How Well Is Your ESD Flooring and Footwear System Working? – Guest Blog

Figure 1: System Resistance Test

by Craig Zander, Transforming Technologies

Craig’s latest Q Source Resource Guest Blog looks at how a Walking Voltage Test reveals how well your ESD flooring & footwear system is working.

The ESD flooring and footwear system is an effective way to ground people that need to be on the move in a factory. ESD footwear, when worn properly, is designed to drain the voltage from a person to the floor and then to ground. Periodic testing of both the floor and the footwear is required to verify proper functioning.

Until recently, a System Resistance Test (ANSI/ESD STM97.1) was all that was needed to qualify an ESD control flooring and footwear system. If the resistance was less than 35 megohms, it was assumed that the person’s voltage would not exceed 100 volts (the upper limit for ANSI/ESD S20.20). However, this testing is done with the person stationary and having both feet flat on the ground. What happens when the person starts moving and the entire foot is not making contact with the floor?

Figure 2: The Walking Test Pattern

The most recent version of ANSI/ESD S20.20 now requires a Walking Voltage Test (ANSI/ESD STM97.2) be performed when qualifying flooring and footwear systems. The test consists of measuring body voltage generated during a six-step pattern used to simulate moving throughout a facility. This test will determine the actual voltage on the person while moving. Research has shown that when tested separately, ESD floors and footwear systems may pass the resistance test, but when used together, can greatly exceed the 100-volt threshold.


Determining the maximum voltage generated by people moving on the factory floor is very valuable information. By knowing the maximum voltage generated you will know that your flooring and footwear investment is performing as designed. You may also be pleasantly surprised to find out that the system is working quite well and you are able to handle devices with much lower Human-Body Model (HBM) damage thresholds.

WT5000

Equipment is available to accurately measure and record the walking voltage. One such instrument is the WT5000. The WT5000 Walking Test Kit (Warmbier WT5000 Electrometer Walking Test Kit) measures and records the walking voltage while providing a graphical readout. The instrument connects to a PC using any Windows version for easy data collection. The WT5000 identifies the peak voltages per the requirements in the standards.

The two-in-one EFM51WT (Transforming Technologies 7100.EFM51.WT Warmbier EFM51WT Field Meter Walking Test Kit) meter holds the PEAK value of the measured body voltage, as well as the LIVE static voltage measured on the operator’s body. The kit includes the EFM51 static field meter, walking test adapter plate, hand probe and conductive carrying case. The EFM51 is a fully functional field meter that, in addition to the Walking Test, measures and detects electrostatic fields, surface potentials, and discharge times (with optional charge plate accessory (part number 7100.EFM51.CPS.SET).

EFM51

You have made the investment in an ESD flooring and footwear system so that people can be mobile while still protecting your products from ESD events. Determining your actual walking voltage generated is critical to knowing that your products are being protected.

CLOSING: Thanks, Craig! We appreciate you filling us in about the necessity of Walking Voltage Tests to ensure proper ESD protection for flooring and footwear systems. Your expertise is invaluable to our Q Source community.

For information about Transforming Technologies and their ESD control/monitoring products (including walking test kits), please visit QSource.com. you.

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What You Need to Know When Selecting ESD Flooring – Guest Blog

by Craig Zander, Transforming Technologies

Craig’s newest Guest Blog, for the Q Source Resource, provides valuable tips about selecting ESD flooring for your workplace

The use of ESD flooring and footwear is a popular way to ground people working with ESD-sensitive devices that cannot use a conventional wrist strap/cord system because they need to be mobile, or because they are working near equipment with moving parts that could pose a hazard. ESD footwear and flooring provide a convenient method to drain the charge from the operator to ground.

There are many options for ESD flooring that are “permanent” solutions, such as conductive tiles and epoxies. These products generally have very good durability and can last for many years. Unfortunately, they also present a few challenges.

PERMANENT ESD FLOOR CHALLENGES

• Cost: ESD floor tiles and epoxies are an expensive option. The cost of the tiles or epoxy in combination with the conductive undercoat and installation expense makes permanent flooring one of the more expensive options.
• Moisture: In some cases, the moisture content in the sub-floor is too high to allow successful or long-term adhesion. Hydrostatic pressure from floors can cause tile lifting or epoxy bubbles. Testing must be done prior to installation to be sure that the floor can be installed.
• Installation: Installing an ESD tile or epoxy floor requires experienced installers. The conductive undercoat must be applied in a precise quantity and manner. Mistakes can lead to poor adhesion and poor electrical readings on the installed floor.
• Maintenance: While new floors may look amazing shortly after installation, they must be maintained to keep their appearance and their electrical performance. Some floors require certain floor finishes, and some floors cannot be waxed or their electrical properties will become diminished.
• Permanence: While a permanent floor can be an advantage, it may be a disadvantage to companies that occasionally change facility layouts or to companies that lease space.

TEMPORARY OR PORTABLE ESD FLOORING

There are a number of options for those that need to ground their operators through footwear and flooring, but do not want a permanent ESD floor.

ESD Mats

ESD mats come in a variety of options including size, thickness, contour, and conductivity. ESD mats are generally placed in front of standing operations and provide a path to ground for the operator and, possibly, a more ergonomic standing surface than the standard floor.

Floor mats may be offered in specific sizes (i.e., 2’ x 3’, 3’ x 4’, etc.), or may be offered with interlock to provide a variety of lengths. They are easy to relocate should production equipment need to be moved.

ESD Runners

ESD floor runners offer a solution in front of long assembly lines, or areas where mobile equipment is being used and needs to be grounded.

ESD floor runners are generally smooth or slightly textured to allow mobile equipment to move, thus they offer less ergonomic benefit than mats.

Interlocking Tiles

ESD interlocking tiles provide an effective way to cover a larger area, or an entire floor, while still offering some portability. The tiles can be easily cut to fit an area and they are free floating on the floor so there are no moisture issues that come with permanent floors. Many of the interlocking tiles also provide ergonomic properties. Yellow safety edges are also available if the floor does not terminate at a wall.

CHOOSING THE RIGHT FLOOR

Whether you select permanent flooring or temporary/portable ESD flooring, you need to verify that the electrical properties of the footwear and flooring combination will meet your requirements.

To be in compliance with ANSI/ESD S20.20 you must verify two specific measurements. First, you need to measure the resistance of the person, through the footwear, through the flooring and to ground (ANSI/ESD STM 97.1 Floor Materials and Footwear – Resistance Measurement in Combination with a Person). Second, you need to verify the voltage being generated by people using your selected footwear (shoes or foot grounders) and flooring (ANSI/ESD STM 97.2 – Floor Materials and Footwear – Voltage Measurement in Combination with a Person).

ANSI/ESD STM97.1 (Warmbier Metriso 3000 Resistance Meter)

ANSI/ESD STM97.2 (Warmbier WT-5000 Walking Test Kit)

We’ve briefly reviewed the factors to be considered when choosing ESD flooring. With these in mind, you can select the floor that meets your needs for ESD properties, overall cost, and ease of use.

Thanks, Craig! That’s excellent information to assist our readers in choosing the proper ESD flooring solution to meet their needs. We’re excited for the next time you share your expertise with our Q Source community.

For information about Transforming Technologies and their ESD control/monitoring products, please visit QSource.com. You may also contact us via email or phone at 800-966-6020 and we will be happy to assist you.

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How to Choose a Continuous Monitor for Your ESD Control Program – Guest Blog

by Craig Zander, Transforming Technologies

In Craig’s latest Guest Blog for Q Source, he provides tips for how to choose a continuous monitor for your ESD control program

The first step in a quality ESD control program is grounding your personnel. People walking in a facility and performing common tasks generate a static charge. If not grounded, the voltage accumulated through this charging may be transferred to your product and can cause significant or catastrophic damage to electronic devices.

The most common method for grounding people handling electronics is by using a wrist strap and coil cord. The wrist strap and cord transfer any voltage from the person to ground. When a wrist strap system is functioning correctly and worn properly, it is extremely difficult to accumulate more than a few volts on a person, which, in all but the most extreme cases, is not enough to cause damage to devices.

Wrist strap systems should be tested on a regular basis.

If the wrist strap system is malfunctioning or worn improperly, the voltage may continue to grow and accumulate to levels that can damage most electronic devices. Therefore, it is very important that the wrist strap system be tested on a regular basis to assure that it is functioning properly.

There are a number of ways that the wrist strap system can be tested, and the best method depends on the number of employees in the facility, the critical nature of the product (i.e., medical, aerospace, military, high value), and budget.

One of the most common methods for verifying wrist strap performance is the wrist strap/footwear test station. The test station(s) is placed near the entrance to the ESD Protected Area (EPA) and employees test their wrist strap to verify its operation before they are allowed to enter the EPA. The testers have a wide range of capability and costs. Some testers have a simple pass/fail indicator while other testers have digital readouts and data logging capabilities to record the test results for each employee. While these testers meet the requirements of regular testing of the wrist strap, there are a number of potential drawbacks:

• Test Frequency: How often the person goes to the test station varies between companies. Some companies require testing at the beginning of each shift while others test every time the person leaves the work station for breaks. In each case, should the test indicate a failure of the wrist strap, there leaves a question as to when the failure occurred and how much product was handled with the failed strap. For high reliability and value products the customers of this company may want to know the disposition of the product that was handled during the time between tests.


• False Security: When testing a wrist strap at a test station, only the wrist strap, cord, and person are tested at that precise moment. The situation could change once the operator reaches the work station. The operator could adjust the strap after testing, the resistance could increase due to dry skin conditions, or the ground jack at the work station could malfunction. All of these scenarios could lead to high voltage accumulation on the operator that would not be detected by the tester.


• Wasted Time: Depending on the size of the company, there can be a line at the test station of employees waiting to test their wrist straps, effectively delaying the time they spend on productive activities.


• Record Keeping: Most companies require their people to sign-in at the tester and record the results. There are some systems that automatically record and store the results after the employee has swiped their ID badge. Someone in the company still must maintain and review the test records to assure that everything is working as designed, which can be tedious and time-consuming.

To address these drawbacks, many companies are now using continuous monitoring to verify that the wrist straps are functioning correctly. Continuous monitors are located at the work station and provide an audible and visual indication when the wrist strap system malfunctions. Once the operator hears the alarm they do not touch the product until the problem is resolved and the system is functioning correctly. With continuous monitoring systems, you avoid waiting in line for testers, eliminate the extensive record keeping, and you remove doubt that the product may have been handled by an ungrounded operator. There are no more decisions to be made on what to do with product that was handled by ungrounded operators, as there is no longer any time between tests.

There are a few options available today for continuous monitoring. Some monitors will simply verify the operator wrist strap, while others will verify the wrist strap, the work surface ground, and possibly other equipment grounds.

Capacitance/Impedance Monitors

Some continuous monitors use capacitance or impedance to verify that the operator is connected to the system. These systems allow the company to use the standard single-wire wrist strap and coil cord system and are typically the lowest cost option for continuous monitoring. These monitors operate by using a capacitance or impedance circuit to estimate the resistance of the operator wearing the wrist strap. Since the system is not making an actual resistance measurement, these systems can sometimes be fooled by high skin resistance of the operator and may provide false passes.

Dual Conductor Resistance Monitors

Dual conductor resistance monitors use a special wrist strap and coil cord to incorporate the operator in a resistance measurement. Instead of the single conductor wire found on standard wrist straps, this monitor uses a dual-wire coil cord and a wrist strap that has two isolated halves. A voltage is sent down one of the wires and into the wrist strap. When the person is wearing the wrist strap properly, their skin completes the circuit and the signal returns down the second wire to the monitor. This system assures that the operator is electrically connected to ground.

Many companies are now using continuous monitors like Transforming Technologies Ranger Series.

While dual conductor resistance monitors provide the most reliability, they also typically have the highest cost and require special wrist straps. A new series of dual-wire resistance monitors (from Transforming Technologies) are priced closer to the single-wire systems, but provide the reliability of dual wire. The CM1601 Resistance Ranger provides dual wire monitoring for a single operator, and the CM1602 Dual-Wire Resistance Ranger monitors the operator and one work surface ground. Transforming Technologies also offers great options for dual-wire wrist straps and cords that provide both excellent quality and value.

Thanks, Craig, for further educating us on how to develop and maintain a successful ESD control system. We look forward to your future Guest Blogs.



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The Importance of Testing & Monitoring Your ESD Grounding Devices – Guest Blog

by Craig Zander, Transforming Technologies

In Craig’s debut Guest Blog for Q Source, he explains the importance of testing and monitoring of ESD grounding devices.

Transforming Technologies PDT 800K Test Station

The first line of defense for protecting electronic devices and assemblies from damage due to Electrostatic Discharge (ESD) is to properly ground all personnel that come in contact with the product. When a person is effectively grounded, all of the voltage that accumulates on their body when moving rapidly travels to ground before it can affect the product.

The most common and reliable method for grounding operators is the wrist strap and coil cord combination. The conductive materials inside the wrist band contact the skin and transfer the voltage from the operator through the cord and to ground. When worn correctly, and tested or monitored, wrist straps are the preferred method for grounding people.

When grounding a person through a wrist strap, ANSI/ESD S20.20 requires the resistance of the person to equipment ground to be less than 3.5 x 107 ohm (35 meg ohm). Typically, the resistance to ground of a person properly connected with a wrist strap is just over 1 meg ohm (the value of the resistor in the cord assembly).

Wrist strap and coil cord assemblies need to be tested or monitored regularly. Some companies chose to test the wrist strap system one or more times per day at central testing stations (for example, the PDT 800K Test Station). Other companies opt to continuously monitor (using a device such as the CM1602 Constant Monitor) the wrist strap connection so that product is not handled if the grounding system fails.
 

Transforming Technologies CM1602 Constant Monitor

There are situations, however, when being connected to a ground jack via a cord is not conducive to efficient or even safe operation. Operations that involve frequent transportation of product within the facility, as well as operations that involve machinery, present a challenge to the wrist strap and coil cord grounding method. In these cases, factories may use a combination of conductive flooring and foot grounders to effectively ground the operator.

The requirements for grounding a person through flooring and footwear have changed in the ANSI/ESD S20.20 2014 Standard. Previous versions of ANSI/ESD S20.20 provided you with two options. If the resistance from the person through the footwear, through the floor and to ground was less than 35 megohm, no further testing was necessary. If the resistance was greater than 35 megohm, you could still meet the requirements of the standard if the resistance was less than 1.0 x 109 ohms and you can demonstrate that the operators generate less than 100 volts. The latest version of S20.20 (ANSI/ESD S20.20-2014) requires the resistance test and the walking voltage test for qualifying flooring and footwear materials together. While many flooring and footwear options may pass the resistance test, it has been discovered that some combinations of floor materials and foot grounding materials do not work well together.

To test the walking voltage generation of flooring and footwear systems you use ANSI/ESD STM 97.2 Floor Materials and Footwear - Voltage Measurement in Combination with a Person. This test involves recording the voltage of a person while they perform a repetitive walking pattern. To record the voltage you can use a charge plate monitor with data recording capability, or a similar instrument with the same specifications listed in the test method.

Body voltage measurement test set-up.
The new software “Digilloscope”
can mark the five highest
peaks automatically and calculate
the average value.

Transforming Technologies developed the Warmbier WT5000 Walking Test Kit to meet the needs of the ANSI/ESD STM 97.2 test. The WT5000 is a battery-operated instrument that is easily transported to various areas of the factory floor. The system includes the trademarked data acquisition and analysis software “Digilloscope for Windows™.”

The WT5000 records the voltage on the operator while they are performing the walking steps called out in the standard. Once several repetitions of the pattern are complete, the software will provide the peak voltage and average value. The data is used to confirm compliance to standards and to determine the lowest possible voltage device (Human Body Model Discharge Threshold) that can be handled in the facility.

Thanks for that very important information about ESD control and testing, Craig. We look forward to future Guest Blogs to learn from your expertise.

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