Area I: Microwave and Millimeter Frequency Electronic Packaging

Our major research area is microwave and millimeter wave frequency packaging with emphasis on multi-layer organic circuits, packages and modules. Our goal is to develop high-performance microwave and millimeter-wave packages and modules in an organic platform that enables significant size, weight and cost reduction with increasing functionality. Organic materials have a mass density of ~1.2 grams/cm3 as compared to a mass density of ceramic, 4 grams/cm3. Figure 1 demonstrates a concept of multi-layer 3-dimensional packaging module in an organic platform. We have worked with a variety of polymer materials such SU-8 and Kapton for microwave and millimeter circuits, components and modules. The modules developed in our lab have applications in gigabit wireless communication, radar and imaging systems.

Since 2003, we have investigated liquid crystal polymer to develop a hermetic organic packaging platform. Hermetic packaging is required to achieve high reliability for both MMICs and RF MEMS. Current state of the art hermetic packages employ metals, ceramics or Si to form an enclosure that is typically sealed using laser welding or high temperature wafer bonding. These materials and sealing processes add significant weight, size, and cost to a system. In collaboration with GE Global Research Center, we have developed a novel process to laminate liquid crystal polymer films onto Si. This process is used to develop hermetically sealed cavities for RF MEMS switches [J11, C1, C9, and C15] (Figures 2 and 3). This newly developed technology has the potential for solving the fundamental problem of RF MEMS packaging and brings RF MEMS devices into usable systems at affordable cost. Using this packaging process, we have designed and implemented a 2-bit phase shifter with RF MEMS switches in a multi-layer organic module and a wideband amplitude compensated true time delay circuit [J1, C1, and C2] (Figures 4 and 5). We have also developed novel multi-layer organic hermetic surface mount packages at Ka-band frequencies (Figures 6 and 7). The feedthrough of these surface mount packages achieves less than 20dB return loss at Ka-band frequencies [C3 and C10]. The result of this research demonstrates that it is possible to use low cost organic hermetic surface mount packages for millimeter wave frequencies. Our paper at the IEEE International Microwave Symposium was selected as Student Finalist in the Student Paper Competition. We have demonstrated that LCP packages can provide a fine leak rate of less than 5X10-8 atm-cc/s, which passes hermetic requirements by Method 1014, MIL-STD-883. The big question is whether these organic packages (while passing the hermetic fine leak rate) can achieve the same reliability as that of metal and ceramic packages. If so, the results of this research will make significant impact on microelectronic and sensor industry. On-going research is to investigate the reliability of these hermetic LCP packages and to scale electrical performance to 110 GHz operation.

We have also designed and implemented baluns in multi-layer structures to demonstrate the packaging of high-density organic modules with embedded passive devices [J6, J15, C16, and C17] (Figures 7 and 8). The balun achieves less 0.5 dB insertion loss and 0.5dB and 5o amplitude and phase imbalance from 6 GHz to 18 GHz. Using these baluns, we have demonstrated a Ku-band push-pull amplifier that achieves 20dB reduction of second-order harmonics from 6 GHz to 18 GHz [C4] (Figure 9). Finally, I have collaborated with Prof. Yoo to develop high speed velocity matched transmission lines for an array of electro-optic modulators and packages for InP chip sets [J5, J7, and J9].

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