Publications by Thomas Maeder | EPFL Graph Search

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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

We report on our Monte Carlo calculations of the conductivity of monosized and conducting spherical particles dispersed in a homogeneous matrix, with interparticle transport mechanism given by electron tunneling. We show that our numerical results can be r ...

The piezoresistive effect of thick-film resistors has found widespread application in pressure and force sensors due to their high strain-sensitivity, stability and low-cost. The main material requirements for these applications are a high piezoresistive response, low noise and low temperature dependence. However, many useful elastic substrate materials are degraded at the standard thick-film processing temperature of 850 °C, and therefore require a lower one. This is achieved by engineering the glass compo

The in-situ growth of PbZrxTi1-xO3 (PZT) and PbTiO3 (PT) thin films by reactive sputter deposition has been investigated for applications with silicon substrates. In-situ deposition from three simultaneously operating magnetron sources was applied. At the selected growth temperature range (550-600 degrees C), self-stabilisation of lead composition by a lar ge desorption rate of Pb on stoichiometric PZT surfaces has been observed. Interlayer mixing was found to be limited to a few monolayers. Both Pt and RuO

Polymer adhesives offer a viable method for mounting silicon dies for high temperature applications. Here a test vehicle for comparing the thermal conductivity of different die attach materials is presented. The setup can be used to determine the degree of ...

This article describes the design and fabrication of a hermetic LTCC package for an optical MEMS chip designed for space applications. The package must ensure electrical and optical connections, mechanical positioning, atmosphere control, and finally low thermally induced stress on the MEMS during final packaging operation. The package consists of a 10-layer LTCC case with a recessed cavity for the MEMS chip, and glass lid (with antireflection coating and thin-film metallisation for soldering) for optical I

A novel sensor based on thick-film + LTCC (low-temperature cofired ceramic) technology has been recently developed for sensing high-frequency 3D magnetic fields in tokamak fusion devices. For integration within the walls of the tokamak, the sensor has to be connected to the mineral-insulated cabling, which is carried out by brazing to ensure sufficient thermal stability. However, thermal mismatch stresses between the braze and the cable vs. the alumina substrate may cause local cracking of the latter during

Synthesis and characterization of oxide@Ag particles that are simultaneously magnetic and conductive 2) Elaboration of composites: dispersion of particles in organic matrix: silicone (PDMS) or thermoplastic (ethylcellulose + wax) 3) Screen printing of composite paste on alumina substrate 4) Curing under controllable and orientable magnetic field Composite materials with a thermoplastic matrix may be re-melted an aligned again.

The aim of this work is to examine the possibility of high performance pressure sensors based on piezoresistive thick films deposited on steel membranes, which combine the performance advantage of thin-film sensors (high-strength steel substrates, assembly without elastomer seal) with the low cost of ceramic thick-film sensors. As standard thick-film firing conditions degrade the properties of most high-strength steels, two routes were explored: 1) application of a special steel, which does not undergo mech

LTCC and thick-film technologies constitute excellent platforms for hermetic and controlled-atmosphere packaging, for applications in MEMS, space, micro/nanofabrication and biological fields. This work presents an active oxygen getter module, based on an integrated LTCC micro-hotplate coated with an oxygen-reactive metal in thick-film form. Gettering is activated by heating the platform, and getter consumption is monitored by the increase of its electrical resistance. Different reactive metals, ceramics or

A Venturi-type flow sensor has been designed and fabricated for neonatal respiratory assistance to control airway pressure and tidal volume. As the low flow range and sensing principle require the measurement of correspondingly very low pressures, a very responsive sensor, based on a polymer membrane acting onto a piezoresistive cantilever force sensor based on low-temperature co-fired ceramic (LTCC), was developed. This paper details the 3D modelling, manufacture, assembly and characterisation of the senso

A novel laser soldering method for hermetic packaging of temperature sensitive devices such as organic electronics, micro- and nanostructures is presented in this work. The package combines a thermally optimized LTCC (Low Temperature Co-fired Ceramic) base with a glass lid. These two parts are soldered together by the use of a laser diode. The advantages of the laser soldered joint is its hermeticity to water and air in regard to glue and plastic, as well as the possibility to heat only the soldered joint.

Purpose: The resistivity dependence on temperature of composite resistors made of carbon fillers dispersed in an organic matrix are known to be strongly affected by the matrix thermal expansion. High positive temperature coefficient (PTC) effects, i.e. ess ...

The influence of Ta, Ti and TiO2 adhesion layers with Pt bottom electrodes and the deposition temperature of the metallization on the nucleation and growth of sol-gel derived Pb(Zr0.53Ti0.47)O-3 thin films is reported. Several different PZT annealing profiles were simultaneously investigated to determine the role of PZT annealing on resultant PZT film microstructures for a given metallization. The adhesion layer was found to primarily influence PZT grain size. Largest grain sizes were observed for substrate

The introduction of micro-spacecrafts in the space industry has led to the development of various micro-propulsion techniques. Microthrusters are micropropulsion devices used in a microspacecraft for precise station keeping, orbit adjustment, attitude control, drag compensation and apogee kicking. The principle of operation of a solid propellant thruster is based on the combustion of a solid energetic material stored in a microfabricated chamber. In the current work, Low-Temperature Co-fired Ceramic (LTCC)

We have developed a robotic interface to train hand and ﬁnger function. HandCARE is a Cable-Actuated REhabilitation system, in which each ﬁnger is attached to an instrumented cable loop allowing force control and a predominantly linear displacement. The de ...

In this work, we present an integrated flow / pressure / temperature multisensor in LTCC (low- temperature co-fired ceramic) technology designed for diagnostics monitoring of standard industrial compressed air circuits and devices, such as valves and actuators. The pressure sensor is based on a membrane carrying a thick-film piezoresistive Wheatstone bridge. Flow is sensed using the constant- temperature anemometric principle, with the sensing thermistors placed in a fluidics channel, which also comprises s

We propose a theory of the origin of transport nonuniversality in disordered insulating-conducting compounds based on the interplay between microstructure and tunneling processes between metallic grains dispersed in the insulating host. We show that if the metallic phase is arranged in quasi- one-dimensional chains of conducting grains, then the distribution function of the chain conductivities g has a power-law divergence for g-->0, leading to nonuniversal values of the transport critical exponent t. We ev

The nature and the role of 1 to 5 nm thick TiO2 seed layers for the growth of textured PbTiO3 and Pb(Zr, Ti)O-3 thin films on textured Pt(111) thin film substrates have been studied. Under otherwise identical in situ sputter deposition process conditions, the PbTiO3 texture could be turned from (100) to (111) orientation by adding the seed layer. This is demonstrated by patterning the TiO2 film. Auger electron spectroscopy and x-ray photoemission spectroscopy showed that the seed layer was a continuous TiO2

Thomas Maeder

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Effect of thick-film materials on the mechanical integrity of high-strength ceramic substrates

Electron tunneling in conductor-insulator composites with spherical fillers

Effect of composition and microstructure on the transport and piezoresistive properties of thick-film resistors

In-situ sputter deposition of PT and PZT films on platinum and RuO2 electrodes

Test vehicle for studying thermal conductivity of die attach adhesives for high temperature electronics

Hermetic package for optical MEMS

Porous thick-film silver metallisation for thermally mismatched brazing operations in tokamak magnetic sensor

Piezo and magneto resistance of magnetically oriented dispersions of magnetic particles covered with silver in bulk and screen-printed elastomer polymers

High performance thick-film pressure sensors on steel

Hermetic package for optical MEMS

LTCC active oxygen getter module for hermetic packaging applications

Ultra-low pressure sensor for neonatal resuscitator

Laser soldering of LTCC hermetic packages with minimal thermal impact

Tuneable PTC effect in polymer-wax-carbon composite resistors

Microstructure of PZT sol-gel films on Pt substrates with different adhesion layers

Realization of a solid-propellant based microthruster using low temperature co-fired ceramics

HandCARE: a cable-actuated rehabilitation system to train hand function after stroke

SMD pressure and flow sensor for compressed air in LTCC technology with integrated electronics

Piezoresistivity and conductance anisotropy of tunneling-percolating systems

Texture control of PbTiO3 and Pb(Zr,Ti)O-3 thin films with TiO2 seeding