Aminosiloxane-modified epoxy resins as microelectronic encapsulants

Amine-terminated poly(dimethylsiloxanes) (ATPDMS) were used to improve the toughness of a cresol-formaldehyde novolac epoxy resin cured with a phenolic novolac resin for electronic encapsulation application. The effect of molecular weight of amine-terminated polysiloxanes on the phase separation of the resultant elastomers from epoxy matrix were investigated. Mechanical and dynamic viscoelastic properties of siloxane-modified epoxy networks were also studied. The dispersed silicone rubbers effectively improve the toughness of cured epoxy resins by reducing the coefficient of thermal expansion and flexural modulus, while the glass transition temperature was hardly depressed. Electronic devices encapsulated with the dispersed silicone rubber-modified epoxy molding compounds have exhibited excellent resistance to the thermal shock cycling test and have resulted in an extended device use life.     

加成型液体乙烯基硅橡胶的研制Ⅱ.白炭黑表面处理对硅橡胶性能的影响

以六甲基二硅氮烷为主要表面处理剂，考察了表面处理剂、处理助剂、水的用量等对白炭黑增强效果的影响。结果表明，处理100份白炭黑时，用25份六甲基二硅氮烷，5份二甲基二乙氧基硅烷，5份水，所得白炭黑对加成型液体硅橡胶增强效果较好。     

光伏组件用密封剂研究进展

介绍了光伏组件国内外研究现状、密封剂的选用原则以及目前应用较为普遍的EVA胶膜的结构与性能.概述了提高聚合物导热性的主要途径,指出了提高组件中EVA胶膜导热性的重要性.     

电子工业用加成型硅橡胶型灌封胶的研究进展

硅橡胶型灌封胶主要由基础聚合物、交联剂、催化剂、填料等组成,灌封胶的性能与胶料的组成、结构有关.重点讨论了加成型硅橡胶的组成对性能的影响,综述了加成型硅橡胶灌封胶在电子工业中的应用研究进展.指出我国硅橡胶生产的原材料大量依赖进口,产品品种少,产品质量有待提高,应加强对成本低、性能好的硅橡胶型灌封胶的研究开发.     

Low-stress over-molding of media-tight electronics using thermoplastic foam injection molding

Due to increasing automation and the associated rising demands on electronic assemblies, a suitable manufacturing process for large-scale production is needed to protect such products. The big challenge in this context is the low-stress encapsulation of the assemblies to protect them from external influences. In this study, the foam injection molding process was used to encapsulate FR4 (epoxy-based PCB) with Polyamid66 (PA66). The focus was on the production of a good assembly in terms of the quality of the bond and the media tightness. These parameters can be used to evaluate the protective effect against the surrounding. In the tests, a leakage rate of 0.025 m/min and shear stress of 6.5 MPa was achieved at low-foaming rates. This leakage is below the maximum acceptable threshold of 0.5 ml/min. The shear stress reaches values comparable to those in injection molding In addition to the requirements for leakage and composite quality, it could be shown that the internal mold pressure is reduced from 450 bar to below 10 bar by foaming. This can be used as the first indication of a reduced shear load on electronic components during over-molding. The suitability of the new solution concept is demonstrated.     

Development of seawater-resistant polyurethane elastomers for use as sonar encapsulants

Polyurethane systems based on aliphatic diisocyanates were evaluated for suitability for use as underwater transducer encapsulants. A preliminary evaluation was performed to select the most promising urethane systems for further development. An investigation was then undertaken to determine the effect of compositional changes on the properties of these urethanes. The compositional parameters investigated were the soft-segment molecular weight, the prepolymer isocyanate content, the composition of the cure formulation, and the cure stoichiometry. These urethanes were subjected to long-term aging in seawater. It was found that this exposure did not significantly effect the physical or dynamic mechanical properties of the urethane.     

甲基乙烯基硅橡胶/丁基橡胶硫化性能和耐热性能研究

通过共混法制备了甲基乙烯基硅橡胶/丁基橡胶复合材料,用DSC研究了复合材料硫化前的结晶性能与硫化性能,用TG研究了复合材料硫化后的热分解性能。根据在不同升温速率下的DSC曲线,用Kissinger方程对复合体系的硫化性能进行动力学研究,得到了交联反应活化能为95.1 kJ/mol、反应级数n为0.78。TG测试表明,复合材料的耐热性介于二者之间。力学测试表明,该材料的综合物理力学性能较好,可以作为阻尼材料使用。     

Viscosity characterization of highly filled photopolymerizable liquid encapsulants for microelectronic devices

In this paper the viscosity of novel photopolymerizable liquid encapsulants (PLEs) for microelectronic devices was characterized as a function of the particle size distribution of the fused silica filler. Microelectronic devices are typically encapsulated using a transfer molding process in which the molding compound flows over the leadframe and wire bonds as it fills the mold. The molding compound should have a low viscosity to minimize problems such as: (1) incomplete mold filling; (2) lead frame movement during cavity filling; and (3) displacement of the wires that connect the die with the leadframe (wire sweep). We have developed a photopolymerizable liquid encapsulant using an epoxy novolac‐based vinyl ester resin that may alleviate these problems. In this contribution, we have investigated the blending of two different particle size distributions of fused silica to tailor the viscosity of PLEs for microelectronic applications. We have characterized the viscosity of highly filled PLEs containing 70.0, 72.0, and 74.0 wt% silica, and found that a blend of particle size distributions with a particle size ratio of 3.13 resulted in the best viscosity reduction. In addition, the PLE viscosity decreased slightly with increasing concentration of a silane coupling agent. The resulting PLEs exhibit low viscosities at ambient temperature while maintaining desirable material properties for microelectronic applications.     

A failure criterion for debonding between encapsulants and leadframes in plastic IC packages

A failure criterion for debonding initiation between molding compounds and copper leadframes in plastic encapsulated integrated circuit (IC) packages is proposed. The leadframe pull-out test is used to evaluate the bond strengths between molding compounds and leadframes in plastic encapsulated IC packages. The normal and shear stress fields along the interface are analyzed using the finite element method. An average stress approach is employed for the interface failure criterion and the tensile and shear interface bond strengths are obtained from the experimental failure loads. In a parametric study, the effects of specimen loading geometry, moisture, and surface contamination of copper leadframes on the interfacial bond strengths are specifically analyzed. The results show that the interface bond strengths determined for the two specimen geometries are consistent.     

Protein functionality modification by extrusion cooking

Cooking extruders process high-protein materials into palatable foods. New applications have been developed for protein extrusion during the past decade. Improvements in functional characteristics of proteins may be achieved through modification of temperature, screw speed, moisture content, and other extrusion parameters. Flavors and odors may be removed during expansion at the extruder die. Extrusion can improve the digestibility of proteins, while reducing gossypol, proteinase inhibitors, allergens, aflatoxins, and other undesirable compounds. In the future the use of extruders as chemical reactors for both animal and plant proteins will provide new food ingredients as well as novel, nutritious foods. Presented at the 81st AOCS Annual Meeting, Baltimore, 1990.     

三元乙丙橡胶共混改性聚丙烯

分别用茂金属催化聚合所得的三元乙丙橡胶(mEPDM)和传统Ziegler-Natta催化剂聚合所得的三元乙丙橡胶(EPDM)对PP进行共混改性。考察了增韧剂质量分数对共混物冲击强度、拉伸强度和热变形温度等力学性能的影响,以及共混物结构形态和结晶行为。结果表明,与PP／EPDM共混物相比,PP／mEPDM共混物的脆韧转变增韧剂临界质量分数小,扯断伸长率高。PP／mEPDM共混物的脆韧转变区间远小于PP／EPDM共混物。随增韧剂质量分数的增加,PP／mEPDM和PP／EPDM共混物的拉伸强度、弹性模量和维卡软化点均单调下降,但后者的下降幅度更大。电镜分析和结晶行为研究表明,PP与mEPDM的相容性优于PP与EPDM的。     

Bitumen chemical modification by thiourea dioxide

This work evaluates a novel bitumen modification through the use of a chemical agent, thiourea dioxide, substance which has been traditionally used as a reducing agent. Thermo-gravimetric analysis demonstrated the formation of new chemical compounds, most probably originated through reactions between products from thiourea dioxide thermal decomposition and some highly polar bitumen molecules. As a result of these reactions, which continues even after 60 days, bitumen permanent deformation resistance at high temperature is enhanced, as indicated by a significant increase in its viscosity and elastic features. On the other hand, thiourea dioxide addition produces changes in the bitumen colloidal nature, which improve its flexibility at low in-service temperatures, and consequently its resistance to thermal cracking under loading. In fact, dynamic bending tests indicated a remarkable decrease in the value of binder glass transition temperature, which was further corroborated by differential scanning calorimetry. As a conclusion, thiourea dioxide can be seen as a promising modifying agent, which can extend the in-service temperature range at which bitumen would present a satisfactory performance.     

乙丙橡胶接枝改性的研究进展

总结了乙丙橡胶接枝改性的研究进展，对接枝方法、接枝物的性能及其应用进行了介绍。常见的乙丙橡胶接枝改性方法包括：（1）对乙丙橡胶进行官能化处理引入过氧等官能团，然后进行自由基或阳离子接枝聚合；（2）在过氧化物引发剂存在下直接进行熔融或溶液接枝聚合；（3）用电子束或γ射线辐照进行接枝聚合；（4）在乙丙橡胶的第三单体上引入原子转移自由基聚合引发活性点，进行活性自由基接枝聚合；（5）将乙丙橡胶溶液乳化后进行“假乳液”接枝聚合。接枝了不同单体的乙丙橡胶可以在热稳定性、机械性能、耐油性、染色性、生物相容性、阻燃性等方面得到改善，从而大大拓宽了乙丙橡胶的应用范围。     

天然橡胶增韧聚氯乙烯的研究

采用未改性的标准天然橡胶(NR)作增韧剂,通过机械共混法制备增韧聚氯乙烯(PVC)复合材料,考察了NR和增容剂用量对PVC增韧效果以及力学性能的影响.结果表明:当NR用量为10份时,材料的冲击强度最高为24.87 kJ/m2;加入增容剂环氧化天然橡胶(ENR)后,材料的冲击强度随其用量的增加而增大,在ENR为5份时其冲击强度为69.86 kJ/m2;氯化聚乙烯(CPE)作增容剂时,其冲击强度先升后降,在4份时达到峰值103.93 kJ/m2;氯化橡胶(CNR)作增容剂在3份时,其冲击强度达到最佳值35.37 kJ/m2;增容增韧后共混物的拉伸强度普遍降低.     

Chemical modification of starch by reactive extrusion

Processes for chemical transformation of starch by extrusion processing (reactive extrusion, REX) are reviewed with a focus on non-food applications. The scope, advantages, limitations and specificity of various REX processes for are examined in this context. The processes covered include: the grafting of monomers from starch as single units, such as ring-opening of epoxides, esterification (with lactones, anhydrides, acids, halides or vinyl esters) phosphorylation and silylation; graft polymerization from starch by radical-induced grafting or the ring-opening polymerization of lactones; reactive compatibilization with polyesters and polyolefins by grafting to or from starch; crosslinking of starch with epichlorohydrin or by phosphorylation; and the degradation of starch thermally or catalyzed by acid or enzymes.     

Preparation of lignin nanoparticles by chemical modification

Lignin is the main natural aromatic polymer and consists of about a quarter of lignocellulosic biomass. That is why products obtained from lignin are very attractive research topics, but it is also a very complex issue due to its complicated structure which depends on the separation method and plant species. To become a widely used raw material, the basic characteristics and structure-dependent properties must be elucidated, initially. For this reason, it is necessary to obtain lignin with superior properties, to be able to compete with fossil resources. This paper presents a chemical method to modify lignin by hydroxymethylation to obtain nanoparticles. Nanotechnology allows using chemical, physical and biological effects that do not occur outside the nanoscale world. To find the best conditions (from the average particle size distribution point of view), three reaction parameters were varied: ratio of lignin/aldehyde, pH and temperature. The following output value has been the average particle size distribution. The obtained data were processed with software in demo version (Modde 9) and resulted regression equation allows us to establish the optimum conditions. At the same time, the reaction products thus synthesized were characterized by FTIR spectroscopy, GPC, and ³¹PNMR spectroscopy. The results confirm that using this reaction, it is possible to synthesize nanoparticles from hydroxymethylated lignin. Lignin derivatives containing high hydroxyl group content have a potential utilization as phenol substitute in the phenol formaldehyde resin synthesis, composites, biocides, etc.     

改进生产工艺降低水泥温度

江苏江阴某公司有一条Φ3.2m×13m开路粉磨生产线,生产P·O42.5R水泥时,成品水泥温度达110℃左右,不能适应混凝土搅拌站中外加剂的使用条件(外加剂使用要求水泥温度低于85℃),为满足混凝土搅拌站的使用要求,我们改进生产工艺,使入库水泥温度<85℃,满足了混凝土搅拌站的使用要求。     

微波辐射木质素磺酸盐接枝改性

研究了微波辐射下的木质素磺酸钠与丙烯酸的接枝共聚反应,对微波辐射和常规加热接枝共聚反应的效果进行了比较,并用红外光谱分析了接枝共聚物的结构。同时测试了接枝共聚物在水煤浆中的分散稳定性能。结果表明,通过微波辐射可以得到较高接枝率的木质素磺酸钠丙烯酸接枝共聚物,其对水煤浆的分散稳定作用有明显的改善。     

硬脂酸对磷石膏的改性研究

为解决磷石膏的亲水性问题,提高其与聚合物的相容性,采用硬脂酸对磷石膏进行表面改性.以活化指数为指标,确定其最佳改性条件:硬脂酸的用量为磷石膏质量的2%,改性时间为20 min,改性温度为60 ℃,pH为7～8.在最佳改性条件下,改性后磷石膏的活化指数达到100%,完全疏水.对改性前后的磷石膏进行了抽提实验和红外光谱测试,结果表明磷石膏与硬脂酸之间发生了化学键合作用.初步工业实验表明,改性磷石膏可用作聚丙烯树脂的无机填料,且其与聚合物的相容性较好,磷石膏/聚丙烯复合材料的力学性能较纯聚丙烯有所提高.