Thermal and Electrical Investigation on LTCC Gas Sensor Substrates

Abstract

Abstract-Metal Oxide (MOx) semiconductor gas sensors typically operate at temperatures of few hundred Celsius degrees and consume hundreds of miliwatts of power. It is therefore, essential, to investigate the heat flux and power consumption in MOx sensors, especially designed for applications in battery-powered devices. The work presents the thermal and electrical investigations on LTCC substrates (Low Temperature Cofired Ceramic) as a base material for gas sensors. A novel shape of substrates with reduced heat capacity is showed. The sensor temperature was modulated with a pulsed heater voltage, therefore decreasing the average power consumption.Index Terms-LTCC, gas sensors, thermal investigation, metal oxide. I. INTRODUCTIONDuring the last several decades, considerable advances in gas sensor technology have been achieved in various applications such as: safety devices [1], environmental monitoring [2], air quality control [3], and health diagnosis [4]. Metal oxide (MOx) semiconductors have become promising gas sensors due to their low cost, short response time, long life and wide range target selectivity [5]. Therefore, numerous researchers presented the investigation results on the following oxides: CuO [6] [12], ZnO [13], etc. Different metal oxide based materials have different reaction activation to the target gases. The chemical and physical processes of working sensors are well known [14], but still sensors behaviours are investigated. However, it is well known that the operating temperature is the most important factor that influences the performance of semiconductor gas sensors. The MOx sensors usually work in o C temperature range [15]. To provide such elevated temperatures a heater is usually embedded into gas sensors substrates. Depending on expected working temperature and substrate built, the consumed power can reach the level of hundreds of miliwatts. The power consumption of gas sensors can be reduced by using a pulsed operation mode, gas sensitive layers working at lower temperatures, changes in substrate design and materials [16]. The search for suitable substrate for Manuscript received December 9, 2014; revised February 13, 2016 Fig. 1 shows the concept of a complete gas sensing device which consists of few elements such as: gas sensitive layer, gas sensor substrate, package, front-end electronics and signal processing. For developed gas sensors the authors used TO-5 package. The electrical connections between sensors pads and case pins were welded with a 0.5 mm thick Pt wire. Fig . 2 shows the gas sensors based on LTCC substrate mounted in TO-5 package. The response of MOx sensors is influenced by various factors, i.e. gas concentration, temperature, gas flow, humidity etc. To provide suitable temperature in a sensitive region, an uniform temperature distribution is required. Therefore, the temperature distribution is a crucial issue that have to be taken into consideration. The temperature distribution in a modified gas sensor substrates was previously reported in [21]. Briefly, it is...

Design, fabrication and characterization of LTCC micro-hotplates for gas-sensing application

“…Also, LTCC meso-hotplates based differential scanning calorimetric system has been demonstrated by Missal et al (2011). Various attempts were reported to reduce the size and power consumption of LTCC micro-heaters for heating and gas-sensing applications (Kita et al , 2000; Rettig and Moos, 2004; Rydosz et al , 2016). Kita et al (2000) has fabricated a micro-heater buried in LTCC structure using laser-cutting technique and illustrated its heating performance (Kita et al , 2000).…”

“…An LTCC micro-hotplate based gas sensor has been designed, simulated and fabricated by Rettig and Moos (2004) and demonstrated for the sensing of propane gas using Cr 2 O 3 layer (Rettig and Moos, 2004). Rydosz et al (2016) investigated the thermal and electrical properties of LTCC-based gas sensors with a novel design (Rydosz et al , 2016). Various sensing layers of metal oxide materials such as ZnO (Maziarz et al , 2012), SnO 2 /In 2 O 3 (Pisarkiewicz et al , 2003), CuO (Rydosz, 2014) and WO 3 (Rydosz et al , 2014) have been used as sensing layer over LTCC substrates for gas-sensor applications.…”

Novel low-temperature sintering ceramic substrate based on indialite/cordierite glass ceramics

“…Recently, low-temperature cofired ceramic (LTCC) materials have combined the advantages of multilayer ceramic and thick film technologies to meet the increasing need for electronics running at extreme operating temperatures and in other harsh environments. [1][2][3][4][5] The low dielectric loss characteristics of the LTCC make it an excellent choice for high-frequency applications and enable circuits and devices that are more efficient. [6][7][8][9][10][11][12][13][14][15] These materials should have low permittivity (ε r < 10), low dielectric loss (tan δ ∼ 10 −3 ), and a low-temperature dependence of resonant frequency (TCf < 20 ppm=°C).…”