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Facility Humidty controls



Facility Humidty controls | 15 June, 2002

What is the value for having humidty controls? I have read the IPC _ 001 standards and it states that the facility requires to be humidty controlled.

I agree that a low humidty controls for ESD is important. But, why have an upper limit? what are the downfalls?

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Facility Humidty controls | 17 June, 2002

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.

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Facility Humidty controls | 18 June, 2002

Hi mates,

think between that Standard and Dave.F covers just about the "why" needs.

for our side we set 40RH% to 60RH%. wonder if there is any industrial engineering basis to this setting?

we do know its "optimal" for our mfg operations and environment ESD control.

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Facility Humidty controls | 1 July, 2002

Would rather have lower humidity and strict ESD rules in place.. than a high humidity condition anyday.. High humidity- 45RH + Paste depending on what you use may become an issue.. Components are sensitive... ever get that vacuum sealed bag you dont use up and store for a few months? Soldering anomalies?

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Facility Humidty controls | 5 July, 2002


Paragraph of ANSI/ESD S20.20 states "Humidity control may be a key element in an ESD control program. Propensity for charge generation and accumulation increases with a reduction in humidity."

Even if charge generation is reduced to 2-300 volts at a high humidity level, component damage may occur depending the component sensitivity level. S20.20 is based upon the assumption of that the component is rated at 100 Volts Human Body Model.

A properly designed and executed ESD Control program should protect ESD sensitive assemblies independent of humidity.

The four basic steps are:

1. Eliminate non-essential insulators like personal items, plastic coffee cups, Styrofoam packaging, etc. 2. Ground personnel and worksurfaces. 3. Transport ESDS devices outside of an ESD protected area in shielding packaging. 4. Neutralize process essential insulators with ionization or other charge mitigating techniques(e.g. the plastic housing of a product into which an ESD sensitive printed circuit boards is mounted). Key rule of thumb: if electrostatic charges of > 2000 volts are present, keep ESDS assemblies > 12 inches away.

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