E-Business
Issue No. 8 - December/ 2002/january
Cheese and Whiskers
by David Twiss
The more erudite reader may recognise the title of this article as the favoured expletive of ‘Ratty’ from Bananas in Pyjamas. Whiskers however have a far more sinister connotation for eBusiness today.
Steel is used extensively in the computer world, and is found in a myriad of places including in the chassis of computers, computer racking, and in the frames of computer room flooring.
To prevent corrosion, industry has long been coating steel with a variety of other materials; zinc is one substance commonly used to prevent corrosion on the surface of steel. The zinc is usually deposited by electro—plating.
It turns out that zinc—plating, can under some circumstances, grow whiskers. Not the big “Ho ho ho” type whiskers, but rather very small whiskers. Typically 2 microns in diameter (i.e. 1/500 mm), and after 2 years of growing, the whiskers can be 500 microns long (0.5 mm). Now just let’s remember that a human hair is around 100 microns , so we are talking about a metal whisker 1/50 the diameter of a human hair. It goes without saying that these whiskers cannot generally be seen without the aid of a microscope, although their effects may be readily apparent.
What effects you may well ask? All is well until these very small and light whiskers break off and float around in the air. So small are these whiskers that they can pass through most filters used in computer systems. Having small bits of metal floating around the inside of one’s computer is, without doubt, a highly undesirable situation.
In computer data centres with raised flooring, pressurised and chilled air is pumped under the floor and is then drawn into individual cabinets. This provides an especially effective mechanism for zinc whiskers to enter a computer chassis from the under floor structure. Computer power supplies and power—control circuitry seem to be particularly popular places for whiskers to gather.
It has been estimated that 1% of co...
