JP2005167029A - Laminated inductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated inductor wherein the amount of a conductor paste is decreased, the DC resistance value thereof is reduced, and the inductance value thereof can be set to a desired value. <P>SOLUTION: The laminated inductor 1 comprises an element 2 and a pair of terminal electrodes 3, 3 formed on both side surfaces of the element 2. The element 2 comprises a magnetic substance laminated part 4 and a coil-shaped conductor 5 built in the magnetic substance laminated part 4. The coil-shaped conductor 5 comprises a plurality of conductor patterns 7 and has a nearly semi-circular cross-section. Further, both ends 5a, 5b of the coil-shaped conductor 5 are led out to the edge of the magnetic substance laminated part 4 and connected to the terminal electrodes 3, 3 respectively. Moreover, the thickness X of the conductor pattern 7 is equal to 90-115% of the distance Y between two conductor patterns 7 adjacent in the lamination direction, and the edges 5c, 5d of the conductor pattern 7 in the widthwise direction thereof are rounded. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a multilayer inductor.

  In general, inductors that can be surface-mounted are roughly classified into a laminated type and a wound type depending on the construction method. Of these, multilayer inductors are relatively easy to downsize, and are therefore used in various devices such as chokes and signals.

As such a multilayer inductor, for example, one described in Patent Document 1 below is known. In Patent Document 1, conductive powder paste, magnetic powder paste, and nonmagnetic powder paste are used, and a single layer thickness is about 30 μm for the magnetic layer and nonmagnetic layer, and about 15 μm for the conductor. A multilayer inductor that has been printed and laminated is disclosed.
JP-A-8-236354

  However, in the conventional multilayer inductor including the one described in Patent Document 1, the internal electrode (conductor) is formed in a sheet shape (thin film shape) having a very small cross-sectional area. Therefore, the DC resistance value which is an important characteristic for choke applications is high. Therefore, it is conceivable to increase the cross-sectional area of the internal electrode. In this case, however, the amount of the conductive paste constituting the internal electrode increases.

  In general, the multilayer inductor is fired during the manufacturing process. At that time, the magnetic layer shrinks due to evaporation of the solvent contained therein, but the internal electrode is thin and hardened without shrinking so much. For this reason, the magnetic layer whose hardness is lower than that of the internal electrode may cause a crack in a portion in close contact with the internal electrode. If a crack occurs, it becomes difficult to obtain a desired inductance value.

  The present invention has been made in view of the above-described problems of the prior art, and provides a multilayer inductor having a low DC resistance value and a desired inductance value while reducing the amount of conductor paste. For the purpose.

  The present invention is constituted by a magnetic body laminate portion obtained by printing and laminating magnetic paste containing ferrite powder, and a plurality of conductor patterns embedded in the magnetic body laminate portion and printed and laminated by conductor paste containing conductive metal powder. A coil-shaped conductor and a pair of terminal electrodes formed on the side surface of the magnetic layered portion and connected to both ends of the coil-shaped conductor, and the coil-shaped conductor has a substantially semicircular cross section. To do.

  According to the coiled conductor of the multilayer inductor according to the present invention, since the cross section is formed in a substantially semicircular shape, the thickness is increased with a small amount of conductor paste compared to the conventional sheet electrode having a rectangular cross section. Can be formed. Therefore, since the cross-sectional area becomes large, the DC resistance value can be reduced.

  Moreover, by forming in the state where thickness increased, the difference between the shrinkage ratio at the time of baking of a conductor pattern and the shrinkage ratio at the time of baking of a magnetic laminated body becomes smaller than the case where it forms in a sheet form. Therefore, it is possible to prevent the occurrence of cracks in the magnetic layered portion in close contact with the conductor pattern, and to set the inductance value to a desired value.

  In this case, the thickness of the conductor pattern is preferably 90 to 115% of the distance between conductor patterns adjacent in the stacking direction. Thereby, since the thickness of the conductor pattern can be increased without causing a short circuit between conductor patterns adjacent in the stacking direction, the direct current resistance value can be reliably reduced.

  Moreover, it is preferable that the edge part of the width direction of a conductor pattern is rounded. Thereby, a gap larger than the gap between the other portion of the conductor pattern and the magnetic layered portion is formed between the edge of the conductor pattern after firing and the magnetic layered portion. For this reason, for example, the thermal stress due to soldering when mounting on a printed circuit board and the effect on the magnetic layered portion due to the stress caused by external force from the printed circuit board are reduced, so the inductance value can be more reliably set. A desired value can be obtained.

  According to the present invention, since the conductor pattern has a substantially semicircular cross section, it is possible to obtain a multilayer inductor that has a low DC resistance value and a desired inductance value with a small amount of conductor paste.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a perspective view showing a multilayer inductor according to an embodiment of the present invention, FIG. 2 is a sectional view taken along a line connecting terminal electrodes of the multilayer inductor shown in FIG. 1, and FIG. FIG. 2 is a cross-sectional view in a direction orthogonal to a line connecting terminal electrodes of the multilayer inductor shown in FIG. 1. FIG. 4 is an enlarged view showing a region A shown in FIG.

  The multilayer inductor 1 includes a rectangular parallelepiped element 2 and a pair of terminal electrodes 3 and 3 formed on both side surfaces of the element 2 in the longitudinal direction. As shown in FIGS. 2 and 3, the element 2 includes a magnetic layered portion 4 made of a magnetic material, and a coiled conductor 5 incorporated in the magnetic layered portion 4 and wound in a coil shape. Yes.

  The coiled conductor 5 is made of a conductive material and has a substantially semicircular cross section. Further, as shown in FIG. 2, both end portions 5a and 5b of the coiled conductor 5 are led out to the edge of the magnetic layered portion 4, and are connected to the terminal electrodes 3 and 3, respectively. Such a coiled conductor 5 is constituted by a plurality of continuous conductor patterns 7 in which a conductor paste is printed and laminated.

  Referring to FIG. 3, the thickness X of the conductor pattern 7 is 90 to 115% of the distance Y between the conductor patterns 7 adjacent in the stacking direction. Further, as shown in FIG. 4, the edges 5c and 5d in the width direction of the conductor pattern 7 are rounded.

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

  First, a magnetic paste and a conductor paste are prepared. For magnetic paste, magnetic powder such as Ni-Cu-Zn-based ferrite powder, Ni-Cu-Zn-Mg-based ferrite powder, Ni-Cu-based ferrite powder and the like are blended together with a binder and a solvent at a predetermined ratio and then kneaded. To make. The conductor paste is prepared, for example, by mixing Ag powder together with a binder and a solvent at a predetermined ratio and then kneading. For kneading, a three roll, a homogenizer, a sand mill or the like is used.

  Next, the above magnetic paste is laminated by a printing method until a predetermined thickness is reached. Then, on the laminated magnetic paste, the above-described conductor paste and magnetic paste are used to form a spiral laminated winding (coiled conductor 5) having a predetermined number of turns (number of turns) into a ferrite magnetic substance (magnetic substance laminate). Part 4) is printed and laminated to form.

  And a raw laminated body is obtained by laminating | stacking magnetic paste on it by the printing method by predetermined thickness. When forming the laminated winding, as shown in FIG. 4, the conductor pattern 7 constituting the coiled conductor 5 has a substantially semicircular cross section, and the conductor pattern 7 has a thickness adjacent to the lamination direction. The thickness is set to 90 to 115% of the distance between the patterns 7. As a result, the thickness of the conductor pattern 7 is increased even with a small amount of conductor paste, as compared with the case of a sheet-like internal electrode (coiled conductor) such as a conventional multilayer inductor. Further, the edges 5c and 5d in the width direction of the conductor pattern 7 are rounded. By rounding the edges 5c and 5d in this manner, after performing a baking process described later, the gap between the edges 5c and 5d of the conductor pattern 7 and the magnetic laminate 4 is shown in FIG. Such gaps 6a and 6b are formed.

  The gaps 6a and 6b are larger than the gap between the other part of the conductor pattern 7 and the magnetic layered portion 4, for example, thermal stress generated in the magnetic layered portion 4 due to soldering when mounted on the printed circuit board. And a space for releasing stress caused by external force from the printed circuit board. Therefore, the influence exerted on the magnetic layered portion 4 is reduced, and a change in inductance value is prevented. The number of turns of the coiled conductor 5 is determined according to the DC resistance and inductance value to be obtained. For example, when the DC resistance is 1Ω or less and the inductance value is 10 μH, the number of turns is 18.5.

  Since such a multilayer body is usually formed in the form of a wafer in which a plurality are arranged, by cutting the wafer into a predetermined size, a plurality of living bodies each containing one coil-shaped conductor 5 are formed. The laminated body element is obtained. At this time, it cut | disconnects so that the end surface of the both ends 5a and 5b of the coil-shaped conductor 5 may each be exposed from the two side surfaces which a laminated body element opposes.

  Thereafter, the laminated element obtained by cutting to a predetermined size is subjected to binder removal and then integrally fired at a predetermined temperature to obtain the element 2. The firing temperature is, for example, about 850 to 900 ° C.

  Next, in the element 2 obtained by firing, a conductive paste mainly composed of Ag is applied to the side surface where the end surfaces of both end portions 5a and 5b of the coiled conductor 5 are exposed, for example, 600 The terminal electrodes 3 and 3 are formed by baking at about ° C. Thereafter, the terminal electrodes 3 and 3 are usually further electroplated. Thus, the multilayer inductor 1 according to this embodiment is completed. The electroplating is preferably performed using copper, nickel and tin, nickel and tin, nickel and gold, nickel and silver, and the like.

  In the multilayer inductor 1 as described above, the thickness of the coiled conductor 5 can be ensured with a small amount of conductor paste compared to the rectangular cross section because the cross section of the coiled conductor 5 is formed in a substantially semicircular shape. . Therefore, since the coil-shaped conductor 5 has a large cross-sectional area, the DC resistance value can be reduced and the amount of the conductor paste can be reduced. Further, by setting the thickness X of the conductor pattern 7 to 90 to 115% of the distance between the conductor patterns 7 adjacent to each other in the stacking direction, each conductor pattern 7 is prevented while preventing a short-circuit between the adjacent conductor patterns 7. 7 can be increased in thickness. For this reason, it is possible to reliably reduce the direct current resistance value while maintaining high reliability.

  Furthermore, the conductive pattern 7 (coiled conductor 5) has a larger shrinkage ratio during firing due to the increase in thickness. For this reason, the difference with the shrinkage | contraction rate of the magnetic body laminated part 4 at the time of baking becomes small. Therefore, the difference in shrinkage between the magnetic layered portion 4 and the conductor pattern 7 during firing is reduced, and the occurrence of cracks at the portion in close contact with the conductor pattern 7 of the magnetic layered portion 4 is suppressed. Thereby, the change of an inductance value is also prevented and a desired inductance value can be obtained.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment. For example, the present invention can also be applied to a sheet method in which an element is manufactured by laminating and pressing a magnetic green sheet on which a conductor pattern constituting a coiled conductor is formed.

  Hereinafter, although an Example and a comparative example are given and it demonstrates in more detail about the multilayer inductor which concerns on this invention with reference to FIGS. 5-9, this invention is not limited to these Examples at all.

  In Example 1, according to the manufacturing method described above, a multilayer inductor was manufactured as follows. The magnetic paste was prepared using Ni—Cu—Zn ferrite powder having an average particle size of 0.7 μm as the magnetic powder, and the conductor paste was prepared using Ag powder having an average particle size of 0.6 μm.

  Next, using these magnetic paste and conductor paste, printing lamination was performed so as to form a 18.5 turn laminated winding in the ferrite magnetic body. At this time, the lamination thickness of one layer is such that the thickness of the conductor pattern made of the conductor paste (thickness X in FIG. 3) is 18 μm, and the ferrite magnetic body (magnetic) made of the magnetic paste positioned between the conductor patterns adjacent in the lamination direction. Body thickness) (thickness Y in FIG. 3) was 16 μm. The total thickness of the ferrite magnetic body incorporating this multilayer winding is 690 μm. And on this ferrite magnetic body, magnetic pastes of 150 μm were laminated by a printing method so as to be sandwiched from above and below, and a raw laminate having a thickness of 990 μm was produced as a whole. Next, this laminate was cut to obtain a laminate element having a length of 1.84 mm and a width of 0.90 mm.

  Next, this laminated body element was co-fired at 865 ° C. after removing the binder to obtain the element shown in FIGS. And the conductive paste which has Ag as a main component was apply | coated to the side surface which exposed the end surface of the both ends of a coil-shaped conductor in this element, and it baked at about 620 degreeC, and formed the terminal electrode. Thus, a 1608-shaped multilayer inductor (Example 1) was obtained.

  FIG. 5 is a diagram illustrating the relationship between the X / Y value and the DC resistance value Rdc [Ω] in the 1608 shape and the 2012 shape. In the same figure, Example 1 shows the above-described 1608-shaped multilayer inductor, and Comparative Example 1 shows a 1608-shaped multilayer inductor having X / Y values different from those of Example 1. In addition, Example 2 and Comparative Example 2 show a 2012-type multilayer inductor having different X / Y values. The multilayer inductors according to Example 2 and Comparative Examples 1 and 2 were manufactured by the same manufacturing method as in Example 1 except that the size and the value of X / Y were changed.

  In Example 1, since X = 18 and Y = 16, X / Y was 1.125 (112.5%), and when the DC resistance value Rdc was measured, as shown in FIG. It was 9Ω. On the other hand, in Comparative Example 1, X / Y was about 0.86, and Rdc was about 1.1Ω.

  In Example 2, X / Y was about 0.9, and Rdc was about 0.32Ω. On the other hand, in Comparative Example 2, X / Y was about 0.68, and Rdc was about 0.45Ω.

  As described above, in the same shape (size), when X / Y is 0.9 or more, that is, when the thickness X of the conductor pattern is 90% or more of the distance Y between the conductor patterns, the DC resistance value Rdc is reduced. It was confirmed that

  Next, various reliability test results in the multilayer inductor according to Example 1 will be described with reference to FIGS. In each reliability test, the change rate (%) of the inductance value (L) when 96, 240, 500, and 1000 hours (h) elapsed in the multilayer inductor according to Example 1 was measured. 6 shows the results of a high temperature load test at 125 ° C., FIG. 7 shows the results of a moisture resistance load test at a humidity of 90% and a temperature of 60 ° C., and FIG. 8 shows a moisture resistance leaving test at a humidity of 90% and a temperature of 60 ° C. A test result is shown and FIG. 9 is a figure which shows the thermal shock test result in temperature -55-125 degreeC.

  As can be seen from FIGS. 6 to 9, in the multilayer inductor according to Example 1, the change rate of the inductance value varies within a range of about 10% in any test, and the change of the inductance value is very large. It was confirmed to be small.

1 is a perspective view showing a multilayer inductor according to an embodiment of the present invention. It is sectional drawing which follows the line | wire which connects the terminal electrodes of the multilayer inductor shown in FIG. FIG. 2 is a cross-sectional view in a direction orthogonal to a line connecting terminal electrodes of the multilayer inductor shown in FIG. 1. It is an enlarged view which shows the area | region A shown in FIG. It is a figure which shows the relationship between the value of X / Y and DC resistance value based on an Example. It is a figure which shows the result of the reliability test based on an Example. It is a figure which shows the result of the reliability test based on an Example. It is a figure which shows the result of the reliability test based on an Example. It is a figure which shows the result of the reliability test based on an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Multilayer inductor, 2 ... Element, 3 ... Terminal electrode, 4 ... Magnetic laminated part, 5 ... Coiled conductor, 5a, 5b ... Both ends, 5c, 5d ... Edge, 6a, 6b ... Gap, 7 ... Conductor pattern.

Claims (3)

A magnetic laminate layer obtained by printing and laminating a magnetic paste containing ferrite powder;
A coiled conductor constituted by a plurality of conductor patterns printed and laminated with a conductor paste containing conductive metal powder, which is built in the magnetic layered portion; and
A pair of terminal electrodes formed on the side surface of the magnetic laminate and connected to both ends of the coiled conductor;
The coil-shaped conductor has a substantially semicircular cross section.   2. The multilayer inductor according to claim 1, wherein the thickness of the conductor pattern is 90 to 115% of the distance between the conductor patterns adjacent to each other in the lamination direction. The multilayer inductor according to claim 1 or 2, wherein an edge in the width direction of the conductor pattern is rounded.

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