JP5156328B2 - Copper alloy powder for conductive material paste - Google Patents

Description

  The present invention relates to a copper alloy powder for a conductive material paste used for forming a circuit conductor or for an external electrode of a multilayer ceramic capacitor.

  Copper powder is often used mainly for conductive material paste used for forming circuit conductors and external electrodes of multilayer ceramic capacitors, but the average particle size of copper powder used in this application is about 0.5 to 10 μm. Since it is very fine and has a large specific surface area, when it is left in the atmosphere, it reacts with oxygen, carbon dioxide gas, sulfurous acid gas, etc., and an oxide film, a basic carbonate film or a sulfate film tends to be formed on the powder particle surface. When the powder with such a surface film is used as, for example, a conductive material paste, the contact resistance between the powder particles increases, causing an increase or variation in circuit resistance. This causes generation of circuit defects due to defective firing. In order to suppress such a phenomenon, it is desirable to make all the processes from the production of copper powder to the production of the final product an inert atmosphere, but in reality, this involves many difficulties.

As a measure for improving such disadvantages of the conventional conductive material paste, a method of alloying Ag with copper (Patent Document 1), a method of Ag plating on copper powder (Patent Document 2), or a copper powder A method of performing rust prevention treatment (Patent Document 3) is proposed.
However, the method of alloying Ag or Ag plating on copper has a problem in terms of cost, and the method using a rust inhibitor, when used as a paste for firing, inhibits sintering and prevents rust inhibitor during firing. Often causes poor sintering due to generation of cracked gas.

Japanese Patent No. 2767729 JP 2000-248303 A JP 2006-117959 A

  As described above, the present invention improves the disadvantages of the conventional copper powder for conductive material paste, has excellent weather resistance, and achieves the same degree of sintering as the conventional copper powder for conductive material paste. The object is to provide alloy powder.

  In order to achieve the above-mentioned object, the present inventor has made various studies on measures for improving the weather resistance without significantly impairing the electric conductivity and sinterability of the substrate by adding an alloy element to copper which is a substrate of the copper powder. This completes the present invention.

  That is, the copper alloy powder for conductive material paste of the first invention is a copper alloy powder in which at least one of Zn and Sn is alloyed with Cu as a main component, and Zn in the copper alloy powder And content of Sn is 0.02-1.2 mass%, Furthermore, the said copper alloy powder contains 0.005-0.05 mass% P, It is characterized by the above-mentioned.

The copper alloy powder for conductive material paste of the second invention is characterized in that the copper alloy powder is produced by pulverization using an atomizing method.
In the copper alloy powder for conductive material paste of the third invention, the content of Zn in the copper alloy powder is 0.05 to 1.0% by mass, and the total content of Zn and P is 0.1% by mass or more. It is characterized by being.

Furthermore, in the copper alloy powder for conductive material paste of the fourth invention, the content of Sn in the copper alloy powder is 0.02 to 0.2% by mass, and the total content of Sn and P is 0.05% by mass or more. It is characterized by being.

The copper alloy powder for conductive material paste according to the fifth aspect of the present invention has a Zn content of 0.02 to 1.0% by mass, a Sn content of 0.01 to 0.2% by mass, and the Zn and P content. The total amount is 0.1% by mass or more, or the total content of Sn and P is 0.05% by mass or more.

The present invention will be described in detail below.
Of the alloying elements shown in the present invention, when both Zn and Sn are alloyed with copper, it is a well-known fact that an oxide film is formed on the surface of the substrate to improve the corrosion resistance and oxidation resistance. In order to obtain a sufficient effect, it is necessary to add several percent or more, and the electrical conductivity of the substrate is greatly reduced. On the other hand, P, like Zn and Sn, has an effect of forming an oxide film on the surface by alloying with copper and improving the corrosion resistance and oxidation resistance. However, P is significantly more of a substrate than Zn and Sn. Reduces electrical conductivity. For this reason, the amount of addition of the conductive material paste is limited to 0.05% by mass or less at the most, but such a small amount addition does not sufficiently improve the corrosion resistance and oxidation resistance.

  However, the present inventors have found that Zn or Sn or both of them coexist with P in the copper substrate, so that the corrosion resistance and oxidation resistance of the substrate are remarkably improved even when the amount of these alloy elements added is extremely small. It was. Although the cause of this is not clear, it is presumed that this is due to the formation of a Zn—P or Sn—P alloy film or a phosphate film on the substrate surface. These films are extremely thin and do not greatly deteriorate the sinterability of the powder particles.

  By using the conductive material paste using the copper alloy powder of the present invention, it is possible to manufacture electronic parts such as circuit conductors having stable quality and external electrodes of multilayer ceramic capacitors.

Hereinafter, the best mode for carrying out the present invention will be described.
Since the copper alloy powder of the present invention has the conductive material paste in mind, the particle size is preferably about 0.5 to 20 μm in volume average diameter. Moreover, the copper alloy powder of the present invention can be produced by blending each component so as to have the above-mentioned content, and pulverizing this blend using a wet reduction method or an atomizing method. The atomizing method is suitable because it can be easily manufactured. Further, in the case of the atomizing method, the alloy element tends to concentrate on the surface of the powder particles during the solidification process, so that there is an advantage that the effect of improving the corrosion resistance and oxidation resistance of the substrate by Zn, Sn, and P is increased.

In the copper alloy powder of the present invention, at least one of Zn and Sn is alloyed with Cu as the main component, and the content of Zn and / or Sn in the copper alloy powder is 0.02 to 1.2 mass%. Moreover, the copper alloy powder only needs to contain 0.005 to 0.05 mass% of P, and the content of Zn, the content of Sn, and the content of P in the copper alloy powder of the present invention are such that the alloy component is Zn, In the case of the two-component system of P, the ranges of 0.05 to 1.0 mass% and 0.005 to 0.05 mass% are appropriate, respectively, and the total of Zn content and P content needs to be 0.1 mass% or more. In the two-component system of Sn and P, the ranges of 0.02 to 0.2% by mass and 0.005 to 0.05% by mass are appropriate, respectively, and the total of Sn content and P content needs to be 0.05% or more. Further, in the three-component system of Zn, Sn, and P, the ranges of 0.02 to 1.0 mass%, 0.01 to 0.2 mass%, and 0.005 to 0.05 mass% are appropriate, respectively, and the total of Zn content and P content is 0.1 mass% or more, or the total of Sn content and P content needs to be 0.05 mass% or more. If any of the above elements is less than the above range, the effect of improving the corrosion resistance and oxidation resistance is hardly observed. Conversely, if the above range is exceeded, the electrical conductivity of the substrate is lowered, and the element cannot be practically used.
Next, examples of the present invention will be described.

<Example 1>
Copper alloy powders having a volume average diameter of 3.0 to 4.0 μm and a composition described in the column of Example 1 in Table 1 were prepared by the water atomization method. The obtained powder was subjected to a sinterability test and a constant temperature and humidity test for 10 days in a constant temperature and humidity tester at 40 ° C. and 60% humidity.
Table 1 also shows the oxygen content measurement results and the sinterability test results of each powder before and after the constant temperature and humidity test, and the powder volume resistance measurement results after the constant temperature and humidity test.
The volume average diameter was measured by a laser diffraction / scattering method (MT300 manufactured by Nikkiso Co., Ltd.).
The amount of oxygen was measured by an inert gas-impulse heating melting method (EMGA-620W manufactured by Horiba, Ltd.).
In the sinterability test, each powder was compacted with a mold at 50 MPa and then sintered in nitrogen at 600 ° C. for 10 minutes, and the measured value of the dimensional change rate in the molding axis direction before and after sintering was used as an index.
Regarding the powder volume resistance, the powder volume resistance when pressurized with a test piece diameter of 25 mm and 800 kg was measured using a powder resistance measurement system (MCP-PD41 manufactured by Mitsubishi Chemical Corporation).

<Comparative Example 1>
A copper alloy powder having a volume average diameter in the range of 3.0 to 4.0 μm by the water atomization method and having a composition described in the column of Comparative Example 1 in Table 1 was prepared. A constant temperature and humidity test for 10 days was performed in a constant temperature and humidity tester having a humidity of 60%.
Before and after the constant temperature and humidity test of each powder, an oxygen amount measurement, a sinterability test, and a powder volume resistance measurement were performed in the same manner as in Example 1. The results are also shown in Table 1.

  From the results shown in Table 1, the copper alloy powder of the present invention has pure oxygen powder or the amount of oxygen even after the constant temperature and humidity test while ensuring almost the same sinterability as compared with the case where Zn, Sn, and P are added alone. It can be seen that the increase and, as a result, the decrease in sinterability is small, the change in powder volume resistance is small, and the weather resistance is excellent.

Claims (5)

  Cu, which is the main component, is a copper alloy powder in which at least one of Zn and Sn is alloyed, and the content of Zn and / or Sn in the copper alloy powder is 0.02 to 1.2% by mass, And the said copper alloy powder contains 0.005-0.05 mass% P, The copper alloy powder for electrically conductive material pastes characterized by the above-mentioned. The copper alloy powder for a conductive material paste according to claim 1, wherein the copper alloy powder is manufactured by pulverization using an atomizing method . The content of Zn of the copper alloy powder in is 0.05 to 1.0 wt%, yet conductive according to claim 1 or 2 the total content of the Zn and P is equal to or not less than 0.1 wt% Copper alloy powder for material paste. The content of Sn in the copper alloy powder in is 0.02 to 0.2 wt%, yet conductive according to claim 1 or 2 the total content of the Sn and P is equal to or not less than 0.05 wt% Copper alloy powder for material paste. The Zn content is 0.02 to 1.0 mass%, the Sn content is 0.01 to 0.2 mass%, and the total content of Zn and P is 0.1 mass% or more, or the content of Sn and P The copper alloy powder for conductive material paste according to claim 1 or 2, wherein the total amount is 0.05 mass% or more.