Solid-Solvent Solder Flux Composition for Low-Residue Processability
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Solution Overview
Problem
The flux used in resin flux cored solder tends to leave residue when heated, causing issues with the soldering process, as it is difficult to maintain fluidity and prevent carbonization, leading to narrowed passages in soldering irons and reduced processability.
Innovation Solution
Incorporating a solid solvent, such as neopentyl glycol or phenol-based solid solvents, which maintain viscosity and prevent volatilization at room temperature, while also acting as activators to remove metal oxides and reduce residue formation during soldering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If rosin is used as the base material of flux, then low residue is achieved, but the flux becomes hard to maintain fluidity and requires higher heating temperature
Solution Approach 1:
The patent modifies the chemical composition parameters of the flux by incorporating specific solid solvents (neopentyl glycol, phenol-based solid solvents) with controlled amounts (70-99.5 wt% solid solvent, 0.5-30 wt% activator). This parameter change allows the flux to maintain appropriate viscosity and fluidity at lower temperatures while still achieving low residue through controlled volatilization.
2Strength
If flux is contained in resin flux cored solder, then strong joint is obtained, but the flux may be adhered to soldering iron and cause burnt deposits
Solution Approach 1:
The patent converts the potential harm of flux residue into a benefit by selecting solid solvents that volatilize cleanly at soldering temperatures. The solid solvent components are chosen to evaporate completely or leave minimal residue, transforming what would be a harmful carbonizing substance into a beneficial volatile component that prevents burnt deposits while maintaining joint strength.
Solution Approach 2:
The flux composition is designed with solid solvents that are intended to be consumed (volatilized) during the soldering process. These components serve their purpose of removing oxides and facilitating bonding, then deliberately evaporate away, leaving minimal trace. This disposable nature of the flux components prevents long-term accumulation of harmful residues in the soldering iron.
3Productivity
If flux is heated to exceed melting point of solder, then soldering is achieved, but the flux residue becomes carbides and narrows passage
Solution Approach 1:
The patent addresses the carbonization problem by selecting solid solvent components that preferentially volatilize before carbonizing. The solid solvents (neopentyl glycol, phenol-based compounds) are chosen for their ability to evaporate cleanly at soldering temperatures, converting what would be carbon-forming material into beneficial vapor that exits through the soldering iron passage without narrowing it.
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 with solid solvents ensures effective removal of metal oxides and minimizes residue formation, maintaining processability and preventing clogging in soldering irons, even at elevated temperatures.
Implementation Method 1
the flux used in soldering generally has effects of chemically removing metal oxides present on solder and a metal surface of a joint target to be soldered
Implementation Method 2
they are volatile at a heat history estimated in the soldering and suppress carbonization by the successive heating
Implementation Method 3
The flux used in the resin flux cored solder is required to be a solid or a liquid but having high viscosity behavior on processability
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2D
AI summary
Provided are flux for resin flux cored solder, flux for flux-coated solder, resin flux cored solder using the flux for resin flux cored solder, flux-coated solder using the flux for flux-coated solder, and a soldering method, which have low residue and are excellent in processability. The flux for resin flux cored solder or flux-coated solder contains a solid solvent in an amount of 70 wt% or more and 99.5 wt% or less, and an activator in an amount of 0.5 wt% or more and 30 wt% or less. In addition, the flux contains a phenol-based solid solvent in an amount of 70 wt% or more and 100 wt% or less, and an activator in an amount of 0 wt% or more and 30 wt% or less. Additionally, the flux contains a phenol-based solid solvent in an amount of more than 0 wt% and 30 wt% or less, a solid solvent other than the phenol-based solid solvent in an amount of 70 wt% or more and 99.5 wt% or less, and an activator in an amount of 0 wt% or more and 30 wt% or less.