The screen printing is used in a variety of production processes in the pattern formation of the conductor, the semiconductor, and the insulator material of electronic parts.Science and technology development is necessary because it is an energy conservation production method in the future.As for products such as our keyboard, GlidePoint,™ and Low-profile Operation Panels, the screen process printing is applied.Here, it reports on the relation between Rheology and fine-patterning of the silver paste as part of the fine-patterning technology with the screen printing.The screen printing is a system that combines various parameters like the characteristic of the ink, the characteristic of the mask, and printing conditions, etc. Therefore, it is said that it will not be easy to develop academically. In addition, the dynamic behavior of ink changes by each material to mix various materials with the product.One method of understanding the characteristic of this ink includes the viscoelasticity measurement with the Rheometer.We obtained the Ag paste that formed a fine pattern easily in the screen process printing by measuring the Shear stress to the frequency dependency and the Shear rate. As a result, the mass production of 0.1mm line & space was achieved on the PET film now.