无铅电子组装材料——导电胶的研究进展

电子产品小型化、便携化、集成化的趋势和人类环保意识的增强,使传统的电子组装材料已不能满足现实的需要。导电胶作为一种无铅、绿色、环境友好的新型电子组装材料,正日益成为电子工业中组装材料的主流。该文对导电胶的组成、分类、导电机理、导电胶的导电填料、聚合物粘料、添加剂等基本组成材料和导电胶性能研究进展作了综述。引用文献43篇。     

提高导电胶性能的研究进展

导电胶作为一种新型的绿色微电子封装互连材料,其应用范围越来越广,并且其代替传统的Pb-Sn焊料已成为必然趋势。介绍了导电胶的研究应用现状,总结了导电胶的优点及存在的问题。综述了近几年来在提高导电胶的电导率、接触电阻稳定性以及力学性能等方面的研究进展,并展望了导电胶未来的发展方向。     

环氧树脂导电胶的研究现状

环氧导电胶是代替Sn/Pb焊料的一种胶黏剂,与传统的Sn/Pb焊料相比,环氧导电胶具有粘接温度低、可控性好、分辨率高、工艺简便以及环保等优点。近年来,科研工作者积极地研发高性能、多功能以及低成本的新型导电胶,以满足不断发展的市场需求。环氧导电胶作为一种新型的复合工业材料,具有巨大的发展潜力以及广阔的应用前景。阐述了影响环氧导电胶黏剂性能的因素以及高性能环氧导电胶的研究状况,并对环氧导电胶黏剂的未来发展作了展望。     

铜粉导电胶研制成功

近些年来,导电胶粘剂在微电子封装、组装行业中得到了广泛应用,目前仍以添加型导电胶占据主导地位。在各种导电胶中金粉导电胶性能最佳,但价格昂贵,应用受限;银粉导电胶效果很好,不过存在着电迁移等弊端,价也很高;铜粉导电胶的导电性能基本接近银粉导电胶,价格便宜,却因铜粉极易氧化而影响导电性能。东北大学材料与冶金学院采用硅烷偶联剂（KH-550）对铜粉进行改性处理,提高了其在导电胶中的分散性、使用过程中的抗氧化性和粘接强度。还将甲醛作为还原剂加入到树脂中,     

微电子封装用导电胶的研究进展

随着现代科学技术的高速发展,电子产品向小型化、便携化和集成化方向发展。导电胶作为一种"无铅、绿色和环境友好"的新型材料取代传统的Pb/Sn材料,已成为电子工业组装材料的主流。简述了微电子封装用导电胶的组成和分类、研究进展和可靠性评估,提出了导电胶在微电子封装中的技术问题,并对其发展趋势和发展前景作了展望。     

新型导电胶的研究与应用

本文介绍了新型复合导电材料--导电胶的种类及其特点,探讨了导电胶的导电机理和影响其性能的主要因素,对导电胶的研究和应用状况也做了简要介绍。     

汉高推出新有机硅导电胶

随着汽车电气系统的结构、工作环境的日趋复杂,其中相关材料性能也必须得到相应提升,汽车传感器材料需要有个更强的抗震性、耐温性。汉高近日开发出一款全新的有机硅导电胶(ECA),能够应对复杂、恶劣的系统环境。ICP4000系列导电胶能够承受200℃的高温,此外能够承受强烈的振动。导电胶是一种固化或干燥后具有一定导电性能的胶粘剂,它通常以基体树脂和导电填料即导电粒子为主要组成成分,通过基体树脂的粘接作用把导电粒子结合在一起,形成导电通路,实现被粘材料的导电连接。由于导电胶的基体树脂是一种胶粘     

一种耐高温导电胶的研制

以酚醛型氰酸酯树脂作为导电胶基体,以片状银粉作为填充材料,制备了耐高温型导电胶。采用咪唑类固化剂、醋酸酯类稀释剂调节导电胶的固化工艺和黏度,并对其进行了热机械性能、机械强度和导电/导热性能研究。研究结果表明：导电胶的玻璃化转变温度为232℃,100和250℃时的动态模量分别为6 271、273 MPa,玻璃化转变前的热膨胀系数为36.63μm/(m·K),高温时可稳定施工作业;该导电胶在320℃条件下静置10 min后剪切强度提升40%,说明高温处理不会影响导电胶的剪切强度;该导电胶的体积电阻率极低(3.48×10^-6Ω·m),导电性能优异,优于市场上同类导电胶。     

微电子互连用导电胶研究进展

导电胶具备无铅、分辨率高、柔韧性好、加工工艺简单、低温操作等优点而使其成为替代传统Sn/Pb钎料的理想的微电子互连材料。本文对微电子互连用导电胶的组成、分类、机理和研究现状等进行了综述。为进一步研究开发新型性/价比高的微电子互连用导电胶提供思路。     

碳系导电胶的研究进展

介绍了导电胶的种类,重点综述了碳系导电胶[如导电炭黑导电胶、石墨导电胶、碳纳米管(CNTs)导电胶、石墨烯导电胶和碳纤维导电胶等]、复合导电胶(如Ag/CNTs导电胶、Ag/石墨烯导电胶等)的研究进展。最后对碳系导电胶的研究方向进行了展望。     

High performance electrically conductive adhesives from functional epoxy,micron silver flakes,micron silver spheres and acidified single wall carbon nanotube for electronic package

To develop high performance electrically conductive adhesives (ECAs), bi-modal ECAs were prepared by a matrix resin, micron silver flakes and micron silver spheres, and tri-modal ECAs were prepared by a matrix resin, micron silver flakes, micron silver spheres and acidified single wall carbon nanotube (ASWCNT). With the increase of nano silver spheres, the bulk resistivity of bi-modal ECAs decreased firstly and then increased while tri-modal ECAs' bulk resistivity firstly increased and then decreased with the increase of ASWCNT due to different electrically conductive channels were formed in them. After aged for 500 h under humid and thermal cycle of constant humidity level of 85% relative humidity at 85 °C, the contact resistance shift of bi-modal ECAs was more than 20% and that of tri-modal ECAs was less than 15% showing tri-modal ECAs had lower and more stable contact resistance. The humid and thermal surroundings had bad effect on the mechanical properties of bi- and tri-modal ECAs, after aged for 500 h, they both were reduced about 50–65%. And a bi-modal ECAs and a tri-modal ECAs were optimized and investigated in detail which can be used in electronic packaging.     

Electrical and mechanical properties of electrically conductive adhesives from epoxy,micro-silver flakes,and nano-hexagonal boron nitride particles after humid and thermal aging

In this study, we incorporated micro-silver flakes and nano-hexagonal boron nitride (BN) particles into a matrix resin to prepare electrically conductive adhesives (ECAs). The humid and thermal aging results under a constant relative humidity level of 85% at 85 °C revealed that the aged ECAs containing 3 wt% of nano-hexagonal BN particles had high reliability. The contact resistance was low and the shear strength high. Nano-hexagonal BN particles have a good effect on the reliability of ECAs that can be used to improve the properties of ECAs.     

Study on the properties of conductive adhesives in various curing manners for MCM applications

In this work, the properties of solvent and solvent-free electrically conductive adhesives (ECAs) in four curing manners and after solder reflows are investigated for multi-chip module applications. The curing behaviors and thermal degradation of solvent and solvent-free ECAs are also studied by differential scanning calorimeter and thermogravimetric analysis, respectively. The bulk resistivity of ECAs in four curing manners is significantly different, even if they are cured at the same temperature and time. The conductive trends of solvent and solvent-free ECAs are also different. The good and poor conductive properties of solvent ECA are obtained at curing temperature starting from room temperature and setting temperature, respectively. However, the results of solvent-free ECA are opposite. All the bulk resistivity and the coefficients of thermal expansion of solvent and solvent-free ECAs tend to decrease after solder reflows. The reasons are studied by thermomechanical analyzer, thermogravimetric analysis, topography and deformation measurement, and scanning electron microscopy.     

Properties investigation on electrically conductive adhesives based on acrylate resin filled with silver microsheets and silver plating carbon fibers

The introduction of highly electrically conductive fillers (Ag microsheets and silver plating carbon fiber) can functionally improve the electrical conductivity of acrylate resin. In this study, Ag microsheets and Ag/CF were thus introduced into acrylate polymer via solution blending method under ultrasonication in order to improve the electrical conductivity of the acrylate resin. The properties and microstructures of Ag microsheets, CF, Ag/CF and ECAs were performed by scan electron microscope (SEM), X-ray diffraction analysis (XRD), etc. SEM images and XRD results illustrated that the impurities in carbon fiber could be completely removed after the adequately alkali treatment. The SEM images showed that large numbers of metallic silver particles were uniformly and densely coated on the surface of the carbon fibers and hybrid fillers (silver microsheets and Ag/CF) could homogeneously disperse in acrylate resin. Electrical conductivity measurements demonstrated that the electrical conductivity of ECAs increased with the increasing content of hybrid fillers and the percolation threshold of ECAs was 5 wt%. The electrical conductivity of ECAs at its percolation threshold was 15.79 S/cm, which was two orders of magnitude higher than that of the ECAs based on acrylate resin filled with silver microsheets. The increment in Ag/CF contents may decrease 180° peel strength and raise shear strength with low content of Ag/CF. The overall performance of ECAs was optimum with 2 wt% Ag/CF. The TGA analysis indicated that ECAs possess excellent thermal stability.     

Electrically conductive adhesives with a focus on adhesives that contain carbon nanotubes

On the basis of an analysis of results presented in the literature, the currently existing knowledge about relationships between the microstructural and physical properties of hard coatings is discussed. Particular emphasis is placed on the role of microstructural features, such as grain boundaries, nonequilibrium structures, impurities, and texture, in controlling the film hardness. On the basis of an analysis of results presented in the literature, the currently existing knowledge of electrically conductive adhesives (ECAs) is discussed. Particular focus is placed on the results obtained with ECAs that contain carbon nanotubes (CNTs) as conductive fillers. The review is divided in curable ECAs based on epoxy resins, and noncurable conductive hot melts and pressure‐sensitive adhesives based on thermoplastic polymers. More literature results were found for epoxy/conductive filler ECAs than for other adhesives. Confirming the assessments made in a book by Li et al., which refers to nanotechnologies in ECAs, we found that only a reduced number of articles allude to polymer/CNT ECAs. Our analysis of the results includes a study of the balance between the viscosity, immediate adhesion, solidification process, electrical conductivity, and mechanical properties of the adhesives. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Sintering behavior and effect of silver nanoparticles on the resistivity of electrically conductive adhesives composed of silver flakes

In this paper, silver nanoparticles with size of 30–50 nm were synthesized by reducing silver nitrate with sodium borohydride and sodium citrate and using PVP as an adsorption agent in the ethanol solution. The experimental results indicate that the morphologies and sintering behaviors of both kinds of silver nanoparticles are impacted by glutaric acid and sintering temperature. The electrically conductive adhesives (ECAs) filled with micro-sized silver flakes and silver nanoparticles as hybrid fillers were fabricated and the electrical properties were investigated based on the fraction of the silver nanoparticles of the total of silver flakes and the curing temperature, etc. The incorporation of the untreated/treated silver nanoparticles into the polymer matrix with 65?wt% silver filler the resistivity increased in almost all cases, especially the high fraction and the low curing temperature. The curing temperature has influence on the resistivity of the ECAs filled with micro-sized silver flakes and the silver nanoparticles due to the sintering of the silver nanoparticles. The addition of 10% treated silver nanoparticles into the ECAs with 60?wt% silver fillers, the resistivity is slightly lower than that of the ECAs with micro-sized silver flakes. In the system of the ECAs with the high loading of silver fillers, the untreated/treated silver nanoparticles have little effect on the electrical conductivity. The results suggest that the morphology and distribution of silver fillers are the key to affect the conductivity of ECAs when nanoparticles are included in the system.     

Novel flexible electrically conductive adhesives from functional epoxy,flexibilizers, micro‐silver flakes and nano‐silver spheres for electronic packaging

In this study, five different flexibilizers were added into a matrix resin to improve the flexibility of electrically conductive adhesives (ECAs). The flexible ECAs were fabricated from the matrix resin and electrically conductive fillers. Their curing was fixed at 150 °C for 30 min. Of the five flexibilizers, 1,3‐propanediol bis(4‐aminobenzoate) (PBA) had the best effect on the electrical, mechanical and thermal properties of the ECAs. During curing, PBA reacted with the functional epoxy in the matrix resin. The soft ether segments in PBA were grafted into the crosslinked epoxy network to form an orderly spaced mesh structure. This led to high‐temperature stability, with the pyrolysis temperature being above 350 °C. Flexible ECAs with a 10% weight ratio of PBA in the matrix resin had the best properties. Their viscosity and bulk resistivity were the lowest. Their flexibility and electrical conductivity were the highest. They also had low storage modulus which could effectively dissipate or reduce the residual shear stress generated by the mismatch of thermal expansion coefficient between chip and substrate. Their impact strength was the lowest, and the toughening effect was so significant that the improvement was about 48% compared to ECAs. © 2013 Society of Chemical Industry     

On the Use of Silver Plated Nano Aluminum Nitride and Silver Plated Chopped Carbon Fiber to Prepare Electrically Conductive Adhesives with High Thermal Conductivity

To satisfy the high electrical and thermal conductivity required for the development of microelectronic products, silver plated aluminum nitride (Ag/AlN) and silver plated chopped carbon fiber (Ag/CF) were added into an acrylate resin to prepare electrically conductive adhesives (ECAs) with high thermal conductivity. The Ag/AlN was prepared by subjecting AlN to an electroless silver plating using a Pb-free activation method. The Ag/AlN has good electrical and thermal conductivity compared to the AlN without treatment. When the weight fraction of Ag/AlN is 45 ωt%, the electrical conductivity of ECAs based on acrylate resin filled with Ag/AlN is 1.5 S/cm, and the thermal conductivity reaches 2.1 W/(m · K). With the addition of 3 ωt% Ag/CF as supplement filler, the electrical conductivity has a sharp increase to 17.8 S/cm because of the formation of conductive networks in the ECAs. However, the shear strength has an apparent loss, falling from 4.2 to 1.1 MPa.     

Self‐healing Ag/epoxy electrically conductive adhesive using encapsulated epoxy‐amine healing chemistry

In this study, a dual‐microcapsule epoxy‐amine self‐healing concept is used for electrically conductive adhesives (ECAs). It provides the ECA samples with the ability to recover mechanical and electrical properties automatically. Epoxy and amine microcapsules were prepared and incorporated into silver/epoxy ECAs. The healing efficiency and bulk resistivity of the undamaged, damaged, and healed specimens were measured, respectively. The optimal loading of the epoxy and amine microcapsules is 6 wt % (weight ratio 1.05), and the bulk resistivity of the healed specimens is 3.4 × 10^?3 Ω cm. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41483.