Sulfonium Salt Plating Solution for Uniform Tin Electrodepositivity
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Solution Overview
Problem
Existing tin or tin alloy plating solutions struggle to achieve both uniform electrodepositivity and void suppression in bump electrodes, as improving one characteristic often conflicts with the other, leading to potential contact failures.
Innovation Solution
A plating solution comprising a stannous salt, an organic or inorganic acid, and a sulfonium salt with aromatic rings, optionally including a nonionic surfactant, complexing agent, and antioxidant, which enhances uniform electrodepositivity and reduces void formation in bump electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the polarization resistance of the electrode surface is increased to improve uniform electrodepositivity, then the uniform electrodepositivity is improved, but the overvoltage of the cathode increases leading to void formation in bump electrodes
Solution Approach 1:
The patent introduces a specific intermediary substance (sulfonium salt with aromatic rings) that acts as a mediator between the electrodeposition process and the electrode surface. This additive modifies the interface properties to achieve both uniform electrodepositivity and suppress void formation by balancing the polarization resistance and overvoltage effects through its unique molecular structure and interaction mechanisms with the electrode surface and metal ions
Solution Approach 2:
The patent changes the chemical composition parameters of the plating solution by incorporating a specific sulfonium salt with aromatic rings (where R1 and R2 are phenyl, hydroxyphenyl, tolyl groups, hydrogen atoms, or alkyl groups, and X is a halogen). This parameter change in the additive composition fundamentally alters the electrodeposition characteristics, enabling simultaneous achievement of uniform electrodepositivity and void suppression by optimizing the electrochemical interface properties
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 achieves improved uniform electrodepositivity and suppresses void occurrence, resulting in high-quality plating films suitable for complex wiring patterns and narrow pitch applications.
Implementation Method 1
a plating solution for tin or a tin alloy which is excellent in uniform electrodepositivity and suppresses generation of voids when a bump electrode is formed
Data Source
AI summary
A plating solution including (A) a soluble salt containing at least a stannous salt; (B) an acid selected from organic acid and inorganic acid or a salt thereof; and (C) an additive containing sulfonium salt with one or more of aromatic rings is provided.