What reliability tests do connectors need?

Four lines, organised by failure mechanism

Electrical performance

• Contact resistance: measure the initial value, then the change after the test. The change matters more than the absolute value — loose terminals, worn plating and fretting corrosion all show up as a shift.
• Insulation resistance: between terminals, and between terminals and the housing.
• Dielectric withstand: verifies that the insulation is not broken down under overvoltage.
• Temperature rise under current: apply the rated current and measure the steady-state rise, to judge whether terminal cross-section and contact quality are matched.

Mechanical performance

• Insertion and extraction force: affects assembly feel and reflects whether terminal normal force is appropriate (too high wears faster, too low makes contact unreliable).
• Terminal retention force: verifies how firmly the terminal is held in the housing and prevents it backing out.
• Vibration and mechanical shock: simulates real vehicle conditions and checks for micro-breaks.
• Locking mechanism strength: holding ability under repeated mating and external force.

Environmental performance

• Temperature cycling / thermal shock: differences in the thermal expansion of materials introduce terminal stress and can break sealing.
• Constant and cyclic damp heat: examines insulation performance and corrosion of metal parts.
• Salt mist: a standard item for chassis and external connectors.
• Ingress protection (IP): water and dust, with the rating set by mounting location.

Material and plating

• Plating thickness and adhesion: too thin and wear resistance is insufficient; too thick and it can affect mating force.
• Tin whiskers: pure tin plating grows whiskers under stress and can cause shorts, so automotive parts generally require mitigation.
• Flame retardancy: UL 94 or the corresponding standard as required by the customer.

Two things automotive use adds

Vibration superimposed on temperature. Real conditions apply vibration and temperature at the same time; testing them separately underestimates the risk. Combined temperature-vibration testing exists precisely for this scenario.

Fretting corrosion. Under small relative movements (vibration, thermal expansion and contraction) the plating on the contact surface wears through, exposes the base metal and oxidises. The symptom is contact resistance rising with service time or mileage. It is the most common failure in automotive connectors and the hardest to find at the design stage, and usually requires a purpose-built test combination to reproduce.

Choosing the reference standard

• General environment: ISO 16750-3 (mechanical), ISO 16750-4 (climatic), the GB/T 28046 series
• Connector-specific: LV 124 (common with German OEMs), USCAR-2 (US OEMs)
• OEM corporate standards: usually stricter than the generic standards and taking precedence over both

When the customer has not specified a standard, issue a list based on the generic standards first, then confirm with the customer whether a corporate standard should be layered on — the difference between the two sets is often substantial.

Where we stand

TMC LAB holds both CMA and CNAS accreditation and covers the electrical, mechanical, climatic and material items for connectors and wiring harnesses, including combined temperature-vibration testing and witness testing on site. Send us the connector model, its mounting location and your customer's standard, and we will propose a test combination organised by failure mechanism.