Precision Copper Machining and Fabrication in Nashua, NH

C101 oxygen-free high-conductivity (OFHC) copper is the premium choice for applications where maximum electrical and thermal conductivity is non-negotiable. With electrical conductivity of 101 percent IACS and thermal conductivity of approximately 390 W/m-K, C101 is specified for RF waveguide components, vacuum system components, and heat-sink blocks in semiconductor process equipment. The oxygen-free designation eliminates the risk of hydrogen embrittlement during brazing or high-temperature processing, which makes C101 essential for vacuum brazed assemblies used in particle accelerator components and high-power RF systems in the defense electronics sector. C110 electrolytic tough-pitch copper is the standard commercial grade with electrical conductivity of 100 percent IACS. Its slightly higher oxygen content (0.04 percent maximum) versus C101 makes it unsuitable for hydrogen-atmosphere brazing but perfectly adequate for most electrical bus bars, terminals, and ground straps that do not undergo high-temperature processing. C110 is more widely stocked than C101 and typically less expensive, making it the pragmatic choice when vacuum brazing or hydrogen annealing is not part of the manufacturing sequence. Tellurium copper (C145) is the machinist's favorite copper alloy. The addition of 0.4 to 0.7 percent tellurium dramatically improves machinability by producing short, brittle chips rather than the long stringy chips that make pure copper notoriously difficult to machine. C145 retains 90 percent of C110 electrical conductivity while enabling much higher machining speeds and better surface finishes. Nashua shops specify tellurium copper for complex precision parts like connector bodies, precision contacts, and switch components where dimensional accuracy and surface finish matter as much as conductivity.

Pure copper alloys like C101 and C110 present real challenges in machining that catch shops accustomed to steel or aluminum off-guard. Copper's ductility produces long, stringy chips that wrap around tooling and workpieces, interfering with cutting and creating surface damage. Its tendency to smear and gall rather than shear cleanly requires sharp tooling geometry, high rake angles, and adequate chip clearance. For these reasons, many Nashua shops prefer to direct copper work toward experienced operators with appropriate chip management practices rather than running copper in general-purpose machining cells. High-speed steel (HSS) tooling with polished flutes and high positive rake angles historically dominated copper machining and still produces excellent results for turning operations. Carbide tooling with polished flutes and fine surface finish on the rake face is necessary for milling and higher-speed turning, particularly for tellurium copper where higher cutting speeds are practical. Coolant selection matters with copper: flood coolant helps manage temperature and flush chips, but certain coolant additives can react with copper and cause staining or discoloration that affects surface finish or conductivity at interfaces. For deep holes and complex internal features in copper, gun drilling and EDM hole drilling provide alternatives to conventional drilling. The gun drill's single-flute design with high-pressure coolant delivery through the tool maintains straightness and finish in deep bores where twist drills would wander and produce oversized holes from chip packing. Copper's high electrical conductivity actually makes it well-suited to EDM erosion in die-sinking applications, though wire EDM requires attention to wire tensioning since copper is soft enough to deflect the workpiece when clamped.

Copper parts for defense electronics and semiconductor equipment typically require surface finishing beyond simple machine-finish. Electroplating is the most common post-process operation, with nickel underlayer plus gold flash (ENIG equivalent in machined-part terms) specified for connector contacts and RF components to prevent oxidation while maintaining solderability and low contact resistance. The nickel layer provides diffusion barrier protection against gold-copper interdiffusion and adds wear resistance to contact surfaces. Tin plating to MIL-T-10727 is specified for general-purpose electrical connectors and bus bar terminations where cost must be controlled. Tin deposits of 0.0003 to 0.0005 inch provide adequate corrosion protection and solderability for most non-RF electrical connections. Silver plating per QQ-S-365 is specified for high-current bus bars and RF waveguide surfaces where contact resistance at current-carrying interfaces must be minimized; silver's electrical conductivity of 105 percent IACS exceeds even copper, reducing interface resistance at bus bar joints. For semiconductor equipment applications, copper surfaces that will contact process gases or fluids may require electropolishing or chemical passivation to minimize particulate generation and surface contamination. Vacuum-compatible copper components for UHV (ultra-high vacuum) applications must be cleaned to ASTM F312 particle count standards and packaged to maintain cleanliness, a requirement Nashua shops serving semiconductor OEMs are equipped to meet.