ESD COMPLIANCE VERIFICATION OF SERVER RACK
Data is the gold mine of the 21st century, from Aerospace to Medical industry, from Shipping to e-commerce industry, every industry is driven by high quality data. Such data is stored in servers and transferred to identified locations using various types of telecom routers. Such servers and routers are stored in server racks. Server racks are used to ensure performance in a combination and when kept in server rack it can increase the performance of the system and also decrease the potential cost of data centres maintenance.
In short, Server rack is a mounting structure, where server and computers are stacked together to ensure performance of expected functions.
In such racksequipment are organized with cable, computer and server. Anyone can access and resolve problem without any difficulty with its shelves, wheels and air flow facility. Typically these racks are kept in air conditioned environment during operation. These racks have door lock system, provided much security from unwanted activities.
In order to ensure long term performance of the server installed in such server rack, it is pertinent the server rack follows specific requirements in order to ensure compliance to ESD controlled requirements. While reviewing such rack we had noted several non compliance issues which can put the long term performance in jeopardy.
Further, during product development and product manufacturing PCBA (Printed Circuit Board Assembly) along with other ESDS (ESD Sensitive) components may be kept or installed on the server racks in a sub-system condition. If the server racks used during such phase of the product are not ESD safe, this can result in significant issues on the components and PCBA’s stored both due to ESD as well as due to EOS from active components within the system.
Five key issues noted during product qualification of Server racks are mentioned below:
Compliance issue identified is, cooling fan is generating voltages beyond the compliance requirement. Further the issue description is, cooling fans in switched ON condition produces 150V-450V at a distance of 10cm from the fan. Such voltage generation does not reduce.
WHEELS OF SERVER RACK
Compliance issue identified is, wheels of server rack are non complaint resulting in generation of charges. Further issue description is, when the wheels with payload is pushed on a non-ESD safe surface, voltage generation of >600V is observed. When the wheels with payload is pushed on a ESD safe surface, voltage generation of >210V is observed.
KEYBOARD TRAY OF RACK
Compliance issue identified is, key board tray is not connected to chassis. Further issue description is, key board tray is not connected with chassis resulting in discontinued resistance path. Such discontinued path is resulting in isolated conductors which can retain charges.
NON-UNIFORM POWDER COATING THICKNESS
Compliance issue identified is, aberration in powder coating thickness resulting in variation of surface resistance. Further issue description, aberration in ESD safe powder coating resulting in variation of resultant resistance path.
Compliance issue identified is, charge generation from cable manager conduit. Further issue description is, non ESD safe cable conduits result in >6kV equivalent static charge resulting in exposure to sub-system level PCBA and ESD sensitive components.
These are key issues identified and result in failures of such server racks during product qualification.
About the writers: Mrinalkanti Mandal, working as ESD Engineer for ESD India and has completed his MTech from IIT Mandi & Susmita Pal, working as the External Relationship Lead for ESD India