ESD Environmentally Produced Problems

Sometimes ESD problems become difficult to eradicate even after having applied many ESD inhibiting techniques, like use of wrist straps, antistatic/conductive flooring and associated foot strap ESD discharging methods, antistatic apparel (smocks), etc… consequently we need to proceed to attack de ESD generating mechanism or ElectroStatic Charge (ESC) phenomena due mainly to an uncontrolled environment.

The key to solve the above mentioned problem is by controlling the environment and its basic components, for example, temperature, air quality, relative humidity and personnel. Workers circulating in the environment must be restricted to an essential minimum, also some of their freedom will have to be restricted eg no food, no drinks, no smoking, no mobile phone operation, etc… Once limited, the number of people moving in and out of the site the amount of uncontrolled air coming through the door will also be proportionally reduced.

Sealing of the location and then proceeding to estimate the amount of heat generated by the equipment inside are the initial necessary steps as to proceed to install adequate air conditioning units. The RAC unit will control temperature (and perhaps RH) and providing a RAC with an appropriate filter the inside air will become much more contaminants’ free, even though the relative humidity (RH) will be somewhat reduced. A study conducted and published by Siemens on the effect of increased room temperature over 140Mbit/s PDH optical transmitter and receiver panels concluded that the expected number of failures per month of each panel (as per their FIT figures) increase by 20% for each step of 10ºC above 25ºC.

Ambient temperature is advised to be kept in the range of 20ºC to 25ºC with a maximum temperature gradient of 1ºC/6min (the temperature comfort threshold for humans is considered to be 25ºC however for electronic devices a best environment is considered to be 20ºC). If relative humidity can be economically controlled, then a good level to keep the environment is around 50% to 60% with a maximum relative humidity gradient of 10%/hr (RH cannot be set too high as condensation of humidity and hence corrosion may occur in devices and components).