Copper Machining & Fabrication in Bowling Green, KY — C101, C110, Tellurium Copper

C101 (Oxygen-Free Electronic copper, OFE, 99.99% Cu minimum) represents the conductivity ceiling — 101% IACS electrical conductivity, thermal conductivity of 226 BTU/hr·ft·°F, and zero oxygen content that ensures weld integrity under hydrogen annealing conditions. It's the specification for high-frequency electronic components, vacuum tube connections, and any application where oxygen-caused blister formation under high-temperature processing would be a failure mode. C101 is soft (50,000 psi tensile, 10,000 psi yield in annealed state) and gummy to machine — it doesn't break chips cleanly, which demands attention to tool geometry and cutting fluid selection. C110 (Electrolytic Tough Pitch copper, ETP, 99.9% Cu, 0.02–0.04% oxygen) is the practical workhorse for most Bowling Green copper applications — wire, rod, bar, sheet, and tube all commonly stocked in C110. It's slightly less pure than C101 but more economical, and its conductivity (100% IACS) is adequate for the vast majority of electrical applications. Conductors, bus bars, rotor bars, and transformer windings are typical C110 applications. Like C101, it machines poorly in the pure sense — long, stringy chips and tendency to smear on tool faces are the key machining challenges.

Tellurium copper (C145, 0.4–0.7% tellurium) exists for one purpose: making copper machinable without sacrificing too much conductivity. The tellurium addition creates discontinuous chips — the same mechanism that makes 12L14 free-machining steel easier to cut than 1018 — converting copper from a near-unmachineable gummy material into one that runs cleanly on CNC turning and milling centers. Machinability rating is approximately 90% that of C360 free-machining brass (the universal standard at 100%), which is dramatically better than C110's roughly 20% machinability rating. The conductivity trade-off is modest: C145 delivers 93–96% IACS electrical conductivity versus 100% IACS for C110. For most Bowling Green applications — electrical connectors, terminal bodies, switchgear components, and bus bar machining where some secondary machined features are required — this trade is highly favorable. The reduced machining time and tool wear savings easily justify the slight conductivity reduction in all but the most conductivity-critical designs. C145 is also weldable (using the same procedures as C110) and easily silver-brazed, making it the default for machined copper components that require joining.

The expansion of electrified powertrains across the automotive platforms built and supplied around Bowling Green is increasing copper demand in the local supply chain. Bus bars — flat conductors that distribute high-current power in inverters, battery management systems, and motor controllers — are typically punched or machined from C110 or C145 sheet and bar. Bowling Green stamping shops with progressive die capability can produce high-volume bus bar blanks from C110 coil; local CNC shops finish-machine mounting holes, chamfer edges for safe handling, and apply silver or tin plating for oxidation resistance at connection interfaces. Heat exchangers and cold plates for thermal management in power electronics use copper for its superior thermal conductivity. Brazed copper cold plates — machined C110 channels assembled with BAg-series silver-brazing filler — can dissipate heat loads of 50–200 W/cm² in power electronics applications. Bowling Green shops serving this market combine machining, cleaning, and brazing capabilities, with leak testing as a standard final inspection step for fluid-path copper assemblies.