IACS

International Annealed Copper Standard — the conductivity benchmark where pure annealed copper at 20 °C equals 100%.

Conductivity is quoted as a percentage of IACS, the 1913 reference value of 58.0 MS/m for annealed copper at 20 °C. ETP and oxygen-free copper both meet 100% IACS; oxygen-free electronic grade runs slightly above it at 101%. Alloying always costs conductivity — tellurium copper holds about 93%, brass drops to 26% and 70/30 cupro-nickel to under 5%. A busbar specification that names a cross-section without naming a minimum IACS is incomplete: the same bar in brass carries a quarter of the current.

Related terms

ETP Copper
Oxygen-Free Copper
Busbar

Where this applies

copper-busbars

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