You�re correct about J-001. It�s interesting though, I find no references to controlling temperature and humidity as an element of an electrostatic discharge control program in the following: * ANSI/ESD S20-20 * "ESD Program Management" by Ted Dangelmayer
Actually, J-001, 3.6.2 has words to the effect that when your plant gets below 30%RH you�d better make sure your ESD controls are working and it is not going to affect your processes.
Turbocharging decreases as humidity levels increases. For instance: Electrostatic voltage (v) Static generation process ||at 10 to 20% RH ||at 65 to 95% RH Walking on carpet ||35,000 ||1,500 Walking on vinyl flooring ||12,000 ||250 Worker sitting at a work bench ||6,000 ||700 Handling a vinyl envelope used for work instructions ||7,000 ||600 Picking-up a sandwich plastic bag from a bench ||20,000 ||1,200 Sitting at polyurethane cushioned bench ||18,000 ||1,500
So a very humid plant is better from an ESD damage reduction standpoint than a very dry plant. And that makes sense, because we get more �sparks� from walking on the carpet, static cling, fly-away hair, etc when the air is dry [ie, winter in the Northeast, summer in the Bay, etc].
OK. So, we agree there should be a lower limit to the humidity. The reason for controlling the upper limit of humidity is that people and some processes just don�t do well when it�s real humid. And they talk about that in J-001 also.
Consider searching the fine SMTnet Archives for further discussion on humidity controls.
reply »