Reduction-Gas Solder Paste With Low Flux Residue
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Solution Overview
Problem
Conventional solder pastes containing reducing agents and activators result in excessive flux residues, increasing environmental load and cost, and some products cannot be washed effectively due to these residues.
Innovation Solution
A solder paste composed of solder powder, a thixotropic agent, and a solvent, without reducing agents or activators, is used in conjunction with a reducing gas to achieve solder bonding, ensuring good wettability and minimizing flux residues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solder paste containing reducing agents and activators is used, then soldering properties improve, but flux residues increase causing corrosion and ion migration
Solution Approach 1:
The invention extracts and removes the reducing agents and activators from the solder paste formulation. By eliminating these problematic components, the patent achieves soldering without the harmful flux residues they typically produce, thereby resolving the contradiction between good soldering properties and reduced corrosion/migration risks.
Solution Approach 2:
The invention creates an inert atmosphere by replacing the chemical reducing agents with a physical reducing environment. The solder paste is applied in a state that prevents oxidation, and the soldering process occurs in a controlled atmosphere that avoids oxide formation without requiring aggressive chemical reducing agents, thus eliminating harmful residues.
2Object-generated harmful factors
If flux residues are washed away with washing liquid, then corrosion and migration are reduced, but environmental load and cost increase
Solution Approach 1:
The invention extracts the source of the problem by removing reducing agents and activators from the solder paste. This eliminates the generation of washable flux residues in the first place, making the washing step unnecessary and thereby eliminating the environmental load and costs associated with washing liquids and processing.
Solution Approach 2:
The solder paste is designed to be self-sufficient without requiring post-soldering washing. By formulating the paste without components that leave harmful residues, the process becomes self-cleaning, eliminating the need for additional washing steps and their associated environmental and economic costs.
3Object-generated harmful factors
If a solder paste free of reducing agents and activators is used, then flux residues are reduced, but solder wettability may be insufficient
Solution Approach 1:
The invention uses an inert atmosphere approach where the solder paste is protected from oxidation through physical means rather than chemical reducing agents. The controlled atmosphere during application and soldering prevents oxide formation, maintaining surface cleanliness and wettability without requiring activators that would leave residues.
Solution Approach 2:
The invention changes the physical and chemical parameters of the solder paste formulation by removing reducing agents and activators. By adjusting the composition to exclude these components while maintaining appropriate viscosity and flow characteristics, the paste achieves good wettability through controlled application and soldering parameters rather than chemical enhancement.
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 reduces flux residues, eliminates the need for washing, and enhances soldering quality by ensuring effective penetration of the reducing gas, thereby improving solder bonding and reducing reliability issues associated with active flux components.
Implementation Method 1
The reducing agent has a role of removing oxide films on surfaces of soldering targets and the solder powder during soldering
Implementation Method 2
a solder paste contains a solder powder and a flux
Data Source
Figure 1A~1B4
Figure 2
Figure 3
AI summary
The present invention is a solder paste that contains no reducing agents or activators, and a method for producing a soldered product for completing solder joints using the solder paste. This solder paste for a reduction gas is used together with a reducing gas, wherein: the solder paste contains a solder powder, a thixotropic agent that is solid at normal temperature, and a solvent; and contains no reducing agents for removing oxidized films or activators for improving reduction properties.