Special Case: Thermal Pads & Backplate Cooling
Thermal Pads: A Miracle Or An Illusion?
Let's make it clear that pads are not a suitable alternative to thermal paste between a CPU/GPU and heat sink. They should only be used to cool components like VRMs, chokes, or memory modules, which typically are farther away from the cooling surface.
In the picture below, we see the cheap tape often used to cover voltage regulators. It's not made from a homogeneous material, which would have surely been expensive to manufacture, but rather a foamed mass that is compressed in relevant parts thanks to pressure applied by the assembled card.
Unfortunately, air is one of the worst mediums for transporting heat due to its terrible thermal conductivity. Thus, if compact thermal pads of sufficient thickness and quality are available, we highly recommend using them instead of the stock foam.
Thermal pads (or tapes) are readily available for little money in a variety of thicknesses (and colors). The depression marks on the original tape provide some help on how and where to properly position the product of your choice.
- The best thermal pad is just good enough
- Avoid foamed pads if possible
- Never use thicker pads than necessary
- Nevertheless, make sure that there is sufficient pressure on the product
Using The Backplate As A Cooler
Nothing improves cooling like an increase in surface area! So now we're going to show you how to convert an existing backplate to a valuable part of the thermal solution.
Let us quickly flash back to the images of the backplate and the foil glued inside. This foil should either be removed completely (as shown in the picture below) or removed partially with something like an X-Acto knife. You'll want to thoroughly clean any spot that'll be in contact with the thermal pads. Remove any adhesive residue and fingerprint oil. The previously-mentioned 2-propanol comes in useful here.
Keep in mind that with very soft or thin backplates, slight pressure could be enough to make the plate touch the PCB. Thus, the non-conductive foil should only be cut and removed where necessary, or additional tape should be used as an insulating layer in relevant areas. Since this tape can also dissipate heat, that's the preferred solution.
In our specific example—the XFX RX 470 4GB—we put two-millimeter-thick thermal pads directly below the GPU package and one very hot memory module. We used a bit of thermal paste to further improve contact with the backplate, since the plate's inner surface isn't very smooth and also bends slightly under tension.
Since the backplate has a number of ventilation holes, we briefly put it back on prior to installation and marked the holes on the thermal tape. This makes it easier to apply the paste in such a way that there is none in those areas, keeping it from spilling out of the holes. This step is especially easy to see on the yellow pad over the VRMs, where the little blobs are positioned exactly between the holes.
These aren't awe-inspiring improvements, but every degree saved is a positive step forward. The memory modules benefit most, as they now remain well below 194°F (90°C). While this primarily helps operational reliability and durability, it also opens up overclocking opportunities that weren't there before.
Again, to summarize:
- Remove glued-on foils and remove glue residue
- Ensure a clean application of the thermal pads; optionally use thermal paste where necessary
- Be aware of holes in the backplate
- Avoid short-circuits (conduct a visual inspection, insert a sheet of paper for testing)
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