Co-fired ceramic

Résumé

Co-fired ceramic devices are monolithic, ceramic microelectronic devices where the entire ceramic support structure and any conductive, resistive, and dielectric materials are fired in a kiln at the same time. Typical devices include capacitors, inductors, resistors, transformers, and hybrid circuits. The technology is also used for robust assembly and packaging of electronic components multi-layer packaging in the electronics industry, such as military electronics, MEMS, microprocessor and RF applications. Co-fired ceramic devices are fabricated using a multilayer approach. The starting material is composite green tapes, consisting of ceramic particles mixed with polymer binders. The tapes are flexible and can be machined, for example, using cutting, milling, punching and embossing. Metal structures can be added to the layers, commonly using filling and screen printing. Individual tapes are then bonded together in a lamination procedure before the devices are fired in a kiln, where the polymer part of the tape is combusted and the ceramic particles sinter together, forming a hard and dense ceramic component. Co-firing can be divided into low-temperature (LTCC) and high-temperature (HTCC) applications: low temperature means that the sintering temperature is below , while high temperature is around . The lower sintering temperature for LTCC materials is made possible through the addition of a glassy phase to the ceramic, which lowers its melting temperature. Due to a multilayer approach based on glass-ceramics sheets, this technology offers the possibility to integrate into the LTCC body passive electrical components and conductor lines typically manufactured in thick-film technology. This differs from semiconductor device fabrication, where layers are processed serially, and each new layer is fabricated on top of previous layers. Co-fired ceramics were first developed in the late 1950s and early 1960s to make more robust capacitors. The technology was later expanded in the 1960s to include multilayer structures similar to printed circuit boards.

Source officielle

https://en.wikipedia.org/wiki/Co-fired_ceramic

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Publications associées (11)

Personnes associées (10)

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Concepts associés (2)

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Solutions for thermally mismatched brazing operations for ceramic tokamak magnetic sensor

Duccio Testa, Peter Ryser, Matthieu Toussaint, Thomas Maeder, Caroline Jacq, Philipp Windischhofer, Xinyue Jiang

To monitor high-frequency fluctuations of the equilibrium magnetic field in tokamaks, a 3D magnetic sensor has been developed. The sensor, which is positioned inside the vacuum vessel behind the protective tiles of the tokamak and is exposed to potential temperatures up to 400°C, is based on thick-film and LTCC (low-temperature co-fired ceramic) technology. To connect the sensor to the cabling that runs inside the vacuum vessel, mineral-insulated cables have to be brazed to the sensor to ensure electrical connection together with mechanical robustness and sufficient thermal stability. As the brazing temperature is about 600°C, direct brazing to the alumina sensor substrate can cause failure by cracking induced by thermal stresses. It arises both by temperature gradients stemming from the localised heating and by the high thermal mismatch of alumina with the braze and wire materials. In previous work, high stresses from temperature gradients were efficiently decoupled by brazing indirectly to alumina beams attached to the main substrate, and local thermal stresses between alumina and braze/wire by using a porous metallisation. However, as the slender alumina beams protruding out of the substrate are somewhat cumbersome and fragile, three alternatives were studied in the present work: 1) testing shorter and more robust beams, 2) replacing the alumina beam by a silver wire, and 3) depositing a porous temperature- and stress-decoupling dielectric to enable direct brazing on the main alumina substrate. These solutions are characterised with respect to their mechanical robustness and of the degree of thermal decoupling with the substrate they provide.

2016

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In this work, we present and analyse the flow-sensing part of a recently-developed multisensor in LTCC (low- temperature co-fired ceramic) technology; this device integrates flow / pressure / temperature sensing and is designed for diagnostics monitoring of standard industrial compressed air circuits and devices such as valves and actuators. In this prototype, flow is sensed using the constant-temperature anemometric principle, with temperature-sensing active and reference thermistors placed in the fluidic channel integrated within the LTCC structure. The LTCC bridge structuration technology and electronics are analysed, and possible improvements in fabrication yield and efficiency outlined.

Elsevier2011

Ultra-low pressure sensor for neonatal resuscitator

Peter Ryser, Thomas Maeder, Caroline Jacq, Nicolas Craquelin, Enrico Haemmerle

In this work, we study in detail the sensing characteristics of piezoresistive force sensors based on structured LTCC (Low Temperature Co-fired Ceramic) cantilevers carrying a thick-film piezoresistive bridge. These devices show much improved sensitivity compared to classical alumina-based devices, but may exhibit abnormally large signal and drift, which indicates the presence of structural defects originating from fabrication issues or deleterious interactions between materials. To eliminate these effects, the fabrication parameters of the LTCC cantilevers have been studied in detail. By varying materials, layer thicknesses, stacking order and lamination parameters, the respective roles of resistor-termination-tape interactions, plastic deformation of conductor tracks and lamination quality of the LTCC sheets may be elucidated.

Elsevier2011