What is ESD, and why is it important?
ESD (electro static discharge) is the transfer of an electrical charge between two electrically charged objects. A well-known example of ESD is the shock you receive after walking across a carpet and touching a metal door handle. However, the heat generated by ESD can cause significant problems in industrial applications, including damage to and failure of electronic components.
Regardless of whether you work in the electronics industry, with any products that ESD can affect, or if static damage is a new problem you face, this guide provides a detailed overview and steps that you can take to mitigate its impact.
- A detailed explanation of electrostatic discharge.
- What causes ESD.
- The types of damage static discharge can cause.
- Steps to protect against ESD (including Faraday cages).
- And much more.
Please continue reading for further info, or use the table of contents to go straight to a specific topic.
What is static electricity?
Before providing further details of ESD and how it happens, it is first essential to define and explain what static electricity is.
Static is effectively a fixed electric charge. Static can typically occur when two different materials rub together (i.e. friction). When this happens, one material becomes positively charged. The other becomes negatively charged. The positively charged material now has an electrostatic charge that transfers when it comes into contact with other specific materials.
To explain this further, all materials and items consist of atoms, which themselves consist of protons, neutrons and electrons. Protons possess a positive electrical charge, neutrons have no charge (neutral), and electrons have a negative charge.
In normal conditions, there are an equal number of protons and electrons. However, when separating materials or rubbing them together (friction), the electrons can move between atoms and even materials. This movement of electrons is known as creating a triboelectric charge.
As the number of protons and electrons becomes unbalanced, an item can hold a positive or negative charge (whether it is positive or negative depends on the movement of and direction of the electrons).
If material is also what is known as an “insulator”, it can hold a charge – which effectively builds up to create static electricity.
A detailed explanation of ESD
Exactly how electrostatic discharge works
ESD stands for electrostatic discharge. ESD is the release of static electricity when two objects come into contact.
In more technical terms, electrostatic discharge “is a sudden and momentary flow of electric current between two electrically charged objects caused by contact, an electrical short or dielectric breakdown”.
As detailed during the explanation of static, ESD first requires a build-up of an electrostatic charge. Typically occurring when two different materials rub together, one of the materials becomes positively charged whilst the other becomes negatively charged (due to the flow of electrons).
This behaviour results in the positively-charged material now having an electrostatic charge. When that charge comes into contact with the right material, it transfers – creating electrostatic discharge.
The impact of ESD
Static discharge is something you will likely have experienced yourself.
For example, you get an electric shock after walking across a carpet and touching a metal doorknob. You will also have seen the most extreme form of ESD – a lightning bolt occurring during a thunderstorm.
For most people, ESD is a momentary nuisance. Whilst you feel the static shock, no physical harm occurs. And whilst some people are more sensitive to static shocks than others, for most, the threshold for feeling static shocks is 2,000 to 4,000 volts.
Although often invisible, this electrostatic discharge generates a considerable amount of heat.
But why should this matter? When the ESD transfers onto an electronic device, the intense heat can melt, vaporise, or otherwise damage the intricate parts of the device. This damage can cause it to fail.
Types of ESD damage
Identifying and defining types of static damage
As mentioned, ESD causes damage primarily due to the extremely high temperatures generated during the charge transfer.
However, there are generally two categories of ESD damage – catastrophic and latent. The latter is also commonly referred to as a latent defect.
Both these forms of ESD damage can occur at various points throughout a product’s or components’ lifecycle. Damage could occur during manufacture, storage, transit, or ongoing use by the end user of the equipment.
It is important to note that ESD can cause other issues for varying industries besides damage to electronics, including igniting explosions in gas, fuel vapour and coal dust.
Catastrophic ESD damage
Firstly, catastrophic damage is (as the name would suggest) where ESD damage causes an item to stop functioning. The heat generated by the static discharge can melt metal circuitry, cause oxide breakdown, or cause a junction failure.
In these scenarios, the ESD damage will prevent the equipment from operating.
Whilst this is commonly caught by manufacturers’ tests before shipping, if the damage occurs after testing, it can lead to the equipment failing during operation.
Latent ESD damage and defects
A latent defect is when ESD causes damage to a component or device but causes only partial degradation. Whilst the item will continue to operate, the lifespan of the item is likely to be significantly reduced.
This ESD damage can have severe implications for items failing during service, potentially leading to significant failures of reliant components, parts, or even complete systems breakdowns.
Causes of ESD
Understanding why ESD occurs
It is critical to understand not only the damage that ESD causes but also the causes of ESD.
As such, there are three main reasons for ESD – people, equipment, and “charged insulators” (materials that will retain a static charge).
Understanding how each leads to ESD can help you prevent and mitigate the impact electrostatic damage can cause to your business.
Firstly, employees and operatives in your business will generate static charges during everyday activities. Charges generated on a person’s body simply by walking, assembling or handling items, plus general movement, can range from a few to thousands of volts. These charges can be passed to electronic componentry (such as PCBs or semiconductors) when handling them, causing significant damage.
Secondly, the movement of equipment such as conveyors, automated assembly machines, and handling aids (such as trolleys, sack trucks, etc.) can also generate charges anywhere between a few and a few thousand volts.
And finally, charged insulators can also result in electrostatic discharge. A charged insulator is effectively a material that can retain a static charge.
Primarily (but not limited to) plastics, these materials can cause ESD damage through what is known as “charge by induction” (where the field from a highly charged item can cause ESD without physical contact).
Why is ESD damage important to businesses?
Businesses can feel the impact of ESD damage in several ways.
Firstly, any catastrophic damage caused to products or equipment – that testing before shipping does not discover – can result in the return of items (and the requirement for replacements to be shipped).
However, items failing due to latent defects can be much more damaging.
Latent failure can result in the failure of larger systems and equipment. In this scenario, there are the costs of servicing, replacement products, and loss of productivity (for example, the halting of automated manufacturing lines or engineers wasting time on site as equipment does not work).
At best, latent defects can cause items to have a reduced lifespan, with the products needing to be replaced more frequently (at a cost to your business or customers).
These issues can result in customer complaints, a reputation for supplying unreliable equipment, and lost ongoing business (customers will potentially switch to competitors’ products).
What is ESD protection?
The impact of ESD damage on your business can be significant.
As a result, electronics manufacturers will aim to create static safe zones which reduce or eliminate the potential for static.
Steps taken can include “grounding” employees using suitable footwear, flooring and wrist straps, excluding non-essential insulators, installing static dissipative work surfaces, and controlling humidity.
However, one of the most critical methods of combating ESD damage is using suitable anti-static packaging and handling equipment.
Anti-static packaging can create a “Faraday cage” that channels any ESD outside the packaging container. The diverting of the charges protects the contents (e.g. sensitive electronics).
Other anti-static or static dissipative materials, including foam, is also commonly used to provide additional protection.
What is a Faraday cage?
In simple terms, a Faraday cage or shield is a sealed enclosure created by electrically conductive materials. Usually, the outer layer blocks external electric fields, both static and non-static. These properties protect the item or device inside.
These cages – utilising any closed shape – can be produced purely from a conductive material. Alternatively, they can be made from a non-conductive material and then wrapped/coated in a conductive substance.
A Faraday cage effect is why using anti-static bags to protect motherboards is common. They are frequently required to protect various electronic equipment from electrostatic discharges.
Using a Faraday cage for anti-static packaging
So can a Faraday cage be used for anti-static packaging?
Whilst a Faraday cage is frequently portrayed as literally a metal mesh or cage, many forms of packaging provide this type of protection.
For example, the well-known Corstat® coated fibreboard is effectively a carbon coating that allows the creation of the Faraday cage. Corriplast® and SSI Schaefer products, by contrast, have carbon impregnated directly into the Polypropylene material during manufacture.
However, simply using a conductive material does not create a Faraday cage. The structural design of the packaging also plays a key role.
How a Faraday cage works
Going into greater detail about how electricity behaves in conductors is the key to understanding how a Faraday cage works.
Metals have negatively charged particles or electrons in them. Without electrical charge, the conductor has the same number of positive and negative particles.
When an external object with an electrical charge approaches the conductor (the metal), the particles separate – and any electrons with an opposite charge to the external item become drawn to it. But any electrons with the same charge are repelled and move away from the object.
The negative and positive particles then end up on opposite sides of the conductor. The following process is a redistribution of charges, resulting in an opposing electrical field. The process cancels out the field of the external object.
The opposing field shields the interior from any exterior static charges, protecting the item inside.
Types of anti-static packaging
Several anti-static packaging products utilise a range of static-safe materials and designs.
Corstat® conductive cardboard
Corstat is the industry standard anti-static packaging range. Many blue-chip and multi-national electronics manufacturers typically use Corstat for its performance, reliability, and cost-effectiveness. Corstat® packaging, manufactured from coated cardboard, is also an environmentally friendly anti-static bag alternative.
Corriplast – a conductive Correx® material – provides durable, reusable packaging and handling containers that are also ESD safe. Typical products include conductive plastic totes, dividers, and layer pads, whilst the majority of Corstat® products are also available in this material.
Similar to Corriplast – but manufactured using a moulded polypropylene – SSI Schaefer conductive bins and boxes provide excellent physical protection and protect contents from static charges.
It is possible to enhance most Corstat®, Corriplast® and SSI Schaefer products using a range of anti-static or conductive foam materials. These provide additional physical and static protection for any ESD-sensitive item.
Could conductive packaging help your business?
Electrostatic discharge has the potential to cause significant issues for your business. Besides damage to parts, components and products (and the costs associated with refunds and replacements), ESD damage can also give your business a reputation for supplying unreliable products, affecting future sales and customer relationships.
Taking the time to understand “what is ESD” and the steps you can take to address it should be a key consideration for your business.
Please get in touch with one of the ESD experts at GWP Conductive if you require any assistance with ESD damage you are experiencing or for advice on the best form of conductive packaging for your business.