Microwave multichip modules using low cost microwave chip on flex packaging technology

Microwave chip on flex (MCOF) is an innovative, low cost extension of Lockheed Martin's high density interconnect (HDI) technology. In MCOF technology, die are attached face down on an adhesive backed pre-patterned polyimide dielectric and then overmolded with an epoxy encapsulant. Laser drilled vias followed by multilayer thin film metallization complete the circuit. Significant cost and weight advantages are attained by replacing traditional module substrates with an epoxy encapsulant. Transmit/receive (T/R) modules, thousands of which may be used in a solid state phased array radar application, are particularly good candidates for this technology. This paper describes the use of MCOF technology to package T/R modules for solid state radar applications. An overview of the MCOF process is first presented, followed by a review of the design and fabrication considerations for MCOF multichip modules. Specific attention is focused on the unique packaging and electrical performance requirements of T/R modules and how these objectives are met by MCOF technology. Finally, reliability considerations for use in military applications are discussed. Potential MCOF failure mechanisms and the MCOF reliability plan are presented.