Abstract : As high-end chips continue to develop towards miniaturisation and integration, the problem of "thermal barrier" is becoming more and more prominent, which has become an important challenge hindering the development of chips towards higher performance, and the development of new high-performance cooling technologies is imminent. Convection cooling technology based on liquid metal, liquid metal thermal interface materials and phase change temperature control technology based on low melting point metal phase change materials, etc., are in the cooling capacity of the traditional cooling technology to achieve a quantum leap, to a large number of devices and equipment facing the "thermal barrier" problem of cooling has brought a new solution. Taking kilowatt-class superchips as an example, we discuss the key role of liquid metals in breaking through the "thermal barrier" problem, and try to promote the development and application of liquid metal advanced cooling technology in the field of superchip cooling in the future.

Keywords: liquid metal, high performance chip cooling, thermal barrier, microchannel heat sink, thermal interface material, phase change material

INTRODUCTION

As a high-tech core technology, chip design and manufacturing is the "crown jewel" in the field of information technology, and its difficulties are mainly reflected in the micro-nano processing technology. The "process" is an important indicator of chip manufacturing technology, reducing the process is conducive to reducing the transistor size and power consumption, increasing the number of transistors in a single chip, and improving the computational efficiency. At present, the mainstream high-end chips on the market have adopted 16 nm, 14 nm or even 10 nm technology. As early as 2015, the U.S. IBM has launched a 7 nm process prototype chip; in 2017, IBM announced that it had broken through the 5 nm process chip manufacturing technology, which makes the number of transistors on a single chip of the size of a fingernail cover can be as high as 30 billion, and its computational performance will be significantly improved.

The pursuit of small process from the chip highly integrated and lightweight development trend. As early as the 1960s, one of the founders of Intel Gordon Moore predicted: "the total number of transistors integrated on semiconductor chips will double every 18 months", later known as "Moore's Law". However, in recent years, the development of "Moore's Law" has encountered a bottleneck. On the one hand, large-scale transistor integration puts higher demands on the manufacturing process, which is on the verge of its technological limit. On the other hand, the high degree of integration of chips has led to the increasingly serious problem of heat generation. During the working process of the chip, almost half of the power will be converted into heat, and if this heat cannot be dissipated in time, it will lead to a continuous rise in chip temperature. When the chip temperature is higher than a certain limit, it will affect its working efficiency, performance, stability, and in serious cases, it may even cause safety accidents. In order to ensure the safe and efficient operation of the chip, the temperature should be controlled below 85 ℃.

In 2004, the international electronics manufacturing programme related technology roadmap made predictions, by 2020 or so, high-performance chip operating power or can reach 360 W, accordingly, its heat heat flow density will be as high as 190 W/cm2, which is close to a nuclear reactor a circuit of heat flow density. Facts show that the development of high-end chip industry has exceeded the technology roadmap predictions, part of the high-performance chip work heat heat flow density has reached 300 W/cm2. 2012 and 2016, the "Nature" magazine two articles pointed out one after another, the chip "thermal barrier" problem has become a key impediment to its further development The development of corresponding high-performance cooling technologies is urgently needed.

Cooling technologies are constantly evolving as the demand for cooling increases. The traditional air natural convection cooling and air forced convection cooling heat dissipation capacity is poor, only for the heat flow density of 10 W/cm2 below the situation; heat pipe cooling is currently the mainstream technology of laptop cooling, generally can cope with the heat flow density in the range of 10 ~ 100 W/m2 cooling needs; for higher heat flow density of the chip cooling, the hot spot of the current research is the liquid cooling technology, especially with water as the liquid cooling technology. Liquid cooling technology, especially water as the work material. Although the cooling capacity of water-cooled technology has been greatly improved compared with traditional technology, the low thermal conductivity of water (0.6 W/(m-K) at room temperature) limits its convective heat transfer capacity, so researchers have proposed a series of measures to strengthen the heat transfer, including nanofluids, microchannels and so on. Microchannel water cooling technology can cope with the extreme cooling demand of, for example, 100~1,000 W/m2 magnitude, but it is difficult to be applied at present due to the problems of high flow resistance and easy to be clogged in the flow channel. Therefore, researchers have been committed to finding more efficient cooling media and cooling methods. Room temperature liquid metal cooling technology was conceived in such a background, and its inherent high thermal conductivity gives it excellent heat transfer capability, so once proposed, it has been highly regarded by scholars at home and abroad.

Translated with DeepL.com (free version)