Electrical Terminal Stamping Process

2. Material Selection and Preparation

2.1 Copper and Copper Alloys

Copper is selected for terminals primarily due to its high electrical conductivity (approximately 101% IACS for C11000 Electrolytic Tough Pitch copper) and formability. Common grades include:

• C11000 (ETP Copper): Excellent conductivity and ductility.

• Copper Alloys (e.g., C26000 Brass, C51000 Phosphor Bronze): Provide higher strength and spring properties for retention clips or contact springs.

Material is supplied as cold-rolled strip coil, typically 0.005–0.060 in. thick. The specified temper (annealed to full hard) directly affects forming behavior. Surface finish, flatness, and cleanliness are verified before stamping to ensure consistent feed and formability.

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3. Die Design and Tooling Considerations

3.1 Progressive Die Configuration

Copper terminals are generally produced using progressive dies, which contain multiple workstations performing sequential operations as the strip advances through the press. Key operations include:

• Blanking: Cutting the external profile of the terminal.

• Piercing: Producing holes, slots, and openings for crimping or mating features.

• Forming/Bending: Creating barrels, tabs, or locking tangs.

• Coining/Embossing: Adjusting surface texture or contact area thickness for improved conductivity.

• Cutoff: Separating the completed terminal from the carrier strip.

The strip remains attached to a carrier during forming to maintain positional accuracy. Modern die sets employ precision-ground tool steels (A2, D2, or carbide inserts) and are designed using CAD/CAM systems to optimize material flow, minimize distortion, and extend die life.

3.2 Alignment and Feed

Die design incorporates pilots and guide pins to ensure accurate strip advancement. Feed pitch is maintained within ±0.001 in. at each station. Automated lubrication reduces tool wear and helps achieve consistent forming loads.

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4. Stamping Press Operation

4.1 Press and Feed Systems

The progressive die is installed in a high-speed mechanical or servo press, typically rated between 30 and 100 tons. Press speeds vary around 100 strokes per minute, depending on part geometry and material thickness.

The copper strip is fed from a coil through a decoiler, straightener, and precision roll feed into the die set. Each press stroke performs multiple simultaneous operations, forming one or more terminals per cycle. The resulting parts may remain on the carrier strip for reel-to-reel handling or be cut free automatically.

4.2 Process Monitoring

In modern production lines, load monitoring systems track tonnage signatures to detect tool wear, misfeeds, or material variation. Optical sensors verify strip presence and correct feed progression. These systems enable immediate shutdown or alarm conditions to prevent damage and ensure part quality.

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5. In-Process and Post-Process Quality Control

5.1 Dimensional Verification

Initial and periodic first-article inspections confirm that terminal dimensions meet print specifications. Optical comparators, micrometers, or coordinate measuring machines (CMMs) are used to verify critical features such as crimp barrel width, tab thickness, and hole location.

Statistical process control (SPC) is often applied to high-volume production to detect drift or variation trends before they result in nonconforming parts.

5.2 Surface and Burr Control

Excessive burrs can compromise electrical connection or damage mating components. Punch-to-die clearance is optimized (typically 5–10% of material thickness), and tool edges are maintained sharp to minimize burr height. Where required, terminals undergo vibratory deburring or brush finishing.

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6. Secondary and Finishing Operations

6.1 Cleaning and Heat Treatment

Following stamping, terminals are cleaned to remove oils and particulates using aqueous or ultrasonic methods. For certain alloys, annealing or stress-relief heat treatment is performed in a controlled atmosphere to achieve specified mechanical properties and minimize springback.

6.2 Electroplating

Plating enhances both conductivity and corrosion resistance. Typical coatings include:

• Tin (Sn): Provides solderability and oxidation protection; cost-effective for most applications.

• Nickel (Ni): Serves as a diffusion barrier and improves wear resistance.

• Gold (Au): Used selectively for low-current, high-reliability signal contacts.

Reel-to-reel selective plating allows coating only the contact zones while leaving the remainder of the part unplated, reducing cost and maintaining crimpability.