Tin (Sn)
Tin is a soft, silvery metal primarily used for corrosion-resistant coatings (tinplate), solder alloys, and as an alloying element in bronze and bearing metals. Its non-toxicity makes it the preferred food-safe coating material, while its low melting point and excellent wetting properties make it indispensable in electronics soldering.
Properties
- Density
- 7,265 kg/m³
- Melting Point
- 232 °C
- Boiling Point
- 2,602 °C
- Thermal Conductivity
- 66.8 W/(m·K)
- Electrical Resistivity
- 1.09 × 10⁻⁷ Ω·m
- Tensile Strength
- 15–45 MPa
- Yield Strength
- 8–30 MPa
- Hardness
- 3–5 HB
- Elongation
- 40–80%
- Crystal Structure
- BCT (β-tin)
Common Grades
- Sn 99.9%: High-purity tin. Tinplate production, chemical applications, food-grade coatings.
- SAC305 (Sn96.5Ag3Cu0.5): Lead-free solder standard for electronics. RoHS-compliant, dominant in PCB assembly.
- Sn63Pb37: Traditional eutectic solder (183°C melting). Still used in aerospace and military electronics.
- Babbitt (Sn-Sb-Cu): Tin-based bearing alloy. Crankshaft bearings, turbine bearings, heavy machinery.
Applications
- Electronics: Lead-free solder paste, wave soldering, component tinning, tin whisker mitigation
- Packaging: Tinplate for food cans, beverage cans, aerosol containers, decorative tins
- Bearings: Babbitt metal bearings, thrust washers, engine main bearings
- Chemical: Organotin stabilizers for PVC, tin oxide for glass coatings, catalyst applications
FAQ
What is RoHS lead-free solder?
RoHS (Restriction of Hazardous Substances) mandates lead-free solder in consumer electronics. SAC305 (96.5% Sn, 3% Ag, 0.5% Cu) is the dominant replacement, melting at 217–220°C versus 183°C for traditional Sn63Pb37. It requires higher soldering temperatures and modified flux chemistry.
What is tin pest?
Tin pest is an allotropic transformation where β-tin (metallic) converts to α-tin (grey, powdery) below 13.2°C. This can cause tin coatings and solder joints to crumble in extreme cold. Modern tin alloys with bismuth or antimony additions suppress this transformation.
Why is tin used for food can coating?
Tin is non-toxic, tasteless, and forms an excellent barrier against food acids and corrosion. Tinplate (steel coated with 1–2.5 μm of tin by electrolysis) is food-safe per EU Regulation 1935/2004. Tin's cathodic protection of steel in acidic food environments (opposite to zinc/iron behavior in alkaline conditions) prevents iron contamination of foods.