In addition to meeting general performance requirements, electrical connectors have three critical core demands: excellent contact performance, stable operation and easy maintenance. Their operational reliability directly determines the normal functioning of the entire equipment circuit and bears relation to the safety of the whole main device. Accordingly, circuits impose extremely stringent standards on the quality and reliability of electrical connectors.
As the core internal components responsible for electrical contact within electrical connectors, contacts play a decisive role in connector reliability. The reliability of contacts is affected by multiple factors, including structural design, processing technology, manufacturing, production management, raw material properties and service environment.
There are numerous parameters influencing electrical contact reliability, mainly covering contact material properties, operating conditions, ambient gases and other aspects. To secure electrical contact reliability by developing solutions against contact failure, it is essential to investigate and analyze the failure mechanism of contact points. Relevant research mainly focuses on the following areas:
Material Research
The properties of all materials degrade over time. Therefore, priority shall be given to high-performance materials that can maintain long-term reliability, followed by evaluation of service environments, ensuring the materials are capable of withstanding harsh working conditions.
Research on Processing & Manufacturing
Manufacturing defects are prevalent among domestically produced connectors in China at present. Insufficient processing capacity creates a substantial performance gap between actual finished connectors and ideal design specifications, which in turn undermines overall reliability.
Research on Environmental Factors
When contacts corrode under atmospheric conditions, the surface geometry of contact areas will alter. Compared with the ideal state, all relevant parameters change not only over time but also with varying operating conditions. This degrades electrical contact performance and ultimately leads to electrical contact failure.
Based on the three major factors causing electrical contact failures mentioned above, this paper mainly discusses the structure, characteristics and design procedures of a specific crown spring, so as to achieve superior service performance and prevent premature electrical contact failures.
1. Crown Spring Structure
Crown springs are divided into inner crown springs and outer crown springs. The outer crown spring is also known as a lantern contact, which is mounted on the outer cylindrical surface of the pin and forms a contact pair with the cylindrical socket, as shown in Figure 1. The inner crown spring is installed inside the inner bore of the socket and forms a contact pair with the cylindrical pin, as shown in Figure 2.
2. Characteristics of Crown Spring
Crown Spring Socket Structure and Contact Reliability
As can be seen from the crown spring structure, when an outer crown spring is adopted, the actual contact surface of the contact element is the outer spherical surface of the lantern head, which makes contact with the cylindrical surface of the socket. For inner crown springs, the inner spherical surface of the inner crown spring contacts the cylindrical surface of the pin. Both configurations feature point-surface contact.
With identical normal force, material and structural parameters, point-surface contact delivers lower compression resistance and film resistance compared with surface-to-surface contact, resulting in a relatively low actual contact resistance for crown spring structures.
In addition, crown springs rely on elastic deformation for locking, which imposes moderate precision requirements on contact components. Accordingly, crown spring sockets/pins offer smooth mating and unmating, stable and reliable contact, excellent resistance to vibration and shock, and high mating cycle life. Compared with wire spring sockets, they are more suitable for mass production and demonstrate superior performance in high-current applications, overcoming the drawback of insufficient current-carrying capacity of wire spring sockets, while maintaining a low cost.
Crown spring sockets feature smooth mating and unmating as well as reliable contact. As one of the widely used contact elements, they generate lower insertion and extraction force and provide softer operation compared with slotted elastic sockets, and are mainly applied to multi-core and high-density electrical connectors.
When pins mate with sockets, the normal force generated by elastic deformation of the contact rings ensures tight contact between contact rings and pins for signal transmission. The mating schematic of crown spring sockets and male pins is shown in Figure 1.
There are numerous factors affecting the contact reliability of electrical connectors. Two indicators, namely single-contact separation force and contact resistance, are commonly adopted to evaluate connector contact reliability.
3. Design Procedures and Key Points of Crown Spring
Sockets are the core components that realize electrical connection in connectors, and crown springs, as the key part of sockets (pins), play a vital role. Therefore, proper selection of crown springs and rational design of crown spring sockets (pins) are critical to meeting electrical performance requirements of contact pairs, including contact resistance, mating force and temperature rise. Great importance must be attached to crown spring selection and the design of crown spring sockets (pins).
Design Procedures of Inner and Outer Crown Springs
l Determine the specific structural form: adopt an inner crown spring or outer crown spring. Select the appropriate crown spring structure according to product application conditions to judge whether the inner or outer crown spring better satisfies the requirements.
l Determine the diameter of pins or sockets. Select a proper pin diameter for the inner crown spring structure and a proper socket diameter for the outer crown spring structure based on the maximum load current during product operation.
l Determine other dimensional parameters. Design the remaining dimensions of the crown spring according to the pin or socket diameter.
l Determine the dimensions of mating parts for the crown spring. Match the pin dimensions to the finalized inner crown spring, and match the socket dimensions to the finalized outer crown spring.
Key Design Points
The unilateral compression of the crown spring after mating shall be controlled within the range of 0.15～0.25 mm.
The structural dimensions of the crown spring directly affect the separation force of the contact pair. With all other parameters unchanged, a larger spherical radius R and longer spherical section length S of the crown spring middle section, as well as a smaller slot width P on the spherical part, will correspondingly reduce the separation force of the contact pair. However, excessively large spherical radius R and spherical section length S, or an overly narrow slot width, are not favorable. Reasonable design of these three parameters is required to achieve appropriate separation force and excellent contact resistance. In addition, the slot width cannot be too narrow to facilitate mold machining and extend mold service life.
An expanded drawing of the crown spring with open ends shall be drawn to facilitate mold design and processing.
All dimensions specified in the design procedures refer to the dimensions of the crown spring under working mating state.
4. Conclusion
In summary, inner and outer crown springs together with their mating pins and sockets are critical assemblies of electrical connectors, which directly govern the reliability of connectors. The service performance of crown spring structures depends not only on the design process, but also on the material and machining technology of matching pins and sockets.
Generally, pins and sockets are mostly made of copper alloy or pure copper to meet the conductivity requirements in practical service, and they are manufactured by mechanical processing. To achieve superior service performance, post surface treatment is required on the surface of inner and outer crown springs. Detailed design procedures for inner and outer crown spring structures will be completed in follow-up research.
Amass High current connector use the crown spring which can help you maintain stable connections in application scenarios such as high-intensity vibration, repeated high and low temperature impacts, small volume, and high current
Amass’s 4th-generation products fully adopt crown spring contact technology, drastically extending service life and enhancing operational stability. They deliver reliable protection for equipment operating under compact size constraints, intense vibration, and repeated thermal shock between high and low temperatures.
Post time: Jul-04-2026