Effects of Au and Pd Additions on Joint Strength, Electrical Resistivity, and Ion-Migration Tolerance in Low-Temperature Sintering Bonding Using Ag2O Paste

A new bonding process using an Ag₂O paste consisting of Ag₂O particles mixed with a triethylene glycol reducing agent has been proposed as an alternative joining approach for microsoldering in electronics assembly, which currently uses Pb-rich, high-temperature solders. Ag nanoparticles were formed at approximately 130°C to 160°C through a reduction process, sintered to one another immediately, and bonded to a metal substrate. An Au-coated Cu specimen was successfully bonded using the Ag₂O paste. The resulting joint exhibited superior strength compared with joints fabricated using conventional Pb-rich solders. To improve ion-migration tolerance, the Ag₂O paste was mixed with Au and Pd microparticles to form sintered Ag-Au and Ag-Pd layers, respectively. The additions of Au and Pd improved the ion-migration tolerance of the joint. Regarding the mechanical properties of the joints, addition of secondary Au and Pd both resulted in decreased joint strength. To match the joint strength of conventional Pb-10Sn solder, the mixing ratios of Au and Pd were estimated to be limited to 16?vol.% and 7?vol.%, respectively. The electrical resistivities of the sintered layers consisting of 16?vol.% Au and 7?vol.% Pd were lower than that of Pb-10Sn solder. Thus, the additive fractions of Au and Pd to the Ag₂O paste should be less than 16?vol.% and 7?vol.%, respectively, to avoid compromising the mechanical and electrical properties of the sintered layer relative to those of contemporary Pb-10Sn solder. Following the addition of Au and Pd to the paste, the ion-migration tolerances of the sintered layers were approximately 3 and 2 times higher than that of pure Ag, respectively. Thus, the addition of Au was found to improve the ion-migration tolerance of the sintered Ag layer more effectively and with less sacrifice of the mechanical and electrical properties of the sintered layer than the addition of Pd.     

Influence of Joining Conditions on Bonding Strength of Joints: Efficacy of Low-Temperature Bonding Using Cu Nanoparticle Paste

We investigated a new low-temperature bonding process utilizing Cu nanoparticle paste without addition of sintering promoter. Joint bonding strengths above 30 MPa were achieved even at a low bonding temperature of 250ºC. We attribute the higher bonding strengths of joints fabricated using the vacuum preheating process to the rapid progression of Cu nanoparticle sintering due to the activated nanoparticle surface at lower temperatures. The increase in bonding strength depended on the applied pressure, in addition to the bonding temperature. The formation of a dimple-like morphology was confirmed in the ductile fracture area. This indicated that the joint bonded strongly with the bonding layer, in agreement with the results of bonding tests carried out on strongly bonded joints. The bonding ability of the joints obtained using Cu nanoparticle paste could be improved by controlling the joint fabrication conditions.     

Y2O3增强Sn-3Ag-0.5Cu复合无铅钎料

研究了稀土氧化物颗粒增强复合无铅钎料Sn-3Ag-0.5Cu-Y2O3的钎焊接头的显微组织形貌、性能特点及有关影响机制.结果表明:Y2O3增强颗粒均匀分布于Sn-3Ag-0.5Cu钎料基体中,不仅细化了钎焊接头中共晶相Ag3Sn和Cu6Sn5相颗粒尺寸,而且也显著提高了钎焊接头的剪切强度.另外适量Y2O3颗粒的添加对钎料润湿性影响不大.     

聚乙二醇含量对纳米TiO2多孔薄膜性质的影响

以钛酸丁酯为无机原料、二乙醇胺作稳定剂,加入聚乙二醇(PEG)作模板制备前驱体溶胶,通过溶胶-凝胶工艺和浸渍提拉技术在玻璃基片上制备了孔径在10～1000nm范围内可调的纳米TiO2多孔薄膜.通过ESEM,AFM,UV-VIS,N2吸附,XPS和XRD等测试手段研究了PEG(1000)的加入量对薄膜结构及性能的影响.结果表明,当100mL溶胶中PEG的加入量在4.0g左右时,可以得到三维扩展的多孔结构,孔的形状规则且分布均匀,孔径为200～500nm,薄膜比表面积可达76.1m2/g,而过多的PEG加入量反而导致薄膜性能下降.     

聚乙二醇含量对纳米TiO2多孔薄膜性质的影响

以钛酸丁酯为无机原料、二乙醇胺作稳定剂,加入聚乙二醇（PEG）作模板制备前驱体溶胶,通过溶胶-凝胶工艺和浸渍提拉技术在玻璃基片上制备了孔径在10～1000nm范围内可调的纳米TiO2多孔薄膜．通过ESEM,AFM,UV-VIS,N2吸附,XPS和XRD等测试手段研究了PEG（1000）的加入量对薄膜结构及性能的影响．结果表明,当100mL溶胶中PEG的加入量在4.0g左右时,可以得到三维扩展的多孔结构,孔的形状规则且分布均匀,孔径为200～500nm,薄膜比表面积可达76.1m2／g,而过多的PEG加入量反而导致薄膜性能下降．     

Fluxless Bonding of Silicon to Ag–Copper Using In–Ag With Two UBM Designs

A fluxless process of bonding silicon to Ag-cladded copper using electroplated In–Ag multilayer structure is developed. The Ag cladding on the copper substrate is a stress buffer to deal with the large mismatch in coefficient of thermal expansion (CTE) between semiconductors such as Si (3 ${hbox {ppm}}/^{circ}{hbox {C}}$) and Cu (17 ${hbox {ppm}}/^{circ}{hbox {C}}$). To manufacture Ag on copper substrate, two techniques are developed. The first is an electroplating process to fabricate a thick Ag layer. The second technique is a novel laminating process that bonds Ag foil directly on Cu substrate. On Si chips, two underbump metallurgy (UBM) structures are designed, Si/Cr/Au and Si/Cr/Ni/Au. To produce a solder layer, Si chips are electroplated with In followed by thin Ag. The thin Ag cap layer prevents oxidation of the inner In region. To achieve a fluxless feature, the bonding process is performed in a vacuum environment (50 mtorrs) to suppress indium oxidation. Compared to bonding in air, the oxygen content is reduced by a factor of 15 200. Using Cr/Au UBM structure, the silicon chip was detached from Cu substrate. The broken interface lies between Si/Cr and ${hbox {Ag}}_{2}{hbox {In}}$ IMC on Cu substrate. Using a new UBM design of Si/Cr/Ni/Au, high-quality joints are produced that comprise of three distinct layers of ${hbox {In}}_{7}{hbox {Ni}}_{3}$, ${hbox {Ag}}_{2}{hbox {In}}$ , and Ag. Microstructure and composition of the joints are studied using a scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX).      

银键合丝力学性能对键合质量的影响

通过调节微合金元素的含量获得3种具有不同力学性能的银键合丝.利用拉伸试验、键合试验、焊线挑断力、焊球推力测试等手段,研究了银键合丝力学性能对键合质量的影响.结果表明,在延伸率相同的条件下,随着微合金元素含量的降低,3种键合丝的断裂负荷降低,初始模量先减小后增大,键合后焊线挑断力和焊球推力均降低,电极金挤出率先减小后增大.银键合丝初始模量较低时在超声和压力的作用下易于变形,焊线内残余应力较低且第二焊点与引线框架结合较好,因此挑断测试时第二焊点与框架材料界面处不易发生脱离,有利于获得更高的键合成功率.     

聚乙二醇共水热合成TiO2纳米晶多孔薄膜

以钛酸丁酯为原料,在水热过程中加入聚乙二醇(分子量2 000)合成TiO2纳米晶,并制备多孔薄膜用于染料敏化太阳能电池(DSSCs)。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、台阶仪、紫外-可见分光光度计(UV-vis)对纳米晶粒的晶体结构、薄膜的表面形貌、厚度和光学吸收性能以及电池的光电能量转换性能随聚乙二醇的加入量变化的规律进行了探索。结果表明,聚乙二醇的加入抑制了锐钛矿相TiO2晶粒的生长,诱导了金红石相的形成。当聚乙二醇的加入量为TiO2质量的5%时性能达到最佳,采用单层多孔薄膜以及不添加四-叔丁基吡啶的电解质组装的电池获得了2.86%的光电能量转换效率。     

Effects of Phenolic Resin Addition on the Electrical Conductivity and Mechanical Strength of Nano-Copper Paste Formed Cu-Cu Joints

Cu-Cu joints bonded by nano-copper pastes with different amounts of phenolic resin were developed at a low temperature (240°C) and a low pressure (1 MPa). The shear strengths of the joints were measured and the bonding layers were observed by scanning electron microscopy. The electrical conductivity of the joints was tested by a parameter analyzer. The results indicated that 2% phenolic resin in the pastes doubled the shear strength of Cu-Cu joints compared to joints made with 0%, 5% and 8% phenolic, because it filled the voids and coated sintered Cu nanoparticles in the joints without affecting the electrical conductivity of the Cu-Cu joint. This was because 2% phenolic paste prevented Cu nanoparticles from oxidation. However, 8% phenolic resin led to an increase of electrical resistivity due to the insulating property of phenolic resin, and a decrease of shear strength due to the hindrance to sintering between the nanoparticles.     

Cu引线超声键合FAB工艺及影响研究

通过对50μm直径铜引线超声键合过程中烧球工艺参数的优化,分析了各参数对烧球质量的影响及原因,并通过键合试验重点讨论了铜球表面质量、形球尺寸等对键合质量的影响.     

Low Temperature Bonding of Alumina/Alumina and Alumina/Copper in Air Using Sn3.5Ag4Ti(Ce,Ga) Filler

Sn3.5Ag4Ti(Ce,Ga) active filler was used for joining alumina with alumina and alumina with copper at 250°C in air. The joining process was done without flux and without the need for pre-metallization of alumina or a protective atmosphere. After mechanical activation of the bonding surfaces of alumina and copper, the filler showed good wetting on both alumina and copper and led to a strong bond between alumina and copper. Through tensile testing, a bonding strength of 23.7 MPa was found in the alumina/copper joint region. The shear strengths for alumina/alumina, copper/copper and alumina/copper joints were 13.5, 14.3, and 10.2 MPa, respectively. The affinity of cerium for oxygen protects titanium from oxidation, giving rise to the reaction of titanium with alumina at such a low temperature. Electron probe microanalyzer (EPMA) elemental mapping revealed that titanium segregates effectively at the alumina/solder interfaces. After aging tests at 200°C and 150°C, a double layer of Cu₃Sn and Cu₆Sn₅ intermetallic compound was formed at the solder/copper interfaces. With an increase of aging periods, the amount of brittle compound in the joints increased and resulted in decreases in the shear strengths of the alumina/copper joints.     

Bi2O3添加剂对Ag2O-Nb2O5-Ta2O5介电性能的影响

以Bi2O3为添加剂，研究其不同质量比对Ag2O-Nb2O5-Ta2O5(ANT)系统介电性能的影响。用XRD衍射和SEM扫描作为技术手段，研究其不同质量比对Ag2O-Nb2O5-Ta2O5系统微观结构的影响。     

添加物对Ag2O-Na2O-Nb2O5-Ta2O5介电性能的影响

添加物对改善(Ag1-xNax)(Nb1-yTay)O3陶瓷系统的各项介电性能起重要的作用.该文着重讨论了改性添加物Sb2O5和矿化剂MnO2的含量对本系统性能的影响.实验表明,w(Sb2O5)对本系统损耗的影响较复杂,应控制在2.5%,而矿化剂MnO2的加入能有效改善本系统的烧结性能,w(MnO2)应控制在2.0%,这样才能将本系统的损耗有效降低至6.0×10-4.     

AlN-to-Metal Direct Bonding Process Utilizing Sintering of Ag Nanoparticles Derived from the Reduction of Ag<Subscript>2</Subscript>O

Bonding between AlN and metals conventionally requires a surface modification process at high temperature such as metallization. The AlN-to-metal direct bonding process by sintering of Ag nanoparticles derived from in situ reduction of Ag₂O microparticles mixed with diethylene glycol is examined. Bonding was conducted at 300–500 °C after a preheating process at 100 °C, and the shear strength exceeded 20 MPa for the joint bonded at 500 °C. The role of preheating in the direct bonding of AlN and Ag was identified. The Ag nanoparticles generated during preheating at 100 °C cover the AlN surface, and they are converted into a thin Ag film. The thin film promotes the formation of a bonding layer, owing to the effective adhesion of the sintered Ag to the film, and contributes to the bonding of Ag and AlN. No interfacial reaction layer is observed. The same bonding process can be applied to other ceramics with poor wettability.     

Chip to Chip Bonding Using Cu Bumps Capped with Thin Sn Layers and the Effect of Microstructure on the Shear Strength of Joints

Chip to chip bonding techniques using Cu bumps capped with thin solder layers have been frequently applied to 3D chip stacking technology. We studied the effect of joint microstructure on shear strength. Joints were formed by joining Sn/Cu bumps on a Si die and Sn/Cu layers on another Si die at 245–330°C using a thermo-compression bonder. Three different types of microstructures were fabricated in the joints by controlling the bonding temperature and time, (1) a Sn-rich phase with a Cu₆Sn₅ phase at the Cu interfaces, (2) a Cu₆Sn₅ phase in the interior with a Cu₃Sn phase at the Cu interfaces, and (3) one single Cu₃Sn phase throughout the whole joint. The joint having a single Cu₃Sn phase had the highest shear strength. Specimens were aged up to 2000 h at 150°C and 180°C. During aging, the microstructures of all joints were transformed in a single Cu₃Sn phase. The shear strength of the joints was very sensitive to the formation of Cu₃Sn and microvoids. Microvoids formed in the solder joints with a Cu₆Sn₅ phase with and without a Sn-rich phase during aging and decreased the shear strength of the joints. Conversely, aging did not induce the formation of microvoids in the joints which originally had only a Cu₃Sn phase and the shear strength was not decreased.     

基于Multi-stage的double stitch工艺在铜线焊中的应用

作为引线键合工艺中传统的焊接材料,金线在稳定性、导电性及价格等方面存在诸多局限,使得铜线焊技术在IC封装领域得到越来越广泛的应用。同时,由于铜线易氧化、硬度高,焊接能力较低,特别是二焊点容易出现拉力不够、开裂等缺陷,使得铜线焊的应用受到限制。针对传统工艺流程,提出Multi-stage方法,并在此基础上实现二焊点的double stitch工艺方法,通过试验证明该方法能够有效提高二焊点拉力,增强焊接强度。     

铜丝球焊中形球过程的数值模拟＊

本文采用数值模拟的方法研究了铜丝球键合技术中的形球过程。通过对超细铜丝在微电弧作用下形球过程中的温度场、速度场和位移场的计算,阐明了铜丝球形成的规律.文中对位移场的计算结果进行了实验验证。     

Growth of Intermetallic Compounds in Thermosonic Copper Wire Bonding on Aluminum Metallization

Interface evolution caused by thermal aging under different temperatures and durations was investigated by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that approximately 30-nm-thick and discontinuous Cu-Al intermetallic compounds (IMCs) were present in the initial bonds before aging. Cu-Al IMCs grew under thermal aging with increasing aging time. The growth kinetics of the Cu-Al IMCs was correlated to the diffusion process during aging; their combined activation energy was estimated to be 1.01 eV. Initially, Al-rich Cu-Al IMCs formed in the as-bonded state and early stage of aging treatment. Cu₉Al₄ was identified by selected-area electron diffraction (SAD) as the only type of Cu-Al IMC present after thermal aging at 250°C for 100 h; this is attributed to the relatively short supply of aluminum to the interfacial reaction.     

Effects of Bonding Temperature and Pressure on the Electrical Resistance of Cu/Sn/Cu Joints for 3D Integration Applications

This study reports the effects of bonding conditions (temperature and pressure) on the bonding morphology and electrical resistance of a Cu/Sn/Cu structure. By carefully characterizing the bond using several analytical methods [scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and transmission electron microscopy (TEM)], we have learned that bonding the samples under various conditions produces greatly different bond morphologies, as well as different prevailing phases in the bonded layer. However, measurements of the electrical resistance of the joints reveal a relative insensitivity to the bonding conditions, signaling that the microstructural evolution and the bond morphology do not strongly influence the resistance.     

表面活性剂对厚膜电子浆料流平性的影响

通过测量丝网印刷后膜层的表面粗糙度来表征厚膜电子浆料的流平性,研究了常用表面活性剂司班 85 及卵磷脂含量对浆料流平性的影响。结果表明,随着有机载体中表面活性剂含量增加,厚膜电子浆料的流平性变差。此外,还初步分析了表面活性剂对提高浆料的分散性和稳定性的作用。