Oxygen-free copper plate and strip
Oxygen-free copper sheet and strip are copper products with extremely high purity (copper content ≥99.95%) and extremely low oxygen content (≤0.003%). Their excellent electrical and thermal conductivity, good plasticity, and weldability make them an irreplaceable force in high-end applications such as electronics, aerospace, and precision instruments. Based on production processes and purity levels, they are divided into two grades: TU1 and TU2. TU1 boasts higher purity (≥99.97%) and an oxygen content of ≤0.002%, making it suitable for applications requiring the highest conductivity. TU2, with slightly lower purity, offers stable performance, a higher cost-performance ratio, and a wider range of applications. Sheet thickness typically ranges from 0.5-10mm, while strip thickness ranges from 0.05-3mm, with widths up to 1000mm. With a surface finish of Ra ≤0.02μm, they meet the stringent requirements of precision machining.
The production process for oxygen-free copper sheet and strip places extremely high demands on the environment and equipment, with the key focus on controlling oxygen content and purity. Electrolytically refined copper (99.99% purity) is first smelted in a vacuum induction furnace or inert gas furnace at a temperature of 1100-1150°C, completely sealed from air to prevent oxidation. Vacuum degassing (vacuum pressure ≤ 1 Pa) removes hydrogen and oxygen during the smelting process to ensure a pure melt. Ingots are cast using semi-continuous casting, with a cooling rate controlled at 50-100°C/min to achieve a fine, uniform grain structure and avoid compositional segregation. During the rolling stage, copper sheet is hot-rolled (thickness ≥ 6mm) or cold-rolled (thickness < 6mm), while strip is formed through multiple cold-rolling passes at speeds of 20-50m/min and a reduction of 15-25% per pass. Intermediate annealing is performed under hydrogen at a temperature of 300-400°C to eliminate work hardening and prevent oxidation. The finished products are precisely straightened (straightness ≤ 0.3mm/m) and slit, and then undergo oxygen content detection (infrared absorption method) and conductivity testing (≥101% IACS) to ensure that they meet quality standards.
In the electronics and information technology sector, oxygen-free copper sheets and tapes are core materials for chip packaging and high-frequency circuits. Semiconductor chip leadframes utilize 0.1-0.3mm thick TU1 oxygen-free copper tape. Its high conductivity reduces signal transmission loss. A chip manufacturer’s 7nm process chip packaging yield increased to 99.2% after adopting this material . The RF module cavity of a 5G base station is fabricated from 2-5mm thick oxygen-free copper sheets with a surface roughness of Ra ≤ 0.01μm , reducing electromagnetic wave reflection loss and improving the signal coverage of a communications equipment manufacturer’s base station by 15% . Supercomputer heat sinks utilize oxygen-free copper sheets with a thermal conductivity of ≥ 390W/(m・K) , keeping chip temperatures below 85 °C and improving equipment operational stability at a supercomputing center by 20%.
The aerospace and precision instrumentation sectors have special requirements for the performance of oxygen-free copper sheets and ribbons. Spacecraft solar array interconnects utilize 0.05mm thick oxygen-free copper ribbon, which can withstand extreme temperature fluctuations (-180°C to 120°C) in space without brittleness. This has resulted in an 8% increase in solar cell efficiency for one satellite. Gyro rotors in inertial navigation systems utilize 5-10mm oxygen-free copper sheets, precision-turned to a roundness of ≤0.001mm, ensuring navigation accuracy (±0.001°/h). This has reduced the failure rate of navigation equipment for one aviation company by 35%. Laser weapon resonators are polished from oxygen-free copper sheets to a surface flatness of ≤0.05μm, minimizing laser energy loss and increasing the laser range of one military project by 10%.
With the advancement of high-end manufacturing, oxygen-free copper sheet and strip continue to achieve breakthroughs in performance. Manufacturers have developed ultra-high-purity oxygen-free copper (99.999%) for use in superconducting circuits for quantum computing chips, achieving a conductivity exceeding 103% IACS. To meet the needs of flexible electronics, ultra-thin oxygen-free copper strip (0.01-0.03mm thick) with an elongation of ≥40% has been developed, suitable for flexible circuits in foldable phones. One manufacturer’s product boasts a flex lifespan of 100,000 cycles. The integrated continuous casting and rolling process has increased material utilization from 70% to 90%, reducing one company’s per-ton steel production cost by 12%. In the future, with the advancement of artificial intelligence and space exploration, oxygen-free copper sheet and strip will continue to develop towards higher purity, thinner gauges, and improved low-temperature toughness, supporting breakthroughs in high-end technology.
