Cu BALL

To provide Cu ball that has less ± dose and high sphericity even when containing at least a certain amount of impurity elements other than Cu. Even when the purity thereof is 99.995% or less and U and Th contents are 5 ppb or less in order to suppress any software errors and decrease connection failure, ± dose is 0.0200 cph/cm 2 or less. Further, the sphericity of the Cu ball is unexpectedly improved by making the purity not more than 99.995%.