Today’s PCB plug-in connectors must accommodate many trends, including increasing miniaturization, rising levels of performance of electronic components, and growing complexity in machine and system engineering.

Despite becoming more and more compact, these connectors must function just as well as their larger counterparts. Connection and locking technologies need to accurately match the application requirements, especially if they must withstand large amounts of vibration, such as in motor and drive applications.

All types of plug-in connectors face big demands. Most importantly, they must be reliable and have a long connection lifespan, even in challenging conditions. To accommodate such requirements in practice, design engineers often choose to combine different types of secure connections, such as screw-based or push-in connections, with a range of locking mechanisms. These include lock-and-release, click-and-lock, the self-locking flange, the screw flange, and snap-in locking.

Contact forces are an important consideration in connection technology. Even the best, most conductive material is rendered ineffective without sufficient contact force. According to Holm’s contact theory, a high-contact force typically causes a low-contact resistance. However, high-contact forces are only effective if their pressure is maintained. This is why contact reliability can be improved through design principles, such as a high-quality copper alloy, and using the Reakdyn principle in screw connection. In the patented Reakdyn screw locking system, the clamping sleeve features a built-in break. As the screw is tightened, it increases the friction in the thread, which prevents the connection from loosening due to vibration. This ensures a more reliable connection.

Plug-in connectors with the lock-and-release system feature tool-free locking, releasing, and unplugging.

Screw connections continue to be the most common termination technology. However, spring-cage connection technology has also established itself in many markets, and push-in spring connections are becoming increasingly popular. PCB plug-in connectors with push-in technology make use of a compression spring. The spring presses the conductor against the copper rail that carries the current. This exerts a constant, predefined force, which in turn facilitates a high-quality electrical connection — vibration-proof, gas-tight, and reliable.

In high-vibration applications, such as motors and drives, the installed components must provide very high safety and long service life. The design engineer must choose the connector and base terminal with the most reliable connection methods and the firmest connection possible. Locking is provided through mechanisms for tightly pressing connectors onto base terminals. Such mechanisms ensure that the connector contacts are connected securely, with high conductivity and without any deterioration over time.

A lock-and-release lever system will automatically interlock the plug-in connector with the base housing when inserted. No further lever action is required to complete locking. To release the plug-in connector, the user simply presses the lever, automatically ejecting the connector. Depending on requirements, the conductors can be wired in several ways, including screw connections and push-in connections. Headers with horizontal or vertical design can increase flexibility. Housings made from liquid crystal polymer (LCP) can withstand high temperatures and are ideal for the reflow soldering process.

Plug-in connectors with the click-and-lock system facilitate secure connections even during fast wire-to-board installation.

The click-and-lock method similarly provides reliability for vibration environments. Again, interlocking is automatic and requires no tools. The user inserts the plug-in connector into the base terminal, and the lateral guides lock in firmly with an audible click. The click-and-lock system greatly simplifies the installation of wire-to-board connections. Here, the click-and-lock mechanism is combined with either a push-in spring-cage connection or a screw connection. Base housings compatible with click-and-lock systems are also available.

When plugging in a connector with a self-locking flange, the lateral snap flanges interlock with the base housing behind the molded mounting noses. This system prevents the connector from being pulled out accidentally, and it also makes the connection vibration-proof. To release the connector, push down the two ergonomically designed locking levers to unplug it from the base terminal. No tools are required to lock, release, or unplug the connector housings. This connection technology is well suited to plug-in connectors based on push-in spring-cage technology.

Ergonomically designed locking levers on the plug-in connector simplify locking and releasing.

Screw-flange locking is the most common of all locking methods. Here, the base housing has lateral threads that are tightly screwed together with the plug-in connector. This principle also facilitates a secure and reliable connection to the base housing. When combined with either screw connections or push-in connections, plug-in connectors that use screw flanges can be used for conducting signals, data, and power.

Pin strips with snap-in locking prevent the installed connectors from accidentally loosening due to vibrations. The pin strips made of high-temperature-resistant polyamide are suitable for reflow and wave soldering processes. Pin strips that use this locking mechanism can be combined with the corresponding plug-in connectors. The connectors can be plugged onto the pin strips and also use push-in connections. Pin strips with snap-in locking provide rugged and reliable connections. They are particularly suitable for the high mechanical stresses and vibrations typically encountered in industrial environments.

Today’s plug-in connector systems bring together secure connections and reliable locking. In case of malfunctions during operation, connectors on machines and systems can be replaced quickly and without requiring any tools, thanks to the different locking mechanisms provided. This helps to ensure ongoing plant and machine availability.

This article was written by Dieudonné Manga, Business Development, Division Device Connectors, at Phoenix Contact GmbH & Co. KG, Blomberg, Germany; and James Dunbar, Product Marketing Manager – PCC, at Phoenix Contact USA, Middletown, PA. For more information, Click Here .


Motion Control & Automation Technology Magazine

This article first appeared in the October, 2014 issue of Motion Control & Automation Technology Magazine.

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