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The full Cu₃Sn solder joint has been widely used in 3D packaging gradually. 270℃ and 1N were chosen as soldering temperature and pressure respectively to fabricate solder joints under different soldering time in order to analyze the process of microstructural evolution.Cu₆Sn₅ morphology with different soldering temperatures and time was also observed respectively to investigate the growth law of Cu₆Sn₅ and the effect of soldering temperature on the Cu₆Sn₅ morphology. The results show that scallop-like Cu₆Sn₅ is formed along the Cu substrate after 30min soldering, and a thin layer of Cu₃Sn is generated between Cu₆Sn₅ and Cu substrate.When the soldering time is increased to 60min, liquid Sn is totally consumed and Cu₆Sn₅ becomes a cohesive whole. With the increase of soldering time, Cu₃Sn grows at the expense of Cu₆Sn₅. Cu₆Sn₅ is totally transformed into Cu₃Sn up to 480min. The growing process of Cu₆Sn₅ includes nucleation, growth, fusion and covering up the big grain. With the increase of soldering temperature, the morphology of Cu₆Sn₅ changes from polyhedron shape to procumbent.