Conductive silver paste is a key functional material for manufacturing electronic components. The rheological property parameters of the conductive silver paste during printing play a significant role in guiding the development of conductive silver paste products. So, what are the main rheological property parameters of the conductive silver paste?

From a macroscopic perspective, the various physical phenomena of the conductive silver paste during the screen printing film formation process are the results of flow and deformation under the action of forces (such as shear force, tensile stress, etc.), that is, various rheological phenomena. From a microscopic viewpoint, the rheological process is the destruction and recovery of the microstructure of the conductive silver paste with significant time dependence. The rheological process can be divided into the following four stages: 
1) During the storage stage of conductive silver paste: It is required that no precipitation occurs. The rheological characteristic parameters mainly refer to the viscosity under the static condition (equivalent to an extremely low shear rate), which is also known as the zero shear viscosity. 
2) During the transfer of conductive silver paste from the paste tank to the screen: It is required that the paste be stirred and thinned as quickly as possible to facilitate its pouring into the screen frame. The rheological characteristic parameters mainly include the shear thinning property and the yield stress value. 
3) Conductive silver paste screen printing stage: It is required to have good adaptability for screen printing, so as to obtain wet film patterns with strictly controllable geometric shapes and thickness. The rheological characteristic parameters include the degree of rapid decrease in viscosity when the shear force increases sharply (during the overprint process), and the magnitude of the normal tensile force and the fracture length (during the process of the screen being raised and separated). 
4) Conductive silver paste leveling and film formation stage: The requirement is for the viscosity of the conductive silver paste to increase rapidly to achieve the designed screen-printed pattern and thickness. The rheological characteristic parameters mainly include the extent to which the viscosity increases sharply when the shear rate decreases rapidly. 
It is extremely difficult to establish a strict correspondence between the qualitative description of the adaptability of conductive silver paste screen printing and the specific rheological characteristic parameters of the conductive silver paste. However, from the above analysis, some important rheological characteristic parameters can still be summarized: 1) Viscosity values at different shear rates; 2) Yield stress values; 3) The viscosity change characteristics during the sudden increase and sudden decrease of shear rate; 4) Normal tensile force and fracture length. 
The rheological properties of conductive silver paste directly affect the performance and stability of the conductive silver paste. Therefore, when preparing conductive silver paste, it is essential to ensure that the produced silver paste has appropriate rheological properties.