Adhesiveless Copper Clad Laminate Etching for PCB Insulation
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Solution Overview
Problem
The existing methods for manufacturing adhesiveless copper clad laminates face challenges in removing metal residues between wirings without side-etching of the copper layer, which affects insulation reliability, especially in high-density and high-voltage applications, and require complex and costly etching processes.
Innovation Solution
A method involving the use of an etching treatment with an iron (III) chloride solution or copper (II) chloride solution followed by a treatment with a permanganate and acetic acid solution, which effectively dissolves the base metal layer residues without dissolving copper, and includes a manganese residue remover to ensure complete removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional etching liquids (iron (III) chloride or copper (II) chloride with hydrochloric acid) are used to etch adhesiveless copper clad laminates, then copper wiring can be formed, but metal residues of the base metal layer remain between wirings causing insulation reliability issues
Solution Approach 1:
The etching process is divided into two distinct stages: first using iron (III) chloride or copper (II) chloride with hydrochloric acid to etch the copper wiring pattern, then separately treating with an alkaline solution containing hypochlorite to remove only the base metal layer residues between wirings. This segmentation allows each step to address a specific requirement without compromising the other.
Solution Approach 2:
An alkaline solution containing hypochlorite (sodium hypochlorite or calcium hypochlorite) is introduced as an intermediary substance that selectively removes base metal layer residues without affecting the copper wiring. This intermediary agent bridges the gap between maintaining wiring integrity and eliminating insulation threats.
2Reliability
If strong etching is applied to remove all base metal layer residues, then insulation reliability improves, but side-etching of the copper layer occurs
Solution Approach 1:
The treatment solution is designed to exhibit different etching characteristics at different locations: the alkaline hypochlorite solution selectively attacks base metal oxides (NiO, Cr2O3) while being inert to copper metal. This local quality differentiation ensures residues between wirings are removed without side-etching of copper wiring edges.
Solution Approach 2:
The chemical parameters of the etching system are changed by using an alkaline environment with hypochlorite instead of acidic etching liquids. This parameter change fundamentally alters the selectivity of the etching action, enabling removal of base metal residues while preserving copper layer integrity through controlled chemical reactivity.
3Reliability
If multiple etching steps are used to remove metal residues, then insulation reliability improves, but process complexity and cost increase
Solution Approach 1:
The harmful base metal layer residues are extracted and removed using a specialized alkaline hypochlorite treatment step that targets only these residues. This extraction approach eliminates the need for repeated acidic etching cycles, simplifying the overall process while maintaining high insulation reliability.
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
This method allows for the removal of metal residues between wirings without side-etching the copper layer, ensuring high insulation reliability and simplifying the process, making it cost-effective and suitable for micro wiring applications.
Implementation Method 1
a process of treatment with an acid oxidant containing permanganate and acetic acid
Implementation Method 2
an iron (III) chloride solution in which iron (III) chloride (FeCl3) is dissolved in water or copper (II) chloride solution in which copper (II) chloride (CuCl22H2O) is dissolved in water and an appropriate amount of hydrochloric acid is added is used as an etching liquid
Data Source
AI summary
A method for manufacturing a printed circuit board enables a metal residue between wirings to be removed inexpensively without side etching of a copper layer while having sufficient insulation reliability for micro wiring working. The method includes forming a base metal layer directly at least on one face of an insulator film without an adhesive, and a copper coat layer formed on the base metal layer to form adhesiveless copper clad laminates, then forming a pattern on the adhesiveless copper clad laminates by an etching method. The etching method includes a process of etching treatment for the adhesiveless copper clad laminates with an iron (III) chloride solution or a copper (II) chloride solution containing hydrochloric acid and then, a process of treatment with an acid oxidant containing permanganate and acetic acid.