Xiaomi Explain Mi Mix Fold Heat Dissipation System and How Solved 2 Major Problem

Mi Mix Fold Heat Dissipation System

As a new direction in the field of mobile smartphones, the foldable screen form brings not only a new experience but also faces the challenge of heat dissipation that has never been experienced before.

Mi Mix Fold heat dissipation system uses the innovative “micro airbag” structure resistant to bending graphite sheet to open up the parallel three-dimensional heat dissipation system on both sides, solving the problem of difficult heat dissipation of the folding screen.

To dissipate heat from a heat source, one of the most effective ways is to increase the effective heat dissipation area. However, the effective heat dissipation area is not always the same for foldable-screen phones, and when in a folded form, the effective heat dissipation area is reduced.

MIX Fold, as a new direction in the field of smartphones, has become one of the future cell phone possibilities with its unique experience and ultimate audio and video entertainment, but this new form also faces many problems that have never been experienced, such as the test of the phone’s heat dissipation capabilities.

At present, folding-screen phones will mainly face these two major heat dissipation problems:

  1. Variable folding screen form, in the folding and unfolding of the heat dissipation capacity, will change.
  2. The internal distribution of components is not balanced, the motherboard and SoC side of the thermal environment will be more severe.

In response to these two problems, Xiaomi has developed a parallel dual three-dimensional cooling system and an innovative “micro airbag” cooling mechanism, which not only provides a powerful cooling system on the left and right sides of the phone but also connects the two, thus realizing a new “butterfly” cooling.

The wings of butterfly cooling: Dual cooling systems on the left and right side, total cooling area twice as large as the non-folding screen.

The Mi MIX Fold is equipped with Qualcomm’s flagship Snapdragon 888 platform, which has a powerful super core and GPU, and brings the same huge heat dissipation pressure along with the ultimate performance.

In the case of uneven heat dissipation between the unfolded and folded forms, to dissipate heat adequately, it is necessary to maximize the heat dissipation efficiency in both forms as much as possible, so the first step is to have a heat dissipation system with enough “luxurious” materials.

In terms of the basic cooling system, the Mi MIX Fold is equipped with the industry’s most luxurious and cutting-edge multi-dimensional cooling technology, including VC liquid cooling solution + thermal gel + multi-layer graphite sheet + material-grade bending-resistant graphite sheet, and a whole copper foil under the screen, with a total cooling area of 22583.7mm².

Even though the heat dissipation capability is unfavorable in the folded form, the total heat dissipation area is extremely advantageous compared to non-folding screen phones because of the larger space inside the machine. Compared to the Xiaomi 11, which has a total cooling area of 12,677mm2, the MIX Fold is almost twice the size of the Xiaomi 11, thus exerting a stronger cooling capability.

But in reality, it is not easy to compare the heat dissipation area with the heat dissipation capacity. Due to the folding screen design of the MIX Fold, the part of the spindle is beyond the reach of conventional heat dissipation materials, so the heat dissipation system of the MIX Fold is roughly divided into two parts according to the folding screen, which Xiaomi figuratively call the parallel dual three-dimensional heat dissipation system.

But this faces a second problem: the internal components on the left and right sides are not balanced, and the motherboard and SoC side will face more heat dissipation pressure.

Bend-resistant graphite material: Innovative “micro-airbag” structure to create a heat tunnel through both sides.

To solve the heat dissipation imbalance, Xiaomi’s R&D engineers conceived a “heat transfer tunnel” to connect the parallel heat dissipation systems on both sides of the spindle, so that the heat from one side of the SoC can be transferred to the other side where the heat dissipation pressure is lower, thus achieving a more balanced and stronger heat dissipation capability.

This is similar to creating a bridge across a river, where heat is like traffic flowing through the bridge to reach the other side quickly, thus invigorating the mobility of the city.

But the key is, how to create this tunnel? To open up the left and right sides, a thermally conductive material is needed to connect the two, and this thermally conductive material must also have the ability to resist bending to cope with the MIX Fold’s possible unfolding or folding at any time.

The answer from Xiaomi’s thermal design engineers is “bend-resistant graphite”. After testing and comparing dozens of heat dissipation solutions, we finally created a bend-resistant graphite thermal conductor with a “micro-airbag” bionic knuckle skin heat dissipation structure for the MIX Fold by improving the graphite sintering process and coating technology.

The thermal performance of the resulting bend-resistant graphite sheet is also excellent, with only a 3-5% drop in thermal performance after 200,000 180-degree bends.

The reason for the emphasis on bend resistance is that while conventional graphite flakes break or slag after 200,000 bends, bend-resistant graphite flakes have a much better thermal performance, with only a 3-5% drop in thermal performance after 200,000 180-degree bends. This is 9-15% lower than that of the fan-shaped structure.

However, achieving a “micro-air bag” structure for bend-resistant graphite sheets is not easy and requires several different process innovations in detail, which we have summarized into two points.

Despite so many breakthrough thermal designs on the MIX Fold, Xiaomi’s thermal design engineers are still not satisfied with the immediate achievements, to solve the problem of different heat dissipation capacity of the whole machine in open or folded form, there are difficulties in triggering temperature identification and the risk of performance loss, Xiaomi’s thermal design engineers have also upgraded the temperature control design side:

Through the new “butterfly” heat dissipation and temperature control design, MIX Fold can provide the best heat dissipation experience at all times, whether it is used for gaming, audio, and video, or photography.


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