A core ball wherein a junction melting temperature and a low alpha dose are set for suppressing a soft error generation and solving a mounting problem. A metallic powder as a core is a sphere. A pure degree of a Cu ball of the metallic powder is equal to or higher than 99.9% but equal to or less than 99.995%. A contained amount of one of Pb and Bi or a total contained amount of Pb and Bi is equal to or higher than 1 ppm. A sphericity of the Cu ball is at least 0.95. A solder plating film for coating the Cu ball comprises Sn—Bi based alloy. U contained in the solder plating film is equal to or less than 5 ppb and Th is equal to or less than 5 ppb. An alpha dose of the core ball is equal to or less than 0.0200 cph/cm2.