Heat pipe heat dissipation of 5G mobile devices

Recently, Fujitsu Laboratories Ltd and the Department of Mechanical System Engineering, Nagoya University, Researchers at Nagoya University have published in Applied Thermal Engineering the research and development of sub-millimeter thin loop heat pipes made of two layers of copper plates for the heat dissipation of 5G smart electronic devices.

Thin loop heat pipe (LHP) characteristics

The loop heat pipe (LHP) developed by the Japanese researchers can be applied to the heat dissipation of ultra-thin compact electronic devices, with the following characteristics:

1, the use of two layers of copper plate, sub-millimeter thick new ring heat pipe;

2, the formation of a groove structure on the thin copper plate to produce capillary force;

3, non-woven fabric made of copper fiber as a liquid suction core to maintain the liquid phase;

4. The thermal resistance of the thin loop heat pipe with a thickness of 0.4mm is 0.21K/W;

5, the thickness of 0.4mm ultra-thin loop heat pipe at 7.5W thermal power thermal resistance of 0.21K/W.

Research and development background of thin loop heat pipes

The researchers said that compared with conventional communication standards such as LTE and 4G, 5G mobile communication systems support high-bandwidth, low-latency broadband communication. 5G can provide services in many areas, including transportation, healthcare, security, agriculture, and social infrastructure. As many devices, including smartphones, tablets, home appliances, OA devices, cars and production equipment, are increasingly connected to communication networks, there is an increasing amount of communication data processing.

As the amount of data processed increases, the amount of heat generated by electronic devices increases. On the other hand, the demand for smaller and lighter electronic devices is also increasing. Due to miniaturization, the area of the circuit board is reduced, and the heat density of electronic equipment and components is increased. In order to cope with the increasing amount of heat generated by electronic components and the higher heat density, advanced thermal management systems are required.

The study found that materials with high thermal conductivity (such as composite metals and graphite sheets) only provide better heat dissipation in the plane direction. However, heat pipe and Vapor Chamber technologies provide much better heat transfer capabilities than solid thermal materials.

Loop heat pipe (LHP) is a two-phase flow heat transfer system that enables long distance heat transfer without auxiliary power. LHP has been researched and developed for applications with high heating components such as cpus, but has not yet been widely used in consumer electronics. Therefore, the high heat problem of consumer electronics under the 5G communication system may provide a useful place for ultra-thin loop heat pipes.

Structure of a new sub-millimeter thin loop heat pipe

1, the new thin loop heat pipe, only using two thin copper plate manufacturing, can simplify the manufacturing process and reduce costs, LHP thickness can also be further reduced from the current 0.6mm;

2. In a thin LHP constructed of two thin copper plates, capillary force is generated by using a fine groove structure formed by a "semi-etching" manufacturing process. The capillary grooves of parallel/vertical working fluid were constructed on two thin copper plates by etching process, and the two copper sheets were diffusion-welded together to form a capillary suction core structure with orthogonal groove core.

3. The working fluid of thin LHP is water, because the combination of water and copper is common in conventional heat pipes. The selection of water ensures its long-term reliability in electronic equipment applications. In addition, the surface tension of water is greater than the surface tension of other working fluids, thus increasing capillary force.