This chapter deals primarily with the screen printing of thick-film paste on ceramic substrates. Information on stencils and solder printing is readily found in treatises dealing with the surface-mount technology. The screen mesh is manufactured by weaving stainless steel wires to form a long sheet. One of the most important parameters of the screen is the mesh count, or the number of wires per unit length. The screen is prepared for use by stretching the mesh by pneumatic or mechanical methods over a large frame capable of accommodating several smaller screen frames. Stencils can be formed by photoetching a pattern through a thin sheet of brass or stainless steel from both sides of the metal. The particle size distribution of a thick-film paste is a compromise between screenability and the properties of the fired film. There are two basic methods of screen printing; the contact process and the off-contact process.