Sn0.7Cu-xNi无铅钎料界面组织与力学性能的研究

研究了Ni颗粒对Sn0.7Cu无铅钎料界面组织、铺展性能和显微硬度的影响规律。结果表明:适量Ni颗粒的加入不仅使基体中的Cu6Sn5弥散分布,还可以改变界面处金属间化合物(IMC)层的形貌,由原先延伸入基体中的针状转变为较为平缓整齐的贝壳状;当Ni含量超过0.05 wt%时,IMC表现出明显的长大趋势,最大厚度达2.463μm;铺展系数和显微硬度随Ni含量的增加表现出先增加后降低的趋势,Ni颗粒的最佳添加量为0.05 wt%。

Fe对Sn0.7Cu无铅钎料显微组织和力学性能的影响

研究了Fe颗粒对Sn0.7Cu无铅钎料显微组织、润湿性能和拉伸性能的影响规律。结果表明:适量Fe颗粒的加入可以细化钎料基体组织,β-Sn基体中的Cu6Sn5由原先的针状过渡为点状;在Sn0.7Cu-0.05Fe中,钎料的润湿角最小,获得了较好的润湿性能;当Fe添加过量时,润湿性能受到一定程度恶化,且表面较粗糙,出现明显的氧化现象;抗拉强度随Fe含量的增加呈现先上升后下降的趋势,Sn0.7Cu-0.05Fe获得了最大抗拉强度,Fe的最佳添加量为0.05 wt%。

Ti对Sn0.7Cu无铅钎料润湿性和界面的影响

研究了Ti的加入对Sn0.7Cu无铅钎料润湿性能以及钎料/Cu界面微观组织的影响。结果表明：在Sn0.7Cu中添加微量Ti,提高了钎料的润湿性能,可使铺展面积提高5%左右,当钎焊时间为3 s时,界面金属间化合物（IMC）形貌由原来的扇贝状变为锯齿状;随着钎焊时间延长,Sn0.7Cu/Cu和Sn0.7Cu0.008Ti/Cu界面IMC层厚度不断增加,其形状逐渐变为板条状,并可观察到IMC在钎料中的溶解、断裂。同等条件下,Ti的加入使界面IMC层的平均厚度减少约10%~25%;晶粒平均尺寸增加20%~75%,且钎焊时间越长,平均尺寸增加越少。

微量Ni对Sn0.7Cu钎料物理性能及钎焊工艺性能影响

SnCu共晶钎料是公认的SnPb钎料最具潜力替代品,尤其在波峰焊上,但与其他无铅钎料相比,该钎料物理性能及铺展性能差,严重影响其广泛应用。本文通过在Sn0.7Cu合金基础上添加微量Ni来改善合金性能。结果表明:随Ni含量(w(Ni)<0.7%)增加,Sn0.7Cu钎料熔点逐渐增加,但变化不大,当w(Ni)0.7%时,钎料Sn0.7Cu0.7Ni的熔点较基体钎料提高了2.8℃;Ni含量对Sn0.7Cu合金导电性能会产生一定影响,随Ni含量增加,电阻率逐渐降低,当w(Ni)0.7%时,Sn0.7Cu0.7Ni合金电阻率较基体钎料降低16.7%;同时,在Sn0.7Cu添加微量Ni会明显改善钎料合金铺展性能,当w(Ni)0.1%时,Sn0.7Cu0.1Ni合金铺展面积最大,较基体钎料提高1倍,这主要与形成的新相Ni3Sn4及钎料与基板件金属间化合物状态有关。

松香及改性松香对Sn0.7Cu钎料的助焊性能研究

分别以松香、氢化松香、歧化松香和聚合松香为主要活性成分配制不同的液体助焊剂,采用扩展率试验法研究各助焊剂对Sn0.7Cu无铅钎料在铜基板上润湿性能的影响,测试了助焊剂的物理性能,分析了扩展率≥75%时的焊点形貌,并与市售无铅焊接用非松香基助焊剂进行对比。结果表明:松香及改性松香含量的增加能提高助焊剂对Sn0.7Cu钎料在铜基板上的扩展率,而酸值对于松香及改性松香的助焊性能影响很大,酸值较高的松香产品具有较好的助焊性能。在相同含量时松香对Sn0.7Cu钎料的助焊效果最好,其后依次为氢化松香、歧化松香和聚合松香;随着质量分数的提高,松香和改性松香扩展率均可提高至70%以上,达到SJ/T 11389—2009中L级无卤素松香基助焊剂要求。除聚合松香外,其余的扩展率可高于75%,达到SJ/T 11389—2009中M级无卤素松香基助焊剂要求,并且各质量分数条件下助焊剂物理稳定性及干燥度均合格,铜板腐蚀性较低,焊后表面绝缘电阻均≥1.0×108Ω;市售810A型无铅非松香基助焊剂的扩展率与松香质量分数40%时的助焊剂具有相似的扩展率,但松香助焊剂所形成的焊点饱满,表面光亮,且成形性更优。

不同脂松香对Sn0.7Cu无铅焊料的助焊性能研究

分别以马尾松松香、湿地松松香和思茅松松香为主要活性成分配制液体助焊剂,采用扩展率试验法研究3种脂松香对Sn0.7Cu焊料在铜基板上润湿性能的影响,测试了助焊剂的物理性能,并分析了扩展率≥75%时的焊点形貌。结果表明：在含量为5%~55%时,随着含量的递增,马尾松松香、湿地松松香及思茅松松香对Sn0.7Cu焊料的扩展率均呈逐渐递增的趋势,并且在相同含量条件下,马尾松松香和思茅松松香的扩展率高于湿地松松香;当含量≥25%时3种松香的扩展率均高于70%,达到SJ/T 11389—2009中L级无卤素松香基助焊剂要求,并且各松香助焊剂物理稳定性和干燥度合格,铜板腐蚀性较低,焊后表面绝缘电阻不低于1.0×108Ω;当马尾松松香和思茅松松香在含量为45%~55%、湿地松松香在含量为55%时扩展率≥75%,达到SJ/T11389—2009中M级无卤素松香基助焊剂要求,其中马尾松松香扩展率高于湿地松松香,并且焊点饱满,表面光亮,成形性优于思茅松松香,因此更适合用作Sn0.7Cu焊料用中等活性助焊剂。

增强颗粒对Sn0.7Cu基复合钎料铺展性能的影响

以Sn0.7Cu共晶钎料作为基体钎料,通过添加微细金属颗粒(1μmAg、1μmNi和8μmCu)形成颗粒增强复合钎料。研究了增强颗粒对复合钎料铺展性能的影响,优选出Sn0.7Cu基复合钎料的最佳增强体。研究表明:Ni(3vol%)颗粒增强Sn0.7Cu复合钎料铺展性能差;Cu(3vol%)颗粒增强复合钎料铺展性能不如Ag(3vol%)颗粒增强复合钎料;对于金属颗粒增强Sn0.7Cu基复合钎料,Ag颗粒为最佳增强体。

Ag对Sn0.7Cu0.12Ni焊料性能影响研究

以Ag-28Cu为中间合金,制备Sn0.7Cu0.12Ni-x Ag焊料合金,通过X射线衍射分析,当Ag含量为0.3wt%时,出现了Ag3Sn金属间化合物相。将焊料在5%浓度的HCl溶液中浸泡腐蚀18天,通过腐蚀速率计算,X射线衍射分析以及扫描电镜图表明:添加微量的Ag元素能够降低Sn0.7Cu0.12Ni焊料的腐蚀速率,提高焊料的抗腐蚀性。

时效处理对Sn0.7Cu-0.5Al_2O_3/Cu焊点界面形态的影响

研究了纳米Al_2O_3颗粒对Sn0.7Cu钎料润湿性的影响,并分析比较了时效0 h和时效250 h后Sn0.7Cu-0.5Al_2O_3/Cu焊点界面IMC的形貌和厚度变化。结果表明:添加微量的纳米Al_2O_3颗粒可以改善Sn0.7Cu钎料的润湿性,但添加过量将降低润湿铺展面积,纳米Al_2O_3颗粒的最佳添加量为0.5%,比Sn0.7Cu钎料的铺展面积提高了30.2%。焊后未时效的焊点钎料晶粒细小,界面处Cu_6Sn_5IMC层较薄,经过150℃时效,钎料晶粒粗化,IMC界面层的厚度明显增加,形貌由扇贝状变为明显的块状,界面的不平度逐步减小。界面层由单一的Cu_6Sn_5IMC层转变为Cu_6Sn_5IMC和Cn_3SnIMC两层,厚度增大了96.5%。

Influence of bismuth on microstructure,thermal properties,mechanical performance,and interfacial behavior of SAC305−xBiCu solder joints

This research sought to improve the properties of SAC305 solder joints by the addition of 1 and 2 wt.%Bi.The effects of bismuth doping on the microstructure,thermal properties,and mechanical performance of the SAC305−xBiCu solder joints were investigated.Bi-doping modified the microstructure of the solder joints by refining the primaryβ-Sn and eutectic phases.Bi-doping below 2 wt.%dissolved in theβ-Sn matrix and formed a solid solution,whereas Bi additions equal to or greater than 2 wt.%formed Bi precipitates in theβ-Sn matrix.Solid solution strengthening and precipitation strengthening mechanisms in theβ-Sn matrix increased the ultimate tensile strength and microhardness of the alloy from 35.7 MPa and 12.6 HV to 55.3 MPa and 20.8 HV,respectively,but elongation decreased from 24.6%to 16.1%.The fracture surface of a solder joint containing 2 wt.%Bi was typical of a brittle failure rather than a ductile failure.The interfacial layer of all solder joints comprised two parallel IMC layers:a layer of Cu6Sn5 and a layer of Cu3Sn.The interfacial layer was thinner and the shear strength was greater in SAC305−xBiCu joints than in SAC305Cu solder joints.Therefore,small addition of Bi refined microstructure,reduced melting temperature and improved the mechanical performance of SAC305Cu solder joints.

Combined effects of Bi and Sb elements on microstructure,thermal and mechanical properties of Sn−0.7Ag−0.5Cu solder alloys

This research investigated the combined effects of addition of Bi and Sb elements on the microstructure,thermal properties,ultimate tensile strength,ductility,and hardness of Sn−0.7Ag−0.5Cu(SAC0705)solder alloys.The results indicated that the addition of Bi and Sb significantly reduced the undercooling of solders,refined theβ-Sn phase and extended the eutectic areas of the solders.Moreover,the formation of SbSn and Bi phases in the solder matrix affected the mechanical properties of the solder.With the addition of 3 wt.%Bi and 3 wt.%Sb,the ultimate tensile strength and hardness of the SAC0705 base alloy increased from 31.26 MPa and 15.07 HV to 63.15 MPa and 23.68 HV,respectively.Ductility decreased due to grain boundary strengthening,solid solution strengthening,and precipitation strengthening effects,and the change in the fracture mechanism of the solder alloys.

Effects of bismuth on growth of intermetallic compounds in Sn-Ag-Cu Pb-free solder joints

The effects of Bi addition on the growth of intermetallic compound (IMC) formation in Sn-3.8Ag-0.7Cu solder joints were investigated. The test samples were prepared by conventional surface mounting technology. To investigate the element diffusion and the growth kinetics of intermetallics formation in solder joint, isothermal aging test was performed at temperatures of 100, 150, and 190℃, respectively. The optical microscope (OM) and scanning electron microscope (SEM) were used to observe microstructure evolution of solder joint and to estimate the thickness and the grain size of the intermetallic layers. The IMC phases were identified by energy dispersive X-ray (EDX) and X-ray diffractometer (XRD). The results clearly show that adding about 1.0% Bi in Sn-Ag-Cu solder alloy system can refine the grain size of the IMC and inhibit the excessive IMC growth in solder joints, and therefore improve the reliability of the Pb-free solder joints. Through observation of the microstructural evolution of the solder joints, the mechanism of inhibition of IMC growth due to Bi addition was proposed.

Effect of diode-laser parameters on shear force of micro-joints soldered with Sn-Ag-Cu lead-free solder on Au/Ni/Cu pad

Soldering experiments with Sn-3.5Ag-0.5Cu lead-free solder on Au/Ni/Cu pad were carried out by means of diode-laser and IR reflow soldering methods respectively.The influence of different heating methods as well as output power of diode-laser on shear force of micro-joints was studied and the relationship between the shear force and microstructures of micro-joints was analyzed.The results indicate that the formation of intermetallic compound Ag3Sn is the key factor to affect the shear force and the fine eutectic network structures of micro-joints as well as the dispersion morphology of fine compound Ag3Sn,in which eutectic network band is responsible for the improvement of the shear force of micro-joints soldered with Sn-Ag-Cu lead-free solder.With the increases of output power of diode-laser,the shear force and the microstructures change obviously.The eutectic network structures of micro-joints soldered with diode-laser soldering method are more homogeneous and the grains of Ag3Sn compounds are finer in the range of near optimal output power than those soldered with IR reflow soldering method,so the shear force is also higher than that using IR reflow soldering method.When the output power value of diode-laser is about 41.0 W,the shear force exhibits the highest value that is 70% higher than that using IR reflow soldering method.

Effect of cerium on microstructure and mechanical properties of Sn-Ag-Cu system lead-free solder alloys

The melting point, spreading property, mechanical properties and microstructures of Sn-3.0Ag-2.8Cu solder alloys added with micro-variable-Ce were studied by means of optical microscopy, scanning electron microscopy(SEM) and energy dispersive X-ray(EDX). The results indicate that the melting point of Sn-3.0Ag-2.8Cu solder is enhanced by Ce addition; a small amount of Ce will remarkably prolong the creep-rupture life of Sn-3.0Ag-2.8Cu solder joint at room temperature, especially when the content of Ce is 0.1%, the creep-rupture life will be 9 times or more than that of the solder joint without Ce addition; the elongation of Sn-3.0Ag-2.8Cu solder is also obviously improved even up to 15.7%. In sum, the optimum content of Ce is within 0.05%-0.1 %.

Preparation and Properties of Particle Reinforced Sn-Zn-based Composite Solder

Particle reinforced Sn-Zn based composite solders were obtained by adding Cu powders to Sn-9Zn melts. The microstructure analysis reveals that in situ CusZn8 particles are formed and distributed uniformly in the composite solders. The strength and plasticity of the composite solders were improved, and creep resistance was considerably enhanced. The wettability of these composite solders is also better than that of Sn-9Zn.

Thermal reliabilities of Sn−0.5Ag−0.7Cu−0.1Al_(2)O_(3)/Cu solder joint

The effects of trace addition of Al_(2)O_(3) nanoparticles(NPs)on thermal reliabilities of Sn−0.5Ag−0.7Cu/Cu solder joints were investigated.Experimental results showed that trace addition of Al_(2)O_(3) NPs could increase the isotheraml aging(IA)and thermal cyclic(TC)lifetimes of Sn−0.5Ag−0.7Cu/Cu joint from 662 to 787 h,and from 1597 to 1824 cycles,respectively.Also,trace addition of Al_(2)O_(3) NPs could slow down the shear force reduction of solder joint during thermal services,which was attributed to the pinning effect of Al_(2)O_(3) NPs on hindering the growth of grains and interfacial intermetallic compounds(IMCs).Theoretically,the growth coefficients of interfacial IMCs in IA process were calculated to be decreased from 1.61×10^(−10 )to 0.79×10^(−10) cm^(2)/h in IA process,and from 0.92×10^(−10) to 0.53×10^(−10) cm^(2)/h in TC process.This indicated that trace addition of Al_(2)O_(3) NPs can improve both IA and TC reliabilities of Sn−0.5Ag−0.7Cu/Cu joint,and a little more obvious in IA reliability.

Effects of rare earth element Ce on solderabilities of micron-powdered Sn-Ag-Cu solder

Several important properties of the micron-powdered Sn-Ag-Cu-Ce solder, including the spreadability, spreading ratio, wetting time, and melting point, were investigated for verifying the effects of rare earth element Ce on solderabilities of micron-powdered Sn-Ag-Cu solder. The solidus and the liquidus of the micron-powdered Sn-Ag-Cu-Ce solder are 193.6℃ and 218.4℃, respectively, about 28℃ and 3℃ lower than the melting point of the block Sn-Ag-Cu solder, which reminds the existence of the surface effect of the micron-powdered solder. By adding Ce into Sn-Ag-Cu alloy, its wetting time on pure copper can be obviously decreased. For the Sn-Ag-Cu-0.03%Ce, the soldering temperature is 250℃, and the wetting time on pure copper is close to 1s, with the soldering temperature approaching to 260℃, the wetting time is dropped to 0.8s, which is close to the wetting time, 0.68s, of Sn-Pb solder at 235℃.

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.

Microstructures and properties of Sn-Ag-Cu lead-free solder alloys containing La

Trace amounts of La were utilized to improve the melting behaviors,microstructures,tensile properties and microhardness of Sn-3.0Ag-0.5Cu lead-free solder alloy. La has little effect on the melting behavior of Sn-3.0Ag-0.5Cu alloy according to the differential thermal analysis(DTA) tests. The X-ray diffraction(XRD) patterns show that β-Sn,Ag3Sn and Cu6Sn5 coexist in the as-cast solder alloys and LaSn3 phases emerge when adding 0.4% La. The microstructures modified by La are more uniform and much finer than that of baseline alloy,and the coarse LaSn3 particles with complex dendrites are observed by optical microscopy(OM) and scanning electron microscopy(SEM) when the addition of La is up to 0.4%. The composition of the LaSn3 phases is identified by energy-dispersive spectroscopy(EDS). There are considerable improvements in mechanical properties with 0.05% and 0.1% addition,but degenerations by adding 0.4%La. The Vickers microhardness of β-Sn and eutectic area are both enhanced with the addition of La and the microhardness of LaSn3 is much larger than those of β-Sn and eutectic area.

Effect of Lanthanum on Driving Force for Cu_6Sn_5 Growth and Improvement of Solder Joint Reliability

By means of adding low content of rare earth element La into Sn60 Pb40 solder alloy, the growth of Cu 6Sn 5 intermetallic compound at the interface of solder joint is hindered, and the thermal fatigue life of solder joint is increased by 2 times. The results of thermodynamic calculation based on diffusion kinetics show that, the driving force for Cu 6Sn 5 growth is lowered by adding small content of La in Sn60 Pb40 solder alloy. Meanwhile, there is an effective local mole fraction range of La, in which, 0 18% is the limited value and 0 08% is the best value.