A kind of production method of ultrafine spherical silver powder for conductive silver paste

Abstract

The invention relates to a method for producing ultrafine spherical silver powder for conductive silver paste. According to the method, thiourea dioxide is used as reducing agents to reduce silver nitrate, oxidation reaction products of the thiourea dioxide and ampholytic surface active agents are used as scattered protectants, thiourea dioxide solutions with the surface active agents, sodium hydroxide solutions and silver nitrate solutions are added into a reactor at the same time in a parallel flow mode, the molar ratio of raw materials of silver nitrate: thiourea dioxide: sodium hydroxide is controlled to be equal to 1:(0.5-0.7):(2-2.8), the pH of the reaction liquid is maintained to range from 11 to 12, the reaction temperature is maintained to range from 30 DEG C to 60 DEG C, after batch charging is completed, stirring continues, reaction is performed for 0.5 to 1 hour, then the reduction reaction is completed, and the excessive thiourea dioxide is decomposed. The silver powder particles are smooth in surface and spherical, the grain size is uniform, the average grain size is 1.2 micrometers to 2.0 micrometers, the tap density is 4.2-5.0 g / cm<3>, the specific surface area is 0.5-1.2 m<2> / g, and the molar yield is 98 percent to 99.5 percent. According to the method, the technology condition is easy to control, the production process is safe and environmentally friendly, few reducing agents are consumed, and the product quality is stable.

Description

technical field [0001] The invention relates to a production method of ultra-fine spherical silver powder for conductive silver paste, especially the production of spherical silver powder using thiourea dioxide as a reducing agent to reduce silver nitrate, and using thiourea dioxide oxidation reaction product and amphoteric surfactant as silver powder dispersion and protection agent The method belongs to the field of new energy and new materials. Background technique [0002] Silver powder is the most widely used and most used precious metal powder in the electronics industry, and it is the basic and key functional material for the production of various electronic components. The rapid development of the electronic information industry has driven the development of the ultra-fine silver powder and conductive paste market. Silver powder is also an important part of the positive electrode paste of solar cells. The rapid development of the solar cell industry has further promo...

AI Technical Summary

Problems solved by technology

[0010] The deficiencies in the existing silver powder preparation technology include: (1) The reducing agents hydrazine hydrate, formaldehyde and hydroquinone are toxic and highly irritating, and the problems of environmental protection and safety are difficult to solve; (2) The cost of reducing agents sodium borohydride and hydroquinone is too high (3) The reducing agent ascorbic acid is sensitive to changes in the acidity, concentration and temperature of the system, and the production conditions are not easy to control; (4) The reducing agent has strong reducibility and needs to be used in conjunction with a large number of dispersing protective agents, resulting in subsequent (5) There is insufficient research on new reducing agents, the feeding ratio of commonly used reducing agents is too large, and there is a lack of safe and stable multifunctional strong reducing agents