WO2011111378A1 - Ceramic electronic component and production method for same - Google Patents

Abstract

A ceramic electronic component is provided with a ceramic sintered compact, and an electrode which abuts the ceramic sintered compact and which contains Ag. The ceramic sintered compact comprises glass material made from borosilicate glass. A plurality of closed pores are distributed in a substantially uniform manner throughout the glass material. The ceramic electronic component has a stable dielectric constant even if the ceramic sintered compact and the electrode have been fired simultaneously.

Description

Ceramic electronic component and manufacturing method thereof

The present invention relates to a ceramic electronic component having an electrode and a ceramic material and a method for manufacturing the same.

In recent years, for example, countermeasures against radiated noise have become a problem as the speed of high-speed interfaces such as USB and HDMI is further increased. Therefore, common mode noise, which is said to cause this radiation noise, is removed by a common mode noise filter. For example, in this common mode noise filter, a ceramic material having a low dielectric constant is used for the following reason.

The common mode noise filter is a dielectric with two coils wound in the same direction. Normally, when a current is passed through a coil, a magnetic field is generated, and a braking effect is caused by self-induction. The common mode noise filter blocks the passage of the common mode noise current by utilizing the interaction of the two coils. Specifically, when a signal current of common mode noise is passed through two coils, both flow in the same direction, so the magnetic fluxes generated in the coils are combined and strengthened. As a result, a stronger braking action works due to the electromotive force due to the self-induction action, and the passage of the common mode noise current can be prevented.

¡By synthesizing and strengthening the magnetic flux generated in the coils by bringing the two coils close to each other, a stronger braking action can be exerted and the function as a common mode noise filter can be exhibited better. However, when the two coils are brought close to each other, the stray capacitance between the coils increases, so that a resonance phenomenon occurs and the passage of the signal current is hindered. Therefore, in order to shorten the distance between the two coils and reduce the stray capacitance between the coils, it is necessary to lower the dielectric constant of the dielectric in which the coil is disposed.

When the dielectric constant of the dielectric varies among multiple common mode noise filter products, the stray capacitance between the coils varies, resulting in variations in the characteristics of the common mode noise filter. In other high-frequency devices and high-speed transmission line substrates, a ceramic material that is a dielectric having a low dielectric constant is desired as an LTCC material that has a high signal propagation speed and can efficiently transmit signals. Even in these ceramic materials, the characteristics are not stable if the dielectric constant varies. Therefore, it is desired to suppress variations in dielectric characteristics of ceramic materials.

Patent Document 1 discloses a ceramic electronic component in which pores are provided inside a ceramic sintered body using an inorganic foaming agent in order to lower the dielectric constant, and a method for manufacturing the same.

If a ceramic sintered body is manufactured by this method, the dielectric characteristics of the ceramic electronic component may vary as a result.

In an electronic component having two or more layers of Ag electrodes therein, the electronic component is designed in consideration of a capacitance value formed between Ag electrodes. Therefore, stabilization of the capacitance value is indispensable for stabilizing the characteristics of the electronic component. The capacitance value C is expressed by the following equation by the dielectric constant ε _{0 of} vacuum, the dielectric constant ε _r of the ceramic material, the area S of the electrodes, and the distance d between the electrodes.

C = ε ₀ · ε _r · S / d
In order to stabilize the capacitance value C, the manufacturing process is optimized so that the electrode area S and the inter-electrode distance d are constant. However, no matter how stable they are, if the dielectric constant ε _r of the ceramic material varies, variations in the capacitance value C, and hence variations in the characteristics of the electronic components, are unavoidable.

As described above, when the dielectric constant varies, it is extremely difficult to control the capacitance value C between the Ag electrodes as designed, and it is desired to suppress local variations in the dielectric constant ε _r .

JP 2002-193691 A

The ceramic electronic component includes a ceramic sintered body and an electrode containing Ag in contact with the ceramic sintered body. The ceramic sintered body has a glass material made of borosilicate glass. The glass material is provided with a plurality of closed pores distributed substantially uniformly.

This ceramic electronic component has a stable dielectric constant even when the ceramic sintered body and the electrode are fired simultaneously.

FIG. 1 is a schematic cross-sectional view of a ceramic electronic component according to an embodiment of the present invention. FIG. 2 is a diagram showing the composition and physical properties of the ceramic sintered body of the ceramic electronic component according to the embodiment of the present invention. FIG. 3A is a schematic cross-sectional view showing a method for manufacturing a ceramic electronic component according to an embodiment of the present invention. FIG. 3B is a schematic cross-sectional view showing the method for manufacturing the ceramic electronic component according to the embodiment of the present invention. FIG. 4 is a diagram showing a dielectric constant of a sample of a ceramic sintered body of a ceramic electronic component according to an embodiment of the present invention.

FIG. 1 is a schematic cross-sectional view of a ceramic electronic component 100 according to an embodiment of the present invention. The ceramic electronic component 100 includes a ceramic sintered body 1, an electrode 2 provided on the surface 101 of the ceramic sintered body 1, and an electrode 502 provided inside the ceramic sintered body 1. The ceramic sintered body 1 includes a glass material 6 and a plurality of fillers 5 dispersed in the glass material 6. A plurality of open pores 3, a plurality of open pores 503, and a plurality of closed pores 4 are formed in the glass material 6 of the ceramic sintered body 1. The glass material 6 is made of borosilicate glass. The electrode 2 contacts the portion 101A of the surface 101 of the ceramic sintered body 1. The plurality of open pores 3 are open to the portion 101 </ b> A of the ceramic sintered body 1. The electrode 502 contacts the portion 501A in the ceramic sintered body 1. The plurality of open pores 3 are open to the portion 101 </ b> A of the ceramic sintered body 1. The plurality of open pores 503 are open to the portion 501 </ b> A of the ceramic sintered body 1. The ceramic electronic component 100 constitutes a capacitor component by the electrodes 2 and 502 facing each other with the ceramic sintered body 1 interposed therebetween. Ceramic electronic component 100 in the embodiment may constitute an inductor component such as a common mode noise filter whose electrodes function as an inductor. Ceramic electronic component 100 in the embodiment may not include one of electrodes 2 and 502.

The plurality of closed pores 4 are uniformly distributed in the ceramic sintered body 1. A value obtained by dividing the total volume of the closed pores 4 in a certain part by the total volume of the ceramic sintered body 1 is defined as the closed porosity of that part. The plurality of closed pores 4 are distributed in the ceramic sintered body 1 so that the porosity is uniform. Alternatively, the plurality of closed pores 4 are distributed so that the number per unit volume in each portion in the ceramic sintered body 1 is uniform, and the diameters of the plurality of closed pores 4 are substantially the same. It is. Thereby, the closed porosity becomes uniform in the ceramic sintered body 1.

The closed pores 4 are pores inside the ceramic sintered body 1 and not communicating with the outside of the ceramic sintered body 1. The closed pores 4 may be independent pores existing alone in the ceramic sintered body 1 or may be so-called continuous vent holes in which a plurality of pores are connected. The open pores 3 are pores that partially communicate with the outside of the ceramic sintered body 1. The open pores 3 may be independent pores that exist independently in the ceramic sintered body 1 or may be continuous vent holes in which a plurality of pores are connected.

When a ceramic sintered body is manufactured by a conventional method disclosed in Patent Document 1, closed pores are not uniformly distributed when fired simultaneously with an Ag electrode, and the pores gather near the Ag electrode. Therefore, the dielectric constant of the portion near the Ag electrode in the ceramic sintered body is lower than that of other portions, and as a result, the dielectric characteristics of the ceramic electronic component may vary.

If the closed pores are not uniformly distributed in the interior and the dielectric constant differs between the part near and far from the electrode, it is extremely difficult to control the capacitance between the electrodes as designed. It is necessary to suppress general variations.

The composition of the borosilicate glass constituting the glass material 6 will be described below.

In Embodiment 1, it is desirable to use a borosilicate glass having a crystallization rate of 90% or less as the glass material 6. In a crystallized glass having a crystallization rate exceeding 90%, the decrease in viscosity at the softening point or higher is not so great that the formation of the open pores 3, 503 and the closed pores 4 is inhibited, and the closed pores 4 are difficult to be uniformly distributed. There is a case.

The glass composition of the borosilicate glass may be made of a material containing at least one selected from Al ₂ O ₃ , ZnO, alkaline earth metal oxide, and alkali metal oxide in addition to SiO ₂ and B ₂ O _3. It is desirable to contain an alkaline earth metal oxide or an alkali metal oxide. In consideration of the influence on the environment, it is desirable that PbO is not substantially contained.

The glass bending point used for the glass material 6 is desirably 550 ° C. or higher and 750 ° C. or lower. When the glass bending point is lower than 550 ° C., the glass material 6 is significantly deformed at the time of firing, and problems such as plating may occur due to poor chemical resistance. In addition, when the glass bending point exceeds 750 ° C., the densification of the glass material 6 is insufficient in a temperature range in which simultaneous firing with the electrodes 2 and 502 made of Ag is possible.

Here, the glass bending point is a temperature that changes from expansion to contraction while the temperature of the glass is raised, and thermomechanical analysis (TMA) measurement of a glass rod-shaped sample (measured with TMA8310 manufactured by Rigaku Corporation). Can be obtained.

The filler 5 is made of a SiO ₂ filler. Thereby, the fixed form property after baking can be maintained, keeping the dielectric constant of the ceramic sintered compact 1 low.

In this embodiment, the inorganic foaming agent is preferably CaCO ₃ or SrCO _3, but may be a mixture obtained by mixing CaCO ₃ and SrCO ₃ . As the inorganic foaming agent, various carbonates, nitrates, sulfates and the like can be used as long as they decompose at 600 to 1000 ° C., for example, BaCO ₃ , Al ₂ (SO ₄ ) ₃ , Ce ₂ (SO ₄ ) ₃ or the like can be used. The decomposition completion temperature of the inorganic foaming agent is above the yield point of the borosilicate glass powder. The decomposition completion temperature of the foaming agent is preferably 600 ° C to 1000 ° C, more preferably 700 ° C to 1000 ° C. If the decomposition completion temperature is within this range, the gas generated during the heating process during firing is suitably trapped in the ceramic sintered body 1.

The decomposition completion temperature is the temperature at which weight reduction is completed in the thermogravimetric (TG) chart of the raw material powder used as the foaming agent, and differential thermal-thermogravimetric simultaneous measurement of the raw material powder (TG-DTA) (TG8120, manufactured by Rigaku Corporation). Can be obtained by measurement). At this temperature, decomposition of the foaming agent is completed, and the closed pores 4 and the open pores 3 and 503 can be formed in the glass material 6.

In addition, the addition amount of the inorganic foaming agent is preferably 3 wt% or less. If the inorganic foaming agent is 3 wt% or more, the majority of the open pores 3, 503 and the closed pores 4 are connected to each other to form so-called continuous vents, which is not preferable because the water absorption rate increases.

When the cross section of the obtained sample was confirmed with an electron microscope, it was confirmed that the pores were uniformly formed in the sample prepared using the foaming agent.

The Ag added to the ceramic sintered body 1 is preferably about 1 wt% to 3 wt% with respect to the borosilicate glass. When Ag is less than 1 wt%, the diffusion of Ag from the electrodes 2 and 502 into the glass material 6 cannot be sufficiently suppressed. When Ag is more than 3 wt%, the electrical insulating property of the ceramic sintered body 1 is inferior. In the method of introducing Ag into the ceramic sintered body 1, it is desirable that Ag is uniformly dissolved in the glass when the glass constituting the ceramic sintered body 1 is produced by a melting method. Or when mixing the filler 5 and glass powder, Ag can be mixed with glass by mixing and baking Ag fine powder or the salt fine powder containing Ag.

Here, a small amount of Ag is added to the ceramic sintered body 1 in order to suppress excessive diffusion of Ag from the electrodes 2 and 502 mainly composed of Ag. Since Ag has a small ion radius, it is easy to be taken into the glass network and to move in the glass melt. By moving Ag ions uniformly into the ceramic sintered body 1 in advance, the movement of Ag from the electrodes 2 and 502 to the ceramic sintered body 1 can be suppressed. Further, by adding a small amount of Ag to the ceramic sintered body 1, the viscosity of the glass melt decreases during sintering, and the fluidity increases, so that the closed pores 4 can be uniformly distributed in the borosilicate glass phase. It becomes.

In the present embodiment, the electrodes 2 and 502 are made of Ag as a conductor, but may be an alloy containing Ag as a main component, such as Ag—Pt or Ag—Pd. By simultaneously firing the electrodes 2 and 502 and the ceramic sintered body 1 in the air, the electrodes 2 and 502 and the ceramic sintered body 1 can be firmly bonded. More specifically, the open pores 3 and 503 are formed in the portions 101A and 501A of the ceramic sintered body 1 in contact with the electrodes 2 and 502, and the electrodes 2 and 502 enter the open pores 3 and 503 during simultaneous firing. Thus, the ceramic sintered body 1 is firmly joined.

Furthermore, the formation method of the electrodes 2 and 502 in this embodiment is not particularly limited, and may be formed by an Ag paste using a printing method such as screen printing that is usually used, or a transfer method. You may form with Ag foil.

(Example)
(1) Preparation of sample of ceramic electronic component 100 A sample of ceramic electronic component 100 was prepared by the method described below.

FIG. 2 is a diagram showing the composition and physical properties of samples Nos. 1 to 8 of the ceramic sintered body 1. 3A and 3B are schematic cross-sectional views showing a method for manufacturing the ceramic electronic component 100.

The ceramic sintered body 1 of this example has a low dielectric constant that enables integral and simultaneous sintering with electrodes 2 and 502 (for example, alloys such as Ag—Pt and Ag—Pd) mainly composed of Ag or Ag. Is a low-temperature sintered ceramic.

First, a borosilicate glass (SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —MgO—CaO—K ₂ O-based glass) having a yield point of 600 ° C., a quartz (SiO ₂ ) filler, and an inorganic foaming agent (CaCO _3). Alternatively, SrCO ₃ ) and Ag powder were weighed and mixed at a predetermined ratio shown in FIG. 2 to prepare a mixture. A plurality of ceramic green sheets 51 containing the mixture as a main component were formed by a doctor blade method using a slurry of the mixture.

Next, a plurality of ceramic green sheets 51 were laminated to produce a ceramic green sheet laminate 51A. Then, as shown in FIG. 3A, a conductive material 52 containing Ag, which is an Ag paste, serving as a meander pattern electrode 2 having a line width of 150 μm is formed on the surface of the ceramic green sheet laminate 51A (ceramic green sheet 51). A printed laminate was produced. Similarly, a laminate in which the conductive material 52 was not applied to the surface of the ceramic green sheet laminate 51A was produced. These laminates were fired in air to produce ceramic sintered body samples. As shown in FIG. 3B, a ceramic sintered body is printed by printing a conductive material 52 on a ceramic green sheet 51 and then laminating a ceramic green sheet laminate 51A (ceramic green sheet 51) so as to cover the conductive material 52. The ceramic electronic component provided with the electrode 502 provided in 1 can be created.

Among the samples of the ceramic sintered body 1 obtained, the samples fired without applying the Ag paste were subjected to defoaming treatment in water after measuring the dry weight, and the weight in water and the water content were measured. The specific gravity by the Archimedes method was calculated using the weight value, and the water absorption rate was calculated. In addition, the closed porosity and open porosity were also calculated. The closed porosity is obtained by dividing the total volume of the closed pores by the total volume of the ceramic sintered body 1, and the open porosity is the total volume of the open pores obtained by sintering the ceramic. Divided by the total volume of the body 1.

The specific gravity, water absorption, open porosity, and closed porosity, which are physical properties of the ceramic sintered body 1, are also shown in FIG.

It should be noted that the sample of the ceramic sintered body 1 produced in this example can be integrally sintered with, for example, ferrite or a kind of ceramic material having different characteristics.

(2) Measurement of dielectric constant Among the obtained ceramic sintered body 1 samples, one surface of the sintered ceramic body 1 without being coated with Ag paste was mirror-polished on one side and the dielectric constant was measured. In addition, for the case where the Ag paste was applied and fired at the same time, the surface on which the electrode 2 was formed was polished to remove the electrode 2, mirror-polished, and the dielectric constant was measured. In both samples, the mirror-polished surface was vacuum-adsorbed to the probe, and the dielectric constant at 6 GHz was measured by the near-field method. The number of samples measured was 20 for each sample number, and the average value and standard deviation of the measured values of dielectric constant were calculated.

FIG. 4 is a diagram showing an average value and a standard deviation of measured values of the dielectric constant of the ceramic sintered body 1 sample. In a device used in a frequency band of about 10 GHz, if a glass material having a dielectric constant of about 3 is applied, it is preferable to suppress variations in dielectric constant within plus or minus 0.1. If it varies further, the design of the ceramic electronic component 100 becomes extremely difficult, and the yield is greatly reduced. Therefore, in a glass material having a dielectric constant of about 3, the standard deviation of the dielectric constant is desirably 0.05 or less. In the ceramic electronic component 100 according to the present embodiment, it is possible to keep variation within this range.

As shown in FIG. 4, in the samples Nos. 6 to 8 in which 1 wt% of the foaming agent and Ag powder are added to the ceramic sintered body 1, the permittivity of the sample fired alone and the sample fired simultaneously with the electrode There is almost no difference in standard deviation, and the dielectric constant is stable.

On the other hand, in the samples of Sample Nos. 2 to 4 where no Ag powder is added to the ceramic sintered body 1, the standard deviation of the dielectric constant becomes large when co-firing with the electrodes. Therefore, the dielectric constant varies in these samples.

From the above, the dielectric constant of the ceramic electronic component 100 in which the closed pores are densely and uniformly distributed is stabilized.

The ceramic electronic component according to the present invention has a stable dielectric constant and is useful for various high-frequency components such as a common mode noise filter.

DESCRIPTION OF SYMBOLS 1 Ceramic sintered body 2 Electrode 3 Open pore 4 Close pore 5 Filler 6 Glass material 51 Ceramic green sheet 52 Conductive material

Claims (5)

1. Ceramic sintered body,
   An electrode containing Ag in contact with the ceramic sintered body;
   With
   The ceramic sintered body has a glass material made of borosilicate glass and a plurality of fillers dispersed in the glass material,
   A ceramic electronic component in which the glass material is provided with a plurality of closed pores distributed substantially uniformly.
2. The ceramic electronic component according to claim 1, wherein the plurality of fillers are made of SiO ₂ filler.
3. The ceramic electronic component according to claim 1, wherein the glass material is provided with a plurality of open pores and the plurality of closed pores.
4. Preparing a ceramic green sheet containing a borosilicate glass powder, a filler, an inorganic foaming agent having a decomposition completion temperature equal to or higher than a glass yield point of the borosilicate glass powder, and Ag;
   Providing a conductive material containing Ag on the ceramic green sheet;
   Firing the ceramic green sheet and the conductive material simultaneously in air;
   A method for manufacturing a ceramic electronic component, comprising:
5. The method for manufacturing a ceramic electronic component according to claim 4, wherein the inorganic foaming agent includes at least one of CaCO ₃ and SrCO ₃ .

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