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。     

EMC所用环保阻燃剂介绍及优缺点比较

随着人们健康环保意识的增强,寻求环保化、低毒化、高效化、多功能化的阻燃剂已成为阻燃剂行业的必然趋势。对于环保模塑料来讲,必须有相对应的符合法令要求的产品。用环保阻燃剂替代原先使用的溴锑阻燃剂加入到基础配方中制备了环保塑封料,文章简单介绍了目前市场上主要的有机及无机阻燃剂的种类,并重点讲述了在环氧塑封料中引用各环保阻燃剂...     

塑封胶吸湿对器件分层影响的研究

进行3种塑封胶的吸湿试验来证实其在相同器件中的不同可靠性表现由吸湿量的差异造成,得到了树脂相同的塑封胶的吸湿量与二氧化硅填充量之间的关系。证实了MSL3条件下塑封胶吸湿遵循Fick定律,并且得到了MSL3条件下3种塑封胶中湿气的扩散系数。综合考虑回流过程中蒸汽压、塑封胶吸湿膨胀和热膨胀,进行了界面分层风险的定量分析。     

The impact of moisture in mold compound preforms on the warpage of PBGA packages

The moisture in the mold compound preforms influenced the resultant mechanical properties as well as the warpage of IC packages after the molding and post mold curing (PMC) process. Moisture will diffuse into the mold compound preforms (compound pallet) after thawing from cold room and exposing to clean room condition before molding process. The moisture will cause the package to swell, and combine with thermal stress, and finally result in the warpage of molded package after molding process. The main objective of this paper is to address the impact of moisture in the compound preforms on the warpage of the PBGA packages and explain the change in mechanical properties under different moisture conditions, e.g., the variations of the flexural modulus, T_g, and CTE with respect to moisture level. The compound preforms exposure to a clean room condition were simulated by a series of experiments. The warpage of PBGA packages were measured by the moiré test. The moisture control during the IC manufacturing process was highlighted in terms of the mechanical properties variation and warpage measurement due to the moisture effects on the mold compound preforms.     

Comparative characterization of chip to epoxy interfaces by molecular modeling and contact angle determination

An investigation of interfacial interaction has been performed between three epoxy molding compound materials and a native silicon dioxide layer (SiO₂) usually found at chip surfaces. The epoxy materials were an industry oriented epoxy molding compound Epoxy Phenol Novolac (EPN), its filled variety EPN^F (with silica particles) and a model aromatic epoxy¹ (2 1 2). All systems are described in full in [1] and [2]. The free surfaces of the solid materials were experimentally analyzed by contact angle measurements of three different liquids (water, methylene-iodide (MI) and glycerol). Results are compared to interfacial energies obtained by analysis of the interfaces in bimaterial molecular models, yielding reasonable agreement. A qualitative prediction regarding the influence of water on the interfacial strength between chip and molding compound is attempted.     

Packaging Effect on MEMS Pressure Sensor Performance

In this study, the effect of epoxy based molding compound packaging on a micro-electro-mechanical system (MEMS) pressure sensor performance is investigated. A series of experiments were conducted to characterize the MEMS sensor over temperature and pressure changes by measuring output voltage signals. The sensor was modeled by a finite element method to investigate the stress developments. The molding compound was assumed as elastic and viscoelastic material to examine the material modeling effect on the calculation results. The model was verified by comparing the calculated results with experimental data. It was found that the stress induced by the molding compound had significant influence on the sensor performance, and the accuracy of the calculations was highly dependent on the modeling of the molding compound. Based on the results, the mechanism of the stress development and its effect on the sensor signal were discussed     

Bromine- and chlorine-induced degradation of gold-aluminum bonds

The presence of bromine (Br) in flame retardant epoxies accelerates the degradation of gold-aluminum wire bonds. This experiment tests degradation by adding 5 wt.% 2,6-dibromophenol to the regular molding compound and holding thermal aging at 175°C and 205°C in ovens for up to 1,008 h. The intermetallic degrading microstructure was examined at different aging times. In order to better understand the mechanism behind the degradation, bulk Au₄Al and Au₅Al₂ single-intermetallic phases were prepared and reacted with molding compound at 205°C. The reactions were analyzed by a JEOL (Japan Electron Optics Ltd., Tokyo) Superprobe JXA-8900R under wavelength-dispersive spectrometry of x-ray mode. A similar chloride degrading study was performed by adding Tetrachlorobisphenol A to the regular molding compound. The results show that Br attacked the Au₄Al phase first and then the Au₅Al₂ phase. The chloride reacted with the Au₄Al phase only.     

Properties of molding compounds to improve package reliability ofSMDs

Package cracking during reflow soldering process is the great problem in the reliability of plastic packages. The technique of lowering the glass transition temperature (Tg) of a molding compound is very effective for improvement of the package cracking resistance because of the properties of low moisture absorption and high adhesion strength for a molding compound. But the package reliability except for the package cracking resistance is also important. In this study, the effects of the Tg for molding compounds on the package reliability was discussed. It was confirmed that decreasing the crosslinking density was an important factor to improve the package cracking resistance. There was no problem in thermal resistance, even if the molding compound has low Tg. However, decreasing the crosslinking density by the lowering of Tg may not satisfy humidity resistance in some cases. It was found to be important to decrease the crosslinking density of molding compounds without lowering Tg in order to improve both the package cracking resistance and the humidity resistance. It was also confirmed that the introduction of rigid structural segments into the matrix resin molecules of the molding compound was a useful technique for achieving excellent package reliability     

Accelerated popcorn testing of high solder-reflow crack resistant molding compounds

In testing the resistance of a molding compound to popcorn failures after solder reflow, there are two basic options for shortening the moisture absorption phase: varying the severity of moisture exposure by varying the temperature and percent relative humidity or maintaining a constant humidity/temperature profile and varying the length of time the compounds are exposed. In addition, the total testing time can be accelerated by the choice of test method. There are three major measurement techniques for evaluating the extent of popcorn cracking: SAM testing; bubble chamber testing; and visual crack inspection. In this paper we will explore the effects of differing lengths of exposure time and the merits of different measurement techniques.A variety of epoxy resins, filler mixtures and adhesion additives were examined in semiconductor molding compounds for solder-reflow crack resistance (popcorn crack resistance). A limited comparison of molding compound high-temperature strength properties and extent of popcorn cracking suggests no strong positive correlation. On the other hand, factors that might have an impact on adhesion properties of the molding compound, such as low melt viscosity resins and putative adhesion additives, appear to have the greatest impact. A molding compound developed with these factors showed no internal or external cracks on 84 lead QFPs (29.2 × 29.2 × 3.68 mm) after 72 h of 85°C/85% R.H. and one 10 s solder dip at 260°C. Nor were any external cracks observed after 168 h of 85°C/85% R.H. and one solder dip. However, minor internal cracks were observed.The most data can be obtained by using bubble chamber testing for large numbers of parts and evaluating a smaller sample of the best of those compounds via SAM testing with crack extension analysis. The length of exposure time affected the parts as expected, with longer times being more severe. There did not appear to be a gradient effect or a threshold level. In general, 72 h allowed the greatest differentiation among the compounds tested for internal defects; external defects were not fully developed until 168 h of moisture exposure.     

SD卡用环保塑封料研究

环氧塑封料是微电子工业和技术发展的基础材料,作为IC产品后道封装的三大主材料之一,随着IC封装技术的发展,IC产品未来发展趋势倾向于小体积和高性能化的方向,对其特性的要求也越来越严格。SD卡为目前流行的存储设备,长兴电子材料(昆山)有限公司开发出针对SD卡的EK5600GHL环保塑封料产品,此产品具有低吸湿率、低收缩率、高流动性及高可靠性的特点,可以满足SD卡封装要求。同时文章还介绍了SD卡用环保塑封料的测试数据、可靠性测试结果和客户端可靠性评估结果。     

QFN用环保塑封料研究

环氧塑封料是微电子工业和技术发展的基础材料,作为IC产品后道封装的三大主材料之一,随着IC封装技术的发展,对其特性的要求也越来越严格。IC产品未来发展趋势倾向于小体积高性能化的方向,QFN即为顺应此发展趋势所开发出来的封装形式。针对此封装形式长兴电子材料(昆山)有限公司开发出EK5600GH环保塑封料产品,此产品具有低吸湿率、低收缩率、高流动性及高可靠性的特点,可以满足QFN封装要求。同时还分别介绍了QFN用环保塑封料的测试数据、可靠性测试结果和客户端可靠性评估结果。     

核壳橡胶在环氧模塑料中分散及增韧改性研究

应用于环氧模塑料时,核壳橡胶的团聚在正常挤出工艺过程中无法再次分散,它的团聚使得环氧模塑料塑封后的塑封体在CSAM图像中产生黑点。将核壳橡胶与表面活性剂在树脂体系中进行混合预搅拌,能够有效地将已打散的核壳橡胶粒子完全隔离开,从而达到分散核壳橡胶粒子的目的。分散好的核壳橡胶在环氧模塑料中能够提高塑封料的飞边性能,降低塑封料的模量,对应力的吸收有促进作用,从而提高环氧模塑料的可靠性。     

环氧模塑料在半导体封装中的应用

环氧模塑料是一种重要的微电子封装材料,是决定最终封装性能的主要材料之一,具有低成本和高生产效率等优点,目前已经成为半导体封装不可或缺的重要材料。本文简单介绍了环氧模塑料在半导体封装中的重要作用和地位;分析了环氧模塑料性能对半导体封装的影响,并对不同半导体封装对环氧模塑料的不同要求进行了分析;最后展望半导体封装和环氧模塑料的未来发展趋势,以及汉高华威公司在新产品开发中的方向。     

Molding compound trends in a denser packaging world: qualificationtests and reliability concerns

This work benchmarks the current reliability tests used by the electronics industry, examines those tests that affect and are affected by molding compounds, discusses the relevance of accelerated testing, and addresses the major reliability issues facing current molding compound development efforts. Six compound-related reliability concerns were selected: moldability; package stresses; package cracking; halogen-induced intermetallic growth at bond pads; moisture-induced corrosion; and interfacial delamination. Causes of each failure type are surveyed and remedies are recommended     

Investigation of delamination control in plastic package

Interfacial delamination control is important for the mechanical reliability of plastic package, especially facing the challenge of lead-free requirement. Efforts of delamination performance improvement including structure, material and process for plastic package were made. It was demonstrated that the improvement of packaging material mechanical properties should depend on the package and purpose and should be the comprehensive consideration of advantage and disadvantage. The fracture mechanics was introduced to explain the mechanism of bumpy interface as the delamination retardant. The moisture absorption experiments of three kinds of molding compound were carried out to confirm that large difference of delamination performance among different molding compounds for the same device in our project was induced by moisture absorption difference, and the relation between the moisture weight absorbed and weight ratio of resin was obtained, given compounds of the same resin. It was substantiated that the moisture absorption of molding compound observes the Fick’s law at (Moisture Sensitivity Level 3) MSL3. Quantitative analyses of the moisture influence at the risk location were conducted to evaluate the risk of delamination with the consideration of vapor pressure during solder reflow, moisture and thermal expansion.     

Characterization of moisture properties of polymers for IC packaging

In this paper we determined the water uptake of a die attach and a molding compound. The two types of polymer which were selected are a die attach filled with silver particles and an epoxy molding compound filled with silica particles. The water absorption is carried out in an adjustable thermal and humidity chamber, SGA-100, at different temperatures and humidity levels. Moisture absorption equilibrium of test data were obtained by experiment. The moisture absorption equilibrium prediction equation was modeled by using the extrapolated experimental data. Diffusion coefficients at different temperature were obtained from the moisture absorption experiments.     

A simple model for the mode I popcorn effect for IC packages

A simple model for the Mode I popcorn effect is presented here for packages with rectangular die pad (P-DSO). A package “stability parameter”, relating to its moisture sensitivity, is derived from the popcorn model. It describes the critical factors for a robust package - molding compound properties and package, leadframe design for a given preconditioning and soldering process. Furthermore, nomograms generated from the model enable an easy estimation of moisture sensitivity levels (between 1 and 5) of packages with different die pad sizes and molding compound underpad thicknesses and for different soldering temperatures ranging from 220°C to 260°C (Pb-free soldering).     

Ion transport in encapsulants used in microcircuit packaging

Most semiconductor devices are encapsulated in epoxy molding compounds. These molding compounds contain ionic contaminants including chloride ions from epichlorohydrin used in the epoxidation of the resin and bromine ions incorporated into the resin as a flame retardant. Chloride ions are known to break down the protective oxide on the surface of aluminum metallization and accelerate corrosion. The encapsulant material is hydrophilic and will absorb moisture from the environment. When the absorbed moisture is combined with ions, there is an opportunity for electrolytic corrosion to occur on the metal surfaces of the device and package elements. However, the rate of corrosion in an encapsulated microcircuit may be expected to depend upon the rate of ion transport through the encapsulant. This paper evaluates two techniques for the measurement of ion diffusion in epoxy molding compounds used for microelectronic encapsulation. The data suggests that ion diffusion rates vary with molding compound formulation, the solution pH and the ion concentration. SEM-EDX analysis and TOF-SIMS analysis indicate that the mode of diffusion of ions in the encapsulants is primarily through the polymer resin matrix as opposed to diffusion at the interface of the resin and the filler particles. Calculated diffusion coefficients were slower than the literature values for moisture diffusion or the diffusion of gases. In fact, under basic conditions, the ions tend to diffuse through the molding compound almost as a front suggesting that the ions bind to the encapsulant and that the diffusion of ions in molding compounds can be modeled using a Type II non-Fickian model.     

塑封IC翘曲问题

为分析封装材料及模塑过程参数对塑封IC翘曲的影响,本文先介绍塑料四边引线扁平封装(PQFP)使用的环氧模塑化合物(EMC)的热特性。并对不同模塑样品的聚合程度(DOC)、热膨胀系数(CTE)、玻璃转变温度Tg、剪切模量G等,运用各种热分析技术进行测量。结合不同封装过程参数,运用三维有限元分析法进行封装翘曲预测。最后对塑料四边引线扁平封装(PQFP)IC翘曲的测量值与预测值进行比较。     

复合陶瓷颗粒/环氧模塑料的制备与性能

选用SiO_2、Al_2O_3、Si_3N_4三种陶瓷颗粒的复合填充环氧模塑料(EMC),研究了不同填料种类、含量对EMC导热系数、热膨胀系数(CTE)、介电常数等性能的影响随着填料百分含量的增加,EMC的热导率、介电常数也随之增加,而其热膨胀系数显著下降相同体积百分含量下,Al_2O_3、Si_3N_4复合体系EMC热导率和介电常数高于SiO_2、Si_3N_4复合体系,而其热膨胀系数比后者低。百分含量为60%时,前者热导率达到2．254 W(m·K)~(-1)、后者达到2．04w(m·K)~(-1)。百分含量为65%时,其CTE分别为1．493×10~(-5)K~(-1)、1．643×10~(-5)K~(-1),同时两体系复合材料的介电常数可以维持在较低水平