Tin Alloy Plating Solution Sulfide Complexing Agents

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Solution Overview

Problem

Existing tin alloy plating solutions face issues with electrolytic and aging stability due to decomposition of complexing agents over time, leading to precipitation of silver ions.

Innovation Solution

Incorporating specific sulfide compounds represented by General Formulas (1), (2), and (3) into the tin alloy plating solution, which act as complexing agents for metals more noble than tin, enhancing water solubility and stability through hydrogen bonding, and optionally combining with surfactants, antioxidants, and complexing agents for improved performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If cyanide compounds are used as complexing agents in tin-silver alloy plating solutions, then the plating bath stability is improved, but the toxicity and handling difficulty increase significantly

Engineering Contradiction:

Improveplating bath stabilityVSAvoidtoxicity

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The patent replaces toxic cyanide compounds with non-toxic alternative complexing agents such as aliphatic sulfides, thiodiglycol, and their derivatives. These alternative compounds achieve the necessary complexation stability without the severe toxicity issues of cyanide, effectively substituting a harmful substance with a safe one that performs the required function.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent modifies the chemical parameters of the complexing agents by using specific aliphatic sulfide compounds with defined molecular structures (containing sulfur and carbon atoms in specific arrangements) and controlling their concentration ranges in the plating bath. This parameter optimization achieves stable complexation while eliminating toxicity.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If conventional non-cyanide complexing agents are used, then toxicity is reduced, but electrolytic and aging stability deteriorate due to decomposition over time

Engineering Contradiction:

ImprovetoxicityVSAvoidelectrolytic and aging stability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent identifies specific structural parameters of the complexing agents (aliphatic sulfide compounds with particular molecular configurations) and optimizes their concentration ranges in the plating bath. This parameter optimization ensures that the complexing agents maintain stable complexation over extended periods without decomposition, achieving both non-toxicity and long-term stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite complexing systems combining multiple components: aliphatic sulfide compounds as primary complexing agents, supplemented by other additives that enhance stability. This composite approach creates a synergistic effect where the combination of substances provides both non-toxicity and superior electrolytic and aging stability compared to single-agent systems.

Inventive Principle:

Principle #40Composite materials

3Stability of the object's composition

If complexing agents are used to stabilize metal ions, then plating bath stability is improved, but the complexing agents decompose over time leading to precipitation

Engineering Contradiction:

Improveplating bath stabilityVSAvoidservice life of complexing agents

Core Design Contradiction:

Stability of the object's compositionVSDuration of action of stationary object

Solution Approach 1:

The patent selects complexing agents with specific chemical structures (aliphatic sulfides with particular carbon chain lengths and configurations) and optimizes their concentration parameters in the plating bath. These parameter optimizations ensure that the complexing agents form stable complexes that resist decomposition over extended periods, extending their service life and maintaining plating bath stability throughout the bath's operational duration.

Inventive Principle:

Principle #35Parameter changes

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 sulfide compounds stabilize metal ions, maintaining electrolytic and aging stability of the plating solution, ensuring uniform film thickness and preventing whisker formation, while also improving solder wettability and mounting strength.

Implementation Method 1

Incorporating specific sulfide compounds represented by General Formulas (1), (2), and (3) into the tin alloy plating solution, which act as complexing agents for metals more noble than tin

Methodology Applied

Scientific EffectComplexation:

Implementation Method 2

enhancing water solubility and stability through hydrogen bonding

Methodology Applied

Scientific EffectHydrogen bonding:

Implementation Method 3

forming a tin alloy plating film by an electroplating method

Methodology Applied

Scientific EffectElectroplating: Electroplating

Data Source

PatentEP3835458B1Tin alloy plating solution

Publication Date: 2023.08.16 MITSUBISHI MATERIALS CORP

AI summary

A tin alloy plating solution includes a soluble tin salt, a soluble salt of a metal more noble than tin, and a sulfide compound represented by General Formula (1). In the General Formula (1), (A) is a hydrocarbon group including no oxygen atom and having 1 to 2 carbon atoms, or (A) is a hydrocarbon group including one or more oxygen atoms and having 2 to 6 carbon atoms. The metal which is more noble than tin is preferably silver, copper, gold or bismuth.