Solid-State Interfacial Reaction between Eutectic Au-Ge Solder and Cu/Ni(P)/Au Metalized Ceramic Substrate and Its Suppression

Eutectic Au-12 Ge solder was employed to bond the SiC power devices to a Si3N4/Cu/Ni（P）/Au multilayered substrate.The high-temperature reliability of the bond was investigated in detail at 200,250,300 and 330 ℃,respectively.NiGe and Ni5Ge3intermetallic compounds（IMCs） were identified at the Au-12Ge/Ni（P） interface by micro X-ray diffraction（μXRD） and scanning electron microscopy（SEM）equipped with energy dispersive X-ray analysis（EDX）.The growth of the Ni-Ge IMCs was dominated by Ni5Ge3layer,which formed at the Ni5Ge3/NiGe interface by outward diffusion of Ni from the Ni（P） layer.The activation energy of the total Ni-Ge IMCs growth was 66 kJ/mol.The shear strength of the bond was tested at both 25 ℃ and the aging temperatures,respectively.The shear strength decreased slightly after aging at 200 and 250 ℃.The shear strength tested at 250 ℃ was 46 MPa after aging at 250 ℃ for 3000 h.The shear strength aged at 300 and 330 ℃ rapidly decreased with aging time due to the rapid growth of the Ni5Ge3IMC.To slow down the interfacial reaction between the high temperature solder and the Ni（P）layer,an approximately 200 nm-thick Ta/TaN/Ta new diffusion barrier（DB） was deposited on the substrate.Analysis by transmission electron microscopy（TEM） equipped with EDX,reveals that the Ta/TaN/Ta DB was bonded well to the Ni（P） layer and the solder.High temperature storage test at 330 ℃ for1500 h reveals that the bond of the SiC devices maintained its high shear strength of approximately56 MPa without decrease.The new DB effectively suppressed the interfacial reaction between the Au-12 Ge solder and the Ni（P） layer of the substrate.

Ag-Au-Ge钎料润湿性的研究

通过对Ag-Au-Ge系三元相图的分析研究,初步研制了熔化温度在490℃的Ag-Au-Ge钎料合金,并对其润湿性进行了测试。润湿性测试结果表明:温度在熔点以上60℃范围内时,Ag-Au-Ge钎料合金与Ni板润湿性良好。

添加合金元素改善Au-Ge钎料组织及性能的研究进展

现如今电子行业纷纷开展了无铅钎料的研究工作,但是对用于高温环境下的无铅钎料的研究十分有限。对于熔化温度在280~400℃范围内的无铅钎料,Au-Sn、Au-Ge、Au-Si等金基钎料已逐步代替传统的高铅钎料,被广泛应用于微电子的耐高温封装领域。其中,Au-Ge合金具有良好的导电性、导热性、耐腐蚀性和高抗拉强度等优点,其耐高温性能明显优于Au-Sn、Au-Si钎料,尤其适用于高温环境。然而,Au-Ge钎料固有的缺点严重影响了其生产应用:一方面,由于Ge元素的存在,Au-Ge合金脆性较大,导致其难以加工成型,产品性能差、成品率低,严重影响了该钎料的推广使用。另一方面,Au-Ge钎料中Au含量较高,使得其成本高昂。因此,除了寻找最佳的Au-Ge钎料的加工方法外,研究者们也纷纷向Au-Ge钎料中加入适当的合金元素进行改性,开发出多种金锗基多元合金体系。对于Au-Ge合金很脆,难以加工成型的问题,研究人员发现水平连铸的方法可以省去加工过程,直接连铸出所需的直径,降低损耗,保证钎料质量。研究者们除了研究Au-Ge二元合金外,还纷纷开展了Au-Ge-X三元合金体系的研究。研究表明,一些低熔点的元素,如Sn、Sb、In等,可以有效降低钎料的熔点。与Au-12Ge合金相比,Sn、Sb元素的加入不仅可以降低钎料合金熔化温度,保持良好的润湿性能,还可抑制界面层的过度生长,从而避免对电性能和力学性能带来的不利影响。其中,添加适量的Sn元素还可以抑制Ge相的长大粗化,提高其高温性能。添加适量的Sb元素能改善Au-Ge钎料的延展性能。Au-Ge-Ni合金可以和GaAs材料形成欧姆连接,提高钎料的电阻率,在钎缝和母材之间形成“等电阻率”过渡,提高钎焊接头强度。但是,在Au-12Ge合金中加入过量的Ni元素会形成粗大的GeNi化合物,该化合物集聚后颗粒变大且分布不均匀,严重降低钎焊接头的强度。在Au-Ge钎料中加入In、Sb元素还可起到细化晶粒的作用。目前,对Au-Ge系三元合金的研究十分有限,在润湿性能、力学性能、焊点可靠性等方面需做进一步的研究。本文介绍了Au-Ge基钎料的研究现状,重点分析了Sn、Ni、In、Sb元素对Au-Ge钎料组织及性能的影响。此外,本文分析总结了Au-Ge基钎料在生产使用中存在的问题以及主要的解决方法,展望了该钎料的未来研究方向,以期为Au-Ge基钎料在高温封装领域的应用提供理论指导。

界面密排六方固溶体提高Au-Ge/Cu焊点的剪切强度

系统研究界面产物形貌、化学成分、力学性能及其对Au−Ge/Cu焊点剪切强度的影响。结果表明,在400℃下钎焊5~60 min后,焊点界面生成密排六方结构固溶体相(HCP)。该HCP相成分为78%~46%Cu,9%~42%Au和~12%Ge(摩尔分数),杨氏模量为105~112 GPa,硬度为4.3~4.7 GPa。钎焊5 min焊点的剪切强度为57 MPa,但钎焊60 min后焊点的剪切强度上升至68 MPa。焊点强度的提高可归因于塑性HCP相的生成及其对脆性(Ge)相的消耗。这说明生成塑性HCP界面产物是一种能有效提高钎焊焊点剪切强度的方法。

A comprehensive review of radiation effects on solder alloys and solder joints

In the realm of military and defence applications, exposure to radiation significantly challenges the performance and reliability of solder alloys and joints in electronic systems. This comprehensive review examines radiation-induced effects on solder alloys and solder joints in terms of microstructure and mechanical properties. In this paper, we evaluate the existing literature, including experimental studies and fundamental theory, to provide a comprehensive overview of the behavior of solder materials under radiation. A review of the literature highlights key mechanisms that contribute to radiation-induced changes in the microstructure, such as the formation of intermetallic compounds, grain growth,micro-voids and micro-cracks. Radiation is explored as a factor influencing solder alloy hardness,strength, fatigue and ductility. Moreover, the review addresses the challenges and limitations inherent in studying the effects of radiation on solder materials and offers recommendations for future research. It is crucial to understand radiation-induced effects on solder performance to design robust and radiationresistant electronic systems. A review of radiation effects on solder materials and their applications in electronics serves as a valuable resource for researchers, engineers, and practitioners in that field.

A review of extreme condition effects on solder joint reliability:Understanding failure mechanisms

Solder joint,crucial component in electronic systems,face significant challenges when exposed to extreme conditions during applications.The solder joint reliability involving microstructure and mechanical properties will be affected by extreme conditions.Understanding the behaviour of solder joints under extreme conditions is vital to determine the durability and reliability of solder joint.This review paper aims to comprehensively explore the underlying failure mechanism affecting solder joint reliability under extreme conditions.This study covers an in-depth analysis of effect extreme temperature,mechanical stress,and radiation conditions towards solder joint.Impact of each condition to the microstructure including solder matrix and intermetallic compound layer,and mechanical properties such as fatigue,shear strength,creep,and hardness was thoroughly discussed.The failure mechanisms were illustrated in graphical diagrams to ensure clarity and understanding.Furthermore,the paper highlighted mitigation strategies that enhancing solder joint reliability under challenging operating conditions.The findings offer valuable guidance for researchers,engineers,and practitioners involved in electronics,engineering,and related fields,fostering advancements in solder joint reliability and performance.

Preventing formation of intermetallic compounds in ultrasonic-assisted Sn soldering of Mg/Al alloys through pre-plating a Ni coating layer on the Mg substrate

Magnesium and aluminum alloys are widely used in various industries because of their excellent properties,and their reliable connection may increase application of materials.Intermetallic compounds(IMCs)affect the joint performance of Mg/Al.In this study,AZ31 Mg alloy with/without a nickel(Ni)coating layer and 6061 Al alloy were joined by ultrasonic-assisted soldering with Sn-3.0Ag-0.5Cu(SAC)filler.The effects of the Ni coating layer on the microstructure and mechanical properties of Mg/Al joints were systematically investigated.The Ni coating layer had a significant effect on formation of the Mg_(2)Sn IMC and the mechanical properties of Mg/Al joints.The blocky Mg_(2)Sn IMC formed in the Mg/SAC/Al joints without a Ni coating layer.The content of the Mg_(2)Sn IMC increased with increasing soldering temperature,but the joint strength decreased.The joint without a Ni coating layer fractured at the blocky Mg_(2)Sn IMC in the solder,and the maximum shear strength was 32.2 MPa.By pre-plating Ni on the Mg substrate,formation of the blocky Mg_(2)Sn IMC was inhibited in the soldering temperature range 240–280℃and the joint strength increased.However,when the soldering temperature increased to 310℃,the blocky Mg_(2)Sn IMC precipitated again in the solder.Transmission electron microscopy showed that some nano-sized Mg_(2)Sn IMC and the(Cu,Ni)_(6)Sn_(5)phase formed in the Mg(Ni)/SAC/Al joint soldered at 280℃,indicating that the Ni coating layer could no longer prevent diffusion of Mg into the solder when the soldering temperature was higher than 280℃.The maximum shear strength of the Mg(Ni)/SAC/Al joint was 58.2 MPa for a soldering temperature of 280℃,which was 80.7%higher than that of the Mg/SAC/Al joint,and the joint was broken at the Mg(Ni)/SAC interface.Pre-plating Ni is a feasible way to inhibit formation of IMCs when joining dissimilar metals.

Effect of Mo and ZrO_(2)nanoparticles addition on interfacial properties and shear strength of Sn58Bi/Cu solder joint

The influence of Mo and ZrO_(2)nanoparticles addition on the interfacial properties and shear strength of Sn58Bi solder joint was investigated.The interfacial microstructures of Sn58Bi/Cu,Sn58Bi+Mo/Cu and Sn58Bi+ZrO_(2)/Cu solder joints were analysed using a scanning electron microscope(SEM)coupled with energy dispersive X-ray(EDX)and the X-ray diffraction(XRD).Intermetallic compounds(IMCs)of MoSn_(2)are detected in the Sn58Bi+Mo/Cu solder joint,while SnZr,Zr_(5)Sn_(3),ZrCu and ZrSn_(2)are detected in Sn58Bi+ZrO_(2)/Cu solder joint.IMC layers for both composite solders comprise of Cu_(6)Sn_(5) and Cu_(3)Sn.The SEM images of these layers were used to measure the IMC layer’s thickness.The average IMC layer’s thickness is 1.4431μm for Sn58Bi+Mo/Cu and 0.9112μm for Sn58Bi+ZrO_(2)/Cu solder joints.Shear strength of the solder joints was investigated via the single shear lap test method.The average maximum load and shear stress of the Sn58Bi+Mo/Cu and Sn58Bi+ZrO_(2)/Cu solder joints are increased by 33%and 69%,respectively,as compared to those of the Sn58Bi/Cu solder joint.By comparing both composite solder joints,the latter prevails better as adding smaller sized ZrO_(2)nanoparticles improves the interfacial properties granting a stronger solder joint.

Effect of Sb content on properties of Sn-Bi solders

The effect of Sb content on the properties of Sn-Bi solders was studied. The nonequilibrium melting behaviors of a series of Sn-Bi-Sb solders were examined by differential scanning calorimetry （DSC）. The spreading test was carried out to characterize the wettability of Sn-Bi-Sb solders on Cu substrate. The mechanical properties of the solders/Cu joints were evaluated. The results show that the ternary alloy solders contain eutectic structure resulting from quasi-peritetic reaction. With the increase of Sb content, the amount of the eutectic structure increases. At a heating rate of 5 ℃/min, Sn-Bi-Sb alloys exhibit a higher melting point and a wider melting range. A small amount of Sb has an impact on the wettability of Sn-Bi solders. The reaction layers form during spreading process. Sb is detected in the reaction layer while Bi is not detected. The total thickness of reaction layer between solder and Cu increases with the increase of the Sb content. The shear strength of the Sn-Bi-Sb solders increases as the Sb content increases.

Effects of Sn element on microstructure and properties of Zn-Cu-Bi-Sn high-temperature solder

The microstructures and properties of the Zn-Cu-Bi-Sn(ZCBS) high-temperature solders with various Sn contents were studied using differential scanning calorimetry(DSC),scanning electron microscopy(SEM) and X-ray diffraction(XRD).The results indicate that the increase of Sn content can both decrease the melting temperature and melting range of ZCBS solders and it can also effectively improve the wettability on Cu substrate.The shear strength of solder joints reaches a maximum value with the Sn addition of 5%(mass fraction),which is attributed to the formation of refined β-Sn and primary ε-CuZn_5 phases in η-Zn matrix.However,when the content of Sn exceeds 5%,the shear strength decreases due to the formation of coarse β-Sn phase,which is net-shaped presented at the grain boundary.

EFFECTS OF RARE EARTH ELEMENT LANTHANUM ON MICROSTRUCTURE AND PROPERTIES OF Ag-Cu-Ti SOLDER ALLOY

The effects of rare earth Lanthanum on the microstructure, the physical property and the microhardness of Ag-Cu-Ti solder alloy are studied. Experimental results indicate that the addition of Lanthanum can evidently improve the wettability and the microhardness of Ag-Cu-Ti solder alloy. Analysis results show that the increase in microhardness is related to the refining and uniform distribution of the intermetallic compounds. Proper content of Lanthanum added in Ag-Cu-Ti alloy solder can be controlled below 0.5% in mass percent.

Interfacial characteristics and microstructural evolution of Sn-6.5Zn solder/Cu substrate joints during aging

The influence of isothermal aging at 150 °C on the microstructural characteristics and microhardness of the Sn-6.5Zn solder/Cu joint was studied. The mechanisms for the formation and evolution of intermetallic compound （IMC） at the interface of the Sn-6.5Zn/Cu joint were also analyzed. The results indicate that a continuous layer consisting of CuZn and Cu5Zn8 IMCs is formed in the interface zone. As the aging time prolongs, the thickness of the IMC layer first increases and then decreases, and the continuous and compactable layer is destroyed due to the decomposition of the Cu-Zn IMC layer. A discontinuous layer of Cu6Sn5 IMC is present within the Cu substrate near the decomposed region. The interface becomes rough and evident voids form after aging. The microhardness of the interface increases owing to the application of aging.

Drop failure modes of Sn-3.0Ag-0.5Cu solder joints in wafer level chip scale package

To reveal the drop failure modes of the wafer level chip scale packages （WLCSPs） with Sn-3.0Ag-0.5Cu solder joints, board level drop tests were performed according to the JEDEC standard. Six failure modes were identified, i.e., short FR-4 cracks and complete FR-4 cracks at the printing circuit board （PCB） side, split between redistribution layer （RDL） and Cu under bump metallization （UBM）, RDL fracture, bulk cracks and partial bulk and intermetallic compound （IMC） cracks at the chip side. For the outmost solder joints, complete FR-4 cracks tended to occur, due to large deformation of PCB and low strength of FR-4 dielectric layer. The formation of complete FR-4 cracks largely absorbed the impact energy, resulting in the absence of other failure modes. For the inner solder joints, the absorption of impact energy by the short FR-4 cracks was limited, resulting in other failure modes at the chip side.

Influence of rapid solidification on Sn-8Zn-3Bi alloy characteristics and microstructural evolution of solder/Cu joints during elevated temperature aging

The effects of rapid solidification on the microstructure and melting behavior of the Sn-8Zn-3Bi alloy were studied. The evolution of the microstructuraI characteristics of the solder/Cu joint after an isothermal aging at 150 ℃ was also analyzed to evaluate the interconnect reliability. Results showed that the Bi in Sn-8Zn-3Bi solder alloy completely dissolved in the Sn matrix with a dendritic structure after rapid solidification. Compared with as-solidified Sn-8Zn-3Bi solder alloy, the melting temperature of the rapid solidified alloy rose to close to that of the Sn-Zn eutectic alloy due to the extreme dissolution of Bi in Sn matrix. Meanwhile, the adverse effect on melting behavior due to Bi addition was decreased significantly. The interfacial intermetallic compound （IMC） layer of the solder/Cu joint was more compact and uniform. Rapid solidification process obviously depressed the formation and growth of the interfacial IMC during the high-temperature aging and improved the high-temperature stability of the Sn-8Zn-3Bi solder/Cu joint.

Cu-Ni/Solder/Ni-Cu互连结构的电迁移

采用Cu-Ni/Solder/Ni-Cu互连结构,在加载的电流密度为0.4×104A/cm2的条件下,得到了界面阴极处金属原子的电迁移.数值模拟揭示了其原因是由于凸点互连结构的特殊性,电子流在流经凸点时会发生流向改变进而形成电流聚集,此处的电流密度超过电迁移的门槛值,从而诱发电迁移.运用高对流系数的热传导方法降低了互连焊点的实际温度,在电迁移的扩展阶段显著减小了高温引起的原子热迁移对电迁移的干扰;因此电迁移力是原子迁移的主要驱动力.在电迁移的快速失效阶段,原子的迁移是热迁移和电迁移共同作用的结果:电迁移力驱动阴极处原子的迁移,造成局部区域的快速温升,从而加剧此处原子的热迁移.

Solder Charge连接器连锡故障解决方案

Solder charge连接器(SBGA)为高速多引脚互联器件,应用于多种通讯产品的子母板间高速互联。在SMT生产过程中,其故障率一直高于同类焊球型封装BGA器件,主要故障表现为相邻两排引脚短路,且故障率表现与来料批次强相关,通过多种工艺方案不能完全解决连锡问题。通过分析Solder charge连接器结构和材料,找到器件连锡的根因,提出了此类器件的设计和焊接改善方案,并进行了实际生产验证,为业界Solder charge连接器(SBGA)类器件焊接提供了可行的解决方案。

Effects of Zn addition on mechanical properties of eutectic Sn-58Bi solder during liquid-state aging

Interfacial reaction, tensile strength and creep resistance of Sn-58Bi-x Zn(x=0, 0.7, mass fraction, %) solder samples during liquid-state aging were investigated. The coarsening of Bi and the growth of Cu-Sn intermetallic compounds(IMCs) in Sn-58Bi-0.7Zn solder sample were both effectively suppressed. With the addition of 0.7% Zn, ultimate tensile strengths(UTSs) of the Sn-58 Bi solder slabs were respectively increased by 6.05% and 5.50% after reflow soldering and liquid-state aging, and those of the Cu/Sn-58Bi/Cu solder joints were also increased by 21.51% and 29.27%, respectively. The increase in strengthening effect of Cu/Sn-58Bi-x Zn/Cu solder joints could be attributed to the fracture surface which was changed from the Cu/IMC interface to the IMC/solder interface due to the finer Bi grain. Nanoindentation results revealed that the creep behavior of Sn-58Bi-0.7Zn solder was significantly improved compared with that of the eutectic Sn-58 Bi solder after reflow soldering and liquid-state aging.

Microstructure evolution and mechanical properties of ultrasonic-assisted soldering joints of 2024 aluminum alloys

Ultrasonic-assisted soldering of 2024 aluminum alloys using a filler metal of Zn-5Al alloy was investigated at the temperature of 400 ℃,which is lower than the solution strengthening temperature of Al-Cu alloys.The ultrasonic vibration with power of 200 W and vibration amplitude of 15 μm at the frequency of 21 kHz was applied on the top samples.The ultrasonic vibration promoted the dissolution of Al elements in the base metal.The reduction of volume fraction of the eutectic phases in the bonds was investigated by increasing ultrasonic vibration time.As the ultrasonic vibration time increased from 3 s to 30 s,the volume fraction of the eutectic phase in the bonds decreased from 12.9% to 0.9%,and the shear strength of the joints was up to 149-153 MPa,increased by 20%.The improvement of the mechanical properties of joints was discussed based on the modulus and hardness of the phases in the bonds and the fracture of the joints.

Electrochemical corrosion of Sn-0.75Cu solder joints in NaCl solution

The corrosion behaviors of Sn-0.75Cu solder and Sn-0.75Cu/Cu joint in 3.5% NaCl（mass fraction） solution were studied by potentiodynamic polarization test and leaching measurement.The polarization curves indicated that the corrosion rate of Sn-0.75Cu solder was lower than that of Sn-0.75Cu/Cu joint.The morphology observation and phase composition analysis on the corroded product at each interesting potential suggested that Sn3O（OH）2Cl2 formed on the surface of Sn-0.75Cu solder at active dissolution stage.As the potential increased from active/passive transition stage,all the surface of Sn-0.75Cu solder was covered by the Sn3O（OH）2Cl2 and some pits appeared after the polarization test.Compared to the Sn-0.75Cu solder alloy,much more Sn3O（OH）2Cl2 formed at active dissolution stage and the pits with bigger size were observed after polarization test for the Sn-0.75Cu/Cu solder joints.The leaching test confirmed that the faster electrochemical corrosion rate resulted in the larger amount of Sn released from the Sn-0.75Cu/Cu solder joints.

Design of Pb-free solders in electronic packaging by computational thermodynamics and kinetics

Computational thermodynamics and kinetics were used to design the Pb-free micro-solders for replacing the conventional Sn-Pb solders because of the health and environmental safety problem. On the basis of CALPHAD (Calculation of Phase Diagrams) method we can easily calculate properties such as the liquidus projection, isothermal and vertical sectional diagrams and phase fraction in multi-component system including Ag, Bi, Cu, In, Sb, Sn, Zn and Pb elements. In addition, other related information such as the surface tension, viscosity of the liquid phase and solidification simulation can also be obtained. DICTRA (Diffusion Controlled Transformation) software was used to simulate the interfacial reactions between substrate and Pb-free solders, which can easily give the information on the growth of intermetallic compounds and moving speed of interface between substrate and solders etc.