Pure Tin can be a pain

One effect of the RoHS directive has been to eliminate lead from solders and plating on components. Many components have moved from a tin/lead content in plating materials to pure tin.

But this has caused difficulty for many equipment manufacturers for whom reliability is extremely important. Pure tin can suffer from the phenomenon known as “Tin Whiskers“. electrically conductive, crystalline structures of tin that sometimes grow from surfaces where 100% pure tin is used as a final finish. This is not a new phenomenon and was recognised as a problem back in the 1940s and since then numerous electronic system failures have been attributed to short circuits caused by tin whiskers that bridge closely-spaced circuit elements maintained at different electrical potentials.

For this reason manufacturers who are very sensitive to reliability issues cannot use pure tin finishes; they need either to be able to access non-RoHS compliant product with lead (where their applications are not subject to the RoHS regulations) or to use an alternative plating material. For many of our customers Gold plating has been an acceptable alternative, though it is more expensive.

At Aerco we have developed a system that identifies which products contain pure tin plating and which do not, so that we can ensure for our customers that, where required, the product they are buying is free from pure tin. It is a big administrative workload as Aerco manages over 20,000 products. We are recording this as part of our RoHS programme. If you need further advise on pure tin issues contact us at sales@aerco.co.uk