Hermetic packages are used to protect microwave and millimeter-wave monolithic integrated circuits against harsh environmental conditions, including changes in atmospheric pressure, humidity, moisture, and other natural hazards that would otherwise disrupt electrical connections or damage delicate electronics. Microelectromechanical systems (MEMS) require hermetic packaging to prevent against contaminating particles and moisture. Hermetic packages have a fine helium leak rate of ~1x10-11 atm-cc/sec and are known to provide the reliability in harsh environments. Current hermetic packages are based on metal and ceramic materials. Ceramic and metal packages are heavier, bulkier, and more expensive than organic counterparts. At the wafer-level packaging, high temperature wafer bonding is used to form hermetic cavities that result in tall structures. While organic packaging technology cannot provide true hermeticity, can it have a low enough leak rate to achieve competitive reliability? This is referred as “reliability without hermeticity” or near hermetic packaging.
In this presentation, we will review the concept of hermeticity and near-hermeticity in electronic packages. Liquid Crystal Polymer (LCP), which has permeation close to glass, will be introduced as the next generation organic material for near-hermetic packaging. We will discuss results of LCP material characterization. We will then present the development of sealing techniques of LCP onto LCP and LCP onto semiconductor materials to form near hermetic cavities for housing MEMS and MMICs. Using the newly developed sealing techniques, we will demonstrate LCP wafer-level packages, surface mount packages and multi-chip modules to 40 GHz. Examples of wafer-level packages include the lamination of LCP onto Si to cap or package RF MEMS switches and a phase shifter with LCP-packaged MEMS. We will also present the development of low-loss surface mount LCP packages to 40 GHz. These surface mount packages are designed with novel feedthroughs that achieve a measured insertion loss of ~0.2 dB to 0.4dB up to 40 GHz and provide embedded filters. We will discuss bond wire compensation schemes, package to printed circuit board transition design techniques, electrical repeatability, and thermal performance of millimeter-wave surface mount packages. Reliability evaluation will be presented to demonstrate the robustness and reliability of LCP packages. Examples of the environmental tests include 1000 hours of 85oC and 85% humidity, temperature cycles, thermal shock, etc. Finally, we demonstrate the development of compact wide bandwidth passive components, multi-chip modules, and phased array antennas in multi-layer LCP boards at Ka-band.
Anh-Vu Pham (SM’03) received the B.E.E. (with highest honors), M.S., and Ph.D. degrees in electrical engineering from the Georgia Institute of Technology, Atlanta, in 1995, 1997, and 1999, respectively. Anh-Vu joined the University of California at Davis in 2002 as an Assistant Professor and was promoted to full Professor in 2008. From 1999 to 2002, he was an Assistant Professor at Clemson University. At UC Davis, Anh-Vu leads the Microwave Microsystems Lab, which has been supported by DARPA, NSF, AFRL and numerous companies for research on RF and millimeter-wave frequency organic packages and multi-chip modules, and RF/millimeter-wave integrated circuits. He is currently a co-director of the Davis Millimeter Wave Research Center. Recently, his group has focused on developing organic packages and modules that can provide hermeticity and reliability as ceramic counterparts. He has published ~100 peer-reviewed papers, several book chapters, and one book. Anh-Vu has served as the Chair of IEEE Microwave Theory and Techniques (MTT) Technical Coordinate Committee on Microwave and Millimeter Packaging (2003-2006), and is currently the Vice Chair of IEEE International Microwave Symposium Technical Committee on Power Amplifiers and Integrated Devices. He received the National Science Foundation CAREER Award in 2001 and the 2008 Outstanding Young Engineer Award from the IEEE Microwave Theory and Techniques Society. He served as a Microwave Distinguished Lecturer of the IEEE MTT for the term 2010-2012. Anh-Vu will serve as the Technical Program Co-Chair for the 2016 IEEE International Microwave Symposium in San Francisco. In 1997, Anh-Vu co-founded RF Solutions (acquired by Anadigics), a fabless semiconductor company providing RFICs for WiFi applications. In 2008, he co-founded Planarmag, Inc and served as the CTO. Planarmag was acquired by Tyco Eletronics in 2010.