As a key component in the automotive circuit system, the automotive PCB relay's contact life and conduction stability directly affect the normal operation and safety of automotive electronic equipment. The performance of the contact is affected by the combined effect of many factors such as circuit parameters and operating conditions. In-depth exploration of these influencing factors will help improve the reliability and service life of the automotive PCB relay.
The current passing through the automotive PCB relay contact is an important factor affecting its life and conduction stability. When a large current passes through the contact, an arc will be generated between the contacts. The high temperature of the arc can reach thousands of degrees Celsius, which will cause the metal on the contact surface to melt and evaporate rapidly, resulting in increased contact material loss and shortened contact life. For example, at the moment of car starting, the PCB relay in the starter circuit needs to connect a large current. Frequent large current switching will accelerate the wear and ablation of the contact. At the same time, the Joule heat generated by the current will increase the contact temperature. Long-term high temperature will accelerate the oxidation of the contact surface, increase the contact resistance, and then affect the conduction stability, which may cause problems such as poor circuit contact and intermittent equipment operation.
The impact of voltage on automotive pcb relay contacts is mainly reflected in the generation and maintenance of arcs. High voltage makes it easier for the air between contacts to be broken down to form arcs, and the higher the voltage, the harder it is to extinguish the arc. If the arc lasts too long, it will cause more serious erosion to the contacts. In addition, voltage fluctuations will also affect the conduction stability of the contacts. When the voltage drops or surges instantly, the contacts may be repeatedly attracted and released. This mechanical vibration will accelerate the wear of the contact surface. At the same time, the arc generated during the opening and closing of the contacts will also aggravate the damage to the contacts and reduce their service life.
In some electronic control systems of automobiles, the operating frequency of the circuit also has a significant impact on the performance of PCB relay contacts. In high-frequency circuits, contacts need to be frequently connected and disconnected, and the mechanical stress and arc erosion times of the contacts per unit time increase significantly. Frequent movement of contacts will cause mechanical fatigue, resulting in cracks and deformation on the contact surface, which in turn affects the contact effect and conduction stability of the contacts. Moreover, high-frequency current will also produce skin effect and proximity effect, change the distribution of current on the contact surface, cause local overheating, and further accelerate the aging and damage of the contact.
During the operation of the car, the temperature variation range of parts such as the engine compartment is large, and the high temperature environment has a significant impact on the performance of the PCB relay contact. High temperature will accelerate the softening and deformation of the contact material, reduce its mechanical strength and wear resistance, and make the contact more easily damaged by mechanical stress and arc. At the same time, high temperature will also accelerate the growth of oxide film on the contact surface, increase contact resistance, and affect conduction stability. In addition, drastic changes in temperature will cause the thermal expansion coefficients of the contact material and the PCB substrate to be inconsistent, resulting in thermal stress. Under long-term action, the connection between the contact and the PCB may become loose, and even cause the solder joint to crack, affecting the normal operation of the relay.
During the driving process of the car, it is inevitable to be subjected to various vibrations and shocks, which pose a threat to the life and conduction stability of the PCB relay contact. Continuous vibration will cause the contact to have a slight displacement and shaking, destroying the good contact between the contacts and causing an increase in contact resistance. Vibration may also cause mechanical fatigue of the contacts, loosening the fixed parts of the contacts, or even causing the contacts to break. When encountering strong impact, the contacts may be out of contact instantly, generating arcs. At the same time, the mechanical stress caused by the impact will also damage the contact structure, reducing the reliability and service life of the contacts.
The external environment of the car will also affect the performance of the PCB relay contacts. In a humid environment, moisture can easily enter the interior of the relay, causing rust and corrosion on the contact surface, increasing the contact resistance and affecting the conduction stability. Environments containing pollutants such as salt spray, sand and dust, and corrosive gases will accelerate the chemical corrosion and wear of the contacts. For example, in coastal areas, salt spray will react chemically with the contact metal to form a corrosion layer and destroy the contact surface structure; sand and dust particles entering the contact gap will hinder the normal closure of the contacts and cause poor contact. These environmental factors will significantly shorten the service life of the contacts.
