Liquid metal thermal paste is the best thermal interface material (TIM) to use for cooling.
Or is it?
It turns out that there may be some pretty big reasons not to use this stuff.
So I’ve gone down a pretty big exploration about liquid metal thermal grease. When to use it, and when to avoid it.
It started with a simple question. My time splintered from there…
Liquid Metal Thermal Paste Ingredients
In short, Liquid metal (LM since I’m going to refer to it a lot) is composed of an alloy mixture called Galinstan.
Okay thanks, Graham…what’s Galinstan?
Galinstan is a mixture (alloy) of three main alloys – Gallium, Indium & Tin.
LM manufacturers will have a different “sauce” to produce what they feel is the best mixture to cool your GPU/CPU. If you ever compare LM between manufacturers, you’ll notice the different viscosities/texture of each.
The main mixture ratios for Galinstan are: 68 wt% Gallium, 22 wt% Indium and 10 wt% Tin (thanks Wikipedia).
This mixture has a wicked low melting point of −19 °C which explains why it’s so easy to spread (and fun to play with).
Coolaboratory Liquid Pro’s mixture, for example, are: gallium, indium, rhodium, silver, zinc and stannous (nobody likes Tin anyways!).
Fun fact, since Gallium is non-toxic – we see it all the time in thermometers (having typed this though, I can’t recall the last time I have actually seen a traditional thermometer).
The biggest reason that we care about all of this is thermal conductivity.
The thermal conductivity, measured in w/mk (the larger, the better conductivity), of each alloy is:
- Gallium – 29 W/(mK)
- Indium – 82 W/(m K)
- Tin – 67 W/(m K)
This explains why LM is so much better than other thermal pastes out there – Gallium is the “worst” of the bunch in the thermal conductivity competition.
Liquid Metal Thermal Paste Risks
Below I will be explaining the 3 main liquid metal thermal paste risks. The first two are the most dangerous, and the 3rd is a longer term issue.
Why Can’t Liquid Metal be used with Aluminum heatsinks?
Danger #1 – Aluminum.
If you’ve considered buying LM before, you will have (hopefully) seen a warning not to mix LM with aluminum heatsinks.
This is because Gallium oozes (diffuses) it’s way through Aluminum’s structure. Once the “oozing” completes, Aluminum will be brittle and easy to break (called Liquid metal embrittlement).
Not something you want to happen to your precious CPU cooler.
Liquid Metal Is Electrically Conductive
Danger #2 – electrically conductive = bad for computer
LM is, wait for it, made of metal. LM will short-circuit your board if it leaks to any of the circuitry.
Either be careful when you apply this stuff carefully (and sparingly) if you’re bold.
As you can see from the picture, use a really small amount and it will go a long ways.
You can also protect the circuitry around it by painting the contacts that may have leaks with clear nail polish.
Use either electrical tape or painters tape and seal all other parts other than the area you will be covering with LM.
Does Liquid Metal Thermal Paste React with Copper?
Possible Danger #3 – Copper and Gallium Still React
Liquid metal (read Gallium) will seep into the copper heatsink. How long this will take depends on the product, and usage mainly.
As I mentioned in the beginning – all LM thermal pastes will have Gallium as their main ingredient.
The good news, Copper will not be destroyed and become brittle like Aluminum.
Gallium will nudge its way into the copper and leave a silverish permanent mark on your heatsink (making copper-gallium alloy). This will cause the LM to appear dried out.
As you can see from the video below, there is a decently thick layer of alloy left on the copper heatsink.
Of course, you can apply additional LM after it dries out, but performance should decrease over time as more alloy is built up and separates the CPU farther from the heatsink (my theory). You want to have the least amount of thermal paste between the heatsinks as possible.
Galinstan is a good thermal conductor, but it’s nowhere close to that of copper.
If you are to apply the LM to a copper heatsink, please make sure to measure your temperatures on a scheduled basis.
Changing your LM every year may be a big enough hassle if you own a laptop – the choice is yours. Certainly, there is no doubt there is performance (and fan speed) improvements with LM.
Lastly, Just because a vendor says its block is made of copper doesn’t mean the metal is pure.
Some alloys look like copper, but react chemically with liquid metal products.
Nickel to the Rescue
I believe a very good place to put LM is between the CPU die and the integrated heat spreader (IHS) – a process called “Delidding”.
First of all, delidding will void any warranty you may have left on your CPU.
The IHS is typically a copper base, covered in Nickel plating.
In short, Nickel is very resistant to the “oozing” effect of Gallium. You may see a little haze, but nothing like that of copper.
Gamers Nexus has an in-depth test of the benefits of adding LM between the CPU die and the IHS.
Liquid Metal vs Thermal Paste
- In most cases, thermal pastes are not electrically conductive – but they still can be electrically capacitive (the ones with metal ingredients). Capacitive is not necessarily a bad thing, it merely means that it may store some electrical energy. Given the other ingredients in the thermal paste, the charge will have nowhere to go.
- Easier to apply – the pastes are more viscous than liquid metal so adding a pea-sized amount to the center of your CPU/GPU is pretty easy.
- Has lesser thermal conductivity (measured in W/mk)
- Compatible with aluminum heatsinks and any application
- Electrically conductive – spilling or the LM bleeding to other parts of your computer will likely cause irreparable short circuits.
- Better thermal conductivity than thermal paste.
- More challenging to apply – patience is required & it is best to protect your application area with electrical tape or clear nail polish
- Destroys aluminum heatsinks.
- Will react with copper heatsinks (to a way lesser degree than aluminum) – so you must check your temperatures over time to make sure your system doesn’t overheat.
I’m all for getting the biggest benefits and coolest temperatures in my builds.
Tom’s Hardware did a huge analysis of 85 thermal compounds and charted them according to their temperature.
In summary of the article, the best LM improved temperatures (depending on the mount) by 1-3°C compared to the best thermal paste.
While there is an improvement with LM in these tests, we’re not talking about a huge temperature difference. In addition, you need to be concerned with all the potential dangers I listed above.
If you’re a serial upgrader (like me) then the copper being affected will not have much of an impact…I’m moving to new CPU coolers/Graphics cards pretty quickly.
If you want to maintain your heatsink/GPU for the long term, you may want to consider using a great thermal paste that is not liquid metal.
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