personal grounding

10 Essential Static Control Products

by Andy on June 15, 2012

ESD-Safe Symbol
When outfitting an ESD-safe area you must cover all of your bases. It only takes one shock to hurt your product, and therefore your bottom line. Here is a list of 10 things you can do to control static in your workplace.

Eliminate Static

1. Mats and Flooring: ESD-safe mats can help control static in many different ways. Work surface mats can dissipate charge from devices on your workbench as well as the product itself, while floor mats can remove static from the operator when used in conjunction with personal grounding.

2. Personal Grounding: While mats can keep the work surface safe, wrist straps and heel grounds remove charge from the operator.

3. Ionizers: If you have any insulative items at your workstation you need an ionizer to neutralize any charge that may build-up.

Remove Static Generators

4. Chairs: By replacing normal chairs with ESD-safe ones you can reduce the amount of charge generated by the operator. This adds a second line of defense against static discharge from the operator, stopping the charge before it starts.

5. ESD-Safe Garments: Along with ESD-safe chairs, special garments can be used to reduce charge generation on operators. By using ESD-safe garments you can allow yourself a full range of motion without having to worry about producing a static shock.

6. ESD-Safe Tools: Your tools will obviously be in contact with your project, so it is imperative to keep them from generating a charge. Luckily there are ESD-safe versions of almost every tool, so you can safely work on any static sensitive project.

7. Storage: Using chairs and garments help reduce static generation while you are working on products, but you need to protect your products even when they are sitting on your shelves. ESD-safe bags and totes can reduce product defects from static discharge in your storage.

8. Shippers: There is even more danger of static generation during shipping than in storage, so it makes sense to protect your product there as well. With proper ESD-safe shippers you can be sure that no matter how much your product moves in transit it will be protected from unwanted static build-up.

Test Equipment

9. Workstation Monitor: Matting and wrist straps are great methods of static control, but they are useless if they are not connected and functioning properly. By using a workstation monitor you can ensure that everything is working correctly.

10. Wrist Strap and Heel Ground Tester: If you do not need to have constant monitoring of your workstation, then you can use a wrist strap and heel ground tester. This allows you to check for problems regularly without having to be connected to a monitor all the time.

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While it is important to know how to keep yourself and your workstation grounded, it can be interesting to understand where your charge goes. Most ESD-safe products seem to whisk your charges away to a nebulous “ground”, but it is not always clear what that means. Typically grounding hardware connects to the earth, using its large neutral charge to negate any built up static on objects.

While talking about ionizers last week, we noted that opposite charges attract. This is what allows the ions to neutralize charges as they fall across a workbench. There is also a corollary rule: similar charges repel. If you have a build up on charges on objects (say too many electrons producing a negative charge) they naturally want to move away from each other. The problem is that they often have no place to go, until they come in contact with another device.

Wrist Ground By grounding yourself to the earth, you give the electrons a path to leave safely. Because the earth is so large, you will discharge fully whenever you are properly grounded to it. If you try to discharge to a small object then you may get rid of some of your charge, but probably not all of it, leaving both you and the object with enough of a charge to damage ESD sensitive devices. The earth, however, can easily support any charge that a device or human in a work area can normally generate, so it serves as a practically infinite container for any extra charge you may gain.

What makes the earth such a good ground? At first it may seem odd that the earth is used to neutralize charges in this way, especially as dry soil can be a very good insulator. The main reason it works so well is the moisture in the ground. Just as lightning can hit trees and travel to the ground through the rain on them (as wood is another great insulator), the moisture in the ground can serve as a great conductor for errant static electricity.

It is important to measure the soil resistivity wherever you are placing your ground, as you want it to be as low as possible. The lower the soil resistivity, the better your grounding system will work. Most times when you are grounding in a building you can use metal beams that are part of the framework, as long as they are driven into the earth and are suitably set up for this use. This can be a great method as these beams tend to be driven very deep in the earth, and the deeper they are set, the lower their resistance. If you do not have access to this framework, you can also connect to a metal rod set into the ground. With this method you need to test various areas to make sure you place the rod in the place with the least resistance, ensuring that the charge can easily make its way into the ground.

That ends our series on grounding. Make sure to check in next Monday for a new series of articles!

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ESD-Safe Bench Mat While personal grounding equipment is important, people are not the only hazard to electronic devices. Any ESD-sensitive device can also be damaged from charges built up while moving it across a work area or from other charged items in the area. To reduce and counteract the build-up of static charges, ESD-safe matting and ionizers are used in areas where electro-static discharge is a concern.

ESD-Safe Matting

ESD-safe mats are integral parts of static safe work areas. These mats discharge any introduced charges through a connected wire and ultimately transfer them to either an electrical or earth grounding point. Connecting to an electrical ground, which is either the screw through the metal plate covering an outlet or a screw on the outlet casing inside the wall is fairly simple while finding and attaching the wire to an earth ground (which is generally a metal rod hammered into the ground before the foundation is poured) is substantially harder. It is important to use a ground tester to make sure that the outlet you are using for your electrical ground is connected properly and safely to an earth ground. A faulty ground could result in damage to ESD-sensitive devices or personal harm if the ground is connected to a live wire.

Matting for ESD-safe work areas are normally dissipative or will have a dissipative top layer. Compared to a conductive surface, a dissipative top layer slows down how fast a static charge drains while still providing a path to ground for any built up charges. By draining the charge more slowly; the dissipative surface provides less risk to the static sensitive devices.

Ionizers

Bench top ionizers and overhead ionizers are used to neutralize insulators and any other devices that are not fully grounded or can’t be grounded. Most ionizers work by using a fan to spread positive and negative ions across an area. These ions are naturally attracted to their opposite charges, so positive ions neutralized negative areas and negative ions neutralize positive areas. Any left over ions will neutralize themselves as they find their opposite charges. This allows for an area of neutral charge by slowly and safely neutralizing charged objects in a work area.

Next week will be our last in this series on grounding, where we will explain how grounding works at the level of the earth. Come back next week for more information and be sure to read our previous articles on grounding below!

Getting Rid of Charges Part 1

Getting Rid of Charges Part 2

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Last week we went over what grounding does and why you need it, so this week we will start to look into methods of grounding. We noted before that static can come from two objects rubbing together. One of the biggest factors in creating an ESD-safe workplace is stopping static from the object that often moves the most: the human body. By walking, sitting down, moving your arms, or any number of other activities your body can generate static, so it is important to use personal grounding equipment to discharge this energy safely.

Heel Ground Shoe Grounds

If you stand or walk around while working with static sensitive equipment then shoe grounds are essential. These devices wrap around your shoes and create a path to ground from your body through the ground strap to the ground. However, in order for these to work properly you must have conductive or dissipative flooring and you must wear a shoe ground on each shoe. When you are walking one foot is off the ground a lot, so you need a continuous path through each shoe. Shoe grounds come in many styles, including heel grounds, toe grounds, and full sole grounds.

Wrist Strap Wrist Straps

When working at a desk shoe grounds are not as effective since your feet are not always touching a grounded surface and are often hanging from your chair or on a footrest. In this instance wrist straps are used to ground the operator, as they provide a constant ground path. Wrist straps can be plugged into an ESD-safe mat, as well as other ground points. Workstation monitors are one such ground, which have the added benefit of testing your equipment and notifying you if any part of your system fails. You can find workstation monitors that just test wrist straps or both wrist straps and ESD-safe mats at the same time.

That is all for this week, make sure to check in next Monday for more information on grounding your workstation!

Getting Rid of Charges Part 1

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Proper personal grounding techniques are probably the most important part of any ESD-safe workstation. However, you may not know what grounding actually does to get rid of a charge. Today I am going to go into some basics of gaining and losing charges, so if you already know how this works, make sure to visit next week when I go into some specific grounding techniques.

What does it mean to gain a static charge?

Static Discharge For an object to gain a charge, it must either lose or gain electrons. The movement of protons and neutrons, the other parts of atoms, tends to be restricted. However, electrons can move across objects and as they move, they create charges on objects. If an area has more electrons than protons then it has a negative charge; if there are more protons than electrons then it is positive.

Different objects can have the ability to allow more or less electrons to move through them. When it is hard for electrons to move through an object, it is called an insulator; when it is easy, it is called a conductor. Glass and plastic are examples of insulators, while most metals are conductors.

How do you gain a static charge?

One of the easiest and most common ways that an object gains a charge is by tribocharging, which is rubbing two different objects together. Because electrons do not move through insulators easily, they can build up a charge when electrons are transferred to them. If you rubbed two conductors together, then the objects would easily return to equilibrium of protons and electrons.

While rubbing two objects together creates a static charge, it is not the action of rubbing or the friction involved that transfers electrons. Electrons move naturally whenever two objects touch. Rubbing them together increases the area of contact, which allows for a larger number of electrons to be transferred.

How do you get rid of a static charge?

When you have a buildup or a lack of electrons on an object, then it has a charge. However, objects naturally want to reach equilibrium of protons and electrons. The fastest way to do this is to ground the object by touching it to a conductor. By touching a conductor, which allows electrons to move freely, the electrons are allowed to flow to whichever object needs more to reach equilibrium.

You cannot always reliably ground yourself just by touching a small conductor, which is where proper grounding techniques come in. In order to fully reach equilibrium, it is most effective to touch a conductor that is connected to the earth. Because the earth is large and the charged object is small, the charged item will fully discharge or gain electrons as needed to reach equilibrium.

Insulators cannot be grounded through this method, as electrons do not move across them easily. Instead of touching an insulator to a ground cable to remove a charge they must be neutralized through ionization. Bench top or overhead ionizers are very useful for this, but we will go into more detail on this method in an upcoming post.

Why does grounding matter?

Grounding is important in any ESD-safe work area to protect objects that are sensitive to static shock. If a person has a charge and touches a circuit board, then there may be a transfer of electrons, more commonly known as a static shock. This static can harm many electronic devices. However, if you are grounded then you will not have a charge, reducing the chances of discharging this destructive static.

Next week we will look at specific grounding techniques, so make sure to check back in on Monday!

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