Liquid metal thermal paste is the best thermal interface material (TIM) to use for cooling.Or is it?
It turns out there may be some pretty big reasons not to use this stuff. So we've explored all there is to know about liquid metal thermal grease. When to use it, and when to avoid it, etc..
It started with a simple question, and time splintered from there.
Liquid Metal Thermal Paste Ingredients
In short, Liquid Metal or LM, is composed of an alloy mixture called Galinstan. Okay thanks… now what’s Galinstan?
Galinstan is a mixture (alloy) of three main alloys – Gallium, Indium, & Tin. LM manufacturers 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 (though when was the last time you actually saw a traditional thermometer?).
The biggest reason 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 we will explain the three main liquid metal thermal paste risks. The first two are the most dangerous, and the third 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).
Here is a great video below on gallium vs. aluminum.
This is 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. Be careful when you apply this stuff carefully (and sparingly) if you’re bold.
As you can see from the picture, a really small amount will go a long way. You can also protect the circuitry around it by painting contacts that may have leaks with clear nail polish.
Use either electrical tape or painter's 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 mentioned in the beginning – all LM thermal pastes will have Gallium as their main ingredient. The good news is 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. 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.
The video below shows dried LM after only one year.
If you 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
A very good place to put the LM is between the CPU die and the integrated heat spreader (IHS) – a process called “Delidding”.
There are concerns with this, though. 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 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 bleeding the LM 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.
We always recommend getting the biggest benefits and coolest temperatures in your 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 listed above.
If you’re a serial upgrader, then the copper affected will not have much of an impact…since you'll be moving to new CPU cooler/graphics card 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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