ESD Control

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:

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

A Minute with Miranda – ESD Packaging with Protektive Pak In-Plant Handler

Welcome back to “A Minute with Miranda.” This week we will be discussing how to store and ship your static sensitive assemblies within and outside of an ESD Protected Area using an In-Plant Handler.

ANSI/ESD S20.20 requires that ESD protective packaging is necessary to store, transport and protect ESD sensitive electronic items during all phases of production and shipment. Beyond the static protection, packaging also provides protection from physical damage, moisture, dust and other contaminates. Per the ANSI/ESD S541 Packaging Standard packaging that is used inside and outside of an EPA shall be low charge generating, constructed from dissipative or conductive material for intimate contact with ESD items and provide electrostatic discharge shielding.

The Protektive Pak In-Plant Handlers are constructed from an impregnated dissipative corrugated material that has a surface resistance range of 1 x 106 to less than 1 x 109 ohms per ANSI/ESD STM11.11. This minimizes the potential of rapid discharge or sparking. The in-plant handlers will shield ESD sensitive items from charge and electrostatic discharges with the lid in place. The partition sets are constructed from the same impregnated dissipative material and are available in over 300 cell size configurations to suit your specific packaging needs.

View the full range of Protektive Pak In-Plant Handlers here.

A Minute with Miranda – Testing an ESD Floor

Welcome back to “A Minute with Miranda.” This week we will be discussing how to test the point-to-point resistance (Rtt) and the resistance-to-ground (Rtg) of a Conductive ESD Floor.

ANSI/ESD S20.20 requires initial and periodic verification of an ESD Flooring System. ANSI/ESD STM7.1 outlines the test methods applicable for the Conductive flooring material. For the Point-to-Point resistance (Rtt) test the flooring will be tested with a resistance measurement meter and
2 x 5lbs cylindrical electrodes positioned 36” apart. The value for the test should be less than or equal to 1 x 106 ohms.

The Resistance Point-to-Ground (Rtg) test should be conducted with a resistance measurement meter and 1 x 5lbs cylindrical electrode. One lead from the meter should be connected to the ground point and the other lead will be connected to the electrode. The test value should be less than or equal to 1 x 106 ohms.

View the full range of SCS Surface Resistance Testers here.

Advantages of Internet of Things (IoT) in ESD Control

In today’s connected world, we are surrounded by home monitoring networks, fitness trackers and other smart systems. They all use an IoT platform to keep us up to-date with the current temperature in our house or the number of steps we have taken in a day. There are many different applications of IoT: Consumer, Commercial, Industrial, and Infrastructure, but is there a way to use this incredibly smart technology to improve ESD Control? Let’s take a look!

What Is The Internet of Things (IoT)?

The Internet of Things (IoT) is used everywhere today – from medical devices, to vehicles, to homes and more! Simply put, IoT:

  • Connects “things” in the physical world to the internet using sensors.
  • Collects data for these “things” via sensors.
  • Analyses the collected data and provides a deeper insight into the “things”.

Another broad definition provided for IoT is:

The Internet of Things (IoT) is the network of physical devices, vehicles, home appliances, and other items embedded with electronics, software, sensors, actuators, and connectivity which enables these things to connect and exchange data, creating opportunities for more direct integration of the physical world into computer-based systems, resulting in efficiency improvements, economic benefits, and reduced human exertions.” [Source]

 

Iot History-min.jpgThe history of IoT [Source]

 

What Is The Industrial Internet of Things (IIoT)?

As mentioned previously, there are many different applications for IoT, but The Industrial Internet of Things (IIoT) applies specifically to manufacturing and industrial processes.

It has slightly different requirements compared to consumer IoT products but the principle is the same: smart machines (incorporating various sensors) accurately and consistently capture and analyze real-time data allowing companies to pick-up problems as soon as (or even before) they appear.

 

Internet of Things (IoT) and Industry 4.0

IoT helped push the 3rd industrial revolution (machine automation) one step further. “Cyber Physical Systems (CPS) dominate the manufacturing floor, linking real objects with information processing, and virtual objects via the internet. The goal is to converge Operational Technology (OT) and Information Technology (IT).” [Source]

The 4th industrial revolution is also referred to as “Industry 4.0”. “At the very core Industry 4.0 includes the (partial) transfer of autonomy and autonomous decisions to cyber-physical systems and machines, leveraging information systems”. [Source]

Industry-4.0-shutterstock_524444866_pk_cut.jpgIndustry 4.0 as fourth industrial revolution [Source]

So, how can companies use the power of IoT and create accessible, real-time feedback on the status of their ESD Control Protected Area (EPA) and ESD control items?

 

Industry 4.0 IoT Platforms in ESD Control

ESD damages can be extremely costly – especially when it comes to latent defects that are not detected until the damaged component is installed in a customer’s system. Conventional ESD control programs incorporate periodic verification checks of ESD control products to detect any issues that could result in ESD events and ESD damage. The problem is that ESD control products (and the EPA as a whole) are not constantly monitored.

Take an ionizer for example: if a company uses ionization to handle process-essential insulators, the ionizers need to be fully reliable at all times. If an ionizer passes one check but is found to be out of balance at the next, the company faces a huge problem: nobody knows WHEN exactly the ionizer failed or if contributed to a charged insulator potentially causing ESD damage.

The Industry 4.0 IoT platform will be a game changer when it comes to creating a reliable and dependable ESD control program. Sensors collecting vital ESD information like field voltage, Electromagnetic Interference (EMI), temperature, humidity etc. in an EPA will help detect potential threats in real-time allowing supervisors to act even before an ESD threat occurs.

 

Advantages of Internet of Things (IoT) in ESD Control

Here is a (by no means exhaustive) list of advantages, IoT can bring to ESD Control:

Collecting Data

The day in an EPA can be busy. Taking the time to capture and record measurements of ionizers, wrist straps, work surfaces, automated processes etc. can be disruptive and is prone to errors. IoT allows data to be collected automatically without any input from users. This helps to increase the accuracy of data and allows operators and supervisors more time focusing on their actual jobs.

Smart-Factory.pngCollecting data is the first step to managing processes – more information

Analyzing Data

Supervisors have all the essential data in one place right in front of them and can make informed decisions; they can provide feedback and give suggestions in case of an ESD emergency. IoT allows to pinpoint areas of concern and prevent ESD events.

24/7 Monitoring

IoT continuously monitors processes and provides a real-time picture of them – no manual checks required. If a potential threat is detected, warnings will show-up immediately. There is no need to worry about potentially damaging sensitive devices because the next scheduled check of ionizers, wrist straps etc. has not been completed yet.

Cutting Costs

The number one reason for adapting an ESD control program is to reduce costs by:

  • Enhancing quality and productivity,
  • Increasing reliability,
  • Improving customer satisfaction,
  • Lowering repair, rework and field service costs and
  • Reducing material, labor and overhead costs.

Reduced Workload and Increased Productivity

IoT pushes all the above even further with the additional benefits of:

  • Reduced workload for operators: Data is collected remotely without any input from users. Operators are not disrupted in their day-to-day activities.
  • Reduced workload for supervisors: Supervisors don’t have to collect and analyze data from personnel testers, field meters, monitors etc. The system does it for them and will highlight any issues.
  • Further increases in productivity and cost reductions: An ESD program can be managed better and with fewer resources.

 

SMT-Line-Layout.jpgStatic Management Program (SMP): the next generation of ESD Process Control – more information

 

Conclusion

IoT will no doubt change ESD control and the way EPAs are monitored. Quantifiable data allows companies to see trends, become more proactive and improve the efficiency of their ESD process control system. IoT will support organizations’ efforts to make more dependable products, improve yields, increase automation and provide a measurable return on investment. Not only will this benefit users and supervisors, but the company as a whole.

SCS Static Management Program (SMP) is the only smart ESD system on the market that continuously monitors your entire ESD process control system throughout all stages of manufacturing. SMP captures data from SCS workstation, equipment and ESD event continuous monitors and provides a real-time picture of critical manufacturing processes.

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

 

Resources:

Bill McCabe: Quick History of the Internet of Things..
Margaret Rouce: industrial internet of things (IIoT)
Michelle Lam: ESD Control in the World of IoT
Ian Wright: What Is Industry 4.0, Anyway?
Pascal Kriesche: Humans vs. machines – who will manage the factory of the future?
Industry 4.0 Resource: Industry 4.0: the fourth industrial revolution – guide to Industry 4.0

Measuring Effectiveness of an ESD Control Program

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:

  1. to determine the sensitivity to ESD of devices being produced or handled.
  2. to confirm that static levels are lower than the critical level, and that new or modified work practices have not introduced high static levels.
  3. 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]

718_Use2.jpg
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).

SRMeter2_use.jpg
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

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.

Tape.JPG
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.

718.jpg
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:

  1. 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.
  2. 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.

ESD-Worksurface-Matting.jpg
Types of Worksurface Matting – click here for more information

  1. 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.
  2. 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:

  1. 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.
  2. 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.
    Wrist-Strap.png
  3. 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:

PersonnelGroundingTesters.png
The Personnel Grounding Checklist

 

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:

  1. Education: to ensure that everyone understands the problem and the proper handling of sensitive devices.
  2. Workstation Grounding: use a dissipative working surface material and dissipative flooring materials as required.
  3. Personnel Grounding: using wrist straps with ground cords and/or foot-grounding devices.
  4. 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.