Low Temperature Co-fired Ceramics (LTCC) is one of the microelectronic techniques. This technology was initially developed as an alternative to Printed Circuit Boards (PCB) and classical thick-film technology, and it has found application in the fabrication of multilayer ceramic boards for electronic devices. Fast and wide development of this technology permitted the fabrication of 3D mechanical structures and integration with various different processes. Thanks to this, LTCC has found application in the manufacturing of various microelectronic devices. This paper presents an overview on LTCC technology and gives a detailed summary on physical quantity sensors fabricated using LTCC technique.

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Overview on low temperature co-fired ceramic sensors

This work presents the development of a highly selective wireless NO 2 gas sensor based on a resonant antenna circuit using a low temperature co-fired ceramic (LTCC) technique. The wireless LTCC based gas sensor consists of a planar inductor-interdigital capacitor (LC) resonant antenna, which incorporates two dimensional (2D) SnS 2 nanoflakes as a model NO 2 gas selective material. The fabrication of the LTCC platform is fully described, a brief description on the characterization of the gas sensitive material is presented and eventually the operation of the system for the sensing of NO 2 gas is investigated. The response of the LTCC template was associated to the changes of its resistance and capacitance due to the alterations in the properties of 2D SnS 2 as a result of physical adsorption of NO 2 gas molecules onto its surface. The wireless gas sensing performance under different operating temperatures and NO 2 gas concentrations are presented. The obtained LC gas sensor is successfully used for the wireless sensing of NO 2 in the background of atmospheric gas at concentrations lower than 0.6 ppm. The developed technology has a great promise for establishing wireless gas sensors for harsh environments

A novel wireless gas sensor based on LTCC technology

A new glass with ultralow glass transition temperature based on 10Li2O–10Na2O–20K2O–60MoO3 (LNKM) has been developed by conventional glass melting and quenching process. The glass has ultralow glass transition and melting temperatures being 198 and 350 °C respectively. The glass exhibits a coefficient of thermal expansion of 17 ppm/°C in the temperature range of 25–300 °C. X-ray diffraction and Raman spectroscopic studies indicate that the glass is partially crystallized. The chemical and elemental composition of the glass is confirmed by X-ray photoelectron spectroscopy. The glass pellet heat treated at 300 °C has a relative permittivity of 5.07 and dielectric loss tangent of 0.006 at 1 MHz. At 9.97 GHz, it shows a relative permittivity of 4.85 and dielectric loss tangent of 0.0009. The temperature dependence of the relative permittivity at 1 MHz and 9.97 GHz of the glass is 307 ppm/°C (temperature range 20–100 °C) and 291 ppm/°C (temperature range 25–85 °C), respectively.

Structural, Dielectric, and Thermal Properties of Pb Free Molybdate Based Ultralow Temperature Glass

In this paper, a microfluidic platform for real-time monitoring of dissolved oxygen in a flowing microfluidic environment fabricated using low temperature co-fired ceramic (LTCC) technology is described. The fabricated Clark-type oxygen sensor consisted of three electrodes (working electrode, counter electrode and Ag/AgCl reference electrode), a solid-state proton conductive matrix (Nafion 117 membrane) and polydimethylosiloxane (PDMS) as the oxygen permeable membrane (OPM). The use of a solid-state proton conductive matrix as the electrolyte in the design of the oxygen sensor makes it feasible integrate this device in a typical LTCC fabrication process. Cyclic voltammetry and chronoamperometry measurement were used to characterize electrochemical properties of the developed oxygen sensor. The reduction current was linearly related with the dissolved oxygen concentration ranging from 0 to 8.1 mg/l under different flow conditions (0.0–1.0 ml/min). The residual currents of the oxygen sensor were less than 3.5% of that measured in oxygen saturated state, and the average response time was 10.9 s. The current device represents an improved Clark-type oxygen sensor with the advantages of easy fabrication, flexible configuration, fast response time, incorporation of microfluidic analyte introduction and real-time detection of dissolved oxygen. The potential applications include material synthesis, cell culture, biological assays incorporating controlled introduction of reagents or analytes and real-time monitoring of dissolved oxygen in a microfluidic environment.

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A low temperature co-fired ceramic based microfluidic Clark-type oxygen sensor for real-time oxygen sensing

This paper presents an integrated piezoelectric accelerometer embedded in Low Temperature Co-fired Ceramic (LTCC). The PZT based sensing element, passive layer and seismic mass were integrated through co-firing with multilayer ceramic tapes. Resonance, frequency and sensitivity measurements were made for two different seismic masses. Results show sensitivity up to 6 mV/g without signal amplification, high linearity of output signal and a resonance frequency of 32.7 kHz. Furthermore, the sensor can easily be tailored to specific applications through adjustment of the seismic mass and stiffness of the sensing beams by modification of their dimensions. Compared to other similar structures, the LTCC–PZT accelerometer exhibited a comparable resonance frequency and outstanding sensitivity, even without signal processing. The presented method also enables the manufacture of structures with acceleration sensing on multiple axes and embedded electronics for a compact system-in-package.

A co-fired LTCC–PZT monomorph bridge type acceleration sensor

Design procedure, technology and basic properties of a piezoelectric Low Temperature Co-fired Ceramics (LTCC) accelerometer are presented in this paper. The sensor consists of a LTCC membrane with a seismic mass. Meggitt InSensor® PZT thick film has been applied as the sensing material. Finite element method (FEM) has been used to analyze the impact of the sensor geometry (membrane thickness, membrane and seismic mass radii) and PZT thick film placement on basic properties (sensitivity and bandwidth) of the device. The LTCC process was optimized in order to create thin and planar ceramic membrane with relatively huge seismic mass. Selected properties of the sensor have been measured and compared with the simulated ones.

Preliminary Model and Technology of Piezoelectric Low Temperature Co-fired Ceramic (LTCC) Uniaxial Accelerometer

This paper describes a case study of an impact of inaccuracies that arise in the LTCC technology on electrical parameters of a chip LTCC balun. The motivation behind this work was to identify stages of the LTCC process that contribute the most to the performance degradation of LTCC devices. We used optical microscopy and X-ray CT (X-ray Computed Tomography) scanning of the balun structure before and after sintering process, respectively. We also made a sensitivity analysis of the balun parameters by means of computer simulation. The results of this analysis were correlated with inaccuracies that were found before. We have learnt that the balun performance degradation result mainly from misalignment of layers during lamination process and poor calibration of a laser cutting tool used for metallization patterning. The outcome of our study may be useful, as a practical guide, to designers developing chip LTCC devices.

Arkadiusz Dąbrowski

Papers

Overview on low temperature co-fired ceramic sensors

Preliminary Model and Technology of Piezoelectric Low Temperature Co-fired Ceramic (LTCC) Uniaxial Accelerometer

Inaccuracies of the LTCC technology and their impact on the chip balun performance

Preliminary model and technology of piezoelectric low temperature co-fired ceramic (ltcc) uniaxial accelerometer

Stability of low ohmic thick-film resistors under pulsed operation