Page 28 - ConnectorSupplier.com 2019 Mil/Aero eBook
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example, if the connector had only nine pins, each pin could safely carry 9A without exceeding the temperature restriction, and if it only had one contact, the per-pin current-carrying capacity rose to 12A. It would also be possible to have a connector with one signal pin capable of carrying a higher current and the others to be nominally rated.
Testing performed in accordance with IEC 60512-5-2 Test 5b shows that Nicomatic’s CMM Series connector contacts can handle between 3A and 12A, depending on the number of low-frequency signal contacts, without surpassing the allowable 30°C temperature rise.
However, these current limits are only for continuous use. So, if current levels only need to exceed the allowable limit for a short duration, then there may be no problem at all. Our European teams have recently worked with a customer who was using a CMM connector with high-power contacts to handle fast-pulse 10A currents and was actually able to advise that the design would perfectly safe using the lower-rated signal contacts, which also offered significant space savings.
Contact design are also crucial to connector performance. There are many different types of contacts, but the main goal of each is to maximize the contact surface in order to reduce contact resistance and self-heating. These characteristics can also be improved with selective gold plating, which may well be specified in corresponding international standards or individual customer specifications. One of the best contact designs for harsh environments features a beryllium-copper (BeCu) sprung ‘mosquito’ female clip, which provides positive pressure between male and female contacts to ensure that the surfaces are always in contact to maintain high signal integrity despite intense shock and vibration up to 100g and15g, respectively.
Connector insulator and body materials are vital as well. Polyphenylene sulfide (PPS) is often used for both, as it is oxygen-free and resistant to radiation and solvents, exhibits no humidity absorption, and reliably withstands even extreme temperature changes without deforming or losing functionality. Materials that resist outgassing are often critical in satellite applications where the payload is sensitive to contaminants.
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