Silicone thermal pad + silicone thermal paste = disintegration?

[Sorachan]

Hi,

 

I just modded a router and posted my progress at another forum: https://www.snbforums.com/threads/ac86u-heatsink-mod.71922/

 

During the process I applied silicone thermal paste on top of the silicone thermal pad just in case the factory pads are not high enought for good conductivity.

 

 

However, someone commented that the paste will cause the pad to disintegrate (melt, collapse, tear). I don't really know how this is possible, how can the same element react to each other?

 

Just wondering anyone experienced disintegration here. Thanks!

[Fasauceome]

Paste not pure silicone, it's suspended in a mixture that makes it liquid. The mixture can react with the pad and also make that liquid.

 

Although the effects can be quite negligible, I recommend replacing the thermal pads with proper replacements either way, instead of pasting over them.

[Sorachan]

17 minutes ago, Fasauceome said:

Paste not pure silicone, it's suspended in a mixture that makes it liquid. The mixture can react with the pad and also make that liquid.

 

Although the effects can be quite negligible. I recommend replacing the thermal pads with proper replacements either way, instead of pasting over them.

From what I understand, thermal paste is a mixture of silicone and polymer compound. As far as I understand both silicone and polymer compound should be really stable, very hard to react chemically. Considering the pad is also silicone, I don't understand how they can react.

 

If possible, I would prefer some concrete evidences rather than speculations, either personal experiences or product chemical composition would be really appreciated.

 

BTW, I'm very certain the liquid (leeched silicone) from thermal pad will be there with or without silicone paste, but it's non-conductive, not really an issue.

[Fasauceome]

11 minutes ago, Sorachan said:

If possible, I would prefer some concrete evidences rather than speculations, either personal experiences or product chemical composition would be really appreciated.

Some thermal pastes have acrylates in them, acrylates are used to dissolve silicone if I recall (though this might only apply to some acrylates and some silicone mixtures)

 

Haven't seen anyone use both thermal paste and a pad at the same time before so there aren't really any examples of this exact thing.

12 minutes ago, Sorachan said:

BTW, I'm very certain the liquid (leeched silicone) from thermal pad will be there with or without silicone paste, but it's non-conductive, not really an issue

Conductivity isn't really something you have to worry about with non-metal pastes

[Sorachan]

1 minute ago, Fasauceome said:

Some thermal pastes have acrylates in them, acrylates are used to dissolve silicone if I recall (though this might only apply to some acrylates and some silicone mixtures)

 

Haven't seen anyone use both thermal paste and a pad at the same time before so there aren't really any examples of this exact thing.

Thanks for the reply. Acrylate polymer should be really stable too, I don't think it can react with silicone unless under really high temperature. Actually, if you think about it, if it can disolve silicone, why the manufacture mix it with silicone?

 

Well, I don't really want to disassemble the router to clean the thermal paste at the moment unless it's proven to disintegrate. I tested thermal conductivity before assemble the router, at the moement it transfers heat well.

 

If nobody tried paste+pad before, guess I will report back after a year if I still remember this issue...

[Fasauceome]

1 minute ago, Sorachan said:

I don't think it can react with silicone unless under really high temperature.

The bummer there is that the pads are purpose built to transfer heat

 

2 minutes ago, Sorachan said:

If nobody tried paste+pad before, guess I will report back after a year if I still remember this issue.

Valuable data

[Sorachan]

42 minutes ago, Fasauceome said:

The bummer there is that the pads are purpose built to transfer heat

The heat it transfer is not anywhere near its melting point, not even near an ordinary CPU...

 

I'm looking at Dow material brochure for silicone thermally conductive materials. I'm reasonably confident it won't react with thermal pad. These products should be very chemically stable, noncorrosive, some even have UL94 rating (flame retardant)...