Phosphor Bronze Springs
Coiling Technologies manufactures phosphor bronze springs, including phosphor bronze compression springs for many applications. Phosphor Bronzes contain copper, tin and phosphorous. The addition of tin increases the corrosion resistance and strength of the alloy. The phosphorous increases the wear resistance and stiffness of the alloy. Leaded phosphor bronze combines good strength and fatigue resistance with good machinability.
| Technical Specification | Phosphor Bronze |
|---|---|
| Nominal Composition |
Sn: 4.5 - 5.5 P: 0.02 - 0.40 Cu: Balance |
| Density |
0.320 lb./in3 |
| Modulus of Elasticity (E) |
15x 106 psi |
| Modulus of Rigidity (G) |
6.3 x 106 psi |
| Coefficient of Expansion |
9 µin/in.-°F (200°F) |
| Electrical Resistivity |
5.2 µΩ.in |
| Thermal Conductivity |
68 Btu/(hr/ft2/in/°F) |
| Min Size |
.003 in (0.080 mm) |
| Max Size |
2.5 in |
| Max Temp |
95oC (200oF) |
| Uses of Phosphor Bronze Springs |
They are widely used in spring washers as it has high wear resistance and corrosion resistance |
Phosphor Bronze Springs FAQs
What is phosphor bronze and what makes it suitable for spring applications?
Phosphor bronze (C51000 and related alloys) is a copper-tin-phosphorus alloy in which tin provides strength and corrosion resistance, and phosphorus serves as a deoxidizing agent while also improving springiness and wear resistance. The alloy's combination of moderate-to-high strength, excellent resistance to corrosion in saltwater and many industrial atmospheres, good electrical conductivity, non-magnetic behavior, and excellent cold-working characteristics makes it well suited for springs in electrical, marine, and industrial applications where both conductivity and corrosion resistance are simultaneously required.
How does phosphor bronze compare to beryllium copper for electrical spring contacts?
Both are used for electrical spring contacts, but they serve different performance tiers. Phosphor bronze C51000 in spring temper achieves tensile strengths of approximately 100,000–130,000 psi with electrical conductivity of approximately 15–18% IACS. Beryllium copper C17200 in the peak-aged condition achieves tensile strengths of 175,000–210,000 psi with conductivity of approximately 22–28% IACS. For high-cycle, high-load contact springs where fatigue life is critical, BeCu is the superior material. For lower-load, cost-sensitive applications, phosphor bronze delivers adequate performance at significantly lower material cost—making it the dominant material for medium-performance electronic spring contacts.
What corrosive environments is phosphor bronze resistant to?
Phosphor bronze offers good corrosion resistance in seawater and marine atmospheres, freshwater systems, many industrial gases, mild acids, and general atmospheric exposure. Its corrosion resistance is superior to carbon steel but generally inferior to stainless steel in strongly oxidizing acids. It performs well in many chloride-containing environments where stainless steel can be susceptible to pitting, and it is a common material for springs in marine hardware, electrical connectors exposed to humidity, and industrial equipment in moist service environments.
What types of springs are manufactured from phosphor bronze?
Phosphor bronze is used for compression springs, extension springs, torsion springs, flat springs, contact springs, and wave springs. It is especially common in small-diameter, flat, or strip spring applications for electronics connectors, switch mechanisms, and battery contacts. Wire diameters for round spring applications typically range from approximately 0.005 inches to 0.250 inches, making it well suited for miniature and precision spring programs.
Is phosphor bronze suitable for food processing or medical device applications?
Phosphor bronze is generally not specified for direct food contact applications without additional evaluation, as copper-based alloys can leach copper ions into food products. For medical device applications, phosphor bronze is used in certain non-implantable instruments but is not appropriate for implanted devices due to biocompatibility concerns. Beryllium copper and Elgiloy are more commonly specified for medical contact springs requiring superior strength and biocompatibility. Engineers should consult applicable regulatory standards (FDA, ISO 10993) when evaluating spring materials for food processing or medical applications.
What are the key applications for phosphor bronze springs in the electronics industry?
In electronics, phosphor bronze springs are ubiquitous as battery contact springs in consumer electronics, SIM card and memory card ejector springs, keyboard switch return springs, RF and signal connector springs, EMI shielding contact springs, and switch mechanism return springs. The combination of adequate conductivity, corrosion resistance, good spring characteristics, and lower cost compared to beryllium copper makes phosphor bronze the dominant material for medium-performance electronic spring contact applications globally.
