Influence of stress on the creep behavior of Cu particle enhancement SnPb based composite solder joints

1. Introduction Mechanical fracture of solder joints is a major cause of failure and it decreases the reliability in electronic systems. With the increased functionality, miniaturization of electronic components, broad op-eration temperature ranges, and increased stress re-quirement, good mechanical properties are de-manded on solder joints. The eutectic tin-lead solder, which has a low melting point (183°C), plays an important role in SMT (surface mount technology). The working temperature…     

纳米Ag颗粒增强复合钎料蠕变性能的研究

制备纳米Ag颗粒增强的Sn-Cu基复合钎料.研究不同温度载荷下复合钎料钎焊接头的蠕变断裂寿命,并与Sn-0.7Cu基体钎料钎焊接头进行对比.此外,确定纳米Ag颗粒增强的Sn-Cu基复合钎料钎焊接头在不同温度和应力水平下的应力指数和蠕变激活能,建立复合钎料钎焊接头的稳态蠕变本构方程.结果表明,在不同的温度和应力下,与Sn-0.7Cu钎料钎焊接头相比,纳米Ag颗粒增强的Sn-Cu基复合钎料钎焊接头的蠕变断裂寿命均有所提高,且具有更高的蠕变激活能,说明复合钎料钎焊接头具有更优的抗蠕变性能.     

应力对SnPb基复合钎料钎焊接头蠕变性能的影响

采用搭接面积为1mm^2的单搭接钎焊接头，研究了恒定温度下，应力对纳米颗粒增强的SnPb基复合钎料钎焊接头的蠕变寿命的影响。结果表明，纳米颗粒增强的SnPb基复合钎料的蠕变抗力优于传统SnPb钎料。同时钎焊接头的蠕变寿命随应力增加而降低，且应力对复合钎料钎焊接头蠕变寿命的影响较传统63Sn37Pb钎料明显。     

SnCu钎焊接头稳态蠕变本构方程建立

以搭接面积为1 mm2微型单搭接钎焊接头为研究对象,采用新型高温蠕变测试装置,测定了Sncu钎焊接头应力指数n和蠕变激活能Q,构建了稳态蠕变本构方程,探讨了蠕变变形机制.结果表明,在低温高应力下,SnCu共晶钎料钎焊接头应力指数为8.73,激活能在59.1～63.2 kJ/mol,位错攀移运动主要受位错管道扩散机制控制;在高温低应力区,Sncu共晶钎料钎焊接头应力指数为6.45,激活能在88.4～97.5 kJ/mol,位错攀移运动主要由晶格自扩散机制控制.     

The influence of temperature on creep behavior of Cu particle enhanced SnPb based composite soldered joints

Creep property of solder alloys is one of the important factors to affect the reliability of soldered joints in SMT(surface mount technology). Particle-enhancement is a way to improve the properties of solder alloys and has caused much more attention than before. Temperatures applied to soldered joints are one of the primary factors of affecting creep properties of particle enhancement composite soldered joints. In this paper single shear lap creep specimens with a 1 mm2 cross-sectional area were fabricated using Cu particle enhancement 63Sn37Pb based composite soldered joints and 63Sn37Pb eutectic soldered joints to examine the influence of temperature on creep behavior of soldered joints. Results indicated that the creep resistance of soldered joints of Cu particle enhancement 63Sn37Pb based composite soldered joint was generally superior to that of the conventional 63Sn37Pb soldered joint. At the same time, creep rupture life of the composite soldered joint was declined with increasing temperature and drop faster than that of the conventional 63Sn37Pb eutectic soldered joint.     

两种无铅钎料的抗蠕变性能与Sn60Pb40钎料的对比分析

对两种无铅钎料Sn-Ag-Cu-Bi和Sn-Ag-Sb模拟封装钎焊接头的蠕变和断裂行为进行了研究,并与传统的Sn60Pb40近共晶钎料进行了对比.结果表明,两种无铅钎料的抗蠕变能力均远优于Sn60Pb40近共晶钎料,其蠕变速率低且蠕变寿命长.钎焊接头蠕变断裂后的扫描电镜分析表明,两种无铅钎料钎焊接头的蠕变断裂呈现明显的沿晶断裂特征,而Sn60Pb40钎料钎焊接头的蠕变断裂机理则为穿晶断裂.     

63Sn37Pb钎焊接头稳态蠕变本构方程的建立

采用高温蠕变测试装置，以简化的Dorn公式为基础．对63Sn37Pb微型单搭接钎焊接头蠕变应变进行了测试．确定了应力指数、蠕变激活能以及相关常数。建立了63Snd7Pb钎焊接头稳态蠕变本构方程，描述了稳态蠕变速率与应力和温度相关性。结果表明，钎焊接头应力指数和激活能均低于钎料本身的应力指数和激活能．说明钎料本身蠕变行为并不能完全代表钎焊接头的蠕变行为。     

不同体积无铅微尺度焊点的蠕变力学性能

采用基于动态力学分析仪的精密蠕变试验方法,对比研究了5.34×107 μm3与7.07×106 μm3两种体积相差近一个数量级的无铅Sn-3.0Ag-0.5Cu微尺度焊点的高温蠕变力学行为与蠕变性能.结果表明,所有微尺度焊点的蠕变曲线均呈现初始蠕变、稳态蠕变和加速蠕变阶段.虽然微尺度焊点的体积存在较大差异,但是它们的蠕变激活能与蠕变应力指数均非常接近.此外,在相同的试验温度与拉伸应力作用下,大体积微尺度焊点的稳态蠕变速率相对小体积焊点更大,而蠕变寿命则呈现完全相反的趋势.     

Environmentally friendly solders 3-4 beyond Pb-based systems

Based on environmental considerations, global economic pressures, enacted by legislations in several countries, have warranted the elimination of lead from solders used in electronic applications.Sn3.5Ag, SnAgCu, and Sn0.7Cu have emerged among various lead-free candidates as the most promising solder alloys to be utilized in microelectronic industries.However, with the vast development and miniaturization of modern electronic packaging, new requirements such as superior service capabilities have been posed on lead-free solders.In order to improve the comprehensive property of the solder alloys, two possible approaches were adopted in the current research and new materials developed were patented.One approach was involved with the addition of alloying elements to make new ternary or quaternary solder alloys.Proper addition of rare earth element such as La and Ce have rendered solder alloys with improved mechanical properties, especially creep rupture lives of their joints.Another approach, the composite approach, was developed mainly to improve the service temperature capability of the solder alloys.Composite solders fabricated by mechanically incorporating various reinforcement particles to the solder paste have again exhibited enhanced properties without altering the existing processing characteristics.The recent progress and research efforts carried out on lead-free solder materials in Beijing University of Technology were reported.The effects of rare earth addition on the microstructure, processing properties, and mechanical properties were presented.The behaviors of various Sn-3.5Ag based composite solders were also explicated in terms of the roles of reinforcement particles on intermetallic growth, steady-state creep rate, the onset of tertiary creep, as well as the overall creep deformation in the solder joints.Thermomechanical fatigue (TMF) behavior of the solder alloys and composite solders were investigated with different parameters such as ramp rate, dwell time, etc.The damage accumulation features and residual mechanical properties of the thermomechanically-fatigued composite solder joints were compared with non-composite solder joints.To match the lead-free alloys, various types of water soluble no-clean soldering flux have also been developed and their properties were presented.     

RE对Sn2.5Ag0.7Cu/Cu焊点性能的影响

利用X射线衍射分析仪(XRD)和JSM-5610LV扫描电镜(SEM)研究RE含量对Sn2.5Ag0.7Cu/Cu焊点界面区显微组织、剪切强度和蠕变断裂寿命的影响。结果表明:Sn2.5Ag0.7CuxRE焊点界面区金属间化合物由靠近钎料侧Cu6Sn5和靠近Cu基板侧Cu3Sn构成;添加微量RE可细化Sn2.5Ag0.7Cu焊点内钎料合金的显微组织和改善钎焊接头界面区金属间化合物的几何尺寸及形态;当RE添加量为0.1%时,焊点的剪切强度最高,蠕变断裂寿命最长。     

Plastic characterization and performance of SnAgCuBiNi/Cu lead-free BGA solder joints

Nanoindentation test is performed on study the plastic and creep properties of the Sn-Ag-Cu (SAC) lead-free ball grid array (BGA) solder joints. The dynamic hardness of two kinds of solder joints decreases with indentation depth increase. SAC0705BiNi/Cu exhibits a higher ultimate dynamic hardness and a smaller indentation depth than SAC305/Cu. Then the strain hardening phenomenon of SAC305/Cu is more obvious compared to that of SAC0705BiNi/Cu. The indentation creep of SAC0705BiNi/Cu solder joint is lower than that of SAC305/Cu solder joint before and after thermal shock. The creep rate sensitive index of SACBiNi/Cu solder joint is lower than that of solder joint. SAC0705BiNi/Cu solder joint is superior to SAC305/Cu solder joint in the anti-creep property. The plasticity of SAC0705BiNi/Cu and SAC305/Cu solder joints are similar. Compared with SAC305 solder, the SAC0705BiNi solder performs higher hardness and solder creep resistance and still maintains a good plasticity.     

Ni对SnAgCuRE钎料及其钎焊接头性能的影响

以商用Sn3.8Ag0.7Cu为参照系,研究了Ni对Sn2.5Ag0.7Cu0.1 RE钎料合金及其钎焊接头性能的影响。研究结果表明,添加0.05%(质量分数)Ni能在不降低Sn2.5Ag0.7Cu0.1RE钎料合金抗拉强度的同时显著提高其伸长率,是商用Sn3.8Ag0.7Cu的1.4倍;相应地钎焊接头的蠕变断裂寿命最长,为未添加Ni时的13.3倍,远高于现行商用Sn3.8Ag0.7Cu的,满足微电子连接高强韧高可靠性无铅钎料合金系的需求。     

RE对SnAgCu钎料合金及焊点性能的影响

利用JSM-5610LV扫描电镜（SEM）及能谱分析（EDS）等测量方法,研究了微量RE对Sn-2.5Ag-0.7Cu无铅钎料的显微组织、润湿特性、拉伸强度及焊点剪切强度和蠕变断裂寿命的影响。结果表明,向Sn-2.5Ag-0.7Cu中添加0.1%RE可明显细化钎料合金的显微组织,改善钎料合金的润湿特性,提高钎料合金的抗拉强度、伸长率及焊点剪切强度,增加焊点的蠕变断裂寿命。当RE添加量为0.5%时,由于形成了RE化合物而明显恶化钎料合金的性能。     

FCBGA器件SnAgCu焊点的热冲击可靠性分析

采用有限元法和Garofalo-Arrheninus稳态本构方程,在热冲击条件下对倒装芯片球栅阵列封装（FCBGA）器件SnAgCu焊点的可靠性进行分析. 结果表明,Sn3.9Ag0.6Cu焊点的可靠性相对较高. 通过分析SnAgCu焊点的力学本构行为,发现焊点应力的最大值出现在焊点与芯片接触的阵列拐角处. 随着时间的推移,SnAgCu焊点的应力呈周期性变化. Sn3.9Ag0.6Cu的焊点应力和蠕变最小,Sn3.8Ag0.7Cu焊点应力和蠕变次之,Sn3.0Ag0.5Cu焊点应力和蠕变最大,与实际的FCBGA器件试验结果一致. 基于蠕变应变疲劳寿命预测方程预测三种SnAgCu焊点的疲劳寿命,发现Sn3.9Ag0.6Cu焊点的疲劳寿命比Sn3.0Ag0.5Cu和Sn3.8Ag0.7Cu焊点的疲劳寿命高.     

The effects of additives to SnAgCu alloys on microstructure and drop impact reliability of solder joints

The impact reliability of solder joints in electronic packages is critical to the lifetime of electronic products, especially those portable devices using area array packages such as ball-grid array (BGA) and chip-scale packages (CSP). Currently, SnAgCu (SAC) solders are most widely used for lead-free applications. However, BGA and CSP solder joints using SAC alloys are fragile and prone to premature interfacial failure, especially under shock loading. To further enhance impact reliability, a family of SAC alloys doped with a small amount of additives such as Mn, Ce, Ti, Bi, and Y was developed. The effects of doping elements on drop test performance, creep resistance, and microstructure of the solder joints were investigated, and the solder joints made with the modified alloys exhibited significantly higher impact reliability.     

锡铅稀土钎料合金的高温蠕变性能

本文对比分析了Ｓｎ６０Ｐｂ４０和Ｓｎ－Ｐｂ－０．０５ＲＥ两种钎料合金在多轴应力状态下蠕的裂规律,初步探讨了主控两种钎料合金蠕变断裂的力学因素,并从金属学角度初步探讨了两种钎料合金的蠕变断裂方式,着重分析了混合稀土对锡铅钎料合金蠕变性能的影响。     

Sn-Cu-Ni焊点纳米压痕试验分析

为研究金属间化合物与无铅焊点力学性能之间的关系,采用纳米压痕法测定了Sn-Cu-Ni焊点中金属间化合物及钎料基体的弹性模量和压痕硬度等力学性能参量．结果表明,Sn-Cu-Ni焊点中（Cu,Ni）6Sn5金属间化合物的弹性模量为113．2GPa±4．8GPa,压痕硬度为5．59GPa±0．32GPa,均与钎料基体有较大差...     

Study on gas metal arc welding procedure of stainless steel

Summary

This paper describes an investigation of the creep rupture properties of welded joints produced from W-containing 9Cr-Mo-W steel. The creep rupture properties of the HAZ are also studied using simulated HAZ specimens subjected to PWHT (post-weld heat treatment). The effect of W on the creep rupture strength of the welded joints is examined.

Creep rupture tests of GTA (TIG) welded joints are conducted. The longest creep rupture time is around 20 000 hours. In the creep rupture tests, the welded joints rupture in the base metal at higher applied stresses, rupturing in the low-ductility fine-grained HAZ adjacent to the base metal at lower applied stresses.

When the welded joints rupture in the base metal, their creep rupture strength is as high as that of the base metal. When the welded joints rupture in the HAZ, however, their creep rupture strength is lower than that of the base metal. The cracking which occurs in the HAZ is TYPE IV cracking which tends to affect the welded joints of ferritic heat-resistant steel. TYPE IV cracking is the type which occurs in the fine-grained HAZ at a lower stress than the creep rupture strength of the base metal without being associated with any heavy deformation.

In the creep rupture tests, the simulated HAZ specimens heated to a temperature around Ac1 and Ac3 give a lower creep rupture strength than that of the base metal. The simulated HAZ specimens heated to the Ac3 temperature give the lowest creep rupture strength.

A comparison of the creep rupture strengths of welded joints produced from 9Cr-Mo-W steel and 9Cr-1 Mo-Nb-V (mod. 9Cr-Mo) steel suggests that W improves the creep rupture strength of both welded joints and base metal.     

Creep properties of Sn-Ag solder joints containing intermetallic particles

The creep behavior of the eutectic tin-silver joints and tin-silver composite solder joints containing 20 vol.% of Cu₆Sn₅, Ni₃Sn₄, and FeSn₂ intermetallic reinforcements introduced by in-situ methods was investigated. These creep tests were carried out using single shear lap solder joints at room temperature, 85°C, and 125°C. The creep resistance was similar in magnitude for all alloys, and with increasing temperature, the stressexponents decreased in a manner consistent with power-law breakdown behavior. The FeSn₂ intermetallic reinforced composite solder was found to be the most creep-resistant alloy at room temperature. Creep failure was observed to occur within the solder matrix in all these solder joints. Although a detailed analysis of the processes involved was difficult because of smearing of the features in the fracture surface, there were indications of grain-boundary separation, ductile fracture, and interfacial separation. For more information, contact K.N. Subramanian, Michigan State University, Department of Materials Science and Mechanics, 3536 Engineering Building, East Lansing, Michigan 48824-1226; (517) 353-5397; fax (517) 353-9842; e-mail subraman@egr.msu.edu.     

无铅焊点及其内部金属间化合物的力学性能研究

采用纳米压痕技术对无铅焊点(Sn3.0Ag0.5Cu、Sn0.7Cu和Sn3.5Ag)及其内部界面金属间化合物(intermetallic compound,IMC)的力学性能进行测试。根据实际工业工艺流程制备无铅焊点试样;利用接触刚度连续测量(CSM)技术对焊点及内部IMC层进行测试,得到IMC层及无铅焊点的弹性模量、硬度等力学性能参数,并根据载荷-位移曲线的保载阶段确定蠕变应力指数。结果表明,Sn0.7Cu的IMC层的弹性模量和蠕变应力指数为无铅焊点的2.03和6.73倍;对无铅焊点的可靠性评估中,将IMC层的影响考虑进去使得结果更为合理。