Back in January 2022, I purchased a 400g tub of K5-Pro to try out on my Gigabyte AORUS RTX 3090 XTREME, you can read the article here.
In short, I would not recommend K5-Pro, GDDR6X junction temperatures were worse than the stock thermal pads, around 30c hotter than the Gelid GP-EXTREME pads and K5-Pro is an absolute nightmare to clean up, it might be okay if used to cool a small IC on a graphics card or PCH on a motherboard, but for anything else, I would steer clear of this product.
Anyhow, after discovering how badly K5-Pro performed, I wanted to remove this stuff as quickly as possible, so I took the card apart and began using a toothbrush and 99.9% isopropyl alcohol — to my surprise, this wasn't that good at removing K5-Pro, it would break the paste down a bit, but it also made the paste stickier and harder to remove from the PCB.
I then began to use water, in conjunction with K5-Pro, in retrospect this was a terrible idea, but at the time it was working and I got the PCB looking decent, take a look.
We went from this...
To this...
Much better, but there was still a lot of K5-Pro around and underneath the GPU die, GDDR6X, Mosfets and other components, this wouldn't normally be a problem, but because I had used water in conjunction with 99.9% IPA, it had meant that some water was trapped underneath these components and wasn't easily removed by the 99.9% IPA bath or leaving the card to dry for a day, this resulted in the card not POSTing and me thinking I had killed an RTX 3090.
Fortunately the card did not die, I left the PCB outside for around 2 weeks and would rotate it in different angles every few days to allow any trapped liquid under the components to escape; here's an illustration of what I mean
Even though I had removed the majority of the K5-Pro and the card was now working, I wasn't happy with how the PCB looked, as there was noticeable amounts of K5-Pro on, underneath and around the GPU die, GDDR6X, Mosfets and other ICs
It was at this point I wanted to completely remove this garbage from the PCB, I had originally planned on using 99.9% IPA again and to use an ultrasonic cleaner, however after searching online and shortly after my first experiment, the company that makes K5-Pro (ComputerSystemsGR), made a video on YouTube, where they advise using white spirit, or paint thinner as it is more commonly known, to properly remove K5-Pro.
This surprised me, but in discussion with daniel_andrei1996 from the Tech Cemetery Discord Server, we agreed it's probably the best shot.
So began my journey on restoring this PCB to it's former glory. I purchased the following
15 litres of 99.9% IPA (you could do this with 10 litres, I just wanted spare)
4 litres of low odour white spirit (in retrospect I would have gotten 8-12 litres)
6 litre ultrasonic cleaner (in retrospect I would have gone with a 10 litre or 15 litre unit for a PCB this big)
You will also want some ESD safe brushes and/or a toothbrush, a plastic box/Tupperware container that is big enough to house the PCB you are cleaning and I would strongly recommend getting some plastic gloves and a respirator, as both of these chemicals are very hard on the skin and you don't want to be breathing either of them in. I would also strongly recommend doing this outside if possible.
Below is the process of what I did, in total this took me around 3~ hours, as I wanted to be thorough. Unfortunately I also didn't take pictures of each step.
Step 1) Disassemble the card to the bare PCB, remove any thermal paste as best as you can, remove the IO bracket, any RGB lights and disassemble the card to the bare PCB as best as you can
Step 2) Place the PCB into the plastic box/Tupperware container and apply enough white spirit so that you can gently swish it around to irrigate and begin dissolving the K5-Pro, you don't need a lot, just enough to cover the PCB so you can swish it around. During this stage you can also use the ESD brushes or a toothbrush to help remove the K5-Pro between the SMDs.
You will want to repeat this on both sides of the PCB, eventually you will notice the white spirit will go from a clear colour to a murky white or grey (depending on the paste/amount of K5 Pro), when this happens, empty the tub and use fresh white spirit, repeat as needed until you are satisfied with the result and once done, remove the PCB from the tub and thoroughly clean the tub to remove any residue of the white spirit.
Step 3) Fill the ultrasonic cleaner with white spirit and turn it on for a few minutes with the PCB inside, when I did this, I could see the K5-Pro being forced out from under the memory modules and other components. You will want to flip the PCB to cover all angles, I did roughly 1-3 minutes per side and I had to use many different angles having only a 6 litre ultrasonic cleaner, if you had a 10-15 litre cleaner, this process would be much simpler.
Remove the PCB from the ultrasonic cleaner once done, drain the ultrasonic cleaner and thoroughly clean the inside of the ultrasonic cleaner using paper towels, a microfiber cloth and water.
Step 4) Take the plastic box/Tupperware container from earlier (ensure it is cleaned of any white spirit) and with the PCB inside it, pour enough 99.9% IPA in to cover the PCB and swish it around, this will displace any white spirit and you will see the white spirit residue rise to the top, it will look like an oil spill in water - repeat as necessary with fresh IPA until this is no longer the case.
Step 5) Take the previously cleaned ultrasonic cleaner, place the PCB inside and fill with 99.9% IPA and repeat step 3 but with 99.9% IPA instead of white spirit. We do this to ensure any white spirit under the GPU die, GDDR6X, Mosfets or other component is removed, as the IPA bath in step 4 might not have gotten everything.
Once this is done, you can turn the ultrasonic cleaner off, drain it, clean everything up and you will want to leave the card to dry for at least 24 hours, preferably near a dehumidifier or on-top of something warm. Alternatively you could use a hair dryer or hot air gun.
Here are some images of the the PCB after this was completed
As you can see, the PCB is now looking much better, I don't have any pictures of it, but you can see the solder balls underneath the GPU die and GDDR6X modules, previously much of this was hidden as it was covered up by the K5-Pro.
I'm happy to report that the card has since been re-assembled (after cleaning the heatsink w/fans removed and backplate with the same method) and has since been torture tested with Furmark and undergone a good 10 hours of gaming without any issues.
In retrospect, I would have never bothered with K5-Pro and would advise everyone to stay away from it, however if you are foolish enough to try it and want to restore your PCB, you will need white spirit, 99.9% IPA, some ESD brushes/toothbrush and an ultrasonic cleaner.
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