Solder Flux Composition for Stable Wetting and Low Voiding
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Solution Overview
Problem
Existing soldering fluxes face challenges in achieving stable wet spreadability and reducing voids, particularly due to variations in heating history and the insufficient reduction of voids despite the addition of organic acids, amines, and halogens.
Innovation Solution
A flux comprising 0.5 wt% to 20.0 wt% of a (2-carboxyalkyl) isocyanurate adduct, 5.0 wt% to 50.0 wt% of rosin, and 5.0 wt% to 30.0 wt% of an acrylic resin, along with optional components like organic acids, amines, and thixotropic agents, which improves wet spreadability and reduces voids in soldering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fluxes are used, then soldering can be performed, but wet spreadability varies significantly depending on heating history
Solution Approach 1:
The patent changes the chemical parameters of the flux by introducing a specific organic acid component (carboxylic acid with 12-22 carbon atoms, preferably stearic acid or behenic acid) at controlled concentrations (0.1-5 wt%). This parameter change stabilizes the flux composition to resist variations in heating history, ensuring consistent wet spreadability across different thermal conditions.
Solution Approach 2:
The patent creates a composite flux formulation combining multiple components: rosin (40-70 wt%), acrylic resin (5-30 wt%), and the specific long-chain carboxylic acid (0.1-5 wt%). This composite material approach integrates materials with complementary properties to achieve both reliable wet spreadability and insensitivity to heating variations.
2Reliability
If organic acids, amines, and halogens are added to improve activity, then soldering performance may be enhanced, but void generation is not sufficiently reduced
Solution Approach 1:
The patent extracts or limits the use of conventional void-generating additives (amines and halogens) while retaining and optimizing the carboxylic acid component. By removing problematic substances and keeping only the beneficial long-chain carboxylic acid at controlled levels, the formulation maintains soldering performance while significantly reducing void generation.
Solution Approach 2:
The patent changes the compositional parameters by strictly limiting amine content to 0-2 wt% and halogen content to 0-3 wt%, while optimizing carboxylic acid concentration. This parameter optimization reduces harmful effects (voids) while preserving necessary soldering activity through the specific carboxylic acid component.
3Reliability
If flux composition is optimized for activity, then wet spreadability improves, but stability across different heating histories deteriorates
Solution Approach 1:
The patent optimizes the parameter of carboxylic acid chain length (12-22 carbon atoms) and concentration (0.1-5 wt%) to achieve a balance where wet spreadability is enhanced while the composition remains stable across different heating histories. The long-chain structure provides thermal stability while maintaining surface activity.
Solution Approach 2:
The patent applies local quality by having different flux components serve specialized functions: rosin provides bulk stability, acrylic resin provides adhesion, and the long-chain carboxylic acid provides localized surface activity and heating history resistance. This functional differentiation achieves both improved wet spreadability and enhanced stability.
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 enhances wet spreadability of solder by removing oxides that cause non-wetting, resulting in improved soldering performance and reduced voids, regardless of heating history.
Implementation Method 1
a flux used for soldering has an effect of chemically removing metal oxides present on surfaces of solder and metal
Implementation Method 2
enabling movement of metallic elements at the boundary between the two surfaces. For this reason, intermetallic compounds may be formed between the surfaces
Implementation Method 3
the substrate is heated in a heating furnace called a reflow furnace to melt the solder
Data Source
Figure 1A~1C
Figure 1D~2B
Figure 2C~3B
AI summary
Provided are flux in which solder wettability is improved, and a solder paste in which the flux is used. The flux contains 0.5-20.0 wt% of a (2-carboxyalkyl)isocyanurate adduct, and 5.0-45.0 wt% of a rosin, and furthermore contains a solvent. The (2-carboxyalkyl)isocyanurate adduct is a mono(2-carboxyalkyl)isocyanurate adduct, a bis(2-carboxyalkyl)isocyanurate adduct, a tris(2-carboxyalkyl)isocyanurate adduct, or a combination of two or more of these.