The morphology of silver powder used for conductive silver paste mainly includes flake silver powder and spherical silver powder

Conductive silver pasteThe conductivity of the conductive film is mainly achieved through the conductivity of conductive silver powder. The resistivity of the conductive film layer after screen printing is not only closely related to the conductive filler silver powder, but also influenced by other components. The selection and addition amount of conductive functional phases are crucial for the conductivity of conductive silver paste. Metallic silver exhibits the best conductivity among all metals and is chemically stable, commonly used as the conductive functional phase of conductive silver paste.

The most representative theories for the conductivity mechanism of conductive silver paste currently include percolation theory, tunneling effect theory, and field emission theory. When the silver content in the slurry is high, the conductive network of the conductive film layer is mainly formed by the direct overlap of conductive silver powder, and the conductivity mechanism is mainly based on the percolation theory; When the silver content is low,Conductive silver powderAlthough it is not sufficient for direct contact, a conductive network can still be formed, mainly relying on the migration of electrons between conductive particles through thermal vibration, making the conductive network smooth, mainly based on the tunneling effect theory of conductive mechanism; When the silver content is low, there is a strong electric field from the outside. At this time, electrons rely on transitions to pass through the organic polymer and onto adjacent conductive particles, making the conductive network smooth, and thus the field emission theory is the main conductive mechanism.

The morphology of silver powder commonly used in conductive silver paste mainly includes flake silver powderSpherical silver powderStudy the powder using four different morphologies of conductive silver powder.

When the content of conductive silver powder in the slurry increases from 50% to 70%, the conductivity of the slurry changes rapidly. As the silver content continues to increase from 70%, the conductivity of the slurry does not change significantly. This is mainly due to the increase in silver content, the relative decrease in resin content, and the decrease in its adhesion to silver powder. The leveling performance and hardness of the slurry are weakened. At the same time, the increase in silver content also increases the cost of the slurry. The results show that the conductive film layer exhibits excellent conductivity when the silver content is between 65% and 70%.