JP3523633B2 - Ceramic capacitors - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a ceramic capacitor.

[0002]

2. Description of the Related Art In the process of manufacturing a ceramic capacitor, a conductive paste is applied on the surface of a ceramic dielectric substrate made of BaTiO ₃ system material or the like and baked to form a capacitive electrode.

Conventionally, a conductive paste forming a capacitor electrode contains a lead component such as lead glass or a lead compound,
It has been pointed out that the lead component has an adverse effect on the environment. Therefore, it has been required to remove the lead component from the conductive paste.

However, when the lead component is removed from the conductive paste, the softening point of the glass contained in the conductive paste rises. This glass has a function of adhering the capacitance electrode to the ceramic dielectric substrate, and if the softening point of the glass rises, the adhesion between the capacitance electrode and the ceramic dielectric substrate decreases. As a result, the adhesive strength of the capacitance electrode to the ceramic dielectric substrate is reduced, and the reliability of the ceramic capacitor is reduced.

As a means for avoiding such a decrease in the adhesive strength of the capacitive electrode, when the composition of the glass contained in the conductive paste is changed to lower the softening point of the glass, a gap between the ceramic dielectric substrate and the capacitive electrode is obtained. The glass component accumulates.
As a result, there arise problems such as a decrease in capacitance of the ceramic capacitor and an increase in dielectric loss.

As described above, if the lead paste is not contained in the conductive paste forming the capacitor electrode, it is difficult to achieve both reliability such as adhesive strength and capacitor characteristics such as capacitance or dielectric loss. .

[0007]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a ceramic capacitor in which a lead electrode is not contained in a capacitor electrode,
And to provide a conductive composition used therein.

Another object of the present invention is to provide a ceramic capacitor capable of avoiding a decrease in the adhesive strength of a capacitor electrode to a ceramic dielectric substrate, and a conductive composition used therefor.

Yet another object of the present invention is to provide a ceramic capacitor capable of avoiding a decrease in capacitance and an increase in dielectric loss,
And to provide a conductive composition used therein.

[0010]

In order to solve the above problems, a ceramic capacitor according to the present invention includes a ceramic dielectric substrate and a capacitance electrode.

The capacitance electrode is attached to the outer surface of the ceramic dielectric substrate and includes a metal, glass, and Bi ₂ O _3, and does not include any Pb or Pb compound, and the metal is Cu or Ag. Contains at least one.

In the above-described ceramic capacitor according to the present invention, the capacitance electrode attached to the outer surface of the ceramic dielectric substrate does not contain Pb or Pb compound.

Further, the capacitance electrode is made of metal, glass, B
i ₂ O ₃ and the metal contains at least one of Cu and Ag. With this composition, it is possible to avoid a decrease in the adhesive strength of the capacitive electrode to the ceramic dielectric substrate, and at the same time,
It was confirmed that the decrease in capacitance and the increase in dielectric loss of the ceramic capacitor can be avoided.

Therefore, in the ceramic capacitor in which the capacitance electrode does not contain a lead component, it is possible to avoid a decrease in the adhesive strength of the capacitance electrode to the ceramic dielectric substrate, and
It is possible to obtain a ceramic capacitor that can avoid a decrease in capacity and an increase in dielectric loss.

In a preferred composition of the capacitive electrode, the content of Bi ₂ O ₃ with respect to the total amount of metal is 0.1 wt% to 10.0.
The range is wt%. Further, the content of glass with respect to the total amount of metal is set in the range of 0.1 wt% to 5.0 wt%.

The present invention further discloses a conductive composition for forming a capacitive electrode on a ceramic dielectric substrate.
This conductive composition contains a metal, glass, and Bi ₂ O ₃ , does not contain Pb or a Pb compound, and the metal contains at least one of Cu and Ag.

A conductive paste is prepared by mixing the above-mentioned conductive composition, a binder, and a solvent. Further, by applying this conductor paste to the outer surface of the ceramic dielectric substrate and baking it, a capacitor electrode is formed on the ceramic dielectric substrate. Therefore, the above-described ceramic capacitor according to the present invention can be obtained.

Other objects, configurations and advantages of the present invention will be described more specifically with reference to the accompanying drawings which are examples. The figures are merely examples.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a plan view showing an embodiment of a ceramic capacitor according to the present invention, and FIG.
It is an expanded sectional view along a line. As shown, the ceramic capacitor according to the present invention is a ceramic dielectric substrate 1
And capacitance electrodes 21 and 22. The ceramic capacitor shown in the figure has two capacitance electrodes 21 and 22,
The number of capacitance electrodes is arbitrary.

The ceramic dielectric substrate 1 is made of BaTiO ₃
It can be composed mainly of a system material, but may be composed mainly of another material, for example, a SrTiO ₃ system material. Further, although the illustrated ceramic dielectric substrate 1 has a disc shape, it may have another shape, for example, a rectangular plate shape. The ceramic dielectric substrate 1 has two outer surfaces 11 and 12 facing each other when viewed in the thickness direction T.

The capacitance electrodes 21 and 22 are attached to the outer surfaces 11 and 12 of the ceramic dielectric substrate 1. For more information,
One capacitance electrode 21 is the outer surface 1 of the ceramic dielectric substrate 1.
1 and the other capacitance electrode 22 is attached to the outer surface 12 of the ceramic dielectric substrate 1, and these two capacitance electrodes 21 and 22 face each other with the ceramic dielectric substrate 1 interposed therebetween.

In the present invention, the capacitance electrodes 21 and 22 attached to the outer surfaces 11 and 12 of the ceramic dielectric substrate 1.
Is configured so as to contain neither Pb nor Pb compound.

Further, the capacitance electrodes 21 and 22 are configured to contain metal, glass, and Bi ₂ O ₃ . At least one of Cu and Ag is used as a metal for forming the capacitor electrodes 21 and 22. It was confirmed that with this composition, it is possible to avoid a decrease in the adhesive strength of the capacitor electrodes 21 and 22 to the ceramic dielectric substrate 1, and at the same time avoid a decrease in the capacity and an increase in dielectric loss of the ceramic capacitor.

Therefore, in a ceramic capacitor in which the capacitance electrodes 21 and 22 do not contain a lead component, it is possible to avoid a reduction in the adhesive strength of the capacitance electrodes 21 and 22 to the ceramic dielectric substrate 1, and to reduce the capacitance and the dielectric loss. A ceramic capacitor that can avoid an increase is obtained.

The preferred composition of the capacitive electrodes 21, 22 is:
The content of Bi ₂ O ₃ relative to the total amount of metal is 0.1 wt%
-10.0 wt%. Further, the content of glass with respect to the total amount of metal is set in the range of 0.1 wt% to 5.0 wt%.

As the glass for forming the capacitance electrodes 21 and 22, for example, borate glass, zinc borosilicate glass, or a combination thereof can be used. Specific examples of the borate glass, for example, SrO-B ₂ O
₃ -Al ₂ O ₃ -ZnO based glass. Specific examples of borosilicate zinc _{glass, ZnO-B 2 O 3 -SiO} 2 -Al 2
O ₃ type glass can be mentioned.

The capacitance electrodes 21 and 22 described above can be formed by applying a conductive paste to the outer surfaces 11 and 12 of the ceramic dielectric substrate 1 and baking it. The conductive paste for this is a conductive composition, a binder,
It can be prepared by mixing with a solvent.

The conductive composition is composed of metal, glass and Bi.
_It may be configured such that it contains ₂ O ₃ and does not contain any Pb or Pb compound. The metal is configured to include at least one of Cu and Ag.

The effects of the present invention will be specifically described below with reference to experimental data.

<Experiment 1> First, seven kinds of conductive compositions were prepared by mixing metal powder, glass frit and Bi ₂ O ₃ . Both the metal powder with Cu powder, both the glass frit with _{SrO-B 2 O 3 -Al 2} O 3 -ZnO based glass. The content of glass frit with respect to the total amount of metal powder was 2.5 wt%, and B was included with respect to the total amount of metal powder.
The content of i ₂ O ₃ is 0.1 wt%, 2.0 wt%, 3.5
wt%, 6.0 wt%, 10.0 wt% or 15.0
It was set to wt%.

Further, a binder and a solvent were mixed with each of these seven kinds of conductive compositions to prepare seven kinds of conductive pastes. An organic vehicle was used as the binder.

Next, using these seven kinds of conductive pastes, ceramic capacitors of Samples 1 to 7 were produced. The ceramic dielectric substrate used for manufacturing the ceramic capacitor has a BaTiO ₃ system material as a main component and a thickness of 0.5.
It has a disk shape of mm. The conductive paste is baked onto two opposing outer surfaces of this ceramic dielectric substrate to
One capacitive electrode was constructed. Diameter of capacitance electrode is 2.5 mm
So that

Next, with respect to the ceramic capacitors of Samples 1 to 7, the electrostatic capacity, the dielectric loss, and the adhesive strength of the capacitive electrode to the ceramic dielectric substrate were measured. The experimental results are shown in Table 1 below.

As described above, B based on the total amount of metal powder
The content of i ₂ O ₃ is preferably 0.1 wt% or more. FIG. 3 is a graph showing the relationship between the Bi ₂ O ₃ content and the capacitance. As shown, the Bi ₂ O ₃ content is 0.1 wt.
%, The capacitance is approximately in a constant range (1.1
1 nF to 1.16 nF). On the other hand, Bi
_{When the} content of ₂ O ₃ is smaller than 0.1 wt%, the capacitance rapidly decreases. That is, Bi ₂ O ₃ content = 0.1w
It can be seen that there is a critical point for capacitance near t%.

FIG. 4 is a graph showing the relationship between the Bi ₂ O ₃ content and the dielectric loss. As shown in the figure, when the Bi ₂ O ₃ content is 0.1 wt% or more, the dielectric loss falls within a substantially constant range (1.59% to 1.86%). On the other hand, when the Bi ₂ O ₃ content is smaller than 0.1 wt%, the dielectric loss rapidly increases. That is, it can be considered that a critical point for dielectric loss exists near the Bi ₂ O ₃ content = 0.1 wt%.

As described above, B based on the total amount of metal powder
The i ₂ O ₃ content is preferably 10.0 wt% or less. FIG. 5 is a graph showing the relationship between the Bi ₂ O ₃ content and the adhesive strength. As shown, the adhesive strength of the capacitive electrode to the ceramic dielectric substrate tends to decrease with increasing Bi ₂ O ₃ content. In the ceramic capacitor, the adhesive strength of the capacitance electrode is required to have a minimum value of about 1.00 Kgf in order to ensure reliability. Bi ₂ O ₃
If the content is 10.0 wt% or less, 1.00 Kgf
The above adhesive strength can be reliably obtained.

More preferably, the Bi ₂ O ₃ content is 2.0.
Wt% or less. Referring to FIG. 5, when the Bi ₂ O ₃ content is 2.0 wt% or less, the adhesive strength shows a substantially constant high value (3.06 Kgf to 3.24 Kgf).
On the other hand, when the Bi ₂ O ₃ content is higher than 2.0 wt%, the adhesive strength sharply decreases. That is, Bi ₂ O ₃
It can be considered that there is a critical point regarding the adhesive strength in the vicinity of the content = 2.0 wt%.

Next, with respect to the ceramic capacitors of Samples 1 to 7, the solder wettability of the capacitor electrode was evaluated (see Table 1). For evaluation of solder wettability, dip into 240 ° C. lead-tin eutectic solder for 2 seconds, and
It was determined that the area of 0% or more was wet with the lead-tin eutectic solder. When the area of less than 70% was wet with the lead-tin eutectic solder, it was marked with x.

With reference to Table 1, in all of the ceramic capacitors of Samples 2 to 7 included in the scope of the present invention, the solder wettability of the capacitance electrode was good.

Next, a pass / fail judgment was made for the ceramic capacitors of Samples 1 to 7. In the pass / fail judgment, the following condition 1
When the conditions were satisfied, it was determined to be acceptable, and when the following condition 1 was not satisfied, it was determined to be unacceptable.

Referring to Table 1, among the samples 2 to 7 included in the scope of the present invention, the content of Bi ₂ O ₃ was 0.1 wt%.
Samples 2 to 6 in the range of ˜10.0 wt% were judged to be acceptable.

<Experiment 2> First, five kinds of conductive compositions were prepared by mixing metal powder, glass frit, and Bi ₂ O ₃ . As in Experiment 1, the metal powder was C
u powder was used, and the glass frit was SrO-B ₂ O ₃
Using -Al ₂ O ₃ -ZnO based glass. The content of glass frit is 0.0wt%, 0.1wt with respect to the total amount of metal powder.
%, 2.5 wt%, 5.0 wt% or 7.5 wt%, and the content of Bi ₂ O ₃ with respect to the total amount of metal powder was 2.0 wt%.

Furthermore, 5 out of these 5 kinds of conductive compositions are used.
A variety of conductive pastes were prepared. The method for preparing the conductive paste is the same as in Experiment 1 above.

Next, using these five kinds of conductive pastes, ceramic capacitors of Samples 8 to 12 were produced. The method for manufacturing the ceramic capacitor is the same as in Experiment 1 above.

Next, with respect to the ceramic capacitors of Samples 8 to 12, the capacitance, the dielectric loss, and the adhesive strength of the capacitance electrode to the ceramic dielectric substrate were measured. The experimental results are shown in Table 2 below.

As described above, the content of glass frit is preferably 5.0 wt% or less with respect to the total amount of metal powder. FIG. 6 is a graph showing the relationship between the glass frit content and the capacitance. As shown in the figure, when the glass frit content is 5.0 wt% or less, the capacitance falls within a substantially constant range (1.18 nF to 1.10 nF). In contrast, the glass frit content is 5.0 wt%
If it is greater than, the capacitance decreases sharply. That is, it can be considered that the critical point regarding the capacitance exists near the glass frit content = 5.0 wt%.

FIG. 7 is a graph showing the relationship between glass frit content and dielectric loss. As shown in the figure, when the glass frit content is 5.0 wt% or less, the dielectric loss falls within a substantially constant range (1.59% to 1.72%).
On the other hand, when the glass frit content is higher than 5.0 wt%, the dielectric loss increases rapidly. That is, it can be considered that a critical point for dielectric loss exists near the glass frit content = 5.0 wt%.

As described above, the content of glass frit is preferably 0.1 wt% or more with respect to the total amount of metal powder. FIG. 8 is a graph showing the relationship between the glass frit content and the adhesive strength. As shown, the adhesive strength is
It tends to increase as the glass frit content increases. In a ceramic capacitor, the adhesive strength of the capacitive electrode to the ceramic dielectric substrate is at least 1.00.
A value of about Kgf is required to ensure reliability.
If the glass frit content is 0.1 wt% or more,
An adhesive strength of 1.00 Kgf or more can be reliably obtained.

More preferably, the glass frit content is 2.5 wt% or more. The glass frit content is 2.
When it is 5 wt% or more, a high adhesive strength of 3.06 Kgf or more can be obtained.

Next, the solder wettability of the capacitor electrode was evaluated for the ceramic capacitors of Samples 8 to 12 (Table 2).
reference). The solder wettability evaluation method is the same as in Experiment 1 above.

With reference to Table 2, in all of the ceramic capacitors of Samples 9 to 12 included in the scope of the present invention, the solder wettability of the capacitor electrode was good.

Next, a pass / fail judgment was made for the ceramic capacitors of Samples 8 to 12. The pass / fail judgment method is also the same as in Experiment 1 above.

Referring to Table 2, among the samples 9 to 12 included in the scope of the present invention, the glass content was 0.1 wt%.
Samples 9 to 11 in the range of ˜5.0 wt% were judged to be acceptable.

<Experiment 3> First, two kinds of conductive compositions were prepared by mixing metal powder, glass frit and Bi ₂ O ₃ . Cu powder or Ag powder was used as the metal powder.
Both the glass frit _{SrO-B 2 O 3 -Al 2} O 3 -ZnO
A system glass was used. The glass frit content was 2.5 wt% with respect to the total amount of metal powder, and the Bi ₂ O ₃ content was 2.0 wt% with respect to the total amount of metal powder.

Furthermore, from these two kinds of conductive compositions, 2
A variety of conductive pastes were prepared. The method for preparing the conductive paste is the same as in Experiment 1 above.

Next, ceramic capacitors of Samples 13 and 14 were produced using these two kinds of conductive pastes.
The method for manufacturing the ceramic capacitor is the same as in Experiment 1 above.

Next, with respect to the ceramic capacitors of Samples 13 and 14, the capacitance, the dielectric loss, the adhesive strength of the capacitance electrode to the ceramic dielectric substrate, and the solder wettability of the capacitance electrode were measured. Further, a pass / fail judgment was performed. The measurement and pass / fail judgment methods are the same as in Experiment 1 above. The experimental results are shown in Table 3 below.

In Table 3, Sample 13 using Cu powder,
As can be seen by comparing with Sample 14 using Ag powder,
Sample 14 using g powder also obtains the same result as sample 13 using Cu powder.

Therefore, it is presumed that even when the mixture of Cu powder and Ag powder is used, the same results as those of Sample 13 using only Cu powder and Sample 14 using only Ag powder can be obtained.

FIG. 9 is a plan view showing a soldering process of the ceramic capacitor shown in FIGS. 1 and 2, and FIG. 10 is an enlarged end view taken along line 10-10 of FIG. As described above, since the solderability of the capacitor electrodes 21 and 22 is good,
As shown in FIGS. 9 and 10, the lead conductors 31 and 32 can be easily soldered to the capacitor electrodes 21 and 22. Specifically, the lead conductor 31 is soldered to the surface of the capacitance electrode 21 with the solder 41, and the lead conductor 32 is soldered to the surface of the capacitance electrode 21 with the solder 42. As the solders 41 and 42, for example, lead-tin eutectic solder is used.

The ceramic capacitor according to the present invention may be structurally integrated by being combined with another electric circuit element such as an inductor, a resistor or a transistor. A specific example is an LC filter that combines a capacitor and an inductor.

[0062]

As described above, according to the present invention, the following effects can be obtained. (A) It is possible to provide a ceramic capacitor in which the capacitor electrode does not contain a lead component, and a conductive composition used therein. (B) It is possible to provide a ceramic capacitor capable of avoiding a decrease in the adhesive strength of a capacitive electrode to a ceramic dielectric substrate, and a conductive composition used for the same. (C) It is possible to provide a ceramic capacitor that can avoid a decrease in capacitance and an increase in dielectric loss, and a conductive composition used for the same.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a ceramic capacitor according to the present invention.

FIG. 2 is an enlarged cross-sectional view taken along the line 2-2 of FIG.

FIG. 3 is a graph showing the relationship between Bi ₂ O ₃ content and capacitance.

FIG. 4 is a graph showing the relationship between Bi ₂ O ₃ content and dielectric loss.

FIG. 5 is a graph showing the relationship between Bi ₂ O ₃ content and adhesive strength.

FIG. 6 is a graph showing the relationship between glass frit content and capacitance.

FIG. 7 is a graph showing the relationship between glass frit content and dielectric loss.

FIG. 8 is a graph showing the relationship between the glass frit content and the adhesive strength.

FIG. 9 is a plan view showing a soldering process of the ceramic capacitor shown in FIGS. 1 and 2;

10 is an enlarged end view taken along line 10-10 of FIG.

[Explanation of symbols]

1 Ceramic dielectric substrate 21, 22 Capacitive electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Miyuki Anbo 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation (56) References JP-A-2-258648 (JP, A) JP-A-58 -68803 (JP, A) JP-A-8-148375 (JP, A) JP-A-2-39408 (JP, A) JP-A-2-39410 (JP, A) (58) Fields investigated (Int.Cl) . ⁷ , DB name) H01G 4/12 H01B 1/16 H01B 1/22

Claims (3)

(57) [Claims] 1. A ceramic capacitor including a ceramic dielectric substrate and a capacitor electrode, wherein the ceramic dielectric substrate is made of a BaTiO ₃ system material.
The capacitance electrode is attached to the outer surface of the ceramic dielectric substrate, contains metal, glass, and Bi ₂ O ₃ , does not contain Pb or Pb compound, and the metal is Cu or Ag . There, the _{glass, SrO-B 2 O 3 -Al} 2 O 3 -ZnO based glass
Lath, the content of which is 0.1 with respect to the total amount of the metal.
The content of Bi ₂ O ₃ with respect to the total amount of the metal is 0.
Ceramic capacitor in the range of 1 wt% to 2.0 wt% . 2. A conductive composition for forming a capacitor electrode on a ceramic dielectric substrate, comprising metal powder, glass and Bi ₂ O ₃ , and containing either Pb or Pb compound. Orazu, wherein the metal powder is Cu or Ag, the _{glass, SrO-B 2 O 3 -Al} 2 O 3 -ZnO based glass
The content of the metal powder is 0.
It is in the range of 1 wt% to 5.0 wt%, and the content of Bi ₂ O ₃ with respect to the total amount of the metal powder is
A conductive composition in the range of 0.1 wt% to 2.0 wt% . 3. A conductive paste for forming a capacitor electrode on a ceramic dielectric substrate, comprising a conductive composition.
A conductive paste comprising a binder and a solvent, wherein the conductive composition is as described in claim 2 , wherein the conductive composition, the binder and the solvent are mixed with each other.