Copper Sourcing in Reading, PA: C101, C110 & Tellurium Copper

Both are very high-conductivity coppers, but they differ in purity and oxygen content. C101 is oxygen-free electronic copper (OFE), processed to remove oxygen, giving it the highest purity and conductivity and, crucially, immunity to hydrogen embrittlement. That makes C101 the right choice for the most demanding electrical and electronic applications, for parts that will be brazed, and for high-vacuum or hydrogen-atmosphere environments where the absence of oxygen prevents embrittlement during heating. C110 is electrolytic tough pitch (ETP) copper, which contains a small amount of oxygen. It still has excellent conductivity, very close to C101 for most practical purposes, but at noticeably lower cost, which is why it's the dominant industrial electrical grade used for busbars, connectors, terminals, and general power-distribution hardware. The practical rule: use C110 for the vast majority of electrical work because it gives you near-top conductivity at a better price, and step up to C101 only when you specifically need the oxygen-free purity, brazing compatibility, or hydrogen-environment immunity. Specifying C101 when C110 would do just adds cost without functional benefit.

Use tellurium copper (C145) whenever a copper part requires significant machining, threading, or tight features and can tolerate a small reduction in conductivity. Pure copper grades like C101 and C110 conduct beautifully but machine terribly, they're soft and gummy, smear instead of chipping cleanly, build up on tools, and produce stringy chips, all of which drive up machining time and make tight tolerances and good surface finishes difficult. Tellurium copper solves that: a small tellurium addition makes the metal break into clean chips and machine many times faster, dramatically cutting machining cost and improving finish, while still retaining around 90% IACS conductivity, which is more than adequate for most electrical applications. So if your part is essentially a forming or stamping job with minimal machining and needs absolute top conductivity, stick with C110 or C101. But if it's a machined component, threaded fitting, or anything with substantial cutting content, tellurium copper usually wins because the machining savings outweigh both the modest material premium and the slight conductivity sacrifice. The decision hinges on how much machining the part needs versus how much conductivity it can give up.

Pure copper is hard to machine because it's soft, highly ductile, and gummy. Instead of forming clean, breakable chips the way steel does, copper tends to smear and tear, which produces poor surface finish, and it builds up on the cutting edge, which degrades accuracy and can ruin a part. It also tends to produce long, stringy chips that tangle around tooling and are difficult to clear. Shops that machine copper well manage it with very sharp tooling that has polished surfaces and positive rake geometry to slice cleanly rather than push the soft metal, generous coolant to flush chips and control built-up edge, and feeds and speeds tuned specifically to break chips. Even with all that, cycle times run longer and tight finishes are harder to hold than on free-machining materials. That's exactly why, when a copper part has meaningful machining content, the better move is often to switch to tellurium copper, which machines cleanly and quickly while keeping most of copper's conductivity. When sourcing pure copper machining, choose a shop with real copper experience, because a shop set up only for steel will struggle with the gumminess and the chip control.

In most electrical applications, yes, plating is recommended and often essential. Bare copper oxidizes and tarnishes when exposed to air and moisture, and that surface oxide layer increases contact resistance at electrical joints, which over time can cause heating, voltage drop, and reliability problems at connections. Plating prevents that. Tin plating is the most common choice for electrical connections because it maintains low contact resistance, resists oxidation, and preserves solderability, making it standard for terminals, connectors, and busbar contact areas. Silver plating is used where the highest conductivity contact surface is needed, such as high-performance switching and power contacts. Nickel plating serves as a barrier layer, often under other platings or where a harder, more wear-resistant surface is needed. The area that actually carries current or makes contact is what typically needs plating, while non-contact surfaces may be left bare, so specify both the plating type and the plated area on your RFQ since masking and racking affect cost. For busbars and power-distribution hardware, the plating spec is often as functionally important as the copper grade itself, so don't treat it as an afterthought.