Electroless Plating Solution for Void-Free Via Filling
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Solution Overview
Problem
Current electroless plating methods struggle to fill large trenches or vias on printed circuit boards without defects such as voids or seams, especially under high alkaline conditions, and fail to maintain stability over time, leading to issues like line breakage and circuit shorting.
Innovation Solution
An electroless plating solution containing a sulfur-based organic compound with a cyclic group is used, which includes a water-soluble metal salt, a reducing agent, and a chelating agent, allowing for defect-free deposition of plating metal into trenches or vias, even under highly alkaline conditions, by acting as a leveler and stabilizer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional electroless plating methods are used to fill large trenches or vias, then plating metal can be deposited by increasing plating thickness, but gaps (voids or seams) are produced below the opening part of the via, causing line breakages
Solution Approach 1:
The patent changes the chemical parameters of the plating solution by introducing a sulfur-based organic compound with a cyclic group under highly alkaline conditions (pH 11-14). This parameter change modifies the plating mechanism to achieve uniform deposition without voids or seams, resolving the contradiction between filling quality and reliability
Solution Approach 2:
The patent uses a composite plating solution system combining water-soluble metal salt, reducing agent, chelating agent, and sulfur-based organic compound with cyclic group. This composite formulation works synergistically to prevent void formation while maintaining solution stability under highly alkaline conditions
2Manufacturing precision
If sulfur-based compound is used in conventional acidic copper sulfate electroplating solution, then voids or seams can be suppressed, but the compound is destabilized and undergoes self-decomposition in highly alkaline electroless plating solution
Solution Approach 1:
The patent changes the pH parameter from conventional acidic conditions to highly alkaline conditions (pH 11-14), and simultaneously introduces a sulfur-based organic compound with a cyclic group that remains stable under these new conditions. The cyclic structure provides enhanced stability against self-decomposition while maintaining the void-suppression function
Solution Approach 2:
The patent replaces the unstable conventional sulfur-based compound (which decomposes quickly in alkaline conditions) with a more stable sulfur-based organic compound containing a cyclic group that can function as a leveler throughout the entire plating process without decomposing
3Manufacturing precision
If conventional electroless plating is used for fine interconnects with 20 μm line width, then circuit patterns can be formed, but misregistration or development defects are produced, causing line breakage or circuit shorting
Solution Approach 1:
The patent employs highly alkaline conditions (pH 11-14) combined with sulfur-based organic compound to achieve uniform and controlled plating deposition. This parameter change improves the precision of circuit pattern formation while preventing defects that lead to line breakage or shorting
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 enables the deposition of plating metal without voids or seams, maintaining stability over time and enhancing the formation of smooth, high-quality plating films, suitable for high-speed signal handling and high interconnect density printed circuit boards.
Implementation Method 1
an electroless plating solution according to the present invention contains at least a water-soluble metal salt, a reducing agent and a chelating agent, and also contains a leveler composed of at least one of sulfur-based organic compounds
Implementation Method 2
plating metal can be deposited by increasing the plating thickness
Implementation Method 3
an electroless plating solution according to the present invention contains at least a water-soluble metal salt, a reducing agent and a chelating agent
Implementation Method 4
an electroless plating solution according to the present invention contains at least a water-soluble metal salt, a reducing agent and a chelating agent
Data Source
AI summary
Disclosed is an electroless plating solution exhibiting a good plating metal filling performance even for larger trenches or vias of several to one hundred and tens of μm, in a manner free from voids or seams, and allowing maintenance of stabilized performance for prolonged time. The electroless plating solution contains at least a water-soluble metal salt, a reducing agent for reducing metal ions derived from the water-soluble metal salt, and a chelating agent. In addition, the electroless plating solution contains a sulfur-based organic compound as a leveler having at least one aliphatic cyclic group or aromatic cyclic group to which may be linked at least one optional substituent. The aliphatic cyclic group or the aromatic cyclic group contains optional numbers of carbon atoms, oxygen atoms, phosphorus atoms, sulfur atoms and nitrogen atoms.