High Reliability Connector Styles

A huge range of products demand high uptime and rugged operation capabilities, which demands rugged connectors be used in a PCB assembly. Rugged connectors come in many varieties and form factors, but most principally they must be designed to resist mechanical shocks, high temperature, and degradation under high voltage and/or ESD. If you’re looking for a rugged connector system, try looking for parts with the characteristics listed below. This article outlines some of the important qualities and features of high-reliability connectors.

What Qualifies as a “High Reliability” Connector?

There are also some important features that are found on connectors that may be qualified for high-reliability applications. These include terminal isolation, locking, keying, retention, and IP ratings.

Partially or Fully Isolated Terminals

The term “isolation” in reference to connector terminals refers to the use of shielding between neighboring contacts on a connector. This type of connector would provide higher isolation against high voltage breakdown compared to a connector without isolated terminals. The isolation between terminals is applied based on the housing, where housing material fills the space between the terminals.

This Mini-Fit connector system from Molex and PCB-mount mating connector has fully isolated terminals on the cable connector and the mating connector.

By placing the housing around the terminals, the terminals can include a keying mechanism to make the connector rotation-proof (polarized). In the case of isolated terminals, this could be done by applying a chamfer along the corner of an edge terminal. More on keying mechanisms can be found in the section below.

Terminal Position Assurance (TPA)

TPA refers to a set of mechanisms used to ensure that each terminal in a connector is fully seated in the connector housing. This is normally done with cable connectors in a wire-to-board connector system. The use of TPA intends to prevent terminals from backing out or becoming dislodged from the connector housing. This can be crucial in applications where a loose connection could lead to equipment failure or safety hazards. They can be more reliable than crimp connectors, although this depends on the TPA mechanism.

When a terminal is fully inserted into a connector housing, some retention mechanism is triggered, which locks the terminal in place in order to keep the terminal properly seated. In some connectors, this might be a plastic or metal tab that snaps into place.

Keying and Retention

This is a broader term referring to mechanisms that ensure polarity is maintained, and that the connector system can be retained together. Keying generally includes mechanisms that prevent polarity reversal or misalignment of pins, such as you would see in shrouded pin headers. Some positive locking mechanisms or TPA mechanisms also provide keying as the mechanism is only engaged when the connector bodies are keyed correctly.

The arrangement of the terminals in this panel-mount connector functions as a keying mechanism.

Retention generally refers to any mechanism that locks the connection in place, and it includes positive locking. However, some retention mechanisms are not positive locking because they must be engaged manually. This could include manually engaged screws or latches that prevent disconnection.

Positive Locking Connectors

Positive locking connectors include a mechanism designed to engage some type of fastener that automatically locks the connection as the two connector bodies are mated. This helps prevent disconnection through vibration, tension, or mechanical shock. The locking mechanism becomes engaged only once the connector is inserted in place on the mating connector. Positive locking mechanisms include:

• Latch locking, where a latch snaps into place on the other part of the connector when the two parts are connected
• Screw locking, where a screw is engaged such that it fully joins and locks the two sides of the connector system
• Bayonet locking, where a set of paired grooves and pins on each side of the connector system slide together and lock the connection

In each of these mechanisms, the user must manually disengage the locking mechanism if the connector system is to be disconnected.

IP Rating

Finally, the connector style you select should ensure whatever IP rating you are trying to reach in your PCBA. The IP rating system, referring to ingress protection, provides ratings specifying the level of solid and liquid infiltration resistance at the connector interface. Connector IP ratings should be chosen to match the expected exposure to solid and liquid contaminants, and the enclosure’s IP rating should match that of the connector.

Waterproof USB Type A connector body. When this fits with its mating connector, you get a waterproof interface.

These are not the only connector styles or characteristics that would qualify as “high reliability,” but they should help you start your search for a rugged connector style that will work best for your system.

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