The electrical conductivity of conductive silver paste is closely related to the characteristics of the silver powder. Among them, the particle size of the silver powder is a key factor. When the silver powder is finer, the conductivity is usually better. This is mainly due to the following reasons:

Increased contact area: The finer the silver powder, the larger the contact surface between the particles. This means that within the same volume, the smaller the silver powder particles, the more contact points can be formed between them, thereby increasing the channels for electron transfer. These additional contact points facilitate the smoother flow of electrons between the silver particles, thereby enhancing the electrical conductivity.

2. Decrease in resistance: As the size of the silver powder particles decreases, the distance that electrons travel between the particles also decreases accordingly. Since the distance that electrons travel becomes shorter, the probability of them colliding with the particle surfaces decreases, thereby reducing energy loss and the generation of resistance. Therefore, finer silver powder particles help to lower the resistance and improve the conductivity.

3. Improvement of filling effect: In conductive silver paste, silver particles are used to fill the voids within the conductive network. When the particle size of the silver is smaller, they can better fill these voids, forming a more compact and uniform conductive network. This improved filling effect helps electrons flow more efficiently within the conductive network, thereby enhancing the overall conductive performance.

4. Enhancement of Tunnel Effect: The tunnel effect is a quantum mechanical phenomenon where electrons can be transmitted between two closely adjacent metal particles through a very thin insulating layer. When the particle size of silver is smaller, the distance between the silver particles also decreases accordingly, which makes the tunnel effect more likely to occur. Therefore, finer silver particles help enhance the tunnel effect and improve the conductivity.

In conclusion, the finer the silver powder in conductive silver paste, the better its electrical conductivity is usually. This is because smaller silver powder particles can increase the contact area, reduce resistance, improve filling effect and enhance tunnel effect, thereby helping to enhance the overall electrical conductivity.