Preparation method of copper-silver composite powder

Abstract

The invention relates to a preparation method of copper-silver composite powder. The copper-silver composite powder has a coated nuclear-shell structure; a nuclear layer is made of copper-silver alloy, and the shell layer is made of silver. The preparation method comprises the steps: firstly, adding a mixed aqueous solution of AgNO3 and Cu(NO3)2.3H2O into a mixed aqueous solution consisting of a reducing agent and a dispersing agent to obtain a copper-silver alloy solution containing the reducing agent; then adding an AgNO3 aqueous solution into the copper-silver alloy solution containing the reducing agent, and leading silver to be deposited and coated on the surface of the copper-silver alloy; and then obtaining the 0.3-3mum copper-silver composite powder after filtering, cleaning, drying and surface densified treatment. In the obtained copper-silver composite powder, the coating of the outer-layer silver is uniform, the compact density is high, the conductivity is good, and the high-temperature oxidation resistance is strong.

Description

technical field [0001] The invention relates to the field of material preparation, in particular to a preparation method of copper-silver composite powder. Background technique [0002] The rapid development of the electronic information industry has driven the development of electronic paste with ultra-fine metal powder as the main functional phase, and with the development of electronic components to miniaturization, precision, and multi-function, the demand for electronic paste The requirements are also getting higher and higher. Common ultrafine metal powders include silver powder, gold powder, palladium powder, nickel powder, aluminum powder, copper powder, etc. Among them, silver powder is widely used in electronic components because of its excellent comprehensive performance. Copper is cheap and has a volume resistivity similar to that of silver, but copper powder is easily oxidized during preparation and use, which reduces the conductivity of the material. The us...

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Problems solved by technology

However, this method first requires pretreatment of the copper powder such as surface cleaning, activation, and sensitization, and copper is easily oxidized during the pretreatment process. In addition, the coating process is relatively slow, and it is difficult to form a uniform coating, resulting in imprecise coating. , and the silver layer coated on the surface is thin, and the oxidation resistance is weak when sintered at high temperature

Usually also adopt the method of introducing reducing agent to promote the reduction of silver ions, so as to obtain a uniform and compact silver coating layer with a certain thickness, but adding reducing agent can easily lead to the homogeneous nucleation of silver, which is not easy to control, and the silver plating solution Poor stability, which reduces the use efficiency and coating effect of silver

[0004] The patent with the notification number CN 101244459B discloses a preparation method of electroless silver-plated copper powder modified with rare earth. Before the copper powder is plated, it is cleaned, Activation, sensitization and ultrasonic assistance, the process is more complicated and the cost is higher

[0005] The patent with the announcement number of CN 1300381C discloses a preparation method of conductive composite copper powder and composite copper conductor paste, which uses the introduction of reducing agent to reduce the silver ion It is reduced to silver and deposited on the surface of copper powder to form a coating structure. The strong reducing agent such as formaldehyde and hydrazine hydrate is used to make the reaction speed fast, which is not easy to reduce the spontaneous nucleation and growth of silver, and reduces the use efficiency of silver.

[0006]The patent with the publication number CN 101214547A changes the surface topography and layout of micron-sized copper-silver particles through chemical reduction, so that it contains nano-level structured surface, although the surface is reduced Sintering or melting temperature, but at high temperature sintering, oxygen can easily pass through the surface layer to oxidize copper. In addition, the system does not use dispersant or ultrasonic dispersion assistance, the dispersion of the system is poor, and the collision between particles is easy to agglomerate during the preparation process. Make the product particle size distribution wide

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