Coumarin Solder Paste Composition for Low-Residue Stable Reflow
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Solution Overview
Problem
In reflow soldering, flux residues on electronic circuit boards degrade insulation reliability and can peel off, causing supply stability issues in solder pastes due to separation of coumarin and solder powder, leading to poor solder paste supply during the process.
Innovation Solution
A flux composition with coumarin, a monoamide-based thixotropic agent, and a solvent, where coumarin is between 10-40 wt% and the thixotropic agent is between 5-30 wt%, with a specific ratio of coumarin to thixotropic agent between 0.4 and 8.0, to prevent separation and reduce flux residues, is used in solder pastes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If coumarin is added to reduce flux residues, then flux residue is reduced, but separation between coumarin and solder powder occurs causing supply stability deterioration
Solution Approach 1:
A thixotropic agent is introduced as an intermediary substance between coumarin and solder powder. This mediator prevents direct separation by maintaining a stable dispersed state through thixotropic properties, allowing coumarin to remain effective at reducing flux residues while preventing phase separation that would compromise supply stability.
Solution Approach 2:
The patent optimizes the concentration parameters of both coumarin and thixotropic agent within specific ranges. By carefully controlling these compositional parameters, the system achieves the optimal balance between flux residue reduction and supply stability, preventing separation while maintaining effectiveness.
2Loss of substance
If coumarin content is increased to improve volatility and reduce residues, then flux residue decreases, but separation from solder powder increases causing supply properties to deteriorate
Solution Approach 1:
The thixotropic agent serves as a mediator that enables higher coumarin content to be incorporated without causing separation. It maintains the homogeneous distribution of coumarin throughout the solder paste, ensuring both high volatility for residue reduction and stable supply properties for ease of operation.
Solution Approach 2:
The patent creates a composite material system combining coumarin, thixotropic agent, and solder powder in specific proportions. This composite structure leverages the synergistic effects of its components to achieve both high coumarin content for residue reduction and stable supply properties, preventing the deterioration that would occur with simple mixtures.
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
This composition effectively suppresses separation and reduces flux residues, enhancing the stability and volatility of solder pastes, ensuring reliable solder paste supply and improved reflow soldering performance.
Implementation Method 1
The thixotropic agent imparts thixotropy to the flux and the solder paste
Implementation Method 2
Coumarin is a compound that is solid at normal temperature, but has high sublimability
Data Source
AI summary
A flux for soldering contains 10 to 40 wt % of coumarin, 5 to 30 wt % of a monoamide-based thixotropic agent and 40 to 80 wt % of a solvent. A solder paste contains the flux and a solder powder. A method for producing a soldered product includes supplying the solder paste to a soldering portion of an electronic circuit board, mounting an electronic component onto the soldering portion and heating the soldering portion up to a temperature at which the solder powder melts in a reducing atmosphere containing a reducing gas to join the electronic component and the electronic circuit board.