Solder Paste Flux Composition to Suppress Solvent Crystallization
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Solution Overview
Problem
The use of solder pastes with solid solvents dissolved in liquid solvents can lead to crystallization during storage, resulting in missing portions during printing due to increased solid solvent content.
Innovation Solution
A flux composition with a liquid solvent having hydroxy groups and two or more solid solvents with hydroxy groups, where the solid solvent content is less than 40% based on the total solvent content, and the liquid solvent is selected from 2-ethyl-1,3-hexanediol, α-terpineol, and isooctadecanol, and the solid solvents from trimethylolpropane, 2,2-dimethyl-1,3-propanediol, and 2,5-dimethyl-2,5-hexanediol, satisfying the formula Xi < 0.2121 × Xj + 31.818, to suppress crystallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the content of solid solvent dissolved in liquid solvent is increased to improve viscosity, then the viscosity of flux is improved, but the solid solvent is crystallized and precipitated during storage under refrigeration causing missing portions at the time of printing
Solution Approach 1:
The patent uses a composite solvent system combining multiple solid solvents (trimethylolpropane, 2,2-dimethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol) with specific liquid solvents. This composite approach creates a synergistic effect where the combination prevents crystallization while maintaining high viscosity, resolving the contradiction between stability and reliability.
Solution Approach 2:
The patent specifies precise compositional parameters: each solid solvent content is controlled at less than 40 mass% based on total solvent content, and the relationship between contents of different solid solvents follows the formula Xi < 0.2121×Xj + 31.818. These parameter controls optimize the flux to maintain viscosity without crystallization, solving the contradiction between improved feature and worsened feature.
2Device complexity
If the content of solid solvent is increased to achieve high viscosity, then the flux maintains its shape better, but crystallization occurs during storage causing printing defects
Solution Approach 1:
By combining multiple solid solvents with complementary molecular structures (trimethylolpropane, 2,2-dimethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol) with liquid solvents, the flux achieves shape stability through composite action rather than relying on high concentrations of a single solid solvent, thereby preventing crystallization and maintaining printing accuracy.
Solution Approach 2:
The liquid solvents act as intermediaries that dissolve the solid solvents and prevent their crystallization. The specific liquid solvent choices (2-ethyl-1,3-hexanediol, α-terpineol, isooctadecanol) mediate between the solid solvents to maintain both shape stability and printing precision by preventing solid solvent precipitation.
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 flux composition effectively suppresses crystallization, maintaining high viscosity and printability of solder pastes, preventing missing portions during printing and allowing for the production of electric circuit boards without defects.
Implementation Method 1
a flux in which a solid solvent and a highly viscous solvent are used in combination with a commonly used liquid solvent... The flux can improve its viscosity by dissolving a solid solvent in a liquid solvent
Implementation Method 2
at least one liquid solvent that has one or more hydroxy groups and is liquid at normal temperature; and at least two solid solvents that respectively have one or more hydroxy groups
Data Source
AI summary
A flux includes: at least one liquid solvent that has one or more hydroxy groups and is liquid at ordinary temperature; and at least two solid solvents that respectively have one or more hydroxy groups and are solid at normal temperature, in which the content of each of the solid solvents is less than 40 mass % based on the total content of the liquid solvent and the solid solvents.