Solder Paste Flux Composition for Stable Viscosity and Clean Residues
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Solution Overview
Problem
Solder pastes using fluxes with hydrogenated castor oil and polymerized rosin experience coloration issues and increased viscosity over time when stored at 30°C, while those with hydrogenated rosin or acid-modified rosin have insufficient reflow properties and high viscosity.
Innovation Solution
A flux composition including specific rosins such as acid-modified rosin, hydrogenated rosin, or acid-modified hydrogenated rosin, combined with a thixotropic agent represented by General Formula (1), which maintains stable viscosity and minimizes coloration of flux residues, while ensuring favorable reflow properties and cleanability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a flux containing hydrogenated castor oil and polymerized rosin is used, then favorable cleanability of flux residues is achieved, but coloration of flux residues occurs
Solution Approach 1:
The patent changes the chemical parameters of the rosin component by specifying acid-modified rosin, hydrogenated rosin, or acid-modified hydrogenated rosin instead of conventional polymerized rosin. This parameter change maintains the cleanability benefits while eliminating the coloration issue through modified chemical structure and composition.
Solution Approach 2:
The patent uses a composite flux formulation combining specific rosin types (acid-modified rosin, hydrogenated rosin, or acid-modified hydrogenated rosin) with hydrogenated castor oil and other components in controlled proportions. This composite approach achieves both favorable cleanability and minimal coloration by synergistic combination of compatible materials.
2Reliability
If a flux containing hydrogenated castor oil and hydrogenated rosin or acid-modified rosin is used, then favorable reflow properties are achieved, but viscosity increases over time when stored at 30°C
Solution Approach 1:
The patent modifies the thixotropic agent parameters by specifying compounds with particular molecular structures (General Formula 1 with specific R11, R12, R21, R22, R13, and n parameters). This parameter optimization maintains favorable reflow properties while minimizing viscosity increase during storage through controlled molecular architecture and interaction characteristics.
Solution Approach 2:
The patent applies local quality by specifying that the thixotropic agent should have particular structural characteristics (hydrocarbon groups with specific carbon atom ranges) that provide different functional properties at different storage and processing conditions, achieving stability during storage while maintaining reflow performance.
3Ease of operation
If a flux containing polymerized rosin is used, then favorable cleanability is achieved, but reflow properties become insufficient
Solution Approach 1:
The patent changes the rosin parameter from polymerized rosin to acid-modified rosin, hydrogenated rosin, or acid-modified hydrogenated rosin. This parameter change preserves the cleanability advantages while restoring sufficient reflow properties through modified chemical composition and structure that balances both functional requirements.
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 stabilizes viscosity, reduces coloration of flux residues, and maintains reflow properties, providing a solder paste with improved storage stability and cleanability.
Implementation Method 1
the thixotropic agent includes a compound represented by General Formula (1)... capable of minimizing the time-dependent changes in viscosity when stored at 30° C.
Implementation Method 2
minimizing the coloration of flux residues while having favorable reflow properties and favorable cleanability of flux residues
Implementation Method 3
having favorable reflow properties... while having favorable reflow properties and favorable cleanability of flux residues
Data Source
AI summary
A flux and a solder paste capable of minimizing the time-dependent changes in viscosity when stored at 30° C. and minimizing the coloration of flux residues while having favorable reflow properties and favorable cleanability of flux residues are provided. As such a flux, a flux containing a rosin, a thixotropic agent, an activator, and a solvent is adopted. The rosin includes one or more selected from the group consisting of an acid-modified rosin, a hydrogenated rosin, and an acid-modified hydrogenated rosin, and the thixotropic agent includes a compound represented by General Formula (1). In General Formula (1), R11 and R12 each independently represent a hydrocarbon group which has 1 to 3 carbon atoms and may have a substituent, or a single bond. R21 and R22 each independently represent a hydrocarbon group which has 7 to 29 carbon atoms and may have a substituent. R13 represents a substituent. n represents an integer of 0 to 4.