Immersion Tin PCB

What is Immersion Tin (ISn) Finish?

Immersion tin is a metallic coating plated onto copper via a chemical displacement reaction, forming a thin (0.8-1.5µm), uniform layer that prevents oxidation.

Key Features

✔ RoHS & lead-free compliant – Safe for modern electronics
✔ Super flat surface – Ideal for ultra-fine-pitch components
✔ Excellent solderability – Forms strong intermetallic bonds
✔ Economical alternative to ENIG – Lower cost with good performance
✔ Suitable for press-fit connectors – Better than ENIG for mechanical insertion

Best Applications

• Fine-pitch BGA & QFN components

• High-speed & RF/Microwave PCBs

• Automotive & consumer electronics

  
  

• Press-fit connector applications

Why Choose Immersion Tin PCB Finish?

✔ Superior flatness – More reliable than HASL for SMT assembly
✔ Great shelf life (~12 months) – Better than OSP with proper storage
✔ Lead-free & eco-friendly – No hazardous metals like lead or nickel
✔ Solder joint reliability – Stronger than ENIG for multiple reflows
✔ Lower cost than ENIG – Affordable high-performance finish

Limitations

• Not wire-bondable – ENIG/ENEPIG is better for IC packaging

• Requires dry storage – Moisture and sulfur exposure can degrade tin

• Thickness control critical – Too thin = poor protection; too thick = brittleness

How Immersion Tin PCB Coating Works

Step-by-Step Process

• Copper Cleaning – Alkaline wash removes oxides and contaminants

• Micro-Etching – Roughens copper for better adhesion

• Pre-Dip Treatment – Prevents oxidation before tin deposition

• Tin Plating – Chemical displacement deposits tin (0.8-1.5µm)

• Post-Treatment & Drying – Ensures uniform coating & stability

Critical Parameters

• Tin thickness (0.8-1.5µm) – Ensures durability without brittleness

• Storage conditions (dry, anti-tarnish packaging) – Extends shelf life

• Process control (pH, temperature) – Prevents tin whiskers

Immersion Tin vs ENIG, OSP, HASL

Best Uses for ISn

✓ High-frequency & RF PCBs – Low signal loss
✓ Fine-pitch/BGA components – Better than HASL
✓ Press-fit & mechanical connectors – More reliable than ENIG