A Chinese TechTuber has revealed how Asus has managed to cool the powerful new AMD Ryzen 9 7945HX3D for laptops, as well as the GeForce RTX 4090 Laptop GPU. Bilibili user Ordinary Uncle Tony disassembled his Asus ROG Strix Scar to quite a daring degree to reveal the AMD APU as shown above and below (h/t HXL).
What you see is AMD’s powerful X3D enhanced mobile APU — without an IHS, of course — with its multiple dies visible. Solder mask, or a similar non-conductive barrier like a lacquer or epoxy resin, has been meticulously applied to the protect the processor circuitry surrounding the dies from the damage which might occur from stray drips and drops of (electrically conductive) liquid metal.
PC enthusiasts will be aware that liquid metal is coveted for its great thermal properties when used as a TIM (Thermal Interface Material), but it has some particular drawbacks.
On desktop processors with liquid metal TIM, the application placement and maintenance of the metallic goo is still tricky, but it can be constrained more simply with a uniformly shaped barrier, stopping it from flowing to areas it should not be.
Asus has been applying liquid metal to high-end laptop processors for several generations now. Before its first commercial laptop use in 2019, Asus says it took two years to experiment with production line application of the conductive but messy liquid. Asus “added a tiny barrier sponge just 0.1mm tall around the CPU socket, safeguarding against any accidental seepage.” This spongy method seems to have become redundant with the X3D mobile processor.
If it applied liquid metal to the AMD Ryzen 9 7945HX3D, it would have been first time Asus has had to cope with the complications of a multi-tile processor. With the exposed dies and electronic components on a mobile chip like the Ryzen 9 7945HX3D, some more complicated TIM wrangling would be called for.
We see that the red solder mask (or similar lacquer coating) is one effective method of mitigating the presence of potentially hazardous room-temperature liquid metallic material. Solder mask is a simple, non-conductive durable barrier that has been used in electronics applications for decades. We wonder if it too is being applied by robots on the production line. Anyway, this application seems to have only been done to protect the X3D APU from liquid metal contamination from the GPU. It looks like the AMD APU contacts with the large vapor chamber cooler via a thermal pad.
In our review of the Asus ROG Strix Scar 17 X3D, we noted the massive cooler and vapor chamber for the CPU and GPU. The hottest area of the system was recorded 56.6 degrees Celsius (133.88 F) on its underside. However, the thermal imagery indicated that the cooling was effective in taking the heat away from the processors and expelling most of it out the back. No evidence of thermal throttling was observed in the demanding benchmark runs.