Piezoelectric active mirror suspension embedded into Low Temperature Co-ired Ceramic Maciej Sobocinski, Mikko Leinonen, Jari Juuti and Heli Jantunen Microelectronics and Materials Physics Laboratories, EMPART Research Group of Infotech Oulu Oulu, Finland maciej@ee.oulu.i Low Teperature Co-ired Ceramic (LTCC) has proven to be a cost effective and lxible technoloy for producing copicated structures: sensors, actuators and microsystems. In this paper, piezoelectric active mirror suspension embedded into LTCC is presente. In the structure the LTCC was used as a package, passive layers of piezoelectric monomophs, suppot for the mirrors and substrate for conductors. Active mirror structure, 17 mm in diameter, was made by copiing 20 layers using standard LTCC processing techniques. Each saple contained a laser micromachined bulk PZT structure which formed a monomoph with LTCC during the iring process. A mirror substrate (0 4m) 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 electromechanicl propeties were investigated with LCR meter, network analyser and laser vibrometer for dfferent arms and the mirror. Active mirror structure xhibited over 1 Im DC displacement for mirror leveing alowing also smal 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 Im displacement whle 13.02 kHz and 2.7 Im was obtained without the mirror. The structure xhibited feasible characteristics for futher utiization as tunable Faby-Perot iter appications, alowing mounting of two active mirros on both sides with distance and angle control. Keywords- piezoelectric, LTCC, Faby-Perot Inteferometer . INTRODUCTION Piezoelectric effect being one of the most effective ways to transfer electrical energy to mechanical displacement has been used in many actuator applications for decades. Among many materials, PZT compositions are the most commonly used piezoelectric ceramics.They present large coupling factors and piezoelectric coeficients making them good materialsfor sensor and actuator applications. Precise movements in nanometer scale up to dozens of micrometers can be generated depending on actuator design and size. A modem PZT device oten requires solid packaging and sophisticated and reliable electrical connections which can be obtained with Low Temperature Co-ired Ceramic (LTCC) technology. The ceramic system constructed as a multilayer structure offers lexible designs, excellent mechanical and electrical properties and relatively low price, thus being very good candidate for advanced packaging solutions. Furthermore, introduction of so called zero-shrinkage tapes such as HeraeusHeralocksigniicantly reduced the problem of sintering shrinkage allowing more precise elements and even co-iring of other materials such as functional ceramics or optical ibers [1-4]. In this paper integration of bulk PZT with LTCC package through co-iring has been presented in order to create active mirror suspension system for Fabry-Perot Interferometer (FPI) based optical ilter. Fabry-Perot Interferometer consist usually of 2 parallel, partially relecting mirrors with air gap in between which determines the transmission spectrum. The solutionof moving mirror allows tuning the length of the air gap thus changing the transmitting wavelength. In cases where tuning has to be order of nanometers, standard mechanical approaches are diicult to apply, therefore other solutions are required. Thermal, electrostatic and piezoelectric tuning systems were presented in previous works [5-8] andpiezoelectric actuation seems to be the most appropriate. The goal of this paper was to introduce modem monomorph piezoelectric actuators formed during co-iring of PZT-LTCC structures to the Fabry-Perot Interferometers. The approach presented in this paper showed in Fig. 1 beneits rom co-iring of piezoelectric ceramics with LTCC in several ways. Integration of bulk PZT materials with HeraeusHeraLock 2000 reduced need for gluing, ensures good electrical connections, boosts actuator's displacement through formation of monomoph structure, improves load bearing capability and reliability [2]. Furthermore, co-iring of bulk PZT materials can be realized only slightly modiied LTCC PZ 29 280 un thick [.ith electrodes] 20 layers L TCC Individual arm signal connection Common ground connecion r :===H - ,nnermirror Outer rrirror Figure I.Schematics of active mirror suspension module [not in scale].