Introducing “A Minute with Miranda”

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:

4 Common Wrist Strap Mistakes and one way to avoid them!

The Mistakes

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!

Wrist Strap note Worn

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.

Disconected Wrist Strap

Disconnected

Operators leave their workstation and forget to re-connect their wrist strap on their return.

Incorrectly Fitted Wrist Strap

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 or Warn Wrist Strap

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!

Dual-Wire ESD Smock

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 ESD Smocks Solution
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

“My footwear tester doesn’t work, heel grounders fail high, help?”

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:

ESD Footwear TesterUpper Resistance Limit
770030 Combo Tester 100 megaohm or 1 x 108 ohms (factory set)
770758 Series Dual Combination TesterThe upper limit is 1 gigaohm or 1 x 109 ohms however the factory setting 35 megaohm or 3.5 x 107 ohms
SmartLog ProThe 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
Foot Grounder Test

Test Method 1 – Resistance of the Foot Grounder

  1. Using a surface resistance tester and its alligator clip, clip the lead to the foot grounder tab
  2. 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:

  1. Use a surface resistance tester, a handheld electrode and a foot electrode
  2. Have the person hold the handheld electrode connect to one lead
  3. Have the other lead connected to the foot electrode
  4. 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

  1. Place the shoe on a metal plate.
  2. Put the 5 lb weight from the surface resistance meter inside the shoe.
  3. Place the other weight on the metal plate next to the shoe.
  4. 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 footplate
ESD Shoe Test with 5 lb Electrodes
ESD Shoe Test with 5 lb Electrodes

Test Method 2 – Resistance of the ESD Shoe Using Two 5 lb Electrodes

  1. Put one of the 5 lb weights from the surface resistance meter inside the shoe.
  2. Put the other weight on the sole of shoe, make like a sandwich
  3. 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.

Shop the Test Equipment Used

A Simple Demonstration on the Differences Between a Pink Poly Antistatic Bag and a Static Shielding Bag

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

Discharge Shielding

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:

For more information on the differences between these two materials, and a demonstration on how to test per ANSI/ESD S11.31 and ANSI/ESD S541 visit this page.

A Minute with Miranda – Charge-Guard™ ESD Surface and Mat Cleaner Wipes

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.

8004 - Charge-Guard™ ESD Surface and Mat Cleaner, 25 Wipes
8004 – Charge-Guard™ ESD Surface and Mat Cleaner, 25 Wipes

New to ESD Control and need help to set up a Workstation?

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.

Personnel Grounding

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.

4 mm snap, 1 megohm resistor

Meets ANSI/ESD S20.20 and ANSI/ESD S1.1

ECWS61M-1

One size fits all blue adjustable single-wire wrist band with 6-foot coil cord

Static Control Garment

Smock Jacket with Knitted Cuffs, 3 Pockets, No Collar, Blue

Creates faraday cage effect around torso and arms of operator

Groundable static control garment systems meets ANSI/ESD S20.20 (Rtg < 3.5 X 107ohms) Requirement Tested Per ANSI/ESD STM2.1 and ESD TR53

Hip-To-Cuff Grounding – Improves productivity, grounds operator with no need for a cord to be attaches to the operator’s wrist

770012

Static Control Worksurface Mat Kits

R7 Series 2-Layer Rubber Mat Kit

Provides a worksurface that does not generate a static charge and will control the discharge rate from all conductors (including ESD susceptible items) that are placed on the surface

Includes table mat, LPCGC151M Common Ground Cord and 3049 Snap Kit

Dissipative Dual Layer Rubber Material

High Strength Nitrile Rubber Compound – Constructed to withstand abrasion, tearing and may be used in soldering applications with flux and other chemicals.

770776 – 770784


ESD Surface and Mat Cleaner

Charge-Guard™ ESD Surface and Mat Cleaner, 25 Wipes

Ideal for Use After Sanitizing an ESD Worksurface with Alcohol

Removes dust, grease, grime, fingerprints, solder flux and other contaminants from ESD mats and other surfaces

Alcohol-Free Formula – Excessive use of alcohol-based cleaners may dry-out mats (vinyl or rubber) and degrade performance

8004

8004 -Charge-Guard™ ESD Surface and Mat Cleaner, 25 Wipes
770031- Combo Wrist Strap and Footwear Tester with Stand

Wrist Strap and Footwear Tester

Combo Wrist Strap and Footwear Tester with Stand

Tests operator’s resistance loop; wrist strap limits 750 kilohms to 10 megohms; footwear limits 750 kilohms to 100 megohms – Determines that operator’s personal grounding device is functioning correctly.

Separate test circuits for wrist straps and foot grounders

Use with Single-Wire Wrist Strap

770031


Surface Resistance Meter

Resistance Pro Meter Kit

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.

770760

770760 -  Resistance Pro Surface Resistance Meter Kit
1000 Series Metal-In Static Shield Bag

Static Shielding Bags

1000 Series Metal-In Static Shield Bag

Metal-In Film Laminate 0.0028” thick (2.8 mil) – Protects ESD sensitive contents from electrostatic fields and electrostatic discharges (ESD)

<10 nJ Discharge Shielding Energy Limit Test per ANSI/ESD STM11.31 – Meets ANSI/ESD S20.20 and ANSI/ESD S541 requirements for ESD shielding packaging inside and outside an ESD Protected Area (EPA)

1000 Series


Conclusion

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.

Need Help with ESD?

Need Help with ESD?

Perhaps you’ve come across this blog post because you find yourself asking:

  • Is my ESD Control Program in compliance?
  • Is ESD costing my company too much time, money or even future business?
  • I’m new to ESD control and don’t know where to start?
  • My company needs to start taking ESD precautions, what do I need for a basic set-up?
  • I am sure we are compliant to ANSI/ESD S20.20, but how can we confirm that?

Complete our ESD Program Checklist to start getting the answers to these questions and more:

What You Should Know Before Using ESD Laminate and Continuous Monitors

There are all kinds of variations and combinations of ESD Laminate and Continuous Monitors used by companies with ESD Programs.. There are some key factors that you need to be aware of if you intend to use ESD Laminate together with a continuous monitor that will monitor the worksurface connections.

It’s important to note that continuous monitors don’t monitor the status/condition of the outer surface of an ESD workstation. The continuous monitor monitors the connection between groundable points on the worksurface (often snaps), not the Resistance to Ground (RTG) of the surface itself. The RTG measurement must be taken separately, per ANSI/ESD TR53-01-18 – Compliance Verification of ESD Protective Equipment and Materials (Pages 6 and 7).

The basic technology is that the monitor applies a low test voltage to the scrim layer in the worksurface. Because the test voltage is so low, the resistance of the scrim layer of the mat must also be low so that the test voltage can complete a circuit of the scrim layer, worksurface connections (snaps) and ground cords. Completing that circuit indicates that the worksurface is electrically connected. The goal is to have the worksurface circuit fail because of a bad connection, not because the scrim layer resistance was too high.  As mentioned earlier, testing the combination of the outer layer and the scrim layer together (RTG) is a separate test.

When choosing a continuous monitor and worksurface combination that will work together it is important to consider the following:

  • Does the worksurface have a separate scrim layer? (vs. a homogenous mat material)
  • Does the continuous monitor spec sheet note the resistance limit of the scrim layer required for the monitor/worksurface alarm system to pass?
    • See the excerpt below from the SCS 724 Continuous Monitor Technical Bulletin – https://www.descoindustries.com/PDF/724-Workstation-Monitor-User-Guide.pdf
      Red Worksurface LED (M) This indicates that a high resistance condition (> 3.7 Megohms) exists across the conductive layer of theworksurface and/or the ground connections. Check the worksurface, ground cords and their connections for continuity. Note the audible alarm may also sound if enabled.”

What this means is if the resistance of the mat scrim layer is greater than 3.7 Megohms then the continuous monitor mat alarm would alarm for a high resistance condition even if the grounding hardware connections to the worksurface were intact. There are other SCS monitors available that will monitor a scrim layer with a resistance as high as 5 x 108.

In summary, it’s critical to know both the upper limit of the “pass” condition of the continuous monitor and the construction of the worksurface material (does it have a scrim layer and if so what is the resistance of the scrim layer?)

ESD Laminate requires extra attention when being considered for use with a continuous monitor for the following reasons:

  • Laminate material is rigid, which makes it more difficult for grounding hardware to make a good contact with the scrim layer.
    • Consider abrading the outer, decorative surface to expose the scrim layer for better contact. Consider a flat bottom drill for this process.
  • Most importantly, perform a test on the resistance between two points on the worksurface to determine if the resistance meets the requirements of the specified monitor (for the SCS 724 that requirement is less than 3.7 Megohms – 3.7 x 106 ). We recommend using an ohm meter with a test voltage similar, if not identical to the test voltage used by the continuous monitor. We recommend performing this test before the purchase/installation of any number of continuous monitor/worksurface combinations.

Worksurface Grounding: Improving the Path-to-Ground of Worksurface Mats

Worksurface and floor mats are most commonly grounded with a dedicated wire that is connected to electrical ground. Traditionally, the connection between the mat and wire is made with a snap. Snap connections can become electrically intermittent or accidentally disconnected, causing the worksurface or floor mat (which can often become ungrounded due to carts rolling over them) to lose its connection to ground.

To improve this connection, a ground cord with threaded holes can help. Threaded connections are recommended because they are more secure than traditional snaps; they allow the ground cord to be optionally bolted to the mat. This keeps the cord from disconnecting, ensuring proper grounding. The path-to-ground integrity of a mat should be periodically verified with a surface resistance meter and/or a continuous monitor.

Watch video of the SCS’s Dome Style Ground Cord with threaded snap connection to see how it works.

A Minute with Miranda – SMP Ground Master

Welcome back to “A Minute with Miranda.” This week we will be covering how the Ground Master Monitor provides continuous monitoring of the path-to-ground impedance and electromagnetic integrity of eight metal ground connections of process tools in your SMT assembly work area.

The Ground Master Monitor continuously monitors eight metal tools for electromagnetic interference (EMI). EMI can cause equipment lockups and malfunction. The Ground Master Monitor will alarm if EMI is detected. The Ground Master will also alarm if the grounded metal tools have a high-frequency noise that can cause electrical overstress (EOS) damage. The Ground Master Monitor provides both a visual and audible alarm for the monitored ground connections. The Ground Master Monitor meets the Continuous Monitor requirements of ANSI/ESD S20.20 in accordance with ESD TR53.

View the Ground Master Monitor Here