Material Characterization of Thick Film Resistor Pastes

The study of material characterization of DuPont 1400 BIROXr thick-film resistor pastes is described. An understanding of the aging mechanisms of thick-film resistors requires a precise knowledge of their chemical composition and material characteristics. This information provides the technical basis for the Arrhenius-type time-temperature extrapolations of accelerated aging data on the resistors in question. We have used X-ray diffraction and fluorescence to obtain a qualitative picture of the DuPont 1400 BIROX pastes. Results indicate that these pastes consist principally of a conductive oxide and glass phases after firing. The conductive oxide phase is a pyrochlore M2Ru207_x (M= Pb and/or Bi), and tile glass phase is a lead borosilicate glass frit. Small amounts of Cd, probably added as a TCR modifier, were also detected. It has also been determined that the proportion of glass phase increases as the sheet resistivity increases. On firing, some chemical reactions were observed, and an increase in the crystallite size of the conductive phase was confirmed. In addition, the chemical composition of the end members (10 and 106 /s) was found to be different from the general composition of the 1400 BIROX series. The conduction mechanism in thick-film resistors is discussed in some detail. The role of additives and the doped glass phase is emphasized. An extensive review of technical, patent, and product literature has been made as a background for the study.