Connector manufacturers have always been at the forefront of sustainability. It started with replacing cadmium plating to meet RoHS requirements and soon expanded to using plastic regrind and bio-based plastics to replace 100% new plastic in connector bodies. Connector manufacturers have recently begun adopting new, more sustainable materials to create high-performance contacts.

The original RoHS regulations in 2003 sparked interest in sustainability throughout the electronics industry. While most attention has been focused on removing lead from solder, the connector industry faces additional challenges, specifically eliminating cadmium and chrome plating. Cadmium is a popular plating in military, aerospace, transportation and industrial applications that require corrosion resistance and guaranteed performance in all weather conditions.

New metal connector bodies are being developed using aluminum with various protective surface platings. These designs can offer a variety of combinations of corrosion resistance, electromagnetic interference (EMI) shielding, and appearance options, including matte colors. Common cadmium alternatives include:

l Tin-Zinc was developed for military applications in extreme environments. It is considered the highest performing replacement for cadmium. It is highly conductive (<5mΩ) and corrosion resistant (500 hours static/5 days cyclic salt spray). It has a matte grey, non-reflective finish and provides cadmium-level protection.

l Zinc nickel plating is a high performance solution for industrial, architectural and transportation applications. It provides high levels of EMI shielding and is rated to withstand 500 hours of static salt spray.

l Zinc-cobalt plating is also used in the industrial, construction and transportation industries, but is not as corrosion resistant as zinc-nickel. It provides a good level of EMI shielding for signal integrity.

l Black zinc nickel is a cost-effective alternative that provides long-lasting corrosion resistance to exposed connector surfaces. It is used in aerospace, ground transportation, and marine applications. It provides the same level of environmental protection, operating temperature range, and electrical performance as cadmium.

l Epoxy Urethane Varnish plating has very high corrosion resistance and was developed specifically for railway applications. It does not provide high levels of EMI protection and is not generally used where signal integrity is an important consideration.

Recycled materials and bioplastics are two ways to improve the sustainability of connector bodies and other connector components. There are two approaches:

l Post-consumer recycled (PCR) plastics are plastic materials, such as bottles, that are collected from recycling plants for cleaning, processing and grinding before being added back into the manufacturing process. Connector manufacturers do not typically use PRC plastics.

l Post-industrial recycled (PIR) plastics are recovered from the manufacturing process. PIR plastics include flashing and other scrap plastics generated during the manufacturing process, as well as rejected finished parts that do not meet specifications. Some connector manufacturers use 40% of regrind for various components such as plastic housings. The use of PIR plastics contributes to sustainability in two ways; it reduces the use of virgin material and the environmental issues associated with producing that material, and it reduces waste in the manufacturing process.

Bioplastics are not necessarily biodegradable, nor are they necessarily made using renewable organic resources. They are defined in three ways:

l Made from organic macromolecules obtained from renewable biological resources such as plants or animals, they may or may not be biodegradable.    

l Made from petroleum resources, it is fully biodegradable.

l Made from a combination of organic macromolecules and petroleum resources, may or may not be biodegradable.

Bio-based polyamide 410 plastic is available, made from at least 70% castor bean renewable material. This material combines the performance advantages of short-chain and long-chain polyamides. Compared to traditional polyamide 66 (PA66, also known as nylon 66), this bio-based alternative has superior mechanical properties and moisture resistance while providing good aesthetics. The bio-based polyamide EcoPaXX is used in sealed and unsealed connector systems that meet the USCAR 050 standard.

The industry has developed a 100% bio-based, high-temperature polyamide specifically for connector applications. It meets the requirements of the International Sustainability and Carbon Certification (ISCC). ISCC is a globally applicable sustainability certification system that covers all sustainable raw materials, including agricultural and forestry biomass, circular and bio-based materials, and renewable energy. The material is an ISCC+ certified mass-balanced solution with the same characteristics, performance and quality as conventional materials. Its production generates a 50% lower carbon footprint than the corresponding fossil-based plastic.

This 100% bio-based, high-temperature polyamide is designed for microminiature connectors with high pin counts, pitches less than 0.3 mm and wall thicknesses as low as 0.1 mm. Its thermal specifications make it suitable for lead-free soldering processes, and it is a 30% glass fiber reinforced material designed to provide high levels of strength and ductility.

While the connector industry has been using bioplastics for years, it is still in the early stages of the adoption process. Overall, bioplastic production accounts for only about 1% of the more than 350 million tons of plastic consumed worldwide each year. The largest application for bio-based plastics is currently packaging, which accounts for more than 50% of the market. The use of various types of bioplastics is surging.

For example, the use of bio-polypropylene is expected to grow six-fold in the coming years. Today, various electronic applications such as connectors only account for about 2% of bioplastics use. There is a lot of room for bioplastics (and PIR plastics) to improve the sustainability of connectors.

The use of nanocrystalline nickel alloys in connectors can significantly reduce the use of gold. Mining and refining gold has a significant negative impact on the environment, using 4kgCO2/troy ounce of life, while nanocrystalline nickel alloys have an LCA impact of 0.2kgCO2/troy ounce. The low LCA impact of nanocrystalline nickel alloy is the result of two factors; it can be used in thinner coatings to achieve the same performance level and it is manufactured using 100% recycled tungsten.

A connector manufacturer has replaced gold contacts on some of the lines of its high-reliability connectors with nanocrystalline metal contacts. Nanostructured metal coatings are easy to integrate into connector manufacturing because they are deposited by conventional interconnect electrodeposition processes. Replacing gold with nanocrystalline metals reduces the environmental impact of the materials used, especially gold, by an average of 7.8 million kg of CO2 emissions per year.

Nanostructured silver has been developed for high-performance, high-power connectors in electric vehicle (EV) applications. EV applications include charger connectors that require low, stable contact resistance and high durability, and high-voltage connectors in EV drivetrains and power systems that require higher temperature ratings.

In terms of durability, the nanostructured silver material is about twice as hard as pure silver. It was tested for 5,000 wear durability cycles on an EV connector with a 5N plugging and unplugging force, with virtually no wear at 5μm thickness. Despite a 4x increase in thickness, conventional silver plating experienced deep wear and exposed the copper substrate. Key performance specifications for nanostructured silver include:

l 220°C run

l Low insertion force

l Thinner cost provides higher wear resistance