Piezoelectric active mirror suspension embedded into Low Temperature Co-fired Ceramic

Low Temperature Co-fired Ceramic (LTCC) has proven to be a cost effective and flexible technology for producing complicated structures: sensors, actuators and microsystems. In this paper, piezoelectric active mirror suspension embedded into LTCC is presented. In the structure the LTCC was used as a package, passive layers of piezoelectric monomorphs, support for the mirrors and substrate for conductors. Active mirror structure, 17 mm in diameter, was made by compiling 20 layers using standard LTCC processing techniques. Each sample contained a laser micromachined bulk PZT structure which formed a monomorph with LTCC during the firing process. A mirror substrate (Ø 4mm) was mounted in the middle of the monomorph arms for evaluation of positioning performance where each of the three arms had independent signal electrodes and a common ground electrode. Electrical and electromechanical properties were investigated with LCR meter, network analyser and laser vibrometer for different arms and the mirror. Active mirror structure exhibited over 1 μm DC displacement for mirror leveling allowing also small changes in mirror angle up to 0.06°. First bending resonance frequency of the structure with the mirror was detected at 11.31 kHz with 4.0 μm displacement while 13.02 kHz and 2.7 μm was obtained without the mirror. The structure exhibited feasible characteristics for further utilization as tunable Fabry-Perot filter applications, allowing mounting of two active mirrors on both sides with distance and angle control.