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Otori (PS5 engineer) translated interview on why they decided to go with liquid metal


May 29, 2020
Don't know if it's been posted. Used a DL site to translate the original Japanese interview.


Adopting "liquid metal" prepared for PS5, the real aim is cost reduction
The person in charge of mechanical design and thermal design talks about PS5 disassembly

"I really wanted to use liquid metal as a heat conductor. It took a lot of determination and preparation. Sony Interactive Entertainment's (SIE) PlayStation 5 (PS5) console is scheduled to launch in November 2020, and Yasuhiro Otori, who is responsible for the mechanical and thermal design of the console, has been working on the PS5 This is how he describes his thoughts on the technology that played a key role in making the He has been involved in the design of the PlayStation since the PS2, and he appeared himself to work on and explain the PS5 in a disassembly video released by SIE on October 7, 2020.

PS5 uses liquid metal as the heat conduction material (TIM) for transferring heat from the main processor (SoC) to the heat sink. Without this liquid metal TIM, the PS5 would have been larger, more expensive, and the cooling fan would have been louder. The noise of the cooling fan during gaming varies depending on the situation, but according to Feng, "the PS5 is generally quieter than the PS4".

Mr. Yasuhiro Otori. He graduated from the Department of Mechanical Engineering, Tokyo University of Science in 1993 and joined Ricoh. In 1998, he joined Sony Computer Entertainment (now Sony Interactive Entertainment), where he worked on the design of the PS2, PS3, PS4 and toio. (Source: SIE)

The PS5 is available with and without an optical disc drive and is priced at US$499 and US$399, respectively, which is a bargain against the specifications. The thermal design contributed greatly to the cost savings in achieving this price. This article will be divided into two parts, Part 1 and Part 2, based on the interview with Mr. Feng.

Why did we use liquid metal TIM?
Preparations for the adoption of liquid metal TIM began about two years ago, when the configuration and shape of the PS5 hardware was roughly decided. In addition to the design, we began to consider various aspects of the adoption of liquid metal TIM, from the manufacturing process to procurement. They decided to use liquid metal TIM because the main processor (SoC) had a high operating frequency, but the die was small and the thermal density was "very high" (Mr. Feng). The heat density of the SoC, especially during gaming, is "much higher" (he said) than the PS4. That's because the PS5's SoC "basically runs at almost full power during gaming" (he says). As a result, TDP (Thermal Design Power) values and the amount of heat generated during gaming are "about the same". On the other hand, it is rare for a PS4 SoC to operate at the very edge of TDP, and even when gaming, it generates only a few percent of its TDP.

The reason why SoC dies are small is that die size is directly related to cost and yield. In other words, the smaller the size of the die, the lower the cost and the more difficult it is for defects to enter the die, leading to higher yields.

Liquid metal TIM is more expensive than conventional thermal conductors such as thermal grease. However, when considering the thermal design of electronic devices, the more effort is put into cooling close to the heat source, the better the "cost performance" is, according to Mr. Feng. This is because if heat can be recovered efficiently near the heat source, there is no need to spend money on heat sinks and cooling fans. On the other hand, if thermal grease is used, an expensive heat sink with high cooling performance is required.

In other words, even if we use liquid metal TIM, which leads to higher costs, we can reduce the total cost of cooling as a result," says Feng. The speed of the cooling fan can also be reduced, which reduces noise. In other words, the use of liquid metal TIM "makes sense in terms of cost and quietness" (Mr. Feng).

So will liquid metal TIM be used in other electronic devices in the future? As for that, "I don't know" (Mr. Feng), but he prefaced it by saying, "As an engineer, the less expensive a device is, the more I want to use it" (Mr. Feng). He believes that liquid metal TIM will be a powerful tool in cases where heat sinks are expensive and in need of help.

Tag teaming up with material manufacturers and know-how on how to apply Liquid metal TIM has many advantages, but it is a material that "poses a challenge to use" (Mr. Feng). For example, because it is conductive, if liquid metal TIM leaks onto the board, there is a risk of a short circuit in the board. In addition, it is highly reactive to aluminum, so it must be kept away from aluminum.

Because of these issues, while they are used in mobile phone base stations and other applications, their use in consumer applications has been limited to a very limited number of laptops and "overclockers," so-called "overclockers," which are enthusiasts who want to increase the operating frequency of their processors.

Therefore, the company took measures to address these issues so that they could be used in game consoles, which are mass-produced in the millions to more than 10 million units per year. For example, a sealed structure was adopted to prevent leakage of the liquid metal TIM. This structure is patented, although it would be obvious if it were to be disassembled and seen. Above all, there is a lot of manufacturing know-how, such as how to apply and automate liquid metal TIM, that is not obvious just by looking at it," said Feng. For example, liquid metal TIM is applied by an automated machine, but "it's a different method than conventional grease," according to Mr. Feng. We cooperated with material manufacturers to realize this liquid metal TIM. The company claims to have added customizations based on existing products.