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|Thick-Film Pressure / Force Sensors on Different LTCC Substrates; a Characterization and Evaluation|
|Keywords: LTCC, sensors, thick film|
|Electro-mechanical systems (MEMS) are fabricated from different materials by various technologies. They are mainly produced by the micro-machining of silicon, but in some applications ceramic materials are a very useful alternative. The laminated 3D structures made by Low-Temperature Cofired Ceramics (LTCC) are especially convenient. To sinter to a dense and non-porous structures at rather low temperatures, compatible with a thick-film technology LTCC materials have to contain some (or a great deal) of a low-melting-point glass phase. Sensors for mechanical quantities are essential parts of MEMS, and screen printed and fired thick-film resistor and piezoelectric materials can be used to sense the mechanical deformations in LTCC based MEMS structures. Thick-film resistors and thick-film PZT (Pb(Zr,Ti)O3) piezoelectric materials were fired on different LTCC substrates. Three LTCC materials (conventional, lead-free and lead-free zero-shrinkage LTCC tapes) were evaluated. Thick-film piezo-resistors in the form of strain-gauges were realised with commercial resistor materials. The PZT paste was prepared from a pre-reacted PZT powder with the composition near the morphotropic phase boundary (Zr/Ti 53/47). Results obtained on relatively inert alumina substrates were used for the comparison. Electrical characteristics of resistors and PZT films on LTCC substrates were measured. Due to the inter-diffusion of oxides between glassy LTCC substrates and active films the electrical characteristics differ, sometimes significantly, from characteristics obtained on alumina. These interactions were studied by the SEM and EDS analyses. Based on obtained results LTCC based ceramic pressure sensors for a low pressure range were designed and evaluated.|
|Marija Kosec, Head of Electronic Ceramics Department
Jozef Stefan Institute