Copper Etching Composition for Galvanic Corrosion Suppression
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Solution Overview
Problem
Existing etching agents for circuit boards fail to effectively suppress partial excessive etching due to galvanic corrosion, especially at lower pH levels, which can lead 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 excessive etching and galvanic corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional etching agents (ammonium fluoride, hydrofluoric acid, or their mixtures) are used to etch solder resist, then etching capability is achieved, but the etched surface becomes rough and causes non-planar problems in subsequent processing
Solution Approach 1:
The patent changes the chemical composition parameters of the etching agent by replacing conventional ammonium fluoride or hydrofluoric acid with a specific formulation containing 1-10 mass% ammonium bifluoride, 1-10 mass% hydrofluoric acid, and 85-98 mass% water. This parameter change transforms the etching mechanism to achieve both effective etching and surface flatness, resolving the contradiction between etching capability and surface quality.
2Ease of manufacture
If conventional etching agents are used, then etching process can be performed, but white spots appear on the circuit board surface affecting appearance quality
Solution Approach 1:
The patent modifies the chemical parameters of the etching system by using ammonium bifluoride combined with controlled hydrofluoric acid concentration (1-10 mass%) and high water content (85-98 mass%). This parameter adjustment changes the etching mechanism to prevent white spot formation while maintaining etching effectiveness, thereby eliminating appearance defects without sacrificing processability.
3Productivity
If multiple etching agents are mixed to improve etching performance, then etching capability increases, but the mixture becomes unstable and generates harmful gases
Solution Approach 1:
The patent stabilizes the etching solution by changing the compositional parameters to include 1-10 mass% ammonium bifluoride, 1-10 mass% hydrofluoric acid, and 85-98 mass% water. This specific parameter range prevents premature reaction and gas generation while maintaining etching effectiveness, resolving the contradiction between performance and stability.
Solution Approach 2:
The patent uses water as an intermediary medium comprising 85-98 mass% of the solution to dilute and stabilize the interaction between ammonium bifluoride and hydrofluoric acid. This intermediary prevents direct harmful reactions while enabling controlled etching, thus maintaining both stability and etching performance.
4Productivity
If conventional etching agents are used, then etching can be performed, but environmental pollution and safety hazards increase
Solution Approach 1:
The patent reduces environmental harm by changing the chemical parameters to use low concentrations of hydrofluoric acid (1-10 mass%) combined with ammonium bifluoride and high water content (85-98 mass%). This parameter modification maintains etching functionality while significantly reducing the generation of harmful gases and environmental pollution compared to conventional high-concentration etching agents.
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 uniform etching, preventing excessive etching and side etching, even at lower pH levels, thus ensuring stable circuit integrity.
Implementation Method 1
an etching agent containing 1 to 10 mass% ammonium bifluoride, 1 to 10 mass% hydrofluoric acid, and 85 to 98 mass% water
Data Source
Figure 1~3
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.