Microstructure and electrical performance of eco-friendly thick film resistor compositions fired at different firing conditions (original) (raw)
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Journal of Materials Science: Materials in Electronics, 2005
CaRuO 3 perovskite-based lead-free thick-film resistors (TFRs) were prepared on 96%-alumina and Low Temperature Co-fired Ceramic (LTCC) substrates. The microstructure evolution, possible interactions, and electrical properties of resistors were investigated. The hot and cold TCR values of all the resistors were measured in the temperature range (+20 to +120 • C) and (+20 to −120 • C), respectively. TFRs with 25% by vol. of CaRuO 3 on alumina exhibit a sheet resistance R s = 5 k /sq. with hot and cold TCR of 225 and 470 ppm/ • C respectively, whereas the same composition gives 1.2 k /sq., 16.5 k /sq. and 0.7 k /sq. for co-fired, post-fired resistors on LTCC and buried resistors, respectively. The hot (HTCR) and cold (CTCR) values were evaluated; HTCR = 190 ppm/ • C and CTCR = 314 ppm/ • C were found for co-fired structures; HTCR = 216 ppm/ • C and CTCR = 205 ppm/ • C for post-fired samples and HTCR = 520 ppm/ • C and CTCR = 350 ppm/ • C for buried in LTCC structures. C 2005 Springer Science + Business Media, Inc.
Environment friendly perovskite ruthenate based thick film resistors
Materials Letters, 2007
It is well known that the dielectric matrix of air-fireable thick film resistors (TFRs) presently used in hybrid microelectronics and passive components invariably consists of a high-lead silicate glass. However, the current trend in the electronic industry is to restrict and eliminate the hazardous elements viz. lead, cadmium etc. from electronic components. An attempt to develop suitable RuO 2 -based or pyrochlore ruthenate based Pb-Cd free TFRs has been only partially successful till now. We report here the preliminary results of a study aimed to investigate the feasibility of CaRuO 3 perovskite-based lead-free TFRs. Our results showed that sheet resistances higher than 1 kΩ/sq. can be easily achieved in a controlled way, with hot and cold temperature coefficients of resistance (TCR) in the range of 325-580 ppm/°C and 180-500 ppm/°C, respectively. Similarly, the compositions also exhibit negligible piezoresistive effects with gauge factor, GF b 1. Additionally, the resistors do not exhibit negative structural features, like bleeding or devitrification of glass, observed in previous attempts to develop reliable lead-free TFRs.
Journal of Materials Science: Materials in Electronics, 2010
The paper presents investigation of four lead free thick film resistor pastes, developed at ITME, denoted R-100, R-1k, R-10k and R-100k with sheet resistivities of 0.1, 1, 10 and 100 kX/h, respectively. The resistors were based on RuO 2 as the conductive phase. The aim of the work was to evaluate the influence of firing conditions of the resistive pastes on a sintering process. The pastes were screen printed onto alumina substrate with prefired AgPd lead-free terminations. They were fired at several temperatures from 750 to 950°C for 10 min at peak temperature, as well as fired at the highest temperature for 6 h, in order to bring the sintering process into the equilibrium. The properties of the resistors, i.e , sheet resistivity and temperature coefficient of resistance (TCR), microstructure changes, glass crystallization upon firing, etc., were examined. Dried and fired resistor samples were evaluated by X-Ray diffraction analysis and by the scanning electron microscopy. The RuO 2 conductive phase maintained the same crystal structure regardless of the firing conditions. No devitrification was observed in lead-free resistors glasses. The lattice constants of RuO 2 were uniform after firing at temperatures over 800°C. The resistors matched the desired resistivity and the TCR was the least temperature dependent at the firing temperatures around 850°C.
PEROVSKITE RUTHENATE-BASED LEAD-FREE THICK FILM RESISTORS
As well known, the dielectric matrix of air-fireable thick film resistors (TFRs) presently used in hybrid microelectronics and passive components invariably consists in a high-lead silicate glass. However the actual trend is to restrict and possibly eliminate Pb from electronic components. Attempts to develop suiTab.RuO2-based or pyrochlore ruthenate-based Pb-Cd free TFRs has been only partially successful till now. We report here the preliminary results of a study aimed to investigate the feasibility of CaRuO3 perovskite-based lead-free TFRs. The results show that sheet resistances larger than 1 KΩ/sq. can be easily achieved in a controlled way, with hot temperature coefficients of resistance in the range of a few hundreds ppm/oC. In addition, the resistors do not exhibit negative structural features, like bleeding or devitrification, observed in previous attempts to develop reliable lead-free TFRs. Keywords: thick film resistors, hybrid microelectronics, perovskite ruthenate-based
Electrical properties of conductive materials used in thick-film resistors
Journal of Materials Science, 1988
Layers of conductive oxide powders (IrO2, RuO2 and Bi2RuzO7) were prepared on alumina substrates by a thick-film technique. The films were fired at 875~ for different dwell times. The temperature dependence of resistance was measured in the range-1 96 to 850 ~ SEM observations of the initial powders and the resistive layer surface after firing, as well as X-ray diffraction investigations, were carried out. The RuO2 and IrO2 oxides exhibit a high sintering ratio and the resistance of the fired layers increases with temperature as in the single crystal. The R(T) curve for Bi2Ru207 layers is in qualitative agreement with the polycrystalline material. The role of the grain surface area and the regions between the grains is dominant.
Synthesis and characterization of CaRuO3 and SrRuO3 for resistor paste application
Journal of Materials Science: Materials in Electronics, 2005
Resistors are used in Hybrid Micro Circuits (HMC) are essentially cermet composites consisting of an intimate mixture of an insulating phase (the glass binder or glass frit) and suitable conducting phase, the relative proportions of which to a greater degree, determine the nominal resistivity of the resultant resistor paste. In this paper, we report resistor pastes formulated by using ruthenium based perovskites of Ca and Sr. Though the ruthenates of alkaline earth elements (Ca and Sr) have high metallic conductivity (28-300 µ cm) and have been extensively used in superconducting and ferroelectric systems, their usage in thick film resistor pastes has rarely been reported. Ca and Sr ruthenates were prepared by air-heating the physical admixtures of respective carbonates of Ca/Sr and RuO 2 at three different temperatures, viz., 500, 800 and 900 • C. In each case, heating was carried out for 15 h. The resultant powders were characterized by TGA/DTA, SEM-EDX and XRD techniques. The solid-state reactions were found to occur between 700-800 • C. But the powder, thus obtained, contained certain amount of carbonate and hence the powders were heated again at 900 • C for 15 h to eliminate detrimental effect of carbonate in resistor paste. The microstructural studies of powders revealed that the average particle size is around 200-400 nm. The resistor paste was formulated by using powder admixtures heated at two different temperatures, viz., 800 and 900 • C. In this paper, we are presenting the preliminary account on synthesis and physico-chemcial, electrical and microstructural properties of powders and fired TFRs.
2009 32nd International Spring Seminar on Electronics Technology, 2009
The series of lead-free thick film resistors were elaborated by Institute of Electronic Materials Technology (ITME) in Warsaw. The paper presents investigations oftwo pastes: R-100 with resistivity 100 Q/a and R-l OOk with resistivity 100 kQ/a. The pastes were screen printed on alumina substrate with AgPd lead-free terminations. Then fired at several temperatures in the range 750-950°C for 10 minutes and 6 hours at highest temperature. Sheet resistivity and thermal coefficient of resistance (TCR) were measured. X-Ray diffractogramms were taken. The conductive phase that was RuG 2 maintained initial crystal structure regardless firing conditions. No devitrification was observed in lead-free resistors glasses. The lattice constants ofRuG 2 were uniform at temperatures over 800°C. The resistors matched the desired resistivity and the TCR was least temperature dependent at the firing temperatures around 850°C.
Lead-free ruthenium-based thick-film resistors: a study of model systems
Journal of Materials Science: Materials in Electronics, 1991
A model system of thick-film resistor (TFR) was prepared starting from RuOa powders and a lead-free glass. The microstructural development was investigated by scanning and transmission electron microscopies, energy dispersive X-ray fluorescence, X-ray diffraction, thermogravimetry and other complementary techniques. The electrical properties of the resistors were analysed with particular attention to sheet resistance, temperature coefficient of resistance, size effects and piezoresistive properties. It was found that these simple systems are interesting with respect to their stability in ageing tests at relatively high temperatures but they are not promising for high-temperature piezoresistive gauges because of low strain sensitivity. Some samples were also prepared with a Bi2Ru2Ov; a notable exchange reaction occurs between the conductive grains and the glass matrix which prevents the formation of pyrochlore-type based resistors with this glassy matrix.