Time to transition to lead-free contacts
Those with limited knowledge of the details of the RoHS, REACH and ELV regulations (Restriction of Hazardous Substances, Registration, Evaluation, Authorisation and Restriction of Chemicals and End of Life Vehicles) may not immediately recognise the importance of a lead-free product range.
As a result of exemptions in environmental regulations, lead is still permitted as a material in a number of applications. But with its lead-free product range, Würth Elektronik ICS shows that this transitional solution does not need to be exploited to the bitter end.
This is the current situation:
The REACH Regulation (EC 1907/2006) regulates the manufacture, placing on the market and use of chemical substances. Here, lead is considered to be a Substance of Very High Concern and is subject to documentation requirements. Since the beginning of 2021, product sellers have been obliged to register in the SCIP database (Substances of Concern In articles as such or in complex objects (Products)) in addition to the IMDS (part number, designation, proportion of SVHC substance) in the automotive sector.
The ELV regulation (Directive 2000/53/EC) regulates the material recycling of motor vehicles within the European Union. The maximum limit value of 0.1 percent applies to lead. An exemption was granted for copper alloys that allows a maximum lead content of four percent. This exemption will be reviewed in 2021.
The RoHS regulation also defines a maximum permissible concentration of lead in homogeneous materials of 0.1 percent by weight. However, ‘copper alloys with a mass content of up to four percent lead’ are permissible under the existing exemption 6c. This exemption is set to formally expire on 21 July 2021. After the end of the exemption, electrical and electronic equipment exceeding the limit of 0.1 percent lead in materials may no longer be sold in Europe.
As expected, the responsible EU department has received numerous applications for a renewed extension of the exemption. However, it is not advisable for manufacturers of electrical and electronic devices or assemblies to continue to do ‘business as usual’. This is because – depending on the development time and product life cycle – there is a risk that a definitive ban on lead in electronic assemblies may make it necessary to redesign a particular ongoing series. This would result in a major conversion effort and large additional investments that could have been avoided had far-sighted design decisions been made.
Copper alloy exemption
What is exemption 6c – copper alloys with a mass content of up to four percent lead – all about? Lead damages the nervous system, various organs and the haematopoietic system in the human body. On the other hand, lead also has characteristics that are beneficial to industry, for example, it improves sliding and friction behaviour. And the latter is also the reason for exemption 6c: Using lead as a minor component of about three percent in so-called machining brass (CuZn39Pb3) ensures good chip breaking and easy lubrication. This reduces friction and workpieces heat up less during the machining process.
Successful product is revised
Würth Elektronik ICS is a successful supplier and manufacturer of PCB-based system solutions and components for the transmission of high currents. Always on the lookout for particularly robust solutions, the manufacturer used press-fit technology in the 1980s to develop contacts as high-current connections of up to 800 A on printed circuit boards and called them Powerelements. Especially in automotive applications, wire-to-board and board-to-board connections need to be as robust and resistant to vibration as possible. Press-fit technology, with its excellent mechanical and electrical properties, offers precisely this advantage. Thanks to press-fit technology, the Powerelements from Würth Elektronik ICS also feature outstanding thermal behaviour at high currents due to the significantly lower contact resistance between pin and PCB. The press-fit pins, which enable robust and gas-tight connections to the PCB by means of cold welding, are made of brass and are milled from the solid. That is why CuZn39Pb3 has been the material of choice so far. However, in view of the inevitable end of exemption 6c that will happen at some point in the future, the question arising at Würth Elektronik ICS was how to phase out the use of lead-containing materials in their Powerelements at an early stage.
For several years now, Würth Elektronik ICS has been looking at alternatives to brass containing lead.
Initially, extensive basic research had to be carried out in cooperation with established manufacturers of primary materials to develop suitable lead-free materials. For example, clarification was sought on how the components silicon, manganese, iron, nickel, phosphorus and indium affect mechanical and electrical properties. The term ‘machining brass’ for the material for which an alternative was sought makes it clear that the decisive factor was the issue of machining in the production of high current contacts. Production parameters had to be developed and validated, such as the optimisation of the cutting geometries, the machining speed or the specific tool selection – and all of this had to be done within the framework of economic efficiency.
Another set of questions concerned the qualification of lead-free Powerelements for specific applications, that is, the investigation and assessment of different lead-free materials with identical evaluation bases for processing (press-fit and soldering technology) on the one hand and the use on the other hand, that is, the mechanical and electrical properties of assembled contact elements. The qualification included, among other things, investigations into press-in forces, pull-out forces, solderability, torques and derating, as well as environmental tests, micrograph tests and vibration tests.
Würth Elektronik ICS presented the first 150 products of its new ‘LF’ (lead-free) product line under the slogan ‘Let it be lead-free.’
Günter Behlau, process engineer at Würth Elektronik ICS, explains: “We’ve found the right materials and adapted the production processes to them. Our LF series is now on the market – this is a big challenge for us but not for our customers. One could exaggerate and say that the new series is “the same in green” in practice.”
The new products correspond to the previous ones in all properties – except for torque: Here they even achieve better values. Prior to the launch of the lead-free alternatives, the common market applications were analysed and a corresponding standard product portfolio of lead-free high-current contacts was compiled. This resulted in component variants that meet the needs of the market as far as possible. The standard product portfolio is available in the Powerelement online shop of Würth Elektronik ICS, where those interested in what the company has to offer will also find technical information on its lead-free products and can request free samples.
Werner Nast, product manager at Würth Elektronik ICS, summarises the strategic importance: “The exemption will presumably be extended due to the numerous requests that have been made to the European Commission responsible. Irrespective of this, we have decided to make our contribution now and offer lead-free Powerelements. Many of our customers’ projects have a total life span lasting several years from development to end of life. The lead-free Powerelements enable our customers to set themselves up for a sustainable future and make themselves independent of political decisions. Plus, they can avoid extensive re-qualifications and ensure process reliability for new developments. This is why many well-known OEMs are already demanding lead-free solutions and we are supplying them.“
Achim Engel, is business development manager in the components division at Würth Elektronik ICS GmbH & Co. KG.