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The paper aims to focus on thick film planar thermistors.

Thick film planar thermistors such as rectangular, sandwich, multilayer, segmented and interdigitated were printed of law temperature NTC paste called NTC 3K3 95/2 (Ei Iritel). Their resistivity was measured at room temperature as a function of volume resistivity variations due to electrode effect (diffusion of PdAg into NTC layer) and variation of geometrical parameters such as length l, width w, thickness d, number of segments n. The experimental data obtained were used in forming a model by the simple fitting procedure for counting diffusion effect on volume resistivity and resistivity dependence on geometrical parameters.

Thermal behavior of NTC thick films was measured in the range of −30‐120°C. Exponential factor B was fitted for measured values and included in the proposed thick film thermistors model. The agreement of measured and calculated data enables simulation of new thermistor geometries.

The paper focuses on the experiment which was the first step in forming a total physical/mathematical model proposed for thick film thermistor resistivity.

The purpose of this paper is to apply negative thermal coefficient (NTC) thick film segmented thermistors (TFSTs) in a micro‐flow sensor for water.

A TFST is printed using NTC paste based on nickel manganite. The resistance of this thermistor is measured in a climatic chamber and the resulting curves are calibrated. A micro‐flow sensor is designed using a self‐heated segmented thermistor. The sensing principle is based on heat loss depending on the water flow intensity through the capillary. Water flow calibration is performed. The sensor sensitivity, inertia, and stability are analyzed.

The micro‐flow sensor exhibits good stability, suitable sensitivity, and inertia for integral measurements of water flow.

Advantages of a micro‐flow sensor using a TFST include low energy consumption, simple measuring procedure, and passive electronics.

This paper describes initial work on a micro‐flow sensor for water using TFSTs.

Ni‐ferrite powder average grain size less than 0.9µm was used for the ferrite paste preparation. Ferrite paste was printed on Al2O3 substrate and fired 850°C/10min. After Ni‐ferrite thick film characterization had been done, simple planar inductor geometry, such as square spirals, were printed on it. Measurements were done, using an HP 4194A impedance analyser. The experimental results were summarized and compared with theoretical predictions given by the electromagnetic analysis using the method of current images for the reason of accounting the effect of magnetic substrate. The computer program, developed here, allows determination of the required thickness of the substrate which will produce inductance enhancement of the given permeability of the substrate material. The same results can also be used to determine the permeability of magnetic film or substrate quickly and are directly applicable to the design of the planar inductors.

The thermal diffusivity of thick film NTC layers based on a metal oxide powder mixture was measured at room temperature by the photoacoustic (PA) technique. The powder mixture was composed of MnO (60 percent), CoO (32 percent) and Fe₂O₃ (8 percent), which were ball milled to nanometer particle size. NTC layers of different thicknesses were made by sequentional screen‐printing followed by drying and co‐firing at 850, 900 and 1,000°C in a hybrid conveyor furnace. The experimental PA phase and amplitude diagrams were numerically analyzed and the thermal diffusivity and electron transport parameters were calculated. An increase of thermal diffusivity with sintering temperature was observed. The fractal structure model was in agreement with the experimental data for modulation frequencies in which the sample behaved as thermally thick.

Thick film symmetrical LC cells with two pairs of terminations were printed on alumina using PdAg paste and crossover dielectric. Planar inductors such as meander, spiral, bispiral, and solenoid in plane were distributed over planar capacitors such as sandwich, interdigitated and segmented. Attenu‐ation and Smith charts of symmetrical EMI LC cells were measured on network analyzer in the range of 1 MHz to 3 GHz. Two or three main LC cells were joined in series to sum attenuation. The obtained results were compared mutually, at first, and than with the cubic (chip) EMI LC filters. The obtained EMI noise suppression was similar, but the filter band of thick film LC cells was much wider.

A variety of thick film planar inductors, designed for applications in the HF range, were printed from conductive PdAg and NiFe₂O₄ ferrite paste on alumina substrate. Pure ferrite powder with a nanometric particle size was used in the NiFe₂O₄ paste preparation. The ferrite thick film layer characterisation was performed on small spirals, after which the following inductor planar geometries were tested together with ferrite layers: meanders, spirals, bispirals and solenoid in plane. Their impedance was analysed with an impedance analyser in the MHz‐GHz range. The results obtained were compared with the properties of the smallest cubic inductors and with the literature data for planar inductors (theoretical and practical). A comparison was made of the L geometries printed. It was observed that better utilisation of the thick ferrite layers was achieved on L geometries with equally distributed windings over the thick ferrite layers.

Various thick film varistor constructions were made and characterised: ‘sandwich’, ‘interdigitated’ and ‘segmented’ varistors. The varistor active layer thickness, the electrode surface value and shape were varied. The Ul characteristics of these varistors were compared mutually, and with the Ul characteristics of the smallest chip varistors. In accordance with the results obtained, it has been shown that thick film printed varistors composed of ZnO and with additives could be applied as discrete components or integrated into a hybrid circuit.

A new model for thick film resistor calculation accounts for the physical effects which make variations in local sheet resistivity and local volume resistivity: geometry and terminal diffusion effects. Taking the criterion of homogeneity in the observations of local resistivity, a resistor is transformed geometrically and electrically into equivalent modular parts. Comparing the resistor transformed by equivalent geometrical and electrical transformation (EGET) with an ideal resistor a new semi‐empirical formula for thick film resistor calculation was evaluated. This model takes into account the technological process which makes possible more accurate resistor projection compared with other models.

A two‐dimensional model for hybrid circuits is presented in this paper. Simulation results of a hybrid power module for different power dissipation of components and ambient temperature are given. The experimental contribution is based on thermal measurements of the realized hybrid power module using a matrix of flip‐chip sensors. Thermal measurements were taken at different ambient temperatures and different hybrid module power values. The temperature distributions obtained theoretically and experimentally are compared and analyzed. Finally, the contribution of the temperature distributions and measured temperatures to the reliability of the hybrid power module is given.