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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


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


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

Tin (Sn)Sn 49.5 to 50.5
Lead (Pb)Pb 30.3 to 33
Cadmium (Cd)Cd 17.5 to 18.5
Antimony (Sb)Sb 0 to 0.2
Bismuth (Bi)Bi 0 to 0.1
Silver (Ag)Ag 0 to 0.1
Indium (In)In 0 to 0.1
Copper (Cu)Cu 0 to 0.080
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
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