Low α-dose tin or tin alloy, and method for producing same

摘要

Disclosed is tin characterized in that a sample of the tin after melting and casting has an α dose of less than 0.0005 cph/cm2. Since recent semiconductor devices are highly densified and of high capacity, there is an increasing risk of soft errors caused by the influence of α rays emitted from materials in the vicinity of semiconductor chips. In particular, there are strong demands for high purification of solder materials and tin for use in the vicinity of semiconductor devices, and demands for materials with lower α rays. Accordingly, an object of the present invention is to clarify the phenomenon of the generation of α rays in tin and tin alloys, and to obtain high-purity tin, in which the α dose has been reduced, suitable for the required materials, as well as a method for producing the same.

主权项

1. A method for producing a low α-dose tin, characterized in that a raw material tin having a purity level of 3N, containing lead isotope 210Pb in an amount of 30 Bq/kg or less, and having a proportion of 206Pb relative to 208Pb, 207Pb, 206Pb and 204Pb of less than 25% is subjected to leaching with an aqueous solution of hydrochloric acid or sulfuric acid, then electrolytic refining is performed using a leachate produced in the leaching as an electrolytic solution, which is controlled to have a pH of 1.0 or less and a content of tin electrolyte of 30 to 180 g/L, and then an electrolytically refined tin obtained by the electrolytic refining is melted and cast to obtain an ingot of the low α-dose tin giving an α-dose of less than 0.0005 cph/cm2 after the melting and casting.