Personal computers require highly functional CPUs. These CPUs must be cooled. Desktop and laptop PCs use fans to cool the CPU with air. If the fans do not operate properly, then the personal computer will stop functioning. Smartphones and smart tablets also contain CPUs, as well as many other components that generate heat, such as batteries, communication units, and cameras. However, a smartphone has no ventilation holes. You can use a smartphone while holding it because no part of the smartphone becomes extremely hot.
You can hold a smartphone without feeling it hot, because the circuits inside the smartphone are covered with special thermal diffusion sheets. These thermal diffusion sheets, the primary component of which is carbon, have excellent thermal diffusion characteristics -- much better than those of copper, which has high thermal diffusion characteristics and has been used for radiating heat.
What is Pyrolytic Graphite Sheet (PGS)
- Schematic Structure of the Graphite Sheet
This sheet is only several 10 μm thick. It looks like a single sheet, but actually consists of several tens of thousands of layers of highly conductive carbon crystal membranes. The carbon in each membrane is closely bonded with each other in a plane. The membranes convert heat into vibration energy and very quickly diffuse it.
As a result, when a carbon crystal membrane is heated, it diffuses the heat very quickly. Therefore, a graphite sheet made of carbon crystal membranes thoroughly diffuses and radiates heat even if its thickness is several 10 μm.
Structure of Pyrolytic Graphite Sheet (PGS)
Each sheet is made by steaming high-polymer films under very high temperature. Since the carbon is closely bonded, the sheet is very strong and does not break even when flexed 30,000 times (R5/180°). Therefore, it provides excellent thermal diffusion characteristics in a limited space that has folds, bends, and differences in level. It also has high electric field-shielding characteristics.
Thanks to these excellent characteristics, smartphones do not become hot when their size and thickness are reduced. Panasonic components and devices are used in these fields.