Contact Resistance Characteristics of Relays Operated in Silicone-Vapor-Containing and Non-Silicone Atmospheres with Different Electrical Load Conditions

Abstract

Influences of vapors evaporated from an acryl-based non-silicone-type polymeric cured material and conventional silicone-containing polymeric cured materials were evaluated with respect to their effects on contact resistance characteristics of relay contacts at an ambient temperature of 120ºC. More specifically, a commercially-available mechanical relay (AgSnIn contacts) was sealed into a metal can with one of these materials, and placed in a heating chamber to operate, at an operating frequency of 0.5 Hz, 40,000 break operations of an inductive DC 14V-1A, 14V-0.4A, 10V-1A, 5V-1A load currents, or a resistive DC 14V-1A load current. Contact resistance values were measured at every 50 operations. As a result, the relays sealed with the acryl-based non-silicone-type polymeric cured material showed no deterioration in contact resistances, irrespective of the load conditions. On the other hand, the relays sealed with the silicone-containing polymeric cured materials showed more significant deteriorations and fluctuations of the contact resistance characteristics, and certain influences of load conditions on their behaviors were recognized.

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“…Vapours emitted from those silicon containing materials can form insulating films, which deposit on the contact surface [76], [77]. During switching, due to electrical arcing, silicon breaks down to silica (silicon-dioxide), compromising contact performance, significantly increasing CR towards the EMR-EOL [78]. Further effects of particles stemming from contaminated environments and the effects of fritting -a sudden breakdown of the CR in the presence of contaminating films are discussed in [1], [79] as well as Appendix B.…”

“…However, as the initial CR is already very small, the increase till failure is typically within the m -range. This poses a challenge for accurately measuring changes in CR, which can be achieved reliably only with a 4-Wire or Kelvin-Wire setup [78]. Therefore, presupposing accurate CR measurements in embedded online health management is FIGURE 4.…”

“…Otherwise, the oxide layer is replaced by silver carbonate layers. Its further worth mentioning, that fluctuations of CR can also be caused by silicon-vapours dissolved from e.g., the EMR enclosure [78].…”