Disconnection resistance in automotive relays: a key factor in ensuring reliable circuit disconnection

Definition and characteristics of disconnection resistance
When the relay contacts are in the disconnected state, the contacts should be completely isolated in theory and there is no current path. But in reality, due to factors such as contact materials, manufacturing processes, and use environment, there will always be a certain resistance between the contacts, which is called disconnection resistance. Ideally, the disconnection resistance should be infinite to prevent any current from passing. However, in reality, although the disconnection resistance is usually large (usually in the megohm level), under certain conditions, this resistance may drop significantly, posing a threat to the safe operation of the circuit.

Factors affecting disconnection resistance
Contact contamination and oxidation: After long-term use, dust, grease or other contaminants may accumulate on the surface of the relay contacts, and even oxidation reactions may occur. The film formed by these contaminants and oxides will reduce the insulation performance between the contacts, resulting in a decrease in disconnection resistance.
Contact wear: Frequent closing and disconnecting operations will gradually wear the contact material, change its surface morphology, increase the contact area between the contacts, and thus reduce the disconnection resistance.
Temperature and humidity: High temperature and high humidity environment will accelerate the corrosion and aging process of the contact material, further affecting the stability of the disconnection resistance.
Arc effect: At the moment of contact disconnection, if the current is large, an arc may be generated. The high temperature of the arc will melt the contact material, forming a tiny metal bridge, resulting in a decrease in disconnection resistance.
Requirements for disconnection resistance of automotive relays
Given the important impact of disconnection resistance on circuit reliability, automotive relays must meet strict disconnection resistance requirements when designed. This requires relay manufacturers to:

Select high-quality contact materials: such as silver alloys, gold alloys, etc. These materials have good conductivity and corrosion resistance, and can slow down the oxidation and wear of contacts to a certain extent.
Optimize contact design and manufacturing process: By precisely controlling the contact gap, shape and surface treatment process, the bounce phenomenon when the contact is closed can be reduced, and the insulation performance when disconnected can be improved.
Implement strict testing and quality control: During the production process, each relay is tested for disconnection resistance to ensure that all products meet the specified standards. At the same time, environmental simulation tests are carried out to evaluate the performance of relays under different temperature and humidity conditions.
Provide maintenance guidelines and replacement suggestions: Automakers and users should regularly check the working status of relays, clean the contact surface in time, and replace aging relays when necessary to maintain the long-term stability and safety of the circuit.