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ISO Solder Alloy 502 (IEC C40A10, Sn95Cu4Ag1)

Solder alloy 502 is a tin-based soldering alloy. Cited properties are appropriate for the as-fabricated (no temper or treatment) condition. C40A10 is the IEC 60672 type for this material. 502 is the ISO numeric designation. Older literature may refer to this material as S-Sn95Cu4Ag1, but this is now discouraged.

It has a moderately high heat capacity among tin-based solder alloys. In addition, it has a moderately high tensile strength and a moderately low thermal conductivity.

The graph bars on the material properties cards below compare solder alloy 502 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

53 GPa 7.7 x 106 psi

Elongation at Break

34 %

Poisson's Ratio


Shear Modulus

19 GPa 2.8 x 106 psi

Tensile Strength: Ultimate (UTS)

58 MPa 8.4 x 103 psi

Thermal Properties

Latent Heat of Fusion

66 J/g

Melting Completion (Liquidus)

350 °C 670 °F

Melting Onset (Solidus)

220 °C 420 °F

Specific Heat Capacity

230 J/kg-K 0.055 BTU/lb-°F

Thermal Conductivity

47 W/m-K 27 BTU/h-ft-°F

Thermal Expansion

22 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

12 % IACS

Electrical Conductivity: Equal Weight (Specific)

15 % IACS

Otherwise Unclassified Properties


7.4 g/cm3 460 lb/ft3

Embodied Carbon

15 kg CO2/kg material

Embodied Energy

260 MJ/kg 110 x 103 BTU/lb

Common Calculations

Stiffness to Weight: Axial

4.0 points

Stiffness to Weight: Bending

17 points

Strength to Weight: Axial

2.2 points

Strength to Weight: Bending

4.5 points

Thermal Diffusivity

28 mm2/s

Thermal Shock Resistance

3.6 points

Alloy Composition

Tin (Sn)Sn 93.8 to 95.7
Copper (Cu)Cu 3.5 to 4.5
Silver (Ag)Ag 0.8 to 1.2
Antimony (Sb)Sb 0 to 0.1
Indium (In)In 0 to 0.1
Bismuth (Bi)Bi 0 to 0.080
Lead (Pb)Pb 0 to 0.070
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

Similar Alloys

Further Reading

ISO 9453: Soft solder alloys - Chemical compositions and forms