Copper 110 (C110) Sheet Fabrication

Conductivity is the argument

Copper 110 sheet is specified for one number: around 101% IACS, better than any other sheet metal at a sensible price. The brasses sit at roughly 28% IACS and the bronzes lower still, so where conductivity is the reason the part exists, the material decision is effectively already made.

Property	Copper 110	What it means for a fabricated part
Conductivity	~101% IACS	The reason for choosing the grade
Formability	Excellent	Deep draws and tight bends are achievable
Bend radius, annealed	~0.5× thickness or tighter	Among the tightest of any sheet metal
Work hardening	Significant	Multi-operation forming may need an inter-anneal
Joining	Excellent brazing and soldering	Electrical assemblies are straightforward
Corrosion	Excellent — a stable patina forms	Roofing and flashing last for generations

The formability is a generous bonus rather than the point. Pure copper is extremely ductile — it stretches a long way before failing, which makes it suitable for complex formed shapes — and it brazes and solders better than almost any other metal, so a formed copper assembly can be joined reliably. Conductivity puts copper on the drawing; formability and joinability are why the sheet route works well for it.

Work hardening and the inter-anneal

Copper work-hardens quickly, and the effect is large enough to shape the process route.

Each forming operation leaves the material stronger and less ductile. On a part with one or two operations that is useful — the finished part is stronger than the sheet it came from. On a part with several operations, or one with a severe draw, the material may need an inter-anneal to restore enough ductility to continue without cracking.

Copper anneals at a relatively low temperature, so the operation itself is straightforward. What matters is that it is planned into the route rather than discovered when a blank cracks partway through a draw.

The practical sequence on a complex formed copper part:

1. Blank and form in the annealed condition
2. Inter-anneal if the forming exhausts the ductility
3. Continue forming to the finished geometry
4. Finish by polishing, brushing or plating

The reducing-atmosphere limit

This is the one technical constraint on copper 110 that is easy to miss and expensive to discover.

Copper 110 is electrolytic tough pitch copper, which contains a small controlled amount of oxygen — typically 0.02–0.04% — present as copper oxide particles at the grain boundaries. That is normally harmless.

But if the metal is heated in a reducing atmosphere — as some brazing and welding processes are — hydrogen diffuses into the copper, reaches those oxide particles and reacts with the oxygen to form steam. Steam cannot escape from inside solid metal, so pressure builds at the grain boundaries until they crack. That is hydrogen embrittlement.

So the rule is:

• Cut, formed, or used at ambient temperature — copper 110 is the sensible choice
• Brazed or welded in a reducing atmosphere, or used in vacuum or RF service — the oxygen-free grade, copper 101, is the correct specification

On an assembly that will be furnace-brazed, saying so at the enquiry is worth more than on most materials, because the alloy choice and the joining route are linked.

The patina is either the design or the problem

Copper’s corrosion behaviour is unusual, and for a visible part it is part of the specification rather than a defect.

Copper forms a stable oxide and then a green patina — verdigris — that adheres to the metal and protects it. Copper roofing and flashing last for generations on that basis. Unlike the rust on a steel part, the patina is not a failure; it is a self-limiting protective layer.

• A part left bare will change colour, from bright copper through brown to green, at a rate that depends on atmosphere and exposure. On architectural work that is usually the point.
• Where a part must stay bright, it needs a lacquer or a plating — nickel for a hard barrier, tin for solderability, silver where contact resistance matters.
• In aggressive environments, copper still performs well but can be attacked by ammonia and by some sulphur compounds. Say what the part touches.

Formed-feature rules

The geometric rules around a bend are at their most forgiving on copper, but they still apply — and one of them is specific to soft material.

Holes and slots must clear the bend. A hole inside the bend zone distorts as the material stretches around the radius. The working rule is to keep a hole at least a distance of roughly two-and-a-half times the material thickness plus the bend radius away from the bend line — measured from the edge of the hole, not its centre. Because annealed copper is so ductile, distortion around a hole is often the first visible sign that a hole is too close to a bend.

Flanges have a minimum length. A flange shorter than roughly four times the material thickness cannot be formed reliably, because the tooling has nothing to grip.

Bend relief prevents tearing, and on a multi-operation part it is worth including rather than relying on the material’s ductility.

Handle the surface carefully. Annealed copper is soft and scratches in handling, and on a visible part a scratch is a permanent defect. Protective film until the last possible moment, and soft tooling faces where it can be arranged, are the standard controls.

Springback is low compared with stainless or aluminium, so the flat pattern is more predictable — but the bend allowance should still account for it.

Where copper 110 sheet is the right choice

• Busbars, conductors and current-carrying links
• Electrical contacts and terminals
• Gaskets and sealing rings
• Heat-exchanger and thermal-management components — see heat sinks
• RF shielding, waveguide and microwave parts
• Electrodes
• Roofing, flashing and architectural sheet, where the patina is the design intent
• Any fabricated part where conductivity is the design driver and the joining route is brazing or soldering

Where copper 110 sheet is the wrong choice

The part will be brazed or welded in a reducing atmosphere. The oxygen content is a hydrogen-embrittlement risk. Specify copper 101.

Conductivity is not the requirement. Copper is expensive and soft. Where the part only needs to be formed and corrosion resistant, brass 260 is the better forming brass — and where it only needs to be formed, mild steel or aluminium costs far less.

Weight is a consideration. Copper’s density is around 8.9 g/cm³, comparable to steel and roughly three times aluminium.

The part must stay bright and will not be coated. Bare copper patinates. A lacquer or a plating has to be specified.

The part is structural. Copper is soft and relatively weak — around 220–250 MPa annealed. It is a conductor and a formed material, not a structural one.

The environment contains ammonia or sulphur compounds. Those attack copper. Name the environment before the material is fixed.

What to put on the drawing

Instead of	Write
Copper sheet	Copper 110 (C110), where conductivity is the driver
Copper 110, reducing-atmosphere brazing	Wrong grade — the oxygen content causes hydrogen embrittlement. Use copper 101
Copper 110, multi-operation draw	Say so — an inter-anneal step may be needed in the route
Copper 110, must stay bright	State the finish — bare copper patinates
Copper 110, visible surface	Say so — annealed copper marks easily and a scratch is permanent
Copper 110, bolts to another metal	Consider the galvanic couple — copper is cathodic and will drive the other metal’s corrosion
Copper 110, ammonia or sulphur environment	Flag it — copper is attacked
Copper 110, conductivity not required	A brass is cheaper and easier to machine

The three lines that decide most copper 110 sheet parts are whether the part will be heated in a reducing atmosphere, how many forming operations are involved, and whether the surface will be visible. The first picks between 110 and 101. The second decides whether an inter-anneal belongs in the route. The third decides the handling and the finishing.

Send the drawing through the request a quote form and the reply comes back within 24 hours with DFM feedback — including a note on the temper, the forming sequence, any inter-anneal, the joining route and the finishing where any of them need settling.