Author Topic: Dielectric grease on 100 kHz I2C tin connectors?  (Read 202 times)

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Offline SlowBro

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Dielectric grease on 100 kHz I2C tin connectors?
« on: October 21, 2019, 02:09:10 pm »
I am building an outdoor device which has one of these DS3231 I2C RTCs. It has tin connectors and will mate to a tin male pin header. Frequency is 100 kHz, voltage is 3.3V, and current is as low as 110uA.

Would the connection be reliable if I used dielectric grease such as this on the connectors? I would think that even though it is a dielectric, the grease would wipe off between the connection points and so it should be safe. I read about this all the time with automotive electronics but I2C is lower wattage, and higher frequency.
« Last Edit: October 21, 2019, 02:32:28 pm by SlowBro »
 

Offline schmitt trigger

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Re: Dielectric grease on 100 kHz I2C tin connectors?
« Reply #1 on: October 21, 2019, 02:19:15 pm »
I have seen it on board connectors which carry CANBUS signals, which are definitively faster than I2C.

But on the other hand, the 120 ohm termination resistor is far stronger than the 10k typical I2C pullup.
 
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Online MagicSmoker

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Re: Dielectric grease on 100 kHz I2C tin connectors?
« Reply #2 on: October 21, 2019, 03:20:37 pm »
...I would think that even though it is a dielectric, the grease would wipe off between the connection points and so it should be safe. ...

When dielectric grease is used correctly then it should either squeeze out or be wiped away from the actual contacting surfaces. So, any sliding contact is a good place to use it, and the barrel of a crimped terminal is okay, too, but not on the flat face of a ring terminal unless you can absolutely guarantee sufficient clamping force will be developed (hint: you usually can't).

 
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Offline SlowBro

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Re: Dielectric grease on 100 kHz I2C tin connectors?
« Reply #3 on: October 21, 2019, 03:23:46 pm »
These are 2.54mm plastic headers, so they wipe.
 

Offline StuartA

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Re: Dielectric grease on 100 kHz I2C tin connectors?
« Reply #4 on: October 22, 2019, 01:39:38 am »
I've never seen a silicone product described as a "dielectric grease" before. Silicone greases have a reputation for creeping, that is, migrating along surfaces. I've always been under the impression that silicones and electrical interfaces don't go together at all. A colleague of mine used to work for a company which banned the used of silicone furniture polish in their admin building for fears that it might somehow get transferred in to the assembly area.

Talking to grease manufacturers about electrical contacts, the response which comes back most often is to use lithium-based grease.
 


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