Copper-Selective Etching Agent for Galvanic Corrosion Control
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Solution Overview
Problem
Existing etching agents for copper in circuit boards fail to effectively suppress partial excessive etching due to galvanic corrosion, especially at lower pH levels, leading to issues like increased electric resistance and disconnection in circuits.
Innovation Solution
An etching agent comprising copper ions, nitrogen-containing compounds, polyalkylene glycol, and halogen ions, with specific concentration ranges, is used to selectively etch copper while maintaining a pH between 6.0 and 8.0, thereby suppressing galvanic corrosion and ensuring uniform etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an etching agent is used to selectively etch copper in a substrate with dissimilar metals, then selective etchability of copper is improved, but galvanic corrosion causes partial excessive etching
Solution Approach 1:
The patent introduces a specific composition of etching agents including copper ions, nitrogen-containing compounds, polyalkylene glycol, and halogen ions as intermediaries to mediate the etching process. This intermediary composition selectively promotes copper dissolution while suppressing the galvanic corrosion effect between copper and noble metals, thereby resolving the contradiction between achieving selective etchability and preventing harmful galvanic corrosion.
Solution Approach 2:
The patent changes the chemical parameters of the etching agent by specifying precise concentration ranges: copper ions (0.5-10.0% by weight), nitrogen-containing compounds (0.1-30.0% by weight), polyalkylene glycol (0.0005-7.0% by weight), and halogen ions (1-250 ppm). These parameter changes optimize the etching process to achieve selective copper etching while suppressing galvanic corrosion.
2Object-affected harmful factors
If an alkaline etching agent with high pH is used to suppress galvanic corrosion, then galvanic corrosion is suppressed, but application to manufacturing process is restricted
Solution Approach 1:
The patent changes the pH parameter of the etching agent from high alkaline (pH 7.8-11) to a lower pH range (pH 6.0-8.0) while compensating with optimized concentrations of copper ions, nitrogen-containing compounds, polyalkylene glycol, and halogen ions. This parameter change enables the etching agent to suppress galvanic corrosion effectively at lower pH levels, thereby expanding its adaptability and versatility for various manufacturing processes.
3Adaptability or versatility
If etching is performed at lower pH to expand application range, then adaptability is improved, but partial excessive etching due to galvanic corrosion increases
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: copper ions (0.5-10.0% by weight), nitrogen-containing compounds (0.1-30.0% by weight), polyalkylene glycol (0.0005-7.0% by weight), and halogen ions (1-250 ppm) to enable effective etching at lower pH (6.0-8.0). This multi-parameter optimization allows the etching agent to maintain broad adaptability while suppressing partial excessive etching even at acidic to neutral pH levels.
Solution Approach 2:
The patent creates a composite etching agent system combining multiple components: copper ions, nitrogen-containing compounds, polyalkylene glycol, and halogen ions. This composite formulation synergistically works to suppress galvanic corrosion and prevent partial excessive etching at lower pH levels, thereby maintaining both adaptability and etching precision across different manufacturing conditions.
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 agent achieves selective etchability of copper with minimal side etching and unevenness, even at lower pH, preventing circuit defects such as increased resistance and disconnection.
Implementation Method 1
When copper conductively (electrically) connected to a metal nobler than copper comes into contact with an etching agent, a phenomenon called galvanic corrosion may occur. The galvanic corrosion is a phenomenon in which, when two metals having different ionization tendencies are put in an electrolyte solution, a local battery is formed by both metals, and the metal having a larger ionization tendency corrodes.
Implementation Method 2
an etching agent that selectively etches a copper layer of a processing target in which a noble metal layer containing a metal nobler than copper and the copper layer coexist
Data Source
AI summary
The present invention includes an etching agent that selectively etches a copper layer of a processing target in which a noble metal layer containing a metal nobler than copper and the copper layer coexist, the etching agent including: a copper ion; one or more nitrogen-containing compounds selected from the group consisting of a heterocyclic compound having two or more nitrogen atoms in a ring and an amino group-containing compound having 8 or less carbon atoms; a polyalkylene glycol; and a halogen ion, in which the polyalkylene glycol is contained in an amount of 0.0005% by weight or more and 7% by weight or less, and the halogen ion is contained in an amount of 1 ppm or more and 250 ppm or less.