| Summary: | 碩士 === 國立臺灣海洋大學 === 機械與機電工程學系 === 103 === Smart phones have become a slim, multifunctional, and high-density mobile communication device. Chips need to possess sound and stable processing performance under various operating conditions. In order to eliminate high temperature effects and to assure longer life circle, heat dissipation in smart phones is an important topic.
This study measures the temperature distribution in a horizontally oriented cell phone as the benchmark. Numerical simulation is conducted to obtain the thermal field under same condition. It is found that the agreement between the two is within a reasonable range (less than 10 %). Thus the numerical model can be regarded as accurate and acceptable. More simulations are executed for phones with various inclination angles. The associated buoyancy effects on the thermal field are observed. Since the heat generated in the CPU accumulates in the PCB, so the neighboring chips are influenced. Heat transfer enhancement via conduction is proposed to correct the waste heat accumulation problem.
It is understood from simulation and analysis that CPU is the primary component for waste heat. It also has significant impact on the power management IC, the audio decoder, and the multichip package RAM. Therefore the temperatures of the four chips are monitored. Several heat dissipation improvements are proposed and the associated effects are examined, such as changing the packaging material, PCB material, and the casing material, and inserting heat sinks on top of CPU with different materials. A combination of the above improvements can decrease the operating temperatures of the chips and solve the waste heat problem effectively. It is also found that the buoyancy effect diminishes with the use of improvements; that is, the thermal fields do not change significantly for different inclination angles.
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