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Event-Triggered Control System for Persulfate Flash Etch

IP.com Disclosure Number: IPCOM000043976D
Original Publication Date: 1984-Oct-01
Included in the Prior Art Database: 2005-Feb-05

Publishing Venue

IBM

Related People

Authors:
Gall, TP Hume, DW Powers, JE [+details]

Abstract

An event-triggered control system for persulfate flash etching allows the work to trigger the measurement of the bath concentration and to automatically adjust the concentration of the bath if it is not within the present limits. This control eliminates the need for conveyor speed adjustments, reduces etchant usage and the need to make up and heat fresh batches, and ensures the uniformity of line widths. This system is designed to be operative only when product 11 is loaded into the flash etcher 12 and sensed by a photocell 13 as it enters the machinery. The photocell 13 triggers a three-minute timer 14 that enables a colorimetric analyzer 15 that measures the copper content of the persulfate solution. If the copper is high, fresh etchant is added automatically, thus maintaining etchant strength at a particular set point.