Solder Paste Flux Composition for Crystallization-Free Printing
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Solution Overview
Problem
The crystallization of solid solvents in solder pastes containing high concentrations of solid solvents dissolved in liquid solvents leads to missing portions during printing, affecting the use of solder pastes.
Innovation Solution
A flux composition comprising specific liquid and solid solvents with controlled mass percentages and the inclusion of a thixotropic agent, which suppresses crystallization and maintains high viscosity, is used in the solder paste.
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 flux can achieve high viscosity and excellent printability, 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 comprising multiple liquid solvents (2-ethyl-1,3-hexanediol, α-terpineol, isooctadecanol) and multiple solid solvents (trimethylolpropane, 2,2-dimethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2-butyl-2-ethyl-1,3-propanediol) with specific hydroxy group configurations. This composite structure allows the flux to maintain high viscosity while preventing crystallization through molecular interactions between different solvent components.
Solution Approach 2:
The patent precisely controls the content parameters of each solvent component, specifying that each solid solvent content is 2 mass% or more and less than 40 mass% based on the total content of liquid solvent and solid solvents. The total content of solid solvents is controlled at 30 mass% or more and less than 80 mass%. These parameter optimizations ensure high viscosity while preventing crystallization during refrigerated storage.
2Stability of the object's composition
If multiple solid solvents are used to prevent crystallization, then the flux maintains stability during storage, but the formulation complexity increases
Solution Approach 1:
The patent simplifies the formulation complexity by establishing clear parameter ranges for each solvent component. By specifying that each solid solvent content should be 2 mass% or more and less than 40 mass%, and the total solid solvent content should be 30 mass% or more and less than 80 mass%, the patent provides a systematic approach to formulating stable flux without excessive complexity.
Solution Approach 2:
The patent assigns specific functional roles to different solvent components based on their local molecular characteristics. The liquid solvents (with specific hydroxy groups) provide base fluidity and dissolution capability, while the solid solvents provide viscosity enhancement and crystallization prevention through their specific molecular structures. This localized functional assignment optimizes performance while managing formulation complexity.
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 prevents crystallization, ensuring consistent printing and improved printability of solder pastes, reducing the occurrence of missing portions and enhancing solder paste performance.
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
As the flux, a resin-based flux including a natural resin such as rosin, a thixotropic agent, a solvent, an activator or the like is widely used
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.