Abstract
PurposeThe purpose of this paper is to present the properties of thick-film resistors made of novel pastes prepared from glass and graphite.Design/methodology/approachGraphite-based resistors were made of thick-film pastes with different graphite-to-glass mass fraction were prepared and examined. Sheet resistance, temperature coefficient of resistance, impact of humidity and short-term overload were investigated. The properties of the layers fired in atmospheres of air at 550°C and nitrogen at 875°C were compared.FindingsGraphite-based resistors with various graphite-to-glass ratios made possible to obtain a wide range of sheet resistance from single O/square to few kO/square. These values were dependent on firing atmosphere, paste composition and the number of screen-printed layers. The samples made of paste with 1:1 graphite-to-glass ratio exhibited the temperature coefficient of resistance of about −1,000 ppm/°C, almost independently on the firing atmosphere and presence of a top coating. The resistors fired in the air after coating with overglaze, exhibited significantly lower sheet resistance, reduced impact of humidity and improved power capabilities.Originality/valueIn this paper, graphite-based resistors for applications in typical high-temperature cermet thick-film circuits were presented, whereas typical graphite-based resistors were fabricated in polymer thick-film technology. Owing to very low cost of the graphite, the material is suitable for low-power passive circuits, where components are not subjected into high temperature, above the typical temperature of operation of standard electronic components.
Highlights
Carbon-based composite materials with proper fillers could exhibit temperature of operation up to 700°C
Various carbon-based composites were reported to work as transparent conductors (Watcharotone et al, 2007), resistive layers (Dziedzic, 1997, 2005; Rao, 2007; Mleczko et al, 2017) or as an active part in sensors for detection of chromium (Hallam et al, 2010), proteins (GomezMingot et al, 2011) or heavy metals (Aragay, Pons and Merkoi, 2011)
Sheet resistance RSQ was determined from equation (1), where R is the resistance of the resistor, and n is the aspect ratio of the resistor (n = l/w): RSQ 1⁄4
Summary
Carbon-based composite materials with proper fillers could exhibit temperature of operation up to 700°C. They are useful in electronics, where harsh conditions are present, e.g. during an electrical discharge or an electron emission. In the literature, it is not clearly defined what are the electrical properties of the graphite and graphene layers/ paths. Marinho et al (2012) used the same technology to prepare the layers from graphene, graphite and carbon black. It shows that the conductivity of the graphene layer is one order of magnitude higher than graphite and on only twice higher than carbon black. The glass filler can reduce the conductivity, but at the same time, it can increase layer reliability, especially at high
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