功耗芯片散热器辐射计算和屏蔽结构设计

Calculation of Power Chip Heat-sink Radiation and Design of the Shielding Structure

减少功耗芯片散热器的辐射是PCB板电磁兼容设计必须解决的问题之一。文中建立了铝制带鳍散热器物理模型,应用有限元法分析了芯片与散热器间能量耦合机理,鳍叶走向、激励源施加方向的改变对散热器辐射方向的影响,研究了屏蔽板最佳尺寸、放置位置对辐射的抑制效果。计算结果表明:制约散热器主辐射方向的是激励源施加方向,与鳍叶走向无关。正确放置的屏蔽板越长,放置位置离散热器越近,对辐射抑制越有利;屏蔽板理想高度是与散热器等高:散热器辐射强度与屏蔽板厚度无线性关系,取值与鳍叶等厚是合理选择。

Reducing the power chip heat-sink radiation is one of the key issues for the PCB electromagnetic compati- bility design. In this paper, the physical model of aluminum heat-sink with fins is established. The energy coupling mecha- nism between the heat-sink and chip is analyzed by means of the lqnite element method. The influence of the fin lobe direc- tion, excitation source direction on the heat-sink radiation direction are also analyzed. The suppression effect of shield plate optimum size and position on the radiation are discussed. It is shown that the restriction for heat-sink main radiation direction are the direction of the excitation source, regardless of the fin lobe direction. If the shield plate is placed correctly, the lon- ger the shield plate, the closer the heat-sink, and the better the radiation suppression effect. The ideal height is equal to the height of the heat-sink. There is no linear relationship between the heat-sink radiation and the shield plate thickness. The value is equal to the thickness of the heat-sink fin is a reasonable choice.