Evaluations of Low-K Deielectric Compositions

Abstract

<p>Thick-film dielectric compositions which devitrify in a controlled way to form a ceramic phase during processing, are available for evaluation as crossover insulation in multilayer circuits. Their advantage over compositions based upon a borosilicate glass is that they provide a surface of greater mechanical stability for successive conductor layers during subsequent firing processes. This results in close alignment being maintained between successive layers of a multilayer circuit.</p> <p>A substantial part of the total manufacturing cost of a thick-film circuit is associated with the noble-metal content of conductor compositions. This has given impetus to the development of Platinum-Silver based pastes in preference to those containing higher percentages of Gold and Palladium. The results of an evaluation of dielectric behaviour using Platinum-Gold electrodes are of little significance if the intention is to use that same dielectric with Platinum-Silver electrodes in production. The interaction of materials at the interfaces during processing is known to alter the properties of the dielectric quite significantly, and the crossover structure must be evaluated as a system if useful data is to be obtained.</p> <p>This project is an evaluation of two multilayer systems based upon proprietary pastes from two different manufacturers; the dielectric is of the glass-ceramic type and the conductor is based upon a Platinum-Silver composition. Although claims are made in the product literature that both systems have equivalent performance, this report will show substantial differences exist when tests are conducted under the kind of conditions experienced during production.</p>