What is ESD (Electrostatic Discharge)?

What is ESD?

ESD, or Electrostatic Discharge, is the flow of current between two objects with different electrostatic charges. When they come into close proximity, there can be a rapid, spontaneous transfer of electrostatic charge.

Electrostatic charges are most commonly created by contact and separation:

  • When two surfaces contact and then separate
  • Electrons can transfer from one surface to the other causing an imbalance
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    Materials found in an EPA (ESD Protected Area)

    There are two different types of materials found in an EPA (ESD Protected Area): Conductors and Insulators.

    Conductors are materials that can easily transfer electrons/charge and can, therefore, be grounded (charges safely taken away from the object and dissipated safely).

    On the other hand, insulators can hold charges but cannot easily transfer charges, so cannot be grounded. Therefore, charges on insulators need to be shielded/neutralised.

    Did you know: To feel a static discharge it must be about 2,000 volts. However, a component can be damaged by as little as 100 volts! Therefore, it is very easy for a component to be damaged without even noticing that the event has occurred.

     
     
    The problem

    Today, more electronic components are used than ever before and in more compact designs. However, the smaller a component, the more sensitive it is and likely to be destroyed or damaged by a sudden surge of static charge.

    If a component is destroyed, it is classed as a catastrophic failure and can normally be detected in an inspection and repaired/replaced. However, latent defects pose a larger problem, since this is when a component has become damaged but still operates so the component could pass through the inspection phase and end up being installed in the field.

    Depending on the damage, the consequence of using a component with a latent defect in the field may result in an early field failure. This could involve costly repair work for the customer and (if other early field failures occur) a loss of business and reputational damage for the supplier.

    One study calculated the repair costs to fix any failure in a component as:
    £7 if the device fails
    £70 if the device fails on the board
    £700 if the device on the board fails in the system
    £7000 if the system fails due to the device on board

    Therefore, it is important to identify the problem as soon as possible and this may not happen with latent damage. Instead, it would be much easier and more cost effective to ensure that any ESD events are controlled from the start with ESD control measurements.

     
    How to Control and Prevent ESD Problems?

    An EPA (ESD Protected Area) is an area in which all items with electrical charges are grounded, or made safe by having their charges neutralised. This means that ESD sensitive items can be handled without the risk of ESD charges damaging them.
    There are different levels of protection which can be assigned to an EPA, and this will depend on the amount of time that needs to be spent handling the component and the importance of preventing a field failure. For example, if maintenance in the field is not possible, or safety depends on the product not failing (as with components used in space, medical devices and aircrafts) then it is essential that the risk of early field failures is prevented by having strict procedures put in place for EPAs.

    An EPA with a high level of protection will consist of the following:

  • Controlled access to the EPA, which records results and prevents entry to anyone who fails the grounding test.
  • Personal grounding: e.g. smock, heel grounders, wrist straps.


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  • Work station grounding: e.g. Mat, ioniser, continuous monitor, ESD floor.
  • If you have any questions about ESD, or you would like help with an enquiry, please do not hesitate to contact us.

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