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!
Operators feel restricted by their wrist strap, do not understand the necessity and stop wearing it, even if only for a short period.
Operators leave their workstation and forget to re-connect their wrist strap on their return.
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.
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.
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!
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:
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
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
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.
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.
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.
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.
Weight of personnel
Sock thickness and material
Any questions regarding this post, please get in contact.
Fairly regularly we are seeing low charging or antistatic Pink Poly bags being used for the wrong application. These bags are made from a tinted polyethylene material with an antistatic coating that can wear away. This turns the bag insulative and high charging over time, making it noncompliant to ANSI/ESD S541 recommendations.
They also lack discharge shielding protection which makes components within the bag susceptible to ESD event damage. It is this distinction that is most important – as Pink Poly bags don’t provide shielding, they should not be used to carry ESD Susceptible (ESDS) items outside the EPA, i.e. when the sensitive item isn’t grounded. Per ANSI/ESD S541-2018, Table 1. ESD Protective Packaging Requirements by Location, Discharge Shielding is Required for Outside the EPA (UPA).
SCS Metallized Shielding bags are constructed from a metalized polyester film and a low charging polyethylene laminate. This provides the bags with a shielding layer that creates a Faraday cage protecting the ESD sensitive components within the bag from possible ESD event damage. The low charging inner layer and outer layer of the bag prevent tribocharging from occurring, minimizing the build-up of ESD charges when handling components. This low charging layer is longer lasting than a pink antistatic bag.
Per ANSI/ESD S541-2018 – Table2. Summary of ESD Protective Properties
“Protects packaged items from the effects of static discharge that are external to the package and limits current flow through package”
Per ANSI/ESD S541-2018 – Per 7.3.1 Electrostatic Discharge Shielding
“Electrostatic discharge shielding materials are capable of attenuating an electrostatic discharge when formed into a container such as a bag”
Watch our video for a simple demonstration on how pink poly bags differ from static shielding bags:
Welcome back to “A Minute with Miranda.” This week we will be covering how to clean your ESD Worksurface Mat.
For optimum performance, the ESD worksurface mat should be cleaned regularly using a recommended ESD mat cleaner. Per the ESD Handbook ESD TR20.20, “Ensure that cleaners that are used do not leave an electrically insulative residue common with some household cleaners.” We recommend using Charge-Guard™ ESD Surface & Mat Cleaner Wipes to clean and maintain ESD mats and other worksurfaces. Charge-Guard™ wipes do not contain silicone or other substances that will leave an insulative residue or inhibit the performance of an ESD surface.
It is recommended to test the surface after cleaning to ensure that all insulative contaminants such as dirt and grime have been removed. Charge-Guard™ ESD Surface & Mat Cleaner Wipes will only leave behind a coating with a surface resistance of less than 1 x 10^9 ohms.
Implementing ESD control measures can be very simple, particularly if you are starting with one or two workbenches. Each workbench would be an individual ESD Protected Area (EPA) and when ESD Sensitive (ESDS) devices are not at the ESD workbench they should be in a closed ESD shielding container or bag. In today’s blog we provide a basic set up for a start-up workbench EPA.
Single-Wire Wrist Straps
Adjustable Wrist Strap, Blue, with 6′ Coil Cord
One size fits all adjustable wrist band with coil cord is used to ground a stationary operator.
Tests Digital Compliance Verification Surface Resistance Meter Kit – Measures resistance point-to-point (Rtt) and resistance-to-ground (Rtg) of worksurfaces, flooring systems, garments, packaging, and other materials in accordance with ESD Association documents: ESD TR53, ANSI/ESD S4.1, ANSI/ESD S7.1, ANSI/ESD STM97.1 and others
Internal Memory – Stores and recalls up to 100 measurements. Captures resistance, temperature, humidity and test voltage.
Whilst this guide provides a high quality but manageable avenue into ESD Control, not all ESD Programs are created equal, every company has different processes. So, get in touch with your requirements or complete our Checklist and SCS will support with a custom qualified parts list based on your application.
Welcome back to “A Minute with Miranda.” This week we will be covering how the WS Aware provides continuous monitoring for an operator at an SMT line.
The SCS WS Aware Monitor is a 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 of two metal tools. In addition, it 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 ESD Handbook ESD TR 20.20 section 188.8.131.52.4 “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 a continuous, reliable ground is needed, then continuous monitoring should be considered or even required.”
View the full range of SCS WS Aware Monitors here.
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.