JPH088191B2 - Conductive paste for electrodes of porcelain capacitors - Google Patents

Description

The present invention relates to a conductive paste suitable for forming an internal electrode of a laminated ceramic capacitor.

[Prior Art] When manufacturing a laminated ceramic capacitor, a conductive paste is printed on a green sheet (unsintered porcelain sheet) in a predetermined pattern so that internal electrodes can be obtained, and a plurality of printed green sheets are printed. The raw chips are laminated, cut into a predetermined size to obtain raw chips, and the raw chips are fired. The external electrodes are provided before or after firing the raw chips. According to this method, since the conductive paste is co-fired with the green sheet, the internal electrodes can be easily formed.

By the way, when a laminated ceramic capacitor is formed by simultaneous firing, if the thermal contraction characteristics in the firing process of the conductive paste for internal electrodes and the ceramic material (green sheet) are significantly different, the ceramic layers and / or the internal electrodes are A crack may occur or the internal electrode may be peeled (delamination) from the porcelain layer. To solve this kind of problem,
It is known to add a glass frit to the internal electrode conductive paste to bring the heat shrinkage closer to that of porcelain.
It is disclosed in Japanese Patent Publication No. 58. Further, JP-A-54-140960 discloses that a porcelain material powder (co-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 the laminated ceramic capacitor, in addition to the above-mentioned problem of delamination, a slight gap of 0.2 μm or less is generated between the dielectric ceramic layer and the internal electrode. There is a problem that water may infiltrate under high temperature and high humidity, or a plating solution may infiltrate at the time of forming external electrodes, resulting in poor insulation between the internal electrodes.

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

[Means for Solving the Problems] The present invention for achieving the above object includes 80 to 99% by weight of a metal powder and 1 to 20% by weight of a glass powder, and the glass powder is Li ₂ O and SiO _{2. 2} and MO (MO is BaO, MgO, Zn
1 mol% of Li ₂ O in the triangle diagram showing the composition with at least one metal oxide of O, SrO and CaO),
The point (A) in which SiO ₂ is 80 mol% and the MO is 19 mol%,
Point (B) at 1 mol% Li ₂ O, 39 mol% SiO _2, 60 mol% MO, 30 mol% Li ₂ O, 30 mol% SiO ₂ , 40% MO Mol% point (C), the Li ₂ O content is 50 mol%, the SiO ₂ content is 49 mol%, the MO content is 1 mol%, and the Li ₂ O content is 19 mol%. ₂ is 80 mol%,
The MO relates to a conductive paste for electrodes of a ceramic capacitor, which is in a region surrounded by five straight lines connecting the point (E) of 1 mol% in order.

[Operation] When the electrodes of the porcelain capacitor are formed by the conductive paste of the present invention, the occurrence of defects due to the high temperature and high humidity environment test of the porcelain capacitor is reduced, and it becomes possible to provide a highly reliable porcelain capacitor. This is considered to be due to the following reasons. The glass powder according to the present invention is in a low viscosity state during firing and precipitates between the dielectric ceramic layer and the electrode during the cooling process. As a result, the space between the dielectric ceramic layer and the electrodes becomes dense, and the infiltration of water or the plating liquid between them and into the dielectric ceramic layer is prevented. In addition, the thin glass layer formed by the above deposition has a high insulating property. Therefore, according to the present invention, it is possible to provide a porcelain capacitor having high dielectric strength and high reliability.

[Example] A conductive paste according to an example of the present invention and a comparative example and a laminated ceramic capacitor using the same will be described.

The conductive paste of this embodiment is used to manufacture the laminated ceramic capacitor 1 shown in FIG. That is, the laminated ceramic capacitor 1 is composed 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. The pair of external electrodes 4 are composed of a Ni layer 4a, a copper layer 4b, and a Pb-Sn solder layer 4c, respectively.

The conductive paste for forming the internal electrodes 3 is composed of nickel (Ni) powder as a metal powder, a co-material (dielectric ceramic powder), and glass powder. When obtaining the glass powder of the conductive paste for forming internal electrodes shown in sample No. 1 in the table, Li ₂ O 0.43 g (1 mol%) SiO ₂ 68.77 g (80 mol%) BaCO ₃ 10.73 g (3.8 mol %) GO 2.19g (3.8mol%) ZnO 4.42g (3.8mol%) SrCO ₃ 8.03g (3.8mol%) CaCO ₃ 5.44g (3.8mol%) Weigh out and add 300cc of alcohol to these, polyethylene pot After stirring with an alumina ball for 10 hours, calcining in air at 1000 ° C for 2 hours, putting this in an alumina pot with 300cc of water, crushing with an alumina ball for 15 hours, and then at 150 ° C for 4 hours After drying for 1 hour, Li ₂ O is 1 mol%, SiO ₂ is 80 mol%, MO is 19 mol% (BaO is 3.8 mol%, MgO is 3.8 mol%, ZnO is 3.8 mol%, SrO is 3.8 mol%, CaO To obtain a powder having a composition of 3.8 mol%). MO is 20 mol% Ba as shown in the MO content column of the table.
It consists of O, MgO, ZnO, SrO and CaO.

Next, 10 g of the above glass powder, 85 g of Ni powder having an average particle size of 1,0 μm and a purity of 99.9% or more, 5 g of the common material, and 9 g of ethyl cellulose dissolved in 91 g of butyl carbitol were placed in a stirrer. After roughly mixing for 5 hours, they were mixed by a roll mill for 1 hour to prepare a conductive paste. The vehicle (Vehi) consisting of ethyl cellulose and butyl carbitol
cle) is 100 in total of glass powder, Ni powder and co-material.
The same 100 parts by weight will be obtained when the parts are weight parts. Also, sample N
The co-material of o.1 is made of powder of the same material as the dielectric porcelain of the laminated porcelain capacitor described later.

Next, in order to fabricate a multilayer ceramic capacitor using this conductive paste, 100 parts by weight of the basic component consisting of (Ca _0.8 Sr _0.1 Ba _0.1 O) (Zr _0.79 Ti _0.2 Si _0.01 ) O ₂ and Li _A dielectric ceramic raw material consisting of 1 part by weight of an additive component composed of ₂ O, SiO ₂ and MO was prepared. The composition of the additive components is 1 mol% of Li ₂ O, 80 mol% of SiO ₂ , and 19 mol% of MO, and the content of MO is 20 mol% of BaO, MgO, and Zn, respectively.
O, SrO, CaO.

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

Then, 30 sheets of green sheets are laminated with the printed surface of the conductive paste facing up and the internal electrodes 3 arranged alternately in opposite directions so that they are arranged as shown in FIG. Then, four green sheets each having a thickness of 60 μm were laminated on each other and pressure-bonded, and then cut into individual chips.

Next, in order to obtain the Ni layers 4a of the pair of external electrodes 4 respectively connecting the internal electrodes 3 exposed on one end surface and the other end surface of the chip of FIG. A conductive paste (Ni paste) was applied to a thickness of about 50 μm and dried.

Next, a green chip provided with the conductive paste for the internal electrodes and the conductive paste for the external electrodes was replaced with H ₂ (2% by volume) + N ₂ (98
(% By volume) in a reducing (non-oxidizing) atmosphere at 1160 ° C for 2 hours, then cool down to 600 ° C, replace the atmosphere with an atmospheric atmosphere (oxidizing atmosphere), and heat at 60 ° C for 30 minutes. Was heat-treated and then cooled to room temperature to obtain a laminated sintered body chip. Further, a copper layer 4b is formed on the Ni layer 4a by electroless plating, and then Pb is formed by electroplating.
The -Sn solder layer 4c was formed to complete the laminated ceramic capacitor 1 shown in FIG. The length of this laminated ceramic capacitor 1 is
The width is 3.2 mm, the width is 2.5 mm, and the thickness is 0.8 mm.

In order to perform the reliability test of this multilayer ceramic capacitor 1, 200 multilayer ceramic capacitors 1 were soldered to the electrodes on the circuit board made of epoxy resin, and the temperature was measured while applying a DC voltage of 50V to each of these. 500 hours (h), 1000 hours (h) in a high-temperature and high-humidity atmosphere of 85 ° C and 90% humidity, 2
The insulation characteristics after being left for 000 hours (h) were examined, and those having an insulation resistance between the pair of external electrodes 4 of 5.0 × 10 ² MΩ or less were determined to be defective. As a result, as shown in the column of insulation failure in the table, 50
At 0h, 1000h, and 2000h, the number of defects in 200 was zero.

For sample Nos. 2 to 49, the conductive paste and the laminated ceramic capacitor were prepared in the same manner as in Sample 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 the reliability test was conducted by the same method, the results shown in the table were obtained. However, the firing temperature was changed in the range of 1100 to 1280 ℃ depending on the type of dielectric ceramic material.

In the dielectric column of the table, the types of the dielectric ceramic layers 2 of the laminated ceramic capacitor 1 are shown as 1 to 6.

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

The second dielectric ceramic indicated by 2 in the table is (Cr _0.61 Ca _0.37 Mg _0.01 Zn _0.01 O) (Ti _0.97 Zr _0.03 ) O ₂ 100 parts by weight of the basic component, B ₂ O ₃ and SiO ₂ . 2 parts by weight of additive component consisting of MO and. However, the composition of the additive components consisted of 10 mol% B ₂ O ₃ , 75 mol% SiO ₂ , and 15 mol% MO, where MO is 10 mol% BaO and 20 mol% MgO. And 5 mol% ZnO, 20 mol% SrO, and 45 mol% CaO.

The third dielectric porcelain indicated by 3 in the table consists of 100 parts by weight of the basic component consisting of (Sr _0.7 Ca _0.3 O) _1.01 (Ti _0.1 Zr _0.9 ) O ₂ and Li ₂ O, SiO ₂ and MO. 1 part by weight of additive components. However, the additive components consisted of 30 mol% Li ₂ O, 60 mol% SiO ₂ , and 10 mol% MO, where MO was 20 mol% BaO, 10 mol% MgO, and 10 mol% MgO. It consists of mol% ZnO, 30 mol% SrO, and 30 mol% CaO.

The fourth dielectric porcelain, designated by 4 in the table, consists of 100 parts by weight of the basic constituents of CaTiO ₃ and 1.5 parts by weight of additive constituents of B ₂ O ₃ , SiO ₂ and MO. However, the additive component consists of 30 mol% B ₂ O ₃ , 50 mol% SiO ₂ , and 20 mol% MO, where MO is 20 mol% BaO, 10 mol% MgO, It consists of 30 mol% ZnO, 20 mol% SrO, and 20 mol% CaO.

The fifth dielectric porcelain, indicated by 5 in the table, consists of 100 parts by weight of the basic constituents of BaTiO ₃ + 0.02CaO and 3 parts by weight of additive constituents of Li ₂ O, SiO ₂ and MO. However, the composition of the additive component is 5 mol% Li ₂ O, 55 mol% SiO ₂ and 40 mol% MO, where MO is 20 mol% BaO and 20 mol% MgO. , 20 mol% ZnO, 20 mol% SrO, and 20 mol% CaO.

The sixth dielectric ceramic indicated by 6 in the table is 100 parts by weight of the basic component 0.97 {(Ba _0.9 Mg _0.05 Ca _0.03 O) _1.01 TiO ₂ } + 0.03CaZrO ₃ , B ₂ O ₃ and SiO ₂ . 0.5 parts by weight of the MO and additional components. However, the additive component consists of 50 mol% B ₂ O ₃ , 49 mol% SiO ₂ , and 1 mol% MO, where MO is 10 mol% BaO, 50 mol% MgO, Consists of 40 mol% CaO.

As the common material in each sample No., the powder of the dielectric ceramic shown in the column of each sample No. dielectric is used.

As is apparent from the table, when the conductive paste having the composition according to the present invention is used to form the internal electrodes, the insulation failure does not occur even after at least 2000 hours in the high temperature and high humidity test of 85 ° C. and 90%.

On the other hand, sample Nos. 6, 7, 8, 14, 19, 20, 21, 25, 26,
In 30, 31, 36 to 49, 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 addition amount of the glass powder of the conductive paste for internal electrodes will be described. The preferable composition of the glass powder is the composition ratio of Li ₂ O—SiO ₂ —MO in FIG.
It can be determined based on the triangular diagram shown by. The point (A) in the triangular diagram shows the composition of sample No. 1 containing 1 mol% of Li ₂ O, 80 mol% of SiO ₂ , and 19 mol% of MO, and the point (B) represents the sample N.
o.2 1 mol% Li ₂ O, 49 mol% SiO ₂ , 50 mol% MO
The point (C) shows the composition of the sample No. 3 having 25 mol% of Li ₂ O, 35 mol% of SiO ₂ , and 40 mol% of MO, and the point (D) shows the composition of the sample No. 3. 4 has a composition of 50 mol% of Li ₂ O, 49 mol% of SiO ₂ , and 1 mol% of MO. Point (E) indicates sample No. 5
The composition of Li ₂ O is 19 mol%, SiO ₂ is 80 mol%, and MO is 1 mol%. The composition of the additive component of the sample belonging to the scope of the present invention connects the first to fifth points (A) to (E) of the triangular diagram in order.
The composition is in the area surrounded by the straight line of the book. Sample N
The composition of the glass powder shown in o.6, 7 and 8 is as shown in Fig. 2
Since it is outside the range shown by connecting the fifth points (A) to (E), insulation failure occurs in the laminated ceramic capacitor using this.

The ratio of glass powder in the conductive paste is sample No. 14, 2
As shown in Nos. 1, 26 and 31, defects occur at 0.5 wt%, but as shown in Sample Nos. 15, 22, 27 and 32, 1 wt%
In the case of, no defect occurs. Therefore, the lower limit of the amount of glass powder added is 1% by weight. In addition, sample No. 19, 25, 3
As shown in 0 and 36, when the addition amount of glass powder is 21% by weight or more, insulation failure occurs, but sample No. 18, 24, 2
If it is 20% by weight like 9 and 35, insulation failure does not occur. Therefore, the upper limit of the amount of glass powder added is 20% by weight.

As shown in sample Nos. 15 and 16, no defect occurs even when the content of the common material in the conductive paste is 0% by weight. Also, sample N
As shown in o.27, 28, 29, no defect occurs even when the amount is 10% by weight. Therefore, the co-ingredient can be added in the range of 0 to 10% by weight, if necessary.

[Modification] The embodiment of the present invention has been described above, but the present invention is not limited to this, and the following modifications are possible, for example.

(A) The melting point of the glass component may be lowered by adding a trace amount of MnO, MnO ₂ or the like to the glass component added to the electrode so long as the object of the present invention is not impaired.

(B) Even when a base metal or a noble metal other than Ni is used as the metal of the conductive paste, the same effect can be obtained.

(C) The common material is preferably the same as the porcelain material of the green sheet to which the conductive paste is applied, but it is not necessary to be exactly the same, and a similar porcelain material can be used.

(D) It can also be used as an electrode material for a single-layer ceramic capacitor.

(E) Before forming the external electrodes 4, the raw chip including the conductive paste layer for internal electrodes is fired, and then the external electrodes 4 are formed.
May be formed.

(F) The firing temperature in the reducing atmosphere is, for example, 1050 ° C to
Various changes can be made within the range of 1300 ° C. Further, the heat treatment temperature in the air atmosphere can be changed within the range of 500 ° C to 1000 ° C.

The amount of the vehicle (g) can be variously changed within a range of, for example, 10 to 200 parts by weight, when the total weight of the metal powder, the glass powder and the additive to be added as required is 100 parts by weight. Also, various known organic binders and solvents for vehicles can be used.

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

[Brief description of drawings]

FIG. 1 is a partially cutaway vertical sectional view showing the principle of a laminated 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 porcelain capacitor, 2 ... Dielectric porcelain layer, 3 ...
… Internal electrodes, 4 …… External electrodes.

Claims (3)

[Claims] 1. A metal powder of 80 to 99% by weight and a glass powder of 1 to 20% by weight, said glass powder being Li ₂ O, SiO ₂ and MO.
(However, MO is at least one metal oxide of BaO, MgO, ZnO, SrO and CaO) in the triangular diagram showing the composition of Li ₂ O 1 mol%, SiO ₂ 80 mol%, The MO is 19
Mol% point (A), Li ₂ O is 1 mol%, SiO ₂ is 39 mol%, and MO is 60.
Mol% point (B), the Li ₂ O content is 30 mol%, the SiO ₂ content is 30 mol%, and the MO content is 40 mol%.
Mol% point (C), Li ₂ O is 50 mol%, SiO ₂ is 49 mol%, and MO is 1
Mol% point (D), Li ₂ O is 19 mol%, SiO ₂ is 80 mol%, and MO is 1
A conductive paste for an electrode of a porcelain capacitor, characterized in that it is in a region surrounded by five straight lines connecting in sequence with the mol% point (E). 2. The conductive paste for an electrode of a porcelain capacitor according to claim 1, further comprising porcelain powder which is the same as or similar to the dielectric porcelain of the porcelain capacitor in a range of 10% by weight or less. 3. The conductive paste for electrodes of a ceramic capacitor according to claim 1, wherein the metal powder is nickel powder.