The removal of lead from electronic components has been an ongoing process since the late 1990s, driven by environmental and health concerns. Subsequently, regulations formalising the process were introduced, such as the Restriction of Hazardous Substances Directive (RoHS), which restricted the use of six hazardous substances, including lead, in electrical and electronic equipment sold in the EU, and the WEEE Directive which covers waste management and recycling of electronic devices.
This article originally appeared in the June’25 magazine issue of Electronic Specifier Design – see ES’s Magazine Archives for more featured publications.
By Daniel Theis, Technical Manager, Rhopoint Components
The electronics industry has largely moved to using lead-free solder alloys, such as tin-silver-copper (SAC), bismuth-tin or tin-copper, and coating materials such as nickel-gold or palladium. Manufacturing processes have had to be changed to accommodate lead-free materials as lead-free solders have higher melting points.
Lead-free soldering is now commonplace but does introduce some reliability issues, such as increased brittleness and risk of tin whiskers. Tin whiskers are hair-like metallic filaments that grow from tin-rich surfaces, creating risks including short-circuits, leading to equipment failure. While not seen as a particular problem for earth-bound commercial and industrial applications, where they can grow at rates of 0.03-9mm per year depending on stress and environmental conditions, space studies suggest whiskers may grow faster in a vacuum under the influence of radiation-induced stress and thermal cycling.
Tin whiskers are a very real issue in high-reliability systems such as aerospace, medical, and defence electronics causing equipment failures as the result of intermittent or permanent short-circuits between contacts or PCB tracks.
The growth of tin whiskers can be reduced by improving the plating process or annealing the final assembly to reduce internal stress, introducing alloying additives to the solder or application of a conformal coating to block whisker growth. None of these procedures can completely overcome the risk of tin whiskers and sensitive, high-reliability equipment requires special attention during manufacture.
The long history and demonstrated reliability of lead solder means it is still used in critical electronic systems such as those to be deployed in space, as well as defence and medical equipment, where environmental concerns are mitigated. Lead solder suppresses the formation of tin whiskers, can deal with extreme temperature fluctuations, is less sensitive to radiation-induced degradation, has low outgassing properties in a vacuum, is less prone to stress fractures, and has less risk of cracking. Lead solder is likely to remain the choice for critical equipment while development of lead-free alternatives is ongoing.
The exponential growth of Low Earth Orbit (LEO) satellites is being fuelled by advancements in technology, reducing launch costs, and increasing demand for global connectivity, and is increasing the demand for high-reliability electronic systems. Projects such as SpaceX’s Starlink, anticipating the launch of some 42,000 satellites, demonstrates the growth of the LEO satellite market.
Secure, reliable hardware is essential as clearly there is no opportunity to service or repair a satellite once launched and failure or loss is very costly, both financially and in terms of lost service. System components which are qualified for use in space are essential, and for the medium-term, lead-solder will continue to be used to maximise system reliability while a reliable alternative is sought. The low volume of the current market for space electronics is a limiting factor for this quest.
Companies manufacturing electronic systems for use in space not only have to source appropriate components but also be aware of changes in their manufacturing process. Across the whole range of components used in a system, this can be a major logistical exercise. Working with a specialist distributor, a wide range of components from the bill of materials (BOM) can be purchased from a single source. The industry contacts a distributor has with its suppliers and the market at large gives them access to the latest market intelligence about new products, materials, changes in standards and regulations, and provides a channel to their customers ensuring a secure supply chain, uninterrupted production, and access to the latest innovation.
This ‘multiplier’ function provided by a distributor such as Rhopoint Components is a valuable resource and can maintain an OEM’s competitive advantage. The ability to provide approved as well as appropriate commercial (COTS) components, provide development samples as well as production quantities and assist with custom designs and replacements for devices which may become obsolete.
