Neutral-pH Etching Composition for Selective Copper Removal
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Solution Overview
Problem
Conventional copper etching processes often damage or corrode electroplated metals and alloys, and existing methods, especially those using acidic or basic ammoniacal solutions, pose hazards and are inefficient for selective etching of copper in the presence of other metals.
Innovation Solution
An etching composition comprising an oxidant, phosphate ions, pyrophosphate ions, or polyphosphate ions, with a neutral or basic pH, is used to selectively etch copper and other metals, while passivating transition and post-transition metals, thereby preventing damage and corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional acidic or basic ammoniacal etching solutions are used, then copper etching capability is achieved, but damage and corrosion of electroplated metals and alloys occur
Solution Approach 1:
The patent changes the pH parameter from conventional acidic or strongly basic ranges to a near-neutral range (pH 6.5-7.5), which fundamentally alters the etching mechanism to reduce harmful effects on electroplated metals while maintaining copper etching capability
Solution Approach 2:
The etching composition uses a composite system combining a specific oxidant (potassium peroxymonosulfate) with phosphate buffers and complexing agents (EDTA, HEDP), creating a synergistic formulation that enables selective copper etching without corroding other metals
2Speed
If selective etching of copper is achieved, then etching speed is improved, but selectivity against other metals deteriorates
Solution Approach 1:
The patent introduces phosphate buffers and complexing agents as intermediary substances that mediate between the oxidant and metal surfaces, enabling the oxidant to selectively attack copper while being blocked or neutralized by other metals through passivation or complex formation
Solution Approach 2:
The near-neutral pH parameter creates optimal conditions for the oxidant to selectively react with copper while other metals remain protected, achieving both high etching speed and high selectivity simultaneously
3Productivity
If conventional etching processes are used, then copper removal is efficient, but hazards are introduced
Solution Approach 1:
The patent employs a stable, non-hazardous oxidant system that can be used at near-neutral pH without requiring specialized handling or safety infrastructure, replacing hazardous conventional etchants with a safer alternative that maintains etching efficiency
Solution Approach 2:
Changing the pH to near-neutral eliminates the need for corrosive acidic or strongly basic solutions, thereby removing associated safety hazards while maintaining effective copper etching through the peroxymonosulfate oxidant system
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The etching composition achieves selective etching of copper and other metals at controlled rates, reducing damage to sensitive metals and extending the useful life of the etching solution, while maintaining a stable pH and preventing metal ion precipitation.
Implementation Method 1
Copper can be etched by an oxidation-dissolution mechanism in which a top layer of copper metal is oxidized to copper oxide(s)
Implementation Method 2
phosphate ions, pyrophosphate ions, polyphosphate ions, or a combination thereof
Data Source
AI summary
An etching composition includes phosphate ions, pyrophosphate ions, polyphosphate ions. or a combination thereof and an oxidant. The etching composition has a neutral or basic pH.