CU CORE BALL, SOLDER PASTE, AND SOLDER JOINT

摘要

Provided is a Cu core ball having a low alpha dose, suppressing the generation of a soft error and having surface roughness not affecting a mounting process. The degree of purity of the Cu ball as a core is equal to or greater than 99.9% and equal to or smaller than 99.995%. The total amount of Pb and/or Bi among impurities contained in the Cu ball is equal to or greater than 1 ppm. The sphericity of the Cu ball is equal to or greater than 0.95. A solder plating film coated on the Cu ball is a Sn solder plating film or a solder plating film comprising a lead-free solder alloy of which the primary component is Sn. In the solder plating film, the amount of U is equal to or smaller than 5 ppb and the amount of Th is equal to or smaller than 5 ppb. The total alpha dose of the Cu ball and the solder plating film is equal to or smaller than 0.0200 cph/cm^2. The surface roughness of the Cu core ball is equal to or smaller than 0.3 μm.