Copper to copper lap joints were press-soldered using a resistance heating apparatus. In this process heating and pressure were applied simultaneously. The copper plate was pre-soldered using Pb-50Sn solder and the alloyed layer was formed. The tensile strengths increased at a pressing load above 45N and the fracture occurred in the copper base metal above a 75N pressing load. The joints fractured in the copper base metal in 150°C and 250°C tensile testing and showed excellent thermal resistance.