JPH08203774A - Ceramic capacitor - Google Patents

Abstract

PURPOSE: To provide a high-performance ceramic capacitor which can prevent the occurrence of solder leach phenomenon, silver migration, etc., and in which electric property, reliability, solderability, life property, etc., are very good and besides capacitance is large and dielectric loss is small. CONSTITUTION: A baked electrode of conductive paste consisting of substance containing copper powder, glass flit, an organic vehicle, and any of boric acid ester organic matter solution, boric acid solution, and solution of organic salt of boron is made on the surface of a dielectric ceramic element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porcelain capacitor, and more particularly to a porcelain capacitor having a copper baking electrode.

[0002]

2. Description of the Related Art When forming electrodes of a porcelain capacitor,
Conventionally, a fine silver powder is used as a conductive component, and a silver paste containing a low-melting glass frit is applied to the dielectric ceramic body by means of a screen printing method or the like, and baked to form it. Was common. This silver-baked electrode has advantages such as excellent electrical properties, good high frequency characteristics, high reliability, and easy and simple electrode film formation.

[0003]

However, in the conventional silver baking electrode, the cost of silver is high and there is a limit to cost reduction.

Further, when a lead wire or the like is soldered to a silver-baked electrode, a "solder erosion phenomenon" in which silver diffuses and migrates in the solder is apt to occur, so that the adhesion of the electrode is deteriorated. Alternatively, the characteristics may be deteriorated such as insufficient electrostatic capacity.

Further, silver migration is likely to occur, and the reliability may be impaired due to a decrease in insulation withstand voltage and the like. Especially, due to thermal shock of soldering,
When it is not possible to prevent microcracks from entering the dielectric ceramic body, silver migrates into these microcracks,
There is a risk that the progress of silver migration will be promoted and the reliability will be reduced.

As a means for improving the above-mentioned drawbacks of the silver-baked electrode, there is a copper-baked electrode disclosed in Japanese Patent Publication No. 1-51003. This copper baking electrode contains copper powder and glass frit containing lead borosilicate, bismuth borosilicate, and zinc borosilicate as a main component.
The volume ratio of the glass frit to the copper powder is 2 to 40%.

This copper-baked electrode is prepared by dispersing copper powder and glass frit in an organic vehicle to form a paste, which is applied to the dielectric ceramic body by a method such as screen printing, and this is applied in a neutral atmosphere (N ₂ ) Formed by baking and heating in.

However, copper-baked electrodes generally need to be baked at a high temperature of 800 ° C. or higher to densify the electrodes. If this sintering and densification is insufficient, the penetration of the solder into the electrodes will occur and the capacitance and the terminal strength will decrease. Also, since copper is a base metal, it must be baked in a neutral atmosphere to prevent oxidation, but if baked in a high-temperature neutral atmosphere, the reduction of the dielectric ceramic body will proceed, and the capacity will decrease when processed into a capacitor. There is a risk of

As a means for improving the above-mentioned defects in the oxidation and solderability of the copper electrode, Japanese Patent Publication No. 1-36233.
There is an electronic component, a conductive film composition and a manufacturing method disclosed in Japanese Patent Laid-Open Publication No. This is characterized in that the boron fine powder is contained in a ratio of 5 to 40 wt% with respect to the copper powder.
In this case, if the amount of boron fine powder is 5 wt% or less, it is said that the oxidation of the base metal fine powder cannot be sufficiently prevented.

Further, there is a non-oxidizing copper thick film conductor disclosed in JP-A-1-220303. This is a copper paste characterized by containing a boron-manganese compound.
There is a problem in that a thick film conductor having good conductivity cannot be obtained by low temperature firing because the conductor is made into a conductor at a baking temperature of 0 ° C.
It is also necessary to apply an inorganic phosphoric acid coat to the surface of the copper electrode.

Further, there is a conductive paste using copper powder disclosed in Japanese Patent Laid-Open No. 3-176903. This is B
And B ₂ O ₃ are contained, and the content of B powder is 3.5 to 3.9 w in the total 100 wt% of copper powder and B powder.
t%. In addition, B ₂ O ₃ is 10 in total of copper powder and B powder.
It is set to 2.0 to 30.0 wt% out of 0 wt%. In this case as well, the reason is that the effect of suppressing oxidation is not observed below the lower limit of each component of B and B ₂ O ₃ .

In both cases, it is considered that the boron (B) compound contained in the copper paste becomes B ₂ O ₃ during firing, and serves to protect copper from a weakly oxidizing atmosphere. However, when used as a capacitor electrode, if the amount of boron compound added is large, the resistance of the electrode film increases even though it functions as an antioxidant, resulting in a reduction in capacitance and an increase in dielectric loss. Causes deterioration of characteristics.

From the above-mentioned problems in the prior art, it can be said that it is advantageous for electrical characteristics such as capacitance and dielectric loss that the amount of boron added is as small as possible without oxidizing the electrodes. That is, the boron compound contained in the copper paste should be defined not by the amount added, but by the ratio in terms of the atomic weight of boron with respect to the amount of copper added. In order to disperse the boron (B) in a small amount, it is judged that the liquid boron additive is superior in dispersibility to B as compared with B, B ₂ O ₃ , and MnB ₂ in which solid components are added.

Therefore, according to the present invention, it is possible to prevent the phenomenon of solder erosion and the occurrence of silver migration, the high frequency characteristics, the reliability, the solderability and the life characteristics are excellent, and the electrostatic capacity is large. An object of the present invention is to provide a high-performance porcelain capacitor with low dielectric loss.

In addition, the capacity decrease rate in the moisture resistance load test,
An object of the present invention is to provide a highly reliable porcelain capacitor with reduced dielectric loss.

[0016]

The invention according to claim 1 is
On the surface of the dielectric porcelain body, copper powder, glass frit, organic vehicle, borate ester organic matter solution, boric acid solution, and a conductive paste consisting of a solution containing an organic salt of boron It is characterized in that a baking electrode is formed.

The invention according to claim 2 is characterized in that the boric acid ester organic material solution is a high boiling point boric acid ester solution or a low boiling point boric acid ester solution to which a high boiling point alcohol is added.

In the invention according to claim 3, the high-boiling boric acid ester among the boric acid ester organic matter is (C _n H _{2n + 1} O)
In ₃ B, it is characterized in that those having n ≧ 4 or more side chains.

The invention according to claim 4 is characterized in that the boric acid ester having a low boiling point in the boric acid ester organic material is any one of methyl borate, trimethyl borate, triethyl borate, and tripropyl borate.

According to a fifth aspect of the present invention, the solution of the organic salt of boron is triethylboron, dimethylamineborane,
It is characterized by being sodium borohydride.

In the invention according to claim 6, the boric acid ester organic substance solution, the boric acid solution, and the organic salt solution of boron are contained in an amount of 0.01 to 9 in terms of the atomic weight of boron with respect to 99.5 to 99.99 wt% of copper powder. It is characterized in that a baking electrode composed of 0.5 wt% is formed.

According to a seventh aspect of the invention, the copper powder and the glass frit which are solid components are 80 to 98 wt% of the copper powder.
%, The glass frit is 2 to 20 wt%, and the organic vehicle is 10 to 30 wt% based on the solid content of the copper powder and the glass frit of 70 to 90 wt%.
It is characterized by the ratio of.

The invention according to claim 8 is characterized in that the glass frit has a softening point of 350 ° C to 500 ° C.

The invention according to claim 9 is characterized in that the dielectric ceramic body is made of barium titanate.

In the present invention, the reason why the weight ratio of the glass frit is limited to the above range is as follows.

That is, if the compounding ratio of the glass frit is specified, it is 2 with respect to 80 to 98 wt% of copper powder.
It is preferable to select in the range of ˜20 wt%. That is, when considering the deterioration of the adhesive strength between the baked electrode and the dielectric ceramic body, the glass frit should be 2 wt% or more, while considering the deterioration of conductivity, acquisition capacity, and dielectric loss. Then, the glass frit is preferably 20 wt% or less. The copper powder used has an SEM particle size of 10 μm or less. If the particle size is out of this range, sintering of the electrode becomes insufficient, which is not preferable.

Further, if the content of the organic borate ester solution is specified, the copper powder is 99.5 to 99.99 w.
It is preferable to select in the range of 0.01 to 0.5 wt% with respect to t%. That is, in consideration of deterioration of the antioxidant, the content may be 0.01 wt% or more,
Also, considering the deterioration of solderability and conductivity, 0.5 wt%
You can do the following:

The copper powder and the glass frit are 90 to 90 wt% with respect to the ratio of 10 to 30 wt% of an inert organic vehicle such as ethyl cellulose dissolved in terpineol.
It is kneaded at a mixing ratio of 70 wt% and made into a paste.

Further, as the glass frit, there is, for example, boron lead zinc based glass. Supposing that the softening point is specified, in consideration of low viscosity at the time of glass baking, diffusion into the ceramic, and poor bonding between the electrode and the ceramic,
The softening point may be set to 350 ° C. or higher, while it may be set to 500 ° C. or lower in consideration of low temperature baking, defective bonding between electrodes and ceramics, dielectric loss, and deterioration of terminal strength.

As a copper antioxidant, a liquid boric acid ester organic material solution is added during paste kneading. This boric acid ester organic material causes B in the solvent to vitrify into B ₂ O ₃ at around 200 ° C. . Since this B ₂ O ₃ coats the copper powder, the oxidation of copper can be protected from the weakly acidic atmosphere during firing.

When the copper powder is protected by B ₂ O ₃ as described above, the glass frit softens at 350 to 450 ° C. after the boron (B) in the conductive paste vitrifies at 200 ° C. Copper has a good wettability with respect to glass frit, and it is possible to form a dense copper electrode to the extent that solder penetration can be prevented at a firing temperature of about 600 ° C.

[0032]

In the porcelain capacitor of the present invention, a boric acid ester organic solution or boric acid solution or a solution of an organic salt of boron is added as a copper antioxidant at the time of kneading the paste. Dispersed and thin B
_{A 2} O ₃ film can be formed on the electrode, and the effect of preventing oxidation of the copper electrode can be obtained. Further, since the copper-baked electrode has the same electrical and physical properties as the silver-baked electrode, it is possible to obtain a porcelain capacitor having excellent high frequency characteristics.

Further, since copper sinters as a conductor at a low temperature of 600 ° C., it is possible to perform the atmosphere firing without reducing the glass frit and the ceramics. Therefore, the reduction of the acquired capacitance due to the reduction of the ceramic does not occur, so that a large electrostatic capacitance can be obtained and a porcelain capacitor with a small dielectric loss can be provided.

[0034]

EXAMPLES The contents of the present invention will be described in detail below based on examples.

(Example 1) First, a process of producing a conductive paste for a copper baking electrode will be described. Japanese Patent Application No. 6-120253 containing 80 wt% of copper powder having a particle diameter of 1 μm and at least one of boron oxide, lead oxide and zinc oxide as main components.
PbO-B ₂ O ₃ -ZnO based glass frit 8 wt% according to JP, and terpineol cellulose 8 wt%
12 wt% of an organic vehicle prepared by dissolving was prepared. Then, a solution of any one of a high boiling borate organic substance, a low boiling borate organic substance in which a high boiling alcohol is added to prevent volatilization, and boron dissolved in an organic solvent is added to each of the copper powders 99.5 to 99.99 wt. %, And added in an amount of 0.01 to 0.5 wt% in terms of boron atomic weight, and sufficiently dispersed by a kneader such as a triple roll to produce various copper baking electrode pastes. .

Of the total 100 wt% of the solid component copper powder and glass frit, 90.9 wt% is copper powder and the remaining 9.1 wt% is glass frit. The organic vehicle is 12 wt% with respect to the total amount of copper powder and glass frit being 88 wt%.

85% by weight of BaTiO ₃
CaZrO ₃ 8.5-12.0 wt%, MgTiO
₃ 0.5 wt% or less, CeO ₂ 0.5 wt% or less, Bi
₂ O ₃ 0.1-1.0 wt%, SnO ₂ 0.1-1.0
After being applied by screen printing to a barium titanate-based ceramic described in JP-B-60-31793, the peak temperature is 6 in a neutral atmosphere (N ₂ ).
Baking heat treatment was performed at a holding time of 00 ° C. for 10 minutes and an IN-OUT time of 60 minutes.

The measurement results of capacitance, dielectric loss (DF), terminal strength, solderability and solder penetration of the thus obtained porcelain capacitor are also shown in Table 1.

In Table 1, the tensile strength of the electrode is 1 diameter.
A diameter of 0.6 mm is applied to the electrode formed by baking the circular dielectric ceramic body of 4.0 mm and the thickness of 0.5 mm as described above.
Was soldered and its tensile strength was measured at a constant speed of 120 mm / min. The solderability was determined by immersing the dielectric ceramic body after baking the electrodes in solder using a rosin-based flux, and visually judging the solderability. Regarding solderability, the soldering area is 90
% Or more was marked with ⊚, 50% or more was marked with ◯, and less than 50% was marked with x.
Those marked with * in Table 1 are outside the scope of the present invention,
Others are within the scope of the present invention.

As is clear from Table 1, the one according to the present invention has good solderability, small dielectric loss, and large terminal strength.

In Table 1, Sample No. 2 has good capacitance and dielectric loss, but poor terminal strength and poor solderability. Sample number 1, 8,
Nos. 9, 10, 14, 15, and 19 have large dielectric loss, low terminal strength, and no soldering.

Further, TG- of tributyl borate shown in FIG.
According to DTA analysis, at around 200 ° C., boron vitrifies and shields copper from the outside air, so that copper can be prevented from oxidizing against oxygen supplied to nitrogen for decomposition of the binder.

[0043]

As described above, according to the present invention, the following effects can be obtained.

First, according to the porcelain capacitor of the present invention, as the copper antioxidant, any one of a boric acid ester organic substance solution, a boric acid solution, and a boron organic salt solution, which is a liquid at the time of kneading the paste, is added. Therefore, it is possible to disperse in a small amount in the paste as compared with the conventional technique, to form a thin B ₂ O ₃ film on the electrode, and to obtain an effect of preventing copper electrode oxidation. Therefore, B ₂ O _{3 in the} form of a glass film is reduced in the electrode surface layer, the dielectric loss is reduced, and the capacitance is improved.

Secondly, since copper sinters as a conductor at a low temperature of 600 ° C., it is possible to carry out the atmosphere firing without reducing the glass frit and the ceramics. Therefore, since the reduction of the acquisition capacity does not occur due to the reduction of the ceramic,
A large capacitance can be obtained, and a porcelain capacitor with a small dielectric loss can be provided.

Thirdly, according to the porcelain capacitor of the present invention, since it can be fired at a low temperature, an inexpensive firing furnace material can be used, and since it can be fired for a short time, a low running cost such as nitrogen gas and electricity can be achieved. Moreover, the manufacturing time is reduced and the cost is reduced. Moreover, the copper baking electrode is
Since it has electrical and physical properties similar to those of the silver-baked electrode, a porcelain capacitor having excellent high frequency characteristics can be obtained.

Fourthly, according to the porcelain capacitor of the present invention, even if microcracks are generated in the dielectric porcelain body due to thermal shock during soldering, there is no silver migration or solder leaching phenomenon. Therefore, it is possible to provide a highly reliable porcelain capacitor without deterioration of reliability and life characteristics due to these.

Fifth, according to the porcelain capacitor of the present invention, since the electrodes are formed by baking, there is provided a porcelain capacitor having a strong adhesive force and a large tensile strength that is unlikely to cause electrode peeling or the like. be able to.

[0049]

[Table 1]

[Brief description of drawings]

FIG. 1 is a TG-DTA analysis chart of tributyl borate.

Claims (9)

[Claims] 1. A dielectric porcelain body containing copper powder, glass frit, an organic vehicle, a boric acid ester organic substance solution, a boric acid solution, and an organic salt solution of boron on the surface thereof. A porcelain capacitor, in which a baking electrode of a conductive paste is formed. 2. The porcelain capacitor according to claim 1, wherein the boric acid ester organic substance solution is a high boiling point boric acid ester solution or a low boiling point boric acid ester solution to which a high boiling point alcohol is added. 3. The high-boiling boric acid ester among the boric acid ester organic matter is one having a side chain of n ≧ 4 in (C _n H _{2n + 1} O) ₃ B.
Alternatively, the porcelain capacitor according to claim 2. 4. The low-boiling-point boric acid ester among the boric acid ester organic substances is any one of methyl borate, trimethyl borate, triethyl borate, and tripropyl borate, according to claim 1 or 2. The listed porcelain capacitor. 5. The porcelain capacitor according to claim 1, wherein the solution of the organic salt of boron is triethylboron, dimethylamineborane, or sodium borohydride. 6. The organic borate solution, boric acid solution,
The solution of the organic salt of boron is copper powder 99.5 to 99.9.
The porcelain capacitor according to claim 1, wherein a baked electrode is formed in a proportion of 0.01 to 0.5 wt% in terms of boron atomic weight with respect to 9 wt%. 7. The copper powder and the glass frit as solid components are composed of 80 to 98 wt% of the copper powder and 2 to 20 wt% of the glass frit, and the organic vehicle is the solid content of the copper powder and the glass frit of 70 to 70 wt%. 90 wt
The porcelain capacitor according to claim 1, wherein the ratio is 10 to 30 wt% with respect to%. 8. The glass frit has a softening point of 350.degree.
It is 500 degreeC, The ceramic capacitor of Claim 1 characterized by the above-mentioned. 9. The ceramic capacitor according to claim 1, wherein the dielectric ceramic body is made of barium titanate.