SPECIAL FEATURE
cable management & labelling
The weakest zinc
Metal whiskers are a crystalline metallurgical phenomenon whereby metal grows fine , filiform hairs .
There is a lack of clear guidance when it comes to the issue of zinc whiskers in data centre environments . Tim Brown of Unitrunk examines the phenomenon and the risks it poses , and looks at what can be done to combat those risks during specification .
There is considerable confusion in the data centre sector over the phenomenon known as zinc whiskers . Despite the risk that zinc whiskers pose , specifications are rarely stringent enough to eliminate the problem altogether , with the cable management industry seemingly bearing the brunt of the attention and focus when other parts of the building specification , such as computer floor tiles and supports , should be equally considered .
So what are zinc whiskers and why are they a problem ? Put simply , metal whiskers are a crystalline metallurgical phenomenon whereby metal grows fine , filiform hairs . Although this phenomenon tends to occur primarily on elemental metal surfaces , it has also been reported on alloy systems . It is accepted that the presence of whiskers can cause short circuits and arcing in electrical and electronic equipment .
Not the cat ’ s whiskers
Looking at zinc whiskers specifically , it is generally accepted that their presence has been responsible for increased system failure rates in computer machine rooms . Zinc whiskers grow from galvanised ( electroplated ) metal surfaces at a rate of up to 1mm per year with a diameter of a few micrometres .
Whisker growth in both zinc and tin is generally believed to occur as a relief mechanism ( similar to a pressure valve ) that will reduce compressive stresses existing within pure metal plating . In general , growth is most likely induced by a range of stresses such as those resulting from : Residual stress within the plating – caused by the plating chemistry , plating process or mechanical working after plating .
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