SnAgCu无铅微焊点剪切力学性能的体积效应

对直径200～600 μm的Sn3.OAg0.5Cu无铅微焊点进行了多次重熔及老化试验,并采用专业的微小焊点力学性能测试仪DAGE4000测试了焊点的抗剪强度,分析了焊点体积差异对焊点抗剪强度的影响,发现SnAgCu无铅焊点的抗剪强度随着焊点体积增大呈下降趋势,体现出明显的体积效应.讨论了老化时间及重熔次数对不同体积焊...     

SnAgCu无铅钎料焊点结晶裂纹

针对印刷电路板(PCB)上无铅钎料SnAgCu微小焊点的结晶裂纹,利用设计的试件重现无铅钎料钎焊过程中产生的结晶裂纹,对无铅钎料结晶裂纹进行模拟,同时研究了微量元素的添加对SnAgCu合金焊点结晶裂纹形成的影响。结果表明,在尺寸很小的焊点上仍然存在明显的结晶裂纹。用焊点结晶裂纹的总长度定量地评价无铅钎料结晶裂纹的敏感倾向,添加Ni和Ce元素能够降低无铅钎料结晶裂纹的形成,而P元素的添加却加剧了结晶裂纹的形成,明显增加了焊点处的结晶裂纹。     

加载速率和钎料厚度对SnAgCu/Cu焊点剪切行为影响

采用四种加载速率(1,0.1,0.01,0.001 mm/s),对四种钎料厚度(0.1,0.2,0.3,0.6 mm)的SnAgCu/Cu搭接焊点进行了剪切破坏试验,分析了不同加载速率以及钎料尺寸对焊点抗剪切性能的影响,并通过扫描电镜(SEM)和能谱仪(EDS)分析了剪切试样断口形貌、裂纹的萌生位置及扩展路径,阐释了SnAgCu/Cu焊点断裂失效机理. 结果表明,加载速率在0.001~1 mm/s范围内,焊点抗剪切强度随加载速率的增加而增大,不同加载速率条件下焊点的断裂模式都为韧性断裂. 不同钎料厚度的SnAgCu/Cu焊点随着焊点厚度的减小,其抗剪切性能提高,表现出明显的体积效应,其裂纹萌生位置逐渐由焊点内部向IMC层转移. 焊点断口形貌为拉伸撕裂型伸长韧窝和剪切平面,断裂机理为微孔聚集型-纯剪切复合断裂.     

Cu基板粗糙度对SnAgCu无铅钎料润湿性的影响

在微电子封装软钎焊领域,钎料的润湿性直接决定焊接接头的性能.文中以不加入外来元素为前提,以SAC305/Cu钎焊体系为研究对象,完成了SAC305钎料在不同粗糙度Cu基板上的润湿铺展试验,研究了Cu基板粗糙度对SnAgCu钎料润湿性及SnAgCu/Cu界面化合物形貌与分布的影响.结果表明,?SnAgCu钎料在Cu基板上...     

元素Ga,Bi对SnAgCu无铅钎料性能的影响

在SnAgCu无铅钎料中添加金属元素Ga,Bi,对其合金进行熔化温度、润湿性、力学性能和微观组织研究.研究表明,添加Ga,Bi有利于降低SnAgCu合金的熔化温度和改善润湿性,并可提高其力学性能.     

Microstructure-based multiscale modeling of elevated temperature deformation in aluminum alloys

A multiscale model for predicting elevated temperature deformation in Al–Mg alloys is presented. Constitutive models are generated from a theoretical methodology and used to investigate the effects of grain size on formability. Flow data are computed with a polycrystalline, microstructure-based model which accounts for grain boundary sliding, stress-induced diffusion, and dislocation creep. Favorable agreement is found between the computed flow data and elevated temperature tensile measurements. A creep constitutive model is then fit to the computed flow data and used in finite-element simulations of two simple gas pressure forming processes, where favorable results are observed. These results are fully consistent with gas pressure forming experiments, and suggest a greater role for constitutive models, derived largely from theoretical methodologies, in the design of Al alloys with enhanced elevated temperature formability. The methodology detailed herein provides a framework for incorporation of results from atomistic-scale models of dislocation creep and diffusion.     

考虑几何必需位错非均匀分布的双相钢细观力学行为模拟

铁素体(F)-马氏体(M)双相钢在生产过程中由马氏体相变造成的铁素体内部的几何必需位错(GND)会保留在最终的材料组织中,而由GND非均匀分布导致的材料局部硬化效应使得铁素体晶粒内部的性能分布同样呈现非均匀特性.为了量化GND局部硬化效应对双相钢力学性能的影响,本文通过电子背散射衍射(EBSD)实验测定与数据分析确定了...     

应变率对无铅焊锡接点力学行为的影响

对150℃条件下经过0,72,288,500 h等温时效的Cu/Sn3.0Ag0.5Cu/Cu焊锡接点试样进行了应变率为2×10^-4,2×10^-2和2 s^-1的拉伸试验,研究了时效时间和应变率对焊锡接点抗拉强度和破坏模式的影响.结果表明,应变率对焊锡接点的抗拉强度有明显强化作用,抗拉强度随应变率的升高而增大.应变率从低到高的过程中,焊锡接点的破坏模式由焊料内部的韧性断裂逐渐转变为界面金属间化合物(intermetallic compound-IMC)层内的脆性断裂.     

Sn-3.5Ag-2Bi无铅焊料的压入蠕变性能

测试了Sn-3．5Ag-2Bi无铅焊料的压入蠕变应力指数n、蠕变激活能Q及其结构常数A,推导了压入蠕变稳态蠕变速率的本构方程,总结了压入蠕变随温度和应力的变化规律以及蠕变塑性变形机制,并初步探讨提高Sn-3．5Ag-2Bi无铅焊料抗蠕变性能的有效途径。结果表明：Sn-3．5Ag-2Bi无铅焊料的应力指数（n）为3．304、蠕变激活能（Q）为61．181kJ／mol,材料的结构常数（A）为0．679;并得出压入蠕变稳态蠕变速率的本构方程：压入蠕变的位移量随温度的升高和应力的增加有规律地变大：通过分析其蠕变前后的微观结构和组织的变化,认为Sn-3．5Ag-2Bi无铅焊料蠕变塑性变形机制主要由位错滑移和位错攀移共同控制。     

Cu对Sn-9Zn无铅钎料电化学腐蚀性能的影响

对Sn-9Zn-xCu钎料在3.5%NaCl溶液中的电化学腐蚀行为进行研究,以揭示添加Cu对Sn-9Zn钎料耐蚀性的影响。结果表明:添加Cu元素使Sn-Zn钎料的腐蚀电位有所增加,即添加Cu元素可以改善Sn-Zn钎料的耐腐蚀性能;XRD检测发现Sn-9Zn-xCu钎料的腐蚀产物中存在Zn5(OH)8Cl2.H2O;随着Cu含量的增加,Zn5(OH)8Cl2.H2O的量逐渐减少,出现Cu的腐蚀产物,腐蚀表面趋于均匀平整,选择性腐蚀减弱,腐蚀产物的黏附性较好。     

低银SnAgCuBiNi无铅钎料润湿及溶解行为分析

对Sn0.8Ag0.5Cu2.0Bi0.05Ni（SACBN）和Sn3.0Ag0.5Cu（SAC305）无铅钎料的显微组织、润湿性能和溶解行为进行了比较研究.结果表明,SACBN钎料显微组织由β-Sn＋共晶体组成,共晶组织为在β-Sn基体上均匀分布细针状的Ag3Sn、粒状的（Cu,Ni）6Sn5和细小粒状的铋.在相同温...     

不锈钢在共晶无铅钎料Sn3.0Ag0.5Cu中的润湿性能及溶蚀特征

研究了不锈钢304和316在无铅钎料Sn3.0Ag0.5Cu中的润湿性能和溶蚀特征。采用润湿平衡法测量结果发现,与不锈钢304相比,不锈钢316显示更具稳定的润湿平衡力;并且不锈钢304在溶蚀性能测试中发现固液界面处发生均匀的界面反应,而不锈钢316则只在某些特定位置处发生固液界面反应。     

电子互连无铅钎料及焊点蠕变行为研究进展

针对近年来无铅钎料及焊点的蠕变失效问题,综合评述了蠕变变形行为及其在焊点可靠性评估中的应用。首先系统地介绍无铅钎料的蠕变行为,探讨含合金元素/颗粒无铅钎料蠕变性能改性机制。其次评述焊点蠕变行为,探讨焊点成分以及不同基板材料对焊点蠕变特性影响的研究进展。再次结合具体电子器件,采用有限元模拟,分析基于有限元的焊点蠕变响应及疲劳寿命预测,评估焊点可靠性。最后针对无铅钎料及焊点蠕变行为的未来发展进行展望,分析其研究中存在的问题及解决办法,为焊点可靠性进一步研究提供理论支撑。     

Structural and elastic properties of eutectic Sn-Cu lead-free solder alloy containing small amount of Ag and In

Sn-Cu alloys have been considered as a candidate for high temperature lead-free microelectronic solders. In the present study, the change in microstructure, attenuation and elastic behavior associated with alloying of Ag and/or In into the eutectic Sn-Cu solder alloy system have been evaluated. The study involved measurements of longitudinal and shear wave velocities, attenuation, hardness, bulk and shear moduli, Young's and Poisson's ratio. The results of attenuation show that a clear attenuating effect in the ternary Sn-Cu-Ag and Sn-Cu-In alloys is realized, whereas the quaternary Sn-Cu-Ag-In solder displays an obscure attenuating effect. The obscure effect is mainly attributed to the competition for In between Sn and Ag, which results in weak interface formed between intermetallic compounds (IMCs) and β-Sn matrix. Likewise, Poisson's ratio results indicate that its value decreases with increasing the elastic moduli and ultrasonic velocities of Ag and In-containing alloys. The analyzed enhanced ductility of Sn-0.7Cu and Sn-0.7Cu-2In alloys and brittleness of Sn-0.7Cu-2Ag and Sn-0.7Cu-2Ag-2In alloys were rationalized on the basis of Poisson's ratio and the quotient of shear modulus to bulk modulus (Pugh's ratio). Microstructural analysis revealed that the origin of change in the elastic properties of the ternary and quaternary alloys is ascribed to smaller β-Sn dendrite grain dimensions and formation of new IMCs in the ternary and quaternary alloys.     

SnAgCu焊点界面金属间化合物的研究现状

SnAgCu系合金钎料是目前最有可能替代SnPb钎料的无铅钎料之一.其在回流焊过程中产生的界面金属间化合物是影响电子产品可靠性的重要因素.综述了SnAgCu钎料在Cu,Ni/Cu,Au/Ni/Cu衬底上回流焊后界面金属间化合物(IMC)的类型和产生过程,并对时效、热冲击、热循环过程中界面金属间化合物的形貌演变以及生长规...     

复配表面活性剂对无铅助焊剂润湿性能影响的研究

助焊剂中的表面活性剂对于降低熔融无铅钎料的表面张力,增加无铅钎料对母材的润湿性具有重要作用.根据表面活性剂的HLB值和分子量,选取了四种不同类型的表面活性剂.以无水乙醇作溶剂,有机酸作活性剂,加入所选表面活性剂,并添加成膜剂、缓蚀剂等其他成分,配制成助焊剂,用于研究表面活性剂对无铅钎料润湿性能的影响.润湿力测试及铺展实...     

镀镍多壁碳纳米管对Sn-3.0Ag-0.5Cu无铅钎料焊点界面行为的影响

采用机械混合法制备了不同含量(0、0.05、0.1、0.2、0.5wt%)镀镍多壁碳纳米管(Ni-CNTs)复合Sn-3.0Ag-0.5Cu(SAC305)无铅钎料。采用F4N回流炉对SAC305-x(Ni-CNTs)钎料进行回流焊,利用电热鼓风干燥箱对焊点试样进行170 ℃时效(t=0、48 h)处理。结合DTA、SEM、EDS等分析手段研究了不同镀镍碳纳米管含量对Sn-3.0Ag-0.5Cu钎料润湿性、熔点和焊点界面金属间化合物(IMC)层的影响。结果表明:Ni-CNTs可以显著改善钎料的润湿性,降低钎料熔点;此外,Ni-CNTs可以有效抑制界面IMC层的生长,同时改变界面IMC组成。综合比较得出Ni-CNTs最佳添加量为0.05%,与Sn-3.0Ag-0.5Cu钎料相比,润湿角降低49.76%,熔点降低0.331 ℃;时效后界面IMC层厚度4.292 μm(t=0 h)、5.238 μm(t=48 h)相对于SAC305钎料界面IMC厚度6.529 μm(t=0 h)、8.255 μm(t=48 h)分别降低了34.26%(t=0 h)、36.55%(t=48 h),界面IMC层相组成转变为(Cu_1-xNi_x)₆Sn₅和(Cu_1-xNi_x)₃Sn。     

冷热冲击对无铅钎料可靠性的影响

文中对比了一种新型低银钎料Sn-Ag-Cu-Bi-Ni（SACBN07）与市场上的SAC305,SAC0307两种无铅钎料的抗冷热冲击性能.利用纳米压痕试验等微观测试方法研究时效后界面组织及力学性能的变化.结果表明,SACBN07的抗冷热冲击性能最好,焊点失效后三种材料中裂纹的扩展路径不同,SAC305失效裂纹位于体钎料中,SACBN07钎料断裂位置逐渐由钎料基体转移到金属间化合物（IMC）层中,而SAC0307断裂位于界面IMC中;钎料中Bi,Ni元素的加入有效地抑制了IMC的生长,相同冷热冲击时间,SACBN07钎料中界面IMC厚度最薄;SACBN07体钎料的硬度受冷热冲击影响最小,时效后仅降低了8.6%,而SAC305与SAC0307分别降低了12.5%和28.3%.     

Progress in the design of new lead-free solder alloys

Various alloy design approaches have been employed to develop new lead-free solder alloys that can not only substitute for the lead-tin solders, but also offer significantly improved mechanical properties. Three new alloys are described in this article. In Sn-3.5Ag-1Zn (melting point ~217°C), the solidification structure and the eutectic precipitate morphology are6 refined by the addition of zinc. As a result, a high-strength, high-ductility solder with significantly improved creep resistance is obtained. In Bi-43Sn+2.5Fe, a eutectic alloy (melting point ~137°C), dispersion hardening by magnetically distributed iron particles retards both high-temperature deformation and microstructural coarsening, thus widening the useful service range of Bi-Sn eutectic alloys to much higher homologous temperatures than are typical for the Sn-Pb eutectic alloy. Lastly, Sn-Zn-In based alloys (melting point ~185°C) have been developed for consideration as a drop-in replacement for the neareutectic Sn-Pb alloy(melting point ~183°C).