ESD and Static Control Questions

Q: What is Static Electricity?

A: Static Electricity can be defined as an electrical charge at rest.  ESD is the transfer of static charges between bodies or objects at different electrical potentials. This may be caused by either direct contact or by induction of an electrostatic field.  Static Charges are generated when two materials are rubbed together. This term is called Triboelectric Generation or Tribocharging

Factors that Influence Tribocharging:

• Intimacy of Contact Speed of Separation
• Conductivity of Materials
• Triboelectric Series Position
• Relative Humidity
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Q: Why can’t bare or sealed concrete be used as a method for controlling static electricity in a electronics manufacturing environment verse utilizing a Conductive or Static Dissipative covering and/or coating?

A: I’ve done some studies on ESD resistive characteristics of the several different floor surfaces. In light of the following question, I just snapped some photos of ESD readings on the following surfaces:

ESD reading on Dry Concrete

Bare concrete (dry). Results- barely conductive, very humidity dependant; in the insulative range(1E09-1E12)

ESD reading on Asphalt

Asphalt. Results- unacceptable; above insulative.

ESD reading on Dirt

Dirt. Results- pretty good, acually comes in at barely dissipative; Upside, cheap; Downside, hard to clean.

Reading on ESD Carpet

ESD Carpet (Ground Zero Information). Results- ESD conductive(2.5e4-1.0E6).

Reading on ESD Tile

ESD Tile (Ground Zero Information). Results – ESD dissipative(1.0E6-1.0E8).

Reading on Sealed Concrete

Sealed Concrete. Results-unacceptable; a sealed concrete is necessary for heavy foot traffic, but the very thing that would make the concrete conductive is sealed out- moisture. This floor could be made dissipative very easily with an ESD chemical (Ground Zero Information).

Reading on Particle Board

Particle board. See asphalt