无铅合金Sn-Ag-Cu的润湿回流曲线研究

对电子封装工业生产中无铅合金焊料的回流曲线工艺进行了研究,引入了3种不同回流因子,即加热因子,预热因子、冷却因子.针对不同回流因子,分析了其剪切试验中剪切断面的形貌和成分,研究表明,大部分条件下断裂一般会发生在焊料内部区域,然而在焊料界面结合较弱时,断裂通常会发生在金属问化合物和基板界面处.总结提出了3种回流因子的合理取值范围,得到回流炉中Sn3.5Ag0.5Cu的最佳回流曲线,为工业上探索新的回流曲线提供了实验方法.     

回流次数对In3Ag焊料微观组织和剪切性能的影响

用扫描电镜和能量色散仪分别对In3Ag焊料焊点基体及其与铜基板界面IMC（Intermetallic compound）层的组织结构进行观察和分析,用力学试验机测试焊点的剪切强度,研究了电子封装中回流次数对In3Ag焊料微观组织和剪切性能的影响。结果表明:随着回流次数的增加,基体中二次相AgIn2显著长大,由颗粒状变为长条状,界面IMC层（成分为（Ag,Cu）In₂）的厚度线性增加,其生长由界面反应速率和组元扩散速率混合控制,焊点剪切强度呈下降趋势,由1次回流的5.03 MPa降到5次回流的2.58 MPa;回流1、2、3次后焊点剪切断裂方式均为焊料内部韧性断裂,回流5次后断裂机制转变为韧脆混合断裂。     

AlN与Mo-Ni-Cu活性封接的微观结构和性能分析

AlN陶瓷是一种性能优良的电子封装材料,但不容易与金属直接连接在一起.实验采用98（Ag28Cu）2Ti活性焊料, 在真空条件下实现了AlN陶瓷与Mo Ni Cu合金的活性封接.利用EBSD、EDS、XRD方法研究了焊接区域以及剪切试样断裂表面的微观结构和相组成,测定了焊区的力学性能和气密性.研究结果显示：在AlN陶瓷界面上有TiN生成,说明陶瓷与焊料之间是一种化学键合,而在Mo Ni Cu合金的界面上有少量的Ni Ti金属间化合物存在.剪切后试样的断裂面上有TiN和AlN,说明断裂发生在靠近陶瓷的焊层区域.焊接试样性能优良：气密性达到1.0×10^-11Pa·m³/s,平均抗弯强度σ_ｂ=78.55MPa,剪切强度σ_τ=189.58MPa.     

自适应无铅焊料的开发与研究

可靠性是电子工业发展所面临的最大难题.随着对无铅焊料的深入研究,消除金属间化合物对焊点机械性能的不利影响,及解决由于印刷电路板与电子材料间的热膨胀系数不同所产生的、在热循环过程中出现的热疲劳现象,都是提高可靠性的途径.提出了开发自适应无铅焊料解决上述问题,阐述了制备自适应无铅焊料的可行性,并展望了此种焊料的良好应用前景.     

时效处理对Sn-Bi系无铅焊料的影响研究

为解决Sn-Bi焊料在焊接时容易产生凝固偏析、降低焊点力学性能的问题,采用对焊点进行时效处理的方法来消除Bi的粗化结晶,从而增强焊料的机械性能.研究表明,焊点在125℃时效处理16 h,粗大块状的Bi全部消融,呈颗粒状均匀分布,焊料中的Sn与焊盘上的Cu生成一层厚度约为3μm的Cu6Sn5金属间化合物,使焊点的剪切强度由40 MPa升高到54 MPa.研究还发现,时效处理后的焊点在100℃下长时间放置,微观组织不再发生变化,说明时效处理提高了焊料基体的抗热性能,因此,可以将125℃/16 h的时效处理作为表面贴装生产工艺流程的一道必要工序,使Sn-Bi焊料真正满足实用要求.     

等温时效对SnAgCu/Cu焊接接头显微组织及强度的影响

研究了SnAgCu焊料与铜基的接头在150℃等温时效后,接头界面金属间化合物的形成与转变.用扫描电镜观察在时效过程中焊接接头的显微组织演变.用X射线能谱仪测定了化合物的成分.结果表明,回流焊接时,在焊料和铜基板之间形成了Cu6Sn5化合物层,随着时效时间的增加,Cu6Sn5的晶粒大小逐渐增加,并且形态逐渐从扇贝状依次转变为针状和杆状,最后转变为颗粒状.与此同时,在焊料及Cu6Sn5金属间化合物层之间形成了杆状的Ag3Sn.焊接接头的抗拉强度的测量表明,抗拉强度随着时效时间的增加开始略有增加而后逐渐下降.断口观察发现,随着时效时间的增加,断裂源从焊料内部向Cu6Sn5界面移动.在化合物层界面发生的断裂是由于化合物晶粒粗化和Cu6Sn5化合物层厚度的增加造成的.     

泡沫Ni/In-48Sn复合焊料钎焊Al合金接头显微结构及力学性能研究

In-48Sn共晶焊料具有熔点低、延展性高、润湿性好等优点,在微波、通信等功能组件的钎焊连接中具有广泛应用。然而,In-48Sn共晶焊料力学性能较差,已难满足新一代功能组件的载荷要求。采用微合金化及微纳米颗粒、纤维强化等方法可在一定程度上提高焊料的强度,但钎焊接头的强度提升效果有限。基于此,本工作采用真空浸渗工艺制备了泡沫Ni强化In-48Sn复合焊料,并采用该复合焊料对表面含Ag镀层的Al合金进行了低温钎焊连接,重点研究了泡沫Ni孔隙率和钎焊时间对接头显微结构及力学性能的影响。研究结果表明,Al合金表面形成了Ag₂In金属间化合物(IMC)层,其随钎焊时间延长不断增厚,且在无Ni骨架阻挡时易向焊缝中生长形成块状结构。In-48Sn焊料与泡沫Ni骨架反应形成了(Ni, Cu)₃-(In, Sn)₇相,延长钎焊时间、减小泡沫Ni孔隙度均会促进该反应相的形成并加快In基焊料的消耗,最终焊缝完全由Ni骨架和IMCs组成,而钎焊接头的剪切强度也相应增加。采用50%Ni-In48Sn复合焊料钎焊120 min时接头剪切强度达到了3...     

应用于功率芯片封装的瞬态液相扩散连接材料与接头可靠性研究进展

功率半导体由于其工作电压高、电流大、放热量大等特点,已逐渐向小型化、高致密化发展.新一代宽禁带半导体器件因其优异的性能可以提高工作温度和功率密度,展现出较好的应用前景,这对与之匹配的电力封装材料提出了更高的要求.随着工作温度的不断升高,高温环境下失稳和运行环境不稳定等安全问题亟需解决,对功率半导体芯片封装接头的高温可靠性提出了更高的要求.且由于污染严重的高铅焊料不满足环保要求,高温无铅焊料的研制与对相应连接技术的研究成为当前的研究重点.瞬态液相扩散连接(Transient liquid phase bonding,TLP bonding)技术通过在低温下焊接形成耐高温金属间化合物接头,以满足"低温连接,高温服役"的要求,在新一代功率半导体的耐高温封装方面有良好的应用前景.针对TLP技术的耐高温封装材料有Sn基、In基和Bi基等.目前TLP连接材料主要有片层状、焊膏与焊片三种形态.其中片层状TLP焊料应用最早,且国内外对于其连接机理、接头性能和可靠性已有较为成熟的研究.近些年开发的基于复合粉末的焊膏与焊片形态TLP焊料具有相对较高的反应效率,但仍需大量理论与实验研究来验证其工业应用前景.本文综述了TLP连接用Sn基与In基焊料的特点,重点阐述了不同形态焊料在TLP连接机理、接头微观组织、力学性能与结构可靠性等方面的国内外研究现状及进展,并且认为接头中缺陷问题的研究以及不同服役条件下物相转化机制和接头失效机理的研究对高可靠性接头的制备具有重要意义.     

键合丝键合界面研究进展

采用引线键合技术对集成电路进行封装时,键合丝与Al焊盘存在异质界面问题,对电子器件的使用性能有很大的影响。本文综述了键合参数、界面金属间化合物(IMC)演变行为及工作环境等方面对界面键合强度和可靠性影响的研究进展,并展望了未来发展前景。     

无铅焊料研究现状与发展展望

随着电子工业飞速发展以及人们环保意识的提高，以“绿色焊接”为主题的电子装配技术对无铅焊料的需求也尤为迫切。本文从焊料可焊性和焊接蛄构的可靠性等方面介绍了近年来国内外无铅焊料研究方面的最新成果；着重概括了为提高焊接性能而在配料组分、金属间化合物析出与组织控制等工作，重点阐明了稀土元素在焊料组织控制中的关键作用；针对我国稀土资源蕴藏丰富的特点，指出了元铅焊料进一步发展的方向。     

不同缓蚀剂对SnAgCu焊膏焊接性能的影响

通过对SnAgCu焊膏/Cu焊接界面IMC层和力学性能进行分析,研究了助焊剂中添加咪唑类缓蚀剂A和喹啉类缓蚀剂B及其复配对SnAgCu焊膏焊接性能的影响.利用扫描电镜(SEM)和能量色散谱仪(EDS)分别对IMC层的微观结构和焊点的组织成分进行观察和分析,采用力学试验机测试焊点的剪切强度和拉伸强度,并通过SEM观察其断口形貌.研究结果表明:缓蚀剂对界面IMC层的生长起到一定控制作用,不添加任何缓蚀剂时,IMC层厚度不均匀,部分呈粗大的柱状结构,平均厚度为7.6μm;而添加0.5%A和0.5%B复配缓蚀剂的焊膏,IMC层最薄而且致密均匀,厚度为3.4μm;添加0.5%A和0.5%B复配缓蚀剂的焊膏,获得了最大的剪切强度和抗拉强度,其中剪切强度为47.92 MPa,剪切断裂模式为韧性断裂,抗拉强度为99.28 MPa,拉伸断裂模式为脆性断裂.     

Influence of Thermal Cycling on the Microstructure and Shear Strength of Sn3.5Ag0.75Cu and Sn63Pb37 Solder Joints on Au/Ni Metallization

The influence of thermal cycling on the microstructure and joint strength of Sn3.5Ag0.75Cu （SAC） and Sn63Pb37 （SnPb） solder joints was investigated. SAC and SnPb solder balls were soldered on 0.1 and 0.9 μm Au finished metallization, respectively. After 1000 thermal cycles between -40℃ and 125℃, a very thin intermetallic compound （IMC） layer containing Au, Sn, Ni, and Cu formed at the interface between SAC solder joints and underneath metallization with 0.1 μm Au finish, and （Au, Ni, Cu）Sn4 and a very thin AuSn-Ni-Cu IMC layer formed between SAC solder joints and underneath metallization with 0.9 μm Au finish. For SnPb solder joints with 0.1 μm Au finish, a thin （Ni, Cu, Au）3Sn4 IMC layer and a Pb-rich layer formed below and above the （Au, Ni）Sn4 IMC, respectively. Cu diffused through Ni layer and was involved into the IMC formation process. Similar interfacial microstructure was also found for SnPb solder joints with 0.9μm Au finish. The results of shear test show that the shear strength of SAC solder joints is consistently higher than that of SnPb eutectic solder joints during thermal cycling.     

Degradation of Sn37Pb and Sn3.5Ag0.5Cu solder joints between Au/Ni (P)/Cu pads stressed with moderate current density

Sn37Pb (SP) and Sn3.5Ag0.5Cu (SAC) ball grid array (BGA) solder joints between Au/Ni (P)/Cu pads were stressed with a moderate current density of 6.0 × 10² A/cm² at an ambient temperature of 125°C up to 600 h. The solder joint reliability was evaluated in terms of temperature measurement, microstructural analysis and mechanical strength test. It was confirmed that no obvious electromigration occurred with this moderate current density. However, the local temperature of solder joints rose considerably due to massive Joule heating, which degraded the solder joint reliability seriously. Phase coarsening was observed for both solders and it was particularly apparent in the SP solder joints. Compared to the SP, the SAC was found to be more reactive and hence a thicker intermetallic compound (IMC) was developed during the current stressing. Nevertheless, the IMC thickening was not as remarkable as expected with current stressing at high temperature. It exhibited a sub-parabolic growth manner that was mainly controlled by grain boundary diffusion. However, a sufficiently thick IMC layer initially formed during reflow soldering and the low diffusivity of the Ni atoms retarded the growth. The shear strength of the solder joints was found to decrease severely with the current stressing time. This degradation was attributed to the large stresses arising from localized thermal mismatch, phase coarsening, volume shrinkage of IMC evolution, Ni–P layer crystallization and the pad cracking during current stressing.     

Reliability of SnAgCu/SnAgCuCe solder joints with different heights for electronic packaging

Finite element simulation and experiments were used to analyze the reliability of SnAgCu/SnAgCuCe solder joints with different heights. With the increase of height of solder joints, the tensile strength of SnAgCu and SnAgCuCe solder joints drops significantly. With the same height, the tensile strength of SnAgCuCe solder joints show enhanced reliability comparing with that of SnAgCu solder joints. The heights of lead-free solder joints can markedly influence the failure modes of SnAgCu/SnAgCuCe solder joints, three models [intermetallic compound (IMC), solder/IMC, solder] can be demonstrated with the variation of height. Based on finite element methods, it is found the maximum stress concentrated location show a relationship with heights of solder joints, smaller height can keep the high reliability of solder joints.     

三价铈离子掺杂氯化钾的光致发光性能

采用水热蒸发法制备了KCl∶Ce3+荧光粉。测量并分析了材料在室温下的真空紫外激发光谱及相应的发射光谱。结果表明激发谱显示6个峰,峰位分别为149、194、206、219、233和251nm。其中149nm的激发峰是基质吸收引起的;194、206、219、233和251nm是Ce3+离子的4f→5d跃迁引起的。发射峰显示双峰结构,峰位分别是311和326nm。此峰对应于Ce3+离子的5d→4f(2F5/2,2F7/2)跃迁。     

Modifying the mechanical properties of lead-free solder by adding iron and indium and using a lap joint test

Eliminating lead in electronics is an environmental consciousness that is taken prior to manufacturing. Lead-free solder has recently been developed to advance that goal. One of the most common types of lead-free solder is Sn–Ag–Cu(SAC). Adding alloying elements can modify the properties of SAC. The present study is devoted to the research and development of SAC for microelectronic packaging applications. The effects of iron and indium addition to SAC were investigated. Four different samples were fabricated by casting: Sn–3.6Ag–0.9Cu, Sn–3.6Ag–0.9Cu–0.2Fe, Sn–3.6Ag–0.9Cu–0.6Fe, and SAC-InCe. Reliability tests were done on Cu and Ni–P substrate. The shear strength of the joint was improved by decreasing the intermetallic compound (IMC) thickness; so the IMCs thickness must be controlled, because the formation of IMC leads to joint embrittlement at the interface. In conclusion, the addition of In and Fe can improve mechanical properties, such as shear strength, but the addition of In appears to be more effective for increasing the fracture toughness. The addition of Fe lowers the wetting angle and it can effectively improve the solder reliability, this improvement in shear behavior for the samples, which were reflowed on Cu substrate, is enhanced compared with the Ni substrate, but 0.6% Fe addition for the Cu substrate illustrates an decrease in fracture strain, because of abnormal growth of Cu₆Sn₅Whiskers in this case.     

基于显式动力学的焊点冲击失效分析

组件级高速剪切测试是用来研究芯片封装中Sn-Ag-Cu焊点冲击可靠性问题的一个重要手段。实验研究表明:随着冲击速度的增加,焊点封装结构的失效会由焊锡母材的韧性破坏向界面金属间化合物(IMC)的脆性断裂过渡;同时,其荷载-位移响应曲线形态也会发生显著的改变。为了能够更详细地了解封装结构的冲击失效行为,并进一步改进其结构设计,该文提出结合焊锡材料应变率相关的动态硬化特性,利用渐进损伤模型来模拟其动态损伤过程;同时,引进一种能够有效表征复合型裂纹扩展的内聚力模型来模拟IMC的脆性动态断裂。与实验结果的对比表明:该文提出的方法能够较为有效地表征焊点封装结构在不同冲击速度下的失效行为。     

The combined effects of ultrasonic wave and electric field on the microstructure and properties of Sn2.5Ag0.7Cu0.1RE/Cu soldered joints

The effect of ultrasonic wave (USW) and electric field (E) on the solderability of Sn2.5Ag0.7Cu0.1RE/Cu was investigated. Compared with the sample soldered conventionally, the solder joint obtained with USW and E assisted resulted in significant changes in the microstructure. The thickness and roughness of the interfacial Cu₆Sn₅ intermetallic compound (IMC) layer decreased by 39 and 56 %, respectively. The shear strength of the solder joint increased by 68 %, and the fracture mechanism of the solder joint transformed from brittle fracture occurred in the interfacial IMC layer to ductile fracture occurred in the solder alloy. The results reveal that reliable soldering of Sn2.5Ag0.7Cu0.1RE/Cu can be achieved with USW and E assisted, despite of low-halogen flux.     

Investigation on high temperature mechanical fatigue failure behavior of SnAgCu/Cu solder joint

In this paper, high temperature mechanical fatigue tests on SnAgCu/Cu solder joints were carried out under three test temperatures (100, 125, 150 °C). Failure mechanism was analyzed through observation of micro-crack evolution and fracture morphology. The results show that the deformation curve of solder joint under high temperature mechanical fatigue tests can be divided into three stages: strain hardening stage, stable deformation stage and accelerated failure stage, which is similar to the curve under creep test condition. In addition, the cyclic life decreases rapidly with increasing temperature. Deformation field in the solder joint is non-uniform and shear strain concentration occurs in solder close to the intermetallic compound (IMC) layer. Micro-crack initiates at the corner of the solder joint and then tend to propagate along interface between Cu substrate and solder. The fracture morphology under three temperatures all exhibits ductile fracture mode and the failure path transforms from cutting through the top of Cu₆Sn₅ to propagation in solder matrix close to IMC layer with increasing temperature.     

回流次数对无铅焊点组织演变及可靠性的影响

目的研究不同回流次数对焊点形貌以及组织演变的影响,并通过力学性能来表征不同回流次数下焊点的可靠性。方法利用置球法将Sn3Ag0.5Cu小球置于Cu基板表面,随后在回流焊机中形成焊点,并进行不同次数回流焊接得到所需焊点,横截镶样打磨腐蚀后,利用光学显微镜、扫描电子显微镜进行显微组织观察,并用推拉试验机进行剪切测试。结果在焊点反应过程中,由于熔融焊料中析出的过饱和Cu和Sn会在焊料部分形成中空的Cu6Sn5管状物和片状的Sn基体,但随着反应的持续,这些物质逐渐消失。在IMC层的形成过程中,伴随着大量Cu6Sn5颗粒的产生,随着反应的持续,颗粒数量逐渐减少,IMC层厚度逐渐增加,但增加速度减缓。结论在IMC层的生长过程中,大块IMC会吞噬Cu6Sn5小颗粒来增加自身体积,从而抑制小颗粒的产生,最终减缓自身的生长。此外随着回流次数的增加,焊点由韧性断裂逐渐转变为韧脆性混合断裂,对焊点可靠性的降低具有一定影响。