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Refining process for producing low alpha tin

a technology of low alpha and tin, applied in the field of high purity tin, can solve the problems of affecting the quality of tin, and affecting and even though initially lowered, to achieve the effect of increasing reducing the alpha particle emission, and improving the quality of tin

Inactive Publication Date: 2013-12-26
HONEYWELL INT INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The patent describes a method for purifying tin by using an ion exchange resin to deposit electrorefined tin from an electrolytic solution. The electrorefined tin has very low alpha particle emissions. The method may also include detecting the alpha particle emissions and determining the likely isotop of the parent isotope responsible. The technical effects include a reduction in alpha particle emissions and improved purity of tin.

Problems solved by technology

One challenge with respect to the use of tin solders in electronic packaging applications is that the elemental tin materials used to manufacture solders contain varying levels of alpha particle emitting isotopes (also referred to as alpha particle emitters).
Alpha particle emissions (also referred to as alpha flux) can cause damage to packaged electronic devices, and more particularly, can cause soft error upsets and even device failure in certain cases.
However, it has been observed that alpha particle emissions, though initially lowered, will typically increase over time to potentially unacceptable levels as the secular equilibrium of the 210Pb decay profile is gradually restored based on any 210Pb remaining in the metallic material.
Problematically, whether an increase in alpha particle emissions of a metallic material following a melting or refining process will eventually reach unacceptable levels is very difficult to assess and / or predict.

Method used

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  • Refining process for producing low alpha tin
  • Refining process for producing low alpha tin
  • Refining process for producing low alpha tin

Examples

Experimental program
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Effect test

example 1

Inclusion of Ion Exchange Resin in an Electrorefining Process

Materials Used

[0064]Monophos resin: an ion exchange resin having sulfonated and phosphomethylated functional groups and available from Eichrom.

[0065]Lewatit MonoPlus TP 260: an ion exchange resin having amino methyl phosphonic acid functional groups and available from Lanxess.

[0066]Reillex HPQ Polymer: an ion exchange resin having poly(4-vinyl-pyridine) functional groups and available from Vertellus.

Electrorefining Process

[0067]An electrolytic solution was added to a 30 liter (L) polypropylene tank equipped with a vertical pump for solution agitation and filtration. A central titanium cathode and two 4N tin anodes (one on each side of the cathode) were positioned in the tank, and a DC power supply was connected to the cathode and anodes for generating the required current density. During the electrorefining process, the DC current passing between the cathode and anodes was regulated to 22 mA / cm2 (20 ASF) at the cathode and...

example 2

Adjustment of Tin Concentration and Current Density in an Electrorefining Process

[0084]The effects of tin concentration and current density were investigated in Samples 21-25. Electrolytic solutions containing sulfuric acid, deionized water, tin, Technistan Antioxidant and Technistan TP-5000 were prepared as described above for the Control.

[0085]During the electrodeposition process, the electrolytic solution from the main tank was pumped through the glass column containing Lewatit MonoPlus TP 260 ion exchange resin. The tin was deposited at 20° C. and onto a cathode having an active area of 72 square inches. The tin concentration of the electrolytic solution, the cathodic current in amps and the cathodic current density in ASF for each sample is provided in Table 10.

TABLE 10Electrorefining process informationTinCurrentconcentrationCurrentdensitySample(g / L)(Amps)(ASF)21205102240153023202550246051025602550

[0086]Before the electrorefining process, the input or pre-refined tin had alpha...

example 3

Determination of Time Required to Diffuse the Target Decay Isotope

[0095]The time required to diffuse the target decay isotope in a tin sample was investigated. Tin samples were refined according to the method disclosed herein. A test sample of the refined tin sample was obtained by cutting a sample from an ingot and rolling the sample to a thickness of 0.45 millimeter. The test sample was heated at 200 C for one hour, and the alpha particle emissions of the test samples were measured using an XIA 1800-UltraLo gas ionization chamber available from XIA L.L.C. of Hayward, Calif. Measurement of the alpha particle emissions required about 24 hours, after which the sample was heated for one hour at 200° C. and then measured for alpha particle emissions. This process (e.g., heat for one hour followed by measurement of alpha particle emissions) was repeated for a total of five heat / measurement cycles. The measured alpha particle emissions and the total hours the sample was heated at 200° C....

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Abstract

A method for purifying tin includes exposing an electrolytic solution comprising tin to an ion exchange resin and depositing electrorefined tin from the electrolytic solution. The deposited electrorefined tin has alpha particle emissions of less than about 0.01 counts / hour / cm2 immediately after the deposition step, and an alpha emissivity of less than about 0.01 counts / hour / cm2 at least 90 days after the deposition step.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims priority to U.S. Provisional Application No. 61 / 714,059, filed Oct. 15, 2012, U.S. Provisional Application No. 61 / 670,960, filed Jul. 12, 2012, and U.S. Provisional Application No. 61 / 661,863, filed Jun. 20, 2012, each of which are herein incorporated by reference in their entirety.FIELD OF THE INVENTION[0002]The present invention relates to high purity tin with reduced alpha particle emissions for the manufacture of semiconductor equipment or the like and manufacturing methods for producing such high purity tin.DESCRIPTION OF RELATED ART[0003]Solders are commonly utilized in semiconductor device packaging and many other electronic applications. While conventional solders have been manufactured primarily from lead, more recent lead-free solders utilize tin and other metals as principal components.[0004]One challenge with respect to the use of tin solders in electronic packaging applications is that the elemental tin...

Claims

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Application Information

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IPC IPC(8): C25C1/14
CPCC25C1/14
Inventor SILINGER, PAUL P.FERY, MARK B.CLARK, BRETT M.GROVE, DEREK E.
Owner HONEYWELL INT INC
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