Question Silicon grease on CPU

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Jun 25, 2019
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Okay so, I've seen an old thread saying using silicon grease instead of thermal paste was possible if low tdp. The question is, do I apply as much silicon grease as I would apply thermal paste, or do I put more?

Thanks :)
 

Darkbreeze

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You could use toothpaste, technically, but I would NEVER EVER recommend it, and I would NEVER EVER recommend using silicon grease either. It's a bad idea. Thermal paste is inexpensive. Get thermal paste, don't use silicon grease even if it's insulating dielectric silicon grease, which you don't clarify that it is.
 
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I have used toothpaste+petroleum jelly for about a year. It brought the temps down from the old paste, but after a year the temps went to 90c and the paste was hard and dry.

Replaced it with good past and temps were much better. Just use thermal paste
 
Jun 25, 2019
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You could use toothpaste, technically, but I would NEVER EVER recommend it, and I would NEVER EVER recommend using silicon grease either. It's a bad idea. Thermal paste is inexpensive. Get thermal paste, don't use silicon grease even if it's insulating dielectric silicon grease, which you don't clarify that it is.
Yeah, it is dielectric, but I kinda don't want to wait few days to get thermal paste :/
 

Karadjgne

Titan
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Neither. What you didn't see, because it wasn't in that article, is that you can also use toothpaste, denture cream and multiple other household pastes instead of thermal paste.

The problem is that the paste does nothing in itself. It's inert material, just a medium to hold the silicates, minerals, diamond dust or other microparticulates that actually do transfer the heat. Silicon grease doesn't contain those items, it's designed to resist transferring heat.

Bad move all around.
 
Jun 25, 2019
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So, would it be alright to TEMPORARILY use silicone grease or toothpaste (for few days at most) if I plan on removing it to put actual thermal paste as soon as I can, which will be very soon?
 
I have used it before. It actually maintains decent temps for temporary use. It dries up quickly, so its not ideal for a long time.

 
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AllanGH

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In truth, the original "heatsink compound" that is used in general electronics is largely composed of silicone grease (some people still refer to it as silicone grease or silicone heatsink compound), so you could use clear silicone grease (like the kind used on Maytag washer damper pads) and achieve satisfactory results.
 

Darkbreeze

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"Toothpaste"? I can't believe the SNARK in this thread.
There, I fixed it for you. You'll notice that all of the veteran members have in one way or another recommended NOT using anything other than actual thermal paste, although, and again I don't recommend it, you CAN use some of these other compounds but it's a VERY, VERY bad idea. Mayonnaise for example contains a lot of oils. What do oils do when they heat up? They get excited and flow. Where do they flow? Wherever they can, and that's bad. Other compounds could have similar issues. Use paste, and not the kind for your teeth.

Otherwise you probably WILL be back here with another thread trying to figure out why your hardware is screwed.
 

Darkbreeze

Titan
Moderator
In truth, the original "heatsink compound" that is used in general electronics is largely composed of silicone grease (some people still refer to it as silicone grease or silicone heatsink compound), so you could use clear silicone grease (like the kind used on Maytag washer damper pads) and achieve satisfactory results.
Sure, you could use it, but it's an insulator, not a conductor, so you'll get poor thermal transfer. Sorry Allan, I guess as a very short term use it's ok and probably won't cause any problems, but in reality you'd probably do better simply mounting the heatsink with nothing between it and the heat spreader at all than you would WITH dielectric grease there. And in a pinch, that's probably what I'd do.
 

Darkbreeze

Titan
Moderator
Dielectric refers to something that is essentially an electrical insulator (di = anti). The term is often used to describe the insulators used between the plates of capacitors where a high dielecrtric constant (air = 1) can increase the capacitance of the capacitor for a given weight and volume. But it is also used for many other kinds of elecrtical insulators. Hence, dielectric grease is a grease that is also an electrical insulator. It can be used for a variety of reasons in an electric or electronic device: lubrication, moisture resistance, corrosion resistance, etc.

A heat sync compound is a mixture of substances that have a high THERMAL conductivity. It may or may not be an electric insulator. It is used to fill the gaps between a heat producing device that needs to be cooled and some kind of heat sync to allow the heat to flow into the heat sync more readily.
A dielectric grease may be and often is one of the components of this mixture as it us frequently desirable to have electric insulation between the electronic device and the heat sync to prevent shorts. Many times the heat sync compound is combined with a thin mica or other type of insulator for this purpose.

The MSDS specs on "permatex dialectic grease" says about half way down says
Quote: "Conditions to Avoid: Heat." end quote..
Dielectric grease acts as a lubricant and sealant.
Heatsink Compound has materials added to improve thermal conductivity.

While dielectric grease is often an ingredient in heatsink compound, on its own it is a poor thermal conductor. So particulates are added to increase the thermal conductivity. Zinc oxide, a low cost material, is commonly added to improve thermal conductivity as the grease itself is not very conductive. That's the white stuff seen in older equipment with the dessicated grease. Fancier thermal conductors are boron nitride and aluminum nitride. The best conductor is silver, over twenty times better than ZnO, but that costs more. See below.

Here's a comparison of the additives:

Emerging Generation Of Thermal. Greases Offers Advantages
Greg Becker, Chris Lee, And Zuchen Lin
Advanced Packaging Magazine
June 2005

In general, the higher the filler loading in a thermal grease, the greater the conductivity. Maximum filler loading is dictated by the polymer viscosity and thermodynamic wettability of the filler by the matrix. Filler loading and application pressure are also factors in determining bond line thickness, which is one of the determinants of overall thermal performance.

Particle size plays a key role in determining the BLT, as large filler particles can act as spacers that prevent an extremely thin bond line. Thermal greases made with smaller particles can achieve thinner bonds and lower thermal resistance, as shown in Figure 2.

Code:
Filler name Thermal conductivity (W/mK) Density (g/cm3)
Al2O3 (alumina) 39 3.98
ZnO (zinc oxide) 21 5.60
SiO2 (silicon dioxide) 1 2.65
BeO (beryllium oxide) 218 2.90
Ag (silver) 427 10.49
Al (aluminum) 237 2.56
AlN (aluminum nitride) 170 3.27
 
TIM is not only a silicone or other type of grease, it's just media to hold very. very fine metal, ceramic or other compound micro particles in suspension. Those are the ones that actually conduct heat, not "grease". That's similar to metallic particles in brake pads, same function, providing heat passage to cool better.
 
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