Electrolube Contact Lubrication Guide

Contact lubricants increase the reliability and lifetime of all current carrying metal interfaces. These include switches, connectors and busbars.

Electrolube have been the leading supplier of contact lubricants since their invention by the founder in the 1950's.

A wide range of products are available covering all common applications, whilst a program of continual development provides speciality products for ever changing customer needs.

Manufactured as tenacious greases and oils, products are available for consistent operation at extremes of temperature and with sensitive plastics that are normally attacked by traditional lubricants.

The use of a suitable contact lubricant will solve the problems of wear, poor signal quality, inconsistent operation and allow the use of less expensive materials. The choice of lubricant can also allow the ‘feel' characteristics of the switch to be optimised.

Benefits of Contact Lubrication

Contact lubricants are specially formulated greases and oils that reduce friction and enhance the electrical performance of current carrying metal interfaces in switches and connectors. Electrolube products are electrically insulative in thick films, preventing tracking. In ultra thin films, i.e. between closed metal contacts, they allow consistent current flow, owing to the ‘Quantum Tunnelling Effect'. They also exhibit a neutral pH thereby avoiding surface corrosion.

Tests have shown that contact lubrication can extend the lifetime of switches by more than 300%, producing excellent performance under all circumstances and preventing the need for expensive maintenance. Contact lubricants also help to improve the reputation of manufacturers by reducing or preventing warranty claims and the associated commercial costs of product recalls.

The effectiveness of even perfectly designed switches can be improved by contact lubricants and, when considered at design stage, significant production cost savings can be achieved by the use of less expensive materials (both plastics Special Plastics Grease SPG and contact metals, Contact Treatment Grease SGB ).

Typical application

The range of applications is vast and can include anything from PC edge connectors to switches in washing machines, kettles, hair dryers and electric blankets. Contact lubricants will bring significant benefits to any application where switches and contacts are fundamental to successful, long term operations.

The use of contact lubricants is widely spread in the automotive industry, where they are employed to ensure reliability, safety, efficiency and to control the ‘feel' of switches.

These lubricants are also used in electric motors and for electroplating. They are available for low current applications as well as traditional switch currents.

How Contact Lubricants Work

Contact technology is constantly developing with new alloys, plastics and customer demands. However, it is still impossible to solve the main cause of switch malfunction i.e. the inability to product a perfectly smooth metal contact surface. This leads to the following problems:

Heat Generation

Microscopic examinations reveals ‘peaks and troughs' on the surface and when the contacts come together, only the peaks are actually touching. The true current carrying surface area is therefore far smaller than it would appear.

As the current is carried by a fraction of the designed surface area, the heat generated is concentrated at the peaks. This, in turn, causes the formation of high resistance oxide layers. As the resistance increases, more power is converted into heat leading to further oxidation.

This spiralling effect creates ‘hot spots' reducing the efficiency of the switch and can cause complete failure as the two surfaces weld together.

Application of an Electrolube contact lubricant solves this problem. The lubricant film dramatically increases the effective surface area as, in thin films, the lubricants allow the passage of electricity. The switch now has the surface area that the designers planned. ‘Hot spots' are eliminated and the contact resistance remains low and stable.

Arcing

As un-lubricated contacts open and close, arcing (mini lightning strikes) can often occur. Arcing is destructive as it generates heat, causing oxide formation, and as the amount of energy is high, corrosive by-products can be formed. These cause corrosion of the surface and can destroy plated contacts.

Ionisation of the air and the associated rise in temperature causes metal transfer between the contacts, resulting in the formation of new ‘peaks and troughs' – a common problem found in high power contacts.

The problem of arcing is compounded in ‘make & break' switches where every time the circuit is opened, the contacts may bounce several times before finally mating. This exacerbates the problems discussed previously and subjects the circuit to repeated surges of current giving a poor signal to noise ratio.

This problem is not found in lubricated switches, as the lubricant fills the air gap between the contacts, preventing arcing, related temperature rises and corrosive chemical formation. As air is excluded from the metal surfaces, airborne contamination cannot form insulative barriers on the metals. Contact lubricants provide a cushion between the contacts to damp the effects of bouncing.

Mechanical Wear

The problems described previously are compounded by the action of the two surfaces rubbing against each other. This occurs in all metal interfaces, whether static or moving. Why static contacts (connectors) suffer from mechanical wear may not be immediately obvious. However, this phenomenon is explained by the fact that connectors and closed contacts are exposed to small amplitude movements caused by vibration, temperature changes etc. These small movements are known as ‘frettage'.

As the surfaces fret, friction causes metal particles to be removed from the peaks breaking through plated surfaces. This exposes surface and underlying metal to effects of oxidation and wear. Additionally the detached metal particles can cause intermittent signal transmission and ultimately switch failure.

A lubricated switch is subject to far less mechanical wear as the lubricant facilitates smooth movement. Friction is therefore greatly reduced, as is wear, extending switch lifetime.

Feel Characteristics

The way a switch ‘feels' when operated has become an indicator of quality particularly within the automotive industry. Contact lubricants, in addition to their technical benefits can also determine the ‘feel' of a switch, whether it be strong and decisive for the dashboard of a commercial vehicle, or smooth and quiet for a luxury car.

Silicone Contamination

Silicone contamination poses particular problems which can also be overcome by contact lubricants. Silicones can be found in mechanical lubricants, sealants, polishes and mould release agents.

As silicone can 'creep' great distances, these products should not be used in switch assembly areas. When silicone is present between moving or vibrating contacts, they react under arcing conditions to form silicon carbide. These crystals abrade the contact surface and cause electrical breakdown.

If a contact lubricant is used on the switch prior to the introduction of silicone these problems are avoided.

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