Electroless Copper Plating Bath Stabilizer for Gloss and Stability
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Solution Overview
Problem
Existing electroless copper plating technologies face challenges in producing copper or copper alloy layers with high mechanical stability, gloss, and adhesion, especially on flexible substrates, and lack effective stabilizing agents that are environmentally friendly and do not compromise layer quality.
Innovation Solution
An electroless copper plating bath comprising copper ions, a reducing agent, a complexing agent, and a specific stabilizing compound that improves bath stability, gloss, and adhesion, while being less toxic and allowing for extended bath lifetime, is developed. This bath includes a compound with pyridine rings that acts as a stabilizer and gloss enhancer, reducing the risk of plate-out and enhancing the properties of both electrolessly deposited and subsequently electrolytically thickened copper layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional stabilizing agents (thiourea, cyanides, nitrogen-containing agents) are used in electroless copper plating baths, then bath stability is improved, but the gloss and smoothness of copper layers deteriorate and toxic environmental harm increases
Solution Approach 1:
The invention extracts and eliminates toxic stabilizing agents (thiourea, cyanides, nitrogen-containing compounds) from the electroless copper plating bath formulation, replacing them with non-toxic alternatives based on compounds of formula (I) that provide stabilization without environmental harm or gloss degradation
Solution Approach 2:
The patent employs short-chain carboxylic acids (formic, acetic, propionic acid) and simple pyridine derivatives as stabilizing agents that are environmentally benign, non-toxic, and can be easily disposed of or regenerated, replacing persistent toxic stabilizers with safer, shorter-lived alternatives
2Stability of the object's composition
If conventional stabilizing agents are used to extend bath lifetime, then bath stability is improved, but the gloss and smoothness of deposited copper layers deteriorate
Solution Approach 1:
The invention introduces compounds of formula (I) as intermediary stabilizing agents that mediate between the need for bath stability and the requirement for glossy deposits. These compounds stabilize the copper complex without adsorbing on the deposit surface in a way that degrades gloss, thus mediating between conflicting requirements
Solution Approach 2:
The patent changes the chemical parameters of the stabilizing agent from conventional toxic compounds to specific non-toxic compounds of formula (I) with controlled concentrations (0.01-10 g/L), adjusting these parameters to achieve both bath stability and gloss maintenance simultaneously
3Area of stationary object
If electroless copper plating is used to form initial layers, then coverage on non-conductive substrates is improved, but mechanical stability and adhesion under stress deteriorate
Solution Approach 1:
The invention creates a composite plating system combining electroless copper deposition with subsequent electrolytic copper thickening. The electroless layer provides coverage and adhesion to the substrate, while the electrolytic layer provides mechanical strength and stress resistance, creating a composite structure that combines advantages of both methods
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 solution provides copper or copper alloy layers with high gloss, mechanical stability, and improved adhesion, especially on flexible substrates, while maintaining bath stability for at least 7 days, and avoids the use of toxic substances, ensuring high production yield and compliance with industrial standards.
Implementation Method 1
electroless plating is the controlled autocatalytic deposition of a continuous film of metal without the assistance of an external supply of electrons
Implementation Method 2
Complexing agents (also called chelating agents in the art) are used to chelate the metal being deposited and prevent the metal from being precipitated from solution
Implementation Method 3
electroless plating is the controlled autocatalytic deposition of a continuous film of metal
Data Source
AI summary
An electroless copper plating bath for depositing a copper or copper alloy layer on a surface of a substrate, including copper ions; a reducing agent; a complexing agent for copper ions; wherein the bath further includes at least one compound according to formula (1):in which Z1 and Z2 are independently selected from the group consisting of hydrogen; carboxylic acid; carboxylate; sulfonic acid; sulfonate; carboxamide; nitrile; nitro; trialkylammonium; 2-carboxyvinyl; 2-vinylcarboxylate; 2-(trialkylammonium)vinyl; hydroxamic acid; and oxime; provided at least one of Z1 and Z2 is not hydrogen;and in which R1, R2, R3 and R4 are:i. R1, R2, R3 and R4 are hydrogen; orii. R1 with R2 form together an aromatic ring, R3 and R4 are hydrogen; oriii. R3 with R4 form together an aromatic ring, R1 and R2 are hydrogen; oriv. both R1 with R2 and R3 with R4 form together an aromatic ring, respectively.