Briefly Introduction about Conductive Silver Paste in Flexible Circuits (2)

Conductive Silver Paste is widely used in flexible circuit especial membrane switch industry for front control keyboard, mainly with Screen Printing method.

There is also wide application in touch screen for Conductive Silver Paste.

Following the last instruction of conductive silver paste, here we continue.

The size of the silver particles is related to the electrical conductivity of the silver paste. 

At the same volume, the particles are large, the probability of contact between the particles is low, and a large space is left, which is occupied by the non-conducting resin, thereby forming a barrier to the conductor particles and reducing the conductivity. 

On the contrary, the contact probability of fine particles is improved, and the electrical conductivity is improved. 

The effect of the size of the particles on the conductivity is only a relative relationship from the above situation. 

Due to the influence of processing conditions and screen printing methods, it is necessary to meet the conditions for the particles to pass through the mesh of the screen, and to meet the conditions for processing silver particles. 

The general particle size can be controlled at 3 to 5 μm. It is equivalent to 1/10～1/5 of the diameter of 250 mesh ordinary silk screen, which can make conductive particles smoothly pass through the mesh and be densely deposited on the substrate to form a full conductive pattern.

The shape of the silver particles is closely related to the electrical conductivity. 

From the general impression, only particles are understood as spherical or nearly spherical particles. 

The conductive particles used to make the conductive printing material are preferably in the form of flakes, flats, and needles. Among them, flakes are more superior. 

The round particles are in point contact with each other, and the flake particles can form face-to-face contact. 

After printing, the flake particles overlap with each other in a certain thickness at a certain thickness, thereby showing better conductivity.  

In the case of the same ratio and the same volume, the resistance of spherical particles is 10-2, while that of flake particles can reach 10-4.