Sn-Cu tin-copper solder alloys: Sn99.3Cu0.7 for electronics, Sn97Cu3 for plumbing
Eutectic Sn99.3Cu0.7 at 227 °C for electronics, Sn97Cu3 for copper pipes
Silver-free tin-copper alloys: Sn99.3Cu0.7 for electronics and electrical engineering, Sn97Cu3 for plumbing and heating. With nickel and germanium they become 99SnCuNiGe (SN100C equivalent).
Why Choose Sn-Cu Alloys
Economic advantages and performance for industrial applications
Sn-Cu Alloy Technical Specifications
Technical characteristics and performance for industrial applications
| Composition | Sn (%) | Cu (%) | Melting Point | Application |
|---|---|---|---|---|
| Sn99.3/Cu0.7 | 99.3 | 0.7 | 227°C | |
| Sn97/Cu3 | 97 | 3 | 227–310 °C |
Sn99.3Cu0.7 for electronics
Sn99.3Cu0.7 is the eutectic composition of the tin-copper system: it melts at 227 °C, about 7 °C above the SAC305 liquidus. It is the most economical lead-free alloy for wave solder pots and for tinning baths for terminals and conductors.
In solder baths the alloy dissolves the copper of pads and leads: the copper content rises, the liquidus increases and the alloy becomes less fluid. For this reason the bath must be analysed periodically. With small additions of nickel and germanium, as in 99SnCuNiGe, copper dissolution and dross formation are reduced.
Sn97Cu3 for plumbing and heating
Sn97Cu3 (EN ISO 9453 no. 402) is the lead-free alloy for capillary soldering of copper pipes in domestic water and heating systems. It has a wide melting range, from 227 to about 310 °C, and is used with a plumbing flux. For temperatures, standards and limits of use, see the page on plumbing and heating.
Available formats
| Alloy | Bars | Solid wire | Flux-cored wire |
|---|---|---|---|
| Sn99.3Cu0.7 | Yes (Dixtra Electronic) | Yes, 0.5–4 mm | Yes (Alfa C, Alfa E, Impetol B, Dixtra No Clean, AIM Glowcore) |
| Sn97Cu3 | — | Yes, 0.5–4 mm | Yes (Alfa C, Alfa E, Impetol B) |
Sn-Cu Application Sectors
Ideal applications for tin-copper alloys
General Electronics
Soldering of standard electronic components, PCBs, connectors. Ideal for high-volume production on a limited budget.
General Industry
Non-critical industrial applications, wiring, electrical components. Excellent value for money.
LED Lighting
Wave soldering of LED modules and drivers produced in high volumes.
Household Appliances
Electrical components for household appliances, controls, sensors. An economical solution for mass production.
Sn-Cu vs SAC: Cost Comparison
Cost and performance analysis for the optimal choice
| Characteristic | Sn-Cu | SAC 305 | Sn-Cu Advantage |
|---|---|---|---|
| Material Cost | Low | High | No silver in the alloy |
| Melting Point | 227°C | 217–220 °C | Eutectic, no melting range |
| Mechanical Strength | Good | Excellent | Adequate for general use |
| Electrical Conductivity | Equivalent | Equivalent | No practical difference |
| Thermal fatigue and creep resistance | Lower | Higher | Adequate for general use and normal temperatures |
Sn-Cu for general applications and high-volume production; SAC305 for SMT reflow and the most critical applications.
Frequently Asked Questions about Sn-Cu Alloys
Answers to the most common questions about tin-copper alloys
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