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Performance of piezoresistive thick-film pressure sensors on steel substrates is hindered by the high required firing temperatures of the layers, which cause degradation of the substrate mechanical properties. Special steels or alloys that are relatively unaffected by these temperatures are available, but their cost is very high. A much more promising alternative is the reduction of the thick-film firing temperature, in order to allow application of the standard high-strength steels used in thin-film cells. Therefore, a series of thick-film materials systems (dielectrics, resistors and conductors) firing at low temperatures (

Ease of fabrication and design flexibility are two attractive features of low temperature co-fired ceramics (LTCC) technology for fabrication of complex micro-fluidic devices. Such structures are designed and processed using different shaping methods, the extent and complexity of which depends on the final device specifications (dimensions, mechanical and functional properties). In this work, we propose a sacrificial layer method based on carbon-black paste, which burns out during the LTCC firing stage. The paper will summarize the preparation of the paste, influence of processing conditions on the final dimensions, and demonstrate the mechanically integrated structures obtained using this technique. Some of those are membranes of various diameters (7-12mm) with a thickness of 40µm and a variety of internal spacing (15-60µm), free-hanging thick-film resistors (TFR) bridges on LTCC for heating micro-volumes. The main methods of the study will be thermo gravimetric analysis (TGA), scanning electron microscopy (SEM) and dilatometry in addition to electronic instruments for device characterization.

Recently, high-strength zirconia-toughened alumina (ZTA) ceramic substrates have attracted interest, because they offer much improved mechanical properties over straight alumina, while maintaining advantages such as good thermal conductivity and chemical stability. This allows their application in high-power electronics and piezoresistive thick-film sensors, where the substrate is subjected to considerable stress. This work examines the impact of processing a range of thick film materials (Ag- and Au-based conductors, and a resistor material widely used in piezoresistive sensors) on the short- and long-term strength of ZTA, as compared to the standard 96% alumina used in thick-film electronics. It is found that many layers substantially reduce the substrate strength, especially in the long term, which is related to enhanced crack growth in the presence of glassy layers. These findings have pronounced implications in piezoresistive sensor design. Key words: piezoresistive, sensors, force, pressure, ZTA, strength, thick-film.

Smart packaging concept has been the driving force for the search of advanced technologies to produce multi-functional micro-scale devices for long years. In this sense, LTCC technology has been recently addressed as the suitable choice for a wide range of applications. In addition to its attractive characteristics for high-frequency applications those have been profited for a long time, it receives a growing attention for sensor applications in the recent years as well. This is due to the easy machinability of the LTCC tapes, which permits realization of complex structures such as membranes, channels, making it a suitable environment for micro-fluidic devices. These devices require utilization of supporting layers in order to prevent defects, often observed in forms of sagging, warpage or curling. The methods for elimination of these defects vary from passive precautions taken during lamination and firing to more elaborate methods such as use of sacrificial layers. The basic idea in the latter method is the preparation of a support, which can then be removed, leaving behind the desired structure. Among a number of alternatives, this paper focuses on and proposes the carbon-black sacrificial paste as an effective and simple method to fabricate membranes. Additionally determination of the open porosity elimination temperature in LTCC and effect of processing parameters on the fabricated structures, will be discussed. The methods of analysis will be TGA (thermo gravimetric analysis), dilatometer and SEM (scanning electron microscopy) analysis.