Provided is low alpha-ray emitting bismuth having an alpha dose of 0.003 cph/cm.sup.2 or less. Additionally provided is a method of producing low alpha-ray emitting bismuth, wherein bismuth having an alpha dose of 0.5 cph/cm.sup.2 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.

Identifying a stable phase of a binary alloy comprising a solute element and a solvent element. In one example, at least two thermodynamic parameters associated with grain growth and phase separation of the binary alloy are determined, and the stable phase of the binary alloy is identified based on the first thermodynamic parameter and the second thermodynamic parameter, wherein the stable phase is one of a stable nanocrystalline phase, a metastable nanocrystalline phase, and a non-nanocrystalline phase. In different aspects, an enthalpy of mixing of the binary alloy may be calculated as a first thermodynamic parameter, and an enthalpy of segregation of the binary alloy may be calculated as a second thermodynamic parameter. In another example, a diagram delineating a plurality of regions respectively representing different stable phases of at least one binary alloy is employed, wherein respective regions of the plurality of regions are delineated by at least one boundary determined as a function of at least two thermodynamic parameters associated with grain growth and phase separation of the at least one binary alloy.

Identifying a stable phase of a binary alloy comprising a solute element and a solvent element. In one example, at least two thermodynamic parameters associated with grain growth and phase separation of the binary alloy are determined, and the stable phase of the binary alloy is identified based on the first thermodynamic parameter and the second thermodynamic parameter, wherein the stable phase is one of a stable nanocrystalline phase, a metastable nanocrystalline phase, and a non-nanocrystalline phase. In different aspects, an enthalpy of mixing of the binary alloy may be calculated as a first thermodynamic parameter, and an enthalpy of segregation of the binary alloy may be calculated as a second thermodynamic parameter. In another example, a diagram delineating a plurality of regions respectively representing different stable phases of at least one binary alloy is employed, wherein respective regions of the plurality of regions are delineated by at least one boundary determined as a function of at least two thermodynamic parameters associated with grain growth and phase separation of the at least one binary alloy.

Identifying a stable phase of a binary alloy comprising a solute element and a solvent element. In one example, at least two thermodynamic parameters associated with grain growth and phase separation of the binary alloy are determined, and the stable phase of the binary alloy is identified based on the first thermodynamic parameter and the second thermodynamic parameter, wherein the stable phase is one of a stable nanocrystalline phase, a metastable nanocrystalline phase, and a non-nanocrystalline phase.

Identifying a stable phase of a binary alloy comprising a solute element and a solvent element. In one example, at least two thermodynamic parameters associated with grain growth and phase separation of the binary alloy are determined, and the stable phase of the binary alloy is identified based on the first thermodynamic parameter and the second thermodynamic parameter, wherein the stable phase is one of a stable nanocrystalline phase, a metastable nanocrystalline phase, and a non-nanocrystalline phase.

According to one embodiment, a tungsten alloy includes a W component and a Hf component including HfC. A content of the Hf component in terms of HfC is 0.1 wt % or more and 3 wt % or less.

According to one embodiment, a tungsten alloy includes a W component and a Hf component including HfC. A content of the Hf component in terms of HfC is 0.1 wt % or more and 3 wt % or less.

A Cu core ball is provided that prevents any soft errors and decreases any connection failure. The Cu core ball includes a solder plating film formed on the surface of a Cu ball that is a Sn solder plating film or is made of a lead-free solder alloy, a principal ingredient of which is Sn. The solder plating film contains U of 5 ppb or less and Th of 5 ppb or less. The Cu ball has a purity of not less than 99.9% Cu and not more than 99.995% Cu. Pb and/or Bi contents therein are at a total of 1 ppm or more. The sphericity thereof is 0.95 or more. The obtained Cu core ball has an dose of 0.0200 cph/cm.sup.2 or less.

A Cu core ball is provided that prevents any soft errors and decreases any connection failure. The Cu core ball includes a solder plating film formed on the surface of a Cu ball that is a Sn solder plating film or is made of a lead-free solder alloy, a principal ingredient of which is Sn. The solder plating film contains U of 5 ppb or less and Th of 5 ppb or less. The Cu ball has a purity of not less than 99.9% Cu and not more than 99.995% Cu. Pb and/or Bi contents therein are at a total of 1 ppm or more. The sphericity thereof is 0.95 or more. The obtained Cu core ball has an dose of 0.0200 cph/cm.sup.2 or less.

According to one embodiment, a tungsten alloy includes a W component and a Hf component including HfC. A content of the Hf component in terms of HfC is 0.1 wt % or more and 3 wt % or less.