ISO Solder Alloy 401 (IEC C7, Sn99.3Cu0.7)
Solder alloy 401 is a tin-based soldering alloy. Cited properties are appropriate for the as-fabricated (no temper or treatment) condition. C7 is the IEC 60672 type for this material. 401 is the ISO numeric designation. Older literature may refer to this material as S-Sn99,3Cu0,7, but this is now discouraged.
It has a moderately low tensile strength among tin-based solder alloys. In addition, it has a moderately high melting temperature and a moderately high thermal conductivity.
The graph bars on the material properties cards below compare solder alloy 401 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
Brinell Hardness
9.0
Elastic (Young's, Tensile) Modulus
50 GPa 7.3 x 106 psi
Elongation at Break
21 %
Poisson's Ratio
0.36
Shear Modulus
19 GPa 2.7 x 106 psi
Tensile Strength: Ultimate (UTS)
29 MPa 4.3 x 103 psi
Thermal Properties
Latent Heat of Fusion
60 J/g
Melting Completion (Liquidus)
230 °C 440 °F
Melting Onset (Solidus)
230 °C 440 °F
Specific Heat Capacity
220 J/kg-K 0.053 BTU/lb-°F
Thermal Conductivity
66 W/m-K 38 BTU/h-ft-°F
Thermal Expansion
22 µm/m-K
Electrical Properties
Electrical Conductivity: Equal Volume
14 % IACS
Electrical Conductivity: Equal Weight (Specific)
17 % 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
1200 L/kg 140 gal/lb
Common Calculations
Stiffness to Weight: Axial
3.8 points
Stiffness to Weight: Bending
17 points
Strength to Weight: Axial
1.1 points
Strength to Weight: Bending
2.9 points
Thermal Diffusivity
40 mm2/s
Thermal Shock Resistance
1.9 points
Alloy Composition
| Sn | 98.5 to 99.5 | |
| Cu | 0.5 to 0.9 | |
| 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