The completion of Berlin Brandenburg International Airport (BER) once again being postponed is no longer newsworthy. As recently as late last year, further delays were anticipated according to the Berliner Morgenpost. This time it wasn't about the completion of the airport itself though, but about the opening of the various duty-free shops, cafés and other establishments that were scheduled to start operating as soon as the airport was ready. However, the airport company told the Berliner Morgenpost that conductor rails needed replacing, causing further delay. What happened? Apparently, a manufacturing defect with the conductor rails caused a problem that suppliers of electronic materials and manufacturers of electronic components are faced with from time to time: whisker formation. Whisker formation on tin-surfaces is a phenomenon known since the 1950s. It was never researched thoroughly, as the solution back then was to add lead to the tin-surface. But ever since the European Union adopted legislative measures in July 2006 to prohibit lead in electronic components, whisker formation once again became an issue.
Whiskers are crystalline, hair-thin excretions that can grow several millimeters long. They may reduce the insulation resistance and/or the distance between adjacent components. If they break, they may cause short circuits on the circuit board or for fine-pitch components. However, the biggest challenges are caused by electric arcs, which can occur at high currents and voltages. The specific conditions required for whisker formation have not yet been fully explored. But it appears that the risk is particularly high if a copper surface is covered with pure tin.
