Conductive microsphere monolayers enabling highly conductive pressure-sensitive adhesive tapes for electromagnetic interference shielding

Conductive adhesive tape is one kind of electromagnetic interference(EMI)shielding materials for electronic packaging.However,the inferior conductivity of the pressure-sensitive adhesive(PSA)layer results in serious electromagnetic leakage at the conjunctions between the conductive tapes and target objects.Adding conductive fillers is a traditional method for highly conductive adhesive tapes.However,the content of conductive fillers is needed to reach the percolation threshold,which is usually as high as tens of percent.High-content fillers result in significant loss of adhesive property and high fabrication cost.Herein,we introduce a rational architecture of conductive microsphere monolayer(CMM)in the PSA layer.The CMM connects the top and bottom surfaces of the PSA layer and improves its conductivity in the z-direction.Importantly,low contents of conductive microspheres(≤5%(mass fraction,w))can achieve the target of conductivity improvement,but not result in the serious loss of the adhesive property.Therefore,the strategy of CMMs can balance the tradeoff between the conductivity and the adhesive property of conductive PSA tapes.Finally,we demonstrate the superior EMI shielding performance of as-made conductive adhesive tapes,indicating their potential applications as the advanced EMI shielding materials in the electronic packaging.

Application of face centred cubic TiB powder as conductive filler for electrically conductive adhesives

Face centred cubic（FCC） TiB ceramic powder synthesized by Ti-boronizing method was used as conductive filler to make ceramic electrically conductive adhesives（ECAs） with the polymer matrix.Electrically conductive properties of the ceramic ECAs were studied.The bulk electrical resistivity varied with the powder content of the FCC-TiB in ECAs.The FCC-TiB filled ECAs also showed the percolation behavior that usually occurred for the metal-filled ECAs,the percolation threshold was located at the content of 60%FCC-TiB.A minimum value of 0.1 Ω·cm was obtained at a content of 75%FCC-TiB.In order to check the reliability of mechanical property,tensile test was done to measure the shear strength,and the shear strength dropped with increasing the content of FCC-TiB powders.It is about 12.26 MPa at the content of 70%TiB powders.The Cu filled ECAs were also prepared for comparison.The properties of the oxidation resistance of the two ECAs were evaluated.The results show that the ceramic ECAs have excellent oxidation resistance and better stability compared with the Cu filled ECAs.

Preparation of Electrically Conductive Filler for Anisotropic Conductive Adhesive

The preparation process of electrically conductive filler for anisotropic conductive adhesive was performed and discussed.The spherical filler contains tri-layer structures: resin core,Ni-P intermediate coating layer,Au outer coating layer.The 4 μm resin spherical cores were synthesized by monodispersion polymerization method.Then they were contributed to electrical conductivity by electrolessly plating Ni-P layer and gold layer.These particles have good corrosion resistance,high stability,and enough mechanical strength.When mixed with thermosetting epoxy resin to produce anisotropic conductive adhesive(ACA),it can realize a good conductive bonding between bumps on dies and pads on substrates.This environmentally friendly conductive material offers numerous advantages over conventional solder technology and is an ideal substitute for the lead-contained solder in electronics packaging.

Mussel‑Inspired Redox‑Active and Hydrophilic Conductive Polymer Nanoparticles for Adhesive Hydrogel Bioelectronics

Conductive polymers(CPs)are generally insoluble,and developing hydrophilic CPs is significant to broaden the applications of CPs.In this work,a mussel-inspired strategy was proposed to construct hydrophilic CP nanoparticles(CP NPs),while endowing the CP NPs with redox activity and biocompatibility.This is a universal strategy applicable for a series of CPs,including polyaniline,polypyrrole,and poly(3,4-ethylenedioxythiophene).The catechol/quinone contained sulfonated lignin(LS)was doped into various CPs to form CP/LS NPs with hydrophilicity,conductivity,and redox activity.These CP/LS NPs were used as versatile nanofillers to prepare the conductive hydrogels with long-term adhesiveness.The CP/LS NPs-incorporated hydrogels have a good conductivity because of the uniform distribution of the hydrophilic NPs in the hydrogel network,forming a well-connected electric path.The hydrogel exhibits long-term adhesiveness,which is attributed to the mussel-inspired dynamic redox balance of catechol/quinone groups on the CP/LS NPs.This conductive and adhesive hydrogel shows good electroactivity and biocompatibility and therefore has broad applications in electrostimulation of tissue regeneration and implantable bioelectronics.

Deformation characterization of conductive particles in anisotropically conductive adhesive simulated by FEM

The deformation behavior and the contact area of conductive particles in anisotropically conductive adhesives (ACA) were investigated by finite element method (FEM). The solid conductive particles are made of pure Ni and Cu. The results indicate that the deformation of the conductive particles is inhomogeneous during fabrication. When the reduction in height is small the deformation concentrates in the area near the contact area. As the reduction in height increases, the strain in the area near the contact area increases, and the metal flows toward the circumference, resulting in the increase of the contact area between the conductive particles and pad. The higher the degree of deformation, the larger the contact area. The regression equations were offered to express the relations between the bounding force and the contact area or the reduction in height. An approach of how to obtain the maximum contact area in ACA was discussed.

Electrochemical migration behavior of Ag-plated Cu-filled electrically conductive adhesives

The electrochemical migration (ECM) behavior of the electrically conductive adhesives (ECAs) filled with pure Ag powder or Ag-plated Cu composite powder with varied Ag:Cu ratios was investigated under the condition of applying constant voltage and distilled water environment.ECM resistance was determined from the current-time curves.The microstructure and composition of ECM dendrite products were analyzed by SEM/EDS and XRD.It was found that the ECM resistance of Ag-plated Cu composite powder-filled ECAs was evidently higher than that of pure Ag powder-filled ECAs.The Ag:Cu ratio of composite powder in ECAs had notable influence on ECM resistance,which was enhanced with the decrease of Ag:Cu ratios.The composition of dendrites formed between cathode and anode during ECM process was not uniform for Ag-plated Cu-filled ECAs.An ECM inhibiting mechanism of Ag-plated Cu composite powder was proposed according to analysis of the electrochemical impedance spectroscopy,Tafel plot and dendrite composition.

Application of silver nanoparticles in electrically conductive adhesives with silver micro flakes

This study has been conducted to evaluate the application of silver nanoparticles(NPs)in Electrically Conductive Adhesives(ECAs),filled with hybrid silver flakes and NPs,and silver flakes as a control sample,at a filler loading of 78 wt.%,83 wt.%and 88 wt.%and cured at 150℃and 180℃,respectively.The results show that the electrical and thermal conductivities of ECAs were improved with the increasing of filler loading and curing temperature.Adding silver NPs in silver flakes negatively affected the electrical and thermal conductivities of ECAs at a low filler mass fraction of 78 wt.%,because the segregation of NPs enlarged the average distance of silver flakes;while it positively influenced the electrical and thermal conductivities of ECAs at a loading ratio of 88 wt.%,probably due to NPs filling in the gaps between silver flakes or even sintering together with each other or with silver flakes,especially when curing at high temperature of 180℃.

Reliability aspects of electronics packaging technology using anisotropic conductive adhesives

Anisotropic conductive adhesive technology for electronics packaging and interconnect application has significantly been developed during the last few years. It is time to make a summary of what has been done in this field. The present paper reviews the technology development, especially from the reliability point of view. It is pointed out that anisotropic conductive adhesives are now widely used in many applications and the reliability data and models have been developed to a large extent for anisotropic conductive adhesives in various applications.

Preparation and Performance of Graphene Oxide Modified Polyurethane Thermal Conductive Insulating Adhesive

A novel graphene oxide (GO) modified polyurethane thermal conductive insulating adhesive with small addition and excellent insulation properties was prepared by in-situ polymerization using GO as thermal conductive filler.The effects of GO content on the mechanical performance,thermal conductivity,thermal stability and insulation properties of the modified polyurethane adhesive were studied.The results showed that the tensile strength and elongation at break of polyurethane adhesive increased at first and then decreased with the increase of GO content.The thermal conductivity and thermal decomposition temperature of GO/PU composite adhesive can be effectively improved by adding appropriate amount of GO.The tensile strength,thermal conductivity and thermal decomposition temperature of polyurethane adhesive reached the maximum when GO content was 1.5 wt%.The novel GO-modified polyurethane adhesive exhibited good insulation property.The development of GO/PU thermal conductive adhesive will provide a facile method for effectively solving the “trade-off” problem between low filling and high thermal conductivity.

Effect of Curing Procedure on the Properties of Copper-Powder-Filled Conductive Adhesives

By means of testing the shear strength with single lap joint, measuring electrical resistivity for cured products and the curing strain with strain gauges, the effect of cure parameters on the properties of HT1012 conductive adhesive filled with copper powder was investigated, and the residual stress in the conductive adhesives was also estimated. The experimental results show that the properties such as shear strength of the adhesives, electrical resistivity of products as well as the residual stress of cured HT 1012 copperfitted conductive adhesive were evidently affected by curing temperature and time. The diagrams of scanning electron microscopy （SEM） and Fourier transform infrared （FT-IR） were also used to determine the properties. The higher mechanical property was achieved under the condition of curing the adhesive 3 h at 60 ℃ as the density of the hydrogen links or linkages existed in the adhesive was relatively higher and the lower electrical resistivity occurred at 80 ℃.

Thermoelectric Behavior of Isotropically Conductive Adhesive

The paper deals with unusual use of one kind of ECA （electrically conductive adhesive）---the ICA （isotropic conductive adhesive）. The main sphere of ECA application is electronic assembly, e.g., it is bonding of semiconductor microchips on printed circuits boards. In this sphere, the ECA compete with soft solder. In spite of this fact, the author utilized of two main ECA characteristics--good electrical conductivity and excellent adhesion to material surfaces to make the fiat thermocouples. Both the design of thermocouples and the measuring device and the measuring workplace arrangement are described. The measured data of thermoelectric voltages are plotted. The thermoelectric （Seebeck＇s） coefficients were calculated from obtained dependences of thermoelectric voltage versus the temperature differences.

THR EFFECT OF OXIDE LAYER FORMATION ON THE ADHESION OF CONDUCTIVE POLYMER COATING TO A MILDSTEEL

Arolled mild steel wascoated byconductive polymers( polyaniline/ MMPand polyaniline/HCSA) andthenim mersedin hot water(50 ℃) fordifferenttimesforstudytheadhesion ofcoatings.It wasfound thatthe adhesion tendsto decrease over time. Thestudyshown that onebrittle and porous Fe3 O4 layer formed between conductive polymercoating and steelsub stratein a moistenvironmentand, asa result, decreased thecoating adhesions.

Highly Stretchable Shape Memory Self-Soldering Conductive Tape with Reversible Adhesion Switched by Temperature

With practical interest in the future applications of next-generation electronic devices,it is imperative to develop new conductive interconnecting materials appropriate for modern electronic devices to replace traditional rigid solder tin and silver paste of high melting temperature or corrosive solvent requirements.Herein,we design highly stretchable shape memory self-soldering conductive(SMSC)tape with reversible adhesion switched by temperature,which is composed of silver particles encapsulated by shape memory polymer.SMSC tape has perfect shape and conductivity memory property and anti-fatigue ability even under the strain of 90%.It also exhibits an initial conductivity of 2772 S cm^(−1) and a maximum tensile strain of~100%.The maximum conductivity could be increased to 5446 S cm^(−1) by decreasing the strain to 17%.Meanwhile,SMSC tape can easily realize a heating induced reversible strong-to-weak adhe-sion transition for self-soldering circuit.The combination of stable conductivity,excellent shape memory performance,and temperature-switching reversible adhesion enables SMSC tape to serve two functions of electrode and solder simultaneously.This provides a new way for conductive interconnecting materials to meet requirements of modern electronic devices in the future.

Design and Characterization of Electrical Connections for Conductive Yarns

The development of flexible and stretchable electronics has attracted much attention.As an important part of wearable electronic systems,the connection between conductive yarns and electronic components affects the stability and accuracy of their electrical reliability.In this paper,three different connections were attempted to electrically and mechanically link two conductive yarns,including soldering followed by waterborne polyurethane(WPU)encapsulation,coating of conductive silver adhesive with WPU encapsulation,as well as coating of conductive silver adhesive with polydimethylsiloxane(PDMS)encapsulation.The surface morphologies and electro-mechanical behaviors of the three created connected conductive yarns were characterized.Compared with their electro-mechanical behaviors of the established three connections,the connection with soldering remained electrically conductive to around 200%,which mainly came from the stress concentration between the stiff soldering and soft conductive yarns.However,the coating of conductive silver adhesive and encapsulated protection of PDMS can make the connected conductive yarns stretchable up to 300%with almost constant electrical resistance.

高灵敏、强粘附性导电水凝胶的制备及在柔性传感中的应用

导电水凝胶由于优异的韧性与生物相容性,在人机交互、电子皮肤领域有良好的应用前景,然而在实际的应用场景中为了得到准确响应的信号则需要更优异的粘附性和灵敏度。本工作以2-丙烯酰胺-2-甲基丙磺酸(AMPS)和丙烯酰胺(AM)共聚制备了导电水凝胶材料,该水凝胶在紫外光照条件下通过巯基攻击碳碳双键快速聚合。其对猪皮肤的粘附强度达到525 kPa,对铝片的粘附强度高达817 kPa。区别于传统的制备方法,本工作在不添加任何导电填料的条件下所制得水凝胶的电导率达到1.08 S/m,且灵敏度因子(GF)达到9.28,避免了因导电填料分散不均而导致的力学性能差且灵敏度不高的问题。此外,该水凝胶有良好的抗冻性,即使在-60℃的条件下仍能正常工作。得益于高灵敏度和强粘附性,P(AMPS-co-AM)水凝胶可组装成柔性应力或应变传感器精确地检测人体不同部位的微小与大幅度动作,具有准确响应性和良好稳定性,在电子皮肤及柔性可穿戴设备领域有很大的应用潜力。

Mussel-inspired nanozyme catalyzed conductive and self-setting hydrogel for adhesive and antibacterial bioelectronics

Adhesive hydrogels have broad applications ranging from tissue engineering to bioelectronics;however,fabricating adhesive hydrogels with multiple functions remains a challenge.In this study,a mussel-inspired tannic acid chelated-Ag(TA-Ag)nanozyme with peroxidase(POD)-like activity was designed by the in situ reduction of ultrasmall Ag nanoparticles(NPs)with TA.The ultrasmall TA-Ag nanozyme exhibited high catalytic activity to induce hydrogel self-setting without external aid.The nanozyme retained abundant phenolic hydroxyl groups and maintained the dynamic redox balance of phenol-quinone,providing the hydrogels with long-term and repeatable adhesiveness,similar to the adhesion of mussels.The phenolic hydroxyl groups also afforded uniform distribution of the nanozyme in the hydrogel network,thereby improving its mechanical properties and conductivity.Furthermore,the nanozyme endowed the hydrogel with antibacterial activity through synergistic effects of the reactive oxygen species generated via POD-like catalytic reactions and the intrinsic bactericidal activity of Ag.Owing to these advantages,the ultrasmall TA-Ag nanozyme-catalyzed hydrogel could be effectively used as an adhesive,antibacterial,and implantable bioelectrode to detect bio-signals,and as a wound dressing to accelerate tissue regeneration while preventing infection.Therefore,this study provides a promising approach for the fabrication of adhesive hydrogel bioelectronics with multiple functions via mussel-inspired nanozyme catalysis.

Electrically Detaching Behavior and Mechanism of Ionic Conductive Adhesives

Design of rapidly detachable adhesives with high initial bonding strength is of great significance but it is full of great challenge. Here, we report the fast electrically detaching behavior (100% detaching efficiency in just 1 min under dozens of DC voltage) and high initial bonding strength (>12 MPa) of epoxy-based ionic conductive adhesives (ICAs). The epoxy-based ICAs are fabricated by introducing polyethylene glycol dimethyl ether (PEGDE) and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM]OTF) into epoxy. The combination of PEGDE and [EMIM]OTF enables the free ions to migrate directively in electric field, and the anchoring of PEG chains onto epoxy chains ensures the long-term reliability of ICAs. The investigation on the electrically detaching mechanism suggests that the enrichment and following rapid interfacial electrochemical reactions of [EMIM]OTF lead to formation of metal hydroxide (Me(OH)n) nanoparticles at the bonding interfaces, thus the strong interactions containing interlocked forces, van de Waals’ forces and hydrogen bonding interactions between ICAs and bonding substrates are destroyed. This work provides a promising direction for detachable adhesives with both high initial bonding strength and high detaching efficiency in short time.

基于无颗粒银导电墨水在不锈钢表面镀银工艺研究

目的采用无颗粒银导电墨水对不锈钢表面进行镀银研究,以绿色环保工艺替代传统电镀银技术。方法主要研究适用于不锈钢基材的前驱体银源、络合剂种类、不锈钢前处理方法、烧结固化温度对不锈钢表面银层微观结构及性能的影响,获得不锈钢基材上微观结构致密、性能良好的银层。采用X射线衍射仪、扫描电子显微镜、激光共聚焦显微镜、数字兆欧表对在不锈钢表面银膜层进行表征。结果不锈钢通过1,2丙二胺溶液处理后,采用银源草酸银为前驱体,此时银层微观结构最致密,具有最佳的附着力等级(5B)和最低的粗糙度(1.237μm),与1,2-丙二胺络合,乙醇为溶剂时,制备出的银层有机物挥发完全,微观结构致密,并且具有最低的接触电阻0.7Ω和粗糙度0.80μm。烧结固化温度为200℃时银层导电性最好。结论采用无颗粒银导电墨水对不锈钢表面进行镀银的新型工艺银层性能良好,可以简化传统电镀技术复杂的操作流程,减少传统电镀工艺所使用氰化物对人体造成的危害,并弥补应用受限的缺点。

某高导热绝缘胶在星载端机可靠性应用评价

针对星载端机对高导热绝缘底填胶可靠性应用需求,开展双组分高导热绝缘胶可靠性及环境适应性综合影响评估。通过导热绝缘胶性能测试标准样件,测试验证本征性能指标及工艺性指标,并分析评估其合格性;设计制作典型BGA菊花链网络结构样件,采用导热胶填充工艺技术,验证导热绝缘胶空洞率对BGA器件焊点的影响,评价其工艺适应性;设计制作星载端机载荷,开展星载产品验收级环境与可靠性试验,验证端机载荷具有经受工作应力和环境应力的能力。该高导热绝缘胶满足星载产品散热及抗高载荷的需求,实现可靠性应用。

胶黏剂检测评价技术研究进展

综述了胶黏剂的检测评价技术,重点介绍了胶黏剂常规性能检测评价技术,包括耐高温和超低温胶黏剂、导电胶黏剂、无色透明胶黏剂、高导热胶黏剂、环保型胶黏剂特种性能的检测评价技术,详细讨论了各种检测评价技术的特点和方法。通过对胶黏剂现有的检测和评价方法系统的梳理、整合,建立起高水平、系统、完整、科学、有效、规范的胶黏剂检测表征与评价体系。结合实际情况,提出了胶黏剂检测评价领域未来研究的发展方向及关键所在。