Circular Turned Multi-Fingered Contact
This contact is machined in beryllium copper with the spring fingers (also known as tines) being an integral part of the contact, rather than a subcomponent. The mating pin is circular to ensure contact is made with all of the tines. This one-part design overcomes the current-carrying limitation of the circular stamped contact clip, while at the same time maintaining signal continuity during conditions of vibration at a smaller size.
This style of contact is used in a wide variety of high-reliability applications where small size and light weight are pre-requisites such as UAVs, military portable equipment, and avionics.
Individual spring contacts (also known as shield fingers or grounding contacts) are a simple folded metal strip design that can be mated with a variety of flat surfaces. The design is used to connect PCBs to other boards or components, to pass signals and current, or to the chassis for grounding. The advantage is that they offer a low cost of ownership — they are both low-cost to purchase and low-cost to assemble onto a PCB. They are usually supplied on tape-and-reel packaging, thus enabling use of advanced manufacturing processes such as pick-and-place machines.
A disadvantage is a risk of over-compression that can result in permanent set, although there are some designs that have a “positive stop” to prevent this.
Typical applications include wearables, mobile devices, and antennas.
Spring Loaded Contact
This design comprises a plunger, spring, and barrel. The plunger is held under pressure by the spring contained in the barrel. The mating part is usually a fixed flat surface either as part of a connector or as an individual PCB pad. This design is used when rapid mating and un-mating of the connector is required in applications where there is a risk of variation in the closing mating dimension. It can also be used in “blind mate” applications where the engagement of the connectors cannot be seen, and precise alignment cannot be achieved. The spring loaded contact is also commonly used as a probe on automatic test equipment. Devices have high durability, with the number of operational cycles being 10,000 or more. These features come with a cost that is noticeably higher than that of the spring contact.
This is an arrangement of twisted wires to form a hyperbola shape between the two ends of a socket. The mating round pin, when inserted, stretches the wires, putting tension on the pin and creating a good electrical contact. The main disadvantage is the particularly high cost of the contact design.
This design offers high durability and is used in applications where shock and vibration are expected such as military, avionic, railway, and other rugged applications.
Contact performance varies considerably due to the contact design, as discussed above, and the manufacturer. Great care and consideration should therefore be paid to the selection of technology and supplier, especially if the connector is to be used in harsh and challenging environments. The customer should ensure that they have a full understanding of their performance and environmental criteria, which can also help connector manufacturers guide them to the most suitable connection technology.
This article was written by Scott Flower, Product Strategy Manager – High-Reliability Connectors at Harwin, Salem, NH. For more information, Click Here.