Manufacturers who need high-conductivity components face a difficult choice. Many materials that conduct electricity well are difficult to form. Those that form easily often lack the electrical performance required. Copper alloys like brass offer strength, but they sacrifice conductivity. C1100 pure copper solves this problem. With 99.9% copper content, it delivers the highest conductivity among commonly stamped metals. It also offers exceptional ductility. But stamping C1100 requires specialized knowledge. Its softness can lead to galling, surface scratches, and oxidation if handled incorrectly. This guide covers the properties, processes, and design considerations you need to stamp C1100 successfully. You will learn how to harness its conductivity without sacrificing quality.
What Makes C1100 Pure Copper Unique?
C1100 is not just another copper alloy. It is electrolytic tough pitch (ETP) copper with a minimum copper content of 99.9%. This high purity gives it properties that set it apart.
High Conductivity
C1100 achieves 98% to 100% IACS (International Annealed Copper Standard). That is the highest rating among stamped metals. For comparison, brass typically offers 28% to 60% IACS. In electrical applications, this difference matters. Higher conductivity means less energy loss as heat and better signal integrity.
Exceptional Ductility
In its soft temper (O), C1100 offers 45% to 50% elongation. It bends, draws, and forms into complex shapes without cracking. This ductility allows draw ratios up to 3:1 in deep drawing operations—much higher than harder copper alloys.
Natural Corrosion Resistance
C1100 develops a protective oxide layer when exposed to air. This layer resists atmospheric corrosion. However, it is less resistant to acids than brass. It performs well indoors and in mild outdoor environments.
Temper Options
C1100 is available in several tempers:
- O (annealed): Softest, most formable. Ideal for intricate stamping.
- H1 (lightly cold-worked): Slightly stronger, still formable. Good for parts needing minor strength.
- H2 to H4: Increasingly harder, less formable. Used when strength is the priority.
For most precision stamping, O temper is the preferred starting point.
How Is C1100 Copper Stamped?
Stamping C1100 requires different techniques than stamping steel or brass. The material is soft, ductile, and prone to galling. Each step must account for these traits.
Progressive Die Stamping
Progressive die stamping is ideal for high-volume parts like electrical terminals. A strip of copper moves through a series of stations. Each station performs a different operation: blanking, bending, piercing, or forming.
For C1100, annealing steps are often integrated into the process. After every three to four stations, the material is annealed to restore ductility. While C1100 work-hardens slowly compared to other metals, progressive forming still builds stress. Annealing keeps the material malleable through the entire process.
Blanking and Piercing
Blanking cuts the basic shape from the copper strip. Piercing cuts holes. For C1100, tool geometry matters greatly.
Use sharp, polished dies with 5% to 7% clearance. Too much clearance creates burrs. Too little clearance causes excessive force and tool wear. The cutting edges must be smooth. Any roughness will transfer to the part or cause the copper to stick.
Bending
C1100 bends easily, but surface cracking is a risk with tight radii. Use wide-radius punches with a minimum radius of 1× material thickness for O temper. For H1 temper, increase to 1.5× material thickness.
A 0.5 mm sheet in O temper needs at least a 0.5 mm bend radius. Going tighter increases the chance of cracking on the outside of the bend.
Deep Drawing
C1100’s ductility makes it excellent for deep drawing. Draw ratios up to 3:1 are achievable. But success depends on controlling the process.
Use slow press speeds, typically 8 to 12 strokes per minute. High speeds generate friction heat, which can degrade the surface and cause sticking. Heavy lubrication is essential. The lubricant must reduce friction without leaving residues that interfere with downstream processes like plating.
Annealing
Annealing restores ductility after forming. Heat C1100 to 400°C to 500°C for 1 to 2 hours, then air-cool. This process recrystallizes the grain structure, removing the effects of work hardening.
For C1100, annealing is needed less frequently than for harder alloys because it work-hardens slowly. But it is still critical after deep drawing or extensive forming.
What Are the Key Challenges in Stamping C1100?
C1100’s softness creates specific challenges. Understanding them is the first step to solving them.
Galling
Galling is the transfer of copper to the die surface. It happens when the material sticks and tears under pressure. Galling leaves rough spots on the part and wears down the tool.
Prevention methods:
- Polish dies to Ra ≤ 0.2 μm. Smooth surfaces reduce friction.
- Use anti-galling lubricants containing graphite or molybdenum disulfide.
- Clean dies every 500 strokes to remove copper buildup.
A manufacturer stamping electrical terminals once switched from standard dies to polished carbide dies with a special lubricant. Galling dropped by over 90%, and die life tripled.
Edge Cracking
Edge cracking happens when small cracks at the cut edge propagate during forming. It is more common in parts that are blanked first and then formed.
Prevention methods:
- Deburr blanks before forming. Sharp edges concentrate stress.
- Avoid sharp die corners. Use radii wherever possible.
- Anneal after blanking for parts with thin sections.
Surface Scratches
C1100’s soft surface scratches easily. Scratches are not just cosmetic. They can create stress risers and affect performance in high-reliability applications.
Prevention methods:
- Use plastic interleaving between stacked sheets.
- Handle parts with clean, padded tools.
- Post-stamping, clean with soft cloths, not abrasive pads.
Oxidation During Annealing
Annealing in air causes copper to oxidize. The surface turns dark or discolored. For parts that need a clean finish or will be plated, this is a problem.
Prevention:
- Anneal in an inert gas environment, such as nitrogen.
- Use vacuum furnaces for critical parts.
- For small-scale work, apply a protective coating before heating.
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