Data Center Contamination
Contamination from Airborne Dust
Dust is ubiquitous. Even with the best filtration efforts, dust will be present in a data center and will settle on electronic hardware.
Failure modes due to dust include but are not limited to the following:
Mechanical effects. Mechanical effects include obstruction of cooling airflow, interference with moving parts, abrasion, optical interference, interconnect interference, or deformation of surfaces (e.g., magnetic media) and other similar effects.
Chemical effects. Dust settled on circuit boards can lead to component corrosion and/or to the electrical short circuiting of closely spaced features.
Electrical effects. Electrical effects include impedance changes and electronic circuit conductor bridging.
Source: Particulate and Gaseous Contamination in Datacom Environments. ASHRAE (ISBN 978-1-936504-78-7)
Contamination from Zinc Whiskers
In Recent Years “Zinc Whisker” Induced Electrical Short Circuits Have Been Cited as the Root Cause of Costly Computer System Failures World-Wide
Zinc whiskers are tiny conductive filaments of zinc typically less than a few millimeters (mm) long and only a few thousandths of a millimeter in diameter. They grow from metal surfaces (e.g., steel) that have been electroplated (galvanized) with zinc for corrosion protection. The growth process consists of an unpredictable incubation period (months or perhaps even years) followed by a period of growth at rates as high as 1 mm/year.
Zinc whiskers are conductive and therefore they will cause electrical shorts if they manage to bridge tightly-spaced electrical conductors. Now that zinc whisker-induced shorts have been so convincingly demonstrated, some former “seemingly inexplicable” shorts are now regarded as explainable as having been caused by zinc whiskers. In recent years many computer equipment failures (servers, routers, switches, etc.) ranging from nuisance glitches to catastrophic system failures have been attributed to zinc whiskers. A search of the web shows that the most often reported source for zinc whiskers is the bottom surface of zinc-plated raised (“access”) floor tiles commonly used in computer room construction. Other sources of zinc whiskers include zinc-plated floor supports/rails, computer equipment racks and hardware such as screws, nuts, washers and bus rails.
Zinc whisker sources on the underside of floor tiles are a long distance from electronic equipment in floor racks. However, experience demonstrates that whiskers are broken free during floor-bumping activities including construction and maintenance, and become entrained in the air flow used for cooling, and then deposit into the distant electronic equipment, as well as into people's lungs.
Source: "Could Zinc Whiskers Be Impacting Your Electronics?", Jay Brusse, NASA Goddard Space Flight Center, 2003
