Solder & Low-Melting Alloy Sn42Bi58
Sn42Bi58 is a eutectic tin-bismuth solder that melts at 138 °C, the low-temperature member of the tin-based solder family alongside SAC and Sn-Cu alloys.
Reference datasheet — Sn42Bi58 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 Sn42Bi58?
Sn42Bi58 is a eutectic tin-bismuth solder that melts at 138 °C, the low-temperature member of the tin-based solder family alongside SAC and Sn-Cu alloys. Engineers use it when reflow heat must stay well below conventional lead-free profiles, and it is stocked as bar, wire, paste, preform, sphere and foil. Mechanical values are modest (62 MPa tensile, 42 MPa yield, 30% elongation, 22 HB) and continuous service is limited to about 85 °C; the bismuth phase is brittle and contact with lead-bearing finishes forms a much lower-melting ternary. Where higher joint service temperature is required, SAC305 is the usual alternative. Sn42Bi58 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). Sn42Bi58 has a yield strength of 42 MPa (6.09 ksi) and a tensile strength of 62 MPa (8.99 ksi) — stronger than 91% of solder & low-melting alloy grades. Elongation at break is 30% and the elastic modulus is 42 GPa (6.09 Msi).
What is Sn42Bi58 used for?
- low-temperature reflow soldering
- heat-sensitive component assembly
- step soldering
- LED/flex circuit assembly
Advantages
- High strength — 42 MPa (6.09 ksi), better than 91% of solder & low-melting alloy grades
Limitations
- Low electrical conductivity — 4.6 % IACS, worse than 93% of solder & low-melting alloy grades
- Poor heat conductor — 19 W/m·K (11 BTU/hr·ft·°F), worse than 92% of solder & low-melting alloy grades
- Limited service temperature — 85°C (185 °F), worse than 86% of solder & low-melting alloy grades
- Limited formability — 35/100, worse than 85% of solder & low-melting alloy grades
Sn42Bi58 properties
Typical room-temperature values; bars are the position among solder & low-melting alloy grades.
Physical3
Sn42Bi58 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
Sn42Bi58 has a yield strength of 42 MPa (6.09 ksi) and a tensile strength of 62 MPa (8.99 ksi) — stronger than 91% of solder & low-melting alloy grades. Elongation at break is 30% and the elastic modulus is 42 GPa (6.09 Msi).
Thermal6
Sn42Bi58 is rated for continuous service to 85°C (185 °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
Sn42Bi58 conducts electricity at 4.6 % IACS, worse than 93% of solder & low-melting alloy grades.
Chemical & Environmental3
Corrosion resistance is fair (45/100), worse than 52% of solder & low-melting alloy grades.
Sustainability3
Producing a kilogram of Sn42Bi58 takes about 180 MJ of energy and emits 12 kg of CO₂ — less than 53% of solder & low-melting alloy grades. Typical recycled content is 25%.
Manufacturability7
Sn42Bi58's machinability is good (55/100, better than 74% of solder & low-melting alloy grades); weldability poor (20/100); formability fair (35/100).
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. Sn42Bi58 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Sn42Bi58
Is Sn42Bi58 easy to machine?
Very soft and gummy with a brittle Bi phase — use sharp, high-rake tools, light cuts and no coolant heating above 60 °C; usually cast or stamped instead of machined.
Can Sn42Bi58 be welded?
Not fusion welded; joints are made by remelting the solder itself (reflow, wave, iron or laser) at 165–200 °C.
Can Sn42Bi58 be formed, bent or molded?
Extrudes and rolls readily into wire, ribbon and preforms at room temperature, but limited ductility means severe bends can crack; atomizes cleanly to Type 3–5 powder for paste.
Sn42Bi58 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 – 58.5 | 58 |
| PbRoHS-grade limit; Pb forms 96 °C ternary eutectic | ≤ 0.1 | |
| Agimpurity | ≤ 0.05 | |
| Cuimpurity | ≤ 0.05 | |
| Sbimpurity | ≤ 0.1 | |
| Feimpurity | ≤ 0.02 | |
| Znimpurity | ≤ 0 | |
| Alimpurity | ≤ 0.01 | |
| Asimpurity | ≤ 0.03 | |
| CdRoHS limit | ≤ 0 | |
| Sn | ≥ 41.5 (balance) |
What surface finishes work on Sn42Bi58?
No plating or anodizing; clean flux residue with IPA or saponified wash and avoid contact with Pb- or Ag-rich finishes that depress the melting point.
Equivalent designations
Standards and trade names that resolve to Solder & Low-Melting Alloy Sn42Bi58 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Also called
- Bi58Sn42 Eutectic
How much does Sn42Bi58 cost?
Sn42Bi58 is a high-cost solder & low-melting alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sn42Bi58 — frequently asked
What is Sn42Bi58 used for?
Sn42Bi58 is typically used for low-temperature reflow soldering, heat-sensitive component assembly, step soldering and LED/flex circuit assembly. In short: 138 °C eutectic melt; lead-free low-temperature reflow; limits board and component heat.
What is the yield strength of Sn42Bi58?
Sn42Bi58 has a typical yield strength of 42 MPa (6.09 ksi) and a tensile strength of 62 MPa (8.99 ksi) — stronger than 91% of solder & low-melting alloy grades.
Is Sn42Bi58 easy to machine?
Reasonably — machinability is rated good (55/100, better than 74% of solder & low-melting alloy grades). Very soft and gummy with a brittle Bi phase — use sharp, high-rake tools, light cuts and no coolant heating above 60 °C; usually cast or stamped instead of machined.
Can Sn42Bi58 be welded?
Not readily — weldability is rated poor (20/100). Not fusion welded; joints are made by remelting the solder itself (reflow, wave, iron or laser) at 165–200 °C.
What surface finishes work on Sn42Bi58?
No plating or anodizing; clean flux residue with IPA or saponified wash and avoid contact with Pb- or Ag-rich finishes that depress the melting point.
Can Sn42Bi58 be formed, bent or molded?
Extrudes and rolls readily into wire, ribbon and preforms at room temperature, but limited ductility means severe bends can crack; atomizes cleanly to Type 3–5 powder for paste.
What is the maximum service temperature of Sn42Bi58?
Sn42Bi58 is rated for continuous use to about 85°C (185 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does Sn42Bi58 cost?
Sn42Bi58 is a high-cost solder & low-melting alloy ($$$$), 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)
- GB/T 20422 (2018)
- ASM Handbook Vol.3: Alloy Phase Diagrams (Bi-Sn system) — ASM International (1992)
- Properties of Lead-Free Solders / Solder Alloy Database — NIST (2002)
- Low-temperature Sn-Bi solder alloy and paste datasheets — Indium Corporation / AIM / (2023)
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.