Interview with Otori VP in Japanese(2/2)
The secret to the PS5's size lies in its cooling fan, and the odd trick in the heatsink
The head of mechanical and thermal design talks about PS5 disassembly (Part 2)
PS5のサイズの秘密は冷却ファンにあり、ヒートシンクに妙技
Sony Interactive Entertainment (SIE) will release PlayStation 5 (PS5) in November 2020, and the company has announced that it will cut costs, improve noise and increase the size of the console's chassis In PS5, liquid metal thermal interface (TIM) is used to efficiently conduct the heat generated by the main processor (SoC) to a large heatsink, which is then cooled by a large cooling fan. In the first part of this article, the TIM of liquid metal was explained. In the second part, we will introduce some innovations for large cooling fans and heat sinks.
The PS5's cooling fan is centrifugal, just like the PS3 and PS4, and is 120mm in diameter. It is 120mm in diameter and is controlled by a servo system like the PS4, which adjusts the fan speed according to heat generation. The centrifugal fan produces airflow in all directions. Compared to the axial fans commonly used in desktop computers, the airflow is a little smaller, but the static pressure is a little higher.
The type of fan to be used is generally chosen based on the required static pressure and flow rate. If the static pressure required for a fan is low, then an axial fan is an option instead of a centrifugal fan. But the centrifugal fan is still in the strike zone" (Otori Yasuhiro, head of the PS5's mechanical and thermal design).
The bigger PS5 comes from a thicker fan
To cool both sides of the main board, the PS5's cooling fan is 45 mm thick, which is thicker than the current PS4 and PS4 Pro. If we divide the SoC-mounted side of the PS5 into "Side A" and the back of the PS5 into "Side B," then the heat emitted from Side B is "equivalent to that of the PS4's SoC," according to Mr. Otori. Therefore, the air is sucked in from both sides of the cooling fan to cool the A and B sides of the main board.
The size of this cooling fan determined the size of the PS5. The fan's thickness was based on the width of the PS5 when it was placed vertically (or the height if it was placed horizontally), and it was asymmetrical when viewed from the front. This is because that is where the optical disk drive is located.
Easy to remove the optical disk drive
When the unit is placed in portrait mode, the right side viewed from the front is on the bottom of the unit when it is placed horizontally. When the system is placed horizontally, the main board is placed underneath the heat sink and power supply module, and the optical disk drive is placed underneath the main board. The purpose of this is to make it easier to support the "Digital Edition" which does not include the drive. If you remove the optical disc drive, the standard PS5 becomes the Digital Edition.
The PS5 measures 390mm x 260mm x 104mm, which is larger than the larger PS4 Pro (approximately 327mm x 295mm x 55mm), which is the larger of the PS4 series. In fact, there were ways to make the PS5 smaller than its current size. For example, we could reduce the size of the PS5 by installing two cooling fans, one for side A and one for side B. However, there was no way to make the PS5 smaller than the current size. However, this would increase the cost of the two cooling fans. In addition, controlling the rotation of the two cooling fans is "more difficult" than controlling only one fan. That is why they decided to use a single large fan to cool both sides of a single main board.
Small details around the cooling fan
Around the cooling fan, measures have been taken to ensure user convenience and safety. For example, the PS5 uses a "dust catcher" that collects dust and other small debris blown away by the centrifugal force of the fan. According to Otori, "It's something we've wanted to introduce for a long time, and we adopted it because we could secure the space. Inside the PS5 is a space where dust blown away by the centrifugal force of the fan can be collected, and the dust can be vacuumed up through the hole that appears when the white exterior cover is removed.
Safety measures were also taken to prevent fingers from accidentally getting into the spinning fan. Removing the outer cover reveals the cooling fan. While it is assumed that the power is turned off when removing the exterior cover, there is no chance of removing the cover without turning it off. In other words, if you remove the exterior cover while the power is on, the cooling fan will still be spinning. This is why we added a cover to prevent fingers from getting into the fan while it is spinning.
However, because the fan cover creates air resistance, it has a three-dimensional shape and has small holes in it to allow the air to flow smoothly. According to Mr. Otori, "This cover was designed by a young engineer who had been with the company for a couple of years".
3D heat pipes and gaps between cooling fins
Even with a large heat sink, the company has achieved both improved cooling performance and cost reduction. Although the heat pipes are used, the shape and airflow of the heat pipes have enabled the company to achieve cooling performance equivalent to that of an expensive vapour chamber with superior cooling performance and reduced costs. For example, the heat pipes are bent in a three-dimensional (three-dimensional) structure. Of the three fins in the heatsink, the heat pipe is made to pass through the upper and lower sides of one fin (fin 1), respectively, to increase the cooling performance of this fin.
The other two fins have some innovations as well. For example, one of the fins (fin 2) is angled at an angle. In addition, we intentionally created a gap between this fin (fin 2) and the other fin (fin 3) to allow the air that has been heated by the first fin (fin 2) to be mixed with air from another source to cool it down and then sent to the second fin (fin 3) to improve the cooling effect on fin 3. I made it. If this gap is also filled with fins, the cooling effect of fin 3 is reduced because once the air is not cooled, it cannot be cooled.
On the B side, there is also a heat sink and heat pipe
In addition to this large item, there is another heat sink in the area that is difficult to see from the disassembly video. That is the heat sink located on the B side of the main board. The main board is sandwiched between the aforementioned A side and B side by a metal shield plate, and in order to cool the power supply system such as the DC-DC converter mounted on the B side, a heat sink and a heat pipe were installed on the shield plate on the B side. In addition, the B-side shield is made of aluminum for cooling, while the A-side shield is made of steel.
There were other structural features as well. One example is the thermal conductivity between the GDDR6 compatible memory mounted on the B side of the main board and the shield board. Instead of the so-called 'stick-on' type thermal conductor in sheet form, it is coated with a liquid material that hardens like rubber after a short time. This is a measure to increase productivity in response to automation.
In the case of the paste-type heat-conductive materials, it is difficult to remove them from the backing board by an automatic machine, so it is necessary to manually remove them. The PS5 uses almost all of the thermal conducive materials used in the PS5, whereas the PS4 series used only some of them.
