Solder & Low-Melting Alloy Sn97Cu3
Sn97Cu3 is a higher-copper lead-free tin-copper solder with an elevated melting range of about 230–250 °C, supplied as wire, cored wire, bar, preforms and powder.
Reference datasheet — Sn97Cu3 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 Sn97Cu3?
Sn97Cu3 is a higher-copper lead-free tin-copper solder with an elevated melting range of about 230–250 °C, supplied as wire, cored wire, bar, preforms and powder. The extra copper raises liquidus and joint strength above eutectic Sn99.3Cu0.7, giving 26 MPa yield, 35 MPa tensile, 35 % elongation, 15 HB and service to about 125 °C. It suits higher-temperature plumbing and industrial joints, but the 300–350 °C process window and wide pasty range make it unsuitable for reflow of heat-sensitive electronics — use Sn99.3Cu0.7 or SAC there. Sn97Cu3 has a density of 7.33 g/cm³ (0.265 lb/in³), lighter than 89% of solder & low-melting alloy grades. It melts at 227°C (441 °F). Sn97Cu3 has a yield strength of 25 MPa (3.63 ksi) and a tensile strength of 35 MPa (5.08 ksi) — weaker than 61% of solder & low-melting alloy grades. Elongation at break is 35% and the elastic modulus is 45 GPa (6.53 Msi).
What is Sn97Cu3 used for?
- High-temperature plumbing joints
- Industrial soldering requiring higher liquidus
- Copper tube and fitting joints in heated lines
- Stepped soldering as the first-stage alloy
- Torch and dip soldering of copper assemblies
- Powder for higher-melting solder pastes
Advantages
- Conducts heat well — 65 W/m·K (37.6 BTU/hr·ft·°F), better than 96% of solder & low-melting alloy grades
- High electrical conductivity — 13.5 % IACS, better than 92% of solder & low-melting alloy grades
- Lightweight — 7.33 g/cm³ (0.265 lb/in³), better than 89% of solder & low-melting alloy grades
- High service temperature — 125°C (257 °F), better than 80% of solder & low-melting alloy grades
Limitations
- High embodied carbon — 18 kg CO₂/kg, worse than 76% of solder & low-melting alloy grades
Sn97Cu3 properties
Typical room-temperature values; bars are the position among solder & low-melting alloy grades.
Physical3
Sn97Cu3 has a density of 7.33 g/cm³ (0.265 lb/in³), lighter than 89% of solder & low-melting alloy grades. It melts at 227°C (441 °F).
Mechanical10
Sn97Cu3 has a yield strength of 25 MPa (3.63 ksi) and a tensile strength of 35 MPa (5.08 ksi) — weaker than 61% of solder & low-melting alloy grades. Elongation at break is 35% and the elastic modulus is 45 GPa (6.53 Msi).
Thermal6
Sn97Cu3 is rated for continuous service to 125°C (257 °F). It conducts heat at 65 W/m·K (37.6 BTU/hr·ft·°F), better than 96% of solder & low-melting alloy grades. Thermal expansion is 23 µm/m·K (12.8 µin/in·°F).
Electrical3
Sn97Cu3 conducts electricity at 13.5 % IACS, better than 92% 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 Sn97Cu3 takes about 300 MJ of energy and emits 18 kg of CO₂ — more than 73% of solder & low-melting alloy grades. Typical recycled content is 30%.
Manufacturability6
Sn97Cu3'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. Sn97Cu3 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Sn97Cu3
Is Sn97Cu3 easy to machine?
Rarely machined; extremely soft and gummy — use very sharp high-rake tools, high speed, low feed and kerosene lubrication if trimming is required.
Can Sn97Cu3 be welded?
Used as a filler, not a base metal; joints are made with iron/flame/dip soldering at 300–350 °C with an active (ISO 9454 2.1.2 / rosin-activated) flux — do not attempt fusion welding.
Can Sn97Cu3 be formed, bent or molded?
Readily extruded and drawn to wire or rolled to foil at room temperature; cast bars solidify over a wide pasty range so avoid disturbing the joint until fully frozen.
Sn97Cu3 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 |
|---|---|---|
| Cuforms primary Cu6Sn5 above the 0.7 % eutectic | 2.5 – 3.5 | 3 |
| Pbimpurity limit (lead-free per RoHS ≤0.1 %) | ≤ 0.07 | |
| Sbimpurity limit | ≤ 0.05 | |
| Biimpurity limit | ≤ 0.1 | |
| Agimpurity limit | ≤ 0.1 | |
| Feimpurity limit | ≤ 0.02 | |
| Asimpurity limit | ≤ 0.03 | |
| Znimpurity limit, embrittles/degrades wetting | ≤ 0 | |
| Alimpurity limit | ≤ 0 | |
| Cdimpurity limit | ≤ 0 | |
| Snbalance, ~97 % | balance |
What surface finishes work on Sn97Cu3?
Joints can be brushed or wiped hot; flux residues must be washed off (water-soluble) or left only if genuinely no-clean; no anodizing, and plating over solder is not practical.
Equivalent designations
Standards and trade names that resolve to Solder & Low-Melting Alloy Sn97Cu3 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Also called
- IEC C30
How much does Sn97Cu3 cost?
Sn97Cu3 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.
Sn97Cu3 — frequently asked
What is Sn97Cu3 used for?
Sn97Cu3 is typically used for high-temperature plumbing joints, industrial soldering requiring higher liquidus, copper tube and fitting joints in heated lines, stepped soldering as the first-stage alloy, torch and dip soldering of copper assemblies and powder for higher-melting solder pastes. In short: higher liquidus than SnCu0.7; stronger lead-free Sn-Cu; step-soldering first stage.
What is the yield strength of Sn97Cu3?
Sn97Cu3 has a typical yield strength of 25 MPa (3.63 ksi) and a tensile strength of 35 MPa (5.08 ksi) — weaker than 61% of solder & low-melting alloy grades.
Is Sn97Cu3 easy to machine?
Not especially — machinability is rated poor (30/100, worse than 60% of solder & low-melting alloy grades). Rarely machined; extremely soft and gummy — use very sharp high-rake tools, high speed, low feed and kerosene lubrication if trimming is required.
Can Sn97Cu3 be welded?
Not readily — weldability is rated poor (20/100). Used as a filler, not a base metal; joints are made with iron/flame/dip soldering at 300–350 °C with an active (ISO 9454 2.1.2 / rosin-activated) flux — do not attempt fusion welding.
What surface finishes work on Sn97Cu3?
Joints can be brushed or wiped hot; flux residues must be washed off (water-soluble) or left only if genuinely no-clean; no anodizing, and plating over solder is not practical.
Can Sn97Cu3 be formed, bent or molded?
Readily extruded and drawn to wire or rolled to foil at room temperature; cast bars solidify over a wide pasty range so avoid disturbing the joint until fully frozen.
What is the maximum service temperature of Sn97Cu3?
Sn97Cu3 is rated for continuous use to about 125°C (257 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does Sn97Cu3 cost?
Sn97Cu3 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
- ISO 9453 — Soft solder alloys: chemical compositions and forms (alloy 402, Sn97Cu3) — ISO (2020)
- EN 29453 / DIN 1707 soft solder alloy tables (L-SnCu3) — CEN / DIN (1993)
- ASM Handbook Vol. 6 — Welding, Brazing and Soldering (solder alloy properties) — ASM International (1993)
- ASM Alloy Phase Diagrams — Sn-Cu system — ASM International (2016)
- Lead-free Sn-Cu solder wire and bar datasheets (Felder, AIM, Nihon Superior class products) — various producers (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.