Solder & Low-Melting Alloy Sn99Cu0.7Ag0.3
Sn99Cu0.7Ag0.3 is a lead-free tin-copper solder with a 0.3 % silver microalloy addition, supplied as bar, solid and flux-cored wire, paste, powder, preforms and spheres.
Reference datasheet — Sn99Cu0.7Ag0.3 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 Sn99Cu0.7Ag0.3?
Sn99Cu0.7Ag0.3 is a lead-free tin-copper solder with a 0.3 % silver microalloy addition, supplied as bar, solid and flux-cored wire, paste, powder, preforms and spheres. The silver improves wetting and mechanical properties over plain Sn99.3Cu0.7 while keeping silver content low for cost control, giving 22 MPa yield, 35 MPa tensile, 40 % elongation, 13 HB and service to about 125 °C. It is aimed at wave soldering as a cheaper stand-in for SAC305, which still offers better joint strength and drop performance. Sn99Cu0.7Ag0.3 has a density of 7.37 g/cm³ (0.266 lb/in³), lighter than 78% of solder & low-melting alloy grades. It melts at 217°C (423 °F). Sn99Cu0.7Ag0.3 has a yield strength of 22 MPa (3.19 ksi) and a tensile strength of 35 MPa (5.08 ksi) — weaker than 70% of solder & low-melting alloy grades. Elongation at break is 40% and the elastic modulus is 47 GPa (6.82 Msi).
What is Sn99Cu0.7Ag0.3 used for?
- Lead-free wave soldering of PCB assemblies
- Cost-optimized SAC-alternative pot alloy
- Selective soldering of through-hole connectors
- Flux-cored wire for hand soldering and rework
- Solder paste for general reflow assembly
- Preforms and spheres for package attachment
Advantages
- Conducts heat well — 60 W/m·K (34.7 BTU/hr·ft·°F), better than 89% of solder & low-melting alloy grades
- High electrical conductivity — 12.5 % IACS, better than 82% of solder & low-melting alloy grades
- High service temperature — 125°C (257 °F), better than 80% of solder & low-melting alloy grades
- Lightweight — 7.37 g/cm³ (0.266 lb/in³), better than 78% of solder & low-melting alloy grades
- Stiff — 47 GPa (6.82 Msi), better than 77% of solder & low-melting alloy grades
Limitations
- Hard to polish — 20/100, worse than 88% of solder & low-melting alloy grades
- High embodied carbon — 19 kg CO₂/kg, worse than 83% of solder & low-melting alloy grades
Sn99Cu0.7Ag0.3 properties
Typical room-temperature values; bars are the position among solder & low-melting alloy grades.
Physical3
Sn99Cu0.7Ag0.3 has a density of 7.37 g/cm³ (0.266 lb/in³), lighter than 78% of solder & low-melting alloy grades. It melts at 217°C (423 °F).
Mechanical11
Sn99Cu0.7Ag0.3 has a yield strength of 22 MPa (3.19 ksi) and a tensile strength of 35 MPa (5.08 ksi) — weaker than 70% of solder & low-melting alloy grades. Elongation at break is 40% and the elastic modulus is 47 GPa (6.82 Msi).
Thermal6
Sn99Cu0.7Ag0.3 is rated for continuous service to 125°C (257 °F). It conducts heat at 60 W/m·K (34.7 BTU/hr·ft·°F), better than 89% of solder & low-melting alloy grades. Thermal expansion is 22.5 µm/m·K (12.5 µin/in·°F).
Electrical3
Sn99Cu0.7Ag0.3 conducts electricity at 12.5 % IACS, better than 82% of solder & low-melting alloy grades.
Chemical & Environmental3
Corrosion resistance is fair (45/100), worse than 52% of solder & low-melting alloy grades.
Sustainability4
Producing a kilogram of Sn99Cu0.7Ag0.3 takes about 340 MJ of energy and emits 19 kg of CO₂ — more than 89% of solder & low-melting alloy grades. Typical recycled content is 30%.
Manufacturability6
Sn99Cu0.7Ag0.3's machinability is poor (25/100, worse than 82% of solder & low-melting alloy grades); formability excellent (85/100).
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. Sn99Cu0.7Ag0.3 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Sn99Cu0.7Ag0.3
Is Sn99Cu0.7Ag0.3 easy to machine?
Rarely machined — extremely soft and gummy; use sharp high-rake tools, kerosene lubricant, and expect smearing rather than chips.
Can Sn99Cu0.7Ag0.3 be welded?
Not weldable in the structural sense; it is itself the filler — joints are made by wave, reflow or iron soldering at 240–265 °C peak.
Can Sn99Cu0.7Ag0.3 be formed, bent or molded?
Cast to bar, extruded/drawn to wire and rolled to ribbon or preforms at room temperature; gas atomization gives Type 3–6 powder for paste.
Sn99Cu0.7Ag0.3 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 |
|---|---|---|
| Aglow-Ag addition to refine microstructure and improve wetting | 0.2 – 0.4 | 0.3 |
| Cunear Sn-Cu eutectic level; limits Cu dissolution | 0.6 – 0.8 | 0.7 |
| PbRoHS impurity limit (J-STD-006 / ISO 9453) | ≤ 0.07 | |
| Sbimpurity | ≤ 0.05 | |
| Biimpurity | ≤ 0.05 | |
| Feimpurity | ≤ 0.02 | |
| Znimpurity — degrades wetting | ≤ 0 | |
| Alimpurity — causes grittiness/dross | ≤ 0 | |
| Cdimpurity | ≤ 0 | |
| Asimpurity | ≤ 0.03 | |
| Sn | balance |
What surface finishes work on Sn99Cu0.7Ag0.3?
No plating or anodizing; keep joints clean of halide residues, and expect natural tarnish/oxide — conformal coating is used where dendrite growth is a risk.
Equivalent designations
Standards and trade names that resolve to Solder & Low-Melting Alloy Sn99Cu0.7Ag0.3 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Also called
- IEC C7A3
How much does Sn99Cu0.7Ag0.3 cost?
Sn99Cu0.7Ag0.3 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.
Sn99Cu0.7Ag0.3 — frequently asked
What is Sn99Cu0.7Ag0.3 used for?
Sn99Cu0.7Ag0.3 is typically used for lead-free wave soldering of PCB assemblies, cost-optimized SAC-alternative pot alloy, selective soldering of through-hole connectors, flux-cored wire for hand soldering and rework, solder paste for general reflow assembly and preforms and spheres for package attachment. In short: low-silver SAC alternative; better wetting than SnCu0.7; cost-controlled wave alloy.
What is the yield strength of Sn99Cu0.7Ag0.3?
Sn99Cu0.7Ag0.3 has a typical yield strength of 22 MPa (3.19 ksi) and a tensile strength of 35 MPa (5.08 ksi) — weaker than 70% of solder & low-melting alloy grades.
Is Sn99Cu0.7Ag0.3 easy to machine?
Not especially — machinability is rated poor (25/100, worse than 82% of solder & low-melting alloy grades). Rarely machined — extremely soft and gummy; use sharp high-rake tools, kerosene lubricant, and expect smearing rather than chips.
Can Sn99Cu0.7Ag0.3 be welded?
Not weldable in the structural sense; it is itself the filler — joints are made by wave, reflow or iron soldering at 240–265 °C peak.
What surface finishes work on Sn99Cu0.7Ag0.3?
No plating or anodizing; keep joints clean of halide residues, and expect natural tarnish/oxide — conformal coating is used where dendrite growth is a risk.
Can Sn99Cu0.7Ag0.3 be formed, bent or molded?
Cast to bar, extruded/drawn to wire and rolled to ribbon or preforms at room temperature; gas atomization gives Type 3–6 powder for paste.
What is the maximum service temperature of Sn99Cu0.7Ag0.3?
Sn99Cu0.7Ag0.3 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 Sn99Cu0.7Ag0.3 cost?
Sn99Cu0.7Ag0.3 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 — ISO (2020)
- J-STD-006 Requirements for Electronic Grade Solder Alloys and Fluxed/Non-Fluxed Solid Solders — IPC/JEDEC (2013)
- GB/T 20422 (2018)
- Properties of Lead-Free Solders / Solder Alloy Property Database — NIST (2002)
- Low-silver SAC0307 alloy technical data (bar, wire, paste) — Indium Corporation / Alpha Assembly / AIM Solder (2023)
- ASM Handbook Vol. 6 — Welding, Brazing and Soldering (soldering section) — ASM International (1993)
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.