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?
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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