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ISO Solder Alloy 137 (Pb78Sn20Sb2)

Solder alloy 137 is a lead-based soldering alloy. Cited properties are appropriate for the as-fabricated (no temper or treatment) condition. 137 is the ISO numeric designation for this material. Older literature may refer to this material as S-Pb78Sn20Sb2, but this is now discouraged.

It has a fairly low ductility and a moderately low electrical conductivity among lead-based solder alloys.

The graph bars on the material properties cards below compare solder alloy 137 to: lead-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

24 GPa 3.4 x 10⁶ psi

Elongation at Break

19 %

Poisson's Ratio

0.42

Shear Modulus

8.3 GPa 1.2 x 10⁶ psi

Tensile Strength: Ultimate (UTS)

34 MPa 4.9 x 10³ psi

Thermal Properties

Latent Heat of Fusion

33 J/g

Melting Completion (Liquidus)

270 °C 520 °F

Melting Onset (Solidus)

190 °C 370 °F

Specific Heat Capacity

150 J/kg-K 0.035 BTU/lb-°F

Thermal Conductivity

38 W/m-K 22 BTU/h-ft-°F

Thermal Expansion

27 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

8.9 % IACS

Electrical Conductivity: Equal Weight (Specific)

7.7 % IACS

Otherwise Unclassified Properties

Base Metal Price

85 % relative

Density

10 g/cm³ 650 lb/ft³

Embodied Carbon

6.3 kg CO₂/kg material

Embodied Energy

100 MJ/kg 45 x 10³ BTU/lb

Embodied Water

660 L/kg 79 gal/lb

Common Calculations

Stiffness to Weight: Axial

1.3 points

Stiffness to Weight: Bending

9.2 points

Strength to Weight: Axial

0.9 points

Strength to Weight: Bending

2.2 points

Thermal Diffusivity

25 mm²/s

Thermal Shock Resistance

3.7 points

Alloy Composition

Lead (Pb)Pb		75.9 to 80
Tin (Sn)Sn		19.5 to 20.5
Antimony (Sb)Sb		0.5 to 3.0
Bismuth (Bi)Bi		0 to 0.25
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
Cadmium (Cd)Cd		0 to 0.0050
Aluminum (Al)Al		0 to 0.0010
Zinc (Zn)Zn		0 to 0.0010