Study On Interfacial Reaction And Reliability Between Lead-free Solder And Au/Ni/SUS304Substrate

With the rapid development of solid state drive, the survival of traditionalmechanical hard disk is facing unprecedented challenge. Therefore, traditionalmechanical hard drives development has no choice but to increase the storagecapacity. Stainless steels were adopted to simplify the actual production processand improve the storage capacity of the mechanical hard disk. Therefore, thereliability of solder joints with stainless steel pads requires indepth study. In thisthesis, the interfacial reaction, shear force and mechanical shock reliability oflead-free solder joints with stainless steel pads have been studied in detail.Four kinds of solder joints SnAgCu-Au/Ni/Cu, SnAgCu-Au/SUS304,SnAgCu-Au/Ni/SUS304, SnAgCuNi-Au/Ni/SUS304were fabricated with twosolders (Sn-3.0Ag-0.5Cu and Sn-2.0Ag-0.75Cu-0.07Ni) and three pads (Au/Ni/Cu,Au/SUS304, and Au/Ni/SUS304) by laser soldering technology. The four kinds ofsolder joints were subjected to thermal cycling and aging test, and then shear forceand mechanical shock experiments were conducted using these treated samples.By aging tests, the interfacial reactions of lead-free solder joints with stainlesssteel pads were studied. The morphology, thickness and type of intermetalliccompounds discussed in this thesis, we found that the interfaces ofSnAgCu-Au/Ni/SUS304and SnAgCuNi-Au/Ni/SUS304solder joints appearedFeSn2after aging9days, and its thickness increased with aging time increasing.The interface of SnAgCu-Au/Ni/SUS304solder appeared ternary compounds(Au,Fe) Sn by200℃aging for24hours.By thermal cycling experiments, the shear force performance of solder jointswith stainless steel pads was studied. The shear force of four solder jointsdecreased with the number of thermal cycles increasing gradually.Thediscontinuous and nano-sized FeSn2in the interface of SnAgCu-Au/SUS304solderlowered joint shear strength. The nano-sized FeSn2and mchanical properties ofsolder lowered the SnAgCuNi-Au/Ni/SUS304solders joint shear strength.By mechanical shock tests, we found that stainless steel pads had greaterimpact on the mechanical shock resistance of solder joints. New structuralSnAgCu-Au/SUS304and SnAgCuNi-Au/Ni/SUS304solder joints had poorreliability of mechanical shock performance, and the mechanical shockperformance of SnAgCu-Au/Ni/SUS304solder joints and SnAgCu-Au/Ni/Cusolder joints were quite. Therefore, the mechanical shock reliability ofSnAgCu-Au/Ni/SUS304solder met the design requirements.