Data centre structural components such as stringers, floor tiles, rack struts are frequently electroplated with zinc. Most electroplated surfaces produce fine filaments of pure zinc metal which squeeze out through flaws in the surface of the film and form zinc whiskers. Under certain conditions, zinc whiskers have the ability to severely disrupt the function of IT equipment.
Understanding How Zinc Whiskers Grow
To disrupt IT equipment, the zinc whiskers must be of a minimum length, and, typically, many whiskers must be airborne at the same instant. The distance between whisker source and target has to be short and the packaging technology within circuit cards has to allow whiskers to short-circuit closely spaced conductors. The most dangerous times for whisker-induced damage are during installation activity, particularly near the front of servers and cabinets. Although, with care, even this can be achieved without service disruption.
You may have a zinc whisker problem if...
Suspect a zinc whisker problem if you have an unusually high rate of power supply failure, often of recently replaced units, or you have multiple simultaneous DASD failure leading to data loss. These losses may coincide with times when the floor void is accessed.
You can use this guide to identify zinc whiskers and potential zinc whisker-growing material.
If you need help, RITEL offers:
Zinc Whisker Sample Analysis - We send you sampling stubs and you take samples from the suspected area. We use optical and electron microscope imagery and EDX-ray analysis to confirm the presence (or absence) of zinc whiskers. We provide a comprehensive report on all samples, we are also happy to talk to you about the findings and their ramifications
On-site Zinc Whisker Inspection - We inspect each object in the data centre (tiles, pedestals, stringers and cabinet components like frames, panels, rails, upright supports) and note if each has the potential to grow zinc whiskers. If we find any suspicious whiskers, we then take samples and use an electron microscope to measure length, and an EDX-ray emission spectrum to verify that the whisker composition is zinc and not, for instance, fibreglass strands which may also be present. Only with this information can the magnitude of the problem be gauged.
If zinc whiskers are confirmed, our experienced technicians can remove them safely using a proven technique. We can also remove zinc whiskers from within cabinets. Once the surface is cleaned of whiskers, whiskers may continue to grow, albeit at a reduced rate. We then recommend a revisit after six months to a year to check for any regrowth.
After establishing the extent of the zinc whiskers problem, we looked at airflow and location of equipment. In [Room A], zones 0 - 2, 5 and 6 were very congested, access to the floor void was limited but because the equipment type was of low susceptibility to damage and the area had low airflow, it was unlikely that whiskers would present a reliability issue. Similarly, zones A, B, F and G contained equipment that was largely unaffected by whiskers. The remaining areas had sufficient airflow, contained approximately 40% whiskered tiles and contained equipment known to be susceptible to damage by zinc whiskers. These areas needed to be addressed in any whisker remediation. In [Room B], a similar demarcation was made. The end of the room nearest to the entrance was likely to suffer little from damaging effects of zinc whiskers because it contained no susceptible equipment. The area farthest from the entrance contained susceptible equipment and whisker removal was strongly recommended. Together with the client, and using this information, we developed and delivered a targeted decontamination plan that addressed their business needs.
The client had upgraded air handlers to increase cooling capacity which then increased the airflow speed through the floor void. Very shortly after, power supplies starting failing at an alarming rate; 15 in 24 hours. We were called in, diagnosed the problem very quickly as zinc whisker contamination and found zinc whiskers coating the underside of floor tiles. We cleaned as soon as the client arranged access, and the client experienced no further problems.
While engaged to do a particle contamination survey, our expert noticed an electroplated telephone switch which, upon closer examination with a bright light, appeared to be growing zinc whiskers. As a result of being advised, the client was able to ensure that all future purchases used an electropainted finish.
A client was planning a major refurbishment and asked for a zinc whiskers survey of a number of sites before the rooms were disrupted. We carefully inspected tiles, stringers, cabinet components (frame, uprights, rails) within a specified distance of the proposed refurbishment and then inspected at sample locations throughout the rest of the room. We found that only the pedestals were electroplated and therefore, presented a risk of growing zinc whiskers. We suggested that, as the pedestals were already installed, they be cleaned, and then watched and reviewed in a year. We also reported to the client any other anomalies we found in the rooms at the time of inspection.