JPH02251122A - Conductive paste for electrode of ceramic capacitor - Google Patents

Abstract

PURPOSE:To obtain a ceramic capacitor having high dielectric strength and reliability by forming an electrode of a ceramic capacitor by means of specific conductive paste. CONSTITUTION:The subject paste contains metal powder 80 to 90wt.% and glass powder 1 to 20wt.%. Then, glass powder has a composition within the range surrounded by six straight lines connecting the first to sixth points A to F of a triangular diagram showing a composition of B2O3, SiO2 and MO (provided that MO is at least one kind of metal oxides of BaO, MgO, ZnO, SrO and CaO. Thereby, a ceramic capacitor having little insulation deterioration due to high-temperature and high-moisture environment.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a conductive paste suitable for forming internal electrodes of a multilayer ceramic capacitor.

[Conventional technology] When manufacturing multilayer ceramic capacitors, conductive paste is printed on green sheets (unsintered ceramic sheets) in a predetermined pattern to form internal electrodes, and multiple printed green sheets are then printed. The raw chips are laminated, the laminated body is cut into a predetermined size to obtain raw chips, and the raw chips are fired. Note that the external electrode is provided before or after firing the raw chip. According to this method, since the conductive paste is fired simultaneously with the green sheet, it becomes possible to easily form the internal electrodes.

By the way, when forming a multilayer ceramic capacitor by simultaneous firing, if the heat shrinkage characteristics of the conductive paste for internal electrodes and the ceramic material (green sheet) in the firing process are significantly different, the ceramic layer and/or internal electrodes may Cracks occur or the internal electrode peels off from the porcelain layer (delamination)
may occur. In order to solve this kind of problem, it was proposed to add glass frit to the conductive paste for internal electrodes in order to make the heat shrinkage similar to that of porcelain.
It is disclosed in Japanese Patent No. 958. Further, Japanese Patent Application Laid-open No. 140960/1984 discloses that a porcelain material powder (common material) that is the same as or similar to the green sheet is added to the conductive paste.

[Problems to be Solved by the Invention] However, in multilayer ceramic capacitors, in addition to the problem of delamination described above, a small gap of 0.2 μm or less is created between the dielectric ceramic layer and the internal electrode. There is a problem in that moisture enters under high temperature and high humidity conditions, or plating liquid enters during the formation of external electrodes, resulting in poor insulation between internal electrodes.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a conductive paste for a ceramic capacitor that can reduce the gap between the ceramic layer and the electrode.

[Means for Solving the Problems] The present invention for achieving the above-mentioned object has the following features:
metal powder and 1 to 20 weight% lath powder, and the lath powder contains B2O3, 5i02, and MO (however, MO
In the triangular diagram showing the composition of at least one metal oxide of BaO1Mg05ZnO1SrO and CaO, the B2O3 is 1 mol% and the Sio2 is 80%.
mol%, the point (A) where the M2O3 is 19 mol%, the B2O3 is 1 mol%, the S I O2 is 39 mol%,
Point (B) where the M2O3 is 60 mol% and the B2Q3
is 29 mol%, the SiO2 is 1 mol%, the M2O
3 is 70 mol%, point (D) is 90 mol% of B2O3, 1 mol% of SiO2, and 9 mol% of M2O3, and 90 mol% of B2O3 and 90 mol% of S
Point (E) where 102 is 9 mol% and the above M2O3 is 1 mol%
and the point (F) where the B2O3 is 19 mol%, the 5i02 is 80 mol%, and the M2O3 is 1 mol%. It is related to conductive paste.

[Function] When the electrodes of a ceramic capacitor are formed using the conductive paste of the present invention, the occurrence of defects in the ceramic capacitor in a high temperature and high humidity environment test is reduced, making it possible to provide a highly reliable ceramic capacitor. This is considered to be due to the following reasons. The glass powder according to the present invention becomes a low viscosity state during firing, and precipitates between the dielectric ceramic layer and the electrode gap during the cooling process. As a result, the space between the dielectric ceramic layer and the electrode becomes dense, and moisture and plating liquid are prevented from penetrating between the two and into the inside of the dielectric ceramic layer. Furthermore, the thin glass layer formed by the above precipitation has high insulation properties. Therefore, according to the present invention, a ceramic capacitor with high dielectric strength and reliability can be provided.

[Example] Conductive pastes according to examples and comparative examples of the present invention and multilayer ceramic capacitors using the same will be described.

The conductive paste of this example is used for manufacturing a multilayer ceramic capacitor 1 shown in FIG. That is, the multilayer ceramic capacitor 1 consists of a dielectric ceramic layer 2, a large number of internal electrodes 3, and a pair of external electrodes 4, and the conductive paste of this embodiment is used to form the internal electrodes 3. In addition, a pair of external rooms 1f
f14 are the Ni layer 4a, the copper layer 4b, and the Pb-3n layer, respectively.
It consists of a solder layer 4C.

The conductive paste for forming the internal electrodes 3 is made of nickel (Ni) powder as a metal powder, a co-material (dielectric ceramic powder), and glass powder, and is shown in Sample No. 1 in Table 6 for forming the internal electrodes. When obtaining glass powder for conductive paste, B2O30,99g (1 mol%) SiO68,38g <80 mol%) B a CO310,67g (3,8 mol%) MgO
2.18g (3.8 mol%) ZnO4.40g (3.8 mol%) SrCO7.98g (3.8 mol%) CaC05.4
1g <3.8 mol%) was weighed, 300cc of alcohol was added to this, stirred for 10 hours using an alumina ball in a polyethylene pot, and then calcined in the air at 1000°C for 2 hours. It was placed in an alumina pot with water, crushed with an alumina ball for 15 hours, and then dried at 150°C for 4 hours, resulting in a B2O3 content of 1 mol%.
SiO2 is 80 mol%, M2O3 is 19 mol% (Ba
2O3 is 3.8 mol%, Mg2O3 is 3.8 mol%, Z
n2O3 is 3.8 mol%, Sr2O3 is 3.8 mol%,
Obtain a powder having a composition of 3.8 mol% Ca2O3. In addition, each MO is 20 as shown in the MO content column of the table.
Mol% BaOlMgO, ZnO, 5rO1Ca2O3
consists of.

Next, add 10 g of the above glass powder and an average particle size of 1°0 μm.
, 85 g of Ni powder with a purity of 99.9% or more, 5 g of common materials, and 9 g of ethyl cellulose dissolved in 91 g of butyl calpitol were placed in a stirrer, roughly mixed for 5 hours, and then mixed for 1 hour in a roll mill. A conductive paste was prepared.

Note that the amount of vehicle consisting of ethyl cellulose and butyl calpitol is the same as that of glass powder and N.
When the total of i-powder and common material is 100 parts by weight, they are the same 100 parts by weight. In addition, the common materials of sample No. 1 are:
It is made of powder of the same material as the dielectric ceramic of the laminated ceramic capacitor, which will be described later.

Next, in order to fabricate a multilayer ceramic capacitor using this conductive paste, (CaSrBaO)(Zro4gT
100 parts by weight of the basic component consisting of lO,80,1,0,1 St )0 0.2 0.01 2 and L i 20 and S
A dielectric porcelain raw material consisting of 102 and 1 part by weight of an additive component consisting of MO was prepared. The composition of the additive components is 1 mol% of L120, 80 mol% of S102, 19 mol% of M2O3, and the content of MO is 20 mol% of each BaO1M.
g01ZnO1SrO, CaO.

Next, an organic binder was added to the above dielectric ceramic raw material and thoroughly kneaded to obtain a slurry. Next, this slurry was formed into a plurality of green sheets having a thickness of 30 μm, on which a conductive paste according to sample No. 1 was screen printed in a predetermined pattern and dried.

Next, while setting the printed side of the conductive paste to -1, 30 green sheets were stacked alternately in opposite directions so that the internal electrodes 3 were arranged as shown in Figure 1, and then the top and bottom of this stack were stacked. Four green sheets each having a thickness of 60 μm were laminated on both sides and pressed together, and then cut into individual chips.

Next, a conductive layer 4a for a pair of external electrodes 4 connecting the internal electrodes 3 exposed on one end surface and the other end surface of the chip shown in FIG. 1 can be obtained. Ni paste (Ni paste) was applied to a thickness of about 50 μm and dried.

Next, the raw chip with the conductive paste for internal electrodes and the conductive paste for external electrodes was mixed with H2 (2% by volume) + N2
(98% by volume) in a reducing (non-oxidizing) atmosphere at 1160°C for 2 hours, then 60%
The temperature was lowered to 0° C., the atmosphere was replaced with an air atmosphere (oxidizing atmosphere), and heat treatment was performed at 600° C. for 130 minutes, followed by cooling to room temperature to obtain a laminated sintered body chip. Further, a copper layer 4b was formed on the N1 layer 4a by electroless plating, and a Pb-8n solder layer 4c was further formed by electroplating, thereby completing the multilayer ceramic capacitor 1 shown in FIG.

This multilayer ceramic capacitor 1 has a length of 3.2 mI+1, a width of 2.5 mm, and a thickness of 0.8 mm+.

In order to conduct a reliability test of this multilayer ceramic capacitor 1,
200 multilayer ceramic capacitors 1 were soldered to electrodes on a circuit board made of epoxy resin, and a DC voltage of 50 V was applied to each capacitor at a temperature of 85°C and a humidity of 90°C.
The insulation properties after being left in a high temperature and high humidity atmosphere for 500 hours (h), 1000 hours (h), and 2000 hours (h) were investigated, and the insulation resistance between a pair of external molds @4 was 5.0XIO2.
Those with a resistance of less than MΩ were considered defective. As a result, as shown in the column of the number of insulation defects in the table, 500h, 1000h, 2000h
In all cases, the number of defects out of 200 was zero.

For samples Nos. 2 to 61, conductive pastes and multilayer ceramic capacitors were prepared in the same manner as for samples No. 1, except that the composition of the conductive paste and/or the composition of the dielectric ceramic material was changed as shown in the table. When a reliability test was conducted using the same method, the results shown in the table were obtained. However, the firing temperature ranges from 1100 to 128 degrees depending on the type of dielectric porcelain material.
It was varied within the range of 0°C.

The types of dielectric ceramic layers 2 of the multilayer ceramic capacitor 1 are indicated by numbers 1 to 6 on the dielectric pillows in the table.

The first dielectric ceramic indicated by 1 in this table is sample No.
It is the same as 1.

The second dielectric ceramic indicated by 2 in the table is (S r o
,elc a O,37M go,olZ n,o
,olo) (T 10.97"' 0.03)
100 parts by weight of basic components consisting of B 203 and Si
and 2 parts by weight of additional components consisting of O2 and MO.

However, the composition of the added ingredients is 10 mol% B2O3, 75 mol% SiO2, 15 mol% MO and The MO consists of 10 mol% BaO, 20 mol% MgO, 5 mol% ZnO, 20 mol% SrO; 45 mol% of CaO.

The third dielectric ceramic indicated by 3 in the table is (Sr
CaO) (TiZr)0.
70.3 1.01 0.1 0.9, 100 parts by weight of the base component, and 1 part by weight of additional components, consisting of L 120, S 102 and MO. however,
The additive components consist of 30 mol% L 120, 60 mol% SiO2, and 10 mol% MO, where the MOs are 20 mol% BaO, 10 mol% MgO, and 10 mol% ZnO. , 30 mol% SrO, and 30 mol% CaO.

The fourth dielectric ceramic, indicated by 4 in the table, contains 100 parts by weight of a basic component consisting of aTiO3, B2O3 and Sz
It consists of 1.5 parts by weight of additional components consisting of O2 and MO. However, the added components consist of 30 mol% B2O3, 50 mol% SiO2, and 20 mol% MO, and the MO is 20 mol% BaO, 10 mol% MgO, and 30 mol%. % ZnO, 20 mol% SrO, and 20 mol% CaO.

The fifth dielectric ceramic indicated by 5 in the table is BaTiO3
100 parts by weight of the basic component consisting of +0.02CaO, L l 20 and S
and 3 parts by weight of additional components consisting of iO2 and MO. However, the composition of the additive components is: 5 mol% L120, 55 mol% SiO2, 40 mol% MO, and the MO is: 20 mol% BaO, 20 mol% MgO, 20 It consists of mol% ZnO, 20 mol% SrO, and 20 mol% CaO.

The sixth dielectric ceramic indicated by 6 in the table is 0.97((
Ba Mgo, o5Cao, o30) 1olT iO
) + 0 , 03 Ca, 1 consisting of Z r O3
00 parts by weight of basic components, B2O3, SiO2 and MO
and 0.5 parts by weight of additional components. however,
The additive components consist of 50 mol% 8203, 49 mol% SIO2, and 1 mol% MO, where the MOs are 10 mol% BaO, 50 mol% MgO, and 40 mol% It consists of CaO.

As is clear from Table 6, the dielectric ceramic powder shown in the dielectric fence of each sample No. is used as the common material in each sample No. Once the electrode is formed, insulation failure will not occur even after at least 2000 hours in a high temperature and high humidity test at 85° C. and 90%.

On the other hand, test fJ No. 7.8.9.10.26.31
．． 32, 36, 37, 41, 42, 48, 51 to 61, defects occur and the object of the present invention cannot be achieved. Therefore, these samples are outside the scope of the present invention.

Next, the composition and amount of the powder of the conductive paste for internal electrodes will be described. The preferred composition of the glass powder is the composition ratio of B2B203-8io2 in Figure 2 (molar)
It can be determined based on the triangular diagram shown in mol)%. Point 1 (A) in the triangular diagram is B2 of sample No. 1
O3 is 1 mol%, S I O2 is 80 mol%, M2O3
shows a composition of 19 mol%, and point (B) is sample No.
B2O3 of 2 is 1 mol%, 5i02 is 39 mol%, M2
O3 shows a composition of 60 mol%, and point (C) is sample No.
, 3 shows a composition of 29 mol% B2O3, 1 mol% SiO2, and 70 mol% M2O3, and point (D) is
Sample No. 4 had a composition of 90 mol% of 8203, 1 mol% of S102, and 9 mol% of M2O3, and point (E)
is sample No. 5, B2O3 is 90 mol%, SiO
It shows a composition of 9 mol% of 2 and 1 mol% of M2O3, and the point (
F) is sample No. 6, B2O3 is 19 mol%, S 1
The composition is 80 mol% of 02 and 1 mol% of M2O3.

The composition of the additive component of the sample that falls within the scope of the present invention is within the region surrounded by six straight lines connecting the first to sixth points (A) to (F> in the triangular diagram in order). Sample No. 7.
The composition of the glass powder shown in 8.9.10 is as follows from 1 to 1 in Figure 2.
Since it is outside the range shown by connecting the sixth points (A) to (F), insulation failure will occur in a laminated ceramic capacitor using this.

The proportion of glass powder in the conductive paste is Sample N.

As shown in 26.32.37.42, defects occur in the case of 0.5% by weight, but sample No. 27.33.3
As shown in 8.43, no defects occur when the amount is 1% by weight. Therefore, the lower limit of the amount of glass powder added is 1% by weight.6 Also, as shown in sample Nos. 31, 36, 41, and 48, if the amount of glass powder added is 21% by weight or more, insulation failure may occur. However, sample No. 30.35.4
If it is 20% by weight, such as 0.47, no insulation failure will occur. Therefore, the upper limit of the amount of glass powder added is 20% by weight.

No defects occurred even when the co-material in the conductive paste was 0% by weight as shown in Sample Nos. 27 to 30.

Furthermore, as shown in Samples Nos. 38 to 40, no defects occurred even in the case of 10% by weight. Therefore, common materials can be set to 0 if necessary.
It can be added in a range of 10% by weight.

[Modifications] Although the embodiments of the present invention have been described above, the present invention is not limited thereto, and, for example, the following modifications are possible.

(a) A trace amount of MnO or Mn may be added to the glass component added to the electrode as long as it does not impede the purpose of the present invention.
02 or the like may be added to lower the melting point of the glass component.

(b) Similar effects can be obtained when a base metal or a noble metal other than Ni is used as the metal of the conductive paste.

(c) It is desirable that the common material is the same as the porcelain material of the green sheet to which the conductive paste is applied, but it is not necessary that it be exactly the same, and similar porcelain materials can be used.

(d) It can also be used as an electrode material for single-layer ceramic capacitors.

(e) Before forming the external electrodes 4, a raw chip containing a conductive paste layer for internal electrodes may be fired, and then the external electrodes 4 may be formed.

(f) The temperature of firing in a reducing atmosphere is, for example, 10
The temperature can be varied within the range of 50°C to 1300°C.

In addition, the heat treatment temperature in the air atmosphere was set at 500°C to 1°C.
It can be varied within a range of 000°C.

(g) The amount of the vehicle can be varied, for example, from 10 to 200 parts by weight, when the total weight of the metal powder, glass powder, and co-materials added as necessary is 100 parts by weight. Furthermore, various known organic binders and solvents can be used for the vehicle.

[Effects of the Invention] As described above, when electrodes of a ceramic capacitor are formed using the conductive paste according to the present invention, it is possible to provide a ceramic capacitor with little insulation deterioration due to high temperature and high humidity environments.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway vertical sectional view showing the principle of a multilayer ceramic capacitor according to an embodiment of the present invention, and FIG. 2 is a triangular diagram showing the composition of glass powder in a conductive paste. 1... Multilayer ceramic capacitor, 2... Dielectric ceramic layer,
3...Internal electrode, 4...External electrode.

Claims (1)

[Scope of Claims] [1] Contains 80 to 99% by weight of metal powder and 1 to 20% by weight of glass powder, and the glass powder includes B_2O_3, SiO_2, and MO (however, MO is BaO, MgO, ZnO, SrO and CaO
A point (A) where the B_2O_3 is 1 mol%, the SiO_2 is 80 mol%, and the MO is 19 mol% in the triangular diagram showing the composition with the B_2
Point (B) where O_3 is 1 mol%, SiO_2 is 39 mol%, MO is 60 mol%, and B_2O_3 is 2 mol%.
9 mol%, the SiO_2 is 1 mol%, the MO is 70
Point (C) of mol% and the above B_2O_3 is 90 mol%,
The point where the SiO_2 is 1 mol% and the MO is 9 mol% (
D), the B_2O_3 is 90 mol%, the SiO_
Connect in order the point (E) where 2 is 9 mol%, the MO is 1 mol%, and the point (F) where the B_2O_3 is 19 mol%, the SiO_2 is 80 mol%, and the MO is 1 mol% 6 A conductive paste for electrodes of a ceramic capacitor, characterized in that it is within an area surrounded by straight lines. [2] The conductive paste for an electrode of a ceramic capacitor according to claim 1, further comprising 10% by weight or less of a ceramic powder that is the same as or similar to the dielectric ceramic of the ceramic capacitor. [3] The conductive paste for an electrode of a ceramic capacitor according to claim 1 or 2, wherein the metal powder is a nickel powder.