基于矢量有限元法的热沉结构电磁辐射研究

摘要

高频、高功率芯片工作时会产生大量的热,热沉可以有效地帮助芯片散热.然而在高频环境下,热沉往往成为主要的电磁辐射源,降低了整个系统的电磁兼容能力,所以有必要对热沉的电磁辐射特性进行研究.本文采用矢量有限元法,从不同的接地方式、散热鳍片数目及厚度变化、鳍片高度变化几个方面分析了热沉的电磁辐射特性,提出了影响谐振频率的关键因素,并从电磁兼容角度提出了热沉设计的注意事项.数值仿真表明,合理的选择接地方式可以有效地提高谐振频率,降低电磁能量辐射;散热鳍片的数目和厚度变化对于谐振频率和电磁辐射没有明显的影响,然而鳍片的高度对于电磁辐射能量影响显著.%Heatsink is often used to cool the chip which woks in high frequency and high power. However, in high frequency environment,the heatsink becomes the main electromagnetic radiation source.Because the EMC capacity of system is decreased due to the heatsink.it is necessary to study the characteristics of heatsink electromagnetic radiation. In the paper, the vector FEM for heatsink is firstly introduced based on electromagnetic field theory.Then the characteristics of heatsink electromagnetic radiation are analyzed by the aspects of grounding methods, number and thickness of cooling fins changes,height of cooling fin changes. The key factors which affect the resonant frequency and the design notes of heatsink are presented. As the simulation results show, the power of electromagnetic radiation can be decreased and die resonant frequency can be improved effectively through selecting reasonable grounding method,the number and thickness of cooling fins changes have little effects on die resonant frequency and power of electromagnetic radiation, however, the power of electromagnetic radiation is impacted remarkably by the height of cooling fin changes.