Sulfonium Borate Complex for Low-Temp Curing
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Solution Overview
Problem
Conventional sulfonium antimonate complexes used as photocationic polymerization initiators produce excessive fluorine ions during cationic polymerization, leading to corrosion issues and inadequate low-temperature, rapid curing properties in thermal cationic polymerizable adhesives, especially when used in electronic part mounting on circuit boards.
Innovation Solution
A novel sulfonium borate complex with specific aralkyl and lower alkyl substituents, combined with a tetrakis(pentafluorophenyl)borate anion, is developed to reduce fluorine ion production and enhance low-temperature curing, achieved by reacting a sodium borate salt with a sulfonium antimonate complex in an organic solvent system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sulfonium antimonate complexes are used as thermal cationic polymerization initiators, then cationic polymerization can be initiated, but excessive fluorine ions are produced causing electrochemical corrosion
Solution Approach 1:
The patent changes the counter anion parameter from SbF6- to BF4-, which fundamentally alters the fluorine ion release characteristics during thermal cationic polymerization. This parameter change reduces fluorine ion production and improves electrochemical corrosion resistance while maintaining initiator functionality
Solution Approach 2:
The patent replaces the conventional sulfonium antimonate complex with a sulfonium borate complex that has lower fluorine ion release potential. The new complex acts as a disposable initiator that completes its function without generating harmful byproducts that would compromise long-term reliability
2Object-generated harmful factors
If conventional sulfonium borate complexes are used to reduce fluorine ion production, then fluorine ion concentration decreases, but low-temperature rapid curing properties deteriorate
Solution Approach 1:
The patent introduces specific local substituents (o-methylbenzyl group or (1-naphthyl)methyl group for R1, and specific lower alkyl groups for R2) at precise positions on the sulfonium cation. These localized structural modifications optimize both the reduced fluorine ion release from BF4- and the low-temperature reactivity, resolving the contradiction between harm reduction and productivity
Solution Approach 2:
The patent creates a composite initiator structure combining the sulfonium cation with specific alkyl substituents and the BF4- anion. This composite design achieves synergistic effects where the cation provides low-temperature reactivity and the anion provides low fluorine ion release, simultaneously satisfying both requirements
3Adaptability or versatility
If sulfonium antimonate complexes are converted to thermal initiators, then photocationic polymerization capability is lost, but thermal cationic polymerization is enabled
Solution Approach 1:
The patent changes the initiator activation parameter from photo-induced to thermal-induced by modifying the molecular structure and counter anion. The sulfonium borate complex is designed to undergo thermal decomposition at elevated temperatures to generate cationic species, enabling thermal polymerization while the BF4- anion minimizes harmful fluorine ion release
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 novel sulfonium borate complex effectively reduces fluorine ion concentration and achieves rapid, low-temperature curing in thermal cationic polymerizable adhesives, providing improved electrochemical corrosion resistance and productivity.
Implementation Method 1
a sulfonium borate complex which serves as a thermal cationic polymerization initiator for a thermal cationic polymerizable adhesive
Implementation Method 2
the sulfonium borate complex of the formula (1) is obtained by reacting a sodium borate salt of the formula (3) with a sulfonium antimonate complex of the formula (2)
Data Source
Figure 1
Figure 2
AI summary
A novel sulfonium borate complex, which can reduce the amount of fluorine ions produced during thermal cationic polymerization, and realize low-temperature, rapid curing properties in a thermal cationic polymerizable adhesive, is represented by the structure of the following formula (1). In the formula (1), R1 is an aralkyl group and R2 is a lower alkyl group. However, when R2 is a methyl group, R1 is not a benzyl group. X is a halogen atom, and n is an integer of 1 to 3.