ESD Environment Considerations for Cleanrooms

People encounter static electricity in everyday life – crackling when you pull your sweater off, walking on carpet then getting a shock when you touch the doorknob, or your hair standing up when the air is low in humidity.

ElectroStatic Discharge (ESD) is when an electric charge is released which can severely damage electronics. As electronic feature sizes have shrunk from mils to microns to 0.1 microns, electronic device features have become more and more sensitive to ESD damage. These fine line widths have pushed electronics manufacturing into cleanrooms in order to maintain an acceptable manufacturing yield.

A static charge occurs when two surfaces come into contact with each other. It can also come from environmental conditions, such as exposure to light, heat and cooling. Mobile processes in semiconductor manufacturing such as spinning, coating and plasma processes also cause static charge. Humans can cause static charge by moving. HEPA filtration is a major contributor to static charge due to the friction of large amounts of air passing thru dense HEPA filters. Static charges cause contamination. Once a surface is charged, it will attract and hold small particles in the air having an opposite electrical charge.

As cleanroom classifications levels are reaching ISO5 and ISO6 in non-electronics manufacturing cleanrooms such as pharma and medical device cleanrooms, companies are realizing that static charge (ionic attraction) of submicron contamination makes removal of these particles much more difficult. Therefore, reducing static electricity in these non-electronics industry cleanrooms has also become a priority.