Materials and Plating for Harsh-Environment Connectors
When designing connectors for use in applications in harsh environments, such as oil refineries, chemical plants, and industrial settings, special consideration must be given to protect not only the component but the end application as well. Depending on the market and application, protection requirements can include, but aren’t limited to, NEMA ratings, surge protection, EMI shielding, environmental sealing and reliability. Each of these requirements can be addressed by design considerations which include the connector materials and plating.
NEMA-Rated Products
Many equipment manufacturers require an industrial connector that, when designed into the box, can maintain a NEMA-rated explosion-proof environment. While this isn’t necessarily a technical challenge, the connector must structurally withstand the NEMA class 7 standard. In applications such as chemical plants, oil exploration and drilling rigs—generally anywhere there is energy production outside of solar, resulting in a potential for explosion—explosion-proof components are paramount. Ultimately, the main concern addresses the materials used to construct the insulator. While a plastic insulator is not suitable because the plastic will blow out during an explosion, a metal connector with a hermetic, glass-sealed insulator will conform to NEMA standards.
Surge Protection
Connectors must also be able to withstand surges common in equipment for harsh environments. Lightning strike, also referred to as transient voltage spike, is a common design consideration for surge. By utilizing capacitor-based filter connectors, including planar array or Chip-on-Flex connectors, surge spikes can be suppressed down to 18 volts or less, depending on the device.
Despite this capability, it is still rather difficult to meet both the surge rating requirements and size constraints as required by equipment manufacturers. Connectors were previously designed with isolated components such as diodes and capacitors to create a filtering network to withstand surge spikes, but the resulting devices required large-size packages to accommodate multiple components. Today, some connector solutions incorporate filter chips placed in an array on the back of the connector and attached to the signal pins, providing surge protection in a much smaller package.
Chip-on-Flex filter connector designs, for example, replace current planar array capacitors with advanced design flex circuits where individual chip capacitors are surface-mounted adjacent to the contact. Because the contact is not soldered directly to the capacitor, thermal stress points associated with the current planar array designs are eliminated. Such designs are EMP- and surge-protected with a zener chip diode and filtered, grounded, and isolated feed-through contact options further ensure a robust design resistant to surge, thermal shock, and vibration.
