Tin-Silver Electroplating Composition for Long-Life Bath Stability
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Solution Overview
Problem
Existing tin-silver alloy electroplating compositions suffer from instability over time, leading to deterioration and the formation of deposits, which affects the quality of electrodepositing tin-silver alloys on semiconductor substrates.
Innovation Solution
An aqueous composition comprising tin and silver ions with specific complexing agents of formula C11 RC12-XC11-RC11, where XC11 is a divalent 5 or 6 membered aromatic N-heterocyclic group, divalent 6 membered aromatic carbocyclic group, or divalent 5 or 6 membered aliphatic N-heterocyclic group, and RC11 is a sulfur-containing group, stabilizes the plating bath for long periods without significant deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional complexing agents are used in tin-silver alloy electroplating compositions, then silver can be stabilized in solution and deposited in parallel to tin, but the composition deteriorates over time showing strong coloring and generating deposits
Solution Approach 1:
The patent changes the chemical structure parameters of the complexing agent by specifying particular sulfur-containing compounds with defined molecular structures (formula I and II). These structural modifications enable the complexing agent to maintain stable coordination with silver ions over extended periods, preventing the deterioration and deposit formation that plagues conventional plating baths while preserving the co-deposition capability with tin.
2Stability of the object's composition
If sulfur containing complexing agents are used to stabilize silver ions, then silver deposition parallel to tin is achieved, but the composition shows deterioration and aging after relatively short time
Solution Approach 1:
The patent employs composite molecular structures combining sulfur-containing functional groups with specific heterocyclic or carbocyclic frameworks. This composite approach creates complexing agents that simultaneously provide strong silver ion coordination (ensuring chemical stability) and enhanced resistance to oxidation and decomposition (ensuring reliability over time), overcoming the limitations of simpler sulfur compounds.
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 composition maintains stability for at least 6 months, enabling effective electrodepositing of tin-silver alloys on semiconductor substrates, particularly tin-silver alloy solder bumps, with improved deposition quality.
Implementation Method 1
complexing agents that are capable of forming a complex with silver in order to allow silver to be (a) stable in the solution in combination with tin, and (b) deposited in parallel to the less noble tin
Implementation Method 2
semiconductor substrates by means of metal electroplating baths
Data Source
AI summary
An aqueous composition including (a) metal ions including tin ions and silver ions and (b) at least one complexing agent of formula C11RC12-XC11-RC11 (C11)and their salts,whereXC11 is selected from(a) a divalent 5 or 6 membered aromatic N-heterocyclic group;(b) a divalent 6 membered aromatic carbocyclic group; and(c) a divalent 5 or 6 membered aliphatic N-heterocyclic group including one N atom and optionally a second heteroatom selected from N and O; all of which may be unsubstituted or substituted by one or more OH or one or more RC14;RC11 is selected from ; andRC12 is selected from RC11, XC11-RC11, H, OH, NRC142, C1 to C10 alkyl, and C1 to C10 alkoxy