Immersion tin plating is a displacement reaction process where copper is dissolved during the deposition of tin, forming a tin layer directly on copper. This process creates a copper-tin intermetallic compound (IMC) that is crucial for soldering applications. Immersion tin layers are particularly attractive in the PCB market due to their robustness, long shelf life of at least 12 months, and absence of nickel, making them suitable for high-frequency applications. Additionally, immersion tin is more corrosion-resistant compared to other finishes, which is beneficial for automotive applications and offers a lower cost alternative to precious metal finishes.
Properties and Benefits of Stannatech 2100
The Stannatech 2100 immersion tin electrolyte introduces several enhancements over existing immersion tin solutions. Key benefits include:
- Reduced Viscosity: The new formulation significantly lowers the viscosity of the immersion tin solution, improving solution exchange and rinsing capabilities, especially in narrow features.
- Improved Soldering Performance: The Stannatech 2100 demonstrates better solder wetting characteristics, achieving lower spreading angles in solder spread tests compared to reference processes.
- Compatibility with Auxiliary Equipment: The process is designed to work seamlessly with existing auxiliary equipment, such as the constan and crystallizer, which help maintain consistent plating conditions and extend the bath life.
Typical Defects in Immersion Tin Plating
Despite its advantages, immersion tin plating can present certain risks and defects:
- Whisker Growth: Caused by the formation of intermetallics during aging, leading to stress and potential whisker formation.
- Copper Diffusion: The absence of a barrier layer allows copper to diffuse through the tin layer, limiting the shelf life of the finish.
- High Ionic Contamination: Poorly cured solder masks can absorb immersion tin chemistry, leading to high ionic contamination levels.
Key Improvements with Stannatech 2100
The Stannatech 2100 addresses several limitations of previous immersion tin processes:
- Enhanced Solution Exchange: The reduced viscosity allows for better solution exchange, preventing excessive copper dissolution and corrosion in narrow areas.
- Improved Rinsing: The lower viscosity facilitates easier rinsing, reducing drag-out of plating chemistry and minimizing ionic contamination.
- Lower Undercut Risk: The process shows a significant reduction in undercutting of solder masks, enhancing overall finish quality.
Soldering Performance Tests
Various soldering performance tests were conducted to evaluate the effectiveness of the Stannatech 2100:
- Solder Spread Test: Results indicated that the Stannatech 2100 achieved lower spreading angles, indicating better solder wetting compared to reference processes.
- Wetting Tests: The Stannatech 2100 consistently performed better in wetting tests, demonstrating superior solderability across different aging conditions.
- Dewetting Tests: The new process showed no failures in dewetting tests, indicating strong solder connections.
Root Causes of Soldering Defects
Common soldering defects associated with immersion tin can often be traced back to:
- Residues on Copper: Contaminants not removed before the tin plating can interfere with IMC growth and solder wetting.
- Inadequate Rinsing: Insufficient rinsing after the immersion tin process can leave residual chemistry that affects solderability.
- Volatile Contaminants: Volatiles from poorly cured solder masks can evaporate during reflow, leading to defects.
Post-Treatment Solutions
To further enhance the performance of immersion tin layers, several post-treatment solutions are available:
- Ionics 2100: Reduces ionic contamination, particularly important for automotive applications.
- Tin Post Treatment 8: Prevents yellowish discoloration of the immersion tin layer after reflow aging.
- Tin Post Treatment 2020: Strengthens the oxide layer, reducing the risk of dewetting defects.
Conclusion
The Stannatech 2100 immersion tin plating process represents a significant advancement in PCB manufacturing, addressing common challenges associated with traditional immersion tin methods. With its reduced viscosity, improved solderability, and compatibility with existing equipment, the Stannatech 2100 is poised to meet the evolving demands of the electronics industry, particularly in high-performance applications such as automotive and high-frequency devices.
As the industry continues to seek solutions that enhance reliability and performance, the Stannatech 2100 stands out as a promising option for next-generation immersion tin plating.
We at ESS ESS TRADING provide complete service and supply of chemicals in India . Contact us : Email: info@essesstrading.in Mobile: 9843019701
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