JP2001118424A - Copper alloy powder for conductive paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper alloy powder for a conductive paste for use as an external electrode of a stacked ceramic condenser, which powder has an excellent sintering property at low temperature and an improved acid resistance. SOLUTION: Disclosed herein is a copper alloy powder for a conductive paste, comprising 50 to 95% by weight of Cu, and 5 to 50% by weight of one or two or more elements selected from the group consisting of Sn and Zn, etc., and having an average particle size of 0.1 to 1 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper alloy powder for a conductive paste having excellent sinterability at a low temperature. Optimal.

[0002]

2. Description of the Related Art Conventionally, a multilayer ceramic capacitor has conventionally been made by printing or spraying a metal powder paste on a ceramic dielectric sheet, stacking a large number of them so as to have an electrode structure with each other, and sintering the integrated one by pressing. It is manufactured by baking an external lead electrode (external electrode).

[0003] Unlike the internal electrodes, the external electrode conductor of the multilayer ceramic capacitor is heated more than necessary to attach the external terminals to the completed sintered body and to connect to the substrate pattern. It is required that the sintering be completed without damaging the dielectric sintered body. On the other hand, since there is no restriction to reduce the cross-sectional area as in the case of the internal electrodes, the electrical resistivity can be increased to some extent. Cu is usually used as the external electrode conductor of the multilayer ceramic capacitor. Cu is easily oxidized by oxygen in the atmosphere during the binder removal and sintering steps. When Cu is oxidized, sintering failure of the electrode and an increase in electric resistivity occur due to the mixing of the oxide. If the atmosphere is reduced, oxidation of Cu is prevented, but the ceramic dielectric is reduced, and good performance as a dielectric cannot be exhibited. Therefore, a powder that starts sintering at a lower temperature than Cu and is not oxidized by the atmosphere at that time is desired.

[0004]

As described above, Cu is easily oxidized by the oxygen in the atmosphere in the binder removal and sintering steps, and the inclusion of oxides may cause poor sintering of the electrodes, There is a problem that resistance increases. On the other hand, if the atmosphere is made to be reducible, oxidation can be prevented, but another problem arises in that the ceramic dielectric is reduced and cannot exhibit sufficient performance.

The present invention has been made in view of the above circumstances, and has been developed to provide a copper alloy powder for a conductive paste comprising a Cu-based alloy and having excellent sinterability at a low temperature, and to provide the same. In particular, it is an object of the present invention to provide a copper alloy powder for a conductive paste which has a low sintering completion temperature and an improved oxidation resistance, and has excellent sinterability at a low temperature.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above problems, and its technical means is characterized in that Cu: 50 to 95% by weight and one or two selected from Sn and Zn. A copper alloy powder for a conductive paste, comprising 5 to 50% by weight of the above elements and having an average particle size of 0.1 to 1 μm.

[0007] The additive element is effective in lowering the recrystallization temperature of Cu and improving the oxidation resistance. The electric resistivity is allowed to be up to 2 to 3 times that of Ni. Selected. If the addition amount of Sn and / or Zn is less than 5% by weight, the effect of improving the oxidation resistance is small, and 50% by weight.
If the ratio exceeds the limit, the electrical resistivity increases significantly. Therefore, the range is limited to 5 to 50% by weight. The particle size was set to a range suitable for a conductive paste forming a uniform film thickness, and the average particle size was set to 0.1 to 1 μm. If the average particle size is less than 0.1 μm, screen printing becomes difficult. On the other hand, the average particle size is 1 μm
If it exceeds, the film thickness will vary, so it was limited to 1 μm or less. The shape of the copper alloy powder is preferably spherical. This is because the paste has excellent dispersibility and fluidity.

[0008] 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 Cu 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.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The copper alloy powder according to the present invention and the alloy powder of the comparative example and the alloy powder having different average particle diameters were experimentally produced. The weight increase rate at the time of temperature rise was measured. The measurement results are shown in Table 1, FIG. 1 and FIG.

The sintering completion temperature is determined by applying pressure to the alloy powder to produce a green compact, and examining the relationship between the height of the green compact and the temperature when the temperature of the green compact is increased. The temperature at which the height of the green compact (sample height) did not change and became constant was defined as the sintering completion temperature. The rate of weight increase was determined by TG measurement at 600 ° C. in an air stream.

[0011]

[Table 1]

In Table 1, No. 1 to No. No. 8 is an embodiment of the present invention. 9-No. 14 is a comparative example. In the examples, the comparative examples No. The sintering temperature is lower than that of 14 (Cu alone), the weight increase due to oxidation is small, and the increase in electrical resistivity is within the allowable range. In comparison, Comparative Example N
o. In No. 9, the electrical resistance was excessive. In No. 12, the particle size is too large, the fluidity of the paste is poor, and the electrical resistivity is large.

FIG. 1 shows the embodiment No. 1 shown in Table 1.
6 and Comparative Example Nos. 14 schematically shows the relationship between the temperature and the sample height for 14, and curves 11 and 12 show examples and comparative examples, respectively. In the example, it can be seen that the sintering completion temperature is lower than the case of using Cu alone. FIG. 2 is a graph schematically showing a relationship of a change in weight of the alloy with a rise in temperature. No. 6 (curve 21) and No. 6 which is a comparative example. 14 (curve 22) is shown. The examples show that the weight change is small and oxidation is difficult.

Further, a conductive paste obtained by dispersing the copper alloy powder of the present invention in an organic solvent was formed on a multilayer ceramic capacitor by a printing method, followed by firing to manufacture external electrodes of the multilayer ceramic capacitor. As a result of external observation of the capacitor, there was no defect such as crack, and the capacitor could be used.

The copper alloy powder of the present invention has a small electric resistivity, a low sintering completion temperature, and is excellent in oxidation resistance. Therefore, it is most suitable for use as an external electrode of a multilayer ceramic capacitor.

[0016]

According to the present invention, as an external electrode of a multilayer ceramic capacitor, copper for a conductive paste having a low electric resistance, a low sintering completion temperature, an improved oxidation resistance, and an excellent sinterability at a low temperature. It has become possible to provide alloy powder at low cost.

[Brief description of the drawings]

FIG. 1 is a graph schematically showing sintering completion temperatures of Examples and Comparative Examples.

FIG. 2 is a graph schematically showing the weight increase rates of Examples and Comparative Examples.

[Explanation of symbols]

 11,12 curve 21,22 curve

Claims (1)

[Claims] 1. Cu: 50 to 95% by weight and Sn, Zn
A copper alloy powder for conductive paste, comprising 5 to 50% by weight of one or more elements selected from the group consisting of: and having an average particle size of 0.1 to 1 μm.