Desco - Questions And Answers

Hi, Can someone please inform me of a standard which refers to ESD requirements at an elevated temperature. Instead of operating at a PCB assembly level of 22°C, what if we operated at 35°C. What are the specials precautions required. -Anonymous, Clayton, Australia

You should follow the same ESD Control practices at 35°C as you would at 22°C. You can obtain a copy of the newest parent ESD Standard from the ESD Association (web site http://www.esda.org/) by going to their web site and downloading at no-charge the ANSI/ESD-S20.20: http://esda.org/standards.html Temperature affects how the air holds moisture and is used to derive Relative Humidity (RH). The warmer the air (the more energetic the air molecules get), the more water moisture the air can hold. Relative Humidity, (usually meant when the term humidity alone is used), is the ratio of the actual water-vapor content of the air to its total capacity at a given temperature; and specific humidity, the mass of water vapor per unit mass of natural air. In ESD, it is the water content in the air plus the energy of these water molecules to collide with surfaces in our space (workbenches, clothes, hair, etc.) The more water content and/or energy, the more collisions and neutralization (tendencies found in warm air) versus the more sedate, less reactive water content/air molecules in colder temperatures. Therefore colder air tends to enhance the natural phenomena of triboelectric generation because it does not inhibit this process as much as warmer air.

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