Thick Films on Ceramics

The thickness of a film is typically on the order of 12-25 pm (0.5-1 mil). After the film has been printed on a substrate, it should be allowed to settle to eliminate the mesh impression in the pattern. The settling time varies from 5 to 20 min depending on the viscosity of the paste. The film is then 

In the past screen printing in high-volume production operation is 200- to 250-pm vias and 150- J.m lines and spaces. Today a number of manufacturers produce circuits with lOO-pm vias and 75-pm spaces and trace design rules. The trends are toward smaller and smaller vias on tighter pitches with finer lines and spaces. Design rules that include 30- to 50-pm vias are under evaluation. 

To obtain finer lines and smaller vias, one can use photoimageable thick-film process for dielectric and conductors and diffusion patterning. The photoimageable thick-film process involves the use of a photoactive paste printed on a substrate and exposed through artwork or a mask to define circuif characteristics, lines, and vias. The materials are developed in an aqueous process and then fired using the conventional thick-film fechnique. Copper, silver, and gold metallizations are used, and layer coxmts of up to 10 circuit layers are possible. 

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