Menu (ESC)

ISO Solder Alloy 402 (IEC C30, Sn97Cu3)

Solder alloy 402 is a tin-based soldering alloy. Cited properties are appropriate for the as-fabricated (no temper or treatment) condition. C30 is the IEC 60672 type for this material. 402 is the ISO numeric designation. Older literature may refer to this material as S-Sn97Cu3, but this is now discouraged.

It has a moderately high electrical conductivity among tin-based solder alloys. In addition, it has a moderately high melting temperature and a moderately high heat capacity.

The graph bars on the material properties cards below compare solder alloy 402 to: tin-based solder alloys (top), all alloys in the same category (middle), and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

Mechanical Properties

Elastic (Young's, Tensile) Modulus

52 GPa 7.5 x 106 psi

Elongation at Break

20 %

Poisson's Ratio


Shear Modulus

19 GPa 2.8 x 106 psi

Tensile Strength: Ultimate (UTS)

57 MPa 8.3 x 103 psi

Thermal Properties

Latent Heat of Fusion

64 J/g

Melting Completion (Liquidus)

310 °C 590 °F

Melting Onset (Solidus)

230 °C 440 °F

Specific Heat Capacity

230 J/kg-K 0.054 BTU/lb-°F

Thermal Conductivity

61 W/m-K 35 BTU/h-ft-°F

Thermal Expansion

22 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

15 % IACS

Electrical Conductivity: Equal Weight (Specific)

18 % IACS

Otherwise Unclassified Properties


7.3 g/cm3 460 lb/ft3

Embodied Carbon

15 kg CO2/kg material

Embodied Energy

250 MJ/kg 110 x 103 BTU/lb

Embodied Water

1180 L/kg 140 gal/lb

Common Calculations

Stiffness to Weight: Axial

3.9 points

Stiffness to Weight: Bending

17 points

Strength to Weight: Axial

2.2 points

Strength to Weight: Bending

4.5 points

Thermal Diffusivity

37 mm2/s

Thermal Shock Resistance

3.6 points

Alloy Composition

Tin (Sn)Sn 95.9 to 97.5
Copper (Cu)Cu 2.5 to 3.5
Bismuth (Bi)Bi 0 to 0.1
Silver (Ag)Ag 0 to 0.1
Antimony (Sb)Sb 0 to 0.1
Indium (In)In 0 to 0.1
Lead (Pb)Pb 0 to 0.070
Gold (Au)Au 0 to 0.050
Arsenic (As)As 0 to 0.030
Iron (Fe)Fe 0 to 0.020
Nickel (Ni)Ni 0 to 0.010
Cadmium (Cd)Cd 0 to 0.0020
Aluminum (Al)Al 0 to 0.0010
Zinc (Zn)Zn 0 to 0.0010

All values are % weight. Ranges represent what is permitted under applicable standards.

Followup Questions

Similar Alloys

Further Reading

ISO 9453: Soft solder alloys - Chemical compositions and forms