Abstract
Microstructure and strength properties of Sn-0.39∿3.9mass%Ag-0.5mass%Cu solder ball bonded by the reflow have been examined for the information of the influence of the cooling rate (5-200K/min) and the Ag addition. The primary Sn grain size has been finer with the faster cooling rate of the reflow. Ag3Sn dispersion precipitate in the primary Sn phase has coarsened with the slower cooling rate. The interface structure of the ball with under 1.21mass% has the flat Cu6Sn5 reaction layer. The column shape Cu6Sn5 layer is observed at the cooling rate over 100K/min. The hardness of the ball bonded at the faster cooling rate increases since the Sn grain size and Ag3Sn dispersion precipitate are finer.
