Low-Residue Flux Composition With Dual-Melting-Point Alcohols
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Solution Overview
Problem
The challenge lies in developing a flux with predetermined rheological characteristics at room temperature and under thermal history conditions for soldering, while minimizing residue formation to enable no-clean applications in electronic components.
Innovation Solution
A flux comprising two alcohol compounds with different melting points, specifically glycerin and 2,5-dimethylhexane-2,5-diol, which provides suitable viscosity ranges at room temperature and elevated temperatures, along with optional additives, to ensure effective spreading of molten solder without excessive residue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If rosin is added to obtain predetermined rheological characteristics, then viscosity control is improved, but residue amount increases
Solution Approach 1:
The invention extracts and removes rosin from the flux composition to eliminate the source of excessive residue, while replacing it with alternative components (alcohol compounds and carboxylic acid) that provide necessary rheological control without the same residue problems. This extraction principle directly addresses the contradiction by eliminating the harmful substance while maintaining functional requirements.
Solution Approach 2:
The invention changes the chemical composition parameters of the flux by specifying precise ranges of alcohol compounds (5-50 wt%), carboxylic acid (1-20 wt%), and water (10-40 wt%), replacing the traditional rosin-based formulation. This parameter change enables the flux to achieve appropriate viscosity and rheological properties during soldering while significantly reducing residue formation, thereby resolving the contradiction between stability and substance loss.
2Stability of the object's composition
If high viscosity solvent is used at room temperature, then flux holding capability is improved, but volatility under thermal history is reduced
Solution Approach 1:
The invention uses a composite solvent system comprising multiple alcohol compounds (such as ethylene glycol, propylene glycol, butanediol) combined with carboxylic acid and water. This composite formulation achieves high viscosity at room temperature for proper flux holding, while the specific composition ensures adequate volatility under soldering thermal history to minimize residue. The synergistic interaction of components resolves the contradiction between stability and temperature response.
Solution Approach 2:
The alcohol compound mixture serves multiple functions simultaneously: it provides high viscosity at room temperature for flux holding capability, maintains appropriate rheological properties during heating, and achieves sufficient volatility under thermal history for low residue. This multi-functionality of the solvent system resolves the apparent contradiction by making a single compositional system that performs all required functions across different temperature conditions.
3Stability of the object's composition
If base agent and thixotropic agent are added, then rheological characteristics are improved, but residue formation increases
Solution Approach 1:
The invention extracts and eliminates traditional base agents (like rosin) and thixotropic agents from the flux formulation, replacing them with a water-alcohol-carboxylic acid system that provides necessary rheological control without contributing to excessive residue formation. This extraction of harmful components while maintaining functional requirements directly resolves the contradiction.
Solution Approach 2:
The flux formulation uses water, alcohol compounds, and carboxylic acid in such proportions and with such properties that the system self-regulates its rheological characteristics during storage and application, eliminating the need for additional base agents or thixotropic agents. This self-service approach provides necessary viscosity and flow control while minimizing residue, resolving the contradiction between rheological stability and residue reduction.
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 achieves predetermined rheological characteristics at both room temperature and soldering conditions, reducing residue formation to allow for no-clean applications in electronic components, ensuring reliable soldering without post-soldering cleaning.
Implementation Method 1
solvents that have a high viscosity at room temperature and, under the thermal history that is assumed for soldering, are converted into the liquid state
Implementation Method 2
2,4-Diethyl-1,5-pentanediol is a solvent that has a high viscosity at room temperature and is volatile under the thermal history that is assumed for soldering
Data Source
AI summary
Provided is a flux capable of obtaining predetermined rheological characteristics both at room temperature and under a thermal history that is assumed for soldering and capable of suppressing the amount of a residue after soldering to realize a low residue. The flux contains a first alcohol compound that has two or more OH groups and has a melting point of lower than 25° C. and a second alcohol compound that has two or more OH groups and has a melting point of higher than 25° C., the first alcohol compound is glycerin, the second alcohol compound is 2,5-dimethylhexane-2,5-diol, the flux has a viscosity of 10 Pa·s or more and 50 Pa·s or less at 25° C. and has a viscosity of more than 0 Pa·s and 1 Pa·s or less at 100° C., and, in a case where 10 mg of the flux is heated up to 25° C. to 250° C. under a N2 atmosphere at a temperature rise rate of 10° C./min, the weight of the flux after heating is 15% or less of the weight of the flux before heating.