An Introduction to Electrostatic Discharge (ESD)

The intention of this blog is to provide resources, information, and tools to support you in your ESD Control endeavours! So, it seems a fitting way to start by introducing you to the subject, but first we must understand…

What is ElectroStatic Charge?

Electrostatic charge or static electricity is defined as an electric charge at rest, it is the imbalance of electrical charge on the surface or within a material, but let’s dig into it a little deeper…

Everything you see around you is made from atoms – your mouse, keyboard, screen, cup of coffee etc. Every atom is constructed of a nucleus, which includes positively charged protons, and one or more negatively charged electrons bound to the nucleus. As atoms have an equal number of electrons and protons, it balances out having no charge.

Structure of an Atom (Source)

The challenge is all materials are capable of tribocharging and generating Electrostatic charges. Most of the time this happens through contact and separation; some everyday life examples are:

  • Opening a plastic bag
  • Unwinding a roll of tape
  • Combing hair
  • A person walking across a floor, with the soles of their feet contacting and separating from the floor.

This simple separation of two surfaces can cause the transfer of electrons between surfaces resulting in one surface being positively and the other one negatively charged, generating static electricity! The amount of static electricity generated depends upon the materials subjected to contact or separation, friction, the area of contact or separation, and the relative humidity of the environment. At lower relative humidity (as the environment is drier) charge generation will increase significantly. Common plastics generally will create the greatest static charges.

“For most people, static electricity is represented by the noise or crackle heard on a radio that interferes with good reception or the shock experienced when touching a metal object after walking across a carpeted room or sliding across a car seat. Static electricity is also observed as static cling when clothes are stuck together after coming out of a clothes dryer. Most of the time, people observe static electricity when the weather is cold and dry.” “While many people tend to think of static electricity as being at rest or not moving, static electricity causes the most concern when it ceases to be stationary.”

[ESD Handbook ESD TR20.20 section 2.1 Basics of Static Electricity, Introduction]

What is Electrostatic Discharge (ESD)?

If two items are at different electrostatic charge levels, as they approach one another, a spark or Electrostatic Discharge (ESD) can occur. This rapid, spontaneous transfer of electrostatic charge can generate heat and melt circuitry in electronic components.

ElectroStatic Discharge (ESD)

ESD events are happening around us all the time, examples from daily life are:

  • Lightning, creating lots of heat and light
  • The occasional zap felt when reaching for a doorknob
  • The occasional zap felt when sliding out of a car and touching the door handle

Yet, most of the daily ESD events cannot be seen or felt. For a person to sense ElectroStatic Discharge (ESD) (the dreaded ‘zap’), a discharge of about 2,000V is needed. To actually see ESD (in form of an arc, e.g. lightning) even greater voltages are required.

While ESD (often referred to as a static shock) may be a nuisance in the home, it is generally harmless, however in the electronics industry ESD is the hidden enemy. Modern electronic circuitry can be literally burned or melted from these miniature lightning bolts. ESD control is therefore necessary to reduce and limit these ESD events.

Many of the common activities you perform daily may generate charges on your body that are potentially harmful to electronic components. Some of these activities include:

  • Walking across a carpet: 1,500 V to 35,000 V
  • Walking over untreated vinyl floor: 250 V to 12,000 V
  • Worker at a bench: 700 V to 6,000 V
  • Picking up a common plastic bag from a bench: 1,200 V to 20,000 V

Many of the CMOS technology components can be damaged by discharges of less than 1,000 volts. Some of the very sophisticated components can be damaged by charges as low as 10 volts.

Types of ESD Devices Damage

So, we’ve established what ESD is and learned that ESD can damage electronics components. But what exactly does this damage look like? We’re so glad you asked!

ESD damage to electronics can lead to catastrophic failures (device failure) or latent defects.

Catastrophic failures occur when a component is damaged to the point where it is DEAD NOW and will never again function. In these cases, the ESD event may have caused a metal melt, junction breakdown or oxide failure. This is the easiest type of ESD damage to find since it can be detected during inspection and testing.

Latent defects occur when ESD weakens or wounds the component to the point where it will still function properly during testing, but over time the wounded component may cause poor system performance. Later, after final inspection or perhaps even in the hands of your customer, a latent defect may become a catastrophic failure.

Costly Effects of ESD

Catastrophic failures are straight forward: they can be detected and repaired at an early manufacturing stage. This is the least costly type of ESD damage.

Latent defects on the other hand are not only hard to find, but they can also severely affect the reputation of your company’s product. Latent defects can cause upset or intermittent failures and can be very frustrating: customers return a product with a problem which the factory fail to detect so it ends up at the customer’s again with the problem unresolved.

The cost for repairing latent defects increases as detection of the failure moves through the system. One study indicated the repair cost to be:

  • £7 Device
  • £7 Device in board – £700
  • £7 Device in board and in system – £7,000
  • £7 Device and system fails – £70,000

Industry experts estimate that product losses in the electronics industry due to static discharge range from 8 to 33%. Others believe the actual cost of ESD damage amount to billions of dollars annually.

Conclusion

ESD is the hidden enemy in the electronics industry:

  • It cannot be felt
  • It cannot be seen
  • It cannot necessarily be detected through normal inspection procedures.

Therefore, it is absolutely crucial to be aware of the most sensitive items in your factory. Technology advances all the time: electronic circuitry gets progressively smaller which leads to a reduction of microscopic spacing of insulators and circuits within components. While this is great news for the consumer with better, faster, and stronger computers, tablets, phones etc., it’s does make it more difficult for the manufacturer to control ESD. The evolution of technology leads to devices being even more sensitive to ESD. As a result, the need for appropriate ESD Protection is now more important than ever.

4 Comments on “An Introduction to Electrostatic Discharge (ESD)

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