As the cornerstone of the field of electronic components, relays play a vital role in circuits. Among them, the reliability of the contacts directly affects the performance of the relay. Contact sticking is not only a technical problem, but also a key factor affecting the life and reliability of relays. This article aims to provide an in-depth analysis of the causes and solutions of sticking relay contacts, providing a comprehensive perspective on understanding this common problem.
Multiple influencing factors of touch points
First of all, as the core component of the relay, the stability and reliability of the contact are the basis for the operation of the entire relay. The state of the contacts is affected by many factors, such as the choice of contact material, the voltage and current applied to the contacts (especially when making and breaking), the type of load, the frequency of making and breaking, environmental conditions, contact method, and Oscillation phenomenon caused by contact opening and closing speed, etc. These factors work together on the contacts, which may lead to a series of failures such as abnormal movement, adhesion, excessive wear, and increased contact resistance.
Inrush current effect under capacitive load
In capacitive loads, such as indicator lights and motors, the inrush current when closed is significantly greater than the normal operating current. Taking a 1W/2uf LED lamp as an example, when many lamps in an office area are connected in parallel and controlled uniformly, the inrush current when the lights are turned on may be 20 to 40 times the normal operating current. The relay will experience a transition state from open to closed during the closing process. In a large current scenario, the repeated occurrence of this "critical on-off" state will generate sparks at the contacts, which will cause damage to the contacts. Remarkable.
Reverse voltage problem in inductive loads
In inductive loads, switching off the load may result in a reverse voltage of hundreds to thousands of volts. This reverse voltage creates a white heat or arc that discharges into the air. Normally, the critical insulation breakdown voltage in air at room temperature is 200 to 300 volts. When a discharge occurs, organic matter such as nitrogen and oxygen in the air will decompose, forming black deposits (such as acids and carbides) on the contact surface. These deposits will adhere between the relay contacts. As the number of switching times increases, uneven marks will form on the surface of the contacts, eventually leading to adhesion of the contacts.
The criticality of relay contact materials
In high-power application scenarios, the adhesion problem of relay contacts has become a key factor in determining its life. Although inrush current and reverse voltage are unavoidable, the key is to choose a contact material with good adhesion resistance. For example, AgSnO2 contact materials are widely used due to their excellent anti-adhesion properties. In addition to the material itself, the technical treatment of the surface treatment process is also crucial. This aspect depends on the process technology level of major manufacturers.
in conclusion
The problem of contact sticking is a complex and multifaceted technical challenge, and its solution requires comprehensive consideration of material selection, design solutions, manufacturing processes and other aspects. By gaining a deeper understanding of the causes and influencing factors of contact sticking, we can not only improve the reliability and life of relays, but also drive technological advancement in the field of electronic components. Future research and innovation should focus on optimizing contact materials and improving manufacturing processes to address this challenge.