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3D Printing、MIM、HIP、Brazing、Spraying、Porous material、PM
CuSn3P7 copper–tin–phosphorus brazing alloy · Copper-based self-fluxing powder/paste
Low melting point · High wettability · Silver-free, environmentally friendly brazing -150 mesh · Powder/ointment form
Core Advantages of CuSn3P7 Brazing Alloy
Strong self-brazing capability
Phosphorus reduces oxide films during brazing, forming phosphate slag; therefore, copper and copper alloys typically do not require an additional flux.
Low melting point · Narrow melting range
Solidus temperature: 650°C; liquidus temperature: 690°C; melting range of only 40°C; excellent fluidity, reducing overheating and deformation of the base material.
High wettability · Dense weld seam
The addition of tin significantly enhances wetting and spreading on copper and brass, resulting in a dense, porosity-free brazed joint with high tensile strength.
Corrosion-resistant · Environmentally friendly and economical
The brazing alloy is resistant to moisture and weak acids and bases, contains no silver or cadmium, complies with RoHS, and has a lower cost than silver-based brazing alloys.
Product Real-World Photos & Microscopic Morphology
Powder SEM (-150 mesh)
Irregular/spherical particles with uniform particle size and good flowability.
Real-life photo of powdered brazing filler metal
Brown-gray powder, packaged in vacuum-sealed aluminum foil bags or plastic canisters.
Real-life photo of paste-type solder alloy
Syringe/plastic can packaging, ready-to-use, with adjustable viscosity.
CuSn3P7 copper-tin-phosphorus self-fluxing brazing filler metal
CuSn3P7 is a silver‑free copper‑based brazing alloy that, by incorporating 2–4% tin and 6–8% phosphorus, significantly lowers its melting point to 650–690°C and imparts self‑fluxing characteristics. It enables brazing of copper and copper alloys—such as red copper, brass, and bronze—with or even without flux, offering a broad process window, dense joints, and excellent corrosion resistance. Produced via vacuum atomization, the primary particle size specification is −150 mesh (≤106 μm), with outstanding flowability; it can be used directly in flame or induction brazing, or blended with organic carriers to form a paste suitable for automated dispensing and screen printing. Compared with high‑silver brazing alloys, CuSn3P7 reduces costs by more than 50% while delivering comparable brazing performance, making it an ideal choice for applications such as refrigeration piping, power busbars, and automotive heat exchangers.
Chemical Composition (wt%, Preferred Grade)
| Grade | Cu | Sn | P | Ni | Solidus (°C) | Liquidus temperature (°C) |
|---|---|---|---|---|---|---|
| qCuP-3 (Featured) |
Bal. | 2-4 | 6-8 | — | 650 | 690 |
| qCuP-4 | Bal. | 6.5-7.5 | 6.4-7.2 | — | 650 | 700 |
| qCuP-1 | Bal. | — | 7.5-8.1 | — | 710 | 770 |
| qCuP-6 | Bal. | 7-8 | 4.8-5.8 | 0.4-1.2 | 620 | 670 |
| qCuP-11 | Bal. | 15.1-16.1 | 4.7-5.7 | 3.8-4.8 | 585 | 605 |
* We primarily promote qCuP-3 (CuSn3P7); other grades are available upon request. Powder form: 150 mesh; particle size customization is also supported.
Solder Paste Specification (CuSn3P7)
| Grade | Alloy powder content (wt%) | Binder (wt%) | Solidus (°C) | Liquidus temperature (°C) | Recommended Process |
|---|---|---|---|---|---|
| CuSn3P7 solder paste | 80-90 | Margin | 650 | 690 | Automatic dispensing, screen printing, manual coating |
* Viscosity can be customized to suit the customer’s dispensing equipment (5,000–300,000 cP), with complete carrier evaporation and minimal residue.
Particle Size Specifications & Physical Properties (Powder Form)
| Particle size specification | Corresponding mesh count | D50 range (μm) | Loose packing density (g/cm³) | Tap density (g/cm³) | Flowability (s/50g) | Recommended Process |
|---|---|---|---|---|---|---|
| ★ -150 mesh | ≤106μm | 55-85 | ≥3.2 | ≥4.2 | ≤28 | Flame brazing, induction brazing, paste materials |
| -200 mesh | ≤75μm | 40-65 | ≥3.4 | ≥4.4 | ≤26 | Precision brazing, paste raw materials |
| -300 mesh | ≤48μm | 25-40 | ≥3.5 | ≥4.5 | ≤25 | Micro brazing, precision dispensing |
* -150 mesh is our standard specification; other particle sizes are available upon request. The powdered product can be blended with an organic carrier to produce solder paste.
CuSn3P7 Brazing Process Reference
| Base material combination | Recommended Brazing Temperature (°C) | Flux Usage | Joint characteristics |
|---|---|---|---|
| Red copper–red copper | 700-750 | Usually no flux is required (self-fluxing). | The brazed joint is dense, with a tensile strength of ≥180 MPa. |
| Red copper–brass | 720-780 | FB102 may be used in small quantities. | Good wetting, with a full brazing angle. |
| Brass - Brass | 740-800 | It is recommended to use FB102. | The brazed joint is bright and exhibits high strength. |
| Copper-steel | 760-820 | FB102/borax is required. | Good compatibility; suitable for non-pressure-bearing components. |
* Pure copper exhibits the best self‑brazing performance; for brass, it is recommended to use a small amount of flux. Induction brazing is best performed at higher temperatures, while flame brazing should be carried out with a neutral flame.
CuSn3P7 vs. conventional copper-phosphorus brazing alloys/silver brazing alloys
| Comparison item | CuSn3P7 | CuP14 (copper phosphide) | BAg silver brazing filler metal |
|---|---|---|---|
| Cost | Low | Extremely low | High |
| Brazing temperature (°C) | 690-900 | 850-900 | 700-800 |
| Self-brazing | Excellent | Excellent | None |
| Wettability (on brass) | Excellent (Sn improvement) | General | Excellent |
| Brazing seam toughness | Medium | Relatively brittle | Excellent |
CuSn3P7, while maintaining low cost and self‑brazing properties, significantly enhances wettability and brazed joint toughness through the addition of tin, making it a highly cost‑effective copper alloy brazing filler metal.
Typical application areas
Refrigeration equipment
Condenser, evaporator, copper piping for air conditioners/refrigerators, compressor fittings
Power and Electrical Engineering
Busbar, wire terminals, switch contacts, grounding terminals
Automobile manufacturing
Radiator, oil cooler, heater core, and pipe fittings
Plumbing hardware
Plumbing fittings, valves, copper fittings, and bathroom hardware
General Industry
Heat exchangers, copper components, and motor manufacturing
Electronics and electrical appliances
Conductive connections, relay contacts, busbars
Powdered brazing filler metal (-150 mesh)
- The powder can be applied directly, or pre‑formed solder tabs can be pressed on.
- It exhibits excellent fluidity, making it well-suited for automated powder feeding and flame brazing.
- It can be blended with other metal powders to formulate special compositions.
- Vacuum-packed for long-term storage without oxidation.
Paste-type brazing filler metal (ready-to-use)
- No on-site mixing of powder and adhesive is required; simply open the container and use.
- Excellent thixotropy, precise dispensing/printing, and no sagging.
- The carrier volatilizes completely, leaving minimal residue (a no‑clean formulation is available).
- Viscosity is adjustable, making it compatible with various dispensing equipment and manual coating processes.
End-to-end testing capability
Each batch of CuSn3P7 powder and solder paste is tested for chemical composition (Cu, Sn, P), particle size distribution, oxygen content, flowability, and tapped density, with a Certificate of Analysis (COA) provided.
Packaging & Delivery
Welding powder packaging
Double-layer aluminum foil bag or plastic canister, vacuum-sealed + iron drum/plastic drum
Specifications: 1 kg, 5 kg, 10 kg, 20 kg
Solder paste packaging
Syringe or plastic container
Store refrigerated; shelf life: 6 months.
Delivery time
In stock and ready to ship; dispatch within 2–5 days after order confirmation.
Customized paste—ships in 3–7 days.
Batch Traceability
Sample retained for each batch; COA report shipped with the goods.
Quality documents are available.
Free sample
Provide samples
For brazing process validation
Technical Support
Provide brazing temperature recommendations and technical guidance.
Inquire Now for Free Samples
Fill out the form on the right or contact us directly; we will provide product samples, technical data sheets, and price quotes to help you quickly complete your additive manufacturing process validation.
Address: No.39, Liandong Yougu lnd. Park, Bachelor Street,Changsha City,Hunan Province, China.
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Address: No.39, Liandong Yougu lnd. Park, Bachelor Street,Changsha City,Hunan Province, China.
