Development status of Silver at Home and abroad preparation Technology and Prospect of Silver Powder for Electronic Industry [Silver Forum]

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At the 2021 China International Silver Industry chain Summit Forum and China Silver Market Application Symposium hosted by (SMM) of SMM Information & Technology Co., Ltd., Professor Huang Hui of Kunming University of Science and Technology introduced the preparation technology and development status of silver powder for electronic industry. Mainly from the development of silver at home and abroad, spherical ultra-fine silver powder preparation technology, flake ultra-fine silver powder preparation technology, nano-silver powder preparation technology, low-cost silver-coated copper powder preparation technology.

The present situation of the Development of Silver at Home and abroad

Silver has good ductility and plasticity, and can be alloyed with gold, copper, cadmium, aluminum, magnesium, tungsten, tin and other metals for electronic and electrical appliances, process accessories and other fields.

Silver is widely used in the fields of mobile phone, electronic industry, new energy, solar cell, wind energy and generator because of its excellent electrical conductivity and chemical stability.

Silver has the strongest reflection characteristics, the fastest photosensitive imaging characteristics, and the sensitivity to light reflection, so it is used in catalyst and imaging industry.

Silver is the most effective antibacterial ability, used in medical treatment, the treatment of large area burn gauze requires silver ion plating.

From the perspective of the import and export market, the domestic silver market demand increased in 2020, and the import and export volume was significantly higher than that in 2019. The domestic demand for silver in 2020 was about 20890 tons, an increase of 2.48 per cent over the same period last year.

With the proposal and layout of global "carbon neutralization", photovoltaic power generation, new energy vehicles and other related industries will usher in a new round of increment, but also led to the demand for silver.

In 2020, the export volume of China's silver products was 3587.60 tons, while the import value of silver products was 4139.85 tons. The situation of the import and export market is as follows:

There is a serious oversupply of primary products, which requires a large number of exports;

Need a large amount of foreign exchange to import silver powder, silver paste and other high-tech products needed by the electronics industry;

A large number of imported silver concentrates are also needed to be smelted into silver ingots for re-export, which not only consumes a lot of energy in our country, but also keeps the pollution in the country.

Preparation Technology of spherical Superfine Silver Powder

Silver powder is the general name of countless solid particle aggregates, and the particle is the smallest unit of powder movement.

The particle size and morphology of silver powder are affected by the type of reducing agent, the type of dispersant, the amount of dispersant, PH value and the concentration of silver nitrate.

The typical silver powder products prepared by the optimized process have the characteristics of high dispersion, high vibrating density and regular morphology.

Ultra-fine silver powder is suitable for high temperature sintered conductive silver paste, conductive adhesive and so on.

Preparation Technology of Flake Superfine Silver Powder

The properties of flake ultra-fine silver powder are stable, and the particles are in surface contact or line contact, so the resistance is relatively low and the conductivity is good. Flake silver powder is one of the important materials of electronic components, which is widely used in thin film switches, filters, carbon film potentiometers, tantalum capacitors, semiconductor chip bonding and other electronic components.

Photovoltaic silver paste is the core accessories of photovoltaic cells, accounting for 10% of the cost of 11%, while the new generation of HIT cells, photovoltaic silver paste needs to be used in a large number of flake silver powder, the market of flake ultra-fine silver powder will usher in rapid development.

At present, the flake ultra-fine silver powder is mainly formed by physical forming, that is, the spherical silver powder is obtained by ball mill, but the purity of the flake silver powder is not high, the surface is uneven, and the thickness of the center and edge of the powder is uneven.

In recent years, with the development of electronic components, the purity and flatness of flake silver powder are required to be improved, and the research on the preparation of flake silver powder by chemical synthesis is in the ascendant.

Preparation Technology of nanometer Silver Powder

In 1959, Richard Feynman, a famous physicist and Nobel laureate, predicted that human beings could use smaller machines to make smaller machines, and eventually they would arrange atoms one by one according to human will to make "products." this is the earliest dream about nanotechnology. In the 1970s, scientists began to put forward the idea of nanotechnology from different angles.

Nano-solid materials usually refer to dense solid materials formed by ultra-fine particles with a size less than 15 nm pressed under high pressure or after a certain heat treatment process.

The object whose transverse structure size is smaller than 100nm, the surface roughness less than 100nm, the assembly system of nanoparticles and porous media, etc., is a three-dimensional nanomaterial composed of one or more nanomaterials in zero-dimensional, one-dimensional and two-dimensional dimensions. Including: nano-multilayer arrays, nano-multilayer films, nano-porous materials, nano-springs and nanocomposites and so on.

Properties of Nanomaterials

From the micro and macro point of view, the nano-scale is neither a typical micro-system nor a typical macro-system, and it is a typical mesoscopic system. When a macroscopic object is subdivided into ultrafine particles (nanoscale), it will show many strange properties, that is, its optical, thermal, electrical, magnetic, mechanical and chemical properties will be significantly different from those of bulk solids.

1. Surface effect-chemical activity

two。 Small size effects affect the characteristics of light, electricity, magnetism, heat, force, etc.

3. Quantum size effect "Fermi energy level-electron energy level > discrete energy level"

4. Macroscopic quantum tunneling effect-quantum mechanics

Preparation Technology of low-cost Silver-coated Copper Powder

Ultra-fine spherical copper powder: copper red spherical metal powder. Suitable for MLCC end electrode copper paste, varistor copper paste, etc.

Ultra-fine dendritic copper powder: suitable for MLCC end electrode copper paste, varistor copper paste and so on.

Flake copper powder: copper red flake metal powder. Suitable for conductive adhesive, electromagnetic shielding materials, conductive rubber, conductive plastics, low temperature electronic paste and other products.