Impression Creep Behavior Of Brazed Joint

Brazing, as one of the major connection technology, has been widely used in different areas such as aviation, aerospace, electronics and chemical industries etc. A lot of research on the microstructure and creep properties of the solder alloy has been studied. But the conventional characterizing method for creep properties cannot be used to study the brazed joints due to their small size. Correspondingly, the creep properties of the solder joint are seldom studied. The indentation technology has the potential to be used to study the creep properties of brazed joints, since no special requirements are needed for the size and shape of to-be-measured materials when using this method.In this investigation, Sn-3.5Ag-0.7Cu/Cu brazed joint is created and its creep properties is measured by impression creep testing. The microstructure and change of element content of Sn-3.5Ag-0.7Cu/Cu are examined by Optical Microscope (OM), Scanning Electron Microscope (SEM) and Energy Dispersive Spectra (EDS). Then we propose a simple dislocation model to qualitatively describe the material flow during impression with a cylindrical indenter. The effect of indenter position on the creep behavior of brazed joint is explained by this dislocation model. The effect of punching stress and temperature is studied on the impressing creep properties, which change from 70-100 MPa and 100-130 ℃, respectively. The results show that the creep resistance of the solder joint reduces gradually with the increase of distance of the punching position to the base cupper. The creep resistance of the solder joint is the lowest when the punching position is in the middle of the weld zone and the largest when the punching position near the interface between the brazing joint and base cupper.