ESD

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

Image scsstaticcontrol March 16, 2022 0

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!

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 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?”

Image scsstaticcontrol February 14, 2022 0

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 Tester	Upper Resistance Limit
770030 Combo Tester	100 megaohm or 1 x 10⁸ ohms (factory set)
770758 Series Dual Combination Tester	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

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.

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.

Shop the Test Equipment Used

770760

Resistance Pro Meter Kit

Large OLED Display
Internal Memory
Measurement Stability Modes
Resistance Range: 1.0 x 10³ to 1.0 x 10¹² Ohms
Under Load Test Voltages (10V or 100V ±5%)
- Meets ANSI/ESD S20.20 resistance testing requirements for product qualification and compliance verification
Made in the United States of America

Learn More

770765

Handheld Electrode

Meets resistance measurement requirements of TR53, ANSI/ESD STM97.1 and more
Compatible with the Following SCS Meters:
- 770760 Resistance Pro Meter Kit
- 701 Analog Surface Resistance Megohmmeter Kit
- SRMETER2 Surface Resistance Meter
Made in the United States of America

Learn More

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

Image scsstaticcontrol November 29, 2021 0

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:

EM Eye – ESD Event Meter Discharging Shielding validation
718 Static Sensor Surface Voltage Test (The 718 meter has been upgraded to the 770716)

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.

Static Shielding Bags

EM EYE – ESD Event Meter

770716 – Static Sensor

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

Image scsstaticcontrol November 11, 2021 0

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

SHOP OR REQUEST A SAMPLE OF CHARGE-GUARD™ WIPES

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

Image scsstaticcontrol October 28, 2021 0

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.

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

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 (R_tt) and resistance-to-ground (R_tg) 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

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.

Get in Touch!

Need Help with ESD?

Image scsstaticcontrol October 18, 2021 0

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:

ESD CHECKLIST

Is Air Humidification Necessary For ESD Control?

Image scsstaticcontrol November 2, 2018 0

Have you ever walked across a car park on a bright cold winter’s day only to get zapped by your car’s door handle? It’s commonly known that these ‘zaps’ are much more common in cold dry weather. It begs the question: if there are less ‘zap, will using air humidifiers in a manufacturing environment prevent ESD damage of sensitive components? Let’s find out!

Humidity

Humidity describes the amount of water vapor in the air. There are 3 main measurements of humidity with the most common one being the relative humidity (RH). It is expressed in percent and describes “how much humidity there is in the air, compared to how much there could be. Meteorologists often use the relative humidity as a measurement to describe the weather at various places.” [Source]

At 0% the air is completely dry; at 100% it is so moist that mist or dew can form. The optimum relative humidity level is somewhere between 40% and 60%:

A lower relative humidity increases charge generation as the environment is drier.
If the humidity level is too high, condensation can form on surfaces.

Charge Generation and ElectroStatic Discharge (ESD)

The simple separation of two surfaces generates an ElectroStatic charge. Examples:

Unwinding a roll of tape
Gas or liquid moving through a hose or pipe
A person walking across a floor with heels and soles contacting and separating from the floor

*Walking across a floor generates ElectroStatic charges.*

The amount of static electricity generated varies and is affected by materials, friction, area of contact and the relative humidity of the environment. A higher charge is generated at low humidity or in a dry environment.

Once an item has generated a charge, it will want to come into balance. If it is in close enough proximity to a second item, there can be a rapid, spontaneous transfer of electrostatic charge. This is called discharge or ElectroStatic Discharge (ESD).

Going back to our earlier example of getting a zap from your car’s door handle:

Charge generation: you walk across the car park with your soles contacting and separating from the floor. A charge is built-up on you.
ElectroStatic Discharge (ESD): you touch the door handle. Charges move from your body to your car until both are balanced out.

Impact of relative humidity on ESD

Many people will notice a difference in the ability to generate static electricity when the air gets dryer (relative humidity decreases). Relative humidity (RH) directly affects the ability of a surface to store an electrostatic charge. “With a humidity level of 40% RH, surface resistance is lowered on floors, carpets, table mats and other areas. … the moisture in the air forms a thin protective “film” on surfaces that serves as a natural conductor to dissipate electric charges. When humidity drops below 40% RH, this protection disappears, and normal employee activities lead to objects being charged with static electricity.” [Source]

In an electronics manufacturing environment lower humidity may result in lower output from production due to an increase in ESD events during manufacturing processes.

Air Humidification and ESD

Air humidifiers are used to add moisture to the air and are commonly used in drier environments to keep humidity at a constant (optimum) level. Given that a lower humidity level increases the risk of ESD events, the obvious questions are:

Can air humidifiers replace normal ESD Control measures?
Are air humidifiers required for complete ESD protection?

Let’s address both questions:

Let’s be very clear about one thing here: air humidifiers cannot replace ESD Control measures.

As explained further above, ESD is caused by two items that are at a different electrostatic equipotential and want to equalize their charges. Adding moisture to the air using humidifiers will not stop this discharge from happening. The only thing you may achieve is a reduction in the number of ESD events. BUT: they will still happen; just walking across a carpet will generate a charge on an operator. If they then touch an ESD sensitive component, discharge will still occur and may damage the component. No humidifier will prevent this.

The only way to control electrostatic charges on a person or object is through ESD grounding – this will ensure any charges generated dissipate to earth:

Operators need to be grounded using wrist straps or a footwear/flooring
Surfaces need to grounded using appropriate matting and ground cords.

For more information on how to create a ESD workstation and how to correctly ground all elements, have a look at this post.

*Grounding of an operator using a wrist strap*

Low air humidity can increase the number of ESD events so it may make sense to keep a factory at a higher humidity level. However, there are many other factors that come into play when choosing the ‘right’ humidity for a manufacturing environment. The recommended humidity range is usually determined by the specifications of the devices and components being assembled. Increasing the humidity in an electronics manufacturing facility can help to reduce ESD events but increased humidity can lead to other unwanted quality issues in an electronics manufacturing environment such as corrosion, soldering defects and the popcorn effect on moisture sensitive devices.

A normal range for humidity in electronics manufacturing is between 30% RH and 70% RH. Some facilities try to maintain a constant moderate RH (~50%), whereas other environments may want lower % RH due to corrosion susceptibility to humidity sensitive parts.
And remember: you will not eliminate ESD by using humidifiers and keeping humidity levels at a higher level. You need an ESD Control Program in place to avoid ESD and associated damages.

Conclusion

Air humidification can help reduce the number of ESD events in an electronics manufacturing environment but at the same time there are other factors (e.g. moisture sensitivity of components) that need to be considered.

A lower relative humidity level increases charge generation as the environment is drier. This will result in more ESD events which can potentially damage sensitive components. The only way to protect sensitive components from ESD damage is by having proper ESD control measures in place and connecting operators, objects and surfaces to ground. This will ensure each element is kept at the same electrical potential and any electrostatic discharge is being removed to ground.

For more information on how to get your ESD control program off the ground or improve an existing program, request a free ESD/EOS Assessment at your facility by one of our knowledgeable local representatives to evaluate your ESD program and answer any ESD questions!

How to Create an ESD Protected Area at an Existing Workstation

Image scsstaticcontrol October 18, 2018 1

When referring to an “ESD Protected Area” or “EPA”, a lot of people imagine rooms or even whole factory floors with numerous workstations. This very common misconception leads to nervousness and even fear when it comes to implementing an ESD Control Program. There is a concern regarding the cost and time implications when establishing an EPA. However, most often, a simple ESD workstation is completely sufficient to fulfill a company’s needs to protect their ESD sensitive products. Today’s post will provide a step-by-step guide on:

How to create an EPA at an existing workstation,
What ESD control products are required
How to correctly set up ESD control products

What is an “ESD Protected Area” or “EPA”?

An EPA is an area that has been established to effectively control Electrostatic Discharge (ESD) and its purpose is therefore to avoid all problems resulting from ESD damage, e.g. catastrophic failures or latent defects. It is a defined space within which all surfaces, objects, people and ESD Sensitive Devices (ESDs) are kept at the same electrical potential. This is achieved by simply using only ‘groundable’ materials for covering of surfaces and for the manufacture of containers and tools. All surfaces, products and people are grounded to Ground.

What is Grounding?

Grounding means linking, usually through a resistance of between 1 and 10 megohms. Movable items (such as containers and tools) are grounded by virtue of lying on a grounded surface or being held by a grounded person. Everything that does not readily dissipate a charge must be excluded from the EPA.

How big does an EPA need to be?

An EPA can be just one workstation, or it could be a room containing several different workstations. “The definition of an EPA depends somewhat on the user environment. An EPA may be a permanent workstation within a room or an entire factory floor encompassing thousands of workstations. An EPA may also be portable as used in a field service situation.” [Handbook ESD TR20.20-2016 Clause 9.0 ESD Protected Areas]

What is needed to convert a Workstation into an EPA?

Creating an EPA at an existing workstation does not need to be complicated or expensive. There are just a few things that are required:

1. Wrist Strap

Wrist straps are the most common personnel grounding devices and are used to link people to ground. They are required if the operator is sitting. A wrist strap is made up of two components:

A wristband that is worn comfortably around the wrist and
A coiled cord that connects the band to Ground or a Wrist Strap Grounding System as explained in #4.

2. Wrist Strap Grounding System

These have been designed to be installed underneath bench tops where they are easily accessible to operators and where they are unlikely to be knocked and damaged or hinder the operator. The grounding cord of the Grounding System needs to be connected to a suitable Ground.

3.Worksurface Mat

ESD protective worksurfaces aid in the prevention of damage to ESD sensitive items (ESDS) and assemblies from electrostatic discharge.

ESD worksurfaces, such as mats, are typically an integral part of the ESD workstation, particularly in areas where hand assembly occurs. The purpose of the ESD worksurface is two-fold:

To provide a surface with little to no charge on it.
To provide a surface that will remove ElectroStatic charges from conductors (including ESDs) that are placed on the surface.

4. Worksurface Mat Grounding Cord

An ESD worksurface needs to be grounded using a ground cord. A ground wire from the surface should connect to Ground. Best practice is that ground connections use firm fitting connecting devices such as metallic crimps, snaps and banana plugs to connect to designated ground points. The use of alligator clips is not recommended.

Where sitting personnel will be grounded via a wrist strap, this method is not feasible for operators moving around in an ESD Protected Area. In those situations, a flooring / footwear system is required.

5. Foot Grounders

Foot grounders are designed to reliably contact grounded ESD flooring and provide a continuous path-to-ground by removing electrostatic charges from personnel. They are easy to install and can be used on standard shoes by placing the grounding tab in the shoe under the foot.

Foot grounders must be worn on both feet to maintain the integrity of the body-to-ground connection Wearing a foot grounder on each foot ensures contact with Ground via the ESD floor even when one foot is lifted off the floor.

6. Floor Mat

Floor matting is an essential component in the flooring / footwear system when grounding moving or standing personnel. The path to Ground from operators via heel grounders to Ground is maintained by using dissipative or conductive flooring.

Floor mats don’t just ground personnel; they are also used to ground ESD control items (e.g. mobile carts or workstations).

7. Floor Mat Grounding Cord

Just like worksurface matting, floor matting needs to be connected to Ground. This ensures that any charges on the operator are dissipated through their heel grounders and the floor matting to Ground. A floor mat grounding cord is used to link the floor mat to Ground.

Alternatively, matting can be grounded via a strip of copper foil.

Installing an ESD Workstation

To install the ESD workstation, it is necessary to ground the worksurface and operator with the following steps:

1.		Lay the worksurface mat flat on the workbench with the stud(s) facing upwards.
2.		Connect the worksurface mat grounding cord to the worksurface mat.
3.		Connect the other end of the worksurface mat grounding cord to Ground.
4.		Place the wristband on the wrist.
5.		Connect the coiled cord to the wristband.
6.		Attach the Wrist Strap Grounding System to the bench. Remember that it needs to be connected to a suitable Ground.
7.		Connect the other end of the coiled cord to the Wrist Strap Grounding System and verify personnel is properly grounded.

If your operators are standing or mobile and grounding via a wrist strap is not feasible, ground the worksurface, and the ESD flooring:

1.		Ground the worksurface mat by following steps #1 to #4 above
2.		Lay the floor mat flat on the floor with the stud(s) facing upwards.
3.		Connect the floor mat grounding cord to the floor mat.
4.		Connect the other end of the floor mat grounding cord to Ground.
5.		Place the foot grounders on the feet and verify personnel is properly grounded.

Conclusion

An EPA can be created at an existing workstation in a facility. To establish an EPA it is important to:

Ground all conductors (including people),
Remove all insulators (or substituting with ESD protective versions) or
Neutralize process essential insulators with an ionizer.

With a few simple steps, you can convert your existing workstation into an ESD workstation. You will need:

Worksurface Mat
Worksurface Mat Grounding Cord
Wrist Strap
Wrist Strap Grounding System

Optional:

Foot Grounders
Floor Mat
Floor Mat Grounding Cord

We hope this article has introduced the basics of an ESD Protected Area (EPA), and the steps needed to create an ESD Workstation.

For more information on how to get your ESD control program off the ground, Request a free ESD/EOS Assessment at your facility by one of our knowledgeable local representatives to evaluate your ESD program and answer any ESD questions!

Measuring Effectiveness of an ESD Control Program

Image scsstaticcontrol October 4, 2018 0

Introduction

Electronic devices and systems can be damaged by exposure to high electric fields as well as by direct electrostatic discharges. A good circuit layout and on-board protection may reduce the risk of damage by such events, but the only safe action at present is to ensure that devices are not exposed to levels of static electricity above the critical threshold.

This can only be achieved by introducing a static control program which usually involves setting up an ESD Protected Area (EPA) in which personnel are correctly grounded and all meet the ESD Standard. However, setting up an EPA does not of itself guarantee a low static environment. Production procedures may change, new materials may be introduced, the performance of older materials may degrade and so on.

Measuring Effectiveness of an ESD Control Program

To ensure the effectiveness of any static control program it is important that regular measurements are carried out:

to determine the sensitivity to ESD of devices being produced or handled.
to confirm that static levels are lower than the critical level, and that new or modified work practices have not introduced high static levels.
to ensure that both new and existing materials in the EPA meet the necessary requirements.

Only after an ‘operational baseline’ has been established by regular auditing will it become possible to identify the origin of unexpected problems arising from the presence of static.

1. Determining the sensitivity of ESD sensitive Devices

It is important to understand the sensitivity of ESD sensitive devices before an action plan can be created. Once you know the sensitivity of the items you are handling, can you work towards ensuring you’re not exceeding those levels.

Part of every ESD control plan is to identify items in your company that are sensitive to ESD. At the same time, you need to recognize the level of their sensitivity. As explained by the ESD Association, how susceptible to ESD a product is depends on the item’s ability to either:

dissipate the discharge energy or
withstand the levels of current.

2. Measurements to prove the effectiveness of an ESD Control Program

Measuring electrostatic quantities poses special problems because electrostatic systems are generally characterized by high resistances and small amounts of electrical charge. Consequently, conventional electronic instrumentation cannot normally be used.

Measuring Electrical Field

Wherever electrostatic charges accumulate, they can be detected by the presence of an associated electric field. The magnitude of this field is determined by many factors, e. g. the magnitude and distribution of the charge, the geometry and location of grounded surfaces and the medium in which the charge is located.

“The current general view of experts is that the main source of ESD risk may occur where ESDS can reach high induced voltage due to external fields from the clothing, and subsequently experience a field induced CDM type discharge.” [CLC TR 61340-5-2 User guide Garments clause 4.7.7.1 Introductory remarks]

Using the 718 Static Sensor to test static fields

A static field meter is often used for ESD testing of static fields. It indicates surface voltage and polarity on objects and is therefore an effective problem-solving tool used to identify items that are able to be charged.

A field meter can be used to:

verify that automated processes (like auto insertion, tape and reel, etc.) are not generating charges above acceptable limits.
measure charges generated by causing contact and separation with other materials.
demonstrate shielding by measuring a charged object and then covering the charged item with an ESD lab coat or shielding bag. Being shielded the measured charge should be greatly reduced.

Measuring ESD Events

ESD events can damage ESD sensitive items and can cause tool lock-ups, erratic behavior and parametric errors. An ESD Event Detector like the EM Eye ESD Event Meter will help detect most ESD events. It detects the magnitude of events and using filters built into the unit, it can provide approximate values for some ESD events for models (CDM, MM, HBM) using proprietary algorithms.

Using the EM Eye ESD Event Meter to detect ESD Events

Solving ESD problems requires data. A tool counting ESD events will help carry out a before-and-after analysis and will prove the effectiveness of implementing ESD control measures.

3. Checking Materials in your EPA

When talking about material properties, the measurement you will most frequently come across is “Surface Resistance”. It expresses the ability of a material to conduct electricity and is related to current and voltage. The surface resistance of a material is the ratio of the voltage and current that’s flowing between two pre-defined electrodes.
It is important to remember that the surface resistance of a material is dependent on the electrodes used (shape as well as distance). If your company implements an ESD control program compliant to the ESD Standard ANSI/ESD S20.20, it is therefore vital to carry out surface resistance measurements as described in the Standard itself. For more information on the definition of resistance measurements used in ESD control, check out this post.

A company’s compliance verification plan should include periodic checks of surfaces measuring:

Resistance Point-to-Point (Rp-p) and
Resistance-to-ground (Rg).

Measuring Surface Resistance of worksurface matting using the
SRMETER2 Surface Resistance Meter

Surface resistance testers can be used to perform these tests in accordance with ANSI/ESD S20.20 and its test method ANSI/ESD S4.1; if these measurements are within acceptable ranges, the surface and its connections are good. For more information on checking your ESD control products, catch-up with this. It goes into depth as to what products you should be checking in your EPA and how they should be checked.

Conclusion

Measurements form an integral part of any ESD control program. Measuring devices help identify the sensitivity of ESD devices that ESD programs are based on, and also are used to verify the effectiveness of ESD control programs set in place. High quality instruments are available commercially for measuring all the parameters necessary for quantifying the extent of a static problem.

We hope the list above has introduced the techniques most commonly used. For more information on how to get your ESD control program off the ground, Request a free ESD/EOS Assessment at your facility by one of our knowledgeable local representatives to evaluate your ESD program and answer any ESD questions!

Effective ESD Control in a Service or Repair Center

Image scsstaticcontrol September 21, 2018 0

The best-equipped service bench in your shop can be a real money-maker when set up properly. It can also be a source of frustration and lost revenue if the threat of ElectroStatic Discharge (ESD) is ignored.

A typical scenario might be where an electronic product is brought in for service, properly diagnosed and repaired, only to find a new symptom requiring additional repair. Unless the technician understands the ESD problem and has developed methods to keep it in check damage from static electricity cannot be ruled out as a potential source of the new problem.

Static electricity is nothing new; it’s all around us and always has been. What has changed is the spread of semiconductors in almost every consumer product we buy. As device complexity increases, often its static sensitivity increases as well. Some semiconductor devices may be damaged by as little as 20-30 volts!

It is important to note that this post is addressing the issue of ESD in terms of control, and not elimination. The potential for an ESD event to occur cannot be completely eliminated outside of a laboratory environment, but we can greatly reduce the risk with proper training and equipment. By implementing a good static control program and developing some simple habits, ESD can be effectively controlled.

The Source of the Problem

Static is all around us. We occasionally will see or feel it by walking on carpet, touching something or someone and feeling the “zap” of a static discharge. The perception level varies but static charge is typically 2000-3000 volts before we can feel it. ESD sensitivity of some parts is under 100 volts – well below the level that we would be able to detect.

Even though carpet may not be used around the service bench, there are many other static “generators” may not be obvious and frequently found around or on a service bench. The innocent-looking Styrofoam coffee cup can be a tremendous source of static. The simple act of pulling several inches of adhesive tape from a roll can generate several thousand volts of static! Many insulative materials will develop a charge by rubbing them or separating them from another material. This phenomenon is known as “tribocharging” and it occurs often where there are insulative materials present.

*Sources of Charge Generation: Unwinding a Roll of Tape*

People are often a major factor in generation of static charges. Studies have shown that personnel in a manufacturing environment frequently develop 5000 volts or more just by walking across the floor. Again, this is “tribocharging” produced by the separation of their shoes and the flooring as they walk.

A technician seated at a non-ESD workbench could easily have a 400-500 volt charge on his or her body caused not only by friction or tribocharging, but additionally by the constant change in body capacitance that occurs from natural movements. The simple act of lifting both feet off the floor can raise the measured voltage on a person as much as 500-1000 volts.

Setting up a “Static Safe” Program

Perhaps the most important factor in a successful static control program is developing an awareness of the “unseen” problem. One of the best ways to demonstrate the ESD hazard is by using a “static field meter”. The visual impact of locating and measuring static charges of more than 1000 volts will get the attention of skeptical individuals.

*Static Field Meter – find more information here*

Education of Personnel

ESD education and awareness are essential basic ingredients in any effective static control program. A high level of static awareness must be created and maintained in and around the protected area. Once personnel understand the potential problem, reinforce the understanding by hanging up static control posters in strategic locations. The technician doesn’t need an unaware and/or unprotected person wandering over and touching things on the service bench.

Workstation Grounding

To minimize the threat of an ESD event, we need to bring all components of the system to the same relative potential and maintain that potential. Workstations can be grounded with the following options:

Establish an ESD Common Grounding Point, an electrical junction where all ESD grounds are connected to. Usually, a common ground point is connected to ground, preferably equipment ground.
The Service Bench Surface should be covered with a dissipative material. This can be either an ESD-type high-pressure laminate formed as the benchtop surface, or it may be one of the many types of dissipative mats placed upon the benchtop surface. The mats are available in different colors, with different surface textures, and with various cushioning effects. Whichever type is chosen, look for a material with surface resistivity of 1 x 10⁹ or less, as these materials are sufficiently conductive to discharge objects in less than one second. The ESD laminate or mat must be grounded to the ESD common grounding point to work properly. Frequently, a one Megohm current limiting safety resistor is used in series with the work surface ground. This blog post will provide more information on how to choose and install your ESD working surface.

*Types of Worksurface Matting – click here for more information*

A Dissipative Floor Mat may also be used, especially if the technician intends to wear foot-grounding devices. The selection of the floor mat should take into consideration several factors. If anything is to roll on the mat, then a soft, cushion-type mat will probably not work well. If the tech does a lot of standing, then the soft, anti-fatigue type will be much appreciated. Again, the mat should be grounded to the common ground point, with or without the safety resistor as desired.
Workstation Tools and Supplies should be selected with ESD in mind. Avoid insulators and plastics where possible on and around the bench. Poly bags and normal adhesive tapes can generate substantial charges, as can plastic cups and glasses. If charge-generating plastics and the like cannot be eliminated, consider using one of the small, low cost air ionizers It can usually be mounted off the bench to conserve work area, and then aimed at the area where most of the work is being done. The ionizer does not eliminate the need for grounding the working surface or the operator, but it does drain static charges from insulators, which do not lend themselves to grounding.

Personnel Grounding

People are great static generators. Simple movements at the bench can easily build up charges as high as 500-1000 volts. Therefore, controlling this charge build-up on the technician is essential. The two best known methods for draining the charge on a person are wrist straps with ground cords and foot or heel grounders. Personnel can be grounded through:

Wrist Straps are probably the most common item used for personnel grounding. They are comprised of a conductive band or strap that fits snugly on the wrist. The wrist strap is frequently made of an elastic material with a conductive inner surface, or it may be a metallic expandable band similar to that found on a watch. For more information on wrist straps, check out this post.
Ground Cords are typically made of a highly flexible wire and often are made retractable for additional freedom of movement. There are two safety features that are usually built into the cord, and the user should not attempt to bypass them. The first, and most important, is a current limiting resistor (typically 1 Megohm) which prevents hazardous current from flowing through the cord in the event the wearer inadvertently contacts line voltage. The line voltage may find another path to ground, but the cord is designed to neither increase or reduce shock hazard for voltages under 250 volts. The second safety feature built into most cords is a breakaway connection to allow the user to exit rapidly in an emergency. This is usually accomplished by using a snap connector at the wrist strap end.
Foot or Heel Grounders are frequently used where the technician needs more freedom of movement than the wrist strap and cord allow. The heel grounder is often made of a conductive rubber or vinyl and is worn over a standard shoe. It usually has a strap that passes under the heel for good contact and a strap of some type that is laid inside the shoe for contact to the wearer. Heel grounders must be used with some type of conductive or dissipative floor surface to be effective and should be worn on both feet to insure continuous contact with the floor. Obviously, lifting both feet from the floor while sitting will cause protection to be lost.Don’t forget to regularly check and verify your personnel grounding items:

Summary

An effective static control program doesn’t have to be expensive or complex. The main concept is to minimize generation of static and to drain it away when it does occur, thereby lessening the chance for an ESD event to happen. The ingredients for an effective ESD program are:

Education: to ensure that everyone understands the problem and the proper handling of sensitive devices.
Workstation Grounding: use a dissipative working surface material and dissipative flooring materials as required.
Personnel Grounding: using wrist straps with ground cords and/or foot-grounding devices.
Follow-up to ensure Compliance: all elements of the program should be checked frequently to determine that they are working effectively.

The ESD “threat” is not likely to go away soon, and it is very likely to become an even greater hazard, as electronic devices continue to increase in complexity and decrease in size. By implementing a static control program now, you will be prepared for the more sensitive products that will be coming.