What exactly is the cause of the contact sticking in relays?

Relays are common switch components in PCB hardware circuits and various electrical control devices. They are widely used in fields such as household appliances, industrial control, and vehicle electronics. Contact failure is a common type of equipment malfunction, and contact sticking is a particularly serious problem. Silver Alloy Electric Tri-Metal Contact, as a mainstream multi-layer composite conductive component, directly determines the reliability of the relay's on-off operation. Contact sticking not only causes equipment malfunction but can also lead to safety hazards such as board burning and fire.

The causes of contact sticking are clearly physical and electrical, and it is not a random failure. Understanding the failure mechanism can help avoid most problems in advance. In simple terms, contact sticking refers to the situation where the moving and static contacts cannot be separated by the spring force after being attracted, and the load remains conductive even after the coil is de-energized. Knocking on the casing can only temporarily fix the problem, and the fault will recur. Trimetal Silver Composite Electrical Contact is used more frequently in inductive loads, high-frequency on-off, and high-current working conditions, and the occurrence probability of contact sticking faults is also of greater concern to the industry.

Contact sticking mainly has three failure modes: arc welding, metal migration, and mechanical jamming. Arc welding at high temperatures accounts for more than 80% of the total faults. When cutting off motors and coil-type inductive loads, extremely high temperatures are generated, melting the surface metal of the contacts, and after cooling, the contacts are directly welded. The silver alloy material on the surface of the Trimetal Silver Contact for Switch has stronger high-temperature resistance and arc resistance, significantly reducing the risk of contact sticking caused by high-temperature welding.

Long-term full-load high-current working conditions can cause metal migration-type cold welding contact sticking. The contact resistance continues to heat up, and the surface metal atoms diffuse with each other, combined with the closing pressure to form adhesion. Many devices that use ordinary single-layer contacts for long-term full-load operation are prone to this type of fault. Trimetal Silver Contact Point has a composite internal structure that can stabilize the contact resistance, reduce the problem of continuous heating-induced metal diffusion, and extend the stable usage period.

Dust accumulation, moisture, aging of the spring, and deformation of the casing can often be misjudged as electrical sticking, and the solutions are completely different. Moisture and dust can corrode the contact surface, exacerbating contact failure and sticking problems. Mechanical fatigue can reduce the separation force of the contacts. The silver alloy on the surface of the Trimetal Contacts Rivet for Switch has outstanding anti-corrosion and oxidation resistance, reducing the causes of sticking due to environmental corrosion, but still requires a good casing protection structure.

There is a common selection mistake in the industry. The rated current marked on relays is only suitable for pure resistive loads, and the actual load of inductive loads will increase by a factor of two. Selecting only based on the nameplate parameters is very likely to damage the contacts. PCB design flaws can also aggravate the loss. The lack of a current-limiting and arc-extinguishing circuit, too fine wiring, and crowded layout can all worsen the contact conditions. Pure Trimetal AgSnO₂ Electrical Silver Contact has a higher current tolerance margin and can be adapted to complex loads, but the circuit protection design still cannot be omitted.

Based on the equipment's usage period, contact sticking can be classified into three types of failures: early, mid, and late. Early failures are mostly due to selection errors and the lack of circuit protection; mid-term failures result from long-term load fluctuations and heat accumulation; late-stage failures are caused by component aging and wear, and the arc is more likely to melt the surface layer of the contacts. The Ag Silver Alloy Trimetal Contact has a superior wear resistance performance compared to ordinary contacts, effectively delaying the occurrence time of aging-type adhesion faults.

Replacing only the Trimetal Silver Electrical Alloy Contact cannot completely solve the adhesion problem. It is necessary to comprehensively manage the problem from five dimensions: load characteristics, contact selection, circuit protection, PCB layout, and usage environment. As a circuit safety gate, the quality of the contacts directly affects the overall safety of the entire machine. Reasonable selection of high-performance composite contacts, combined with standardized circuit design, can reduce contact adhesion faults from the source and ensure the long-term stable operation of the electrical system.

We have self-developed and mass-produced Silver Alloy Electric Tri-Metal Contact, optimizing the ratio of the three layers of metals. The silver layer is evenly and stably distributed, with outstanding arc resistance and anti-metal migration capabilities. It is suitable for various relays in industrial control, vehicles, and household appliances. It has a complete range of specifications and supports customized processing. It can significantly reduce the occurrence rate of contact adhesion faults and effectively extend the service life of the relay as a whole. Engineers with sample testing, batch purchasing, and customization requirements are welcome to come for consultation and cooperation at any time.