Detailed Introduction to Copper Powder

Copper powder is a metal powder with copper as the main component. It has unique physical and chemical properties, and a wide range of application fields. Here is a detailed introduction:

I. Basic Properties

1. Composition and Purity

Its main component is copper (Cu), with a purity usually over 99%. Some high-purity copper powders can even reach more than 99.99% purity. Depending on application requirements, it may also contain small amounts of alloying elements such as zinc, aluminum, and tin.

2. Physical Characteristics

  • Color and Appearance: Pure copper powder has a purplish-red metallic luster and a smooth surface; it may turn black or brown when oxidized.
  • Density: It has a density of about 8.92 g/cm³. The high density helps improve the compaction performance of the powder.
  • Particle Size and Morphology: The particle size ranges widely, from nanoscale (e.g., 300 nanometers) to micron scale (e.g., 5 microns, 10 microns). It has various morphologies, including spherical, near-spherical, dendritic, and flaky. Copper powders with different morphologies suit different application scenarios.
  • Electrical and Thermal Conductivity: Copper powder inherits the excellent electrical and thermal conductivity of copper metal, with low resistivity. It is an ideal choice for making conductive materials and heat dissipation components.

3. Chemical Properties

Copper powder easily reacts with oxygen and water vapor in the air to form copper oxide or basic copper carbonate, so you need to store it in a sealed container. In acidic or alkaline environments, copper powder may undergo chemical reactions. You should avoid contact with strong acids, strong bases, halogens and other substances.

II. Main Varieties and Characteristics

1. Electrolytic Copper Powder

With the continuous development of the powder metallurgy industry, the requirements for electrolytic copper powder are getting higher and higher. The apparent density of the powder ranges from 0.6 g/cm² to 3.0 g/cm³, the purity ranges from 99.5% to 99.99%, and it has low lead content (≤100 ppm). Users from different industries have different requirements for electrolytic copper powder:
  • Electrical Carbon Industry: It requires good electrical conductivity and wear resistance. So the electrolytic powder needs a large surface area, low apparent density, and good formability. This ensures the same electrical conductivity with as little electrolytic copper powder as possible, and also provides better wear resistance.
  • Powder Metallurgy Components and Cold-Pressed Diamond Tool Industry: It needs good formability and compressibility. The electrolytic copper powder should have an appropriate apparent density. This makes it easy to mix with other component powders without segregation, thus avoiding green compact cracking and other phenomena.
  • Oil-Impregnated Bearing Users: It requires large and uniform pores and good fluidity. Therefore, to improve the quality of oil-impregnated bearings, the electrolytic copper powder needs high apparent density and coarse particle size.

2. Atomized Copper Powder

The atomization method produces copper powder by breaking the molten copper liquid stream with a high-pressure medium (water or gas). It is also called the double-stream atomization method and belongs to the physical powder making method. According to different atomization media, it divides into water atomization and gas atomization. Gas atomization further includes inert gas (such as nitrogen) atomization and air atomization.
The atomization method only needs to overcome the binding force between liquid metal atoms to disperse into powder. Compared with the mechanical crushing method that uses mechanical force to break the binding between solid metal atoms, it consumes much less energy. It is a simple and economical powder making method.
Atomized copper powder has lower cost than electrolytic copper powder, and most of them are spherical or irregular particles. The characteristic requirements for different application scenarios are as follows:
  • Powder Metallurgy Users: Atomized copper powder has high apparent density and good fluidity, but its formability is slightly worse than that of electrolytic copper powder, and the green compact strength is low.
  • Improved Process: The low apparent density atomized copper powder (oxidation-reduction copper powder) prepared by the water atomization + oxidation-reduction process solves the formability problem well. It can partially replace electrolytic copper powder for application, but the domestic output of this type of copper powder is small. Deep oxidation and re-reduction can further reduce the apparent density, but it consumes high energy. So you should try to reduce the apparent density of copper powder during the atomization process, and then perform oxidation-reduction to reduce costs and ensure good formability.

3. Bronze Alloy Powder

Bronze alloy powder is an alloy powder with copper as the main component, added with elements such as tin, lead, and zinc. It has unique properties and a wide range of applications.
(1) Main Composition and Types
  • Common Composition: Its main component is copper (Cu), and it is added with elements such as tin (Sn), lead (Pb), and zinc (Zn). Different proportions of added elements form alloy powders with different properties.
  • Common Grades: 663 alloy powder (contains copper, tin, zinc, lead and other elements, suitable for oil-impregnated bearings, bearing bush materials, etc.); CuSn series (such as CuSn10, CuSn15, CuSn20, CuSn33, etc.), with copper and tin as the main components. Different tin contents lead to different properties, and they are often used in diamond tools, friction materials and other fields.
(2) Application Fields
  • Powder Metallurgy Components: It is used to manufacture mechanical parts such as oil-impregnated bearings, bearing bushes, gears, and cams. It has the characteristics of friction reduction, self-lubrication, and high precision.
  • Diamond Tools: As the matrix material of diamond tools, it can closely combine with diamond particles, improve the cutting efficiency and service life of the tools. It is widely used in stone processing, ceramic cutting and other fields.
  • Friction Materials: It is used in friction materials such as brake pads and clutch discs, providing good friction performance and wear resistance.
  • Electronic Components: Some high-performance bronze alloy powders can be used in electronic components such as electronic connectors and heat sinks, meeting the requirements of electrical conductivity, thermal conductivity and corrosion resistance.

4. Brass Alloy Powder

Common brass alloy powders include CuZn7, CuZn20, CuZn30 and other CuZn series alloy powders. They have excellent corrosion resistance and wear resistance, and are mainly used in powder metallurgy friction materials, diamond tools and printing and packaging "imitation gold powder".
Generally, the zinc content of CuZn series brass powder is 10%~40%. The melting temperature range of the alloy can range from 1045℃ for CuZn10 alloy to 960℃ for CuZn30 alloy. As the zinc content increases, the melting temperature decreases. The application scenarios for different particle sizes are as follows:
  • Powder Metallurgy Components: CuZn20 and CuZn30 powders are mostly irregular in shape, with a particle size of -100 mesh (≤150μm) and an apparent density of 2.3~3.2 g/cm³.
  • Diamond Tools: -200 mesh (≤75μm) and -300 mesh (<48μm) CuZn alloy powders can avoid dimensional deviation problems caused by sintering and melting of pure zinc powder.

5. Silver-Coated Copper Powder

Silver-coated copper powder is a new type of high-conductivity material. It uses advanced surface treatment technology to deposit silver coatings of different thicknesses on the surface of copper micro-nano particles. This improves the oxidation resistance and conductivity of the copper powder, making it a composite metal powder material.
 
Application Fields: As a high-quality high-conductivity filler, it can be added to coatings (paints), adhesives, inks, polymer slurries, plastics, rubbers, etc. It can make various conductive and electromagnetic shielding products. It is widely used in the conductive and electromagnetic shielding fields of various industrial sectors such as electronics, electromechanics, communications, printing, aerospace, and ordnance. For example, it is used for the conductive and electromagnetic shielding effects of electronic, electrical, and communication products such as computers, mobile phones, electronic medical equipment, and electronic instruments.
 
Special Applications: Future 5G hardware products have special requirements such as high thermal conductivity and sensitivity to interference signals. This will greatly increase the demand for heat dissipation, conductive, and shielding materials. In conductive coating technology, silver-coated copper powder can prepare conductive films through spraying, printing, or coating. These films are widely used in solar cells, touch screens, flexible electronics and other fields. They can provide reliable conductive performance and reduce costs.