【作者】 聂士东；

【导师】 王群；

【作者基本信息】 北京工业大学 ， 材料学， 2007， 硕士

【摘要】 本课题着重研究电磁屏蔽的难点——低频磁屏蔽问题。对低频磁屏蔽理论、影响磁屏蔽效能的各种因素、铝基体电镀前处理工艺稳定性、软磁合金膜的制备工艺及其磁屏蔽性能等进行了研究。首先,在平面波屏蔽理论的基础上,重点分析了低频磁屏蔽理论,得出了磁场与屏蔽体垂直时及磁场与屏蔽体平行时磁屏蔽效能的计算表达式;理论计算结果表明屏蔽体的磁导率、厚度、腔体半径对磁屏蔽效能均有较大影响。理论计算与实际测量吻合较好。其次,对铝合金电镀前处理液的稳定性及浸层质量进行了分析研究。实验结果表明,氢氧化钠、氧化锌、络合剂及NiCl2含量对前处理液稳定性及浸层质量均有不同程度的影响;按NaOH:100~150g/L、KNaC4H4O6·4H2O:10~20g/L、ZnO:5~10g/L、NiCl2:5~10g/L配置前处理液的稳定性最佳,且所得浸层致密有光泽,浸层覆盖率高达95%,电镀层光亮,结合力良好。再次,对软磁合金低频磁屏蔽膜的制备工艺进行了深入研究。试验结果显示,镀层合金成分受镀液主盐浓度及施镀电压的共同影响;对于0.25dm2的单面铝箔,施镀电压为1.5~1.7V之间时所得镀层光亮、均匀,且无麻点和烧焦现象;控制镀层中P含量在1~20%之间可分别得到晶态、纳米晶态及非晶态三种结构的镀层;镀液中当有NaH2PO4存在时,镀层中P的来源主要是由NaH2PO4提供;六种镀液电流效率在79~85%之间,且无较大差异,电流效率相对较高。最后,对所得镀层的性能进行了测试分析。镀层结合力试验及金相观察显示,镀层结合力良好,厚度均匀;合金镀层以颗粒状堆积模式生长,颗粒直径细小;X射线衍射显示在2θ=44.5°附近衍射峰明显宽化,所得镀层为纳米晶态合金镀层;磁性能测试结果显示镀层矫顽力小,初始磁导率高,软磁性能良好;在100MHz~1.5GHz频率范围内镀层屏蔽效能达85~100dB,在工频磁场下磁屏蔽效能达到12dB,在10~50Gs不同强度的静磁场下磁屏蔽效能为3.5~5.2dB。更多还原

【Abstract】 This dissertation mainly research on the difficult part of electromagnetic shielding--low-frequency magnetic field shield, contents low-frequency magnetic shielding theory, effecting factors on magnetic shielding effectiveness, stability of pretreatment immerse zinc alloy solution, preparation technique of low-frequency magnetic shielding film and properties of plating layer.First of all, the dissertation analyzed low-frequency magnetic shielding theory, educed magnetic shielding effectiveness’precise analytic equation of magnetic field upright shield frame and magnetic field parallel shield frame; Magnetic conductivity, thickness and semidiameter of shielding system markedly influence magnetic shielding effectiveness.Secondly, the stability of pretreatment immerse zinc alloy solution was analyzed. Experimentation results show that NaOH、complex agent、ZnO and NiCl2 markedly influence on the stability of the immerse zinc alloy solution and the quantity of immerse layer. When NaOH100~150g/L、KNaC4H4O6·4H2O10~20g/L、ZnO5~10g/L、NiCl25~10g/L, the zinc alloy immerse solution have optimal stability, and can obtain compact、glossiness immerse film, the cover rate is 95%, plating layer is brightness and integrate well with fundus.Thirdly, the preparation technics of low-frequency magnetic shielding film was researched. Experimentation results show that metal salt in plating solution and plating voltage markedly influence on alloy content in plating layer. For 0.25dm2 single aluminum foil, when plating voltage between 1.5 and 1.7V, can obtain brightness and symmetrical plating layer, crystal、nano-crystal and un-crystal structure of plate layer can be obtained when P content between 1~20%in plating solution. P element in plating layer mainly come from NaH2PO4; electric current efficiency of six different kinds of plating solution is 79~85%.Lastly, the property of the plate layer was analyzed. Test result show that the thickness of the plate layer is consistent and has high integrate with the fundus. Plate layer growth in grain shape accumulate mode, grain diameter is fine; X-ray shows that diffraction peak at 2θ=44.5°is obviously broadened, indicate that the frame of the plate layer is nano-crystal. magnetic characteristic test show that the soft magnetic performance of the plate layer is fine. It’s electromagnetic shielding effectiveness attains 80~100dB at 100MHz~1.5GHz and 12dB at 50Hz and 3.5~5.2dB at static magnetic field of different intensity.更多还原