Electrolytic Regeneration of PCB Copper Etchant With Low Ammonia Loss
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Solution Overview
Problem
Existing oxidative regeneration methods for alkaline copper-ammonia chloride etching solutions in printed circuit boards result in ammonia gas waste, inefficiency, and pollution, particularly in weakly-alkaline etching processes, due to high fresh air flow rates and low oxidation rates of monovalent copper-ammonia complexes.
Innovation Solution
An electrolysis-assisted method and apparatus for oxidative regeneration using an electrolytic cell with an anode and cathode zones, controlled ORP values, and etching replenisher to regenerate copper-etching agents, reducing reliance on spray-oxygen absorption systems and minimizing ammonia pollution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxygen in air is adopted as oxidant with spray device and tail gas treatment device, then oxidative regeneration of copper-etching agent is achieved, but ammonia gas is constantly released and requires high fresh air flow rate which increases pollution and material waste
Solution Approach 1:
The patent replaces the mechanical spray-oxygen absorption system with an electrolysis-based oxidative regeneration system. The electrolysis cell uses electrical energy to generate oxidants in situ, eliminating the need for high-volume air spraying and associated ammonia gas release. This substitution transforms a mechanical/aerodynamic process into an electrochemical one, directly addressing the pollution problem while maintaining regeneration effectiveness.
Solution Approach 2:
The patent employs strong oxidants generated through electrolysis (such as chlorine, hypochlorite, or ozone) to accelerate the oxidative regeneration of copper-etching agents. These strong oxidants achieve rapid and efficient regeneration without requiring high fresh air flow rates, thereby preventing ammonia gas pollution while ensuring reliable regeneration performance.
2Productivity
If high fresh air flow rate is used for oxidative regeneration, then copper-etching agent regeneration is maintained, but ammonia water raw material is wasted and etching performance may fail due to ammonia deficiency
Solution Approach 1:
The electrolysis-based system replaces the air-spraying mechanical system, enabling controlled in-situ generation of oxidants through electrical energy. This eliminates the need for high fresh air flow rates that cause ammonia water evaporation and material waste, while maintaining efficient copper-etching agent regeneration through electrochemical oxidation.
Solution Approach 2:
The electrolysis system enables the etching solution to regenerate its own copper-etching agents through in-situ electrochemical oxidation. The system uses electrical energy to generate oxidants that directly act on the spent copper complexes, creating a self-sustaining regeneration process that minimizes material loss and eliminates the need for continuous high-volume air supplementation.
3Reliability
If spray device and tail gas treatment device are arranged, then oxidative regeneration system is established, but device complexity increases with multiple components
Solution Approach 1:
The patent extracts and eliminates the complex spray device and tail gas treatment device from the oxidative regeneration system. By using electrolysis to generate oxidants directly in the etching solution, the system removes the need for separate spray nozzles, air supply systems, and gas treatment equipment, dramatically simplifying the overall system architecture while maintaining regeneration capability.
Solution Approach 2:
The electrolysis cell integrates the oxidative regeneration function directly into the etching solution processing system. The electrochemical oxidation occurs in situ within the solution circulation system, merging the regeneration function with the existing etching process equipment and eliminating the need for separate spray and gas treatment subsystems.
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
Enhances etching efficiency, reduces ammonia waste and pollution, and optimizes ammonia utilization by accelerating oxidative regeneration of copper-etching agents in alkaline copper-ammonia chloride solutions.
Implementation Method 1
An electrolysis cell with an electrolytic cell separator is selected, wherein the electrolysis cell is divided into an anode cell zone and a cathode cell zone by the electrolytic cell separator
Implementation Method 2
a reaction of oxidatively regenerating a copper-etching agent is performed in the anode cell zone during the electrolysis
Implementation Method 3
the electrolysis cell is divided into an anode cell zone and a cathode cell zone by the electrolytic cell separator
Data Source
AI summary
Provided are a method for electrolysis-assisted oxidative regeneration of an alkaline copper-ammonia chloride etching working solution, and an apparatus using the same. The method includes the following steps: (1) selecting an electrolytic cell provided with an electrolytic cell separator; (2) with the alkaline copper-ammonia chloride etching working solution as an anode electrolyte, conducting electrolysis in the electrolytic cell, where a reaction of oxidatively regenerating a copper-etching agent occurs in the anode cell zone; and during the electrolysis, an etching working solution circularly flows between the etching machine and the anode cell zone of the electrolytic cell; and (3) during the electrolysis, controlling an oxidation-reduction potential (ORP) potential value of the anode electrolyte at 300 mV or less, and feeding an etching replenisher into the alkaline copper-ammonia chloride etching working solution to participate in the reaction of oxidatively regenerating the copper-etching agent.