Solder & Low-Melting Alloy Bi58Sn42
ISO Solder Alloy 301
Bi58Sn42 is the bismuth-first designation for the eutectic bismuth-tin fusible alloy, melting at approximately 138 °C with a zero freezing range.
Reference datasheet — Bi58Sn42 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
What is Bi58Sn42?
Bi58Sn42 is the bismuth-first designation for the eutectic bismuth-tin fusible alloy, melting at approximately 138 °C with a zero freezing range. It is specified where lead-free joining or thermal actuation must happen at low temperature, and is available as bar, wire, cored wire, paste, preform, foil and powder. Properties are 65 MPa tensile, 42 MPa yield, 40% elongation and 22 HB with service to about 80 °C, and machinability rates only 30. It must never be combined with lead-bearing platings, which form a 96 °C eutectic; for lower melting points, Field's Metal is the nearest indium-bearing option. Bi58Sn42 has a density of 8.56 g/cm³ (0.309 lb/in³), heavier than 52% of solder & low-melting alloy grades. It melts at 138°C (280 °F). Bi58Sn42 has a yield strength of 42 MPa (6.09 ksi) and a tensile strength of 65 MPa (9.43 ksi) — stronger than 91% of solder & low-melting alloy grades. Elongation at break is 40% and the elastic modulus is 42 GPa (6.09 Msi).
What is Bi58Sn42 used for?
- low-temperature soldering
- thermal fuse links
- electronic component attachment
- sensor/thermal switch alloys
Advantages
- High strength — 42 MPa (6.09 ksi), better than 91% of solder & low-melting alloy grades
Limitations
- Poor heat conductor — 19 W/m·K (11 BTU/hr·ft·°F), worse than 92% of solder & low-melting alloy grades
- Low electrical conductivity — 5 % IACS, worse than 90% of solder & low-melting alloy grades
- Limited service temperature — 80°C (176 °F), worse than 88% of solder & low-melting alloy grades
- Limited formability — 60/100, worse than 78% of solder & low-melting alloy grades
Bi58Sn42 properties
Typical room-temperature values; bars are the position among solder & low-melting alloy grades.
Physical3
Bi58Sn42 has a density of 8.56 g/cm³ (0.309 lb/in³), heavier than 52% of solder & low-melting alloy grades. It melts at 138°C (280 °F).
Mechanical11
Bi58Sn42 has a yield strength of 42 MPa (6.09 ksi) and a tensile strength of 65 MPa (9.43 ksi) — stronger than 91% of solder & low-melting alloy grades. Elongation at break is 40% and the elastic modulus is 42 GPa (6.09 Msi).
Thermal6
Bi58Sn42 is rated for continuous service to 80°C (176 °F). It conducts heat at 19 W/m·K (11 BTU/hr·ft·°F), worse than 92% of solder & low-melting alloy grades. Thermal expansion is 15 µm/m·K (8.33 µin/in·°F).
Electrical3
Bi58Sn42 conducts electricity at 5 % IACS, worse than 90% of solder & low-melting alloy grades.
Chemical & Environmental3
Corrosion resistance is fair (50/100), better than 70% of solder & low-melting alloy grades.
Sustainability4
Producing a kilogram of Bi58Sn42 takes about 190 MJ of energy and emits 11 kg of CO₂ — more than 50% of solder & low-melting alloy grades. Typical recycled content is 25%.
Manufacturability7
Bi58Sn42's machinability is poor (30/100, worse than 60% of solder & low-melting alloy grades); weldability poor (20/100); formability good (60/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the solder & low-melting alloy family
Yield strength against density for every solder & low-melting alloy grade FabDigit runs. Bi58Sn42 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Bi58Sn42
Is Bi58Sn42 easy to machine?
Very soft with a low melting point, so chips smear and load the tool. Use sharp, high-rake tooling, low speeds and generous coolant; in practice parts are cast or stamped rather than conventionally machined.
Can Bi58Sn42 be welded?
This is a filler alloy, not a structural welding material. Joints are made by reflow, wave or iron soldering at peak temperatures of roughly 165–190 °C; never mix with lead-bearing coatings, which produce a 96 °C eutectic.
Can Bi58Sn42 be formed, bent or molded?
The eutectic composition flows well and freezes at a single temperature, so it casts to bar, extrudes to wire, rolls to foil and stamps into preforms easily. Room temperature is already a high homologous temperature, so work hardening is not retained.
Bi58Sn42 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Bieutectic composition 57.6 wt% Bi | 57 – 59 | 58 |
| PbPb-free impurity limit; with Pb forms 96 °C ternary eutectic | ≤ 0.1 | |
| Sbimpurity | ≤ 0.05 | |
| Cuimpurity | ≤ 0.05 | |
| Agimpurity | ≤ 0.05 | |
| Feimpurity | ≤ 0.02 | |
| Znimpurity, affects wetting | ≤ 0 | |
| Alimpurity, affects wetting | ≤ 0.01 | |
| Asimpurity | ≤ 0.03 | |
| CdRoHS restricted | ≤ 0 | |
| Snbalance, about 41–43 % | balance |
What surface finishes work on Bi58Sn42?
Remove flux residues with IPA or an aqueous wash; the alloy is not anodized or plated. Store under vacuum or nitrogen for long periods to limit oxidation — a matte grey joint appearance is normal.
Equivalent designations
Standards and trade names that resolve to Solder & Low-Melting Alloy Bi58Sn42 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ISO
- Solder Alloy 301
- Also called
- IEC B580
How much does Bi58Sn42 cost?
Bi58Sn42 is a high-cost solder & low-melting alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Bi58Sn42 — frequently asked
What is Bi58Sn42 used for?
Bi58Sn42 is typically used for low-temperature soldering, thermal fuse links, electronic component attachment and sensor/thermal switch alloys. In short: lead-free 138 °C eutectic; zero freezing range; fusible and solder duty.
What is the yield strength of Bi58Sn42?
Bi58Sn42 has a typical yield strength of 42 MPa (6.09 ksi) and a tensile strength of 65 MPa (9.43 ksi) — stronger than 91% of solder & low-melting alloy grades.
Is Bi58Sn42 easy to machine?
Not especially — machinability is rated poor (30/100, worse than 60% of solder & low-melting alloy grades). Very soft with a low melting point, so chips smear and load the tool. Use sharp, high-rake tooling, low speeds and generous coolant; in practice parts are cast or stamped rather than conventionally machined.
Can Bi58Sn42 be welded?
Not readily — weldability is rated poor (20/100). This is a filler alloy, not a structural welding material. Joints are made by reflow, wave or iron soldering at peak temperatures of roughly 165–190 °C; never mix with lead-bearing coatings, which produce a 96 °C eutectic.
What surface finishes work on Bi58Sn42?
Remove flux residues with IPA or an aqueous wash; the alloy is not anodized or plated. Store under vacuum or nitrogen for long periods to limit oxidation — a matte grey joint appearance is normal.
Can Bi58Sn42 be formed, bent or molded?
The eutectic composition flows well and freezes at a single temperature, so it casts to bar, extrudes to wire, rolls to foil and stamps into preforms easily. Room temperature is already a high homologous temperature, so work hardening is not retained.
What is the maximum service temperature of Bi58Sn42?
Bi58Sn42 is rated for continuous use to about 80°C (176 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does Bi58Sn42 cost?
Bi58Sn42 is a high-cost solder & low-melting alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- J-STD-006 Requirements for Electronic Grade Solder Alloys — IPC/JEDEC (2013)
- IEC 61190-1-3 Solder alloys for electronic soldering applications — IEC (2017)
- GB/T 20422 (2018)
- ASM Handbook Vol.3: Alloy Phase Diagrams (Bi-Sn) — ASM International (1992)
- NIST Properties of Lead-Free Solders Database — NIST (2002)
- Sn42/Bi58 Alloy Technical Data — Indium Corporation (2023)
- Low-Temperature Lead-Free Solder Alloy Data — AIM Solder (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.