半固化片浸渍加工技术的新进展

高密度互连印制电路板制造需要高性能可靠性的覆铜板及半固化片基材。为满足这一需求，在覆铜板及半固化片生产中，就要在半固化片（prepreg，简称为PP，或称：预浸粘结片）的加工设备水平上获得提高。当前，在提高环氧-玻纤布基覆铜板及半固化片加工质量和水平的重点之一，是要克服在浸渍加工中出现的半固化片中含有微小气泡、树脂胶浸透性差、漏浸、胶含量不均匀等问题。这些质量问题的存在，会严重影响此工序以后所制出的覆铜板、多层板的可靠性。     

改善固化工艺降低覆铜板内应力

内应力是导致覆铜板的粘接强度及其稳定性降低的最根本的原因,降低内应力是处理覆铜板翘曲度超标的关键。本文主要讨论降低内应力的基本措施,然后从固化工艺上进行分析,寻找解决问题的方法。     

新一代无铅兼容PCB基板材料的最新研究进展（2）

（续上期）2.1.22 各种覆铜板的热分层时间 图16为各种覆铜板的T288比较,各覆铜板包括聚苯醚／环氧、加填料聚苯醚／环氧、热心性聚苯醚、加填料180℃Tg Non-Dicy FR-4、加填料150℃Tg Non-Dicy FR-4、加填料150℃Tg Dicy周化FR-4、加填料170℃Tg无卤FR-4、未加填料175℃Tg Dicy固化FR-4、无铅热稳定性175℃Tg Dicy固化FR-4。     

含氮酚醛在无卤覆铜板中的应用研究

采用含氮酚醛固化含磷环氧,成功开发出综合性能优良的无卤覆铜板。比较了线性酚醛和含氮酚醛固化’行为,系统考察了不同结构的含氮酚醛树脂及其用量对无卤板材性能的影响。     

二氨基二苯砜固化环氧树脂的促进剂研究

二氨基二苯砜作为一种高耐热低吸湿的环氧树脂固化剂常用于覆铜板领域。研究了不同促进剂对二氨基二苯砜固化环氧树脂反应的影响，表明：2-乙基-4-甲基咪唑和三氟化硼单乙胺络合物，都对二氨基二苯砜固化环氧树脂有一定的促进作用，BF3·MEA可以降低体系的反应温度，提高固化速率；而2-乙基-4-甲基咪唑可以形成更完善的交联结构，具有更高的耐热性。     

纳米氢氧化铝／磷酸酯阻燃环氧树脂体系的研究

为确定环境友好型覆铜板阻燃体系，利用差热分析对纳米氢氧化铝／磷酸酯阻燃环氧树脂体系进行了研究。通过对体系固化反应动力学的分析，首先求得固化工艺温度，为确定合理固化工艺提供依据；然后利用Kissinger方法和Crane理论求出了体系的两个同化反应动力学参数，     

焦作覆铜板正踏上提升之路——河南焦作地区覆铜板制造业浅评

大约在上世纪末，在中国的河南省焦作地区，突然出现几家覆铜板制造厂，规模都很小，设施简陋，材料是被行业称为“垃圾料”的废半固化片。本来，这类以废半固化片为主要原材料的小工厂，早在上世纪八十年代始，无论在北方，还是覆铜板制造业发达的南方，都有所分布。大概是几年之间，焦作地区的这类覆铜板厂，迅速扩张，而且很集中，于是，焦作覆铜板在业界就逐渐有了名气。     

兼具耐CAF、优良PCB加工性及耐热性无铅覆铜板的开发

通过改性双氰胺与改性酚醛复合固化环氧树脂,在保证原来FR-4板料的良好加工性基础上提高了板材耐热性,并且提高了耐CAF性能,开发出满足无铅焊接的覆铜板。     

环氧树脂固化不完全的危害

本文分析了环氧布板中环氧树脂固化不完全对于覆铜板和线路板性能的影响。结果表明,由于环氧树脂固化不完全,将导致板的性能降低。     

高性能无卤／无铅覆铜板的制备

以苯并嗯嗪树脂（BOZ）、邻甲酚酚醛环氧树脂（CNE）、线性苯酚酚醛树脂（PN）、含磷阻燃剂以及一定量的无机填料作为树脂基体,选用适宜的溶剂,获得了加工性良好的树脂胶液,并利用差示扫描量热分析（DSC）研究了该多元体系的固化机理。通过调整树脂组分用量及优化工艺条件,制得了高耐热／湿热、低吸水率、综合性能良好的玻纤布基覆铜板,有望在“无卤无铅”化领域中得到应用。     

Towards model-based engineering of optoelectronic packaging materials: dielectric constant modeling

Increases in data transmission speeds of optoelectronic devices have consequently increased high-frequency requirements for optoelectronic packaging materials including substrate, EMC/EMI shielding, adhesive and encapsulant (molding and underfill) materials. Most of those materials are polymer/filler composites, and critical materials properties for the device design and packaging include the effective dielectric constant, dielectric loss and their frequency and filler concentration dependence. This work presents a systematic theoretical investigation of the effective dielectric constant of polymer/filler composite materials, and its dependence on the filler concentration, the filler/polymer interaction, and the size of fillers. Our results demonstrate that, in contrary to the prevailing views, the filler concentration dependence of the effective dielectric constant is non-monotonic. Depending on the dielectric constant ratio between filler and polymer matrix, and the degree of interaction between filler and matrix, the effective dielectric constant exhibits an extreme as a function of filler concentration. In addition, our model is demonstrated to contain the Maxwell–Wagner formulation as an asymptotic limit. The present results have significant implications to the targeted formulation of optoelectronic packaging materials.     

焊丝熔化填充方式对激光焊接熔池影响的数值模拟

结合激光深熔焊的焊接特性,建立焊丝熔化后进入熔池过程的三维瞬态激光焊接热-流耦合模型。研究了焊丝熔化填充方式对匙孔三维形态、熔池流动行为的影响,最后分析了焊丝熔化填充对匙孔稳定性的影响机制。计算结果表明,焊丝熔化以自由过渡的形式落入熔池对匙孔的形态影响较大,对匙孔前壁的挤压作用非常明显,造成了匙孔闭合、倒塌的情况;焊丝熔化沿熔池边缘流入熔池对匙孔的形态影响相对较小,匙孔下部会出现内凹的现象。焊丝熔化进入熔池之后在匙孔后方的熔池会产生两个顺时针的流动漩涡,流动漩涡的存在会使熔池内部流动行为更加复杂。     

Effect of underfill filler settling on thermo-mechanical fatigue analysis of flip-chip eutectic solders

Underfills containing filler particles exhibit filler settling during the (capillary-based) wicking and curing processes, thus causing the reliability estimation to deviate from that of the presumed base of no filler settling. This paper examines the thermo-mechanical responses of the solder joints in flip-chip packaging to various conditions of filler settling. We built five y-dependent profiles for describing the uniform, bilayered, and gradual settling of filler spheres in the through-depth direction of the underfill and used the Mori-Tanaka method to calculate the effective material properties of the filler-resin underfill compound by considering a linearly elastic, temperature-dependent resin with a glass transition temperature range of 70-130 °C. For each settling profile we analyzed the fatigue indicators, referred to as the inelastic shear strain ranges and the inelastic shear strain energy densities of the solder joints, and compared their magnitudes against the extent of filler settling. The results show that the fatigue indicators depend on the extent of filler settling. A greater extent of bilayered filler settling produced larger (in magnitude) fatigue indicators. The fatigue indicators associated with gradual filler settling, however, were almost always smaller, on average, than those associated with no filler settling, indicating that some types of filler settling might favor a longer solder fatigue life. This preliminary but intriguing finding may be partially explained by considering the asymmetric thermal mismatch in the through-depth direction of the underfill; a comparatively good thermal match near the bottom side of the solder joints may compensate for the thermal mismatch at the top side, thus contributing to an overall better thermal match in the solder joint.     

环氧塑封料中填充剂的作用和发展

环氧塑封料占据整个半导体封装市场的90％左右,而填充剂含量占环氧塑封料的60％～90％,因此填充剂的性能直接影响环氧塑封料的加工性能、机械性能、导热性能和半导体器件的封装工艺性能、导热性能、可靠性能等。另外,当今社会电子技术日新月异,集成电路正向着超大规模、超高速、高密度、大功率、多功能、绿色环保化的方向发展,因此对环氧塑封料的性能要求愈来愈高,相应的填充剂性能也有了许多新的要求,并且也出现了许多新型填充剂。文中详细地介绍了环氧塑封料中填充剂的作用,各种填充剂对环氧塑封料和封装器件的性能影响以及环氧塑封料中填充剂的分类和发展。     

Optimization of thermal interface materials for electronics cooling applications

Thermal interface materials (TIMs) are used in electronics cooling applications to decrease the thermal contact resistance between surfaces in contact. A methodology to determine the optimal volume fraction of filler particles in TIMs for minimizing the thermal contact resistance is presented. The method uses finite element analysis to solve the coupled thermo-mechanical problem. It is shown that there exists an optimal filler volume fraction which depends not only on the distribution of the filler particles in a TIM but also on the thickness of the TIM layer, the contact pressure and the shape and the size of the filler particles. A contact resistance alleviation factor is defined to quantify the effect of these parameters on the contact conductance with the use of TIMs. For the filler and matrix materials considered-platelet-shaped boron nitride filler particles in a silicone matrix-the maximum observed enhancement in contact conductance with the use of TIMs was by a factor of as much as nine.     

Filler size and content effects on the composite properties of anisotropic conductive films (ACFs) and reliability of flip chip assembly using ACFs

Flip chip assembly on organic board using anisotropic conductive films (ACFs) is gained more attention because of its many advantages. But to obtain more reliable flip chip assembly, it is necessary to have low coefficient of thermal expansion (CTE) value of ACFs. To control the CTE of ACF materials, non-conductive silica fillers were incorporated into ACFs. The effect of non-conductive silica filler content and size on cure kinetics and thermo-mechanical properties of ACFs was studied. Furthermore, filler content and size effects on reliability of flip chip assembly using ACFs were also investigated. In accordance with increasing filler content, curing peak temperature and storage modulus (E′) increased. But CTE decreased as the filler content increased. The effect of filler size on composite properties and assembly reliability showed similar tendency with the filler content effect. The smaller filler size was applied, the better composite properties and reliability were obtained. Conclusively, incorporation of non-conductive fillers, particularly in case of smaller size and higher content, in ACFs improves the material properties significantly, and as a result, flip chip assembly using ACFs is resulted in better reliability.     

Dependence of Flip Chip Solder Reliability on Filler Settling

Thermomechanical reliability of solder joints in flip-chip packages is usually analyzed by assuming a homogeneous underfill ignoring the settling of filler particles. However, filler settling does impact flip chip reliability. This paper reports a numerical study of the influence of filler settling on the fatigue estimation of flip-chip solder joints. In total, nine underfill materials ( 35 vol% silica filler in three epoxies with three filler settling profiles for each epoxy) are individually introduced in a 2-D finite element (FE) model to compare the thermal response of flip chip solder joints that are surrounded by the underfill. The results show that the fatigue indicators for the solder joints (inelastic shear strain increments and inelastic shear strain energy density) corresponding to a gradual, nonuniform filler profile studied in this paper can be smaller than those associated with the uniform filler profile, suggesting that certain gradual filler settling profiles in conjunction with certain resin grades may favor a longer solder fatigue lifetime. The origin of this intriguing observation is in the fact that the solder fatigue indicators are a function of the thermal mismatch among the die, substrate, solder, and underfill materials. The thermal mechanics interplayed among these materials along with a gradual filler profile may allow for minimizing thermal mismatch; and thus lead to lower fatigue indicators.      

Flexible,Multifunctional, Magnetically Actuated Nanocomposite Films

Filler nanoparticles greatly enhance the performance of polymers and minimize filler content in the resulting nanocomposites. At the same time, they challenge the manufacturing of such nanocomposites by filler agglomeration and non‐uniform spatial distribution. Here, multifunctional nanocomposite films are made by capitalizing on flame‐synthesis of ceramic or metal filler nanoparticles followed by rapid, in situ deposition on sacrificial substrates, resulting in a filler film with controlled porosity. The polymer is then spin‐coated on the porous film that retained its stochastic but uniform structure, resulting in nanocomposites with homogeneous filler distribution and high filler‐loading. By sequential repetition of this procedure, sophisticated, multilayer, free‐standing, plasmonic‐ (Ag‐Fe₂O₃) and phosphorescent‐superparamagnetic (Y₂O₃:Eu³⁺‐ Fe₂O₃) actuators are made by precisely tuning the polymer thickness between each functional nanostructured layer. These actuators are quite flexible, have fast response times, and exhibit superior superparamagnetism due to their high filler content and homogeneous spatial distribution.     

电子封装用SnAgCuGa钎料的改性

针对SnAgCu钎料存在的熔点偏高、润湿性较差等不足,研究了不同Sb含量对SnAg3.5Cu0.7Ga1钎料性能的影响。结果表明,随着Sb含量的增加,SnAg3.5Cu0.7Ga1钎料的固液相线呈增长趋势,但均低于230℃;Sb含量添加0.5%时,SnAg3.5Cu0.7Ga1合金在240℃无卤素松香助焊剂下润湿性变化不大,当Sb含量达到1.0%以上时,SnAg3.5Cu0.7Ga1合金的润湿性随着Sb含量的增加而提高。添加少量的Sb可以提高SnAg3.5Cu0.7Ga1无铅钎料的抗氧化性,随着Sb含量的增加,产生裂纹时的循环次数依次增加,可以提高钎焊铜合金接头的热疲劳强度。     

硅微粉填料在覆铜板中应用的研究进展

近年，在CCL的新品开发、性能改进方面，采用无机填料的技术已成很重要的手段。而在众多无机填料中，硅微粉越来越突出其重要地位。文章主要通过介绍、分析日本近年发表的此方面专利内容，阐述CCL业在硅微粉应用技术方面的新的进展。