JP2005223279A - Chip-type electronic component and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a chip-type electronic component and its manufacturing method, in which the variations in the serial resistances can be suppressed by suppressing the generation of a grain boundary across a linear conductor built into a ceramic substrate. <P>SOLUTION: An inductor comprises a ceramic substrate 10, a coil 15 made of a metal wire built in the substrate 10, and external electrodes 20, 20 formed on the surface of the substrate 10 and connected with the coil 15. The coil 15 contains 99.99 wt.% or higher Ag, and contains at least any one from among Fe, Cr, Co, Ni, Cu, Pb, Bi as an impurity, wherein the total amount of Fe, Cr, Co, Ni, Cu, Pb, Bi is 100 wt.ppm or lower. At least all of single Fe, Cr, Co, Ni, Cu, Pb, Bi is 60 wt.ppm or lower. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a chip-type electronic component and a manufacturing method thereof, and more particularly to a chip-type electronic component that is an inductor such as a choke coil and a noise filter and a manufacturing method thereof.

  Conventionally, various types of chip type inductors used for common mode choke coils, noise filters, and the like have been provided, and the chip type impedance element described in Patent Document 1 can be given as an example.

  This chip-type impedance element has a conductor made of Ag incorporated in a ceramic base, the average particle diameter of the conductor made of Ag is ½ or less of the wire diameter, and the conductor is at least of Ni, Cu, Cr. It is disclosed that the direct current resistance is stabilized by including 0.01 to 1% by weight of one.

However, as described in Patent Document 1, even if the average particle diameter of the conductor is controlled, a grain boundary transverse to the length direction of the conductor is generated, and it is difficult to stabilize the DC resistance. That is, as shown in FIG. 4 (A), when a transverse grain boundary 2 that causes disconnection occurs in the conductor 1 made of Ag, the conductor 1 is displaced as shown in FIG. It becomes unstable.
Japanese Patent Laid-Open No. 11-97247

  SUMMARY OF THE INVENTION An object of the present invention is to provide a chip-type electronic component capable of suppressing the occurrence of grain boundaries crossing a linear conductor built in a ceramic substrate and suppressing variations in DC resistance, and a method for manufacturing the same. There is.

  In order to achieve the above object, a chip-type electronic component according to the present invention includes a ceramic base, an internal conductor made of a metal wire built in the ceramic base, and formed on the surface of the ceramic base and connected to the internal conductor. In the chip-type electronic component provided with the external electrode, the metal wire contains 99.99% by weight or more of Ag, and contains at least one of Fe, Cr, Co, Ni, Cu, Pb, Bi as an impurity, The total amount of Fe, Cr, Co, Ni, Cu, Pb, Bi is 100 ppm by weight or less, and at least all of Fe, Cr, Co, Ni, Cu, Pb, Bi is 60 ppm by weight or less. It is characterized by being.

  In the chip-type electronic component according to the present invention, the total amount of impurities of the inner conductor made of Ag (meaning metal impurities that affect the crystallinity of Ag of the inner conductor when the substrate is sintered) is 0.001% by weight. The internal conductor is crossed with respect to the length direction during the sintering of the ceramic substrate because all of these metal impurities are prepared so as to be not more than 60 ppm by weight. Grain boundary growth is suppressed, variation in DC resistance is suppressed, and the incidence of defective products can be reduced to 0%.

  The method for manufacturing a chip-type electronic component according to the present invention is a method for manufacturing the chip-type electronic component, comprising the steps of preparing a ceramic slurry, and injecting the ceramic slurry into a mold loaded with the metal wire. The method includes a step of press forming to form the ceramic substrate, a step of sintering the ceramic substrate, and a step of forming the external electrode on the surface of the ceramic substrate.

  According to the manufacturing method of the present invention, it is possible to efficiently manufacture a chip-type electronic component in which variation in DC resistance is suppressed and the occurrence rate of defective products is extremely low.

  Embodiments of a chip-type electronic component and a manufacturing method thereof according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows a chip-type electronic component according to an embodiment of the present invention. This electronic component is an inductor, in which a coil 15 made of Ag is incorporated as an internal conductor in a rectangular parallelepiped ceramic base 10 made of ferrite or the like, and is electrically connected to both ends of the coil 15 at both ends of the ceramic base 10. The formed external electrodes 20 and 20 are formed.

  The coil 15 is obtained by winding an Ag wire having a diameter of 0.2 mm for 6 turns with a coil diameter of 2 mm and a pitch between wires of 0.4 mm, and affects the component, particularly the crystallinity of Ag during sintering of the substrate. The content of impurities (Fe, Cr, Co, Ni, Cu, Pb, Bi) will be described later.

  Here, an example of the inductor manufacturing method performed by the present inventors will be described with specific numerical values.

First, a ceramic slurry was prepared. That is, NiCuZn ferrite raw material powder (powder particle size 2 μm, specific surface area 2.5 m ² / g), the following additives and water were added to the pot, and mixed in a ball mill for 20 hours to obtain a ceramic slurry. .

Dispersant: Polyoxyalkylene glycol, 2.0% by weight with respect to raw material powder weight Antifoam: Polyether-based antifoaming agent, 0.5% by weight with respect to raw material powder weight Binder: Acrylic binder, 0.5% by weight of raw material powder weight Water: 50% by weight of raw material powder weight

Next, the following molded bodies were obtained in the first wet pressing step. That is, a predetermined amount of the ceramic slurry was put into a mold, covered with a filter that allows only moisture to escape, and then packed so as not to leak the slurry. Then, water was removed from the slurry at a pressure of 100 kgf / cm ² for 5 minutes to obtain a plate-like molded body.

  Next, the coil 15 was installed on the plate-shaped molded body. In order to prevent deformation of the coil 15, it is desirable to install the coil 15 in a direction in which the axial direction of the coil 15 is horizontal. Further, in order to prevent displacement of the coil 15, it is desirable to fix the coil 15 with a small amount of adhesive or slurry.

Next, the molded object which incorporated the coil 15 in the 2nd wet press process was obtained. That is, the plate-like molded body to which the coil 15 was fixed was placed in a mold, a predetermined amount of the ceramic slurry was put in, covered with a filter through which only moisture was removed, and then packed so that the slurry did not leak. Then, moisture was removed from the slurry at a pressure of 100 kgf / cm ² for 5 minutes to obtain a molded body in which the coil 15 was incorporated.

  The molded body obtained in the second wet pressing step was dried at 40 ° C. for 50 hours. The molded body thus dried was placed in an alumina sheath and sintered at 900 ° C. for 2 hours. The sintered body was cut or polished and finished into a predetermined shape.

  Next, external electrodes 20 and 20 electrically connected to both end portions of the coil 15 were formed on both end portions of the surface of the sintered body having a predetermined shape, thereby obtaining an inductor.

  The inventors of the present invention have variously changed the total amount of impurities (Fe, Cr, Co, Ni, Cu, Pb, Bi) with respect to the Ag wire of the coil 15 and variously changed the content of the impurities alone. The inductor was manufactured under the same conditions by changing, and the DC resistance was measured.

  With respect to the total amount of impurities contained in the Ag line, as shown in the graph of FIG. 2, when the total amount of impurities was 100 ppm by weight or less, the DC resistance did not vary and the defect rate became 0%. As for the content of impurities alone, as shown in the graphs of FIGS. 3 (A) and 3 (B), there was no variation in DC resistance when the content was approximately 60 ppm by weight or less, and the defect rate was 0%. .

  Here, the DC resistance is defective means that the measured DC resistance value is 50% or more larger than the design value.

  When an impurity (at least one of Fe, Cr, Co, Ni, Cu, Pb, and Bi) is added to Ag as the material of the coil 15, the recrystallization temperature of Ag where grain boundaries exist increases, Crystal growth at the time of settling is slowed down. Sintering of ferrite with Ag as an internal conductor is usually 850 to 940 ° C. for about 2 hours. When the temperature is lower than 850 ° C., ferrite is not sintered, so that sufficient strength and sintered density cannot be obtained. However, at a normal sintering temperature and a large impurity content, the diffusion of Ag progresses and a grain boundary (see FIG. 4) transverse to the length direction of the Ag wire is generated, and the DC resistance is reduced. Rise.

  Therefore, in order not to generate a grain boundary transverse to the length direction of the Ag line in the temperature range of 850 to 940 ° C., the total amount of impurities and the content alone are adjusted to lower the recrystallization temperature of Ag. It is necessary to reduce the grain boundary at the sintering temperature.

  According to the experiments by the present inventors, as shown in FIGS. 2 and 3, the Ag wire contains 99.99% by weight or more of Ag and contains at least Fe, Cr, Co, Ni, Cu, Pb, and Bi. If any of them is contained as impurities, the total amount of the impurities is 100 ppm by weight or less, and at least all of Fe, Cr, Co, Ni, Cu, Pb, and Bi are independently 60 ppm by weight or less, direct current The defect rate of resistance became 0%.

  By adjusting the amount of the impurity contained in the Ag line as described above, such an effect is suppressed by preventing the occurrence of a grain boundary crossing the length direction of the Ag line and eliminating the deviation of the Ag line. Due to that.

  In the present invention, the impurities are Fe, Cr, Co, Ni, Cu, Pb, Bi, and the lower limit of the total amount including at least one of these elements is not particularly specified, but it is 1 ppm by weight or more. preferable. Moreover, it is preferable that the lower limit of individual content of each element which is an impurity is also 1 ppm by weight, respectively.

(Other examples)
The chip-type electronic component and the manufacturing method thereof according to the present invention are not limited to the above-described embodiments, and can be variously modified within the scope of the gist.

  In particular, the materials and numerical values given in the above examples are merely examples. For example, as the binder added in the process of preparing the ceramic slurry, a vinyl acetate binder can be used in addition to the acrylic binder.

It is a perspective view which shows one Example (inductor) of the chip-type electronic component which concerns on this invention. It is a graph which shows the defect rate of DC resistance with respect to the total amount of the impurity in the inner conductor (Ag line) of the inductor. It is a graph which shows the defect rate of DC resistance with respect to content in the impurity alone in the inner conductor (Ag line) of the inductor. It is explanatory drawing which shows typically the grain boundary and disconnection similar state in the internal conductor (Ag line) of the said inductor.

Explanation of symbols

10 ... ceramic substrate 15 ... coil (internal conductor)
20 ... External electrode

Claims (2)

In a chip-type electronic component comprising a ceramic base, an internal conductor made of a metal wire built in the ceramic base, and an external electrode formed on the surface of the ceramic base and connected to the internal conductor,
The metal wire contains 99.99% by weight or more of Ag and contains at least one of Fe, Cr, Co, Ni, Cu, Pb, and Bi as an impurity, Fe, Cr, Co, Ni, Cu, Pb, Bi And the total amount of Fe, Cr, Co, Ni, Cu, Pb, Bi alone is 60 ppm by weight or less.
Chip-type electronic components characterized by It is a manufacturing method of the chip type electronic component according to claim 1,
Preparing a ceramic slurry;
Injecting the ceramic slurry into a mold loaded with the metal wire and wet pressing to form the ceramic substrate;
Sintering the ceramic substrate;
Forming the external electrode on the surface of the ceramic substrate;
A method for manufacturing a chip-type electronic component, comprising:

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