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Moisture related to ESD

Al Carrillo


Moisture related to ESD | 31 January, 2000

Hi Everybody,

Somebody knows if is required to have a special %RH to avoid increse the ESD even We have ESD conveyors, tables, in some cases inonizers, the operators wear ESD smacks and shoes and whole equipment and lines have Humand ground.

any comment is aprecaited


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Jason Bentley


Re: Moisture related to ESD | 31 January, 2000

from what I know the moisture does play a foctor in the ESD but if you are looking for wether or not it will provide more ESD I dont think so. If you keep your operators grounded with 2 Foot straps thats all the grounding that you need unless you are sitting down. (in refrence to popular comments) you need two ground straps for the feet or else you are shocking a board every time that you lift the ground strap off of the ground.

hope that this helps Jason

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Re: Moisture related to ESD | 31 January, 2000

Al, Check out the link below. Hey Jason, How is everything at Solectron?

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Re: Moisture related to ESD | 31 January, 2000

Alvaro: Have you been down to Brazil lately?

From our operator training program:

Problem #1 with ESD. Our day-to-day activities produce tremendous charges.

|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

� And the level of charge generated varies with the relative humidity (RH) level. This variability caused by humidity helps explain why we seem to get more "carpet shocks" in the winter, when the air is dry, than in the summer, when the air is moist.

This is because most common insulating materials such as wood, fabric, paper, or masonry contain a certain amount of moisture, which is dependent on the relative humidity of the air. To some extent, the moisture content, in turn, affects the conductivity of these materials and their ability to hold static charges.

Relative humidity|Conductivity Higher >50%|More conductive Lower <30%|More insulating

Logically, it would follow that high humidity would be an effective means of controlling static electricity, but high humidity:

� Still allows generation of unacceptable charges, even though not a large as low humidity. � Contributes to other problems including oxidation and soldering difficulties. � Is uncomfortable and expensive to generate and control.

Bla bla bla

Our "ESD Prevention And Control" procedure says:

4.2.7 Humidification. The Company maintains relative humidity and temperature according to procedure MOP-09-05, Solder Control.

Our "Solder Control" procedure says:

3.1.4 Controlled Environment. The Company controls the environment of the soldering area to limit the entry of contamination within the limits defined as the preferred environment in the figure below.

The figure shows a graph with temperature on the y-axis and humidity on the x-axis. The "preferred environment" is bounded by the closed, four sided figure made by connecting the points (84�F, 30%RH), (78�F, 70%RH), (68�F, 70%RH), and (72�F, 30%RH) with four straight lines. (Hopefully, that�s no too obscure of a description.) In the production area, the allowable variation within the above limits are:

Rate of temperature change|3�C (5.2�F) change per hour Desired setting|With �10%

Bla Bla Bla

Good luck and stay away from the Hydrogen, bud

Dave F

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