Wave Soldering Additive Layer for Lead-Free Oxide Scavenging
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Solution Overview
Problem
Lead-free solder alloys require higher soldering temperatures than conventional lead-tin solders, which can damage components, and the accumulation of metal oxides in the solder bath leads to dross formation, affecting the purity and reliability of solder joints.
Innovation Solution
A stable liquid active additive layer with nucleophilic and/or electrophilic end groups, such as dimer acid, is maintained on the solder bath to scavenge and assimilate metal oxides, reducing the soldering temperature and minimizing dross formation, thereby improving the purity and viscosity of the solder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free solder alloys are used to eliminate hazardous lead, then environmental safety is improved, but soldering temperature must be increased above 260°C which can damage electronic components
Solution Approach 1:
An organic active additive layer is introduced as an intermediary substance between the solder bath and the environment. This layer scavenges metal oxides from the molten solder, preventing dross formation and improving wetting characteristics, thereby enabling reliable soldering at lower temperatures without lead
Solution Approach 2:
The chemical composition of the solder bath is modified by adding organic active additives that change the surface properties and oxide scavenging capabilities. This parameter change allows the solder to maintain reliability at reduced temperatures below 260°C
2Reliability
If soldering temperature is increased to 270-275°C for lead-free solder alloys, then soldering reliability is improved, but component damage risk increases
Solution Approach 1:
The organic active additive layer acts as a mediator that improves oxide removal from the solder surface, enhancing wetting and joint reliability without requiring temperature increases
Solution Approach 2:
The invention converts the harmful effect of metal oxides (which normally require high temperatures to overcome) into a benefit by using the organic additive to selectively scavenge and remove oxides, allowing low-temperature reliable soldering
3Object-generated harmful factors
If manual dross removal is performed from solder bath, then visible dross is eliminated, but solder metal is lost and production time is reduced
Solution Approach 1:
The organic active additive continuously scavenges metal oxides from the solder bath during operation, preventing dross accumulation without requiring shutdowns for manual removal, thereby maintaining continuous production
Solution Approach 2:
The solder bath self-cleans through the continuous action of the organic additive layer that automatically scavenges and removes metal oxides as they form, eliminating the need for manual intervention
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 allows for reliable solder joints to be formed at temperatures below 260°C with lead-free solder alloys, reducing dross formation and enhancing wetting capabilities, leading to improved soldering efficiency and joint quality.
Implementation Method 1
A liquid layer of active additive for scavenging and assimilating metal oxide is introduced onto a solder bath
Implementation Method 2
The active additive comprises a material that is stable at the temperature of the bath, effectively bars oxygen in air from reaching a quiescent surface of the bath, and has the ability to assimilate oxide of at least one metal in the bath
Implementation Method 3
The active additive comprises a material that has the ability to assimilate oxide of at least one metal in the bath
Data Source
AI summary
A process by which molten solder is purified in-situ, making the soldering process more efficient and yielding better results, particularly for lead-free soldering. Lead-free solder becomes practical for use since the temperature for reliable soldering is reduced. A layer of active additive is maintained on the surface of molten solder for scavenging metal oxide from the solder and assimilating metal oxide into a liquid layer. The active additive is an organic liquid having nucleophilic and/or electrophilic groups. As an example, a layer of dimer acid maintained on a wave soldering apparatus scavenges metal oxide from the bath, and assimilates dross that may form on the surface. Scavenging metal oxide cleanses the bath and lowers viscosity of the solder, and PC boards or the like soldered on the wave have reliable solder joints.