Static electricity is a great source for fun science experiments. Simply by rubbing objects against wool, we can make balloons and paper pieces stick to everyday objects like combs and plastic pens. While it can be a terrific way to entertain the kids, static electricity is no laughing matter.
Electrostatic Discharge is a major hazard in many industries. This seemingly innocuous effect can ruin expensive electronic components and cause damage worth millions of dollars to companies. In many ways, static charges are like the proverbial ant that can take down an elephant.
Why is that? How can something so harmless cause so much damage to equipment? Is static electricity also dangerous for humans? What is the link between humidity and static electricity management? How does air in a high-humidity environment affect static? We will answer all these questions and more in this article.
What is Electrostatic Discharge?
Electrostatic discharge or ESD is a sudden discharge of static electric current between two different objects which have been charged to different electric potentials. The static charge flows quickly between them when the objects come close to each other.
Electrostatic charge can build up in objects in several ways. Usually, static electricity will build up in objects through friction – when the objects are rubbed against each other, electrons in the atoms on the exterior are removed.
These free-moving electrons build up at one object, creating a positive charge at one end and a negative charge at the other. This method of charging through frequent contact between objects is also called the triboelectric effect.
You don’t necessarily have to rub two objects to get the triboelectric effect. Simply walking across a carpeted floor in a room with low humidity can create a negative charge of several thousand volts at the soles of your shoes.
There are several other ways in which an electrostatic discharge can occur besides through the triboelectric effect. They include induction, ion bombardment, and contact with an already charged object.
However, these other forms are less common in day-to-day regular settings. In certain workplaces, ESD charge generated by the triboelectric effect is the most common potential threat to productivity.
Impact of Static Electricity on Humans and Workplaces
Static electricity does not cause direct serious harm to humans. At its worst, a severe static build-up in your body will give you a small jolt or shock. This often happens in autumn, when dry weather increases the risk of triboelectric effect.
As soon as you touch something metallic, like a doorknob, the current will flow and give you a shock. However, the impact of ESD in the workplace is of a greater concern, especially where electronic equipment is involved in a major way.
Static Electricity Damage to Electronics
ESD is usually measured in coulombs. However, you can measure the electrostatic potential between two objects in volts, which is a far more convenient metric for understanding the damage potential of static.
On a normal day of 65% relative humidity, a human being can create 1,500 volts of static simply by walking across a carpeted floor. If the humidity level dips to 20%, the static electricity potential increases to a whopping 35,000 volts.
Certain electronic components are incredibly sensitive to even minor discharges of current. These devices/components are labeled “electrostatic discharge sensitive” or ESDS. You can seriously damage an ESDS component with just 10 volts of electric discharge.
The damage is primarily caused by a localized build-up of heat. This heat can damage sensitive circuits and semiconductors. Devices with more complex and miniature circuits are at higher risk of ESD damage – PC components like hard disks, motherboards, and processors are an excellent example.
In the past, ESD was a major headache mainly for PC manufacturers. These days, with the ubiquity of electronic chips and components in any device, the level of ESD risk exposure has expanded considerably.
Still, the larger electronics manufacturing industry is the most vulnerable to ESD events. Some experts have called it a silent assassin or even a hidden tax on the industry, bringing revenues down by approximately 6.5% annually.
The long-term impact of static electricity is elevated by the fact that it can affect an ESDS component in potentially two different ways:
- An ESD event can cause catastrophic damage, causing the component to fail immediately
- An ESD event can also cause latent damage to the component
With catastrophic damage, the outcome is self-evident and easily detectable during quality testing of a product. It may malfunction or simply fail to turn on. Pertaining to this, latent damage is not detectable at this stage – it will often rear its head a few months or years into the life of the product.
While direct damage results in wasted components and rejected products, latent damage can hurt your business through product recalls, warranty/RMA requests, or refund requests from customers. On a substantial scale, it can also damage the reputation of your brand.
Static Electricity is a Workplace Hazard to Employees
In daily settings, the static electricity build-up is just a minor nuisance to people. However, in an industrial setting, it can become a potentially life-threatening hazard under the right circumstances. According to OSHA guidelines, the main threat from ESD is via the sparks it sometimes creates.
If there are any flammable liquids or other easily combustible substances in the workplace, static electricity can create a genuine fire hazard. This can include fuels and solvents like gasoline, benzene, toluene, and other mineral spirits.
Controlling Static Charge Build-Up in Workplaces
ESD protection is already a well-established protocol in the electronic manufacturing industry these days. The basic principles have been established over the last 20-30 years. However, other industries are also being forced to catch up.
With the increase in the number of electronic components in industrial machinery and tools, even manufacturers in the non-electronics segments require ESD protection these days. To create a proper protection plan, firms have to conduct an ESD risk assessment.
Understanding the potential sources and routes of ESD incidents is a good place to start.
Common Sources of Static in the Workplace
Mini-Circuits, a global leader in the design and manufacture of microwave, RF, and IF components, has created a very illuminating list of common sources of static in the workplace. The list includes the following sources and associated materials/activities/processes:
- Waxed, painted, or plastic work surfaces
- Waxed floors, either with vinyl tiling or sealed concrete
- Common clothes that are worn by employees, with synthetic materials like nylon
- Vinyl, wood, or fiberglass chairs
- Common packaging materials like plastic bags, foam, trays
- Tools like spray cleaners, heat guns, blowers
Steps to Create a Static-Free Work Zone
Organizations can take multiple steps to reduce the risk of ESD in the workplace. Due to the risk of latent and catastrophic damage, you need ESD protection all along the manufacturing process, from start to finish.
This can involve a comprehensive list of the following steps:
- Create anti-static workstations using anti-static coatings or mats
- Workers should use grounded anti-static bracelets on their wrists
- Remove all high-risk materials and surfaces from the production area
- Enforce the use of anti-static protective clothing among employees
- Install monitoring stations to check the static levels in employees
- Use anti-static packaging materials for transporting ESDS components
However, even these steps may not be adequate for complete protection against ESD in the workplace. You also need to control another critical variable – relative humidity.
The Connection Between Humidity and Static Electricity
There is a high correlation between humidity levels in the air and the rate at which static builds up on surfaces. This is why the risk of ESD is higher in certain seasons like autumn. It is also higher in certain parts of the world.
The key factor here is water. In general, water is a poor conductor of electricity when compared to other substances like metals. It is actually the dissolved salts and minerals that make water a conductor of currents. Pure water is an excellent insulator.
Based on this, most water found in nature contains dissolved impurities that give it at least some levels of electrical conductivity. Against that, the atmosphere is made up of largely inert gases which are extremely poor conductors of electricity.
In the surrounding air, water vapor is the best conductor – with higher water content in the atmosphere, the electrical conductivity can increase significantly. This has a direct implication for ESD. Static builds up on a surface because it has no other place to go.
When the air is dry, the level of static build-up will increase significantly. In contrast, increased water levels allow at least some of the static charge to dissipate. And the most commonly used measure of water content in the air is Relative Humidity.
What is Relative Humidity?
Dry air has the capacity to hold “x” amount of water vapor. This “x” is not a constant – the maximum capacity can change with changes in ambient temperature. Absolute humidity measures the actual amount of water in the air at any given point in time.
It does not look at how much more humidity the air can hold at that particular point in time, due to the existing temperature settings. Essentially, absolute humidity measured in kg/m3 gives an incomplete picture of the moisture settings in the atmosphere.
Relative Humidity solves this issue by including temperature in the equation. It tells us the quantity of water vapor in the air as a percentage of the total humidity the air could hold at that temperature. The relative humidity is expressed in percentages.
The normal range of humidity in indoor settings is somewhere in the range of 30% – 60%. At these levels, humidity does not cause any discomfort to humans.
Direct Link Between ESD and Humidity Levels
Static electricity buildup is not a major concern in warm tropical regions with normal humidity levels that routinely go above 70% and even 80%. In the drier temperate climate zones, the humidity levels can plunge in autumn and winter as the cold air can only hold less water vapor.
From an electronics manufacturing safety perspective, Relative Humidity levels above 30% are generally considered better. For maximum safety, the humidity levels should be closer to 60%. Conversely, the risk of dangerous electrostatic discharges is highest when humidity levels fall below 30%.
Here is a look at the potential build-up of ESD at different humidity levels to prove this point:
- Working at a regular workbench will create only 100 V of static if the relative humidity is above 60%. Below 20% humidity, it can produce 6,000 V of static.
- Walking across a carpeted floor in high humidity above 60% has a chance of creating up to 1,500 V. In low humidity below 20%, this is amplified to 35,000 V.
Even a low static discharge of 10 V can inflict damage on electronic circuits. Manufacturers have to take all possible precautionary measures. And that includes regulating the humidity levels in the workplace, particularly if the facility is located in a temperate zone that has cool autumn/cold winters.
Industries Most Affected by ESD
Military and Defense
Precise humidity control is vital to the dependability and effectiveness of a strategic industry such as military and defense equipment. Inadequate levels of humidity in defense operations and storage facilities may lead to serious ESD issues, including inefficient systems performance, critical electrical/electronic component and ammunition failure, damage or malfunction, and barriers to the military vehicles and machinery uptime.
When optimal levels of relative humidity between 40 and 60 percent is maintained, it helps ensure reliable maintenance and readiness of the military and defense equipment. It also lowers the risk of accidents and injuries that may occur from potential combustion or electrical shock incidents due to equipment failure. Indoor relative humidity levels of 40 to 60 percent are also appropriate for durable electrostatic paint & powder coatings, which can improve the equipment’s operational readiness and reduce downtime.
Military ammunition, explosives, gun powder, and other combustible materials must be stored at optimal RH levels in order to minimize the incident of chemical degradation and improve usage rates and battle readiness. Maintaining the right air humidity levels also cuts down the risk of static discharge, enabling a safer operational environment due to a reduced risk of explosions and other hazards.
Humidity control in the avionics industry is vital to protect the aviation equipment as a whole as well as individual sensitive electronics and electrical components. For instance, a relative humidification level of 40 to 60% may be ideally suited for equipment protection against corrosion, breakdowns, and spoilage at various stages of manufacturing, storage, and aircraft operations.
Excessively high or low relative humidity levels damage the intricate electronic avionic parts, lead to inherent component defects, and result in an adequate curing environment for coatings, paints, composites, and welding. Electronic component failure, while the aircraft is in flight, is a serious risk if the aviation equipment is produced in an inconsistent humidification environment, making it vulnerable to electrostatic discharge during operation.
In absence of the correct humidity levels during manufacturing, the solder paste may also become dry, making the electronics components brittle and susceptible to breakdown in the field. On the other hand, management of appropriate humidification during avionics manufacturing lowers the incidence of electronics equipment and component failures and increases flight safety, manufacturing, and delivery deadlines.
Humidity Control in Electronics Manufacturing – Precision Humidifier Systems
In many office settings, low humidity is preferred for the comfort of employees. Firms usually achieve this through the use of air conditioners and de-humidifiers. However, the demands of a high-precision industrial production facility are far more complex than office buildings and other commercial spaces.
In many industries, ranging from horticulture, paper manufacture/printing, and electronics manufacturing, precise humidity levels are essential for the safety of components, raw materials, and the final product. And the best way to achieve this is via industrial-grade humidification systems.
A modern industrial humidifier system can help you in many ways. But in the context of electronics manufacturing, one of the key advantages of a humidifying system is reducing static electricity.
Now, all zones in an electronics manufacturing facility do not have the same temperature conditions. Heavy machinery and certain processes can create these micro-climate zones where the average temperature and humidity levels are different from the other areas.
For example, a machine that runs hot will have dry air in its immediate vicinity, which can increase the risk of static electricity buildup. Precision humidifier systems can address these micro-climate zones using precise grids of nozzles to deliver increased humidity at specific zones.
Highly precise and automated control mechanisms are also valuable from a safety perspective. While high humidity is desirable, it can damage facilities and encourage mold growth if left uncontrolled. This is where precision humidifier systems like the MicroCool FOCUS come into the picture.
Choose MicroCool FOCUS for Precise Humidity Control in Electronics Manufacturing
For many industrial humidification applications, MicroCool IBEX fogging system works best. But in high-precision settings, such as electronics manufacturing, there are often small spaces involving critical applications that need specialized humidification. Looking into this unique need of the electronics manufacturing industry, MicroCool FOCUS system was developed about a decade ago, which represents a breakthrough concept in fogging systems for highly specialized requirements of electronics manufacturing and other similar high-precision industries.
Working differently from the conventional humidification systems, each nozzle in the MicroCool FOCUS humidity control equipment has a built-in solenoid that controls and directs the nozzle’s operation. This ensures that there is no risk of draining and dripping nozzles in the zone. The FOCUS POD and FOCUS X CELL nozzles are connected to a manifold line with high pressure, which connects to the pump unit.
The specialized FOCUS pumps are designed to maintain a precise and consistent pressure of 1000 psi/70 Bar in the manifold line. This ensures that when the solenoids in the nozzle housing open, the precise, powerful pressure is present at once. The constant availability of high pressure at the nozzles is a key advantage, but there are several other useful features as well that distinguish the MicroCool FOCUS fogging solution. These include UV light sterilization and Reverse Osmosis for hygienic water quality, advanced protective safety features, and a single-zone controller (optional) for temperature and humidity.
To learn more about the MicroCool FOCUS specifications or customization options, you can speak to our resident fog expert. To book an appointment, please give us a call at 1-800-322-4364, or fill up a form available here.