Contact lubricants can extend switch lifetime

Typically electrically insulative in thick films, contact lubricants are particularly effective in ultra-thin films as they allow the current to flow. As no metal interfaces are entirely even and smooth, the lubricants are applied to such surfaces in thin films and completely fill in all surface imperfections, which in turn improves contact and electrical performance as well as prolonging the contact life by reducing hot spots, frettage and arcing.

By filling in the air gaps between the contacts, contact lubricants also dramatically increase the effective surface area, preventing arcing and the related temperature rise and oxide formation. They also provide a barrier to airborne contamination and reduce the effects of friction by facilitating smooth movement. In addition, the use of contact lubricants are typically evaluated for their ‘feel’ characteristics, improving the quality of movement of a switch or in simple plastic/plastic contacts, for example.

To extend the performance of switches, there are many practical considerations that must be taken into account. One of the most common factors to consider is whether there are any plastics surrounding the contact area. Plastics compatibility can vary depending on the type of plastic and lubricant being used. More sensitive plastics, such as polycarbonate, require a specialist lubricant formulated using synthetic base oils, such as Electrolube’s CG60. In the case of less sensitive plastics, such as polyamide, mineral oil based lubricants may be suitable and in some cases can provide enhanced electrical performance.

Electrical performance is evaluated by measuring the mV drop of the contacts/switches over a specified number of cycles. This is usually in excess of 20,000 usage cycles. The performance of various contact lubricants can vary depending on the formulation and intended end use. For example, some materials have a more stable low mV drop over a large number of cycles but compromise on their plastics compatibility. It is therefore important to consider all electrical requirements, material compatibility and environmental influences when choosing the correct lubricant.

Environmental influences can include temperature changes, humidity exposure and corrosive atmospheres, which can affect the consistency of the contact lubricant and in turn result in reduced performance, particularly in terms of reducing friction. Temperature changes can also result in a difference in compatibility of materials, for example, at higher temperatures the plastics compatibility may be reduced. It is therefore vital that the operating temperature range of the connector or switch is compared to the operating temperature range of the lubricant and ‘in use’ tests are performed.

Humid environments are common and most contact lubricants will withstand high humidity for prolonged periods. Electrolube designed a series of tests to illustrate different environments and can provide further assistance with correct product selection. Following combined humidity and salt mist testing, the synthetic lubricants, such as Electrolube CG53A provided the best protection. As an extreme test, an oxidative environment containing chlorine was created and maintained at 35˚C for 2 months and results again showed that Electrolube CG53A provided exceptional protection, closely followed by CG60 and CG70.