Solder & Low-Melting Alloy Sn20Pb80
ASTM Sn20 · JIS H20A · GB HLSnPb20-80
Sn20Pb80 is a high-lead tin–lead solder (20% Sn, 80% Pb; H20A, HLSnPb20-80) with a wide 183–277 °C melting range and a high liquidus.
Reference datasheet — Sn20Pb80 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 Sn20Pb80?
Sn20Pb80 is a high-lead tin–lead solder (20% Sn, 80% Pb; H20A, HLSnPb20-80) with a wide 183–277 °C melting range and a high liquidus. It is used for step soldering and power-device die attach, where the first joint must stay solid through later lower-temperature reflow, and is stocked as bar, solid and cored wire, paste, preform and sphere. The alloy is soft and weak: 29 MPa tensile, 40% elongation, 11 HB. Lead content excludes it from RoHS-compliant assemblies except under exemption, and the long freezing range makes it poor for fine-pitch wave soldering; Sn10Pb90 offers a higher solidus. Sn20Pb80 has a density of 10.2 g/cm³ (0.368 lb/in³), heavier than 81% of solder & low-melting alloy grades. It melts at 183°C (361 °F). Sn20Pb80 has a yield strength of 16 MPa (2.32 ksi) and a tensile strength of 29 MPa (4.21 ksi) — weaker than 80% of solder & low-melting alloy grades. Elongation at break is 40% and the elastic modulus is 23 GPa (3.34 Msi).
What is Sn20Pb80 used for?
- step soldering
- die-attach in power devices
- high-temperature joint applications
Limitations
- Needs corrosion protection — 35/100, worse than 94% of solder & low-melting alloy grades
- Heavy — 10.2 g/cm³ (0.368 lb/in³), worse than 81% of solder & low-melting alloy grades
- Low strength — 16 MPa (2.32 ksi), worse than 80% of solder & low-melting alloy grades
- Low stiffness — 23 GPa (3.34 Msi), worse than 75% of solder & low-melting alloy grades
Sn20Pb80 properties
Typical room-temperature values; bars are the position among solder & low-melting alloy grades.
Physical3
Sn20Pb80 has a density of 10.2 g/cm³ (0.368 lb/in³), heavier than 81% of solder & low-melting alloy grades. It melts at 183°C (361 °F).
Mechanical10
Sn20Pb80 has a yield strength of 16 MPa (2.32 ksi) and a tensile strength of 29 MPa (4.21 ksi) — weaker than 80% of solder & low-melting alloy grades. Elongation at break is 40% and the elastic modulus is 23 GPa (3.34 Msi).
Thermal6
Sn20Pb80 is rated for continuous service to 120°C (248 °F). It conducts heat at 39 W/m·K (22.5 BTU/hr·ft·°F), worse than 59% of solder & low-melting alloy grades. Thermal expansion is 26.5 µm/m·K (14.7 µin/in·°F).
Electrical3
Sn20Pb80 conducts electricity at 10 % IACS, better than 54% of solder & low-melting alloy grades.
Chemical & Environmental3
Corrosion resistance is fair (35/100), worse than 94% of solder & low-melting alloy grades.
Sustainability4
Producing a kilogram of Sn20Pb80 takes about 70 MJ of energy and emits 4.8 kg of CO₂ — less than 74% of solder & low-melting alloy grades. Typical recycled content is 50%.
Manufacturability6
Sn20Pb80's machinability is poor (30/100, worse than 60% of solder & low-melting alloy grades); weldability poor (20/100); formability excellent (90/100).
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. Sn20Pb80 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Sn20Pb80
Is Sn20Pb80 easy to machine?
Extremely soft and gummy — use sharp high-rake tools, low speed and no dwell; usually cast, extruded or stamped rather than machined.
Can Sn20Pb80 be welded?
Not fusion welded; joints are made by soldering at 300–330 °C with active (rosin-activated or acid) flux because of the wide 183–277 °C pasty range.
Can Sn20Pb80 be formed, bent or molded?
Readily cast into bars/preforms and cold-extruded into wire; slow flow and long freezing range make it ideal for wiping but poor for fine-pitch wave soldering.
Sn20Pb80 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 |
|---|---|---|
| SnASTM B32 alloy Sn20 | 19.5 – 20.5 | 20 |
| Sbgrade A (≤0.12); grade B variants allow 0.20–0.50 Sb | ≤ 0.12 | 0.05 |
| Bi | ≤ 0.25 | |
| Cu | ≤ 0.08 | |
| Ag | ≤ 0.02 | |
| Fe | ≤ 0.02 | |
| Zn | ≤ 0.01 | |
| Al | ≤ 0.01 | |
| As | ≤ 0.03 | |
| Cd | ≤ 0 | |
| Pb | balance |
What surface finishes work on Sn20Pb80?
Surface dulls to grey oxide; clean flux residues after soldering; not anodizable and too soft for polishing or plating without an underlayer.
Equivalent designations
Standards and trade names that resolve to Solder & Low-Melting Alloy Sn20Pb80 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- Sn20
- GB (China)
- HLSnPb20-80
- JIS
- H20A
How much does Sn20Pb80 cost?
Sn20Pb80 is a high-cost solder & low-melting alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sn20Pb80 — frequently asked
What is Sn20Pb80 used for?
Sn20Pb80 is typically used for step soldering, die-attach in power devices and high-temperature joint applications. In short: high-temperature step solder; wide 183–277 °C pasty range; lead-bearing, non-RoHS.
What is the yield strength of Sn20Pb80?
Sn20Pb80 has a typical yield strength of 16 MPa (2.32 ksi) and a tensile strength of 29 MPa (4.21 ksi) — weaker than 80% of solder & low-melting alloy grades.
Is Sn20Pb80 easy to machine?
Not especially — machinability is rated poor (30/100, worse than 60% of solder & low-melting alloy grades). Extremely soft and gummy — use sharp high-rake tools, low speed and no dwell; usually cast, extruded or stamped rather than machined.
Can Sn20Pb80 be welded?
Not readily — weldability is rated poor (20/100). Not fusion welded; joints are made by soldering at 300–330 °C with active (rosin-activated or acid) flux because of the wide 183–277 °C pasty range.
What surface finishes work on Sn20Pb80?
Surface dulls to grey oxide; clean flux residues after soldering; not anodizable and too soft for polishing or plating without an underlayer.
Can Sn20Pb80 be formed, bent or molded?
Readily cast into bars/preforms and cold-extruded into wire; slow flow and long freezing range make it ideal for wiping but poor for fine-pitch wave soldering.
What is the maximum service temperature of Sn20Pb80?
Sn20Pb80 is rated for continuous use to about 120°C (248 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does Sn20Pb80 cost?
Sn20Pb80 is a high-cost solder & low-melting alloy ($$$$), 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
- ASTM B32 Standard Specification for Solder Metal — ASTM International (2020)
- GB/T 3131 (2020)
- ASM Handbook Vol.6 — Welding, Brazing and Soldering (Solder alloy properties) — ASM International (1993)
- ASM Handbook Vol.3 — Alloy Phase Diagrams (Pb-Sn) — ASM International (1992)
- Sn-Pb solder alloy datasheets (bar, wire, preform, paste) — AIM/Indium/Nihon Superior-type producer literature (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.