Characterization and optimization of LTCC for high density large area MCM´s

High reliability military systems place stringent demands on the performance of miniaturization efforts using traditional packaging techniques. The new requirements are necessitated by the demand for higher circuit density, fine line resolution, mixed signal circuitry, low noise, low EMI emission and susceptibility, higher temperature, and diverse severe mechanical and environmental requirements. Due to the aggressive integration requirements, circuit designs must often be manufactured “one-up” due to their expanded size. As a result, yield numbers can go down drastically from lot to lot and design to design due to reliance on the fabrication of a single circuit per panel. Therefore, a thorough understanding of the materials and how they respond to the standard fabrication processes must be established to arrive at cost effective high performance assembly. This paper summarizes Lockheed Martin´s experience in the characterization of low temperature cofired ceramic (LTCC) materials for use in large area high density hermetic MCM and multilayer interconnect boards (MIB) currently being designed and implemented in the next generation of military electronics. This paper presents the methods used in characterization of the shrinkage of standard off-the-shelf materials during typical processing steps such as printing, drying, and touch-up, as well as cofiring. In addition, techniques utilized to increase yield on large area ceramic MIBs (surface area >20 in²) such as design enhancement, tooling improvement, via fill process optimization, and handling are reviewed and illustrated