Joined: Mon Apr 23rd, 2018
Reputation Points: 242
In radio frequency low power installations, in particular at low frequencies and/or when the connector has very little air gap, completely flooding the connector is perfectly acceptable. Flooding a connector is not acceptable at high power, because most greases will carburize when subjected to an arc. Greases also change the dielectric constant, lowering the dielectric constant in the connector. This may create an impedance bump at very high frequencies, the problem's effect on the system being entirely dependent on the length of the bump in electrical degrees and the amount of the bump. (Not all things that show on a TDR meaningfully alter performance, but they do indicate a potential problem.)
In regular low voltage multiple-pin circuit connectors, such as automotive applications, flooding with a proper insulating grease of low-viscosity dielectric grease is perfectly acceptable unless a manufacturer recommends against it. The grease should have good stability and not contain metals in any form, and be specifically designed for use as a dielectric grease. This generally is a silicone dielectric grease, although some Teflon based greases are acceptable.
In single low-voltage terminals or connections, such as metal-to-metal joints, grounds, or battery posts, almost any pure grease of light viscosity will be acceptable. Caution should be used with greases containing metallic powders to be sure any metal is compatible with the embedded grease metal. Connection enhancement from embedded metal powder is very minor, if it exists at all, and unless you match the grease to the connector material, risk of interaction with base metals might increase.
In single high voltage connections, such as spark plug boots or other high voltage connectors (x-ray, neon sign, or HV power lines), only pure dielectric silicone greases should be used. Generally a light coating or wipe is all that is required. Dielectric grease will actually increase voltage breakdown across insulators, especially in the presence of moisture. Never use or allow a metalized grease around HV connections.
The important physical characteristic is that any grease must have low enough viscosity to push out of the way at contact points, be water or liquid resistant, and be stable enough to remain in place as a protectant against moisture and air for a long time. It will not do any good to apply a grease that does not do required functions of excluding air and moisture, and lubricating the interface to prevent galling or fretting, for extended periods of time.
Contrary to Internet rumors, advertisements, and articles low viscosity silicone dielectric grease will NOT insulate pressure connections. Silicone dielectric grease will prolong connection life as well as, and have just as good conduction performance, as a properly selected metallic powder grease (conductive grease). On the other hand, and improperly selected "conductive" grease can actually cause connection problems.
Buy yourself some. You'll be glad you did. If it melts and oozes out of the connector then look for a higher temp version, usually containing more pure silicone: https://shop.advanceautoparts.com/p/permatex-dielectric-tune-up-grease-33-oz-81150/7010435-p?c3ch=PLA&c3nid=7010435-P&adtype=pla_with_promotion&gclid=EAIaIQobChMI1LWnvPmE3gIVwcDACh3wOQFjEAQYAyABEgJUkPD_BwE&gclsrc=aw.ds&dclid=CPXnt6n7hN4CFVJgAQod3kMOCw
Last edited on Sun Oct 14th, 2018 03:18 am by Bird76Mojo