Electroless Palladium Plating Liquid Bismuth Stabilizer
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Solution Overview
Problem
Existing electroless palladium plating liquids with sulfur compounds suffer from segregation issues that compromise corrosion resistance and solder bondability, necessitating improved bath stability and performance.
Innovation Solution
Employing bismuth or bismuth compounds as stabilizers in electroless palladium plating liquids, combined with water-soluble palladium compounds, complexing agents, and reducing agents, to enhance film properties and bath stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a sulfur compound is used as a bath stabilizer, then bath stability is improved, but sulfur segregates in the palladium film causing loss in corrosion resistance and solder bondability
Solution Approach 1:
The patent changes the chemical substance parameter from sulfur compound to bismuth compound as the bath stabilizer. This parameter substitution resolves the contradiction by providing bath stability through bismuth's unique properties - it forms stable complexes with palladium at low concentrations (0.01-10 ppm) without causing segregation in the deposited film, thereby maintaining both bath stability and film quality.
2Reliability
If electroless palladium plating is inserted between electroless nickel plating and electroless gold plating, then corrosion resistance and solder bondability are improved, but the process complexity increases
Solution Approach 1:
The patent extracts the sulfur compound from the bath stabilizer role and replaces it with bismuth compound. This extraction eliminates the harmful segregation effect while preserving the essential bath stabilization function, allowing the three-layer plating structure to maintain its reliability benefits without the detrimental sulfur segregation problem.
3Reliability
If bismuth compound is used as a stabilizer instead of sulfur compound, then corrosion resistance and solder bondability are improved, but bath stability may be compromised
Solution Approach 1:
The patent optimizes the concentration parameter of bismuth compound to 0.01-10 ppm, which is sufficiently low to prevent segregation and improve film quality, yet high enough to provide adequate bath stabilization. This precise parameter control resolves the apparent contradiction between bath stability and film quality.
Solution Approach 2:
The patent creates a composite plating system combining electroless nickel, electroless palladium (with bismuth stabilizer), and electroless gold layers. The bismuth-stabilized palladium layer acts as an intermediate composite structure that provides both the reliability benefits of the multi-layer system and the bath stability needed for consistent deposition.
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 electroless palladium plating with superior corrosion resistance, solder bondability, and wire bondability, matching or exceeding the performance of sulfur-stabilized systems while maintaining bath stability.
Implementation Method 1
bismuth or a bismuth compound as a stabilizer
Implementation Method 2
electroless palladium plating liquid
Implementation Method 3
forming a film by electroless plating
Implementation Method 4
at least one of ammonia, an amine compound, an aminocarboxylic acid compound, and carboxylic acid as a complexing agent
Implementation Method 5
at least one of hypophosphorous acid, phosphorous acid, formic acid, acetic acid, hydrazine, a boron hydride compound, an amine borane compound, and salts thereof, as a reducing agent
Data Source
AI summary
An electroless palladium plating liquid, with excellent bath stability, that can provide a film with excellent corrosion resistance, solder bondability, and wire bondability is provided. The invention is an electroless palladium plating liquid, containing: a water soluble palladium compound; at least one of ammonia, an amine compound, an aminocarboxylic acid compound, and carboxylic acid as a complexing agent; and bismuth or a bismuth compound as a stabilizer. Preferably the electroless palladium plating liquid further contains at least one of hypophosphorous acid, phosphorous acid, formic acid, acetic acid, hydrazine, a boron hydride compound, an amine borane compound, and salts thereof as a reducing agent.