Electroconductive Adhesives: Comparison of Three Different Polymer Matrices. Epoxy, Polyimide and Silicone

Electrically conductive organic adhesives are used in the microelectronics manufacturing industry for the attachment of silicon dies. These adhesives are composite materials which owe their conductivity to the incorporation of silver flakes. Several polymers have been formulated into electrically-conductive adhesives to meet different applications in the microelectronics industry; these are an epoxy resin, a polyimide and a silicone polymer. The purpose of this paper is to examine properties of these die-bonding adhesives in order to determine the advantages or disadvantages of these materials. This study offers a comparison of hardening chemistry, chemical purity, processing, electrical, thermal, and mechanical properties of three conductive adhesives based on an epoxy, a polyimide and a silicone polymer. We discuss correlation of composite properties with the structure of each matrix. The results indicate that the choice of the matrix is dictated by the application for which the electronic grade conductive adhesive is to be used and the desired properties for best reliability and performance.     

Development of Polypyrrole/Epoxy Composites as Isotropically Conductive Adhesives

As a possible replacement for lead bearing solders, metal filled isotropically conductive adhesives (ICAs) have shown a lot of potential recently. But still they have to come a long way and overcome their limitations like low impact strength and moisture instability. The current paper attempts to address the limitations of these ICAs by using intrinsically conducting polymer as a filler in place of metals. Conducting polymer (CP) polypyrrole (PPy) was incorporated as a filler in an epoxy/anhydride (EP) system and its application as an isotropic conductive adhesive was studied. PPy was synthesized by chemical polymerization using dodecyl-benzene sulphonic acid (DBSA) as dopant. The composites with varying PPy concentrations were studied for curing behavior and thermal degradation properties using DSC and TGA, respectively. The composites show good impact properties and conductivity at very low filler concentrations. SEM observations established that PPy particles were dispersed in the epoxy matrix uniformly. The overall characteristics of these conductive adhesives establish that they can be used as conductive adhesives in the electronics industry.     

Conductive resins used for tantalum capacitors — mechanical study of bonded joints

Silver-filled polymer coatings and adhesives are used to ensure the cathodic junction of tantalum capacitors. The aim of the present work was to choose new polymerizable materials agreeing with an industrial thermal test: Rapid Test Solder Heating (RTSH). In a first step, the physical chemistry of the main commercial coatings used at the present time was studied. Four commercial silver coatings (epoxy, polyester, polyimide and polyacrylate binders) and one conductive epoxy adhesive were tested. The tensile strengths of the different joints were evaluated both at room temperature and 150°C. The examination of the metallographic cross sections and of the surface fractures were conducted using a scanning electronic microscope (SEM). The failure strength of the joints is discussed in relation with the nature of the binders, the temperature, the cure cycles and the presence of silver fillers blended with the polymer resins.     

耐高温有机胶粘剂研究进展

对国内外耐高温有机胶粘剂进行了综述。对环氧树脂、酚醛树脂、聚氨酯、聚酰亚胺、有机硅和氰酸酯等耐高温有机胶粘剂的性能和应用进行了全面讨论,并对其今后的发展趋势进行了展望。     

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。     

Development of Polyaniline/Epoxy Composite as a Prospective Solder Replacement Material

In this paper we present a novel application of a conducting polymer, polyaniline, as a conductive filler for the development of isotropically conductive adhesives. We have developed isotropically conductive adhesives using protonic acid-doped polyaniline as the conducting filler in an anhydride-cured epoxy system. Fundamental material characterization like DSC, TGA and SEM of the samples was conducted to study their properties. Conductivity of these materials was measured by the four probe method while impact properties were studied by lap shear and drop tests. Samples were aged at 85°C/～100% RH for more than 500 h and the effects of aging were studied. Conductivity value of 10^?3 S/cm was obtained at 25% PANI filler concentration. These results demonstrate the potential of such systems to function as isotropically conductive adhesives.     

纳米SiO2-Al2O3协同改性有机硅压敏胶的性能研究

采用纳米SiO2和Al2O3两种粉体协同对有机硅压敏胶进行改性,并以改性后的压敏胶为胶黏剂,聚酰亚胺薄膜、云母纸、无碱玻璃布为基材制备柔软复合材料。研究了纳米粒子含量和比例对有机硅压敏胶耐热性和柔软复合材料电性能的影响。实验结果表明:适量的纳米SiO2和Al2O3加到有机硅压敏胶中,使压敏胶的表观分解温度和复合材料的击穿场强得到明显提高。     

耐高温有机胶黏剂研究进展

对国内外耐高温有机胶黏剂的研究进展进行了综述。对耐高温有机胶黏剂的定义、种类做了简明阐述。对环氧树脂、酚醛树脂、有机硅、聚酰亚胺、聚氨酯、氰酸酯等耐高温胶黏剂的制备、性能和应用进行了较详细的论述。分别讨论了各种耐高温有机胶黏剂基体树脂的结构和性能特点以及提高上述胶黏剂耐高温性能的改性方法。对聚苯并咪唑和聚喹嚼啉胶黏剂进行了简介。最后,对耐高温有机胶黏剂今后的发展趋势进行了展望。     

Polymer molecular behaviors at buried polymer/metal and polymer/polymer interfaces and their relations to adhesion in packaging

Packaging materials are widely used in modern microelectronics. The interfacial structures of packaging materials determine the adhesion properties of these materials. Weak adhesion or delamination at interfaces involving packaging materials can lead to failure of microelectronic devices. Therefore, it is important to investigate the molecular structures of such interfaces. However, it is difficult to study molecular structures of buried interfaces due to the lack of appropriate analytical techniques. Sum frequency generation (SFG) vibrational spectroscopy has recently been used to probe buried solid/solid interfaces to understand molecular structures and behaviors such as the presence, coverage, ordering, orientation, and diffusion of functional groups at buried interfaces and their relations to adhesion in situ in real time. In this review, we describe our recent progress in the development of nondestructive methodology to examine buried polymer/metal interfaces and summarize how the developed methodology has been used to elucidate adhesion mechanisms at buried polymer/metal interfaces using SFG. We also elucidated the molecular interactions between polymers and various model and commercial epoxy materials, and the correlations between such interactions and the interfacial adhesion, providing in-depth understanding on the adhesion mechanisms of polymer adhesives.     

分离膜高分子材料及进展

膜材料是膜分离技术的关键。本文主要介绍了具有重要应用和发展前景的5类高分子膜材料纤维素膜材料、聚酰亚胺膜材料、有机硅膜材料、液晶复合高分子膜材料、高分子金属络合物膜材料。内容涉及结构、性能、改进方法、用途等。     

Transmission and Mechanical Properties of Optical Adhesives

The optical, mechanical and durability performance of selected epoxy, polyester, UV-curable acrylic, cyanoacrylate and silicone adhesives were evaluated and measured for bonding applications of optically transparent glasses in the visible and infra-red regions of the electromagnetic spectra.

From the initially selected adhesives only the UV-curable modified acrylic, two-component silicone and room temperature cured epoxy, were found to be of high performance characteristics, having good transmission properties and enhanced endurance in a combination of heat and humidity and following thermal cycling.

Sodium chloride substrates served as adherends for the transmission characterization of the optical adhesives, due to their high transmission properties in the 0.4-10 m μ spectral range. A modified lap shear specimen was designed for studying the mechanical properties and failure mechanisms of the adhesives and their durability in a humid and not environment. Finally, a two-piece glass doublet was used for investigating the optomechanical characteristics of the optical adhesive following environmental conditioning and thermal shock cycling.

Due to the inherent C-C bond, polymer adhesives are limited in utility, as far as transparency is concerned, close to 3.5 μm and in most of the 8-12 μm spectral range.     

低成本室温快速固化环氧树脂胶粘剂的研制

以双酚A环氧树脂为基料，低分子聚酰胺650为固化剂，添加复合固化促进剂，制得低成本室温快速固化胶粘剂。所用原材料均为易购市售工业品，配制简单，使用方便。     

石墨烯/导电聚合物复合防腐蚀材料制备及应用研究进展

石墨烯/导电聚合物复合材料不仅具有石墨烯优异的屏蔽性能和导电聚合物良好的氧化还原特性,还能协同发挥二者的功能,在金属防腐蚀领域有着巨大的应用潜力。本文综述了石墨烯/导电聚合物复合防腐蚀材料的制备方法,包括电化学方法、化学氧化法、分散液混合法和化学气相沉积法（CVD）;并全面总结了石墨烯/导电聚合物复合材料在防腐蚀涂层中的应用及性能。制备的石墨烯/导电聚合物复合材料可以通过电化学方法、溶剂挥发法制成石墨烯/导电聚合物防腐蚀薄膜涂层,还可以混入成膜物树脂中制备树脂复合防护涂层。讨论了石墨烯/导电聚合物在制备过程、薄膜涂层和树脂复合涂层应用中的优势与不足,提出了构建结构可控、综合性能好的复合防腐涂层是石墨烯/导电聚合物复合防腐蚀材料的未来主要发展趋势。     

Hygrothermal cycling effects on the durability of phenolic based composites

Work has been performed to investigate the thermal and mechanical properties of carbon fiber/phenolic resin composites as engineering materials for the aerospace industry. These materials are cost effective while displaying excellent temperature and fire resistance as well as good mechanical properties. All phenolic and epoxy composite specimens used here were prepared by resin transfer molding (RTM) to model a cost‐effective process. Hygrothermal cycling effects on the property changes of phenolic composites were evaluated through thermal, mechanical, and morphological tests. The fracture performance of a phenolic composite modified with a silicone‐based additive decreased after fewer hygrothermal cycles than unmodified phenolic and epoxy composites. Results from dynamic mechanical analysis (DMA) experiments showed that the modified phenolic composite was more significantly affected by the hygrothermal cycling than the unmodified phenolic composites. Fatigue tests showed that the phenolic composites that were not exposed to hygrothermal cycling had more resistance to fatigue cycles than the epoxy composites.     

Preparation of thermally stable and flame-retardant sugarcane bagasse-ammonium dihydrogen phosphate/epoxy composites and their performance

Epoxy resin was often applied in fiber-reinforced composite materials, adhesives, and encapsulation materials. However, epoxy was easily flammable and limited its usage in certain applications. The study recycled and reused agricultural waste sugarcane bagasse to prepare a halogen-free bio-based intumescent flame retardant and then mixed with epoxy resin to prepare a composite containing polymer with improved thermal properties and flame retardancy of the materials. The work followed the concept of circular economy and sustainability. Bagasse-ammonium dihydrogen phosphate (ADP) flame retardant was added to an epoxy resin to prepare epoxy/bagasse-ADP composites, an effective flame-retarding composite material through hydrothermal method. Adding bagasse-ADP increased the thermal stability and flame retardancy of the composite materials compared with that of pure epoxy. For the material with 30 wt% added bagasse-ADP, the char yield was 32.3 wt%, which was 18.2 wt% higher than that of pure epoxy (14.1 wt%) through thermogravimetric analysis. In addition, the limiting oxygen index increased from 21% to 30%, and the UL-94 classification improved from “Fail” to “V-0.” This performance was attributed to the nitrogen, phosphorus, and silicon content of the flame retardant.     

Graphene/nanorubber reinforced electrically conductive epoxy composites with enhanced toughness

Graphene platelets (electrically conductive 2D filler) and rubber nanoparticles (0D soft filler) can work together to develop electrically conductive and toughened epoxy composite adhesives. In this study, complementing effect between graphene platelets (GnPs) and rubber nanoparticles (RnPs) within an epoxy matrix is reported. In the 3-phase composite adhesive, the 2D graphene platelets form global conductive network and rubber nanoparticles provide a viscoelastic phase inside the epoxy, both complementing each other to develop electrically conductive and toughened epoxy composite adhesives. Fracture toughness (K_1c) and critical strain energy release rate (G_1c) of the epoxy were augmented by 422% and 872%, respectively by adding 1 wt% RnPs and it recorded electrical percolation threshold at 0.78 vol% GnP. Also, the Young's modulus and strength of epoxy/1 wt% RnP composite were promoted from 1.57 to 2.32 GPa when 1 wt% GnP is added. Scanning electron microscopy analysis was conducted to investigate the toughening mechanism of epoxy/RnP/GnP and epoxy/GnP composites. Lap shear strength tests on epoxy composite adhesives confirm the reinforcement effect of GnPs and toughness effect of RnPs.     

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     

某高导热纤维及其复合材料性能研究

研究了某高导热纤维/环氧树脂单向层复合材料的导热系数和力学性能,发现某高导热纤维/环氧树脂单向层复合材料导热性能提高的同时其个别复合材料性能降低;分析认为某高导热纤维与环氧树脂的界面性能是影响复合材料力学性能的重要因素,同时研究了某高导热纤维的表面微观形貌和表面化学特性、结晶度及某高导热纤维/环氧树脂浸胶丝束的力学性能...     

石墨纸-BaTiO_3/PI一体化复合薄膜的制备及研究

聚合物复合薄膜超级电容器因其可实现大面积制备、性能可靠等优点,引起了能源领域的广泛关注。如何实现导电层与介电层的一体化加工制备,是叠片式薄膜超级电容器的重要研究方向。本文介绍了以溶液混合法制备的钛酸钡/聚酰亚胺复合薄膜作为介电材料,以石墨纸作为电极材料以及复合薄膜的载体,利用提拉法制备石墨纸-钛酸钡/聚酰亚胺一体化复合薄膜,实现导电层与介电层直接成型的一体化制备过程。利用红外(FT-IR)、扫描电镜(SEM)、EIS和LCR电桥仪对复合薄膜进行表征分析。实验结果表明聚酰亚胺亚胺化完全,钛酸钡在复合薄膜中分散良好,复合薄膜的介电损耗非常小,很好地满足了高介电材料的应用要求。     

Electrical conductivity of epoxy/silicone/carbon black composites: Effect of composite microstructure

The objective of this work is to study the effect of electrical conductivity and physical‐mechanical properties of carbon black (CB) filled polymer composites. This goal is achieved by synthesizing epoxy/silicon phase separated blend structure of composites filled with CB. The percolation threshold of epoxy/silicone/CB composites decreased and the total conductivity increased compared to the pure epoxy/CB composite. A threefold increase was obtained with tensile strength of epoxy/silicone/CB composite with 25 wt% of silicone and 5 wt% of CB in comparison with epoxy/CB systems. This composite has conductivity of about 10⁻⁶ S/cm, which is six orders of magnitude higher than for epoxy/CB composites at the same concentration of CB. POLYM. COMPOS., 35:2234–2240, 2014. © 2014 Society of Plastics Engineers