Controlling ESD in your manufacturing cleanroom, or other controlled facility where spark generation or electric current can damage your products or create other disastrous effects, is challenging. People working in your cleanroom are the main source of ESD. Just walking from the entrance to their workstation or merely picking up a tool or filling a vial can generate thousands of volts ready to leap from their body. The lower the humidity, the higher the chances of a damaging discharge. For many industrial cleanrooms, even charges as lows as 30 volts can wreak havoc.
This built-up static charge can easily discharge becoming human-body model (HBM) discharge. If the discharge does not destroy a static-sensitive device, it may lurk on the device itself having transferred from the cleanroom personnel. Then, later, the device can discharge damaging the device.
Just like in cleanrooms where the controls are designed to prevent particle or biological contamination, it is using the right cleanroom supplies with the right procedures that prevents ESD contamination or your microelectronics, medical devices, or other electro-sensitive products. ESD requires strict preparedness and diligence to prevent from interrupting cleanroom processes.
How Electrostatic Discharge Occurs
Before we dive into key ways to control ESD, let’s review how electrostatic discharge can occur:
- Tribocharging: Electrically charged objects of dissimilar materials without safe dissipation are prone to discharge when they come into contacted with each other and then are separated. “Tribo”, a Greek word, means “rubbing”, but in actuality objects simply touching can produce dangerous sparks when bonded atoms with a deficit of electrons attract the extra electrons of other atoms.
- Electrostatic induction: Occurs when a material that has an excess of positive charges (+) is brought sufficiently close enough to another neutrally charged material that the it influences the neutral material to become positively charged on one side and negatively charged on the other. Electrostatic induction is also referred to as electrostatic influence. The neutrally charged object may become positively charged by induction.
Steps to Control Static in ESD Cleanrooms
- Designate an Electrostatic Discharge Protected Area in your facility to keep ESD-sensitive electronics away from charging-prone materials such as synthetic surfaces containing plastic, nylon, wax, fiberglass, or foam.
- Manage the ambient environment keeping humidity at 50-60% and temperature at 70-75°F (21-24°C).
- Regularly clean filtration systems.
- Use ESD workstations and tools are static-dissipative, particularly for static-sensitive electronic components.
- Ground all conductive parts.
- Use ESD-safe microscope accessories.
- For non ESD-safe surfaces apply a static-dissipative urethane coating.
- Check for ESD with a multimeter.
- Utilize dry anti-static wipes and other methods to keep surfaces and components free of dust and charged particles.
- Utilize specifically formulated anti-ESD cleaners for glass and computer screens.
- Utilize ESD brushes and vacuum pens to clean dust particles and solder debris.
- Utilize soldering products and techniques that minimize and dissipate charge build-up.
- Use LED light source with improved resistance to vibration & shock.
- Evaluate any defective manufactured components to determine source of damage.
In addition to the general environment and manufacturing process recommendations above, a key source of electrostatic charge are your workers. Our cleanroom experts can help you with cleanroom supplies to control this problem. Here are some of the most common ways to utilize cleanroom supplies and products designed to control ESD.
Grounded Wrist Straps
Wrist straps are the first line of defense to control ESD from personnel in most cleanroom environments. Properly grounded wrist straps not only prevents static charge accumulation, but also it keeps the worker at (or near) the same potential as the work are so no discharge can occur. Continuous monitoring or daily testing at test stations is recommended to control ESD.
Tacky Mats
Utilize sticky mats at entrances to remove dust and debris from entering the ESD area that can be a source of charge.
Cleanroom Floor Mats
Another way to control ESD from cleanroom personnel is to use ESD-protective floor mats in conjunction with ESD-control footwear. The floor mats with anti-static footwear set a ground path to dissipate the static charge so less is accumulated on the personnel. The use of floor mats also minimizes static charge accumulation equipment and fixtures that contact the floor like chairs, rolling carts, and other objects that move across the floor.
It is important to note that the ground resistance must be the same amongst personnel, footwear, floor, and wrist straps.
Shoes
ESD-control cleanroom footwear is used in conjunction with ESD-protective floor mats to ensure that the proper electrical contact between the personnel and the floor mat. The contact is necessary to dissipate static charge accumulation. Insulated footwear prevents static charge from moving from the person to the floor to ground.
Anti-Static Gloves or Finger Cots
Anti-static or static dissipative gloves or finger cots virtually eliminate ESD from the most frequently moved part of cleanroom personnel, the hands and fingers. If you are not wearing gloves or finger cots, the tools or units that the personnel touch are grounded through their bodies. Without the hand or finger protection, personnel conduct static electricity that can discharge damaging components. ESD-control gloves and finger cots also protect personnel from receiving ESD which can be powerful. Plus, using protection also protects units from other contaminants.
Cleanroom Clothing
Clothing material can generate electrostatic charge, especially in very dry cleanroom environments. Because clothing usually is electrically isolated from the person’s body, static charges on fabrics may not dissipate to the person’s body and then to ground. Grounded ESD-control garments reduce electrostatic charges on a person’s clothing.
Control ESD with a Clean Cleanroom
Most contaminants are introduced through personnel. The contaminants not only directly interfere with cleanroom processes, but also can cause ESD-control supplies such as floor mats not to work properly. It is important to follow guidelines for cleaning ESD-control supplies with appropriate ESD cleaning supplies and disinfectants. Remember to carefully select cleaning tools that do not introduce static charge.
These are the primary means to control ESD from cleanroom personnel, footwear, and other supplies that fit your clean room environment. Feel free to ask questions about any of our products. If you don’t see a product you need on our website, let us know as we carry full lines of all our manufactures and only list popular products on this site.
In addition to using technique to ensure good contact with the surface, it is vital to ensure that no area of the surface is missed. Wiping in straight lines with overlapping strokes helps to cover all areas completely. Each stroke should overlap the previous by 10 to 25%.
In conclusion, the hand-wiping of surfaces and equipment is an integral part of the manufacturing process in many cleanrooms. Cleaning and disinfection in a pharma cleanroom and many other controlled environments are critical processes to protect patient safety and product quality. More effective and consistent hand cleaning and disinfection will result in greater consistency, quality and safety in the overall process and the resulting product.
Using presaturated cleanroom wipes offers many benefits to critical environments. Talk with our cleanroom consultants to about what wipes and solvents work best for your protocols. We offer free samples to ensure that your presaturated wipes work well for your facility and staff.