JPH0696996A - Conductive paste composition - Google Patents

Abstract

(57) [Abstract] [Purpose] Suppresses redox of palladium at high temperature
Provided is a conductive paste composition capable of preventing delamination. [Constitution] Palladium-containing powder and 0.03 at least one selected from zinc stearate and / or aluminum stearate per 100 parts by weight of palladium.
.About.4 parts by weight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste composition suitable for an internal electrode of a laminated ceramic capacitor.

[0002]

2. Description of the Related Art A general method for manufacturing a monolithic ceramic capacitor is as follows: barium titanate, lead titanate, a composite perovskite compound containing lead, etc. As a material, palladium or an alloy powder of palladium and silver, or
Screen printing a paste containing a metal powder containing a mixed powder of palladium powder and silver powder, etc., a plurality of the printed green sheets, then cut into a predetermined size, in the air or nitrogen atmosphere, 800-1400
It is baked at ℃.

However, palladium once undergoes a phase change to palladium oxide which is a thermodynamically stable phase at a temperature of 400 to 820 ° C., and then returns to palladium again at 820 ° C. or higher. When changing to palladium oxide, the electrode layer expands, and when returning to palladium, the electrode layer contracts. For this reason, stress may be generated in the dielectric layer and the electrode layer due to the difference in thermal expansion, and the electrode layer may be lifted up or cracks may be generated in the dielectric layer to cause defects. This defect is usually called delamination. Therefore, if the oxidation of palladium can be suppressed, the contraction at the time of reduction can also be suppressed and the occurrence of delamination can be prevented.

Several improved methods have been proposed to prevent such rapid shrinkage and oversintering of palladium. For example, it has been proposed to delay the firing shrinkage rate of palladium by adding an iridium organic resin salt or a rhodium organic resin salt to the palladium paste (JP-A-3-80513). However, there is a problem in that the wettability between these metals and the dielectric is poor and the adhesive strength between the electrode and the dielectric is weakened.

On the other hand, a method of delaying the sintering of palladium by adding a clay component containing montmorillonite as a main component to a palladium paste has been proposed (Japanese Patent Laid-Open No. 57-121072). However, this method has a problem that the silica component and the alumina component, which are clay components, diffuse into the dielectric and deteriorate the dielectric properties. Further, since the clay component remaining in the palladium electrode has an insulating property, the resistance value of the electrode itself is increased, and the high frequency characteristics of the multilayer capacitor are deteriorated.

Therefore, there is no rapid sintering shrinkage at high temperature,
The development of a paste that does not cause delamination has been earnestly desired.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an inexpensive conductive paste composition which has excellent continuity of electrode layers and can keep the specific resistance of the electrode layers low.

[0008]

In order to achieve the above object, the paste composition of the present invention comprises a palladium-containing powder,
Zinc stearate and / or 100 parts by weight of palladium
Alternatively, it is characterized in that 0.03 to 4 parts by weight of at least one selected from aluminum stearate is contained.

[0009]

The palladium-containing powder may be any one of palladium simple substance powder, palladium-silver alloy powder, palladium-gold alloy powder, or the like, and these may be mixed and used.

The amount of zinc stearate and / or aluminum stearate added must be 0.03 to 4 parts by weight per 100 parts by weight of palladium. This is because if it is less than 0.5 part by weight, it is not so effective in suppressing the oxidation and shrinkage of palladium, and if it exceeds 4 parts by weight, the specific resistance value of the electrode after firing becomes too high.

It is not necessary to specify the timing of adding the additive,
For example, the palladium-containing powder and the vehicle may be added when kneading with a three-roll mill or the like.

The vehicle is a resin in which a binder is dissolved in a solvent. The resin used is ethyl cellulose,
Cellulose resins such as nitrocellulose and acrylic resins such as butyl methacrylate and methyl methacrylate can be mentioned. Examples of the solvent include alcohol solvents such as terpineol and decanol, naphtha solvents such as mineral spirit and supersol, and ketone solvents such as methyl ethyl ketone.

Since the weight of the palladium-containing metal powder increases when it is oxidized, the degree of oxidation of the palladium-containing metal powder is
It can be evaluated by measuring the weight change of the palladium powder during heating.

[0014]

EXAMPLE 50 g of palladium powder (average particle size: 0.3 μm, spherical shape), a vehicle consisting of 14 parts by weight of ethyl cellulose and 86 parts by weight of terpineol, and 32.85 g of zinc stearate or aluminum stearate were mixed in the proportions shown in Table 1. After pre-kneading with a 3-roll mill, 16 g of mineral spirits were added and main kneading was performed to obtain a paste. As a comparative example, a paste containing no zinc stearate or aluminum stearate was obtained by the same method as above.

The above paste was placed in a watch glass and dried in a vacuum dryer at 120 ° C. for 12 hours to evaporate the solvent component.
The dried solid matter was crushed in a mortar and used as a powder 30 mg of 42 mesh under powder as a thermogravimetric analyzer (TG
The maximum oxidation weight gain was measured using A). The measurement conditions are a temperature rising rate of 20 ° C./min and a heating temperature range of 25 to 1100.
C., air flow rate 100 ml / min. The maximum oxidation weight increase rate was calculated by the ratio of the difference between the maximum oxidation weight during measurement and the oxidation weight at 1050 ° C. and the oxidation weight at 1050 ° C. It is shown that the lower the maximum rate of increase in oxidation is, the more the oxidation of the palladium powder is suppressed.

Further, the above paste is applied on an alumina substrate,
Using a 325 mesh stainless screen, the resistance measurement pattern has a width (W) = 1.55 mm and a total length (L) = 9.
Printing was performed with a continuous vertical lattice pattern having a shape ratio (L / W) = 60 of 3 mm, dried at 120 ° C. for 10 minutes, and then baked in a box furnace at 1300 ° C. for 2 hours to form an electrode. The electrode thickness was measured using a surface roughness meter, the resistance was measured by a four-terminal method with a digital multimeter, and the specific resistance was calculated.

[0017]

[Table 1]

According to this, the composition of the present invention has a remarkably low maximum oxidation weight increase rate as compared with the product without zinc stearate or aluminum stearate, delamination is prevented, and the specific resistance is 30 μΩ · cm. It can be seen that it does not exceed the range and has excellent characteristics. It is also found that when zinc stearate is added in an amount of more than 4 parts by weight per 100 parts by weight of palladium, the specific resistance exceeds 30 μΩ · cm.

[0019]

As described above, according to the present invention, it is possible to provide a conductive paste which has a small shrinkage during firing, can effectively prevent delamination, and has a small specific resistance.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication H01B 1/22 Z 7244-5G H01G 1/01 9174-5E

Claims (1)

[Claims] 1. A palladium-containing powder and palladium 10
At least one selected from zinc stearate and / or aluminum stearate per 0.0 parts by weight of 0.0
A conductive paste composition containing 3 to 4 parts by weight.