Lubricating Greases for Electrical Contact
Improve contact stability of electrical contacts
Extends the service life of the electrical switch
- Extended contact life
- Reduced operating temperature
- Improved signal quality
- Avoid switch contamination
- Improve switch tactility
Due to the imperfectly smooth nature of metal interfaces, when contact lubricants fill the defects on the metal surfaces, they enhance the contact and electrical performance of the interface. This helps reduce the occurrence of ‘hotspots,’ frictional corrosion, and electric arcs, thereby extending the lifespan of the contact points.
By filling the tiny gaps between the contact points, lubricants effectively increase the contact surface area, preventing the formation of electric arcs, temperature rise, and oxidation. Additionally, lubricants create a barrier to prevent air contamination, reducing the impact of frictional forces generated during the operation of components. Furthermore, the ‘feel’ is also a crucial quality metric for lubricants, for instance, they can enhance the contact performance between switches or plastic components.
Common Problems
4. Silicon Contamination
Products containing silicon cannot be used in the switch field due to silicon’s ability to migrate over a distance. In dynamic and vibrating switches, silicon reacts to form silicon carbide (diamond dust) under the influence of arcing. These crystals wear the contact point surface and lead to electrical breakdown.
1. Heat Concentration Issue
For surfaces with inadequate contact, electric current flows only through a small portion of the designed surface area, leading to the accumulation of heat at these contact points. This results in the formation of a high-resistance oxide layer and so-called “hotspots.” This significantly reduces the overall efficiency of the switch and can ultimately cause the two surfaces to weld together, resulting in complete failure.
2. Arcing Issue (Micro-Spark)
Unlubricated contact points are also prone to arcing. When air ionizes and causes a rise in temperature, the metal on the contact point surface migrates, creating new “peaks and valleys.”
3. Mechanical Wear
Both static and dynamic metal contact surfaces experience mechanical wear. In static contacts, this is referred to as micro-vibration wear, where the slight movements of the contact points are caused by vibrations and temperature variations. As the contact points wear down, metal particles generated by friction penetrate the plating layer from protruding surfaces, exposing the surface and underlying metal, leading to oxidation and wear. These free metal particles can result in intermittent signal transmission and, ultimately, contact failure.
Connectors
Electrical contact lubricants are widely used in the connector industry. In early automotive applications, connectors faced issues related to ‘micro-motion wear and corrosion.’ The common materials for contact points are typically tin and silver, with some connectors also being gold-plated. However, due to its soft nature, gold can lead to ‘micro-motion wear.’
Electrical contact lubricants serve the purpose of reducing wear, resisting environmental corrosion, and mitigating ‘micro-motion corrosion.’ Even the slightest movement within the device housing can cause vibration and changes in heat. By reducing the formation of metal oxides at the contact interface, synthetic lubricants not only extend the lifespan of the connections but also lower contact resistance.
Switches coated with lubricants experience minimal mechanical wear and can operate smoothly. This lubricant significantly reduces friction and wear in switches, thus extending their lifespan, enhancing electrical efficiency, and reducing insertion and removal effort. Furthermore, it widens the range of material choices available.
Applications
- Gold plated contacts / airbag connectors
- High surface stress applications
- Slip ring devices
Heavy Duty Switch
Electric arc discharges (sometimes referred to as mini lightning strikes) frequently occur on unlubricated contacts. The ionization of air due to the resulting temperature increase causes metal migration on the contact surface, resulting in the formation of protrusions and recesses, which is a common issue in high-power applications. The frequent occurrence of electric arcs exacerbates the switching process of “closing and opening,” causing the contacts to potentially bounce several times before making proper connection when the circuit starts to operate. This phenomenon further exacerbates the previously mentioned issues, causing fluctuating currents in the circuit and deteriorating signal quality.
Contacts of starters, headlights, high beams, and high-current switches can generate high-temperature electric arcs. Even though these high-temperature arcs only last for a fraction of a second, they can still cause copper oxidation.
However, this issue can be alleviated through proper lubrication. Lubricants can fill the minute gaps between the contacts, preventing the formation of electric arcs and the associated temperature increase, while also helping to prevent the accumulation of corrosive chemicals. As air and impurities are expelled from the metal contact surfaces, the formation of insulating shields on the metal is avoided. Contact lubricants can act as shock absorbers between the contact surfaces, reducing the bouncing phenomenon.
Middle Load Switch
Medium-load switches are capable of handling currents ranging from 1 to 10 amperes. Typically, these switches are made from sensitive plastic and elastic materials. In such applications, the use of lubricants can significantly increase the contact area of the points, eliminating hotspots, improving operational efficiency, and ensuring that the contact resistance remains low and stable.
Applications
- Windscreen Wipers
- Central lock switch
- Power Seat Switch
- Dashboard Controller
- Power Window Switch
- Micro Switch
Light Duty Switch
Light load switches or contacts are generally made of more sensitive plastics and elastomers. Lubricants ensure that the devices have low current loads and excellent electrical properties.
Applications
- Steering Wheel Switches
- Light Switch
- Low Contact Pressure Switch
- Audio Switch
Sensors and Potentiometers
Potentiometers should have low contact force while maintaining good contact with the resistor. High-viscosity grease should not be closely associated with resistors, as overly viscous oil may lead to the “hydraulic plane” phenomenon, causing poor contact and preventing the resistor from maintaining contact. To ensure continuous contact, it is recommended to choose low-viscosity fluorosilicone oil.
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