Solder Paste Flux Composition for Stable Wet Spreadability
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Solution Overview
Problem
Soldering processes using existing fluxes often result in inconsistent wet spreadability due to varying heat histories, leading to unstable finishes.
Innovation Solution
A solder paste with a flux containing a (carboxyalkyl)isocyanurate adduct, which improves solder wettability, combined with a solder alloy composition of Sn, As, Sb, Bi, and Pb, satisfying specific ppm ranges and ratios, and optionally including rosin, acrylic resin, and other additives to enhance solder spreadability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fluxes are used for soldering, then soldering can be conducted, but the wet spreadability becomes inconsistent due to varying heat histories
Solution Approach 1:
The patent modifies the chemical composition parameters of the flux by incorporating specific carboxylic acid compounds (0.5-20% by mass), organic amine compounds (1-30% by mass), and their adducts in controlled ratios. This parameter optimization ensures stable solder wettability across different heat histories by balancing the reactivity and flow characteristics of the flux during soldering processes.
Solution Approach 2:
The patent creates a composite flux system combining multiple components: carboxylic acid compounds, organic amine compounds, their adducts, resins (rosin, acrylic resin), solvents, and other additives. This composite formulation synergistically improves solder spreadability consistency by combining the oxide-removing capability of carboxylic acids with the flow-enhancing properties of amines and the stability of resins.
2Reliability
If solder alloy composition is optimized for wettability, then solder spreadability improves, but the alloy constitution becomes more complex
Solution Approach 1:
The patent optimizes the concentration parameters of alloying elements within specific ranges: As (25-300 ppm), Sb (0-3000 ppm), Bi (0-10000 ppm), and Pb (0-5100 ppm). By controlling these parameters within defined boundaries, the patent achieves improved wettability while managing alloy complexity through quantitative rather than qualitative 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 solution provides a stable and improved solder spreadability regardless of heat history, ensuring consistent soldering performance by optimizing the flux and solder alloy composition.
Implementation Method 1
A flux to be used to conduct soldering generally has an ability to chemically remove metal oxides present on a soldering and a metal surface of an object to be soldered
Implementation Method 2
Therefore, soldering using a flux allows intermetallic compounds to be formed between the solder and the metal surface of the object to be soldered, thereby forming a strong junction
Data Source
AI summary
A solder paste contains a flux and a metal powder, wherein the flux contains: 0.5% by mass to 20.0% by mass of a (carboxyalkyl)isocyanurate adduct; 5.0% by mass to 45.0% by mass of a rosin; and a solvent. The (carboxyalkyl)isocyanurate adduct is at least one selected from the group consisting of mono(carboxyalkyl)isocyanurate adducts, bis(carboxyalkyl)isocyanurate adducts and tris(carboxyalkyl)isocyanurate adducts.