Browse Prior Art Database

Hydrocyclone Particle Removal System for a Chromium Etching Station

IP.com Disclosure Number: IPCOM000107649D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 92K

Publishing Venue

IBM

Related People

David, LD: AUTHOR [+2]

Abstract

The purpose of this invention is extension of the life of chromium etchant solution (aqueous potassium permanganate and sodium phosphate buffer). It achieves this by removing manganese dioxide (MnO2) particles from the solution. The benefits are: (1) longer etchant life with corresponding savings of the cost of the chemicals and their disposal, (2) improved product quality due to less particulate contamination, (3) less etch station downtime because of less frequent cleaning and maintenance work, and (4) safer operation due to less chemical handling and cleaning by operators.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Hydrocyclone Particle Removal System for a Chromium Etching Station

       The purpose of this invention is extension of the life of
chromium etchant solution (aqueous potassium permanganate and sodium
phosphate buffer).  It achieves this by removing manganese dioxide
(MnO2) particles from the solution.  The benefits are: (1) longer
etchant life with corresponding savings of the cost of the chemicals
and their disposal, (2) improved product quality due to less
particulate contamination, (3) less etch station downtime because of
less frequent cleaning and maintenance work, and (4) safer operation
due to less chemical handling and cleaning by operators.

      Ordinary filtration of potassium permanganate solution retains
the MnO2 from etching and KMnO4 decomposition.  The continuous
filtration system force-feeds the etchant through the MnO2 .  The
MnO2 further catalyzes KMnO4 decomposition, and formation of
additional MnO2 .  Preservation of the etchant requires removal of
the MnO2 from the etchant requires removal of the MnO2 from the
etchant stream.  MnO2 formation may also promote recrystallization of
the sodium phosphate buffer.  This reduces the pH.  Both pH and
permanganate reductions lower the etch rate unacceptably.

      A hydrocyclone system is the key feature of this invention.  It
consists of one or more small (0.5" nominal inside diameter)
cyclones.  This sedimentation system removes particles down to 4-6
microns in diameter.  (The current filtration method removes
particles down to 10 microns.)  The cyclone deposits the MnO2 and
other insolubles in an accumulator tank.  This takes them out of
contact with the chemical stream.  Thus, the MnO2 can no longer
catalyze decomposition of the etchant.  The design of th...