to configure a coil conductor 12 in helical form. In outermost layers 23a and 23b of the coil conductor layer 23, a first outer conductor 13a exposed to the first side surface 25a is connected to a first end of the coil conductor 12, which is an end portion of one outermost layer, that is, the outermost layer 23a. Further, a second outer conductor 13b exposed to the second side surface 25b is connected to a second end of the coil conductor 12, which is an end portion of the other outermost layer, that is, the outermost layer 23b.

(13) The first outer conductor 13a and the second outer conductor 13b are laminated in parallel with the lamination of the coil conductor layers 23 in a lamination process of the coil conductor layers 23. The first end of the coil conductor 12 is connected to the first outer conductor 13a via an extended electrode 15a, and the second end of the coil conductor 12 is connected to the second outer conductor 13b via an extended electrode 15b.

(14) In order to increase the aspect ratio, a thickness t1 of the coil conductor layer 23 in the lamination direction (up-down direction in FIG. 1) along the first side surface 25a and the second side surface 25b is sufficiently secured, and is thicker than a thickness t2 of each of outermost layers 24a and 24b of the insulator layer 24. Widths of the first and second outer conductors 13a and 13b along the lamination direction have the same width, that is, a width d1, which is shorter than a coil length d2 of the coil conductor 12. In other words, a step g is interposed between the outermost layer 23a of the coil conductor layer 23 and the first outer conductor 13a, and an end portion in the lamination direction of the first outer conductor 13a is positioned on an inner side in the lamination direction relative to the outermost layer 23a of the coil conductor layer 23. Accordingly, the width d1 of the first outer conductor 13a is shorter in the lamination direction than the coil length d2 of the coil conductor 12.

(15) Similarly, another step g is interposed between the outermost layer 23b of the coil conductor layer 23 and the second outer conductor 13b, and an end portion in the lamination direction of the second outer conductor 13b is so formed as to be positioned on an inner side in the lamination direction relative to the outermost layer 23b of the coil conductor layer 23. Accordingly, the width of the second outer conductor 13b is shorter in the lamination direction than the coil length d2 of the coil conductor 12.

(16) Further, since the width d1 of each of the first outer conductor 13a and the second outer conductor 13b is shorter than the coil length d2, a distance d3 between the third side surface 25d and the end portion in the lamination direction of each of the first outer conductor 13a and the second outer conductor 13b is greater than the thickness t2 of the outermost layer 24b of the insulator layer 24. Also, a distance d3 between the fourth side surface 25e and the end portion in the lamination direction of each of the first outer conductor 13a and the second outer conductor 13b is greater than the thickness t2 of the outermost layer 24a of the insulator layer 24. With this configuration, when viewed from a direction orthogonal to the first side surface 25a or the second side surface 25b, both the end portions in the lamination direction of each of the first outer conductor 13a and the second outer conductor 13b overlap with part of each of the outermost layers 23a and 23b of the coil conductor layer 23.

(17) As illustrated in FIG. 1, a metal layer 16 plated with, for example, nickel Ni and tin Sn is formed on the first outer conductor 13a exposed to the first side surface 25a and the second outer conductor 13b exposed to the second side surface 25b. The metal layer 16 may be formed of silver Ag, copper Cu, lead Pd, gold Au, or the like. Further, the insulator layer 24 is formed of a ceramic material such as glass, ferrite or alumina, or a resin, etc., and the coil conductor 12 is formed of a good conductor such as silver Ag, copper Cu, or gold Au.

(18) As described above, since the width d1 of each of the first outer conductor 13a and the second outer conductor 13b is formed to be shorter than the coil length d2, the metal layer 16 is accommodated within the first side surface 25a and the second side surface 25b, and therefore, the metal layer 16 is unlikely to extend onto the third side surface 25d and the fourth side surface 25e.

(19) Next, a manufacturing process of the laminated inductor component of the present embodiment will be described with reference to FIGS. 2A to 2Q.

(20) As illustrated in FIG. 2A, by repeating a process in which an insulating paste containing borosilicate glass as the main ingredient is applied onto a carrier film (not illustrated) by screen printing, an insulator layer 17a for an outer layer having an appropriate thickness is formed.

(21) Next, as illustrated in FIG. 2B, a photosensitive insulating paste is applied onto the insulator layer 17a for the outer layer by screen printing, and an insulating paste layer 18a including an opening 18 is formed by a photolithography process. The opening 18 is a portion where the insulating paste layer 18a is removed and the insulator layer 17a for the outer layer is exposed, and the portion other than the opening 18 is a portion where the insulating paste layer 18a remains. A step g is formed at an end portion of the opening 18.

(22) Next, as illustrated in FIG. 2C, by the application of the photosensitive insulating paste and the photolithography process, a bank portion 18b is formed by laminating an insulating paste layer at only one side of the opening 18 in a predetermined range, and a groove 19a is formed between the bank portion 18b and the step g.

(23) Note that the bank portion 18b may be formed by removing part of the insulating paste layer 18a without depending on only the lamination of the insulating paste layer. As for the shape of the groove 19a, a step on the bank portion 18b side is formed to be high relative to the opening 18, and the bank portion 18b is a base portion at a time when the insulator layer 24 is laminated.

(24) Next, as illustrated in FIG. 2D, the groove 19a is filled with the photosensitive conductive paste layer to be the outermost layer 23a of the coil conductor layer 23 and the first and second outer conductors 13a and 13b, by the screen printing and the photolithography process.

(25) Next, as illustrated in FIG. 2E, an insulating paste layer 18c including the via 14 is formed, and as illustrated in FIG. 2F, a groove 19b for forming the coil conductor layer 23 and the first and second outer conductors 13a and 13b is formed.

(26) Thus, as illustrated in FIGS. 2G to 2N, by laminating the insulating paste layer and the conductive paste layer in sequence, the insulating paste layer 18a to an insulating paste layer 18f, the coil conductor layer 23, and the first and second outer conductors 13a and 13b are laminated.

(27) Then, as illustrated in FIGS. 2N to 2P, the outermost layer 23b of the coil conductor layer 23 is so formed as to include the step g, and as illustrated in FIG. 2Q, an insulator layer 17b for an outer layer is further formed, whereby the outermost layer 24b of the insulator layer 24 is formed along the step g.

(28) The lamination process illustrated in FIGS. 2A to 2Q is described for one laminated inductor component. However, in practice, a large number of laminated inductor components may be manufactured as a mother multilayer body in which the stated laminated inductor components are arranged in matrix form.

(29) In this case, the mother multilayer body is cut with a dicing machine into individual multilayer bodies 11 each including a single coil conductor 12, and thereafter the individual multilayer bodies 11 are fired. Then, after barrel finishing is performed on the multilayer body 11, by the outer conductors 13a and 13b of the multilayer body 11 being plated with the metal layer 16, the laminated inductor component including the coil conductor 12 is formed inside the multilayer body 11.

(30) FIG. 3 shows a change in a Q factor with respect to an input signal of about 1 GHz, when the thickness t2 of each of the outermost layers 24a and 24b of the insulator layer 24 and the line width of the coil conductor layer 23 are changed in the laminated inductor component constituted as described above. In this figure, a characteristics line A shows a case where the thickness t2 of each of the outermost layers 24a and 24b is about 6 μm and the line width of the coil conductor layer 23 is about 15 μm, a characteristics line B shows a case where the thickness t2 is about 16 μm and the line width of the coil conductor layer 23 is about 20 μm, and a characteristics line C shows a case where the thickness t2 is about 28 μm and the line width of the coil conductor layer 23 is about 25 μm.

(31) As shown in FIG. 3, when the thickness t2 is reduced, it is possible to increase the aspect ratio of the coil conductor 12 within a limited outer shape size of the multilayer body 11 and to improve the Q factor.

(32) Next, action of the laminated inductor component of the present embodiment constituted as described above will be described.

(33) In the laminated inductor component of the present embodiment, the thickness t1 of the coil conductor layer 23 is increased, so that the resistance of the coil conductor 12 is reduced. In particular, since a high-frequency signal flowing through the coil conductor 12 mainly passes through an inner diameter side surface of the coil conductor 12, when the thickness t1 of the coil conductor layer 23 increases, alternating current resistance (Rac) decreases. Therefore, the Q factor of the laminated inductor component is improved.

(34) Here, as the thickness t1 of the coil conductor layer 23 increases, the coil length d2 increases; however, the width d1 of each of the outer conductors 13a and 13b is shorter than the coil length d2. Therefore, the metal layer 16, with which the surfaces of the outer conductors 13a and 13b are plated, does not extend onto the third side surface 25d and the fourth side surface 25e of the multilayer body 11. As a result, generation of a variation in the outer diameter dimension of the laminated inductor component is suppressed. Further, since the metal layer 16 does not extend onto the third side surface 25d and the fourth side surface 25e of the multilayer body 11, a range in which the passage of magnetic flux is prevented is reduced, and efficiency in obtaining inductance in the laminated inductor component is improved.

(35) Note that the first and second outer conductors 13a and 13b are formed being laminated through the same process as the lamination process of the coil conductor layer 23 and the outermost layers 23a and 23b thereof. Therefore, dimensional accuracy of positioning of the first and second outer conductors 13a and 13b in the lamination direction is improved with respect to the coil conductor layer 23 and the outermost layers 23a and 23b thereof. Accordingly, dimensional accuracy of the width d1 of each of the first and second outer conductors 13a and 13b as well as the step g is improved.

(36) With the laminated inductor component constituted as described above, the following effects can be obtained.

(37) (1) Since the width d1 of each of the first and second outer conductors 13a and 13b is made shorter than the coil length d2 of the coil conductor 12, it is possible to prevent the metal layer 16, with which the first and second outer conductors 13a and 13b are plated, from extending onto the third side surface 25d and the fourth side surface 25e. Accordingly, it is possible to suppress the variation in the outer diameter dimension of the multilayer body 11 incorporating the inductor formed of the coil conductor 12, and to smoothly mount the multilayer body 11 to the mounting position by the mounting device in the mounting process, and to prevent the occurrence of short circuit with an adjacently mounted component.

(38) (2) By making the distances d3 between both the end portions in the lamination direction of the first and second outer conductors 13a, 13b and the third and fourth side surfaces 25d, 25e be greater than the thicknesses t2 of the outermost layers 24a and 24b of the insulator layer 24, it is possible to increase the aspect ratio of the coil conductor layer 23 without increasing the outer shape of the multilayer body 11. Accordingly, it is possible to reduce the resistance of the coil conductor 12 and to improve the Q factor of the inductor formed of the coil conductor 12.

(39) (3) Since it is possible to prevent the metal layer 16, with which the first and second outer conductors 13a and 13b are plated, from extending onto the third side surface 25d and the fourth side surface 25e, efficiency in obtaining the inductance can be enhanced.

(40) (4) Since the first and second outer conductors 13a and 13b can be formed being laminated through the same process as the lamination process of the coil conductor 12, the positional accuracy of each of the first and second outer conductors 13a and 13b with respect to the coil conductor 12 can be enhanced. Further, in comparison with a case where the first and second outer conductors 13a and 13b are formed in different processes, the number of processes can be decreased.

(41) The above embodiment may be modified as follows.

(42) As illustrated in FIG. 4A, the steps g may be formed not at the connection portions between the first and second outer conductors 13a, 13b and the extended electrodes 15a, 15b, but at the connection portions between the outermost layers 23a, 23b of the coil conductor layer 23 and the extended electrodes 15a, 15b. Like in the above-described embodiment, these steps g can be formed in the process illustrated in FIG. 6A. In this case, by forming the steps g, the thickness in the lamination direction of each of the extended electrodes 15a and 15b is thinner than the thickness of each of the outermost layers 23a and 23b of the coil conductor layer 23.

(43) As such, as illustrated in FIG. 5, it is preferable that a line width w2 of each of the extended electrodes 15a and 15b be formed wider than a line width w1 of the coil conductor layer 23, and that the cross-sectional area of each of the extended electrodes 15a and 15b be formed equal to or larger than that of the outermost layers 23a and 23b of the coil conductor layer 23 respectively. Thus, an increase in resistance at each of the portions of the extended electrodes 15a and 15b can be suppressed.

(44) As illustrated in FIG. 4B, at the connection portions between the extended electrodes 15a, 15b and the first and second outer conductors 13a, 13b, by forming slopes 21, as the steps, at end portions in a longitudinal direction of the first and second outer conductors 13a and 13b, the width of each of the first and second outer conductors 13a and 13b along the lamination direction may be configured to be shorter than the coil length.

(45) As illustrated in FIG. 4C, at the connection portions between the extended electrodes 15a, 15b and the first and second outer conductors 13a, 13b, by forming slopes 22, as the steps, on the extended electrodes 15a and 15b, the width of each of the outer conductors 13a and 13b along the lamination direction may be configured to be shorter than the coil length.

(46) The slopes 21 and 22 illustrated in FIGS. 4B and 4C can be formed in the process illustrated in FIG. 2B, for example, by changing the thickness of the insulating paste 18a to be applied at an end portion of the groove 19a, as illustrated in FIG. 6B, by a pattern printing method with a screen mask where used is the screen mask in which only a portion for forming the step is open. Alternatively, at the end portion of the groove 19a, the above-mentioned slope may be formed by increasing the number of times of application. According to these methods, the step is formed at the end portion of the groove 19a, and the insulating paste flows from a thicker application-thickness portion toward a thinner application-thickness portion of the insulating paste layer 18a to form the slope.

(47) The step g and the slopes 21, 22 as illustrated in FIGS. 4A to 4C may be formed by half-etching while adjusting an exposure amount, a development time, and an amount of etching in a photolithography process.

(48) The manufacturing process of the laminated inductor component of the present embodiment is merely an example, and other known methods may be used. For example, the layer may be formed by spin coating or spray coating, or may be patterned by laser processing or drilling. Further, a sheet lamination method, a printing lamination method, or the like may be used.

(49) The metal layer is not limited to a layer formed by plating, and may be a resin electrode or a metal layer formed by sputtering.

(50) In the embodiment, although the width d1 is made shorter than the coil length d2 by the lamination process, the width d1 of each of the first outer conductor 13a and the second outer conductor 13b may be formed to be shorter than the coil length d2 by, for example, a pressing process in the sheet lamination method.

(51) The multilayer body 11 may have a mounting area of “0201”, i.e., about 0.2 mm×about 0.1 mm, or “0402”, “0603”, “1005” or the like. The above-discussed embodiment is particularly useful in a case of forming a multilayer body having a size of equal to or smaller than “0402”.

(52) While some embodiments of the disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the disclosure. The scope of the disclosure, therefore, is to be determined solely by the following claims.