Application of plasma cleaning process in MEMS filter micro-assembly

To solve the problems of low efficiency and high void rate in the process of the MEMS filter (die) attach and increase the strength of wire bonding between the die and microwave circuit board, plasma cleaning process was introduced in the micro-assembly process of the MEMS filter switch module. The spreading area of the solder melted on the copper was analyzed before and after the plasma cleaning process. Process parameters including plasma flow, radio frequency time and radio frequency power were optimized by the orthogonal test. It is demonstrated that the plasma cleaning process is effective to decrease the void rates in die attach and enhance the wire bonding strength, thus improve the reliability of the MEMS filter module micro-assembly.

Feasibility Study of a Capacitive MEMS Filter Using Electrostatic Levitation

We introduce a capacitive MEMS filter that uses electrostatic levitation for actuation and sensing. The advantage of this electrode configuration is that it does not suffer from the pull-in instability and therefore tremendously high voltages can be applied to this system. A large sensing voltage will produce a large output signal, which boosts the signal to noise ratio. The filter outputs about a 110mV peak-to-peak signal when operated at 175V, and can be boosted to 175mV by increasing the voltage to 250V. Because pull-in is eliminated, voltages much higher than 250V can be applied. An outline of the filter design and operating principle is discussed. A model of the filter is derived and analyzed to show the mechanical response and approximate peak-to-peak signal output. This study shows the feasibility of a capacitive sensor that is based on electrostatic levitation, and outlines the advantages it has over traditional parallel-plate electrode configurations. This design is promising for signal signal processing applications where large strokes are important.