ESD Compliance – Ground Zero Electrostatics Blog

04 Aug

Managing Static and ESD in Call Centers

Thanks to movies and TV, no matter how old you are, you’ve probably seen the old switchboards – whether it’s on Agent Carter or reruns of the Andy Griffith Show – and computers that barely fit inside a room – like in The Imitation Game or the TV show Manhattan.

Nowadays, of course, we carry the switchboard and the computer in a handy-dandy pocket device.

Likewise with emergency services. When we call 9-11, we expect a prompt response, and the person on the other end of the line assures us that police, fire, or ambulance are already in route as they continue to gather our information.

Computers help planes land, monitor traffic on the freeways, and even park your car for you.

But for all the advances in technology, there have been setbacks as well.

In the old days, phone and computer systems were built “solid-state.” Everything was confined within one unit and was protected from outside forces. Internally, they were defended from ElectroStatic Discharge (ESD) by microcircuit gate protectors.

Unfortunately, these gate protectors, while highly effective, tended to slow down the machines they were protecting – kind of like how some companies’ virus protection forces their machines to crawl.

As technology progressed, emergency services, military bases, and flight control centers started abandoning these more stringent preventative measures, in favor of speed.

The end result being, while these computers and call centers are protected in buildings made to withstand hurricanes, earthquakes and power outages, they can be disabled or even rendered completely useless by the tiniest static shock.

Which is why the proper ESD protection and protocols are so important in these mission critical locations.

Another factor to consider is that these facilities are typically open 24-hours a day and have hundreds of people pass through them on a regular basis. Some of them are trained and properly equipped with ESD shoes, heel grounders and even personal wrist straps, but certainly not all of them.

And when there’s a crisis and everyone needs to scramble to get the problem solved, the first thing to go is proper ESD procedures.

The answer is to make these facilities as static proof (or charge proof) as possible.

Like your skin (the largest organ in the human body), flooring is the largest and most vulnerable area for ESD buildup and discharge, if it’s not handled properly.

There are many options for ESD flooring, as we’ve discussed in prior posts, but in this instance, there are really only one option: carbon-fiber laced carpet.

The first thing you should know is that not all ESD carpet is created equal. Some companies promote and sell an ESD carpeting that is treated with a chemical to reduce static that disintegrates over time and must be reapplied.

Avoid these – you don’t want your static protection to be subject to a random timetable. Again, these facilities are always open. You’ll want to invest in a carpet whose static-prevention comes from the permanent physical composition of the materials.

For the same reason, you’ll want to invest in an ESD carpeting that is certified by ANSI/ESDA standards and reduces static regardless of the humidity levels or footwear worn by the personnel.

As an added bonus look for ESD carpet that is low maintenance, crush resistant, able to handle heavy foot traffic and comes with a lifetime warranty.

Contact us today for more information or to talk about your ESD flooring options. We would love to be your full service, seamless ESD solution provider.

28 Jul

5 Reasons Why Static Programs Fail

On May 6, 1937, the German passenger airship LZ 129 Hindenburg caught fire and was destroyed, killing 36 people in front of national news cameras and effectively ending the Zeppelin flying experiment.

The Hindenburg was larger than 4 Goodyear blimps combined, or about as long as 2/3 the height of the Empire State Building.

It was rainy that day, and the mooring ropes dragged along the ground as the airship came down to dock in Manchester Township. The prevailing theory is that the wet dragging ropes generated a static charge that traveled up them onto the ship.

There the charge ignited the Hydrogen fuel and… boom. Once considered the future of air travel, flying airships would not be utilized, either commercially or for military use until the end of World War II.

All caused by a single spark.

Much like the Hindenburg disaster, your company’s program to control electrostatic discharge (ESD) can be toppled with a few small errors that blossom into larger problems if they aren’t properly accounted and planned for.

So today, let’s look at the 5 common reasons why your static control programs could fail.

Sure! We have ESD Protocols, Right?

Most companies that deal with sensitive electronics and circuit boards also require that their vendors, third party suppliers, and subcontractors have an ESD program in place. Often even before signing a contract, an engineer is sent in to audit the ESD practices. And from time to time they will do spot-checks to verify that those practices are still in place.

Some companies, in an effort to hold on to their contract or cut expenses, will simply throw together a minimum program that can be audited. It’s done as inexpensively as possible and often doesn’t have any true protocols – training, preventative maintenance, and enforcement fall by the wayside.

You’d never do that, right? Well, except…

This is Gonna Cost How Much?

Top management are always looking at ways to work more economically. Unfortunately, if they are not properly briefed on the importance of proper ESD protection protocols, they may see many aspects of the ESD program as expensive and possibly unnecessary.

This isn’t their fault, they just need to be better educated. Which may be your job. The fact is, the expense for good, well-developed ESD protection protocols is dwarfed by the cost to replace or repair non-functioning components, not to mention the company’s reputation.

Excellent ESD companies are led from the top down, with company leadership not only showing financial support for ESD preventative programs, but also making time to attend training themselves, praise persons and departments with the best implementation, and allocate time and funds for ongoing training and improvement of existing programs.

Otherwise, you might end up in a pinch…

Here’s a Band-Aid for that Severed Limb!

You might have heard the old saw, ‘if there’s no time to do it right the first time, how are you going to find time to fix it later?’

Unfortunately, many companies appear to follow a different maxim – there’ll always be time to do it over.

Like our last reason, the problem is often financial. Momentary solutions that can be quickly applied to fix individual problems becomes the norm, despite the fact that the long term expense is much higher.

The best, most cost-effective solutions are applied right the first time and “solve” lots of problems by the fact that they prevent so many of them for happening. Then you don’t get into a situation where you’re spending a lot more to fix what could have been an easily avoided minor problem, but is now mission critical.

But that’s not going to help unless…

Training? We Don’t Need no Stinking Training!

Proper ESD prevention is a team effort, but many companies underestimate the size of the team involved. As mentioned before, upper level management should take an interest in training, and in fact, every employee should be given at least a rudimentary class or video in how to follow the company’s practices.

It’s not enough to train the engineers of you haven’t informed the janitorial staff that cleans their sensitive work areas after they leave for the day how to properly do so.

Secretaries, interns, sales people – everyone who has the potential to walk into or affect an Electrostatic Protection Area (EPA) needs to know how to properly behave to minimize risk.

And finally…

We Only Use the Best – the Best We Can Afford, That Is.

Yes, it keeps coming back to price. But price should not be the only factor in deciding who to buy your ESD supplies from. Not all companies are created equally. Not all ESD products are held to the highest standard.

You want to find a vendor that can supply your ESD needs who can guarantee all of their products are properly tested, meet or exceed industry standards, and have the certification to prove it.

Always be sure to properly vet your chosen vendor, making sure they meet these requirements and be willing to ask for clients you can speak to and recommendations you can verify. If they’re reputable, they’ll be more than willing to have you check them out with their existing happy clients.

ESD prevention is no casual task. Your company may not have the risk of ending 36 lives, but putting best practices into place can certainly save jobs, computers and your clients.

We’d love to be the experts you can count on for your full service, seamless ESD solutions. For more information or advice on your specific ESD prevention needs – or any other ESD questions, please contact us today.

14 Jul

Monitors & Meters: Which One Do You Need?

Monitors and meters may seem like merely a question of semantics. And in most of the world it is, monitors are analogous with meters and vice versa.

But when you’re dealing with electrostatic discharge (ESD) prevention, both have specific purposes and uses that set them apart from one another. And it’s important you know which is which before you start or continue your work with items that can be harmed by ESD.

Monitor: What’s Happening in the Room?

In plain language, in an ESD Prevention situation, the Monitor (noun) keeps known sources of ESD in systematic reviews. It monitors (verb), the ‘progress’ or quality of ESD buildup over a period of time.

So we have monitors for people, that connect to their personal wrist straps, or connect between them and the ESD matting that they are using – in effect, monitoring both.

The key to a good ESD monitor is make sure they provide constant monitoring of the potential ESD in the room. If the monitor fails, a single spark of static electricity can cost hundreds of dollars in damage before it’s quelled.

Meter: Where Is It?

Meters, in an ESD prevention situation, operate more as the means to locate the sources of ESD build up.

Much like the meters used for testing in construction situations, meters will show the relative ESD levels, allowing the user to pinpoint the exact spot where ESD is being generated or not dispersed properly.

This can be on ESD mats, clothing, people and flooring.

Specialty meters can detect and pinpoint ESD specifically in a cleanroom or ionized area.

There are meters that look at a wide variety of potential ESD buildups and smaller units that check select areas only. And meters that check the humidity, temperature, electrical resistance, and any or all of these at once.

There is a secondary subset of meters that you should also be aware of – Testers.

Testers check the grounding of electrical receptacles to ensure they are actually grounded. Imagine the problems and expense of not realizing your electrical plugs were not grounded and subsequently having to discard or repair any sensitive electronics that had been worked on or assembled during the time the ground was inactive.

There are also testers for personal wrist straps and grounding cords.

Are You ESD Aware?

So, the answer to our question above is YES.

It’s not an either/or situation. It’s both. Each tool has its purpose within your ESD control situation, and both are effective in their job – which is generating awareness of ESD.

We would love to be your full service, seamless ESD solution provider; contact us today for more information.

22 Jun

Are You Grounded: A Look at Cables, Clamps, and Drums

Do you remember the cell phone gas fire scares of the early 2000’s? Because of a couple of erroneously spread Internet rumors, people all across the world became convinced that use of their cell phones while at the gas pump could lead to explosions, injuries, even death!

Despite the fact that the rumors were all proven to be false, several gas station chains, including the one whose safety report was misquoted to create the rumors, posted stickers warning against cell phone use. One Chicago suburb even passed a law banning the use of cell phones at gas stations.

If you look closely, those stickers are still on a majority of gas pumps, at least in the US and Canada. But while there has never been a case where cell phones caused gas fires, the same is NOT true for static electricity.

We’ve talked a lot in the past about the danger even a small electroStatic discharge (ESD) can pose to sensitive electronics. But in a combustible atmosphere, that tiny spark can cause a lot more damage than the cost of replacing a damaged circuit board.

Static is Everywhere

Walking across a room, rustling your clothing, even just the act of raising your arm to scratch your nose can generate a sufficient static buildup to create a subsequent ESD if not dissipated. Under normal conditions, you won’t even notice the buildup until you feel the shock of the discharge being released.

When you’re not working with sensitive electronics, you probably don’t even consider this to be a problem, certainly not in your home or driving in your car. But like all charges, if it’s not given a route to ground, the charge continues to build, increasing the voltage. And if you happen to be in an area with flammable liquids, vapors and even dust, that static charge can cause explosive consequences.

The first step to avoid incidents in any environment conducive to these volatile exposures is to eliminate as many potential ignition sources as possible. But there are often unconsidered, hidden dangers, especially in an industrial setting that can act as accidental ignition switches.

Isolated Conductors = Hidden Dangers

Isolated conductors are conductive objects – metal flanges, fittings or valves in pipework systems, portable drums – which are either inherently or accidentally insulated from being grounded. Because of this, any static charge they generate becomes a potential ignition point.

The best way to avoid this problem is by utilizing bonding and grounding. Bonding is the process of joining two or more objects or containers with electrically conductive wires to neutralize the potential charge between them. Grounding is a more specific form of bonding where an object or container is connected to the ground.

There are a variety of ways to effectively employ bonding and grounding. While OSHA does not give clear directives on how to ground, they do specify when and where grounding as well as bonding procedures should exist.

Getting Grounded

The most obvious example to point to is the common ground, seen in every building – a metal rod is attached to the outside of a building and literally grounded a few inches into the soil. While this method works great for homes, the size of large industrial expanses, such as warehouses or factory floors, means other methods may be more suitable.

For manufacturing or large storage areas, there are a few options. They all involve grounding clamps connected to grounding cables.

If the area has access to the building’s main cold water pipe, a very common semi-permanent solution is to use a bronze pipe clamp as an alternative to the direct building ground. C-Grounding clamps are another popular semi-permanent solution. Of course, always check the reliability of the ground conductivity in these instances.

If you’re like many industrial complexes, though, the isolated conductors are often temporary items, like drums, containers and vessels that come and go as needed. For these instances, you can get a variety of steel- or aluminum-constructed clamps that attach to the container, connecting it through a stainless steel cable to a grounding point, making the drum or vessel safe.

Depending on the environment, you can also effectively ground using the drop valve of a mixing tank or connecting your ground cable to a previously grounded surface – a table or workstation that is already connected to the grounding apparatus.

Whatever method you choose, bonding and grounding are essential for the safety of everyone working in an industrial environment, whether they’re piecing together circuit boards, helicopters… or gas pumps.

We would love to be your full service, seamless ESD solution provider; contact us today for more information.

15 Jun

Conductive, Dissipative, or Anti-Static Flooring?

You’re hard at work at your latest assignment. Your boss wants you to put together a complete plan for creating a large-scale electrostatic protection area (EPA) for a client who will be assembling various sensitive electronics and they want to avoid any risk of losing their investment due to electrostatic discharge (ESD).

You’ve selected the grounding cables, the workstations, the custom cut matting, containers and furniture, all designed to minimize or eliminate the slightest chance of ESD damage. But a curious thing happens when you research the proper flooring.

A simple Internet search for ESD flooring yields numerous options, more than you expect and you start to notice they all fall under 3 categories. In an instant, you’re faced with a decision, just like the game show, “Let’s Make a Deal.”

Suddenly, Monty Hall (or Wayne Brady, the current host!) is staring at you, asking do you want to choose door number one, number two, or number three: conductive, dissipative, or anti-static? The clock is ticking… How do you decide?

Door #1

For starters, let’s eliminate one of your options. Much like the ‘ZONKS’ of the game show, ‘anti-static’ is a worthless term in your ESD vocabulary. By strict definition, anti-static refers to a material that resists generating a charge. At one time it did designate a level of resistance, but was so overused and misunderstood, the term was removed from the ANSI/ESD standards.

So likewise, eliminate the term ‘anti-static’ from your discussion.

Deciding between the other two doors requires a closer look at the specific needs of the area for which the flooring is intended.

We’ve talked in another article about Ohms (Ω) and how they are the unit of measurement for resistance to electrical current.

Door #2

Because of the size and scope of most areas where it is necessary, the most common form of ESD flooring is referred to as ‘Static Conductive.’ Conductive flooring is at the low end of the electrical resistance scale.

Conductive carpeting may even be laced with carbon lines or metallic yarn fibers to encourage the flow of electricity. Because of the low electrical resistance, electrons flow easily across and through the surface, and can be grounded safely and quickly. This carpeting or vinyl tile is laid down with a conductive adhesive and grounded through the use of conductive tape or copper strips that run to a common ground.

This type of flooring is also generally a little more cost-effective than a dissipative solution.

Door #3

On the higher end of the resistance scale falls ‘Static Dissipative’ flooring. The higher resistance of these materials keeps the electrical charge more under control as it slowly flows over the surface and into a ground. Dissipative flooring is much more common in shared office environments where everyday shoes are more common, as opposed to a location where every element, from furniture to footwear, is controlled.

In our example above, the client will be assembling sensitive electronics like circuit boards and such in a large-scale environment. In this instance, a vinyl tile, or a poured epoxy flooring with conductive properties would most likely be the best option.

In an office setting where a company has their own IT department that fixes and assembles computers within the same facility, a dissipative, static resilient tiled floor would be a better fit.

But the fact is, these are very simplified examples of the myriad of variables that you can encounter when selecting the proper ESD controlled flooring. Your best option is to talk to an expert.

We’d love to be the experts you can count on for your full service, seamless ESD solutions. For more information or advice on your specific ESD flooring needs – or any other ESD questions, contact us today.

25 May

What Are the Standards for Electrostatic Protection?

So, you’ve just been tasked with building or designing your first Electrostatic Protection Area (EPA). You’ve started doing your research, but there are so many choices, from so many different companies. Suppliers, manufacturers, third party providers… If only there was some established standard for judging the efficacy and reliability of all those pieces and parts.

Well, you’re in luck! In 2007, the American National Standards Institute (ANSI) in cooperation with ElectroStatic Discharge Association (ESDA) released a unified set of standards for the design, implementation and maintenance of ElectroStatic Discharge control programs.

In the midst of World War I, five engineering organizations recognized the need to develop standards that could eliminate confusion and could be adhered to across all disciplines, without regard to politics, profits or personal preferences. These groups reached out to the U.S. Departments of War, Navy, and Commerce to form an impartial third party non-profit organization, then known as the American Engineering Standards Committee.

Following the war, the organization spent the next 20 years establishing several safety protocols still observed today, like eye protection, hard hat standards and in-house electrical safety while at the same time reaching out to other similarly tasked international organizations.

When the United States entered World War II, the organization, which would eventually come to be known as ANSI, helped to accelerate the war effort and productivity, created more effective quality control measures, as well as helping to advance photography, radio, and even the development of Velcro.

In 1970’s, ANSI established a public review process and began the herculean effort of moving the United States to the metric system. While the general public never really connected with the metric system, the effort did bring ANSI to the forefront of private sector companies who discovered standardization was a way to stay more competitive in an increasingly global economy.

With the advancement of personal computers in the late 70’s and early 80’s, engineers at several companies recognized a need for more understanding of electrostatic discharge and its prevention. They formed the ESD Association, a non-profit, voluntary professional organization that for almost 35 years has sponsored educational programs and developed standards to help eliminate losses due to electrostatic discharges.

Together, leaning on the historical experience of both military and several commercial organizations, ANSI and ESDA developed the definitive standard for ESD protection, the very cleverly named ANSI/ESD S20.20-2007.

Covering about every conceivable area of ElectroStatic Discharge, the ANSI/ESD S20.20-2007 utilizes both the human body model and the machine model to provide a broad set of guidelines for ESD protection.

The Human Body Model is the military standard that defines and rates the vulnerability of an electronic device to the ESD generated by a human being touching it. The Machine Model works similarly, except it rates the vulnerability of a device receiving a machine discharge into ground. It was originally developed by car manufacturers as their plants moved to more mechanized production technology. The Human Body Model is about 10 times more sensitive than the Machine Model.

There is a lot to explore in the ANSI/ESD S20.20-2007 guidelines, but for the purpose of this primer, the document highlights 3 fundamental ESD control principles:

All conductors should be grounded. This includes the personnel and the surfaces they are working on. We recommend, at a minimum, personal grounding wrist straps, ESD table or bench mats, and a common ground cord.
Necessary non-conductors – certain circuit board materials, device packaging, etc. – cannot lose their electrostatic charge by being grounded and appropriate precautions must be implemented.
Static protective materials, such as ESD shielding bags or ESD totes and boxes must be utilized when transporting sensitive electronics outside a properly prepared EPA.

There are slightly less stringent standards that apply to floors and bench mats, but ANSI/ESD S20.20-2007 is the highest and most comprehensive guideline so far. So when you’re shopping for the parts needed to establish your EPA area, always look for companies that maintain that standard in their products and services.

We would love to be your full service, seamless ESD solution provider; contact us today for more information.

04 May

Finding ESD Storage Solutions

There’s a classic scene that appears, with some variation, in every James Bond film. Bond gets assigned a new mission and he goes to see MI-6’s Quartermaster, or “Q.” Q gives Bond everything he needs to complete the mission, including a few items that seem unusual or out of place.

Of course, as Bond fans know, these elements will at some point be combined to facilitate a distraction so Bond can escape. And usually that distraction is a rather large explosion.

One wonders how he was transporting the items before so that they didn’t explode in his Armani suit.

Of course, in real life, when items combine, the result isn’t usually an explosion. Or is it?

As we’ve mentioned before, the amount of Electrostatic Discharge (ESD) required to cause significant damage to sensitive electronics is far below the threshold where a human being can feel it.

By the time our bodies create a static charge that we can feel, it’s somewhere between 3 & 17 times stronger than what most electronics can handle without suffering damage.

Even just the controlled blowing of air, like the old canned air computer dust removal techniques can cause static ESD build-up that can be transferred to your sensitive electronics. And that tiny electrostatic discharge can cause latent or catastrophic failure, costing you time and money.

We’ve discussed selecting the proper shielding bags in a previous post. Another important weapon in your Electrostatic Discharge defense arsenal is anti-static ESD storage containers.

ESD Storage Containers

ESD storage containers are typically made of a conductive material, such as polypropylene or high density polyethylene and provide an added layer of protection, shielding your work areas and personnel from the harmful effects of ESD.

The conductive material provides a barrier which these fields cannot penetrate and prevents the build-up of electrostatic charge. The bins, totes and miscellaneous storage containers come in both static dissipative and conductive. Both control a potential electrostatic discharge, one by resisting it, the other by neutralizing it.

Additionally, be on the lookout for non-ESD protected items that may stray into the Electrostatic Protected Area – transparent tape, plastic sandwich bags, water bottles, Styrofoam coffee cups, even just pieces of paper – can be the source of an uncontrolled electrostatic discharge.

Of course, all of these storage solutions should be used within the minimum guidelines of an Electrostatic Protection Area, that is, wrist straps, ESD mats and a common ground.

We would love to be your full service, seamless ESD solution provider; contact us today for more information.

07 Jul

Demonstrating CDM Discharge using Common Hand Tools

Q:

What is the significance of the time to the charge generation in tribocharging?

Why is it that in tribocharging, there is a big charge produce in short period of time while small charge will be generated at long time? ( at the same force)

(I took the liberty here to respond to the question and go a bit further and look at CDM Testing as described in a recent issue of Conformity.)

A: First a little background about charge as it relates to ESD (ElectroStatic Discharge).

Triboelectric charge is merely the contact and separation of materials. “It involves the transfer of electrons between materials.” Which materials lose electrons and which gain them depends on the materials.

Static electricity can be measured in coulombs, and related to voltage potential via the equation: q=CV. q = charge in coulombs, C = Capacitance, V = Voltage

The industry typically uses electrostatic potential and thus uses voltage to look at this energy form. Voltage is merely charge potential with respect to a ground point or reference and measured in volts (v).

Insulators or materials with high resistance restricts or prevents flow of electrons across (surface) or through (volume) it’s material.

Conductors or materials with low resistance easily allows the flow of electrons across it (surface) or through (volume) it’s material.

Insulators and isolated conductors can tribocharge to high voltages and will remain for a long time… so long as energy is not transferred via induction (isolated conductors) by bringing other objects into it’s vicinity and grounding the other object, by grounding the isolated conductor, or by balanced ionization (isolated conductors or insulators).

When isolated conductors are grounded, they (becoming grounded conductors) will enable electrons to flow easily to ground and the charge upon it will become neutralized and reduced to near zero.

Insulators cannot be grounded. They can induce charge to isolated conductors and can cause electrical overstress/ESD events to isolated conductors at the time they are grounded via the charge field and do not need to contact the isolated conductors in order to do so.

Here’s another way to say that; “CDM (Charged Device Model) charging can produce two separate discharge events. Here’s how it works. If you ground a conductor (the conductive blade of a screwdriver for example) while it is in the presence of any item carrying an electrostatic field ( a charged piece of plastic or clothing), the conductor will acquire an electrostatic charge that may be sufficient to cause damage when discharged.”

Human Body Model, as is described in ANSI/ESD S20.20-2007… and the ESD control thereof, is concerned with limiting the voltage in the EPA for the protection of ESDS devices (ESD sensitive devices) to 100 volts and a discharge to within that level in less than 0.3 seconds for ESD Technical Elements (some quicker) at minimum.

I need to know what specifically are you interested in; the HBM, MM (Machine Model), or CDM (Charged Device Model)? Keep in mind, that “volt per volt, MM discharge is an order magnitude more powerful than HBM discharge because the resistance of human body has been removed from the equation.”

In the article in Conformity, “Demonstrating CDM Discharge Using Common Hand Tools” provided by the ESDA, they state; “The damage threat from hand tools is CDM charging of the hand tool, accompanied by MM discharge to the component or device.”

Source: Conformity : ESD Open Forum April 2009 pg 20.

The following pics depict the testing I did in my lab in accordance with what I’d learned from a recent Conformity article from the ESD Open Forum entitled Demonstrating CDM Discharge using Common Hand Tools. It involves charge, not by contact, but by induction;

1-non-esd-screwdriver2

2-shockstop-treated-screw-driver2

3-gz-shock-stop-sample1

4-charging-dp-with-silk1

5-zeroing-field-meter1

6-donning-wrist-strap1

7-confirm-blade-is-at-zero-on-non-esd-sd4

8-touching-blade-for-cdm-charge2

9-cdm-charge-potential-measurement1

10-zeroing-shock-stop-treated-sd-blade4

11-confirm-zero-volts-on-shock-stop-treated-sd1

12-recharging-dp-with-silk1

13-touching-blade-on-esd-treated-sd-for-cdm-charge1

14-cdm-measurement-for-esd-treated-sd1

15-rechecking-cdm-on-non-esd-sd1

16-remeasuring-cdm-on-non-esd-sd1

18 Jun

We don't need no stinking wrist straps, do we?

Q: I have read the White Paper 1: A Case for Lowering Component Level HBM/MM ESD Specifications and Requirements and found the ESD Control Programs and Resulting Data (Chapter 1, Page 20-23) particularly interesting.

Assuming a production environment with ESD flooring, footwear (and clothing), by the time a person walks to a workstation and sits down, the voltage of this persons should not exceed 500V (or even 100V as seen in Figure 3). That would mean even a seated operator in this case would not need to wear wrist strap, that theory would be correct right? After sitting down and this person sits on a stool (feet off the floor) with resistance to floor < 1.0x10exp9ohms, any HBM risk would be further reduced wouldn’t it?

A: Hello ****. Nice try. Even if you have an ESD flooring system and even if you have ESD footwear and even if you have an ESD task chair with ESD casters or an ordinary task chair with an ESD chair cover (very effective as well), ESD smock on… you STILL have to wear the wrist strap when seated at an ESD workstation.

The only time, per ANSI/ESD S20.20-2007 page 4, 8.2 Personnel Grounding, that personnel in the EPA (ESD Protected Area) should be without a wrist strap is when doing standing or walking about operations, and then two conditions must be met;
· “When the total resistance of the system (from the person, through the footwear and flooring to the grounding / Equipotential bonding system) is less than 3.5E7 Ω…”
· “When the total resistance of the system (from the person, through the footwear and flooring to the grounding / Equipotential bonding system) is greater than 3.5E7 Ω and less than 1.0E9 Ω and the BVG is less than 100 v per 97.2…”

This is what is said about seated personnel:

“When personnel are seated at ESD protective workstations, they shall be connected to the grounding / Equipotential bonding system via a wrist strap system.”

Hope this helps. I guess you could say redundancy is good in the realm of ESD. It’s the weak link in the chain that will cause an ESD event. If someone lifts their ESD footwear from the ESD flooring system while seated, they can tribocharge to above 100 volts. It takes only 0.3 seconds of charge time to exceed 20.20 requirements. If personnel is seated and getting up to go to break, it seems best to stand up, remove the wrist strap from the wrist, carefully set it down and walk away from the ESD workstation. Worst case is to take the wrist strap off while still seated, set it down, put your hand on the ESD workstation and near ESDS devices, then stand up out of the task chair before leaving the work station. Under proper conditions and with good bench mats, clean ESD floors, ESD task chairs, etc. in place, no ESD event. The problem with ESD events is that we cannot see, hear, feel them.

The only alternative to not wearing a wrist strap while seated may be the used of a smock with a grounding coil cord attached to it. You can see the footnotes on the 20.20 document at the bottom of page 4 for further details.

We adhere to and meet or exceed requirements put forth in ANSI/ESD S20.20-2007 or IEC 61340-5-1, which assumes a target HBM of 100 volts and less.

17 Mar

Should ESD shoes, heel grounders be worn outside?

Q: Is it ok to wear ESD shoes or heel, toe, or sole grounders outside?

A: No. MIL-HDBK-263B Appendix 1 page 101 40.1.2 states, “Conductive shoes, shoe covers, or heel grounders should be used to discharge personnel on conductive floors. These items should only be worn in the ESD protected areas and should be kept clean so that contaminants do not inhibit their conductive interface with the floor.”

So, to protect your investment, for good house keeping and maintenance, longevity of the ESD personal equipment, just don them before going into the EPA and take them off when you leave.

Do this and keep them clean (vacuum inside of shoes weekly and maybe clean outsoles and grounders with soapy water once a week) and you’ll get more wear out of them and they’ll be more effective.