High-Concentration Tin Sulfonate Solution Production
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Solution Overview
Problem
Existing methods for producing tin methanesulfonic acid aqueous solutions for electrolytic tin plating face issues such as increased oxidation of divalent tin ions to tetravalent tin ions, leading to turbidity and precipitation of tin dioxide, as well as high process costs due to excessive bleed-and-feed operations, especially when trying to achieve high tin concentrations.
Innovation Solution
A high-concentration tin sulfonate aqueous solution is developed with a divalent tin ion concentration of 360 g/L to 420 g/L and a tetravalent tin ion concentration of 10 g/L or less, achieved through a neutralization method where methanesulfonic acid is diluted and cooled, and stannous oxide is added at a low temperature to suppress oxidation and precipitation, while maintaining low impurity levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the concentration of tin is increased to reduce bled solution amount and process cost, then productivity improves, but the concentration of tetravalent tin ions increases and tin dioxide is generated, causing solution turbidity
Solution Approach 1:
The patent changes the temperature parameter during the neutralization reaction, maintaining it at 25°C or lower to suppress the oxidation of divalent tin ions to tetravalent tin ions. This parameter change allows achieving high tin concentration (400 g/L or more) while preventing tin dioxide generation and solution turbidity, thus resolving the contradiction between productivity improvement and harmful factor generation.
2Productivity
If the concentration of free methanesulfonic acid is increased to improve electrolytic dissolution efficiency of tin metal, then productivity improves, but the solubility of tin methanesulfonic acid decreases, causing crystal precipitation during storage
Solution Approach 1:
The patent optimizes the concentration parameter of free methanesulfonic acid to be 40 g/L or less, which balances the electrolytic dissolution efficiency with the storage stability. This parameter optimization prevents tin methanesulfonic acid crystal precipitation during storage while maintaining adequate dissolution efficiency, resolving the contradiction between productivity and composition stability.
3Productivity
If the concentration of free methanesulfonic acid is increased to achieve high tin concentration, then productivity improves, but the amount of bled solution increases, causing process cost to increase
Solution Approach 1:
The patent maintains the free methanesulfonic acid concentration at 40 g/L or less, which reduces the amount of bled solution required during electrolytic tin plating operations. This parameter control achieves high tin concentration (400 g/L or more) while minimizing substance loss through reduced bleeding, thereby resolving the contradiction between productivity improvement and substance loss.
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 results in a transparent, stable, and cost-effective tin sulfonate solution that reduces the amount of feed solution needed, prevents tin dioxide precipitation, and maintains excellent storage stability, thereby improving plating performance and semiconductor product quality.
Implementation Method 1
a method of subjecting stannous oxide powder and methanesulfonic acid to a neutralization reaction
Implementation Method 2
an electrolytic tin plating bath of a tin methanesulfonic acid aqueous solution
Data Source
AI summary
The present invention provides a high-concentration tin sulfonate aqueous solution, in which a divalent tin ion (Sn2+) concentration is 360 g/L to 420 g/L, a tetravalent tin ion (Sn4+) concentration is 10 g/L or less, a free methanesulfonic acid concentration is 40 g/L or less, a Hazen unit color number (APHA) is 240 or less, and a turbidity is 25 FTU or less. This aqueous solution is produced such that stannous oxide powder whose temperature is adjusted to a temperature of 10° C. or lower is added to an aqueous methanesulfonic acid solution having a concentration of 60% by mass to 90% by mass when the aqueous solution circulates in a state of being maintained at the temperature of 10° C. or lower, and the stannous oxide powder is dissolved.