Electrical Conduction by Percolation in Thick Film Resistors

Abstract

Thick film resistors are widely used in microelectronic devices, however the mechanism of electrical conduction in these resistors has not yet been fully understood. In particular the anomalous behaviour of the temperature coefficient of resistance (T.C.R.) vs. temperature for a purely ohmic resistor has not been explained. The anomaly is that the T.C.R. is negative at low temperatures, is zero around room temperature and becomes positive at higher temperatures. This paper demonstrates that the electrical conduction mechanism in thick film resistors can be described by the electron percolation theory already proposed to explain charge transport in amorphous semiconductors. The thick film structure consists of conductive grains with a diameter of 0.1 m to 0.3 m separated by dielectric layers.

Influence of the metal migration from screen-and-fired terminations on the electrical characteristics of thick-film resistors

“…Moreover, it is demonstrated that the resulting picture fits the framework of a recently proposed model 3 6 even though only unconvincing explanations were proposed up to now. Figure 2 shows how the experimental measurements satisfactorily fit the proposed equation in a wide temperature range.…”

Fabrication and study of the electrical properties of PbO/Fe based composite resistors

“…This is because firing temperature helps in healing some of the crystal defects formed during the high pressure pressing process in the moulder and also firing the resistor helps in burning -out any resin type materials left in the resistor itself (Forlani and Prudenziati, 1998). Fig.…”

“…These cermets films like any other thin film resistors (TFRs) are not homogeneous but consist of small particles of Cromium in the matrix of SiO 2 ( Forlani and Prudenziati, 1976). Cermets structured resistors, like TFRs based on Bi 2 Ru 2 O 7 , exhibit a high stability and very low Temperature Coefficient of Resistance (TCR) (Avadhanu andKshirsagar, 2007, Forlani andPrudenziati, 1998). Screen printing and firing onto a substrate is a method used for producing (TFRS).…”

Some observations on the accelerated ageing of thick-film resistors

“…Hill and Forlani and Prudenziati 2 have shown that electrical conduction in thick-film resistors can be explained using the concepts of electron percolation and hopping between conductive sites, and a model has been proposed for the temperature dependence of resistivity (p(T)), 3 ---exp (1) in which 3 is a constant and To is the activation temperature. Both are dependent on the density (N) of conductive sites and the decay constant (a) for the electron wavefunction in the resistor glaze.…”