Modern electrical engineering is subject to one trend more than ever: miniaturization. Assemblies and their components must not only become increasingly powerful but also increasingly smaller. Nevertheless, they are often used under harsh real-world conditions. Components, as well as connector, are therefore becoming increasingly delicate while withstanding the same level of stress. A high-quality connector, however, not only withstands this stress just as well as its older and larger counterpart, but even better. This is due to advancements in material composition and product design, such as in the geometry of the insulating body (Fig. 1).

 A variety of factors affect the robustness of a connector. One of these is the contact surface (contact surface). This significantly determines the connector’s service life, which is typically measured in insertion cycles (mating cycles). During field use, the connector is subjected to certain micro-movements. These lead to surface abrasion and, consequently, to oxidation (Fig. 2).

The contacts of a connector are stamped or turned. However, during the stamping process, an inhomogeneous, sharp-edged surface forms on the underside of the stamped strip that is visible under a microscope. Conventional systems make contact along this sheared edge (stamped edge), which results in increased surface abrasion and, consequently, higher contact contact resistance. This can be avoided by bending the spring tulip 90 degrees in the so-called stamping-bending process, so that it makes contact with the male contact via the smooth, rolled surface (Fig. 3).
 
However, it is not only the design of the spring strip (Female) but also that of the blade strip (Male) that is crucial for the connector’s longevity. This is because the blade strips must also be cleanly stamped and further processed to avoid defective, sharp geometries.

connector with a so-called “hermaphroditic” contact system, on the other hand, are even more robust. Their distinctive feature lies in the identical contact geometries of the two connector halves—Plug and Socket. Both therefore feature both a spring and a blade. This ensures that each pin is contacted by two springs, with the Plug and Socket interlocked so they cannot separate from one another. While a double-sided spring contact strip (Female) always ensures at least one contact point under mechanical stress, the interlocking geometries in gender-neutral contact systems guarantee that signal transmission always occurs via two contact points. This high level of redundancy thus ensures maximum contact reliability (Fig. 5).

  In this process, the press-fit pin has a larger diagonal dimension than the PCB hole diameter. The connector pin is flexible in the press-fit zone so that the PCB is not deformed by the physical forces during the insertion process. Deformation is therefore limited to the press-fit zone (Fig. 8). A cold welding forms between the contact pin and the metallized PCB hole: a gas-tight, corrosion-resistant, low-resistance, and electrically conductive mechanical connection that is also suitable for potting. It is also specified in DIN EN 60352-5 and maintains reliable contact even under very high mechanical and thermal stresses, such as vibration, bending, and extreme temperature fluctuations, and can even withstand shock loads of up to 200g.
 
Due to its outstanding robustness and a failure rate (FIT rate) ten times better than that of automatically soldered connector, the press-fit technology is frequently used in high-security applications where signal transmission must not be interrupted under any circumstances, such as in airbag systems or ABS and ESP modules.

 The insulation body geometry of a connector also helps protect the contacts from damage during operation or installation. It should be designed so that the vulnerable contacts are shielded inside the connector.

 Lead-in chamfers can also prevent damage during assembly. They help compensate for any misalignment of the circuit boards in any direction during mating. With the aid of an additional catch area, the two connector halves can be mated without damage even in the event of a center or angular misalignment (Fig. 10).

Some connectors (connector) also feature board locks. These are metal brackets attached to the insulator (insulator) and soldered to the printed circuit board (Fig. 11). In this way, they provide additional stability—even under adverse conditions such as vibration and shock.

The tolerance range of a connector plays a decisive role in assessing its robustness. If the connector cannot compensate for given tolerances, mechanical movements lead to wear or even damage to the connection. During installation, lead-in chamfers provide support to enable damage-free mating of male and Female. However, even when mated, micro-movements must be accommodated. This is achieved through the geometry of the contacts and insulating bodies. If a connector has a float-Funktion, it can compensate for up to ±0.4 mm even during operation. This function is becoming increasingly important, as it plays a crucial role when a printed circuit board is populated with multiple connectors. In the field, however, stresses arise not only in the x and y directions but also in the z direction (Fig. 12).

 Various testing methods are used to thoroughly evaluate connectors (connector) for their robustness characteristics. In these tests, variables such as dielectric withstanding voltage (voltage withstand) and contact resistance (contact resistance) are examined both before and after a stress test, and the condition of the contacts is visually inspected. For example, the effects of 500 mating cycles on the dielectric withstanding voltage can be assessed, or a climatic test can determine whether several hours at -55°C followed by 125°C have a negative impact on the contact resistance of the connector. In the temperature shock test, the connector must withstand rapid alternation between these extreme temperatures 100 times, for 30 minutes each. Furthermore, the axial and angular angular misalignment during mating, as well as the tolerance range when mated, should not only be verified theoretically using a CAD model but also extensively tested in practice, with their load-bearing capacity empirically confirmed. It is equally important that various tests critical to the contact surface (contact surface) be performed in combination to simulate real-world conditions. For example, mating cycles and mixed flowing gas tests could be conducted in combination to ensure that the connector’s performance in terms of contact resistance (contact resistance) and dielectric strength (dielectric withstanding voltage) has not deteriorated and that the contacts have not been damaged (Fig. 14).