03 Mar

Selecting the Proper Shielding Bags

Choosing the Right Shielding Bag

In Michio Kaku’s book, Physics of the Future, he notes that today’s smart phones have more computing power than NASA had in the 60’s when they were plotting and launching the moon landings.

The latest SONY Playstation can outperform the supercomputers the US Government used in 1997 – 14 years after the movie WarGames.

In 1965, Gordon Moore, one of the founders of Intel, observed what became known as “Moore’s law.” He postulated that computers would progressively become more dense while at the same time increasing their processing speed.

This can be both good and bad news for computers. The bad news being that every time a component gets 10% smaller, it gets 10x more sensitive to electrical shocks, even those coming from simple static electricity. Static in your workplace can be dangerous and expensive if you’re not properly prepared.

One important weapon in your arsenal for defense against Electrostatic Discharge (ESD) is shielding bags.  Which bag is best? They all have their pros and cons to consider.

Pink Poly Bags

The earliest defense against ESD was created in the 1960’s.  Dissipative Poly Bags, usually referred to as Pink Poly bags because of their unique color – introduced as an easy way to differentiate their static control abilities from standard plastic bags – are coated with a chemical that resists static.

Unfortunately, Pink Poly bags have no shielding capability. An ESD of any significance will travel through the bag and potentially damage components inside. They are best utilized today to package support or processing materials that do not themselves need shielding.

The antistatic properties of the bags help to protect sensitive components near the bags. This makes them a helpful solution as opposed to normal plastic bags, but you should always have a grounding system in place – mats and personal wrist straps at a minimum.

Black Conductive Poly Bags

Black Poly Bags are obviously a step up from their Pink predecessors. But in this case, their advantages are also their biggest flaw. Like the Pink Poly’s, the Black bags are antistatic, with the added benefit of some conductivity, designed to help protect its contents from ESD’s.

The problem lies in how quickly the bags dissipate the electrical charge. The rapid discharge of the ESD can actually generate a spark between the person or object creating the charge, and because the bags lack an additional insulation layer inside the bag, that charge can easily penetrate it.

Plus, there’s the added complication of the bag’s color. The conductive carbon leaves the bag opaque, requiring the contents to be removed to be seen, leaving the potential for damage.

The biggest benefit of the Black Poly’s was some shielding at a lower price point.  But in recent years, shielding bags have become much more affordable, and reputable vendors have effectively eliminated them from their inventory.

Shielding Bags

Shielding bags combine the antistatic and dissipative qualities of the poly bags with metal shielding and a polyester insulator (or dielectric) layer. Where Pink Poly’s stop about 10% and Black Poly’s 30%, Shielding Bags stop 97% of electrostatic pulses.

Shielding bags are classified in two ways:

Buried Metal (Metal-In)

Buried Metal bags consist of a dissipative poly layer, glued or laminated on top of a metallized polyester – usually aluminum, but sometimes nickel or copper – laid over an additional dielectric polyester layer.

The metal between two layers of plastic offers better protection than the alternative.

Surface Metal (Metal Out)

In Surface Metal bags, the layers are ordered differently, with the poly and the dielectric polyester glued together, then coated with a nickel sprayed with an abrasion resistance coating.

Unfortunately, the outside metal coating causes a faster dissipation of electrical charges, resulting in sparking issues similar to that of the Black Poly Bags, although not as dangerous.

Moisture Barrier Bags

For long term storage or moisture sensitive items, Moisture Barrier bags provide the ultimate protection. These bags are similar to, but stronger than normal shielding bags and provide an additional protection with a moisture vapor barrier.

There are two types of Moisture Barrier bags: Foil and Tyvek (utilizing the DuPont material) or Heavy Metallization.  Both provide similar levels of protection, the difference primarily being the higher cost of the Tyvek structured bags.

Static protective bags should always be implemented as part of a more comprehensive static control environment, which should always include proper grounding tools.  And while expenditures are always a factor, consider the insignificant price of proper protective measures when compared to the cost of replacing the delicate components inside the package.

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

25 Feb

Building an Electrostatic Protected Area (EPA)

How to Build an Electrostatic Protected Area

Almost everyone’s familiar with the image of a white “cleanroom” or “bunny suit.” They show up in just about every depiction of people working in computer facilities in popular entertainment, and it’s a highly sought after specialty ‘armor’ in the video game Fallout 4.

What most people may not know is that the suits are designed not to protect the person inside, but the delicate circuitry they’re working on.  But not everyone who works with small, sensitive electronics needs to spend money for a full-on, disposable suit.

If you work with a lot of small electronics, a more affordable solution is to put together an electrostatic protected area (or EPA).  This doesn’t have to take up a lot of space and can actually be quite portable.  It just needs to be done properly.

Let’s start with the basics and work our way up to the safest and most expensive options.

Simple EPA

At a bare minimum, all personnel working within an EPA should have a personal grounding wrist strap.  These make sure any excess energy is grounded – forced away – from the electronic devices and circuit boards being handled.

Connected to that grounding strap is a dissipative mat. Dissipative means quite simply to disperse or disappear.  A properly designed and implemented dissipative mat does for the surface what the grounding wrist strap does for the person – protects sensitive electronics from electrical discharges.

Mats can be purchased pre-cut or in rolls, depending on what your needs are.

Attached to both of these is a common point cord, also referred to as a grounding cord.  These cords are fully insulated and take any electrostatic charges away from the person and the ESD mat to be grounded safely.

Often these simple options are packaged together as a field service or workstation kit that can be purchased as one unit to avoid forgetting any key elements.

Now that we’ve established the minimum requirements for an EPA, let’s look at additional options that can be easily implemented within your system to further insure the safety of the components and reduce the risk and excess cost of replacement.

From the Ground Up

For more permanent EPA installations, there are a variety of flooring options that can be integrated.  Everything from conductive and dissipative vinyl tiles to anti-static carpeting that can be utilized in the work area or just in the area surrounding your EPA system.  You can even add flooring with a high-end moisture barrier as well as anti-static protection.

Sole Protection

One of the most obvious ways we build up a potentially dangerous electrostatic discharge is just by walking.  Static charges build up naturally.  While a personal grounding wrist strap will help dissipate the charge, there are additional options for your feet.

Shoe covers with conductive strips are a quick, low cost addition to an existing EPA system and great for alleviating the risk of allowing visitors into the EPA area.

For employees whose duties mean they spend substantial time in the EPA area, you can add foot and heel grounders, toe grounders and sole grounders.

For even more protection, grounders can be upgraded to ESD shoes.  These come in a variety of styles for your business setting – even weatherproof boots and hiking models.

Additional Considerations

Adding isolation protocols and ESD protective containers can also complement your EPA system and reduce the chance of any accidental charges building up or discharging into your electronic components.

Of course grounding should be a consideration with any additions to your EPA system.  Whether it’s flooring or matting, grounding cords with a built in resistor add that much more protection to your area.  And the more working parts you have, the more grounding capability you require.

There are simple options to increase the grounding ability of any size EPA system, as well as monitors that can be added to the system – at the personal or system-wide level.

And if you really feel the need to cover yourself top to bottom, there are more workable clothing options as well.

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

12 Feb

ESD: Grounding, Isolation & Prevention

The Pilllars of ESD Protection

We’ve all had it happen. We’re opening our car door on a cold day, or we’ve just shuffled in our socks to the door and the moment we reach out, pop! A small snap of static electricity reminds us that we’re alive.

Think back to when you were a kid – your dad or uncle perhaps, showed you the power of static electricity by rubbing a balloon on your head and sticking it to the wall or causing your hair to rise up of its own accord. These tricks with static electricity are great for a chuckle or two. When you’re rubbing the balloon or your socks on the floor, it creates an imbalance of electrons, and that potential energy rests on your body or the surface of the balloon, waiting to discharge. Eventually it does and this sudden restoring of the electrons to their neutral state is called an electrostatic discharge or ESD.

That little tiny jolt of static electricity seems small but is really 3,000 volts – for humans, it’s the amperage that gets you. Unfortunately, for small electronics: circuit boards, semiconductors or even simple devices around the home, much smaller static discharges – ones too light to ever be sensed by our skin – can cause minor errors, or even completely destroy a device’s usefulness. In this situation, ESD is no laughing matter.

In a business—especially one that manufactures or handles a lot of electronics, but even in a typical office environment—this kind of damage can get expensive quickly.

So today, we’re going to talk about the three pillars of controlling ESD: Grounding, Isolation and Prevention.

Grounding

If you’ve worked with small electronics much at all, you’re probably aware that there are certain things you should do to prevent damage to that circuitry. You’re probably familiar with the third prong on many electrical cords. Just like the grounding plug diminishes the risk of you being electrocuted, grounding yourself and your work area keeps your circuit boards and electrical components safe by discharging any built up static electricity.

At a bare minimum, utilizing a grounding wrist band is extremely helpful. Many sellers include disposable bands when they ship electronic components, but we highly recommend owning and utilizing your own personal metal ground wrist strap that connects directly to your work surface with a personal ground cord. Always make sure the wrist strap is snug and is touching the skin to allow the charge to dissipate.

Isolation

Static charges cannot penetrate containers that are made of conductive materials or have a conductive layer. That’s why electronic components usually arrive in metallized shielding bags or a conductive tote box. Don’t forget you must ground them before opening. And don’t set these components just anywhere. What many people fail to realize is that simple items that can be found on any normal work surface – even an ESD mat – can also cause unnecessary static buildup that could lead to a fatal discharge.

Transparent tape, plastic sandwich bags, water bottles, Styrofoam coffee cups, even paperwork or blueprints can hold a static charge just waiting to wreak havoc on unsuspecting components. And even if you are properly grounded, holding the components too close to your clothing can also result in an ESD.

Prevention

Always take proper precautions when working on electronic components. Follow all of the tips above, and if you’re going to be working on several components or multiple projects, we recommend investing in some ESD bench and table matting for your work surface. It integrates well with a personal ground cord and wrist band and is the best solution for ESD prevention. A few dollars spent here as well as on ESD protective containers can mean plenty of money saved on ruined components as well as lost time while waiting for replacements.

Following these simple suggestions can mean a much safer environment for both you and your electronic components – and you can leave the static charge at home for parlor tricks.

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

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.