identifies the problems and indicates the engineering considerations for producing high density fine line hybrids. the industry standard for high reliability thick film circuits is presently 10 mil lines and 10 mil spaces. work has been done to reduce this to 5 mil lines and 5 mil spaces with 3 mil lines and 3 mil spaces possible and additional effort for going down to 2 mil lines and 2 mil spaces. a survey of available thick film gold pastes was made. the metallization materials were evaluated for print definition, particle size, density, conductivity, and adhesion. a problem encountered is the increased impedance of the line as it approaches 2 mils in width. by using a higher density gold (92percent or greater solids), improved conductivity can be attained. multilayer dielectrics were evaluated for surface finish, pin holes and via resolution. a via resolution of 3 to 5 mils is necessary for fine line multilayer. the other critical requirement is to have a surface finish approaching that of the substrate another area investigated was screen fabrication requirements for fine line printing