To solve the peeling and scattering problem of fine metallic balls out of a substrate due to film swelling by a method wherein the whole solder plating bath is arranged in a vessel and the vessel pressure is sustained at most at a specific value and after reducing the dissolved O2 amount at most a specific value, solder plating films in a specific thickness are formed on the outer peripheral surfaces of the fine metallic balls.
The whole solder plating bath is arranged in a vessel while holding the pressure in the vessel at most at 27kPa, the dissolved O2 amount in the plating bath is fully discharged so as to reduce the dissolved O2 amount at most at 2ppm. Next, electroplating is performed while sustaining the vessel pressure at most at 27kPa. Through these procedures, the H2 gas produced from the surface of the plating film can be quickly discharged. Resultantly, in the case of thermal fitting the fine metallic balls having the produced solder plating films to a package board, the solder plating films can avoid the swelling thereof, thereby peeling and scattering of the fine metallic balls from the package board is greatly reduced.
YAMASHITA OSAMU
KIKUI FUMIAKI
SAIGO TSUNEKAZU
