Research On Preparation Process Of PMNT Thin/thick Films And MEMS Cooler

With the rapid development of micro electro mechanical system (MEMS),the MEMS equipment increasingly becomes microminiature and multifunctional.Cooling and thermal management have played a key role in accommodatingincreased in power while maintaining component temperatures at satisfactorylevels to meet performance and reliability objectives. The traditional coolingtechnology could not satisfy the refrigeration request now, and then ferroelectricMEMS Microcooler had the vital significance.Pb(Mg1/3Nb2/3)O3-PbTiO3 are being investigated extensively in theferroelectric materials. Because PMNT have good pyroelectric properties andsmall dielectric constant and dielectric loss, it is a prior material for ferroelectricMEMS microcoolers. In this paper, the fabrication process and properties ofPMNT thin/thick films and powders, with the preparation process of MEMSMicrocooler were systemtically studied from experimental aspects.First,PMNT ferroelectric thin films have been synthesized by Sol-Gelmethod with lead acetate trihydrate(Pb(CH3COO)2·3H2O), magnesium acetatetrihydrate(Mg(CH3COO)2?4H2O), niobium ethoxide(Nb(OC2H5)5) and tetrabuthltitanate(Ti(OC4H9)4) as the starting materials. The thin films have excellentferroelectric and pyroelectric properties, which have the pyroelectric coefficientof 10-8C·cm-2·K-1 when the processing is 700℃×1h at 25°C.Second, PMNT ceramic powder was prepared by sol-gel and coprecipitationmethod. The powder grains are nonaggregated and the average grain sizedistribution is 1~5μm and 50~100nm respectively. Compared with sol-gelmethod, PMNT powders prepared by coprecipitation method have the advantageof small size and homogeneous distribution, which are the candidate materialsfor fabricating ferroelectric thick films.Nanopowders have been gained by themethod of pumping slowly the sol to alkazid solution. The dispersion propertiesof powders were improved by the method of infrared-drying and organic solventclean.Based on the above, PMNT thick films with the thickness of 2~30μm havebeen successfully fabricated by 0-3 composite process. PMNT thick films areuniform, dense and crack, with pyroelectric coefficient of 10-8C·cm-2·K-1 between20°C and 30°C. In addition, the effects of dispersant and ultrasonic on sol havebeen analyzed.The wet etching of PMNT thin/thick films was also studied andHF/HNO3/H2O(1:2:40) etching solution was confirmed.At last, the preparationg process of ferroelectric MEMS Microcooler wasstudied. The 8×8,16×16 and 32×32 array micropattern of ferroelectric MEMSmicrocooler have been successfully prepared and laid solid foundations for theresearch and development of high performance ferroelectric MEMS microcooler.