Grade A Tin refers to ultra-high-purity refined tin with a minimum purity of 99.99% Sn. It represents one of the highest commercial purity levels available and is used where chemical cleanliness, electrical reliability, and metallurgical consistency are critical.
General Information
| Property | Value |
|---|---|
| Purity | ≥ 99.99% Sn |
| Allotropic Form | β-Tin (White Tin) |
| Crystal Structure | Body-Centered Tetragonal (BCT) |
| Mechanical Strength | Very low |
Applicable Standards
| Standard | Designation |
|---|---|
| ASTM | B339 |
| ISO | 21948 |
| EN | 610 |
| JIS | H2108 |
Strengthening & Metallurgical Behavior
Grade A Tin is not heat treatable. Strengthening mechanisms are limited to minor work hardening and grain size control, both of which have limited practical effect due to the soft nature of pure tin.
Higher purity improves chemical stability but also increases susceptibility to tin whisker formation in coatings and creep deformation under sustained load.
Key Characteristics
✔ Ultra-high chemical purity
✔ Excellent wetting and solderability
✔ Non-toxic and RoHS compliant
✔ Highly corrosion resistant
✔ Stable SnO₂ passive oxide layer
❌ Very low mechanical strength
❌ Poor high-temperature stability
Refining & Processing Properties
Grade A Tin is produced through a controlled refining sequence involving primary smelting, fire refining, and electrolytic refining. Electrolytic refining is essential to reach the 99.99% purity level.
| Processing Aspect | Behavior |
|---|---|
| Castability | Excellent |
| Rolling / Forming | Excellent |
| Machinability | Poor (too soft) |
| Solder Compatibility | Excellent |
Available Forms
Tin ingots (bars, pigs)
Granules / shots
Tin wire
Tin foil and sheets
Electroplating anodes
High-purity tin powder
Applications of Grade A Tin
Electronics & Electrical
High-reliability solders
Semiconductor packaging
Capacitor electrodes
Tin electroplating anodes
Chemical & Laboratory
Reference materials
Analytical calibration standards
Chemical synthesis
Food & Pharmaceutical
Food-grade tin coatings
Pharmaceutical containers
Advanced Materials
Alloy master material
Research & metallurgy studies
Emerging battery and energy systems
Advantages
✔ Maximum chemical purity
✔ Superior solder joint reliability
✔ Excellent corrosion resistance
✔ Full regulatory compliance (RoHS, REACH)
✔ Predictable metallurgical behavior
Limitations
❌ Not suitable for structural applications
❌ Tin whisker risk in pure tin coatings
❌ Low creep resistance
❌ Higher cost than lower purity grades
Grade A Tin vs Lower Grades
| Feature | Grade A (99.99%) | Commercial Tin (99.8–99.9%) |
|---|---|---|
| Purity | Ultra-high | High |
| Electrical Reliability | Excellent | Good |
| Whisker Risk | Higher | Lower |
| Cost | Higher | Lower |
| Precision Use | Critical | General |
Why Choose Grade A Tin?
Choose Grade A Tin when purity is non-negotiable, electronics reliability is critical, impurity-driven failures must be avoided, and regulatory compliance is mandatory.
Engineering Insight:
Grade A Tin is selected for consistency and cleanliness—not for strength.