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Open Repair Using Copper Sulfate With High Frequency AC and a Small DC Bias

IP.com Disclosure Number: IPCOM000121272D
Original Publication Date: 1991-Aug-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Partridge, JP: AUTHOR [+3]

Abstract

A method for repairing open circuits was described in [1] using unacidified copper sulfate solution and Joule heat supplied by a high frequency AC current flowing through the open circuit covered with the electrolyte to grow copper dendrites in the gap, thereby connecting the open ends. In that description the DC current was blocked capacitively to avoid etching the positively biased region of the circuit.

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Open Repair Using Copper Sulfate With High Frequency AC and a Small
DC Bias

      A method for repairing open circuits was described in [1]
using unacidified copper sulfate solution and Joule heat supplied by
a high frequency AC current flowing through the open circuit covered
with the electrolyte to grow copper dendrites in the gap, thereby
connecting the open ends.  In that description the DC current was
blocked capacitively to avoid etching the positively biased region of
the circuit.

      We have subsequently found that a small DC current (voltage) is
beneficial under carefully controlled conditions to cause copper
dendrite growth across the open region with improved electrical,
metallurgical and geometrical characteristics.  We have undertaken a
number of experiments and observed the following about 50 mV of DC
across a 75 mm gap for lines 75 mm in width using 50 kHz AC
current and a 1 molar solution of copper sulfite covering the gap
region during repair:
1.   Dendrites grow from only one side of the gap (the more cathodic
or negatively biased side).
2.   Dendrites are generally more rugged and thicker in diameter.
3.   Electrical and mechanical contact generally occurs in a direct
path from the center of one end of the circuit to the other, thus
avoiding circuitous paths that often extend from growth initiated at
corners.  The more direct contact path prevents excessive line
distortion and/or linewidth increase.
4.   The copper that forms the den...