Page 9 - 2021 Connectivity Components: Everything but the Connectors eBook

Common RoHS non-compliant platings:
• Cadmium, generally olive drab (OD), is regularly employed as a coating over electroless nickel. • Yellow or Type II Zinc utilizes hexavalent chromium.
• Green zinc cobalt is less frequently applied.
The prevalence of environmental and safety concerns has prompted the development of RoHS-compliant alternative plating materials. While many provide harsh environment protection similar to that of conventional (RoHS non- compliant) materials, their aesthetic qualities are often somewhat different.
Common RoHS-compliant platings:
• Black zinc nickel is electrolytic nickel plating with a secondary treatment which turns the surface black.
• Nickel Teflon – Nickel PTFE (polytetrafluoroethylene) is a co-deposit on metal substrates and a lower-cost alternative to black zinc nickel.
• Zinc alloy is a layer of zinc bonded to steel through electrogalvanization.
• Stainless steel passivation is a layer of chromium oxide on a stainless steel surface.
• Electroless nickel deposits an even layer of nickel-phosphorus alloy.
• Anodization is the formation of a protective, insulating oxide layer on metal by electrolytic action.
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» RoHS-compliant black zinc nickel is increasing specified as an alternative plating material.
Less popular RoHS-compliant platings include black zinc cobalt, space- grade electroless nickel, and gray zinc over electroless nickel for use in extreme harsh environments.
The future of connector shell materials, plating, and purpose
Advances in non-metallic materials science, specifically composites, are expected to drive the future of shell materials and plating. It is widely anticipated that as the costs of these state-of-the-industry materials and processes (e.g., composites and specialty platings) go down, their utilization will go up. Prices of composites are also anticipated to decline due to optimized manufacturing techniques and an increase in high-volume commercialized usage. RoHS-compliant black zinc nickel plating is projected to replace RoHS non-compliant olive drab cadmium on many metal connector shells. This is achievable, as zinc nickel and cadmium demonstrate equivalent performance parameters, i.e., continuity/conductivity, durability, temperature range, and salt-spray rating.
The status quo of connector shells will be challenged by future designs driven
by advanced requirements, including those relating to fiber optics, mass adoption of low smoke/zero halogen (LSZH) materials, and regulations impacting reclaimed/renewable materials
resulting from “clean” manufacturing processes.
While carbon fiber is the state-of-the-industry structural composite material employed by the auto industry, its price is roughly 10 times that of stainless steel. Mass adoption of stainless steel as a fuel-efficiency regulatory response will likely accelerate new manufacturing automation technologies to significantly reduce overall costs. Other materials are being considered for future use in connector shells:
• Nanocompositesincorporatenanosizedparticlesintoamatrixofstandardmaterial.Theadditionofnanoparticles facilitates a significant improvement in mechanical strength, durability, and electrical or thermal conductivity. While still in development for commercial interconnect usage, these materials will become more prevalent as manufacturing techniques are automated.
• Advanced thermoplastic composites are higher performing than existing thermoplastic composites. Fabrication techniques targeting connector-shell-sized products are now being optimized.