Boundary layer fracture in composite solder joints

摘要

Composite solder connections, modeled as miniature single-lap shear layers between copper plates, were fabricated and pulled to fracture. The solder layers (3.1× 3.1× 0.50 mm) were eutectic lead-tin/particulate Cu6Sn5 composites. Under load,shear fractures extended along paths about 10μm inside of the interfaces from opposite edges. These boundary layer fractures were characterized and a fracture model was developed. A corresponding test method for measuring J{sub}II andδ{sub}II, the crack extension energy and crack tip shear displacement for Mode II crack growth, is given, and the results are discussed. Composite strengthening is shown to significantly improve the ductility and the creep life, properties associated with improvedreliability and creep-fatigue life.