Lubricants for Separable Connectors

About two dozen lubricating fluids were tested for use on electrical contacts on card edge or pin-and-socket connectors. The lubricants selected for screening represented a cross section of thewide variety of natural and synthetic materials available on the market. Among them were polyphenyl ethers, natural and synthetic hydrocarbons, several types of esters, polygiycols, some fluorinated materials, a few silicones, and some proprietary formulations. Lubricants were evaluated on the basis of volatility and their ability to prevent fretting corrosion on tin-to-solder contacts. Limited tests were also done on their spreading characteristics, their thermal degradation properties, and their effect on contact resistance. The objective of the work was to develop guidelines in the selection of contact lubricants for field testing. The lubricants were ranked on the basis of weight loss from thin deposits of the samples on solder foil coupons at 65°C. Fretting experiments were done by forcibly moving a printed circuit card finger between a pair of spring contacts cut from actual cards and connectors. The time required for contact resistance to increase from a few milliohms to 2 was determined as a function of the amount of lubricant present.