Audiophile Inquiries: Exploring Oxygen Free Copper

History of oxygen free copper

Oxygen-free copper, also known as OFC or oxygen-free electronic (OFE) copper, is a type of copper that has been refined to reduce oxygen content to below 0.001%. Oxygen is considered a contaminant in copper because it can have detrimental effects on its electrical conductivity and other physical properties. The history of oxygen-free copper is intertwined with the development of more pure and high-quality copper for various applications.

Copper has been used by humans for thousands of years due to its excellent electrical and thermal conductivity, malleability, and corrosion resistance. However, early forms of copper were not completely pure, containing impurities like oxygen and other elements. The desire for purer copper with improved conductivity emerged as technology developed and more demanding applications arose.

In the 1950s, oxygen-free copper was first produced to meet the needs of the electronics industry, particularly in vacuum tubes and high-frequency applications. The telecommunications industry, which required materials with exceptional conductivity, played a significant role in driving the demand for oxygen-free copper.

The production of oxygen-free copper involves several refining stages to reduce the oxygen content. Initially, impure copper is smelted and converted into anodes, which are then electrolytically refined to achieve higher purity. Through this process, impurities, including oxygen, are removed, resulting in a purer copper product.

Over the years, advancements in refining techniques and growing demand for higher-purity copper have led to the development of various grades of oxygen-free copper, such as C10100, C10200, and C11000. These specific grades are often used in applications requiring exceptional electrical conductivity, such as electrical circuits, busbars, transformers, and high-end audio equipment.

In summary, the history of oxygen-free copper begins with the need for higher-purity copper in the electronics industry. The refinement processes used to reduce oxygen content have evolved over time, leading to the production of various grades of oxygen-free copper that have widespread use in modern applications.

Process to make oxygen free copper

The process to produce oxygen-free copper involves several refining steps to remove impurities, including oxygen, from the copper. Here are the general steps involved in making oxygen-free copper:

  1. Smelting: The process begins with copper ores being smelted to obtain raw copper. Smelting involves heating the ores in a furnace to separate the copper from other elements and impurities.
  2. Conversion to Anodes: The raw copper obtained from smelting is further processed to form anodes. Anodes are large copper plates or bars that will act as the raw material for the refining process.
  3. Electrorefining: Anodes are placed in an electrolytic bath, typically containing a copper sulfate solution. An electrolysis process is used to refine the copper anodes. During electrolysis, a direct electric current is passed through the electrolyte. This causes copper from the anodes to dissolve and deposit onto a cathode, which is made of high-purity copper and acts as a starter sheet. The impurities, including oxygen, in the anodes remain behind.
  4. Repetitive Electrorefining: The cathode produced in the previous step goes through repetitive electrorefining cycles to further purify the copper. This process helps to remove additional impurities and oxygen content from the copper.
  5. Vacuum Deoxidation: After the initial electrorefining cycles, the copper is still not completely oxygen-free. To further reduce the oxygen content, the copper is subjected to a vacuum deoxidation process. In this step, the copper is heated in a vacuum environment, which helps to remove any remaining gases, including oxygen.
  6. Final Electrorefining: To achieve oxygen-free copper, the refined copper undergoes final electrorefining cycles. These cycles, similar to the earlier steps, help to further purify the copper by removing any trace impurities, ensuring the lowest possible oxygen content.

The exact process may vary depending on the specific refining methods used by different manufacturers. However, these steps give a general idea of how oxygen-free copper is produced. The goal is to progressively refine the copper while minimizing the oxygen content to achieve the desired high-purity result.

How do contaminates effect oxygen free copper

Contaminants in oxygen-free copper can have various effects on its properties, particularly its electrical conductivity. Oxygen is one of the primary contaminants present in copper, and it can significantly impact the performance of oxygen-free copper. Here are a few ways contaminants can affect oxygen-free copper:

  1. Electrical Conductivity: Oxygen is a major impurity that affects the electrical conductivity of copper. As the oxygen content increases, the conductivity of the copper decreases. Oxygen atoms disrupt the crystal lattice structure of copper, impeding the flow of electrons and resulting in higher resistance. Higher resistance leads to increased power losses and reduced efficiency in electrical and electronic applications.
  2. Mechanical Properties: Contaminants, including oxygen, can also influence the mechanical properties of oxygen-free copper. Oxygen can form small oxide particles within the copper matrix, affecting its tensile strength, ductility, and overall mechanical integrity. Higher oxygen content can make the copper more brittle and prone to cracking or other mechanical failures.
  3. Corrosion Resistance: Oxygen in copper can contribute to corrosion, especially in the presence of moisture or other corrosive agents. Oxidation reactions can occur, leading to the formation of copper oxide on the surface of the copper. This oxide layer can degrade the copper’s corrosion resistance, potentially leading to surface deterioration and increased electrical resistance.
  4. Thermal Conductivity: While oxygen content primarily affects electrical conductivity, it can also have slight effects on thermal conductivity. Higher oxygen content may slightly reduce the thermal conductivity of copper, impacting its ability to efficiently conduct heat.

To ensure the desired performance, oxygen-free copper is manufactured with a very low oxygen content, typically below 0.001%. The reduction of contaminants, especially oxygen, through refining processes, helps optimize the electrical and mechanical properties of the copper. This high-purity oxygen-free copper is then used in applications where exceptional conductivity, low resistivity, and minimal adverse effects from impurities are required.

How does iron effect oxygen free copper

Iron contamination in oxygen-free copper can have a negative impact on its electrical performance. Iron is considered an impurity and can affect the conductivity and other electrical properties of copper. Here’s how iron contamination can influence the electrical performance of oxygen-free copper:

  1. Increased Electrical Resistance: Iron atoms disrupt the crystal lattice structure of copper, hindering the flow of electrons through the material. This increased resistance can lead to higher power losses and reduced electrical conductivity. Even a small amount of iron contamination can significantly impact the overall conductivity of oxygen-free copper.
  2. Formation of Intermetallic Compounds: Iron in copper can form intermetallic compounds, such as copper-iron alloys, which can have different electrical properties than pure copper. These compounds can introduce additional resistance and alter the conductivity of the copper. The presence of intermetallic compounds may also affect the stability and reliability of electrical connections, leading to potential reliability issues in electronic devices.
  3. Impaired Superconducting Properties: Oxygen-free copper is often used in applications where superconductivity is desired, particularly in high-performance electrical and electronic systems. Iron contamination can disrupt the superconducting properties of copper by introducing disorder and impurities in the material. This can hinder the formation of superconducting electron pairs and reduce the critical temperature at which copper exhibits zero electrical resistance.
  4. Degraded High-Frequency Performance: Oxygen-free copper is commonly employed in high-frequency applications, such as radio frequency (RF) circuits and transmission lines, due to its excellent electrical conductivity. However, iron contamination can cause increased losses at high frequencies due to eddy currents and skin effect. These effects can degrade the performance of copper in high-frequency applications and lead to reduced efficiency and signal degradation.

To ensure optimal electrical performance, it is crucial to maintain the purity of oxygen-free copper and minimize iron contamination. Industry standards and quality control measures are employed during the manufacturing process to limit impurities such as iron and achieve the desired high-purity oxygen-free copper with superior electrical properties.

How does cryogenically treating copper effect its electrical performance

Cryogenic treatment, which involves subjecting a material to extremely low temperatures, can have certain effects on the electrical performance of copper. While the impact may vary depending on the specific application and conditions, here are a few general effects of cryogenically treating copper:

  1. Reduced Electrical Resistance: Cryogenic treatment can help reduce the electrical resistance of copper. Cooling the copper to cryogenic temperatures can enhance the alignment of crystal grains and reduce lattice defects, thereby improving the electron flow and reducing resistance. This effect can be particularly beneficial in high-current applications where low resistance is crucial.
  2. Increased Superconductivity: Copper is not a superconductor under normal conditions. However, cryogenic treatment can enhance the superconducting properties of copper. Cooling copper to extremely low temperatures can induce superconductivity, allowing the material to exhibit zero electrical resistance. This property is particularly valuable in certain applications, such as superconducting wires used in MRI machines and particle accelerators.
  3. Enhanced Signal Transmission: Cryogenically treated copper can improve the transmission of electrical signals. By reducing electrical resistance and minimizing signal loss, cryogenic treatment can help maintain signal integrity and reduce distortion. This effect is especially relevant in high-frequency applications where signal quality and performance are essential, such as in high-speed data transmission or RF circuits.
  4. Improved Stability: Cryogenic treatment can enhance the stability and reliability of copper in electrical applications. The low temperatures can reduce the movement of atoms and limit the occurrence of thermal fluctuations, which can lead to changes in electrical properties. This increased stability can contribute to consistent electrical performance over a wider range of operating conditions.

It is worth noting that the effects of cryogenic treatment on copper may depend on factors such as the initial purity of the copper, the specific cryogenic temperatures used, and the duration of the treatment. Additionally, cryogenic treatment may not always be necessary or beneficial for all copper applications, particularly those where normal operating temperatures do not reach extreme lows.


In conclusion, the presence of contaminants, such as iron or oxygen, in oxygen-free copper can significantly impact its electrical performance. Iron contamination can increase electrical resistance, form intermetallic compounds, and impair superconductivity, ultimately affecting the conductivity and stability of the copper. Oxygen, as a major impurity, reduces electrical conductivity, alters mechanical properties, and affects corrosion resistance. These effects can reduce the efficiency, reliability, and longevity of oxygen-free copper in electrical and electronic applications.

To mitigate these impacts, strict quality control measures are employed during manufacturing processes to minimize impurities and maintain the high purity of oxygen-free copper. This ensures optimal electrical conductivity, mechanical properties, and corrosion resistance. By maintaining low levels of contaminants, oxygen-free copper can achieve superior electrical performance, making it suitable for various high-performance applications where low resistance, high conductivity, and reliability are essential.

Additional information

These two files are different versions of the same document. The older version has considerably more information while the graphs are easier to read on the newer version. Enjoy!

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