【作者】 曹琦；

【导师】 龚荣洲； 冯则坤；

【作者基本信息】 华中科技大学 ， 微电子学与固体电子学， 2005， 硕士

【摘要】 在当今电子信息技术时代,随着计算机、移动通信、卫星通讯等高速发展,电磁干扰在军用和民用电子信息领域的影响越来越大。同时为实现通信高速化,时钟脉冲频率升高,随之而来的电磁波干扰频率也越来越高。为了抑制高频发射噪声引起的电磁波泄漏,就需要开发频率高损耗大的电磁波吸收材料,有效地吸收噪声能量。本论文简要介绍抗EMI材料吸收电磁波机理,讨论了不同材料的吸收电磁波性能。由于金属磁性材料的饱和磁感应强度高过于铁氧体,微波段的磁导率高,有利于实现薄层化, Snoek极限值所到达的频率高过于铁氧体材料,所以可以采用金属磁性材料来满足GHz频段抗干扰器件的要求。同时,金属磁性材料居里温度较高,在处理好氧化问题后,温度稳定性比铁氧体材料好。于是,近年来提出了使用橡胶或者环氧树脂作粘结剂的铁硅铝系软磁合金粉末。本文采用扁平化工艺及绝缘包覆工艺,对铁硅铝系软磁合金粉末进行改性,详细介绍了两种改善合金微粉吸收性能的工艺流程。对实验样品进行了SEM分析,观察了颗粒形貌对材料性能的影响。总结了不同球磨时间以及不同绝缘介质含量对于材料电磁性能的影响规律。分析单层吸波材料(含导电衬底)对电磁波的反射率公式,计算不同样品反射率,结果表明,球磨扁平化工艺及绝缘包覆工艺可有效地改善铁硅铝金属粉末的微波吸收性能。经改性后的铁硅铝系软磁金属粉末在1.0-3.5GHz频段内具有较好的吸波性能,可应用于抗电磁干扰。更多还原

【Abstract】 With the rapid development of computer science, mobile communication and satellite communication, the Electromagnetic Interference (EMI) technology has been greatly applied in military and civil fields of the electronics and information. In order to communicate in high speed, the clock-pulse frequency was raised, followed by increasing of the EMI frequency. Electromagnetic absorbing materials with high frequency and high loss are required to absorb the noise energy, aiming at restraining the electromagnetic leak induced by high-frequency emission noise. The theory of absorbing electromagnetic wave by EMI resistance materials is introduced in this paper, and the absorbing performances of different materials are discussed. The metal magnetic material was adopted to satisfy EMI resistance equipment in GHz frequency, due to its higher saturation magnetic susceptibility than the ferrite material, lamella structure and higher frequency in Snoek limit than that of the ferrite material. Meanwhile, the temperature stability of the metal magnetic material is much better than that of the ferrite material after oxidation, as a result of the higher Curie temperature. Then soft magnetic metal powders with the Fe-Si-Al composition are employed in recent years, with the felt dope of latex or the epoxy colophony. The electromagnetic interference resistance characteristic of the Fe-Si-Al magnetic alloy powder was improved by flattening the metallic materials and chemical coating method in this paper. Two kinds of technical flows for improving the absorbing performance of the powder were introduced in detail. SEM analysis of the sample was carried out and the influence of the grain morphology on the performance of the material was observed, as well as the influence of different boll-milling time and different additive contents of isolative medium on the electromagnetic performance of the powder. The formulas of reflection coefficient of absorbing materials with electric substrates were analyzed and the reflection coefficient of different material sample was computed. The result shows that the proposed boll-milling flattening and isolative coating technology will dramatically improve the performance of absorbing materials in the frequency of 1.0-3.5GHz, which makes it possible to apply the material to EMI resistance.更多还原