WO2007074580A1

WO2007074580A1 - Laminated coil part

Info

Publication number: WO2007074580A1
Application number: PCT/JP2006/321884
Authority: WO
Inventors: Tomohide Iwasaki
Original assignee: Murata Manufacturing Co., Ltd.
Priority date: 2005-12-29
Filing date: 2006-11-01
Publication date: 2007-07-05
Also published as: TWI317528B; JPWO2007074580A1; KR100820025B1; CN101103420B; JP4530044B2; TW200733153A; KR20070088748A; CN101103420A

Abstract

A laminated coil part that realizes relaxing of any internal stress attributed to shrinkage of ferrite occurring at the time of firing of laminate, preventing any drop of impedance. There is provided a laminated coil part comprising laminate main part (21) of a first ferrite having coil (10) disposed in its interior and comprising laminate end parts (22) of a second ferrite formed at both end portions along the direction of coil axis (A). The first ferrite constituting the main part (21) and the second ferrite constituting the end parts (22) are different from each other in composition, and the shrinkage ratio at firing of the second ferrite is greater than that at firing of the first ferrite.

Description

Specification

Multilayer coil parts

Technical field

[0001] The present invention relates to a multilayer coil component, and more particularly to a multilayer coil component such as a chip inductor in which a coil is incorporated in a multilayer body made of ferrite.

Background art

In general, laminated coil components such as chip inductors are formed by laminating a sheet of ferrite and a coil conductor, and connecting the ends of the coil conductor via via-hole conductors to form a spiral coil. Is provided. In addition, when this type of multilayer coil component is used as a noise countermeasure, a large impedance I z I is desired as a high performance. However, in the conventional multilayer coil parts, the characteristics changed due to the ferrite shrinkage during firing, and it was difficult to obtain a desirable impedance I z I.

[0003] Patent Document 1 discloses a multilayer inductor in which a bonded body layer is surface bonded to the upper and lower surfaces of a ferrite magnetic layer, and the linear expansion coefficient of the bonded body layer is smaller than that of the ferrite magnetic layer. In this multilayer inductor, the bonded body layer can suppress the expansion and contraction of the ferrite magnetic layer, and the temperature dependence of the inductance value can be suppressed. However, in this multilayer inductor, the stress caused by the shrinkage difference between the coil conductor and the ferrite during firing of the multilayer body cannot be relaxed, and the reduction of the impedance I z I cannot be prevented. Patent Document 1: Japanese Patent Laid-Open No. 4-302104

Disclosure of the invention

Problems to be solved by the invention

[0004] Accordingly, an object of the present invention is to provide a laminated coil component that can relieve internal stress caused by a shrinkage difference between a coil conductor and ferrite during firing of the laminated body and prevent a reduction in impedance. .

Means for solving the problem

In order to achieve the above object, a laminated coil component according to the present invention includes a laminated body main portion made of a first ferrite having a coil disposed therein, and both of the laminated body main portion in the coil axial direction. A laminate end made of a second ferrite formed on at least one of the ends, and the first ferrite and the second ferrite have different ferrite compositions, and when the second ferrite is fired The shrinkage ratio of the first ferrite is larger than the shrinkage ratio during firing of the first ferrite.

[0006] In the multilayer coil component according to the present invention, the second ferrite disposed outside the multilayer body during firing of the multilayer body is more than the first ferrite disposed inside including the coil. It contracts greatly, has a small shrinkage rate, is inhibited by the coil conductor, promotes the contraction of the first ferrite, and relaxes the tensile stress generated in the first ferrite. As a result, the tensile stress generated in the first ferrite around the coil conductor is relaxed and the impedance is prevented from lowering.

[0007] In the laminated coil component according to the present invention, if Ni—Cu—Zn ferrite or Ni—Zn ferrite is used as the first ferrite and the second ferrite, good characteristics can be obtained. . In particular, if the Zn content of the second ferrite is set higher than the Zn content of the first ferrite, the shrinkage rate during firing of the second ferrite increases, and the stress generated in the first ferrite Increases the relaxation effect. The second ferrite only needs to contain 25 to 70 mol% of Zn.

[0008] Further, the coil is preferably formed in a spiral shape by connecting a coil conductor made of Ag metal via a via-hole conductor. Ag makes it possible to obtain laminated coil parts with low electrical resistance and good characteristics (Q value).

The invention's effect

[0009] According to the present invention, the shrinkage rate during firing of the second ferrite disposed outside the laminate is greater than the shrinkage rate during firing of the first ferrite disposed inside including the coil. Therefore, when the laminate is fired, the second ferrite promotes the shrinkage of the first ferrite, and the tensile stress generated in the first ferrite is relieved and the impedance is prevented from being lowered. Brief Description of Drawings

FIG. 1 is a schematic perspective view showing a first embodiment of the laminated coil component according to the present invention.

FIG. 2 is a sectional view of the first embodiment.

FIG. 3 is an exploded perspective view of the first embodiment. FIG. 4 is a schematic diagram showing an outline of a stress distribution. (A) shows a conventional example, and (B) shows a first example.

[Fig. 5] Schematic diagram of the results of simulating the stress distribution, (A) shows the conventional example and (B) shows the first example.

FIG. 6 is a graph showing impedance characteristics.

FIG. 7 is a schematic perspective view showing a second embodiment of the laminated coil component according to the present invention.

FIG. 8 is an exploded perspective view of a second embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the laminated coil component according to the present invention will be described with reference to the accompanying drawings.

[0012] (Refer to the first embodiment, FIGS. 1 to 6)

As shown in FIG. 1, a laminated coil component 1A according to the first embodiment of the present invention includes a laminated main body 21 made of a first ferrite having a coil 10 disposed therein, and both ends in a coil axial direction A. And a laminated body end portion 22 made of a second ferrite formed on the upper portion (upper and lower portions), and external electrodes 23 are provided on the left and right end portions of the laminated body 20. Figure 2 shows the cross section.

Specifically, as shown in FIG. 3, a ferrite sheet 25 in which the coil conductor 11 and the extraction electrode 12 are formed, a ferrite sheet 26 in which the coil conductor 11 having a predetermined pattern is formed, and a plain ferrite sheet 27 are laminated. is there. The sheets 25 and 26 are made of the first ferrite and form the main part 21. The sheet 27 is made of a second ferrite and forms the end 22. Each coil conductor 11 forms a spiral coil 10 via a via-hole conductor 13 formed at one end. FIG. 3 is a schematic exploded view, and the number of sheets is not accurately shown.

[0014] The first ferrite forming the main portion 21 and the second ferrite forming the end portion 22 have different ferrite compositions, and the second ferrite has the first ferrite having a shrinkage ratio during firing. Those having a composition larger than the shrinkage ratio during firing are used. The ferrite composition and shrinkage will be described later.

[0015] Here, a manufacturing method of the laminated coil component will be described. There are two types of manufacturing methods. In the first method, a desired pattern is formed by a printing method such as screen printing with a conductive paste on a ferrite green sheet in which through holes are formed, and the sheet is formed into a spiral coil. A laminated coil component is obtained by laminating, crimping, cutting, and firing so that a magnetic layer is formed. In the second method, a ferrite coil and a conductor material are alternately printed by a printing method such as screen printing to form a spiral coil, and a laminated coil component is obtained by crimping, cutting and firing.

Specifically, the laminated coil component 1A was manufactured through the following steps. First, prepare ferrite sheets 25-27. Ni-Cu-Zn-based ferrites, Ni-Zn-based ferrites, Cu-Zn-based ferrites, etc. can be used in addition to the first and second ferrites that are preferred for materials with high magnetic permeability. The second ferrite uses a material with a higher thermal shrinkage than the first ferrite. The heat shrinkage rate is adjusted by changing the content of elements such as Ni, Zn, and Cu contained in the flight. For example, it can be adjusted by changing the Zn content.

[0017] Holes for via hole conductors are formed in the prepared ferrite sheets 25 and 26, and the internal conductors (the coil conductor 11 and the lead electrode 12) are printed. The internal conductor should have a low resistance value to achieve a high Q (quality factor) as an inductance element. For example, precious metals mainly composed of Ag, Au, Pt and the like and the power of these alloys, base metals such as Cu and Ni, and alloys thereof can be used. Ag was used in the production of the first example.

Next, the sheets 25 to 27 shown in FIG. 3 are laminated and pressure-bonded to produce a laminate 20 including the coil 10 therein. The above steps are performed in a state where a plurality of units of coils 10 are arranged in a matrix as a mother substrate, and this mother laminate is cut into one unit laminate (chip) 20. Then, the obtained laminate 20 is degreased and fired. Thereafter, external electrodes 23 are formed on the left and right ends of the laminate 20. The external electrode 23 is formed from the left and right end surfaces of the laminate 20 to the upper and lower surfaces and the side surfaces, and is connected to the extraction electrode 12 at the end surfaces. The external electrode 23 contains Ag or the like as a main component, and an adhesive layer is formed on the surface.

[0019] The manufactured laminated coil component 1A has a long side of 1. Omm, a short side of 0.5mm, and a height of 0.5mm. In addition, the second ferrite of the outer layer 22 is FeO force S50 mol%, ZnO 15 mol%, NiO

twenty three

Is 20mol% and CuO is 15mol%. The first ferrite of the inner layer 21 is Fe 2 O

2 3 is 35 mol%, ZnO power is 0 mol%, NiO is 10 mol%, and CuO is 15 mol%.

[0020] Fig. 4 (A) schematically shows the stress distribution generated during firing in a conventional multilayer coil component, and Fig. 4 (B) schematically shows the stress distribution generated during firing in the multilayer coil component 1A of the first embodiment. Indicate. As shown in Fig. 4 (A), in conventional laminated coil components, coil Due to the difference in shrinkage between the body and the flight, a large tensile stress is generated on the flight as shown by the arrow. The strongest magnetic field is generated in the ferrite inside the coil conductor. In this strong magnetic field ferrite, tensile stress is generated in a direction parallel to the magnetic field. When the stress of ferrite acted, the electrical properties of the material deteriorated, resulting in a decrease in impedance I z I.

On the other hand, in the multilayer coil component 1A of the first embodiment, as shown in FIG. 4B, the thermal contraction rate of the second ferrite at the end 22 is the heat of the first ferrite at the main portion 21. Since the contraction rate is larger, the end 22 contracts greatly in the direction orthogonal to the coil axis direction A of the coil 10. Since the main portion 21 has a small thermal contraction rate and the coil conductor 11 exists, the main portion 21 cannot sufficiently contract and a tensile stress is generated in the first ferrite. This tensile stress is offset by the large compression of the end 22. As a result, the tensile stress around the coil conductor 11 that is a strong magnetic field portion is relieved, and the impedance I Z I is prevented from decreasing.

[0022] Fig. 5 (A) is a schematic diagram of the simulated stress distribution in the conventional multilayer coil component shown in Fig. 4 (A), and Fig. 5 (B) is a schematic diagram of Fig. 4 (B). FIG. 3 is a schematic diagram of a simulated stress distribution in the laminated coil component 1 A of one embodiment. 4 and 5, the outward arrow indicates tensile stress, and the inward arrow indicates compressive stress.

[0023] In the simulation of the stress distribution, the linear expansion coefficient of the ferrite was 2. Since shrinkage during firing at 880 ° C is ^{23% 614 X 10- 4 (0.} 23/880) . The linear expansion coefficient of the coil conductor was set to 5.68 2 X 10 ⁵ because the shrinkage ratio upon firing at 880 ° C was 5%.

[0024] Fig. 6 is a graph showing the impedance IZI characteristics. Curve Y shows the characteristics of the conventional multilayer coil components shown in Figs. 4 (A) and 5 (A), and curve X shows Fig. 4 (B). FIG. 5B shows the characteristics of the laminated coil component 1A of the first embodiment shown in FIG. 5 (B). As is apparent from this graph power, the impedance I z I is improved overall (particularly, in the band of 10˜: LlOOMHz) in the laminated coil component 1A of the first embodiment.

[0025] Here, in Table 1 below, the tensile stress value (+) and the contraction stress around the coil conductor 11 related to Samples 1 to 7 and the conventional example in which the thickness and contraction rate of the end portion 22 are variously changed are shown. Indicates the integral difference of the value (one) as an integer value. The area around the coil conductor is centered on the center of coil 10. This means that the width and height are twice as large as the coil 10.

[table 1]

As is apparent from Table 1, the integral difference of the conventional example is +10, whereas the samples 1 to 7 of the first embodiment have a small integral difference! /. In the first example, we will explain with specific numerical values. The revealed laminated coil component 1A is sample 2, the integral difference is +1, and the stress generated in the inner layer 21 is 1.465 NZmm ² . Stress generated in the inner layer 21 is 0. 3 5. ONZmm ² is a suitable range.

[0028] By the way, the shrinkage rate of ferrite can be adjusted by the Zn content, and the composition of ferrite having various shrinkage rates is shown in Table 2 below.

[0029] [Table 2]

cm

[0030] (Refer to the second embodiment, FIGS. 7 and 8)

In the laminated coil component 1B shown in FIG. 7, the coil 50 is arranged in the main part 61 of the laminated body made of the first ferrite so that the coil axial direction A is arranged in parallel to the mounting surface 5. A laminate end portion 62 made of a second ferrite is provided at both end portions in the axial direction A (left and right end portions of the laminate 60).

Specifically, as shown in FIG. 8, each of the ferrite sheets 65 to 68 is formed of the second ferrite having a large shrinkage at both ends and the other portion is formed of the first ferrite. . The coil conductor 51, the extraction electrode 52 and the via hole conductor 53 are formed on the ferrite sheet 65, the via hole conductor 53 is formed on the ferrite sheet 66, and the coil conductor 51 and the via hole conductor 53 are formed on the ferrite sheet 67. These ferrite sheets 65 to 67 are laminated, and a plain ferrite sheet 68 is laminated on the upper and lower portions thereof to form a spiral coil 50. Although not shown, the external electrodes are provided at both left and right ends of the multilayer body 60.

[0032] Also in this laminated coil component 1B, since the end portions 62 made of the second ferrite having a large shrinkage rate are formed at both ends in the coil axial direction A, the coil is the same as in the first embodiment. The tensile stress around the conductor 51 can be relaxed to prevent the impedance IZI from decreasing.

[0033] (Other embodiments)

The laminated coil component according to the present invention can be variously modified within the scope of the gist of the present invention, not limited to the above embodiment.

[0034] In particular, the end portion of the laminated body made of the second ferrite having a large shrinkage rate may be provided on one side which is not necessarily provided on both sides of the laminated body. The shape of the coil conductor formed on the ferrite sheet is arbitrary. Furthermore, the present invention can be applied not only to multilayer inductors but also to LC composite parts.

[0035] In the embodiment, the first and second ferrites are composed of the same composition system ferrite, but may be composed of different composition system ferrites. However, if the first and second ferrites are composed of the same composition type of flites, the adhesion between them becomes better.

Industrial applicability

[0036] As described above, the present invention is useful for laminated coil components, and particularly when the laminated body is fired. It is excellent in that the internal stress caused by the shrinkage difference between the coil conductor and ferrite can be relieved and the impedance can be prevented from decreasing.

Claims

The scope of the claims

[1] The main part of the laminate composed of the first flight in which the coil is disposed,

A laminate end made of a second ferrite formed on at least one of both ends in the coil axial direction of the laminate main part, and

The first ferrite and the second ferrite have different ferrite compositions, and the shrinkage rate during firing of the second ferrite is larger than the shrinkage rate during firing of the first ferrite, Laminated coil parts.

[2] The first ferrite and the second ferrite are Ni—Cu—Zn based ferrite or Ni

The multilayer coil component according to claim 1, wherein the multilayer coil component is a Zn-based ferrite.

[3] The multilayer coil component according to [1] or [2], wherein the Zn content of the second ferrite is greater than the Zn content of the first ferrite .

[4] The laminated coil component according to any one of [1] to [3], wherein the second ferrite contains 25 to 70 mol% of Zn.

[5] The coil according to claim 1 or 4, wherein the coil is formed in a spiral shape by connecting a coil conductor made of Ag via via-hole conductors. A laminated coil component according to any one of the above.