Reliability Analysis of Aging in Joint Microstructures for Sn-Ag-Cu Solder Joints During Thermal Cycling

This study illustrates test results and comparative literature data on the influence of isothermal aging and thermal cycling associated with Sn-1.0Ag-0.5Cu (SAC105) and Sn-3.0Ag-0.5Cu (SAC305) ball grid array (BGA) solder joints on three board finishes (ImAg, ENIG, ENEPIG). The resulting degradation shows that the characteristic lifetimes for both SAC105 and SAC305 decrease in the order ENIG > ENEPIG > ImAg. SAC305, with a higher relative fraction of Ag3Sn IMC within the solder, performs better than SAC105. SEM and EDX analysis shows continuous growth of Cu-Sn intermetallic compounds (IMC) on SAC/ImAg systems and Cu-Ni-Sn IMC on SAC/ENIG/ENEPIG systems at board side solder joints, which eventually cause fatigue failures.

Study of the Solid-State Joining Process for Endless Hot Rolling

In this study, the joint strength and microstructure of carbon steels welded by an super-deformation joining process in air were investigated. The two block of model steels are overlapped and heated. The steels are welded with 1000% deformation at approximately 1000°C.The joint strengths are evaluated by uniaxial tension testing. The joint microstructures and fractured surfaces are investigated with OM and SEM. The results revealed that the mechanical properties of joint are close to the matrix’s, the grains adjacent to the interface are merged into one grain, which indicates that both blocks are soundly joined,fracture surface was covered with dimple indicating ductile fracture occurred. Joint fracture behavior is initiated by the brittle fracture of scale inclusions and growth around the internal oxides. Surface scale is the most important factor of sound joining.

Grade E550 Heavy Steel Plate by TMCP for Offshore Energy Exploration

This paper introduces the study and production on steel plate of Grade E550 in60mm thick by Thermo-mechanical processing (TMCP) and tempering for offshoreinfrastructure purpose. The steel plate obtained high strength and goodtoughness in both the base materials and the weld joints. Microstructure and precipitation characteristicswere examined in the plate is comprised of bainite with a small amount ofpre-eutectoid ferrite. Parallel arranged lath bainite characterizes thebainitic structure with high density of dislocations and precipitates. Carbides MxCy averaging 200nm indimension and MC type Carbonitrides in several nano to a dozen nano carbidesdistribute in the bainite ferrite and the bainte lath interfaces. Compatiblemechanical properties were achieved at welded joint. Microstructures were analysed in the welding heataffected zone (HAZ).

Characteristics of YAG-MIG Hybrid Welding 6061 Aluminum Alloy with Different States

With the diversification of manufacture methods, joining the same materials with different states becomes indispensable in practical application. The hybrid welding has broad application prospects. It not only reduces the strict assembled gap before welding, but also improves the joint properties by filling wire during the welding process. 6061 aluminum alloys with different states were welded by YAG-MIG hybrid welding. The characteristics of welded joint, including microstructures, the tensile properties, microhardness and fracture, were investigated. The results show that the microstructures are different significantly in different states. Besides, the grain boundaries of the joint microstructures become unclear after heat treating. The strength and the elongations of welded joints could reach to that of the base metal. The tensile fracture occurs in the fusion zone and near 6061-O alloy. And the fracture presents ductile rupture. Meanwhile, the effect of the small pores in the weld on the joints tensile properties is slight.