Before it became fashionable, connector makers were at the forefront of sustainability. It started with replacing cadmium plating to meet RoHS requirements and soon expanded to using plastic regrinds and bio-based plastics instead of 100% new plastics for connector bodies. Connector makers have more recently embraced new, more sustainable materials for high-performance contacts.

This article looks at sustainable connectors from the outside in, starting with a review of sustainable plating for connectors, looks at improving the sustainability of connector bodies and housings, and closes by reviewing developments related to more sustainable and higher-performance contact materials.

Sustainable plating for connectors
The initial RoHS regulations in 2003 jump-started interest in sustainability across the electronics industry. While most attention was focused on getting the lead out of solders, the connector industry had additional challenges, particularly eliminating cadmium and chromium platings. Cadmium was a popular plating for military, aerospace, transportation, and industrial applications that needed corrosion resistance and guaranteed performance in all weather conditions.

New metal connector bodies were developed using aluminum with various protective surface platings. These designs can provide multiple combinations of corrosion resistance, electromagnetic interference (EMI) shielding, and appearance choices, including matte colors. Among the commonly used alternatives to cadmium are:

• Tin zinc plating was developed for military applications in extreme environments. It’s considered to be the highest-performing alternative to cadmium. It’s highly conductive (< 5 mΩ) and corrosion resistant (500 hours static/5 days cyclic salt spray). It has a matt grey, non-reflective finish and provides cadmium-level protection.
• Zinc nickel plating is a high-performance solution for industrial, construction, and transportation applications. It provides a high level of EMI shielding and is rated for 500 hours of static salt spray.
• Zinc cobalt plating is also used in the industrial, construction, and transportation industries but offers less corrosion resistance than zinc nickel. It provides a good level of EMI shielding for signal integrity.
• Black zinc nickel is a cost-effective alternative and provides long-lasting corrosion resistance to exposed connector surfaces. It’s used in aerospace, ground transportation, and marine applications. It offers the same level of environmental protection, operating temperature range, and electrical performance as cadmium.
• Epoxyurethanic varnish plating provides very high corrosion resistance and was developed specifically for railroad applications. It does not offer high levels of EMI protection and is not generally used where signal integrity is an important consideration.

PCR and PIR regrinds
Regrinds and bioplastics are two approaches to increasing the sustainability of connector bodies and other connector components. There are two approaches to regrinds:

Post-consumer regrind (PCR) plastic are plastic materials like bottles collected from recycling plants for cleaning, processing, and grinding, then added back into the manufacturing flow. Connector makers do not generally use PRC plastics.

Post-industrial regrind (PIR) plastics are recaptured from a manufacturing process. PIR plastics include flashings and other waste plastic from the manufacturing process as well as rejected finished parts that don’t meet specifications. Some connector makers use 40% regrind material for various components like plastic housings (Figure 1). The use of PIR plastics helps sustainability in two ways; it reduces the use of virgin material and the environmental concerns associated with producing that material, and it reduces waste from the manufacturing process.

Bioplastics
Bioplastics are not necessarily biodegradable and are not necessarily made using renewable organic resources. They are defined in three ways:

• Made from organic macromolecules obtained from renewable biological resources like plants or animals and may or may not be biodegradable
• Made from petroleum resources and are completely biodegradable
• Made from a combination of organically based macromolecules and petroleum resources and may or may not be biodegradable

Bio polyamides
Bio-based polyamide 410 plastic is available and made with at least 70% renewable materials from castor beans. This material combines the performance benefits of short and long-chain polyamides. Compared with conventional polyamide 66 (PA66, also called nylon 66), the bio-based alternative offers superior mechanical performance and moisture resistance while providing good aesthetics. The bio-based polyamide EcoPaXX is used in sealed and unsealed connector systems that meet USCAR 050 standards (Figure 2).

A 100% bio-based high-temperature polyamide has been developed specifically for connector applications. It meets the International Sustainability and Carbon Certification (ISCC) requirements. ISCC is a globally applicable sustainability certification system and covers all sustainable feedstocks, including agricultural and forestry biomass, circular and bio-based materials, and renewables. This material is an ISCC+-certified mass-balancing solution and delivers the same characteristics, performance, and quality as the conventional material. Its production generates a carbon footprint up to 50% lower than the corresponding fossil-based plastic.

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

Room for growth
While the connector industry has been using bioplastics for several years, it’s still relatively early in the adoption process. Overall, bioplastic production is only about 1% of the over 350 million tons of annual global plastic consumption. The largest current application for bio-based plastics is packaging, which accounts for over 50% of the market. The use of various types of bioplastics is proliferating. For example, bio-polypropylene use is projected to grow by 6X in the next few years. Today, multiple electronics applications like connectors account for only about 2% of bioplastic use (Figure 3). There’s plenty of room for growth in bioplastics (and PIR plastics) to improve the sustainability of connectors.

Nanocrystalline metal contacts
The use of a nanocrystalline nickel alloy in connectors enables a substantial reduction in the use of gold. Mining and refining gold has significant negative environmental impacts that can be calculated using a life cycle assessment (LCA). The LCA impact of gold has an equivalent impact of 800 kg CO2 per troy ounce of gold mined. The LCA impact of nickel is 0.4 kg CO2/troy ounce, while the LCA impact of the nanocrystalline nickel alloy is 0.2 kg CO2/troy ounce. The low LCA impact of the nanocrystalline nickel alloy is a result of two factors; it can be used in thinner platings to achieve the same level of performance, and its fabrication uses 100% recycled tungsten.

One connector maker has replaced the gold contacts on some lines of its high-reliability connectors with nanocrystalline metal contacts. Nanostructured metal coatings are easily integrated into connector manufacturing since they are deposited through a traditional electrodeposition process for interconnects. Replacing gold with nanocrystalline metals has reduced the environmental impact of the materials used, especially the gold, equivalent to saving an average of 7.8 million kg of CO2 annually.

Nanostructured silver
Nanostructured silver has been developed for high-performance, high-power connectors in electric vehicle (EVs) applications. EV applications include charger connectors that need low, stable contact resistance and high durability and high voltage connectors in the EV drivetrain and power system that need higher temperature ratings. In terms of durability, the nanostructured silver material is about double the hardness of pure silver. It was subjected to 5000 cycles of wear durability testing on an EV connector with 5N mating force and showed little to no wear at 5 μm thick. Despite being 4x thicker, traditional silver plating experienced deep galling wear and exposed the copper substrate. Key performance specifications of the nanostructured silver include (Figure 4).

• 220 °C operation
• Low insertion force
• Thinner costings provide increased wear durability

Like bioplastics, nanostructured nickel alloys and nanostructured silver are very early in the adoption process. There are many opportunities to increase their use and further improve the sustainability of connectors.

Summary
Connectors have made a lot of progress toward improved sustainability. It’s not new, but it has been happening since the RoHS regulations were first announced. It began with replacing cadmium and chromium platings with more environmentally friendly and sustainable alternatives. Today it extends to various types of sustainable plastics for connector bodies and housings and nanostructured metals for contacts. There are numerous opportunities to continue increasing the sustainability of connectors.

References

Bio-Polyethylene (Bio-PE), Bio-Polypropylene (Bio-PP) and Bio-Poly(ethylene terephthalate) (Bio-PET): Recent Developments in Bio-Based Polymers Analogous to Petroleum-Derived Ones for Packaging and Engineering Applications, MDPI polymers
Eco-friendly Options for Harsh Environment Connector Plating, Allied Components
Electric Vehicle Connectors, Xtalic
Improving connector performance and sustainability, DSM
Innovation Helps Amphenol Reduce Environmental Impact by 78Million Kg CO2
International Sustainability and Carbon Certification, ISCC System
Renewable polyethylene, Wikipedia
Third-Party Environmental Claim Validation for Industry’s First Bioplastic Resin-Based Connector, Molex