Engineering Contact Engagement and Normal Force for Long-Term Connector Performance

Aerospace and defense connectors must reliably operate in the most extreme environments. These components face sustained mechanical stress from vibration, temperature swings and occasional connector engagement. While housings and shielding guard the exterior, true reliability is determined at the contact itself—where signal transmission either holds or breaks down.

Problems rarely begin with an obvious failure. They often start with subtle degradation such as increasing resistance or signal instability. At the heart of this deterioration is a delicate relationship between contact force and physical fit. To that end, how can engineers design electrical and mechanical connections that provide reliable performance without compromising their longevity?

Two core design elements determine a connector’s endurance: contact engagement and normal force. Contact engagement defines how much surface area makes metal-to-metal contact. Normal force refers to the pressure applied to maintain mechanical contact and electrical flow.

Signal degradation and mechanical wear often trace back to uneven force distribution or misaligned contacts. Rounded interfaces assist with wiping and debris removal, while flatter shapes spread pressure more evenly and reduce strain during mating.

Reliable performance hinges on careful calibration under real-world conditions.

Premature wear and instability often result from incorrect force distribution. Too much contact load can accelerate plating wear, deform connector housings or overstress spring elements—especially in dense or lightweight systems. Too little pressure, on the other hand, increases contact resistance and makes the connector more vulnerable to fretting corrosion and signal dropouts under vibration.

The critical design objective is to apply only as much force as necessary to preserve long-term mechanical and electrical reliability. For instance, gold-plated contacts can remain stable with as little as 10 grams of force in ideal lab conditions, but real-world systems often require more force to maintain consistent performance. In mission-critical applications, where vibration, shock and thermal shifts are common, higher pressure may be required to sustain performance.

Excessive engagement also introduces challenges. Longer contact wipes can help clean oxidized surfaces, but additional overlap eventually stops improving conductivity. Once asperities (the tiny peaks and valleys that carry current) have been wiped and aligned, further engagement only increases friction. This added mechanical stress accelerates plating degradation and risks deforming housings, particularly in dense or lightweight systems. Beyond a certain point, added overlap contributes to wear without enhancing conductivity.

Various design factors affect how well a connector maintains electrical flow and endures real-world use. Each choice impacts the entire system. Contact geometry determines how stress is distributed at the interface and how effectively surfaces wipe clean. Rounded shapes create high-pressure points for effective scrubbing, while flat geometries distribute force more broadly.

Spring design affects preload, fatigue resistance and consistency of applied force across cycles. Too much spring tension can damage the housing, while too little causes instability.

Material selection also matters. Conductivity, resistance to corrosion and surface hardness all impact how well the contact resists premature wear over time. Choosing the right metal—gold, palladium-nickel or beryllium copper, for example—depends on both the electrical requirements and mechanical environment.

Connector designs must be validated under real-world conditions to preserve dependability across a product’s service life. Mating and unmating tests verify whether a connector survives hundreds of cycles—typically 200 for standard military designs and 500 or more for premium aerospace-grade systems.

Dielectric and resistance testing confirm that electrical continuity holds. Environmental simulations, including shock, vibration, humidity and oxidation exposure, reveal potential wear mechanisms that may not appear in static lab tests.

Standards such as EIA 364F and EIA 364-1000 define the mechanical and environmental tests used to qualify aerospace connectors. Temperature cycling from –55°C to +125°C replicates typical thermal extremes. Specialized systems for cryogenic or space applications may be tested from –200°C to +200°C. Humidity testing at 95 percent relative humidity assesses how well the system resists moisture. Shock and vibration tests measure whether contact remains secure under motion. Engagement force tests confirm whether mechanical connections hold across repeated use.

Connectors from AirBorn, a Molex company, are engineered to perform consistently across frequent mating, physical stress and environmental extremes. From defense systems to spaceflight hardware, these solutions have been validated in use cases where signal integrity and mechanical durability cannot be compromised.

AirBorn provides electronic solutions that support the full product lifecycle. This includes everything from early design through prototyping and full-scale production. Explore AirBorn connectivity solutions to see how precision engineering translates into reliability in the most challenging aerospace and defense environments.

GO DEEPER: Read the full report: Defining and Advancing Rugged, Reliable Connectivity in Aerospace and Defense