Design, characterization and realization of thin film packaging for both broadband and high power applications

• Main Author: Aboush, Zaid Emmanuel
• Published: Cardiff University 2007
• Subjects: 621.3815
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.584049

In recent years, high frequency MMICs have witnessed rapid development in terms of miniaturization, higher powers and increasing functionality, whilst the cost per unit has been simultaneously reduced. Cost-wise, modern packages have been unable to follow the same trend as the reduction seen in semiconductor costs and in some cases the package cost has even become a significant part of the overall module cost. Historically, the diverse range of MMIC applications has always demanded electrically transparent packages to house the on-chip circuits and isolate them from the hostile ambient environment. The other vital role for MMIC packages is to provide good thermal dissipation for the circuits they contain. Thermal issues associated with most packages have led to the invention of different kinds of thermal pastes and strips to help dissipate the excessive heat generated by active devices. However, the thermal design of the package itself remains the basic foundation for a package with good thermal behaviour. To evaluate the performance of high frequency semiconductor packaging a number of different electrical and thermal measurement setups have been developed. Passive electrical measurements are the most common and easiest measurements to perform as the package is tested without an active device inside. Active measurements involve measuring the package with an active device inside and can become problematic, especially when characterizing high power transistors with low output impedances, such as Si LDMOS transistors with output powers in excess of 30 Watts. This thesis deals with three main issues central to the problems encountered in modern high frequency MMIC packaging. Firstly, the development of new low-power low cost packages utilising cutting edge materials such as liquid crystal polymer (LCP) to compete with the traditional ceramic substrate packages. Secondly, the development of new high power laminate based packages optimised for electrical and thermal characteristics. Finally, the development of passive and active measurement systems used to characterize the developed packages. The active measurement system is based on the load-pull concept to measure and characterise high power packaged transistors. This system is also capable of measuring the waveforms at the device reference plane, which enables the optimised design of Power Amplifiers (PAs).