Lead-containing solder bumps

Abstract

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.

Description

RELATED PATENT DATA [0001] This application is related to U.S. Provisional Application Ser. No. 60 / 417,241, which was filed on Oct. 8, 2002.TECHNICAL FIELD [0002] The invention pertains to semiconductor packages; lead-containing solders and anodes; and methods of removing alpha-emitters from materials. BACKGROUND OF THE INVENTION [0003] Solders are commonly utilized in semiconductor device packaging. If the solders contain alpha particle emitting isotopes (referred to herein as alpha particle emitters), emitted alpha particles can cause damage to packaged semiconductor devices. Accordingly, it is desired to reduce the concentration of alpha particle emitters within the solders. [0004] An exemplary prior art semiconductor package is shown in FIG. 1 as a package 50, with the exemplary package representing a flip-chip construction. The package comprises a semiconductor component 12 (such as, for example, an integrated circuit chip). The package also comprises a board 14 utilized to sup...

AI Technical Summary

Problems solved by technology

If the solders contain alpha particle emitting isotopes (referred to herein as alpha particle emitters), emitted alpha particles can cause damage to packaged semiconductor devices.

The solders utilized in package 50 can be problematic, as discussed above, in that the solders can contain alpha particle emitters.

Alpha particles are problematic for semiconductor devices because the alpha particles can induce so-called soft errors.

However, the errors will typically cause at least one round of incorrect calculations.

However, the source which is frequently most problematic for semiconductor device packages is solder utilized for forming various interconnections relative to semiconductor dies.

It is possible to commercially obtain lead having an alpha flux of from 0.002 to 0.02 cts / cm2 / hr, but it is very difficult to obtain a material with a lower alpha flux.

Among the difficulties associated with reducing the concentration of alpha flux emitters in a material to extremely low levels is a difficulty in measuring the concentration of the emitters at flux levels below 0.002 cts / cm2 / hr.

Unless the concentration can be measured, it is difficult to monitor a purification process to determine if alpha particle emitters are being removed.

For instance, it can be difficult to determine at any given stage of the purification process if alpha particle emitters are fractionating with a material or away from the material.

Although the discussion above focuses on removing alpha particle emitters from lead-containing solders, it should be understood that alpha particle emitters are also problematic in other materials.

However, the solders can still have an undesirable amount of alpha particle emitters present therein.

Various problems exist with all of the sources.

For instance, the first source utilizes very old Pb, and such is often poorly refined and therefore contains various radionuclides as contaminants.

The second source typically does not have a low enough alpha particle emitter concentration to meet the ultimately desired requirements of the semiconductor industry.

The third source is very energy intensive to form, and therefore is not commercially feasible.

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