JP5229323B2 - Multilayer coil component and manufacturing method thereof - Google Patents

Description

  According to the present invention, a helical coil is arranged inside a magnetic ceramic element formed by firing a ceramic laminated body in which a magnetic ceramic layer and a coil-forming internal conductor mainly composed of Ag are laminated. The present invention relates to a laminated coil component having a provided structure.

  In recent years, the demand for downsizing of electronic parts has increased, and the mainstream of coil parts is also shifting to the multilayer type.

  By the way, in the laminated coil component obtained by simultaneously firing the magnetic ceramic and the inner conductor, the internal stress generated due to the difference in thermal expansion coefficient between the magnetic ceramic layer and the inner conductor causes the magnetic characteristics of the magnetic ceramic to be reduced. There is a problem in that the impedance value of the laminated coil component is lowered and variations are caused.

  Therefore, in order to eliminate such problems, the sintered magnetic ceramic element is immersed in an acidic plating solution, and a gap is provided between the magnetic ceramic layer and the internal conductor, thereby providing an internal structure. A multilayer impedance element has been proposed in which the influence of stress on a magnetic ceramic layer by a conductor is avoided to eliminate a decrease or variation in impedance value (Patent Document 1).

  However, in the multilayer impedance element of Patent Document 1, the magnetic ceramic element is immersed in the plating solution, and the plating solution penetrates into the inside from the portion where the internal conductor is exposed on the surface of the magnetic ceramic element. Since a discontinuous gap is formed between the magnetic ceramic layer and the inner conductor, the inner conductor and the gap are formed between the magnetic ceramic layers, and the inner conductor becomes thin. In some cases, through holes are formed in the inner conductor, and the ratio of the inner conductor occupying between the ceramic layers must be reduced.

Therefore, there is a problem that it is difficult to obtain a product with low DC resistance. In particular, when the product is a small product such as a product of 1.0 mm × 0.5 mm × 0.5 mm or a product of 0.6 mm × 0.3 mm × 0.3 mm, the magnetic ceramic layer is thinned. In addition to providing both the internal conductor and the air gap between the magnetic ceramic layers, it is difficult to form a thick internal conductor, and through holes are easily formed in the internal conductor. For this reason, there is a problem that not only the direct current resistance cannot be reduced, but also the internal conductor is easily disconnected due to a surge or the like, and sufficient reliability cannot be ensured.
Japanese Patent Laid-Open No. 2004-22798

  The present invention solves the above-mentioned problems, and can reduce the problem of internal stress without forming a gap between the internal conductor and the surrounding magnetic ceramic, and occupies the internal conductor. An object of the present invention is to provide a highly reliable laminated coil component that has a high rate, low resistance, and is less likely to cause disconnection of an internal conductor due to surge or the like.

In order to solve the above problems, the laminated coil component of the present invention is
The internal conductor is connected between layers in a magnetic ceramic element including a plurality of laminated magnetic ceramic layers and an internal conductor mainly composed of Ag and disposed via the magnetic ceramic layer. A laminated coil component having a helical coil formed by:
The inner conductor coverage, which is the ratio of the area of the region covered with the inner conductor to the region where the inner conductor is to be disposed, is 99.5% or more,
While the pore area ratio of the magnetic ceramic constituting the side gap portion that is a region between the side portion of the inner conductor and the side surface of the magnetic ceramic element is in the range of 6 to 20%,
There is no gap at the interface between the inner conductor and the magnetic ceramic around the inner conductor, and the interface between the inner conductor and the magnetic ceramic is dissociated.

In addition, the manufacturing method of the laminated coil component of the present invention,
Formed by using a plurality of laminated magnetic ceramic green sheets and a conductive paste containing Ag in the range of 80 to 90% by weight and having a smaller sintering shrinkage than the magnetic ceramic green sheets. A ceramic multilayer body having a plurality of internal conductor patterns for firing, a magnetic ceramic element having a spiral coil therein, and a side portion of the internal electrode formed by firing the internal conductor pattern; Forming a magnetic ceramic element having a pore area ratio in the range of 6 to 20% of the magnetic ceramic constituting the side gap portion which is a region between the side surfaces of the magnetic ceramic element;
By causing the acidic solution to reach the interface between the inner conductor and the surrounding magnetic ceramic from the side surface of the magnetic ceramic element through the side gap portion, the inner conductor and the surrounding magnetic ceramic And a step of cutting the bond at the interface.

In addition, the manufacturing method of the laminated coil component of the present invention,
Coil formation formed by using a plurality of laminated magnetic ceramic green sheets and a conductive paste containing Ag in the range of 80 to 90% by weight and having a sintering shrinkage smaller than that of the magnetic ceramic green sheets. And firing a ceramic laminate including a plurality of internal conductor patterns, and having a spiral coil therein and one of a pair of end portions of the spiral coil on each of a pair of side surfaces facing each other Is exposed, and the pore area ratio of the magnetic ceramic constituting the side gap portion , which is a region between the side portion of the inner conductor formed by firing the inner conductor pattern and the side surface of the magnetic ceramic element, is Forming a 6-20% magnetic ceramic element;
Forming external electrodes on the pair of side surfaces of the magnetic ceramic element in which the pair of end portions of the spiral coil are exposed;
And a step of plating the surface of the external electrode using an acidic plating solution.

  As the conductive paste, it is more preferable to use a conductive paste containing Ag in the range of 83 to 89% by weight.

Since the multilayer coil component of the present invention has a high internal conductor coverage of 99.5% or more and there is no air gap at the interface between the internal conductor and the surrounding magnetic ceramic, the internal conductor between the magnetic ceramic layers is It is possible to keep the occupancy rate of Moreover, since the interface between the inner conductor and the magnetic ceramic is dissociated, the stress generated due to the difference in sintering shrinkage between the magnetic ceramic and the inner conductor is suppressed from being applied to the magnetic ceramic. It becomes possible.
Therefore, the resistance is low, the internal conductor is not easily broken by surges, etc., the characteristics such as inductance and impedance are good, and the rate of change in characteristics in reliability tests such as thermal shock tests is small. It becomes possible to obtain a high laminated coil component.
The inner conductor coverage may be 99.5% or more. However, when the inner conductor coverage is 99.8% or more, it is possible to obtain a laminated coil component with better characteristics and high reliability.

Further, a side of the inner conductor, the side gap portion is a region between the side surface of the magnetic ceramic element, since the pore area ratio of the magnetic ceramic so that the range 6 to 20% pores By allowing an acidic solution to enter the inside of the magnetic ceramic element from the side gap portion, which is a porous region having an area ratio of 6 to 20%, to reach the interface between the internal conductor and the surrounding magnetic ceramic, Thus, the bond at the interface between the inner conductor and the magnetic ceramic can be reliably cut (that is, the interface is dissociated). Therefore, the interface between the inner conductor and the magnetic ceramic is dissociated, and it becomes possible to obtain a laminated coil component with good characteristics in which the stress is sufficiently relaxed.

The method for manufacturing a laminated coil component of the present invention includes a magnetic ceramic green sheet and a conductive paste containing Ag in a range of 80 to 90% by weight and having a smaller sintering shrinkage than that of the magnetic ceramic green sheet. A ceramic multilayer body having a plurality of internal conductor patterns for forming a coil formed by firing is fired to form a magnetic ceramic element having a spiral coil therein , and the internal conductor pattern is fired. A magnetic ceramic element in which the pore area ratio of the magnetic ceramic constituting the side gap portion, which is a region between the side portion of the internal electrode and the side surface of the magnetic ceramic element, is in the range of 6 to 20% is formed. Therefore, it is possible to obtain a laminated coil component having a high internal conductor coverage of 99.5% or more and a high occupation ratio of the internal conductor, and magnetic properties. By penetrating the acidic solution from the side of the ceramic element through the side gap and reaching the interface between the inner conductor and the surrounding magnetic ceramic, the bond between the two is broken, and the inner conductor and the surrounding magnetism are cut off. The interface with the body ceramic can be in a dissociated state. In other words, the stress is relaxed without thinning the inner conductor as in the case of the conventional laminated coil component in which a gap is provided to cut the bond between the inner conductor and the surrounding magnetic ceramic. Can be realized.
Therefore, it has low resistance, high occupancy of the internal conductor, it is difficult for the internal conductor to break due to surges, etc., and it has good characteristics such as inductance and impedance, and characteristics in reliability tests such as thermal shock tests. A highly reliable laminated coil component with a small change rate can be efficiently manufactured.

  Moreover, the manufacturing method of the laminated coil component of the present invention includes a plurality of laminated magnetic ceramic green sheets and Ag in a range of 80 to 90% by weight, and the sintering shrinkage ratio is higher than that of the magnetic ceramic green sheets. A ceramic laminate including a plurality of internal conductor patterns for forming a coil, which is formed using a small conductive paste, is fired, and a spiral coil is provided inside, and a spiral is formed on each of a pair of side surfaces facing each other. A magnetic ceramic element in which one of the pair of end portions of the coiled coil is exposed and the pore area ratio of the side gap portion is 6 to 20% is formed, and the pair of ends of the spiral coil is exposed. After forming an external electrode on a pair of side surfaces of the body ceramic element, the surface of the external electrode is plated using a plating solution containing an acidic substance. Therefore, even when the external electrode covers the end face of the magnetic ceramic element, the plating solution (acid solution) is removed from the inner conductor and the surrounding magnetic body from the porous side gap portion having a pore area ratio of 6 to 20%. The stress applied to the magnetic ceramic can be relaxed by reliably penetrating the interface with the ceramic and cutting the bond at the interface between the inner conductor and the surrounding magnetic ceramic. As a result, it is possible to efficiently manufacture a laminated coil component having a high internal conductor coverage of 99.5% or more, good characteristics, and high reliability.

  In addition, when plating is used as an acidic solution and plating is performed, the plating solution (acidic solution) is permeated into the magnetic ceramic element at the same time, so that it is not necessary to add a new process to the existing process. Thus, it becomes possible to manufacture a highly reliable multilayer coil component.

  In the present invention, the desired effect can be obtained by forming an internal conductor pattern using a conductive paste having an Ag content of 80 to 90% by weight. By setting the range to 83 to 89% by weight, it becomes possible to reliably manufacture a laminated coil component having an internal conductor coverage of 99.8% or more, good characteristics, and excellent mechanical strength. The present invention can be further effectively realized.

It is front sectional drawing which shows the structure of the laminated coil component concerning one Example (Example 1) of this invention. It is a disassembled perspective view explaining the manufacturing method of the laminated coil component concerning Example 1 of this invention. It is side surface sectional drawing which shows the structure of the laminated coil component concerning Example 1 of this invention. It is a figure explaining the measuring method of the pore area ratio of the laminated coil components of Example 1 of this invention and a comparative example. It is a figure which shows the SEM image of the internal conductor of the sample of the sample number 4 provided with the requirements of this invention. It is a figure which shows the SEM image of the internal conductor of the sample of the sample number 8 which does not have the requirements of this invention. It is a figure which shows the SIM image of the surface (WT surface) processed by FIB after mirror-polishing the cross section of the laminated coil component of Example 1 of the present invention (sample No. 3 in Table 1). It is a figure which shows the SEM image of the torn surface by the three-point bending test of the laminated coil component (sample No. 3 of Table 1) of Example 1 of this invention. It is a figure which shows the relationship between the softening point and impedance of the zinc borosilicate type | system | group low softening point glass added to the magnetic body ceramic.

DESCRIPTION OF SYMBOLS 1 Magnetic body ceramic layer 2 Inner conductor 2a Side part of inner conductor 3 Magnetic body ceramic element 3a Side surface of magnetic body ceramic element 4 Spiral coil 4a, 4b Both ends of spiral coil 5a, 5b External electrode 8 Side gap part 9 Outer layer Area 10 Multilayer coil component (Multilayer impedance element)
11 Magnetic ceramic 21 Ceramic green sheet 21a Ceramic green sheet without internal conductor pattern 22 Internal conductor pattern (coil pattern)
23 Laminate (Unfired magnetic ceramic element)
24 Via hole A interface

  In the multilayer coil component of the present invention, it is desirable to use, for example, a material mainly composed of NiCuZn ferrite as the magnetic ceramic layer.

  Further, it is desirable that the inner conductor has no through hole and the entire region where the inner conductor is to be disposed is covered with the inner conductor. However, if the inner conductor coverage is 99.5% or more, the magnetic body It is possible to obtain a highly reliable laminated coil component that can maintain a high occupation ratio of the inner conductor between the ceramic layers, has a low direct current resistance, and hardly breaks the inner conductor due to a surge or the like.

  In order to realize a state in which there is no void at the interface between the inner conductor and the surrounding magnetic ceramic and the interface between the inner conductor and the magnetic ceramic is dissociated, It is desirable to break the bond at the interface by allowing an acidic solution to enter the interface with the ceramic.

Moreover, when manufacturing the laminated coil component of this invention, it is desirable to make the sintering shrinkage rate of an internal conductor smaller than the sintering shrinkage rate of a magnetic ceramic.
By making the sintering shrinkage rate of the inner conductor smaller than the sintering shrinkage rate of the magnetic ceramic, the periphery of the inner conductor is pushed by the magnetic ceramic during the sintering shrinkage of the inner conductor. As a result, the inner conductor is densely filled into the space where the inner conductor is to be formed inside the magnetic ceramic. The dense inner conductor thus densely packed can reduce the direct current resistance and improve the surge resistance.
Also, by reducing the sintering shrinkage rate of the inner conductor than the sintering shrinkage rate of the magnetic ceramic, the pore area rate of the side gap portion is ensured without lowering the sinterability, and the portion is more acidic. It is possible to make it easier for the solution to enter.

In addition, when the sintering shrinkage rate is less than 0%, the inner conductor does not shrink during firing or expands more than before firing, which may cause structural defects or affect the chip shape. Absent.
In addition, when the sintering shrinkage rate of the inner conductor is 15% or more, the pore ratio distribution is less likely to be generated inside the magnetic ceramic element, and the acidic solution is sufficiently infiltrated into the inside from the side gap portion of the magnetic ceramic element. Is not preferable because it becomes difficult.

Further, as the shrinking behavior of the inner conductor in the firing step, it is preferable that the inner conductor is flattened from about 300 ° C. and then flattened up to the maximum temperature of firing or expanded by about 5%.
The sintering shrinkage behavior of the inner conductor includes the content of the conductive component (Ag powder) in the conductive paste for forming the inner conductor, the amount of the organic vehicle contained in the conductive paste, the type of varnish, the molding pressure of the laminate, Since it relates to a degreasing / firing profile and the like, a desired sintering shrinkage can be achieved by appropriately selecting these conditions.

  As in the present invention, a conductive paste having an Ag content of 80 to 90% by weight as a conductive paste for forming an internal conductor has a smaller sintering shrinkage than a magnetic ceramic green sheet. It becomes possible to obtain.

In addition, by using a conductive paste having an Ag content of 80 to 90% by weight, it is possible to suppress and prevent the formation of through holes in the internal conductor in the firing step, and the internal conductor coverage is 99.5%. This is possible.
The Ag content is in the range of 80 to 90% by weight because when the Ag content is less than 80% by weight, the internal conductor coverage is less than 99.5%, and when the Ag content exceeds 90% by weight, This is because it is difficult to produce a conductive paste for forming a conductor, and the sintering shrinkage rate of the inner conductor becomes too small to cause a structural defect.

Further, by limiting the Ag content to the range of 83 to 89% by weight (narrower range), it is possible to more reliably suppress and prevent the formation of a gap at the interface between the magnetic ceramic layer and the internal conductor. However, the inner conductor coverage can be increased to 99.8% or more.
Note that the Ag powder as the conductive material constituting the conductive paste desirably has a high purity with impurities of 0.1% by weight or less. In addition, when there are many impurities, the internal conductor corrodes by an acidic solution, and the malfunction that DC resistance increases may arise.

  In addition, as in the method of manufacturing a laminated coil component according to the present invention, after the external electrode is formed (baked), an acidic solution is allowed to permeate from the side gap portion of the magnetic ceramic element, so that the magnetic ceramic (ferrite) and the internal conductor The acidic solution can reach the interface to break the bond at the interface and relieve the stress.

  In order to ensure that the acidic solution can reach the interface between the magnetic ceramic (ferrite) and the internal conductor, the pore area ratio of the side gap portion of the magnetic ceramic element is set to 6 to 20%. It is necessary. When the pore area ratio of the side gap portion of the magnetic ceramic element is less than 6%, it becomes difficult to permeate the acidic solution to the interface between the inner conductor and the magnetic ceramic, and the interface between the magnetic ceramic and the inner conductor is bonded. Can't cut. On the other hand, if the pore area ratio exceeds 20%, the acidic solution can be easily infiltrated, but this is not preferable because the mechanical strength of the magnetic ceramic is lowered.

  The pore diameter is desirably in the range of 0.1 to 0.6 μm. This is because when the pore diameter is less than 0.1 μm, it becomes difficult for the acidic solution to reach the interface between the inner conductor and the surrounding magnetic ceramic from the side gap portion, and when the pore diameter is larger than 0.6 μm, the magnetic ceramic element This is due to a decrease in strength.

As described above, according to the present invention, as the conductive paste for forming the internal conductor, a paste having a high content of Ag as the conductive component is used, and the internal shrinkage rate is higher than the sintering shrinkage rate of the magnetic ceramic layer. By reducing the sintering shrinkage rate of the conductor, it becomes possible to make the pore area ratio of the side gap portion 6 to 20%. By infiltrating the acidic solution from this side gap portion, the inner conductor and its surroundings can be obtained. It is possible to make the interface between the inner conductor and the magnetic ceramic dissociated without forming a gap between the magnetic ceramics.
As a result, it is possible to obtain a laminated coil component that has a low DC resistance, can prevent disconnection due to a surge, and can obtain high impedance with little variation.
Hereinafter, the features of the present invention will be described in more detail with reference to examples of the present invention.

  FIG. 1 is a front sectional view schematically showing the structure of a laminated coil component (a laminated impedance element in this embodiment 1) according to one embodiment of the present invention, and FIG. 2 is an exploded view showing a method for manufacturing the laminated coil component of FIG. FIG. 3 is a side sectional view of the laminated coil component shown in FIG.

  A laminated coil component 10 according to the first embodiment includes a laminated magnetic ceramic layer 1 and a helical coil formed by connecting an internal conductor 2 composed mainly of Ag and laminated through the magnetic ceramic layer 1. The magnetic ceramic element 3 having 4 is provided. A pair of external electrodes 5 a and 5 b are disposed at both ends of the magnetic ceramic element 3 so as to be electrically connected to both ends 4 a and 4 b of the spiral coil 4.

Further, as schematically shown in FIG. 1, there is no air gap at the interface A between the inner conductor 2 and the surrounding magnetic ceramic 11, and the inner conductor 2 and the surrounding magnetic ceramic 11 are Although it is almost in close contact, it is configured such that the inner conductor 2 and the magnetic ceramic 11 are dissociated (not coupled) at the interface.
Further, the side gap portion 8 which is a region between the side portion of the inner conductor 2 and the side surface of the magnetic ceramic element 3 is configured to be in a porous state in which the pore area ratio is in the range of 6 to 20%. ing.
In this laminated coil component 10, the inner conductor coverage, which is the ratio of the area of the region covered with the inner conductor 2 to the area of the region where the inner conductor 2 is to be disposed, is 99.8% or more. Thus, the internal conductor 2 is formed.

Next, the manufacturing method of this laminated coil component 10 is demonstrated.
(1) A magnetic material was weighed in a proportion of 48.0 mol% Fe ₂ O ₃ , 29.5 mol% ZnO, 14.5 mol% NiO, and 8.0 mol% CuO, and was prepared in a ball mill for 48 hours. Wet mixing was performed.
Then, the wet-mixed slurry was dried with a spray dryer and calcined at 700 ° C. for 2 hours.
The obtained calcined product was wet pulverized for 16 hours by a ball mill, and after the pulverization was completed, a predetermined amount of binder was mixed to obtain a ceramic slurry.
Then, this ceramic slurry was formed into a sheet shape to produce a ceramic green sheet having a thickness of 25 μm.

(2) Next, after forming a via hole at a predetermined position of the ceramic green sheet, a conductive paste for forming an internal conductor was printed on the surface of the ceramic green sheet to form a coil pattern (internal conductor pattern). .
As the conductive paste, a conductive paste having an impurity content of 0.1 wt% or less, Ag powder, varnish, and a solvent, and an Ag content of 85 wt% was used.

(3) Next, as schematically shown in FIG. 2, a plurality of ceramic green sheets 21 on which the inner conductor pattern (coil pattern) 22 is formed are stacked and pressure-bonded. After laminating ceramic green sheets 21a on which no is formed, pressure bonding was performed at 1000 kgf / cm ² to obtain a laminated body (unfired magnetic ceramic element) 23 as a pressure-bonding block.
The unfired magnetic ceramic element 23 includes a laminated spiral coil in which internal conductor patterns (coil patterns) 22 are connected via via holes 24. The number of turns of the coil is 7.5 turns.

(4) Then, after this crimped block (unfired magnetic ceramic element) 23 is cut into a predetermined size, the binder is removed, and the firing temperature is changed between 820 ° C. and 910 ° C. to be sintered. Thus, a magnetic ceramic element provided with a spiral coil was obtained.
In this case, the sintering shrinkage rate during firing of the magnetic ceramic (ferrite) and the internal conductor is 13 to 20% for the magnetic ceramic, and 8% for the internal conductor.
Note that when the firing temperature is in the range of 820 ° C. to 910 ° C., the sintering shrinkage rate of the inner conductor is substantially constant.

  When a magnetic ceramic element having a magnetic ceramic layer having an sintering shrinkage characteristic as described above and an internal conductor is fired, a pore area ratio distribution is generated inside the magnetic ceramic element, and the internal conductor shown in FIG. The side gap portion 8, which is a region between the side portion 2 a of the magnetic ceramic element 3 and the side surface 3 a of the magnetic ceramic element 3, has the upper surface of the upper outermost layer of the inner conductor 2 in the magnetic ceramic element 3 and the magnetic body. The outer layer region 9 between the upper surface of the ceramic element 3 and the outer layer region 9 between the lower surface of the lower outermost layer of the inner conductor 2 in the magnetic ceramic element 3 and the lower surface of the magnetic ceramic element 3 The pore area ratio increases. That is, the outer layer region 9 is more densely sintered, and the side gap portion 8 has a larger pore distribution.

  As described above, the outer layer region 9 is more densely sintered and the distribution of the pores in the side gap portion 8 is increased by making the sintering shrinkage rate of the inner conductor 2 smaller than that of the magnetic ceramic 11. This is because a difference in sintering shrinkage between the inner conductor 2 and the magnetic ceramic 11 occurs, and the inner conductor 2 suppresses the sintering shrinkage of the magnetic ceramic 11.

  The sintered shrinkage rate of the magnetic ceramic is measured by stacking ceramic green sheets, crimping them under the same pressure conditions as those used to actually manufacture laminated coil components, cutting to a predetermined size, firing, and laminating The sintering shrinkage in the direction along the direction was measured by measuring with a thermomechanical analyzer (TMA).

Moreover, the measurement of the sintering shrinkage rate of the inner conductor was performed by the following method.
First, the conductive paste for forming the inner conductor was thinly spread on a glass plate and dried, and then the dried material was scraped off and pulverized into a powder in a mortar. Then, it is uniaxial press-molded under the same pressure conditions as when manufacturing laminated coil parts in a mold, cut to a predetermined size and fired, and the sintering shrinkage along the press direction is measured with TMA did.

(5) Then, a conductive paste for forming an external electrode is applied to both ends of a magnetic ceramic element (sintered element) 3 having a spiral coil 4 inside, dried, and then baked at 750 ° C. External electrodes 5a and 5b (see FIG. 1) were formed.
The conductive paste for forming the external electrode includes Ag powder having an average particle diameter of 0.8 μm, B-Si—K-based glass frit having an average particle diameter of 1.5 μm and varnish having excellent plating resistance. A conductive paste blended with a solvent was used. And the external electrode formed by baking this electroconductive paste was a precise | minute thing which is hard to be eroded by the plating solution at the following plating processes.

  (6) Then, Ni plating and Sn plating were performed on the formed external electrodes 5a and 5b to form a two-layered plating film having a Ni plating film layer as a lower layer and a Sn plating film layer as an upper layer. Thereby, as shown in FIG. 1, the laminated coil component (laminated impedance element) 10 which has the structure provided with the helical coil 4 inside the magnetic body ceramic element 3 is obtained.

In the plating step, an acidic solution having a pH of 4 containing nickel sulfate at a rate of about 300 g / L, nickel chloride at a rate of about 50 g / L, boric acid at a rate of about 35 g / L was used as the Ni plating solution. .
Further, as the Sn plating solution, an acidic solution containing about 70 g / L of tin sulfate and about 100 g / L of ammonium sulfate and having a pH of 5 was used.

[Evaluation of characteristics]
The laminated coil component produced as described above was subjected to impedance measurement and bending strength measurement by a three-point bending test by the following methods.
In addition, the SEM observation of the inner conductor was performed by the following method, and the inner conductor coverage, which was the ratio of the area of the region covered with the inner conductor to the area of the region where the inner conductor was to be disposed, was measured.
Furthermore, in the step (6), the pore area ratio of the side gap portion was measured by the following method for the magnetic ceramic element before plating the external electrode.

(a) Measurement of Impedance For 50 samples, impedance was measured using an impedance analyzer (HP 4291A manufactured by Hewlett-Packard Company), and an average value (n = 50 pcs) was obtained.

(b) Measurement of bending strength With respect to 50 samples, measurement was performed by the test method specified in EIAJ-ET-7403, and the strength at the time of fracture probability = 1% when weibull plotted was taken as the bending strength. (N = 50 pcs).

(c) Measurement of inner conductor coverage The inner conductor coverage was measured by breaking the laminated coil component manufactured by the above method with a nipper along the laminated surface of the magnetic ceramic layer, exposing the inner conductor, The surface of the conductor is observed with a scanning electron microscope (SEM), and the ratio of the area of the region covered with the inner conductor to the area of the region where the inner conductor is to be disposed is obtained by the following equation (1). Coverage.
Inner conductor coverage (%) = (B / A) × 100 (1)
A: The area of the region where the inner conductor is to be disposed, that is, the area of the region to be covered by the inner conductor without the through hole.
B: The area of the area covered by the internal conductor, that is, the value obtained by subtracting the area of the through hole formed in the internal conductor from A, and if there is no through hole, B = A and the internal conductor coverage is 100%. It becomes.

(d) Measurement of pore area ratio A cross section (hereinafter referred to as “WT plane”) defined by the width direction and thickness direction of the magnetic ceramic element before plating is mirror-polished and focused ion beam processing (FIB processing) is performed. The observed surface was observed with a scanning electron microscope (SEM), and the pore area ratio of the side gap portion and the outer layer region of the sintered magnetic ceramic was measured.

Specifically, the pore area ratio was measured by image processing software “WINROOF (Mitani Corporation).” The specific measurement method is as follows.
FIB equipment: FIB 200TEM manufactured by FEI
FE-SEM (scanning electron microscope): JEOL JSM-7500FA
WinROOF (image processing software): manufactured by Mitani Corporation, Ver. 5.6

<Focused ion beam processing (FIB processing)>
As shown in FIG. 4, FIB processing was performed at an incident angle of 5 ° on the polished surface of the sample mirror-polished by the above-described method.

<Observation by Scanning Electron Microscope (SEM)>
SEM observation was performed under the following conditions.
Acceleration voltage: 15 kV
Sample tilt: 0 ° Signal: Secondary electron Coating: Pt
Magnification: 5000 times

<Calculation of pore area ratio>
The pore area ratio was determined by the following method: a) Determine the measurement range. If it is too small, an error due to the measurement location occurs.
(In this example, it was 22.85 μm × 9.44 μm)
b) If the magnetic ceramic and the pore are difficult to distinguish, adjust the brightness and contrast. c) Perform binarization and extract only pores. If the “color extraction” of the image processing software WinROOF is not complete, it is manually compensated.
d) If a part other than the pore is extracted, the part other than the pore is deleted.
e) The total area, the number, the area ratio of the pores, and the area of the measurement range are measured by “total area / number measurement” of the image processing software.
The pore area ratio in the present invention is a value measured as described above.

  Table 1 shows the inner conductor coverage, the pore area ratio of the side gap and the pore area ratio of the outer layer region, the impedance (| Z |) value, the bending strength value, and the firing temperature measured as described above. The presence or absence of a gap at the interface between the magnetic ceramic and the internal conductor by SEM observation of the FIB processed surface and the presence or absence of delamination at the interface between the magnetic ceramic and the internal conductor when the laminated coil component is broken are also shown.

In Table 1, in the SEM observation of the FIB processed surface, no gap is observed at the interface between the magnetic ceramic and the internal conductor, and peeling occurs at the interface between the magnetic ceramic and the internal conductor when the laminated coil component is broken. The recognized samples (samples 1 to 6) are “There is no gap at the interface between the inner conductor containing Ag as a main component and the magnetic ceramic around the inner conductor, and the inner conductor and the magnet are magnetic. It is a sample having the requirement of the present invention that the interface with the body ceramic is dissociated.
On the other hand, sample No. 7 has a pore area ratio of 2% in the side gap portion, the plating solution (acid solution) does not penetrate from the side gap portion, and the bond at the interface between the internal conductor and the magnetic ceramic is not cut. A sample that remains in a bound state and does not have the requirements of the present invention.
Sample No. 8 is a sample manufactured using a conductive paste having an Ag content of 76% by weight as a conductive paste for forming an internal conductor, and the internal conductor coverage is 94.6%. It is a sample that does not have the requirements of the present invention that does not reach the inner conductor coverage of 99.5% defined by the present invention. The sample of sample number 8 is the same as the sample of sample number 4 (using a conductive paste having an Ag content of 85% by weight) except that a conductive paste having an Ag content of 76% by weight is used. It was produced under the conditions.

  As described above, the sintering shrinkage rate during firing of the magnetic ceramic (ferrite) and the inner conductor is 13 to 20% for the magnetic ceramic, whereas that for the inner conductor is 8%. Since the sintering shrinkage rate is smaller than the sintering shrinkage rate of ferrite, the interface between the internal conductor and the magnetic ceramic is firmly bonded at the stage after firing is finished.

However, when the pore area ratio of the side gap portion is large to some extent by applying, for example, Ni plating to the sample in which the interface between the inner conductor and the magnetic ceramic is firmly bonded, the plating is performed, Ni plating solution penetrates from the pores in the area not covered by the external electrode of the magnetic ceramic element (multilayer coil component), reaches the interface between the internal conductor and the magnetic ceramic, and reaches the interface between the internal conductor and the magnetic ceramic. The bond is broken at.
On the other hand, when the pore area ratio of the side gap portion is small, the plating solution cannot penetrate inside, and the bond cannot be cut at the interface between the internal conductor and the magnetic ceramic.

  The sample No. 7 in Table 1 is a sample having a low pore area ratio of 2% in the side gap portion, and the interface between the internal conductor and the magnetic ceramic is bonded even after the plating process. When ruptured, no separation was observed at the interface between the magnetic ceramic and the inner conductor. Therefore, in the case of the sample of Sample No. 7, since the stress is applied to the magnetic ceramic due to the sintering shrinkage of the internal conductor, the impedance is remarkably lowered.

  The conductive paste having an Ag content of 76% by weight used in the sample of sample number 8 has a high sintering shrinkage rate of 22%, which is higher than the sintering shrinkage rate of the surrounding magnetic ceramic (ferrite). A gap is formed between the magnetic ceramic and the inner conductor, and a through hole is partially formed in the inner conductor, so that the inner conductor coverage is as low as 94.6%. Also, the impedance is somewhat lower than the sample No. 4 sample.

FIG. 5 shows the sample No. 4 having the requirements of the present invention (using a conductive paste having an Ag content of 85% by weight and a sintering shrinkage of 8%, an inner conductor coverage of 100%, and a side gap portion) FIG. 6 shows an SEM image of the inner conductor of a sample having a pore area ratio of 11%. FIG. 6 shows a sample No. 8 that does not satisfy the requirements of the present invention (produced using a conductive paste having an Ag content of 76% by weight). And an SEM image of the inner conductor of the sample having a low inner conductor coverage of 94.6%.
As shown in FIG. 5, in the case of the sample of sample number 4, a dense inner conductor without through holes is formed. However, in the sample of sample number 8, as shown in FIG. It can be seen that it is formed.

Further, with respect to the sample No. 8 and the sample No. 4, the DC resistance was further measured, and a surge 30 kV application test was performed. The results are shown in Table 2.
The direct current resistance was measured using MULTITIMER (Hewlett-Packard 34401A). Further, the surge 30 kV application test was performed by applying the discharge capacitor 150 pF, discharge resistance 330Ω, contact discharge, and 30 times at 0.1 second intervals by the test method specified in IEC61000-4-2.

  As shown in Table 2, in the case of the sample No. 8 sample that does not satisfy the requirements of the present invention, the DC resistance is 0.43Ω, compared to the DC resistance 0.26Ω of the sample No. 4 sample that satisfies the requirements of the present invention. It was also confirmed that, even in a surge test with 30 kV applied, four disconnections that occurred in the sample No. 4 occurred in 100 samples.

  On the other hand, in the case of samples Nos. 1 to 6, when the pore area ratio of the side gap portion is 6% or more, the plating solution penetrates into the magnetic ceramic element, and the bonding at the interface between the internal conductor and the magnetic ceramic is sufficient. Since it was cut and the internal conductor coverage was 99.5% or more, it was confirmed that a good multilayer coil component having a low impedance reduction characteristic was obtained.

  In the case of samples Nos. 1 to 6, the SEM observation of the FIB processed surface shows no gap at the interface between the magnetic ceramic and the internal conductor, but when the laminated coil component is broken, the magnetic ceramic and the internal Delamination is observed at the interface with the conductor. Therefore, the Ni plating solution penetrates from the pores in the region not covered by the external electrode of the magnetic ceramic element (laminated coil component), reaches the interface between the internal conductor and the magnetic ceramic, and is magnetic It can be seen that the bond at the interface of the body ceramic is broken.

In addition, since the pore area ratio of the sample of sample number 1 is as high as 26%, although the decrease in impedance is small, the decrease in the adhesion strength is recognized.
Therefore, from the standpoint of securing a high bending strength while suppressing a decrease in impedance, it is desirable that the pore area ratio of the side gap portion is in the range of 6 to 20% as in Sample Nos. 2 to 6.
Moreover, when the pore area ratio is 8 to 16% as in sample numbers 3 to 5, the impedance and the bending strength are more stable, which is further preferable.

FIG. 7 shows a SIM image of the surface (WT surface) processed by FIB after mirror-polishing the cross section of the laminated coil component (sample No. 3 in Table 1) of the example of the present invention.
This SIM image is obtained by observing the surface processed by FIB after mirror polishing of the WT surface of the laminated coil component after plating at a magnification of 5000 times with a SIM. It can be seen that is not allowed.

Further, FIG. 8 shows an SEM image of a fracture surface of the laminated coil component of the example (sample No. 3 in Table 1) by a three-point bending test.
In the SEM observation of the fracture surface, as can be seen from FIG. 8, there is a gap, but this is because the interface between the inner conductor and the magnetic ceramic is dissociated, so that the inner conductor extends at the time of fracture and is pulled out to the front. It is thought that a gap was sometimes formed. A similar gap is observed when the sample is broken with a nipper.

In Example 2, an example of a laminated coil component manufactured using a magnetic ceramic added with glass is shown.
Fe ₂ O ₃ : 48.0 mol%, ZnO: 29.5 mol%, NiO: 14.5 mol%, CuO: 8.0 mol% Weighed magnetic material for 48 hours in a ball mill and slurry It was.
Then, this slurry was dried with a spray dryer and calcined at 700 ° C. for 2 hours to obtain a calcined product.

Then, zinc borosilicate low softening point crystallized glass is added to this calcined material at a ratio of 0 to 0.6% by weight, wet milling is performed for 16 hours with a ball mill, and a predetermined amount of binder is mixed. Thus, a ceramic slurry was obtained. Note that the zinc borosilicate low-softening point crystallized glass may be added before calcination.
The zinc borosilicate crystallized glass added here is a glass having a composition of 12 wt% SiO ₂ -60 wt% ZnO-28 wt% B ₂ O ₃ , softening point 580 ° C., crystallization temperature 690 ° C., grain size Glass with a diameter of 1.5 μm.
As the composition of the glass, in the basic _{composition, BaO, K 2 O, CaO} , Na 2 O, Al 2 O 3, SnO 2, SrO, may contain additives such as MgO.

Then, this ceramic slurry was formed into a sheet to obtain a ceramic green sheet having a thickness of 25 μm.
Thereafter, an unfired laminated body (magnetic ceramic element) having a laminated helical coil therein was produced by the same method as the steps (2) to (4) in Example 1 above.
Then, this laminate was sintered by adjusting the firing temperature so that the pore area ratio of the side gap portion was 11%.

Then, the bending strength was measured by an impedance and a three-point bending test under the same method and conditions as in Example 1.
Table 3 shows the impedance (| Z |) value and bending strength value of each sample using magnetic ceramics with different glass addition amounts.

As shown in Table 3, by adding zinc borosilicate crystallized glass, a magnetic ceramic having a predetermined pore area ratio, high mechanical strength, and high permeability even when the density is low. Can be obtained. In addition, the internal conductor coverage is as high as 99.9%. Therefore, it is possible to obtain a laminated coil component having a high bending strength without causing a decrease in impedance.
The amount of zinc borosilicate crystallized glass is preferably in the range of 0.1 to 0.5% by weight, and more preferably in the range of 0.2 to 0.4% by weight.

  Moreover, the composition of the zinc borosilicate crystallized glass used in Example 2 was changed to produce a zinc borosilicate crystallized glass having a softening point in the range of 400 to 770 ° C. And the addition amount of this zinc borosilicate type | system | group crystallized glass was 0.3 weight%, others produced the laminated coil component by the same method and conditions as the case of the said Example 1, and impedance of the obtained laminated coil component Was measured. The result is shown in FIG.

As can be seen from FIG. 9, a high impedance (| Z |) value can be obtained by setting the softening point of the glass to be used in the range of 500 to 700 ° C.
A glass softening point of less than 500 ° C. is not preferable because the fluidity is lowered to inhibit the sintering of the magnetic ceramic or the glass is evaporated to cause a decrease in magnetic permeability.
Further, when the glass softening point exceeds 700 ° C., sintering of the magnetic ceramic is hindered, the magnetic permeability is lowered, and the impedance is lowered, which is not preferable.

In the present invention, there is no particular restriction on the method for controlling the pore area ratio of the side gap,
(1) A method of adjusting the sintering shrinkage difference between the magnetic ceramic and the inner conductor in the range of 5 to 20%,
(2) A method of adjusting the thickness of the inner conductor with respect to the thickness of the magnetic ceramic sheet (for example, 10 to 50 μm) within a range of 5 to 50 μm, for example.
(3) A method of adjusting the particle size of the ceramic constituting the magnetic ceramic sheet within a range of, for example, 0.5 to 5 μm,
(4) A method of adjusting the binder content of the magnetic ceramic sheet in the range of, for example, 8 to 15% by weight,
(5) The pore area ratio of the side gap can be controlled by combining the above (1) to (4).

In Example 3, an example of a laminated coil component manufactured using a magnetic ceramic in which SnO ₂ is added to NiCuZn ferrite is shown.

Fe ₂ O ₃ 48.0 mol%, ZnO 29.5 mol%, NiO 14.5 mol%, CuO 8.0 mol%, and SnO ₂ in a proportion of 0 to 1.25 wt% based on the main component (ie The magnetic material raw material weighed at a ratio of 0 to 1.2% by weight on the outer shell) was wet mixed in a ball mill for 48 hours to form a slurry.

The obtained slurry was dried with a spray dryer and calcined at 700 ° C. for 2 hours to obtain a calcined product.
To this calcined product, 0.3% by weight of zinc borosilicate low-softening point crystallized glass was added, and after wet milling for 16 hours in a ball mill, a predetermined amount of binder was added and mixed to obtain a ceramic slurry. Obtained.

Thereafter, an unfired laminated body (magnetic ceramic element) having a laminated spiral coil therein was produced in the same manner as in Example 2.
Then, this laminate was sintered by adjusting the firing temperature so that the pore area ratio of the side gap portion was 11%.

Then, in the same manner as in Example 2, the bending strength was measured by an impedance and a three-point bending test. In addition, 50 samples of each sample were subjected to 2000 cycles of a thermal shock test at −55 ° C. to 125 ° C., the rate of change in impedance before and after the test was measured, and the maximum value was obtained.
Table 4 shows the impedance (| Z |) value, bending strength, and maximum value of the rate of change of impedance (| Z |) before and after the thermal shock test for each sample with the added amount of SnO ₂ changed.

As can be seen from Table 4, as the amount of SnO ₂ added increases, the rate of change in impedance before and after the thermal shock test decreases.
However, since the bending strength and the impedance are also lowered, the SnO ₂ addition amount is preferably in the range of 0.3 to 1.0% by weight.
Furthermore, when the SnO ₂ addition amount is in the range of 0.5 to 0.75% by weight as in sample numbers 19 and 20, it is possible to obtain a laminated coil component with more stable characteristics, which is particularly desirable.

  In each of the above embodiments, the case of manufacturing by a so-called sheet laminating method including a step of laminating ceramic green sheets has been described as an example, but the magnetic ceramic slurry and the conductive paste for forming the inner conductor are used. These can be prepared by a so-called sequential printing method in which these are printed so as to form a laminate having the configuration shown in each example.

  Furthermore, it is formed by, for example, transferring a ceramic layer formed by printing (coating) a ceramic slurry on a carrier film onto a table and printing (coating) an electrode paste on the carrier film. It is also possible to manufacture by a so-called sequential transfer method in which the electrode paste layer is transferred and this is repeated to form a laminated body having the configuration as shown in each example.

  The laminated coil component of the present invention can be manufactured by another method, and the specific manufacturing method is not particularly limited.

  Further, the present invention can also be applied to a multilayer inductor having an open magnetic circuit structure partially including a nonmagnetic ceramic.

In each of the above embodiments, the plating solution used for plating the external electrode is used as an acidic solution, and the laminated coil component is immersed in this plating solution, so that the interface between the internal conductor and the surrounding magnetic ceramics is obtained. However, it is also possible to configure so that the laminated coil component is immersed in a NiCl ₂ solution (PH 3.8 to 5.4) at a stage prior to the plating step, for example. . It is also possible to use other acidic solutions.

  In each of the above embodiments, the case where laminated coil components are manufactured one by one (in the case of individual products) has been described as an example. However, in the case of mass production, for example, a large number of coil conductor patterns are mother ceramic green sheets. After printing on the surface of the ceramic ceramic sheet and laminating and bonding multiple sheets of this mother ceramic green sheet to form an unfired laminated body block, the laminated body block is cut in accordance with the arrangement of the coil conductor pattern and used for individual laminated coil parts. It is possible to manufacture by applying a so-called multi-cavity method in which a large number of laminated coil components are simultaneously manufactured through the step of cutting out the laminated body.

  Further, although cases have been described with the above embodiments as examples where the laminated coil component is a laminated impedance element, the present invention can be applied to various laminated coil components such as a laminated inductor and a laminated transformer.

  The present invention is not limited to the above embodiment in other points as well, and relates to the thickness of the internal conductor, the thickness of the magnetic ceramic layer, the dimensions of the product, the firing conditions of the laminate (magnetic ceramic element), etc. Various applications and modifications can be made within the scope of the invention.

As described above, according to the present invention, it is possible to alleviate the problem of internal stress without forming a gap between the internal conductor and the surrounding magnetic ceramic, and the internal conductor coverage is 99.99. If it is 5% or more, it is possible to obtain a highly reliable laminated coil component that has a high occupation ratio of the internal conductor, low resistance, and is less likely to cause disconnection of the internal conductor due to a surge or the like.
Therefore, the present invention can be widely applied to various laminated coil components including a laminated impedance element and a laminated inductor having a configuration in which a coil is provided in a magnetic ceramic.

Claims (4)

The internal conductor is connected between layers in a magnetic ceramic element including a plurality of laminated magnetic ceramic layers and an internal conductor mainly composed of Ag and disposed via the magnetic ceramic layer. A laminated coil component having a helical coil formed by:
The inner conductor coverage, which is the ratio of the area of the region covered with the inner conductor to the region where the inner conductor is to be disposed, is 99.5% or more,
While the pore area ratio of the magnetic ceramic constituting the side gap portion that is a region between the side portion of the inner conductor and the side surface of the magnetic ceramic element is in the range of 6 to 20%,
There is no air gap at the interface between the inner conductor and the magnetic ceramic around the inner conductor, and the interface between the inner conductor and the magnetic ceramic is dissociated. . Formed by using a plurality of laminated magnetic ceramic green sheets and a conductive paste containing Ag in the range of 80 to 90% by weight and having a smaller sintering shrinkage than the magnetic ceramic green sheets. A ceramic multilayer body having a plurality of internal conductor patterns for firing, a magnetic ceramic element having a spiral coil therein, and a side portion of the internal electrode formed by firing the internal conductor pattern; Forming a magnetic ceramic element having a pore area ratio in the range of 6 to 20% of the magnetic ceramic constituting the side gap portion which is a region between the side surfaces of the magnetic ceramic element;
By causing the acidic solution to reach the interface between the inner conductor and the surrounding magnetic ceramic from the side surface of the magnetic ceramic element through the side gap portion, the inner conductor and the surrounding magnetic ceramic Cutting the bond at the interface; and
A method for manufacturing a laminated coil component, comprising: Coil formation formed by using a plurality of laminated magnetic ceramic green sheets and a conductive paste containing Ag in the range of 80 to 90% by weight and having a sintering shrinkage smaller than that of the magnetic ceramic green sheets. And firing a ceramic laminate including a plurality of internal conductor patterns, and having a spiral coil therein and one of a pair of end portions of the spiral coil on each of a pair of side surfaces facing each other Is exposed, and the pore area ratio of the magnetic ceramic constituting the side gap portion, which is a region between the side portion of the inner conductor formed by firing the inner conductor pattern and the side surface of the magnetic ceramic element, is Forming a 6-20% magnetic ceramic element;
Forming external electrodes on the pair of side surfaces of the magnetic ceramic element in which the pair of end portions of the spiral coil are exposed;
And a step of plating the surface of the external electrode using an acidic plating solution.   4. The method of manufacturing a laminated coil component according to claim 2, wherein a conductive paste containing Ag in a range of 83 to 89% by weight is used as the conductive paste.

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