What is ESD?

Electrostatic discharge (ESD) is the rapid transfer of charge between two objects at different electrical potentials.

What causes ESD?

Electrostatic charge is produced when two materials are brought into frictional contact and then separated. Everyday examples include combing your hair using a plastic comb or removing an item from a plastic bag. An extreme example is the discharge of thunder clouds through a lightning strike.

Objects can also become charged when placed close to another highly charged item and momentarily grounded. An example is a PCB lying next to a charged plastic box; if it is briefly touched by a grounded person or object, it can acquire its own charge. This charge may then produce an ESD event.

Why is ESD a problem in the electronics industry?

ESD is a serious issue in for the electronics industry. Modern microcircuits contain vast quantities of microscopic components (a PC processor can have 30 million transistors in 1cm²). An ESD event into such a component causes electrical and thermal stress on the tiny circuit elements; this can result in destruction of the device, changes to the working characteristics, or degradation leading to premature failure in use.

The last effect is called Latent Damage and is, potentially, the most expensive type of ESD damage due to the cost of providing replacements or repairs in the field.

What can be done to prevent ESD?

ESD damage can be prevented by introducing suitable protective measures, with the aim of minimising the risk of producing electrostatic charge.

This is achieved by restricting the direct handling of ESD-sensitive devices to an ESD Protected Area (EPA). An EPA can be an individual work station or scaled up to a complete manufacturing area.

All non-essential insulators are excluded, personnel are grounded through wrist straps or footwear and all work surfaces and equipment are selected to be groundable (i.e. conductive or static dissipative) or low-charging.

To protect products in transit outside an EPA, it is essential to use packaging that shields ESD-sensitive components or provides physical isolation from ESD and electrostatic fields.