Effect of bonding on the packaged RF MEMS switch

Thermal mismatch induced by the die bonding structure will have significant effect on the reliability and performance of RF MEMS switch. In this paper, a Cell Library Method (CLM) is introduced as an alternative against conventional FEM simulation to simplify the study on packaging of RF MEMS for X-band operation. The calculations derived from CLM are in good agreement with the results simulated by ANSYS. Strain caused by thermal stress which is generated during the die bonding process obviously increases the pull-in voltage. According to the research, the pull-in voltage of the RF MEMS switch with no stress on the beam will varied from 25V to 43V after bonding process (a 400-micron-long beam is taken for example). If the excitation voltage remains unchanged, the switching time of silicon-based fixed-fixed polysilicon surface-micromachined beam will extend to be about 2 times as that of before bonding (a 200-micron-long beam is taken for example).