SnAgCu系无铅钎料合金力学性能及钎焊性能研究

利用光学显微镜、扫描电子显微镜(SEM)和能谱分析仪(EDX)及Instron电液伺服疲劳拉伸试验机,对SnAgCu系无铅钎料合金的力学性能和钎焊性能进行了研究.结果表明,适量的稀土元素Ce的添加显著地延长了Sn3Ag2.8Cu钎焊接头在室温下的蠕变断裂寿命,Sn3Ag2.8Cu-0.1Ce钎焊接头的蠕变断裂寿命超过Sn3Ag2.8Cu钎料的9倍;同时,使Sn3Ag2.8Cu合金的延伸性能也得到了显著改善,伸长率达到15.7%;Sn3Ag2.8Cu-0.1Ce与铜基板的扩散层厚度比Sn37Pb厚,但是比Sn3Ag2.8Cu薄.     

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。     

Bi对Sn-0.3Ag-0.7Cu无铅钎料熔点及润湿性能的影响

研究了添加适量的Bi元素对低银型Sn-0．3Ag-0．7Cu无铅钎料合金性能的影响,应用差示扫描量热仪和SAT-5100型润湿平衡仪对Sn-0．3Ag-0．7Cu·xBi（x=0.1,3,4．5）钎料的熔点、润湿性能作了对比试验分析。结果表明,一定量Bi元素的加入可以降低Sn-0．3Ag-0．7Cu钎料合金的熔点,并改善其润湿性能。但过多的Bi元素会导致钎料的液固相线温度差增大,塑性下降,造成焊点剥离缺陷。综合考虑得到Sn-0．3Ag-0．7Cu-3．0Bi无铅钎料具有最佳的综合性能。     

微量稀土元素铈对Sn-Ag-Cu无铅钎料物理性能和焊点抗拉强度的影响

研究了微量稀土元素铈对Sn-3．5Ag-0．5Cu无铅钎料的物理性能、润湿性能、焊点抗拉强度和显微组织的影响。结果表明，添加微量的铈后，钎料的导电性能提高，密度下降；铈含量（质量分数）在0．03％和0．05％时可以改善钎料的润湿性；特别是0．03％质量分数时晶粒组织最为细小均匀，焊点抗拉强度也最高；当铈含量（质量分数）大于0．1％时对钎料的性能产生不利影响，润湿时间升高，焊点抗拉强度大幅降低，因此稀土元素铈的最佳含量（质量分数）应为0．03％。     

Fe粉对Sn-3Ag-0.5Cu复合钎料组织及性能的影响

通过在钎料中添加Fe粉颗粒,研究其对Sn-3Ag-0.5Cu复合无铅钎料的黏度、熔点、钎焊接头界面微观组织、与Cu基板之间的润湿性及焊点力学性能的影响。结果表明:微米级Fe粉的添加增加了复合钎料焊膏单位体积内焊粉的接触面积,使得焊膏内摩擦力增大,导致复合钎料焊膏的黏度增加;微米级Fe粉的添加对Sn-3Ag-0.5Cu钎料的熔化特性没有显著影响;钎焊时,由于重力偏聚及界面吸附作用,Fe粉颗粒集中沉积于Sn-3Ag-0.5Cu-Fe/Cu钎焊接头界面处靠近钎料一侧,由于增大液态钎料黏度而导致钎料与Cu板间的润湿性降低;与Sn-3Ag-0.5Cu/Cu相比,Sn-3Ag-0.5Cu-Fe/Cu界面处钎料一侧粗大的β-Sn枝晶区消失,取而代之的是细小的等轴晶。Sn-3Ag-0.5Cu-1%Fe/Cu的剪切强度为46 MPa,比Sn-3Ag-0.5Cu/Cu剪切强度提高39%;靠近界面金属间化合物处钎料基体的显微硬度提高约25%。     

Improving the shear strength of Sn–Ag–Cu–Ni/Cu–Zn solder joints via modifying the microstructure and phase stability of Cu–Sn intermetallic compounds

This study focuses on the correlation between high-speed impact tests and the interfacial reaction in Sn-3.0Ag-0.5Cu-0.1Ni/Cu (wt%) and Sn-3.0Ag-0.5Cu-0.1Ni/Cu-15Zn solder joints. Adding Ni into the Sn–Ag–Cu solder alters the interfacial morphology from scallop type to layer type and exhibits high shear strength after reflow in both solder joints. However, the shear strength of Sn-3.0Ag-0.5Cu-0.1Ni/Cu solder joints degrades significantly after thermal aging at 150 °C for 500 h. It is notable that Sn-3.0Ag-0.5Cu-0.1Ni/Cu-15Zn solder joints still present higher shear strength after aging at 150 °C. The weakened shear strength in Sn-3.0Ag-0.5Cu-0.1Ni/Cu solder joints is due to stress accumulation in the interfacial (Cu,Ni)₆Sn₅ compound induced by the phase transformation from a high-temperature hexagonal structure (η-Cu₆Sn₅) to a low-temperature monoclinic structure (η'-Cu₆Sn₅). However, doping small amounts of Zn into (Cu,Ni)₆(Sn,Zn)₅ can inhibit the phase transformation during thermal aging and maintain strong shear strength. These experiments demonstrate that Sn-3.0Ag-0.5Cu-0.1Ni/Cu-15Zn solder joints can act as a stable connection in the micro-electronic packaging of most electronic products at their average working temperatures.     

Sn-0.3Ag-0.7Cu-xNd钎料显微组织及性能

研究了稀土元素Nd的添加量对超低银无铅钎料Sn-0.3Ag-0.7Cu的润湿性能、显微组织和力学性能的影响.结果表明,微量Nd元素的加入可以显著改善Sn-0.3Ag-0.7Cu超低银无铅钎料的润湿性能和焊点的力学性能,并且能够起到细化基体组织的作用.当钎料中Nd元素的质量分数达到0.1%时,钎料的综合性能最佳,基体组织最为均匀细化.虽然Ag元素含量的降低使钎料的性能有所下降,但是加入适量Nd元素后钎料的润湿性能已接近传统Sn-3.8Ag-0.7Cu钎料.     

Sn-3.0Ag-0.5Cu-xNi无铅焊料及焊点的性能

研究了Ni元素对Sn-3.0Ag.0.5Cu无铅钎料熔点、润湿性、拉伸性能及焊点性能的影响.结果表明,镍的添加对Sn-3.OAg-0.5Cu钎料的润湿性有所改善,添加量为0.03%～0.1%时,随着镍含量的增加,润湿时间逐渐递减,润湿力逐渐增大,镍含量在0.05%时润湿时间最短,镍含量在O.1%时润湿力最大.但当镍含量到0.15%时,润湿时间反而增长,润湿力下降;镍提高了合金的抗拉强度、断后伸长率及焊点的抗剪强度.当镍含量为0.05%时,抗拉强度最高,当镍含量为0.1%时,断后伸长率和抗剪强度最高,扫描断口表现为明显的韧性断裂特征;镍的添加量为0.05%~0.1%效果较好.     

BGA单板结构与板级结构焊点剪切力学行为分析

采用试验方法研究BGA封装结构中焊点的剪切力学行为. 分析并比较了Sn-3Ag-0.5Cu,Sn-0.3Ag-0.7Cu,Sn-0.3Ag-0.7Cu-0.07La和Sn-0.3Ag-0.7Cu-0.07La-0.05Ce四种钎料焊点在单板结构与板级结构中的力学性能. 结果表明, 单板结构中焊点的抗剪强度高于板级结构中焊点的抗剪强度. 在单板结构中,高银焊点的抗剪强度最大,加入稀土元素的低银焊点只是得到了一定程度上的改善,然而对于板级结构,加入稀土元素的低银焊点剪切力学性能基本与高银焊点相当. 在同等拘束条件下,低银焊点的延展性优于高银焊点. 此外,对于同一种钎料而言,单板结构中的焊点断裂在体钎料上,而板级结构则断裂在IMC/体钎料界面处.     

Nd对Sn-3.8Ag-0.7Cu/Cu焊点高温可靠性的影响

通过研究150 ℃时效条件下Sn-3.8Ag-0.7Cu-0.05Nd/Cu焊点剪切力变化和界面微观结构演变,探讨稀土元素Nd对焊点高温可靠性的影响及其影响机制. 结果表明,不同时效时间后Sn-3.8Ag-0.7Cu-0.05Nd/Cu焊点剪切力明显高于Sn-3.8Ag-0.7Cu/Cu焊点,且时效过程中Sn-3.8Ag-0.7Cu-0.05Nd/Cu焊点剪切力的下降速率低于原焊点. 这是由于0.05%Nd可将界面原子扩散系数由1.88 × 10?10 cm2/h降低至1.10 × 10?10 cm2/h,即通过抑制界面金属间化合物的粗化来提高焊点的高温可靠性.     

Sn-6Bi-2Ag(Cu, Sb)无铅钎料合金微观组织分析

利用差示扫描量热计 (DSC)测定了Sn 6Bi 2Ag ,Sn 6Bi 2Ag 0 .5Cu ,Sn 6Bi 2Ag 2 .5Sb三种新无铅钎料合金的熔化温度。结果表明 ,少量Cu的加入能降低Sn Bi Ag系无铅钎料合金的熔化温度 ,而Sb的加入使合金的熔化温度升高。利用光学显微镜 (OM )、扫描电子显微镜 (SEM )、能谱分析 (EDX)对合金的微观组织进行了分析与比较 ,钎料合金的微观组织与冷却条件和合金元素的含量有关 ,Sb的加入使析出相的尺寸细化。硬度测定表明Sn Bi Ag(Cu ,Sb)无铅钎料合金的硬度远大于纯Sn的硬度 ,加入少量的Cu(0 .5 % ) ,Sb(2 .5 % )对Sn Bi Ag系钎料合金的硬度影响较小     

Wetting and interfacial reaction characteristics of Sn-1.2Ag-0.5Cu-xIn quaternary solder alloys

Through the use of a wetting balance technique, the wetting characteristics of Sn-1.2Ag-0.5Cu-xIn quaternary solder alloys with respect to the In content and soldering temperature were investigated to validate the applicability of compositions with a low Ag content as solder material. It was found that a small addition (0.4–0.6 wt.%) of In significantly improved the wetting properties of the Sn-1.2Ag-0.5Cu-xIn composition at soldering temperatures ranging from 230 °C to 240 °C due to the excellent wetting property of In. In an observation of the interfacial reaction, it was found that the added In element did not participate in the interfacial reaction with a Cu or Ni pad, unlike in the Sn-Ag-Cu-In case, which has a high In content. The package or boardside IMC layers in Sn-1.2Ag-0.5Cu-0.4In joints were thinner than those of Sn-3.0Ag-0.5Cu, especially after aging.     

Sn-Ag-Cu-In无铅钎料润湿性能及显微组织

在Sn-1.2Ag-0.6Cu合金中添加0～1.0%的In元素,研究了Sn-Ag-Cu-In无铅钎料的熔化温度、润湿性能及显微组织.结果表明,添加In元素对钎料的熔化温度有一定的降低作用,在相同的试验温度下,含铟钎料粘度更低,流动性更强,钎料的润湿性能随之改善.低银Sn-Ag-Cu钎料在空气中的润湿时间在260℃才达到...     

Comparative Study on Solid-State and Metastable Liquid-State Aging for SAC305/Cu Joints

In order to study the in?uence of the physical state of solder on the interfacial reaction of dip-soldered Sn-3.0 Ag-0.5 Cu/Cu system, two kinds of experiments were designed, including:(1) solid-state aging between the solder and Cu substrate;(2)liquid-state aging between the metastable supercooled liquid-state solder and Cu substrate. The aging times were 30, 60,120 and 180 min, respectively, and the aging temperature was 8 ℃ lower than the melting point of the Sn-3.0 Ag-0.5 Cu(SAC305) alloy(217 ℃). The experimental data revealed that the physical state of the solder obviously affected the formation of the intermetallic compound(IMC), and resulted in the difference in the diffusion of atoms on the interface between the SAC305 solder and Cu substrate. The IMC interface after aging for 30 min presents unique characteristics compared with that of the sample after dip soldering. The IMC interface of solid-state aged SAC305/Cu couple is relatively planar, while the IMC interface under metastable supercooled liquid-state aging conditions presents scallop-like shape.     

热循环对Sn58Bi(纳米Ti)/Cu焊点界面与性能影响

为了改善Sn-58Bi低温钎料的性能,通过在Sn-58Bi低温钎料中添加质量分数为0.1%的纳米Ti颗粒制备了Sn-58Bi-0.1Ti纳米增强复合钎料。在本文中,研究了纳米Ti颗粒的添加对-55～125 _^oC热循环过程中Sn-58Bi/Cu焊点的界面金属间化合物(IMC)生长行为的影响。研究结果表明：回流焊后,在Sn-58Bi/Cu焊点和Sn-58Bi-0.1Ti/Cu焊点的界面处都形成一层扇贝状的Cu₆Sn₅ IMC层。在热循环300次后,在Cu₆Sn₅/Cu界面处形成了一层Cu₃Sn IMC。Sn-58Bi/Cu焊点和Sn-58Bi-0.1Ti/Cu焊点的IMC层厚度均和热循环时间的平方根呈线性关系。但是,Sn-58Bi-0.1Ti/Cu焊点的IMC层厚度明显低于Sn-58B/Cu焊点,这表明纳米Ti颗粒的添加能有效抑制热循环过程中界面IMC的过度生长。另外计算了这两种焊点的IMC层扩散系数,结果发现Sn-58Bi-0.1Ti/Cu焊点的IMC层扩散系数(整体IMC、Cu₆Sn₅和Cu₃Sn IMC)明显比Sn-58Bi/Cu焊点小,这在一定程度上解释了Ti纳米颗粒对界面IMC层的抑制作用。     

微连接用Sn-2.5Ag-0.7Cu(0.1RE)钎料焊点界面Cu6Sn5的长大行为

利用XRD、SEM及EDAX研究了钎焊和时效过程中低银Sn-2.5Ag-0.7Cu(0.1RE)/Cu焊点界面区显微组织和Cu6Sn5金属间化合物的生长行为。结果表明,钎焊过程中焊点界面区Cu6Sn5金属间化合物的厚度是溶解和生长两方面共同作用的结果;随时效时间的增加,焊点界面区Cu6Sn5的形貌由扇贝状转变为层状,其长大动力学符合抛物线规律,由扩散机制控制;添加0.1%(质量分数,下同)的RE能有效减慢界面Cu6Sn5金属间化合物在钎焊及时效过程中的长大速度,改变焊点的断裂机制,提高其可靠性。     

Ni/P/Ce元素对SnAgCu无铅钎料性能和组织的影响

研究添加微量单一Ni、P或稀土Ce元素对Sn3.0Ag0.5Cu(质量分数, %)无铅钎料熔化温度、润湿性能、时效前后钎焊接头的剪切强度和显微组织的影响。结果表明：单一Ni、P和稀土Ce元素的添加,对Sn3.0Ag0.5Cu钎料合金的熔化温度影响很小;P元素的加入能够增大合金的润湿力,缩小润湿时间。加入单一的Ni或稀土Ce元素对合金的润湿性能和接头时效前的剪切强度影响不大,但能够很好地抑制高温时效引起的接头剪切强度的下降。此外,P 元素的添加明显地改善了合金的抗氧化性能,但稀土Ce元素的添加对其有所恶化。这些性能的改变与微量Ni、P或稀土Ce元素对其显微组织的影响有关     

纳米压痕法测量Sn-Ag-Cu无铅钎料BGA焊点的力学性能参数

对Sn-3．0Ag-0．5Cu无铅体钎料和Sn-4．0Ag-0．5Cu无铅钎料BGA(ball grid array)焊点进行了Berkovich纳米压痕法实验,通过改变不同的加载速率研究了钎料的蠕变特征．钎料压痕载荷位移曲线蠕变部分表现出了明显的加载速率相关性．基于Oliver-Pharrr法确定的体钎料和BGA焊点的Young’S模量分别为9．3和20GPa．基于压痕做功概念确定的体钎料和BGA焊点的应变速率敏感指数分别为0．1111和0．0574．钎料的力学性能有着明显的尺寸效应。     

Understanding the Influence of Copper Nanoparticles on Thermal Characteristics and Microstructural Development of a Tin-Silver Solder

This paper presents and discusses issues relevant to solidification of a chosen lead-free solder, the eutectic Sn-3.5%Ag, and its composite counterparts. Direct temperature recordings for the no-clean solder paste during the simulated reflow process revealed a significant amount of undercooling to occur prior to the initiation of solidification of the eutectic Sn-3.5%Ag solder, which is 6.5 °C, and for the composite counterparts, it is dependent on the percentage of copper nanopowder. Temperature recordings revealed the same temperature level of 221 °C for both melting (from solid to liquid) and final solidification (after recalescence) of the Sn-3.5%Ag solder. Addition of copper nanoparticles was observed to have no appreciable influence on melting temperature of the composite solder. However, it does influence solidification of the composite solder. The addition of 0.5 wt.% copper nanoparticles lowered the solidification temperature to 219.5 °C, while addition of 1.0 wt.% copper nanoparticles lowered the solidification temperature to 217.5 °C, which is close to the melting point of the ternary eutectic Sn-Ag-Cu solder alloy, Sn-3.7Ag-0.9Cu. This indicates the copper nanoparticles are completely dissolved in the eutectic Sn-3.5%Ag solder and precipitate as the Cu₆Sn₅, which reinforces the eutectic solder. Optical microscopy observations revealed the addition of 1.0 wt.% of copper nanoparticles to the Sn-3.5%Ag solder results in the formation and presence of the intermetallic compound Cu₆Sn_5. These particles are polygonal in morphology and dispersed randomly through the solder matrix. Addition of microsized copper particles cannot completely dissolve in the eutectic solder and projects a sunflower morphology with the solid copper particle surrounded by the Cu₆Sn₅ intermetallic compound coupled with residual porosity present in the solder sample. Microhardness measurements revealed the addition of copper nanopowder to the eutectic Sn-3.5%Ag solder resulted in higher hardness.     

基于纳米压痕法的无铅BGA焊点的循环力学行为

采用纳米压痕法通过循环加载卸载方式研究了最大载荷、循环次数及保载时间对Sn-3.0Ag-0.5Cu和Sn-0.3Ag-0.7Cu 2种钎料BGA焊点循环性能的影响.结果表明,Sn-Ag-Cu系无铅BGA焊点的循环性能具有很大的载荷依赖性,随着最大载荷的增加,BGA焊点的损伤累积增加且前几周循环中损伤累积很大,其后逐渐减小并趋于稳定;循环次数增加,使BGA焊点抵抗变形的能力稍有降低;保载时间增加,蠕变位移不断增加,蠕变和疲劳共同作用会加速焊点失效;Sn-0.3Ag-0.7Cu钎料BGA焊点的能量损耗大于Sn-3.0Ag-0.5Cu钎料BGA焊点.