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What Is Electrostatic Discharge (E.S.D)?

Electrostatic discharge (E.S.D) is an uncontrolled surge of “static” between objects with different voltage potentials.

Have you ever felt a random zap when touching a doorknob or a screen? This zap you have experienced is known as static electricity.

What Is Static Electricity?

Static electricity is a stationary electric charge, typically produced by friction, which causes sparks, crackling or the attraction of dust or hair.

All items are made of small atoms. These atoms are made up of even smaller items called protons, neutrons and electrons. The protons are charged positive, the neutrons have no charge and the electrons are charged negative. Under normal conditions, there are the same amount of protons and electrons giving atoms no charge. However, these electrons can move. When separating or rubbing together materials, electrons can move from atom to atom or from one material to another (triboelectric charges). This can mean that atoms can hold a positive or negative charge. (Dependant on movement and direction of electrons). If the material in question is an insulator, this charge can be held and not move. This is called static electricity.

What Is Electrostatic Discharge (ESD)?

Electrostatic discharge can occur when two surfaces come into contact and create friction with each other. Examples include: walking over synthetic floors, rubbing of synthetic garments, shifting of plastic boxes, unrolling of PVC adhesive tape and moving of conveyor belt.

This builds up an electrostatic charge as one surface becomes positively charged and the other surface becomes negatively charged causing an imbalance. 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. If the electrostatic charge comes into contact with the right material, it transfers and causes an ESD event. ESD can also occur when a high electric field develops between two objects in close proximity.

In a normal environment like your home, there are innumerable ESD events occurring, most of which you do not see or feel. It takes a discharge of about 2,000 volts for a person to feel the “zap”. It requires a much larger ESD event to arc and be seen (e.g. lightning). While a discharge may be a nuisance in the home, ESD is the hidden enemy in a high tech manufacturing environment. 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.

ESD can result in:

  • Higher costs
  • Lower quality
  • Unhappy customers

Types of ESD Damage

Electrostatic damage to electronic devices can occur at any point from manufacture to field service. Damage results from handing the devices in uncontrolled surroundings or when poor ESD control practices are used. Generally damage is classified as either a catastrophic failure or a latent defect.

There are two types of ESD events, catastrophic and latent defects.

Catastrophic:

When an electronic device is exposed to an ESD event it may have caused a metal melt, junction failure or oxide breakdown, permanently damaging its circuitry and resulting in failure. Such failure can usually be detected when the device is tested before shipping. If the ESD event occurs after the test the damage will go undetected until the device fails in operation.

Overview:

  • A device is exposed to ESD and no longer works.
  • The device circuitry is permanently damaged.
  • Such failures are usually caught when tested and before shipping.

A catastrophic failure is a limited cost:

  • It is the easiest type of ESD damage normally detected during testing.

Latent:

A latent defect is much more difficult to identify. A device may be partially degraded yet continue to perform its intended function. However, the operating life of the device maybe reduced dramatically. This could cause premature systems failure which could prove extremely hazardous and very costly.

Overview:

  • A device is exposed to ESD and is partially damaged, yet it continues to perform its intended function.
  • Latent defects are much harder to identify since they occur over a long period of time.
  • This may pass testing and be shipped to a customer and fail whilst in service.
  • It can significantly shorten the operating life of the device and it can be very costly.

A latent failure is a higher cost due to:

  • Customer support
  • Servicing facility
  • Replacement equipment
  • Loss of reputation
  • Loss of customers

It is important to note that ESD damage can occur at any time! 

For example:

  • Goods input
  • Acceptance
  • Production
  • Assembly
  • Testing
  • Storing
  • Packing
  • Shipping
  • Maintenance

ESD Is A Huge Problem For Many Industries

Did you know people are the primary source of electrostatic charges?

Static electricity has been an industrial problem for centuries. As early as the 1400’s, European forts were using static control procedures and devices to prevent electrostatic discharge igniting gun powders and other explosives.

The electrostatic discharge (ESD) phenomena have been known since the Greek civilisation was dominant thousands of years ago. People in cold climates were very familiar with the ESD effect in a low-relative humidity environment as was frequently experienced in indoor environments in the winter time.

As electronic components changed from electronic tubes to solid state electronics in the 1950s, companies became concerned with damage to electronic components and interruption of normal operation of electronic equipment. This article is primarily addressing the interruption effects of ESD to packaged electronic equipment.

Within today’s electronics industry, it is widely accepted that electrostatic discharge (ESD) events are a significant cause of device failure and that implementing static control measures is not only desirable but essential. Damage to this industry has been estimated at billions of dollars annually. However while the costs of static control measures can be high, the return on investment certainly does justify the implementation of such measures.

ESD problems have magnified during the past 3 decades because of 2 reasons:

1) The increased use of insulating man-made fibre’s and plastics for clothing, furnishing, flooring etc.

2) The ever-increasing sensitivity of integrated circuits due to smaller and smaller conductors and components within the circuitry.

ESD can change the characteristics of a semi-conductor device, degrading or destroying it. Controlling ESD begins with understanding how electrostatic discharge occurs in the first place. Electrostatic charge is most commonly created by the contact or separation of two materials. This is known as “triboelectric charging”, it involves the transfer of electrons between materials.

Static discharge that is released can set fire on flammable concoction or vapours in laboratories or even destroy highly sensitive and costly electronic components in factories. It can also draw in contaminants in clean settings or even lead products to stick together and interfere with the overall manufacturing process. Common plastics generally create the greatest static charges.

Component Spark ESD - Bondline

Why Is Managing ESD Important?

Static discharge is destructive to sensitive electronic components. Even 1 volt of electricity is enough to cause damage but most devices need around 100 volts to cause damage that is beyond repair.

Humans cannot feel a static discharge unless it is 2,000 volts or higher. So, if you don’t feel a zap, it doesn’t mean a static discharge did not happen or damage your electronic components.

There are many industries that depend on electronic components and their reliability to work in harsh conditions, so the need for reliable ESD equipment is very important.

Often, electronic component producers are not aware that static discharge has damaged their products during the assembly process, unless they test all components one by one or see their final product fail after assembly. If these products were used in an industry like aerospace, one minor problem on a small component could lead to an enormous failure, which is why ESD is a major challenge for many industries.

Typical Electrostatic Voltages

Walking across a carpet: 1,500 – 35,000 volts.

Operator at a bench: 100 – 6,000 volts.

Walking over untreated vinyl floor: 250 – 12,000 volts.

Picking up a common plastic bag from a bench: 1,200 – 20,000 volts.

Chair with urethane foam: 1,500 – 18,000 volts.

What Voltage Can Damage Components?

The voltage can be as little as 10 volts depending on the size, sensitivity and type of component. To comply with the British standard 100V is the maximum threshold that can be produced within an EPA.

Potential Difference

Potential difference causes ESD when there is a difference in charge between two objects. These can include work surfaces, articles of clothing, people, flooring and shelving/conveyers.

ESD Symbols

Protection symbol

Used to designate all ESD protective products such as bags, boxes, garments. A letter is added under the symbol to indicate the primary function:

C – conductive D – dissipative S – shielding L – low charging

Anti Static Symbol

EPA label

Used to designate EPA equipments such as tables, trolleys and chairs.

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Basic symbol

The basic symbol consists of a yellow hand within a black triangle. It is intended to identify devices and assemblies which are ESD sensitive.

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How Can You Prevent ESD?

Nowadays, investing in ESD protection is an essential element of electronics-based industries as it’s applied in every stage of manufacturing, production, repairing and testing.

Many industries want to avoid the occurrence of an ESD event and reduce static discharge in the workplace. By ensuring you have the essential EPA equipment, you would prevent the risk of static discharge from damaging components and entering your EPA.

Essential EPA Equipment You Should Use:

  • ESD mats and flooring ESD mats and flooring dissipates charge through the top layer (dissipative layer) of the mat, travels through to the conductive layer and through the stud to earth.
  • Wrist-straps and cords Carry the charge away from the person and discharge the static safely to ground. The cables are always fitted with a 10^(6) Ω resistor next to the skin. The cables are usually connected to earth through a stud on a mat or straight to an earth bonding point.
  • Heel grounders and ESD shoes Heel grounders and ESD Shoes work in a similar way. They only pass the charge into an ESD Floor.
  • ESD garments The main purpose for wearing conductive smocks is to suppress static fields on employee clothing. The conductive fibres woven into the material provide a Faraday cage that prevents dangerous fields from extending to and damaging sensitive products. There shall be electrical conductivity between all parts of the garment.
  • ESD gloves – ESD sensitive device can experience a damaging discharge if touched by a person, even if that person is properly grounded. Increasing the electrical path’s contact resistance is one way to control the speed of the discharge. A good way to accomplish this is by wearing static dissipative cots and gloves.

Remember these 4 golden rules:

  • 1) Assume that all active components are sensitive to ESD.
  • 2) Handle electronic components only in the ESD protected area (EPA) and only when you are properly grounded.
  • 3) Store and transport the ESD-sensitive items in ESD protective containers.
  • 4) Check regularly the ESD protection system, internal and external (suppliers).

Creating an Electrostatic Protected Area (EPA)

An EPA (ESD Protected Area) is a defined space where no items or activity are able to cause damage to a sensitive device. In the simplest case – a field work station – it may consist of a dissipative mat, a wrist strap and common grounding facility for both. The maximum allowed electrostatic field in an EPA is 100V/cm.

  • Define a boundary with suitable signage and physical barriers.
  • Provide effective methods for grounding personnel – wrist straps, static dissipative floor with suitable footwear.
  • Install static dissipative work surfaces, grounded to a common earth facility.
  • Ensure that all containers and bins are non-insulative – i.e. conductive or static dissipative.
  • Provide effective packaging for transit outside EPAs. The function of this packaging is to shield or separate sensitive electronics from ESD events.
  • Ensure that all trolleys used within the EPA are grounded.
  • Install test equipment for daily checking of personal grounding items – wrist straps and/or footwear, with a system for recording checks.
  • Exclude all non-essential insulators. Consider the use of ionisers for neutralising charges on process-essential insulators.
  • Identify and provide training for all staff involved in the handling of ESD sensitive items or who may be required to operate within the EPA.
  • Implement checking and auditing procedures for the ESD Protection Programme.

Click here for a more detailed guide.

Electronics Manufacturing - Bondline

ESD Training

Want to learn more about ESD? We offer a full ESD training course to help you improve your knowledge on electrostatic discharge. The training course is conducted via a comprehensive training facility, effective through personal involvement. This can be tailored to your requirements at your premises. The course is ideal for production personnel, engineers, support staff and managers who want to refresh their knowledge on ESD or want to learn about it.

The training focuses on the causes of static generation, the effects of static discharge, and the materials and methods necessary for prevention and protection. The course content will reflect the facilities and current practice.

Understanding the phenomenon is enhanced through practical demonstrations and audience participation. Courses can also be presented on a ‘one to one’ ‘train the trainer’ basis.

Costs will depend on the amount of information/ training required. All training is designed to meet the requirements of IEC-61340-5. Please contact us below if you would like more information about our ESD training course.

Contact Us

Our company’s objective is to prevent ESD with our diverse range of anti-static products. By using our anti-static products, it can prevent further damage to electrical components and devices whilst also promoting a static-safe working environment.

If you would like further advice on how to control ESD or if you are interested in our ESD training programme, please contact our sales team either by email, live chat or telephone where we will be happy to help you find a solution and answer any queries. Email: sales@bondline.co.uk   Tel: 01793 511000.

Start grounding your workplace with our best-selling ESD products:

                      

Earth Bonding Plug       High Comfort Wrist-Strap        Straight Grounding Leads

 

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