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.

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.

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.

Effect of Ag and Ni on the melting point and solderability of SnSbCu solder alloys

To improve the properties of Sn10Sb8Cu solder alloy, two new solders （SnSbCuAg and SnSbCuNi） were formed by adding small amounts of Ag or Ni into the solder alloy. The results show that the melting point of the SnSbCuAg solder alloy decreases by 14.1℃ and the spreading area increases by 16.5% compared to the matrix solder. The melting point of the SnSbCuNi solder alloy decreases by 5.4℃ and the spreading area is slightly less than that of the matrix solder. Microstructure analysis shows that adding trace Ag makes the melting point decline due to the dispersed distribution of SnAg phase with low melting point. Adding trace Ni, Cu6Sn5 and （Cu, Ni）6Sn5 with polyhedron shape on the copper substrate can be easily seen in the SnSbCuNi solder alloy, which makes the viscosity of the melting solder increase and the spreading property of the solder decline.

Influence of cobalt content on microstructure and corrosionperformance of extruded Sn-9Zn solder alloys

The Pb-free solders have attracted a great deal of attention recently due to the environmental concerns.The present work focuses on the effect of cobalt content(0,0.5 and 3.0)on the microstructural characteristics,melting point and corrosion performance of extruded Sn-9Zn solder alloys.The results reveal that the Zn-rich precipitates with spherical or needle-like shape in the Sn-9Zn-xCo alloys are refined remarkably by forming the γ-Co5Zn21 and Co2Sn2Zn Co-contained intermetallic compounds,though the melting point and eutectic reaction temperature decrease slightly.It is suggested that the corrosion property of the extruded Sn-9Zn-xCo alloys is improved significantly by adding the cobalt element,while the content should be controlled reasonably.Combining the corrosion morphology,the influence of cobalt content on the corrosion behavior of the Sn-9Zn-xCo alloys is analyzed in terms of the refined microstructure and the enhanced passive film stability.

Effect of Rare Earths on Microstructure and Properties of Sn2.0Ag0.7CuRE Solder Alloy for Surface Mount Technology

A new type of lead-free solder alloy Sn2.0Ag0.7CuRE was fabricated under vacuum condition. The microstructure and properties of the material, such as tensile strength, elongation, melting range, conductance and spreading area were all investigated. Result shows that when the content of RE ≤ 0.1% （mass fraction）, RE distribute uniformly in the solder alloy, and the tensile strength and conductance of Sn2.0Ag0.7CuRE solder alloy are better than those of traditional Sn37Pb solder. Its elongation and spreading area are almost equal to those of Sn37Pb solder. When the content of RE reaches 0.5%, RE compounds can be easily found around the boundaries of grains and phases, and the tensile strength and elongation and spreading area of Sn2.0Ag0.7CuRE solder alloy all decrease sharply. Therefore, RE amount added to the Sn2.0Ag0.7CuRE solder alloy under 0.1% is proper.

Dendritic Growth, Eutectic Features and Their Effects on Hardness of a Ternary Sn–Zn–Cu Solder Alloy

The present investigation is based on the results of a directionally solidified （DS） Sn-9 wt%Zn-2 wt%Cu alloy, including primary/secondary/tertiary dendrite arm spacings of the Sn-rich matrix, the morphologies of the eutectic mixture and the corresponding interphase spacing, the nature and proportion of the Cu-Zn intermetallic compound （IMC）. The main purpose is to establish interrelations of these microstructure features with experimental solidification thermal parameters, such as cooling rates and growth rates （v）, macrosegregation and hardness. Such interrelations are interesting for both industry and academy since they represent a tool permitting the preprogramming of final properties based on the design of the microstructure. In the case of Sn-Zn-Cu alloys, hardly anything is known about the combined effects of the length scale of the microstructure and fraction and distribution of the primary IMC on hardness. The alloy microstructure is composed of a β-Sn dendritic region, surrounded by a eutectic mixture of α-Zn and β-Sn phases and the γ-Cu5Zn8 IMC. The eutectic interphase spacing varies in the range 1.2-3.6 μm, with the α-Zn phase having a globular morphology for ν 〉 0.5 mm/s and a needle-like morphology for ν 〈 0.3 mm/s. A modified Hall-Petch-type experimental expression relating hardness to the interphase spacing is proposed.

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.

Effect of indium addition on the microstructural formation and soldered interfaces of Sn-2.5Bi-1Zn-0.3Ag lead-free solder

The microstructural formation and properties of Sn-2.5Bi-xln-lZn-0.3Ag （in wt%） alloys and the evolution of soldered interfaces on a Cu substrate were investigated. Apart from the relatively low melting point （about 195C）, which is close to that of conventional eutectic Sn-Pb solder, the investigated solder presents superior wettability, solderability, and ductility. The refined equiaxial grains enhance the me- chanical properties, and the embedded bulk intermetallic compounds （IMCs） （Cu6Sn5 and CusZns） and granular Bi particles improve the joint reliability. The addition of In reduces the solubility of Zn in the 13-Sn matrix and strongly influences the separation and growth behaviors of the IMCs. The soldered interface of Sn-2.5Bi-xln-lZn-0.3Ag/Cu consists of Cu-Zn and Cu-Sn IMC layers.

Interfacial intermetallic compound growth and shear strength of low-silver SnAgCuBiNi/Cu lead-free solder joints

The growth rule of the interfacial intermetallic compound （IMC） and the degradation of shear strength of Sn-0.SAg-0.5Cu-2.0Bi-0.05Ni （SACBN）/Cu solder joints were investigated in comparison with Sn-3.0Ag-0.5Cu （SAC305）/ Cu solder joints aging at 373, 403, and 438 K. The results show that （Cul-x,Nix）6Sn5 phase forms between the SACBN solder and Cu substrate during soldering. The interracial IMC thickens constantly with the aging time increasing, and the higher the aging temperature, the faster the IMC layer grows. Compared with the SAC305/Cu couple, the SACBN/Cu couple exhibits a lower layer growth coefficient. The activation energies of IMC growth for SACBN/Cu and SAC305/Cu couples are 111.70 and 82.35 kJ/mol, respectively. In general, the shear strength of aged solder joints declines continuously. However, SACBN/Cu solder joints exhibit a better shear strength than SAC305/Cu solder joints.

Microstructure and properties of an Al–Ti–Cu–Si brazing alloy for SiC–metal joining

An Al–Ti–Cu–Si solid–liquid dual-phase alloy that exhibits good wettability and appropriate interfacial reaction with SiC at 500–600°C was designed for SiC–metal joining. The microstructure, phases, differential thermal curves, and high-temperature wetting behavior of the alloy were analyzed using scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, and the sessile drop method. The experimental results show that the 76.5Al–8.5Ti–5Cu–10Si alloy is mainly composed of Al–Al2Cu and Al–Si hypoeutectic low-melting-point microstructures (493–586°C) and the high-melting-point intermetallic compound AlTiSi (840°C). The contact angle, determined by high-temperature wetting experiments, is approximately 54°. Furthermore, the wetting interface is smooth and contains no obvious defects. Metallurgical bonding at the interface is attributable to the reaction between Al and Si in the alloy and ceramic, respectively. The formation of the brittle Al4C3phase at the interface is suppressed by the addition of 10wt% Si to the alloy. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

Effects of Cu addition on growth of Au-Sn intermetallic compounds at Sn-xCu/Au interface during aging process

The growth of Au-Sn intermetallic compounds(IMCs) is a major concern to the reliability of solder joints in microelectronic,optoelectronic and micro-electronic-mechanical system(MEMS) which has a layer of Au metallization on the surface of components or leads.This paper presented the growth behavior of Au-Sn IMCs at interfaces of Au metallization and Sn-based solder joints with the addition of Cu alloying element during aging process,and growth coefficients of the Au-Sn IMCs were calculated.Results on the interfacial reaction between Sn-xCu solders and Au metallization during aging process show that three layers of Au-Sn IMCs including AuSn,AuSn2 and AuSn4 formed at the interface region.The thickness of each Au-Sn IMC layer vs square root of aging time follows linear relationship.Calculation of the IMC growth coefficients shows that the diffusion coefficients decrease with the addition Cu elements,which indicates that Cu addition suppresses the growth of Au-Sn IMCs layer.