Method of producing low alpha-ray emitting bismuth, and low alpha-ray emitting bismuth

Abstract

Provided is low alpha-ray emitting bismuth having an alpha dose of 0.003 cph/cm2 or less. Additionally provided is a method of producing low alpha-ray emitting bismuth, wherein bismuth having an alpha dose of 0.5 cph/cm2 or less is used as a raw material, the raw material bismuth is melted in a nitric acid solution via electrolysis to prepare a bismuth nitrate solution having a bismuth concentration of 5 to 50 g/L and a pH of 0.0 to 0.4, the bismuth nitrate solution is passed through a column filled with ion-exchange resin to eliminate polonium contained in the solution by an ion-exchange resin, and bismuth is recovered by means of electrowinning from the solution that was passed through the ion-exchange resin. Recent semiconductor devices are of high density and high capacity, and therefore are subject to increased risk of soft errors caused by the effects of alpha rays emitted from materials in the vicinity of semiconductor chips. In particular, there is a strong demand for higher purification of solder materials used near semiconductor devices, and there is a demand for low alpha-ray emitting materials. Therefore, the present invention aims to elucidate the phenomenon of alpha ray generation from bismuth, and to provide a low alpha-ray emitting, high-purity bismuth that can be applied to the required materials and a production method thereof, as well as to provide an alloy of low alpha-ray emitting bismuth and tin and a production method thereof.

Dependencies are inferred from the claim text.