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
0.36
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
Density
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
| Sn | 95.9 to 97.5 | |
| Cu | 2.5 to 3.5 | |
| Bi | 0 to 0.1 | |
| Ag | 0 to 0.1 | |
| Sb | 0 to 0.1 | |
| In | 0 to 0.1 | |
| Pb | 0 to 0.070 | |
| Au | 0 to 0.050 | |
| As | 0 to 0.030 | |
| Fe | 0 to 0.020 | |
| Ni | 0 to 0.010 | |
| Cd | 0 to 0.0020 | |
| Al | 0 to 0.0010 | |
| 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