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Improvement of the Separation of Used and Fresh Etchants

IP.com Disclosure Number: IPCOM000106502D
Original Publication Date: 1993-Nov-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Scheithauer, A: AUTHOR [+2]

Abstract

This article describes a new design of the etch chamber during the formation of printed circuit boards to achieve a more rapid and effective separation of used and fresh etchants.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 68% of the total text.

Improvement of the Separation of Used and Fresh Etchants

      This article describes a new design of the etch chamber during
the formation of printed circuit boards to achieve a more rapid and
effective separation of used and fresh etchants.

      During the manufacture of PCBs a Cu-plated carrier is coated
with a photomask and the respective structures are produced by an
etch process using CuCl2 as the etchant.  Furthermore, the etchant
contains 'Cu' sup <2 plus> HCl, 'H' sub 2 'O', and NaCl.

According to the equation

       Cu + 'Cu' sup <2 plus> ---> 2 'Cu' sup <1 plus>
monovalent copper is produced by this etch process.  This monovalent
copper, however, decreases the etch rate, this being a disadvantage
concerning the desired uniform etch rate which is achieved if only
the starting components are present.

      This is especially disadvantageous for fine line products,
which are etched more strongly at the beginning of the etch process
(less 'Cu' sup <1+> in the etchant), causing relatively narrow
conducting lines.  If many parts are to be etched, i.e., the etchant
contains a lot of 'Cu' sup <1 plus>, the etch rate decreases and the
conducting lines are not optimally etched.  When producing fine line
products this will lead to a high rate of defective rejects.

      A separation of used and freshly added etchant can be achieved
by a redesign of the etch chamber, thus avoiding a decrease of the
etch rate.

      The Figure shows two embo...