INFLUENCE OF ENCAPSULATING RESINS ON THE STABILITY OF THICK-FILM RESISTORS.

The present study concerns epoxy, phenolic and silicone resins from different suppliers. Epoxy resins seem to be inconvenient for this application due to the presence of amine groups in the catalyzer interacting with metal-oxide content in the resistor or due to mechanical effects during the thermal cycling of the devices. Even though phenolic resins are very convenient from an economical point of view and provide a satisfactory mechanical protection, they are unable to guarantee a barrier to humidity. Silicon resins have shown the best compatibility with thick-film resistors and seem to provide the best protection. As for the resistor materials compositions of palladium-oxide-silver, ruthenium and iridium have been evaluated with the different resins. The long-term better stability seems to be guaranteed by Ru-based compositions.