Effect of Ce on solderability of Sn-Cu-Ni solder

Abstract A small amount of rare earth Ce was added to Sn-Cu-Ni solder alloy, and the solderability of Sn-0. 5Cu-0. 05Ni- xCe solders on Cu and Au/Ni/Cu substrates was determined by the wetting balance method. The effects of atmosphere, temperature, substrate, and Ce addition on the solderability of Sn-Cu-Ni-xCe solder were studied, respectively, and Auger electron spectroscopy （ AES） analysis in the depth direction of the alloy was carried out to discuss the effect of Ce addition on the solderability. The results indicate that the greatest improvement on the solderability of Sn-Cu-Ni-xCe is obtai^d with around O. 05wt. % -0. 07wt. % Ce addition, for Ce element keeps high content in a specific area in the depth direction from the surface of Sn-Cu-Ni alloy, which decreases the surface tension of molten solder. It is also found that the solderability of Sn-Cu-Ni-xCe solder on Au/Ni/ Cu substrate is better than that on Cu substrate. In N2 atmosphere, the wetting times of Sn- Ca-Ni-xCe alloys are reduced by 10% - 35% , below 1 s at 260 ℃ on Ca substrate, and about 1s at 250 ℃ on Au/Ni/Ca substrate.

Preventing formation of intermetallic compounds in ultrasonic-assisted Sn soldering of Mg/Al alloys through pre-plating a Ni coating layer on the Mg substrate

Magnesium and aluminum alloys are widely used in various industries because of their excellent properties,and their reliable connection may increase application of materials.Intermetallic compounds(IMCs)affect the joint performance of Mg/Al.In this study,AZ31 Mg alloy with/without a nickel(Ni)coating layer and 6061 Al alloy were joined by ultrasonic-assisted soldering with Sn-3.0Ag-0.5Cu(SAC)filler.The effects of the Ni coating layer on the microstructure and mechanical properties of Mg/Al joints were systematically investigated.The Ni coating layer had a significant effect on formation of the Mg_(2)Sn IMC and the mechanical properties of Mg/Al joints.The blocky Mg_(2)Sn IMC formed in the Mg/SAC/Al joints without a Ni coating layer.The content of the Mg_(2)Sn IMC increased with increasing soldering temperature,but the joint strength decreased.The joint without a Ni coating layer fractured at the blocky Mg_(2)Sn IMC in the solder,and the maximum shear strength was 32.2 MPa.By pre-plating Ni on the Mg substrate,formation of the blocky Mg_(2)Sn IMC was inhibited in the soldering temperature range 240–280℃and the joint strength increased.However,when the soldering temperature increased to 310℃,the blocky Mg_(2)Sn IMC precipitated again in the solder.Transmission electron microscopy showed that some nano-sized Mg_(2)Sn IMC and the(Cu,Ni)_(6)Sn_(5)phase formed in the Mg(Ni)/SAC/Al joint soldered at 280℃,indicating that the Ni coating layer could no longer prevent diffusion of Mg into the solder when the soldering temperature was higher than 280℃.The maximum shear strength of the Mg(Ni)/SAC/Al joint was 58.2 MPa for a soldering temperature of 280℃,which was 80.7%higher than that of the Mg/SAC/Al joint,and the joint was broken at the Mg(Ni)/SAC interface.Pre-plating Ni is a feasible way to inhibit formation of IMCs when joining dissimilar metals.

A review of soldering by localized heating

In recent years,the rapid development of the new energy industry has driven continuous upgrading of high-density and high-power devices.In the packaging and assembly process,the problem of differentiation of the thermal needs of different modules has become increasingly prominent,especially for small-size solder joints with high heat dissipation in high-power devices.Localized soldering is con-sidered a suitable choice to selectively heat the desired target while not affecting other heat-sensitive chips.This paper reviews several local-ized soldering processes,focusing on the size of solder joints,soldering materials,and current state of the technique.Each localized solder-ing process was discovered to have unique characteristics.The requirements for small-size solder joints are met by laser soldering,microres-istance soldering,and self-propagating soldering;however,laser soldering has difficulty meeting the requirements for large heat dissipation,microresistance soldering requires the application of pressure to joints,and self-propagating soldering requires ignition materials.However,for small-size solder junctions,selective wave soldering,microwave soldering,and ultrasonic soldering are not appropriate.Because the magnetic field can be focused on a tiny area and the output energy of induction heating is large,induction soldering can be employed as a significant trend in future research.

Interfacial reaction behavior and mechanical properties of 5A06 Al alloy soldered with Sn-1Ti-xGa solders at a low temperature

Active soldering of 5A06 Al alloy was performed at 300 ℃ by using Sn-1Ti and Sn-1Ti-0.3Ga active solders, respectively. Theeffects of soldering time on the microstructure and mechanical properties of the joints were investigated. The results showed that the Sn-1Tisolder broke the oxide film on the surface of the Al substrate and induced intergranular diffusion in the Al substrate. When Ga was added tothe solder, severe dissolution pits appeared in the Al substrate due to the action of Sn-1Ti-0.3Ga solder, and many Al particles were flakedfrom the matrix into the solder seam. Under thermal stress and the Ti adsorption effect, the oxide film cracked. With increasing solderingtime, the shear strength of 5A06 Al alloy joints soldered with Sn-1Ti and Sn-1Ti-0.3Ga active solders increased. When soldered for 90 min,the joint soldered with Sn-1Ti-0.3Ga solder had a higher shear strength of 22.12 MPa when compared to Sn-1Ti solder.

Research Progress on the Solder Joint Reliability of Electronics Using in Deep Space Exploration

The spacecraft for deep space exploration missions will face extreme environments,including cryogenic temperature,intense radiation,wide-range temperature variations and even the combination of conditions mentioned above.Harsh environments will lead to solder joints degradation or even failure,resulting in damage to onboard electronics.The research activities on high reliability solder joints using in extreme environments can not only reduce the use of onboard protection devices,but effectively improve the overall reliability of spacecraft,which is of great significance to the aviation industry.In this paper,we review the reliability research on SnPb solder alloys,Sn-based lead-free solder alloys and In-based solder alloys in extreme environments,and try to provide some suggestions for the follow-up studies,which focus on solder joint reliability under extreme environments.

Effect of Strain Rate on Tensile Behavior of Sn-9Zn-xAg-ySb;{(x, y) = (0.2, 0.6), (0.2, 0.8), (0.6, 0.2), (0.8, 0.2)} Lead-Free Solder Alloys

The tensile properties of Sn-9Zn-xAg-ySb;{(x, y) = (0.2, 0.6), (0.2, 0.8), (0.6, 0.2), (0.8, 0.2)} lead-free solders were investigated. All the test samples were annealed at 150°C for 1 hour. The tests are carried out at room temperature at the strain rate of 4.17 × 10-3 s-1, 20.85 × 10-3 s-1, and 208.5 × 10-3 s-1. It is seen that the tensile strength increases and the ductility decrease with increasing the strain rate over the investigated range. From the strain rate change test results, the strain sensitivity values are found in the range of 0.0831 to 0.1455 due to the addition of different alloying elements.

大尺寸AlN活性金属焊接覆铜基板的界面结合机理

基于190 mm×139 mm×0.635 mm的大尺寸AlN表面活性金属钎焊(AMB)覆铜板工艺制程,开展其界面显微组织、物相组成等的研究,确定钎焊界面结合机理,为制备大尺寸、低气孔、高剥离强度AlN-AMB覆铜板提供支持。结果表明,在大尺寸AlN-AMB覆铜板钎焊过程中,Ag-Cu-Ti合金钎料中的Ag-Cu合金与Cu箔扩散溶合,形成强的冶金结合界面。同时,钎料中的活性Ti原子向AlN基板表面扩散,并与其反应,生成厚度为0.5~1μm的TiN反应层,形成强的反应结合界面。此外,钎料熔体难以填充基板的AlN晶界和凹坑,其中的Ti原子也不与Y-Al-O第二相颗粒反应,导致AlN基板表面TiN反应层不连续分布,形成气孔,降低大尺寸AlN-AMB覆铜板的界面结合强度及可靠性。

SnAgCu/SnBi混装焊点的热循环可靠性研究

Sn-Bi和Sn-Ag-Cu混装焊点是利用低熔点的Sn-58Bi锡膏将高熔点的Sn-3.0Ag-0.5Cu(SAC305)的小球回流焊接在印制电路板(PCB)上,从而实现高温芯片的低温焊接工艺.文中研究了SnAgCu/SnBi混装焊点在热循环条件下的可靠性并通过有限元模拟揭示了混装焊点热循环可靠性的应变演变行为.热循环试验发现混装焊点的寿命要优于SAC305无铅焊点.有限元计算表明,结构混装焊点内SnBi钎料层的添加能够减小最大非弹性应变范围,从而提升混装焊点的热循环可靠性.

基于焊层裂纹扩展的IGBT性能退化建模与分析

在疲劳载荷作用下,绝缘栅双极型晶体管(insulated gate bipolar transistor,IGBT)会发生结构损伤与性能退化,影响电力电子系统可靠性。对此,首先基于传热学理论推导焊层疲劳裂纹长度与热阻的关系,并以Darveaux模型表征IGBT焊层裂纹演化规律,提出一种IGBT性能退化模型及其待定系数的估计方法。其次,考虑实际工况的非平稳特征,利用响应面法建立IGBT变幅疲劳载荷模型,并基于雨流计数法与线性累积损伤准则实现IGBT性能退化量的评估。最后,以一款IGBT产品为例,实施功率循环试验,基于试验数据开展性能退化建模与分析,验证了模型与算法的有效性。

PCB中耐高温有机可焊保护剂成膜机理及性能研究

印制电路板铜焊盘表面生成耐高温有机可焊保护剂(HT-OSP)膜是克服无铅高温回流焊工艺并获得良好焊点的关键。选用2-[(2,4-二氯苯基)甲基]-1H-苯并咪唑(C_(14)H_(10)Cl_(2)N_(2))作为成膜剂,在铜层表面生成了HT-OSP膜。理论计算结合对比实验,研究C_(14)H_(10)Cl_(2)N_(2)分子与Cu原子反应生成HT-OSP膜机理。基于量子化学密度泛函理论,模拟C_(14)H_(10)Cl_(2)N_(2)分子与Cu^(+)之间的络合反应;利用红外光谱对HT-OSP膜中的特征官能团进行表征;借助X射线光电子能谱测试HT-OSP膜中Cu元素的化合价;设计对比实验分析Cu^(2+)对生成HT-OSP膜的影响。结果表明:HT-OSP膜生成机理是C_(14)H_(10)Cl_(2)N_(2)分子与Cu原子发生反应生成HT-OSP膜并沉积在铜层表面,Cu^(2+)通过络合反应促进HT-OSP膜生长。另外,HT-OSP膜的分解温度高达531℃,HT-OSP膜保护的铜层放置在自然环境中180天没有被氧化,证明HT-OSP膜具有优异的耐热性和抗氧化性。

电子封装高温焊料研究新进展

随着先进封装和第三代半导体的快速发展,具有高熔化温度、耐持久温度考验的高温焊料逐渐成为学界追逐的热点,也成为推动电子产业无铅化和升级换代等“卡脖子”问题的瓶颈。本文综述了传统高温Sn-80Au和Pb-Sn焊料、IMC焊料、纳米及纳米-微米混合焊料,提出未来高温焊料在成分上必将以金、银、铜、铝等金属或石墨烯、碳纳米管等轻质、高导热、高熔化温度的碳基材料及其复合材料为主流;在微观尺度上,纳-微米混合焊料既具有纳米焊料的温度效应,又具有颗粒选择的灵活性,能在一定程度上解决纳米焊料的氧化、团聚及烧结时的相转变等问题;基于颗粒焊料的多尺度、颗粒种类选择的多维度,具有低温快速制备、高温长期服役的IMC高温焊料也具有极大的前途。加速高温焊料研发,突破低温封装、高温服役的技术瓶颈,必将极大推动先进封装和功率封装的快速发展。

基于度量学习的电路焊点缺陷检测方法

针对目前电路焊点缺陷检测方法效率低、准确度差、焊点图像样本量小的问题,提出了一种基于度量学习的快速识别焊点缺陷的方法.首先利用工业相机搭配远心镜头获取焊点图像.通过挖掘焊点图像特征,设计交点检测法来分割焊接单元图像,制作焊点缺陷数据集.在此基础上,设计焊点图像全局特征与局部表征提取方法来对焊点的两类特征进行融合,并对注意力机制进行改进,加入到全局特征提取模块中.对焊点缺陷的检测实验结果表明该方法最终实现了准确率达到98.4%,满足焊点缺陷检测的实际生产要求.

基于能量最小化的CCGA焊点形态仿真研究

为了确定某陶瓷柱栅阵列(CCGA)器件实现高焊接可靠性时的工艺参数组合范围,并研究焊点形态随不同参数变化的规律,以钎料润湿角、钎料体积以及焊柱偏移量作为关键变量因素,利用基于能量最小化原理的Surface Evolver软件,计算了不同因素水平组合下的实际焊点形态,并对参数化建模过程进行了详细介绍。通过对比形态结果与焊点可接收标准,寻找能够产生合格焊点的参量范围,为实际焊点微连接生产工艺提供合理的工艺指导。

某高导热绝缘胶在星载端机可靠性应用评价

针对星载端机对高导热绝缘底填胶可靠性应用需求,开展双组分高导热绝缘胶可靠性及环境适应性综合影响评估。通过导热绝缘胶性能测试标准样件,测试验证本征性能指标及工艺性指标,并分析评估其合格性;设计制作典型BGA菊花链网络结构样件,采用导热胶填充工艺技术,验证导热绝缘胶空洞率对BGA器件焊点的影响,评价其工艺适应性;设计制作星载端机载荷,开展星载产品验收级环境与可靠性试验,验证端机载荷具有经受工作应力和环境应力的能力。该高导热绝缘胶满足星载产品散热及抗高载荷的需求,实现可靠性应用。

基于双目结构光的三维立体电路板焊点定位

三维立体电路将传统二维集成电路拓展至三维,在提高了电路板形状设计柔性的同时,也提升了电路板上元器件焊点定位的复杂度.为了降低三维立体电路加工过程中的人力成本,提高加工效率,设计了一种用于焊接机床对三维立体电路板焊点定位的双目结构光系统,并针对双目结构光系统在与焊接机床结合应用过程中存在的坐标转换、焊点识别困难等问题,从硬件与算法层面提出了解决方案.在软硬件的配合下,可以简单快速地完成双目结构光系统与焊接机床之间的坐标转换,并对电路板焊点完成定位与坐标计算,代替了人工对三维立体电路板焊点测量定位的复杂流程.实验表明,提出的方案具有较高的精度,能够满足机床焊接元器件过程中对焊点的定位需求.

温度与镀层对Sn-Cu-Ni无铅钎料润湿性能的影响

采用润湿平衡法测定了在不同试验温度下Sn-Cu-Ni无铅钎料在Cu,Au/Ni/Cu,SnBi/Cu三种基板上的润湿时间和润湿力,研究了钎焊温度对Sn-Cu-Ni无铅钎料在不同基板上润湿性能的影响。结果表明,温度升高使Sn-Cu-Ni无铅钎料的表面张力减小,能显著缩短钎料在铜片上的润湿时间,提高润湿力;Ni/Au或SnBi等镀层能显著降低钎料/基板界面张力,因此Sn-Cu-Ni无铅钎料在Au/Ni/Cu或SnBi/Cu基板上的润湿性能优于在Cu基板上的润湿性能。

氮气保护对Sn-Cu-Ni-Ce无铅钎料润湿性的影响

基于润湿平衡原理测定了不同温度与不同气氛下Sn-Cu-Ni-Ce钎料在Cu基板上的润湿行为，研究了气氛、温度以及微量稀土元素Ce对其润湿性能的影响。结果表明。采用氮气保护时，Cu基板表面张力提高，钎料表面张力降低，润湿时间缩短了20％～50％，润湿力也显著提高；温度升高使Sn-Cu-Ni-Ce钎料的表面张力减小，显著缩短了钎料在Cu基板上的润湿时间；稀土元素Ce可显著降低熔融钎料的表面张力和钎料，基板间的界面张力，从而使Sn-Cu-Ni-Ce钎料的润湿性能较Sn-Cu-Ni钎料有了显著的改善。

基于波峰焊桥连改善的设计优化研究

波峰焊是一种常见的电装工艺焊接方式,而桥连是波峰焊工艺最为常见的焊接缺陷之一。介绍了波峰焊接桥连产生的机理,并分析了焊盘间距过近、引脚出脚长度过长,以及器件布局方向不当三种典型可制造性设计引起桥连的原因,并探讨了有助于波峰焊接桥连改善的可制造性设计优化方案。

回流焊工艺对SMT器件热翘曲的影响

集成电路正在向小型化、高集成度的方向发展,回流焊工艺已成为其组装过程中的关键技术。在回流焊过程中集成电路容易发生热翘曲现象。采用阴影云纹法对PBGA1296、PBGA1024器件在不同回流焊温度、升降温速率的回流焊工艺下的热翘曲进行测量,在此基础上通过建模仿真对实验结果进行分析。结果表明,采用表面贴装技术(SMT)的BGA器件的热翘曲会随着回流焊温度的升高而增大,回流焊升降温速率较快同样会导致严重的热翘曲。实验结果与仿真结果高度一致,进而验证了仿真模型的准确性和有效性。采用实验结合有限元分析的方法为改善集成电路热翘曲提供了参考。

温度循环和随机振动载荷下堆叠封装焊点可靠性模拟研究

采用有限元模拟研究了堆叠封装(Package on package, PoP)在温度循环和随机振动载荷下的焊点可靠性,包括封装内部的基板堆叠焊点和封装外部的板级互连焊点。通过应力分析定位危险焊点并计算焊点在温度循环下的疲劳寿命。模拟结果表明:在温度循环载荷下,应力主要集中于基板边角处焊点,基板堆叠焊点的疲劳寿命为3 002周次,板级互连焊点的疲劳寿命为1 552周次;在随机振动载荷下,两层焊点的应力值均较低,在50~2 000 Hz的随机振动频率范围内具有较高的可靠性。