ISO Solder Alloy 151 (Sn50Pb32Cd18)
Solder alloy 151 is a tin-based soldering alloy. Cited properties are appropriate for the as-fabricated (no temper or treatment) condition. 151 is the ISO numeric designation for this material. Older literature may refer to this material as S-Sn50Pb32Cd18, but this is now discouraged.
It has a moderately low electrical conductivity among tin-based solder alloys. In addition, it has the lowest melting temperature and a moderately low embodied energy.
The graph bars on the material properties cards below compare solder alloy 151 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
39 GPa 5.7 x 106 psi
Elongation at Break
37 %
Poisson's Ratio
0.37
Shear Modulus
14 GPa 2.1 x 106 psi
Tensile Strength: Ultimate (UTS)
46 MPa 6.7 x 103 psi
Thermal Properties
Latent Heat of Fusion
47 J/g
Melting Completion (Liquidus)
150 °C 290 °F
Melting Onset (Solidus)
150 °C 290 °F
Specific Heat Capacity
190 J/kg-K 0.046 BTU/lb-°F
Thermal Conductivity
44 W/m-K 25 BTU/h-ft-°F
Thermal Expansion
26 µm/m-K
Electrical Properties
Electrical Conductivity: Equal Volume
10 % IACS
Electrical Conductivity: Equal Weight (Specific)
10 % IACS
Otherwise Unclassified Properties
Density
8.8 g/cm3 550 lb/ft3
Embodied Carbon
9.2 kg CO2/kg material
Embodied Energy
160 MJ/kg 68 x 103 BTU/lb
Embodied Water
920 L/kg 110 gal/lb
Common Calculations
Stiffness to Weight: Axial
2.5 points
Stiffness to Weight: Bending
13 points
Strength to Weight: Axial
1.4 points
Strength to Weight: Bending
3.2 points
Thermal Diffusivity
26 mm2/s
Thermal Shock Resistance
3.2 points
Alloy Composition
| Sn | 49.5 to 50.5 | |
| Pb | 30.3 to 33 | |
| Cd | 17.5 to 18.5 | |
| Sb | 0 to 0.2 | |
| Bi | 0 to 0.1 | |
| Ag | 0 to 0.1 | |
| In | 0 to 0.1 | |
| Cu | 0 to 0.080 | |
| Au | 0 to 0.050 | |
| As | 0 to 0.030 | |
| Fe | 0 to 0.020 | |
| Ni | 0 to 0.010 | |
| 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