Mechanical modelling and life cycle optimisation of screen printing

The application of thick film pastes and adhesives is a screen printing method in the mass production of thick films and low temperature co-fired ceramic circuits. During this process, the paste is printed by a rubber squeegee onto the surface of the substrate through a stainless steel metal screen masked by photolithographic emulsion. We consider the off-contact screen printing method in this paper, because it is now the standard printing method in the microelectronics industry. In our research a Finite Element Model (FEM) was created in ANSYS Multiphysics software to investigate screen deformation and to reduce stress in the screen in order to extend its life cycle. An individual deformation measuring setup was designed to validate the FEM model of the screen. By modification of geometric parameters of the squeegee, the maximal and the average stress in the screen can be reduced. Furthermore, tension of the screen decreases in its life cycle, which results in worse printing quality. The compensation of this reducing tension and the modified shape of the squeegee are described in this paper. Using this approach, the life cycle of the screen could be extended by decreased mechanical stress and optimised off-contact.