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.

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℃.

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.

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.

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.

高性能环氧树脂基ECA的制备及机理分析

电子设备对小型化、高功率密度等要求越来越高,无铅化的提出使人们摒弃了传统的锡铅合金焊料,逐渐将目光转向新型的封装结构和材料,聚合物导电粘合剂又称导电胶(Electrically Conductive Adhesive,ECA),便是其中之一。本文系统地讨论对比了两大类环氧树脂作为基体的ECA性能,制备了一种高强度高导电的环氧树脂基导电银胶作为一种新的封装连接材料并解释了其性能优异的原因,传统聚合物在固化过程中形成的大量孔洞得到有效降低,ECA的电导率和强度从而得到大幅度提高。所制备出的高性能环氧树脂基ECA能够更好的适应封装材料的强度和导电导热需求。

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。

多道次ECAE动态成型Al-Mg-Si合金导线组织与性能

借助S4800扫描电子显微镜、Philips DM420透射电子显微镜、SANS CMT5105电子万能材料试验机和QJ48双臂直流电桥,研究了多道次ECAE动态成型Al-Mg-Si合金导线的组织与性能。结果表明:4道次ECAE动态成型可制备平均尺寸在10μm左右甚至更小的Al-Mg-Si合金导线晶粒。随着Mg、Si含量的增加,合金导线的抗拉强度增大,伸长率与等效导电率降低。经160~170℃/7h时效处理后,Al-0.59%Mg-0.59%Si合金导线的抗拉强度、伸长率和等效导电率分别为305.71~309.63 MPa,4.7%~5.4%和55.18%IACS^56.33%IACS,与目前国产Al-Mg-Si合金导线(295 MPa,52.5%IACS)相比,导电性能显著提高。

G-Eco-AAc/OTF复合层导电水凝胶的制备及在柔性传感领域的应用

导电水凝胶作为一种高性能聚合物材料,被广泛应用于柔性传感器与储能设备等领域。然而,大多数导电水凝胶均为单层结构,且力学性能较弱。而复合层水凝胶可以通过各层之间的结合,进行力学性能上的互补。因此,需要从水凝胶的结构上进行设计,使其具有优异的力学性能,并具有更多功能。在此,通过原位聚合的方式,将石墨烯层、Ecoflex弹性体和AAc/OTF水凝胶进行聚合,制备了一款兼具黏附性能、力学拉伸性能和导电性能的复合层水凝胶G-Eco-AAc/OTF。由于水凝胶表面羧基、羟基和磺酸基团的存在,该水凝胶材料展示了良好的黏附性。将G-Eco-AAc/OTF复合层导电水凝胶应用于运动传感领域,可对手指、手腕、肘部和膝盖处进行信号的监测,并且测试结果稳定。这为下一代可穿戴柔性传感设备奠定了基础。

一种无溶剂型电子封装用导电胶的研制

为了解决导电胶黏剂因综合性能不足而导致大规模应用的受限,本文以酚醛环氧、多官能环氧为导电胶树脂基体,选用了4,4′-二氨基二苯砜(DDS)作为固化剂,片状银粉作为导电填料,通过调节银粉和固化剂的用量,制备了有良好流变性、导电性、力学性能的导电胶。通过分析测试,得到导电胶的黏度为32 800 mPa·s,触变指数为4.0,体积电阻率为4.34×10^(-4)Ω·cm,剪切强度为17 MPa,热导率为3.96 W/(m·K),Cl^(-)、Na^(+)和K^(+)分别仅为6.79×10^(-5)、6.31×10^(-5)和<10^(-5)。该导电胶综合性能优异,可应用于电子元器件及其他导电导热功能性材料的粘接。

导电胶在高温老化与温度冲击中的失效模式研究

针对我国航天领域使用较为广泛的HD-903型改性环氧树脂导电胶,本研究采用高温老化和温度冲击来加速导电胶在服役环境中的变化,从而对导电胶的可靠性展开研究。在试验过程中,通过对导电胶试样的形貌组织进行观察,并测量其体积电阻率和芯片剪切强度,通过其性能的变化来反映导电胶内在变化的规律。研究结果表明:在150℃下老化过程中,导电胶的体积电阻率先下降随后不断增加,同时芯片剪切强度先升高后下降。高温老化5000 h后体积电阻率相比老化前增加81.0%,芯片剪切强度为老化前的56.5%。温度冲击3000次后,导电胶的体积电阻率较试验前升高77.2%,芯片剪切强度仅为试验前的13.8%。分析认为,导电胶在高温老化中主要发生银粉的氧化和树脂基体的老化,一方面破坏银粉与树脂基体之间的界面结构,另一方面树脂基体的老化使其发生严重松弛,引起体积电阻率的大幅提高和胶体强度的下降。在温度冲击过程中,由于导电胶与芯片、可伐镀金基板的热膨胀系数存在差异,由此在交变应力载荷作用下引发粘接接头的蠕变和疲劳,先后在接头靠近芯片一侧和靠近基板一侧分别产生裂纹并逐渐扩展,最终造成接头强度的大幅度降低。

太阳能叠瓦组件用导电胶黏剂的研制

针对叠瓦组件对导电胶黏剂的要求,研制了基于丙烯酸基体树脂的单组分导电胶。对导电胶的粘度和触变性能,存储期和可操作时间,固化速度,黏结性能,导电性能等进行了全面表征。结果表明研制的导电胶具有杰出的综合性能。将导电胶用于叠瓦组件的粘接,并验证组件的功率,组件功率接近理论功率。制备的导电胶在商业化的叠瓦组件上具有较为广阔的应用前景。

耐400℃高温氰酸酯导电胶的制备与性能

为了解决芯片密封封装时管壳高温焊接导致的芯片脱粘、封装内产气等问题,本工作首次以耐高温氰酸酯树脂为基体、高纯片状Ag粉为填料,制备了耐400℃高温的氰酸酯导电胶。微观结构分析结果表明,片状Ag颗粒在氰酸酯基体中随机分布,形成了较好的导热导电网络,且去除Ag粉表面有机物可以有效抑制氰酸酯导电胶粘接固化后气泡和裂纹的产生。热性能分析表明氰酸酯导电胶具有优异的热稳定性,其在300℃下的失重率仅有0.06%,400℃下的失重率小于0.3%,远低于目前公开报道的导电胶在相同温度下的失重率。氰酸酯导电胶的玻璃化温度(Tg)为240℃,低于和高于Tg时的热膨胀系数分别为51.2×10^(-6)/℃和162.2×10^(-6)/℃,具有较宽的使用温度范围。环境实验和力学性能测试表明,氰酸酯导电胶具有优异的粘接性能和环境适应性,330℃固化后的导电胶在环境测试后平均芯片剪切强度高达18.4 MPa。本工作制备的氰酸酯导电胶具备优异的综合性能,对电子封装用高温导电胶的研发和应用具有重要的参考价值。

树枝状银粉及表面处理对导电银胶的性能影响

针对导电胶电导率较低,接触电阻不稳定,冲击强度差等问题,研究树枝状银粉作为导电填料对导电胶性能的影响,结果表明,与片状银粉制备的导电胶相比,掺杂树枝状银粉的导电胶表现出更好的导电性能,其体积电阻率降低了0.8×10^(-3)Ω·cm。在此基础上,探索了油酸和KI等表面处理剂对导电胶的导电性、力学特性等影响,并分析了导电胶导电性能的提升机制。结果表明,表面处理剂种类对导电胶性能具有选择性的改善作用,KI处理后的导电胶具有较好的导电性能,且树枝状银粉为填料的导电胶表现出最低的电阻(0.9Ω)。油酸处理后的导电胶表现出较好的力学性能,且片状银粉为填料的导电胶具有较好的剪切力(570 N),为导电胶产品研发提供技术支撑。

不同形貌镀银铜粉导电胶的制备及表征

采用凝胶法制备了高导电率导电胶,其导电填料为基于铜粉的树枝状、片状和球状镀银铜粉。通过四探针测试仪,测量了导电胶的体积电阻率,表征了导电胶的导电性能。采用旋转流变仪和万能拉力机得到导电胶的黏度和剪切强度,分析了导电胶的流变特性和力学性能。结果表明:三种形貌中,由于树枝状粒子的接触点最多且导电通道数量大,使得相同含量下,树枝状镀银铜粉导电胶的导电性能最优。在180℃下添加量为70%的树枝状镀银铜粉导电胶,固化时间2 h,拉拔附着力和黏度为19 MPa和1.08×10^(6) mPa·s,最佳体积电阻率为3.5×10^(-4)Ω·cm。研究结果为制备高性能导电胶提供了可行的方案。

天线罩表面导电涂层的制备工艺及性能研究

为解决由碳纤维复合材料制备的雷达天线罩自身导电性能差、反射能力弱和空间防护能力不高的问题,先通过电弧喷涂技术在Q235钢模具表面制备铝涂层,然后在碳纤维复合材料固化的过程中将其转移至天线罩表面。研究了电弧喷涂时的主要工艺参数对铝涂层孔隙率的影响,得到最佳的工艺参数为:空气压力0.6 MPa,喷涂距离300 mm,喷涂电压28 V。扫描电镜表征和热淬法测试表明,通过上述方法在天线罩表面制备的导电涂层均匀连续,表面致密,无裂纹、空腔和外来夹杂物,结合力良好。

导电胶粘剂的研究进展

导电胶粘剂的发展对电子技术的发展有着极其重要的意义。介绍了导电胶粘剂的分类、组成、导电机理和研究现状,并指出了导电胶粘剂在实际应用中需要解决的问题。

基于电磁感应的典型干旱区土壤盐分空间异质性

为研究干旱区土壤盐分空间异质性,指导农业生产实践,运用大地电导率仪(EM38、EM31)对研究区域进行移动式磁感调查,获取表观电导率(ECa)。同时,通过27个校准点的采样和ECa测量,建立土壤盐分的电磁感应解译模型。干旱区土壤盐分质量分数与EM38、EM31水平模式读数(H38、H31)显示出良好的相关性(R=0.935),可以利用ECa结合GIS和地统计学知识研究土壤盐分的空间分布。采用两种方法进行研究:一种是先利用解译模型获取磁感调查点的土壤盐分质量分数,然后进行地统计分析研究其空间分布;另一种是先利用地统计分析研究H38和H31的空间分布,然后利用解译模型通过栅格运算计算盐分质量分数,精度检验显示前者预测值与实测值之间的相关性更好(R2,0.888>0.873);标准差较低(std.0.414<0.426),具有更高的预测精度。研究结果表明,基于电磁感应研究干旱区土壤盐分空间异质性是切实可行的,这对于土壤盐渍化的快速诊断,指导农业生产和促进精准农业的发展具有重要的意义。

LED典型失效机理

鉴于LED芯片尺寸较小,散热和成本的压力,LED封装难度很大,暴露出来的可靠性问题也最多。LED失效后,往往能够通过电参数测试、内部形貌分析、剖面检查、SEM检查等方法暴露失效现象、分析出失效机理,最终提出改进意见,提高器件的良品率。根据失效分析实例剖析了LED典型失效机理:LED芯片缺陷和腐蚀;LED芯片粘结用导电胶腐蚀、使用不当导致开路或短路;LED芯片金丝键合损伤;LED封装结构设计不当,导致机械应力集中损伤芯片;LED器件使用不当——过流烧毁、ESD损伤、焊接不良或焊料迁移。并分别提出了相应的改进建议。