Connectors are metal components used in the electronics industry to transfer or receive electrical power or sensation. They are made from a number of metals such as tin, lead, palladium, silver and gold.

Connectors in service fail for many reasons, but the root cause of most failures is surface wear, including wear caused by fretting, or micro-motion between 5 and 100 microns, at the connector interface.  External vibration, thermal expansion and contraction, and electromagnetic interactions cause this motion. A change in temperature due to equipment usage or outside temperature variation and atmospheric pollutants can also contribute to connector failures. During the fretting motion, the metallic surfaces wear away and metal oxides are formed at the point of contact. Eventually, the thickness of the metal oxide film causes the resistance at the metallic interface of the connector to increase to the point that the metallic surfaces are forced apart and the connector fails.

To prevent formation of metal oxides, gold is electroplated on non-noble metal surfaces, but the gold surface  eventually wears away exposing the non-noble metallic sub layer, which will oxidize. Tin and tin alloys are the most common and least costly connector interfaces, but tin is much softer than electroplated gold and it oxidizes quickly.

Contact lubricants have been used to prevent such failures. Properly formulated lubricants lower insertion-withdrawal forces and wear, reduce the galvanic corrosion and tarnishing of contact finishes, and prevent the fretting corrosion of base metals such as tin and tin-lead plating.

A properly formulated contact lubricant decreases the dynamic coefficient of friction, reduces adhesive wear, provides atmospheric corrosion protection, prevents fretting corrosion and does not migrate away from the point of contact.

A thin film of contact connector lubricant is applied on both the male and female parts where the connection will take place by either dipping, spraying, brushing or atomizing. This film of lubricant acts as a barrier between the metal parts and the atmosphere. It offers wear protection and lowers the insertion-withdrawal forces. The lubricant film also protects the connector from fretting corrosion as well as all other forms of corrosion such as galvanic, radiation, high temperature, chemical acid, biological, etc.

Connector lubricants, properly designed and formulated, will possess the following properties and characteristics.

High thermal and oxidation stability, so that the lubricant will last the life of the connector

High resistance to chemical, radiation, acids and other types of contaminants.

Compatibility with metals, elastomers and adhesives.

High surface tension so the lubricant will not migrate beyond the connector area.

Common industrial lubricants based on polyalphaolefins, esters, silicones and fluorinated hydrocarbons are  migrating fluids as their surface tensions are in the range of 20-25 dynes/cm. This property, along with lack of long- term thermal stability, makes these lubricants less desirable for connector applications.

Polyphenyl Ethers, or PPEs, are synthetic polymers that encompass a broad class of materials that have been found useful in extreme environments. PPEs are non-halogenated, low to high viscosity fluids distinguished by exceptionally low vapor pressure and excellent thermal stability. They are highly resistant to degradation from heat, oxygen, radiation and chemical attack. PPEs have a high surface tension of 50 dynes/cm and, therefore, are non-migrating fluids. They are compatible with most metals and elastomers commonly used in electrical/electronic applications. PPEs are considered safe and essentially non-toxic when normal hygienic practices are employed.

Santovac® Connector Lubricants have a 30-year history of commercial service for connectors with precious and base metal contacts in telecom, automotive, aerospace, instrumentation and general-purpose applications. Many billions of contacts have been improved by the use of Santovac PPE-based lubricant formulations. The formulations form a highly stable, non-spreading film (15-20 Microns) on the connectors/terminals and provides long-term lubrication and protection even when the connectors are exposed to aggressive atmospheres. Santovac Connector Lubricants reduce insertion force, minimize wear and maintain low and stable contact resistance. In addition these lubricants eliminate all forms of corrosion including "fretting corrosion". These lubricants will continue to work for decades or the life of the equipment. An ultraviolet dye is incorporated in all Santovac Connector Lubricants for easy identification during quality control inspections. PPE’s have been certified by Telecordia / Bellcore, AT&T and Bell Labs.

In addition to the above-mentioned products, we manufacture a large family of products formulated depending on connector design, construction, temperature and environment to meet the specific need of the customers. These lubricants are dispersed in evaporative solvents. After the solvent evaporates, a film, which can range from 5 to 250 micro-inches, is formed on the surface of connectors. Specific film thickness for a particular application is determined by a number of factors, such as the temperature, vibration and atmosphere where these connectors are expected to operate for the life of the equipment. These lubricants contain a UV tracer die, detectable by black light, for quality control inspection during the production operation.

Notes:

All Connector lubricants contain a UV fluorescent detector tracer, unless no tracer is specified.

A guide to connector curing methods and application is available upon request.

A study was conducted with typical automotive connectors having gold and tin plated contacts. Mated connectors were cooled and contact resistance and separation forces were determined at 0, -20 and -40ºC. It was found that there was no significant change of contact resistance at all test temperatures compared to the control non-lubricated connector samples at room temperature. Results of our testing are shown in Table 1

Table 1

Gold Contacts Lubricated with Santovac OS-138

Milliohms

Fretting is a major cause of connector failure. Fretting causes the metallic interface inside a connector to erode and causes the buildup of oxide debris at the point of contact. This accumulation of oxide debris will eventually cause the contact resistance to become unstable and fail.

Ployphenyl ethers have a long history of being used for the purpose of maintaining a low and stable contact resistance under fretting conditions.

Experiments conducted on tin-lead connectors with polyphenyl ethers show the contact resistance at the beginning of the experiment at 50 g normal force and 200 g normal force (figure 2 and 3) for 5,000 cycles

Fig. 1:  A contact resistance pattern for an unlubricated tin/lead sample tested at 50 grams normal force and 50 µm fret amplitude

Fig. 2: A contact resistance pattern for a tin/lead sample lubricated with a thick film of OS-124 and tested at 50 grams normal force and 50 µm fret amplitude.

Fig. 3: A contact resistance pattern for a tin/lead sample lubricated with a thin layer of OS-124 and tested at 200 grams normal force and 50 µm fret amplitude

A major advantage of polyphenyl ethers is their exceptional thermal and oxidative properties. They are stable in air to at least 250ºC, which is well beyond the thermal limits of nearly all electronic connectors. Since polyphenyl ethers are non-spreading, their lifetimes are determined primarily by their rate of loss from volatilization. The temperature limit depends on the configuration of the connector and the criterion of failure. For a 20 year product life a 2-5% coating of OS-124 will protect connectors for up to 150ºC. A 2-5% coating of OS-138 has been estimated to have product life up to 40 years and can withstand temperatures up to 350ºC for short periods and up to 125ºC for extended periods of time.

Aggressive atmospheres for connectors are high humidity environments that contain air pollutants such as sulfur dioxide, hydrogen sulfide and mineral acid vapors. Contact finishes less than about 100 micro inches are porous and this can result in corrosion with resultant contact failure. Creep of tarnish products from pores and un-plated edges of stamped contacts including galvanic corrosion has been a problem.

A thin film coating of polyphenyl ether is effective for controlling all forms of corrosion, but improved protection is obtained with formulated polyphenyl ethers listed in this brochure as ACCL-series products.

With the development of connectors having an increasingly larger number of contacts, connector manufactures needed to reduce insertion forces, and coatings of 1-2% of OS-124 were found to reduce the coefficient of friction to about 0.15-0.20 from values as high as 0.80 for solvent cleaned contacts. These reductions were observed for the common metal contacts including gold plate, palladium, palladium-nickel plating, tin-based coatings and precious metal inlays.

Thicker films of polyphenyl ethers have been successfully used for controlling vibration in automotive and other static equipment.

A film of 10-20% film was tested at a major automotive connector manufacturer. The results showed that polyphenyl ethers absorbed up to 80% of the vibration while a conventional lubricant absorbed only 20% of the vibration. We believe this to be due to the inherent non-migrating property of polyphenyl ethers

Most elastomers and plastic suitable for high temperature application are compatible with polyphenyl ethers.

Test Conditions: (300ºF/150ºC for 168 hrs total immersion)

Manuel E. Joaquim, Connector Contact lubrication with polyphenyl ethers, A review, 30th annual connector and interconnection symposium Sep 22-24, 1997

Manuel E. Joaquim, Contact Resistance and Separation Force at low temperature of polyphenyl ethers on lubricated Connectors. 31st Annual Connector and intwerconnection Symposium, Oct 19-21, 1998

Manuel E. Joaquim Key Benefits of Connector Lubricants, Connector Specifier, Oct 2002

Neil Aukland & Manuel E. Joaquim , Lubricants Extend the life of Sensor Connectors, Sensors, May 2000,vol 17 No.5

Manuel E. Joaquim, Mussen Elektronische, Auto and Elektronik, Aug 5-2002

Leslie Rudnick & Ronald Shubkin. Book on Synthetic Lubricants and High-Performance Functional Fluids, Edition 2 Marcel Dekker Inc. New York.