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Measurement of Indium Hydroxide in Lead Indium Solder

IP.com Disclosure Number: IPCOM000084865D
Original Publication Date: 1976-Jan-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

DiGiacomo, G: AUTHOR

Abstract

A 10-30% solution of sulfuric acid is applied to a test subject for a sufficient time for In+++ ions to reach equilibrium. The sulfuric acid dissolves the indium in the indium hydroxide in preference to the indium in the solder, so that 99% or more of the In+++ ions are attributable to the indium hydroxide and not to the solder. A useful amount of the indium ions (about 50%) remains in the solution.

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Measurement of Indium Hydroxide in Lead Indium Solder

A 10-30% solution of sulfuric acid is applied to a test subject for a sufficient time for In+++ ions to reach equilibrium. The sulfuric acid dissolves the indium in the indium hydroxide in preference to the indium in the solder, so that 99% or more of the In+++ ions are attributable to the indium hydroxide and not to the solder. A useful amount of the indium ions (about 50%) remains in the solution.

A few microliters of the solution are withdrawn from the test subject, and a measured amount is evaporated on a silicon wafer. The indium in the residue that is left on the wafer is measured by a microprobe. The microprobe test is calibrated by a similar microprobe test on an indium film of known thickness.

The test is particularly useful for measuring indium hydroxide corrosion in the solder joints of an integrated circuit device, because indium hydroxide has sufficient electrical conductivity that electrical tests may not detect a solder joint that has corroded and may fail during mechanical stress.

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