## 1 Introduction
[28] experimentally explored the use of PCM for the thermal management of portable electronic devices under steady conditions using paraffin with a melting temperature in the range of 53-56 \({}^{\circ}\)C. The experimental setup was designed to simulate the applications of typical portable electronic devices a decade ago, allowing an investigation of the influence of different orientations to gravity (inclinations) of the package on the melting and solidification of the PCM. An aluminum enclosure (\(80\times 132\times 20\) mm) filled with PCM was studied for heat input levels ranging from 6 to 12 W. The orientation of the PCM package to gravity was observed to have a negligible effect while increasing power input led to an increase of the melting rate. [PERSON] et al. [10; 12] presented the first experimental study testing PCM temperature management using real tablet PC components. PCM encapsulated in aluminized laminated film with a thickness of only 2 mm was used. Two different PCMs were investigated: \(n\)-eicosane and a commercially available PCM PT-37. A real mock tablet PC was used to study the effect of adding the PCM layers on the thermal performance of the tablet. A Kapton heater was used to simulate the thermal dissipation of the electronic components. The temperatures at the outer surface of the PCM layer as well as of the cover were measured during charging, with a constant heat power input ranging from 2 to 8 W. The effect of different orientations to gravity was also studied. The results showed that the encapsulated PCM led to a lower back cover temperature. More precisely, a reduction of 20 \({}^{\circ}\)C of the back cover temperature was achieved with the encapsulated PCM. It was observed that the inclination of the tablet does not have a significant influence on the back cover temperature during solidification and melting. The work from those four research groups are the only ones currently published in easily accessible open literature dealing with thin temperature management of electronics. Moreover, the approach of integrating PCM packages into tablet computers and smartphones is not yet at an industrializing stage. No patents could be found by the authors where PCM is used as part of the thermal management system of thin portable electronics. As showed in the previous literature discussion, as short as it is based on the novelty of work on the subject, it has thus far been proven that adding PCM into those devices leads to reduced overheating and an enlarged holding time, and studies have shown that knowledge of the temperature distribution inside the PCM is crucial to the overall thermal understanding of the process because of the low conductivity of the PCM. However, too few information on the influence of thin PCM packages on the thermal performance is available. Furthermore, virtually no information on the temperature distribution and the local state (solid, liquid, melting) of the PCM during the transient process is available; this is due to the complexity of isolating the PCM thermal behavior during the transient process due to the complex thermal behavior of all the other components of real portable electronics (screen, battery, internal components). Thermal spreaders are also implemented in commercially available handheld devices. Thermal spreaders are thin material layers with a large thermal conductivity, which may be used to increase heat transfer from the heat source to the sink. For example, some SoC used in the newest tablet generations are covered with an electromagnetic shield that also serves as a thermal spreader [30]. The influence of thermal spreaders on the thermal management of electronics has been studied by some investigators [31; 32; 33]. However, no experimental evaluations on the combination of thin PCM packages and thermal spreaders in thin electronic devices have been discovered by the author.