Crimping is a critical process in wiring harness manufacturing, ensuring reliable electrical and mechanical connections. Poor crimping can lead to intermittent faults, overheating, or complete failure. Below are the key criteria for judging crimping quality in automotive terminals.

1. Visual Inspection Criteria

A. Wire Positioning

✅ Acceptable:

• Wire strands are fully inserted into the crimp barrel.
• No broken or stray strands outside the crimp.

❌ Unacceptable:

• Wire is under-inserted or over-inserted.
• Strands are protruding or cut.

B. Crimp Symmetry & Shape

✅ Acceptable:

• Uniform crimp wings (no asymmetry).
• No cracks or splits in the terminal material.

❌ Unacceptable:

• Uneven crimp wings (misaligned tooling).
• Terminal material is cracked or deformed.

C. Insulation Crimp (If Applicable)

✅ Acceptable:

• Insulation is compressed but not pierced.
• No conductor strands trapped in the insulation crimp.

❌ Unacceptable:

• Insulation is cut or excessively deformed.
• Conductor strands are visible in the insulation crimp.

2. Mechanical Strength Testing

A. Pull-Force Test (Per ISO 19650, USCAR-21)

Failure Modes:

• Wire Break: Good crimp (failure at wire, not crimp).
• Crimp Pull-Out: Poor crimp (terminal releases wire).

B. Bend Test (Flexibility Check)

• Crimped terminal should withstand 3x 90° bends without breaking.

3. Electrical Performance Testing

A. Contact Resistance (Per USCAR-2, LV214)

• Max Allowable Resistance: < 1 mΩ (for power terminals).
• Measured with 4-wire Kelvin method to exclude lead resistance.

B. Voltage Drop Test

• Under rated current, voltage drop should be < 50 mV for signal terminals.

4. Cross-Sectional Analysis (Microsectioning)

A gold standard for crimp quality assessment:

Defects Detected:

• Under-Crimp (low compression → high resistance).
• Over-Crimp (terminal cracked or weakened).

5. Crimp Height Measurement

• Must match terminal manufacturer’s specification (e.g., 0.5 ± 0.05 mm).
• Checked with go/no-go gauge or optical measurement systems.

6. Environmental & Durability Tests

A. Thermal Cycling

• -40°C to +125°C, 500 cycles (no resistance increase > 10%).

B. Salt Spray Test (Corrosion Resistance)

• 96 hrs exposure (per ISO 9227) – no significant corrosion.

C. Vibration Test

• 10–2000 Hz, 50 m/s² (per ISO 16750-3) – no loosening.

7. Process Control & Documentation

• Crimp Force Monitoring (CFM): Records force vs. time to detect tool wear.
• Batch Traceability: Each crimp should be logged (for recalls).

Summary: Crimp Quality Checklist

Common Failure Causes & Fixes

Conclusion

Automotive terminal crimping must meet mechanical, electrical, and environmental standards. Visual checks, pull tests, cross-sectioning, and process monitoring ensure reliability. EV high-voltage terminals require even stricter validation due to safety risks.