C10100 (OFE) vs C11000 (ETP) Copper - Knowledge

The High-Temperature Difference

Specifying the wrong grade of copper for a high-temperature application is an expensive mistake. While C11000, electrolytic tough pitch or ETP copper, and C10100, oxygen-free electronic or OFE copper, look identical to the naked eye and offer similar electrical conductivity, their performance under high heat is drastically different. If a manufacturing process involves brazing, welding, or glass-to-metal sealing in a reducing atmosphere, choosing C11000 can result in catastrophic failure. The culprit is hydrogen embrittlement.

The Trap of C11000 ETP Copper

C11000 is the most common copper used in general electrical wiring, with a purity of 99.90 percent and good conductivity. However, it contains a microscopic amount of oxygen, typically 0.02 to 0.04 percent or 200 to 400 ppm, intentionally left in the metal during casting to improve flowability. For standard applications at room temperature this oxygen is harmless, but exposed to temperatures above 400 degrees C in an environment containing hydrogen gas, such as during vacuum brazing or welding, a destructive reaction occurs. Hydrogen atoms penetrate the metal lattice and react with the trapped oxygen to form water vapor, and this trapped steam expands rapidly, creating intense internal pressure. The result is microscopic blistering and severe cracking along the grain boundaries, and the copper becomes completely brittle and loses structural integrity.

100 Percent Immunity with C10100 OFE

C10100 is specifically smelted and cast under stringent vacuum conditions to eliminate oxygen and other volatile elements. With a guaranteed purity of 99.99 percent and oxygen levels strictly controlled below 5 ppm, there is simply no oxygen left in the matrix to react with hydrogen. Because it is completely oxygen-free, C10100 achieves 100 percent immunity to hydrogen embrittlement.

When Must You Specify C10100

Specify C10100 for ultra-high vacuum systems, where outgassing is unacceptable in electron tubes, particle accelerators, and high-frequency tubes; for cryogenic cooling and magnetic resonance imaging, where C10100 maintains mechanical strength and thermal conductivity at sub-zero temperatures; and for precision CNC machining and brazing of switchgear contacts and RF coaxial connectors, where high-purity material ensures assemblies do not crack under thermal stress.

Technical Comparison

C10100 has copper purity of 99.99 percent minimum versus 99.90 percent for C11000, oxygen content below 5 ppm versus 200 to 400 ppm, 100 percent immunity versus high susceptibility to hydrogen embrittlement, zero outgassing versus high outgassing in ultra-high vacuum, conductivity of 101 percent IACS minimum versus 100 to 101 percent, and thermal conductivity of 391 W per meter per Kelvin versus 388.

Supply Chain Verification

A major issue in global sourcing is receiving oxygen-free copper that is actually standard ETP copper, and visual inspection cannot tell the difference. Verify the chemical composition of every batch using spectrometer analysis, and require batch-specific material test reports confirming the oxygen limit.