In the microelectronics industry, lead-containing solder is widely used due to its ease of operation, good wettability, and low cost. However, lead and its compounds are toxic substances that can harm the environment and human health with long-term use. Currently, commonly used lead-free solders include Sn-Bi and Sn-Ag-Cu, which have the characteristic of low melting points. When electronic packaging materials need to withstand high temperatures, these solders cannot meet the requirements.Silver solderThey have high electrical conductivity, thermal conductivity, and thermal fatigue resistance. In addition, silver has a higher melting point. Therefore, silver is a suitable high-temperature resistant electronic packaging material. When the size of silver particles is reduced to the nanoscale, their melting point significantly decreases due to size effects. Thus, silver nanoparticles can be used as silver solder in the field of electronic packaging to achieve low-temperature connections and high-temperature service.Silver solderMost of them are single-component, and their connection performance still needs improvement. For example, small-sized silver nanoparticles have a lower sintering temperature but exhibit high porosity in the sintered body, small grain size, and many defects. However, large-sized silver nanoparticles have larger grain sizes and fewer defects in the sintered body but have higher sintering temperatures and porosity.

To address the issues present in existing technologies, technicians provide a new type ofSilver solder, this composite nano-silver solder has advantages such as low sintering temperature and low porosity in the sintered body, making it suitable for connecting copper or copper-plated materials. It adopts the following technical scheme: a composite nano-silver solder characterized by being composed of two different sizes of nano-silver particles; the particle sizes of the two different sizes of nano-silver particles are 30-50 nanometers and 100-150 nanometers respectively. When the substrate is bare copper, polish, clean, and dry the surface to be connected; cleaning involves ultrasonic cleaning with alcohol for at least thirty minutes. When the substrate is a copper-nickel/silver plated layer, clean and dry the surface to be connected; washing involves rinsing with deionized water and alcohol.

The preparation principle of this silver solder is: utilizing the size effect of nano-powders can lower the sintering temperature of the powders to achieve low-temperature sintering connections for copper substrates. This invention mixes different sizes of nano-silver particles to obtain a composite nano-silver solder composed of small-sized silver particles and large-sized silver particles, where small-sized silver particles serve as fillers to improve initial packing density and bond large-sized silver particles; large-sized nano-silver particles are used as a framework to reduce initial grain defects and enhance the stability of the sintered structure. The low-temperature sintering connection of copper-based materials is achieved through the combined action of small-sized and large-sized nano-silver particles.

Compared with existing technologies, this new type ofSilver solderhas advantages: 1. It has low sintering temperature and low porosity in the sintered body, making it suitable for preparing copper or copper-plated connectors to achieve low-temperature connections for copper substrates in the electronic packaging industry, which helps reduce costs. 2. The low-temperature connection with copper-based materials results in high shear strength for the obtained connection components, with a relatively uniform and dense connection layer. 3. The preparation method for this silver solder is simple to operate, safe and reliable, cost-effective, and has broad market development potential.