How to protect electrical connections long term

[kb1gtt]

I'm wondering how to protect an electrical connection long term. I've read the TIN commandments put out by Tyco, and I've recently had an issue on an OEM vehicle where the VR wheel sensor failed after a couple years. So I'm wonder what suggestions people have for ensuring a good long term connection.

I've heard some people claim that they put in a dab of dielectric grease before connecting the plug, I guess the grease prevents scratches in the TIN coating which prevents long term corrosion. However I don't think silicon grease is the way to go, I tend to thing generic grease is better as it''s not an electrical isolator. There is also NOX which I guess it also good.

So what other suggestions do people have? Also why do you suggest it?

[clcorbin]

If the contact can't scrap the dialectric grease out of the way when the connection is made, you have a BAD connector. Look at an assembled and then removed pin from a good contact under a magnifying lamp and see how much "damage" is visible on the male pin just from being assembled and disassembled once. That is why all connectors have a maximum number of connection cycles life.

From my understanding of the point of dialectric grease is three fold (please correct me if I am wrong):

• Reduce the likely hood of arcing from the contacts by providing some insulation
• Seal the contacts from oxygen in the atmosphere
• Seal the contacts from moisture in the atmosphere and other

Using conductive grease is a bad idea as you cannot guarantee that there will not be any traces of the conductive grease going between adjacent pins in the plug (unless it is a single pin plug of course...). I know that on my motorcycle (1979 Yamaha XS1100), when I have had to replace connectors, I have been pretty liberal with the use of dialectric grease on the new contacts when I assemble them.

The other choices are gold pins (corrosion resistant) and sealed connectors to minimize oxygen and water penetration to the pins.

[kb1gtt]

My understanding of dielectric grease is that it will push out of the way, and will minimize the scratches when you make a contact. My understanding is that the TIN plating commonly used on contacts is not very reactive with air, water or water and air. The corrosion you get is from the nickle that is used as part of the plating. The nickle likes to grow crystals, and these crystals are what cause the corrosion. This is assuming you're not using a brass light bulb ferrule in a TIN socket of course, I'm assuming TIN coating on both sides of the connection. From here http://en.wikipedia.org/wiki/Plating#Tin_plating I see

Tin is also widely used in the electronics industry because of its ability to protect the base metal from oxidation thus preserving its solderability. In electronic applications, 3% to 7% lead may be added to improve solderability and to prevent the growth of metallic "whiskers" in compression stressed deposits, which would otherwise cause electrical shorting.

I believe that oxidation is not the issue. I believe the TIN coating tend to create crystals, just like in those TIN whiskers. These crystals need a place to start growing, and if you have less scratches, you'll have less crystal growth.

The grease simply prevents the scratches, which prevents areas where crystals can grow. Dielectric grease is generally a low compression grease so your contacts will generally make contact. However I suspect that it would make the contact resistance increase. This is where I think that normal grease would be better, as it might offer some mild conductivity which would them help decrease the contact resistance. I would also suggest using a low compression grease, not white lithium grease, as the lithium crease is a high compression grease and will probably not push out of the way properly. I think that will make a higher contact resistance. I've heard of folks using NOX, but in reality, I don't have any real references. It's all guess work that takes years of analysis to determine if a connector is going to corrode faster or not. I feel there must be a white paper or something similar out there. Or at least someone else with some years of experience about what seems to work well for them.

[clcorbin]

All in all, I kind of look at it like this: A LOT of people have spent a lot of time developing dielectric grease just for this application. None of us are experts in the field of electrical contact protection, so why should we be second guessing those folks on the correct "stuff" to protect the electrical contacts?

To me, it is kind of like me deciding that moly grease would provide better wear protection to the main bearings on my car, so I swap out the engine oil for it. Not all the facts are known and the result wouldn't be very good...

The whole tin whiskers thing is a problem primarily with lead free solder and small surface mount parts with close contacts. I've never heard of it being an issue with large scale electrical contacts before. Not saying it can't be, but why buy trouble you don't need? And, if you are really worried about tin plated contacts, use gold plated ones. They generally ARE better, but they cost three times as much (depending...).

Clint