Fracture mechanism of QFP micro-joints soldered with Sn-Pb and SnAgCu solders
(College of Materials Science and Technology Nanjing University of Aeronautics and Astronautics Nanjing 210016 China)
Abstract: Tensile strengths of QFP micro-joints with different pitches were tested by means of micro-joints tester. On the basis of those results, the effects of QFP pitches’ numbers on the mechanical properties were studied and the microstructures of cracks of micro-joints were analyzed based on facts of SEM and EDS. The results indicate that of tensile strengths micro-joint of 48 pitches are lower than that of 100 pitches and the tensile strength of soldered joint is higher than that of solder itself. The fracture mechanism of QFP soldered joint with Sn-Pb solder acts as the interface cavity impair ductile rupture while the fracture mechanism of QFP soldered joint with lead-free solder shows trans-crystalline toughness rupture which belongs to micro-holes coalescence fracture.
Key words: QFP； micro-joints； tensile strength； fracture mechanism