🔌 COPPER
Copper Stamping for Electrical and Thermal Parts: Grades, Conductivity, and Forming
Copper gets stamped for one reason above all others: it carries current and heat better than almost anything you can afford. The catch is that pure copper is soft, gummy, and prone to galling and burr, so temper selection and die clearance matter more than raw strength. Most copper stamping is a balancing act between holding conductivity and getting clean, formable parts.
ISO 9001IATF 16949ISO 14001
Conductivity versus formability: the core tradeoff
C101 (oxygen-free electronic, OFE) and C110 (electrolytic tough pitch, ETP) are the two dominant stamping coppers, both rated around 100-101% IACS conductivity. C110 is the everyday choice for busbars, terminals, lugs, and contacts; C101 is specified where oxygen-free purity matters, such as parts that will be brazed in hydrogen or used in high-vacuum and semiconductor environments, because ETP copper can suffer hydrogen embrittlement. Functionally they stamp similarly.
The forming tradeoff is temper. Soft (annealed) copper has high elongation, around 35-45%, and draws and bends beautifully, but it is gummy, burrs badly, and parts deform easily in handling. Hard tempers stamp cleaner with crisper edges but lose ductility for tight bends and reduce, slightly, the spring and fatigue behavior of contacts. Shops pick the temper to match the forming severity: soft for deep draws, half-hard or hard for flat contacts and terminals that need edge crispness and a little springiness.
Where tellurium copper earns its place
Tellurium copper (C145) trades a small amount of conductivity, still around 90-95% IACS, for dramatically better machinability and somewhat cleaner stamping behavior thanks to the tellurium acting like the lead in free-machining brass. It is the grade to reach for when a stamped copper part also needs significant machining, tapping, or threading as a secondary op, because pure C101/C110 machines like chewing gum and produces poor threads.
In pure stamping with no machining, C110 usually wins on cost and conductivity. But for hybrid parts, stamped blanks that then get drilled, tapped, or precision-turned, tellurium copper saves enough secondary-machining time and tool wear to justify the conductivity give-up. It is common in electrical connectors, welding-electrode components, and contact parts that combine forming with machined features.
Burr, galling, and plating reality
Soft copper's gumminess makes burr control the central challenge. Die clearance is set carefully, often around 6-10% of thickness, and tooling is kept sharp because a dull edge tears rather than shears copper, throwing up large burrs that then short or interfere in electrical assemblies. Galling and material pickup onto the die are managed with hard coatings and clean lubrication, and tooling is maintained frequently on high-volume runs.
Most stamped copper gets plated, tin, nickel, silver, or gold over nickel, to prevent oxidation and improve solderability and contact resistance. The stamping lubricant must clean off completely before plating, since residue causes adhesion failures and skip plating. For automotive electrical parts this runs under IATF 16949 control with documented plating thickness and solderability testing. Bright, oxide-free edges from clean shearing matter because oxidized copper raises contact resistance.
Frequently Asked Questions
Both are high-conductivity coppers rated around 100-101% IACS and they stamp very similarly, so the choice is about purity and environment, not formability. C110 is electrolytic tough pitch (ETP) copper, the everyday workhorse for busbars, terminals, and lugs, and it is cheaper and more widely stocked. C101 is oxygen-free electronic (OFE) copper, which removes the small residual oxygen content in ETP. That oxygen matters in two cases: parts brazed or annealed in hydrogen atmospheres can suffer hydrogen embrittlement in C110 but not C101, and high-vacuum or semiconductor applications often specify oxygen-free copper for outgassing and purity reasons. For ordinary electrical stamping where the part will be plated and used at room temperature, C110 is the right, cheaper choice. Specify C101 only when hydrogen processing, vacuum service, or a purity spec genuinely requires it, because you pay a premium for the oxygen-free grade.
Pure copper in soft tempers is ductile and gummy, around 35-45% elongation, so instead of shearing cleanly it tends to flow and tear, throwing up large burrs, especially as the die edge dulls. In electrical assemblies those burrs are a real problem because they can short adjacent conductors or interfere with mating parts. Shops control burr by keeping cutting edges sharp and re-sharpening tooling on a tight schedule, by setting die clearance carefully (commonly around 6-10% of thickness), and by selecting a harder temper when the forming allows, since half-hard and hard copper shear more cleanly than annealed. For parts that must be burr-free, a deburring or tumbling secondary operation is added, though that can round edges and must be controlled on contact parts. Choosing the right temper for the job is the single biggest lever: use soft copper only when deep forming requires it, and harder tempers for flat terminals and contacts.
Choose tellurium copper (C145) when the stamped part also needs significant machining, drilling, tapping, or threading as a secondary operation. Pure C101 and C110 machine terribly, gumming up tools and producing rough threads and poor surface finish, whereas tellurium copper machines almost like free-machining brass while retaining around 90-95% IACS conductivity. So for a connector body that is stamped and then tapped, or a contact that is blanked and then precision-turned, tellurium copper saves enough machining time and tool wear to justify the small conductivity sacrifice. If the part is pure stamping with no machined features, stick with C110 for better conductivity and lower cost. The decision is really about whether secondary machining is on the routing: yes means tellurium copper, no means standard ETP copper.
Copper is an expensive, exchange-traded commodity, and its price swings significantly, so material is the dominant and most variable cost in copper stamping. Quotes commonly include a metal-price surcharge or escalation clause tied to the COMEX or LME copper price, and long-term contracts often index the copper portion separately from the conversion cost. Because copper is dense and costly, scrap matters: the skeleton web and trim are significant value, and reputable shops credit back the recovered scrap copper, which can meaningfully reduce net part cost, so nesting efficiency is worth optimizing. Plating, especially silver or gold over nickel, adds further cost and is itself subject to precious-metal price moves. When comparing quotes, separate the metal cost from the conversion and plating cost so you can see what is commodity exposure versus what is the shop's actual value-add, and confirm how scrap credit is handled.
Last updated: July 2026
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