Electrostatic Discharge

Electrostatic Discharge (ESD)

Electrostatic Discharge (ESD) ruins electronic components.

Let’s take a look at ESD, it’s causes and devastating effects:


The term ESD describes the phenomenon itself rather clearly:

In an ESD event, a sudden flow of electricity is conducted between two objects as they come into contact with one another.

ESD causes electrical/thermal damage. As we’ve already covered, electronic components have specifications as to how much thermal heat they can withstand. Any one part of a PCB or integrated circuit is designed to conduct (transport) a maximum amount of electrical current. Once this threshold is passed, the component/board/circuit becomes damaged.

This is why static electricity is a primary concern to electronics designers, manufacturers and distributors.


Static Electricity

It’s safe to say that most of us understand static at an elementary level: Walk across your living room carpet while wearing socks and the next metal object you touch will give you a quick jolt. Generally speaking, static electricity is harmless to us. Most of the time we’re unaware of its presence and effects.

Static electricity is an imbalance of negative and positive electrical charges on the surface of a material. It involves the transfer of electrons – which are said to have a negative charge – from one object to another.

Because some materials are more “willing” to give away their electrons and others are more “willing” to receive them, we get the flow of electrons between objects with different amounts of electron charge.

A more thorough explanation of static electricity can be seen here:


Causes of ESD in Electronic Components

Electronic components can fall prey to ESD in a variety of ways.

In the Field:

ESD can occur as a result of Electronic Overstress (EOS). If a PCB or integrated circuit is designed incorrectly, utilizes inadequate components or succumbs to layout error, EOS may rear its ugly head somewhere down the line. This is because these types of miscalculations can result is the overheating of circuit components.

When electrical components are subjected to excess thermal energy, they begin to malfunction. As excess currents pass through a component, it overheats, and because thermal energy transfers from one component to the next, the second component is then pre-heated. The amount of electron capacity is lowered so – in effect –  its charge is altered. Due to this, the next component in line may bear the thermal overstress of the first component.

chain-reaction
EOS & ESD create a chain reaction.

This is the reason so much time is put into PCB layout and design…even the most minuscule details are of major consequence!

Using the wrong materials or placing the wrong components next to each other can be conducive to board failure. Multi layer boards and thru hole technology – now industry standards – make PCB manufacture an even more complicated endeavor.

PCB’s may appear to be functioning properly during testing even though it might be partially damaged from an ESD event. The original ESD event will weaken the component and cause a premature failure later in its lifespan while it’s in the field. This is considered a latent defect, the likes of which have been seen numerous times over the years.

In Manufacture and Transit:

As mentioned above, human beings conduct electricity and we generate it constantly. Any time we come into contact with another object and then separate, we’re generating a static charge! 

This is why the electronics industry utilizes a variety of anti static measures to ensure that electronics are not subjected to an excess transfer of electric currents:

THIS IS SOMETHING WE’RE GOING TO DISCUSS IN OUR NEXT POST.

VoltageSometimes though, anti static measures are not effective enough to prevent ESD events from taking place. If during manufacture, someone not wearing the proper anti static protection comes into contact with a PCB, an ESD event can occur.

Similarly, if during transit a PCB is contained within an inadequate anti static environment, an ESD event can occur.

There are many variables to consider when examining ways in which to prevent ESD. An ESD event at one component can produce an EOS failure on an adjacent component or even one on the opposite side of the board entirely. ESD and EOS events are similar in that they both incorporate current overstress conditions.


Effects of ESD

ESD can be produced in any of the following ways:

  • Human contact.
  • During troubleshooting, testing and repair.
  • Contact with/placement next to insulative or conductive materials.
  • Rapid movement of air.
  • Placement in improper packaging.

ESD can result in:

  • Bulges, burns and holes in PCB traces
  • Melted metal.
  • Severed connections.
  • Heat stress.
  • Complete PCB failure.

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