Abstract
Liquidus plane and some cross sectional phase diagrams of Cu-Ag-P and Cu-Sn-P ternary alloys at copper rich corner were established using differential thermal analysis and microscopic observations. Primary phase planes of copper solid solution (Cu) and Cu3P phase were divided by a straight line which started from Cu-P system binary eutectic composition. In respect of the primary phase, the addition of tin was similar to the phosphorus addition, because the primary phase changed from Cu phase to Cu3P phase at lower phosphorus. The phosphorus equivalent of tin was determined to be 0.238 in case of mass % expression. The phosphorus equivalent' of silver was only 0.066.
The spreadability of Cu-Sn-P filler metals were inferior to that of Cu-Ag-P, which is explained by the thermodynam c calculation that tin oxide is not so easily reduced by phosphorus. The activation energy of erosion of copper base metal was coincided well with that of diffusion of tin in solid copper.
