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ISO Solder Alloy 301 (IEC B580, Bi58Sn42)

Solder alloy 301 is an alloy that does not fit into any substantial classification group in the database. Cited properties are appropriate for the as-fabricated (no temper or treatment) condition. B580 is the IEC 60672 type for this material. 301 is the ISO numeric designation. Older literature may refer to this material as S-Bi58Sn42, but this is now discouraged.

It has a moderately low melting temperature among alloys in the same category. In addition, it has a moderately high ductility and a moderately low heat capacity.

The graph bars on the material properties cards below compare solder alloy 301 to: minor element 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


Elastic (Young's, Tensile) Modulus

40 GPa 5.7 x 106 psi

Elongation at Break

51 %

Poisson's Ratio


Shear Modulus

15 GPa 2.1 x 106 psi

Tensile Strength: Ultimate (UTS)

55 MPa 8.0 x 103 psi

Tensile Strength: Yield (Proof)

49 MPa 7.1 x 103 psi

Thermal Properties

Latent Heat of Fusion

55 J/g

Melting Completion (Liquidus)

140 °C 280 °F

Melting Onset (Solidus)

140 °C 280 °F

Specific Heat Capacity

160 J/kg-K 0.039 BTU/lb-°F

Thermal Conductivity

19 W/m-K 11 BTU/h-ft-°F

Thermal Expansion

14 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

4.7 % IACS

Electrical Conductivity: Equal Weight (Specific)

4.9 % IACS

Otherwise Unclassified Properties


8.7 g/cm3 550 lb/ft3

Embodied Carbon

13 kg CO2/kg material

Embodied Energy

210 MJ/kg 89 x 103 BTU/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

27 MJ/m3

Resilience: Unit (Modulus of Resilience)

30 kJ/m3

Stiffness to Weight: Axial

2.5 points

Stiffness to Weight: Bending

13 points

Strength to Weight: Axial

1.8 points

Strength to Weight: Bending

3.7 points

Thermal Diffusivity

13 mm2/s

Thermal Shock Resistance

7.2 points

Alloy Composition

Bismuth (Bi)Bi 56.5 to 59
Tin (Sn)Sn 41 to 43
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
Copper (Cu)Cu 0 to 0.050
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

Further Reading

ISO 9453: Soft solder alloys - Chemical compositions and forms