The ESD Control Program Handbook. Jeremy M. Smallwood

ESD control flooring Not defined Not defined ESD protective packaging Surface resistance ≥10¹¹ Ω Surface and volume resistance ≥10¹¹ Ω Antistatic General Widely used to described materials used in static control; can mean almost anything Not defined The property of a material that inhibits triboelectric charging (ESD ADV1.0‐2009) ESD control footwear Note: Has defined meaning under ISO 20345 in process industry hazard work Not defined Not defined ESD control flooring Not defined Not defined ESD protective packaging Not defined Materials that have reduced amount of charge accumulation as compared with standard packaging materials

Table 1.3 Example of how meanings of conductive, dissipative, and insulative can vary with context in static control in other industries (IEC 60079‐32‐1:2013).

Object	Measurement	Conductive	Dissipative	Insulative
Material	Volume resistivity (Ωm)	<105	≥105 to 109	≥109
Clothes	Surface resistance (Ω)		<2.5 × 1010	≥2.5 × 1010
Footwear	Leakage resistance (Ω)	<105	≥105 to <108	≥108
Gloves	Leakage resistance (Ω)	<105	≥105 to –<108	≥108
Floor	Leakage resistance (Ω)	<105	≥105 to <108	≥108

      1.7.4 Point‐to‐Point Resistance

In ESD control, it is convenient to make simple measurements to evaluate the surface properties of a material or item of equipment. One simple way of evaluating a surface is to place two electrodes on it and measure the resistance between them. The electrodes are often cylindrical in form. This is called a point‐to‐point resistance measurement. Standard test methods based on this approach are often used. Examples of point‐to‐point resistance test methods are given in Chapter 11.

      

      1.7.5 Resistance to Ground

      As explained earlier, in ESD control work, voltages on conductors are often eliminated or controlled by providing an electrical connection for the charge to pass to earth (ground). It is often required to know the resistance from an object or surface to ground to help understand the charge dissipation paths. This is known as resistance to ground. Examples of measurement methods for this are given in Chapter 11.

      1.7.6 Combination of Resistances

In practice, the resistance of a ground path may be due in part to several components. If these are effectively in series (Figure 1.4), the effect is to add the resistance of all component contributors R₁…R_n to get a total resistance R_tot.

If resistance of ground paths is in parallel (Figure 1.5), they are combined as

Figure 1.4 Resistances in series.

Figure 1.5 Resistances in parallel.

1.8 Capacitance

The voltage V on a conductor is related to the stored charge Q as

      The variable C is the capacitance of the conductor. In electrostatics, any conductive object has capacitance; it is just the relationship between the stored charge and the object's voltage.

      In practice, the capacitance of an object can vary with proximity of other conductors and materials (see Chapter 2).

      A charged capacitor stores energy. The energy W stored in a capacitance C at voltage V is given by

      This can also be expressed as

      An object in free space (with nothing in the near vicinity) still has capacitance. For a spherical conductor of radius r in air or a vacuum, this capacitance C is

In practice, the capacitance of an object may be due in part to the proximity to several objects. If these are effectively in parallel (Figure 1.6), the effect is to add the capacitance of all component contributors C₁…C_n to get a total capacitance C_tot as