Spring contacts - small powerhouses with up to 15A

PC & Industry 04/2023
Spring contacts – small powerhouses with up to 15A (.pdf) >>


Spring contacts - high integration density and very small design

Spring contacts have become indispensable in today's electronics. With their high level of integration and very small designs, they facilitate assembly and thus significantly reduce costs. Spring contact probes are the first choice, especially in communication technology, where slim and design-oriented constructions are required. They reduce manual work time and open up new design and arrangement options for industrial designers and engineers.

The spring contacts are used for power and data transmission and can handle currents of up to 15A per pin. They have a high tolerance range and are particularly suitable for contacting uneven surfaces. They have a long service life of at least 10.000 cycles. Contact is made by touching a spring-loaded pin and enables temporary electrical connections between two devices. Unlike other connectors using the stamping process, spring contacts do not require a mold and are manufactured using high-precision lathes, making them relatively inexpensive.

Structure of a spring contact

A contact pin consists of a plunger, a spring and a pin sleeve. As standard, the piston and pin sleeve are made of brass and the springs are made of stainless steel. The plunger and barrel are additionally coated with gold to provide excellent electrical conductivity and a high level of protection against corrosion and oxidation. Other materials such as nickel, palladium-nickel, brass and palladium-cobalt in silver and black are optionally available to meet the requirements of special applications. Partially different coatings of the individual parts are also possible.

Right angle design connector with Super AP coating
space-saving right-angle connector with partial Super-AP coating

special coating

The Super AP coating is of particular interest for wearables. This coating is extremely resistant to electrolytic or galvanic corrosion and has a very low resistance. Compared to conventional gold coatings, the Super AP coating is twice as resistant to salt water, five times more resistant to perspiration and even 30 times more resistant to electrolysis. Electrical contacts are thus effectively protected against corrosion caused by sweat or moisture.

Wearable products such as fitness trackers, smartwatches or heart rate monitors are often used in environments where they come into contact with sweat and moisture. The Super AP coating minimizes corrosion of the electrical contacts and ensures long life and effective functioning of the devices.

Construction of spring contact
Design variants of spring contacts: back drill design, bias design, 4P design with ball, 4P design with cap

Design variants of spring contacts

Spring contacts are available in different lengths from 1mm to 41mm. For smaller constructions, it becomes innovative Back drill design applied to achieve the desired spring force. Here, the spring used is longer than the hollow piston. From a length of 3,5mm this is standard bias design used in which the piston is beveled at an angle of up to 18° at its end. This guarantees 100% contact with the pen sleeve and reduces signal interference from vibration.

For applications with high current carrying capacity and vibration resistance requirements (>3A), the bias design is supplemented by the 4P design added. Here, the piston, the compression spring and the sleeve are supplemented by a stainless steel ball as the fourth component to prevent the compression spring from burning up due to insufficient lateral forces at high currents. Alternatively, a cap can also be used.

This will be the case with high-current applications from 5A 4P design with cap deployed. The sleeve of the piston is additionally reinforced and a special structure inside the spring contact increases the contact area.

The spring force varies between 25 and 400 g depending on the type of spring contact. A minimum spring force of 60 g is recommended for stable signal transmission and 110 g for efficient power transmission. The higher the spring force, the better the piston is pressed against the housing wall and enables a stable current flow. The standard operating temperature of the spring contacts is -40° to +85°. If special materials are used, the range of application can be extended to up to 150°C in the long term.

Rolling head, spring contact with ball tip
Rolling pins for 360° rotations

Special design variants for individual constructions

The selection of different connection types such as SMD, THT, crimp and solder cups as well as design variants such as the rolling pins or the Screw pin enables a high degree of design freedom in the construction. The solder cup allows, for example, direct cable contacting with spring and mating contacts. In combination with a suitable connector housing, an easy-to-implement, wired, spring-loaded interface solution is possible.

Regular spring contact probes are designed for vertical movement. Spring contacts in the rolling pin design have an integrated ball in the pin tip and allow continuous contact in up to 360° rotations. In order to guarantee 100% contact of the piston with the pin barrel and to significantly reduce transmission disturbances due to vibrations, the rolling pin is constructed on the basis of the bias design. These pins are currently available with a current rating of 1A-6A.

Screw Pin, spring contact with screw thread
Screw Pin, spring contact with screw thread

Spring contacts in screw or right angle design: an option for small devices

If devices require contacting in a very small space, spring contacts in screw or right angle design are an option. Spring contacts in screw design have an integrated screw thread and can be screwed into a printed circuit board to save space. Right angle contacts on the other hand, are placed directly flush on the printed circuit board. Double ended spring contacts are another design option and offer a spring loaded contact at both ends. They can be used to create temporary or permanent connections between two circuit boards. Since there is only one sleeve, the material and weight are also reduced.

Connectors based on spring contacts: easy to implement

The realization of plugs based on spring contacts is very simple. Several spring contact probes can be combined in a plastic housing to form a spring contact connector. These connectors can be customized in terms of pitch, pin count and housing dimensions. There is no maximum number of spring contact pins in a connector, so multi-row solutions are also possible, especially when high currents are to be transmitted. The minimum pin spacing varies depending on the size and rating of the spring contact probe. A possible pin distance (pitch) is 2,54 mm. Due to the large number of spring contacts, particularly small connectors, waterproof solutions up to IP68, special solutions for high-current applications and magnetic connectors can also be implemented.

Spring contact based connector Spring contact based connector

Magnetic plugs

In contrast to conventional plug-in systems, which require a certain insertion depth for optimal locking magnetic connector system based on spring contacts with a very flat and planar design. The implementation of magnets ensures a self-guiding, as well as shock and vibration resistant connection between connector and device. This makes it very easy and convenient to use, especially in difficult or small installation situations.

The polarity of the magnets prevents incorrect connection, which ensures high contact and functional reliability. In addition, the magnetic force can be adjusted to the respective requirement through different compositions and the limit values ​​of sensitive devices, especially in medical technology, can be sufficiently taken into account. In contrast to conventional plugs, the stress during contact and the associated wear on the socket with magnetic plugs is minimal. An installation depth of just a few millimeters is sufficient for reliable contacting. Sealing with elastomer materials or the direct overmoulding of the plug with plastic ensure a system that can be cleaned and disinfected very well. Even protection classes up to IP68 for immersion disinfection are possible.

Another advantage of direct implementation or overmoulded system solutions is that assembly times and costs can be significantly reduced. The risk of moisture and dirt penetrating the interior of the device is also virtually eliminated. Prototypes of an individual magnetic plug can be realized quite easily using 3D printing and manual further processing for the first installation tests and testing of the magnetic force.

Magnetic connector with spring contacts
Custom magnetic connector with spring contacts

 

Design and production from a single source

Our product design experts are your partner for tailor-made magnetic connectors. We offer a comprehensive design and development of individual connectors from a single source. We will be happy to advise you on the selection of the optimal materials and support you with our experience.

In our Spring contact product range we have a wide range of over 300 different standard pins that we can select to suit your application and build into bespoke connectors. We also offer customization of the spring contacts to ensure they perfectly match your specific needs.

Almost all spring contacts can be supplied with a cap for automated circuit board assembly. This enables faster assembly and easier handling. We ensure that the quality and performance of our connectors meet the highest standards and meet the needs of our customers.

Contact N&H Technology >>