Investigation of mechanical property and fracture morphology of lead-free soldered joints of fine pitch devices

Soldering experiments of fine pitch devices were carried out using diode-laser soldering sy stem and IR reflow soldering with SnPb, SnAgCu, SnAg, and the tensile strengths of soldered joints were measured by Micro-joints Tester.The results indicate that mechanical properties of fine pitch devices soldered joints with laser soldering system is better than that of fine pitch devices soldered joints with IR reflow soldering method, especially for SnAg soldered joints, and the mechanical properties of lead-free soldered joints is also better than that of Sn-Pb solder.The characteristics of fracture morphology of micro-joints were also analyzed by SEM.It is found that the fracture mechanism of micro-joints soldered with laser soldering system is toughness fracture, and mangled edges appear in a fixed direction.While the fracture morphology of micro-joints soldered with IR reflow soldering method has less and lower dimples than that with diode-laser soldering system.Both the dimple crack mechanisms under the wow soldering methods belong to transgranular crack.