Methods of refining lead-containing materials
View Patent ↗The invention includes solder materials having low concentrations of alpha particle emitters, and includes methods of purification of materials to reduce a concentration of alpha particle emitters within the materials. The invention includes methods of reducing alpha particle flux in various lead-containing and lead-free materials through purification of the materials. The invention also includes methods of estimating the fractionation of a low concentration of one or more alpha particle emitters during purification of a material.
1. A method of refining a lead-containing material, comprising:
providing an initial composition of the lead-containing material, the initial composition having an alpha flux of greater than or equal to 0.002 cts/cm 2 /hr; and
purifying the lead-containing material to form a second composition of the lead-containing material, the second composition having an alpha flux of less than 0.001 cts/cm 2 /hr,
wherein the purifying comprises electrorefining utilizing a bath comprising nitric acid and water, with the nitric acid being present at a concentration of from about 2% to about 50%, by volume.
2. The method of claim 1 wherein the purifying additionally comprises zone refining, chemical etching or a combination thereof.
3. The method of claim 1 wherein the purifying comprises electrorefining utilizing a bath consisting essentially of nitric acid and water, with the nitric acid being present at a concentration of from about 2% to about 50%, by volume.
4. The method of claim 1 wherein the lead-containing material of the second composition is at least 99.99% lead by weight.
5. The method of claim 1 wherein the second composition has an alpha flux of less than 0.0005 cts/cm 2 /hr.
6. The method of claim 1 wherein the second composition has an alpha flux of less than 0.0002 cts/cm 2 /hr.
7. The method of claim 1 wherein the second composition has an alpha flux of less than 0.0001 cts/cm 2 /hr.