Photoimageable Thick Films for Multichip Modules

The evolution of today's high speed electronic systems has resulted in the need for modules which are able to provide all chip‐to‐chip interconnection with very fine top level and buried conductor traces, and a dielectric with a very dense via grid pattern. As standard thick film technology is capable of pitches only down to 250 µm, new photoimageable thick film pastes have been developed in order to achieve a higher resolution. These materials allow one to combine the advantages of screen printing as a deposition technique with photolithography for the patterning. The image is produced by exposing the printed paste through a photomask to define either lines or vias, so that a very high resolution (50 (µm pitch), similar to that available in MCM‐D or MCM‐L, can be achieved. This paper describes the processing of the photoimageable dielectric and conductor pastes. As an example of the capability of this technology, a module for electro‐optical interconnection is presented.