High electromagnetic shielding of plastic package for 2.5-Gb/s optical transceiver modules

A lightweight, low-cost plastic package for a 2.5-Gb/s optical transceiver module, that also has good electromagnetic shielding properties, has been fabricated using woven continuous carbon fiber (CCF) epoxy composite. The shielding effectiveness (SE) of the CCF epoxy composite has been modeled theoretically and measured from 500 MHz to 3 GHz using the ASTM D4935 and a near-field test method. Two types of weaving patterns were studied: a balanced twill structure (BTS) and a parallel structure. The BTS was able to achieve an SE of about 80 dB under plane wave conditions and about 50 dB under near-field conditions because of the numerous conductive between crossing fibers. The SE of the proposed package is at least 20 dB greater than the previous package which used a liquid crystal polymer composite. In addition to better shielding performance, the proposed package costs less because it uses less carbon fiber. The proposed package for an optical transceiver is suitable for use in a low-cost lightwave transmission system     

Electromagnetic shielding of nylon-66 composites applied to laser modules

Electromagnetic shielding of nylon-66 composites applied to laser modules was studied experimentally and theoretically. The effects of conductive carbon fiber length and weight percentage upon the shielding effectiveness (SE) of nylon composites were investigated. The SE of long carbon fiber filled nylon-66 composites was found to be higher than short carbon fiber composites under the same weight percentage of carbon fibers. In addition, higher electromagnetic shielding was obtained for the composite with higher carbon fibers contents at the same length. The SE of conductive carbon fiber filled nylon-66 composites was measured to be 42 dB at a low frequency of 30 MHz and 50 dB at a high frequency of 1 GHz. The SE predicted by theoretical models and measured by experiments were in good agreement for filled nylon-66 composites with different length fiber.     

A carbon nanotube polymer-based composite with high electromagnetic shielding

A novel, polymer-based carbon nanotube (CNT) composite with high electromagnetic (EM) wave shielding effectiveness (SE) and high mechanical properties was developed. Two types of CNTs with different aspect ratios and morphologies are compared in this study. Amorphous carbon and graphite powder are used as reference materials. The liquid crystal polymer (LCP) and melamine formaldehyde (MF) are used as polymer matrices to study the orientation effect of CNTs in a polymer matrix. The influences of orientation, aspect ratio, mass fraction, and morphology of CNTs upon the shielding effectiveness (SE) of CNT/polymer composites are investigated. The experimental results show that the higher the orientation, the aspect ratio, and the weight percentage of nanomaterials are in the composite, the higher the polymer composites’ SE. The nanomaterials’ morphology, especially CNTs, also affects the SE value of the polymer composite. The highest SE for the CNT/LCP composite obtained is >62 dB. The theoretically calculated SE data are consistent with experimentally obtained data.     

The influence of fiber orientation on electromagnetic shielding in liquid-crystal polymers

The influence of conductive carbon-fiber orientation and weight percentage on the electromagnetic (EM) shielding effectiveness (SE) in liquid-crystal polymer (LCP) composites was investigated experimentally and theoretically. The experimental results show that the SE of LCP composites with longitudinal fiber orientation is higher than random fiber orientation under the same weight percentage of carbon fibers filled. This is because longitudinal fiber orientation is parallel to the electric field of the incident EM wave, and most of the energy of the incident wave is reflected by the longitudinal fiber. In comparison with nylon66 composites, the SEs of LCP composites with longitudinal fiber orientation are also higher than nylon66 composites with the same content of carbon fibers. Furthermore, the SE of 20% conductive carbon-fiber-filled LCP composites was measured to be 50 dB at a frequency of 0.3 GHz and 53 dB at 1 GHz, which is at least 10 dB higher than that of nylon66 composites. The SE predicted by theoretical models and measured by experiments was in good agreement for carbon-fiber-filled LCP composites of longitudinal and random fiber orientations.     

钢筋混凝土对地铁弓网离线电弧屏蔽效能的研究

为了研究地铁站钢筋混凝土层对地铁弓网离线电弧的屏蔽效能, 基于有限积分法(Finite Integration Technique, FIT)计算并分析了钢筋混凝土对平面波的屏蔽效能; 讨论了不同混凝土结构对屏蔽效能的影响因素; 实测得到了某地铁站的屏蔽效能.研究结果表明:素混凝土对电磁波的屏蔽效能具有一定的周期性, 增加厚度对高频段的屏蔽效能影响不大; 钢筋网的屏蔽效能在0.1~0.8 GHz频带范围内大于30 dB; 双层钢筋混凝土在0.1~1.3 GHz频带范围内的屏蔽效能大于40 dB; 实测屏蔽效能在整体上跟数值计算结果吻合得较好, 验证了本文方法计算钢筋混凝土对地铁弓网离线电弧屏蔽效能的正确性.     

镍基电磁波屏蔽复合涂料制备及在EMC中的工程应用

针对日益严重的电磁环境污染问题,根据电磁波屏蔽材料对电磁波作用原理,用镍粉和金属纤维作为复合填料,以丙烯酸树脂作粘结剂,按照涂料制备的方法,制备了一种能屏蔽电磁波的复合涂料。将其应用在某有线电视网和电子工作间,进行对比法测试,结果表明:在射频段,该材料将有线电视传输网设备中的干扰场强度降低了40%~50%,在电子工作间上的屏蔽效能达到了30~50dB。     

Lightweight and Anisotropic Porous MWCNT/WPU Composites for Ultrahigh Performance Electromagnetic Interference Shielding

Lightweight, flexible and anisotropic porous multiwalled carbon nanotube (MWCNT)/water‐borne polyurethane (WPU) composites are assembled by a facile freeze‐drying method. The composites contain extremely wide range of MWCNT mass ratios and show giant electromagnetic interference (EMI) shielding effectiveness (SE) which exceeds 50 or 20 dB in the X‐band while the density is merely 126 or 20 mg cm^?3, respectively. The relevant specific SE is up to 1148 dB cm³ g^?1, greater than those of other shielding materials ever reported. The ultrahigh EMI shielding performance is attributed to the conductivity of the cell walls caused by MWCNT content, the anisotropic porous structures, and the polarization between MWCNT and WPU matrix. In addition to the enhanced electrical properties, the composites also indicate enhanced mechanical properties compared with porous WPU and CNT architectures.     

一种新型电磁屏蔽复合涂料的研制

以镀锡镍硅酸钙镁矿物晶须与镍粉为复合填料,以环氧树脂作为粘结剂,按照涂料制备的方法,研制了一种新型电磁波屏蔽复合材料——镀锡镍硅酸钙镁矿物晶须／镍粉／环氧树脂电磁波屏蔽复合材料,并介绍了其主要特点及市场前景。测试结果表明：在300kHz～1．5GHz范围内,其屏蔽效能为37．197～46．139dB。     

Absorption-Dominant Electromagnetic Interference Shielding through Electrical Polarization and Triboelectrification in Surface-Patterned Ferroelectric Poly[(vinylidenefluoride-co-trifluoroethylene)-MXene] Composite

Extensive utilization of electronic devices and wireless equipment require human to take affirmative measures to weaken unwanted electromagnetic wave radiations. Herein, a ferroelectric poly[(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)-MXene]-poly(3,4-ethylenedioxythiophene) (PEDOT) multilayered film is developed that can increase electromagnetic interference (EMI) shielding performance through electrical polarization. The MXene is encapsulated by a P(VDF-TrFE) matrix, which inhibits oxidation, and a highly conductive MXene is created conductive network resulting in enhancement EMI shielding effectiveness (EMI SE). Furthermore, the surface pattern inducing multiple scattering and PEDOT layer contributes to the increasing absorption due to the electrically conductive PEDOT. Thanks to the electrically polarized and negatively charged P(VDF-TrFE)-MXene, the composite film demonstrates superior EMI SE and absolute EMI SE (SSE_t) are exhibited remarkable ≈61 dB and 15230 dB cm²g⁻¹ with high absorptivity (0.87) at thickness of 120 µm in X-band. Additionally, P(VDF-TrFE)-MXene composite film is applicable to motion and thermo-resistive sensor due to the negatively charged P(VDF-TrFE) and thermo-resistive property of PEDOT, respectively, for multifunctionality. This work provides a feasible avenue for flexible absorption dominant EMI shielding materials via electrical polarization with remarkable EMI shielding performance.     

Ultrathin Wood-Derived Conductive Carbon Composite Film for Electromagnetic Shielding and Electric Heating Management

Recently, wood-based composites have absorbed widespread concern in the field of electromagnetic interference (EMI) shielding due to their sustainability and inherent layered porous structure. The channel structure of wood is often used to load highly conductive materials to improve the EMI shielding performance of wood-based composites. However, there is little research on how to use pure wood to prepare ultrathin EMI shielding materials. Herein, ultrathin veneer is obtained by cutting wood in parallel to the annual rings. Then, carbonized wood film (CWF) is prepared by a simple two-step compressing and carbonization. The specific EMI shielding effectiveness (SSE/t) of CWF-1200 with an ultrathin thickness (140 µm) and high electrical conductivity (58 S cm⁻¹) can reach 9861.41 dB cm² g⁻¹, which is much higher than other reported wood-based materials. In addition, the zeolitie imidazolate framework-8 ( ZIF-8) nanocrystals are grown in situ on the surface of the CWF to obtain CWF/ZIF-8. CWF/ZIF-8 exhibits an EMI shielding effectiveness (SE) of up to 46 dB and an ultrahigh SSE/t value of 11 330.04 dB cm² g⁻¹ in X band. In addition, the ultrathin CWF also shows an excellent Joule heating effect. Therefore, the development of ultrathin wood-based film provides a research basis for wood biomass to replace traditional non-renewable and expensive electromagnetic (EM) shielding materials.     

Structured Reduced Graphene Oxide/Polymer Composites for Ultra‐Efficient Electromagnetic Interference Shielding

A high‐performance electromagnetic interference shielding composite based on reduced graphene oxide (rGO) and polystyrene (PS) is realized via high‐pressure solid‐phase compression molding. Superior shielding effectiveness of 45.1 dB, the highest value among rGO based polymer composite, is achieved with only 3.47 vol% rGO loading owning to multi‐facet segregated architecture with rGO selectively located on the boundaries among PS multi‐facets. This special architecture not only provides many interfaces to absorb the electromagnetic waves, but also dramatically reduces the loading of rGO by confining the rGO at the interfaces. Moreover, the mechanical strength of the segregated composite is dramatically enhanced using high pressure at 350 MPa, overcoming the major disadvantage of the composite made by conventional‐pressure (5 MPa). The composite prepared by the higher pressure shows 94% and 40% increment in compressive strength and compressive modulus, respectively. These results demonstrate a promising method to fabricate an economical, robust, and highly efficient EMI shielding material.     

Ordered Mesoporous Carbon/Fused Silica Composites

A series of novel, dense, and interesting ordered mesoporous carbon (OMC)/fused silica composites with different carbon contents has been prepared by a controllable but simple sol‐gel method followed by hot‐pressing. In the as‐sintered OMC/fused silica composites the carbon particles still exist in the form of perfectly ordered carbon nanowires. Conductivity measurements on the composites indicate that these novel composites are electrically conductive and have a typical percolation threshold of 3.5–5 vol% OMC. The electromagnetic interference (EMI) shielding efficiency (SE) of an OMC/fused silica composite containing 10 vol% OMC is as high as 40 dB in the X band which is higher than that of a carbon nanotube (CNT)/ fused silica composite with the same carbon content (～30 dB). This indicates that these conductive OMC/fused silica composites are very suitable for an application as EMI shielding materials. Upon increasing the volume content of OMC in the composite the overall contribution as well as the increase rate of the microwave absorption are larger than those of the microwave reflection, which suggest that OMC/fused silica composites may also be promising electromagnetic (EM) wave absorbing materials. Based on the promising properties of these composites this work will hopefully lead to the development of new low‐cost and highly efficient EMI shielding or EM wave absorbing materials.     

密封条式屏蔽门的屏蔽效能仿真分析

使用中间层电路模型（ILCM）近似仿真分析屏蔽门对屏蔽室屏蔽效能的影响,对模型理论公式进行了推导和仿真,得出密封条式屏蔽门的屏蔽效能与影响参数之间的关系,为选择更适合屏蔽门密封的材料提供理论依据,并选择了两种材料进行对比验证,证明了推导出的关系是正确的,同时也预测了密封条结构的屏蔽室的屏蔽效能。仿真结果表明,我们选择的密封条式结构和材料能够满足屏蔽室的要求。     

Nickel filament polymer-matrix composites with low surface impedance and high electromagnetic interference shielding effectiveness

The processing of nickel filaments of 0.4 Μm diameter gives polyethersulfone-matrix composites with high electromagnetic interference shielding effectiveness, high reflection coefficient and low surface impedance at 1-2 GHz. With 7 vol.% nickel filaments, the composite exhibited shielding effectiveness 87 dB (compared to 90 dB for solid copper), surface impedance 1.2 Ω (same as for solid copper), tensile strength 52 MPa, modulus 5 GPa, ductility 1.0%, and density 1.87 g/cm³.     

High Electromagnetic Shielding of a 2.5-Gbps Plastic Transceiver Module Using Dispersive Multiwall Carbon Nanotubes

A novel polyimide film, consisting of finely dispersed multiwall carbon nanotubes (MWCNTs) in an ionic liquid (IL), is demonstrated to be high shielding effectiveness (SE) for use in packaging a 2.5-Gbps plastic transceiver module. The IL-dispersed MWCNT composite exhibits a high SE of 40 ~ 46 dB. By comparison, the composite fabricated by nondispersive process requires a higher loading of MWCNTs at 50 wt- % than the IL-dispersed process at only 30 wt-%. The electromagnetic susceptibility (EMS) performance is experimentally evaluated by the eye diagram and bit-error-rate for a 2.5-Gbps lightwave transmission system. The package housing fabricated by the dispersive MWCNT composites shows an enhanced EMS performance, an improved mask margin, and a lower-power penalty. These results indicate that the IL-dispersed MWCNT composites are suitable for packaging low-cost and high-performance optical transceiver modules used in the fiber to the home lightwave transmission systems.     

Low-cost and low-electromagnetic-interference packaging of optical transceiver modules

The low-cost and low-electromagnetic-interference (EMI) packaging of optical transceiver modules employing housings of plastic composites are developed and fabricated. Optical transceiver modules fabricated by the plastic composites with transmission rates of 1.25 and 2.5 Gb/s are tested to evaluate the electromagnetic (EM) shielding against emitted radiation from the plastic packaging. The results show that these packaged optical transceiver modules with their high shielding effectiveness (SE) are suitable for use in low-cost and low-EMI Gigabit Ethernet lightwave transmission systems. By comparison of cost, weight, and shielding performance for optical transceiver modules fabricated by the housings of nylon and liquid-crystal polymer with carbon fiber filler composites, woven continuous carbon fiber (WCCF), and nanoscale hollow carbon nanocapulses (HCNCs) epoxy composites, the WCCF composite shows lower cost, lighter weight, and higher EM shielding than the other types of composites. Future studies may develop the low-cost and low-EMI optical transceiver modules using nanoscale HCNCs that have the combination of excellent physical and mechanical properties, light weight, and thinness compared with the conventional fabrication techniques.     

金属网栅电磁屏蔽窗口薄膜的设计与制备

通过光刻掩膜技术、电阻热蒸发沉积技术制备电磁屏蔽窗口金属网栅薄膜,研究金属网栅的红外透射率和电磁屏蔽效能。为了能有效地屏蔽电磁波,使用CST Studio Suite电磁仿真软件设计不同周期、线宽的金属网栅,采用光刻掩膜技术、电阻热蒸发技术在双面抛光单晶硅基片上完成线宽为30μm,周期分别为350μm、450μm、550μm、650μm、750μm的金属网栅薄膜的制备。采用真空型傅立叶红外光谱仪和矢量网络分析仪分别对不同结构参数金属网栅薄膜的光谱特性和电磁屏蔽效能进行测试。结果:实现在双面抛光单晶硅基底上制备的网栅在12~18 GHz频段内,网栅的电磁屏蔽效能均达到12 dB以上。在3~5μm波段的透射率损失仅为8%。为了得到既具有高透光率,又具有强电磁屏蔽效能金属网栅薄膜需要合理设计金属网栅的线宽和周期。制备过程中网栅的光学-电学特性不仅受周期和线宽影响,掩膜板的加工精度、金属网栅的加工缺陷等也会造成不同程度的影响。     

High‐Performance Epoxy Nanocomposites Reinforced with Three‐Dimensional Carbon Nanotube Sponge for Electromagnetic Interference Shielding

Light‐weight and high‐performance electromagnetic interference (EMI)‐shielding epoxy nanocomposites are prepared by an infiltration method using a 3D carbon nanotube (CNT) sponge as the 3D reinforcement and conducting framework. The preformed, highly porous, and electrically conducting framework acts as a highway for electron transport and can resist a high external loading to protect the epoxy nanocomposite. Consequently, a remarkable conductivity of 148 S m^?1 and an outstanding EMI shielding effectiveness of around 33 dB in the X‐band are achieved for the epoxy nanocomposite with 0.66 wt% of CNT sponge, which is higher than that achieved for epoxy nanocomposites with 20 wt% of conventional CNTs. More importantly, the CNT sponge provides a dual advantage over conventional CNTs in its prominent reinforcement and toughening of the epoxy composite. Only 0.66 wt% of CNT sponge significantly increases the flexural and tensile strengths by 102% and 64%, respectively, as compared to those of neat epoxy. Moreover, the nanocomposite shows a 250% increase in tensile toughness and a 97% increase in elongation at break. These results indicate that CNT sponge is an ideal functional component for mechanically strong and high‐performance EMI‐shielding nanocomposites.     

静电放电电磁脉冲激励下材料屏蔽效能研究

为更好地评价电磁屏蔽材料对静电放电电磁脉冲的屏蔽效能,对静电放电脉冲激励下的材料的屏蔽效能进行了时域测试研究。以静电放电电磁脉冲为注入源,结合宽带同轴测试夹具和数字存储示波器,对一种平面材料的屏蔽效能进行了时域测试。通过得到的屏蔽前后的信号,计算了不同激励电压下该材料的峰值屏蔽效能,结果表明激励电压的大小对该材料的电磁脉冲屏蔽效能影响不大。通过对屏蔽前后信号的FFT 变换计算了其频域幅频特性曲线,与频域实验测试所得的幅频特性曲线进行了对比,结果比较一致。表明该时域测试系统能够可靠地评价材料对高压静电放电电磁脉冲激励下的衰减能力。     

弹体内置矩形腔屏蔽效能分析

为提高导弹强电磁脉冲防护能力,采用有限积分法对弹体内置矩形腔体的屏蔽效能 进行了数值模拟。重点分析了双层嵌套腔体屏蔽效能与单层腔体屏蔽效能之间的关系, 以及末制导雷达天线转动对壳体屏蔽效能的影响。结果表明：双层嵌套在L频段可提高屏蔽 效能3 0 dB左右,但在S频段嵌套腔体与内层腔体的屏蔽效能相当;当外层腔体与内层腔体上孔缝 共 振频率相近时,嵌套腔体屏蔽效能会急剧恶化;天线转动对屏蔽效能的影响与入射波频段相 关。该研究对提高导弹电磁防护能力具有指导意义。