ISO Solder Alloy 123 (Pb95Sn5)
Solder alloy 123 is a lead-based soldering alloy. Cited properties are appropriate for the as-fabricated (no temper or treatment) condition. 123 is the ISO numeric designation for this material. Older literature may refer to this material as S-Pb95Sn5, but this is now discouraged.
It has a moderately low heat capacity among lead-based solder alloys. In addition, it has a fairly low electrical conductivity and a very high ductility.
The graph bars on the material properties cards below compare solder alloy 123 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
Brinell Hardness
8.0
Elastic (Young's, Tensile) Modulus
18 GPa 2.6 x 106 psi
Elongation at Break
45 %
Poisson's Ratio
0.44
Shear Modulus
6.2 GPa 0.91 x 106 psi
Tensile Strength: Ultimate (UTS)
28 MPa 4.0 x 103 psi
Thermal Properties
Latent Heat of Fusion
26 J/g
Melting Completion (Liquidus)
310 °C 600 °F
Melting Onset (Solidus)
300 °C 570 °F
Specific Heat Capacity
130 J/kg-K 0.032 BTU/lb-°F
Thermal Conductivity
23 W/m-K 13 BTU/h-ft-°F
Thermal Expansion
29 µm/m-K
Electrical Properties
Electrical Conductivity: Equal Volume
8.8 % IACS
Electrical Conductivity: Equal Weight (Specific)
7.1 % IACS
Otherwise Unclassified Properties
Base Metal Price
75 % relative
Density
11 g/cm3 690 lb/ft3
Embodied Carbon
4.5 kg CO2/kg material
Embodied Energy
74 MJ/kg 32 x 103 BTU/lb
Embodied Water
500 L/kg 59 gal/lb
Common Calculations
Stiffness to Weight: Axial
0.9 points
Stiffness to Weight: Bending
7.8 points
Strength to Weight: Axial
0.69 points
Strength to Weight: Bending
1.8 points
Thermal Diffusivity
16 mm2/s
Thermal Shock Resistance
3.8 points
Alloy Composition
| Pb | 93.5 to 95.5 | |
| Sn | 4.5 to 5.5 | |
| Sb | 0 to 0.5 | |
| 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 | |
| Cd | 0 to 0.0050 | |
| 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