JP2002060877A - Ni alloy powder for conductive paste - Google Patents

Abstract

(57) [Problem] To provide a Ni alloy powder for a conductive paste excellent in heat resistance, in which the sintering start temperature is raised and oxidation resistance is improved. Kind Code: A1 A Ni alloy powder for conductive paste is Ni: 70.
９９99.9% by mass and V, Cr, Zr, Nb, Mo, T
a, one or more elements selected from the group consisting of
1 to 30% by mass, average particle size of 0.1 to 1 μm
And has higher performance than the comparative example (Ni alone).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Ni alloy powder for a conductive paste used for forming internal electrodes of a multilayer ceramic capacitor.

[0002]

2. Description of the Related Art Conventionally, a multilayer ceramic capacitor has conventionally been obtained by printing or spraying a metal powder paste on a ceramic dielectric sheet, stacking a large number of such dielectric sheets so as to have an electrode structure with each other, and integrating them by pressure bonding. Sintering and baking an external extraction electrode. Such a multilayer ceramic capacitor has characteristics such that the thickness of the effective dielectric can be reduced, a large capacitance-volume ratio can be obtained, the internal inductance is small, and it can be used in a high frequency band, for example, on the order of GHz.

In such a multilayer ceramic capacitor, since the ceramic dielectric and the internal electrode are simultaneously fired, it is necessary that the electrode material has a melting point higher than the sintering temperature of the ceramic and does not react with the ceramic. For this reason, noble metals such as Pt and Pd have been used before, but have the disadvantage of being expensive. In order to solve this drawback, the sintering temperature of the dielectric ceramic is set to 900 to
The temperature is reduced to 1100 ° C., and an electrode material using an Ag—Pd alloy or using an inexpensive metal such as Ni has been put to practical use.

[0004]

However, since Ni has a lower melting point than a dielectric, the difference in sintering temperature between the Ni electrode and the dielectric is large. Therefore, there is a problem that cracks and peeling of the electrodes, defective firing of the dielectric, and the like are likely to occur in the firing step. Ni is easily oxidized by oxygen in the atmosphere in the binder removal step and the sintering step. As a result, there is a problem that the electrode becomes poor in sintering or the electric resistivity increases due to the mixing of the oxide. conventionally,
Although the oxidation of Ni is prevented by reducing the atmosphere, firing in an oxidizing atmosphere is preferable in order to sufficiently exhibit the performance of the ceramic dielectric. Therefore, it is preferable that the electrode material can be fired in an oxidizing atmosphere.

Therefore, sintering is started at a higher temperature than Ni,
At that time, a powder that is not oxidized by the atmosphere is desired. The present invention has been made in view of the above circumstances, and it is an object of the present invention to develop and provide an excellent Ni alloy powder for conductive paste composed of an alloy mainly composed of Ni. In particular, it is an object of the present invention to provide a conductive paste Ni alloy powder having an excellent heat resistance in which the sintering start temperature is increased and the oxidation resistance is improved.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the technical means characterized by it is that Ni: 70 to 99.9% by mass and V, Cr, Zr, N
b, Mo, Ta, W, one or more elements selected from the group consisting of 0.1 to 30% by mass and an average particle size of 0.1 to 30% by mass.
Ni for conductive paste characterized by being 1 to 1 μm
Alloy powder. The present invention increases the sintering start temperature of Ni and improves the high-temperature hardness, while adding an element that does not significantly increase the electrical resistivity. As the element for increasing the sintering temperature, an element having a high melting point, a large atomic radius and difficult to diffuse was selected. That is, V, Cr, Zr, Nb, Mo, T
One or more elements selected from the group consisting of a and W are used as alloying elements. In addition, by alloying, activity reduction and formation of passive state can be achieved, and heat resistance can be improved.

[0007] When the added weight is less than 0.1% by mass, the effect of improving heat resistance and oxidation resistance is small, and when it exceeds 30% by mass, the electrical resistivity increases remarkably, and the resistance is significantly higher than that of conventional Ni. Therefore, it was limited to the range of 0.1 to 30% by mass. Preferably Ni: 90 to 99.8 mass% and V,
One or more elements selected from the group consisting of Cr, Zr, Nb, Mo, Ta, and W are 0.2 to 10% by mass. The average particle size was set to an appropriate particle size as a conductive paste for forming a uniform film thickness, and was 0.1 to 1 μm. If the thickness is less than 0.1 μm, screen printing or the like becomes difficult. Further, if the thickness exceeds 1 μm, the film thickness varies, so the thickness is limited to 1 μm or less.

The shape of the Ni alloy powder is preferably spherical. This is because the paste has excellent dispersibility and fluidity. Such an alloy powder can easily produce a spherical powder having a uniform particle size by a chemical vapor reaction. For example, a chloride of Ni and a chloride of an element to be alloyed are each heated and evaporated, and these vapors are mixed and reduced by hydrogen gas. The composition of the alloy and the particle size of the powder can be controlled by changing the reaction conditions. In a chemical vapor reaction, a heterogeneous metal element is mixed at the atomic level, so that a uniform alloy can be obtained.

The conductive paste can be manufactured in a conventional manner. For example, a paste can be produced by mixing 1 to 5 parts by weight of a binder such as ethyl cellulose and 5 to 20 parts by weight of a solvent such as terpineol with 100 parts by weight of a Ni alloy powder.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The Ni alloy powder according to the present invention and the alloy powder of the comparative example, and the Ni alloy powder in which the average particle size was changed, were experimentally produced and are shown in Table 1. The sintering start temperature of these Ni alloy powders, the electrical resistivity, and the temperature at which the mass increase reaches 0.2% when the temperature was increased were measured. Table 2 shows the measurement results.

[0011] The sintering start temperature is determined by the height of the green compact (sample height) when a green compact is produced by applying pressure to the alloy powder and the temperature of the green compact is increased. The relationship between the temperatures was investigated, and the temperature at which the height of the green compact began to decrease was defined as the sintering start temperature. The mass increase rate is determined by TG (thermogravim).
(entry) measurement in an air stream.

[0012]

[Table 1]

[0013]

[Table 2]

FIG. 1 schematically shows the relationship between temperature and sample height for an alloy powder composed of 99.5% by mass of Ni and 0.5% by mass of Cr as Example 2 and Ni alone as Comparative Example 1. The curves 11 and 12 are shown in Example 2,
Comparative Example 1 is shown. In Example 2, it can be seen that the sintering start temperature is higher than in the case of using Ni alone. FIG. 2 is a graph schematically showing a relationship of a change in mass of the alloy with a rise in temperature.
In Example 2 (curve 21), the mass increase start temperature was lower than in Comparative Example 1 (curve 22), indicating that oxidation was difficult.

After laminating a plurality of dielectric sheets produced by the doctor blade method and a conductive paste obtained by dispersing the Ni alloy powder of the present invention in an organic solvent by a printing method, It was fired to produce a multilayer ceramic capacitor. The obtained multilayer ceramic capacitor was free from defects such as cracking and peeling, and exhibited good operating characteristics in a higher frequency band than before.

The Ni alloy powder of the present invention has a small electric resistivity, a high sintering start temperature, and is excellent in oxidation resistance, and thus is most suitable for use as an internal electrode of a multilayer ceramic capacitor.

[0017]

According to the present invention, as a conductive paste metal for a multilayer ceramic capacitor, it exhibits good operating characteristics in a high frequency band, a small electric resistance, a high sintering start temperature, and a high oxidation resistance. It has become possible to provide an improved Ni alloy powder for conductive paste having excellent heat resistance.

[Brief description of the drawings]

FIG. 1 is a graph schematically showing sintering start temperatures of Example 2 and Comparative Example 1.

FIG. 2 is a graph schematically showing the rate of mass increase in Example 2 and Comparative Example 1.

[Explanation of symbols]

 11,12 curve 21,22 curve

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01G 4/30 301 H01G 4/30 301C

Claims (1)

[Claims] 1. Ni: 70 to 99.9% by mass and V, C
r, Zr, Nb, Mo, Ta, W, one or more elements selected from the group consisting of 0.1 to 30% by mass, and an average particle size of 0.1 to 1 μm. Ni alloy powder for conductive paste.