Decrease in fatigue life of Sn - 3.8 wt-%Ag - 1.2 wt-%Cu alloy solder joints due to thermal cycling

Abstract

Copper plates joined with a thin solder layer (60 μm thick) of Sn - 3.8 wt-%Ag - 1.2 wt-% Cu alloy were subjected to heat treatments: a thermal cycling of a temperature range between 321 K and 381 K (Δ T = 60 K) and an isothermal heating at 357 K, and then subjected to a fatigue test at 6 MPa stress amplitude. Solder joints made with a thin solder layer of Sn - Pb eutectic alloy were also examined for comparison. After heat treatments, the η phase developed and dispersed at the bonding interface of the solder joints with increasing numbers of thermal cycling and with increasing time of isothermal heating. Small voids also appeared in the η phase after heat treatments. Fine cracks appeared in the η phase after thermal cycling for 2000 cycles and higher, but no cracks were observed after isothermal heating. There was no large difference in fatigue lifetime after thermal cycling between Sn - Ag - Cu alloy solder joints and Sn - Pb eutectic alloy solder joints. The fatigue lifetime of Sn - Ag - Cu alloy solder joints and Sn - Pb eutectic alloy solder joints was 2 - 3 × 105 with no thermal cycling and was greatly reduced to 0.1 - 0.6 × 10⁵ after 8000 thermal cycles. The fatigue lifetime was also decreased to 0.6 - 1.0 × 10⁵ after isothermal heating for 16 000 min, but the decrease in fatigue lifetime was gradual compared to that after thermal cycling. The decrease in fatigue lifetime after smaller numbers of thermal cycles is explained by coarsening of the η phase, and the large decrease in fatigue lifetime after a large number of thermal cycles is explained by the appearance of cracks in the η phase during thermal cycling.     

Influence of thermal cycling on fatigue strength of Cu/Sn/Cu solder joints

Abstract

The influence of thermal cycling on the fatigue life of Cu/Sn/Cu solder joints has been examined. Copper plates were bonded with tin foil (with a solder thickness of 60 µm) and suffered thermal cycling in a temperature range of 55 or 125 K. Then they were subjected to fatigue testing at a shear stress amplitude of 2 MPa and a frequency of 3.6 Hz. With the increasing number of the thermal cycles, the fatigue life decreased from 3.0×10⁵ to 5.0×10⁴ at thermal cycle 6000. However, the fatigue life did not change so much during thermal cycling in different temperature ranges. When the solder joints suffered the thermal cycling, the η phase at the bonding interface coarsened and elongated, and its arrangement became irregular. After larger numbers of thermal cycles, fine cracks appeared in the η phase parallel to the interface. After fatigue testing, circular patterns were observed inside the bonded region on a fracture surface, and their shape and size became irregular and larger with the increasing number of thermal cycles, respectively. These showed that the reduction in fatigue life was caused by improved propagation of the fatigue crack following changes in the morphology and arrangement of the η phase during thermal cycling.     

Thermal cycling test in Sn-Bi and Sn-Bi-Cu solder joints

The eutectic SnBi solder alloy is a candidate for Pb-free replacement of the conventional eutectic SnPb solders. This study presents series of results on the binary eutectic SnBi and ternary SnBi-1 wt % Cu a solder joints. Compositional analysis and wettability of the as-fabricated solder alloys are reported. In addition, microstructure, adhesion strength, fracture surface and contact resistance of the solder joints are also evaluated. The results of the wetting balance show that the addition of 1 wt % Cu has little effect on the contact angle of the eutectic SnBi solder alloy with various metallization layers. The adhesion strength of solder joints degrades abruptly after 2000 thermal cycles. In addition, thermal cycling would result in cracking in the solder joints, which is due to the mismatch in thermal expansion coefficients. Portions of the thermal fatigue cracks nucleate at the edge of the solder fillet, and then propagate along the solder/conductor interface. Some cracks are, however, through the Al₂O₃ substrate. The contact resistance of the solder/Cu joint does not increase after thermal cycling since the resistivity of Cu₆Sn₅ is lower than that of the solder. The solder joints of 42Sn-58Bi/Cu, SnBi-1Cu/Cu, 42Sn-58Bi/PtAg, and SnBi-1Cu/PtAg assemblies maintain their integrity after 2000 thermal cycles since the increase in contact resistance is rather small (ΔR<0.5 mΩ).     

Re‐calibration of Engelmaier's Model for Leadless,Lead‐free Solder Attachments

In this paper, the solder attachment fatigue model created by Werner Engelmaier is re‐calibrated in order to make it applicable in conjunction with leadless, lead‐free solder attachments. Sn3.8Ag0.7Cu solder attached ball‐grid‐array components are addressed to three thermal cycling test profiles. Based on the results, both physical and statistical parameters are obtained and compared with the values relevant to tin–lead solder assemblies. The validity of the statistical distribution selection (two‐parameter Weibull) is studied. Acceleration factors correlating different test profiles are obtained, and they are found to be only weakly dependent on the test vehicle type. Copyright © 2006 John Wiley & Sons, Ltd.     

热循环条件下SnAgCu/Cu焊点金属间化合物生长及焊点失效行为

研究了热循环过程中SnAgCu/Cu焊点界面金属间化合物的生长规律及焊点疲劳失效行为。提出了热循环条件下金属间化合物生长的等效方程以及焊点界面区不均匀体模型,并用有限元模拟的方法分析了热循环条件下焊点界面区的应力应变场分布及焊点失效模式。研究结果表明:低温极限较低的热循环,对应焊点的寿命较低。焊点的失效表现为钎料与金属间化合物的界面失效,且金属间化合物厚度越大,焊点中的累加塑性功密度越大,焊点越容易失效。     

Effect of thermal ageing on (Sn-Ag, Sn-Ag- Zn)/PtAg, Cu/Al2O3 solder joints

As-fabricated solders of eutectic Sn-Ag and ternary Sn-3.5 wt% Ag-1 wt% Zn alloys are coupled with metallized substrates including PtAg/Al2O3 and Cu/Al2O3 to simulate the solder joint in microelectronics. The growth mechanism of intermetallics and the mechanical properties of solder joints after thermal ageing (150 °C and 200 °C) are evaluated. In this study, a 1206 passive device/solder/metallization/Al2O3 surface mount technology (SMT) assembly is employed, and a Cu stud is attached on the ceramic substrate assembly to evaluate mechanical properties and the fracture morphology by the pull-off test. In addition, microstructure evolution of the interfacial morphology, elemental and phase distribution are probed with the aid of scanning electron microscopy (SEM), electron probe micro-analysis (EPMA) and X-ray diffraction (XRD) techniques. There are two intermetallics (Cu3Sn and Cu6Sn5) formed at the eutectic Sn-Ag solder/Cu metallized layer interface, while only Cu6Sn5 is observed in the Sn-3.5 Ag-1Zn/Cu system. However, in the PtAg metallized substrate, only Ag3Sn is present, regardless of which solders are employed. Cu6Sn5 and Ag3Sn in the Sn-3.5 Ag-1Zn system contain 2–5 at% Zn due to the higher solubility of Zn in both Cu and Ag. The adhesion strength decreases as the time increases for all solder joint systems in the thermal ageing test. The solder joint with eutectic Sn-Ag alloy exhibits higher fracture load than that with Sn-3.5 Ag-1Zn alloy. From the fracture surface analysis, as the ageing time increases, the fracture takes place from the solderconductor interface toward the inside of the IMC (intermetallic compound). © 1998 Kluwer Academic Publishers     

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.     

Life expectancies of Pb-free SAC solder interconnects in electronic hardware

The transition from lead (Pb) bearing solder to Pb-free solder has arisen in response to government restrictions on the use of lead (Pb) by the European Union. As a result, electronic manufacturers have sought a material comparable to the conventional 63Sn37Pb solder that has been traditionally used to assemble electronic hardware. Based on extensive review of various solder combination, the majority of electronic manufacturers appear to be adopting a tin–silver–copper (SAC) solder as a popular Pb-free solder replacement. Significant investments have been made by many researchers to characterize the material behavior and durability of this solder system. While the exact composition of the SAC solder is still in question, it now appears that the 96.5Sn3.0Ag0.5Cu (SAC305) solder is gaining wider acceptance as the favored Pb-free replacement, for surface mount assemblies that are going to be subjected predominantly to cyclic thermal environments. This paper presents a review of our current understanding of the life expectancy of Pb-free SAC solder interconnects for electronic hardware. To this end, the paper focuses on material characterization of SAC solder, as well as its temperature cycling and vibration fatigue reliability. From this review, SAC solder interconnects are shown to be suitable for providing adequate life expectancies for temperature cycling in electronic hardware. However, it is clear that there are differences between SAC and the conventional Sn37Pb solder, that need to be understood in order to design reliable electronic hardware.     

Microstructure transformation of Sn base solders under isothermal aging and thermal shearing cycling conditions

Abstract

The diffusion of atoms and the growth behaviour of intermetallic compounds (IMCs) at both Sn–3·5Ag–0·5Cu/Cu and 63Sn–37Pb/Cu interfaces under isothermal aging and thermal shearing cycling conditions have been investigated. The results show that a Cu₆Sn₅ IMC layer is formed at both the Sn–Ag–Cu/Cu and Sn–Pb/Cu interfaces, and the morphology of Cu₆Sn₅ changes gradually from scallop structure to plate-like structure with increasing number of thermal shearing cycling, while two IMCs, Cu₆Sn₅ and Cu₃Sn, are formed at the Sn–Ag–Cu/Cu and Sn–Pb/Cu interfaces after isothermal aging for 100 h. The IMC growth follows parabola growth kinetics, implying that the IMC growth is controlled by the diffusion of Cu atoms. In Sn–Ag–Cu solder, Ag₃Sn, forming uniform particles after reflowing, congregates gradually to be chunk-like.     

Effect of solder filler thickness on the mechanical stability of fiber-solder-ferrule joint under temperature cyclic loading

The base materials of package and ferrule are often gold-coated Kovar and Invar, they both have relatively low coefficient of thermal expansion (CTE). Solder 63Sn37Pb dissolves Au substantially and forms brittle AuSn₄, which may cause catastrophic failure in the fiber-solder-ferrule (FSF) joint in the long-term application. It is well known that thermal fatigue creep is one of the crucial factors affecting the life and reliability of a solder joint in electronic and optoelectronic assemblies. Therefore, it is important to understand the behavior of the FSF joint under thermal cyclic loading. In this study, four different thicknesses of solder filler in a FSF joint were examined. By using the finite element method (FEM), the equivalent creep strains of eutectic lead-tin solder were compared. The joints were subjected to 5 cycles of temperature cycling test, i.e., −65 to 150^∘C. It was found that the thicker solder filler is subjected to a larger equivalent creep strain than the thinner solder filler. It is discussed the vertical shift of the optical fiber, which is sensitive to temperature and has effects on the power loss coupling. Modeling and experimental results show that 0.5 mm is the best inner diameter of ferrule that provides the lowest displacement and, thus, the lowest power loss under temperature cycle.     

Interfacial microstructure and hardness of nickel (Ni) nanoparticle-doped tin–silver–copper (Sn–Ag–Cu) solders on immersion silver (Ag)-plated copper (Cu) substrates

Sn–Ag–Cu composite solder has been prepared by adding Ni nanoparticles. Interfacial reactions, the morphology of the intermetallic compounds (IMC) that were formed, the hardness between the solder joints and the plain Cu/immersion Ag-plated Cu pads depending on the number of the reflow cycles and the aging time have all been investigated. A scallop-shaped Cu₆Sn₅ IMC layer that adhered to the substrate surface was formed at the interfaces of the plain Sn–Ag–Cu solder joints during the early reflow cycles. A very thin Cu₃Sn IMC layer was found between the Cu₆Sn₅ IMC layer and the substrates after a lengthy reflow cycle and solid-state aging process. However, after adding Ni nanoparticles, a scallop-shaped (Cu, Ni)–Sn IMC layer was clearly observed at both of the substrate surfaces, without any Cu₃Sn IMC layer formation. Needle-shaped Ag₃Sn and sphere-shaped Cu₆Sn₅ IMC particles were clearly observed in the β-Sn matrix in the solder-ball region of the plain Sn–Ag–Cu solder joints. Additional fine (Cu, Ni)-Sn IMC particles were found to be homogeneously distributed in the β-Sn matrix of the solder joints containing the Ni nanoparticles. The Sn–Ag–Cu–0.5Ni composite solder joints consistently displayed higher hardness values than the plain Sn–Ag–Cu solder joints for any specific number of reflow cycles–on both substrates–due to their well-controlled, fine network-type microstructures and the homogeneous distribution of fine (Cu, Ni)–Sn IMC particles, which acted as second-phase strengthening mechanisms. The hardness values of Sn–Ag–Cu and Sn–Ag–Cu–0.5Ni on the Cu substrates after one reflow cycle were about 15.1 and 16.6 Hv, respectively–and about 12.2 and 14.4 Hv after sixteen reflow cycles, respectively. However, the hardness values of the plain Sn–Ag–Cu solder joint and solder joint containing 0.5 wt% Ni nanoparticles after one reflow cycle on the immersion Ag plated Cu substrates were about 17.7 and 18.7 Hv, respectively, and about 13.2 and 15.3 Hv after sixteen reflow cycles, respectively.     

Sn2.5Ag0.7CuxRE钎料时效焊点界面IMC研究

以Sn2.5Ag0.7CuxRE/Cu钎焊为研究对象,借助于扫描电镜和X衍射检测手段,研究了二硫化钼介质下时效焊点界面IMC组织结构特征及生长行为。实验结果表明:时效焊点界面Cu6Sn5IMC呈现由波浪状→扇贝状→层状的形态变化。焊点界面Cu6Sn5和Cu3Sn IMC的生长厚度与时效时间平方根呈线性关系,Cu6Sn5IMC具有较小的生长激活能、较大的生长系数。添加0.1%(质量分数)RE时,界面Cu6Sn5和Cu3Sn IMC的生长激活能最大,分别为81.74 kJ/mol和92.25 kJ/mol,对应焊点剪切强度最高。     

Microstructures formed from mixed solders on copper substrate

Abstract

With the development and use of a variety of Pb free solders, it is probable that some solder joints in electronic assemblies may be made with solders of two different compositions. To investigate possible microstructures resulting from such procedure, samples were prepared using small balls of four different Sn–Ag–Cu (SAC) Pb free solders, as well as Sn–Zn–Al solder, melted together with eutectic Pb–Sn solder paste and also various SAC solder pastes, on a copper substrate. It was observed that using eutectic Pb–Sn solder paste with an SAC solder ball introduced some Pb–Sn eutectic microstructure and changed the ternary eutectic present from Ag₃Sn–Cu₆Sn₅–Sn to Ag₃Sn–Pb–Sn. Use of an SAC solder paste with Sn–Zn–Al solder introduced an apparent Ag–Cu–Zn ternary compound, replacing Zn lamellae of the Sn–Zn eutectic. With eutectic Pb–Sn solder paste, the Pb–Sn–Zn ternary eutectic was formed. It was noted that use of a high Sn solder results in rapid dissolution of the copper substrate.     

Microstructural evolution of 96.5Sn–3Ag–0.5Cu lead free solder reinforced with nickel-coated graphene reinforcements under large temperature gradient

In this study, 96.5Sn–3Ag–0.5Cu (SAC305) lead-free composite solder containing graphene nanosheets (GNS) decorated with Ni nanoparticles (Ni-GNS) was prepared using a powder metallurgy method. A lab-made set-up and a corresponding Cu/solder/Cu sample design for assessing thermo-migration (TM) was established. The feasibility of this setup for TM stressing using an infrared thermal imaging method was verified; a temperature gradient in a solder joint was observed at 1240 K/cm. Microstructural evolution and diffusion of Cu in both plain and composite solder joints were then studied under TM stressing conditions. Compared to unreinforced SAC305 solder, the process of diffusion of Cu atoms in the composite solder joint was significantly reduced. The interfacial intermetallic compounds (IMCs) present in the composite solder joint also provide a more stable morphology after the TM test for 600 h. Furthermore, during the TM test, the Ni-GNS reinforcement affects the formation, migration and distribution of Ni–Cu–Sn and Cu–Sn IMCs by influencing the dissolution rate of Cu atoms.     

Influence of cerium oxide (CeO2) nanoparticles on the microstructure and hardness of tin–silver–copper (Sn–Ag–Cu) solders on silver (Ag) surface-finished copper (Cu) substrates

Nano-sized, non-reacting, non-coarsening CeO₂ particles with a density close to that of solder alloy were incorporated into Sn–3.0 wt%Ag–0.5 wt%Cu solder paste. The interfacial microstructure and hardness of Ag surface-finished Cu substrates were investigated, as a function of reaction time, at various temperatures. After the initial reaction, an island-shaped Cu₆Sn₅ intermetallic compound (IMC) layer was clearly observed at the interfaces of the Sn–Ag–Cu based solders/immersion Ag plated Cu substrates. However, after a prolonged reaction, a very thin, firmly adhering Cu₃Sn IMC layer was observed between the Cu₆Sn₅ IMC layer and the substrates. Rod-like Ag₃Sn IMC particles were also clearly observed at the interfaces. At the interfaces of the Sn–Ag–Cu based solder-Ag/Ni metallized Cu substrates, a (Cu, Ni)–Sn IMC layer was found. Rod-like Ag₃Sn and needle-shaped Cu₆Sn₅ IMC particles were also observed on the top surface of the (Cu, Ni)–Sn IMC layer. As the temperature and reaction time increased, so did the thickness of the IMC layers. In the solder ball region of both systems, a fine microstructure of Ag₃Sn, Cu₆Sn₅ IMC particles appeared in the β-Sn matrix. However, the growth behavior of the IMC layers of composite solder doped with CeO₂ nanoparticles was inhibited, due to an accumulation of surface-active CeO₂ nanoparticles at the grain boundary or in the IMC layers. In addition, the composite solder joint doped with CeO₂ nanoparticles had a higher hardness value than the plain Sn–Ag–Cu solder joints, due to a well-controlled fine microstructure and uniformly distributed CeO₂ nanoparticles. After 5 min of reaction on immersion Ag-plated Cu substrates at 250 °C, the micro-hardness values of the plain Sn–Ag–Cu solder joint and the composite solder joints containing 1 wt% of CeO₂ nanoparticles were approximately 16.6 and 18.6 Hv, respectively. However after 30 min of reaction, the hardness values were approximately 14.4 and 16.6 Hv, while the micro-hardness values of the plain Sn–Ag–Cu solder joints and the composite solder joints on Ag/Ni metallized Cu substrates after 5 min of reaction at 250 °C were approximately 15.9 and 17.4 Hv, respectively. After 30 min of reaction, values of approximately 14.4 and 15.5 Hv were recorded.     

Effects of trace amount addition of rare earth on properties and microstructure of Sn–Ag–Cu alloys

Ternary lead free solder alloys Sn–Ag–Cu were considered as the promising alternatives to conventional SnPb alloys comparing with other solders. In the present work, effects of trace amounts of rare earth Ce on the wettability, mechanical properties and microstructure of Sn–Ag–Cu solder have been investigated by means of scanning electron microscopy and energy dispersive X-ray analysis systematically. The results indicate that adding trace amount of rare earth Ce can remarkably improve the wettability, mechanical strength of Sn–Ag–Cu solder joint at different temperature, especially when the content of rare earth Ce is at about 0.03%, the tensile strength will be 110% times or more than that of the lead free solder joint without rare earth Ce addition. Moreover, it was observed that the trace amount of rare earth Ce in Sn–Ag–Cu solder may refine the joint matrix microstructure, modify the Cu₆Sn₅ intermetallic phase at the copper substrate/solder interface, and the intermetallic compound layer thickness was reduced significantly. In addition, since rare earth Ce possesses a higher affinity to Sn in the alloy, adding of rare earth Ce can also lead to the delayed formation and growth of the intermetallic compounds of Ag₃Sn and Cu₆Sn₅ in the alloy.     

Interfacial reaction and mechanical reliability of eutectic Sn–0·7Cu/immersion Ag-plated Cu solder joint

Abstract

In this study, the interfacial reaction and joint reliability of immersion Ag-plated Cu substrate with the Sn–0·7Cu (wt-%) ball–grid array (BGA) solder was investigated. During reflow, the Ag plating layer was dissolved completely into the molten Sn–Cu solder and some of the Cu layer was also dissolved into the molten solder. The dissolved Ag and Cu were precipitated as Ag₃Sn and Cu₆Sn₅ intermetallic compounds (IMCs) in the solder matrix. Upon reflow, the Sn–Cu solder exhibits an off-eutectic reaction to produce the eutectic phase and precipitate (Cu₆Sn₅ and Ag₃Sn). The Cu–Sn IMC layer was formed at the solder/Cu interface after reflow, and the IMC layer grew during aging treatment. During the shear tests, the failure mode switched from a bulk-related failure to an interface-related failure. After aging for 250 h, the joint failed partially at the solder/Cu₆Sn₅ interface. The brittle fracture was linked to the formation of thick Cu–Sn IMC layer.     

Solderability, IMC evolution, and shear behavior of low-Ag Sn0.7Ag0.5Cu-BiNi/Cu solder joint

The solderability, intermetallic compounds (IMC) evolution, and shear behavior of the low-Ag Sn0.7Ag0.5Cu-3.5Bi-0.05Ni (SAC0705-BiNi)/Cu solder joint was investigated by comparing with Sn0.7Ag0.5Cu (SAC0705)/Cu and Sn3.0Ag0.5Cu (SAC305)/Cu solder joints. Experimental results demonstrated that the melting temperature of Sn0.7Ag0.5Cu-BiNi solder alloy was lower than that of SAC0705 and SAC305 solder. But the melting range of Sn0.7Ag0.5Cu-BiNi was wider. Compared with the other two kinds of alloys, SAC0705-BiNi showed the best wettability. SAC0705/Cu, SAC0705-BiNi/Cu, and SAC305 solder joints appeared similar IMC morphologies and grain size at the beginning of soldering, but evolved to different appearance as the soldering process proceeded. The growth rate of the IMC grains in SAC0705-BiNi/Cu solder joint was the lowest because of the refinement of Ni. SAC0705-BiNi/Cu solder joint showed the highest shear strength before and after being aged, mainly due to the enhancement of solid solution strengthening and dispersion strengthening of Bi and Ni in the bulk solder, as well as the refinement of Ni at the soldering interface.     

Reactive wetting of Sn–2.5Ag–0.5Cu solder on copper and silver coated copper substrates

In the present work, wetting characteristics and morphology of intermetallic compounds (IMCs) formed between Sn–2.5Ag–0.5Cu lead-free solder on copper (Cu) and silver (Ag) coated copper substrates were compared. It was found that, Ag coated Cu substrate improved the wettability of solder alloy. The average values of contact angles of solder alloy solidified on Ag coated Cu substrate were reduced to about 50 % as compared to contact angles obtained on Cu substrates. Flow restrictivity for spreading of solder on Ag coated Cu was found to be lower as compared to Cu substrate. The spreading of solder alloy on Ag coated Cu exhibited halo zone. Coarse needle shaped Cu₆Sn₅ IMCs were observed at the solder/Cu substrate interface whereas at the solder/Ag coated Cu interface Cu₆Sn₅ IMCs showed scallop morphology. The formation of Cu₃Sn IMC was observed for the spreading of solder alloy on both substrates. The solder/Ag coated Cu substrate interface exhibited more particulates of Ag₃Sn precipitates as compared to solder/Cu substrate interface. The improved wettability of solder alloy on Ag coated Cu substrate is due to the formation of scallop IMCs at the interface.     

Effect of thermal cycles on interface and mechanical property of low-Ag Sn1.0Ag0.5Cu(nano-Al)/Cu solder joints

Low-Ag content SnAgCu solder has drawn more and more researchers’ attention due to the low cost. In this paper, the effect of 0.1 wt% nano-Al particles on interface reaction between Sn1.0Ag0.5Cu and Cu substrate was investigated, and the growth of intermetallic compounds (IMC) and mechanical property of solder joints during ??55 to 125 °C thermal cycling were also analyzed. The results show that the Cu₆Sn₅ IMC formed at the as-soldered interface and grow obviously with the increase of thermal cycling. The growth rate of IMC in the SnAgCu–0.1Al/Cu is lower than that of SnAgCu/Cu, which indicates that the nano-Al particles can inhibit the diffusion coefficient of IMC layers. Moreover, the shear force of two kinds of solder joints decrease during thermal cycling, but the shear force of SnAgCu–0.1Al is higher than that of SnAgCu.