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Technique for Chloride Ion Control in Ferric Chloride

IP.com Disclosure Number: IPCOM000103218D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 64K

Publishing Venue

IBM

Related People

Covert, K: AUTHOR [+2]

Abstract

Ferric chloride etchants are widely used to etch a variety of metals including copper, *Invar, and stainless steel. Studies have demonstrated that the concentration of chloride ions in solutions of acidic ferric chloride is a key parameter affecting the etch rate and quality of the etched part. In order to control etching processes sufficiently for the increasing demands of new products, a method for on-line determination of total chloride concentration in ferric chloride concentration in ferric chloride etchants was required.

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Technique for Chloride Ion Control in Ferric Chloride

      Ferric chloride etchants are widely used to etch a variety of
metals including copper, *Invar, and stainless steel. Studies have
demonstrated that the concentration of chloride ions in solutions of
acidic ferric chloride is a key parameter affecting the etch rate and
quality of the etched part.  In order to control etching processes
sufficiently for the increasing demands of new products, a method for
on-line determination of total chloride concentration in ferric
chloride concentration in ferric chloride etchants was required.

      The method devised utilizes commercially available ion-
selective electrodes for chloride ion, in conjunction with a specific
supporting electrolyte, to measure total chloride ion concentration
directly in the etchant.  The electrodes cannot be used directly in
etching solution without modifying the solution for several reasons:
pH is below operating range for the electrode; chloride ion
concentration typically is above operating range for the electrode;
much of the chloride in solution is complexed with metal ions and
cannot be measured directly unless freed up.

      Thus, the supporting electrolyte used must raise the solution
pH to a value greater than 2.0; dilute the total chloride ion
concentration to less than 1 molar; dissociate all complexed chloride
so that free chloride equals total chloride; and chelate the metal
ions so that they will not precipitate out at...