Marina Santo Zarnik

Alternative test methods using IEEE 1149.4

IEEE 1149.4 infrastructure has been aimed primarily for printed circuit board (PCB) interconnect test, parametric test of discrete components and functional test of IC cores. Methods to perform these tests have been published and experimental results using evaluation samples of IEEE 1149.4 ICs have been reported. So far, most attention has been paid to test and measurement techniques for the first two issues. Proposed methods typically employ IEEE 1149.4 infrastructure in the function of a built-in test probe that enables external test and measurement equipment to access the internal PCB points via the analog test bus. This paper describes an alternative approach based on functional transformation of the tested board by means of the existing IEEE 1149.4 resources. In this way, efficient go no-go functional test can be performed. Case studies are given to illustrate the proposed approach.

Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) Material for Actuator Applications

Due to its large piezoelectric and electrostrictive responses to an applied electric field the ()Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) solid solution has been widely investigated as a promising material for different actuator applications. This paper discusses some of the recent achievements in the field of PMN-PT piezoelectric and electrostrictive actuators manufactured from PMN-PT single crystals, bulk ceramics, or thick films. The functional properties of PMN-PT materials and some representative examples of the investigated PMN-PT actuator structures and their applications are reported.

Capacitive pressure sensors realized with LTCC technology

This work is focused on pressure sensors designed as a ceramic capsule consisting of a circular edge-clamped deformable diaphragm, which is bonded to the rigid ring, and the ring is fixed on the base substrate. These three elements form the cavity of the pressure sensor. The capacitive pressure sensor is based on changes of the capacitance values between two electrodes. One thick-film electrode is deposited on the diaphragm and the other on the rigid substrate. The distance between electrodes and the area of electrodes define the initial capacitance of the capacitive pressure sensor, and together with the geometry and flexibility of the diaphragm define the sensitivity of the sensor. The diaphragm with the diameter of 9 mm made with low-temperature cofired ceramic (LTCC) has a thickness of 200 mum and the distance between electrodes is about 70 mum. The initial capacitance is around 10 pF. The capacitive ceramic pressure sensor is the part of the electronic conditioning circuit with the frequency output. The typical output frequency is about 10 kHz and sensitivities are between 2.5 and 3.5 Hz/kPa.

Packaging technologies for pressure‐sensors

Pressure‐sensor miniaturization requires high‐density packaging. This means that designers are constantly faced with all kinds of challenging, and sometimes impossible, requirements. In this paper we will present three examples with specific technologies and aspects of miniaturization and packaging. The first example is a pressure switch, the second a pressure sensor and the third a smart pressure sensor.

The influence of thermal stresses on the phase composition of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 thick films

The influence of thermal stresses versus the phase composition for 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 (0.65PMN–0.35PT) thick films is being reported. The thermal residual stresses in the films have been calculated using the finite-element method. It has been observed that in 0.65PMN–0.35PT films a compressive stress enhances the thermodynamic stability of the tetragonal phase with the space group P4mm.

Design study for a thick-film piezoelectric actuator in an LTCC structure

In this paper we present the results obtained in the early design phase of a ceramic micro-electro-mechanic system (CMEMS) with an integrated piezoelectric actuator providing a valve function for the regulation of pressure. Different constructions of thick-film piezoelectric displacement actuators integrated in a low-temperature co-fired ceramic (LTCC) substrate implemented using conventional thick-film technology were considered. The characteristics of the thick-film piezoelectric ceramics printed and fired on appropriate ceramic substrates are similar to those of bulk materials, only certain material parameters are degraded to some extent for thinner layers. The preliminary FE analyses revealed the influence of selected technology-dependent parameters, e.g., the thickness of the thick films and the degradation of the piezoelectric material properties, on the characteristics of the actuator.

The LTCC combustor for ceramic micro-reactor for steam reforming

One of the possibilities for achieving portable power systems is a low-temperature fuel-cell system integrated with a fuel processor. A fuel processor is needed to make the hydrogen from liquid fuels (mainly methanol), as the required fuel for PEM (polymer-electrolyte membrane) fuel cells. The LTCC (Low Temperature Co-fired Ceramics) technology was used to prepare prototypes of microreactors for the steam reforming of liquid fuels with water into hydrogen. The 3D LTCC structures with buried cavities and channels, including two evaporators (fuel and water), the mixing chamber, the reformer and the combustor were realized. The combustor component was prepared by lamination of 22 LTCC green tapes (Du Pont 951). The main parts are eight burners realized as buried cavities. In the burners the platinum based catalyst is deposited to assist the oxidation - burning - of the methanol with the air. Thick-film platinum based heaters and temperature sensors are incorporated within the structure. The component was tested with different flow rates of liquid methanol − 1 ml/h to 5 ml/h - and air − 7 l/h to 15 l/h. The obtained temperatures were between 250°C and 450°C.

Study on optimization of capacitive pressure sensor using coupled mechanical-electric analysis

The object of the paper is a pressure sensor realized in thick-film technology developed at “Jožef Stefan” Institute. This pressure sensor is also the object of a common project which has the goal to optimize the sensor design acting mainly on layout parameters. Some of the sensor parameters are determined by the LTCC process, for instance the thickness of diaphragm whose thickness is a multiple of foil thickness. The novelty in the proposed paper is the use of specific simulation tools to give an estimate of sensor output characteristics. Using this technique it is possible to optimize the layout and construction of the sensor. The finite-element simulation is used to outline the output characteristic: capacitance versus pressure. This simulation implies the coupled field analysis from mechanical deflection of sensor diaphragm to electrical field quantities, in this case the capacitance. The analysis will take into account beside geometrical parameters the temperature dependence of materials properties. This fact will give a better appreciation of real life behavior of manufactured sensors, and can suggest some specific packaging methods.

PZT thick films for pressure sensors: Characterisation of materials and devices

Different piezoelectric materials can be used in micro-electro-mechanical systems (MEMS) for transducers i.e. actuators and sensors of mechanical quantities. Lead zirconate titanates (PZTs) are the most common ceramic materials used as piezoelectric transducers. The ceramic MEMS are made by LTCC (low temperature cofired ceramic) and thick-film technology. They have been extensively used due to their superior piezoelectric properties. The use of thick-film PZT materials on LTCC substrate is not a trivial task due to the interaction between the printed PZT layers and the LTCC substrates during firing. The microstructural, electrical and piezoelectric characteristics of the thick PZT films on relatively inert alumina substrates and on LTCC tapes were studied. To minimise the possible interactions between glassy LTCC substrates and active PZT films for some samples the intermediate barrier layers were used. To characterise the thick PZT films on ceramic substrate the dielectric permittivities (epsiv), dielectric losses (tgdelta), and piezoelectric coefficients (d33) were measured. The thick-film piezoelectric resonant pressure sensor on LTCC structure was designed and samples were fabricated (Figure 2). The thick-film PZT actuator on the ceramic diaphragm induces the vibration of the diaphragm at its resonant frequency. The applied pressure bends the diaphragm and generates additional stress, which shifts the resonant frequency. This is used as the output signal of the piezoelectric resonant pressure sensor. The resonant frequencies are shifted around 26 kHz. The calculated sensitivities are 2.5 Hz/kPa.

FE modeling of capacitive pressure sensors realized in LTCC technology

Although the pressure sensor market is dominated by silicon based sensors, in recent years ceramic based sensors have proved interesting and have been increasingly researched due to their material properties which qualify them for use in harsh environments. This paper describes the use of finite element analysis (FEA) to determine the functioning of a diaphragm-type ceramic capacitive pressure sensor starting from mechanical pressure and obtaining the output signal in form of an electrical capacitance. The capability of the software (Ansys/Multiphysics) to realize multi-field analysis will be used here in a very intensive way. Of major concern is the possibility to anticipate the influence of different liquid media on this category of pressure sensors developed using LTCC (Low Temperature Co-fired Ceramic).