Zinc Whiskers

High failure rates were encountered on PCBs and power supplies within data processing equipment in a large data processing centre in North East England. The problem was traced to small metallic particles of zinc being deposited on the PCBs and causing inter-track conduction. The source of the zinc was the galvanised coating on the underside of the raised floor tiles. Examination found that zinc whiskers were present and were being carried in the airflow from the pressurised under floor plenum into the intake vents of the equipment.

What are zinc whiskers?

Zinc whiskers 'grow' from metal surfaces that have been coated with zinc to help protect them from corrosion. Whisker growth appears to be limited to electroplated surfaces, rather than those that have been hot-dipped or sprayed, and is caused by internal stresses incurred during the plating process. Fine zinc filaments, normally only a few microns in width, but of several hundred microns to a few mm in length, develop from the plated surface. A mass of zinc whiskers removed from a computer installation is shown in image 1.

Although zinc whiskers have been found on a wide range of surfaces, access floor tiles are of particular concern, as they have large surface areas, and are often moved during day-to-day maintenance. The zinc whiskers are fragile and can easily be broken off the tile - some whiskers may then get into the supply airflow and be carried to the hardware via the ducting beneath the flooring.

The consequences of a long zinc whisker getting into the wrong place can be catastrophic. These conductive whiskers have posed a threat to the electronics for many years but older electronic designs with larger gaps between components and pins were less likely to be compromised. As circuitry has evolved it has become more closely packed and operating voltages are lower. The whiskers can be long enough to bridge many gaps between pins of components in current installations and the ever denser geometry of newer technologies means that this problem is likely to increase.

If you suspect Zinc Whiskers IT Cleaning are able to arrange for your site to be assessed. If they are found we are able to remove them for you to an acceptable level.

Scanning Electron Images