Cleanroom – Ground Zero Electrostatics Blog

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.

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.

16 Jun

How do we test ESD conductive or dissipative gloves?

Q: How do we test ESD conductive or dissipative gloves?

A: The glove industry offers gloves for the protection of ESD sensitive items by using materials that will provide specific measurable “intrinsic electrical resistance of gloves and finger cots” as per ANSI/ESD SP15.1-2005.

Some materials are being used which reduce the amount of charge generation “and/or have static dissipative properties to reduce charge accumulation”, such as Nitrile or vinyl. I would image cotton could be effective based on the layer of sweat on our skin. But if you require ESD gloves in the Static Conductive range, those would need to be specifically made for that purpose. I’m currently working on nailing down an exact value of what these gloves should read and how that affects the ESD testing of it and the closest I could find comes from a test fixture from Prostat called the CAFÉ, or Constant Area & Force Electrode. They recommend using 1.5 to 10 volts when the measurement of glove in combination with personnel through a wrist strap assembly without the 1 meg Ω resistor is less than 1 meg ohm. They use 10 volts between 1.0E6 Ω and 1.0E7 Ω. Then they use 100 volts for above that. This is fairly easy to do using a sophisticated megger like the 801 in manual mode, otherwise the mere testing of the glove per 15.1 could be a challenge.

Here’s what confuses about ANSI/ESD S20.20-2007 and -1999 …

What’s the range of the glove and finger cots? Only in 20.20-2007 Tables 1, 2, and 3 final column does it give us “Required Limits” to measure up against. So then what? Go to manufacturing specs. Some list a value, some don’t. Be careful how they’re categorized; anti-static (describes that it’s low charging but doesn’t really quantify a resistance range unless you’re talking about packaging), static dissipative (1.0E6 Ω to 1.0E9 Ω ??), and static conductive (less than 1.0E6 Ω but greater than what?? 1.0E4 Ω rings a bell, but I’d hope it’s not less than that.).

Ok, so for our Static Conductive or black finger cots, they measure between 1.0E6 Ω and 1.0E8 Ω per ASTM D257 and meet the static decay specs per MIL-STD-81705B from 5000 to less than 100 volts in less than 0.01 seconds.

So here’s the upshot; My improvisation in measuring ESD gloves and finger cots involves using the PFA-861-H Handle (see attached), a DUT (esd glove), and a wrist strap without the 1 meg ohm resistor for measurements known to be below about 1.0E7 Ω , I hook that up to my meg ohmmeter and see what I get (see attached photos).

wand wand-and-sd-glove wand-and-sc-glove

This ESD TR20.20-Handbook has a wealth, a plethora of information about ESD gloves and finger cots, such as referring to yet other standards such as ANSI/ESD STM11.11 Surface Resistance Measurement of Static Dissipative Planar Material , and let’s not forget ANSI/ESD STM11.12 Volume Resistance Measurement of Static Dissipative Planar Materials, oh, and of course ANSI/ESD STM11.13 Two-Point Resistance Measurement of Static Dissipative and Insulative (what the??) Material, then it goes on to tell us to use the CAFÉ method, which is specifically designed for resistance measurements at the thumb and fingertips, which can yield much lower results than those obtained by the above test BECAUSE THEY INVOLVE A REAL LIVE PERSON, THE WAY THEY ARE ACTUALLY USED IN PRACTICE! Oh, and they say you can only measure once due to a “person’s skin emissions”. Fair enough. Time to reorder?

So… If this info helps anybody, let me know and send over a comment.