As mobile devices become more complex and higher in performance despite the smaller in size, heat concentration at localized areas has become a problem. In recent years, passive cooling using phase change materials (PCMs) have drawn attention as thermal management methods for mobile devices. PCMs reduce the temperature increase rate due to their latent heat properties. This reduction in the temperature increase rate is called a "delay effect". Moreover, microencapsulated PCMs (MPCMs) are attracting attention because they keep the melted PCMs from leaking. In this study, PCM sheets containing MPCM/polyethylene composite material are investigated for the thermal management of mobile devices. Namely the authors conduct a series of experiments using the PCM sheet with high thermal conductivity sheet mounted into a simply modeled mobile device. Effects of the mass, the latent heat, the thermal conductivity, the configuration of the PCM sheet, and high thermal conductivity sheet on the temperature of a smart phone simulator are investigated. A finite element analysis (FEA) is also conducted considering the phase change of PCMs to investigate the optimal dimension and shape of PCMs. As a result, the delay effect of PCMs and effectivity of a copper sheet pasted on the PCMs are verified by experiments. Moreover, FEA shows that using the PCM sheet with high thermal conductivity sheet has an advantage for the thermal management of mobile devices and gives an optimal condition of the PCM sheets.

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As sma 苴 phones become more complex ， higher in performance and smaller in size ， heat ooncentradon at localized areas is becoming a problem ． Therefore ， the aim of this paper is to examine the effect ofhigh thermal conductive materials for heat dissipation in order to solve this problem ． The thermal conduc 廿vity of 血 e outer case of the sman phone was changed using finite element method ( FEM ) to simulate high thermal conduc 廿ve materials or composite materials with anisotropy ． The Inaximum temperature gradually decreased and the minimum 胎 mperature grad圃 ly increased with increasing the thermal conduc 缸 vity of the outer case ， Moreover ， 血 ethemlal conductivity in the longer砒 ection of the smart phone was important for lowering the maximum temperature ． In this paper， it is found that applying high therrnal conductive materials to the outer case is effective fbr uniforrning the heat dispersing ．

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