颗粒增强Sn-Ag基无铅复合钎料显微组织与性能

通过外加法向Sn-3.5Ag焊料中加入体积分数为10%的微米级Cu、Ni颗粒制备了无铅复合钎料,对钎料的显微组织、拉剪及润湿性能进行了研究。结果表明,颗粒周围以及基板界面处的显微组织中生成了金属间化合物,其形态及大小因加入颗粒而不同。颗粒的加入提高了钎料钎焊接头的剪切强度,其中Cu颗粒增强的接头的剪切强度提高了33%,Ni颗粒的提高了20%。两种复合钎料的铺展面积均下降了约15%,其中Cu颗粒增强复合钎料润湿角由11°增加到18°。     

Sn3．5Ag0．75Cu钎料与Au／Ni／Cu焊盘接头老化过程中IMC组织的演变

通过SEM（Scanning Electron Microscope）背散射照片和EDX（Energy Dispersive X-Ray Spectroscopy）成分分析研究了无铅钎料Sn3．5Ag0．75Cu与Au／Ni／Cu焊盘接头在老化过程中其界面金属间化合物（IMC）的生长演变过程；在175℃温度条件下老化72h后发现Cu可以穿过Ni层参与形成界面金属间化合物（Au，Ni，Cu）Sn4和（Au，Ni，Cu）6Sn5；基于金属间化合物生长动力学理论计自得该焊点结构中AuSn4生长的活化能为53．78KJ／mol。[第一段]     

添加微量稀土元素的SnAgCu无铅钎料的研究

介绍目前国际上较为公认的SnAgCu系无铅钎料的特点,并汇总了国际上相关专利的情况.同时,结合本实验室的专利技术,介绍了添加微量稀土对SnAgCu系无铅钎料性能的影响,并着重研究了稀土对显微组织,特别是金属间化合物的影响规律.研究结果表明:从综合性能角度考虑,添加稀土的作用明显,特别是显著改善了钎料的抗蠕变性能,稀土添加量的最佳范围在w(0.05～0.25)%之间.适量的稀土添加,可有效抑制金属间化合物的生长,细化组织.     

无铅钎料焊点界面与剪切行为的研究

研究了三种不同合金钎料回流时间和老化时间对焊点界面行为和剪切性能的影响。结果表明:回流时间和老化对金属间化合物的生长和剪切力有相似的影响;焊后界面处和焊料中均有明显的金属间化合物;随着回流时间和老化时间的延长,金属间化合物生长明显。层厚不断增大;界面形貌从长针状转变成扇贝状,并且齿高减小;合金成分对剪切力影响不明显。在中速应变率下,剪切力减小。Sn-3.5Ag显现出较好的剪切性能,剪切力为77~82 N。     

微电子组装中Sn-Zn系无铅钎料的研究与开发

无铅钎料的研究开发是我国电子材料行业目前面临的紧迫课题.其中Sn-Zn系无铅钎料具有低的熔点,优良的力学性能,能获得可靠的钎焊接头,且其原材料丰富、价格便宜,有望替代Sn-Pb钎料.但该系钎料易氧化,抗腐蚀性较差,目前还未得到广泛的采用.介绍了开发新型无铅钎料应满足的要求,及几种有潜力的Sn-Zn系无铅钎料.     

热输入及掺Ni对Sn-Ag钎料强度的影响

Sn-Ag共晶钎料中添加Ni颗粒,在钎料内部形成强化相,达到强化效果。研究了Ni颗粒的添加配比对强化效果的影响,并提出了热输入概念,通过调节热输入量控制钎料的强度。结果表明,φ(Ni)为5%是最佳配比,当热输入量为5.07时,其强度值最高,达60.71 MPa。比未添加Ni的钎料提高50%以上。     

Ag含量对Sn-Zn-Ag无铅钎料腐蚀性能的影响

在Sn-Zn共晶钎料中加入不同含量的Ag元素制成Sn-9Zn-xAg无铅钎料,利用失重法、扫描电镜的腐蚀形貌观察以及EDS成分分析,分析了Sn-9Zn-xAg无铅钎料在3%NaCl溶液浸泡腐蚀情况下的腐蚀行为,并与Sn-Pb以及Sn-Zn钎料进行比较.结果表明:随着Ag含量的增加,钎料合金的抗腐蚀性能有所提高.     

无铅钎料Sn-0.7Cu机械合金化研究

利用扫描电子显微镜和差热分析仪,研究了Sn-0.7Cu粉末的机械合金化过程;同时将机械合金化获得的粉末制成焊膏,进行铺展实验,并对金相组织进行了分析.研究结果表明,机械合金化是一种制备钎料粉体的方法;粉末的最终颗粒尺寸可通过合适的工艺参数来控制;用机械合金化获得的钎料粉体制成的焊膏,其铺展面积及润湿角方面与传统的熔炼法获得的钎料差别不大,铺展试样的金相组织由富Sn相、Cu6Sn5和少量Cu3Sn相组成.     

Sn-Zn系无铅钎料最新进展

Sn-Zn系钎料熔点与传统Sn-37Pb钎料十分接近,成本低廉,被研究者所推崇。由于Zn的存在导致Sn-Zn钎料润湿性差及抗氧化性不足,阻碍了该钎料的发展。添加合金元素和纳米颗粒是改善Sn-Zn钎料组织和性能行之有效的方法之一,为国内外研究者所推崇。结合国内外Sn-Zn系无铅钎料最新研究成果,探讨添加微量的合金元素In、Ni、Cr、Ga、Bi、Cu、Al、Ag、稀土元素及纳米颗粒对钎料润湿性、抗氧化性、力学性能、显微组织和界面组织的影响,同时简述有关钎剂对Sn-Zn的影响,并对Sn-Zn系钎料的发展趋势进行分析与展望。     

锡基无铅钎料的性能研究与新进展

介绍了现阶段锡基无铅钎料的使用和生产情况,归纳了钎料合金的特点,综述了不同系列无铅钎料的熔化特性、焊后的剪切强度及可焊性等,总结了目前无铅钎料研究所取得的新成果、新进展以及存在的问题。从锡晶须,虚焊等方面指出了无铅钎料可靠性的不足,并提出部分解决方案,指出了无铅钎料的发展趋势和应用前景。     

Mechanical properties of intermetallic compounds on lead-free solder by moiré techniques

In this paper, methods for determining elastic moduli and coefficients of thermal expansion (CTE) of intermetallic compounds (IMC) formed at the interfaces between lead-free solder and metal substrates are presented. For the determination of elastic moduli, two kinds of lead-free solder—SnZn and Sn—were used; the metal substrates were copper and nickel. Nanoindentation techniques were adopted to determine the elastic moduli of Cu_33.5Zn_66.6, Cu₃Sn, Cu₆Sn₅, and Ni₃Sn₄. Results for Cu_33.5Zn_66.6 are new to the literature, and others values are in good agreement with those presented in the literature. On the other hand, for CTE determination, two moiré techniques, namely reflection moiré and shadow moiré, were developed to measure the deformation of IMC/metal composite structures subjected to thermal loading. Finite-element analyses using ANSYS were then performed as a convolutional process, and the genetic search algorithm was used to optimally obtain the CTE of IMC. The CTE of Cu_33.5Zn_66.6 was found to be approximate to that of copper, and the CTE of Cu₃Sn was 10% larger. This method is also applicable to on-wafer films and IMC on micrometer order, such as the case of solder/IMC/under bump metallization.     

纳米压痕法分析无铅焊点内界面金属化合物的力学性能

根据实际工艺流程和服役工况制备了微电子封装中3种无铅焊点(Sn3.0Ag0.5Cu、Sn0.7Cu和Sn3.5Ag)内界面金属化合物(IMC)的试样;利用扫描电镜(SEM)和能量色散X射线荧光光谱仪(EDX)对所制IMC的形貌和化学成分进行了分析;另外,借助纳米压痕仪,采用连续刚度测量(CSM)技术在不同的加载速率下对所制IMC的弹性模量和硬度进行了测量。结果表明,3种无铅焊点内的IMC均为Cu6Sn5,其弹性模量分别为98.93±3.37,113.55±4.58和(102.16±3.11)GPa,硬度分别为5.18±0.14,5.78±0.11和(5.55±0.19)GPa。     

Sn-58Bi-0.5Ce/Cu界面金属间化合物的性能研究

研究了Sn-58Bi-0.5Ce/Cu钎焊接头在120℃时效过程中界面组织形貌及金属间化合物层(IMC)的厚度变化。结果表明:在Sn-58Bi-0.5Ce/Cu钎焊接头界面处形成了较为平坦的双层金属间化合物,靠近钎料的上层为Cu6Sn5相,邻近Cu基板的下层为Cu3Sn相。等温时效处理后,IMC层逐渐凸起,且随着时效时间的增加,IMC层不断增厚。通过对实验数据进行拟合,得到钎焊接头界面IMC层的生长速度常数为5.77×10–17m2/s。     

Morphology and growth kinetics of intermetallic compounds in solid-state interfacial reaction of electroless Ni-P with Sn-based lead-free solders

A comparative study of solid/solid interfacial reactions of electroless Ni-P (15 at.% P) with lead-free solders, Sn-0.7Cu, Sn-3.5Ag, Sn-3.8Ag-0.7Cu, and pure Sn, was carried out by performing thermal aging at 150°C up to 1000 h. For pure Sn and Sn-3.5Ag solder, three distinctive layers, Ni₃Sn₄, SnNiP, and Ni₃P, were observed in between the solder and electroless Ni-P; while for Sn-0.7Cu and Sn-3.8Ag-0.7Cu solders, two distinctive layers, (CuNi)₆Sn₅ and Ni₃P, were observed. The differences in morphology and growth kinetics of the intermetallic compounds (IMCs) at the interfaces between electroless Ni-P and lead-free solders were investigated, as well as the growth kinetics of the P-enriched layers underneath the interfacial IMC layers. With increasing aging time, the coarsening of interfacial Ni₃Sn₄ IMC grains for pure Sn and Sn-3.5Ag solder was significantly greater than that of the interfacial (CuNi)₆Sn₅ IMC grains for Sn-0.7Cu and Sn-3.8Ag-0.7Cu solders. Furthermore, the Ni content in interfacial (CuNi)₆Sn₅ phase slightly increased during aging. A small addition of Cu (0.7 wt.%) resulted in differences in the type, morphology, and growth kinetics of interfacial IMCs. By comparing the metallurgical aspects and growth kinetics of the interfacial IMCs and the underneath P-enriched layers, the role of initial Cu and Ag in lead-free solders is better understood.     

Morphology of intermetallic compounds formed between lead-free Sn-Zn based solders and Cu substrates

The morphologies of intermetallic compounds formed between Sn-Zn based solders and Cu substrates were investigated in this study. The investigated solders were Sn-9Zn, Sn-8.55Zn-0.45Al, and Sn-8.55Zn-0.45Al-0.5Ag. The experimental results indicated that the Sn-9Zn solder formed Cu₅Zn₈ and CuZn₅ compounds on the Cu substrate, while the Al-containing solders formed the Al_4.2Cu_3.2Zn_0.7 compound. The addition of Ag to the Sn-8.55Zn-0.45Al solder resulted in the formation of the AgZn₃ compound at the interface between the Al_4.2Cu_3.2Zn_0.7 compound and the solder. Furthermore, it was found that the cooling rate of the specimen after soldering had an effect on the quantity of AgZn₃ compound formed at the interface. The AgZn₃ compound formed with an air-cooling condition exhibited a rougher surface and larger size than with a water-quenched condition. It was believed that the formation of the AgZn₃ compound at the interface occurs through heterogenous nucleation during solidification.     

内生无铅复合钎料在不同工艺条件下的制备及性能研究

通过采用不同工艺的内生法在Sn-3.5Ag共晶钎料基体中引入弥散分布的Cu6Sn5颗粒,制得了内生无铅复合钎料。研究了不同工艺条件对该钎料力学性能及电迁移行为的影响。结果表明,在冷却速度(0.1℃/s)较慢时制备的钎料,其内生Cu6Sn5颗粒细小,分布最均匀,且团聚程度较轻,另外,其钎焊接头力学性能最好;通5 A电流384 h后,其正负极金属间化合物层厚度的差异保持在约1.2μm,说明Cu6Sn5颗粒的引入提高了钎料的抗电迁移性能。     

无铅焊点在热疲劳和电迁移作用下的组织演变

研究了Cu/Sn-58Bi/Cu焊点接头在室温和55℃下通电过程中阴极和阳极界面处微观组织的演变,电流密度均采用104A/cm2。结果表明,室温条件下通电达到25 d,Bi原子由阴极向阳极发生了扩散迁移,在阳极界面处形成了厚度约22.4μm的均匀Bi层,而阴极出现了Sn的聚集。加载55℃通电2 d后,焊点发生了熔融,阴极界面处形成了厚度为34.3μm的扇贝状IMC,而阳极界面IMC的厚度仅为9.7μm。在IMC层和钎料基体之间形成了厚度约7.5μm的Bi层,它的形成阻碍了Sn原子向阳极界面的扩散迁移,进而阻碍了阳极界面IMC的生长,导致了异常极化效应的出现。     

Effects of intermetallic morphology at the metallic particle/solder interface on mechanical properties of Sn-Ag-based solder joints

Mechanical incorporation of metallic particles in the Sn-Ag-based solder resulted in various intermetallic compound (IMC) morphologies around these particles during reflow. Unlike with the Ni particles, the IMCs formed around Cu and Ag particles are relatively insensitive to reflow profiles employed. The IMC formed around the Ni particles ranges from “sunflower” morphology to “blocky” morphology with increasing time and temperature above liquidus during the heating part of the reflow profile. Mechanical properties, such as simple shear strength and creep behavior, of these composite solders were affected by the IMC morphologies in the composite solders investigated. Sunflower-shaped IMC formed around an Ni particles resulted in higher simple shear strength and better creep properties.