Are you regularly getting complaints from your operators that wrist straps are awkward or uncomfortable? As a result, do you come across them not being worn properly? Unfortunately, we see wrist straps being misused regularly. Here, you can find just 4 of the many mistakes we see with wrist straps, but do not fear, there is a solution!
Not Worn
Operators feel restricted by their wrist strap, do not understand the necessity and stop wearing it, even if only for a short period.
Disconnected
Operators leave their workstation and forget to re-connect their wrist strap on their return.
Incorrectly Fitted
For various reasons the wrist strap might not be fitted correctly, whether it be for comfort or by accident. Either way, it leaves the wrist strap potentially not functioning as it should.
Damaged
Operators used old or damaged wrist straps that might pass at the tester but could be intermittently failing whilst being worn. Perhaps the coiled cords have been patched up or the wristband is looking old and worn.
The Solution?
Wear SCS Groundable Static Control Smocks for hands-free grounding!
SCS ESD Smocks have a Hip-to-Cuff Grounding feature that allows for hands-free grounding by connecting a coiled cord to the snap on the side of the smock. This is directly connected to the conductive kitted cuff that acts as a wristband. Leaving the operator with a hands-free alternative to a wrist strap. Both Single-Wire and Dual-Wire options are available so even if you are using dual-wire continuous monitors, there is an option for you!
SCS Smocks – a hands-free alternative to wrist straps
In general, wearing Static Control Garments offers many benefits to controlling Electrostatic Discharge (ESD) and more. To learn more about the role of ESD Garments in the ESD Protected Area (EPA) visit this blog post.
Watch A Minute with Miranda on Static Control Garments:
Why do you need ESD smocks?
How to care for your ESD smocks
Testing Resistance Point-to-Point Rpp for an ESD Smock
We occasionally hear from customers who have ESD footwear (Foot Grounders or ESD Shoes) that is failing high on their ESD footwear tester (personnel grounding tester). There is often an assumption that the issue is a faulty tester or out of spec footwear. However, most of the time the problem turns out to be as simple as a “bad match”. This is between the upper resistance setting of the footwear tester and the resistance of the ESD footwear.
The first step in identifying the cause of the problem is to identify the upper limit setting of the tester being used.
Upper Test Limits of ESD Testers
The upper limit settings on SCS footwear testers are:
The upper limit is 1 gigaohm or 1 x 109 ohms however the factory setting 35 megaohm or 3.5 x 107 ohms
SmartLog Pro
The upper limit 1 gigaohm or 1 x 109 ohms however the factory setting 35 megaohm or 3.5 x 107 ohms
Identifying the Resistance of the ESD Footwear
The next step is to identify the resistance of the ESD footwear being used, both by itself and with a person wearing the footwear.
Heel Grounders/Foot Grounders
Foot Grounder Test
Test Method 1 – Resistance of the Foot Grounder
Using a surface resistance tester and its alligator clip, clip the lead to the foot grounder tab
Clip the other lead to the cup material
This test will tell you the overall resistance of the tab, resistor (if there is one), and the cup material
If the foot grounder tab to cup resistance exceeds the upper limit of the footwear tester it’s very likely that you won’t pass on the tester.
Test Method 2 – Resistance of the Foot Grounder and Person Together
Use test method from TR53-01-15, 8.3.2 Meter, which has been summarised below:
Use a surface resistance tester, a handheld electrode and a foot electrode
Have the person hold the handheld electrode connect to one lead
Have the other lead connected to the foot electrode
Place one foot on the foot electrode making sure your other foot is not on an ESD floor or the electrode
This test will tell you the overall resistance of the whole foot grounder and person.
If the result is higher than the upper limit of your footwear tester you will not pass at the tester.
ESD Shoes
When we hear about ESD Footwear failing regularly at the personnel grounding tester, more often than not it is ESD Shoes that are failing rather than foot grounders.
Test Method 1 – Resistance of the ESD Shoes Using Foot Plate Electrode
Place the shoe on a metal plate.
Put the 5 lb weight from the surface resistance meter inside the shoe.
Place the other weight on the metal plate next to the shoe.
Lean on the weight inside the shoe and test.
This will give the resistance of the shoe itself from inside the shoe to the bottom of the shoe.
ESD Shoe test with footplate
ESD Shoe Test with 5 lb Electrodes
Test Method 2 – Resistance of the ESD Shoe Using Two 5 lb Electrodes
Put one of the 5 lb weights from the surface resistance meter inside the shoe.
Put the other weight on the sole of shoe, make like a sandwich
Press the Test
See what the resistance of the shoe is using either of these methods and compare it to the testers upper limit.
Perform the TR53 test below, see what the resistance is of the person and ESD shoe while the shoe is being worn.
The same test from TR53 used for foot grounders above can also be used for ESD Shoes. This will provide you with the total resistance is of the person and ESD shoe.
Conclusion
The tests above will identify a clear discrepancy between footwear resistance and tester settings, but there can also be other factors in play. These factors should be considered when the footwear resistance and the tester settings are close to being the same.
Tester accuracy
Test voltage
Weight of personnel
Sock thickness and material
Humidity
Any questions regarding this post, please get in contact.
Welcome back to “A Minute with Miranda.” This week we will be covering how to test ESD footwear entering an ESD Protected Area (EPA).
Per the ESD Handbook ESD TR20.20, A system test of the footwear in combination with the existing or proposed flooring materials in the plant should be made to ensure that the criteria for the facility are met. When using a footwear checker it is important to make sure the upper and lower resistance limits of the checker match the user’s requirements. When testing the footwear should test within the range of 1 x 106 to 1 x 108 ohms.
Heel, sole and toe grounders should be worn on both feet to ensure effective use. They should be worn by all personnel and visitors within an ESD controlled area. If worn improperly, the heel, sole and toe grounders become ineffective. ESD footwear should be tested daily before use within an ESD Protected Area (EPA).
Welcome back to “A Minute with Miranda.” This week we will be covering how the WS Aware Monitor provides for continuous monitoring of an ESD Workstation setup.
The SCS WS Aware Monitor is a dual workstation continuous monitor for operators, ESD Worksurfaces and metal tools. It will continuously monitor the path-to-ground integrity and body voltage of two operators. It also monitors the path-to-ground integrity for two conductive or dissipative worksurfaces and two metal tools. It also continuously monitors for electromagnetic interference (EMI) on two metal tools which may cause electrical overstress (EOS) damage. The WS Aware Monitor eliminates the need for periodic testing and record keeping of wrist straps.
Per the ESD Handbook ESD TR20.20 section 18.4.2 “Some continuous monitors can monitor worksurface ground connections. A test signal is passed through the worksurface and ground connections. Discontinuity or over limit resistance changes cause the monitor to alarm. Worksurface monitors test the electrical connection between the monitor, the worksurface, and the ground point. However, the monitor will not detect insulative contamination on the worksurface.”
View the full range of SCS WS Aware Monitors here.
Welcome back to “A Minute with Miranda.” This week we will be covering why you need to use ESD footwear within your ESD Protected Area (EPA).
Per the ESD Handbook ESD TR20.20, Personnel may also be grounded through the use of ESD footwear with an ESD Flooring system. This method is useful for situations where personnel are mobile or standing in areas where a wrist strap is not feasible and ESDS items must be handled or transported. ESD protective footwear is designed to reduce body charge levels by providing a conductive path from the body to the ESD flooring material.
Heel, sole and toe grounders should be worn on both feet to ensure effective use. They should be worn by all personnel and visitors within an ESD controlled area. If worn improperly, the heel, sole and toe grounders become ineffective. ESD footwear should be tested daily before use within an ESD Protected Area.
Welcome back to “A Minute with Miranda.” This week we will be covering how to use the WS Aware Monitor for continuous monitoring of SCS wrist straps when at an ESD Workstation.
The SCS WS Aware Monitor is a dual workstation continuous monitor for operators, ESD Worksurfaces and metal tools. It will continuously monitor the path-to-ground integrity and body voltage of two operators. The WS Aware Monitor eliminates the need for periodic testing and record keeping of wrist straps. The WS Aware Monitor features operator body voltage detection. It will alarm if the operator generates or comes into contact with voltage that would be dangerous to an ESD susceptible item. Per the ESD Handbook ESD TR20.20 section 5.3.2.4.4 “Typical test programs recommend that wrist straps that are used daily should be tested daily. However, if the products that are being produced are of such value that knowledge of continuous, reliable ground is needed, then continuous monitoring should be considered or even required.”
Welcome back to “A Minute with Miranda.” This week we will be discussing how to test the point-to-point resistance (or Rpp) of an ESD Smock.
ANSI/ESD S20.20 requires initial and periodic verification of ESD Control items – this includes ESD Smocks. ANSI/ESD STM2.1 outlines the test method applicable for ESD Smocks: the ESD Smock is to be placed on an insulative surface and 2 x 5lbs cylindrical electrodes are to be positioned on each cuff before taking the measurement. The Resistance Point-to-Point Rpp of the groundable smock needs to be less than 1 x 109 ohms.
Welcome back to “A Minute with Miranda.” This week we will be covering how to properly wear a wrist strap.
ANSI/ESD S20.20 requires seated personnel to be
connected to the grounding / equipotential bonding system via a wrist strap.
The total resistance of the Wrist Strap System needs to be less than 3.5 x 10^7 ohms. The key to a wrist strap is
the intimate contact of the band to the skin and that the coil cord is
connected to ground. Wrist straps need to be tested at least daily before
handling any ESD sensitive devices.
Operators can choose between elastic and metal wristbands. Elastic wristbands are comfortable to wear and easy to adjust. Metal wristbands generally last longer and are easier to clean. View the full range of SCS Wrist Straps here.
Welcome back to “A Minute with Miranda.” This week we will be covering how to launder your ESD Smocks.
SCS Static Control Smocks should be laundered periodically for proper operation. Smocks should be washed by hand or with a standard household washing machine using cold or warm water with a non-ionic liquid detergent. Avoid using bleach, fabric softeners or dry detergents as these can contaminate the conductive fibers and make the garment insulative .
After washing the smocks they should either be hung dry or tumbled dry at low heat. High heat can degrade the conductive fibers within the garment and degrade the ESD properties.
With normal wearing and washing conditions, SCS Static Control Smocks will maintain their ESD properties for a minimum of 100 washings.
SCS Smocks meet the requirement for Groundable Static Control Garment System per ANSI/ESD S20.20 required limit of less than 3.5 x 107 ohm Rtg tested per ANSI/ESD STM2.1 and ESD TR53.
SCS is excited to announce a brand new video series discussing real-life ESD problems and solutions. This is a great educational resource for anybody new to ESD or just wanting to learn more about best practices.
Each episode will focus on one issue commonly found in an ESD Protected Area – at the same time we will present solutions so you know how to tackle the problem should you ever face it in your own factory.
A new episode will be published each week so make sure you subscribe to our YouTube channel to get notified when a new video is available. Episodes 1 and 2 are now live so don’t waste a second longer and catch-up now:
