孔缝对内置电路板壳体屏蔽效能的影响

Influence of Apertures on Shielding Effectiveness for Shell of Loaded PCB

电子设备屏蔽效能的好坏直接影响着电路系统的电磁兼容性能,而其金属壳体上的孔缝造成的电磁泄漏是一个不容忽视的问题。以内置电路板的开缝屏蔽壳体为研究对象,应用FEM(有限元法)分析了不同的孔缝尺寸、电路板尺寸、电路板位置对壳体屏蔽效能的影响。并进一步研究了电路板上金属微带线受电磁干扰信号影响而产生感应电流的变化规律:走线越长,离缝隙越近,感应电流数值越大,其峰值出现在腔体的谐振频率处。根据计算结果,提出了优化设计屏蔽腔及其腔内电子设备的建议。本文研究对于更为有效地利用金属壳体防御电磁干扰,提高系统电磁兼容性具有指导意义。

Shielding effectiveness of electronic equipment directly influences the EMC performance of the circuit system.And the electromagnetic leakage from apertures of metal shell is an issue which can not be ignored.In this paper,the PCB which is set in rectangular shielding shell is the research object.The influence of different apertures sizes,different board sizes and different board position on shielding effectiveness was analyzed by applying the FEM（finite element method）.Variation regularity of induced current which is resulting from interaction between metal microstrip line of the PCB board and the electromagnetic interference signals was further studied.The longer the trace,the closer from the slot,the greater the induced current value.The peak appears in the cavity resonant frequency.Some suggestions from calculation results are presented for optimized design of shielding and electronic equipment in the body of shell.The study is instructive for more effective use of metal shell to defense EMI and will improve the system electromagnetic compatibility.