Copper–iron (C19500) is a heat-treatable, high-strength, high-softening-resistance, high-fatigue-resistance alloy with a moderate electrical conductivity.
CuFePCoSn was developed by Olin Brass USA in the 1970s as an enhancement of C19400. It has a finer dispersion of particles after heat treatment plus an addition of cobalt, leading to superior strength and the ability to withstand higher temperatures for a longer time. It is the strongest of the copper-iron conductivity alloys.
The precipitation heat treatment involves heating the alloy to 800 to 900oC and water quenching. This is called solution treatment and the alloy is in its softest condition.
Subsequent precipitation (age) hardening at lower temperatures of 450 to 600oC results in the formation of very finely dispersed precipitates in the alpha matrix; these are responsible for the higher strength and temperature resistance.
The alloy has a combination of properties as below:
- Tensile strength: 360-670 N/mm2
- 0.2% Proof strength: 170-650 N/mm2
- % Elongation: 26-2
- Hardness (HV): 100-190
- Electrical conductivity: 50% IACS
- Thermal conductivity: 200 W/moC
Soldering and brazing are excellent. Butt, seam, gas shielded arc and laser welding are good. Oxyacetylene, coated metal arc and spot welding are fair.
Machinability rating is 18% which is fair. Free machining brass is 100%.
The alloy has excellent cold and hot formability.
Resistance to Corrosion
The alloy has good resistance to corrosion in industrial and marine atmospheres. It is insensitive to stress corrosion cracking. However, it is susceptible to attack in the presence of ammonia, sulphur, hydrogen sulphide and mercury.
Resistance to Softening
A major application for this alloy is leadframes which are subject to a range of temperatures during semi-conductor manufacture. These temperatures are 500, 350 and 200oC
To determine the resistance to softening, standard tensile test samples were prepared, heated to the above temperatures and the proof strength measured at specified time intervals.
The results for CuFePCoSn are summarised below and compared to Cu-ETP.
- At 500oC
There is no loss of strength after 70 seconds.
Cu-ETP loses strength after 5 seconds.
- At 350oC
There is no loss of strength after 2 hours.
Cu-ETP loses strength after 20 seconds.
- At 200oC
There is no loss of strength after 4 hours.
There is a slight loss of strength for Cu-ETP.
Clearly CuFePCoSn has outstanding properties at the temperatures that may be encountered during semi-conductor manufacture. This is expressed as a high softening resistance.
CuFePCoSn has the highest strength of any of the copper iron alloys and an excellent resistance to softening. This allows parts to be reduced in size without sacrificing performance in many cases.
- Wiring harness for automobiles
- Edge connectors for printed circuit boards.
CuFePCoSn is available as bar, plate, sheet and strip.
Below is the specification for US. For equivalent standards from other countries visit the Copper Key website.
- USA: C19500 (American Society for Testing and Materials ASTM designation).
Further information on copper–iron C19500, and other conductivity materials, is available at the Copper Alloys Knowledge Base.
Application Example 1: Miniaturised Electrical Connectors
Because of its combination of high strength and good electrical conductivity, parts made from Copper–iron C19500 may be reduced in size without sacrificing performance. This is particularly important in automobile components where the ability to reduce vehicle weight leads to improved performance.
Application Example 2: Leadframe
Copper–iron C19500 has outstanding softening resistance, high-strength and fatigue-bending-resistance which makes it suitable for leadframe manufacture.