Non-etching Copper Adhesion Composition for Fine PCB Structures
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Solution Overview
Problem
Conventional etching methods for preparing copper surfaces in printed circuit board manufacturing are not suitable for producing finest lines and structures, as they risk removing excessive copper, especially when dealing with thin copper layers, leading to inconsistencies and potential complete removal of the copper layer.
Innovation Solution
An aqueous acidic non-etching non-resist composition is used, containing heterocyclic compounds with a thiol moiety and quaternary ammonium polymers, which provides excellent adhesion to copper surfaces without roughening, allowing for the formation of finest copper structures with minimal copper removal (up to 0.2 µm), ensuring consistent adherence of polymeric deposits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional etching methods are used to roughen copper surfaces, then adhesion of polymeric deposits is improved, but excessive copper removal occurs leading to loss of copper layer integrity
Solution Approach 1:
The invention changes the chemical parameters of the treatment composition by using a non-oxidizing acidic composition with specific pH range (0.5-3.0) and controlled copper ion concentration (1-100 ppm), allowing surface treatment without excessive copper removal. This parameter optimization enables adhesion promotion while preserving copper layer integrity.
Solution Approach 2:
The invention creates a copper oxide layer that serves as an intermediate bonding layer, copying the beneficial roughening effect of etching while avoiding copper loss. The controlled oxidation produces a surface structure that promotes adhesion without the material removal associated with conventional etching methods.
2Reliability
If etching is performed to create surface roughness, then resist reception and adherence are improved, but manufacturing precision is reduced due to copper layer variation
Solution Approach 1:
The invention optimizes treatment parameters including pH (0.5-3.0), temperature (20-80°C), and treatment time (1-30 minutes) to achieve consistent surface preparation without copper loss. This controlled parameter regime ensures uniform treatment across the copper surface, maintaining thickness precision while achieving reliable resist adhesion.
Solution Approach 2:
The invention replaces the mechanical removal process (etching) with a chemical deposition process (controlled oxidation). Instead of mechanically removing copper to create roughness, the method chemically deposits a thin oxide layer that provides the desired surface characteristics without compromising dimensional precision.
3Strength
If strong oxidants are used for copper surface treatment, then adhesion is enhanced, but harmful factors increase due to copper corrosion and material loss
Solution Approach 1:
The invention converts the potentially harmful effect of oxidation into a beneficial process by using controlled, mild oxidation instead of strong oxidizing etchants. The copper oxide formed is not removed but retained as a beneficial intermediate layer that promotes adhesion, turning what could be corrosive damage into a useful surface modification.
Solution Approach 2:
The copper oxide layer acts as an intermediary between the copper substrate and the polymeric deposit. This intermediate layer provides chemical bonding sites for both the copper and the polymer, facilitating strong adhesion without requiring aggressive oxidation or direct polymer-copper contact that would cause corrosion.
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 composition achieves strong and consistent adhesion of polymeric deposits to copper surfaces without etching, maintaining the copper layer integrity, even on thin surfaces, thereby enabling the creation of fine copper structures without excessive copper loss, as demonstrated by visual inspection and tape tests.
Implementation Method 1
the copper surface is not have a rough surface, but is substantially smooth and, nevertheless, good adherence of the polymeric deposit is achieved
Implementation Method 2
which is free of an oxidant for copper or the copper alloys
Data Source
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AI summary
To achieve good adherence of a resist coating, more specifically a photo imageable resist coating, to a copper base while ensuring that the copper base being very thin is not compromised, a non-etching non-resist composition for the treatment of the copper base is provided, said composition comprising at least one adhesion agent selected from the group comprising (i) heterocyclic compounds comprising at least one thiol moiety and (ii) quaternary ammonium polymers having the following general chemical formula: {N+(R3)(R4)-(CH2)a-N(H)- C(Y)-N(H)-(CH2)b-N+(R3)(R4)-R5}n 2n X-, with R1, R2, R3, R4, R5, Y and X- being defined as claimed.