Abstract: A nano-silver paste which can be used in low temperature sintering was prepared by chemical reduction method. By analyzing the microstructure, mechanical properties and failure modes of pressureless low temperature sintered nano-silver joints, the gradual microstructure evolution of the pressureless sintered silver joints was systematically discussed, and the influence of joint size on the connection performance and reliability of sintered silver was obtained. By heating the joint to 250 ℃ with the sintering time of 1 hour, the shear strength of pressureless sintered joint reached 70 MPa or more when the joint area was less than or equal to 3 mm × 3 mm. As the joint area increased, the shear strength of the solder joint gradually decreased. However, when the solder joint size was 10 mm × 10 mm, the shear strength remained above 20 MPa. The fracture interface morphology showed that the larger the joint area, the lower the plastic deformation of the sintered silver. It was interesting that there was a gradual microstructure evolution from the center to the edge of the joints of all sizes, and violent plastic deformation occurred at the edges.