Solder Paste Flux Composition for Wetting and Void Reduction
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Solution Overview
Problem
Existing soldering fluxes face challenges in achieving stable wet spreadability and reducing void generation, particularly due to variations in heating history and the limited effectiveness of organic acids and halogens in improving wettability and void reduction.
Innovation Solution
A flux containing a (carboxyalkyl) isocyanurate adduct, preferably combined with rosin and acrylic resin, which enhances wet spreadability and reduces void formation by removing oxides that cause non-wetting during soldering in a reflow furnace.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fluxes with organic acids, amines, and halogens are used to improve activity, then wettability is enhanced, but void generation is not sufficiently reduced
Solution Approach 1:
The patent changes the chemical composition parameters of the flux by incorporating specific compounds (carboxylic acid with 12-24 carbon atoms, sulfur compound, and phosphorus compound) in optimized proportions. This parameter change resolves the contradiction by achieving both improved wettability and reduced void generation through the synergistic effect of these specific chemical components.
Solution Approach 2:
The patent creates a composite flux formulation by combining multiple active ingredients (carboxylic acid, sulfur compound, phosphorus compound) with resin and solvent. This composite approach allows the flux to simultaneously achieve enhanced wettability from the carboxylic acid and reduced void generation from the sulfur and phosphorus compounds, resolving the technical contradiction.
2Reliability
If heating history varies during soldering, then soldering results become unstable, but consistent finishing quality is required
Solution Approach 1:
The patent incorporates sulfur compounds and phosphorus compounds in the flux formulation that act as cushioning agents against variations in heating history. These compounds provide a buffer effect that stabilizes the soldering process, ensuring consistent finishing quality regardless of heating variations through their controlled chemical reactions during the soldering process.
Solution Approach 2:
The patent optimizes the concentration parameters of multiple flux components to create a formulation that is less sensitive to heating history variations. By carefully balancing the proportions of carboxylic acid, sulfur compound, phosphorus compound, and resin, the flux achieves stable performance across different heating conditions.
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 improves solder wettability and reduces voids, leading to better temperature cycle reliability and consistent soldering performance 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
Implementation Method 3
the substrate is heated in a heating furnace called a reflow furnace to melt the solder
Implementation Method 4
intermetallic compounds may be formed between the surfaces of the solder and the metal which is a joining object by performing soldering using the flux, whereby firm joining is obtained
Data Source
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 (carboxyalkyl)isocyanurate adduct, and 5.0-45.0 wt % of a rosin, and furthermore contains a solvent. The (carboxyalkyl)isocyanurate adduct is a mono(carboxyalkyl)isocyanurate adduct, a bis(carboxyalkyl)isocyanurate adduct, a tris(carboxyalkyl)isocyanurate adduct, or a combination of two or more of these.