Copper Adhesion via Organic Acid Oxidation
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Solution Overview
Problem
Conventional etching solutions for copper surfaces are not suitable for producing ultra-fine circuitry on printed circuit boards, as they remove too much copper, risking the removal of the copper layer and compromising the consistency of the copper base, especially when depositing very thin copper layers by electroless plating.
Innovation Solution
An aqueous adhesion promoting solution with organic acids and peroxide compounds is used to form a thin copper oxide phase on copper or copper alloy surfaces, minimizing copper removal and enhancing adhesion of organic resist materials, with a pH value between 1.8 and 5, and a copper oxide layer thickness of 5 to 300 nm, as determined by atomic force microscopy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional etching solutions are used to roughen copper surfaces, then adhesion of organic resist material is improved, but copper layer removal increases excessively
Solution Approach 1:
The patent changes the chemical parameters of the etching solution by using organic acids (formic acid, acetic acid, propionic acid, butyric acid, or their salts) instead of conventional strong mineral acids. This parameter change reduces the etching aggressiveness while maintaining adhesion promotion, thereby minimizing copper layer removal while still achieving sufficient surface roughening for resist adhesion.
Solution Approach 2:
The patent employs readily available organic acids that are less aggressive than conventional etchants, effectively using a milder, more controllable chemical agent that provides sufficient etching action without excessive copper removal, balancing adhesion improvement with material conservation.
2Strength
If etching is performed to achieve good adhesion, then surface roughness is improved, but copper thickness variation increases
Solution Approach 1:
By changing to organic acid-based etching solutions with controlled pH and composition, the etching process becomes more uniform and controllable. This reduces localized variations in copper thickness while still achieving the necessary surface roughness for good resist adhesion, thereby improving manufacturing precision.
Solution Approach 2:
The patent applies a controlled, moderate etching action that is sufficient to create the necessary surface roughness for adhesion but stops before causing excessive copper removal or thickness variation. The organic acid system allows for this controlled partial action to be achieved effectively.
3Ease of manufacture
If strong oxidants are used for etching, then surface preparation is effective, but copper layer integrity is compromised
Solution Approach 1:
The patent uses mild organic acid systems that provide effective surface preparation without the aggressive action of strong oxidants. These gentler chemicals maintain copper layer integrity while still achieving the necessary surface activation and roughness for subsequent resist adhesion, ensuring process 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
The method achieves high adhesion of organic resist materials on copper or copper alloy surfaces, allowing for the formation of fine copper structures with minimal copper removal (0.05 to 0.1 µm), ensuring consistent copper layers and improved surface roughness, suitable for ultra-fine circuitry production.
Implementation Method 1
an aqueous adhesion promoting solution comprising at least one organic acid and a peroxide compound... which forms on the copper or copper alloy surface a layer of copper oxide phase(s)
Implementation Method 2
an aqueous adhesion promoting solution comprising at least one organic acid and a peroxide compound... providing a method for increasing the adhesion of organic resist materials on a copper or copper alloy surface
Data Source
AI summary
The present invention relates to a method for increasing the adhesion of organic resist materials on copper or copper alloy surfaces. The copper or copper alloy surface is contacted with an aqueous adhesion promoting solution comprising at least one organic acid, a peroxide compound and optionally one or more substances selected from the group consisting of urea, derivatives thereof and water-soluble polymers.