Page 339 - System on Package_ Miniaturization of the Entire System

Radio Fr equency System-on-Package (RF SOP) 313

emerging as the strategic direction primarily driven by the need to miniaturize the system
and improve functionality. Recent developments in advanced 3D packaging technologies
such as TSV will provide additional opportunities for significant miniaturization and
power consumption in the SOP concept. The SOP concept further allows heterogeneous
integration of different devices with different architectures and differently processed
characteristics. Recent work at the Georgia Institute of Technology demonstrated packaged
microwave amplifiers within LCP [73]. A 13- to 25-GHz GaAs bare die, low-noise amplifier
is embedded inside a multilayer LCP package made from seven layers of thin-film LCP.
This new packaging topology has inherently unique properties that could make it an
attractive alternative, in some instances, to traditional metal and ceramic hermetic
packages. The active device, in this example, is enclosed in a package consisting of several
laminated CO laser-machined LCP superstrate layers. Measurements demonstrate that
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the LCP package and its 285°C packaging process have minimal effects on the monolithic
microwave integrated circuit RF performance. These findings show that both active and
passive devices can be integrated together in laminated multilayer packages. This active
and passive compatibility demonstrates a unique approach to form compact, vertically
integrated (3D) RF system-on-package modules [73].
New challenges such as RF-MEMS integration and packaging have been at the leading
edge of the packaging research. Various approaches have been developed by universities
and leading packaging companies. Nevertheless, there is still a lack of standardization,
leading to excessive cost for the development of final products. Eventually, the ideal
packaging technology will emerge with the standards for environmental protection,
hermetical sealing, accelerated testing, and mechanical stability, among others.
Innovative shielding solutions are also emerging using metallized cavities, or
electromagnetic bandgap (EBG) structures as well as advanced simulation platforms to
predict electromagnetic interference and crosstalk within complex and miniaturized
microsystems. EBG topologies are also emerging for use in confining radiating field of
antenna elements, thus leading to more efficient isolation of the rest of the module,
while achieving miniaturization of the antenna.
Also emerging are new design approaches based on optimization algorithms such
as design of experiments (DOE), feed-forward neural networks, and genetic algorithms
to generate comprehensive models taking into account the fabrication and layout
parameters and their impact on electrical performance in multilayer configurations.
In addition to smart and miniaturized systems packaging, new materials and
chemical processes are the most important technologies that can lead not only to
miniaturization by ultrathin films but also can achieve RF component properties that
have never been achieved. The thin-film nanomaterials with unparalleled properties in
capacitance, inductance, and resistance will lead to a wide variety of new applications
that have not been imagined so far.

Acknowledgments
The authors would like to acknowledge the financial support of the Packaging Research
Center, NSF, NASA, and DARPA. The authors would also like to thank Ramanan
Bairavasubramanian, Nickolas Kingsley, Stephen Horst, Daniela Staiculescu, Stephan
Pinel and Kyutae Lim who contributed to the technologies reported in this chapter and
Dhanya Athreya for the inductor section write up and Jin Hyun Hwang for the capacitor
section write up.