DISTRIBUTION The key to connector reliability


Connectors are the lifelines of nearly every modern electronic device — from portable medical monitors and military communication systems to smartphones and consumer electronics.


W


hen a connector fails, the entire system’s reliability is compromised, often damaging not only performance but also the reputation of the manufacturer. Despite major advancements in connector technology, reliability issues continue to surface, usually long after products have entered service. Too often, these failures  frustrated and manufacturers scrambling for corrective actions that could have been avoided.


What many design engineers still overlook is that connector reliability is not a mystery. There exists a proven, physics- based predictor of long-term connector performance: Hertz stress.


What is Hertz stress?


Hertz stress — or Hertzian contact stress —  when two curved metal surfaces deform slightly under load. In connector design, that deformation determines how much of the contact surfaces actually meet at the microscopic level, creating metal-to-metal  The higher the Hertz stress, the stronger and more stable the conductive path. A landmark  successful connector designs exhibit Hertz stress values an order of magnitude greater than those that fail. This principle remains valid today, even as connectors have evolved to become smaller, lighter and more capable of withstanding vibration, shock and other environmental extremes.


The science behind stable contact resistance


Every metallic connection relies on a network of microscopic contact points, or asperities (often referred to as ‘A-spots’), where the  The quality of these A-spots depends on


 contact geometry, material hardness and applied normal force.


The total contact resistance (Rt) is the sum of three components: • Rt=Rb+Rc+RfRt = Rb + Rc + RfRt=Rb+Rc+Rf • Where: • Rb = bulk resistance (based on contact materials)


• Rc = constriction resistance (linked to asperity distribution and size)


•


 contamination)


 and the most detrimental. All metals develop   higher the resistance and the less stable the 


Designing for optimal Hertz stress A common misconception is that simply increasing the normal force will improve contact reliability. In reality, excessive force can cause material fatigue and reduce connector life. The key lies in geometry, not brute force.


Connectors designed with domed or curved contact surfaces generate higher Hertz stress across smaller contact areas. This concentrated force enables the contact  more stable A-spots without overstressing the material.


The contrast can be illustrated by  under identical load. The domed geometry channels the same normal force into a smaller area, producing a stronger, more consistent connection.


When motion matters: The role of contact wipe


 for static pressure to penetrate, contact movement, or “wipe”, becomes essential. Wipe refers to the sliding action between mating contacts that helps remove oxides  However, the amount of wipe must be carefully controlled. Too little movement fails to clean the surface; too much can create new debris and increase resistance. The IBM and ITT studies showed that geometries


34 APRIL 2026 | ELECTRONICS FOR ENGINEERS


producing the highest Hertz stress also promote effective wipe action, achieving a stable, self-cleaning interface.


Design lessons from industry leaders


The IBM research, conducted in collaboration with ITT connector engineers, became a foundation for modern connector design. ITT subsequently redesigned many of its contact systems to achieve high Hertz stress — a principle embedded in several of its current product lines.


One example is the ITT Cannon Universal Contact, which features a domed mating area engineered to deliver high Hertz stress  reliable contact across multiple axes (X, Y and Z) and maintains consistent electrical performance in compact, mobile devices. Applications range from medical instruments and handheld radios to security systems, GPS devices and consumer electronics. Another ITT innovation, the Cannon QLC (Quad Lock Connect) series, applies the same Hertz stress design principles to serve demanding industrial, instrumentation and medical environments, including portable ultrasound systems, patient monitors and semiconductor tools.


Reliability is predictable, not accidental


Connector reliability doesn’t have to be a gamble. The physics are well understood, and the principle is clear: high Hertz stress equals dependable contact performance. By prioritizing Hertz stress in connector design and selection, engineers can prevent failures before they occur — saving time, cost and reputation.


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