Tuesday, April 9, 2019

Thermal mods

This is a response to a question on the Gamers Nexus Patreon.

Delidding
Removes the IHS of a CPU or GPU to enable some of the following modifications.

    Glue removal (die to IHS transfer improved)
        the black glue holding the IHS on the CPU adds distance from the CPU die to the IHS. Removing the sealant eliminates this gap. This improves temperatures as the heat has to travel through less thermal interface material to reach the IHS

    TIM replacements (die to IHS transfer improved)
        The stock thermal paste under a CPU's IHS is design for extra long lifespans not for max thermal performance. Replacing the stock TIM with a more conductive material gives you better temperatures.

    IHS replacements (heat transfer through IHS improved)
        The stock IHS isn't manufactured to any super strict tolerances. Custom IHSs can be made to be flatter and have more contact area to the cooler than the stock IHS and even use more thermally conductive materials(like silver). This improves thermal transfer through the IHS.

    Direct die (die to heatsink transfer)
        With the right configuration it's possible to completely elimitate the IHS. This means that heat now has a much more direct path to the actual cooler.

    Die sanding/lapping (heat transfer through die improved)
        The circuitry actually making up a CPU/GPU is located at the bottom of the die and doesn't penetrate all that deep into it. So reducing the amount of silicon that heat has to go through to leave the die leads to better temperatures. This is very risky and tedious to do.

    Liquid Metal (thermal transfer material)
        Liquid metal alloys tend to come in thermal conductivity around 65W/mK this makes it a far superior to conventional thermal pastes that top out around 10-15W/mK. The down sides are that it's expensive. It destroys aluminum. It diffuses into copper and stains nickle. However in high thermal density applications it significantly out performs normal thermal pastes. High thermal density applications are primarily intel CPU dies. Using liquid metal on 450-700mm^2 300-500W GPU doesn't see anywhere near as much benefit as a 100-500mm^2 intel kabylake die putting out 150-600W. For ambient liquid metal is the end all be all of thermal transfer materials. For sub ambient liquid metal doesn't work as it hardens and loses contact around -20 to 10C depending on the alloy.*

    Indium Solder (thermal transfer material)
        CPUs that don't use a conventional thermal paste under the IHS use a relatively thick layer of indium solder. Indium solder is inferior to liquid metal as it has roughly the same thermal conductivity but is much thicker. It also seems to require the use of thicker silicon dies for reliability. However solder is vastly superior to conventional thermal pastes. Delidding soldered CPUs to run sub zero cooling is ineffective as solder is superior to even direct die thermal paste(for complex reasons). At ambient replacing indium solder with direct die or liquid metal improves thermal transfer to the heatsink/IHS.

    IHS sanding/lapping (IHS to cooler transfer improved)
        If you have a soldered CPU or don't want to buy a custom IHS for your delidded one sanding down your stock IHS is a good way to flatten it out which leads to more direct thermal transfer from the IHS to the cooler.

General Note: If your cooler is incapable of dissipating enough heat cramming heat into it faster is not really gonna achieve anything. (Using liquid metal on an aircooler that already has it's heatpipes completely saturated isn't gonna achieve much)

* Liquid metal on top of a CPU die is as far as I'm concerned a requirement for good cooling even in direct die applications as the there's just not enough contact area on CPU dies for thermal paste to do a good job. Also if you don't mind the negatives of liquid metal, using it on top of an IHS of a high heat output CPU can help shave of a few °C.

2 comments:

  1. upload those twitch live streams to youtube as well ... please

    ReplyDelete
  2. Excellent post.

    One thing I have noticed about certain sites is that, even though they have tons of content, the site looks great and the headlines are eye catching is that the material is simply filler. It’s downright unreadable. You can forget it 6 seconds after you read it. Not the case with your post though, really enjoyed it reading it and it held my attention all the way through! Keep it up.

    Read my Latest Post

    ReplyDelete